Abstract 2925: Safety and efficacy of EZH2 and BRD4 dual targeting in EZH2Y641mut germinal centre-derived lymphoma

A significant proportion of diffuse large B cell lymphoma (DLBCL) and follicular lymphoma (FL) patients harbor a gain-of-function, heterozygous somatic mutations of the methyltransferase gene EZH2. Despite acceptable safety profile and early signs of activity in clinical trials, single agent treatment with EZH2 inhibitors is unlikely to be curative in aggressive lymphomas. In an effort to established novel rational combinations, we have evaluated the activity and mechanism of action of the EZH2 small molecule inhibitor CPI169 as single agent and in combination with BET bromodomain inhibition, using preclinical models of DLBCL and FL with distinct EZH2 mutational status. CPI169 anti-tumor activity and specificity was assessed in vitro in 10 DLBCL and FL cell lines, including cells expressing basal or ectopic EZH2mut. Molecular bases of its activity were determined by gene expression profiling (GEP), qPCR and western blot, followed by automated exploratory data analysis. Biomarkers validation was made in vitro and in vivo, using a mouse xenotransplant model of EZH2mut DLBCL, considering both exposure to CPI169 single agent and/or combination treatment with a BRD4 inhibitor, CPI203. CPI169 induced dose-dependent proliferation blockade in EZH2mut, but not EZH2wt DLBCL and FL cell lines, independently of EZH2 expression level or basal methyltransferase activity. Loss of H3K27me3 mark upon CPI169 treatment was associated with upregulation of gene sets related to G1 cell cycle blockade, mTOR and P53 pathways, and MYC signaling. Accordingly, combination with the MYC-interfering drug, BET inhibitor CPI203, achieved a synergistic anti-proliferating activity in EZH2 mutated cases and in mice bearing EZH2mut DLBCL tumors. Activity of EZHi/BRD4i combo was characterized by lower mitotic index, increased loss of H3K27me3 mark, in association with MYC downregulation. GEP analysis, followed by automated exploratory data analysis and validation by a siRNA screening, further identified the PI3K/AKT-regulated gene and mitosis regulator, YPEL2, and the regulator of innate-like B lymphocyte maturation, KLHL14, as crucial factors involved in the efficacy of MYC/EZH2 dual targeting. In conclusion, CPI169 shows significant activity and safety as single agent in EZH2 mutated-DLBCL and FL cases and displays synergistic interaction in vitro and in vivo with BRD4 inhibition, mediated by the modulation of a limited set of EZH2-regulated genes.

Citation Format: Aranzazu Chamorro-Jorganes, Marcelo L. Ribeiro, Nuria Profitos-Peleja, Diana Reyes-Garau, Clara Recasens-Zorzo, Juan G. Valero, Marc Armengol, Patricia Perez-Galan, Ray Butler, Antonio Postigo, Francesc Bosch, Gael Roue. Safety and efficacy of EZH2 and BRD4 dual targeting in EZH2Y641mut germinal centre-derived lymphoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2925.

Boosting γδ T cell-mediated antibody-dependent cellular cytotoxicity by PD-1 blockade in follicular lymphoma

Follicular lymphoma (FL) is a common non Hodgkin's lymphoma subtype in which immune escape mechanisms are implicated in resistance to chemo-immunotherapy. Although molecular studies point to qualitative and quantitative deregulation of immune checkpoints, in depth cellular analysis of FL immune escape is lacking. Here, by functional assays and in silico analyses we show that a subset of FL patients displays a 'high' immune escape phenotype. These FL cases are characterized by abundant infiltration of PD1⁺ CD16⁺ TCRVγ9Vδ2 γδ T lymphocytes. In a 3D co-culture assay (MALC), γδ T cells mediate both direct and indirect (ADCC in the presence of anti-CD20 mAbs) cytolytic activity against FL cell aggregates. Importantly, PD-1, which is expressed by most FL-infiltrating γδ T lymphocytes with ADCC capacity, impairs these functions. In conclusion, we identify a PD1-regulated γδ T cell cytolytic immune component in FL. Our data provide a treatment rational by PD-1 blockade aimed at boosting γδ T cell anti-tumor functions in FL.

Abstract 3288: The chemokine receptor CXCR4 and the cannabinoid receptor CB2R form heterodimers in non-Hodgkin lymphoma (NHL) and solid tumors leading to functional crosstalk

Background: A major hallmark of cancer cells, including both solid tumors and hematological neoplasias, is the ability to disseminate and generate distant/distal metastasis.Two families of proteins that play a role in dissemination and metastasis are the cannabinoid and the chemokine receptors. Moreover, cannabinoids also impair uncontrolled cancer cell growth and induce apoptosis. Both receptors are members of the G-protein coupled receptor (GPCR) super family, and may combine among themselves to generate new and unique biochemical and functional characteristics. We have focused our study in the chemokine receptor 4 (CXCR4), overexpressed in several human cancer types and associated with an aggressive phenotype, and in the cannabinoid receptor 2 (CB2R). Recently, it has been reported that CB2R forms heterodimers with different receptors such as CB1R and HER2. In the case of CB2 with HER2, the co-expression and the formation of these heterodimers correlate with poor prognosis in breast cancer.

Aim: To characterize CXCR4 and CB2 expression and heterodimer formation in non-Hodgkin lymphoma (NHL), colorectal cancer (CRC) and pancreatic cancer, together with their role in tumor cell dissemination and proliferation.

Results: We have characterized the expression of CXCR4 and CB2 in several NHL models (Chronic Lymphocytic Leukemia (CLL), Follicular Lymphoma (FL), Mantle Cell Lymphoma (MCL) and Diffuse Large B-Cell Lymphoma (DLBCL)), colorectal cancer (CRC) and in pancreatic cancer. Flow cytometry analysis showed high CXCR4 expression in most of the cell lines, while CB2R expression was moderate. Noteworthy, hypoxia increased the expression of both CXCR4 and CB2. Preliminary immunohistochemistry results using primary tumors and their matched metastasis indicate that CXCR4 and CB2R expression is heterogenous. By means of Proximity Ligation Assay (PLA), we have uncovered that the formation of CXCR4-CB2R heterodimers in NHL, CRC and pancreatic cancer models. Moreover, we have confirmed that these heterodimers modulate pathway activation and function of both receptors. In this sense, using the CRC cell line SW480 and p42/p44 ERK phosphorylation a as read-out, we have proved that CXCR4 pathway activation by its agonist CXCL12 is decreased by co-treatment with the CB2R antagonist JTE907. Conversely, CB2R activation by its agonist JWH133 is hampered by the CXCR4 antagonist AMD3100. Furthermore, CB2R blockade by JTE907 interferes with CXCL12-induced cell migration assessed by wound healing assay.

Conclusions: We have described for the first time the formation of CXCR4-CB2 heterodimers in NHL, CRC and pancreatic cancer models together with its implications in downstream receptor crosstalk and cellular function. These results establish the proof-of-concept to target CXCR4-CB2 heterodimers as a new therapeutic intervention in these neoplasias.

Citation Format: Martina Guerrero, Rosa Griera, Maria Perez, Gaël Roué, Joan Bosch, Peter J. McCormick, Jordi Camps, Patricia Perez-Galan. The chemokine receptor CXCR4 and the cannabinoid receptor CB2R form heterodimers in non-Hodgkin lymphoma (NHL) and solid tumors leading to functional crosstalk. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3288.

Abstract 5317: Preclinical evaluation of IQS019, a novel BCR kinase inhibitor, in in vitro and in vivo models of non-Hodgkin lymphoma

Constitutive activation of B-cell receptor (BCR) signaling is a hallmark of several B-cell non-Hodgkin lymphoma (B-NHL), including diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), follicular lymphoma (FL) and chronic lymphocytic leukemia (CLL). Despite the promising clinical activity of the first BCR kinase inhibitors in some of these entities, the design of new compounds is warranted to improve the survival of B-NHL patients who are poorly responsive, and/or who eventually develop resistance to current BCR-targeting therapies. In this context, we recently described the synthesis of IQS019, a 4-aminopyrido[2,3-d]pyrimidine with improved inhibition pattern against the three BCR-related kinases Lyn, Syk and Btk, when compared to reference BCR kinase inhibitors. Here, by assessing the activity of IQS019 in a panel of 21 human cell lines and 17 primary samples representative of the main B-NHL subtypes, we show that doses of IQS019 in the micromolar range allowed to a rapid and dose-dependent de-phosphorylation of both constitutive and Ig-activated Syk, Lyn and Btk in CLL, MCL, FL and DLBCL cell lines and CLL primary cultures. IQS019 treatment impairs cell proliferation and CXCL12-dependent cell migration, and leads to the induction of caspase-dependent apoptosis. Of interest, in CLL primary cells, these effects were independently of IGVH mutational status. In xenotransplant mouse models of MCL and FL, daily dosing of 2 mg/kg IQS019 for two weeks demonstrated to be safe for the animals and allowed to a 50-60% reduction in tumor outgrowth and glucose uptake, together with a 52% decrease in cell infiltration into the spleen (p < 0.05). These effects were accompanied by a significant (p < 0.05) downregulation of p-Syk, p-Lyn and p-Btk, and consequent mitotic arrest and induction of apoptosis in human malignant B cells. Altogether, these results define the BCR kinase inhibitor IQS019 as a potential candidate in antitumor therapy against a variety of B-NHL subtypes with aberrant activation of BCR pathway.

Citation Format: Patricia Balsas, Jocabed Roldan, Laura Jimenez, Vanina Rodriguez, Raimon Puig de la Bellacasa, Jordi Teixido, Alba Matas-Cespedes, Alexandra Moros, Antonio Martinez, Elias Campo, Jose I Borrell, Patricia Perez-Galan, Dolors Colomer, Gael Roue. Preclinical evaluation of IQS019, a novel BCR kinase inhibitor, in in vitro and in vivo models of non-Hodgkin lymphoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5317. doi:10.1158/1538-7445.AM2015-5317

Abstract 1691: Synergistic anti-tumor activity of lenalidomide with the BET bromodomain inhibitor CPI203 in bortezomib-resistant mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive B lymphoid neoplasm genetically characterized by the t(11;14)(q13;q32) leading to the overexpression of cyclin D1. As a consequence of its poor responses to conventional chemotherapy and relatively short patient survival, new therapeutic strategies are required. Despite the promising introduction of the proteasome inhibitor bortezomib in the treatment of MCL, not all the patients respond and relapse frequently occurs. To unravel the factors involved in the acquisition of bortezomib resistance in vivo, immunodeficient mice were engrafted with a set of MCL cell lines with different levels of sensitivity to the drug, followed by gene expression profiling of the tumors and functional validation of the identified gene signatures. We observed an increased tumorigenicity of bortezomib-resistant MCL cells in vivo, that was associated with plasmacytic differentiation features, like IRF4 and Blimp-1 upregulation. As the immunomoduladory drug lenalidomide has been shown to modulate IRF4 expression in various B-cell malignancies, we assessed its activity in in vitro and in vivo settings by means of flow cytometry, western blot, antibody array, real-time PCR, immunofluorescence, in vivo imaging, and immunohistochemistry. In vitro, lenalidomide as single agent was found to exert antitumor activity in 4/11 MCL cell lines, corresponding to those cells with either primary or acquired resistance to bortezomib. Lenalidomide-treated cells showed decreased IRF4 expression, increased cytosolic amounts of p27 and caspase-dependent apoptosis. Accordingly, mice bearing bortezomib-resistant tumors and treated for 3 weeks with a lenalidomide regimen of 10-50 mg/kg/day, showed a 30 to 45% reduction in tumor burden when compared to vehicle-treated mice (p=0.04), with several hallmarks of lenalidomide activity, like downregulation of IRF4 and its target gene MYC, decreased mitotic index, p27 cytosolic accumulation and caspase-3 processing. Importantly, the inhibition of tumor growth induced by the combination of lenalidomide with bortezomib (0.15 mg/kg, twice a week) was 37% and 66% greater than that for lenalidomide alone and vehicle arms, respectively (p=0.02). Moreover, repression of MYC in bortezomib-resistant cells by gene knockdown or treatment with CPI203, a BET bromodomain inhibitor, synergistically induced cell death when combined with lenalidomide therapy. Accordingly, co-treatment of mice with lenalidomide plus CPI203 synergistically reduced MYC and IRF4 expression and tumor burden, and induced caspase processing. Together, these results suggest that exacerbated IRF4/MYC signaling is associated to bortezomib resistance in MCL in vivo and warrant clinical evaluation of lenalidomide plus BET inhibitor combination in MCL cases refractory to proteasome inhibition.

Citation Format: Alexandra Moros, Vanina Rodriguez, Ifigenia Saborit-Villarroya, Arnau Montraveta, Patricia Balsas, Peter Sandy, Antonio Martinez, Emmanuel Normant, Patricia Perez-Galan, Elias Campo, Dolors Colomer, Gael Roue. Synergistic anti-tumor activity of lenalidomide with the BET bromodomain inhibitor CPI203 in bortezomib-resistant mantle cell lymphoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1691. doi:10.1158/1538-7445.AM2014-1691

Abstract 993: Upregulation of B-cell activation genes and negative regulators of apoptosis determines resistance to bendamustine in chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia (CLL), the most common leukemia in Western countries, is characterized by the accumulation of monoclonal CD5+ B cells in the blood, bone marrow, lymph nodes, spleen and other lymphoid organs. Bendamustine hydrochloride, a cytotoxic agent comprising structural features of both an alkylating drug and a purine nucleoside analog, was recently approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of CLL and indolent B cell non-Hodgkin's lymphoma (NHL). Although several recent clinical trials have documented the activity of bendamustine in CLL, the mechanisms of bendamustine resistance in CLL cells have not been yet elucidated.

We analyzed the ex vivo cytotoxicity of bendamustine in cells from 48 CLL cases by incubating them with bendamustine 25 μM for 24 hours. Cell death was assessed by annexinV-PI labeling and cases were classified as bendamustine-resistant (cytotoxicity below 30%) or bendamustine-sensitive (cytotoxicity over 30%) cases. We found that sensitivity of CLL primary cells correlated with the mutational status of IGHV gene, being the IGHV-unmutated cases significantly more resistant to bendamustine (p<0.015) than those cases with mutated IGHV. Although the number of cases analyzed was low, no correlation with the mutational status of NOTCH1 or SF3B1 was observed.

We compared the gene expression profiling of bendamustine-resistant and bendamustine-sensitive groups by performing a high-throughput analysis of basal gene expression in CLL cells with the U219 Affymetrix array. After a supervised analysis using the Rank Products method and a FDR below 0.001, we observed 393 up-regulated genes and 415 down-regulated genes in the bendamustine-resistant group. Annotation of the differentially expressed genes identified some well-known markers of prognosis in CLL, together with genes related to apoptosis regulation and B cell activation. One of the genes with a highest positive fold-change and most relevant according to its role in cell cycle progression, apoptosis and transformation was C-MYC.

These results suggest that overexpression of genes related to proliferation and B-cell activation could be involved in CLL resistance to bendamustine therapy, which is known to be clinically more effective in indolent than in aggressive lymphomas. Further studies will assess whether this set of overexpressed genes might be useful as biomarkers to predict the sensitivity to bendamustine and open the door to new combinatorial strategies that might overcome resistance to bendamustine in CLL patients within the context of tailored medicine

Citation Format: Eriong Lee-Verges, Arnau Montraveta, Magda Pinyol, Pedro Jares, Cristina Arimany-Nardi, Marta Aymerich, Neus Villamor, Marçal Pastor-Anglada, Armando Lopez-Guillermo, Patricia Perez-Galan, Gael Roue, Elias Campo, Dolors Colomer. Upregulation of B-cell activation genes and negative regulators of apoptosis determines resistance to bendamustine in chronic lymphocytic leukemia cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 993. doi:10.1158/1538-7445.AM2013-993

Abstract 2088: NVP-BKM120 decreases cell survival and antagonizes resistance signals derived from protective tissue microenvironment by interfering with the Akt/FoxO3a/Bim axis in CLL cells

Phosphatidylinositol-3-kinase (PI3K) pathway is a key component of many cancers survival. Particularly, PI3K is constitutively activated in chronic lymphocytic leukemia (CLL) due to microenvironment signals, including stromal cell interaction, CXCR4 activation and B-cell receptor (BCR) triggering. Because of the importance of PI3K for CLL-microenvironment cross-talk and chemotherapy resistance, we investigated the activity of the NVP-BKM120, an orally available pan class I PI3K inhibitor.

Here, we show that NVP-BKM120 promoted mitochondrial apoptosis in primary CLL cells independently of common prognostic markers. At the molecular level, NVP-BKM120 blocked PI3K signalling, resulting in decreased phosphorylation of Akt and FoxO3a while downregulating Mcl-1 and inducing Bim. Importantly, selective knockdown of BIM rescued cells from NVP-BKM120-induced apoptosis. Moreover, NVP-BKM120 enhanced the activity of the BH3-mimetic ABT263 in CLL cells, leading to synergistic apoptosis induction. We also found that NVP-BKM120 inhibited BCR- and stromal-induced Akt activation as well as induced Bim in presence of BCR-derived and stromal survival signals. In stromal cocultures, NVP-BKM120 sensitized CLL cells towards bendamustine and fludarabine. Furthermore, NVP-BKM120 downregulated secretion of chemokines after BCR triggering and inhibited CLL cell chemotaxis and actin polymerization toward CXCL12.

Altogether, our data suggest that NVP-BKM120 displays a dual mechanism of action, directly decreasing cell survival and antagonizing survival and drug-resistance signals derived from protective tissue microenvironment.

Citation Format: Laia Rosich, Ifigenia Saborit-Vilarroya, Monica Lopez-Guerra, Silvia Xargay-Torrent, Arnau Montraveta, Marta Aymerich, Neus Villamor, Elias Campo, Patricia Perez-Galan, Gael Roue, Dolors Colomer. NVP-BKM120 decreases cell survival and antagonizes resistance signals derived from protective tissue microenvironment by interfering with the Akt/FoxO3a/Bim axis in CLL cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2088. doi:10.1158/1538-7445.AM2013-2088

Abstract 1942: Activity of lenalidomide in vitro and in vivo models of bortezomib-resistant mantle cell lymphoma involving the modulation of c-myc/p27 axis

Mantle cell lymphoma (MCL) is an aggressive B lymphoid neoplasm genetically characterized by the t(11;14)(q13;q32) leading to the overexpression of cyclin D1. As a consequence of its poor responses to conventional chemotherapy and relatively short patient survival, new therapeutic strategies are required. Despite the promising introduction of the proteasome inhibitor bortezomib in the clinical practice, not all the patients respond and relapse frequently occurres after initial response. When comparing the behavior of both bortezomib-resistant and bortezomib-sensitive cell lines in a xenotransplant mouse model, we observed an increased tumorigenecity of bortezomib-resistant cells in vivo, suggesting a major capacity of these tumors to interact with lymphoid microenvironment. As the immunomoduladory drug lenalidomide has been shown to modulate tumor-stroma interaction in several B cell malignancies, we assessed the activity in vitro and in vivo of this agent either alone or combined with the proteasome inhibitor in both bortezomib-resistant and bortezomib-sensitive samples. Lenalidomide single agent was found to exert modest antitumoral activity in 2/10 MCL cell lines, corresponding to those cells with either primary or acquired resistance to the proteasome inhibitor. Conversely, mice bearing bortezomib-resistant tumors and treated for 3 weeks with a 10-50 mg/kg/day regimen of lenalidomide, showed a 30 to 45% reduction in tumor burden when compared to vehicle-treated group (p<0.05). The corresponding biopsies harbored several hallmarks of lenalidomide activity in malignant B cells such as CD80 and CD40L upregulation, together with a remarkable decrease in mitotic index, c-myc down-regulation, p27 cytosolic accumulation and caspase-3 processing. Similarly, bortezomib-resistant MCL cell lines treated for 72h with 1 microM lenalidomide showed lower c-myc levels, as well as p27 accumulation, caspase-3/7 activity and apparition of hypodiploid cells. When combined to bortezomib therapy (0.15 mg/kg, twice a week), lenalidomide induced a 37% and a 66% inhibition of tumor growth when compared to lenalidomide and vehicle groups, respectively (p=0.02). In accordance, lenalidomide showed synergistic effect in vitro with bortezomib in co-culture system associating the MCL cell line Jeko-1 to the dendritic-like cells BDCM, by modifying the secretion pattern of these latest. Altogether, these results suggest that single agent lenalidomide is preferentially effective in MCL cases resistant to bortezomib, by targeting c-myc-driven tumorigenesis. Additionally, lenalidomide may overcome the protection offered by lymphoid tumor microenvironment toward bortezomib treatment, thus warranting a promising clinical activity of lenalidomide-bortezomib combination in MCL cases refractory to bortezomib.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1942. doi:1538-7445.AM2012-1942

Abstract LB-361: The novel PI3K kinase inhibitor NVP-BKM120 shows in vitro and in vivo efficacy in follicular Lymphoma by disrupting microenvironment survival signaling

Follicular lymphoma (FL) is the second most common B- cell non Hodgkin Lymphoma and is characterized by the t(14;18)(q32;q21), leading to over expression of Bcl-2. However, this genetic alteration is not sufficient for tumor development and progression, and it is accepted FL pathogenesis as the result of a functional cross talk between the genetic alterations and the influence of its immune microenvironment in the bone Marrow (BM) and lymph nodes (LN). Although FL is an indolent tumor, up to one-third of cases can progress to a more aggressive disease leading to short survival. The immune microenvironment in the LN plays an important role in tumor development and progression and two outcome-related signatures IR1 and IR2, have been identified by gene expression profiling. IR1, composed of genes expressed by T-cells associated with a more favorable clinical course, and IR2, enriched for genes expressed by macrophages and follicular dendrytic cells (FDC) associated with an inferior clinical course. Recently, PI3K has become an attractive target in cancer therapy. In FL, PI3K/AKT pathway is constitutive activated as a consequence of survival signals coming from tumor microenvironment through cytokine/chemokine secretion (IL4/IL4R, CXCR4/CXCL12) and ligand-receptor interactions that include B-cell receptor (BCR) and CD40/CD40L.Thus, we have evaluated the potential interest of the novel and specific PI3K inhibitor NVP-BKM120 (Novartis) as a new therapy in FL. We found that NVP-BKM120 induces variable cytotoxic and cytostatic effect in FL cell lines, and limited toxicity in FL primary samples (10-20%) in accordance with results with other specific PI3K inhibitors in different models. NVP-BKM120 efficiently blocks constitutive activation of PI3K/AKT pathway in FL cells, and completely abrogates AKT activation derived from co-culture with BM stromal cells or FDCs or consequent to BCR ligation. NVP-BKM120 interferes with tumor cell-microenvironment interactions by blocking SDF1α/CXCL12-induced migration and significantly reduces the secretion of several cytokines (p<0.01), including GM-CSF, G-CSF, CCL2, CCL7, CCL8, IL1, IL7, IL8 and IL10 in a FL-FDC co-culture model. Finally, we have evaluated the in vivo efficacy of this compound in a xenograft mouse model (subcutaneous injection of the FL cell line RL), and NVP-BKM120 reduced tumor size by 35%. Immunohistochemistry analysis revealed a marked decreased in the expression of pAKT and its downstream target pS6rp in tumors from NVP-120-treated mice. These results warrant further studies of NVP-BKM120 in FL. We are now trying to increase its therapeutic index by combination with the BH3-mimetic ABT-263 which is able to antagonize the over expression of Bcl-2, not affected by NVP-BKM120 action, or anti-CD20 antibodies, commonly present in FL current regimens.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-361. doi:1538-7445.AM2012-LB-361

Treatment-induced oxidative stress and cellular antioxidant capacity determine response to bortezomib in mantle cell lymphoma

PURPOSE

Proteasome inhibition disrupts protein homeostasis and induces apoptosis. Up to 50% of patients with relapsed mantle cell lymphoma (MCL) respond to bortezomib. We used gene expression profiling to investigate the connection between proteasome inhibition, cellular response, and clinical efficacy.

EXPERIMENTAL DESIGN

We assessed transcriptional changes in primary tumor cells from five patients during treatment with bortezomib in vivo, and in 10 MCL cell lines exposed to bortezomib in vitro, on Affymetrix microarrays. Key findings were confirmed by western blotting.

RESULTS

MCL cell lines exposed to bortezomib in vitro showed upregulation of endoplasmic reticulum and oxidative stress response pathways. Gene expression changes were strongest in bortezomib-sensitive cells and these cells were also more sensitive to oxidative stress induced by H2O2. Purified tumor cells obtained at several timepoints during bortezomib treatment in 5 previously untreated patients with leukemic MCL showed strong activation of the antioxidant response controlled by NRF2. Unexpectedly, activation of this homeostatic program was significantly stronger in tumors with the best clinical response. Consistent with its proapoptotic function, we found upregulation of NOXA in circulating tumor cells of responding patients. In resistant cells, gene expression changes in response to bortezomib were limited and upregulation of NOXA was absent. Interestingly, at baseline, bortezomib-resistant cells displayed a relatively higher expression of the NRF2 gene-expression signature than sensitive cells (P < 0.001).

CONCLUSION

Bortezomib triggers an oxidative stress response in vitro and in vivo. High cellular antioxidant capacity contributes to bortezomib resistance.

Abstract 3493: ON 01910. Na, a clinical trial stage multi-kinase inhibitor, induces apoptosis in chronic lymphocytic leukemia (CLL) cells through inhibition of PI3K/AKT and activation of the JNK pathway resulting in NOXA and BIM upregulation

Chronic Lymphocytic leukemia (CLL), the most common leukemia in Western countries, is a clinically heterogeneous disease characterized by the accumulation of mature B lymphocytes, where disease progression is driven by survival and proliferation signals provided by the tumor microenvironment. ON 01910. Na (Onconova Therapeutics) belongs to the family of styryl benzyl sulfones, a novel family of non-ATP competitive kinase inhibitors. ON 01910. Na is under clinical development in hematologic and solid tumors. Here we show that ON 01910. Na induced apoptosis in CLL samples (n=28) in vitro, without showing significant toxicity against T-cells or normal B-cells. Twenty four CLL samples were highly sensitive to ON 01910. Na (mean IC50=0.89 μM) a concentration readily achieved in phase I clinical trials, three showed moderate sensitivity (mean IC50=4.26 μM) and one was resistant (IC50 &gt;8 μM). There were no significant differences in ON01910. Na cytotoxicity against CLL cells expressing mutated (mean IC50=1.33 μM) or unmutated (mean IC50 =1.22μM) IgVH sequences. ON 01910. Na was similarly effective against tumor cells carrying 17p or 11q deletions. ON 01910. Na activated Bax and Bak, leading to mitochondrial depolarization. To delineate the upstream pathways underlying ON 01910. Na induced apoptosis, we performed Gene Expression Profiling (GEP) in CLL cells treated in vitro for 4 and 10 hours with ON 01910. Na. Gene Set Enrichment Analysis (GSEA) identified gene sets indicating BCR and PI3K inhibition (FDR&lt;0.2). In keeping with PI3K inhibition, we found that ON 19010. Na inhibited phosphorylation of Akt and Foxo3a, and FOXO3 target genes, including Bim, were upregulated. In addition, GSEA identified induction of AP-1 gene sets (FDR&lt;0.01) suggesting the generation of reactive oxygen species (ROS) by ON 01910. Na. Consistently, we found a rapid increase in ROS in cells treated with ON 01910. Na and ROS scavengers protected cells from its cytotoxic effect. ROS upregulated the proapoptotic BH3-only protein Noxa, and knockdown of Noxa by shRNA decreased the sensitivity to the drug by 60%. Our results identify ON 01910. Na as a promising agent in the treatment of CLL with an interesting dual mechanism of action: inhibition of the PI3K/AKT survival pathway with Foxo mediated upregulation of BIM and the induction of oxidative stress resulting in Noxa upregulation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3493.