Expression of the multi-drug resistance proteins and the pregnane X receptor in treated and untreated retinoblastoma

Purpose: To compare the expression of pregnane xenobiotic receptor and certain multi-drug resistance proteins in retinoblastoma. Methods: Using tissue microarray analyses, we studied 62 pathology specimens for expression of pregnane xenobiotic receptor, multi-drug resistance 1/P glycoprotein, multi-drug resistance proteins 1, 2, and 4, and breast cancer resistant protein. Results: Comparing tumors treated with primary enucleation with tumors treated with chemotherapy and/or radiation showed no significant differences in the expression of multi-drug resistance proteins or pregnane xenobiotic receptor. Pregnane xenobiotic receptor was correlated with multi-drug resistance protein 2 expression (p 0.001). Conclusion: Our results indicate selection, rather than induction, of chemoresistant cells as a cause for treatment failure in managing retinoblastoma with primary systemic chemotherapy.