Cancer cells consistently exhibit decreased stiffness; however, the onset and progression of this change have not been
characterized. To study the development of cell stiffness changes, we evaluated the shear stiffness of populations of
cells during transformation to a carcinogenic state. Bronchial epithelial cells were exposed to sodium arsenite to initiate
early stages of transformation. Exposed cells were cultured in soft agar to further transformation and select for clonal
populations exhibiting anchorage-independent growth. Shear stiffness of various cell populations in G1 was assessed using
a novel non-invasive assay that applies shear stress with fluid flow and evaluates nanoscale deformation using quantitative
phase imaging (QPI). Arsenic-treated cells exhibited reduced stiffness relative to control cells, while arsenic clonal lines,
selected by growth in soft agar, were found to have reduced stiffness relative to control clonal lines, which were cultured in
soft agar but did not receive arsenic treatment. The relative standard deviation (RSD) of the stiffness of Arsenic clones was
reduced compared with control clones, as well as to the arsenic-exposed cell population. Cell stiffness at the population
level exhibits potential to be a novel and sensitive framework for identifying the development of cancerous cells.