Leukemia, Myelodysplasia, Transplantation

AML cells in the bone marrow

Results of preclinical research suggest the wild-type version of SYK pairs with mutated FLT3 to promote progression of acute myelogenous leukemia (AML).

And this molecular partnership promotes AML cells’ resistance to FLT3 inhibitors.

However, adding a SYK inhibitor to the mix can override this resistance. In an animal model of AML, treatment with a combination of FLT3 and SYK inhibitors was significantly more effective than either inhibitor alone.

These findings, published in Cancer Cell, raise hopes that treatment strategies focusing on both enzymes simultaneously could improve outcomes for patients with FLT3-ITD AML.

“Patients whose AML cells express FLT3-ITD are among the highest-risk group of patients with AML,” said study author Kimberly Stegmaier, MD, of the Dana-Farber Cancer Institute in Boston. “Their AML is particularly difficult to treat.”

In 2009, researchers in Dr Stegmaier’s lab discovered that SYK, a kinase that had attracted attention for its role in other malignancies, could be a potential drug target in AML. Unlike other cancer-associated kinases, SYK rarely undergoes mutations or other genomic alterations in cancer cells, remaining in its wild-type form.

With the current study, Dr Stegmaier and her colleagues set out to better understand SYK’s role in AML. The team screened AML cell lines to reveal the full scope of the enzyme’s molecular interactions. And they found evidence of strong interactions between wild-type SYK and mutated FLT3, particularly FLT3-ITD.

“We wanted to understand the cooperative oncologic effects by which SYK contributes to AML,” Dr Stegmaier said. “The concept of a normal enzyme aiding a mutant one has not yet been widely explored, and so we were both surprised and pleased to see FLT3-ITD come up as a high-priority hit in our screens.”

Through experiments in cell lines, primary patient samples, and animal models, the researchers found that SYK and FLT3-ITD’s interactions are a key ingredient in the progression of myeloproliferative neoplasms into AML. AML cells’ continued growth after turning malignant also relied on these interactions.

In addition, the team found that SYK’s hyperactivated form can promote resistance to the FLT3-targeting drug quizartinib. However, a combination of quizartinib and the SYK inhibitor PRT062607 overcame this resistance, significantly increasing survival and reducing signs of disease in a FLT3-ITD AML mouse model.

Highlighting their findings’ clinical relevance, the researchers found strong SYK activity in cells from FLT3-ITD AML patients. The cells were also highly sensitive to SYK inhibition.

“These data affirm that SYK is an important target in AML,” Dr Stegmaier said. “They also suggest that interactions between oncologic kinases and SYK or other wild-type enzymes may contribute to resistance of kinase inhibitors more broadly.”

Dr Stegmaier added that, over the course of this research, the team has developed a suite of tools that could prove useful for future clinical studies of treatments with SYK inhibitors or SYK inhibitors in combination with FLT3 inhibitors.

“We have not only identified SYK as a candidate treatment target in AML, but we have also identified a specific population of patients with AML more likely to respond to SYK inhibitors: patients with FLT3 mutations,” she said.

“Moreover, we have developed tools for identifying patients with high levels of SYK and FLT3 activation and can monitor these 2 targets while patients are receiving treatment. Predictive biomarkers of response are becoming increasingly important in the development of effective clinical trials of targeted therapies.”

AML cells in the bone marrow

Results of preclinical research suggest the wild-type version of SYK pairs with mutated FLT3 to promote progression of acute myelogenous leukemia (AML).

And this molecular partnership promotes AML cells’ resistance to FLT3 inhibitors.

However, adding a SYK inhibitor to the mix can override this resistance. In an animal model of AML, treatment with a combination of FLT3 and SYK inhibitors was significantly more effective than either inhibitor alone.

These findings, published in Cancer Cell, raise hopes that treatment strategies focusing on both enzymes simultaneously could improve outcomes for patients with FLT3-ITD AML.

“Patients whose AML cells express FLT3-ITD are among the highest-risk group of patients with AML,” said study author Kimberly Stegmaier, MD, of the Dana-Farber Cancer Institute in Boston. “Their AML is particularly difficult to treat.”

In 2009, researchers in Dr Stegmaier’s lab discovered that SYK, a kinase that had attracted attention for its role in other malignancies, could be a potential drug target in AML. Unlike other cancer-associated kinases, SYK rarely undergoes mutations or other genomic alterations in cancer cells, remaining in its wild-type form.

With the current study, Dr Stegmaier and her colleagues set out to better understand SYK’s role in AML. The team screened AML cell lines to reveal the full scope of the enzyme’s molecular interactions. And they found evidence of strong interactions between wild-type SYK and mutated FLT3, particularly FLT3-ITD.

“We wanted to understand the cooperative oncologic effects by which SYK contributes to AML,” Dr Stegmaier said. “The concept of a normal enzyme aiding a mutant one has not yet been widely explored, and so we were both surprised and pleased to see FLT3-ITD come up as a high-priority hit in our screens.”

Through experiments in cell lines, primary patient samples, and animal models, the researchers found that SYK and FLT3-ITD’s interactions are a key ingredient in the progression of myeloproliferative neoplasms into AML. AML cells’ continued growth after turning malignant also relied on these interactions.

In addition, the team found that SYK’s hyperactivated form can promote resistance to the FLT3-targeting drug quizartinib. However, a combination of quizartinib and the SYK inhibitor PRT062607 overcame this resistance, significantly increasing survival and reducing signs of disease in a FLT3-ITD AML mouse model.

Highlighting their findings’ clinical relevance, the researchers found strong SYK activity in cells from FLT3-ITD AML patients. The cells were also highly sensitive to SYK inhibition.

“These data affirm that SYK is an important target in AML,” Dr Stegmaier said. “They also suggest that interactions between oncologic kinases and SYK or other wild-type enzymes may contribute to resistance of kinase inhibitors more broadly.”

Dr Stegmaier added that, over the course of this research, the team has developed a suite of tools that could prove useful for future clinical studies of treatments with SYK inhibitors or SYK inhibitors in combination with FLT3 inhibitors.

“We have not only identified SYK as a candidate treatment target in AML, but we have also identified a specific population of patients with AML more likely to respond to SYK inhibitors: patients with FLT3 mutations,” she said.

“Moreover, we have developed tools for identifying patients with high levels of SYK and FLT3 activation and can monitor these 2 targets while patients are receiving treatment. Predictive biomarkers of response are becoming increasingly important in the development of effective clinical trials of targeted therapies.”

AML cells in the bone marrow

Results of preclinical research suggest the wild-type version of SYK pairs with mutated FLT3 to promote progression of acute myelogenous leukemia (AML).

And this molecular partnership promotes AML cells’ resistance to FLT3 inhibitors.

However, adding a SYK inhibitor to the mix can override this resistance. In an animal model of AML, treatment with a combination of FLT3 and SYK inhibitors was significantly more effective than either inhibitor alone.

These findings, published in Cancer Cell, raise hopes that treatment strategies focusing on both enzymes simultaneously could improve outcomes for patients with FLT3-ITD AML.

“Patients whose AML cells express FLT3-ITD are among the highest-risk group of patients with AML,” said study author Kimberly Stegmaier, MD, of the Dana-Farber Cancer Institute in Boston. “Their AML is particularly difficult to treat.”

In 2009, researchers in Dr Stegmaier’s lab discovered that SYK, a kinase that had attracted attention for its role in other malignancies, could be a potential drug target in AML. Unlike other cancer-associated kinases, SYK rarely undergoes mutations or other genomic alterations in cancer cells, remaining in its wild-type form.

With the current study, Dr Stegmaier and her colleagues set out to better understand SYK’s role in AML. The team screened AML cell lines to reveal the full scope of the enzyme’s molecular interactions. And they found evidence of strong interactions between wild-type SYK and mutated FLT3, particularly FLT3-ITD.

“We wanted to understand the cooperative oncologic effects by which SYK contributes to AML,” Dr Stegmaier said. “The concept of a normal enzyme aiding a mutant one has not yet been widely explored, and so we were both surprised and pleased to see FLT3-ITD come up as a high-priority hit in our screens.”

Through experiments in cell lines, primary patient samples, and animal models, the researchers found that SYK and FLT3-ITD’s interactions are a key ingredient in the progression of myeloproliferative neoplasms into AML. AML cells’ continued growth after turning malignant also relied on these interactions.

In addition, the team found that SYK’s hyperactivated form can promote resistance to the FLT3-targeting drug quizartinib. However, a combination of quizartinib and the SYK inhibitor PRT062607 overcame this resistance, significantly increasing survival and reducing signs of disease in a FLT3-ITD AML mouse model.

Highlighting their findings’ clinical relevance, the researchers found strong SYK activity in cells from FLT3-ITD AML patients. The cells were also highly sensitive to SYK inhibition.

“These data affirm that SYK is an important target in AML,” Dr Stegmaier said. “They also suggest that interactions between oncologic kinases and SYK or other wild-type enzymes may contribute to resistance of kinase inhibitors more broadly.”

Dr Stegmaier added that, over the course of this research, the team has developed a suite of tools that could prove useful for future clinical studies of treatments with SYK inhibitors or SYK inhibitors in combination with FLT3 inhibitors.

“We have not only identified SYK as a candidate treatment target in AML, but we have also identified a specific population of patients with AML more likely to respond to SYK inhibitors: patients with FLT3 mutations,” she said.

“Moreover, we have developed tools for identifying patients with high levels of SYK and FLT3 activation and can monitor these 2 targets while patients are receiving treatment. Predictive biomarkers of response are becoming increasingly important in the development of effective clinical trials of targeted therapies.”

Living near overhead power lines in early life does not increase a child’s risk of developing leukemia, according to a study published in the British Journal of Cancer.

An earlier study using information on childhood leukemia diagnosed between 1962 and 1995 suggested there was an elevated risk for children born within 600 meters of overhead power lines.

But now, updated data indicate that children born after the 1980s don’t have an increased risk.

According to researchers, this strongly suggests there is no direct biological effect of power lines on leukemia risk.

They believe the previous findings could be explained by changes in the characteristics of people living near power lines. The results might also be a chance finding or have resulted from problems with the study design.

“It’s very encouraging to see that, in recent decades, there has been no increased risk of leukemia among children born near overhead power lines,” said lead study author Kathryn Bunch, of the University of Oxford.

“More research is needed to determine precisely why previous evidence suggested a risk prior to 1980, but parents can be reassured from the findings of this study that overhead power lines don’t increase their child’s risk of leukemia.”

Expanding on previous findings

Several years ago, Dr Bunch’s colleagues at the University of Oxford set out to determine if proximity to high-voltage power lines affected the risk of childhood cancers in England and Wales, using data spanning the period from 1962 to 1995.

The team found evidence to suggest a relationship between childhood leukemia risk and the proximity to power lines of the mother’s residence at the time of the child’s birth. This included all 400 kV and 275 kV power lines and a small fraction of 132 kV lines (Draper et al, BMJ 2005).

Dr Bunch and her colleagues decided to extend this study by including more recent data, as well as cases and control subjects from Scotland. The group evaluated 132 kV, 275 kV, and 400 kV power lines and looked at subjects living greater distances from the power lines than those included in the previous study.

The researchers analyzed 53,515 children enrolled in the National Registry of Childhood Tumours from 1962 to 2008 and a group of matched controls.

The team found that, for the entire study period, there was no evidence of an increased risk of leukemia among subjects living closer to power lines. The relative risk of leukemia for children living 0 m to 199 m from power lines, compared with those living 1000 m or more from power lines (for all voltages), was 1.12.

There did appear to be an increased risk of leukemia when the researchers analyzed data according to decade. However, this risk declined over time.

The relative risk of leukemia for children living 0 m to 199 m from power lines, compared with those living 1000 m or more from power lines, was 4.50 in the 1960s, 2.46 in the 1970s, 1.54 in the 1980s, 0.99 in the 1990s, and 0.71 in the 2000s.

The elevated risk in the 1980s was not statistically significant, the researchers noted. They also pointed out that, even in the decades when the risk appears to be present, there is no evidence that it extended beyond the 600 m limit of the original analysis.

The fact that the risk declined over time suggests the leukemia is unlikely to have arisen from any physical effect of the power lines, the researchers said. They believe it’s more likely the result of changing population characteristics.

Living near overhead power lines in early life does not increase a child’s risk of developing leukemia, according to a study published in the British Journal of Cancer.

An earlier study using information on childhood leukemia diagnosed between 1962 and 1995 suggested there was an elevated risk for children born within 600 meters of overhead power lines.

But now, updated data indicate that children born after the 1980s don’t have an increased risk.

According to researchers, this strongly suggests there is no direct biological effect of power lines on leukemia risk.

They believe the previous findings could be explained by changes in the characteristics of people living near power lines. The results might also be a chance finding or have resulted from problems with the study design.

“It’s very encouraging to see that, in recent decades, there has been no increased risk of leukemia among children born near overhead power lines,” said lead study author Kathryn Bunch, of the University of Oxford.

“More research is needed to determine precisely why previous evidence suggested a risk prior to 1980, but parents can be reassured from the findings of this study that overhead power lines don’t increase their child’s risk of leukemia.”

Expanding on previous findings

Several years ago, Dr Bunch’s colleagues at the University of Oxford set out to determine if proximity to high-voltage power lines affected the risk of childhood cancers in England and Wales, using data spanning the period from 1962 to 1995.

The team found evidence to suggest a relationship between childhood leukemia risk and the proximity to power lines of the mother’s residence at the time of the child’s birth. This included all 400 kV and 275 kV power lines and a small fraction of 132 kV lines (Draper et al, BMJ 2005).

Dr Bunch and her colleagues decided to extend this study by including more recent data, as well as cases and control subjects from Scotland. The group evaluated 132 kV, 275 kV, and 400 kV power lines and looked at subjects living greater distances from the power lines than those included in the previous study.

The researchers analyzed 53,515 children enrolled in the National Registry of Childhood Tumours from 1962 to 2008 and a group of matched controls.

The team found that, for the entire study period, there was no evidence of an increased risk of leukemia among subjects living closer to power lines. The relative risk of leukemia for children living 0 m to 199 m from power lines, compared with those living 1000 m or more from power lines (for all voltages), was 1.12.

There did appear to be an increased risk of leukemia when the researchers analyzed data according to decade. However, this risk declined over time.

The relative risk of leukemia for children living 0 m to 199 m from power lines, compared with those living 1000 m or more from power lines, was 4.50 in the 1960s, 2.46 in the 1970s, 1.54 in the 1980s, 0.99 in the 1990s, and 0.71 in the 2000s.

The elevated risk in the 1980s was not statistically significant, the researchers noted. They also pointed out that, even in the decades when the risk appears to be present, there is no evidence that it extended beyond the 600 m limit of the original analysis.

The fact that the risk declined over time suggests the leukemia is unlikely to have arisen from any physical effect of the power lines, the researchers said. They believe it’s more likely the result of changing population characteristics.

Living near overhead power lines in early life does not increase a child’s risk of developing leukemia, according to a study published in the British Journal of Cancer.

An earlier study using information on childhood leukemia diagnosed between 1962 and 1995 suggested there was an elevated risk for children born within 600 meters of overhead power lines.

But now, updated data indicate that children born after the 1980s don’t have an increased risk.

According to researchers, this strongly suggests there is no direct biological effect of power lines on leukemia risk.

They believe the previous findings could be explained by changes in the characteristics of people living near power lines. The results might also be a chance finding or have resulted from problems with the study design.

“It’s very encouraging to see that, in recent decades, there has been no increased risk of leukemia among children born near overhead power lines,” said lead study author Kathryn Bunch, of the University of Oxford.

“More research is needed to determine precisely why previous evidence suggested a risk prior to 1980, but parents can be reassured from the findings of this study that overhead power lines don’t increase their child’s risk of leukemia.”

Expanding on previous findings

Several years ago, Dr Bunch’s colleagues at the University of Oxford set out to determine if proximity to high-voltage power lines affected the risk of childhood cancers in England and Wales, using data spanning the period from 1962 to 1995.

The team found evidence to suggest a relationship between childhood leukemia risk and the proximity to power lines of the mother’s residence at the time of the child’s birth. This included all 400 kV and 275 kV power lines and a small fraction of 132 kV lines (Draper et al, BMJ 2005).

Dr Bunch and her colleagues decided to extend this study by including more recent data, as well as cases and control subjects from Scotland. The group evaluated 132 kV, 275 kV, and 400 kV power lines and looked at subjects living greater distances from the power lines than those included in the previous study.

The researchers analyzed 53,515 children enrolled in the National Registry of Childhood Tumours from 1962 to 2008 and a group of matched controls.

The team found that, for the entire study period, there was no evidence of an increased risk of leukemia among subjects living closer to power lines. The relative risk of leukemia for children living 0 m to 199 m from power lines, compared with those living 1000 m or more from power lines (for all voltages), was 1.12.

There did appear to be an increased risk of leukemia when the researchers analyzed data according to decade. However, this risk declined over time.

The relative risk of leukemia for children living 0 m to 199 m from power lines, compared with those living 1000 m or more from power lines, was 4.50 in the 1960s, 2.46 in the 1970s, 1.54 in the 1980s, 0.99 in the 1990s, and 0.71 in the 2000s.

The elevated risk in the 1980s was not statistically significant, the researchers noted. They also pointed out that, even in the decades when the risk appears to be present, there is no evidence that it extended beyond the 600 m limit of the original analysis.

The fact that the risk declined over time suggests the leukemia is unlikely to have arisen from any physical effect of the power lines, the researchers said. They believe it’s more likely the result of changing population characteristics.

Tumor cells with DNA damage

after treatment with etoposide

Credit: CNIO

A compound that interferes with the cell cycle can increase the antineoplastic effects of etoposide, according to research published in Cell Reports.

Etoposide works by inhibiting topoisomerase II (TOP2), a protein needed for DNA repair during cell division.

Researchers discovered a relationship between TOP2 and Cdh1, a protein that (along with Cdc20) controls cell division by activating the anaphase-promoting complex/cyclosome (APC/C).

So the team hypothesized that combining etoposide with a compound that inhibits Cdh1 might improve etoposide’s antineoplastic effects. Experiments in cancer cell lines confirmed this theory.

Marcos Malumbres, PhD, of the Spanish National Cancer Research Centre (CNIO) in Madrid, and his colleagues began this research by investigating Cdh1 in vitro and in mouse models.

The team found that a decrease in Cdh1 activity increases cells’ TOP2 levels. So they decided to combine etoposide with a Cdh1 inhibitor and evaluate the effect on cancer cells, which divide more than normal cells and therefore have a greater dependency on TOP2 to maintain DNA integrity.

The researchers tested proTAME, a small molecule that targets APC/C-Cdh1 and APC/C-Cdc20, in combination with etoposide. And they found the drugs had a synergistic effect against cancer cells.

In experiments with a lung cancer cell line (A549) and 2 breast cancer cell lines (HeLa and MCF7), administering proTAME and etoposide together proved more effective than administering either compound alone.

The researchers believe these findings could apply to other malignancies as well. Etoposide has demonstrated activity against a number of cancers, including leukemias, lymphomas, and multiple myeloma.

The team said their next step is to study the etoposide-proTAME combination in patients and investigate the malignancies in which this therapeutic strategy would be most effective.

The researchers also noted that previous studies have shown Cdh1 is inactive in some patients due to various oncogenic mutations. So stratifying patients according to their tumor’s Cdh1 status could optimize treatment with etoposide.

Tumor cells with DNA damage

after treatment with etoposide

Credit: CNIO

A compound that interferes with the cell cycle can increase the antineoplastic effects of etoposide, according to research published in Cell Reports.

Etoposide works by inhibiting topoisomerase II (TOP2), a protein needed for DNA repair during cell division.

Researchers discovered a relationship between TOP2 and Cdh1, a protein that (along with Cdc20) controls cell division by activating the anaphase-promoting complex/cyclosome (APC/C).

So the team hypothesized that combining etoposide with a compound that inhibits Cdh1 might improve etoposide’s antineoplastic effects. Experiments in cancer cell lines confirmed this theory.

Marcos Malumbres, PhD, of the Spanish National Cancer Research Centre (CNIO) in Madrid, and his colleagues began this research by investigating Cdh1 in vitro and in mouse models.

The team found that a decrease in Cdh1 activity increases cells’ TOP2 levels. So they decided to combine etoposide with a Cdh1 inhibitor and evaluate the effect on cancer cells, which divide more than normal cells and therefore have a greater dependency on TOP2 to maintain DNA integrity.

The researchers tested proTAME, a small molecule that targets APC/C-Cdh1 and APC/C-Cdc20, in combination with etoposide. And they found the drugs had a synergistic effect against cancer cells.

In experiments with a lung cancer cell line (A549) and 2 breast cancer cell lines (HeLa and MCF7), administering proTAME and etoposide together proved more effective than administering either compound alone.

The researchers believe these findings could apply to other malignancies as well. Etoposide has demonstrated activity against a number of cancers, including leukemias, lymphomas, and multiple myeloma.

The team said their next step is to study the etoposide-proTAME combination in patients and investigate the malignancies in which this therapeutic strategy would be most effective.

The researchers also noted that previous studies have shown Cdh1 is inactive in some patients due to various oncogenic mutations. So stratifying patients according to their tumor’s Cdh1 status could optimize treatment with etoposide.

Tumor cells with DNA damage

after treatment with etoposide

Credit: CNIO

A compound that interferes with the cell cycle can increase the antineoplastic effects of etoposide, according to research published in Cell Reports.

Etoposide works by inhibiting topoisomerase II (TOP2), a protein needed for DNA repair during cell division.

Researchers discovered a relationship between TOP2 and Cdh1, a protein that (along with Cdc20) controls cell division by activating the anaphase-promoting complex/cyclosome (APC/C).

So the team hypothesized that combining etoposide with a compound that inhibits Cdh1 might improve etoposide’s antineoplastic effects. Experiments in cancer cell lines confirmed this theory.

Marcos Malumbres, PhD, of the Spanish National Cancer Research Centre (CNIO) in Madrid, and his colleagues began this research by investigating Cdh1 in vitro and in mouse models.

The team found that a decrease in Cdh1 activity increases cells’ TOP2 levels. So they decided to combine etoposide with a Cdh1 inhibitor and evaluate the effect on cancer cells, which divide more than normal cells and therefore have a greater dependency on TOP2 to maintain DNA integrity.

The researchers tested proTAME, a small molecule that targets APC/C-Cdh1 and APC/C-Cdc20, in combination with etoposide. And they found the drugs had a synergistic effect against cancer cells.

In experiments with a lung cancer cell line (A549) and 2 breast cancer cell lines (HeLa and MCF7), administering proTAME and etoposide together proved more effective than administering either compound alone.

The researchers believe these findings could apply to other malignancies as well. Etoposide has demonstrated activity against a number of cancers, including leukemias, lymphomas, and multiple myeloma.

The team said their next step is to study the etoposide-proTAME combination in patients and investigate the malignancies in which this therapeutic strategy would be most effective.

The researchers also noted that previous studies have shown Cdh1 is inactive in some patients due to various oncogenic mutations. So stratifying patients according to their tumor’s Cdh1 status could optimize treatment with etoposide.

The National Institute

of General Medical Sciences

By analyzing the whole genomes of 3-year-old twin sisters—one healthy and one with multi-lineage leukemia (MLL)—researchers have identified a possible therapeutic target for leukemias.

Their research pointed to a molecular pathway involving the gene SETD2, which can mutate in blood cells as DNA is being transcribed and replicated.

The team confirmed the importance of this pathway via follow-up experiments using samples from leukemia patients and mouse models of the disease.

“We reasoned that monozygotic twins discordant for human leukemia would have identical inherited genetic backgrounds and well-matched tissue-specific events,” said Gang Huang, PhD, of Cincinnati Children’s Hospital Medical Center in Ohio.

“This provided a strong basis for comparison and analysis. We identified a gene mutation involving SETD2 that contributes to the initiation and progression of leukemia by promoting the self-renewal potential of leukemia stem cells.”

Dr Huang and his colleagues recounted this discovery in Nature Genetics.

The team showed that the onset of aggressive and acute leukemia is fueled by a spiraling cascade of multiple genetic mutations and chromosomal translocations.

In comparing data from the twins, the researchers identified a chromosomal translocation in the MLL-NRIP3 fusion gene.

When they activated MLL-NRIP3 in mouse models, the animals developed MLL, but it took a long period of time. This suggests that additional epigenetic and molecular events must be involved to induce full-blown leukemia.

The researchers went on to show that activation of MLL-NRIP3 cooperated with the molecular cascade (including mutations in SETD2) to cause leukemia.

The initial clue came when the team was looking for additional genomic alterations in the leukemic cells of the sick twin. They discovered that activation of MLL-NRIP3 started the molecular cascade that led to bi-allelic mutations in SETD2, a tumor suppressor that regulates the histone modification protein H3K36me3.

During transcriptional elongation, SETD2 and H3K36me3 normally mark the zone for accurate gene transcription along the DNA. In the case of the sick twin, the mutations and molecular cascade disrupted the H3K36me3 mark, leading to abnormal transcription and MLL.

To confirm the importance of these findings, the researchers analyzed blood samples from 241 patients—134 with acute myeloid leukemia and 107 with acute lymphoblastic leukemia. This revealed 19 somatic SETD2 mutations in 15 patients (6.2%).

SETD2 mutations were more common in patients with MLL rearrangements than those without—22.6% (6/27) and 4.6% (8/173), respectively. And patients with SETD2 mutations had decreased levels of global H3K36me3.

In follow-up tests on cell cultures of pre-leukemic cells and mouse models, the researchers saw the same progression of genetic mutations and related molecular events fuel the growth of leukemic cells.

The team also noticed that SETD2 mutation activated 2 genes—mTOR and JAK-STAT—that are known to contribute to leukemia and other cancers. So the researchers decided to test 2 mTOR inhibitors—Torin1 and rapamycin—on pre-leukemic cells generated by SETD2 mutations.

That treatment prompted a marked decrease in cell growth, indicating that SETD2 mutations activate numerous molecular pathways to generate leukemia.

Dr Huang said the tests also suggest there are multiple opportunities to find new molecular targets for developing more effective drugs—in particular, those that would target the MLL fusion-SETD2-H3K36me3 pathway to treat acute and aggressive leukemias.

The researchers are following up their current study by identifying additional pathways activated by mutations of SETD2. They also are looking for possible new molecular targets and therapeutic strategies to block disruptions in the SETD2-H3K36me3 pathway.

The National Institute

of General Medical Sciences

By analyzing the whole genomes of 3-year-old twin sisters—one healthy and one with multi-lineage leukemia (MLL)—researchers have identified a possible therapeutic target for leukemias.

Their research pointed to a molecular pathway involving the gene SETD2, which can mutate in blood cells as DNA is being transcribed and replicated.

The team confirmed the importance of this pathway via follow-up experiments using samples from leukemia patients and mouse models of the disease.

“We reasoned that monozygotic twins discordant for human leukemia would have identical inherited genetic backgrounds and well-matched tissue-specific events,” said Gang Huang, PhD, of Cincinnati Children’s Hospital Medical Center in Ohio.

“This provided a strong basis for comparison and analysis. We identified a gene mutation involving SETD2 that contributes to the initiation and progression of leukemia by promoting the self-renewal potential of leukemia stem cells.”

Dr Huang and his colleagues recounted this discovery in Nature Genetics.

The team showed that the onset of aggressive and acute leukemia is fueled by a spiraling cascade of multiple genetic mutations and chromosomal translocations.

In comparing data from the twins, the researchers identified a chromosomal translocation in the MLL-NRIP3 fusion gene.

When they activated MLL-NRIP3 in mouse models, the animals developed MLL, but it took a long period of time. This suggests that additional epigenetic and molecular events must be involved to induce full-blown leukemia.

The researchers went on to show that activation of MLL-NRIP3 cooperated with the molecular cascade (including mutations in SETD2) to cause leukemia.

The initial clue came when the team was looking for additional genomic alterations in the leukemic cells of the sick twin. They discovered that activation of MLL-NRIP3 started the molecular cascade that led to bi-allelic mutations in SETD2, a tumor suppressor that regulates the histone modification protein H3K36me3.

During transcriptional elongation, SETD2 and H3K36me3 normally mark the zone for accurate gene transcription along the DNA. In the case of the sick twin, the mutations and molecular cascade disrupted the H3K36me3 mark, leading to abnormal transcription and MLL.

To confirm the importance of these findings, the researchers analyzed blood samples from 241 patients—134 with acute myeloid leukemia and 107 with acute lymphoblastic leukemia. This revealed 19 somatic SETD2 mutations in 15 patients (6.2%).

SETD2 mutations were more common in patients with MLL rearrangements than those without—22.6% (6/27) and 4.6% (8/173), respectively. And patients with SETD2 mutations had decreased levels of global H3K36me3.

In follow-up tests on cell cultures of pre-leukemic cells and mouse models, the researchers saw the same progression of genetic mutations and related molecular events fuel the growth of leukemic cells.

The team also noticed that SETD2 mutation activated 2 genes—mTOR and JAK-STAT—that are known to contribute to leukemia and other cancers. So the researchers decided to test 2 mTOR inhibitors—Torin1 and rapamycin—on pre-leukemic cells generated by SETD2 mutations.

That treatment prompted a marked decrease in cell growth, indicating that SETD2 mutations activate numerous molecular pathways to generate leukemia.

Dr Huang said the tests also suggest there are multiple opportunities to find new molecular targets for developing more effective drugs—in particular, those that would target the MLL fusion-SETD2-H3K36me3 pathway to treat acute and aggressive leukemias.

The researchers are following up their current study by identifying additional pathways activated by mutations of SETD2. They also are looking for possible new molecular targets and therapeutic strategies to block disruptions in the SETD2-H3K36me3 pathway.

The National Institute

of General Medical Sciences

By analyzing the whole genomes of 3-year-old twin sisters—one healthy and one with multi-lineage leukemia (MLL)—researchers have identified a possible therapeutic target for leukemias.

Their research pointed to a molecular pathway involving the gene SETD2, which can mutate in blood cells as DNA is being transcribed and replicated.

The team confirmed the importance of this pathway via follow-up experiments using samples from leukemia patients and mouse models of the disease.

“We reasoned that monozygotic twins discordant for human leukemia would have identical inherited genetic backgrounds and well-matched tissue-specific events,” said Gang Huang, PhD, of Cincinnati Children’s Hospital Medical Center in Ohio.

“This provided a strong basis for comparison and analysis. We identified a gene mutation involving SETD2 that contributes to the initiation and progression of leukemia by promoting the self-renewal potential of leukemia stem cells.”

Dr Huang and his colleagues recounted this discovery in Nature Genetics.

The team showed that the onset of aggressive and acute leukemia is fueled by a spiraling cascade of multiple genetic mutations and chromosomal translocations.

In comparing data from the twins, the researchers identified a chromosomal translocation in the MLL-NRIP3 fusion gene.

When they activated MLL-NRIP3 in mouse models, the animals developed MLL, but it took a long period of time. This suggests that additional epigenetic and molecular events must be involved to induce full-blown leukemia.

The researchers went on to show that activation of MLL-NRIP3 cooperated with the molecular cascade (including mutations in SETD2) to cause leukemia.

The initial clue came when the team was looking for additional genomic alterations in the leukemic cells of the sick twin. They discovered that activation of MLL-NRIP3 started the molecular cascade that led to bi-allelic mutations in SETD2, a tumor suppressor that regulates the histone modification protein H3K36me3.

During transcriptional elongation, SETD2 and H3K36me3 normally mark the zone for accurate gene transcription along the DNA. In the case of the sick twin, the mutations and molecular cascade disrupted the H3K36me3 mark, leading to abnormal transcription and MLL.

To confirm the importance of these findings, the researchers analyzed blood samples from 241 patients—134 with acute myeloid leukemia and 107 with acute lymphoblastic leukemia. This revealed 19 somatic SETD2 mutations in 15 patients (6.2%).

SETD2 mutations were more common in patients with MLL rearrangements than those without—22.6% (6/27) and 4.6% (8/173), respectively. And patients with SETD2 mutations had decreased levels of global H3K36me3.

In follow-up tests on cell cultures of pre-leukemic cells and mouse models, the researchers saw the same progression of genetic mutations and related molecular events fuel the growth of leukemic cells.

The team also noticed that SETD2 mutation activated 2 genes—mTOR and JAK-STAT—that are known to contribute to leukemia and other cancers. So the researchers decided to test 2 mTOR inhibitors—Torin1 and rapamycin—on pre-leukemic cells generated by SETD2 mutations.

That treatment prompted a marked decrease in cell growth, indicating that SETD2 mutations activate numerous molecular pathways to generate leukemia.

Dr Huang said the tests also suggest there are multiple opportunities to find new molecular targets for developing more effective drugs—in particular, those that would target the MLL fusion-SETD2-H3K36me3 pathway to treat acute and aggressive leukemias.

The researchers are following up their current study by identifying additional pathways activated by mutations of SETD2. They also are looking for possible new molecular targets and therapeutic strategies to block disruptions in the SETD2-H3K36me3 pathway.

Monoclonal antibodies

Credit: Linda Bartlett

Adding the alkylating agent cyclophosphamide to treatment with a monoclonal antibody (mAb) can overcome drug resistance in mice with acute lymphoblastic leukemia (ALL), researchers have reported in Cell.

mAbs such as rituximab and alemtuzumab are designed to bind to proteins found on the surfaces of tumor cells.

Once the mAbs flag the tumor cells, macrophages destroy them. But the drugs have little effect on tumor cells that hide out in the bone marrow.

Experiments in mice with B-cell ALL revealed that cyclophosphamide stimulates the immune response in bone marrow, eliminating the reservoir of cancer cells that can produce new tumors after treatment with a mAb.

Finding hidden ALL cells

Michael Hemann, PhD, of MIT’s Koch Institute for Integrative Cancer Research in Cambridge, Massachusetts, and his colleagues began this research by administering alemtuzumab to the mice.

The drug successfully cleared most ALL cells, but some remained hidden in the bone marrow, which has been identified as a site of drug resistance in many cancers.

The researchers found that, within the bone marrow, alemtuzumab successfully binds to ALL cells. But macrophages do not attack the cells due to the presence of lipid compounds called prostaglandins, which repress macrophage activity.

Scientists believe the bone marrow naturally produces prostaglandins to help protect the immune cells maturing there. Tumor cells that reach the bone marrow can exploit this protective environment to aid their own survival.

The finding is an important contribution to scientists’ understanding of how mAbs act against ALL, according to Ravi Majeti, MD, PhD, of Stanford University in California, who was not involved in this research.

“There clearly has been a lack of understanding about why antibody therapies have been relatively unsuccessful as monotherapies,” Dr Majeti said.

Tricking the immune system

Dr Hemann and his colleagues then tested a variety of anticancer drugs in combination with alemtuzumab. And they discovered that cyclophosphamide can “rewire” the bone marrow microenvironment to make it much more receptive to macrophages, allowing them to destroy the tumor cells hiding there.

“After you treat with cyclophosphamide, you get this flux of macrophages into the bone marrow, and these macrophages are now active and very capable of consuming the targeted tumor cells,” Dr Hemann said.

“Essentially, we are tricking the immune system to suddenly recognize an entity that it wouldn’t typically recognize and aggressively go after antibody-bound tumor cells.”

Following treatment with this combination, the mice survived and remained free of ALL for the duration of the study, which was about 18 months.

However, the researchers found that timing of drug delivery was critical. Alemtuzumab and cyclophosphamide must be administered together so that cyclophosphamide can create the right type of environment for macrophages to become activated in the bone marrow.

The team also obtained good results by combining cyclophosphamide with rituximab.

They now plan to test cyclophosphamide with other mAbs and begin testing the alemtuzumab-cyclophosphamide combination in patients.

Monoclonal antibodies

Credit: Linda Bartlett

Adding the alkylating agent cyclophosphamide to treatment with a monoclonal antibody (mAb) can overcome drug resistance in mice with acute lymphoblastic leukemia (ALL), researchers have reported in Cell.

mAbs such as rituximab and alemtuzumab are designed to bind to proteins found on the surfaces of tumor cells.

Once the mAbs flag the tumor cells, macrophages destroy them. But the drugs have little effect on tumor cells that hide out in the bone marrow.

Experiments in mice with B-cell ALL revealed that cyclophosphamide stimulates the immune response in bone marrow, eliminating the reservoir of cancer cells that can produce new tumors after treatment with a mAb.

Finding hidden ALL cells

Michael Hemann, PhD, of MIT’s Koch Institute for Integrative Cancer Research in Cambridge, Massachusetts, and his colleagues began this research by administering alemtuzumab to the mice.

The drug successfully cleared most ALL cells, but some remained hidden in the bone marrow, which has been identified as a site of drug resistance in many cancers.

The researchers found that, within the bone marrow, alemtuzumab successfully binds to ALL cells. But macrophages do not attack the cells due to the presence of lipid compounds called prostaglandins, which repress macrophage activity.

Scientists believe the bone marrow naturally produces prostaglandins to help protect the immune cells maturing there. Tumor cells that reach the bone marrow can exploit this protective environment to aid their own survival.

The finding is an important contribution to scientists’ understanding of how mAbs act against ALL, according to Ravi Majeti, MD, PhD, of Stanford University in California, who was not involved in this research.

“There clearly has been a lack of understanding about why antibody therapies have been relatively unsuccessful as monotherapies,” Dr Majeti said.

Tricking the immune system

Dr Hemann and his colleagues then tested a variety of anticancer drugs in combination with alemtuzumab. And they discovered that cyclophosphamide can “rewire” the bone marrow microenvironment to make it much more receptive to macrophages, allowing them to destroy the tumor cells hiding there.

“After you treat with cyclophosphamide, you get this flux of macrophages into the bone marrow, and these macrophages are now active and very capable of consuming the targeted tumor cells,” Dr Hemann said.

“Essentially, we are tricking the immune system to suddenly recognize an entity that it wouldn’t typically recognize and aggressively go after antibody-bound tumor cells.”

Following treatment with this combination, the mice survived and remained free of ALL for the duration of the study, which was about 18 months.

However, the researchers found that timing of drug delivery was critical. Alemtuzumab and cyclophosphamide must be administered together so that cyclophosphamide can create the right type of environment for macrophages to become activated in the bone marrow.

The team also obtained good results by combining cyclophosphamide with rituximab.

They now plan to test cyclophosphamide with other mAbs and begin testing the alemtuzumab-cyclophosphamide combination in patients.

Monoclonal antibodies

Credit: Linda Bartlett

Adding the alkylating agent cyclophosphamide to treatment with a monoclonal antibody (mAb) can overcome drug resistance in mice with acute lymphoblastic leukemia (ALL), researchers have reported in Cell.

mAbs such as rituximab and alemtuzumab are designed to bind to proteins found on the surfaces of tumor cells.

Once the mAbs flag the tumor cells, macrophages destroy them. But the drugs have little effect on tumor cells that hide out in the bone marrow.

Experiments in mice with B-cell ALL revealed that cyclophosphamide stimulates the immune response in bone marrow, eliminating the reservoir of cancer cells that can produce new tumors after treatment with a mAb.

Finding hidden ALL cells

Michael Hemann, PhD, of MIT’s Koch Institute for Integrative Cancer Research in Cambridge, Massachusetts, and his colleagues began this research by administering alemtuzumab to the mice.

The drug successfully cleared most ALL cells, but some remained hidden in the bone marrow, which has been identified as a site of drug resistance in many cancers.

The researchers found that, within the bone marrow, alemtuzumab successfully binds to ALL cells. But macrophages do not attack the cells due to the presence of lipid compounds called prostaglandins, which repress macrophage activity.

Scientists believe the bone marrow naturally produces prostaglandins to help protect the immune cells maturing there. Tumor cells that reach the bone marrow can exploit this protective environment to aid their own survival.

The finding is an important contribution to scientists’ understanding of how mAbs act against ALL, according to Ravi Majeti, MD, PhD, of Stanford University in California, who was not involved in this research.

“There clearly has been a lack of understanding about why antibody therapies have been relatively unsuccessful as monotherapies,” Dr Majeti said.

Tricking the immune system

Dr Hemann and his colleagues then tested a variety of anticancer drugs in combination with alemtuzumab. And they discovered that cyclophosphamide can “rewire” the bone marrow microenvironment to make it much more receptive to macrophages, allowing them to destroy the tumor cells hiding there.

“After you treat with cyclophosphamide, you get this flux of macrophages into the bone marrow, and these macrophages are now active and very capable of consuming the targeted tumor cells,” Dr Hemann said.

“Essentially, we are tricking the immune system to suddenly recognize an entity that it wouldn’t typically recognize and aggressively go after antibody-bound tumor cells.”

Following treatment with this combination, the mice survived and remained free of ALL for the duration of the study, which was about 18 months.

However, the researchers found that timing of drug delivery was critical. Alemtuzumab and cyclophosphamide must be administered together so that cyclophosphamide can create the right type of environment for macrophages to become activated in the bone marrow.

The team also obtained good results by combining cyclophosphamide with rituximab.

They now plan to test cyclophosphamide with other mAbs and begin testing the alemtuzumab-cyclophosphamide combination in patients.

Doctor evaluating a patient

Credit: CDC

Results of population-based research suggest that financial status may affect survival in patients with chronic myeloid leukemia (CML) living in the UK.

The study showed that, despite equal access to the same clinical care and treatment, survival rates were significantly lower for patients living in more deprived areas.

The researchers said this difference might be explained by lower rates of treatment compliance in the less affluent population.

“These findings highlight the importance of conducting comprehensive, population-based studies to examine treatment pathways across the entire patient population, rather than solely concentrating on findings from clinical trials,” said study author Alexandra Smith, PhD, of the University of York in the UK.

She and her colleagues recounted their findings in BMJ Open.

The team analyzed data from 242 patients who were diagnosed with CML from September 2004 to August 2011. Ninety-seven percent of patients had chronic-phase disease at presentation, and 86% were Ph-positive.

Fifty-five percent of patients were younger than 60 at diagnosis, and 60% were male. Fifty-nine percent lived in deprivation quintiles 1 to 3, and 41% lived in the less affluent quintiles 4 and 5.

Ninety-seven percent of patients received treatment with tyrosine kinase inhibitors (TKIs)—94% imatinib and the rest dasatinib. Three percent of patients were not treated with TKIs due to death, relocation, refusal, a more serious competing comorbidity, or the use of supportive care alone.

Factors affecting survival

The minimum follow-up was 1.5 years, and the maximum was 8.5 years. The overall 5-year survival was 79%. And the relative survival, which took into account the background mortality in the general population, was 89%.

The relative survival curves did not differ significantly between the 2 age groups. Five-year relative survival was 90% for patients younger than 60 and 87% for those older than 60.

Gender also had little impact on relative survival. The 5-year rates were 90% for men and 89% for women.

However, relative survival differed significantly according to affluence. The 5-year relative survival was 95% for the most affluent patients (quintiles 1 to 3) and 80% for the least affluent (quintiles 4 and 5).

Although 41% of all patients lived in the less affluent areas, this group accounted for about 60% of the deaths.

The researchers said this finding could not be attributed to biological features of disease or access to therapy. But they believe a lack of treatment compliance could be the cause.

“We suspect a major factor is that we are not supporting patients sufficiently to allow them to be fully compliant with a treatment that needs to be taken every day to be effective,” said Russell Patmore, MD, of Castle Hill Hospital in the UK.

“We would encourage all teams treating patients with CML to use these findings to focus their resource where it is likely to be most beneficial. This includes helping patients to manage their CML by explaining fully the importance of daily treatment and providing easy access to ongoing support.”

Doctor evaluating a patient

Credit: CDC

Results of population-based research suggest that financial status may affect survival in patients with chronic myeloid leukemia (CML) living in the UK.

The study showed that, despite equal access to the same clinical care and treatment, survival rates were significantly lower for patients living in more deprived areas.

The researchers said this difference might be explained by lower rates of treatment compliance in the less affluent population.

“These findings highlight the importance of conducting comprehensive, population-based studies to examine treatment pathways across the entire patient population, rather than solely concentrating on findings from clinical trials,” said study author Alexandra Smith, PhD, of the University of York in the UK.

She and her colleagues recounted their findings in BMJ Open.

The team analyzed data from 242 patients who were diagnosed with CML from September 2004 to August 2011. Ninety-seven percent of patients had chronic-phase disease at presentation, and 86% were Ph-positive.

Fifty-five percent of patients were younger than 60 at diagnosis, and 60% were male. Fifty-nine percent lived in deprivation quintiles 1 to 3, and 41% lived in the less affluent quintiles 4 and 5.

Ninety-seven percent of patients received treatment with tyrosine kinase inhibitors (TKIs)—94% imatinib and the rest dasatinib. Three percent of patients were not treated with TKIs due to death, relocation, refusal, a more serious competing comorbidity, or the use of supportive care alone.

Factors affecting survival

The minimum follow-up was 1.5 years, and the maximum was 8.5 years. The overall 5-year survival was 79%. And the relative survival, which took into account the background mortality in the general population, was 89%.

The relative survival curves did not differ significantly between the 2 age groups. Five-year relative survival was 90% for patients younger than 60 and 87% for those older than 60.

Gender also had little impact on relative survival. The 5-year rates were 90% for men and 89% for women.

However, relative survival differed significantly according to affluence. The 5-year relative survival was 95% for the most affluent patients (quintiles 1 to 3) and 80% for the least affluent (quintiles 4 and 5).

Although 41% of all patients lived in the less affluent areas, this group accounted for about 60% of the deaths.

The researchers said this finding could not be attributed to biological features of disease or access to therapy. But they believe a lack of treatment compliance could be the cause.

“We suspect a major factor is that we are not supporting patients sufficiently to allow them to be fully compliant with a treatment that needs to be taken every day to be effective,” said Russell Patmore, MD, of Castle Hill Hospital in the UK.

“We would encourage all teams treating patients with CML to use these findings to focus their resource where it is likely to be most beneficial. This includes helping patients to manage their CML by explaining fully the importance of daily treatment and providing easy access to ongoing support.”

Doctor evaluating a patient

Credit: CDC

Results of population-based research suggest that financial status may affect survival in patients with chronic myeloid leukemia (CML) living in the UK.

The study showed that, despite equal access to the same clinical care and treatment, survival rates were significantly lower for patients living in more deprived areas.

The researchers said this difference might be explained by lower rates of treatment compliance in the less affluent population.

“These findings highlight the importance of conducting comprehensive, population-based studies to examine treatment pathways across the entire patient population, rather than solely concentrating on findings from clinical trials,” said study author Alexandra Smith, PhD, of the University of York in the UK.

She and her colleagues recounted their findings in BMJ Open.

The team analyzed data from 242 patients who were diagnosed with CML from September 2004 to August 2011. Ninety-seven percent of patients had chronic-phase disease at presentation, and 86% were Ph-positive.

Fifty-five percent of patients were younger than 60 at diagnosis, and 60% were male. Fifty-nine percent lived in deprivation quintiles 1 to 3, and 41% lived in the less affluent quintiles 4 and 5.

Ninety-seven percent of patients received treatment with tyrosine kinase inhibitors (TKIs)—94% imatinib and the rest dasatinib. Three percent of patients were not treated with TKIs due to death, relocation, refusal, a more serious competing comorbidity, or the use of supportive care alone.

Factors affecting survival

The minimum follow-up was 1.5 years, and the maximum was 8.5 years. The overall 5-year survival was 79%. And the relative survival, which took into account the background mortality in the general population, was 89%.

The relative survival curves did not differ significantly between the 2 age groups. Five-year relative survival was 90% for patients younger than 60 and 87% for those older than 60.

Gender also had little impact on relative survival. The 5-year rates were 90% for men and 89% for women.

However, relative survival differed significantly according to affluence. The 5-year relative survival was 95% for the most affluent patients (quintiles 1 to 3) and 80% for the least affluent (quintiles 4 and 5).

Although 41% of all patients lived in the less affluent areas, this group accounted for about 60% of the deaths.

The researchers said this finding could not be attributed to biological features of disease or access to therapy. But they believe a lack of treatment compliance could be the cause.

“We suspect a major factor is that we are not supporting patients sufficiently to allow them to be fully compliant with a treatment that needs to be taken every day to be effective,” said Russell Patmore, MD, of Castle Hill Hospital in the UK.

“We would encourage all teams treating patients with CML to use these findings to focus their resource where it is likely to be most beneficial. This includes helping patients to manage their CML by explaining fully the importance of daily treatment and providing easy access to ongoing support.”

AML cells

Credit: Lance Liotta

Researchers have found evidence to suggest that methylation patterns in hematopoietic stem cells (HSCs) can be used to determine prognosis in patients with acute myeloid leukemia (AML).

The team discovered that patients with methylation patterns resembling those of healthy individuals lived longer than patients with substantially different patterns.

If validated in clinical trials, this finding could be used to help physicians tailor treatment according to a patient’s needs.

Ulrich Steidl, MD, PhD, of the Albert Einstein College of Medicine in New York, and his colleagues described this research in The Journal of Clinical Investigation.

The investigators knew that aberrations in HSC methylation can prevent the cells from differentiating into mature blood cells, which leads to AML.

So they speculated that comparing how closely the methylation patterns in cells from AML patients resemble the patterns found in healthy individuals’ HSCs might foretell the patients’ response to treatment.

To find out, the researchers first looked at methylation patterns in HSCs from healthy individuals. The team found that most cytosines are methylated in healthy HSCs.

And where demethylation occurs, it’s mainly limited to one particular stage of HSC differentiation—the commitment step from short-term HSC to common myeloid progenitor.

The investigators then set out to identify loci with the most significant methylation changes across differentiation stages. Their analysis revealed a set of 561 loci that distinguished between the 4 stages of HSC development they investigated.

The team next wanted to determine whether the methylation status of these loci was affected in AML. So they developed an epigenetic signature score based on loci methylation. A patient’s score increased the more his methylation pattern differed from that of a healthy individual.

The researchers tested their scoring method using data from 3 cohorts of AML patients. In each of these groups, patients with low scores had approximately twice the median survival time of patients with high scores.

Specifically, the investigators evaluated AML patients in a trial testing 2 different doses of daunorubicin (Fernandez et al, NEJM 2009).

Among patients receiving lower-dose daunorubicin, those with lower epigenetic signature scores had a median overall survival (OS) of 19 months, compared with 10.8 months for patients with higher scores (P=0.0165).

The researchers observed similar results in the patients receiving a higher dose of daunorubicin. The median OS in the group with low epigenetic signature scores was 25.4 months, compared with 13.2 months in the group with high scores (P=0.0062).

Likewise, in a third cohort of AML patients, those with a low epigenetic signature score had significantly better OS than those with a high score—a median of 28.1 months and 14.9 months, respectively (P=0.0150).

The investigators performed the same analyses using a commitment-associated gene-expression signature. And they found their epigenetic signature was more effective at predicting patient survival.

Dr Steidl and his colleagues are now studying the genes found in the aberrant epigenetic signatures to determine if they play a role in causing AML.

AML cells

Credit: Lance Liotta

Researchers have found evidence to suggest that methylation patterns in hematopoietic stem cells (HSCs) can be used to determine prognosis in patients with acute myeloid leukemia (AML).

The team discovered that patients with methylation patterns resembling those of healthy individuals lived longer than patients with substantially different patterns.

If validated in clinical trials, this finding could be used to help physicians tailor treatment according to a patient’s needs.

Ulrich Steidl, MD, PhD, of the Albert Einstein College of Medicine in New York, and his colleagues described this research in The Journal of Clinical Investigation.

The investigators knew that aberrations in HSC methylation can prevent the cells from differentiating into mature blood cells, which leads to AML.

So they speculated that comparing how closely the methylation patterns in cells from AML patients resemble the patterns found in healthy individuals’ HSCs might foretell the patients’ response to treatment.

To find out, the researchers first looked at methylation patterns in HSCs from healthy individuals. The team found that most cytosines are methylated in healthy HSCs.

And where demethylation occurs, it’s mainly limited to one particular stage of HSC differentiation—the commitment step from short-term HSC to common myeloid progenitor.

The investigators then set out to identify loci with the most significant methylation changes across differentiation stages. Their analysis revealed a set of 561 loci that distinguished between the 4 stages of HSC development they investigated.

The team next wanted to determine whether the methylation status of these loci was affected in AML. So they developed an epigenetic signature score based on loci methylation. A patient’s score increased the more his methylation pattern differed from that of a healthy individual.

The researchers tested their scoring method using data from 3 cohorts of AML patients. In each of these groups, patients with low scores had approximately twice the median survival time of patients with high scores.

Specifically, the investigators evaluated AML patients in a trial testing 2 different doses of daunorubicin (Fernandez et al, NEJM 2009).

Among patients receiving lower-dose daunorubicin, those with lower epigenetic signature scores had a median overall survival (OS) of 19 months, compared with 10.8 months for patients with higher scores (P=0.0165).

The researchers observed similar results in the patients receiving a higher dose of daunorubicin. The median OS in the group with low epigenetic signature scores was 25.4 months, compared with 13.2 months in the group with high scores (P=0.0062).

Likewise, in a third cohort of AML patients, those with a low epigenetic signature score had significantly better OS than those with a high score—a median of 28.1 months and 14.9 months, respectively (P=0.0150).

The investigators performed the same analyses using a commitment-associated gene-expression signature. And they found their epigenetic signature was more effective at predicting patient survival.

Dr Steidl and his colleagues are now studying the genes found in the aberrant epigenetic signatures to determine if they play a role in causing AML.

AML cells

Credit: Lance Liotta

Researchers have found evidence to suggest that methylation patterns in hematopoietic stem cells (HSCs) can be used to determine prognosis in patients with acute myeloid leukemia (AML).

The team discovered that patients with methylation patterns resembling those of healthy individuals lived longer than patients with substantially different patterns.

If validated in clinical trials, this finding could be used to help physicians tailor treatment according to a patient’s needs.

Ulrich Steidl, MD, PhD, of the Albert Einstein College of Medicine in New York, and his colleagues described this research in The Journal of Clinical Investigation.

The investigators knew that aberrations in HSC methylation can prevent the cells from differentiating into mature blood cells, which leads to AML.

So they speculated that comparing how closely the methylation patterns in cells from AML patients resemble the patterns found in healthy individuals’ HSCs might foretell the patients’ response to treatment.

To find out, the researchers first looked at methylation patterns in HSCs from healthy individuals. The team found that most cytosines are methylated in healthy HSCs.

And where demethylation occurs, it’s mainly limited to one particular stage of HSC differentiation—the commitment step from short-term HSC to common myeloid progenitor.

The investigators then set out to identify loci with the most significant methylation changes across differentiation stages. Their analysis revealed a set of 561 loci that distinguished between the 4 stages of HSC development they investigated.

The team next wanted to determine whether the methylation status of these loci was affected in AML. So they developed an epigenetic signature score based on loci methylation. A patient’s score increased the more his methylation pattern differed from that of a healthy individual.

The researchers tested their scoring method using data from 3 cohorts of AML patients. In each of these groups, patients with low scores had approximately twice the median survival time of patients with high scores.

Specifically, the investigators evaluated AML patients in a trial testing 2 different doses of daunorubicin (Fernandez et al, NEJM 2009).

Among patients receiving lower-dose daunorubicin, those with lower epigenetic signature scores had a median overall survival (OS) of 19 months, compared with 10.8 months for patients with higher scores (P=0.0165).

The researchers observed similar results in the patients receiving a higher dose of daunorubicin. The median OS in the group with low epigenetic signature scores was 25.4 months, compared with 13.2 months in the group with high scores (P=0.0062).

Likewise, in a third cohort of AML patients, those with a low epigenetic signature score had significantly better OS than those with a high score—a median of 28.1 months and 14.9 months, respectively (P=0.0150).

The investigators performed the same analyses using a commitment-associated gene-expression signature. And they found their epigenetic signature was more effective at predicting patient survival.

Dr Steidl and his colleagues are now studying the genes found in the aberrant epigenetic signatures to determine if they play a role in causing AML.

CliniMACS system

Credit: Miltenyi Biotec

The US Food and Drug Administration (FDA) has granted approval for a device system that can prevent graft-vs-host disease (GVHD).

The CliniMACS CD34 Reagent System is intended for use in patients with acute myeloid leukemia who are in first complete remission and undergoing stem cell transplant (SCT) from a matched, related donor.

This in vitro system enriches CD34+ hematopoietic stem cells from a donated apheresis product, while depleting other cells that can cause GVHD.

The system employs a reagent consisting of a CD34 antibody conjugated to an iron-containing nanoparticle. It enriches CD34+ cells by passing the antibody/nanoparticle-labeled cell suspension through a magnetic separation column, which is provided as part of a single-use, disposable tubing set.

Magnetically labeled CD34+ target cells are retained within the separation column, while the unlabeled cells flow through. The CD34+ cells can be recovered by removing the magnetic field and eluting the targeted CD34+ cells into a collection bag.

The FDA’s approval of this system was based on data from a phase 2 study (BMT CTN 0303) conducted by the Blood and Marrow Transplant Clinical Trials Network (Pasquini et al, JCO 2012).

The trial included 128 patients undergoing SCT from a matched, sibling donor. Forty-four patients received grafts that were T-cell depleted (TCD) using the CliniMACS system as the sole form of immune suppression. The other 84 patients received T-cell-replete grafts and pharmacologic immune suppression therapy (IST).

The 2 groups were largely similar, although more patients in the TCD arm received treatment regimens that included radiation—100% vs 50%.

Neutrophil engraftment was similar between the 2 groups. At 28 days, 96% of patients in the IST arm and 100% in the TCD arm had achieved engraftment.

Patients in the TCD arm had a significantly lower rate of chronic GVHD than those in the IST arm. The TCD patients also had a lower rate of acute GVHD, but the difference was not significant.

At 100 days, the rates of grade 2-4, acute GVHD were 39% with IST and 23% with TCD grafts (P=0.07). At 2 years, the rates of chronic GVHD were 19% with TCD grafts and 50% with IST (P<0.001).

There were no significant differences between the 2 groups with regard to graft rejection, leukemia relapse, treatment-related mortality, disease-free survival, or overall survival. However, patients in the TCD arm had a higher rate of GVHD-free survival at 2 years—41% vs 19% (P=0.006).

The CliniMACS CD34 Reagent System is manufactured by Miltenyi Biotec. For more information on the system, see the company’s website.

CliniMACS system

Credit: Miltenyi Biotec

The US Food and Drug Administration (FDA) has granted approval for a device system that can prevent graft-vs-host disease (GVHD).

The CliniMACS CD34 Reagent System is intended for use in patients with acute myeloid leukemia who are in first complete remission and undergoing stem cell transplant (SCT) from a matched, related donor.

This in vitro system enriches CD34+ hematopoietic stem cells from a donated apheresis product, while depleting other cells that can cause GVHD.

The system employs a reagent consisting of a CD34 antibody conjugated to an iron-containing nanoparticle. It enriches CD34+ cells by passing the antibody/nanoparticle-labeled cell suspension through a magnetic separation column, which is provided as part of a single-use, disposable tubing set.

Magnetically labeled CD34+ target cells are retained within the separation column, while the unlabeled cells flow through. The CD34+ cells can be recovered by removing the magnetic field and eluting the targeted CD34+ cells into a collection bag.

The FDA’s approval of this system was based on data from a phase 2 study (BMT CTN 0303) conducted by the Blood and Marrow Transplant Clinical Trials Network (Pasquini et al, JCO 2012).

The trial included 128 patients undergoing SCT from a matched, sibling donor. Forty-four patients received grafts that were T-cell depleted (TCD) using the CliniMACS system as the sole form of immune suppression. The other 84 patients received T-cell-replete grafts and pharmacologic immune suppression therapy (IST).

The 2 groups were largely similar, although more patients in the TCD arm received treatment regimens that included radiation—100% vs 50%.

Neutrophil engraftment was similar between the 2 groups. At 28 days, 96% of patients in the IST arm and 100% in the TCD arm had achieved engraftment.

Patients in the TCD arm had a significantly lower rate of chronic GVHD than those in the IST arm. The TCD patients also had a lower rate of acute GVHD, but the difference was not significant.

At 100 days, the rates of grade 2-4, acute GVHD were 39% with IST and 23% with TCD grafts (P=0.07). At 2 years, the rates of chronic GVHD were 19% with TCD grafts and 50% with IST (P<0.001).

There were no significant differences between the 2 groups with regard to graft rejection, leukemia relapse, treatment-related mortality, disease-free survival, or overall survival. However, patients in the TCD arm had a higher rate of GVHD-free survival at 2 years—41% vs 19% (P=0.006).

The CliniMACS CD34 Reagent System is manufactured by Miltenyi Biotec. For more information on the system, see the company’s website.

CliniMACS system

Credit: Miltenyi Biotec

The US Food and Drug Administration (FDA) has granted approval for a device system that can prevent graft-vs-host disease (GVHD).

The CliniMACS CD34 Reagent System is intended for use in patients with acute myeloid leukemia who are in first complete remission and undergoing stem cell transplant (SCT) from a matched, related donor.

This in vitro system enriches CD34+ hematopoietic stem cells from a donated apheresis product, while depleting other cells that can cause GVHD.

The system employs a reagent consisting of a CD34 antibody conjugated to an iron-containing nanoparticle. It enriches CD34+ cells by passing the antibody/nanoparticle-labeled cell suspension through a magnetic separation column, which is provided as part of a single-use, disposable tubing set.

Magnetically labeled CD34+ target cells are retained within the separation column, while the unlabeled cells flow through. The CD34+ cells can be recovered by removing the magnetic field and eluting the targeted CD34+ cells into a collection bag.

The FDA’s approval of this system was based on data from a phase 2 study (BMT CTN 0303) conducted by the Blood and Marrow Transplant Clinical Trials Network (Pasquini et al, JCO 2012).

The trial included 128 patients undergoing SCT from a matched, sibling donor. Forty-four patients received grafts that were T-cell depleted (TCD) using the CliniMACS system as the sole form of immune suppression. The other 84 patients received T-cell-replete grafts and pharmacologic immune suppression therapy (IST).

The 2 groups were largely similar, although more patients in the TCD arm received treatment regimens that included radiation—100% vs 50%.

Neutrophil engraftment was similar between the 2 groups. At 28 days, 96% of patients in the IST arm and 100% in the TCD arm had achieved engraftment.

Patients in the TCD arm had a significantly lower rate of chronic GVHD than those in the IST arm. The TCD patients also had a lower rate of acute GVHD, but the difference was not significant.

At 100 days, the rates of grade 2-4, acute GVHD were 39% with IST and 23% with TCD grafts (P=0.07). At 2 years, the rates of chronic GVHD were 19% with TCD grafts and 50% with IST (P<0.001).

There were no significant differences between the 2 groups with regard to graft rejection, leukemia relapse, treatment-related mortality, disease-free survival, or overall survival. However, patients in the TCD arm had a higher rate of GVHD-free survival at 2 years—41% vs 19% (P=0.006).

The CliniMACS CD34 Reagent System is manufactured by Miltenyi Biotec. For more information on the system, see the company’s website.

Cell undergoing mitosis

(endoplasmic reticulum in

green, mitochondria in red,

and chromosomes in blue)

Wellcome Images

The dynein-binding protein Lis1 is critical for hematopoietic stem cell (HSC) function and blood formation, according to a paper published in Nature Genetics.

Investigators found that Lis1 regulates asymmetric division of HSCs, ensuring the cells correctly differentiate to provide an adequate supply of new blood cells.

The research also indicated that Lis1 plays a key role in leukemias, as leukemic stem cells rely on the protein to regulate and sustain their growth.

“[Asymmetric division] is very important for the proper generation of all the cells needed for the development and function of many normal tissues,” said study author Tannishtha Reya, PhD, of the University of California, San Diego School of Medicine.

When cells divide, Lis1 controls orientation of the mitotic spindle, an apparatus of subcellular fibers that segregates chromosomes during cell division.

“During division, the spindle is attached to a particular point on the cell membrane, which also determines the axis along which the cell will divide,” Dr Reya said. “Because proteins are not evenly distributed throughout the cell, the axis of division, in turn, determines the types and amounts of proteins that get distributed to each daughter cell.”

When the investigators deleted Lis1 from mouse HSCs, differentiation was radically altered. Asymmetric division increased and accelerated differentiation.

This led to an oversupply of specialized cells and an ever-diminishing reserve of undifferentiated stem cells, which eventually resulted in a bloodless mouse.

“What we found was that a large part of the defect in blood formation was due to a failure of stem cells to expand,” Dr Reya said.

“Instead of undergoing symmetric divisions to generate 2 stem cell daughters, they predominantly underwent asymmetric division to generate more specialized cells. As a result, the mice were unable to generate enough stem cells to sustain blood cell production.”

The investigators next looked at how leukemic stem cells in mice behaved when the Lis1 signaling pathway was blocked. And the team discovered that these cells also lost the ability to renew and propagate.

“In this sense, the effect Lis1 has on leukemic self-renewal parallels its role in normal stem cell self-renewal,” Dr Reya said.

She added that these findings shed new light on the fundamental regulators of cell growth, both in normal development and in cancer.

“Our work shows that elimination of Lis1 potently inhibits cancer growth and identifies Lis1 and other regulators of protein inheritance as a new class of molecules that could be targeted in cancer therapy,” she said.

However, it remains to be seen whether inhibiting Lis1 in cancer cells would produce unacceptable consequences in normal cells as well.

“Agents that target Lis1 might be more specific and less toxic [than chemotherapy],” Dr Reya said, “which would give them significant clinical value.”

Cell undergoing mitosis

(endoplasmic reticulum in

green, mitochondria in red,

and chromosomes in blue)

Wellcome Images

The dynein-binding protein Lis1 is critical for hematopoietic stem cell (HSC) function and blood formation, according to a paper published in Nature Genetics.

Investigators found that Lis1 regulates asymmetric division of HSCs, ensuring the cells correctly differentiate to provide an adequate supply of new blood cells.

The research also indicated that Lis1 plays a key role in leukemias, as leukemic stem cells rely on the protein to regulate and sustain their growth.

“[Asymmetric division] is very important for the proper generation of all the cells needed for the development and function of many normal tissues,” said study author Tannishtha Reya, PhD, of the University of California, San Diego School of Medicine.

When cells divide, Lis1 controls orientation of the mitotic spindle, an apparatus of subcellular fibers that segregates chromosomes during cell division.

“During division, the spindle is attached to a particular point on the cell membrane, which also determines the axis along which the cell will divide,” Dr Reya said. “Because proteins are not evenly distributed throughout the cell, the axis of division, in turn, determines the types and amounts of proteins that get distributed to each daughter cell.”

When the investigators deleted Lis1 from mouse HSCs, differentiation was radically altered. Asymmetric division increased and accelerated differentiation.

This led to an oversupply of specialized cells and an ever-diminishing reserve of undifferentiated stem cells, which eventually resulted in a bloodless mouse.

“What we found was that a large part of the defect in blood formation was due to a failure of stem cells to expand,” Dr Reya said.

“Instead of undergoing symmetric divisions to generate 2 stem cell daughters, they predominantly underwent asymmetric division to generate more specialized cells. As a result, the mice were unable to generate enough stem cells to sustain blood cell production.”

The investigators next looked at how leukemic stem cells in mice behaved when the Lis1 signaling pathway was blocked. And the team discovered that these cells also lost the ability to renew and propagate.

“In this sense, the effect Lis1 has on leukemic self-renewal parallels its role in normal stem cell self-renewal,” Dr Reya said.

She added that these findings shed new light on the fundamental regulators of cell growth, both in normal development and in cancer.

“Our work shows that elimination of Lis1 potently inhibits cancer growth and identifies Lis1 and other regulators of protein inheritance as a new class of molecules that could be targeted in cancer therapy,” she said.

However, it remains to be seen whether inhibiting Lis1 in cancer cells would produce unacceptable consequences in normal cells as well.

“Agents that target Lis1 might be more specific and less toxic [than chemotherapy],” Dr Reya said, “which would give them significant clinical value.”

Cell undergoing mitosis

(endoplasmic reticulum in

green, mitochondria in red,

and chromosomes in blue)

Wellcome Images

The dynein-binding protein Lis1 is critical for hematopoietic stem cell (HSC) function and blood formation, according to a paper published in Nature Genetics.

Investigators found that Lis1 regulates asymmetric division of HSCs, ensuring the cells correctly differentiate to provide an adequate supply of new blood cells.

The research also indicated that Lis1 plays a key role in leukemias, as leukemic stem cells rely on the protein to regulate and sustain their growth.

“[Asymmetric division] is very important for the proper generation of all the cells needed for the development and function of many normal tissues,” said study author Tannishtha Reya, PhD, of the University of California, San Diego School of Medicine.

When cells divide, Lis1 controls orientation of the mitotic spindle, an apparatus of subcellular fibers that segregates chromosomes during cell division.

“During division, the spindle is attached to a particular point on the cell membrane, which also determines the axis along which the cell will divide,” Dr Reya said. “Because proteins are not evenly distributed throughout the cell, the axis of division, in turn, determines the types and amounts of proteins that get distributed to each daughter cell.”

When the investigators deleted Lis1 from mouse HSCs, differentiation was radically altered. Asymmetric division increased and accelerated differentiation.

This led to an oversupply of specialized cells and an ever-diminishing reserve of undifferentiated stem cells, which eventually resulted in a bloodless mouse.

“What we found was that a large part of the defect in blood formation was due to a failure of stem cells to expand,” Dr Reya said.

“Instead of undergoing symmetric divisions to generate 2 stem cell daughters, they predominantly underwent asymmetric division to generate more specialized cells. As a result, the mice were unable to generate enough stem cells to sustain blood cell production.”

The investigators next looked at how leukemic stem cells in mice behaved when the Lis1 signaling pathway was blocked. And the team discovered that these cells also lost the ability to renew and propagate.

“In this sense, the effect Lis1 has on leukemic self-renewal parallels its role in normal stem cell self-renewal,” Dr Reya said.

She added that these findings shed new light on the fundamental regulators of cell growth, both in normal development and in cancer.

“Our work shows that elimination of Lis1 potently inhibits cancer growth and identifies Lis1 and other regulators of protein inheritance as a new class of molecules that could be targeted in cancer therapy,” she said.

However, it remains to be seen whether inhibiting Lis1 in cancer cells would produce unacceptable consequences in normal cells as well.

“Agents that target Lis1 might be more specific and less toxic [than chemotherapy],” Dr Reya said, “which would give them significant clinical value.”

AML in the bone marrow

Studies have suggested that mutations in isocitrate dehydrogenase-1 and 2 (IDH1 and IDH2) are present in approximately 20% of all acute myeloid leukemias (AMLs), and this implies that mutant IDH proteins are attractive drug targets.

With this in mind, a group of scientists generated a transgenic mouse model of the most common IDH2 mutation in human AML.

Experiments conducted with this model revealed that mutant IDH2 contributes to leukemia initiation and is required for the maintenance of leukemic cells in a living organism.

The researchers said these findings, published in Cell Stem Cell, confirm a potent oncogenic role for IDH2 and support its relevance as a therapeutic target for AML.

Furthermore, the model can be used to evaluate the pharmacological efficacy of IDH2 inhibitors, either alone or in combination with other compounds.

“The real hope is that we would one day be able to treat IDH2-mutant leukemia patients with a drug that targets this genetic abnormality,” said senior study author Pier Paolo Pandolfi, MD, PhD, of Beth Israel Deaconess Medical Center (BIDMC) in Boston.

He and his colleagues knew that IDH1 and IDH2 proteins are critical enzymes in the TCA cycle, which is centrally important to many biochemical pathways. Mutated forms of these proteins gain a novel ability to produce 2-hydroxyglutarate (2HG), a metabolite that has been shown to accumulate at high levels in cancer patients.

“Our goal was to generate an animal model of mutant IDH that was both inducible and reversible,” said Markus Reschke, PhD, also of BIDMC.

“This enabled us to address an important unanswered question: Does inhibition of mutant IDH proteins in active disease have an effect on tumor maintenance or progression in a living organism?”

The researchers studied 2 different models: a retroviral transduction model and a genetically engineered model in which IDH mice were crossed with mice harboring other leukemia-relevant mutations.

In the first model, the IDH mutation was combined with the oncogenes HoxA9 and Meis1a, 2 downstream targets of numerous pathways that are deregulated in AML.

The results showed evidence of differentiation within 2 weeks of genetic deinduction of mutant IDH. And 2 weeks later, 6 of 8 animals showed complete remission with elimination of any detectable leukemic cells.

The researchers said these results were both surprising and encouraging, demonstrating a situation in which IDH mutation occurs as an early event, and leukemic transformation occurs as a result of subsequent genetic hits.

“The retroviral model enabled us to observe that mutant IDH2 is essential for the maintenance of HoxA9/Meis1a-induced AML,” said Lev Kats, PhD, of BIDMC. “But this was still a surrogate model. This isn’t what happens in human patients, per se.”

The researchers therefore went on to develop a transgenic model that more closely recapitulates the genetics of human AML.

“By crossing the mutant IDH2 animals with other leukemia-relevant mutations, including mutations in the FMS-like tyrosine kinase 3 [FLT3], we observed that compound-mutant animals developed acute leukemias,” Dr Reschke said. “This exciting finding told us that mutant IDH2 contributes to leukemia initiation in vivo.”

As with the retroviral transduction model, genetic deinduction of mutant IDH2 in the context of a cooperating FLT3 mutation resulted in reduced proliferation and/or differentiation of leukemic cells, further demonstrating that mutant IDH2 expression is required for leukemia maintenance.

“This model has validated mutant IDH proteins as very strong candidates for continued development of targeted anticancer therapeutics,” Dr Pandolfi said. “The model will also be of paramount importance to study mechanisms of resistance to treatment that may occur.”

AML in the bone marrow

Studies have suggested that mutations in isocitrate dehydrogenase-1 and 2 (IDH1 and IDH2) are present in approximately 20% of all acute myeloid leukemias (AMLs), and this implies that mutant IDH proteins are attractive drug targets.

With this in mind, a group of scientists generated a transgenic mouse model of the most common IDH2 mutation in human AML.

Experiments conducted with this model revealed that mutant IDH2 contributes to leukemia initiation and is required for the maintenance of leukemic cells in a living organism.

The researchers said these findings, published in Cell Stem Cell, confirm a potent oncogenic role for IDH2 and support its relevance as a therapeutic target for AML.

Furthermore, the model can be used to evaluate the pharmacological efficacy of IDH2 inhibitors, either alone or in combination with other compounds.

“The real hope is that we would one day be able to treat IDH2-mutant leukemia patients with a drug that targets this genetic abnormality,” said senior study author Pier Paolo Pandolfi, MD, PhD, of Beth Israel Deaconess Medical Center (BIDMC) in Boston.

He and his colleagues knew that IDH1 and IDH2 proteins are critical enzymes in the TCA cycle, which is centrally important to many biochemical pathways. Mutated forms of these proteins gain a novel ability to produce 2-hydroxyglutarate (2HG), a metabolite that has been shown to accumulate at high levels in cancer patients.

“Our goal was to generate an animal model of mutant IDH that was both inducible and reversible,” said Markus Reschke, PhD, also of BIDMC.

“This enabled us to address an important unanswered question: Does inhibition of mutant IDH proteins in active disease have an effect on tumor maintenance or progression in a living organism?”

The researchers studied 2 different models: a retroviral transduction model and a genetically engineered model in which IDH mice were crossed with mice harboring other leukemia-relevant mutations.

In the first model, the IDH mutation was combined with the oncogenes HoxA9 and Meis1a, 2 downstream targets of numerous pathways that are deregulated in AML.

The results showed evidence of differentiation within 2 weeks of genetic deinduction of mutant IDH. And 2 weeks later, 6 of 8 animals showed complete remission with elimination of any detectable leukemic cells.

The researchers said these results were both surprising and encouraging, demonstrating a situation in which IDH mutation occurs as an early event, and leukemic transformation occurs as a result of subsequent genetic hits.

“The retroviral model enabled us to observe that mutant IDH2 is essential for the maintenance of HoxA9/Meis1a-induced AML,” said Lev Kats, PhD, of BIDMC. “But this was still a surrogate model. This isn’t what happens in human patients, per se.”

The researchers therefore went on to develop a transgenic model that more closely recapitulates the genetics of human AML.

“By crossing the mutant IDH2 animals with other leukemia-relevant mutations, including mutations in the FMS-like tyrosine kinase 3 [FLT3], we observed that compound-mutant animals developed acute leukemias,” Dr Reschke said. “This exciting finding told us that mutant IDH2 contributes to leukemia initiation in vivo.”

As with the retroviral transduction model, genetic deinduction of mutant IDH2 in the context of a cooperating FLT3 mutation resulted in reduced proliferation and/or differentiation of leukemic cells, further demonstrating that mutant IDH2 expression is required for leukemia maintenance.

“This model has validated mutant IDH proteins as very strong candidates for continued development of targeted anticancer therapeutics,” Dr Pandolfi said. “The model will also be of paramount importance to study mechanisms of resistance to treatment that may occur.”

AML in the bone marrow

Studies have suggested that mutations in isocitrate dehydrogenase-1 and 2 (IDH1 and IDH2) are present in approximately 20% of all acute myeloid leukemias (AMLs), and this implies that mutant IDH proteins are attractive drug targets.

With this in mind, a group of scientists generated a transgenic mouse model of the most common IDH2 mutation in human AML.

Experiments conducted with this model revealed that mutant IDH2 contributes to leukemia initiation and is required for the maintenance of leukemic cells in a living organism.

The researchers said these findings, published in Cell Stem Cell, confirm a potent oncogenic role for IDH2 and support its relevance as a therapeutic target for AML.

Furthermore, the model can be used to evaluate the pharmacological efficacy of IDH2 inhibitors, either alone or in combination with other compounds.

“The real hope is that we would one day be able to treat IDH2-mutant leukemia patients with a drug that targets this genetic abnormality,” said senior study author Pier Paolo Pandolfi, MD, PhD, of Beth Israel Deaconess Medical Center (BIDMC) in Boston.

He and his colleagues knew that IDH1 and IDH2 proteins are critical enzymes in the TCA cycle, which is centrally important to many biochemical pathways. Mutated forms of these proteins gain a novel ability to produce 2-hydroxyglutarate (2HG), a metabolite that has been shown to accumulate at high levels in cancer patients.

“Our goal was to generate an animal model of mutant IDH that was both inducible and reversible,” said Markus Reschke, PhD, also of BIDMC.

“This enabled us to address an important unanswered question: Does inhibition of mutant IDH proteins in active disease have an effect on tumor maintenance or progression in a living organism?”

The researchers studied 2 different models: a retroviral transduction model and a genetically engineered model in which IDH mice were crossed with mice harboring other leukemia-relevant mutations.

In the first model, the IDH mutation was combined with the oncogenes HoxA9 and Meis1a, 2 downstream targets of numerous pathways that are deregulated in AML.

The results showed evidence of differentiation within 2 weeks of genetic deinduction of mutant IDH. And 2 weeks later, 6 of 8 animals showed complete remission with elimination of any detectable leukemic cells.

The researchers said these results were both surprising and encouraging, demonstrating a situation in which IDH mutation occurs as an early event, and leukemic transformation occurs as a result of subsequent genetic hits.

“The retroviral model enabled us to observe that mutant IDH2 is essential for the maintenance of HoxA9/Meis1a-induced AML,” said Lev Kats, PhD, of BIDMC. “But this was still a surrogate model. This isn’t what happens in human patients, per se.”

The researchers therefore went on to develop a transgenic model that more closely recapitulates the genetics of human AML.

“By crossing the mutant IDH2 animals with other leukemia-relevant mutations, including mutations in the FMS-like tyrosine kinase 3 [FLT3], we observed that compound-mutant animals developed acute leukemias,” Dr Reschke said. “This exciting finding told us that mutant IDH2 contributes to leukemia initiation in vivo.”

As with the retroviral transduction model, genetic deinduction of mutant IDH2 in the context of a cooperating FLT3 mutation resulted in reduced proliferation and/or differentiation of leukemic cells, further demonstrating that mutant IDH2 expression is required for leukemia maintenance.

“This model has validated mutant IDH proteins as very strong candidates for continued development of targeted anticancer therapeutics,” Dr Pandolfi said. “The model will also be of paramount importance to study mechanisms of resistance to treatment that may occur.”