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Metabolic Changes Contribute to Melphalan Resistance in Multiple Myeloma

ABSTRACT: Multiple myeloma is an incurable hematological malignancy that impacts tens of thousands of people every year in the U.S. Treatment for eligible patients includes three stages: induction, consolidation with stem cell rescue, and maintenance. High dose therapy with the DNA alkylating agent, melphalan, remains the primary drug for consolidation therapy in conjunction with autologous stem cell transplant. As a result, melphalan resistance remains a clinical challenge. Here, we use proteometabolomics to examine mechanisms of melphalan resistance in two cell line models. Drug metabolism, steady-state metabolomics, activity-based protein profiling (ABPP), acute treatment metabolomics, and immunoblotting analyses have allowed us to further elucidate metabolic processes contributing to melphalan resistance. Proteometabolomics data indicate that both drug resistant cells have higher levels of pentose phosphate pathway metabolites than their naïve counterparts. Interestingly, we also observed cell line specific changes in purine, pyrimidine and glutathione metabolism that are linked to the differences in steady state metabolism of naïve cells and highlight the heterogeneity of melphalan resistance in these models. Because of the diversity of metabolic changes, our data suggest that omics approaches will be needed to fully examine melphalan resistance in patient specimens and define personalized strategies to optimize the delivery of this therapy.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): B Cell

DISEASE(S): Multiple Myeloma

SUBMITTER: John Koomen

LAB HEAD: Ken Shain, MD/PhD

PROVIDER: PXD019725 | Pride | 2020-07-17

REPOSITORIES: Pride

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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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Metabolic Changes Contribute to Melphalan Resistance in Multiple Myeloma

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