Aim: To determine the expression of soluble MICA (sMICA) in serum of patients with breast tumor, and explore the roles of sMICA in immune escape.
Methods: ELISA was used to examine the sMICA in peripheral blood. The expression of NKG2D were identified by Flow cytometry. The cytotoxicity of NK cells to breast cancer cells was observed with MTT assay.
Results: sMICA was not detected in the serum of healthy person, but(76.8+/-22.3) ng/L in breast benign tumor patients and (205.4+/-71.3) ng/L in breast malignant tumor patients. There was positive correlation between sMICA levels and breast cancer stage. After incubation with sMICA, NK cells got decrease in cytotoxicity from (76.2+/-6.7) % to (48.4+/-4.1) % .The expression of NKG2D and secretion of IFN-gamma decreased at the same time. IL-15 up-regulated the expression of NKG2D on NK cells and increased NK cells cytotoxicity to breast cancer cells.
Conclusion: sMICA level is positive correlated with breast cancer TNM stage. sMICA reduced the expression of NKG2D, impaired NK-mediated immune surveillance and led to immune escape of breast tumor. IL-15 could up-regulate the expression of NKG2D and increase NK cells cytotoxicity.