Effect of alpha- and gamma-Interferon and tumor necrosis factor on colony formation of two human renal tumor xenografts in vitro

The in vitro antitumor activity of alpha‐ and gamma‐interferon as well as tumor necrosis factor was tested on two human renal cell carcinoma xenografts—RC‐43 and NC‐65. A dose‐dependent inhibition of colony formation in soft agar was found for both tumor lines. NC‐65, however, showed no sensitivity for gamma‐interferon. Combination drug tests showed a synergistic effect on colony formation of both tumor lines. The strongest inhibition was shown by the combination of alpha‐interferon and tumor necrosis factor. We conclude that both interferons as well as tumor necrosis factor show direct in vitro cytostatic effects against renal tumor direct in vitro cytostatic effects against renal tumor cells.