PROJECT SUMMARY – OVERALL This Program Project grant will establish the fully integrated interdisciplinary programs of research and core facilities that are necessary to develop a fundamental understanding of the complex interplay between two rapidly emerging fields in cancer therapy: 1) targeted radionuclide therapy (TRT) and 2) immunotherapy. Our overarching objectives are to develop a detailed mechanistic understanding of the immunomodulatory capacity of TRT agents and to evaluate and compare the ability of these agents to elicit cooperative therapeutic interactions in combination with immunotherapies. To achieve this, we will employ a representative variety of TRT agents to deliver radiation in vivo using clinically relevant murine tumor models and companion canines that have spontaneously developed cancers. We will determine the precise dosimetry for each radionuclide-, TRT vector-, and tumor model. This will facilitate studies of dose-, dose-rate-, and dose-range-dependent effects on the host immune system, tumor infiltrating immune cells, cytokine expression in the tumor microenvironment, immune susceptibility of tumor cells, mechanisms of immune suppression, and the development of antigen- specific adaptive immunity. We will determine the functional consequences of these effects by testing the broad hypothesis that, by modulating tumor immune tolerance and functional immunogenicity at all tumor sites, TRT will increase response to certain cancer immunotherapies. We will test this in the following Program Projects: Project 1: Novel TRTs for Dosimetry-Guided Immunomodulation Project 2: TRT to enhance tumor cell immune susceptibility and response to immune checkpoint inhibitors Project 3: Combining TRT with a localized in situ vaccine to overcome immune suppression in the tumor microenvironment and augment T cell responses Project 4: TRT with tumor-specific vaccine to stimulate and expand T-cell activation These highly integrated projects will not only benefit from the methods and findings generated in one another, but they also will directly benefit from the expertise and service of four essential Core Facilities: 1) Advanced imaging and dosimetry core (AIDC), 2) Radiopharmaceutical and radiochemistry core (RPRC), 3) Biostatistics and bioinformatics core (BBC), and 4) Administrative core. Complementing these are robust institutional facilities that will enable successful completion of our proposed studies. Our multidisciplinary team brings together the broad expertise needed to mobilize these resources in pursuit of our proposed objectives. These efforts will further benefit from robust institutional matching support, leadership of a strong Internal Advisory Committee, invaluable Industry collaborations, and expertise of an External Advisory Board. Because of the immediate and broad potential for clinical translation of our results, these studies portend an opportunity to improve the treatment of any oncology patient, regardless of cancer...