[Anti-tumor effect of human recombinant TNF]

In this article, the clinical effects of rH-TNF on various cancer patients and the mechanism of self-induction of defense against rH-TNF cytotoxicity in tumor cells and the counter measures against this are reviewed. 1) Clinical effects of rH-TNF Intratumoral administration of rH-TNF was performed in 7 patients and clinical efficacy (PR + MR) was observed in 3/7 (42.9%). Also a reduction of leukemia cells in peripheral blood was observed in all 4 leukemia patients following intravenous (i.v.) administration of rH-TNF. Furthermore, in 2 multiple myeloma patients, the myeloma protein and plasma cells in bone marrow were reduced by i.v. administration of rH-TNF. 2) Self-induction of defense against rH-TNF cytotoxicity Investigation of the effect of TNF on RNA and protein synthesis by tumorigenic and normal cell lines showed that their synthesis in tumor cells was increased at 12 h and peaked at 24 h of incubation with TNF, while that in normal diploid fibroblast (HEL) cells was apparently unaffected by the presence of TNF. Artificial inhibition of either RNA or protein synthesis by L-M cells, upon addition of Act D or CHI increased the cytotoxic effect of TNF, thus suggesting that the elevated RNA and protein synthesis is related not to the cytotoxic reaction itself but rather to a defense mechanism. Similar incubation of HEL cells with TNF in the presence of either inhibitor resulted in the occurrence of cytotoxicity not observed with TNF alone, thus suggesting the existence of a defense mechanism in normal, TNF-resistant cells which is absent or greatly weakened in tumor cells. 3) Combination therapy of rH-TNF with various anticancer drugs. A synergistic increase in the cytotoxic effects of rH-TNF and anti-cancer drugs was demonstrated in vitro The cytotoxicity of rH-TNF against L-M cells in combination with MMC, ADM, Ara-C, ACD, DM, CDDP, VCR and 5-FU was 4 to 347 times as high as that of rH-TNF alone. These results suggest that combination therapy including rH-TNF and anti-cancer drugs may be of value in the treatment of malignancy in human patients.