[Role and mechanism research on reversal of 5-fluorouracil resistance by epigallocatechin gallate in gastric cancer drug-resistance cells lines SGC-7901/5-FU].

To study the role and molecular mechanism of epigallocatechin gallate (EGCG) in reversing drug-resistance to 5-fluorouracil (5-FU) in gastric cancer drug-resistant cell line SGC-7901/5-FU.Drug-resistance gastric cancer cell line (SGC-7901/5-FU) was established by high doses of repeated impact joint drug concentration increment methods. The cell viability of the parent cell line and the drug-resistance cell line were determined by standard MTT assay. Cell survival rate of drug-resistance was calculated by the formula [(A490 of the treatment group / A490 of the control group) × 100%]. Cell half inhibitory concentration (IC50) and resistance index (RI) were calculated by the Graphpad prime 6.0 software(RI=IC50 value of drug-resistance cells / IC50 value of parent cells). The apoptosis rate of SGC-7901/5-FU cells was quantified by flow cytometry after staining with annexin-V and PI. Western blot was used to detect the protein expression of drug-resistance-related proteins (ABCG2, P-gp, MDR-1 and GST-π) and apoptosis-related proteins (PARP, Survivin, Bax and bcl-2).IC50 value was significantly increased in drug-resistant cells compared with parental cells [(64.7±3.9) mg/L and (4.1±0.3) mg/L, respectively, t=26.46, P=0.000], and the RI was 15.6. Proliferation activity in the drug-resistant cells was higher than that in parental cells at different 5-FU concentrations (all P<0.05). In drug-resistant cells, the IC50 value of 5-FU combined with EGCG group obviously decreased compared with 5-FU group [(7.3±0.1) mg/L and (63.1±1.4) mg/L respectively, t=40.84, P=0.000], and the RI was 0.12. Proliferation activity in drug-resistant cells was significantly decreased after EGCG treatment at different 5-FU concentrations (all P<0.05). Cell apoptosis rates in control group, 5-FU group, EGCG group and 5-FU combined with EGCG group were (3.0±1.0)%, (7.0±1.3)%, (6.0±1.2)% and (18.0±1.4)%, while apoptosis rate in 5-FU combined with EGCG group was significantly higher than those of other 3 groups(F=129.5, P=0.000). Western blot revealed that after EGCG treatment, the expression levels of drug-resistance-related proteins (ABCG2, P-gp, MDR-1 and GST-π) in the drug-resistant cell line SGC-7901/5-FU decreased significantly; the expression levels of apoptosis marker protein PARP and pro-apoptotic protein Bax increased significantly; and the expression levels of anti-apoptotic protein Survivin and Bcl-2 decreased significantly (all P<0.05).EGCG can reduce the resistance of gastric cancer resistant cell line SGC-7901/5-FU, whose role may be via the inhibition of the expression of drug-resistance-related proteins, and the elevation of the protein expression ratio of PARP/Survivin and Bax/Bcl-2.