PROJECT SUMMARY Despite recognition of the broad consequences of inflammation in cancer biology, the mechanistic impact on the tumor landscape remains incompletely understood. Indeed, innate and adaptive immune functions in cancer can be beneficial or detrimental and the opposing roles highlight the gap of knowledge in our understanding of how inflammation sculpts the tumor microenvironment (TME). This Program Project will address this gap of knowledge by defining and delineating how cytokines modulate the functions of the multiple cell types composing the tumor microenvironment. Our previous work has revealed the potential for these inflammatory cytokines to regulate a spectrum of cancer cell phenotypes, including their self-renewal and cellular hierarchy or stemness, that are associated with the epithelial-mesenchymal transition (EMT). Moreover, these phenotypes are commonly associated with cancer progression through modulation of differentiation potential, cell-cell interactions and mobility, fibrosis, and sensitivity to multiple therapeutic modalities. The program is now centered on two major themes. The first is to define the signaling mechanisms that govern how cytokines (type I IFNs, IL- 17,TGFβ) modulate (both positively and negatively) the EMT process. The cellular targets include stem-like tumor cells as well as the non-tumor derived populations, including fibroblasts and immune cells. The second theme relates these cell-specific EMT responses to specific effects on metastasis, fibrosis, and resistance to multiple therapeutic strategies. Our major goal is to parlay our improved understanding of cytokine effects in the TME into specific improvements in cancer therapy. Collectively the three projects in the application will test the following overarching hypothesis: Cytokine signals have distinct and sometimes conflicting mechanistic roles in cancer progression though alterations in EMT and cancer stem cell development. Such mechanisms lead to critical phenotypic properties responsible for continuous metastatic spread and resistance to multiple therapeutic modalities (chemotherapy, immune therapy). This hypothesis will be tested by (1) defining the signaling events initiated by TGFβ, IL-17, and/or Type I IFNs and the endpoint changes in specific gene expression that are causally linked with control of TME and cancer cell phenotypes, (2) determination of how these specific signaling pathways and gene expression events are mechanistically responsible for acquisition of therapeutic resistance and (3) evaluation of the distinct cell type contributions to tumor phenotypes and therapeutic resistance, with emphasis on tumor cell intrinsic mechanisms, immune cell infiltrates and activities, and stromal cell control of tumor access.