Evaluation of the antitumor activity of recombinant human gamma-interferon employing human melanoma xenografts in athymic nude mice.
Three human melanoma cell lines (G-361, HT-144, and SK-MEL-3) that were highly sensitive to growth inhibition in vitro by recombinant human interferon (rHuIFN-gamma) were adapted to grow as s.c. xenografts in athymic nude mice. Take rates were greater than 90% for all three tumors, with in vivo doubling times of 15, 4, and 15 days for G-361, HT-144, and SK-MEL-3, respectively. Commencing 3 days posttumor implantation mice were treated with daily s.c. injections of rHuIFN-gamma for 30 days over a dose range of 2.4-326 megaunits/mouse/day at a site distinct from the tumor implant. Tumors were measured twice weekly and mice were observed daily for deaths and morbidity until day 60 postimplantation. No apparent antitumor activity was observed in either the G-361 or HT-144 tumors at any dose despite the achievement of high rHuIFN-gamma blood levels. Intralesional treatment of the HT-144 xenograft with rHuIFN-gamma at 240 megaunits/mouse/day did not significantly retard tumor growth or increase lifespan. However, the SK-MEL-3 tumor showed a significant response at the 326-megaunit dose as noted by a tumor growth delay of 11.8 days in treated versus control animals and by an increased number of 60-day survivors. The tumor growth suppression appeared to be greater during the treatment period than during the subsequent observation period. Other experiments employing 326, 530, and 860 megaunits rHuIFN-gamma/mouse/day in mice bearing the SK-MEL-3 tumor demonstrated tumor growth delays of 4.2, 4.8, and 19.8 days, respectively, suggesting a dose response. These data support the conclusions that (a) in vitro antiproliferative activity of rHuIFN-gamma is not necessarily predictive of in vivo efficacy; and (b) relatively high doses of rHuIFN-gamma appear to be required for demonstrating an in vivo antitumor effect in this model.
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007371:Interferon-gamma / Q000627:therapeutic use*; D008545:Melanoma / Q000188:drug therapy*; D051379:Mice; D008819:Mice, Nude; D011994:Recombinant Proteins / Q000627:therapeutic use*; D014183:Transplantation, Heterologous
D000970:Antineoplastic Agents; D011994:Recombinant Proteins; D007371:Interferon-gamma