The Effect of Geometry and TGF-β Signaling on Tumor Cell Migration from Free-Standing Microtissues

Recapitulation of 3D multicellular tissues in vitro is of great interest to the field of tumor biology to study the integrated effect of local biochemical and biophysical signals on tumor cell migration and invasion. However, most microengineered tissues and spheroids are unable to recapitulate in vitro the complexities of 3D geometries found in vivo. Here, lithographically defined degradable alginate microniches are presented to produce free-standing tumor microtissues, with precisely controlled geometry, high viability, and allowing for high cell proliferation. The role of microtissue geometry and TGF-β signaling in tumor cell migration is further investigated. TGF-β is found to induce the expression of p-myosin II, vimentin, and YAP/TAZ nuclear localization at the periphery of the microtissue, where enhanced nuclear stiffness and orientation are also observed. Upon embedding in a collagen matrix, microtissues treated with TGF-β maintain their geometric integrity, possibly due to the higher cell tension observed around the periphery. In contrast, cells in microtissues not treated with TGF-β are highly mobile and invade the surrounding matrix rapidly, with the initial migration strongly dependent on the local geometry. The microtissues presented here are promising model systems for studying the influence of biophysical properties and soluble factors on tumor cell migration.