Interferon α2b differentially affects proliferation of two human renal cell carcinoma cell lines differing in the P-glycoprotein-associated multidrug-resistant phenotype

Abstract

Purpose : Interferon α (IFNα) has been used in the immunotherapy of renal cell carcinoma (RCC), but the various mechanisms of its antiproliferative effects are poorly understood. Recent evidence suggests that IFNα is involved in the up-regulation of multidrug resistance (MDR) gene expression, and that the MDR gene product, P-glycoprotein (Pgp), facilitates the transport of several cytokines, some of which have been implicated in mediating tumor antiproliferative effects. We hypothesized that IFNα-induced antiproliferative activity may require Pgp-mediated transport, and that susceptibility to IFNα may thus correlate with Pgp expression. Methods : Pgp expression by the human RCC cell lines KTCTL-2 and KTCTL-26 was characterized by immunofluorescence staining, using the Pgp-specific primary antibodies C219 and JSB1. KTCTL-2 and KTCTL-26 cell lines were subsequently treated with IFNα2b, and growth kinetics of treated and control cell cultures were determined daily by cell counting. Results : KTCTL-2 expresses Pgp at low levels, whereas KTCTL-26 is a highly expressing cell line. IFNα2b treatment abrogated cell proliferation in KTCTL-26, whereas proliferation of KTCTL-2 was only partially inhibited. Conclusions : We have identified two RCC cell lines that differ in the MDR phenotype and exhibit different responses to the antiproliferative activity of IFNα2b. These preliminary findings raise the possibility that susceptibility to the antiproliferative effects of IFNα2b may correlate with Pgp expression, and further studies are warranted.