Involvement of protein kinase C and an elastase-like enzyme in the processing of transforming growth factor-α in human colon carcinoma cell lines

✍ Scribed by Alan E. Levine

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: French
• Weight: 710 KB
• Volume: 58
• Category: Article
• ISSN: 0020-7136
• DOI: 10.1002/ijc.2910580121

✦ Synopsis

Human colon carcinoma cell lines secrete transforminggrowth factor-a (TGF-a). Previous work indicated that the apparent m.w. of the TGF-a secreted by these cells ranged between 5 and 25 kDa. The more differentiated CEO cell line secreted a higher percentage of high m.w. TGF-a than did the poorly differentiated HCT I 16 cell line. In addition, the HCT I 16 cells secreted 5-fold more TGF-a. Treatment of HCT I 16 and CEO cells with a phorbol ester (TPA) resulted in a 4-fold increase in TGF-a in the conditioned media of both cell types. The TPA-induced release of TGF-a was blocked by an inhibitor of elastase-like enzymes. This suggested a role for protein kinase C (PKC) in TGF-a processing in colon carcinoma cells. Direct measurement of PKC activity indicated that the HCT I16 cells (which secrete more fully processed TGF-a) had 10-fold more PKC activity than GEO cells. The presence of an elastase-like activity in detergent extracts and the ability of an elastase inhibitor to block the TPA-induced secretion of TGF-a suggests that PKC and an elastase-like enzyme are involved in the processing and secretion of TGF-a by human colon carcinoma cell lines.