IDENTIFICATION OF CYTOKERATIN SUBSPECIES ALTERED IN RAT EXPERIMENTAL ESOPHAGEAL TUMORS BY SUBTRACTIVE CLONING

By using the subtractive hybridization method, two complementary DNA c lones differently expressed in rat normal esophageal epithelium and sq uamous cell carcinoma induced by administration of precursors of N-nit rososarcosine ethyl eater were isolated. A rat homologue of the human 50-kDa type I cytokeratin 14 was cloned for the first time and shown t o be expressed preferentially in squamous cell papillomas and carcinom as, whereas it was weakly expressed or absent in normal squamous epith elial cells and in hyperplastic lesions. A rat homologue of the mouse 57-kDa type II cytokeratin showed strong expression in both normal and tumor tissues. These results are well consistent with the reported al teration of keratin subspecies in human esophageal cancers, therefore, encouraging us to use this experimental system as a model for human e sophageal carcinogenesis.