| Objective Effect and mechanism of2-amino-4-(S-Butanesulfonyl imino) butyric acid(BSO) and acetylcysteine (NAC), which change intracellular glutathione (GSH), onsensitivity of gastric adenocarcinoma SGC7901cells to anticancer drugs doxorubicinStar (ADM) and etoposide (VP-16) were investigated, providing valuable clues tofurther research on gastric cancer chemotherapy sensitizer drug.Methods (1)The concentration of BSO which is not toxic to SGC7901cells wasdetermined by MTT assay and used for following experiments. IC50of antitumor drugADM and VP-16to SGC7901was also measured. The ROS level was assayed after20%IC50ADM and20%IC50VP-16treatment, or combined pretreatment with non-toxicconcentrations of BSO and5mmol/L NAC.(2) IC50of SGC7901after combinedtreatment of BSO/NAC and ADM/VP-16was determined. The level of ROS aftercombined treatment of BSO/NAC and20%ADM/VP-16was also determined.(3) GSHcontent was determined when SGC7901was treated with5mmol/L NAC or not.(4) Theactivity of γ-GCS was determined when SGC7901was treated with5mmol/LNAC/BSO or not.(5) The level of MRP1and P-GP was determined when SGC7901was treated with5mmol/L NAC/BSO or not.Results(1) The IC50and concentration of BSO which is not toxic to SGC7901cells was3.5and0.7mg/ml, respectively. IC50of ADM and VP-16to SGC7901was4ug/ml and17ug/ml, respectively. The ROS level was5.820.97,5.12，4.29or2,73after treatmentof BSO,5mmol/L NAC,20%IC50ADM or20%IC50VP-16, no treatment,respectively.(2) IC50of SGC7901after combined treatment of non-toxic concentrations of BSO andADM/VP-16was1.12ug/ml and4.74ug/ml. IC50of SGC7901after combinedtreatment of5mmol/L NAC and ADM/VP-16was4.42ug/ml and21.23ug/ml, which were significantly higher than that in control (p<0.01). The level of ROS was6.30and6.08after combined treatment of non-toxic concentrations of BSO and20%ADM/VP-16, and was2.09and3.00after combined treatment of5mmol/L NACand20%ADM/VP-16, which were significantly different from control group (p<0.01).(3) GSH content was0.18and12.67umol/g protein when SGC7901was treated with5mmol/L NAC, which were significantly different from2.31in control (p<0.01).(4)The activity of γ-GCS was7.62umol/g protein under treatment of non-toxicconcentrations of BSO, which was lower than control (10.80umol/g protein). However,treatment of5mmol/L NAC had no effect on the activity of γ-GCS (11.43vs.10.8umol/g protein, p﹥0.05)(5) The level of MRP1and P-GP didn’t change whenSGC7901was treated with5mmol/L NAC/BSO or not.Conclusions(1) BSO is a specific inhibitor of γ-GCS, NAC has no significant effect onthe activity of γ-GCS.(2) BSO significantly inhibited the intracellular GSH, combinedtreatment of BSO with ADM/VP-16could increase the intracellular ROS level,indicating it was an effective sensitizer for chemotherapy drugs.(3) NAC significantlypromoted intracellular GSH, and decreased ROS level, reduced sensitivity of tumorcells to chemotherapy drug.(4) Non-toxic concentrations of BSO and5mmol/L NACdid not significantly change the expression level of MRP1or P-GP, which indicate thatneither BSO nor NAC could change expression of tumor cell resistance protein,providing new ideas to solve tumor resistance. |
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