Utilizing the power of lymph nodes to generate long-lasting, systemic anti-cancer immune responses has the potential to eradicate metastatic cancers from patients as seen with the recent success of immunotherapy in a subset of patients. The presence of lymph node metastases, however, brings with it a worse prognosis and the recommendation for systemic therapy for most cancer patients. Over the past 5+years our laboratory has shown that—beyond being a biomarker of the aggressiveness of the cancer—lymph node metastases play previously unrecognized roles in cancer progression, including by escaping the lymph node and seeding distant metastases. Our preliminary data also show that metastatic lymph nodes are immune suppressed, which leads to poor systemic anti-cancer immune responses and allows cancer progression. For patients with lymph node metastasis, immune suppression of lymph nodes needs to be overcome for successful immunotherapy. For the proposed work, we have generated strong preliminary data for two complementary mechanisms that we hypothesize cancer cells use in metastatic lymph nodes to drive immune suppression. First, our data show that a subset of cancer cells in metastatic lymph nodes express MHC class II molecules but not co-stimulatory molecules. We hypothesize that interactions of MHCII positive cancer cells with naïve lymphocytes will lead to CD4 T-cell suppression and Treg formation, limiting anti-cancer immune responses (Aim 1). We will determine the consequences of MHCII expression on cancer cells in metastatic lymph nodes for anti-cancer immune responses. Second, our data show limited lymphocyte infiltration into metastatic lesions in lymph nodes due to remodeling of high-endothelial venules. Further, we show that losartan treatment can induce lymphocyte infiltration into lymph node metastases. In the proposed work, we will determine the mechanism driving lymphocytic infiltration after losartan treatment and test the hypothesis that these infiltrated lymphocytes can be activated to promote anti-cancer immune responses (Aim 2). Finally, to generate an anti-cancer immune response against metastatic lymph node lesions, both lymphocytic activation (Aim 1) and infiltration (Aim 2) are required. Improving only one will likely not be sufficient to drive an anti-cancer immune response. Thus, we will test translational approaches to inhibit MHCII cancer cell expression to prevent suppression of lymphocytic immune response in combination with losartan to drive lymphocytic infiltration of metastatic lymph nodes (Aim 3). Our novel research program will discover critical mechanisms of immune suppression of metastatic lymph nodes as well as develop therapeutic strategies to overcome these mechanisms. To achieve these goals, we have assembled a world-class team of experts in lymph node metastasis (T. Padera), immunology (Mempel), cancer microenvironment (Jain), systems biology (Beyaz), pathology (R. Padera), clinical translation (Taghian) and ...