P-glycoprotein expression and multidrug resistance in cutaneous T-cell lymphoma

Advanced-stage cutaneous T-cell lymphoma (CTCL) is generally resistant to s tandard chemotherapy. Because P-glycoprotein (P-gp) has been detected in ot her types of resistant solid tumors, leukemias, and lymphomas, we analyzed P-gp expression in CTCL. Twenty-seven patients with CTCL and circulating Se zary cells in the peripheral blood as observed on a peripheral smear treate d at the Yale Photopheresis Center between 1987 and 1993 were identified. T wenty-five of these patients had skin biopsies evaluated for expression of P-gp using JSB-1 (Accurate Chemical), MRK-16 (gift of T. Tsuruo), and UIC-2 (gift of E. Metchner). P-gp expression was considered present if immunorea ctivity was noted with two of the three antibodies. Eighteen of 25 patients (72%) evaluated exhibited expression. The patients were treated with vario us combinations of drugs consisting of topical and systemic steroids, elect ron beam therapy, psoralens in combination with UV light A (PUVA), systemic chemotherapy, and photopheresis before testing the tissue for P-gp express ion. Treatment with systemic chemotherapy in P-gp-positive patients produce d responses in 3 and no responses in 11 patients (4 were lost to follow-up) . Seven patients did not express P-gp: One patient responded to treatment, five did not respond and one patient was lost to follow-up. These results d emonstrate that P-gp is frequently expressed in CTCL. P-gp expression in ou r study was not a useful predictor of drug resistance.