| Objective To investigate the effect of BSO and NAC to IC50values of MMC and5-FU on gastric adenocarcinoma cell line (SGC7901) and resistance cisplatinSGC7901/DDP cell line by altering the contents of intracellular GSH and further to theresearch the relationship between changing of intracellular redox status and MultidrugResistance (MDR).The study also may provided a valuable basic research to anti-cancertherapy in clinic.Methods (1) The value of50%inhibitory concentration of CDDP,5-FU and MMC toSGC7901/DDP cells and SGC7901cells was calculated on the basis of the measuredOD values using an MTT colorimetric assay. Besides RI (Resistant Index) were figuredout on the basis of IC50values.(2) TO select the sublethal concentration of BSO andanalyze the effects of BSO on the IC50values of two cells to5-FU and MMC.(3)analyze the effects of N-acetylcysteine (NAC) on the IC50values of two cells to5-FUand MMC and the statistic variances.(4) to observe the reverse effects of NAC toBSO (5) Alteration of intracellular GSH by various concentrations of BSO or NACtreatment and expression of Mrp1suing RT-PCR, meanwhile analysis of statisticvariances.Results (1) SGC7901/DDP cell exhibited more resistance to different drugs compared with its parental cell (p<0.05) and the RI was6.20folds in CDDP,3.49folds in5-FUand1.97folds in MMC respectively.(2) After different concentrations of BSOpretreatment, the IC50-values of5-FU in both cells were significantly decreased.Meanwhile, BSO could increase the chemo-sensitivity of SGC7901/DDP cell to MMC(p<0.05). Although BSO could slightly decline IC50value of SGC7901cell by MMCtreatment (p<0.05), there was no a statistical difference between the chemo-sensitivitiesof the cells with BSO and relevant control (p>0.05).(3) It is obvious that there wereremarkable increases in the IC50-values of both MMC and5-Fu in SGC7901/DDP cellspretreated with5mM N-acetylcysteine (NAC)(p<0.05). On the other hand, though theresistance of SGC7901cells to MMC was also elevated by NAC pretreatment (p<0.05),the phenomenon had not happened to5-FU (p<0.05).(4) It was displayed that NACcould partly restore the inhibition of BSO on the chemo-resistances of both cells to5-Fu(p<0.05) and decline the inhibition of BSO on the chemo-resistance of SGC7901/DDPcells to MMC (p<0.05). However, there was not the statistical significance to the effectof MMC on SGC7901cells with BSO pre-treatment (p>0.05).(5) SGC7901/DDP cellshave higher GSH contents compared to SGC7901cells (p<0.05), and then NAC alonetreatment could increase the levels of GSH in both cells (p<0.05). Similarly, after allcells treated by BSO in different concentrations, there were significant reductions ofintracellular GSH levels in concentration-dependent manner. Subsequent experimentsshowed that the inhibition on intracellular GSH by BSO treatment was partiallyreversed by the addition of NAC. The trend of the alteration of intracellular GSH wasbasically consistent with the chemo-resistance of SGC7901/DDP cells to multiple drugsbut not that of SGC7901cells. The NAC treatment could upgrade the expression ofMrp1gene and BSO had the opposite effect in SGC7901/DDP cells，but the effectshave not observed in SGC7901cells.Conclusions (1) SGC7901/DDP cells could produce cross-resistance to5-Fu and MMC.It was therefore indicated that SGC7901/DDP cells was multidrug resistant cell line.(2)After BSO pretreatment, SGC7901/DDP cells were more sensitive than SGC7901cells to multiple chemical drugs.(3) Compared with its parent cells, After NAC pretreatment,SGC7901/DDP cells were more resistant than SGC7901cells to multiple chemicaldrugs.(4) NAC could partly restore the inhibition of BSO on the chemo-resistances ofSGC7901/DDP cells to5-Fu and MMC（5）The study suggested that the alteration ofintracellular micro-environment redox state could change the multidrug resistance invitro which might affect the expression of MRP1gene. |
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