Differential contribution of the mitochondrial translation pathway to the survival of diffuse large B-cell lymphoma subsets

Diffuse large B-cell lymphomas (DLBCLs) are a highly heterogeneous group of tumors in which subsets share molecular features revealed by gene expression profiles and metabolic fingerprints. While B-cell receptor (BCR)-dependent DLBCLs are glycolytic, OxPhos-DLBCLs rely on mitochondrial energy transduction and nutrient utilization pathways that provide pro-survival benefits independent of BCR signaling. Integral to these metabolic distinctions is elevated mitochondrial electron transport chain (ETC) activity in OxPhos-DLBCLs compared with BCR-DLBCLs, which is linked to greater protein abundance of ETC components. To gain insights into molecular determinants of the selective increase in ETC activity and dependence on mitochondrial energy metabolism in OxPhos-DLBCLs, we examined the mitochondrial translation pathway in charge of the synthesis of mitochondrial DNA encoded ETC subunits. Quantitative mass spectrometry identified increased expression of mitochondrial translation factors in OxPhos-DLBCL as compared with the BCR subtype. Biochemical and functional assays indicate that the mitochondrial translation pathway is required for increased ETC activity and mitochondrial energy reserves in OxPhos-DLBCL. Importantly, molecular depletion of several mitochondrial translation proteins using RNA interference or pharmacological perturbation of the mitochondrial translation pathway with the FDA-approved inhibitor tigecycline (Tigecyl) is selectively toxic to OxPhos-DLBCL cell lines and primary tumors. These findings provide additional molecular insights into the metabolic characteristics of OxPhos-DLBCLs, and mark the mitochondrial translation pathway as a potential therapeutic target in these tumors.