Potential promotion of metastatis of circulating breast cancer cells through interactions with mesenchymal stem cells (MSCs).

Abstract

Abstract Abstract #1052 Introduction
 Mesenchymal Stem Cells (MSCs) are a subset of pluripotent non-haematopoeitic stem cells within the bone marrow stroma. Chemokines secreted by MSCs have been shown to influence the morphology and proliferative activity of cells within their vicinity. Dynamic reciprocal interactions occurring between circulating breast cancer cells and MSCs within the bone marrow microenvironment may facilitate further metastatic propagation and dissemination. Monocyte Chemotactic Protein-1 (MCP-1/CCL2) and Stromal Cell Derived factor 1-α (SDF-1a/CXCL12) are inflammatory chemokines with tumorigenic potential that may facilitate the cultivation of a pre-metastatic niche. Both of these chemokines have been associated with promoting and directing metastatic spread in breast cancer patients, and are know to be secreted by MSCs. The aim of this study was to elucidate the impact MSCs have on breast cancer cells and to potentially identify factors mediating these effects.
 Methods
 MSCs were isolated from bone marrow aspirates of healthy volunteers, and their pluripotency confirmed prior to use. Breast Cancer Cell lines (MDA-MB-231 & T47D) were cultured individually and on a monolayer of MSCs for a period of 72hrs. Conditioned medium was harvested from cells cultured individually and co-culture populations. The concentrations of CCL2, CXCL12 and VEGF were quantified using ELISA. Breast cancer cells were retrieved following co-culture using epithelial specific magnetic beads. RNA was extracted and changes in expression of target genes following co-culture with MSCs was investigated using RQ-PCR. Targets included CCL2, CXCL12, their cognate receptors CCR2 and CXCR4, as well as Her2, Ki-67, MMP11 - genes previously related to breast cancer tumorigenicity.
 Results
 While there was no significant change in secretion of SDF-1α or VEGF upon direct co-culture of breast cancer cells with MSCs, there was a significant increase in MCP-1 secreted by the mixed cell populations compared to those cultured alone (P<0.05). CCL2 gene expression was upregulated in breast cancer cells retrieved following co-culture (MDA-MB-231: 4 fold increase; T47D: 1.7 fold increase) and expression of its principal receptor, CCR2, was also increased in T47D cells. CXCL12 gene expression was upregulated in MDA-MB-231 cells (4.2 fold). There was no significant change in CXCL12 expression in the T47D cells, however expression of its principal receptor, CXCR4, was upregulated. MMP11, a marker of invasive potential, was upregulated in both epithelial cell lines while Ki-67 and Her2 expression remained unchanged.
 Conclusion
 Direct contact with MSCs causes a distinct change in breast cancer cells as demonstrated by genetic modifications across a range of genes associated with breast cancer tumorigenicity. These results highlight the potential role MSCs play in facilitating the creation of a pre-metastatic niche and supporting the progression of engrafted tumour cells. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1052.