(188aj) A Microfluidic Approach to Quantify Three-Dimensional Directed Cellular Migration of Highly Invasive Cancer Cells

In the tumor microenvironment (TME) cancer cells are often exposed to different, competing gradients that can influence their migratory behavior. Directional cues such as concentration gradients of growth factors or differences in extracellular matrix (ECM) stiffness bias the directed movement of cells through chemotaxis and durotaxis, respectively. Several approaches have been developed to study the tactic movement of cancer cells in two-dimensional (2D) environments; however, these studies cannot recapitulate the spatial and temporal cues encountered by cells in three-dimensional (3D) environments. Moreover, recent studies have found that cell signaling and cell movement in 3D environments differ from those in 2D environments. In this study, a microfluidic approach is utilized to generate different types of chemotactic cues similar to those found in the TME to elicit a dynamic cellular response. The device consists of a top PDMS layer with three parallel fluidic channels imprinted into it placed on top of an agarose slab encased in a Plexiglas chamber. The center channel is seeded with cells in a collagen matrix to facilitate 3D migration of the cells. The device is designed such that chemical gradients can be established through the agarose perpendicular to the direction of flow to establish ‘flow-free’ chemical gradients. Preliminary experiments used this device to study the biophysical response of migrating MDA-MB-231 cells to stable gradients of serum and growth factors EGF and SDF-1α, both found in the TME. Next, the temporal behavior of the chemical gradients was altered to create time-varying, oscillating chemical gradients by tuning the identify of the source channel between ‘on’ (with growth factors) and ‘off’ (without growth factors) to assess the memory of the migrating cells and quantify their directional persistence. A strength of this microfluidic approach is its ability to be modified to incorporate different types of competing or complementary gradients. The device presented here has the potential to be modified to include nanostructures in the agarose to elicit durotactic gradient or additional channels to create orthogonal chemical gradients to directly assess cellular decision making.