Expression of multidrug resistance-1 and multidrug resistance-associated protein genes in pediatric rhabdomyosarcoma.

Overexpression of multidrug resistance-1 (MDR-1), and multidrug resistance-associated protein (MRP) genes has been linked with resistance to chemotherapy in vitro and in vivo. Their role in chemotherapy resistance in pediatric rhabdomyosarcoma is unclear. The study was undertaken to analyze the expression of MDR-1 and MRP genes in the embryonal and the alveolar subtypes of rhabdomyosarcoma and to elucidate its clinical relevance. Twenty-three rhabdomyosarcoma samples were analyzed for the expression of MDR-1 and MRP genes using a semi-quantitative competitive RT-PCR assay. MRP gene expression was associated with a reduction in survival (p=0.02). The overall survival of patients with tumors positive or negative for MRP expression were 50% (95% confidence interval, 30-70%) and 93% (95% confidence interval, 76-100%) respectively. In contrast, the expression of MDR-1 gene was not predictive of survival. These findings suggest that MRP expression could be a prognostic factor in patients with rhabdomyosarcoma.