The 8-nm
keratin filament is a major component of the cytoskeleton of epithelial cells and epithelial-derived
cancers (
carcinomas). Recently, it has been shown that the pattern of
keratins produced by an esophageal epithelial cell undergoes change upon malignant transformation. In order to evaluate the potential importance of these differences in providing improved diagnostic techniques for pathology, we have investigated the consistency of the patterns of
keratins expressed in normal esophageal epithelium,
squamous cell carcinoma (SQCC) of the esophagus, and cultured esophageal epithelial cells. In six patients, the
keratin pattern expressed by SQCC of the esophagus and corresponding normal esophageal epithelium was consistently different as judged by immunoblot analysis of electrophoretically separated
protein extracts. Whereas the SQCCs typically expressed major
keratins with molecular weights of 58,000, 56,000, 50,000, and 46,000, the normal esophageal epithelium produced two major
keratins with molecular weights of 58,000 and 52,000 and a minor
keratin with a molecular weight of 56,000. When normal esophageal epithelial cells were grown in tissue culture, their
keratin pattern changed, and
keratins with molecular weights of 58,000, 56,000, 52,000, 50,000, 46,000, and 40,000 were expressed. Although some minor variations in
keratin patterns were seen, the major differences in
keratin pattern expressed by normal esophageal epithelial tissue, SQCC of the esophagus, and cultured esophageal cells were consistent and reproducible.