Sijunzi decoction-treated rat serum induces apoptosis of side population cells in gastric carcinoma

Sijunzi decoction (SJZD) is a traditional Chinese herbal medicine. Previous studies have indicated that SJZD exhibits antitumor activity. However, the underlying molecular mechanism has not been fully elucidated. To explore the antitumor mechanism of SJZD, the effects of serum from rats treated with SJZD on the proliferation of MKN-28 and HGC-27 gastric carcinoma cell lines were systematically investigated. It was found that SJZD-treated rat serum significantly inhibited the growth of MKN-28 and HGC-27 cells in vitro. The results obtained from a colony formation assay showed that SJZD-treated rat serum decreased the colony formation ability of MKN-28 and HGC-27 cells. The apoptosis rate in MKN-28 and HGC-27 cells was also increased following treatment with SJZD-treated rat serum. Flow cytometry with cell sorting revealed the presence of side population (SP) cells in MKN-28 and HGC-27 cells though Hoechst 33342 staining, and verapamil reduced the SP percentage. Further analysis showed that SJZD-treated rat serum promoted the apoptosis of SP cells in MKN-28 and HGC-27 cell lines by upregulating Bax, caspase-3 and PARP and downregulating bcl-2. These data revealed the therapeutic effect of SJZD-treated rat serum on gastric carcinoma. Following the preliminary identification of the inhibitory effect on the growth of gastric cancer cells in vitro, the growth inhibitory effect of SJZD-treated rat serum on SP cells was confirmed, and this inhibition particularly involved the induction of cell apoptosis.