Mechanosensitivity of Cancer Cells in Contact with Soft Substrates Using AFM

Abstract

Cancer cells are usually found to be softer than normal cells, but their stiffness changes when they are in contact with different environments because of mechanosensitivity. For example, they adhere to a given substrate by tuning their cytoskeleton, thus affecting their rheological properties. This mechanism could become efficient when cancer cells invade the surrounding tissues, and they have to remodel their cytoskeleton in order to achieve particular deformations. Here we use an atomic force microscope in force modulation mode to study how local rheological properties of cancer cells are affected by a change of the environment. Cancer cells were plated on functionalized polyacrylamide substrates of different stiffnesses as well as on an endothelium substrate. A new correction of the Hertz model was developed because measurements require one to account for the precise properties of the thin, layered viscoelastic substrates. The main results show the influence of local cell rheology (the nucleus, perinuclear region, and edge locations) and the role of invasiveness. A general mechanosensitive trend is found by which the cell elastic modulus and transition frequency increase with substrate elasticity, but this tendency breaks down with a real endothelium substrate. These effects are investigated further during cell transmigration, when the actin cytoskeleton undergoes a rapid reorganization process necessary to push through the endothelial gap, in agreement with the local viscoelastic changes measured by atomic force microscopy. Taken together, these results introduce a paradigm for a new-to our knowledge-possible extravasation mechanism.

Role of a kinesin motor in cancer cell mechanics

“…We found that a grade II (RT112) and a grade III (KU) bladder cancer lines are softer than normal urinary human (NHU) cells at the intracellular scale ( Figure 1A), consistent with previously published results 36,37 . When KIF20A was inhibited, intracellular rigidity decreased in both cell lines ( Fig.…”

“…Intracellular relaxation experiments of beads trapped by optical tweezers (Fig.1B) allowed us to measure two phenomenological parameters, the rigidity index and the bead step amplitude, and to extract the complex shear modulus using a model based on power law rheology (see Methods). These measurements confirmed that lower grade (RT112) cells are softer than higher grade (T24) cells 36,37 ( Fig. 1B).…”

“…Cell stiffness is often altered in pathological situations including fibrosis and cancer [32][33][34][35][36] . In most cancers, isolated cancer cells have been shown to be softer than their healthy counterparts 36,37 .…”

Single-cell immuno-mechanics: rapid viscoelastic changes are a hall-mark of early leukocyte activation

“…The role of these mechanical changes is not clear yet. Cell contractility and cell stiffness are correlated in muscle cells [63][64][65][66][67] ; fibroblasts 33 and epithelial cancer cells 68 getting stiffer also get more viscous. Although the inner structure of leukocytes differs from these cell types, the increase in stiffness and viscosity that we observe during activation might be a manifestation of conserved cytoskeletal-based properties among mammalian cells.…”

Intracellular mechanics: connecting rheology and mechanotransduction

“…Recently, a mechanotransduction signaling pathway involving actomyosin contractility, focal adhesion kinase FAK and Yes-associated protein YAP has been deciphered in ovarian cancer cells [54 ]. In the context of cancer again, the elastic modulus of bladder cancer cells was shown to increase with substrate rigidity [55 ]. A novel signaling pathway in cell-substrate adhesion-induced mechanotransduction was recently discovered and involves the metabolic sensor AMP-activated protein kinase (AMPK) [56 ].…”