MRP expression of testicular cancers and its clinical relevance.

Background: The expression of a multidrug resistance associated protein (MRP) has been investigated in a variety of human tumors. However, there is a lack of data regarding its expression in germ cell testicular tumors (GCTTs). Patients and Methods: MRP expression was examined by immunohistochemistry (IHC) using mouse monoclonal antibody (MRPm6) against human MRP in 56 testis cancer specimens. This antigen was also correlated with the histology, metastatic behavior, clinical stage and tumor suppressor protein p53 immunostaining of GCTTs. Results: All testis tumors, regardless of their histology, metastatic status and clinical stage gave positive signals. MRP was positive not only in the cytoplasm but, very interestingly, in the nuclei. Conclusion: Our results suggested that ala GCTTs express high levels of MRP protein with no relation to any of clinicopathological variables investigated here. Since germ cell tumors are very sensitive to chemotherapy, the role of MRP as mediator of drug resistance seems unconvincing in this malignancy. MRP is located in the cytoplasm and the nuclei of tumor cells and may be involved in transportation and/or redistribution certain substrates from the nucleus to the cytoplasm.