Pharmacological modulation of CXCR4 cooperates with BET bromodomain inhibition in diffuse large B-cell lymphoma

Constitutive activation of the chemokine receptor CXCR4 has been associated with tumor progression, invasion, and chemotherapy resistance in different cancer subtypes. Although the CXCR4 pathway has recently been suggested as an adverse prognostic marker in diffuse large B-cell lymphoma, its biological relevance in this disease remains underexplored. In a homogeneous set of 52 biopsies from patients, an antibody-based cytokine array showed that tissue levels of CXCL12 correlated with high microvessel density and bone marrow involvement at diagnosis, supporting a role for the CXCL12-CXCR4 axis in disease progression. We then identified the tetra-amine IQS-01.01RS as a potent inverse agonist of the receptor, preventing CXCL12-mediated chemotaxis and triggering apoptosis in a panel of 18 cell lines and primary cultures, with superior mobilizing properties in vivo than those of the standard agent. IQS-01.01RS activity was associated with downregulation of p-AKT, p-ERK1/2 and destabilization of MYC, allowing a synergistic interaction with the bromodomain and extra-terminal domain inhibitor, CPI203. In a xenotransplant model of diffuse large B-cell lymphoma, the combination of IQS-01.01RS and CPI203 decreased tumor burden through MYC and p-AKT downregulation, and enhanced the induction of apoptosis. Thus, our results point out an emerging role of CXCL12-CXCR4 in the pathogenesis of diffuse large B-cell lymphoma and support the simultaneous targeting of CXCR4 and bromodomain proteins as a promising, rationale-based strategy for the treatment of this disease.

The BET bromodomain inhibitor CPI203 overcomes resistance to ABT-199 (venetoclax) by downregulation of BFL-1/A1 in in vitro and in vivo models of MYC+/BCL2+ double hit lymphoma

High-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements, mostly known as double-hit lymphoma (DHL), is a rare entity characterized by morphologic and molecular features between Burkitt lymphoma and the clinically manageable diffuse large B-cell lymphoma (DLBCL). DHL patients usually undergo a rapidly progressing clinical course associated with resistance to standard chemo-immunotherapy. As a consequence, the prognosis of this entity is particularly poor with a median overall survival inferior to 1 year. ABT-199 (venetoclax) is a potent and selective small-molecule antagonist of BCL-2 recently approved for the treatment of a specific subtype of lymphoid neoplasm. In this study, we demonstrate that single-agent ABT-199 efficiently displaces BAX from BCL-2 complexes but fails to maintain a significant antitumor activity over time in most MYC+/BCL2+DHL cell lines and primary cultures, as well as in a xenograft mouse model of the disease. We further identify the accumulation of the BCL2-like protein BFL-1 to be a major mechanism involved in acquired resistance to ABT-199. Noteworthy, this phenomenon can be counteracted by the BET bromodomain inhibitor CPI203, since gene expression profiling identifies BCL2A1, the BFL-1 coding gene, as one of the top apoptosis-related gene modulated by this compound. Upon CPI203 treatment, simultaneous downregulation of MYC and BFL-1 further overcomes resistance to ABT-199 both in vitro and in vivo, engaging synergistic caspase-mediated apoptosis in DHL cultures and tumor xenografts. Together, these findings highlight the relevance of BFL-1 in DH lymphoma-associated drug resistance and support the combined use of a BCL-2 antagonist and a BET inhibitor as a promising therapeutic strategy for patients with aggressive DHL.

Abstract 2169: Pharmacological modulation of CXCL12-CXCR4 intracellular trafficking potentiates the in vitro and in vivo activity of the BET bromodomain inhibitor CPI203 in diffuse large B-cell lymphoma

Constitutive activation of CXCR4, a chemokine receptor commonly overexpressed in cancer, is associated with tumor progression, invasion, and chemotherapy resistance. Although the CXCR4 pathway has recently been suggested as an adverse prognostic marker in diffuse large B-cell lymphoma (DLBCL), its biological relevance remains underexplored as the evolution of the malignant clone has been traditionally thought to rely mainly on microenvironment-independent factors, including MYC. To evaluate a possible interplay between CXCR4 and MYC signaling in DLBCL we have analyzed the expression of CXCR4 and its ligand CXCL12 in tissue biopsies of a homogeneous cohort of 86 patients with de novo DLBCL, and correlated it with clinico-pathological characteristics and gene expression profiling. We found that co-expression of CXCL12 and CXCR4 was associated with an inferior overall survival when compared to the sole expression of CXCR4 (p=0.017). An ELISA-based array covering 175 human cytokines further showed that tissue levels of CXCL12 best correlated with high microvessel density (p=0.02) pointing out a role for both CXCR4 and CXCL12 in DLBCL tumor aggressiveness. In support of the established role of nuclear CXCR4 on tumor metastasis, abundant nuclear CXCR4 was detected in DLBCL primary tumors and cell lines compared to normal tonsils. This feature was significantly associated with the migratory potential of the tumor cells, thus suggesting CXCR4 as a potential therapeutic target to hamper lymphoma cell dissemination. In silico and in vitro screening of a CXCR4 inhibitor (CXCR4i) library further identified the tetra-amine IQS-01.01 as a potent inhibitor of CXCR4 nuclear translocation. IQS-01.01 prevented CXCL12-mediated chemotaxis and triggered apoptosis in a panel of 14 DLBCL cell lines and primary cells, with improved pharmacological properties than the standard CXCR4i, AMD3100. Mechanistically, IQS-01.01-mediated blockage of CXCR4 signaling was associated with downregulation of p-AKT, p-ERK1/2 and MYC. The combined use of IQS-01.01 with the BET bromodomain inhibitor CPI203 exerted a synergistic cytotoxic effect in DLBCL cell lines in vitro (mean combination index: 0.6±0.2). In a xenotransplant model of DLBCL the IQS-01.01/CPI203 combination decreased tumor burden (p=0.004) through prevention of CXCR4 nuclear import and MYC downregulation, resulting in a synergistic apoptosis induction. Our results point out an emerging role of nuclear CXCR4 in the pathogenesis of DLBCL and support the simultaneous targeting of CXCR4 and BET bromodomain as a promising, rationale-based strategy for DLBCL.

Citation Format: Clara Recasens-Zorzo, Teresa Cardesa-Salzmann, Laia Ros-Blanco, Anna Esteve-Arenys, Guillem Clot, Martina Guerrero-Hernández, Alejandra Valera, Alejandra Moros, Gonzalo Gutierrez, Isolda Casanova, Ramón Mangues, Alejandra Sanjuan, Pablo Menéndez, Vanina Rodriguez, Antonio Martínez, Pedro Jares, Dolors Colomer, Jordi Teixidó, José Ignacio Borrell, Elias Campo, Armando López-Guillermo, Luís Colomo, Patricia Pérez-Galán, Gaël Roué. Pharmacological modulation of CXCL12-CXCR4 intracellular trafficking potentiates the in vitro and in vivo activity of the BET bromodomain inhibitor CPI203 in diffuse large B-cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2169. doi:10.1158/1538-7445.AM2017-2169

ZEB1-induced tumourigenesis requires senescence inhibition via activation of DKK1/mutant p53/Mdm2/CtBP and repression of macroH2A1

OBJECTIVE

Understand the role of ZEB1 in the tumour initiation and progression beyond inducing an epithelial-to-mesenchymal transition.

DESIGN

Expression of the transcription factor ZEB1 associates with a worse prognosis in most cancers, including colorectal carcinomas (CRCs). The study uses survival analysis, in vivo mouse transgenic and xenograft models, gene expression arrays, immunostaining and gene and protein regulation assays.

RESULTS

The poorer survival determined by ZEB1 in CRCs depended on simultaneous high levels of the Wnt antagonist DKK1, whose expression was transcriptionally activated by ZEB1. In cancer cells with mutant TP53, ZEB1 blocked the formation of senescence-associated heterochromatin foci at the onset of senescence by triggering a new regulatory cascade that involves the subsequent activation of DKK1, mutant p53, Mdm2 and CtBP to ultimately repress macroH2A1 (H2AFY). In a transgenic mouse model of colon cancer, partial downregulation of Zeb1 was sufficient to induce H2afy and to trigger in vivo tumour senescence, thus resulting in reduced tumour load and improved survival. The capacity of ZEB1 to induce tumourigenesis in a xenograft mouse model requires the repression of H2AFY by ZEB1. Lastly, the worst survival effect of ZEB1 in patients with CRC ultimately depends on low expression of H2AFY and of senescence-associated genes.

CONCLUSIONS

The tumourigenic capacity of ZEB1 depends on its inhibition of cancer cell senescence through the activation of a herein identified new molecular pathway. These results set ZEB1 as a potential target in therapeutic strategies aimed at inducing senescence.

Binge ethanol drinking during adolescence modifies cocaine responses in mice

Binge ethanol drinking is an emerging pattern of excessive consumption among adolescents and young adults. Repeated ethanol intoxication has negative consequences during critical periods of brain development. Therefore, binge ethanol intake represents a vulnerability factor that promotes subsequent manifestations of neuropsychiatric disorders. In this study, we investigated the effects of oral binge ethanol intake during adolescence on the subsequent effects of cocaine in C57BL/6 mice. Firstly, we evaluated the oral ethanol intake of two binge ethanol procedures with different ethanol concentrations (20% v/v versus 30%, v/v). The highest ethanol intake was found in mice exposed to the lower ethanol concentration (20% v/v). In a second experiment, mice exposed to binge ethanol procedure were evaluated to study the effects of cocaine on locomotor activity, behavioural sensitization, and the reinforcing effects of cocaine in the self-administration paradigm. Mice exposed to ethanol binging showed discrete detrimental effects in responses to cocaine in the different experiments evaluated. Our findings revealed that the pattern of binge ethanol consumption in adolescent mice here evaluated produced a weak facilitation of cocaine responses. The present study highlights the importance of interventions to limit the deleterious effects of binge ethanol drinking during adolescence.