Effects of tumor type and burden on carcass lipid depletion in mice.

Cancer bearing is frequently accompanied by weight loss, yet the factors causing cancer cachexia remain unclear. This study compares how tumor type and tumor burden affect host carcass fat depletion. Nude mice were inoculated with human malignant melanoma, human colon adenocarcinoma, or murine sarcoma cells, or were noninjected controls. Body weights, tumor burdens, and carcass lipid contents were measured. Carcass weights of melanoma-bearing mice were significantly lower than those of sarcoma-bearing mice, mice exposed to colon cancer antigens but without tumor growth, or control mice (all p less than 0.02). The degree of carcass lipid loss in melanoma-bearing mice (mean tumor burden 3.5% of total body weight [TBW]) was almost three times that of sarcoma-bearing mice (p less than 0.05), which had more than twice the tumor burden (mean tumor burden 7.8% TBW). Exposure to colon cancer antigens without tumor growth resulted in essentially no carcass lipid depletion compared with control mice. These findings argue against a mass effect of tumor as being solely responsible for host fat mobilization and suggest that carcass lipid depletion in tumor-bearing nude mice is more a function of tumor type than of tumor burden.