Epithelial–mesenchymal interactions in breast cancer: evidence for a role of nuclear localized b-catenin in carcinoma-associated fibroblasts Eldo T Verghese, 1,2, * Hrishikesh Shenoy, 2,3, * Victoria J Cookson, 2 Caroline A Green, 2 Jo Howarth, 1 R H Partanen, 2 Steven Pollock, 2 Alison Waterworth, 1,2 Valerie Speirs, 2 Thomas A Hughes 2 & Andrew M Hanby 1,2 1 Department of Histopathology, Leeds Teaching Hospital NHS Trust, 2 Leeds Institute of Molecular Medicine, University of Leeds, and 3 Department of Surgery, Leeds Teaching Hospital NHS Trust, Leeds, UK Date of submission 12 May 2010 Accepted for publication 24 March 2011 Verghese E T, Shenoy H, Cookson V J, Green C A, Howarth J, Partanen R H, Pollock S, Waterworth A, Speirs V, Hughes T A & Hanby A M (2011) Histopathology 59, 609–618 Epithelial–mesenchymal interactions in breast cancer: evidence for a role of nuclear localized b-catenin in carcinoma-associated fibroblasts Aims: Characteristics of the stroma around tumours are critical in defining the behaviour of cancers. b-Catenin is well established as a critical regulator of carcinogen- esis, acting as a transcriptional co-activator in the nuclei of epithelial cancer cells. We have examined the prevalence and influence of nuclear b-catenin within the stromal fibroblasts of breast cancer. Methods and results: We examined b-catenin expression in 201 breast cancers and adjacent normal tissue. Fibroblasts expressing nuclear b-catenin were present in a significantly greater proportion of tumour tissues than normal tissues. The presence of fibroblasts with nuclear b-catenin in tumours correlated with survival; tumours with prevalent positive fibroblasts were asso- ciated significantly with relatively good prognoses. Functional studies to examine influences of fibroblasts with nuclear b-catenin, showed fibroblasts transfected to allow overexpression of b-catenin were capable of inducing increases in both proliferation and invasion of breast cancer cell lines. Conclusion: The presence of fibroblasts with nuclear b-catenin in tumours is a good prognostic indicator, although in the context of tissue culture models these cells can increase the growth and metastatic potential of cancer cells. These apparently paradoxical observa- tions underline the complexity of epithelial–stromal signalling within tumours and highlight an area for further study. Keywords: beta-catenin, breast, cancer, epithelial, fibroblast, interaction, stromal Abbreviations: CAF, carcinoma-associated fibroblasts; CM, conditioned medium; IHC, immunohistochemistry; TMA, tissue microarray Introduction Interactions between cancer cells and the stroma have critical influences on carcinogenesis. For example, the stroma can modify cancer cell proliferation, motility, differentiation and apoptosis. 1 Stroma consists of both extracellular matrix and cells, including fibroblasts, adipocytes and endothelial cells. Of these, fibroblasts are the most numerous and most often in close proximity to tumour cells, therefore potentially have the greatest effect on tumour behaviour. 2 Furthermore, it is well established that tumour cells alter local fibroblast behaviour, most clearly demonstrated by desmoplasia, and consequently carcinoma-associated Address for correspondence: Professor A M Hanby, Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St James’s University Hospital, Leeds LS9 7TF, UK. e-mail: A.M.Hanby@leeds.ac.uk *These authors contributed equally to this study. Ó 2011 Blackwell Publishing Limited. Histopathology 2011, 59, 609–618. DOI: 10.1111/j.1365-2559.2011.03917.x