Interferon potentiates cytotoxic effects of 5-fluorouracil on cell proliferation of established human cell lines originating from neoplastic tissues.

A potentiation of the cytotoxic effects of 5-fluorouracil (5-FU) on human tumor cells by interferon was examined. The human neoplastic cell lines used were HeLa (uterine cervical cancer), MCF-7 (mammary cancer), WI-38 CT-1 (embryonic lung fibroblasts transformed in culture by Co-60 gamma-ray irradiation), KMM-1 (myeloma) and Raji (Burkitt's lymphoma). The normal human cell strain used was WI-38 (normal human lung fibroblasts). The cytotoxic effects were determined by colony formation for HeLa, MCF-7, WI-38 CT-1 and WI-38 cells, and by cell growth for KMM-1 and Raji cells. Each cell line was different in sensitivity to interferon or 5-FU. Interferon potentiated synergistically the cytotoxic effects of 5-FU on HeLa, WI-38 CT-1 and KMM-1 cells. In the case of Raji cells, the cytotoxic effects of the combination of interferon and 5-FU were additive. Neither synergistic nor additive lethal effects of the combination of the 2 agents were observed in MCF-7 and WI-38 cells. The present results indicate a possibility that interferon and 5-FU can mutally reduce the amount of the other needed to treat cancer patients.