Use of multidrug-resistance gene (MDR1) expression levels to predict outcome to adjuvant cisplatin/gemcitabine based chemotherapy in patients with with locally advanced urothelial cancer

Abstract

e22081 Background: The human MDR1 gene encodes an integral membrane protein, P glycoprotein (Pgp), whose function is the energy dependent export of substances from the inside of cells, and from membranes, to the outside. MDR1 mRNA levels have been shown to influence metabolism of cancer drugs. We tested whether MDR1 gene expression is associated with outcome in patients with locally advanced bladder cancer. Methods: 43 formalin fixed paraffin embedded (FFPE) tumor samples from patients with locally advanced and/or lymph node-positive bladder cancer undergoing treatment with cisplatin/gemcitabine were analyzed.FFPE tissues were dissected using laser-captured microdissection and analyzed for MDR1 expression using a quantitative real- time RT-PCR method. Gene expression values (relative mRNA levels) are expressed as ratios between the target gene and internal reference gene (beta-actin). Results: MDR1 was significantly correlated to overall survival. We included tumor stage (pT), lymph node status (pN) and the blood vessel invasion along with the measured gene expression in a stepwise multivariate Cox proportional hazards regression model. The overall model fit had a significance level of p=0.04 (<0.05). The relative risk for shorter survival in patients with High MDR1 expression was 1.9. Conclusions: These results suggest that MDR1 gene expression levels predict response and overall survival in patients with locally advanced urothelial cancer. MDR1 gene expression levels may allow the selection of patients who benefit likely from adjuvant cisplatin/gemcitabine based chemotherapy. Further studies are warranted to study this association. [Table: see text]