NKR+CD8+ T Cells and Inkt Cells Protect Mice from AOM/DSS-induced Colorectal Cancer under Conditions of IFNγ-mediated Hyperinflammation.

Interferon-gamma (IFNγ) is a pivotal cytokine in immune surveillance and inflammation, yet its precise role in colorectal cancer (CRC) remains controversial due to its dual involvement in tumor suppression and immune evasion. Although natural killer cell receptor (NKR)+CD8+ T cells and invariant natural killer T (iNKT) cells contribute to anti-tumor immunity, how these cells regulate CRC progression under IFNγ-mediated, inflammatory conditions remains unclear. An azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC model was established in heterozygous Yeti mice with IFNγ-mediated hyperinflammation. Using flow cytometry and histology, we evaluated tumor burden, histopathology, and immune cell infiltration in tumor tissues. NKR+CD8+ T cells were induced by IL15 treatment, and their anti-tumor efficacy was validated by adoptive transfer. The functional contribution of iNKT cells was assessed using iNKT cell-deficient Yeti/Jα18 knockout (KO) mice. Clinical relevance was determined by analyzing public transcriptomic datasets from non-metastatic and metastatic CRC patients using gene set enrichment (GSE) and protein interaction network (STRING) analyses. We found that Yeti mice display significantly blunted CRC development compared to wild-type (WT) controls. Furthermore, these IFNγ-mediated anti-tumor immune responses were attributed to increased tumor infiltration by CD8+ T cells expressing NKRs. Adoptive transfer experiments demonstrated that NKR⁺CD8⁺ T cells are potent anti-tumor effectors. Tumor-infiltrating iNKT cells in Yeti mice exhibited enhanced IFNγ and reduced IL10 production. Yeti mice lacking iNKT cells exhibited reduced tumor infiltration by NKR+CD8+ T cells, indicating that iNKT cells, particularly those producing IFNγ, are critical for controlling CRC development. Through GSE and STRING analyses, we found that non-metastatic patients exhibited increased IFNγ responses, reflected by greater enrichment of IFNγ-related gene ontology categories, compared with metastatic patients. NKR+CD8+ T cells in Yeti mice with elevated IFNγ levels suppress CRC development in an iNKT cell-dependent manner, suggesting that NKR+CD8+ T cells and iNKT cells cooperate to drive optimal anti-tumor immune responses against CRC during IFNγ hyperinflammation. Our findings highlight a potential immunotherapeutic strategy for CRC by reinforcing IFNγ-dependent anti-tumor responses.