Among EGFR ligand secreted by MF in cancer, HB-EGF has emerged as a paracrine factor that contributes to intercellular communications between MF and tumor cells in uterine cervical[26] and breast[36] carcinoma. In human CCA specimens, HB-EGF immunoreactivity

was detected in MF. In addition to MF, we also detected an expression of HB-EGF in tumor cells. Therefore, we can assume that HB-EGF participates in the autocrine and paracrine activation of EGFR. HB-EGF produced by MF is likely to act only on tumor cells in CCA because EGFR was only detected in these cells. The expression of HB-EGF by MF prompted us to hypothesize that MF may constitute an additional source of ligands required to activate EGFR on the cancer cell surface. EGFR heterodimerizes with other receptors of the ErbB/HER family (i.e., ErbB/HER2 and ErbB/HER3). Upon

Selleckchem Kinase Inhibitor Library stimulation of CCA cells with HB-EGF, EGFR and, to a lesser extent, ErbB/HER2 and ErbB/HER3 are activated (data not shown). Thus, a potential contribution of ErbB/HER2 and/or ErbB/HER3 through EGFR heterodimerization cannot be excluded in the cross-talk between MF and tumor cells in CCA. To date, the role of HB-EGF in CCA has see more not been explored. In vitro, an HB-EGF-neutralizing Ab inhibited activation of EGFR and dispersion of CCA cells in response to HLMF-CM. Consistently, exogenous addition of HB-EGF to CCA cells caused cell migration and invasion, as previously described in many cancers.[37, 38] Although HB-EGF activated EGFR and downstream pathways, including ERK1/2, we were unable to show an effect of HB-EGF on CCA cell proliferation. Thus, stimulation of EGFR by HB-EGF in CCA cells is likely to play a role in tumor invasion and metastasis, which is consistent with the IHC and genomic profiling studies that demonstrated high EGFR expression in patients with aggressive phenotype and poor prognosis CCA.[7, 11, 12, 14, 39] In addition to EGFR overexpression, Sia et al. have recently showed an enrichment of EGFR activation in a subgroup

of CCA.[7] From our studies, we may hypothesize that activation of EGFR is related to EGFR ligand produced by Tau-protein kinase stroma cells. It would be worthwhile to explore the gene expression profiling of stroma in this subgroup of CCA tumors. Through the production of soluble factors, cancer cells have the ability to communicate with stromal myofibroblasts located arround them. This point has been stressed in several cancers, including HCC,[40] colorectal,[21] uterine cervical cancers,[26] and in CCA.[33] Our results showed that EGFR activation in CCA cells promotes the expression of TGF-β1. TGF-β1 is expressed in a vast majority of CCA. As previously reported,[41-43] we detected TGF-β1 in carcinoma cells and its receptor, TGF-β RII, both in carcinoma and stromal MF. Recently, Andersen et al.