Drug transporters and multiple drug resistance in the most common pediatric solid tumors

Solid tumors account for approximately 30% of all pediatric cancers. Although chemotherapy has largely contributed to strongly improve patient outcome, multidrug resistance (MDR) remains one of the major mechanisms limiting the overall survival. The enhanced efflux rate of chemotherapeutic drugs from tumor cells through drug transporters is one of the most important mechanisms of MDR. Drug transporters play a pivotal role in preserving the balance between sensitivity and resistance of tumor cells to anti-neoplastic drugs. Their functional activities have been barely investigated in pediatric solid malignancies. Here, we provide evidence from the current literatures on drug transporters and MDR in the most common types of pediatric solid tumors, including neuroblas-toma, Wilms' tumor, rhabdomyosarcoma, retinoblastoma, medulloblastoma and hepatoblastoma.