γ‐T3 Increases the Sensitization of Gastric Cancer Cells to OXA by a Regulation of ARHGAP29

γ-Tocotrienol (γ-T3) exhibits potent anti-cancer effects in vitro and in vivo. Our previous study demonstrated that γ-T3 modulates autophagy activity in gastric cancer (GC) cells via the GSK-3β/β-Catenin pathway. In this study, we further explored whether γ-T3 also enhances the chemosensitivity of GC cells to oxaliplatin (OXA) by regulating ARHGAP29, and verified the direct binding between γ-T3 and ARHGAP29 as well as the physical interaction of ARHGAP29 with GSK-3β. We employed cell viability assays, flow cytometry, tumor cell spheroid formation assays, RT-qPCR, Western blot analysis, and stable overexpression transfection. Additionally, cellular thermal shift assay (CETSA), co-immunoprecipitation (Co-IP), and chloroquine (CQ) rescue CCK-8 assays were performed for molecular interaction and autophagy function verification; we established a xenografted tumor model using MKN45 cells in BALB/c nude mice (nu/nu). γ-T3 and OXA inhibited GC cell proliferation in vitro and in vivo, with a synergistic effect when combined (CI = 0.55 in MKN45 cells). In a mouse model, intraperitoneal injection of γ-T3 (20 mg/kg b.w.) and OXA (2.0 mg/kg b.w.) suppressed MKN45 cell xenograft growth. This was related to cell cycle arrest and inhibition of cancer stem cells (CSCs). γ-T3 alone or combined with OXA altered autophagy-related protein levels after 48 h treatment, with elevated LC3-II/LC3-I ratio and Beclin1 expression, and reduced p62 abundance, functional rescue with autophagy inhibitor CQ confirmed that the changed autophagy contributes to drug-induced cell death, and this phenotypic change was accompanied by suppressed GSK-3β/β-Catenin pathway activity. ARHGAP29 was inversely correlated with GC prognosis; CETSA results validated the direct intracellular binding between γ-T3 and ARHGAP29, and Co-IP assays confirmed physical interaction between ARHGAP29 and GSK-3β. γ-T3 inhibited the expression of ARHGAP29 at protein and mRNA levels in a time- and dose-dependent manner, whether alone or with OXA. Overexpression of ARHGAP29 reversed the synergistic effects of γ-T3 and OXA in GC cells, further supporting the regulatory linkage between ARHGAP29 and the GSK-3β/β-Catenin axis. The combination of γ-T3 and OXA represents a promising therapeutic strategy to elevate oxaliplatin sensitivity and alter autophagy-related marker expression in GC, at least partially via the ARHGAP29-associated modulation of GSK-3β/β-Catenin signaling.