Tumor cell stimulation of collagenase production by fibroblasts.
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Collagenolytic enzymes produced by tumor cells are believed to play a significant role in the destruction of surrounding normal tissue and, in certain experimental animal systems, the ability of tumor cells to degrade type-IV collagen (basement membrane collagen) correlates positively with those cells' metastatic capacity. We measured collagenolytic activity levels of extracts from freshly excised colorectal carcinoma tissues and of conditioned media from primary organ culture (total of 114 tissues from 53 patients) by using purified radiolabelled type-I (rat tail) and type-IV (mouse Engelbreth-Holm-Swarm [EHS] sarcoma) collagens. Both type-IV and type-I collagenolytic activity levels of extracts from tumor and adjacent mucosa ranged from less than 1 to 80 ng/hr/mg wet tissue, and no significant differences between mucosa and carcinoma tissues were observed. In conditioned media, the type-IV collagenolytic activity was low for normal mucosa and benign tumors and slightly higher for carcinoma than for mucosa. In 5 of 32 primary tumors, collagenolytic activity levels were 2-5 times higher than in the rest of the tumors and mucosal tissues. There were no significant differences in collagenolytic activity levels of conditioned media and tissue extract from colorectal carcinoma of different Dukes' stages. Deep and superficial areas of primary tumors released similar type-IV collagenolytic activity levels, suggesting that there was little intratumoral heterogeneity in the release of this enzyme.
The events leading to neutrophil collagenase activation in vivo were analyzed using phorbol myristate acetate (PMA) stimulated neutrophil supernatant. Under the conditions when this supernatant was incubated with the serine proteinase inhibitor, phenylmethylsulfonyl fluoride (PMSF), and then treated with the oxidant, hypochlorous acid (HOCl), collagenase was activated. When cathepsin G, a known activator of neutrophil collagenase, was also present, less HOCl was required to activate the latent collagenase. These experiments support the conclusion that activation of neutrophil collagenase occurs in vivo by both an oxidant and an enzymatic mechanism where the effectiveness of oxidants is enhanced by cathepsin G.
Pig synovial and human skin fibroblast procollagenases were treated with highly purified tryptase, the major proteinase of human mast cells, to determine whether this trypsin-like proteinase could activate the latent form of collagenase and so be involved in connective tissue breakdown. No significant activation of either human or pig procollagenase was found, but the highest concentration of tryptase partially destroyed procollagenase. Tryptase did not degrade type I collagen or proteoglycan. These data indicate that human mast cell tryptase does not contribute to connective tissue breakdown via procollagenase activation or via proteoglycan degradation.