Interaction between dactinomycin and tumor necrosis factor in mesothelioma. Cachexia without oncolysis.

There is no effective therapy for human malignant mesothelioma, and its susceptibility to recombinant cytokines has not been studied extensively. Recombinant human tumor necrosis factor alpha (rHuTNF alpha) was evaluated for its in vitro and in vivo antitumor activity using a human malignant mesothelioma cell line [DeH128(m)], both in culture and heterotransplanted in nude mice. In vitro, rHuTNF alone had no direct antimesothelioma activity assessed using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide assay, but in combination with the transcription inhibitor, dactinomycin (AD), mesothelioma cell metabolic activity was inhibited (80% of control). The effects of this combination of agents were studied on DeH128(m) cells heterotransplanted as subcutaneous tumors in nude mice. In vivo there was no significant inhibition of tumor growth by combined rHuTNF alpha and AD therapy, but the combination produced marked cachexia in doses at which each component (rHuTNF alone or AD alone) was well tolerated. The authors conclude that the well-described in vitro interaction between AD and rHuTNF also operates in vivo to produce cachexia and that the combination of these two agents is likely to have a low therapeutic index in malignant mesothelioma.