Objective: To investigate the natural killer cell stimulatory receptor NKG2D and its soluble ligand MICA(sMICA) expression in peripheral blood in hepatocellular carcinoma (HCC).
Methods: Blood samples of 40 patients and 20 healthy persons were collected to detect NKG2D by flow cytometry analysis.Serum levels of sMICA were determined by ELISA.The association of sMICA levels wth clinical features were analyzed.
Results: The expression of NKG2D in HCC (71.97±4.96)% was significantly lower than that in healthy group(91.45±3.16)%. The serum levels of sMICA was found to be significantly elevated in HCC compared with heathy subjects (median, 191.3pg/mL vs. 74.9pg/mL，P＜0.05).The levels of sMICA correlated significantly with presence of tumor thrombi in portal vein and advanced clinical tumor-node-metastasis (P＜0.05）. Spearman rank correlation displayed that the expression of NKG2D was negatively correlated with the levels of sMICA（r=-0.591，P＜0.05）.
Conclusions:  The expression of NKG2D in HCC is significantly decreased. The levels of sMICA correlates significantly with progression of HCC. NKG2D-sMICA may play a critical role in tumor immunological escape in HCC,and may contribute to HCC progression.