CARD11 gain of function upregulates BCL2A1 expression and promotes resistance to targeted therapies combination in B-cell lymphoma

A strategy combining targeted therapies is effective in B-cell lymphomas (BCL), such as mantle cell lymphoma (MCL), but acquired resistances remain a recurrent issue. In this study, we performed integrative longitudinal genomic and single-cell RNA-sequencing analyses of patients with MCL who were treated with targeted therapies against CD20, BCL2, and Bruton tyrosine kinase (OAsIs trial). We revealed the emergence of subclones with a selective advantage against OAsIs combination in vivo and showed that resistant cells were characterized by B-cell receptor (BCR)-independent overexpression of NF-κB1 target genes, especially owing to CARD11 mutations. Functional studies demonstrated that CARD11 gain of function not only resulted in BCR independence but also directly increased the transcription of the antiapoptotic BCL2A1, leading to resistance against venetoclax and OAsIs combination. Based on the transcriptional profile of OAsIs-resistant subclones, we designed a 16-gene resistance signature that was also predictive for patients with MCL who were treated with conventional chemotherapy, underlying a common escape mechanism. Among druggable strategies to inhibit CARD11-dependent NF-κB1 transduction, we evaluated the selective inhibition of its essential partner MALT1. We demonstrated that MALT1 protease inhibition led to a reduction in the expression of genes involved in OAsIs resistance, including BCL2A1. Consequently, MALT1 inhibition induced synergistic cell death in combination with BCL2 inhibition, irrespective of CARD11 mutational status, both in vitro and in vivo. Taken together, our study identified mechanisms of resistance to targeted therapies and provided a novel strategy to overcome resistance in aggressive BCL. The OAsIs trial was registered at www.clinicaltrials.gov #NCT02558816.

Abstract 2981: Loss of the small GTPase RHOA enhances lymphomagenesis and impairs the activity of lenalidomide in mantle cell lymphoma

The small GTPase Ras homolog family member A (RHOA) is one of the most extensively investigated members of the Rho GTPase family, that acts as a molecular switch controlling a wide variety of signal transduction pathways. Although RHOA has long been implicated in malignant transformation in solid tumors, recent evidences have demonstrated its tumor suppressor activity in different subgroups of B-cell non-Hodgkin lymphoma (B-NHL). Here, using a panel of 11 cell lines covering the most common and/or aggressive B-NHL subtypes, we observed that the lowest mRNA and protein levels of RHOA are found in mantle cell lymphoma (MCL), the most aggressive entity with a median overall survival of 5-7 years. Depletion of RHOA expression and activity was carried out in the two RHOA+ MCL cell lines, REC-1 and Z-138, by CRISPR/Cas9-mediated gene edition followed by RHOA pulldown activation assay. In RHOA knockout (KO) subclones, cell proliferation was increased by 40%, in association with a 10-fold increase in mitotic index and a 3-fold potentiation of cell migration, as assessed respectively by CellTitter-Glo assay, histone H3-pSer10 labeling and Transwell assay, thus suggesting a tumor suppressor role of RHOA in MCL malignancy. Comparative RNA-seq analysis of RHOAWT and RHOAKO MCL subclones then highlighted a crucial role of RHOA and its downstream signaling in the control of MCL cell proliferation, cell cycle and cell migration. Interestingly, the immunomodulatory drug lenalidomide has previously shown to regulate such processes and to be clinically active in patients with relapsed/refractory MCL. In a co-culture system associating RHOAWT MCL cells with peripheral blood-derived effector cells, we observed that lenalidomide treatment facilitated the formation of immunological synapse, as revealed by simultaneous immunodetection of effector T cells, target B cells and perforin, and by quantification of lactate dehydrogenase (LDH) release. Conversely, lenalidomide exhibited minimal effect in the RHOAKO MCL co-cultures, as shown by a 30-40% decrease in the formation of immune synapse and a 4-fold decrease in LDH secretion. Taken together, these data provide the first insight into the tumor suppressive activity of RHOA in MCL and into its requirement for the immune-mediated mechanism of action of lenalidomide in this disease. Ongoing in vivo validation studies will be presented.

Citation Format: Juliana C. Santos, Marcelo L. Ribeiro, Gael Roue. Loss of the small GTPase RHOA enhances lymphomagenesis and impairs the activity of lenalidomide in mantle cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2981.

Abstract 2205: TG-1701, a novel irreversible Bruton's kinase (BTK) inhibitor, cooperates with ublituximab-driven ADCC and ADCP in in vitro and in vivo models of ibrutinib-resistant mantle cell lymphoma

Mantle cell lymphoma (MCL) is a rare subtype of aggressive B-cell non-Hodgkin lymphoma (NHL) that remains incurable with standard therapy. The first-in-class Bruton's tyrosine kinase (BTK) inhibitor ibrutinib has proven to be an effective agent for patients with relapsed/refractory MCL, although development of a cysteine to serine mutation at the BTK catalytic site (BTKC481S) or over-activation of the NF-kB pathway can impair MCL response to most BTK inhibitors (BTKis). TG-1701 is a novel irreversible inhibitor highly specific to BTK, with improved selectivity when compared to ibrutinib, currently being evaluated in a phase 1 clinical trial in non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) patients. Here we show that, when compared to irreversible and reversible BTKis including ibrutinib, acalabrutinib, and ARQ-531, TG-1701 showed similar cytotoxic activity either in ibrutinib-sensitive or in ibrutinib-resistant MCL cells. We then evaluated the activity of TG-1701 and ibrutinib on anti-CD20 antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP), as ibrutinib has previously been show to block rituximab-mediated ADCC due to off-target inhibition of ITK (Kohrt et al., Blood 2014). In sharp contrast with ibrutinib, which partially antagonized rituximab activity, we found that TG-1701 did not impair the anti-CD20-mediated ADCC and ADCP in a multicellular co-culture system that associated MCL to effector cells. In another set of cell-based assays, we showed that the treatment with TG-1701 led to a strong decrease in IL-10 expression, together with a significant increase in IL-2, IL-6 and IL1RN gene transcription, thus associating TG-1701 exposure with the promotion of an immune response within the tumor microenvironment (TME). Accordingly, TG-1701 cooperated with the novel anti-CD20 antibody ublituximab and the novel PI3Kδ-CK1ϵ dual inhibitor umbralisib in reducing the tumor growth in both ibrutinib-sensitive (REC1) and ibrutinib-resistant (UPN-1res) mouse models of MCL. In accordance with in vitro data, the antitumor activity of the drug combination was associated with increased production of IL-2, IL-6 and TNFα, and with an increased infiltration of mouse macrophages and NK cells. Altogether, these data warrant further clinical investigation of TG-1701-mediated engagement of TME-related anti-tumor effect, and clinical evaluation of the triple combination of TG-1701, ublituximab, and umbralisib, is ongoing.

Citation Format: Marcelo L. Ribeiro, Diana Reyes-Garau, Meritxell Vinyoles, Marc Armengol, Hari Miskin, Francesc Bosch, Pablo Menendez, Emmanuel Normant, Gael Roue. TG-1701, a novel irreversible Bruton's kinase (BTK) inhibitor, cooperates with ublituximab-driven ADCC and ADCP in in vitro and in vivo models of ibrutinib-resistant mantle cell 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 2205.

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.

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

In vivo intratumoral Epstein-Barr virus replication is associated with XBP1 activation and early-onset post-transplant lymphoproliferative disorders with prognostic implications

Post-transplant lymphoproliferative disorders are life-threatening complications following hematopoietic or solid organ transplantation. They represent a spectrum of mostly EBV-driven lymphoplasmacytic proliferations. While the oncogenic effect of EBV is related to latent infection, lytic infection also has a role in lymphomagenesis. In vitro, EBV replication is linked to plasma cell differentiation and XBP1 activation, although this phenomenon has never been addressed in vivo. We analyzed for the first time latent and lytic intratumoral EBV infection in a series of 35 adult patients with a diagnosis of post-transplant lymphoproliferative disorder (26M/9F, median age 54 years). A complete EBV study was performed including the analysis of the latent EBER, latent membrane protein-11, and EBV nuclear antigens as well as the immediate-early BZLF1/ZEBRA and early BMRF1/EADE31 lytic genes. XBP1 activation was assessed by nuclear protein expression. EBV infection was observed in 28 (80%) cases being latency II and III the most frequently observed 22 (79%). Intratumoral EBV replication was detected in 17 (60%) cases. Among these, XBP1 activation was observed in 11/12 evaluable cases associated with strong cytoplasmic immunoglobulin expression consistent with plasma cell differentiation. Intriguingly, the combination of latency III infection and EBV replication identified a high-risk subgroup of patients with significantly shorter survival (overall survival at 1 year 18% vs 48%) and early-onset (median of 7 vs 26 months) post-transplant lymphoproliferative disorder. Moreover, these patients appear to be more heavily immunosuppressed, so they exhibit lower rates of rejection and graft vs host disease but higher rates of cytomegalovirus reactivation. In conclusion, EBV replication is associated with plasma cell differentiation and XBP1 activation with prognostic implications. Both latency III and lytic EBV infection are related to aggressive and early-onset post-transplant lymphoproliferative disorder. These results suggest that immunohistochemical study of latent and lytic EBV genes in the clinical practice may help to select higher-risk patients to new therapies including antiviral treatments.

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

Autophagy controls everolimus (RAD001) activity in mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive neoplasm, which lacks effective therapy. The mechanistic target of rapamycin (MTOR) kinase inhibitor everolimus (RAD001) has shown activity in preclinical and clinical models of MCL, despite the fact that its mechanism of action has not been fully elucidated. We found that everolimus activity in MCL cells is closely linked to AKT phosphorylation status, and that the prevention of AKT rephosphorylation upon everolimus treatment by means of a selective AKT inhibitor, greatly enhances everolimus activity. Furthermore, our data show that an accumulation of autophagic vacuoles correlates with a lack of efficacy of dual AKT-MTOR targeting and that the complete therapeutic potential of this strategy can be restored by ATG gene selective knockdown or secondary inhibition of autolysosome formation by hydroxychloroquine. We thus demonstrated for the first time that the use of an autophagy inhibitor can overcome resistance to the combination of MTOR and AKT inhibitors in MCL cell lines and primary samples, demonstrating the prosurvival role of autophagy in AKT-MTOR compromised cells, and pointing out some potential opportunities using this triple combinational strategy in hematological malignancies.

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

Abstract C72: Counteracting autophagy allows to overcome resistance to the mTOR everolimus in mantle cell lymphoma

Background: Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoid neoplasm genetically characterized by the t(11;14)(q13;q32) leading to the overexpression of cyclin D1, which causes cell cycle deregulation at the G1-S phase transition. As a consequence of its poor response to conventional chemotherapy and relatively short patient survival, new therapeutic strategies are required.

The phosphatidylinositol 3-kinase/Akt/mTOR survival pathway is constitutively activated in MCL, thereby making the mTOR inhibition a very attractive strategy for its treatment. The first clinical studies conducted in relapsed MCL patients have reported a significant, but relative short duration of response to the oral rapamycin derivative everolimus (RAD001). In this context, our aim was to analyze the mechanism of action related to resistance/sentitivity of this drug in MCL cells, and to propose further combination strategies.

Methods: The sensitivity to everolimus was analyzed in MCL primary cultures, MCL cell lines and peripheral blood lymphocytes from healthy donors. Cells were treated for up to 72h with increasing doses of everolimus, followed by cytotoxicity quantification, cell-cycle determination and western blot analysis of the PI3K/Akt/mTOR pathway. Autophagy was studied by LC3I/II expression and Cell-ID™ Green staining of autophagolysosomes by flow cytometry and fluorescence microsopy.

Results: Everolimus exerted heterogeneous antitumoral effect on MCL cells, while sparing normal cells. This effect was associated with G1 cell-cycle arrest and reduced phosphorylation of the mTOR downstream targets, 4E-BP1 and S6. However, Akt re-phosphorylation was observed after 48h of everolimus treatment, suggesting feedbacks loops within the mTOR signaling pathway. Accordingly, everolimus combination studies with the Akt inhibitor VIII, isozyme-selective (Akti-1/2) showed synergistic cytotoxic effect in MCL cells and overcame Akt mechanism of resistance in a sub-set of MCL samples. When compared to these samples, increased levels of autophagic hallmarks such as autophagic vacuoles and LC3 processing were found in everolimus/Akti-1/2 low-responsive cells. In these cells, the combination with the autophagy inhibitor hydroxychloroquine overcame the resistance to mTOR/Akt inhibitors, and efficiently induced apoptosis, thus suggesting a prosurvival role of autophagy.

Conclusions: This study suggests that targeting autophagy as anticancer therapy may represent an attractive sensitizing strategy for everolimus-based therapy in MCL.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C72.

Abstract A209: The nucleoside analogue acadesine exerts antitumoral activity and cooperates with anti-CD20 monoclonal antibodies in in vitro and in vivo models of mantle cell lymphoma

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm characterized by the t(11;14)(q13:q32) that involves cyclin D1 overexpression and consequent cell cycle deregulation at the G1 phase. This entity is generally characterized by an aggressive course and a bad prognosis. Recently, a specific subtype of MCL has been described, showing best outcomes and that might be managed more conservatively than conventional MCL. These cases are characterized by non-nodal presentation, predominantly hypermutated IgVH, lack of genomic complexity, and absence of SOX11 expression. Acadesine is a nucleoside analogue initially developed as a cardioprotective agent, and which has shown a wide range of metabolic effects, including the activation of AMP-activated protein kinase (AMPK). Acadesine was shown to induce apoptosis in primary cells from several B lymphoid neoplasms and has been entered in a phase I/II clinical trial with relapsed/refractory chronic lymphocytic leukemia (CLL) patients. This clinical study has shown that acadesine plasmatic levels in the micro molar range are achievable and safe when CLL patients are treated with the drug. To evaluate the antitumoral properties of acadesine in MCL, we exposed a set of 11 MCL primary cultures and 9 MCL cell lines for up to 48h with increasing doses of the drug. Cytotoxicity and cytostatic effects were then assessed by flow cytometry detection of annexinV/propidium iodide labeling and MTT proliferation assay, respectively. In both MCL cell lines and MCL primary cultures, we observed a heterogeneous response to the drug, with no correlation to common genetic alterations such as deletion/mutation of P53, ATM or P16 genes. Rec-1, Jeko-1, UPN-1 and JVM-2 were the more sensitive cell lines, with a mean lethal dose 50 (LD50 of 1.57 mM at 24 h and 0.95 mM) at 48h, while 2 cell lines (HBL-2 and Granta-519) showed resistance to the compound (LD50 > 50 mM). Among MCL primary cultures, acadesine showed selective cytotoxic activity against malignant B cells while sparing accompanying T cells at pharmacologically achievable doses. Of note, those cases corresponding to the indolent MCL group showed increased sensitivity to the drug at 24h of treatment, when compared to conventional MCL cases (p=0.03). We observed that acadesine efficiently activates the intrinsic apoptotic pathway in MCL cells by reducing Mcl-1 levels, leading to conformational activation of Bax and Bak, mitochondrial depolarization, generation of reactive oxygen species and caspases processing. In drug combination assays, acadesine showed a synergistic effect when combined with the CD20 monoclonal antibody Rituximab. Finally, SCID mice were subcutaneously inoculated with 107 Jeko-1 cells. At day 12 post-inoculation, mice were randomized and administered for 18 days with either 400 mg/kg acadesine 5 days weekly, Rituximab 10mg/kg weekly, both drugs or vehicle. The combination was significantly more effective than Rituximab or Acadesine monotherapy (P < 0.01). In summary, these results suggest that acadesine exerts significant antitumoral activity in both in vitro and in vivo model of MCL, while its combination with CD20 monoclonal antibodies may represent a new therapeutic approach for this entity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A209.

Abstract 2623: Induction of Bmf and Bim in Vorinostat-induced apoptosis in mantle cell lymphoma

OBJECTIVES: Mantle cell lymphoma (MCL) is an incurable B-cell neoplasm harboring the t(11;14)(q13;q32) which leads to the overexpression of cyclin D1, with the consequent cell cycle deregulation. Usually, MCL is characterized by bad prognosis and an aggressive course of the disease. Current therapies have shown limited efficacy. Recently, Histone Deacetylase Inhibitors (HDACis) have been successfully introduced for the treatment of several cancers, including hematological malignancies. Accordingly, tumor suppressor genes are frequently epigenetically silenced in these entities, due to histone deacetylation in their promoters. Therefore, our purposes were to evaluate the antitumoral properties of the HDACi suberoylanilide hydroxamic acid (Vorinostat; Merck & Co) in MCL, and to describe the molecular mechanisms involved in HDACi signaling in this disorder.

METHODS: MCL cell lines and primary MCL cells were used. HDAC activity was measured using a colorimetric HDAC Assay Kit. Flow cytometry was used to determine sensitivity to Vorinostat through measurement of AnnexinV binding, and to analyze apoptosis features. Vorinostat anti-tumoral signaling was evaluated by RQ-PCR determination of gene transcription, western blot analysis and acetyl Histone H4 ChIP assays.

RESULTS: Vorinostat exhibited a heterogeneous cytotoxic effect among MCL cell lines, with a median LD50 of 6.6 μM after 24-hour incubation. Nevertheless, cytotoxicity increased notably after 48h of exposure to the drug with LD50 ranging from 0.4 to 5.3 μM. Interestingly, 7 out of the 10 MCL primary samples tested were extremely sensitive to the compound (with a median LD50 of 2.2 μM after 24-hour incubation). Vorinostat increases the acetylation of H3 and H4 histones, as well as inhibits global HDAC activity in just 1 hour of incubation. The drug notably decreases cyclin D1 protein levels while induces upregulation of the proapoptotic BH3-only proteins Bmf and Bim, triggering the mitochondria-dependent cell death and activation of the caspases cascade. Acetyl Histone H4 ChIP assays showed that Vorinostat increases acetylation of BMF and BIM gene promoters, consequently up regulating Bim and Bmf mRNA levels.

CONCLUSIONS: This study suggests that Vorinostat could define a new and attractive therapeutic approach for the treatment of MCL. We identify BMF and BIM as possible crucial target genes of HDAC inhibitors in MCL cells, promoting the induction of mitochondria-mediated apoptosis.

GRANTS: This work is supported by Ministerio de Ciencia e Innovación SAF 06-8850; S. X-T is a fellow from Ministerio de Ciencia e Innovación (FPU predoctoral fellowship).

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 2623.