PVRIG is Expressed on Stem-Like T Cells in Dendritic Cell-Rich Niches in Tumors and Its Blockade May Induce Immune Infiltration in Non-Inflamed Tumors.

Cancers that are poorly immune infiltrated pose a substantial challenge, with current immunotherapies yielding limited clinical success. Stem-like memory T cells (TSCM) have been identified as a subgroup of T cells that possess strong proliferative capacity and that can expand and differentiate following interactions with dendritic cells (DCs). In this study, we explored the pattern of expression of a recently discovered inhibitory receptor poliovirus receptor-related immunoglobulin domain protein (PVRIG) and its ligand, poliovirus receptor-related ligand 2 (PVRL2), in the human tumor microenvironment. Using spatial and single-cell RNA transcriptomics data across diverse cancer indications, we found that among the T-cell checkpoints, PVRIG is uniquely expressed on TSCM and PVRL2 is expressed on DCs in immune aggregate niches in tumors. PVRIG blockade could therefore enhance TSCM-DC interactions and efficiently drive T-cell infiltration to tumors. Consistent with these data, following PVRIG blockade in patients with poorly infiltrated tumors, we observed immune modulation including increased tumor T-cell infiltration, T-cell receptor (TCR) clonality, and intratumoral T-cell expansion, all of which were associated with clinical benefit. These data suggest PVRIG blockade as a promising strategy to induce potent antitumor T-cell responses, providing a novel approach to overcome resistance to immunotherapy in immune-excluded tumors.

Mechanosensitive membrane domains regulate calcium entry in arterial endothelial cells to protect against inflammation.

Endothelial cells (ECs) in the descending aorta are exposed to high laminar shear stress, and this supports an antiinflammatory phenotype. High laminar shear stress also induces flow-aligned cell elongation and front-rear polarity, but whether these are required for the antiinflammatory phenotype is unclear. Here, we showed that caveolin-1-rich microdomains polarize to the downstream end of ECs that are exposed to continuous high laminar flow. These microdomains were characterized by high membrane rigidity, filamentous actin (F-actin), and raft-associated lipids. Transient receptor potential vanilloid (TRPV4) ion channels were ubiquitously expressed on the plasma membrane but mediated localized Ca2+ entry only at these microdomains where they physically interacted with clustered caveolin-1. These focal Ca2+ bursts activated endothelial nitric oxide synthase within the confines of these domains. Importantly, we found that signaling at these domains required both cell body elongation and sustained flow. Finally, TRPV4 signaling at these domains was necessary and sufficient to suppress inflammatory gene expression and exogenous activation of TRPV4 channels ameliorated the inflammatory response to stimuli both in vitro and in vivo. Our work revealed a polarized mechanosensitive signaling hub in arterial ECs that dampened inflammatory gene expression and promoted cell resilience.

Polarized Mechanosensitive Signaling Domains Protect Arterial Endothelial Cells Against Inflammation.

Endothelial cells (ECs) in the descending aorta are exposed to high laminar shear stress, which supports an anti-inflammatory phenotype that protects them from atherosclerosis. High laminar shear stress also supports flow-aligned cell elongation and front-rear polarity, but whether this is required for athero-protective signaling is unclear. Here, we show that Caveolin-1-rich microdomains become polarized at the downstream end of ECs exposed to continuous high laminar flow. These microdomains are characterized by higher membrane rigidity, filamentous actin (F-actin) and lipid accumulation. Transient receptor potential vanilloid-type 4 (Trpv4) ion channels, while ubiquitously expressed, mediate localized Ca 2+ entry at these microdomains where they physically interact with clustered Caveolin-1. The resultant focal bursts in Ca 2+ activate the anti-inflammatory factor endothelial nitric oxide synthase (eNOS) within the confines of these domains. Importantly, we find that signaling at these domains requires both cell body elongation and sustained flow. Finally, Trpv4 signaling at these domains is necessary and sufficient to suppress inflammatory gene expression. Our work reveals a novel polarized mechanosensitive signaling hub that induces an anti-inflammatory response in arterial ECs exposed to high laminar shear stress.