Engineering a 3D collective cancer invasion model with control over collagen fiber alignment.

Prior to cancer cell invasion, the structure of the extracellular matrix (ECM) surrounding the tumor is remodeled, such that circumferentially oriented matrix fibers become radially aligned. This predisposed radially aligned matrix structure serves as a critical regulator of cancer invasion. However, a biomimetic 3D model recapitulating a tumor's behavioral response to these ECM structures is not yet available. In this study, we have developed a phase-specific, force-guided method to establish a 3D dual topographical tumor model in which each tumor spheroid/organoid is surrounded by radially aligned collagen I fibers on one side and circumferentially oriented fibers on the opposite side. A coaxial rotating cylinder system was employed to construct the dual fiber topography and to pre-seed tumor spheroids/organoids within a single device. This system enables the application of different force mechanisms in the nucleation and elongation phases of collagen fiber polymerization to guide fiber alignment. In the nucleation phase, fiber alignment is enhanced by a horizontal laminar Couette flow driven by the inner cylinder rotation. In the elongation phase, fiber growth is guided by a vertical gravitational force to form a large aligned collagen matrix gel (35 × 25 × 0.5 mm) embedded with >1000 tumor spheroids. The fibers above each tumor spheroid are radially aligned along the direction of gravitational force in contrast to the circumferentially oriented fibers beneath each tumor spheroid/organoid, where the presence of the tumor interferes with the gravity-induced fiber alignment. After tumor invasion, there are more disseminated multicellular clusters on the radially aligned side, compared to the side of the tumor spheroid/organoid facing circumferentially oriented fibers. These results indicate that our 3D dual topographical model recapitulates the preference of tumors to invade and disseminate along radially aligned fibers. We anticipate that this 3D dual topographical model will have broad utility to those studying collective tumor invasion and that it has the potential to identify cancer invasion-targeted therapeutic agents.