Disrupting metformin adaptation of liver cancer cells by targeting the TOMM34/ATP5B axis

Metformin, a well‐known antidiabetic drug, has been repurposed for cancer treatment; however, recently observed drug resistance and tumor metastasis have questioned its further application. Here, we found that long‐term metformin exposure led to metabolic adaptation of hepatocellular carcinoma (HCC) cells, which was characterized by an obvious epithelial–mesenchymal transition (EMT) phenotype and compensatory elevation of oxidative phosphorylation (OXPHOS). TOMM34, a translocase of the outer mitochondrial membrane, was upregulated to promote tumor metastasis in response to metformin‐induced metabolic stress. Mechanistically, TOMM34 interacted with ATP5B to preserve F(1)F(O)‐ATPase activity, which conferred mitochondrial OXPHOS and ATP production. This metabolic preference for OXPHOS suggested a large requirement of energy supply by cancer cells to survive and spread in response to therapeutic stress. Notably, disturbing the interaction between TOMM34 and ATP5B using Gboxin, a specific OXPHOS inhibitor, increased sensitivity to metformin and suppressed tumor progression both in vitro and in vivo. Overall, this study demonstrates a molecular link of the TOMM34/ATP5B‐ATP synthesis axis during metformin adaptation and provides promising therapeutic targets for metformin sensitization in cancer treatment.