Suberoylanilide hydroxamic acid enhances the antitumor activity of oxaliplatin by reversing the oxaliplatin-induced Src activation in gastric cancer cells

Oxaliplatin and the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA), also known as vorinostat, are potent antitumor agents. The aim of this study was to investigate the effect of SAHA on the antitumor efficacy of oxaliplatin in gastric cancer and the interaction between oxaliplatin and SAHA. Cell growth inhibition was evaluated using Cell Counting Kit-8 and colony formation assays. Xenografts established in nude mice were used to assess tumor growth in vivo. Western blot analysis was used to detect the expression of acetyl-histone H3, phosphorylated histone H2AX (gamma H2AX), B-cell lymphoma 2 (Bcl-2), cleaved caspase-3, cleaved poly (ADP-ribose) polymerase (PARP), phosphorylated- (p-) Src, Src, Akt and p-Akt in gastric cancer cells. The in vitro growth of SGC-7901, Hs746T and MKN28 gastric cancer cells was found to be dose-dependently inhibited by oxaliplatin and SAHA. Furthermore, combined treatment was observed to be more effective in inhibiting cancer cell growth and colony formation than monotherapy. Similar effects were found in the xenografts. A positive interaction was identified between oxaliplatin and SAHA (between-subject effects of oxaliplatin and SAHA, P<0.001). In addition, combined exposure to oxaliplatin and SAHA increased gamma H2AX expression and decreased Bc1-2 expression. The expression of cleaved caspase-3 and PARP was also increased with combination treatment. Oxaliplatin-induced Src phosphorylation was detected in gastric cancer cells, as we have previously reported. However, this effect was inhibited by SAHA. The oxaliplatin-induced Src phosphorylation was not impaired with Akt inhibition. In conclusion, oxaliplatin and SAHA exhibited a positive interaction when used in combination and were found to suppress gastric cancer cell survival and growth. The reversal of oxaliplatin-induced Src activation may be responsible for this positive interaction.