Activities of proteinases and of a proteinase B inhibitor in tumors of the human uterus.

The activities of an acid proteinase, of an alkaline proteinase, of a lysine aminopeptidase and of a proteinase B inhibitor were measured in benign and malignant tumors of the human uterus. In carcinomas of the corpus uteri the activity of the acid proteinase (cathepsin D) was increased compared to normal endometrium. This could probably be the result of cell destruction within the tumor. In leiomyomas of the uterus the activities of the alkaline proteinase, of the lysine aminopeptidase, and of the proteinase inhibitor were decreased compared to the normal myometrium. These results suggest that a decrease in the rate of degradation of myofibrillar proteins relative to the rate of protein synthesis may be responsible for the growth of myomas.