NOVEL S100 PROTEINS IN HUMAN ESOPHAGEAL EPITHELIAL-CELLS - CAAF-1 EXPRESSION IS ASSOCIATED WITH CELL-GROWTH ARREST

CAAF1 and CAAF2, newly identified calcium-binding proteins from bovine amniotic fluid, have been revealed to be members of the S100 protein family preferentially produced by fetal squamous epithelial cells, inc luding epidermal keratinocytes. Having previously cloned the cDNA of h uman CAAF1 protein from the esophageal epithelium, me report here on t he characteristic expression pattern of CAAF1 and related S100 protein s in human esophageal epithelial cells. Normal cells of the human esop hageal epithelium expressed CAAF1, and also expressed the homologous n ovel S100 proteins including CAAF2, MRP8, and MRP14, but not S100 alph a. An immunohistochemical study with specific monoclonal antibodies ag ainst CAAF1 proteins demonstrated that CAAF1 proteins were produced by the esophageal epithelial cells in the process of cell differentiatio n. The immature proliferating cells in the epithelium did not produce CAAF 1 proteins, but the differentiated cells expressed CAAF 1, which overlay the immature cells and were stratifying in the epithelium. The se CAAF1-producing cells did not show any proliferating activities. Es ophageal carcinoma cells did not express CAAF1, except for the keratin ized cells with no proliferating activity. In addition, the forced exp ression of CAAF 1 proteins in the carcinoma cells resulted in a marked decrease in DNA synthesis. These findings indicate that human esophag eal epithelial cells express the multiple genes of S100 proteins inclu ding CAAF proteins, and that CAAF 1 is closely associated with the ter minal differentiation of these cells. CAAF 1 expression also might pla y some role in cell growth.