Ulti mately, the frequent development of drug resistance and the lack of alternatives for the treatment of drug resis tant disease are responsible for a 5 year survival of approximately 30% in ovarian cancer patients with advanced disease. Indeed, 90% of the deaths from ovar ian cancer can be attributed to drug resistance. Studies have shown that ovarian cancer resistance is multifactorial and may involve increased drug inactiva tion efflux, increased DNA repair, alterations in cell cycle control, and changes in apoptotic threshold. For example, the copper transporter CTR1 has been shown to mediate cisplatin uptake and cells with decreased CTR1 exhibit increased resistance to cisplatin. Another pathway, the PTEN PI3K AKT axis, has been suggested to play an important role in the development of drug resistance in several malignancies, including ovarian cancer.

Overall, these studies indicate that a better understanding of the mechanisms of drug action and drug resistance may ultimately lead to new approaches for circumventing resistance and improve patient survival. However, in purchase WIKI4 spite of recent advances, the exact pathways important for the development of drug resistance in ovarian cancer remain unclear. A bet ter understanding of the molecular mechanisms leading to drug resistance may provide new opportunities for the development of strategies for reversing or circum venting drug resistance. In this manuscript, we generate novel drug resistant ovarian cancer cell lines independently selected for resis tance to cisplatin, doxorubicin or paclitaxel, and we use gene expression profiling to identify genes and pathways that may be important to the development of drug resis tance in ovarian cancer.

Methods Cell line and generation of drug resistance sub lines The ovarian cancer cell line OV90 was obtained from The American Type BAY 57-1293 Culture Collection and grown in MCDB 105,Media 199 containing 15% bovine serum and antibiotics at 37 C in a humidified atmosphere of 5% CO2. The che motherapeutic drugs cisplatin, doxorubicin, and pacli taxel were purchased from Sigma. The resistant sub lines were generated by exposure to the drugs for four to five cycles. For each cycle, the cells were exposed to each individual drug for twenty four hours, and then trans ferred to normal media where they were allowed to grow for 2 weeks.

Following this two week period, the cells were re exposed to the drug to initiate the next cycle. Illumina Microarray and data analysis RNA samples were purified using the RNeasy kit. Biotinylated cRNA was prepared using the Illu mina RNA Amplification Kit according to the manufacturers directions starting with approxi mately 500 ng total RNA. Hybridization to the Sentrix HumanRef 8 Expression BeadChip, washing and scanning were performed according to the Illumina BeadStation 5006 manual.