Mechanotransduction of strain regulates an invasive phenotype in newly transformed epithelial cells

Our organs and tissues are in constant motion, exposing epithelial cells to mechanical stretch. However, how these external forces impact cellular morphology, organization and dynamics in healthy and diseased tissues is still being elucidated. In several studies, we and others have shown how mechanical stresses and strains in the epithelium can modulate the dynamics and invasiveness of transformed cells. Carcinoma, the most common type of cancer, develops in the sheets of cells forming the epithelium and lining our organs and cavities. It usually begins with the transformation of a single cell via the activation of oncogenes such as Ras. Here, we show in a model system how mechanical stretch in epithelial sheets results in a more invasive phenotype in transformed cells. Cyclic strain prevents the formation of strong circumferential belts of actin in Ras V12 cells and greatly promoting the formation of Ras V12 protrusions, typical of a more invasive phenotype. We also show that Ras V12 and wild type MDCK cells possess distinct sensitivity to strain. External forces remodel their actin cytoskeletons and adhesion complexes differently, resulting in a more invasive system dynamic. Our work demonstrates that the Rho-ROCK mechanotransduction pathway is involved in regulating a mechanically-induced switch to a more invasive phenotype. In a mechanically dynamic microenvironment, transformed cells exhibit drastically different cellular dynamics and movements when compared to static conditions. They grow larger invasive protrusions, potentially making them harder to be eliminated from healthy tissues. The insights gained in this study reveal the complex dynamics at play in healthy and transformed epithelial cells which are found in a mechanically active microenvironment.