(157m) Extended 3D Cancer Cell Migration in Response to an Oscillating Chemical Gradient Breaks the Spatial Range Limitations of Conventional Chemotaxis

In the tumor microenvironment (TME) cancer cells are exposed to spatial and temporal pulsing of chemical gradients which influences the directed migration of cells via a chemotactic response. Traditional cellular chemotaxis in vitro studies utilize stable chemical gradients in two-dimensional (2D) environments; however, in vivo conditions result in both competing and oscillating gradients which the individual cells must sense and interpret to elicit a migratory response. Moreover, chemotaxis studies in a 2D environment do not recapitulate the spatial and temporal cues encountered by cells in three-dimensional (3D) environments. Recent studies have found that cell signaling and cell movement in 3D environments differ from those in 2D environments. Additionally, studies have shown that cells typically lack the capacity to detect external gradients under constant and high magnitude chemoattractant concentrations. Long-range chemotaxis is possible via the temporal pulsing of spatial gradients by establishing and eliminating the chemical gradient. In this study, a microfluidic approach was utilized to generate stable and tunable chemical gradients to elicit a dynamic cellular response during 3D chemotaxis in triple-negative breast cancer cells. The microfluidic device consists of three parallel channels imprinted into top polydimethylsiloxane (PDMS) device coupled with a bottom 3% (v/v) agarose slab enclosed in a Plexiglas chamber. The bottom agarose hydrogel allows for passive diffusion perpendicular to the direction of flow in the outer two channels into a center, ‘flow-free’ migration channel. A constant source solution with a chemoattractant was infused into one of the outermost channels to induce a linear chemical gradient across the migration channel. Time-dependent gradient oscillation was controlled by tuning the source solution flow rate between ‘on’ and ‘off’ for a defined time. The flow rate of the outer channels could be modulated to build and erase gradients allowing for temporal control over the gradient within the device. COMSOL simulation confirmed the oscillating pattern chemical gradient in the device. To study 3D chemotaxis, triple-negative breast cancer cells MDA-MB-231) were seeded into the migration channel in a collagen (2mg/mL) hydrogel to study how cancer cells respond to time-varying external chemical gradients. Preliminary results showed that the population of breast cancer cells responded to 20% FBS oscillating gradient (8 h on, 2 h off, 8 h on) by extending the migratory distance and chemotactic persistence compared to both a non-oscillatory stable chemical gradient and random migration in the absence of an external gradient. Extended cell migration in in-vitro chemotaxis mimics the cell behavior in an in vivo microenvironment that has the potential to the study of metastasis and drug screening.