Mechanical interactions between cells and the extracellular matrix (ECM) are critical to the metastasis of cancer cells. Along with the enhanced ability of metastatic cells to remodel ECM by catalyzing both degradation and cross-linking of ECM fibers, increased mechanical compliance confers these cells with a distinct advantage in reaching the other side. In the past several years, experimental perturbations of ECM stiffness in vitro have revealed the importance of 'outside-in' signaling in effecting cellular behavior and phenotype, and the physiological relevance of a 3D microenvironment has become increasingly clear. We have established a 3D model system investigating cell-ECM mechanics using an atomic force microscope (AFM) mounted on and synchronized with a confocal laser scanning microscope (CLSM). Along with the use of well-defined sphero-conical AFM probes with micrometer sized radii, the advancement of novel AFM indentation data analysis methods to correctly determine elastic moduli in a depth-dependent manner enables us to determine the stiffness of cells that are embedded in gels. Multi-color fluorescent labeling of the cell and ECM components, as well as the AFM probe, provides the detailed geometry of not only the cell and gel, but also of their contact with and deformation by the AFM tip during indentation, all of which are integral to the proper interpretation of force-indentation curves on such heterogeneous samples.In this talk, we present results from experiments with collagen-embedded metastatic MDA-MB-231 breast cancer cells and immortalized non-tumorigenic MCF-10A mammary epithelial cells. Collagen I matrices ranging ~10-50 �m in thickness and ~100-10,000 Pa in elastic modulus are covalently attached to dishes. After polymerization, MDA-MB-231 and MCF-10A cells are seeded on the gels. The cells are given various amounts of time to adhere and/or invade the gel before fluorescent staining and combined mechanical/confocal measurements.

Mechanical properties of breast cancer cells embedded in matrices

245th National Meeting (2013)

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