Expression of P-Glycoprotein in Non-Hodgkin's Lymphomas

Drug resistance has been shown to be associated with the expression of P-glycoprotein (P-gp), the product of the mdr-1 gene. In the present study the expression of P-gp in 57 cases B-cell non Hodgkin lymphoma NHL was assessed before chemotherapy. Six cases of reactive lymphoid tissue and 11 cases of solid tumors were also studied. The expression of P-gp was evaluated by immunocyto- and histochemical methods, using three different Monoclonal Antibodies C219, JSB-1 and MRK16 directed against separate epitopes of P-gp. Comparable frequencies of cases positive for P-gp were found in low grade (6/40) and high grade (3/17) lymphomas. The pattern of staining was predominantly cytoplasmic, although a Golgi-associated dot like pattern of staining was also seen, mostly with JSB-1 MAb. Both cases of Hairy cell leukemia were P-gp positive. P-gp expression was also found in the endothelium of small capillaries and some high endothelial venules, as well as in macrophages, in both lymphomas and reactive lymphoid tissues. P-gp expression was found in a low frequency in NHL, suggesting that clinical drug resistance may already be predicted at the time of diagnosis and thus may serve as a guide in the choice of chemotherapeutical regiment.