Multidrug resistance-associated protein 1 (MRP1) expression in neuroblastoma cell lines and primary tumors

Background and Procedure. MRP1 expression by neuroblastomas was evaluated b y Northern blot analysis in 21 cell lines and 90 primary untreated tumors. Cytotoxicity assay in cell lines was performed for five anticancer drugs us ed in treating neuroblastoma. Results. MRP1 expression did not correlate wi th drug resistance or with MYCN RNA expression in cell lines. MRP1 expressi on was higher in drug-sensitive cell lines established after chemotherapy r elative to cell lines at diagnosis, but highly drug-resistant cell lines sh owed low MRP1 expression. Positive expression of MRP1 RNA in primary tumors was associated with a poorer survival relative to MRP1-negative tumors. Ho wever, MRP1 expression levels did not correlate with age, stage, MYCN ampli fication, or MYCN expression, and higher MRP1 expression was not associated with a worse outcome. Conclusions. In neuroblastoma, positive MRP1 RNA exp ression at diagnosis has prognostic significance, but high drug resistance is conferred by mechanisms other than MRP1. Med. Pediatr. Oncol. 35:619-622 , 2000. (C) 2000 Wiley-Liss, Inc.