Establishment of cisplatin-resistant ovarian yolk sac tumor cells and investigation of the mechanism of cisplatin resistance using this cell line

Background: Cisplatin is used as a key drug for ovarian yolk sac tumor (YST), but relapse may occur. Details of the molecular mechanism responsible for cisplatin resistance remain unclear. Methods: We established cisplatin-resistant ovarian YST cells (NOY1-CR) from parent NOY1. To characterize these cells, we examined cross-resistance to other anticancer drugs. Then, cDNA microarray analysis was performed to quantify gene expression in NOY1 and NOY1-CR cells. The expression of several potential genes related to drug resistance was compared with parent cells by real-time PCR and Western blotting. Knockdown experiments using small interfering RNA (siRNA) were also performed to confirm the genetic association with drug resistance. Results: The IC₅₀ for cisplatin of NOY1-CR was 22.3-fold higher than that for parent cells. NOY1-CR cells showed cross-resistance to some drugs, but not to VP-16 and bleomycin. Microarray analysis identified 315 up-regulated and 412 down-regulated genes in NOY1-CR cells. Knockdown of GSTA1, which was up-regulated in resistant cells, by GSTA1 siRNA restored cisplatin sensitivity in NOY1-CR cells. Conclusions: Our data suggest the molecular mechanisms of cisplatin resistance and show the potential for GSTA1 to become a novel therapeutic target for cisplatin-resistant ovarian YST.