Expression of multidrug-resistance-associated protein gene in human soft-tissue sarcomas

We examined the mRNA expression of the multidrug- resistance-associated protein gene (MRP) in soft-tissue sarcomas and compared it with the expression of the multidrug resistance gene (MDR1), using the reverse transcriptase/polymerase chain reaction. We investigate 39 samples from 33 cases of soft-tissue sarcomas (11 liposarcomas, 9 malignant fibrous histiocytomas, 6 leiomyosarcomas, 4 malignant schwannomas, 3 fibrosarcomas, 3 synovial sarcomas, and 3 epithelioid sarcomas) and 7 benign soft-tissue tumors. All samples were obtained prior to chemotherapy. An expression of MRP mRNA was noted in 56% of soft-tissue sarcoma specimens. The co-expression of MRP and MDR1 was recognized in 15 samples (38%) (5/11 liposarcomas, 5/9 malignant fibrous histiocytomas, 3/6 leiomyosarcomas, 2/3 fibrosarcomas) and significantly correlated with histological grade (P=0.0165). A positive and significant correlation was found between MRP and MDR1 expression in soft-tissue sarcomas(P=0.0013). In benign soft-tissue tumors, 1 chemodectoma and 1 neurothekeoma showed low MRP expression; however, no case showed co-expression of MRP and MDR1.