Regulation of epithelial cell growth by ZBP-89: potential relevance in pancreatic cancer.

ZBP-89 (ZNF148) is a Zinc finger Binding Protein of 89 kDa that binds GC-rich DNA elements. Originally, it was expression cloned using a DNA element mediating EGF regulation of the gastrin promoter. ZBP-89 functions as both a transcriptional activator and repressor. A variety of extracellular regulators including TGFbeta, retinoic acid and butyrate stimulate ZBP-89 gene expression. Butyrate activation of p21WAF1 is potentiated by ZBP-89 through the recruitment of the co-activator p300, while chronic stimulation by butyrate increases ZBP-89 gene expression correlating with cell differentiation. ZBP-89 stimulates growth arrest and apoptosis through its ability to bind the p21WAF1 promoter or its ability to form protein-protein interactions with p53. ZBP-89 protein is elevated in a variety of gastrointestinal cancers as well as the pancreas. In particular, ZBP-89 is normally expressed in pancreatic islets and ducts and in about 30% of pancreatic adenocarcinomas.