Evaluation of impaired triglyceride fatty acid transport and oxidation for the detection of cancer in mice.

We have tested the hypothesis proposed by Costa, Lyles, and Ullrich. (Effect of Human and Experimental Cancer on the Conversion of 14C Tripalmitin to 14CO2. Cancer (Phila.), 38:1259-1265, 1976) that the transport and/or oxidation of triglyceride fatty acids is markedly impaired in rodents bearing a growing s.c. carcinoma. Specifically, we have tested whether oxidation of triglyceride fatty acids is depressed in cancer-bearing animals. Mice inoculated s.c. with Ehrlich carcinoma cells were given injections (i.v. and i.p.) of 14C-labeled triglyceride fatty acids prepared as very-low-density lipoproteins by physiological methods or (i.p.) with [-14C]tripalmitin dissolved in peanut oil during both early (3 to 4 days) and advanced (7 to 8 weeks) stages of tumor growth. Specific activity of the expired 14CO2 was measured for periods ranging from 1 to 7 hr following injections. Because cancer-bearing mice can become severely hypertriglyceridemic, plasma triglyceride pool sizes were also measured during each experiment to account for the effects of possible differential dilution of the tracers. At no instance did we find any significant differences between specific activities of expired 14CO2 or plasma triglyceride pool sizes of the cancer-bearing animals and controls. Thus, a cancer-induced impairment of triglyceride fatty acid transport and metabolism to CO2, such as reported by Costa et al., does not seem to be a universal phenomenon in rodents.