Effects and mechanisms of trifluridine alone or in combination with cryptotanshinone in inhibiting malignant biological behavior of gastric cancer

Background: The incidence of gastric cancer (GC) ranks fourth among all malignant tumors worldwide, and the fatality rate ranks second among all malignant tumors. Several Chinese traditional medicines have been used in the treatment of advanced gastric cancer. This study aims to investigate the effect of combinational use of natural product cryptotanshinone (CTS) with anti-cancer drug trifluorothymidine (FTD) in GC.Methods: Cell Counting Kit-8 assay was used to detect the inhibitory effect of the combinational or separate use of FTD and CTS on the growth of HGC-27 and AGS GC cells. The combined index of FTD and CTS was calculated using CompuSyn software. To understand the mechanism, we applied flow cytometry to study the cell cycle and cell apoptosis after treatment. We also investigated the amount of FTD incorporated into the DNA by immunofluorescence assay. The expression of relevant proteins was monitored using western blot. Furthermore, the effect of using TAS-102 in combination with CTS was studied in xenograft tumor nude mice model.Results: FTD and CTS inhibited the growth of GC cells in a dose-dependent manner, respectively. They both exhibited low to sub-micromolar potency in HGC-27 and AGS cells. The combination of FTD and CTS showed synergistic anticancer effect in HGC-27 cells and AGS cells. Our mechanism studies indicate that FTD could block HGC-27 cells at G2/M phase, while CTS could block HGC-27 cells at G1/G0 phase, while FTD combined with CTS could mainly block HGC-27 cells at G2 phase. FTD in combination with CTS significantly increased the apoptosis of HGC-27 cells. We observed that CTS treatment increased the incorporation of FTD into the DNA HGC-27 cell. FTD treatment activated STAT3 phosphorylation in HGC-27 cells, while CTS treatment down-regulated the concentration of p-STAT3. Interestingly, the combination of CTS and FTD reduced STAT3 phosphorylation induced by FTD. In the in vivo experiments, we observed that the combination of TAS-102 with CTS was significantly more potent than TAS-102 on tumor growth inhibition.Conclusions: FTD combined with CTS has a synergistic anti-gastric cancer effect as shown by in vitro and in vivo experiments, and the combined treatment of FTD and CTS will be a promising treatment option for advanced gastric cancer.