P-GLYCOPROTEIN EXPRESSION IN SOFT-TISSUE SARCOMAS

Multidrug resistance (MDR) is an important problem in chemotherapy for neoplastic disease. In humans, MDR is mainly mediated by P-glycoprote in (P-gp), a product of the MDR1 gene, which acts as a transmembrane p rotein pump and eliminates chemotherapeutic agents from the cells. Exp ression of P-gp was immunohistochemically studied by using two monoclo nal antibodies, JSB-1 and C-219, on paraffin-embedded sections from 55 patients with soft-tissue sarcoma. The histological diagnosis of tumo rs was malignant fibrous histiocytoma in 24 cases, liposarcoma in 9, s ynovial sarcoma in 7, malignant neurogenic tumors in 6, leiomyosarcoma in 5, others in 4. The histological grade was determined on the basis of criteria previously proposed by us. Out of 55 cases, 34 (62%) were positive for P-gp expression. There was a significant difference in P -gp expression between high-grade (90%) and intermediate and low-grade tumors (46%) (P < 0.005). Tumors expressing P-gp had a less favorable prognosis than P-gp-negative tumors in the high- and intermediate-gra de tumors. The current study demonstrated that the estimation of P-gp expression could be used to select appropriate therapeutic modalities.