Interstitial collagenase and stromelysin mRNA expression was examined in six rat cell lines isolated after transfection of embryo fibroblasts with polyomavirus large-T and T24-ras oncogenes. Increased levels of stromelysin mRNA were observed in tumors formed by cells with low levels of stromelysin expression before injection, whereas interstitial collagenase mRNA levels were not elevated in tumors. The lung colonizing - but not the chemoinvasive capacity - of two of these cell lines increased following growth in vivo. The increase in stromelysin expression in tumors was not necessarily paralleled by an increase in ras expression. These findings may be relevant to the phenomenon of clonal dominance of metastatic cells in primary tumors.

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