Tumor growth factor-b (TGF-b) signaling in cancer has been implicated in growth suppression of early lesions and enhancing tumor cell invasion and metastasis. However, the cellular mechanisms that determine this signaling output in individual tumors are still largely unknown. In endothelial cells, TGF-b signaling is modulated by the TGF-b coreceptor endoglin (CD105). Here we demonstrate that endoglin is expressed in a subset of invasive breast cancers and cell lines and is subject to epigenetic silencing by gene methylation. Endoglin downregulation in non-tumorigenic MCF10A breast cells leads to the formation of abnormal acini in 3D culture, but does not promote cell migration or transformation. In contrast, in the presence of activated ErbB2, endoglin downregulation in MCF10A cells leads to enhanced invasion into a 3D matrix. Consistent with these data, ectopic expression of endoglin in MDA-MB-231 cells blocks TGF-b-enhanced cell motility and invasion and reduces lung colonization in an in vivo metastasis model. Unlike endothelial cells, endoglin does not modulate Smadmediated TGF-b signaling in breast cells but attenuates the cytoskeletal remodeling to impair cell migration and invasion. Importantly, in a large cohort of invasive breast cancers, lack of endoglin expression in the tumor cell compartment correlates with ENG gene methylation and poor clinical outcome.

not available at time of publication. Abstract not available at time of publication. Retrospective studies on male breast cancer (MBC) have suff ered from small numbers of cases available from any one centre; thus a signifi cant problem in eff ectively studying this disease is accruing suffi ciently large numbers to allow comparative analysis of biomarkers associated with response. Using a coordinated multicentre approach, we present the fi rst large-scale study to address the relevance of the expression of hormone receptors in MBC and female breast cancer (FBC) using immunohistochemistry combined with a novel bioinformatics approach. Following ethical approval, 523 archival blocks (260 MBCs and 263 matched FBCs) were obtained retrospectively. Tissue microarrays were constructed and sections stained for ERα, ERβ1, ERβ2, ERβ5, total PR, PRA, PRB and AR and typed using CK5/6, CK14, CK18 and CK19 by immunohistochemistry. Following scoring, a range of ordination techniques were conducted on the datasets including hierarchical clustering and principal component analysis (PCA) + ) were infrequent in both. Hierarchical clustering revealed common clusters between MBC and FBC including total PR-PRA-PRB and ERβ1/2 clusters. ERα occurred on distinct clusters between males and females. AR, ERβ1, ERβ2 and ERβ5 all existed on the same cluster but with a diff erent substructure, particularly around the positioning of AR. ERα associated with this cluster in the male but not the female group. PCA confi rmed that in both groups strong infl uences came from PR-PRA-PRB. In MBC strong infl uences additionally came from AR and ERβ1, ERβ2 and ERβ5, whereas in FBC strong infl uences came from ERα alone. Our data support the hypothesis that breast cancer is biologically diff erent in male and females, which could have implications for therapy. Introduction The response rarely sustains long among the responders for Herceptin (trastuzumab) monotherapy treatment. It is still poorly understood how Herceptin exerts its mechanism of action and how the acquired resistance to this drug occurs. Materials and methods We used a multidisciplinary approach including fl uorescence resonance energy transfer and biochemical methods to assess the eff ects of Herceptin on various signalling pathways and to determine the acquired resistance mechanisms of Herceptin in various HER2-positive breast cell lines and a BT474 xenograft model. Results We have shown that Herceptin does not decrease HER2 phosphorylation despite the eff ect on HER2 receptor downregulation. HER2 phosphorylation is maintained by the activation of EGFR, HER3 and HER4 via their dimerisation with HER2 in breast cancer cells. The activation of EGFR, HER3 and HER4 is induced by HER ligand release, including heregulin and betacellulin. The release of HER ligands is mediated by ADAM proteases including ADAM17/TACE. Furthermore, we demonstrated that the feedback loop involving HER ligands and ADAM proteases is activated due to a decrease in PKB phosphorylation induced by Herceptin t...