Interstitial collagenase (matrix metalloproteinase 1) associated with the plasma membrane of both neoplastic and nonneoplastic cells.

Epithelial cell lines (BC1, BC3, BC4, and BC5), derived from 4 separate invasive and metastatic rat mammary carcinomas, all secreted interstitial collagenase (matrix metalloproteinase 1, MMP 1) in culture. Neither a cloned cell line (A5P/B10), derived from a noninvasive rat epithelial tumor, nor nonneoplastic rat fibroblasts secreted the enzyme. Western blot analyses of proteins extracted from the plasma membranes indicated the presence of interstitial collagenase (MMP 1) on the surface of all of the 6 cell lines. These data suggest that the control of collagenolysis may involve the association of collagenase molecules with the plasma membrane. The aggressiveness of malignant tumors may be due in part to the breakdown of such a control.