Collagen Stiffness Modulates MDA-MB231 Cell Metabolism Through Adhesion-Mediated Contractility
48 Pages Posted: 7 Jun 2018 Sneak Peek Status: Under ReviewMore...
Extracellular matrix (ECM) mechanical properties play a key role in cancer cell aggressiveness. Increasing substrate stiffness upregulates cancer invasion, cell contractility and focal adhesion formation. In addition to matrix properties, alteration in energy metabolism is a known characteristic of cancer cells (i.e., Warburg effect) and modulates cell invasion. However, there has been little evidence to show that substrate stiffness is able to affect cancer cell metabolism. Thus, we investigated changes in energy metabolism in response to varying collagen matrix stiffness in different cancer cells, MDA-MB231, AA375MM and U251MG and non- tumorigenic breast cell line MCF10A. Using the phasor approach to fluorescent lifetime imaging microscopy (FLIM), we measured the lifetime ratio of the free:bound state of NADH and determined if these cells altered their metabolism when plated on varying ECM density. This approach is a powerful tool that allows us to map the metabolic trajectory of each living cell within its cellular compartments. In our studies, we found that MDA-MB231 cells had an increase in bound NADH, indicating oxidative phosphorylation (OXPHOS), as collagen substrate density decreased. When inhibiting myosin-II contractility with Y-27632 or blebbistatin, the MDA-MB231 cells on glass shifted from glycolysis (GLY) to OXPHOS, confirming the intricate relationship between mechanosensing and metabolism in these highly invasive tumor cells. The human glioblastoma cell line, U251MG, showed an opposite trend compared to the invasive MDA-MB231 cells. However, the human melanoma cell line, A375MM did not show any significant changes in metabolic indices when they were grown on surfaces with varying collagen density but changed when grown on glass surfaces. MCF10A cells showed no changes in metabolism across all surfaces. In addition, OXPHOS or GLY inhibitors to MDA-MB231 cells showed dramatic shifts from OXPHOS to GLY or vice versa. There were slight changes detected in MCF10A cells. These results provide an important link between cellular metabolism, contractility and ECM stiffness in human breast cancer.
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