To demonstrate that the anorexia and depletion of cachexia reverses on tumor removal, F344 rats underwent sarcoma resection when their food intake fell to 0 g/day. In survivors of surgery, reversal in food intake was apparent within 3 days postoperatively, followed after 2 days by gain in host weight.
To detect whether the transmission of anorexia/cachexia in these tumor-bearing (TB) rats was via the circulation, four groups were studied: single non-tumor bearing (NTB); single TB; parabiotic NTB; and parabiotic TB. The measured blood exchange rate between parabiotic halves was 1.2–1.5%/min. No cachectic effect was detected in either half of the NTB parabionts. There was no evidence of sarcoma metastases in the tumor-free half of the parabiotic TB pair. All the rats associated with the presence of tumor showed cachectic effects but the degree and timing of effect varied among the three conditions, single TB, parabiotic TB half, and parabiotic tumor-free half. In all variables examined (fall in food intake, time of first fall in food intake, host weight loss, elevation of blood urea nitrogen) the severities were always in the same sequence: single TB > parabiotic TB half > parabiotic tumor-free half > NTB. In addition, the TB parabiotic pair had a significantly longer survival time and grew a significantly larger tumor than did the single TB animal. The parabiotic tumor had a slower initial growth rate and a slower deceleration rate than the singlet tumor.
These results provide evidence for the humoral mediation of cancer-associated cachexia.