Transforming growth factor-alpha precursors in human colon carcinoma cells.

Among the proteins of the epidermal growth factor family, transforming growth factor-alpha (TGF-alpha) may be an especially reliable indicator of metastasis or prognosis in human colorectal carcinomas. Moreover, anomalous forms of TGF-alpha have been detected in several tissues of cancer origin, suggesting a role of these forms in the development of the disease. This study was designed to identify the presence of TGF-alpha precursors in different colon cancer cell lines by mean of immunocytochemistry and western blotting techniques. Pro-TGF-alpha was detected in all cell lines tested. Staining for pro-TGF-alpha was observed in cytoplasm. Monoclonal antibody to TGF-alpha detected two bands of 20 and 21 kDa. Polyclonal antibody to pro-TGF-alpha revealed five bands ranging from 15 to 24 kDa. All these proteins were also detected in nonmalignant cells expressing a transfected rat pro-TGF-alpha gene. In conclusions, transformation in these human colon carcinoma cells is not due to the presence of anomalous forms of TGF-alpha precursors.