Expression of cathepsin L and its endogenous inhibitors in immortal and transformed fibroblasts

Methods: The activities of cathepsin L and its endogenous inhibitors were a nalyzed in rat embryo fibroblasts, immortalized and transformed by differen t genes. Results: Regardless of the transfecting agent used (DNA of adenovi rus SA7 or polyomavirus LT gene), the immortal cells showed an increase in the cathepsin L activity tin both lysates and conditioned media) compared t o primary fibroblasts. Transformed cells exhibited either an increase (with c-Ha-vas gene) or decrease (with E7 HPV gent) in cathepsin L activity in l ysates as opposed to immortal cells. Conclusions: The data are suggestive o f alterations in the trafficking of cathepsin L upon fibroblast transfectio n with polyomavirus LT gene and E7 HPV gene. An endogenous inhibitor(s) of cysteine proteinase was found in conditioned media, but not in lysates, of all cell cultures studied and its activity in normal fibroblasts was higher than in media of immortal and transformed cells. (C) 2001 Elsevier Science B.V. All rights reserved.