Interrogating Mechanisms of Suppressed Tpex Immunotherapy Response in Metastatic Tumor-Draining Lymph Nodes

PROJECT SUMMARY/ABSTRACT Tumor-reactive CD8 T cells become exhausted and lose their capacity to kill cancer cells in the tumor microenvironment. Progenitor-exhausted CD8 T cells (Tpex) found primarily in tumor-draining lymph nodes retain their stem-like properties and respond to immune checkpoint blockade. However, our group’s recent work suggests that Tpex responses to ICB are disrupted in the metastatic lymph nodes of head and neck cancer patients. Mass cytometry showed that fewer Tpex are present in metLN; spatial proteomics also revealed that Tpex were less likely to co-localize with their differentiated, cytotoxic counterparts and more likely to be surrounded by immunosuppressive CD4 T and dendritic cells (DC). Furthermore, in a retrospective analysis of patients with recurrent head and neck cancer, we found that those with metLN were less likely to respond to ICB. To investigate the biology underlying the interruption of Tpex responses to ICB in metLN, we will use the metastatic 4MOSC1 (ICB responsive) and 4MOSC2 (ICB non-responsive) orthotopic mouse models of head and neck cancer. In our preliminary studies, we have identified immune cell subsets, including endogenous Tpex, in the tdLN of 4MOSC1 tumors and have established workflows for the isolation and co-culture of T cells and DC from individual tdLN in vitro. This proposal will use the 4MOSC1/2 mouse model of head and neck cancer to evaluate mechanisms by which Tpex responses to ICB are disrupted in metLN. Aim 1 will interrogate whether defects in the S1P/S1PR1 lymphocyte migration axis in metLN affect Tpex responses to ICB. Aim 2 will evaluate whether activation of Tpex in metLN confers cell-intrinsic defects that affect their capacity to differentiate, survive, and signal through their T cell receptor. Aim 3 will identify mechanisms by which metastases in tdLN affect the polarization of CD4 T cells and activation of DC proximal to Tpex. Aims 1 and 2 will use well-established in vivo and in vitro methods; Aim 3 will use spatial proteomic and transcriptomic tools. These studies will be the first to mechanistically interrogate how early tumor-reactive CD8 T cell responses are impeded in metLN. Uncovering this biology has the potential to elucidate novel strategies for potentiating immunotherapy responses in patients with advanced, metastatic disease in several cancer types. This research project and fellowship training will be conducted at a top-funded research institution, the University of California, San Francisco (UCSF), in the laboratory of Dr. Matthew Spitzer with expert mentorship from Dr. Jason Cyster and Dr. Karin Pelka. Dr. Spitzer is an expert in CD8 T cell and lymph node biology, systems immunology, and high-dimensional single cell analyses. Dr. Cyster is a world-class scientist who discovered the lymphocyte trafficking mechanism explored in Aim 1. Dr. Pelka is a cancer immunologist with expertise in the spatial biological tools to be utilized in Aim 3. Overall, this institution and team provide a rich training environment for completion of this research and the development of professional skills necessary for a career in academic research.