γ-T3 inhibits ARHGAP29 in the sensitization of gastric cancer cells to OXA by autophagy

Background In the past years, chemoresistance greatly limited the clinical therapeutic efficiency of oxaliplatin (OXA) in gastric cancer (GC). γ-Tocotrienol (γ-T3), a subtype of vitamin E, has attracted a lot of attention on monotherapies or with traditional chemotherapeutic agents. Therefore, the co-treatment of γ-T3 with OXA could be an excellent measure to combat this problem. Methods This study investigated the effects of γ-T3 combined with oxaliplatin (OXA) on the proliferation, cell cycle, autophagy, and ARHGAP29/GSK-3β/β-Catenin signaling pathways in gastric cancer cells, employing methods such as MTT and MB assays, flow cytometry, Western blot, real-time quantitative PCR, immunohistochemistry, and molecular docking, as well as in vivo assessment using a nude mouse xenograft model to evaluate the synergistic antitumor effects of γ-T3 and OXA. Results In this study, we found that treatment of γ-T3 with OXA inhibited the proliferation and arrested the cell cycle of MKN45 cells and AGS cells, especially better synergistic effects could be gotten in combination of γ-T3 (26.3µmol/L) and OXA (600nmol/L) in MKN45 cells (CI = 0.55). Compared to the control group (30% alcohol), nude mice injected with γ-T3 (20mg/kg b.w.) or OXA (2.0 mg/kg b.w) by intraperitoneal (IP) suppressed the growth of MKN45 cell xenografts, and the efficacy was significantly augmented by co-treatment of γ-T3 and OXA. In addition, ARHGAP29 was negatively correlated with the prognosis of gastric cancer and exhibited binding activity to γ-T3. Combination treatment with γ-T3 and OXA specially down-regulated ARHGAP29 expression in MKN45 cells and xenografts, and then further inhibited downstream GSK-3β/β-Catenin signaling by autophagy induced, resulting from increased LC3-Ⅰ/LC3-Ⅱ ratio and Beclin1 expression, and decreased p62 expression. Overexpression of ARHGAP29 reversed the autophagy-induced decrease in the cell viability of MKN45 cells via a GSK-3β/β-Catenin signaling. Conclusions Our findings indicated that γ-T3 exerts a synergistic effect of OXA on inducting autophagy and inhibiting the progression of GC, partially via ARHGAP29/GSK-3β/β-Catenin pathways.