Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 28: Biomedical Applications

BP 28.5: Talk

Friday, March 30, 2007, 12:00–12:15, H44

Strain Energy during Tumor Cell Invasion in 3-D Collagen Gels — •Thorsten Koch, Claudia Mierke, Daniel Paranhos Zitterbart, Stefan Münster, and Ben Fabry — Friedrich-Alexander-Universität Erlangen-Nürnberg - Zentrum für Medizinische Physik und Technik - Lehrstuhl für Physikalisch-Medizinische Technik - Henkestraße 91 - D-91052 Erlangen

Cells cultured on 2D rigid substrates behave differently from cells suspended in a 3D connective tissue matrix, e.g. in 3D cells exhibit a more elongated morphology, less pronounced stress fiber formation, and marked differences in focal adhesion composition. In this study we compared the strain energies resulting from forces exerted on 2D vs. 3D extracellular matrices by MDA-MB-231 breast carcinoma cells. Cells were plated on the surface of 2D polyacrylamide hydrogels (Young’s modulus E=1.5 and 6 kPa), or 3D collagen gels (E=50 Pa), and allowed to spread onto, or invade into, the gels for two days. Gel deformation was quantified by tracking the 3D positions of embedded fluorescent beads (ø 1 µm). The undeformed state was obtained by disrupting the actin cytoskeleton and hence force transmission with Cytochalasin-D (4 µM). The strain energy, calculated from displacements of beads between the initial and final states, was U=1.01 pJ (E=6 kPa) and U=0.2 pJ (E=1.5 kPa) on 2D gels. Surprisingly, cells in a soft 3D matrix generated significantly higher strain energy U=(1.8 ± 0.2) pJ (n=47). These results demonstrate that tumor cells can exert substantial forces on surrounding tissue during invasion that cannot be inferred from traction measurements in 2D.