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Chromosomal deletion and chromatin remodeling Drive ABT-199 Resistance in B-cell Lymphomas [RNA-seq]

ABSTRACT: Drug-tolerant “persister” cells underlie the emergence of drug-resistant clones and allow residual tumors to survive therapy; thus, represent an attractive therapeutic target to mitigate relapse. With the promising outcome, yet some resistance cases surfaced after the approval of venetoclax (ABT-199), we defined a novel invasive drug resistance mechanism induced by Bcl2 inhibitor via examining the evolution of drug tolerant persister clones generated with ABT-199 treatment. The ABT-199 drug-tolerant persister cells showed genetic alteration by losing the copy number at 18q21 paralleled with BCL2, PMAIP1 and TCF4 gene downregulation. The persister status are generated through major enhancer-remodeling mediated transcriptional activation of the super enhancer, which offered unique opportunity for overcoming the drug resistance. The insight of major determinant for ABT-199 persistence evolution identified the molecular vulnerability in Bcl2 inhibitor resistant lymphoma cells through CDK7 pathway inhibition. The combined CDK7 and BCL2 inhibition was found to be more effective against ABT-199 persistence ex vivo and in vivo rather than the parental line, and CDK7 inhibition eliminated the persister phenotype by blocking dynamic active enhancer formation to further prevent the evolution of drug resistance. Together, these studies unified genetic alteration and non-mutational adaptive response as a drug resistance mechanism, more importantly, demonstrated a rationale for transcriptional inhibition-based combination strategies to prevent and overcome drug resistance in B-cell malignancies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE116129 | GEO | 2019/05/01

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.

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Chromosomal deletion and chromatin remodeling Drive ABT-199 Resistance in B-cell Lymphomas [RNA-seq]

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