Abstract 2161: Pharmacological downregulation of BFL-1 by the BET bromodomain inhibitor CPI203 overcomes ABT-199 resistance in MYC+/BCL2+ double hit lymphoma

Abstract

Double-hit lymphoma (DHL) is a rare subtype of B-cell lymphoma characterized by MYC and either BCL2 or BCL6 chromosomal rearrangements. DHL cases may have different morphology and are included in the updated 2016 WHO classification as a new category of high grade B-cell lymphoma with rearrangements. DHL patients usually undergo a rapidly progressing clinical course and are poorly responsive to standard chemo-immunotherapy. As a consequence, the prognosis of this entity is particularly poor with a median overall survival of approximately one year. ABT-199 (venetoclax) is a potent and selective small-molecule antagonist of BCL-2 recently approved for the treatment of some lymphoid malignancies. In this study, we demonstrate that single-agent ABT-199 efficiently displaces pro-apoptotic 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 DHL. We further identify the accumulation of the BCL2-like protein, BFL-1, to be a major mechanism involved in acquired resistance to ABT-199. We show this phenomenon to be manageable by the BET bromodomain inhibitor CPI203, since gene expression profiling identifies BCL2A1 as one of the top apoptosis-related gene modulated by the compound. Upon CPI203 treatment, simultaneous downregulation of MYC and BFL-1 at both mRNA and protein levels further overcomes resistance to ABT-199 both in vitro and in vivo, allowing DHL cultures and tumor xenografts to undergo synergistic caspase-mediated apoptosis. Together, these findings highlight the relevance of BFL-1 in DHL-associated drug resistance and support the combined use of BCL-2 antagonist and BET inhibitor as a promising therapeutic strategy in patients with aggressive DHL. Citation Format: Anna Esteve-Arenys, Juan Garcia-Valero, David Gonzalez, Aránzazu Chamorro-Jorganes, Vanina Rodriguez, Ivan Dlouhy, Itziar Salaverria, Elias Campo, Dolors Colomer, Antonio Martinez, Grzegorz Rymkiewicz, Patricia Pérez-Galán, Armando Lopez-Guillermo, Gaël Roué. Pharmacological downregulation of BFL-1 by the BET bromodomain inhibitor CPI203 overcomes ABT-199 resistance in MYC+/BCL2+ double hit 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 2161. doi:10.1158/1538-7445.AM2017-2161

TRIM17 and TRIM28 antagonistically regulate the ubiquitination and anti-apoptotic activity of BCL2A1

“…To date, this strategy has not provided inhibitors of BCL2A1, possibly because of the atypical shape of BCL2A1 hydrophobic groove which sequesters a restricted spectrum of BH3-only proteins, namely NOXA, PUMA and BIM [11][12][13]. Moreover, in some cases, resistance to these BH3 mimetics developed by cancer cells involves de novo synthesis of BCL2A1 protein [14][15][16].…”

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

“…By integrating multi-omics and functional analysis, we have demonstrated here that GOF mutations result in NFkB-dependent induction of BCL2A1. Recent publications have highlighted its critical role in venetoclax resistance in hematological malignancies 12,29,46 . Our BH3-profiling results suggest the dynamic sequestration of the BH3-only proteins by BCL2A1 at the mitochondrial level after targeting BCL2, MCL1, and BCLXL, as recently described in CLL 30 .…”

“…Among the top genes associated with OAsIs resistance (Fig. 3B), BCL2A1, an anti-apoptotic member of the Bcl-2 family, has previously been described as a major venetoclax resistance factor 12,29,30 . In accordance with the MCL_R16 signature pattern, the BCL2A1 RNA level was: 1) significantly higher at relapse compared to inclusion (p<0.0001) (Fig.…”

Antitumor Activity of the Novel BTK Inhibitor TG-1701 Is Associated with Disruption of Ikaros Signaling in Patients with B-cell Non–Hodgkin Lymphoma

“…Total and nuclear protein extracts were obtained from MCL cell lines and tumor specimens using RIPA (Sigma-Aldrich), the Nuclear/Cytosol Fractionation Kit (BioVision), and T-PER (Thermo Scientific) buffers, respectively, and subjected to SDS-PAGE, as previously described (22,23). Membrane-transferred proteins were revealed by incubating with primary and secondary (Supplemental Materials and Methods) followed by chemiluminescence detection using the ECL system (Pierce) and a Fusion FX imaging system (Vilber Lourmat).…”

“…BTKi-treated REC-1 and JEKO-1 cells (2-3 × 10 5 ) were seeded on poly-L-lysinecoated glass coverslips and stained as previously (23) with anti-Ikaros antibody (Cell Signaling Technology). Fluorescence signal was acquired on a Leica microscope and quantified using the LAS X (Leica) and Image J (RRID:SCR_003070) softwares.…”