AACR Annual Meeting 2014

SAN DIEGO—Preclinical research has revealed a mechanism of rituximab resistance in chronic lymphocytic leukemia (CLL), as well as a possible new treatment approach.

The study suggests the TNF-family member BAFF contributes to CLL cells’ resistance to direct and rituximab-induced natural killer (NK) cell reactivity.

However, the BAFF-specific antibody belimumab can overcome this resistance and restore CLL cells’ sensitivity to chemotherapy.

Julia Wild, a PhD student at Eberhard Karls University in Tuebingen, Germany, and her colleagues presented these findings at the AACR Annual Meeting 2014 as abstract 148.

“It is widely known that NK cells’ ability to react against lymphoblastic leukemia is impaired, as compared to myeloid leukemia,” Wild said. “And we now think we’ve identified a factor involved in this—a member of the tumor necrosis factor family called BAFF.”

Previous research showed that NK cells’ ability to target malignant cells and mediate antibody-dependent cellular cytotoxicity (ADCC) is compromised in CLL, but the underlying mechanisms were not clear. Wild and her colleagues therefore speculated that BAFF, which regulates B-cell proliferation and survival, plays a role.

The researchers’ initial experiments revealed that NK cells express BAFF at the mRNA level and release the protein in a soluble form, with levels depending on the state of activation.

The team then assessed BAFF expression in primary CLL cells. They collected cells from 17 CLL patients and analyzed surface expression of the 3 BAFF receptors. All 17 samples were positive for BAFF-R and TACI, and about 53% (9/17) were positive for BCMA.

Additional experiments revealed that BAFF enhances the metabolic activity of primary CLL cells. To uncover this result, the researchers incubated the cells with increasing concentrations of BAFF. And they compared untreated cells to cells treated with belimumab, isotype control, BAFF, BAFF plus belimumab, and BAFF plus isotype control.

The team then compared untreated CLL cells to cells treated with fludarabine and cyclophosphamide (Flu/Cy); Flu/Cy plus BAFF; and Flu/Cy, BAFF, and belimumab.

They found that BAFF protects CLL cells from chemotherapy-induced death. However, belimumab inhibits the protective effects of BAFF and restores CLL cells’ sensitivity to chemotherapy.

The researchers then performed cytotoxicity assays in primary CLL cells, comparing untreated cells to cells exposed to BAFF alone; rituximab alone; BAFF and rituximab; BAFF and belimumab; and rituximab, BAFF, and belimumab.

They found that lysis was highest among cells treated with rituximab alone or rituximab, BAFF, and belimumab, with comparable results in these 2 groups.

The team also evaluated CLL cell lysis due to ADCC induction. They analyzed peripheral blood mononuclear cells from CLL patients, comparing untreated cells to cells exposed to rituximab alone; rituximab and BAFF; rituximab, belimumab, and BAFF; and rituximab, bevacizumab, and BAFF.

Results showed that CLL cell survival was lowest (and comparable) in cells treated with rituximab alone or rituximab, belimumab, and BAFF.

“When CLL cells are cultured in the presence of BAFF, cytotoxicity is decreased as compared to untreated cells, and this is not only for direct NK-cell activity, but also for ADCC-mediated activity,” Wild summarized.

“But we can block this effect with belimumab, which suggests we could use this antibody for CLL treatment.”

SAN DIEGO—Preclinical research has revealed a mechanism of rituximab resistance in chronic lymphocytic leukemia (CLL), as well as a possible new treatment approach.

The study suggests the TNF-family member BAFF contributes to CLL cells’ resistance to direct and rituximab-induced natural killer (NK) cell reactivity.

However, the BAFF-specific antibody belimumab can overcome this resistance and restore CLL cells’ sensitivity to chemotherapy.

Julia Wild, a PhD student at Eberhard Karls University in Tuebingen, Germany, and her colleagues presented these findings at the AACR Annual Meeting 2014 as abstract 148.

“It is widely known that NK cells’ ability to react against lymphoblastic leukemia is impaired, as compared to myeloid leukemia,” Wild said. “And we now think we’ve identified a factor involved in this—a member of the tumor necrosis factor family called BAFF.”

Previous research showed that NK cells’ ability to target malignant cells and mediate antibody-dependent cellular cytotoxicity (ADCC) is compromised in CLL, but the underlying mechanisms were not clear. Wild and her colleagues therefore speculated that BAFF, which regulates B-cell proliferation and survival, plays a role.

The researchers’ initial experiments revealed that NK cells express BAFF at the mRNA level and release the protein in a soluble form, with levels depending on the state of activation.

The team then assessed BAFF expression in primary CLL cells. They collected cells from 17 CLL patients and analyzed surface expression of the 3 BAFF receptors. All 17 samples were positive for BAFF-R and TACI, and about 53% (9/17) were positive for BCMA.

Additional experiments revealed that BAFF enhances the metabolic activity of primary CLL cells. To uncover this result, the researchers incubated the cells with increasing concentrations of BAFF. And they compared untreated cells to cells treated with belimumab, isotype control, BAFF, BAFF plus belimumab, and BAFF plus isotype control.

The team then compared untreated CLL cells to cells treated with fludarabine and cyclophosphamide (Flu/Cy); Flu/Cy plus BAFF; and Flu/Cy, BAFF, and belimumab.

They found that BAFF protects CLL cells from chemotherapy-induced death. However, belimumab inhibits the protective effects of BAFF and restores CLL cells’ sensitivity to chemotherapy.

The researchers then performed cytotoxicity assays in primary CLL cells, comparing untreated cells to cells exposed to BAFF alone; rituximab alone; BAFF and rituximab; BAFF and belimumab; and rituximab, BAFF, and belimumab.

They found that lysis was highest among cells treated with rituximab alone or rituximab, BAFF, and belimumab, with comparable results in these 2 groups.

The team also evaluated CLL cell lysis due to ADCC induction. They analyzed peripheral blood mononuclear cells from CLL patients, comparing untreated cells to cells exposed to rituximab alone; rituximab and BAFF; rituximab, belimumab, and BAFF; and rituximab, bevacizumab, and BAFF.

Results showed that CLL cell survival was lowest (and comparable) in cells treated with rituximab alone or rituximab, belimumab, and BAFF.

“When CLL cells are cultured in the presence of BAFF, cytotoxicity is decreased as compared to untreated cells, and this is not only for direct NK-cell activity, but also for ADCC-mediated activity,” Wild summarized.

“But we can block this effect with belimumab, which suggests we could use this antibody for CLL treatment.”

SAN DIEGO—Preclinical research has revealed a mechanism of rituximab resistance in chronic lymphocytic leukemia (CLL), as well as a possible new treatment approach.

The study suggests the TNF-family member BAFF contributes to CLL cells’ resistance to direct and rituximab-induced natural killer (NK) cell reactivity.

However, the BAFF-specific antibody belimumab can overcome this resistance and restore CLL cells’ sensitivity to chemotherapy.

Julia Wild, a PhD student at Eberhard Karls University in Tuebingen, Germany, and her colleagues presented these findings at the AACR Annual Meeting 2014 as abstract 148.

“It is widely known that NK cells’ ability to react against lymphoblastic leukemia is impaired, as compared to myeloid leukemia,” Wild said. “And we now think we’ve identified a factor involved in this—a member of the tumor necrosis factor family called BAFF.”

Previous research showed that NK cells’ ability to target malignant cells and mediate antibody-dependent cellular cytotoxicity (ADCC) is compromised in CLL, but the underlying mechanisms were not clear. Wild and her colleagues therefore speculated that BAFF, which regulates B-cell proliferation and survival, plays a role.

The researchers’ initial experiments revealed that NK cells express BAFF at the mRNA level and release the protein in a soluble form, with levels depending on the state of activation.

The team then assessed BAFF expression in primary CLL cells. They collected cells from 17 CLL patients and analyzed surface expression of the 3 BAFF receptors. All 17 samples were positive for BAFF-R and TACI, and about 53% (9/17) were positive for BCMA.

Additional experiments revealed that BAFF enhances the metabolic activity of primary CLL cells. To uncover this result, the researchers incubated the cells with increasing concentrations of BAFF. And they compared untreated cells to cells treated with belimumab, isotype control, BAFF, BAFF plus belimumab, and BAFF plus isotype control.

The team then compared untreated CLL cells to cells treated with fludarabine and cyclophosphamide (Flu/Cy); Flu/Cy plus BAFF; and Flu/Cy, BAFF, and belimumab.

They found that BAFF protects CLL cells from chemotherapy-induced death. However, belimumab inhibits the protective effects of BAFF and restores CLL cells’ sensitivity to chemotherapy.

The researchers then performed cytotoxicity assays in primary CLL cells, comparing untreated cells to cells exposed to BAFF alone; rituximab alone; BAFF and rituximab; BAFF and belimumab; and rituximab, BAFF, and belimumab.

They found that lysis was highest among cells treated with rituximab alone or rituximab, BAFF, and belimumab, with comparable results in these 2 groups.

The team also evaluated CLL cell lysis due to ADCC induction. They analyzed peripheral blood mononuclear cells from CLL patients, comparing untreated cells to cells exposed to rituximab alone; rituximab and BAFF; rituximab, belimumab, and BAFF; and rituximab, bevacizumab, and BAFF.

Results showed that CLL cell survival was lowest (and comparable) in cells treated with rituximab alone or rituximab, belimumab, and BAFF.

“When CLL cells are cultured in the presence of BAFF, cytotoxicity is decreased as compared to untreated cells, and this is not only for direct NK-cell activity, but also for ADCC-mediated activity,” Wild summarized.

“But we can block this effect with belimumab, which suggests we could use this antibody for CLL treatment.”

SAN DIEGO—A dual kinase inhibitor shows potential for treating the heterogeneous acute myeloid leukemia (AML) population, researchers say.

The inhibitor, SEL24-B489, targets both PIM and FLT3 mutants. In experiments, it exhibited more consistent activity across AML cell lines than inhibitors directed only at PIM or FLT3.

SEL24-B489 also demonstrated synergistic activity with cytarabine, both in AML cell lines and mouse models of the disease.

The researchers believe these results suggest SEL24-B489 could potentially treat a range of AML patients and might prove effective regardless of FLT3 status.

“When you have a very heterogeneous population of AML patients, some of them have different FLT mutations, and the problem with FLT inhibitors has been the resistance that occurs in the tyrosine kinase domain,” said Krzysztof D. Brzózka, PhD, of Selvita, the Kraków, Poland-based company developing SEL24-B489.

“We believe that since FLT is upstream, and PIM kinases are downstream of the FLT signaling, we will have higher chances

of overcoming resistance because we are targeting the same pathway at 2 independent nodes.”

Dr Brzózka and his colleagues presented research to support this theory at the AACR Annual Meeting 2014 as abstract 1749.*

The researchers evaluated SEL24-B489 in a range of AML cell lines: MV4-11, MOLM-13, MOLM-16, KG-1, CMK, and HL-60. The drug showed “strong cytotoxicity” across the cell lines, independent of FLT3 status.

The team also compared SEL24-B489 to the PIM inhibitor AZD1208 and the FLT3 inhibitor AC220 in MV4-11 cell lines and MOLM-16 cell lines.

In MV4-11 cells, the IC₅₀ was 0.003 μM for AC220, 0.15 μM for SEL24-B489, and 2.24 μM for AZD1208. In MOLM-16 cells, the IC₅₀ was 0.07 μM for AZD1208, 0.1 μM for SEL24-B489, and >10 μM for AC220.

The researchers then evaluated SEL24-B489 in combination with cytarabine.

“The molecule shows very strong synergistic effects with cytarabine, both in vitro and in vivo,” Dr Brzózka said. “The combination index in vitro is approximately 0.1, 0.2. And in vivo, that translates to [nearly] 100% tumor growth inhibition.”

Tumor growth inhibition (TGI) measured 60% when mice received cytarabine alone at 50 mg/kg. TGI was 77% with SEL24-B489 alone at 25 mg/kg and 82% with SEL24-B489 alone at 50 mg/kg.

But with 25 mg/kg of SEL24-B489 and 50 mg/kg of cytarabine, TGI was 89%. And when both drugs were given at 50 mg/kg, TGI was 99%.

The researchers also assessed SEL24-B489 alone in mouse models of AML. In mice injected with MV4-11 cells, SEL24-B489 at 25 mg/kg BID reduced tumor volume by more than 50%, when compared to untreated control mice. And SEL24-B489 at 75 mg/kg BID reduced tumor volume by more than 80%.

In mice injected with MOLM-16 cells, SEL24-B489 at 25 mg/kg BID reduced tumor volume by more than 80%, when compared to untreated control mice. And SEL24-B489 at 75 mg/kg BID reduced tumor volume by more than 100%.

Finally, the team evaluated the safety of SEL24-B489 via repeated 5-day and 10-day toxicology studies in rats.

And they concluded that doses of 100 mg/kg QD x 5 and 25 mg/kg BID x 10 were safe, based on data concerning body weight gain, as well as results of clinical chemistry, hematology, necropsy, and histological analyses.

“Overall, SEL24-B489 has very good oral bioavailability and initial safety profiling,” Dr Brzózka said. “Both in vitro and in vivo, it shows a pretty promising therapeutic index.”

He and his colleagues are now studying SEL24-B489 in dogs, and Selvita is looking for a partner company to help move the drug to phase 1 trials.

*Information in the abstract differs from that presented at the meeting.

SAN DIEGO—A dual kinase inhibitor shows potential for treating the heterogeneous acute myeloid leukemia (AML) population, researchers say.

The inhibitor, SEL24-B489, targets both PIM and FLT3 mutants. In experiments, it exhibited more consistent activity across AML cell lines than inhibitors directed only at PIM or FLT3.

SEL24-B489 also demonstrated synergistic activity with cytarabine, both in AML cell lines and mouse models of the disease.

The researchers believe these results suggest SEL24-B489 could potentially treat a range of AML patients and might prove effective regardless of FLT3 status.

“When you have a very heterogeneous population of AML patients, some of them have different FLT mutations, and the problem with FLT inhibitors has been the resistance that occurs in the tyrosine kinase domain,” said Krzysztof D. Brzózka, PhD, of Selvita, the Kraków, Poland-based company developing SEL24-B489.

“We believe that since FLT is upstream, and PIM kinases are downstream of the FLT signaling, we will have higher chances

of overcoming resistance because we are targeting the same pathway at 2 independent nodes.”

Dr Brzózka and his colleagues presented research to support this theory at the AACR Annual Meeting 2014 as abstract 1749.*

The researchers evaluated SEL24-B489 in a range of AML cell lines: MV4-11, MOLM-13, MOLM-16, KG-1, CMK, and HL-60. The drug showed “strong cytotoxicity” across the cell lines, independent of FLT3 status.

The team also compared SEL24-B489 to the PIM inhibitor AZD1208 and the FLT3 inhibitor AC220 in MV4-11 cell lines and MOLM-16 cell lines.

In MV4-11 cells, the IC₅₀ was 0.003 μM for AC220, 0.15 μM for SEL24-B489, and 2.24 μM for AZD1208. In MOLM-16 cells, the IC₅₀ was 0.07 μM for AZD1208, 0.1 μM for SEL24-B489, and >10 μM for AC220.

The researchers then evaluated SEL24-B489 in combination with cytarabine.

“The molecule shows very strong synergistic effects with cytarabine, both in vitro and in vivo,” Dr Brzózka said. “The combination index in vitro is approximately 0.1, 0.2. And in vivo, that translates to [nearly] 100% tumor growth inhibition.”

Tumor growth inhibition (TGI) measured 60% when mice received cytarabine alone at 50 mg/kg. TGI was 77% with SEL24-B489 alone at 25 mg/kg and 82% with SEL24-B489 alone at 50 mg/kg.

But with 25 mg/kg of SEL24-B489 and 50 mg/kg of cytarabine, TGI was 89%. And when both drugs were given at 50 mg/kg, TGI was 99%.

The researchers also assessed SEL24-B489 alone in mouse models of AML. In mice injected with MV4-11 cells, SEL24-B489 at 25 mg/kg BID reduced tumor volume by more than 50%, when compared to untreated control mice. And SEL24-B489 at 75 mg/kg BID reduced tumor volume by more than 80%.

In mice injected with MOLM-16 cells, SEL24-B489 at 25 mg/kg BID reduced tumor volume by more than 80%, when compared to untreated control mice. And SEL24-B489 at 75 mg/kg BID reduced tumor volume by more than 100%.

Finally, the team evaluated the safety of SEL24-B489 via repeated 5-day and 10-day toxicology studies in rats.

And they concluded that doses of 100 mg/kg QD x 5 and 25 mg/kg BID x 10 were safe, based on data concerning body weight gain, as well as results of clinical chemistry, hematology, necropsy, and histological analyses.

“Overall, SEL24-B489 has very good oral bioavailability and initial safety profiling,” Dr Brzózka said. “Both in vitro and in vivo, it shows a pretty promising therapeutic index.”

He and his colleagues are now studying SEL24-B489 in dogs, and Selvita is looking for a partner company to help move the drug to phase 1 trials.

*Information in the abstract differs from that presented at the meeting.

SAN DIEGO—A dual kinase inhibitor shows potential for treating the heterogeneous acute myeloid leukemia (AML) population, researchers say.

The inhibitor, SEL24-B489, targets both PIM and FLT3 mutants. In experiments, it exhibited more consistent activity across AML cell lines than inhibitors directed only at PIM or FLT3.

SEL24-B489 also demonstrated synergistic activity with cytarabine, both in AML cell lines and mouse models of the disease.

The researchers believe these results suggest SEL24-B489 could potentially treat a range of AML patients and might prove effective regardless of FLT3 status.

“When you have a very heterogeneous population of AML patients, some of them have different FLT mutations, and the problem with FLT inhibitors has been the resistance that occurs in the tyrosine kinase domain,” said Krzysztof D. Brzózka, PhD, of Selvita, the Kraków, Poland-based company developing SEL24-B489.

“We believe that since FLT is upstream, and PIM kinases are downstream of the FLT signaling, we will have higher chances

of overcoming resistance because we are targeting the same pathway at 2 independent nodes.”

Dr Brzózka and his colleagues presented research to support this theory at the AACR Annual Meeting 2014 as abstract 1749.*

The researchers evaluated SEL24-B489 in a range of AML cell lines: MV4-11, MOLM-13, MOLM-16, KG-1, CMK, and HL-60. The drug showed “strong cytotoxicity” across the cell lines, independent of FLT3 status.

The team also compared SEL24-B489 to the PIM inhibitor AZD1208 and the FLT3 inhibitor AC220 in MV4-11 cell lines and MOLM-16 cell lines.

In MV4-11 cells, the IC₅₀ was 0.003 μM for AC220, 0.15 μM for SEL24-B489, and 2.24 μM for AZD1208. In MOLM-16 cells, the IC₅₀ was 0.07 μM for AZD1208, 0.1 μM for SEL24-B489, and >10 μM for AC220.

The researchers then evaluated SEL24-B489 in combination with cytarabine.

“The molecule shows very strong synergistic effects with cytarabine, both in vitro and in vivo,” Dr Brzózka said. “The combination index in vitro is approximately 0.1, 0.2. And in vivo, that translates to [nearly] 100% tumor growth inhibition.”

Tumor growth inhibition (TGI) measured 60% when mice received cytarabine alone at 50 mg/kg. TGI was 77% with SEL24-B489 alone at 25 mg/kg and 82% with SEL24-B489 alone at 50 mg/kg.

But with 25 mg/kg of SEL24-B489 and 50 mg/kg of cytarabine, TGI was 89%. And when both drugs were given at 50 mg/kg, TGI was 99%.

The researchers also assessed SEL24-B489 alone in mouse models of AML. In mice injected with MV4-11 cells, SEL24-B489 at 25 mg/kg BID reduced tumor volume by more than 50%, when compared to untreated control mice. And SEL24-B489 at 75 mg/kg BID reduced tumor volume by more than 80%.

In mice injected with MOLM-16 cells, SEL24-B489 at 25 mg/kg BID reduced tumor volume by more than 80%, when compared to untreated control mice. And SEL24-B489 at 75 mg/kg BID reduced tumor volume by more than 100%.

Finally, the team evaluated the safety of SEL24-B489 via repeated 5-day and 10-day toxicology studies in rats.

And they concluded that doses of 100 mg/kg QD x 5 and 25 mg/kg BID x 10 were safe, based on data concerning body weight gain, as well as results of clinical chemistry, hematology, necropsy, and histological analyses.

“Overall, SEL24-B489 has very good oral bioavailability and initial safety profiling,” Dr Brzózka said. “Both in vitro and in vivo, it shows a pretty promising therapeutic index.”

He and his colleagues are now studying SEL24-B489 in dogs, and Selvita is looking for a partner company to help move the drug to phase 1 trials.

*Information in the abstract differs from that presented at the meeting.

SAN DIEGO—Experiments conducted in the lab and the clinic suggest the enzyme heparanase enhances resistance to chemotherapy in multiple myeloma (MM).

Researchers first found that expression of heparanase, an endoglycosidase that cleaves heparan sulfate, is highly elevated in MM patients after chemotherapy.

The team then used MM cell lines to investigate the mechanism behind this phenomenon.

Their results indicate that, by inhibiting heparanase, we might be able to prevent or delay relapse in MM.

Vishnu Ramani, PhD, of the University of Alabama Birmingham, and his colleagues conducted this research and presented the results at the AACR Annual Meeting 2014 (abstract 1708).

Several years ago, Dr Ramani’s colleagues (in the lab of Ralph Sanderson, PhD) identified heparanase as a master regulator of aggressive MM. Since then, research has suggested that heparanase fuels aggressive MM by upregulating the expression of pro-angiogenic genes, driving osteolysis, upregulating prometastatic molecules, and controlling the tumor microenvironment.

“We have done a lot of work on the biology of how this molecule works in myeloma, but the one thing I was really interested in was its role in drug resistance,” Dr Ramani said.

So he and his colleagues decided to study heparanase levels in 9 MM patients undergoing chemotherapy. The team isolated tumor cells from patients before and after 2 rounds of chemotherapy and compared heparanase levels at the different time points.

“What we find—and this is really remarkable—is that the expression of heparanase over rounds of therapy goes up several thousand-fold, and this is in the majority of patients,” Dr Ramani said. “In 8 out of 9 patients that we studied, at the end of chemotherapy, the cells that survive have extremely high levels of heparanase.”

To gain more insight into this phenomenon, the researchers studied it in MM cell lines. The team introduced bortezomib to RPMI-8226 and CAG cells and found that heparanase levels increased “dramatically” after treatment.

“The treatment is not only increasing the heparanase expression inside the cell,” Dr Ramani explained. “What the cells do is that, if you continue the treatment, they die, but they don’t take the heparanase with them. They leave it out in the media, and this can be taken in by other cells. So this can activate other cells to promote aggressive tumor growth too.”

Additional investigation revealed that the NF-κB pathway plays a role—namely, chemotherapy activates the pathway to upregulate heparanase. But inhibiting NF-κB activity can prevent that increase in heparanase.

The researchers tested the NF-κB inhibitors BAY 11-7085 and BMS345541 in combination with bortezomib. And they found that both agents prevented bortezomib from elevating heparanase expression in CAG cells.

Dr Ramani and his colleagues also evaluated heparanase levels in chemoresistant MM cell lines. Heparanase levels were 4-fold higher in a doxorubicin-resistant MM cell line and 10-fold higher in a melphalan-resistant cell line, when compared to a wild-type MM cell line.

Next, the researchers compared MM cells with high heparanase expression to those with low heparanase expression. And they discovered that high heparanase levels protect cells from chemotherapy.

After treatment with bortezomib, cells with high heparanase expression were significantly more viable than those with low expression (P<0.05). And there was a significantly higher percentage of apoptotic cells among the low-heparanase population compared to the high-heparanase population (P<0.05).

“If you take cells that have high heparanase and another group of cells that have low heparanase and expose both of them to therapy, the cells with high heparanase always survive better because the heparanase upregulates certain pathways, like the MAP kinase pathway, which helps the cells to survive the onslaught of chemotherapy,” Dr Ramani said. “So myeloma cells are actually hijacking the heparanase pathway to survive better after therapy.”

Building upon that finding, the researchers decided to assess whether inhibiting ERK activity might help cells overcome heparanase-mediated chemoresistance. And experiments showed that the ERK inhibitor U0126 can sensitize cells with high heparanase levels to treatment with bortezomib.

To take this research to the next level, Dr Ramani and his colleagues are collaborating with a company called Sigma Tau, which is developing a heparanase inhibitor called SST-0001. A phase 1 study of the drug in MM patients has been completed, and phase 2 studies are currently recruiting patients in Europe.

Dr Ramani is now conducting experiments in mice to determine how the inhibitor might work in combination with chemotherapy and when it should be administered in order to overcome treatment resistance. He is also looking for other molecular pathways that could be involved in heparanase-related treatment resistance.

SAN DIEGO—Experiments conducted in the lab and the clinic suggest the enzyme heparanase enhances resistance to chemotherapy in multiple myeloma (MM).

Researchers first found that expression of heparanase, an endoglycosidase that cleaves heparan sulfate, is highly elevated in MM patients after chemotherapy.

The team then used MM cell lines to investigate the mechanism behind this phenomenon.

Their results indicate that, by inhibiting heparanase, we might be able to prevent or delay relapse in MM.

Vishnu Ramani, PhD, of the University of Alabama Birmingham, and his colleagues conducted this research and presented the results at the AACR Annual Meeting 2014 (abstract 1708).

Several years ago, Dr Ramani’s colleagues (in the lab of Ralph Sanderson, PhD) identified heparanase as a master regulator of aggressive MM. Since then, research has suggested that heparanase fuels aggressive MM by upregulating the expression of pro-angiogenic genes, driving osteolysis, upregulating prometastatic molecules, and controlling the tumor microenvironment.

“We have done a lot of work on the biology of how this molecule works in myeloma, but the one thing I was really interested in was its role in drug resistance,” Dr Ramani said.

So he and his colleagues decided to study heparanase levels in 9 MM patients undergoing chemotherapy. The team isolated tumor cells from patients before and after 2 rounds of chemotherapy and compared heparanase levels at the different time points.

“What we find—and this is really remarkable—is that the expression of heparanase over rounds of therapy goes up several thousand-fold, and this is in the majority of patients,” Dr Ramani said. “In 8 out of 9 patients that we studied, at the end of chemotherapy, the cells that survive have extremely high levels of heparanase.”

To gain more insight into this phenomenon, the researchers studied it in MM cell lines. The team introduced bortezomib to RPMI-8226 and CAG cells and found that heparanase levels increased “dramatically” after treatment.

“The treatment is not only increasing the heparanase expression inside the cell,” Dr Ramani explained. “What the cells do is that, if you continue the treatment, they die, but they don’t take the heparanase with them. They leave it out in the media, and this can be taken in by other cells. So this can activate other cells to promote aggressive tumor growth too.”

Additional investigation revealed that the NF-κB pathway plays a role—namely, chemotherapy activates the pathway to upregulate heparanase. But inhibiting NF-κB activity can prevent that increase in heparanase.

The researchers tested the NF-κB inhibitors BAY 11-7085 and BMS345541 in combination with bortezomib. And they found that both agents prevented bortezomib from elevating heparanase expression in CAG cells.

Dr Ramani and his colleagues also evaluated heparanase levels in chemoresistant MM cell lines. Heparanase levels were 4-fold higher in a doxorubicin-resistant MM cell line and 10-fold higher in a melphalan-resistant cell line, when compared to a wild-type MM cell line.

Next, the researchers compared MM cells with high heparanase expression to those with low heparanase expression. And they discovered that high heparanase levels protect cells from chemotherapy.

After treatment with bortezomib, cells with high heparanase expression were significantly more viable than those with low expression (P<0.05). And there was a significantly higher percentage of apoptotic cells among the low-heparanase population compared to the high-heparanase population (P<0.05).

“If you take cells that have high heparanase and another group of cells that have low heparanase and expose both of them to therapy, the cells with high heparanase always survive better because the heparanase upregulates certain pathways, like the MAP kinase pathway, which helps the cells to survive the onslaught of chemotherapy,” Dr Ramani said. “So myeloma cells are actually hijacking the heparanase pathway to survive better after therapy.”

Building upon that finding, the researchers decided to assess whether inhibiting ERK activity might help cells overcome heparanase-mediated chemoresistance. And experiments showed that the ERK inhibitor U0126 can sensitize cells with high heparanase levels to treatment with bortezomib.

To take this research to the next level, Dr Ramani and his colleagues are collaborating with a company called Sigma Tau, which is developing a heparanase inhibitor called SST-0001. A phase 1 study of the drug in MM patients has been completed, and phase 2 studies are currently recruiting patients in Europe.

Dr Ramani is now conducting experiments in mice to determine how the inhibitor might work in combination with chemotherapy and when it should be administered in order to overcome treatment resistance. He is also looking for other molecular pathways that could be involved in heparanase-related treatment resistance.

SAN DIEGO—Experiments conducted in the lab and the clinic suggest the enzyme heparanase enhances resistance to chemotherapy in multiple myeloma (MM).

Researchers first found that expression of heparanase, an endoglycosidase that cleaves heparan sulfate, is highly elevated in MM patients after chemotherapy.

The team then used MM cell lines to investigate the mechanism behind this phenomenon.

Their results indicate that, by inhibiting heparanase, we might be able to prevent or delay relapse in MM.

Vishnu Ramani, PhD, of the University of Alabama Birmingham, and his colleagues conducted this research and presented the results at the AACR Annual Meeting 2014 (abstract 1708).

Several years ago, Dr Ramani’s colleagues (in the lab of Ralph Sanderson, PhD) identified heparanase as a master regulator of aggressive MM. Since then, research has suggested that heparanase fuels aggressive MM by upregulating the expression of pro-angiogenic genes, driving osteolysis, upregulating prometastatic molecules, and controlling the tumor microenvironment.

“We have done a lot of work on the biology of how this molecule works in myeloma, but the one thing I was really interested in was its role in drug resistance,” Dr Ramani said.

So he and his colleagues decided to study heparanase levels in 9 MM patients undergoing chemotherapy. The team isolated tumor cells from patients before and after 2 rounds of chemotherapy and compared heparanase levels at the different time points.

“What we find—and this is really remarkable—is that the expression of heparanase over rounds of therapy goes up several thousand-fold, and this is in the majority of patients,” Dr Ramani said. “In 8 out of 9 patients that we studied, at the end of chemotherapy, the cells that survive have extremely high levels of heparanase.”

To gain more insight into this phenomenon, the researchers studied it in MM cell lines. The team introduced bortezomib to RPMI-8226 and CAG cells and found that heparanase levels increased “dramatically” after treatment.

“The treatment is not only increasing the heparanase expression inside the cell,” Dr Ramani explained. “What the cells do is that, if you continue the treatment, they die, but they don’t take the heparanase with them. They leave it out in the media, and this can be taken in by other cells. So this can activate other cells to promote aggressive tumor growth too.”

Additional investigation revealed that the NF-κB pathway plays a role—namely, chemotherapy activates the pathway to upregulate heparanase. But inhibiting NF-κB activity can prevent that increase in heparanase.

The researchers tested the NF-κB inhibitors BAY 11-7085 and BMS345541 in combination with bortezomib. And they found that both agents prevented bortezomib from elevating heparanase expression in CAG cells.

Dr Ramani and his colleagues also evaluated heparanase levels in chemoresistant MM cell lines. Heparanase levels were 4-fold higher in a doxorubicin-resistant MM cell line and 10-fold higher in a melphalan-resistant cell line, when compared to a wild-type MM cell line.

Next, the researchers compared MM cells with high heparanase expression to those with low heparanase expression. And they discovered that high heparanase levels protect cells from chemotherapy.

After treatment with bortezomib, cells with high heparanase expression were significantly more viable than those with low expression (P<0.05). And there was a significantly higher percentage of apoptotic cells among the low-heparanase population compared to the high-heparanase population (P<0.05).

“If you take cells that have high heparanase and another group of cells that have low heparanase and expose both of them to therapy, the cells with high heparanase always survive better because the heparanase upregulates certain pathways, like the MAP kinase pathway, which helps the cells to survive the onslaught of chemotherapy,” Dr Ramani said. “So myeloma cells are actually hijacking the heparanase pathway to survive better after therapy.”

Building upon that finding, the researchers decided to assess whether inhibiting ERK activity might help cells overcome heparanase-mediated chemoresistance. And experiments showed that the ERK inhibitor U0126 can sensitize cells with high heparanase levels to treatment with bortezomib.

To take this research to the next level, Dr Ramani and his colleagues are collaborating with a company called Sigma Tau, which is developing a heparanase inhibitor called SST-0001. A phase 1 study of the drug in MM patients has been completed, and phase 2 studies are currently recruiting patients in Europe.

Dr Ramani is now conducting experiments in mice to determine how the inhibitor might work in combination with chemotherapy and when it should be administered in order to overcome treatment resistance. He is also looking for other molecular pathways that could be involved in heparanase-related treatment resistance.

SAN DIEGO—Results of a pilot study suggest an experimental molecule can increase hemoglobin levels in patients with hematologic malignancies who are suffering from anemia.

The molecule, lexaptepid pegol (NOX-H94), is a pegylated L-stereoisomer RNA aptamer that binds and neutralizes hepcidin.

In this phase 2 study, 5 of 12 patients who received lexaptepid pegol experienced a hemoglobin increase of 1 g/dL or greater and qualified as responders.

Researchers presented these results at the AACR Annual Meeting 2014 as abstract 3847. The study was supported by NOXXON Pharma AG, the Berlin, Germany-based company developing lexaptepid pegol.

“Our concept is to treat anemia by inhibiting the activity of hepcidin,” said study investigator Kai Riecke, MD, of NOXXON Pharma.

“Hepcidin regulates iron in the blood. The problem is that, in quite a few tumors, hepcidin reduces iron in the circulation, and, over a long period of time, that leads to iron-restricted anemia.”

So Dr Riecke and his colleagues tested their antihepcidin molecule, lexaptepid pegol, in anemic cancer patients. The team enrolled patients with hemoglobin levels less than 10 g/dL who had been diagnosed with multiple myeloma, chronic lymphocytic leukemia, Hodgkin lymphoma, or non-Hodgkin lymphoma.

The patients had a median age of 64 years (range, 35-77). At baseline, the mean hemoglobin was 9.5 ± 0.2 g/dL, the mean serum ferritin was 1067 ± 297 μg/L, the mean serum iron was 34 ± 6 μg/dL, and the mean transferrin saturation was 16.7 ± 3.4%.

The patients received twice-weekly intravenous infusions of lexaptepid pegol for 4 weeks, and the researchers observed patients for 1 month after treatment. Patients were not allowed to receive erythropoiesis-stimulating agents or iron products during the study period.

The results showed increases in hemoglobin of 1 g/dL or greater, which qualified as a response, in 5 of the 12 patients (42%). Three patients achieved a response within 2 weeks of treatment initiation. All 5 patients maintained the increase in hemoglobin throughout the follow-up period.

There was no clear difference in response among the different malignancies, Dr Reike said. But he also noted that, as the study included a small number of patients, it wasn’t really possible for the researchers to make a fair comparison.

In addition to increasing hemoglobin levels, lexaptepid pegol decreased the mean serum ferritin from 1067 μg/L to 815 μg/L in the entire cohort of patients (P=0.014) and from 772 μg/L to 462 μg/L in responders (but this was not significant).

Reticulocyte hemoglobin increased from 22.7 pg to 24.9 pg (P=0.019) in responding patients, but there was no increase in non-responders. (Data for this measurement were only available for 3 of the responders—but all 7 of the non-responders—due to differences in measurement capabilities at the different research sites).

“During the treatment, we saw a very nice increase in reticulocyte hemoglobin, which shows, in these patients, the red blood cells were able to take up iron and build up more hemoglobin,” Dr Riecke said.

The researchers also observed an increase in the mean reticulocyte index in responding patients, from 0.9 to 1.2, although the increase was not significant.

“So this shows that, not only do you have an increase in hemoglobin within each reticulocyte, but you have an increase in the number of reticulocytes—something that we didn’t really expect in the beginning,” Dr Riecke said. “And this may be a sign that the efficacy of erythropoiesis is improved.”

Additionally, responding patients experienced a decrease in soluble transferrin receptor levels, from 10.0 mg/L to 8.6 mg/L, although this was not significant. Soluble transferrin receptor levels remained unchanged in non-responders. (Data for this measurement were only available for 3 of the responders and 4 of the non-responders.)

“The decrease in soluble transferrin receptor levels is a sign that, in the beginning, the cells were very iron-hungry, and then their hunger was satisfied—at least to a certain extent—during the treatment with our drug,” Dr Reike said. “This is a sign that, by reducing hepcidin, more iron is being released into the circulation, and this iron can effectively be used for erythropoiesis.”

Dr Reike added that, although the researchers did observe some adverse effects in the patients, none of these could be clearly attributed to lexaptepid pegol.

Some of the patients did have low blood pressure shortly after treatment, but that may have been influenced by factors other than treatment, he said. Furthermore, in the phase 1 study of lexaptepid pegol in healthy subjects, the only adverse effect that occurred in the treatment arm (and not in the placebo arm) was headache.

Based on these results, NOXXON is now planning—and recruiting for—a study of lexaptepid pegol in dialysis patients.

SAN DIEGO—Results of a pilot study suggest an experimental molecule can increase hemoglobin levels in patients with hematologic malignancies who are suffering from anemia.

The molecule, lexaptepid pegol (NOX-H94), is a pegylated L-stereoisomer RNA aptamer that binds and neutralizes hepcidin.

In this phase 2 study, 5 of 12 patients who received lexaptepid pegol experienced a hemoglobin increase of 1 g/dL or greater and qualified as responders.

Researchers presented these results at the AACR Annual Meeting 2014 as abstract 3847. The study was supported by NOXXON Pharma AG, the Berlin, Germany-based company developing lexaptepid pegol.

“Our concept is to treat anemia by inhibiting the activity of hepcidin,” said study investigator Kai Riecke, MD, of NOXXON Pharma.

“Hepcidin regulates iron in the blood. The problem is that, in quite a few tumors, hepcidin reduces iron in the circulation, and, over a long period of time, that leads to iron-restricted anemia.”

So Dr Riecke and his colleagues tested their antihepcidin molecule, lexaptepid pegol, in anemic cancer patients. The team enrolled patients with hemoglobin levels less than 10 g/dL who had been diagnosed with multiple myeloma, chronic lymphocytic leukemia, Hodgkin lymphoma, or non-Hodgkin lymphoma.

The patients had a median age of 64 years (range, 35-77). At baseline, the mean hemoglobin was 9.5 ± 0.2 g/dL, the mean serum ferritin was 1067 ± 297 μg/L, the mean serum iron was 34 ± 6 μg/dL, and the mean transferrin saturation was 16.7 ± 3.4%.

The patients received twice-weekly intravenous infusions of lexaptepid pegol for 4 weeks, and the researchers observed patients for 1 month after treatment. Patients were not allowed to receive erythropoiesis-stimulating agents or iron products during the study period.

The results showed increases in hemoglobin of 1 g/dL or greater, which qualified as a response, in 5 of the 12 patients (42%). Three patients achieved a response within 2 weeks of treatment initiation. All 5 patients maintained the increase in hemoglobin throughout the follow-up period.

There was no clear difference in response among the different malignancies, Dr Reike said. But he also noted that, as the study included a small number of patients, it wasn’t really possible for the researchers to make a fair comparison.

In addition to increasing hemoglobin levels, lexaptepid pegol decreased the mean serum ferritin from 1067 μg/L to 815 μg/L in the entire cohort of patients (P=0.014) and from 772 μg/L to 462 μg/L in responders (but this was not significant).

Reticulocyte hemoglobin increased from 22.7 pg to 24.9 pg (P=0.019) in responding patients, but there was no increase in non-responders. (Data for this measurement were only available for 3 of the responders—but all 7 of the non-responders—due to differences in measurement capabilities at the different research sites).

“During the treatment, we saw a very nice increase in reticulocyte hemoglobin, which shows, in these patients, the red blood cells were able to take up iron and build up more hemoglobin,” Dr Riecke said.

The researchers also observed an increase in the mean reticulocyte index in responding patients, from 0.9 to 1.2, although the increase was not significant.

“So this shows that, not only do you have an increase in hemoglobin within each reticulocyte, but you have an increase in the number of reticulocytes—something that we didn’t really expect in the beginning,” Dr Riecke said. “And this may be a sign that the efficacy of erythropoiesis is improved.”

Additionally, responding patients experienced a decrease in soluble transferrin receptor levels, from 10.0 mg/L to 8.6 mg/L, although this was not significant. Soluble transferrin receptor levels remained unchanged in non-responders. (Data for this measurement were only available for 3 of the responders and 4 of the non-responders.)

“The decrease in soluble transferrin receptor levels is a sign that, in the beginning, the cells were very iron-hungry, and then their hunger was satisfied—at least to a certain extent—during the treatment with our drug,” Dr Reike said. “This is a sign that, by reducing hepcidin, more iron is being released into the circulation, and this iron can effectively be used for erythropoiesis.”

Dr Reike added that, although the researchers did observe some adverse effects in the patients, none of these could be clearly attributed to lexaptepid pegol.

Some of the patients did have low blood pressure shortly after treatment, but that may have been influenced by factors other than treatment, he said. Furthermore, in the phase 1 study of lexaptepid pegol in healthy subjects, the only adverse effect that occurred in the treatment arm (and not in the placebo arm) was headache.

Based on these results, NOXXON is now planning—and recruiting for—a study of lexaptepid pegol in dialysis patients.

SAN DIEGO—Results of a pilot study suggest an experimental molecule can increase hemoglobin levels in patients with hematologic malignancies who are suffering from anemia.

The molecule, lexaptepid pegol (NOX-H94), is a pegylated L-stereoisomer RNA aptamer that binds and neutralizes hepcidin.

In this phase 2 study, 5 of 12 patients who received lexaptepid pegol experienced a hemoglobin increase of 1 g/dL or greater and qualified as responders.

Researchers presented these results at the AACR Annual Meeting 2014 as abstract 3847. The study was supported by NOXXON Pharma AG, the Berlin, Germany-based company developing lexaptepid pegol.

“Our concept is to treat anemia by inhibiting the activity of hepcidin,” said study investigator Kai Riecke, MD, of NOXXON Pharma.

“Hepcidin regulates iron in the blood. The problem is that, in quite a few tumors, hepcidin reduces iron in the circulation, and, over a long period of time, that leads to iron-restricted anemia.”

So Dr Riecke and his colleagues tested their antihepcidin molecule, lexaptepid pegol, in anemic cancer patients. The team enrolled patients with hemoglobin levels less than 10 g/dL who had been diagnosed with multiple myeloma, chronic lymphocytic leukemia, Hodgkin lymphoma, or non-Hodgkin lymphoma.

The patients had a median age of 64 years (range, 35-77). At baseline, the mean hemoglobin was 9.5 ± 0.2 g/dL, the mean serum ferritin was 1067 ± 297 μg/L, the mean serum iron was 34 ± 6 μg/dL, and the mean transferrin saturation was 16.7 ± 3.4%.

The patients received twice-weekly intravenous infusions of lexaptepid pegol for 4 weeks, and the researchers observed patients for 1 month after treatment. Patients were not allowed to receive erythropoiesis-stimulating agents or iron products during the study period.

The results showed increases in hemoglobin of 1 g/dL or greater, which qualified as a response, in 5 of the 12 patients (42%). Three patients achieved a response within 2 weeks of treatment initiation. All 5 patients maintained the increase in hemoglobin throughout the follow-up period.

There was no clear difference in response among the different malignancies, Dr Reike said. But he also noted that, as the study included a small number of patients, it wasn’t really possible for the researchers to make a fair comparison.

In addition to increasing hemoglobin levels, lexaptepid pegol decreased the mean serum ferritin from 1067 μg/L to 815 μg/L in the entire cohort of patients (P=0.014) and from 772 μg/L to 462 μg/L in responders (but this was not significant).

Reticulocyte hemoglobin increased from 22.7 pg to 24.9 pg (P=0.019) in responding patients, but there was no increase in non-responders. (Data for this measurement were only available for 3 of the responders—but all 7 of the non-responders—due to differences in measurement capabilities at the different research sites).

“During the treatment, we saw a very nice increase in reticulocyte hemoglobin, which shows, in these patients, the red blood cells were able to take up iron and build up more hemoglobin,” Dr Riecke said.

The researchers also observed an increase in the mean reticulocyte index in responding patients, from 0.9 to 1.2, although the increase was not significant.

“So this shows that, not only do you have an increase in hemoglobin within each reticulocyte, but you have an increase in the number of reticulocytes—something that we didn’t really expect in the beginning,” Dr Riecke said. “And this may be a sign that the efficacy of erythropoiesis is improved.”

Additionally, responding patients experienced a decrease in soluble transferrin receptor levels, from 10.0 mg/L to 8.6 mg/L, although this was not significant. Soluble transferrin receptor levels remained unchanged in non-responders. (Data for this measurement were only available for 3 of the responders and 4 of the non-responders.)

“The decrease in soluble transferrin receptor levels is a sign that, in the beginning, the cells were very iron-hungry, and then their hunger was satisfied—at least to a certain extent—during the treatment with our drug,” Dr Reike said. “This is a sign that, by reducing hepcidin, more iron is being released into the circulation, and this iron can effectively be used for erythropoiesis.”

Dr Reike added that, although the researchers did observe some adverse effects in the patients, none of these could be clearly attributed to lexaptepid pegol.

Some of the patients did have low blood pressure shortly after treatment, but that may have been influenced by factors other than treatment, he said. Furthermore, in the phase 1 study of lexaptepid pegol in healthy subjects, the only adverse effect that occurred in the treatment arm (and not in the placebo arm) was headache.

Based on these results, NOXXON is now planning—and recruiting for—a study of lexaptepid pegol in dialysis patients.

SAN DIEGO—Preclinical research suggests that combining a BET inhibitor with lenalidomide may overcome resistance to bortezomib in mantle cell lymphoma (MCL).

Experiments in MCL cell lines and mouse models of the disease showed that lenalidomide alone is active in bortezomib-resistant cells and tumors.

But the anticancer effects are more pronounced with the addition of the BET inhibitor CPI203.

“So we think that this new combination based on BET inhibition and lenalidomide may be helpful for the design of new therapies in the subset of MCL patients resistant to bortezomib,” said study investigator Gael Roue, PhD, of IDIBAPS in Barcelona, Spain.

Dr Roue and his colleagues presented this research in a poster at the AACR Annual Meeting 2014 (abstract 1691*). The team included researchers from Constellation Pharmaceuticals, the company developing CPI203.

With this research, the investigators wanted to assess the possibility of targeting IRF4 and MYC signaling and overcoming bortezomib resistance with lenalidomide-based therapies.

To that end, they tested lenalidomide in 9 MCL cell lines. They found the drug’s antitumor activity is mediated by inhibition of the plasmacytic differentiation program in bortezomib-resistant MCL.

The team then evaluated the effects of lenalidomide on REC-1 cells injected into SCID mice. And they found that lenalidomide significantly reduced tumor growth compared to vehicle control (P=0.04).

The researchers next injected mice with REC-1 cells and treated them with 50 mg/kg of lenalidomide, 0.15 mg/kg of bortezomib, both agents, or vehicle control. The mice received lenalidomide 5 days a week and bortezomib twice a week for up to 18 days.

Lenalidomide alone significantly reduced tumor volume when compared to control (P=0.04). The same was true of the combination treatment compared to control (P=0.02).

The investigators also noted a 25% increase in MYC expression in cells and tumors that were resistant to bortezomib. So they speculated that inhibiting MYC could increase lenalidomide activity.

“This was the rationale for combining lenalidomide with a BET inhibitor,” Dr Roue said. “BET inhibitors are known to inhibit MYC transcription, to inhibit MYC signaling, in multiple myeloma and lymphoma cells.”

The researchers first evaluated the effects of CPI203 alone. They cultured 9 MCL cell lines and peripheral blood mononuclear cells from 2 healthy donors with increasing concentrations of CPI203 and assessed cytotoxicity, MYC levels, and cell viability.

They found that CPI203 was active in all the cell lines tested, but it didn’t affect the proliferation or viability of the healthy cells. And CPI203 activity was linked to the downregulation of MYC.

The team then tested CPI203 in combination with lenalidomide. They treated REC-1 cells for 72 hours with 0.1 μM to 0.5 μM of CPI203 and/or 1 μM to 5 μM of lenalidomide.

“[W]e observed synergistic activity in vitro, linked to a complete disappearance of MYC and also of IRF4,” Dr Roue said.

Finally, the investigators tested the 2 agents in mice with bortezomib-resistant MCL. The mice were injected with REC-1 cells and randomized to treatment with lenalidomide at 50 mg/kg/day, CPI203 at 2.5 mg/kg BID, both agents, or vehicle control.

“We found that by treating mice with [both agents] for 3 weeks, we reached 80% tumor remission, which was linked to inhibition of mitosis, complete disappearance of MYC and IRF4 protein levels, and induction of apoptosis in about 30% to 40% of the tumors.”

The researchers said these results suggest the lenalidomide-BET inhibitor combination warrants investigation in MCL patients who are refractory to bortezomib.

*Information in the abstract differs from that presented at the meeting.

SAN DIEGO—Preclinical research suggests that combining a BET inhibitor with lenalidomide may overcome resistance to bortezomib in mantle cell lymphoma (MCL).

Experiments in MCL cell lines and mouse models of the disease showed that lenalidomide alone is active in bortezomib-resistant cells and tumors.

But the anticancer effects are more pronounced with the addition of the BET inhibitor CPI203.

“So we think that this new combination based on BET inhibition and lenalidomide may be helpful for the design of new therapies in the subset of MCL patients resistant to bortezomib,” said study investigator Gael Roue, PhD, of IDIBAPS in Barcelona, Spain.

Dr Roue and his colleagues presented this research in a poster at the AACR Annual Meeting 2014 (abstract 1691*). The team included researchers from Constellation Pharmaceuticals, the company developing CPI203.

With this research, the investigators wanted to assess the possibility of targeting IRF4 and MYC signaling and overcoming bortezomib resistance with lenalidomide-based therapies.

To that end, they tested lenalidomide in 9 MCL cell lines. They found the drug’s antitumor activity is mediated by inhibition of the plasmacytic differentiation program in bortezomib-resistant MCL.

The team then evaluated the effects of lenalidomide on REC-1 cells injected into SCID mice. And they found that lenalidomide significantly reduced tumor growth compared to vehicle control (P=0.04).

The researchers next injected mice with REC-1 cells and treated them with 50 mg/kg of lenalidomide, 0.15 mg/kg of bortezomib, both agents, or vehicle control. The mice received lenalidomide 5 days a week and bortezomib twice a week for up to 18 days.

Lenalidomide alone significantly reduced tumor volume when compared to control (P=0.04). The same was true of the combination treatment compared to control (P=0.02).

The investigators also noted a 25% increase in MYC expression in cells and tumors that were resistant to bortezomib. So they speculated that inhibiting MYC could increase lenalidomide activity.

“This was the rationale for combining lenalidomide with a BET inhibitor,” Dr Roue said. “BET inhibitors are known to inhibit MYC transcription, to inhibit MYC signaling, in multiple myeloma and lymphoma cells.”

The researchers first evaluated the effects of CPI203 alone. They cultured 9 MCL cell lines and peripheral blood mononuclear cells from 2 healthy donors with increasing concentrations of CPI203 and assessed cytotoxicity, MYC levels, and cell viability.

They found that CPI203 was active in all the cell lines tested, but it didn’t affect the proliferation or viability of the healthy cells. And CPI203 activity was linked to the downregulation of MYC.

The team then tested CPI203 in combination with lenalidomide. They treated REC-1 cells for 72 hours with 0.1 μM to 0.5 μM of CPI203 and/or 1 μM to 5 μM of lenalidomide.

“[W]e observed synergistic activity in vitro, linked to a complete disappearance of MYC and also of IRF4,” Dr Roue said.

Finally, the investigators tested the 2 agents in mice with bortezomib-resistant MCL. The mice were injected with REC-1 cells and randomized to treatment with lenalidomide at 50 mg/kg/day, CPI203 at 2.5 mg/kg BID, both agents, or vehicle control.

“We found that by treating mice with [both agents] for 3 weeks, we reached 80% tumor remission, which was linked to inhibition of mitosis, complete disappearance of MYC and IRF4 protein levels, and induction of apoptosis in about 30% to 40% of the tumors.”

The researchers said these results suggest the lenalidomide-BET inhibitor combination warrants investigation in MCL patients who are refractory to bortezomib.

*Information in the abstract differs from that presented at the meeting.

SAN DIEGO—Preclinical research suggests that combining a BET inhibitor with lenalidomide may overcome resistance to bortezomib in mantle cell lymphoma (MCL).

Experiments in MCL cell lines and mouse models of the disease showed that lenalidomide alone is active in bortezomib-resistant cells and tumors.

But the anticancer effects are more pronounced with the addition of the BET inhibitor CPI203.

“So we think that this new combination based on BET inhibition and lenalidomide may be helpful for the design of new therapies in the subset of MCL patients resistant to bortezomib,” said study investigator Gael Roue, PhD, of IDIBAPS in Barcelona, Spain.

Dr Roue and his colleagues presented this research in a poster at the AACR Annual Meeting 2014 (abstract 1691*). The team included researchers from Constellation Pharmaceuticals, the company developing CPI203.

With this research, the investigators wanted to assess the possibility of targeting IRF4 and MYC signaling and overcoming bortezomib resistance with lenalidomide-based therapies.

To that end, they tested lenalidomide in 9 MCL cell lines. They found the drug’s antitumor activity is mediated by inhibition of the plasmacytic differentiation program in bortezomib-resistant MCL.

The team then evaluated the effects of lenalidomide on REC-1 cells injected into SCID mice. And they found that lenalidomide significantly reduced tumor growth compared to vehicle control (P=0.04).

The researchers next injected mice with REC-1 cells and treated them with 50 mg/kg of lenalidomide, 0.15 mg/kg of bortezomib, both agents, or vehicle control. The mice received lenalidomide 5 days a week and bortezomib twice a week for up to 18 days.

Lenalidomide alone significantly reduced tumor volume when compared to control (P=0.04). The same was true of the combination treatment compared to control (P=0.02).

The investigators also noted a 25% increase in MYC expression in cells and tumors that were resistant to bortezomib. So they speculated that inhibiting MYC could increase lenalidomide activity.

“This was the rationale for combining lenalidomide with a BET inhibitor,” Dr Roue said. “BET inhibitors are known to inhibit MYC transcription, to inhibit MYC signaling, in multiple myeloma and lymphoma cells.”

The researchers first evaluated the effects of CPI203 alone. They cultured 9 MCL cell lines and peripheral blood mononuclear cells from 2 healthy donors with increasing concentrations of CPI203 and assessed cytotoxicity, MYC levels, and cell viability.

They found that CPI203 was active in all the cell lines tested, but it didn’t affect the proliferation or viability of the healthy cells. And CPI203 activity was linked to the downregulation of MYC.

The team then tested CPI203 in combination with lenalidomide. They treated REC-1 cells for 72 hours with 0.1 μM to 0.5 μM of CPI203 and/or 1 μM to 5 μM of lenalidomide.

“[W]e observed synergistic activity in vitro, linked to a complete disappearance of MYC and also of IRF4,” Dr Roue said.

Finally, the investigators tested the 2 agents in mice with bortezomib-resistant MCL. The mice were injected with REC-1 cells and randomized to treatment with lenalidomide at 50 mg/kg/day, CPI203 at 2.5 mg/kg BID, both agents, or vehicle control.

“We found that by treating mice with [both agents] for 3 weeks, we reached 80% tumor remission, which was linked to inhibition of mitosis, complete disappearance of MYC and IRF4 protein levels, and induction of apoptosis in about 30% to 40% of the tumors.”

The researchers said these results suggest the lenalidomide-BET inhibitor combination warrants investigation in MCL patients who are refractory to bortezomib.

*Information in the abstract differs from that presented at the meeting.

AACR Annual Meeting 2014

SAN DIEGO—The use of hormone therapy may lower the risk of B-cell non-Hodgkin lymphoma (NHL) in menopausal women, according to a presentation at the AACR Annual Meeting 2014.

Researchers found that menopausal women who used hormone therapy were about 30% less likely than their untreated peers to develop NHL.

And the risk of NHL decreased further if a woman began receiving hormone therapy at a younger age and used it for a longer period of time.

Sophia Wang, PhD, of City of Hope National Medical Center in Duarte, California, presented these findings at the meeting as abstract 2918.

“The connection between lymphomas and menopausal hormone therapy use hinges on understanding the disease’s biology and the window of susceptibility,” Dr Wang said. “Hormone therapy is of interest because the loss of estrogen coupled with aging in women result in decreased immune function, which can elevate the risk of non-Hodgkin lymphoma.”

For this study, Dr Wang and her colleagues examined data from the Los Angeles Cancer Surveillance Program. They compared 685 postmenopausal women diagnosed with B-cell NHL to 685 postmenopausal women without lymphoma.

The researchers assessed the women’s use of menopausal hormone therapy, which included estrogen alone or estrogen with progestin in pill, patch, topical cream, or injected forms.

After controlling for factors such as age, race, and socioeconomic status, Dr Wang and her colleagues found that women who reported using any form of menopausal hormone therapy were approximately 30% less likely to be diagnosed with B-cell NHL, compared to women who reported never using hormone therapy.

An additional analysis showed that the risk reduction was even greater for women who initiated menopausal hormone therapy at 45 years of age or younger and used it for at least 5 years.

This group was approximately 40% less likely to be diagnosed with B-cell NHL compared to those who had never used hormone therapy.

Dr Wang said further research is needed to determine the exact biological mechanisms that might be linked to a lower NHL risk. These mechanisms could include supporting a healthy immune system or reducing inflammation.

She also cautioned that these findings are preliminary and should not change current recommendations and guidelines for menopausal hormone therapy use.

Due to well-established evidence tying menopausal hormone therapy to elevated risks of breast and endometrial cancers, the American Cancer Society recommends that women considering or using this therapy do so at the lowest effective dose for the shortest amount of time needed and that they discuss with their physicians other treatments to alleviate menopausal symptoms.

AACR Annual Meeting 2014

SAN DIEGO—The use of hormone therapy may lower the risk of B-cell non-Hodgkin lymphoma (NHL) in menopausal women, according to a presentation at the AACR Annual Meeting 2014.

Researchers found that menopausal women who used hormone therapy were about 30% less likely than their untreated peers to develop NHL.

And the risk of NHL decreased further if a woman began receiving hormone therapy at a younger age and used it for a longer period of time.

Sophia Wang, PhD, of City of Hope National Medical Center in Duarte, California, presented these findings at the meeting as abstract 2918.

“The connection between lymphomas and menopausal hormone therapy use hinges on understanding the disease’s biology and the window of susceptibility,” Dr Wang said. “Hormone therapy is of interest because the loss of estrogen coupled with aging in women result in decreased immune function, which can elevate the risk of non-Hodgkin lymphoma.”

For this study, Dr Wang and her colleagues examined data from the Los Angeles Cancer Surveillance Program. They compared 685 postmenopausal women diagnosed with B-cell NHL to 685 postmenopausal women without lymphoma.

The researchers assessed the women’s use of menopausal hormone therapy, which included estrogen alone or estrogen with progestin in pill, patch, topical cream, or injected forms.

After controlling for factors such as age, race, and socioeconomic status, Dr Wang and her colleagues found that women who reported using any form of menopausal hormone therapy were approximately 30% less likely to be diagnosed with B-cell NHL, compared to women who reported never using hormone therapy.

An additional analysis showed that the risk reduction was even greater for women who initiated menopausal hormone therapy at 45 years of age or younger and used it for at least 5 years.

This group was approximately 40% less likely to be diagnosed with B-cell NHL compared to those who had never used hormone therapy.

Dr Wang said further research is needed to determine the exact biological mechanisms that might be linked to a lower NHL risk. These mechanisms could include supporting a healthy immune system or reducing inflammation.

She also cautioned that these findings are preliminary and should not change current recommendations and guidelines for menopausal hormone therapy use.

Due to well-established evidence tying menopausal hormone therapy to elevated risks of breast and endometrial cancers, the American Cancer Society recommends that women considering or using this therapy do so at the lowest effective dose for the shortest amount of time needed and that they discuss with their physicians other treatments to alleviate menopausal symptoms.

AACR Annual Meeting 2014

SAN DIEGO—The use of hormone therapy may lower the risk of B-cell non-Hodgkin lymphoma (NHL) in menopausal women, according to a presentation at the AACR Annual Meeting 2014.

Researchers found that menopausal women who used hormone therapy were about 30% less likely than their untreated peers to develop NHL.

And the risk of NHL decreased further if a woman began receiving hormone therapy at a younger age and used it for a longer period of time.

Sophia Wang, PhD, of City of Hope National Medical Center in Duarte, California, presented these findings at the meeting as abstract 2918.

“The connection between lymphomas and menopausal hormone therapy use hinges on understanding the disease’s biology and the window of susceptibility,” Dr Wang said. “Hormone therapy is of interest because the loss of estrogen coupled with aging in women result in decreased immune function, which can elevate the risk of non-Hodgkin lymphoma.”

For this study, Dr Wang and her colleagues examined data from the Los Angeles Cancer Surveillance Program. They compared 685 postmenopausal women diagnosed with B-cell NHL to 685 postmenopausal women without lymphoma.

The researchers assessed the women’s use of menopausal hormone therapy, which included estrogen alone or estrogen with progestin in pill, patch, topical cream, or injected forms.

After controlling for factors such as age, race, and socioeconomic status, Dr Wang and her colleagues found that women who reported using any form of menopausal hormone therapy were approximately 30% less likely to be diagnosed with B-cell NHL, compared to women who reported never using hormone therapy.

An additional analysis showed that the risk reduction was even greater for women who initiated menopausal hormone therapy at 45 years of age or younger and used it for at least 5 years.

This group was approximately 40% less likely to be diagnosed with B-cell NHL compared to those who had never used hormone therapy.

Dr Wang said further research is needed to determine the exact biological mechanisms that might be linked to a lower NHL risk. These mechanisms could include supporting a healthy immune system or reducing inflammation.

She also cautioned that these findings are preliminary and should not change current recommendations and guidelines for menopausal hormone therapy use.

Due to well-established evidence tying menopausal hormone therapy to elevated risks of breast and endometrial cancers, the American Cancer Society recommends that women considering or using this therapy do so at the lowest effective dose for the shortest amount of time needed and that they discuss with their physicians other treatments to alleviate menopausal symptoms.

Update: The hold on this trial has been lifted. Click here for additional details.

Memorial Sloan-Kettering Cancer Center has temporarily suspended enrollment in a study of chimeric antigen receptor (CAR) T-cell therapy, due to 2 patient deaths.

The study is an evaluation of CD19-targeted CAR T cells in patients with B-cell acute lymphoblastic leukemia (ALL).

Of the 22 patients enrolled on the study to date, 10 have died. But only 2 of these deaths gave researchers pause and made them question enrollment criteria.

Six deaths were a result of disease relapse or progression, and 2 patients died of complications from stem cell transplant.

The 2 deaths that prompted the suspension of enrollment occurred within 2 weeks of the patients receiving CAR T cells.

“The first of these patients had a prior history of cardiac disease, while the second patient died due to complications associated with persistent seizure activity,” said Renier Brentjens, MD, PhD, of Memorial Sloan-Kettering in New York.

“As a matter of routine review at Sloan-Kettering for adverse events on-study, our center made the decision to pause enrollment and review these 2 patients in greater detail.”

“And as a consequence of this review, we’ve amended the enrollment criteria in regards to comorbidities, thereby excluding patients with cardiac disease, and adjusted the T-cell dose based on the extent of disease, [in the] hope that this modification will reduce the cytokine release syndrome that these patients with morphological disease have experienced.”

The researchers expect the trial to resume enrollment soon.

Some results from this study were recently published in Science Translational Medicine, and Dr Brentjens presented the latest results at the AACR Annual Meeting 2014 in San Diego (abstract CT102*).

Thus far, the researchers have enrolled 22 adult patients who had relapsed or refractory B-ALL, were minimal residual disease-positive, or were in the first complete remission (CR1) at enrollment. Patients in CR1 were monitored and only received CAR T cells if they relapsed.

The remaining patients received re-induction chemotherapy (physician’s choice), followed by CAR T-cell infusion. After treatment, the options were allogeneic transplant, a different salvage therapy, or monitoring.

In all, 20 patients received a CAR T-cell dose of 3 x 10⁶ T cells/kg. Eighty-two percent of patients initially achieved a CR, and 72% had a morphologic CR. The average time to CR was about 24.5 days.

Twelve of the responders were eligible for transplant. Of the 8 patients who ultimately underwent transplant and survived, 1 relapsed, but the rest remain in remission.

Dr Brentjens noted that some patients developed cytokine release syndrome, and this was related to the amount of disease present at the time of CAR T-cell infusion.

“Those patients that had only minimal residual disease at the time of CAR T-cell infusion . . .  less than 5% blasts, generally had either no fever or very transient, low-grade fever,” he said.

“In contrast, all those patients that had morphologic residual disease at the time of CAR T-cell infusion demonstrated a high, persistent spike in fevers . . . , became hypotensive, and required transfer—for additional, closer monitoring—to our ICU.”

The researchers initially treated these patients with high-dose steroids, which reduced cytokine levels in the serum and ameliorated fevers. But it also rapidly reduced T-cell populations to undetectable levels.

Fortunately, another group of researchers subsequently discovered that the monoclonal antibody tocilizumab can treat cytokine release syndrome without inducing this side effect. So Dr Brentjens and his colleagues began using this drug and found it both safe and effective.

*Information in the abstract differs from that presented at the meeting.

Update: The hold on this trial has been lifted. Click here for additional details.

Memorial Sloan-Kettering Cancer Center has temporarily suspended enrollment in a study of chimeric antigen receptor (CAR) T-cell therapy, due to 2 patient deaths.

The study is an evaluation of CD19-targeted CAR T cells in patients with B-cell acute lymphoblastic leukemia (ALL).

Of the 22 patients enrolled on the study to date, 10 have died. But only 2 of these deaths gave researchers pause and made them question enrollment criteria.

Six deaths were a result of disease relapse or progression, and 2 patients died of complications from stem cell transplant.

The 2 deaths that prompted the suspension of enrollment occurred within 2 weeks of the patients receiving CAR T cells.

“The first of these patients had a prior history of cardiac disease, while the second patient died due to complications associated with persistent seizure activity,” said Renier Brentjens, MD, PhD, of Memorial Sloan-Kettering in New York.

“As a matter of routine review at Sloan-Kettering for adverse events on-study, our center made the decision to pause enrollment and review these 2 patients in greater detail.”

“And as a consequence of this review, we’ve amended the enrollment criteria in regards to comorbidities, thereby excluding patients with cardiac disease, and adjusted the T-cell dose based on the extent of disease, [in the] hope that this modification will reduce the cytokine release syndrome that these patients with morphological disease have experienced.”

The researchers expect the trial to resume enrollment soon.

Some results from this study were recently published in Science Translational Medicine, and Dr Brentjens presented the latest results at the AACR Annual Meeting 2014 in San Diego (abstract CT102*).

Thus far, the researchers have enrolled 22 adult patients who had relapsed or refractory B-ALL, were minimal residual disease-positive, or were in the first complete remission (CR1) at enrollment. Patients in CR1 were monitored and only received CAR T cells if they relapsed.

The remaining patients received re-induction chemotherapy (physician’s choice), followed by CAR T-cell infusion. After treatment, the options were allogeneic transplant, a different salvage therapy, or monitoring.

In all, 20 patients received a CAR T-cell dose of 3 x 10⁶ T cells/kg. Eighty-two percent of patients initially achieved a CR, and 72% had a morphologic CR. The average time to CR was about 24.5 days.

Twelve of the responders were eligible for transplant. Of the 8 patients who ultimately underwent transplant and survived, 1 relapsed, but the rest remain in remission.

Dr Brentjens noted that some patients developed cytokine release syndrome, and this was related to the amount of disease present at the time of CAR T-cell infusion.

“Those patients that had only minimal residual disease at the time of CAR T-cell infusion . . .  less than 5% blasts, generally had either no fever or very transient, low-grade fever,” he said.

“In contrast, all those patients that had morphologic residual disease at the time of CAR T-cell infusion demonstrated a high, persistent spike in fevers . . . , became hypotensive, and required transfer—for additional, closer monitoring—to our ICU.”

The researchers initially treated these patients with high-dose steroids, which reduced cytokine levels in the serum and ameliorated fevers. But it also rapidly reduced T-cell populations to undetectable levels.

Fortunately, another group of researchers subsequently discovered that the monoclonal antibody tocilizumab can treat cytokine release syndrome without inducing this side effect. So Dr Brentjens and his colleagues began using this drug and found it both safe and effective.

*Information in the abstract differs from that presented at the meeting.

Update: The hold on this trial has been lifted. Click here for additional details.

Memorial Sloan-Kettering Cancer Center has temporarily suspended enrollment in a study of chimeric antigen receptor (CAR) T-cell therapy, due to 2 patient deaths.

The study is an evaluation of CD19-targeted CAR T cells in patients with B-cell acute lymphoblastic leukemia (ALL).

Of the 22 patients enrolled on the study to date, 10 have died. But only 2 of these deaths gave researchers pause and made them question enrollment criteria.

Six deaths were a result of disease relapse or progression, and 2 patients died of complications from stem cell transplant.

The 2 deaths that prompted the suspension of enrollment occurred within 2 weeks of the patients receiving CAR T cells.

“The first of these patients had a prior history of cardiac disease, while the second patient died due to complications associated with persistent seizure activity,” said Renier Brentjens, MD, PhD, of Memorial Sloan-Kettering in New York.

“As a matter of routine review at Sloan-Kettering for adverse events on-study, our center made the decision to pause enrollment and review these 2 patients in greater detail.”

“And as a consequence of this review, we’ve amended the enrollment criteria in regards to comorbidities, thereby excluding patients with cardiac disease, and adjusted the T-cell dose based on the extent of disease, [in the] hope that this modification will reduce the cytokine release syndrome that these patients with morphological disease have experienced.”

The researchers expect the trial to resume enrollment soon.

Some results from this study were recently published in Science Translational Medicine, and Dr Brentjens presented the latest results at the AACR Annual Meeting 2014 in San Diego (abstract CT102*).

Thus far, the researchers have enrolled 22 adult patients who had relapsed or refractory B-ALL, were minimal residual disease-positive, or were in the first complete remission (CR1) at enrollment. Patients in CR1 were monitored and only received CAR T cells if they relapsed.

The remaining patients received re-induction chemotherapy (physician’s choice), followed by CAR T-cell infusion. After treatment, the options were allogeneic transplant, a different salvage therapy, or monitoring.

In all, 20 patients received a CAR T-cell dose of 3 x 10⁶ T cells/kg. Eighty-two percent of patients initially achieved a CR, and 72% had a morphologic CR. The average time to CR was about 24.5 days.

Twelve of the responders were eligible for transplant. Of the 8 patients who ultimately underwent transplant and survived, 1 relapsed, but the rest remain in remission.

Dr Brentjens noted that some patients developed cytokine release syndrome, and this was related to the amount of disease present at the time of CAR T-cell infusion.

“Those patients that had only minimal residual disease at the time of CAR T-cell infusion . . .  less than 5% blasts, generally had either no fever or very transient, low-grade fever,” he said.

“In contrast, all those patients that had morphologic residual disease at the time of CAR T-cell infusion demonstrated a high, persistent spike in fevers . . . , became hypotensive, and required transfer—for additional, closer monitoring—to our ICU.”

The researchers initially treated these patients with high-dose steroids, which reduced cytokine levels in the serum and ameliorated fevers. But it also rapidly reduced T-cell populations to undetectable levels.

Fortunately, another group of researchers subsequently discovered that the monoclonal antibody tocilizumab can treat cytokine release syndrome without inducing this side effect. So Dr Brentjens and his colleagues began using this drug and found it both safe and effective.

*Information in the abstract differs from that presented at the meeting.

BALB/c mice

Credit: Aaron Logan

SAN DIEGO—Researchers have found evidence to suggest there may be little difference between an immune response that kills cancer cells and one that stimulates tumor growth.

The team set out to determine whether the immune responses that mediate cancer immunosurveillance and those responsible for inflammatory facilitation are qualitatively or quantitatively distinct.

They tested antibodies in mouse models of a few different cancers, including rituximab in Burkitt lymphoma.

And they found that lower antibody concentrations stimulated tumor growth, while higher concentrations inhibited growth, and the dose range was “surprisingly narrow.”

The researchers reported these findings in a paper published in PNAS and a poster presentation at the AACR Annual Meeting 2014 (abstract 1063).

“We have found that the intensity difference between an immune response that stimulates cancer and one that kills it may not be very much,” said principal investigator Ajit Varki, MD, of the University of California, San Diego School of Medicine.

“This may come as a surprise to researchers exploring two areas typically considered distinct: the role of the immune system in preventing and killing cancers and the role of chronic inflammation in stimulating cancers. As always, it turns out that the immune system is a double-edged sword.”

The concept of naturally occurring immunosurveillance against malignancies is not new, and there is compelling evidence for it. But understanding this process is confounded by the fact that some types of immune reaction promote tumor development.

Dr Varki and his colleagues looked specifically at a non-human sialic acid sugar molecule called Neu5Gc. Previous research showed that Neu5Gc accumulates in human tumors from dietary sources, despite an ongoing antibody response against it.

The researchers deployed antibodies against Neu5Gc in a mouse tumor model to determine whether and to what degree the antibodies altered tumor progression. The team found that low antibody doses stimulated growth, but high doses inhibited it.

The effect occurred over a “linear and remarkably narrow range,” according to Dr Varki, generating an immune response curve or “inverse hormesis.” Moreover, this curve could be shifted to the left or right simply by modifying the quality of the immune response.

The researchers uncovered similar findings in experiments with mouse models of colon and lung cancer, as well as when they used rituximab in a model of Burkitt lymphoma.

Dr Varki said these results could have implications for all aspects of cancer research. The immune response can have multiple roles in the genesis of cancers, in altering the progress of established tumors and in anticancer therapies that use antibodies as drugs.

Dr Varki is a co-founder of the company Sialix, Inc., which has licensed UC San Diego technologies related to anti-Neu5Gc antibodies in cancer.

BALB/c mice

Credit: Aaron Logan

SAN DIEGO—Researchers have found evidence to suggest there may be little difference between an immune response that kills cancer cells and one that stimulates tumor growth.

The team set out to determine whether the immune responses that mediate cancer immunosurveillance and those responsible for inflammatory facilitation are qualitatively or quantitatively distinct.

They tested antibodies in mouse models of a few different cancers, including rituximab in Burkitt lymphoma.

And they found that lower antibody concentrations stimulated tumor growth, while higher concentrations inhibited growth, and the dose range was “surprisingly narrow.”

The researchers reported these findings in a paper published in PNAS and a poster presentation at the AACR Annual Meeting 2014 (abstract 1063).

“We have found that the intensity difference between an immune response that stimulates cancer and one that kills it may not be very much,” said principal investigator Ajit Varki, MD, of the University of California, San Diego School of Medicine.

“This may come as a surprise to researchers exploring two areas typically considered distinct: the role of the immune system in preventing and killing cancers and the role of chronic inflammation in stimulating cancers. As always, it turns out that the immune system is a double-edged sword.”

The concept of naturally occurring immunosurveillance against malignancies is not new, and there is compelling evidence for it. But understanding this process is confounded by the fact that some types of immune reaction promote tumor development.

Dr Varki and his colleagues looked specifically at a non-human sialic acid sugar molecule called Neu5Gc. Previous research showed that Neu5Gc accumulates in human tumors from dietary sources, despite an ongoing antibody response against it.

The researchers deployed antibodies against Neu5Gc in a mouse tumor model to determine whether and to what degree the antibodies altered tumor progression. The team found that low antibody doses stimulated growth, but high doses inhibited it.

The effect occurred over a “linear and remarkably narrow range,” according to Dr Varki, generating an immune response curve or “inverse hormesis.” Moreover, this curve could be shifted to the left or right simply by modifying the quality of the immune response.

The researchers uncovered similar findings in experiments with mouse models of colon and lung cancer, as well as when they used rituximab in a model of Burkitt lymphoma.

Dr Varki said these results could have implications for all aspects of cancer research. The immune response can have multiple roles in the genesis of cancers, in altering the progress of established tumors and in anticancer therapies that use antibodies as drugs.

Dr Varki is a co-founder of the company Sialix, Inc., which has licensed UC San Diego technologies related to anti-Neu5Gc antibodies in cancer.

BALB/c mice

Credit: Aaron Logan

SAN DIEGO—Researchers have found evidence to suggest there may be little difference between an immune response that kills cancer cells and one that stimulates tumor growth.

The team set out to determine whether the immune responses that mediate cancer immunosurveillance and those responsible for inflammatory facilitation are qualitatively or quantitatively distinct.

They tested antibodies in mouse models of a few different cancers, including rituximab in Burkitt lymphoma.

And they found that lower antibody concentrations stimulated tumor growth, while higher concentrations inhibited growth, and the dose range was “surprisingly narrow.”

The researchers reported these findings in a paper published in PNAS and a poster presentation at the AACR Annual Meeting 2014 (abstract 1063).

“We have found that the intensity difference between an immune response that stimulates cancer and one that kills it may not be very much,” said principal investigator Ajit Varki, MD, of the University of California, San Diego School of Medicine.

“This may come as a surprise to researchers exploring two areas typically considered distinct: the role of the immune system in preventing and killing cancers and the role of chronic inflammation in stimulating cancers. As always, it turns out that the immune system is a double-edged sword.”

The concept of naturally occurring immunosurveillance against malignancies is not new, and there is compelling evidence for it. But understanding this process is confounded by the fact that some types of immune reaction promote tumor development.

Dr Varki and his colleagues looked specifically at a non-human sialic acid sugar molecule called Neu5Gc. Previous research showed that Neu5Gc accumulates in human tumors from dietary sources, despite an ongoing antibody response against it.

The researchers deployed antibodies against Neu5Gc in a mouse tumor model to determine whether and to what degree the antibodies altered tumor progression. The team found that low antibody doses stimulated growth, but high doses inhibited it.

The effect occurred over a “linear and remarkably narrow range,” according to Dr Varki, generating an immune response curve or “inverse hormesis.” Moreover, this curve could be shifted to the left or right simply by modifying the quality of the immune response.

The researchers uncovered similar findings in experiments with mouse models of colon and lung cancer, as well as when they used rituximab in a model of Burkitt lymphoma.

Dr Varki said these results could have implications for all aspects of cancer research. The immune response can have multiple roles in the genesis of cancers, in altering the progress of established tumors and in anticancer therapies that use antibodies as drugs.

Dr Varki is a co-founder of the company Sialix, Inc., which has licensed UC San Diego technologies related to anti-Neu5Gc antibodies in cancer.