Zinc finger protein 217 contributes to natural killer cell dysfunction in murine colorectal cancer

Abstract

Immune cells play active roles in the surveillance and control of colorectal cancer (CRC) progression. Natural killer (NK) cells are powerful anti-tumor effector cells but their regulatory mechanisms in the CRC tissues have not been thoroughly elucidated. In this research using a murine inflammatory colorectal cancer model, we characterized the phenotype and function of NK cells. We found signs of NK cell dysfunction in CRC tissues, including up-regulation of exhaustion markers, down-regulation of activating receptors, deficiencies in degranulation and cytokine expression, and weak cytolytic effect. Interestingly, zinc finger protein 217 (ZNF217), a transcription repressor, was significantly up-regulated in CRC-associated NK cells. In vitro assays revealed that ZNF217 knockdown promoted NK cell cytolytic activity, implying that ZNF217 is an inhibitory factor of NK cell function. Adoptive transfer assays indicated that ZNF217 knockdown also resulted in enhancement of NK cell function in vivo and subsequently suppressed CRC development. Furthermore, hypoxia rather than exhaustion up-regulated ZNF217 expression in NK cells. ZNF217 knockdown promoted NK cell resistance to hypoxia-mediated NK cell dysfunction. Therefore, we discovered a novel regulatory factor of NK cell dysfunction during CRC development.