Immune Checkpoint Inhibitors Regulate K⁺ Channel Activity in Cytotoxic T Lymphocytes of Head and Neck Cancer Patients

Area of Science:

• Immunology
• Molecular Biology
• Oncology

Background:

• The interaction between programmed death receptor-1 (PD-1) and its ligand (PD-L1) suppresses T cell function in head and neck squamous cell carcinoma (HNSCC).
• PD-1 overexpression reduces intracellular calcium (Ca2+) fluxes, impairing T cell effector functions.
• PD-1 blockade in HNSCC patients enhances KCa3.1 and Kv1.3 ion channel activity, Ca2+ signaling, and CD8+ T cell mobility, but the underlying mechanism remains unclear.

Purpose of the Study:

• To investigate the effects of blocking PD-1 and PD-L1 on ion channel function and intracellular Ca2+ signaling in CD8+ peripheral blood T cells (PBTs).
• To elucidate the mechanism by which PD-L1/PD-1 interaction regulates ion channel function in HNSCC patients and healthy donors (HDs).

Main Methods:

• Single-cell electrophysiology and live microscopy were employed to assess ion channel function and Ca2+ signaling.
• Experiments involved CD8+ PBTs from HNSCC patients and HDs, utilizing anti-PD-1 and anti-PD-L1 antibodies.
• Patch-clamp experiments with PI3 kinase modulators were used to investigate the role of phosphatidylinositol 3-phosphate (PI3P).

Main Results:

• Anti-PD-1 and anti-PD-L1 antibodies significantly increased KCa3.1 and Kv1.3 channel activity in CD8+ PBTs from HNSCC patients.
• PD-L1 exposure inhibited KCa3.1 activity and Ca2+ signaling in CD8+ PBTs from HDs, an effect reversed by anti-PD-1 treatment.
• PD-L1-induced KCa3.1 inhibition was rescued by intracellular PI3P application, suggesting a role for PI3 kinase signaling.

Conclusions:

• Immune checkpoint blockade enhances T cell function in HNSCC patients by increasing KCa3.1 and Kv1.3 ion channel activity.
• The PD-L1/PD-1 pathway modulates T cell function through ion channel regulation, potentially involving PI3 kinase signaling.
• This study provides mechanistic insights into how immune checkpoint inhibitors improve T cell responses in HNSCC.