Lipolytic activity of anemia-inducing substance from tumor-bearing rabbits

Anemia-inducing substance (AIS) is a protein of approximately 50,000 molecular weight secreted by malignant tumor tissue that depresses erythrocyte and immuno-competent cell functions; in this study, its biological effects on adipocytes were examined. Changes in body weight, total body fat, and food intake were investigated in rabbits after VX2 carcinoma transplantation, and the results showed reductions of 11%, 24%, and 30%, respectively, at 40 days after transplantation compared with baseline values (before transplantation). The values were even more markedly reduced 70 days after transplantation. When cyclic plasma perfusion (2 times/wk) was started at 40 days after transplantation, the values at 70 days after transplantation (30 days after beginning plasma perfusion) recovered to 91%, 84%, and 87%, respectively, of the baseline values. AIS fractions were isolated from rabbit plasma by using a phenyl-Sepharose column before transplantation, 40 and 70 days after transplantation, and 30 days after start of plasma perfusion, and AIS activity and lipolytic activity were measured. The results showed enhancement of AIS activity and lipolytic activity as the tumors grew. Lipolytic activity also returned to baseline value as AIS was removed by adsorption by plasma perfusion, and there was a high correlation between lipolytic activity and AIS kinetics. These results strongly suggest that AIS might be one of the substances involved in the enhanced lipolytic activity in advanced tumor-bearing subjects.