The clinically available supplement pyruvate enhances the therapeutic effect of bortezomib in Multiple Myeloma by modulating mitochondrial metabolism.

Multiple myeloma (MM) is a hematological malignancy characterized by plasma cells residing in the bone marrow. Despite advancements in treatment, including proteasome inhibitors (PIs) such as bortezomib (Bz), drug resistance remains a major challenge. Metabolic reprogramming supports MM survival and drug resistance, with mitochondria emerging as promising therapeutic targets through their control of OXPHOS and mitochondrial reactive oxygen species (Mito-ROS). Using metabolic flux analyses, flow cytometry, and Western blot analysis, we identified pyruvate as a central metabolic intermediate, which not only enhances mitochondrial respiration and Mito-ROS production, but also the Integrated Stress Response (ISR) pathway. Conversely, metformin, an inhibitor of OXPHOS, was still able to activate the ISR pathway, but rather reduced Bz-induced cytotoxicity by decreasing both protein synthesis, and ROS production. Results were confirmed on primary murine and patient samples. Moreover, analysis of the CoMMpass study revealed that patients with prolonged progression-free survival under PI treatment showed enrichment in OXPHOS-related genes, highlighting the importance of mitochondrial metabolism in regulating MM responses to Bz. These data suggest that targeting pyruvate metabolism to increase ROS production could offer a strategy to enhance Bz activity in MM.