The induction of multidrug resistance in human cervical carcinoma cell lines by estrogenic hormones

The role of estrogenic hormones on the induction of drug resistance was studied in cervical cancer cell lines, SiHa and Caski. After the cells were inoculated with estradiol (E2) or diethylstilbestrol (DES) in various dosages, the cell survival rates with adriamycin treatment were examined by MTT (3-[4,5-dimethyl-thiazole-2-yl]-2,5-diphenyl-tetrazolium-bromide) test and the intracellular accumulation of adriamycin was evaluated by flow cytometry. In the same condition, the expression of multidrug resistance gene-1 (mdr-1 gene) was detected either by Northern blot hybridization for mdr-1 mRNA or by immunoblot for P-glycoprotein 170. The data in this study indicated that estrogenic hormones had the capacity to induce drug resistance in cervical carcinoma cell lines. When cells were treated with estrogenic hormones and adriamycin simultaneously, the intracellular accumulation of adriamycin declined and corresponded with the drug resistance. Since the expression of the mdr-1 gene induced by E2 or DES results in drug resistance, it is suggested that the mdr-1 gene in SiHa cells may contain the estrogenic responsive element (ERE) in its regulatory region. However, the mechanism of drug resistance induced by estrogenic hormones in Caski cells is different from SiHa cells due to the absence of mdr-1 gene expression. Despite that, this experiment may provide a model to investigate the relationships between estrogenic hormones and drug resistance in other female genital cancers.