Phenotypic Study Of Human Colorectal Cancer Tumor Infiltrating G-NK Cells

Previous studies identified a new subpopulation of NK cells in peripheral blood mononuclear cells(PBMC)of healthy donors.This new group of NK cells was named g-NK cells because of the absence of the signal adaptor molecule-FcεRIγ.Functional assays show that g-NK cells respond significantly better to antibody Fc fragment stimulation than conventional NK(Conventional NK,c-NK)cells,as evidenced by stronger cytokine secretion,proliferation and anti-apoptotic ability.Previous studies only detected g-NK cells in the peripheral blood of healthy individuals,while the distribution of g-NK in the tumor microenvironment remains unclear.To this end,we set out to investigate the number and phenotype of colorectal cancer infiltrating g-NK cells by flow cytometry,ELISA,q PCR,and tissue digestion,and compared with c-NK cells.Specifically,we studied the percentage distribution,phenotypic characters of g-NK cells and their correlation with clinicopathological features as well as with HCMV infection.Moreover,we measured the expression of 17 genes in colorectal cancers that have been reported to mediated resistance to NK cell killing.The results showed that the proportion of NK cells in peripheral blood of CRC patients was significantly larger than that in tumor tissues;and g-NK cells were present in both tumor tissues and peripheral blood of CRC patients.The frequencies of g-NK cells and c-NK cells in tumor tissues were different from those in peripheral blood.The expression of inhibitory molecules KIR2DL1,KIR2DL2/3 and KIR3DL1 molecules were higher on g-NK cells than on c-NK cells in tumor tissues;while the expression of activating receptors NKG2C,CD16,and Perforin,GZMB and Ki67 molecules was lower than on c-NK cells.In addition,the expression of inhibitory receptor TIGIT was lower on g-NK than on c-NK cells in tumor tissues.The frequency of g-NK cells in PBMC and tumor tissue was higher in HCMV~+CRC patients than in HCMV~-CRC patients.Age is positively correlated with the percentage of NK cells in PBMC,but negatively associated with the percentage of NK cells in tumor tissue.The expression of 17 regulatory genes that regulate resistance to NK cell killing in vitro was generally higher in CRC than in normal tissues,though their correlation with g-NK cells did not reach a significant level,possibly due to the small sample size.This study shed the first light on the phenotype of g-NK cells infiltrating CRC,and laid the foundation for further detailed investigation of tumor infiltrating g-NK cells,such as function,metabolism,regulation of genome-wide epigenetics and gene expression,etc.