The migration process is a physically integrated molecular phenomena that contributes to many physiological motility in vivo processes such as development, immune surveillance and cancer metastasis. To understand cell migration it is necessary to consider the cell's environment, cell type and morphology as well as the internal organization of the cells, i.e. its cytoskeleton and focal adhesions. This work focuses on the study of migrating bladder cancer cells on two--dimensional deformable substrates. The analysis of a panel of three cell lines with different invasive capacity is presented. The ability of cancer cells to respond to their environment is analysed and the migration process is described in terms of traction stresses. The internal reorganization of cells structure is studied by microscopic observation of the actin filaments, the myosin motors and the sites of force transmission, i.e. the focal adhesions. The complementary relationship among different invasive capacities of cancer cells, traction stresses as well as the forces exerted on the lamellipodium and internal structures of cells are discussed. It is found that several parameters can be used for discriminating invasiveness, such as migration type, traction forces, focal adhesion areas, as well as the migration diffusivity index. This study therefore constitutes a first attempt to differentiate various invasive cells using migration on soft substrates.
