Manifestations of cancer cachexia induced by colon 26 adenocarcinoma are not fully ascribable to interleukin-6.

In order to further clarify the role of interleukin 6 (IL-6) in the pathogenesis of cachexia, recombinant human IL-6 (hIL-6) was administered s.c. by osmotic pump for 9 days at a dose of 1 or 10 micrograms/day into CDF1 mice inoculated with a non-cachexia-inducing subclone of colon 26 adenocarcinoma (clone 5), or with a cachexia-inducing subclone (clone 20) of this malignancy. The serum level of IL-6 in non-cachectic mice with clone-5 tumors was 35% lower than in cachectic mice bearing clone 20 of colon 26 adenocarcinoma on the 19th day after tumor inoculation. IL-6 administration induced anemia, thrombocytosis and visceral organ hypertrophy not only in mice with clone-5 tumors but also in control mice with no tumor burden. Lipolysis and proteolysis became conspicuous when a large dose (10 micrograms/day) of IL-6 was infused into mice with clone-5 tumors. However, IL-6 supplementation did not induce loss of body weight, a decline in food intake or lymphocytopenia, which were characteristically observed in cachectic mice with clone-20 tumors. In conclusion, IL-6 appears to be a permissive factor for the development of cachexia but, while it can induce some of the symptoms typical of cachexia, it cannot in itself induce the full cachectic syndrome.