| The migration of tumor cells of different invasivity is studied, and traction forces are determined in time on soft substrates (Young modulus 10 kPa). It is found that the outliers of the traction stresses are quite relevant to differentiate different cancer cell lines which are more or less invasive. Here we tested two different epithelial bladder cancer cell lines, one invasive (T24), and a less invasive one (RT112). Invasive cancer cells move in a nearly periodic motion, with peaks in velocity corresponding to higher traction forces exerted on the substrate, whereas the less invasive cell develops almost constant time-dependent traction stresses. The dynamics of focal adhesions as well as cytoskeleton features reveal different mechanisms activated to migrate, depending on their invasiveness. T24 invasive cells show an interconnected cytoskeleton linked to mature adhesion sites, leading to small traction stresses, whereas less invasive cells (RT112) show a less-structured cytoskeleton, unmature adhesions corresponding to higher traction stresses. Migration velocities are smaller in the case of less invasive cells. The MSD (Mean Squared Displacement) shows super-diffusive motions with a higher exponent for the more invasive cancer cells. Further correlations between traction forces and the actin cytoskeleton reveal an unexpected pattern with a large actin rim at the RT112 cell edge where higher forces are colocalized, whereas a more usual cytoskeleton with stress fibers and focal adhesions is found for T24 cancer cells. Thus the method can be an interesting one to differentiate cancer cell invasiveness. |
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