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Combinatorial targeting of MYC/BCL2 double-hit lymphoma with mitochondrial complex I and BCL2 inhibitors

ABSTRACT: Activation of the MYC oncogene is common in B-cell lymphomas, and frequently associated with compensatory events that dampen Myc-induced apoptosis, such as over-expression of anti-apoptotic Bcl2-family proteins. For example, concurrent translocations of MYC and BCL2 in a subset of Diffuse large B-cell lymphoma (DLBCL) lead to the high-grade “double-hit” lymphoma subtype (DHL), characterized by dismal prognosis in the face of current front-line regimens, thus calling for the pursuit of tailored therapeutic strategies. Here, we show that Myc and Bcl2 modulate the sensitivity of B-cells to IACS-010759, a selective inhibitor of mitochondrial respiratory complex I. Myc activation in non-transformed lymphoid precursors suppressed endogenous Bcl2 and sensitized the cells to IACS-010759-induced apoptosis. Treatment with the Bcl2 inhibitor venetoclax also sensitized to IACS-010759, while overexpression of Bcl-2 was protective. IACS-010759 engaged an ATF4-driven Integrated Stress Response (ISR) with dual anti- and pro-apoptotic effects, the latter mediated by the CHOP transcription factor, which contributed to selective killing of Myc-overexpressing cells. In line with the above data, IACS-010759 and venetoclax synergized in killing human DHL cells, and showed strong combinatorial effects in a pre-clinical setting. In a Bcl2-negative Burkitt’s lymphoma cell line, instead, IACS-010759 synergized with the Mcl-1 inhibitor S63845. Altogether, our data point to the combination of IACS-010759 with distinct Bcl2-family inhibitors for therapeutic reactivation of the intrinsic apoptotic pathway in Myc-associated B-cell lymphomas

ORGANISM(S): Mus musculus

PROVIDER: GSE149073 | GEO | 2022/03/01

REPOSITORIES: GEO

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Project description:Drug-tolerant “persister” tumor cells underlie the emergence of drug-resistant clones contribute to relapse and disease progression; thus, identifying actionable targets that disable persisters and mitigate relapse are a high priority need. Although the BCL2-targeting agent venetoclax (ABT-199) has shown promising responses in mantle cell and double hit B cell lymphomas, resistance often arises, yet mechanistically how this occurs is unclear. Here we report that ABT-199 resistance can evolve from persister clones that have selective deletions at 18q21 that involve the drug target BCL2 and the apoptotic regulators Noxa (PMAIP1) and TCF4. Notably, reprogramming of super enhancers (SE) in persisters contributes to resistance, where there is a selection for SE-directed overexpression of the apoptotic regulator BCL2A1 and oncogenic transcription factors IKZF1 and FOXC1. At the same time, the SE reprogramming confers an opportunity for overcoming ABT-199 resistance. An unbiased drug screen on a platform that recapitulates the lymphoma microenvironment revealed that persisters are vulnerable to inhibitors of transcription initiation and elongation, and especially so to inhibitors of cyclin-dependent kinase 7 (CDK7) that is essential for transcription initiation. Specifically, CDK7 loss or inhibition eliminated the persister phenotype by disabling SE-driven expression of BCL2A1, IKZF1 and FOXC1. Thus, the co-treatment of ABT-199 with CDK7 inhibitors blocked the evolution of drug resistance, and provoked tumor regression in models of mantle cell lymphoma (MCL) and double hit lymphomas (DHL) that overexpress both MYC and BCL2. Together, these findings establish loss of apoptotic regulators and an adaptive transcriptional response as drug resistance mechanisms in lymphoma, more importantly, establish a rationale for transcription inhibition-based combination strategies to prevent and overcome drug resistance in B cell malignancies toward BCL2 inhibitor.

Project description:MYC translocations are the biologic hallmark of Burkitt lymphomas but also occur in other mature B-cell lymphomas. If accompanied by chromosomal breaks targeting the BCL2 and/or BCL6 oncogenes, these MYC translocation-positive (MYC+) lymphomas are called double-hit lymphomas (DHLs); otherwise, the term single-hit lymphoma (SHL) is applied. In order to characterize the biologic features of these MYC+ lymphomas other than Burkitt lymphomas, we explored, after exclusion of molecular Burkitt lymphoma (mBL) as defined by gene expression profiling (GEP), the molecular, pathological and clinical aspects of 80 MYC translocation (MYC+) lymphomas (31 SHL, 26 BCL2+/MYC+, 14 BCL6+/MYC+, 6 BCL2+/BCL6+/MYC+ and 3 MYC+ lymphomas with unknown BCL6 status). Comparison of SHL and DHL revealed no difference in frequency of MYC partner (IG/non-IG), genomic complexity or MYC expression and no differences in GEP. DHL showed a more frequent GCB-like GEP and higher IGH and MYC mutation rates. GEP revealed 130 differentially expressed genes between BCL6+/MYC+ and BCL2+/MYC+ DHL. BCL2+/MYC+ DHL showed a more frequent GCB-like GEP. Analysis of all lymphomas according to MYC partner (IG/non-IG) revealed no substantial differences. In contrast to mBL and lymphomas without MYC break, SHL and DHL patients had similar poor outcome. Our data suggest that after excluding mBL, MYC+ lymphomas could be biologically widely lumped without further need for subclassification. 32 diffuse large B-cell lymphoma samples were hybridized to HG-U133A Affymetrix GeneChips. In addition, this study contains 30 already published samples, which contribute to GSE4475 (Hummel et al. 2006 (PMID 16760442)), as well as 18 already published samples from GSE22470 (Salaverria et al. 2011 (PMID 21487109)). No re-normalisation of the published samples was performed. The complete dataset representing: (1) the 32 diffuse large B-cell lymphoma Samples, (2) the 30 Samples from GSE4475 and (3) the 18 Samples from GSE22470, is linked below as a supplementary file

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Combinatorial targeting of MYC/BCL2 double-hit lymphoma with mitochondrial complex I and BCL2 inhibitors

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