Thursday, April 25, 2024
4/25/2024
PD-1 blocking agents have achieved significant success as anti-cancer therapeutics. The mechanism(s) of how PD-1 compromises anti-tumor function remain poorly understood. Although in trans engagement of PD-1 expressed in T cells by its ligands expressed on APC or cancer cells inhibits T cell activation, evolving discoveries provide evidence that PD-L1:B7-1(CD80) in cis and PD-1:PD-L1 in cis non-canonical interactions occur when these molecules are co-expressed on APC, and disrupt the canonical interaction between PD-1 and PD-L1 in trans and T cell inhibitory signaling. Thus, expression of PD-L1 in the tumor microenvironment (TME) is not synonymous with PD-1-mediated T cell inhibition. We generated an antibody that recognizes PD-1pY248 (pPD-1), which is required for PD-1 inhibitory signaling, and detected pPD-1 in mouse and human. We found pPD-1+ T cells in cultures, in mouse tumor models and patient biopsies, but also in CD8+ T central memory (TCM) cells in the peripheral blood of healthy individuals. In tumor bearing mice, pPD-1 was expressed in tumor infiltrating CD8+ T lymphocytes but mostly in Treg. We generated mice with conditional targeting of Pdcd1 gene (PD-1f/f) and selectively eliminated PD-1 in Treg (Pdcd1f/fFoxP3cre). In tumor-bearing Pdcd1f/fFoxP3cre mice, Treg displayed enrichment in pathways regulating lipid metabolism, fatty acid oxidation, and production of monocyte/macrophage chemotactic protein-1 (MCP-1) and GABAergic neurotransmitter with known immunosuppressive function. These features correlated with a significant increase of B cells and M2-like macrophages, diminished activation of tumor infiltrating T cells, and increased tumor growth. Our results reveal a previously unappreciated network by which Treg-selective blockade of PD-1 signaling reshapes the immunological landscape and suggest that abrogation of PD-1 signaling in distinct cell types differentially impacts the TME. Our findings indicate that pPD-1 is a powerful marker to identify T cells subjected to PD-1 inhibitory signaling and support the novel hypothesis that cell-specific detection of PD-1 signaling by pPD-1 might predict the outcome of checkpoint immunotherapy. To investigate these, we will pursue the following specific aims: 1. To identify the immunological and biochemical properties of pPD-1+ T cells in the context of cancer. We will characterize pPD-1+ CD8+ TIL and Treg by single cell immunoprofiling, and investigate how T cell subset- specific PD-1 signaling reshapes the TME by using our Pdcd1f/fCD8cre and Pdcd1f/fFoxP3cre mice. 2. To identify the molecular and functional properties of pPD-1+ cells in healthy individuals. We will examine how PD-1 signaling shapes the properties of T cells in healthy individuals and in cancer patients and uncover why only cancer-mediated PD-1 signaling induces TEX. 3. To determine expression, function and prognostic significance of pPD-1+ TIL in cancer patients. We will examine cell-specific PD-1 expression and signaling in patient biopsies, co-expression of PD-1/pPD-1, PD- L1 and CD80, and determine their prognostic significance.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).
