The high attrition rate of drug candidates in clinical trials has lead to a critical need for alternatives to currently used in vitro assays and animal models that better predict clinical outcome, especially in cancer therapeutics. Three-dimensional in vitro tumor models that incorporate specific tissue properties and physico-chemical stimuli more closely mimic in vivo conditions. Nortis developed a technology for generating vascularized tissue microenvironments in disposable microfluidic devices. During this contract this technology will be utilized to develop a vascularized breast tumor microenvironment assay to assess anti-cancer therapeutic efficacy. Specific Objective 1 will establish quantifiable metrics to measure changes in microenvironment properties. Specific Objective 2 will utilize these metrics to demonstrate the assay can measure drug-dependent responses in a panel of breast cancer cell lines. Specific Objective 3 will develop a 24-unit perfusion platform that supports automated analysis of the assay. The ultimate goal of the project is a platform for the high content screening of anti-cancer drug candidates that can be utilized with currently existing analysis systems. If successful, this technology will significantly enhance the efficiency of anti-cancer drug development. Additionally, this assay promises important new insights about the contribution of the tumor microenvironment to cancer and therapeutic development.