HSP90 Facilitates Oncogene-Induced Metabolic Reprogramming in B-Cell Lymphomas

Abstract The chaperone HSP90 is used by B-cell lymphomas to support the stability of proteins involved in oncogenic processes such as signaling and anti-apoptosis. While HSP90 inhibitors decrease the levels of these client proteins favoring cell death they also prompt cellular counter-regulatory mechanisms that diminish the efficacy of these drugs. Improving the clinical activity of HSP90 inhibitors will depend on understanding the complexity of HSP90 functions. Here we show that HSP90 facilitates the function of MYC by improving the efficiency of metabolic pathways through the orchestration of enzymatic networks, and that HSP90 inhibition impairs the metabolic fitness of DLBCLs without client protein degradation. Moreover, drugs inducing sub-lethal metabolic stress in DLBCL cells cause apoptosis upon HSP90 inhibition. To identify metabolic enzymes actively chaperoned by HSP90 we integrated the information from proteomics and metabolomics in DLBCL cell lines. Proteomics was performed from the cytoplasmic fraction of OCI-Ly1 and OCI-Ly7 cells chemically precipitated with PU-H71, an HSP90 inhibitor that selectively binds to HSP90 contained in active multi-chaperone complexes.STRING network analysis of the metabolic client proteins identified several hubs highly enriched for enzymes involved in metabolism of nucleotides (e.g. IMPDH2, CTPS1, CAD), carbohydrates (e.g. G6PD, HK2) and proteins (e.g. MTHFR, ASNS). Functionality of the network was assessed by metabolomics from OCI-Ly1 cells treated with PU-H71 500 nM for 6 h (sub-lethal). This dose and timing assured HSP90 inhibition but no client protein degradation. The proteomics and metabolomics mapping into KEGG pathways showed a significant overlap, indicating that HSP90 preferentially interacts with proteins representing regulatory hubs to coordinate their committed activity and thus secure the flow of the pathway. We quantified the effect of HSP90 on the activity of metabolic networks by measuring glycolysis (by lactate production and medium acidification) and mitochondrial respiration (by oxygen consumption) in OCI-LY1 and OCI-LY7 cell lines upon PU-H71. We found that inhibition of HSP90 decreased glycolysis by 20-25% and respiration by 25% (p To understand the mechanistic relevance of these findings to lymphomagenesis, we analyzed the HSP90 metabolic proteome for common features and found it was significantly enriched (chi-square p Disclosures Yang: Regeneron Pharmaceuticals: Employment. Cerchietti: Lymphoma Research Foundation: Research Funding; Leukemia and Lymphoma Society: Research Funding; Weill Cornell Medicine - New York Presbyterian Hospital: Employment; Celgene: Research Funding.