8th Annual Symposium
Physics of Cancer
October 4-6, 2017
|PoC - Physics of Cancer - Annual Symposium|
In situ mechanobiology of epithelia in health and disease
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The onset of metastasis occurs when cancer cells invade and breach the basement membrane (BM) that provides mechanical support to epithelial tissues. Yet, it remains unclear what triggers cancer cells to breach the BM, and how ‘triggered’ cells breach the BM. We have established an in vitro assay using native BM interface for culturing epithelial cells and demonstrated that native BMs isolated from human tissues act as a native substrate for culturing epithelial cells in terms of composition, architecture and stiffness. These are required to act jointly in order to achieve apico-basal polarity, tissue barrier formation and stiffness properties of the epithelial layer similarly to secretory epithelia in vivo. The native BM serves several advantageous over reconstituted Matrigel - ECM extract that originates from mouse tumor ascites. Besides variations in thickness and biochemical composition, we found that Matrigel is mechanically 100-fold more compliant (i.e., softer) than native BMs and demonstrated that stiffness and architecture of the native alpha-5 laminin chain has a key role in activating ï¢1 integrin and establishing physiologically relevant epithelial mechanophenotype. During cancer progression in vivo, cancer cells can perforate BM using proteolysis and the cancer cell invasion is associated with decrease in cellular stiffness and correlated to changes in cell and BM morphology. The role of stromal cells in this process has not yet been resolved. Therefore, we examined if carcinoma-associated fibroblasts (CAFs) isolated from cancer patients promote cancer cell invasion through a BM. In the presence of CAFs, moderately invasive cancer cells invade in a matrix metalloproteinase-independent manner. Using live imaging and atomic force microscopy, we could show that CAFs actively pull, stretch and soften the BM, forming gaps through which cancer cells can migrate. By exerting contractile forces, CAFs alter the organization and physical properties of native BM, making it permissive for cancer cell invasion. Finally, we propose that, in addition to proteolysis, mechanical interactions between CAFs and BM represent an alternative mechanism of BM breaching. Given their mechano-biological relevance, native BMs allow us to further understand mechanosignaling processes between epithelia and surrounding stromal layers at the BM interface in physiological and pathological states.