Interactions of breast cancer cells with the microenvironment of the human bone marrow

e22097 Background: Bone is one of the most favored sites for metastasis of breast cancer cells (BrCa) resulting in the formation of osteolytic and/or osteoblastic lesions. There is increasing evidence that the bone marrow (BM) microenvironment plays a pivotal role in modulating tumor cell homing to the bone, metastasis and progression. However, the molecular crosstalk between BrCa cells and the cellular and extracellular components of the bone marrow leading to osteotropism still remains a poorly characterized step in the metastatic process. Methods: Cell adhesion and migration assays using the invasive MDA-MB-231 and the noninvasive MCF7 BrCa cell lines were performed to investigate the impact of BM components on cellular functions of tumor cells. Results: Cell-matrix adhesion assays showed a strong and concentration-dependent attachment of BrCa cells to several extracellular matrix components present in the human bone marrow such as fibronectin, different laminin isoforms, collagens type I and IV or tenascin-C. Moreover, the BrCa cells attached avidly to the BM-derived primary osteoblasts, whereas the binding to stromal cells was significantly weaker. Notably, cell-cell adhesion experiments with primary osteoclasts revealed an anti-adhesive effect on tumor cell binding leading to no attachment activity of BrCa cells with the cell surface of primary osteoclasts. The influence of cellular components of the BM on tumor cell migration was analyzed by cell migration assays using conditioned media of osteoblasts, osteoclasts and stromal cells or a modified Transwell chamber technique. The migration assays with invasive MDA-MB-231 cells clearly showed that osteoblasts, but not osteoclasts or stromal cells released factors which led to a faster wound closure, suggesting an enhanced migratory ability of the metastatic tumor cells, whereas the migration of nonmetastatic MCF7 cells was unaffected. Conclusions: These data indicate that the crosstalk with osteoblasts affects both the adhesive and the migratory ability of BrCa cells favoring the bone colonization process. Furthermore, the presented experimental conditions may provide useful tools to study effects of antiresorptive drugs like bisphosphonates to improve therapeutic strategies for treatment metastatic bone disease. No significant financial relationships to disclose.