P-Glycoprotein Expression and Multidrug Resistance in Cutaneous T-cell Lymphoma

Abstract

Advanced-stage cutaneous T-cell lymphoma (CTCL) is generally resistant to standard chemotherapy. Because P-glycoproteiri (P-gp) has beeti detected in other types of resistant solid tumors, leukemias, and lymphomas, we analyzed P-gp expression in CTCL. Twenty-seven patients with CTCL and circulating Sezary cells in the peripheral blood as observed on a peripheral smear treated at the Yale Photopheresis Center between 1987 and 1993 were identified. Twenty-five of these patients had skin biopsies evaluated for expression of P-gp using JSB-I (Accurate Chemical), MRK-16 (gift of T. Tsuruo), and UIC-2 (gift of E. Metchner). P-gp expression was considered present if immunoreactivity was noted with two of the three antibodies. Eighteen of 25 patients (72%) evaluated exhibited expression. The patients were treated with vairiaus combinations of drugs consisting of topical and systemic steroids, electron beam therapy. psoralens in combination with UV light A (PUVA), systemic chemotherapy, and photophersis before testing the tissue for P-gp expression. Treatment with systemic chemotherapy in P-gp-positive patients produced responses in 3 and no responses in II patints (4 were lost to follow-up). Seven patients did not express P-gp: One patiem responded to treatment. five did not respond, and one patient was lost to follow -up. These results demonstrate that P-gp is frequently expressed in CTCL. P-gp expression in our study was not a useful predictor of drug resistance.