Project Summary/Abstract Tumor metastasis is responsible for the vast majority of deaths from epithelial cancers, including breast cancer. Understanding how cancer cells spread to distant sites, persist as dormant disseminated tumor cells (DTCs), and eventually recur is essential to improving the treatment of this disease. The long-term goal of my research group is to identify pathways that regulate these processes to enable the development of therapies that can prevent or treat metastatic recurrences. We recently identified a role for the antioxidant stress response transcription factor NRF2 in promoting the survival and local recurrence of mammary tumors following targeted therapy. We found that NRF2 is activated following diverse targeted therapies as a consequence of metabolic and oxidative stress. NRF2 remains constitutively activated in recurrent tumors, where it functions to promote recurrence through regulating redox homeostasis and nucleotide metabolism. While these results identify a function for NRF2 in local recurrence, a role for NRF2 in promoting metastatic dissemination remains relatively unexplored. Emerging evidence suggests that metastatic dissemination is associated with metabolic and oxidative stress. Consistent with this, we recently found that the NRF2 transcriptional program is elevated in metastatic tumors from patients with breast cancer. However, a thorough understanding of NRF2 regulation during metastatic dissemination, and how NRF2 activation functionally affects metastasis, remains unknown. This proposal will build on this work to define the regulation and function of NRF2 during metastasis in breast cancer. In new preliminary data, we found that NRF2 suppresses pro-inflammatory signaling in breast cancer. Consistent with this, NRF2 knockdown leads to infiltration of immune cells into the tumor microenvironment. Based upon these findings, the central hypothesis for this proposal is that NRF2 promotes breast cancer progression by inhibiting pro-inflammatory signaling between cancer cells and the tumor immune microenvironment. We will test this hypothesis through three specific aims. In Aim 1, we will define the mechanism and function of NRF2 regulation of the tumor immune microenvironment. In Aim 2, we will determine the role of NRF2 suppression of inflammatory signaling in promoting the outgrowth of disseminated tumor cells. In Aim 3 we will test whether targeting metabolic pathways can prevent the growth of NRF2-high tumors. Our work will reveal new information on how NRF2 functions to regulate tumor progression and may uncover novel therapeutic opportunities to prevent metastatic recurrence.