SYNERGISTIC CYTOTOXICITY OF HUMAN RECOMBINANT TUMOR-NECROSIS-FACTOR-ALPHA COMBINED WITH MICROTUBULE EFFECTORS

Combinations of human recombinant tumour necrosis factor-alpha (rhTNF-alpha) with each of four different agents disturbing the microtubule system of the cellular cytoskeleton were tested for synergistic cytotoxic action against murine melanoma B16K and L-M(S) cells. In addition to the known microtubule effectors colchicine, vincristine, and taxol, the influence of the fluorenone-azomethine derivative alpha-diphenylene-N-{p-[bis-(beta-hydroxyethyl)-amino]-phenyl}-nitrone (DHPN) on the rhTNF-alpha cytotoxicity was studied. Applying a novel computer-based isobole method [Suehnel J (1990) Antiviral Res 13:23-40] concentration ranges of synergistic, zero, and antagonistic interaction were found after in vitro combination of rhTNF-alpha with each of the drugs tested in a 72-h cytotoxicity assay. In contrast, a 24-h exposure of B16K cells to these combinations still did not inhibit in vitro colony formation to a greater extent than either drug alone. A preliminary in vivo experiment revealed an increased antitumour effect after treatment of established subcutaneous melanoma B16 tumours with a combination of rhTNF-alpha and DHPN.