This Funding Opportunity Announcement (FOA) is designed to promote research on tumor microenvironment with the focus on understanding the role of host stroma in tumorigenesis and responses to treatment. Through this FOA, the National Cancer Institute (NCI) and National Institute of Neurological Disorders and Stroke (NINDS) invite cooperative agreement applications from groups of investigators interested in forming Research Centers serving as components of an interactive NCI Tumor Microenvironment Network (TMEN). The main scientific objectives of TMEN are: 1) to generate a comprehensive understanding of composition of the stroma in normal tissues as well as its roles in tumor initiation, progression, and metastasis; 2) to delineate mechanisms of tumor-stroma interactions in human cancer; and 3) to identify the mechanism(s) by which tumor stroma may affect responses to treatment. In addition to these general NCI priorities, NINDS is particularly interested in research programs relevant to primary brain tumors or peripheral nervous system tumors. TMEN members will be expected to participate in collaborative efforts (to be developed within TMEN) that are directed at: 1) developing resources and reagents critical to the analysis of the tumor microenvironment; 2) developing novel technologies for use in tumor microenvironment research; and 3) outreach activities to facilitate dissemination of such resources and technologies to the broader research community. TMEN infrastructure is expected to establish repositories of critical reagents, resources, and information as well as promote and facilitate interdisciplinary collaborations both within and outside the Network.