Dual Metabolic Blockade by Metformin and Dichloroacetate Induces Lethal Energy Crisis in Chemoresistant NSCLC

Acquired chemoresistance, often linked to metabolic adaptation, severely limits therapeutic efficacy in non-small cell lung cancer (NSCLC). Strategies targeting resistance-associated metabolic plasticity are urgently needed. Here, we investigated the combination of Metformin (mitochondrial Complex I inhibitor) and Dichloroacetate (DCA; PDK inhibitor) in chemo-sensitive human A549 NSCLC cells and an acquired Doxorubicin-resistant subline (A549-DR). A549-DR cells displayed significant Doxorubicin resistance (∼15.6-fold; IC50: 3.9 µM vs 0.25 µM in parental A549) and exhibited enhanced glycolysis (higher ECAR) while retaining substantial oxidative phosphorylation (OxPhos) capacity. While single-agent Metformin or DCA showed limited cytotoxicity, their combination induced potent synergistic cell death (Combination Index < 0.5) specifically in A549-DR cells compared to parental A549 (CI ∼ 0.8-1.1). Mechanistically, Metformin inhibited OxPhos, while DCA promoted pyruvate entry into the TCA cycle, preventing compensatory glycolysis. This dual blockade precipitated a catastrophic metabolic collapse uniquely in A549-DR cells, marked by simultaneous suppression of OxPhos (OCR) and glycolysis (ECAR), leading to severe ATP depletion (∼85% reduction), hyperactivation of the energy sensor AMPK, and robust induction of apoptosis (∼58% Annexin V positive). Parental A549 cells were less susceptible, experiencing moderate metabolic inhibition and apoptosis (∼32% Annexin V positive). Our findings highlight a powerful synergistic strategy that exploits the acquired metabolic vulnerabilities of chemoresistant NSCLC cells, inducing an irrecoverable energy crisis and offering a promising therapeutic approach to counteract treatment failure.