It has been long appreciated that changes in the extracellular matrix (ECM) in the tumor microenvironment can drive tumor progression. With the recent advance in imaging techniques changes in the organization of ECM components like collagen have been described. Circumferentially organized collagen fibers are reorganized into radially aligned fibers, leading to directed migration or contact guidance away from the tumor. This collagen organizational signature has been proposed as a diagnostic indicator of potential invasion, linking contact guidance to invasion. Unfortunately, while there is an abundance of information on contact guidance in 2D environments, much less is known about contact guidance in 3D environments. In addition, collagen fiber networks can exhibit a large variation in properties separate from alignment that regulate the ability of cells to sense and respond to contact guidance cues, effectively altering the relationship between collagen organization and invasion. My long-term goal is to understand how tumor, stromal and immune cells integrate multiple cues for directional migration in the tumor microenvironment by using various engineering approaches. The objective of this research is to understand the role of the organization and composition of collagen I matrix in directing contact guidance. The specific aims of this proposal include: (1) Assess the relative contributions of topology and confinement in explaining the differences between contact guidance in 2D and 3D environments, (2) Test the hypothesis that changes in fiber structure such as fiber and crosslinking density as well as degree of alignment regulate the contact guidance of cancer cells and (3) Test the hypothesis that collagen I binding proteins that promote adhesion or de-adhesion regulate the contact guidance of cancer cells. Epitaxial growth of collagen fibers on mica as well as magnetic alignment of collagen fibers in gels will be used to engineer environments with specify contact guidance characteristics. Cell migration will be assessed using live cell microscopy in 2D, 3D and hybrid environments. Understanding how different properties of collagen fiber networks regulate contact guidance will further refine the prognostic ability of diagnostic biopsy images. Quantification of collagen fiber density, measurement of mechanical properties of the biopsy, a proxy for crosslinking density, and staining of additional collagen binding partners will give insight into the efficiency of contact guidance away from an individual tumor. Future work will be geared towards making these measurements in vivo and in biopsies from mouse tumor models and correlating these biophysical and compositional properties to tumor progression or prognosis.