Cysteine proteinase cathepsin L expression correlates closely with the metastatic potential of H-ras-transformed murine fibroblasts.

A set of H-ras-transfected mouse C3H 10T1/2 cell lines that vary in their experimental and spontaneous metastatic potential has been analysed for the level of expression of the cysteine proteinase cathepsin L, also known as the major excreted protein (MEP). We found a good positive correlation between the extent of ras expression, the metastatic potential, and the amount of the secreted protease in nine independently isolated lines. There was an increased abundance of the MEP mRNA in cells with increased ras expression, suggesting that this gene is under ras control. Expression of glyceraldehyde phosphate dehydrogenase mRNA was also elevated.