Design of Fiber Networks for Studying Metastatic Invasion.

Cancer metastasis, the dissemination of cancer cells from the primary tumor site to distal organs in the body, is one of the leading causes of cancer-related deaths globally. It is now appreciated that metastatic cells take advantage of specific features of surrounding fibrous extracellular matrix that favors invasion. However, the exact contributions of the role of fiber feature size, orientation, and organization remain only partially described. Here using non-electrospinning Spinneret based Tunable Engineered Parameters (STEP) fiber platform, we detail our quantitative findings over the past decade on cancer cell behavior in environments of controlled fiber dimensions, orientation, and hierarchy that can mimic essential features of native ECM. We present a biophysical model of invasion along aligned fibers that starts with cells forming protrusions followed by invasion of cells from a monolayer in single, multi-cell chain and collective modes. Using a mismatch of fiber diameters, we describe a new method to protrutype single protrusions and describe migratory behavior of cells in different shapes. Altogether, control over fiber geometry and network architecture enables the STEP platform to unlock a new paradigm in the interrogation of the fundamental biophysical mechanisms underlying the migratory journey of cells during cancer metastasis.

Cancer Protrusions on a Tightrope: Nanofiber Curvature Contrast Quantitates Single Protrusion Dynamics.

Cell migration is studied with the traditional focus on protrusion-driven cell body displacement, while less is known on morphodynamics of individual protrusions themselves, especially in fibrous environments mimicking extracellular matrix. Here, using suspended fibers, we report integrative and multiscale abilities to study protrusive behavior independent of cell body migration. By manipulating the diameter of fibers in orthogonal directions, we constrain cell migration along large diameter (2 µm) base fibers, while solely allowing cells to sense, initiate, and mature protrusions on orthogonally deposited high-curvature/low diameter (∼100, 200, and 600 nm) protrusive fibers and low-curvature (∼300 and 600 nm width) protrusive flat ribbons. In doing so, we report a set of morphodynamic metrics that precisely quantitate protrusion dynamics. Protrusion growth and maturation occur by rapid broadening at the base to achieve long lengths, a behavior dramatically influenced by curvature. While flat ribbons universally induce the formation of broad and long protrusions, we quantitatively protrutype protrusive behavior of two highly invasive cancer cell lines and find breast adenocarcinoma (MDA-MB-231) to exhibit sensitivity to fiber curvature higher than that of brain glioblastoma DBTRG-05MG. Furthermore, while actin and microtubules localize within protrusions of all sizes, we quantify protrusion size-driven localization of vimentin and, contrary to current understanding, report that vimentin is not required to form protrusions. Using multiple protrusive fibers, we quantify high coordination between hierarchical branches of individual protrusions and describe how the spatial configuration of multiple protrusions regulates cell migratory state. Finally, we describe protrusion-driven shedding and collection of cytoplasmic debris.