Changes in tissue and serum activity of cathepsin B-like cysteine proteinase during colorectal carcinogenesis by 1,2-dimethylhydrazine in mice.

The activity of cathepsin B-like cysteine proteinase in the mice colon was studied during carcinogenesis induced by 1,2-dimethylhydrazine dihydrochloride (DMH). Before starting the treatment with DMH, the activity of the observed enzyme was very low in the colorectal area but the activity in the serum was rather high. In the course of carcinogenesis, the local activity markedly increased in the stroma equally as in the cells of developing tumors while the serum activity slightly decreased. Following the total ovariectomy, no significant changes in the local activity or in the serum activity were found. Possible causes of these variations are discussed.