Studies on the effects of laminin, E-8 fragment of laminin and synthetic laminin peptides PA22-2 and YIGSR on matrix metalloproteinases and tissue inhibitor of metalloproteinase expression.

Based on a previous observation of laminin-mediated increase in type IV collagenolytic activity of human melanoma (A-2058) and fibrosarcoma (HT-1080) cell lines (Turpeenniemi-Hujanen T, et al. Laminin increases the release of type IV collagenase from malignant cells. J Biol Chem 1986;261:1883-1889), the goal of this study was to identify the proteinases involved. A soluble type IV collagenase assay and substrate gel electrophoresis were used to assess the effect of laminin and laminin peptides on type IV collagenolytic activity. The laminin-mediated increase in type IV collagenolytic activity was not due to augmented expression or induction of three known type IV collagenolytic matrix metalloproteinases (MMP), i.e., 72-kilodalton gelatinase/type IV collagenase (MMP-2), stromelysin (MMP-3), and 92 kilodalton gelatinase/type IV collagenase (MMP-9). Furthermore, laminin did not modulate the expression of the tissue inhibitors of metalloproteinases (TIMP), TIMP-1 and TIMP-2. The E-8 fragment of laminin and the YIGSR laminin peptide had no effect on type IV collagenolytic or MMP/TIMP activities. However, the IKVAV containing PA22-2 laminin peptide selectively stimulated type IV collagenolytic activity of the A-2058 melanoma cell line, although it did not modulate MMP/TIMP activity. Laminin from three different sources of the Engelbreth-Holm-Swarm tumor was found to contain type IV collagenolytic activity. When laminin was added to harvested culture supernatants of the A-2058 and HT-1080 cell lines, the increase in type IV collagenolytic activity was comparable with that observed in supernatants from cells incubated with laminin for 48 hours. Analysis of the laminin preparations revealed five MMP forms ranging in molecular weight from approximately 58 to 105 kilodalton, which may represent latent and active forms of MMP-2 and MMP-9. These findings suggest that proteinases present in the Engelbreth-Holm-Swarm laminin may account for most, if not all, of the observed laminin-mediated increase in type IV collagenolytic activity. However, the PA22-2-mediated increase in type IV collagenolytic activity of the A-2058 melanoma line remains to be elucidated.