Induction of MDR1-gene expression by antineoplastic agents in ovarian cancer cell lines

Background: Development of resistance to anticancer drugs is a major concern in clinical oncology and might be particularly involved in the secondary treatment failure frequently seen in ovarian cancer. Clinical observation of the multidrug resistance (MDR) phenotype is often associated with overexpression of the mdr1-gene. However, until now the mdr1-inducing potential of commonly used antineoplastics has been only incompletely explored. Materials and Methods: We perfomed short-term cultures of 7 established ovarian cancer cell lines exposed to either blank medium or one of three single anticancer drugs (cisplatin, doxorubicin, paclitaxel) at concentrations related to the clinically achievable plasma peak concentration. Mdrl-transcripts were detected using the highly specific quantitative real time RT-PCR. To calibrate each approach, mdrl-mRNA content was calculated in relation to co-amplified GAPDH-mRNA. Results: Mdrl-mRNA was detectable in each cell line. In 13 assays (62%) the specific anticancer drug being tested induced mdr1-transcription. No decrease in mdrl-mRNA concentration was observed. The method described here is easy to perform and could be of striking value in predicting the development of tumor chemoresistance. Conclusion: Our data indicate that mdrl-induction by antineoplastics is one of the reasons for failure of ovarian cancer therapy but may vary from one individual to another.