Loss of Collagenase Gene Expression in Immortalized Clones of SV40 T Antigen-transformed Human Diploid Fibroblasts

We isolated a cDNA clone whose expression was lost during immortalization. The subtractive hybridization was performed between a genetically matched pair of mortal and immortal lines of SV40 T antigen-transformed MRC-5. The clone was found to code human interstitial collagenase. The expression of collagenase gene was almost completely shut off in seven out of eight independent immortalized clones. In addition, the levels of collagenase expression were dramatically increased toward crisis in the T antigen-transformed but mortal cells. These findings suggest the possibility that the regulatory mechanism of collagenase expression is related to both processes of in vitro aging and immortalization.