Project1: The role of intravascular pressure and shear stress on tumor cell arrest, survival and proliferation in the microvascular niche

Project 1: SUMMARY Metastatic colonization requires that circulating tumor cells (CTCs) overcome the physical stressors and homeostatic barriers that make successful metastasis an unlikely outcome. Very little is known about metastatic subpopulations, the adaptations that allow them to circumvent homeostatic barriers, and the mechanisms used to cope with these stressors and either proliferate or enter into dormancy. The intravascular environment is known to be inhospitable to CTCs, yet several lines of clinical evidence indicate that physical interactions with activated platelets, fibrin thrombi, immune cells and the formation of clusters with other cancer cells influences metastatic potential. Furthermore, the mechanism of extravasation within the microvasculature is mediated by endothelial interactions, cytoskeletal forces, nuclear deformations, and matrix proteolysis. It has long been recognized that metastatic tropism is determined by intrinsic organ properties. We hypothesize that secondary colonization is the culmination of a sequence of low probability events for which only a small subpopulation of CTCs has adapted to cope with these stressors. To investigate the mechanisms of arrest, extravasation, and colonization we have developed in vitro vascular networks that recapitulate the geometry and function of the microvascular networks where circulating tumor cells initiate metastatic lesions. Importantly, we are able to precisely engineer the microvascular environment by controlling cellular constituents, extracellular components, and the physical stressors to systematically distinguish the effect of specific perturbations on cancer cell arrest, transmigration, and colonization with high temporal and spatial resolution. In Aim 1, we create cancer cell thrombi and clusters to determine the effect of interactions with platelets, fibrin, and cancer cells on the arrest, transmigration, and colonization. In Aim 2, we extend the capabilities of our microvascular platforms to recapitulate the organ-specific microvascular environments of liver and dermis to examine combined effects of different flow and endothelial barrier function. In Aim 3, we will use specific molecular interventions to target tumor cell adhesion, contractility, nuclear deformability, and matrix degradation to quantify the effect on intravascular adhesion, transendothelial migration, and long-term extravascular fate. In Aim 4, we will measure nuclear deformation and quantify chromatin reorganization during transmigration and determine if quantitative measures of chromatin reorganization fates extravasated cells to a dormant phenotype (Core B). Taken together, we hypothesize that methodical in vitro observation combined with and validated by intravital studies (Project 2) and computational modeling (Core A) will lead to new insights regarding the specific mechanisms that enable CTCs to circumvent physical stressors. By engineering the physical environment, we will generate the knowledge leading to novel therapeutic opportunities to block or reverse the coping phenotype.