Synergistic antiproliferative effect of the combination of natural human tumor necrosis factor-alpha and natural murine interferon-alpha/beta against colon-26 adenocarcinoma hepatic metastases in a murine model.

To prevent the development of hepatic metastases after surgery for colorectal cancer, it is important to inhibit the growth of any micrometastases which occur during the operation. We used a hepatic metastasis model in mice to investigate the effects of combination therapy with natural human tumor necrosis factor-alpha (nHuTNF-alpha) and natural murine interferon-alpha/beta (nMuIFN-alpha/beta). Decreased formation of hepatic metastases by murine colon-26 carcinoma was recognized following a single injection of nHuTNF-alpha, nMuIFN-alpha/beta, or both. These inhibitory effects were synergistic. NK activity was also measured, because notaral lerller cells not only have an anti-tumor effect but are also a representative of the host immune system. Both nHuTNF-alpha and nMuIFN-alpha/beta were able to activate NK cells, and the combination of the cytokines more significantly augmented NK activity. The in vivo elevation of NK activity induced by nHuTNF-alpha, nMuIFN-alpha/beta, or their combination may be one of the mechanisms of their antiproliferative effect on experimental hepatic metastases of murine colon-26 carcinoma.