Differences in expression of metalloproteinases and plasminogen activators in murine melanocytes and B16 melanoma variants: lack of association with in vitro invasion.

We investigated in vitro chemotactic responses to fibronectin and laminin, invasion through reconstituted basement membrane (Matrigel) and secretion of matrix metalloproteinases and plasminogen activators by non-tumorigenic Mel-ab melanocytes; B16 melanoma; and the metastatic sublines, B16F1, B16F10 and B16BL6. In vitro chemotactic and invasive ability were not associated with in vivo metastatic potential. Secretion of various matrix-degrading enzymes was not related to in vitro invasion. Conditioned media from all B16 melanoma sublines, but not from Mel-ab cells, contained the M(r) 92,000 progelatinase. The activated M(r) 85,000 species was present only in conditioned media from Mel-ab, B16 and B16F1 cells. Mel-ab cells secreted copious amounts of the M(r) 72,000 progelatinase, and the M(r) 66,000 active form was also present in conditioned media. Secretion of the M(r) 72,000 progelatinase by B16 melanoma sublines was markedly lower, and only conditioned media from B16 cells contained the activated M(r) 66,000 form. Furthermore, cell lysates of Mel-ab cells contained a M(r) 67,000 metalloproteinase which was absent in the tumor cells. All cells secreted tissue plasminogen activator; however, the metastatic B16F1, B16F10 and B16-BL6 cells also secreted urokinase plasminogen activator. Our results indicate that matrix metalloproteinase secretion by itself is not associated with tumorigenicity or metastatic potential. Secretion of urokinase plasminogen activator, and not tissue plasminogen activator, reflected the metastatic characteristics of the B16 melanoma tumor sublines.