Serum and tissue proteinase-like peptidase activities in women undergoing total mastectomy for breast cancer.

Serum proteinase-like peptidases and proteinase inhibitor activities have been determined in 40 women with breast cancer at presentation and following total mastectomy. Activities of these enzymes have also been determined in homogenates of malignant (n = 13) and non-malignant (n = 11) breast tissue and benign breast lesions (n = 10). Following surgical treatment, the serum collagenase-like, cathepsin B-like and cathepsin H-like peptidase activities were significantly reduced. In addition, the activities of collagenase-like, cathepsin B-like and elastase-like peptidases were significantly higher in malignant breast tissue than in either non-malignant tissue from the same breast, or benign breast lesions. These findings are consistent with the suggestion that proteinases may have a role in tumour invasion.