Cachectin activity in the serum of cachectic, tumor-bearing rats.

Cachectin/tumor necrosis factor has been postulated to be a possible mediator of cancer cachexia. Using a sensitive bioassay, we attempted to detect circulating cachectin activity in the serum of sarcoma-bearing rats and to correlate levels with measurements of cachexia and the extent of disease. In addition, we resected the tumor to determine the time course of reversal of cachexia and the disappearance of cachectin activity in the serum. Circulating cachectin activity was not detectable in the serum of non-tumor-bearing rats or in tumor-bearing rats until 28 days after implantation. With evidence of food intake and body weight decline, cachectin activity became detectable in the serum and levels increased as cachexia and tumor burden increased. Serum cachectin activity levels correlated directly with tumor burden and inversely with food intake and body weight change. After resection of the tumor, food intake and body weight increased and serum cachectin activity became undetectable. Serum triglyceride levels were higher in cachectic tumor-bearing rats than in pair-fed non-tumor-bearing controls, and levels decreased after tumor resection as cachectin activity decreased. The results suggest that cachectin is a humoral mediator of cachexia in this rat-tumor model.