Keratin protein identification in dimethylbenzanthracene-induced hamster cheek-pouch squamous cell carcinomas

Individual keratin proteins were identified in 10 DMBA induced squamous cell carcinomas (SCC) of the hamster cheek pouch. SDS-polyacrylamide gel electrophoresis of water-insoluble cytoskeletal extracts from the tumor tissue demonstrated alterations in the protein distribution normal for the site. Immunoblot analysis with a broad spectrum polyclonal antikeratin antiserum identified the keratins in the preparations and confirmed changes in their distribution in the tumor preparations. The major keratin species for all the tumor tissues ranged in molecular weight from 45 to 57kd. The normal tissues had keratins with molecular weights from 45 to 73kd. The absence of high molecular weight keratins was a prominent feature in all the cancers. The histologic appearance of the tumors was varied but the distribution of the keratins was not correlated with the various histologies. The results demonstrate that changes in keratin gene expression occur in DMBA-induced cheek-pouch carcinomas but the precise alterations in the keratin proteins from those seen normally are not predictable.