Mapping the CXCR4 receptor on breast cancer cells.

The CXCR4 receptor triggers cell migration and, in breast cancer, promotes metastasis. To date, the dynamic assembly of CXCR4 on the cell surface as a mediator of receptor binding is not well characterized. The objective of this work is to quantify the density, spatial organization, and magnitude of binding of the CXCR4 receptor on live metastatic breast cancer (MBC) cells. We measured the Young's modulus, the CXCR4 surface density, and CXCR4 unbinding force on MBC cells by atomic force microscopy. We conclude that the CXCR4 density, spatial organization, and matrix stiffness are paramount to achieve strong binding.