Effect of fibroblast interferon on colony tumor growth of miscellaneous solid human tumors

The antiproliferative effect of fibroblast interferon (IF-beta) on the colony tumor growth of 42 miscellaneous carcinomas (15 gastric, 11 breast, eight colon, five ovarian, three bronchial) and two malignant melanomas were assayed in a semisolid, double-layered agar culture system. Of the 44 evaluable experiments only four tumor specimens (three breast-, one gastric carcinoma) showed at least a 30% inhibition of colony formation due to application of interferon at concentration of 1,000 IU/ml or less. In these cases, a dose response relationship of the interferon effect was obvious. Yet, in the majority of carcinomas investigated, interferon had no antiproliferative influence on colony tumor growth and was markedly inferior to a simultaneously tested cytostatic agent (adriamycin). Our in vitro results contradict a general direct cytotoxic action of interferon on human solid carcinomas.