Stromal-epithelial cell cross-talk in the breast tumour microenvironment elicits changes in tumour epithelial cell gene expression.

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Abstract Abstract #1053 Introduction Tumour growth & progression in breast cancer is a product of autocrine & paracrine actions of factors secreted by malignant epithelial & stromal populations in the tumour microenvironment. Stromal cells, recognised as prominent modifiers of cancer progression, are thought to play a critical role in controlling neoplastic epithelial cell function. Although chemokines, which are chemotactic cytokines, have been postulated as mediators of stromal-epithelial cell signalling, the precise nature of such intricate interactions remains incompletely understood. The aim of this study was to investigate stromal cell-mediated modification of breast cancer epithelial cells.
 Methods Two breast cancer cell lines with different hormone receptor profiles (ER+ MDA-MB-231 & ER- T47D) were cultured individually & on confluent monolayers of stromal cells isolated from primary breast tumours. Co-culture supernatants were harvested for chemokine quantitation by ELISA. Following direct co-culture breast cancer epithelial cells were retrieved from mixed populations with EpCAM specific magnetic beads & RNA extracted. Changes in gene expression in epithelial cells resulting from interaction with stromal cells were identified by RQ-PCR using primers for the chemokines Monocyte Chemotactic Protein-1 (MCP-1/CCL2), & Stromal Cell Derived Factor-1α (SDF-1α/CXCL12), as well as their respective receptors, CCR2 & CXCR4. Changes in expression of genes involved in invasion (MMP11 & HER-2) and proliferation (Ki67) were also analysed.
 Results Expression of CCR2 & CXCR4 was confirmed in epithelial cell lines. Co-cultures of epithelial & stromal cells secreted significantly higher levels of MCP-1 than the cells cultured alone, while the reverse was true of SDF-1α secretion (Table 1). RQ-PCR revealed changes in gene expression of epithelial cells retrieved following co-culture with tumour stromal cells. The highly invasive MDA-MB-231 cells showed upregulation of both CCL2 & CXCL12 genes (2-3 fold increase) following interaction with tumour stromal cells, while the non invasive T47D cells showed downregulation of these genes. Expression of genes specifically associated with invasion, Her2 & MMP11, were elevated (1-2 fold increase) following exposure to tumour stromal cells, with little or no change observed in the proliferative marker Ki67.
 
 Conclusion Tumour stromal cells induce altered secretion & expression of tumourigenic chemokines & invasion-associated genes in breast cancer epithelial cells, mediated through direct cell contact. These results further define the tumour promoting role of stromal cells & highlight these interactions as potential therapeutic targets. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1053.