Differential impact of TIM-3 ligands on NK cell function

Area of Science:

• Immunology
• Oncology
• Cell Biology

Background:

• T-cell immunoglobulin and mucin-domain containing molecule 3 (TIM-3) is an immune checkpoint receptor found on various leukocytes, especially in the tumor microenvironment.
• Effective TIM-3-targeting therapy requires understanding its four ligands (galectin-9, phosphatidylserine, HMGB1, CEACAM1) and their unique interactions with TIM-3.
• The study investigates TIM-3+ natural killer (NK) cells in head and neck squamous cell carcinoma (HNSCC).

Purpose of the Study:

• Assess the prevalence and function of TIM-3+ NK cells in HNSCC patients.
• Determine differential effects of TIM-3 ligands on TIM-3+ NK cell functions.
• Identify the most immunosuppressive TIM-3 ligand.
• Evaluate if targeting ligand-mediated TIM-3 signaling enhances NK cell effector functions.

Main Methods:

• Single-cell RNA sequencing and flow cytometry to analyze TIM-3+ NK cells in HNSCC tumors and blood.
• In vitro assays (killing, proliferation, cytokine production) to assess ligand modulation of NK cell functions.
• The Cancer Genome Atlas survival analysis and digital spatial profiling to explore etiology-associated differences in HNSCC outcomes.

Main Results:

• TIM-3 is highly expressed on circulating and tumor-infiltrating NK cells, co-expressing with CD44 and indicating heightened effector potential.
• Galectin-9 significantly suppresses NK cell cytotoxicity and proliferation via TIM-3 and CD44, but enhances IFN-γ release in a TIM-3-dependent manner.
• An elevated intratumoral TIM-3+ NK cell gene signature correlates with worse outcomes in HPV+ HNSCC patients, possibly due to higher galectin-9 levels.

Conclusions:

• TIM-3 ligand signaling exhibits complex functional impacts on NK cells.
• Targeting TIM-3 alone is likely insufficient for effective cancer immunotherapy, as indicated by recent clinical trials.