Effect of diallyl trisulfide on the expression of folate receptor α in human gastric cancer cell lines BGC823 and AGS and the related regulatory mechanism / 肿瘤研究与临床

ABSTRACT

Objective:To investigate the effect of diallyl trisulfide (DATS) on the expression of folate receptor α (FRα) in human gastric cancer cells and the related regulatory mechanism.Methods:Human gastric cancer cell lines BGC823 and AGS were selected, BGC823 cells were treated with 10, 20, 40, 80 μmol/L DATS for 48 hours, and AGS cells were treated with 5, 10, 20, 40 μmol/L DATS for 48 hours. Cells treated with 6 μmol/L histone deacetylase (HDAC) inhibitor trichostatin A (TSA) were used as positive control for epigenetic study, and cells untreated with DATS were used as negative control. The apoptosis of gastric cancer cells induced by DATS was detected by flow cytometry. After BGC823 and AGS cells were treated by DATS for 48 hours, they were replaced with DATS-free cell culture medium and cultured for different time to detect the changes in FRα protein expression. BGC823 and AGS cells were treated with 6 μmol/L TSA or 40 μmol/L DATS. The protein expression levels of FRα, HDAC1 and HDAC2, and histone H3 lysine 9 acetylation (H3K9ac) and histone H4 lysine 5 acetylation (H4K5ac) were detected by Western blot. BGC823 cells were inoculated into BALB/c nude mice to establish tumor bearing model. The nude mice in DATS group were injected intraperitoneally with 10 mg/kg DATS for 16 days, and then the protein in tumor-bearing tissues was extracted to detect the expression of target protein, while the control group was injected with equal dose of 0.9% NaCl solution.Results:The expressions of FRα protein in BGC823 and AGS cells were up-regulated in a dose-dependent way after gradient concentrations of DATS treatment ( F = 65.68, P < 0.01; F = 26.65, P < 0.01). After changing the cell culture medium without DATS, the expressions of FRα protein in BGC823 and AGS cells gradually decreased and returned to the initial levels ( F = 74.57, P < 0.01; F = 30.92, P < 0.01). With the increase of DATS concentration, the apoptosis rates of BGC823 and AGS cells increased ( F = 32.95, P < 0.01; F = 38.97, P < 0.01). After TSA treatment, FRα protein expressions in BGC823 and AGS cells were up-regulated by 4.5 times ( t = -12.62, P < 0.01) and 3.6 times ( t = -10.00, P < 0.01). After 40 μmol/L and 20 μmol/L DATS treatment, the expression level of FRα protein in BGC823 and AGS cells was up-regulated (both P < 0.01), the expressions of HDAC1 and HDAC2 were inhibited (all P < 0.01), and the levels of H3K9ac and H4K5ac acetylation modification increased (all P < 0.01). The results of tumor-bearing nude mice experiment showed that the volume of transplanted tumor in DATS group was smaller than that in the control group [(214±39) mm 3 vs. (577±98) mm 3], and the difference was statistically significant ( t = 4.86, P < 0.01). Compared with the control group, FRα protein expression in the transplanted tumor tissues of DATS group was up-regulated about 2 times ( t = -5.29, P < 0.01), and the expression levels of HDAC1 and HDAC2 proteins were down-regulated ( t = 9.36, P < 0.01; t = 9.88, P < 0.01). Conclusions:DATS up-regulates the expression of FRα protein in human gastric cancer BGC823 and AGS cells in a dose-dependent and reversible manner. The mechanism may be related to the effect of DATS on histone acetylation modification in tumor cells.