Drug Resistance Studies Using Fresh Human Ovarian Carcinoma and Soft Tissue Sarcoma Samples

Abstract

The relevance of continuous cell line cultures to the problem of clinical anticancer drug resistance is unclear. There is also mounting scepticism regarding the use of tumour cell lines with in vitro acquired drug resistance, possessing high levels of resistance unlikely to be seen in the clinical setting. To overcome some of these problems we have initiated a study of drug resistance using fresh tumour material obtained from patients suffering from ovarian cancer and soft tissue sarcoma (STS). Studies involving ovarian cancer have involved over 30 specimens of stage III-IV disease. For these samples we have specifically focused on the multidrug-resistant (MDR) phenotype, examining the role of proteins P-glycoprotein (Pgp), multidrug resistance-protein (MRP) and lung-resistance-associated protein (LRP). Techniques have involved chemosensitivity testing, immunocytochemistry and flow cytometry, to measure Pgp function (drug efflux capacity with modulator reversal). Pgp was the most commonly expressed marker and its expression correlated with survival. MDR modulation using cyclosporins was shown to chemosensitise a proportion of the samples. Hence, in vitro screening can help to identify patients likely to benefit from resistance reversal strategies. Studies involving STS have looked at a combination of MDR and p53 disruption (commonly seen in this disease). Data have been examined alongside clinical data and the course of disease has been closely monitored. Although our studies are ongoing, we have identified a group of patients with aggressive disease showing marked drug resistance in vitro. All patients have relapsed with persistent disease following chemotherapy or radiotherapy. A number of chemoresistant patients showed a combination of p53 disruption in the presence of an MDR phenotype. Feedback from these translational studies should be used to guide the selection of patients for clinical trials using resistance reversal strategies and may suggest new targets for drug development.