Abstract

The development of multidrug-resistant tumor cell population is a major problem in the chemotherapy of human cancer. These cells are often cross resistant to unrelated drugs and the precise mechanisms of multidrug resistant phenotype of tumor cells has not been fully elucidated. Cisplatin resistant tumor cell (SNU-1/Cis₅) was induced from human stomach cancer cell line (SNU-1) in vitro. Growth profiles of survival cells were observed during 5 days by thiazolyl blue (MTT) assay. To investigate the cross resistance of various anticancer drugs in SNU-1 and SNU-1/Cis5, We compared the value of IC₅₀-drug concentration at 50% survival of control and gained relative resistances (RR). The RR for SNC-1/Cis₅ were as follows; vinblastine, > 43.0; epirubicin, 22.9; dactinomycin, 16.0; etoposide, 15.0; vincristine, 9.2; adriamycin, 5.7; aclarubicin, 5.3. But 5-fluorouracil, methotrexate, daunorubicin have not cross resistance with cisplatin. Resistant inhibition values of 10µM verapamil for SNU-1/Cis₅ were as follows; vincristine, 13.1; epirubicin, 10.0; etoposide, 6.3; vinblastine, 4.4; dactinomycin, 3.6; daunorubicin, 2.4. Membrane proteins of 51,400 and 81,300 daltons were identified by radioiodination with SDS-PAGE, which might represented the drug resistance.

• Keywords: Multidrug resistance (MDR);Verapamil;P-glycoprotein