Quantifying ECM micromechanical remodeling by an invading tumor

Tumors are known to remodel the local extracellular matrix (ECM) in which they live. This remodeling causes the stiffness of the ECM to change, and is a major footprint in diagnosing tumors, specifically metastatic solid tumors such as breast or brain tumors. However, most studies up to date conduct bulk rheology or macroscopic rigidity experiments on the remodeled ECM. By using optical tweezers based assays, we are able to probe the local remodeling of the ECM and measure the local micromechanics as the tumor continuously expands and invades into the surrounding ECM. We find that the tumor can introduce strong mechanical anisotropy as well as stiffen the ECM. We find that these remodelings are spatially and temporally dependent on the tumor invasion dynamics. We hypothesize that the found remodelings are dominated by two factors, the volume preservation of cells and the traction force generated by cells. We also test our results by using different geometries of tumors.