PROJECT SUMMARY Cancer cells, extracellular matrix (ECM) and carcinoma-associated fibroblasts (CAFs) are three critical factors contributing to tumor progression in colorectal cancer and squamous cell carcinoma, among other cancer types. CAFs are often associated with the development of high-grade malignancies of poor prognoses because CAFs secrete metastasis-promoting cytokines and abnormally deposit collagen, facilitating integrin- dependent cancer invasion and forming hindrance of anti-cancer drug delivery. Despite the detailed studies about the role of CAFs in tumor progression, the mechanism by which stromal cells become CAFs is still not clear: how normal fibroblasts in stroma are transformed to CAFs during early stages of cancer? In this project, I will test the hypothesis that cancer cells facilitate CAF induction by mechanically reorganizing extracellular matrix and thus breaking down the diffusion barrier of CAF-inducing factors. A coculture system containing colorectal cancer spheroids and multiple types of stromal cells as the testing platform will be constructed for the preliminary tests. If proven valid, I will use my hypothesis to develop new treatments where ECM remodeling is suppressed to decrease the rate of tumor progression in colorectal cancer. Two treatment strategies will be tested: (1) direct applying ECM crosslinking agents in the tumor microenvironment; (2) implanting genetically engineered fibroblasts secreting ECM crosslinking enzymes and other anti-cancer biomolecules. Colorectal cancer mouse models will be used to evaluate the efficacy of the new treatments.