In situ analysis of CCR8+ regulatory T cells in lung cancer: suppression of GzmB+ CD8+ T cells and prognostic marker implications.

BACKGROUND: CCR8-expressing regulatory T cells (Tregs) are selectively localized within tumors and have gained attention as potent suppressors of anti-tumor immunity. This study focused on CCR8+ Tregs and their interaction with CD8+ T cells in the tumor microenvironment of human lung cancer. We evaluated their spatial distribution impact on CD8+ T cell effector function, specifically granzyme B (GzmB) expression, and clinical outcomes. METHODS: A total of 81 patients with lung squamous cell carcinoma (LSCC) who underwent radical surgical resection without preoperative treatment were enrolled. Histological analyses were performed, utilizing an automated image analysis system for double-stained immunohistochemistry assays of CCR8/Foxp3 and GzmB/CD8. We investigated the association of CCR8+ Tregs and GzmB+ CD8+ T cells in tumor tissues and further evaluated the prognostic impact of their distribution profiles. RESULTS: Histological evaluation using the region of interest (ROI) protocol showed that GzmB expression levels in CD8+ T cells were decreased in areas with high infiltration of CCR8+ Tregs, suggesting a suppressive effect of CCR8+ Tregs on T cell cytotoxicity in the local tumor microenvironment. Analysis of the association with clinical outcomes showed that patients with more CCR8+ Tregs and lower GzmB expression, represented by a low GzmB/CCR8 ratio, had worse progression-free survival. CONCLUSIONS: Our data suggest that local CCR8+ Treg accumulation is associated with reduced CD8+ T cell cytotoxic activity and poor prognosis in LSCC patients, highlighting the biological role and clinical significance of CCR8+ Tregs in the tumor microenvironment. The GzmB/CCR8 ratio may be a useful prognostic factor for future clinical applications in LSCC.

S-531011, a Novel Anti-Human CCR8 Antibody, Induces Potent Antitumor Responses through Depletion of Tumor-Infiltrating CCR8-Expressing Regulatory T Cells.

Although regulatory T cells (Treg) are inhibitory immune cells that are essential for maintaining immune homeostasis, Tregs that infiltrate tumor tissue promote tumor growth by suppressing antitumor immunity. Selective reduction of tumor-infiltrating Tregs is, therefore, expected to activate antitumor immunity without affecting immune homeostasis. We previously reported that selective Treg depletion targeted by a C-C motif chemokine receptor 8 (CCR8) resulted in induction of strong antitumor immunity without any obvious autoimmunity in mouse models. Thus, herein, we developed a novel humanized anti-CCR8 monoclonal antibody, S-531011, aimed as a cancer immunotherapy strategy for patients with cancer. S-531011 exclusively recognized human CCR8 among all chemokine receptors and showed potent antibody-dependent cell-mediated cytotoxicity activity toward CCR8+ cells and neutralization activity against CCR8-mediated signaling. We observed that S-531011 reduced tumor-infiltrating CCR8+ Tregs and induced potent antitumor activity in a tumor-bearing human-CCR8 knock-in mouse model. Moreover, combination therapy with S-531011 and anti-mouse programmed cell death 1 (PD-1) antibody strongly suppressed tumor growth compared with anti-PD-1 antibody alone with no observable adverse effects. S-531011 also depleted human tumor-infiltrating Tregs, but not Tregs derived from human peripheral blood mononuclear cells. These results suggest that S-531011 is a promising drug for inducing antitumor immunity without severe side effects in the clinical setting.

Immunotherapy Targeting CCR8+ Regulatory T Cells Induces Antitumor Effects via Dramatic Changes to the Intratumor CD8+ T Cell Profile.

Regulatory T cells (Tregs) contribute to the formation of a tumor-immunosuppressive microenvironment. CCR8 is reportedly selectively expressed in tumor Tregs, and an anti-CCR8 Ab can exert potent antitumor effects by eliminating intratumor Tregs in murine tumor models. In this study, we analyzed changes to intratumor immunity after anti-CCR8 Ab administration, especially in CD8+ T cells, which are involved in cancer cell killing, using the CT26 colorectal carcinoma mouse model. Immunophenotyping of tumor-infiltrating cells by mass cytometry after Ab administration on day 5 of tumor inoculation revealed that CD8+ T cell subsets were dramatically altered in the CCR8 Ab-treated group, with an increase in naive cells and nonexhausted effector cells and a decrease in exhausted cells with high expression levels of TOX. These results were corroborated with flow cytometry analysis. Delayed administration of the anti-CCR8 Ab on day 9 or 12, when the amount of CCR8+ Tregs and CD8+ T cell exhaustion were more progressed, also resulted in a decrease in exhausted CD8+ T cells, leading to tumor regression. Finally, we confirmed that high CCR8+ Treg infiltration was associated with high TOX expression in CD8+ T cells in human cancer patients. In conclusion, administration of an anti-CCR8 Ab can dramatically alter the activation and exhaustion state of intratumor CD8+ T cells, resulting in strong antitumor effects. In cancer patients with an advanced tumor-immunosuppressive environment, CD8+ T cell exhaustion has progressed along with CCR8+ Treg induction. Therefore, targeted depletion of CCR8+ Tregs is expected to be effective in these patients.

Prostaglandin D2 Modulates Neuronal Excitation of the Trigeminal Ganglion to Augment Allergic Rhinitis in Guinea Pigs.

Prostaglandin D2(PGD2) is involved in the pathogenesis of allergic rhinitis. However, the sensory nervous system-mediated contributions of PGD2to the symptoms of allergic rhinitis remain unclear. We investigated the involvement of PGD2in these symptoms and in neuronal excitation by in vivo and ex vivo experiments. In an ovalbumin-induced model of allergic rhinitis in guinea pigs, the number of sneezing, nasal rubbing, and nasal secretion events were assessed after the nasal cavity instillation of PGD2, histamine, or a combination of PGD2and histamine. In situ hybridization for PGD2receptor 1 (DP1) mRNA transcripts and immunohistochemical analysis of histamine H1receptor protein expression in guinea pig trigeminal ganglion (TRG) were performed. The effects of DP1receptor activation on the excitability of TRG neurons to electrical and histamine stimuli were assessed using whole-cell patch-clamp recordings. Histamine induced more sneezing, nasal rubbing, and nasal secretion events than PGD2 PGD2augmented histamine-induced responses, whereas pretreatment with a DP1receptor-selective antagonist completely suppressed PGD2-induced augmentation. DP1receptor mRNA transcripts and H1receptor protein expression could be detected in TRG neurons. Moreover, a DP1receptor agonist caused significant increases in the number of histamine-induced action potentials and depolarization, and reduced the current threshold in small-diameter neurons. Our findings show that PGD2-DP1receptor signaling augments the symptoms of allergic rhinitis via the sensory nervous system by modulating nasal neuronal activation to various stimuli, such as histamine. These findings suggest that DP1receptor antagonist has therapeutic potential for the treatment of allergic rhinitis.