Glutathione S‑transferase isozyme alpha 1 is predominantly involved in the cisplatin resistance of common types of solid cancer.

The roles of glutathione S‑transferase pi 1 (GSTP1), glutathione S‑transferase mu 2 (GSTM2) and glutathione S‑transferase alpha 1 (GSTA1) in cisplatin (DDP)‑resistance of solid cancer cells (A549/DDP, SKOV3/DDP and SGC7901/DDP) were compared following expression downregulation with small interfering RNAs (siRNAs). DDP cytotoxicity was reflected by its half maximal inhibition concentration (IC50) calculated from data using a Cell Counting Kit‑8 assay; cell apoptosis was examined using flow cytometry and Hoechst 33342 staining. Higher activities of GST were detected in the cytosol of DDP‑resistant cells, compared with those in the parental DDP‑susceptible cells. The silencing efficacy of each positive siRNA was supported by western blot analysis. GSTP1 silencing resulted in a 4‑fold sensitization of SGC7901/DDP cells to DDP cytotoxicity, but negligible sensitization of SKOV3/DDP and A549/DDP cells. GSTM2 silencing sensitized SKOV3/DDP and A549/DDP cells to DDP cytotoxicity by ~2‑fold, but did not sensitize SGC7901/DDP cells. Notably, GSTA1 silencing enhanced DDP cytotoxicity in SGC7901/DDP cells by 6‑fold, in A549/DDP cells by 5‑fold and in SKOV3/DDP cells by 2‑fold. The combined actions of positive siRNAs and DDP increased the percentages of apoptotic cells in the DDP‑resistant solid cancer cells compared with the combined actions of DDP and the negative siRNAs. The present findings indicated that GSTA1 is a predominant GST isozyme associated with DDP resistance of SGC7901/DDP, A549/DDP and SKOV3/DDP cells; GSTA1‑specific inhibitors may be general sensitizers of SGC7901/DDP, A549/DDP and SKOV3/DDP cells to DDP cytotoxicity through the promotion of cell apoptosis.