PROJECT SUMMARY / ABSTRACT Harnessing the immune system to fight cancer has proven to be remarkably effective, but most patients who are treated with immunotherapy do not respond. Our understanding of what determines the response to immunotherapy remains poor. Immune recognition and destruction of cancer cells occurs at the level of the tumor microenvironment (TME), but the human TME has been difficult to study due to a lack of suitable preclinical models, the challenges in acquiring adequate patient tumor tissues, and a lack of analytic tools to study the complex interplay between cancer and the immune system. In this proposal, we will directly investigate the changes immunotherapy produces in the TME of patients over time by utilizing samples from a serial multi-site tumor biopsy approach in two trials of in situ vaccination (ISV) in follicular lymphoma. we are leveraging technological advances in single cell genomics and multiparameter histology platforms to study limited samples in great depth as well as bioinformatics advances that allow us to extract important information from large complex datasets with a goal of identifying the key tumor-immune interactions before treatment and the evolution of immune responses with treatment. We will focus on how T-cell phenotypes and clonotypes change after ISV and relate to tumor responses (Aim 1), on whether tumor cell responses to ISV may enhance the generation of anti-tumor immunity (Aim 2), and on interactions between cells in the TME (Aim 3). This comprehensive approach will yield critical insights into the determinants of successful immunotherapy. This work will be undertaken by Tanaya Shree, MD PhD, a fellow in the Department of Oncology at the Stanford University School of Medicine. Dr. Shree completed a dual MD/PhD program at Cornell/ Rockefeller University/ Sloan-Kettering where she discovered that tumor-associated macrophages helped murine breast cancer survive chemotherapy and that dampening critical macrophage functions could improve chemotherapy efficacy. At Stanford, Dr. Shree continues to investigate cancer and the immune system, having developed two investigator-initiated immunotherapy trials, studied the immune health of lymphoma survivors, and established expertise in immunology and high-dimensional assays for studying mechanisms of immunotherapy. Dr. Shree will be mentored in this work by Ronald Levy, MD, and Hanlee Ji, MD. Both are physician-scientists who have made significant contributions to the fields of cancer immunotherapy and genomics and have mentored numerous successful independent researchers. In addition, a distinguished committee of advisors, consisting of Drs. Crystal Mackall, Garry Nolan, and Ash Alizadeh, will guide her research and career development. Dr. Shree’s training plan focuses on didactic and practical training in advanced immunology, bioinformatics, and biostatistics to complement her substantial skills and experience in biomedical research.