Post-radiation targeting of TIGIT and CD96 improved immunotherapy efficacy in head and neck squamous cell carcinoma

Immunotherapy is a promising treatment for drug-resistant cancers. However, its effectiveness against head and neck squamous cell carcinoma (HNSCC) is limited. This indicates the need to explore additional factors that can predict tumor response to new therapies and improve or supplement their effects. Therefore, we aimed to investigate whether the post-radiation usage of anti-TIGIT and/or anti-CD96 could enhance the antitumor response in HNSCC.

HNSCC tissues, as well as human and mouse cell lines, were examined to evaluate the effects of radiation on immune checkpoint receptors (TIGIT, CD96, and CD226) and tumor ligands (CD155, CD112, CD113, and CD111). Overall and disease-free survival, along with factors related to these immune checkpoint receptors and ligands, were detected. Moreover, we investigated the effects of radiation dose and exposure time on the expression of these receptors and ligands in vitro and in vivo. Tumor growth and survival rates were then evaluated using TIGIT and/or CD96 inhibitors injected intraperitoneally after exposure to radiation. Finally, various proliferative and immunological parameters of the tumor microenvironment were determined using immunohistochemistry and flow cytometry. Statistical analyses were performed using Student's t-test, one-way analysis of variance, or two-way analysis of variance.

Elevated levels of TIGIT, CD96, CD155, CD112, CD113, and CD111 were observed in both HNSCC tissues and the cell lines. Radiation increased the expression of these inhibitory receptors and ligands. Thus, anti-TIGIT and anti-CD96 were used to target the upregulated expression of the receptors TIGIT and CD96, respectively. This treatment combination inhibited tumor growth by boosting apoptosis, reducing tumor cell proliferation, and restoring the cytotoxic functions of CD4⁺ and CD8⁺ T cells after radiation therapy.

Our findings suggest that TIGIT and CD96 could be markers of the clinical stage and treatment response of HNSCC. Therefore, administering anti-TIGIT and anti-CD96 after radiotherapy may provide a novel approach for incorporating immunoradiotherapy into HNSCC treatment.