PROJECT SUMMARY/ABSTRACT Activated Antigen Presenting Cells (APCs) engulf and display tumor antigen to T cells, initiating the immune response against cancer. However, in cancer patients, APCs are often immune suppressed, resulting in inhibition of T cells, promotion of tumor growth and failure of immunotherapy in solid malignancies. At present, there is no clinical treatment option capable of activating APCs to an immune stimulatory phenotype while simultaneously delivering tumor antigen to drive antigen presentation and antitumor immunity. Without new approaches to enhance antigen presentation, cancer immunotherapy will likely continue to be limited to a small percentage of patients. In a significant step forward, our lab has developed a liposome delivery system (C3- liposomes) that can target all three APCs: dendritic cells, macrophages and B cells (Francian, 2017). Furthermore, preliminary results indicate that C3-liposomes deliver tumor antigen and activating compounds to APCs, leading to T cell activation and elimination of tumors in a murine cancer model. The following strategies have been identified for improving tumor antigen presentation using C3-liposomes. Aim 1: Evaluate immune response to C3-liposome delivery of antigen and TLR agonist combinations. Toll-like receptor (TLR) agonists, which lead to activation of Antigen Presenting Cells, will be encapsulated in C3-liposomes along with MHCI and MHCII binding ovalbumin (OVA) peptides to determine the optimal formulation for eliciting an immune response. Aim 2: Examine C3-liposome prophylactic efficacy using a MUC1 transgenic mouse model. In cancer patients, MUC1 is overexpressed in more than 75% of solid malignancies such as breast, colorectal, stomach, pancreatic, bladder and other cancers, making MUC1 an ideal tumor antigen. The goal of this aim is to determine the prophylactic benefit of C3-liposome MUC1 peptide delivery using transgenic mice and tumors that express human MUC1. Aim 3: Determine if C3-liposome encapsulation of multiple tumor antigens improves responsiveness to checkpoint immunotherapy. Multiple antigens from the B16-F10 melanoma tumor cell line will be delivered with C3-liposomes and tested with checkpoint blockade immunotherapy to determine efficacy in treating a melanoma mouse model of cancer. The proposed aims will evaluate the effectiveness of C3-liposomes for enhancing antigen presentation and creating an immune response against cancer. At the same time, this study will also build capacity for biomedical research and significantly enhance biomedical research education for undergraduate and graduate students at UAA. Ultimately, C3-liposomes could improve tumor antigen delivery and when used in combination with current immunotherapy, increase the percentage of patients who respond to treatment.