Modulation of the expression of interstitial and type-IV collagenases in coculture of HT1080 fibrosarcoma cells and fibroblasts.

Members of the metalloproteinase family (MMPs) are known to play a crucial role in the metastatic cascade. Here, we report some investigations about the synthesis of interstitial and type-IV collagenases (gelatinases A and B) in a model of coculture of human fibroblasts and HT 1080 fibrosarcoma cells. The interstitial collagenase activity, mainly found in the conditioned medium of fibroblasts, and its mRNA level were increased in the in vitro coculture model. In contrast, gelatinase A was produced by both cell types. The HT 1080 cells additionally synthesised gelatinase B. In coculture, an enhancement of gelatinase A and the presence of its activated form were observed. Northern blot analysis demonstrated that this enzymatic enhancement occurred at a pretranslational level. The stimulation of the interstitial collagenase activity was partially mediated through soluble factor(s), whereas increased gelatinase A appeared to require direct cell-cell interactions. The extracellular matrix component, type-I collagen, stimulated the enzymatic activities released by the individual cells, but it did not modulate the synthesis of interstitial collagenase in coculture. Our results demonstrate that distinct MMPs are modulated by distinct mechanisms, all depending on specific interactions between tumour cells and host fibroblasts.