title: Correlating confocal microscopy and atomic force indentation reveals metastatic cancer cells stiffen during invasion into collagen I matrices.
abstract: Mechanical interactions between cells and their microenvironment dictate cell phenotype and behavior, calling for cell mechanics measurements in three-dimensional (3D) extracellular matrices (ECM). Here we describe a novel technique for quantitative mechanical characterization of soft, heterogeneous samples in 3D. The technique is based on the integration of atomic force microscopy (AFM) based deep indentation, confocal fluorescence microscopy, finite element (FE) simulations and analytical modeling. With this method, the force response of a cell embedded in 3D ECM can be decoupled from that of its surroundings, enabling quantitative determination of the elastic properties of both the cell and the matrix. We applied the technique to the quantification of the elastic properties of metastatic breast adenocarcinoma cells invading into collagen hydrogels. We found that actively invading and fully embedded cells are significantly stiffer than cells remaining on top of the collagen, a clear example of phenotypical change in response to the 3D environment. Treatment with Rho-associated protein kinase (ROCK) inhibitor significantly reduces this stiffening, indicating that actomyosin contractility plays a major role in the initial steps of metastatic invasion.
authors.affiliation: Department of Physics, Arizona State University, Tempe, AZ 85287.|Center for Biological Physics, Arizona State University, Tempe, AZ 85287.
authors.forename: Jack R
authors.initials: JR
authors.lastname: Staunton
authors.affiliation: Department of Physics, Arizona State University, Tempe, AZ 85287.|Center for Biological Physics, Arizona State University, Tempe, AZ 85287.
authors.forename: Bryant L
authors.initials: BL
authors.lastname: Doss
authors.affiliation: Department of Physics, Arizona State University, Tempe, AZ 85287.|Center for Biological Physics, Arizona State University, Tempe, AZ 85287.|Biodesign Institute, Arizona State University, Tempe, AZ 85287.|Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287.
authors.forename: Stuart
authors.initials: S
authors.lastname: Lindsay
authors.affiliation: Department of Physics, Arizona State University, Tempe, AZ 85287.|Center for Biological Physics, Arizona State University, Tempe, AZ 85287.|Biodesign Institute, Arizona State University, Tempe, AZ 85287.
authors.forename: Robert
authors.initials: R
authors.lastname: Ros
mesh_terms: D000465:Algorithms; D045744:Cell Line, Tumor; D024042:Collagen Type I / Q000378:metabolism*; D055119:Elastic Modulus; D005109:Extracellular Matrix / Q000378:metabolism*; D006801:Humans; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008962:Models, Theoretical; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology*
chemical_list: D024042:Collagen Type I
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