Combination of Vismodegib and Paclitaxel Enhances Cytotoxicity via Bak-mediated Mitochondrial Damage in EGFR-Mutant Non-Small Cell Lung Cancer Cells

Half of NSCLC patients harbor epidermal growth factor receptor (EGFR) mutations, and their therapeutic responses are remarkably different from patients with wild-type EGFR (EGFR-WT) NSCLC. We previously demonstrated that the Hedgehog Inhibitor vismodegib (Vis) potentiates paclitaxel (PTX)-induced cytotoxicity via suppression of Bax phosphorylation, which promotes accumulation of mitochondrial damage and Apoptosis in EGFR-WT NSCLC cells. In this study, we further delineated the Anticancer activity and underlying mechanisms of this combination treatment in EGFR-mutant NSCLC cells. MTS/PMS activity and trypan blue exclusion assays were used to assess cell viability. Apoptosis was monitored by chromosome condensation, annexin V staining, and cleavage of PARP and Caspase-3. Western blots were conducted to track proteins of interest after treatment. Reactive Oxygen Species (ROS) level was monitored by 2',7'-dichlorodihydrofluorescein diacetate. Mitochondrial status was analyzed by tetramethylrhodamine, ethyl ester. Hedgehog signaling was induced by PTX, which rendered H1975 and PC9 cells insensitive to PTX-induced mitochondrial Apoptosis via suppression of Bak. However, Vis enhanced PTX-induced Bak activation, leading to mitochondrial damage, ROS accumulation, and subsequent Apoptosis. Our findings suggest that the combination of Vis and PTX could be a potential therapeutic strategy to increase PTX sensitivity of EGFR-mutant NSCLC.