Aims: Despite surgical resection, pancreatic cancer carries a poor prognosis. In search for new molecular therapeutic targets, we investigated the expression of the HER-family and gene amplification of HER-2 in pancreatic adenocarcinomas of different stages.Methods: Tissue of 45 resected patients was analysed for all HER-family 1-4 expression by immunohistochemistry and HER-2 gene amplification was assessed by multiplex ligation-dependent probe amplification and chromogenic in situ hybridization. The type of surgery, location, stage and grade of the tumour, as well as involvement of the resection margins were correlated with HERexpressions and univariate and multivariate survival analysis performed.

HER2-positive breast cancer accounts for 25% of all cases and has a poor prognosis. Although progress has been made in understanding signal transduction, little is known of how HER2 achieves gene regulation. We performed whole genome expression analysis on a HER2+ and HER2− breast cancer cell lines and compared these results to expression in 812 primary tumors stratified by their HER2 expression level. Chip-on-chip with anti-RNA polymerase II was compared among breast cancer cell lines to identify genes that are potentially activated by HER2. The expression levels of these HER2-dependent POL II binding genes were determined for the 812 HER2+/− breast cancer tissues. Genes differentially expressed between HER2+/− cell lines were generally regulated in the same direction as in breast cancer tissues. We identified genes that had POLII binding in HER2+ cell lines, but without significant gene expression. Of 737 such genes “poised” for expression in cell lines, 113 genes were significantly differentially expressed in breast tumors in a HER2-dependent manner. Pathway analysis of these 113 genes revealed that a large group of genes were associated with stem cell and progenitor cell control as indicated by networks centered on NANOG, SOX2, OCT3/4. HER2 directs POL II binding to a large number of genes in breast cancer cells. A “poised” class of genes in HER2+ cell lines with POLII binding and low RNA expression but is differentially expressed in primary tumors, strongly suggests a role of the microenvironment and further suggests a role for stem cells proliferation in HER2-regulated breast cancer tissue.