Objective  This work aims to evaluate MHC class Ⅰ chain-related gene A (MICA) expression on the cell membrane of esophageal cancer cells, and soluble MICA expression in the serum of patients with esophageal cancer. The work also aims to investigate the function of MICA in esophageal cancer.

  Methods  Flow cytometry was performed to detect the expressions of membranous MICA (mMICA) in esophageal cancer tissues and cell lines and natural-killer group 2, member D (NKG 2D) in natural killer (NK) cells. En zyme-linked immunosorbent assay was performed to examine the secretion of soluble MICA (sMICA) in the peripheral blood. The effect of sMICA on NKG 2D expression was observed in the group experiments.

  Results  mMICA was not detected in normal esophageal tissues, but the mMICA expression level was 31.7% in esophageal cancer tissues. The maximum expression level was (42.2 ± 3.6)%. sMICA was not detected in the serum of healthy subjects, but the sMICA expression level was74.67 % in esophageal cancer tissues with a concentration of (1 977.30 ± 292.67)ng/L. A positive correlation was observed between sMICA levels and esophageal cancer stage. sMICA content was higher in cancer patients with distant metastasis compared with those without metastasis. However, the content had no relationship with nodal metastasis and pathologic types. NKG2D expression was down-regulated, and the NK cell cytotoxicity to the esophageal cancer cell line ECA-109 decreased after the NK cells were cultured in sMICA serum.

  Conclusion  MICA is expressed on the membrane of some esophageal cells. sMICA level is positively correlated with the Tumor-Node-metastasis stages of esophageal cancer. sMICA can reduce the expression of NKG2D and can result in immunity to esophageal cancer.