Cytokeratin-type intermediate filaments are a polygenic family of insoluble
proteins that vary according to cell of origin and have been proposed as potentially useful markers of differentiation in epithelial
malignancies. Because gastrointestinal
malignancies resemble each other in their expression of many soluble
antigens, we compared the cytokeratins of seven colonic, three gastric, six pancreatic, and one duodenal
carcinoma cell lines, and one colon
villous adenoma cell line. Cytokeratins were characterized by one- and two-dimensional gel electrophoresis, immunoblotting, and immunocytochemistry. These cell lines expressed combinations of cytokeratins 7, 8, 18, and 19, which are typical of the "simple" epithelial pattern found in normal ductal and glandular tissues of the gastrointestinal tract. However,
pancreatic carcinoma cell lines expressed additional cytokeratins that are normally found in stratified squamous epithelium and epidermoid (
squamous cell) carcinomas. These additional cytokeratins consisted of
cytokeratin 16 in all six cell lines and cytokeratins 4, 13, and 16 in one cell line. These results suggest that
cytokeratin patterns represent stable markers that may aid in distinguishing gastrointestinal
malignancies.