Suppressing T cell motility induced by anti-CTLA-4 monotherapy improves antitumor effects

Area of Science:

• Immunology
• Cancer Biology
• Radiation Oncology

Background:

• Cancer immunotherapy aims to overcome immune tolerance by targeting pathways like cytotoxic T lymphocyte-associated protein 4 (CTLA-4).
• Anti-CTLA-4 monoclonal antibody (mAb) therapy shows promise but its efficacy is limited in poorly immunogenic tumors.
• Combining anti-CTLA-4 mAb with other treatments, such as ionizing radiation (IR), can enhance anti-tumor immune responses.

Purpose of the Study:

• To investigate the mechanisms by which anti-CTLA-4 mAb treatment, alone and in combination with IR, affects tumor-infiltrating CD8+ T lymphocytes (TILs).
• To determine the role of natural killer cell group 2D (NKG2D) receptor and its ligand RAE-1 in the combined therapy's efficacy.

Main Methods:

• Utilized a murine carcinoma model to study endogenous TILs after treatment with anti-CTLA-4 mAb (9H10) alone or in combination with IR.
• Assessed TIL motility and arrest, MHC class I-dependent interactions, and expression of RAE-1 on tumor cells.
• Investigated the effect of anti-NKG2D mAb on TIL arrest in the combination therapy group.

Main Results:

• Anti-CTLA-4 mAb monotherapy (9H10) reversed TIL arrest in vivo.
• The combination of 9H10 and IR restored MHC class I-dependent TIL arrest.
• IR induced RAE-1 expression on tumor cells, and anti-NKG2D mAb blocked the TIL arrest observed with combined IR/9H10 therapy.

Conclusions:

• Anti-CTLA-4 mAb therapy enhances TIL motility.
• NKG2D receptor ligation by RAE-1 on tumor cells, induced by IR, counteracts the pro-motility effect of anti-CTLA-4 therapy.
• The combination of anti-CTLA-4 mAb and IR enhances anti-tumor activity by promoting TIL arrest through NKG2D signaling.