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

METHODS: The activities of cathepsin L and its endogenous inhibitors were analyzed in rat embryo fibroblasts, immortalized and transformed by different genes. RESULTS: Regardless of the transfecting agent used (DNA of adenovirus SA7 or polyomavirus LT gene), the immortal cells showed an increase in the cathepsin L activity (in both lysates and conditioned media) compared to primary fibroblasts. Transformed cells exhibited either an increase (with c-Ha-ras gene) or decrease (with E7 HPV gene) in cathepsin L activity in lysates as opposed to immortal cells. CONCLUSIONS: The data are suggestive of alterations in the trafficking of cathepsin L upon fibroblast transfection 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.

Plasminogen activators, kallikrein-like proteinase and type I and type IV collagenases at various stages of oncogenic transformation.

Comparative studies of membrane-associated, intracellular and secreted activities of serine (uPA, kallikrein-like proteinase) and metalloproteinases (type I and IV collagenases) were carried out on rat embryo fibroblasts, sequentially immortalized and transformed by two different genes. Using this experimental model it was shown that (1) activity of uPA was expressed at the stage of immortalization solely; (2) intracellular and secreted activity of type I and IV collagenases decreased during process of transformation, (3) kallikrein-like proteinase activity was not revealed either in the primary or in transformed cells, (4) Z-Phe-Arg-MCA hydrolysis was the result of the action of cysteine proteinases alone; the increase in this activity was correlated with the stages of oncogenic transformation of fibroblasts.

Proteolytic enzymes at various stages of oncogenic transformation of rat fibroblasts. I. Aspartyl and cysteine proteinases.

Aspartyl and cysteine proteinases at distinct stages of carcinogenesis were analyzed in rat embryo fibroblasts, sequentially immortalized and transformed by 2 different genes: the early region of simian adenovirus SA7 and c-Ha-ras oncogene. The dynamics of expression and distribution of proteinases throughout the transformation process were examined. It was shown that in immortalized and transformed cells the activities of the aspartyl and cysteine proteinases were expressed to a variable degree and that the expression was dependent on cell-propagation time in vitro. The increase in activity both of cathepsin-D-like aspartyl proteinase and of cathepsin-L- and -B-like cysteine proteinases in cell lysates was correlated with the stages of fibroblast transformation (immortalization and tumorigenic transformation). In all cell types the major part of cysteine proteinases was localized inside the cell, while the cathepsin-D-like proteinase was apparently predominant among secreted proteinases. The cathepsin-L-like proteinase accounts for the major part of the cysteine-proteinase activity as measured by Z-Phe-Arg-MCA hydrolysis. We suggest that considerable portions of the cathepsin-D- and -L-like proteinases in all cell lines studied are secreted as a complex with inhibitor(s) and that inhibitor expression plays an important role in regulating the activity of cathepsin-D-like proteinase at different stages of transformation. Cathepsin-L-like proteinase is probably secreted in the precursor form.