Differential expression of the multidrug resistance-related protein MRP1 in the histological compartments of nephroblastomas

Nephroblastomas (Wilms' tumors) are curable with survival rates above 80%. Some tumors, however, fail to respond to therapy and those patients have a. poor prognosis. In a search for prognostic markers, we investigated the ex pression of the multidrug resistance-related protein 1 (MRP1) in 32 nephrob lastomas by means of immunohistochemistry. The immunohistochemical results were validated with a real-time RT-PCR technique. MRP1 expression was heter ogeneous and predominately found in the blastemal and epithelial compartmen ts compared to the stromal elements of nephroblastomas. We found significan t relationships of MRP1 expression to survival of patients and to expressio n of p53, HSP70, and LRP/MVP. The relationship between MRP1 and p53 express ion is a clue that the transcriptional control of MRP1 by p53 reported for other tumor types may also take place in nephroblastomas. The correlation o f MRP1 to other drug resistance genes, e.g. HSP70 and LRP/MVP in nephroblas tomas indicates that the co-expression of different drug resistance genes m ay be under a common regulation of still unknown transcription factors.