Induction of hepatic metallothioneins in tumor-bearing IL-6-null mice

Interleukin-6 (IL-6) has been thought to play a key role in the induction of hepatic metallothionein (MT) synthesis in tumor-bearing animals. In order to clarify the role of IL-6 and to distinguish its effect from those of other cytokines, we inoculated IL-6-null and B6J129Sv (wild-type control) mice SC with 1 × 10⁷ Ehrlich carcinoma cells and examined tumor growth, hepatic MT, and serum cytokines. We have found that tumor growth was followed by an increase of hepatic MT in both IL-6-null and wild-type mice and that the two strains of mice had a similar hepatic MT induction followed by zinc accumulation in the liver. These results could be explained by our finding that tumor-bearing IL-6-null mice had a high level of tumor-secreted IL-6 in the blood. In conclusion, by utilizing tumor-bearing IL-6-null mice, we have demonstrated that IL-6 secreted from the tumor cells is responsible for the tumor-evoked increase of hepatic MT level.