Tumor growth and food intake in interleukin-6 gene knock-out mice.

Interleukin (IL)-6 has potential antitumor activity and at the same time is responsible for tumor-derived cachexia. Using IL-6 gene knock-out (GKO) mice, we investigated the effect of IL-6 deficiency on the survival time, tumor growth and daily food intake of mice inoculated with Ehrlich ascites carcinoma. IL-6 GKO mice gained weight due to tumor growth more rapidly than the wild-type mice. The daily food intake of wild-type mice declined on day 2 after tumor inoculation and was only 37% on day 8. In contrast, the daily food intake of IL-6 GKO mice was constant for the first 7 days after tumor inoculation. Although wild-type mice suffered from cachexia, their survival time was significantly longer than that of IL-6 GKO mice. We propose that both IL-6 secretion and cancer cachexia syndrome may be involved in the defense mechanism against tumor progression.