Co-expression of specific acid and basic cytokeratins in teratocarcinoma-derived fibroblasts treated with 5-azacytidine.

Epithelial cells always co-express acidic and basic keratin polypeptides. Mesenchymal cells, which do not normally contain keratins, can be induced by the inhibitor of DNA methylation 5-azacytidine to synthesize the basic keratin Endo A. In the present paper we show that the acidic keratins Endo B and Endo C can also be induced by 5-azacytidine in teratocarcinoma-derived fibroblasts. Furthermore, individual cells in which Endo B and/or Endo C keratins are found, always co-express the basic polypeptide Endo A. Other cytokeratins are not or very rarely found. Interestingly, Endo A, B, and C are usually associated in vivo and are known to be the first keratin polypeptides appearing during the development of the mouse embryo.