CD226 overexpression restrains NK92-associated IL-22 and limits an IL-22RA1-pSTAT3-CD155 circuit in the NSCLC tumor microenvironment

Background The immunosuppressive tumor microenvironment (TME) drives tumor immune escape in non-small-cell lung cancer (NSCLC). Tumor-expressed CD155 down-regulates NK-cell CD226; however, whether reduced NK-cell CD226 reciprocally modulates tumor-cell CD155 and the underlying regulatory mechanism remain unclear. Methods Public transcriptome datasets GSE32863 and TCGA-LUAD were analyzed. CD226-overexpressing NK92 cells and primary NK cells from CD226-knockout mice were applied in co‑culture systems with NSCLC/LLC tumor cells. Gain-and loss-of-function assays using recombinant IL-22, IL-22 neutralizing antibody and STAT3 siRNA were performed, combined with flow cytometry, RT-qPCR, western blot, ELISA and functional cytotoxicity, proliferation and invasion assays. Results LUAD tumor tissues exhibited decreased CD226 but elevated PVR (CD155) and IL-22RA1 expression, correlating with clinical survival outcomes. CD226 overexpression restrained NK-cell-derived IL-22 transcription and secretion. NK-cell-produced IL-22 triggered tumor-cell CD155 upregulation via IL-22RA1-pSTAT3 signaling. CD226-high NK cells displayed stronger anti‑tumor cytotoxicity, while exogenous IL-22 impaired NK-mediated tumor killing. Murine CD226-deficient primary NK cells reproduced this regulatory circuit. Conclusion CD226 overexpression restrains NK-cell-derived IL-22 and interrupts an IL-22RA1-pSTAT3-CD155 immune-evasive circuit in NSCLC. This work supports combinatorial NK-cell engineering and IL-22-targeted immunotherapeutic strategies.