Metabolic-epigenetic reprogramming with low-dose metformin and valproic acid sensitizes drug-tolerant persister cells to cisplatin in gastric and liver cancer

The emergence of chemoresistance remains a major obstacle to effective cancer therapy, driven in part by the survival of drug-tolerant persister cells (DTPs). A previous study from our laboratory demonstrated that pre-sensitization with a histone deacetylase (HDAC) inhibitor followed by cisplatin (CDDP) significantly reduces DTP formation; however, surviving DTP cells may contribute to tumor relapse through additional adaptive mechanisms. In the present study, we investigated the metabolic and mitochondrial adaptations associated with DTP survival in gastric and liver carcinoma cell lines using TEM, immunoblotting, metabolic assays, and in vivo xenograft studies. DTP cells exhibited increased levels of mitochondrial fusion proteins MFN1 and MFN2 along with activation of the PGC-1α/NRF2/TFAM axis, indicating enhanced mitochondrial biogenesis and oxidative phosphorylation. These alterations were associated with increased ATP production and antioxidant survival responses. Furthermore, low-dose pre-sensitization with valproic acid (VPA), a class I HDAC inhibitor, and metformin (MET), a mitochondrial complex I inhibitor, followed by CDDP treatment, significantly enhanced cell death in DTPs. In the NOD-SCID xenograft mouse model, VPA/MET/CDDP treatment resulted in enhanced anti-tumor efficacy, substantial tumor regression at lower doses, and reduced systemic toxicity. Tumor tissue analysis further revealed increased H3K9 acetylation, reduced Ki67 expression, altered AMPK levels, and elevated caspase-3 expression, consistent with metabolic disruption and induction of apoptosis. Collectively, these findings provide initial evidence for a clinically relevant strategy to inhibit or delay tumor relapse.