AIDS-related lymphomas (ARL) progressively become resistant to conventional chemotherapy. We have developed three B cell lines from tumor biopsies of AIDS patients with non-Hodgkin's lymphoma (NHL). The ARL cell lines were shown to be resistant to a panel of cytotoxic cytokines, toxins and drugs such as tumor necrosis factor, diphteria toxin, ricin, adriamycin, cis-platinum and anti-Fas antibody. However, when these cell lines were pretreated with low concentrations of interferon-gamma (IFN-gamma), (50 U/ml or 150 U/ml) for 24 to 48 h, the tumor cells became sensitive to these cytotoxic agents. Pretreatment of ARL with IFN-gamma stimulated proliferation while IFN-gamma inhibited the growth of ovarian tumor cell lines. Further, following treatment with IFN-gamma, the secretion of TNF-alpha by ARL lines was significantly decreased and TNF-alpha surface receptor expression was downregulated. The expression of several surface antigens on ARL was upregulated by IFN-gamma. These findings demonstrate that treatment of ARL with IFN-gamma stimulated cell proliferation, modulated several surface antigens, inhibited TNF-alpha secretion and sensitized the tumor cells to cytotoxicity by various drugs/toxins. These findings may be clinically relevant in the treatment of drug-refractory ARL.

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