SIRT3 activation by oroxylin A phosphate diethyl ester triggers mitochondrial dysfunction and apoptosis in non-small cell lung cancer.

Lung cancer remains the leading cause of cancer mortality worldwide, and outcomes for advanced non-small cell lung cancer (NSCLC) are limited by resistance and toxicity. Sirtuin 3 (SIRT3), a mitochondrial NAD+-dependent deacetylase, regulates mitochondrial homeostasis and redox balance, but its therapeutic potential in NSCLC is incompletely defined. Here, bioinformatic analyses, structure-based virtual screening, and in vitro and in vivo validation were used to evaluate SIRT3 modulation in NSCLC. Although SIRT3 mRNA expression varied across lung cancer cohorts, higher SIRT3 expression was associated with better overall survival in lung adenocarcinoma (LUAD), and protein-level analyses demonstrated reduced SIRT3 expression in lung cancer specimens. Immunohistochemical analysis of clinical specimens and western blotting of NSCLC cell lines further confirmed reduced SIRT3 expression in lung cancer. To identify a SIRT3-targeting compound, we performed structure-based virtual screening using the SIRT3 crystal structure and prioritized oroxylin A phosphate diethyl ester (OA-OEt), a derivative of oroxylin A. OA-OEt markedly enhanced SIRT3 activity and exhibited stronger antiproliferative effects than oroxylin A in H1299 and A549 cells. Mechanistically, OA-OEt suppressed cell growth, induced G2/M arrest, and increased apoptosis. OA-OEt disrupted mitochondrial homeostasis, including elevated mitochondrial superoxide, reduced SOD2, altered mitochondrial dynamics markers, and impaired mitochondrial respiration; mitochondrial ROS scavenging partially rescued apoptosis. In an H1299 xenograft model, OA-OEt reduced tumor growth without overt body-weight loss and increased tumor SIRT3 and cleaved caspase-3 with consistent mitochondrial marker changes. Collectively, these findings support SIRT3 as a functionally tumor-suppressive mitochondrial regulator in NSCLC and suggest that OA-OEt may represent a promising SIRT3-activating lead compound.