DIFFERENTIAL EXPRESSION OF TYPE-I CYTOKERATINS IN HAMSTER-CHEEK POUCHEPITHELIUM FOLLOWING TREATMENT WITH DIMETHYLBENZANTHRACENE

Cytokeratin (CK) expression in untreated, paraffin-treated or dimethyl benzanthracene (DMBA)-treated hamster cheek pouch epithelium was inves tigated utilizing monoclonal antibodies AE1 or AE3, which react with t ype I or type II CKs, respectively, and by in situ hybridization utili zing type I CK-specific probes. The latter were isolated from a cDNA l ibrary of hamster cheek pouch mRNA and designated CK 13 and CK 10 base d on their respective homologies (>95% amino acids) with murine CK 13 and human CK 10. Treatment of hamster cheek pouch epithelium with DMBA resulted in increased expression of type I CK, detected immunohistoch emically with monoclonal AE1, but decreased expression of type II CKs detected with AE3. Despite an overall increase in type I CKs, in situ hybridization demonstrated differential expression of type I CKs with altered distribution of CK 13 mRNA and reduced expression of CK 10 mRN A, providing additional sensitive markers for DMBA-associated changes in CKs. These changes were constant at 2 to 22 weeks in the pre-neopla stic and neoplastic epithelium following the initial application of DM BA.