Mitochondrial protein translation is a heightened dependence and therapeutic vulnerability of chemo-refractory triple negative breast cancer

Abstract

Triple negative breast cancer (TNBC) patients harboring residual cancer burden following completion of conventional neoadjuvant chemo-immunotherapy regimens have poor relapse-free and overall survival rates and limited therapeutic options. We and others have demonstrated that mitochondrial function is required for the survival of chemo-refractory TNBC. Here, we define the mitochondrial translation machinery as a critical and targetable dependency underlying chemo-refractory TNBC. Analyses of human and orthotopic patient-derived xenograft (PDX) mass spectrometry proteomics datasets revealed that mitochondrial protein translation-related signatures were among the top associated with chemoresistance. These signatures included core mitoribosome components and the mitoribosome-associated factor Oxidase (Cytochrome C) Assembly 1-Like (OXA1L), which was consistently enriched in chemoresistant versus chemosensitive TNBC across datasets. OXA1L, a key mediator of mitochondrial translation and electron transport chain (ETC) assembly, has not been functionally characterized in cancer. We therefore tested whether OXA1L-dependent mitochondrial translation sustains mitochondrial function and chemoresistance in TNBC. Knockdown (KD) of OXA1L in human TNBC cells reduced ETC protein levels, mitochondrial respirasome supercomplex levels, ATP production, and oxidative phosphorylation (oxphos), establishing a requirement for OXA1L in maintaining mitochondrial bioenergetics in TNBC. OXA1L was required for the characteristic oxphos elevation induced by carboplatin (CRB), and KD significantly enhanced CRB sensitivity, demonstrating that mitochondrial translation supports adaptive metabolic responses to chemotherapy. To explore the translational potential of targeting the mitoribosome in TNBC, we leveraged the bacterial ancestry of mitochondria to repurpose the FDA-approved antibiotic tigecycline (TIG) as a mitochondrial translation inhibitor. Direct measurement of mitochondrial nascent peptide levels revealed that, while CRB elevated mitochondrial translation, TIG potently suppressed mitochondrial translation as monotherapy and in combination with CRB or docetaxel (DTX). TIG abolished CRB-induced oxphos, decreased oxphos in combination with DTX, and significantly improved chemotherapy sensitivity in human TNBC cell lines, PDX-derived spheroids, and in vivo. TIG sensitivity associated with mitochondrial translation-related proteomic signatures, concordant with PDX and patient-derived signatures associated with chemoresistance. Together, these data identify OXA1L-dependent mitochondrial translation as a targetable dependency that sustains mitochondrial function and chemoresistance in TNBC, demonstrate that its inhibition enhances chemotherapeutic response, and nominate a mitochondrial translation-related protein signature as a candidate predictive biomarker of TIG sensitivity and chemoresistance. These findings support mitochondrial translation inhibition as a potential therapeutic strategy in chemo-refractory disease. DISCLOSURESGVE is co-founder, Chief Scientific Officer, and an equity stakeholder of Nemea Therapeutics, Inc. G.V.E. formerly received sponsored research funding from Chimerix Inc. G.V.E. receives experimental compounds from the Lead Discovery Center of Germany and from Jazz Pharmaceuticals. MLB is a co-inventor at Nemea Therapeutics. MTL is a founder and limited partner in StemMed Ltd. and a manager in StemMed Holdings, its general partner. MTL is a founder and equity stakeholder in Tvardi Therapeutics Inc. The BCM PDX models, are exclusively licensed to StemMed Ltd., resulting in royalty income to MTL when used for commercial purposes. LED is a compensated employee of StemMed Ltd; however, the PDX models resulting in royalty income to LED were not included in this study. All other authors have nothing to disclose.