Abstract 3038: Investigating novel targeted therapies for double hit diffuse large B-cell lymphoma (DH-DLBCL)

Background: Molecular studies divide DLBCL into three subtypes with distinct pathogenesis and clinical outcomes: activated B-cell (ABC), germinal center B-cell (GCB) and primary mediastinal lymphoma (PML). Florescence in situ hybridization (FISH) studies identified another subgroup of DLBCL, classified as DH-DLBCL, with a poor clinical outcome harboring concurrent gene rearrangements of the c-MYC, BCL2 and/or BCL6 proto-oncogenes, resulting in the over-expression of c-Myc, Bcl2 and Bcl6 proteins. Previously, our retrospective review from single institution series revealed that 30 out of 611 DLBCL patients had aberrations in c-MYC and BCL2 or BCL6 by FISH. These patients exhibited inferior response rates (RR) to rituximab-based chemotherapy, and a shorter progression-free survival (PFS)/overall survival (OS), suggesting that newer therapies are in dire need. DH-DLBCL is characterized by de-regulation of apoptosis and cell cycle progression, resulting in rapid cellular proliferation and resistance to apoptotic stimuli. In ABC-DLBCL, anti-apoptotic factor MCL-1 is implicated in poor prognosis leading to resistance to standard chemotherapy. C-MYC transcriptionally upregulates Mcl1. Translocation of c-MYC in DH-DLBCL may contribute to the aggressive phenotype and chemotherapy resistance via the MCL-1 pathway. We hypothesize that dual inhibition of both anti-apoptotic proteins BCL2 and MCL1 is an effective strategy in inducing lymphoma cell death in DH-DLBCL. Materials & Methods: At the pre-clinical level, we studied 3 novel therapeutic agents targeting BCL2 (ABT-199), c-MYC (JQ-1), and various cell cycle regulatory proteins (p21) and other BCL2 family members affecting ABT-199 activity (irreversible proteasome inhibitor carfilzomib(CFZ)) using DH lymphoma (DHL) cell lines (Val, DOHH-2, ROS-50). DHL cell lines were exposed to ABT-199 (0-10 uM), JQ-1 (0-100 uM) and carfilzomib (CFZ) (0-50 nM) at 24, 48 and 72 hours. Changes in cell viability were evaluated using Presto Blue assay. Subsequently, DHL cells were exposed to doublet combinations of ABT-199, JQ-1 and CFZ for 48 hours. Coefficient of synergy was calculated using CalcuSyn. Results: In vitro, ABT199, JQ-1, and CFZ induced cell death in a dose- and time-dependent manner. Significant synergistic activity was observed by combining ABT199 with CFZ and to a lesser degree with JQ-1. Conclusion: ABT199 exhibited strong synergistic activity with CFZ. Dual targeting of BCL2 and c-MYC pathways results in synergisti