Primary Study On The Tumor Evasion Mechanism By The Active Receptor Of NK Cell NKG2D And The Soluble Ligand MICA In The Patients With Gastric Cancer

Objective: To detect the expression of the immunoreceptor NKG2D on the natural killer cell surface in the patients with gastric cancer and the serum levels of soluble MICA of peripheral blood in the patients with gastric cancer. To observe the features of NKG2D-sMICA in patients with gastric cancer of different patho cell differentiation degrees, the relationship between NKG2D-sMICA and the stage of gastric cancer and the relationship between NKG2D- sMICA and the metastasis of gastric cancer. To discuss the function of NKG2D-sMICA in anti-tumor mechanism and its relation with immune escape mechanism in gastric cancer. To discuss the relationship between NKG2D-sMICA and prognosis.Method: We collected the peripheral blood examples of research objects. Flow cytometry analysis was used to detect the expression of the immunoreceptor NKG2D on the natural killer cell surface. The serum levels of soluble MICA of peripheral blood were determined by MICA-specific enzyme-linked immuneosorbent assay. The data were analyzed by SPSS11.5 .Result:1. The expression of NKG2D on NK cell in the patients with gastric cancer and health donors were (81.97±3.79)% and (90.88±3.76)% respectively. The NKG2D expression in malignant group was significantly low(t=11.3,p﹤0.05).2. The serum levels of sMICA in the patients with gastric cancer and health donors were (359.45±114.15) pg/ml and (210.07±31.01) pg/ml respectively. sMICA levels in the patients were significantly higher than those of the health donors(t=16.58,p﹤0.05).3. Both the expression of NKG2D on NK cell and the serum levels of sMICA in the patients with gastric cancer showed no correlation with cell differentiation. There were not significant differences among the poorly differentiated,the moderately differentiated and the well differentiated adenocarainoma(p>0.05).4. The expression of NKG2D on NK cell in the patients with gastric cancer steped down gradually accompany with the increase of the TNM stages. There were significant differences between stage II and III,stage II and IV,stage III and IV(p﹤0.05). The serum levels of sMICA in the patients with gastric cancer steped up gradually accompany with the increase of the TNM stages. There were significant differences between stage II and III,stage II and IV,stage III and IV(p﹤0.05). 5. The expression of NKG2D on NK cell in the patients with gastric cancer steped down gradually accompany with the aggravate of metastasis extent. The serum levels of sMICA in the patients with gastric cancer steped up gradually accompany with the aggravate of metastasis extent.Conclusion:1. The expression of NKG2D on NK cell in the patients with gastric cancer was significantly low. The drop may be an crucial reason for the descend of the activity of NK cells.This implies that NKG2D plays a critical role in the immunosurveillance of tumors.2. sMICA-release of MICA from cancer cells may reduce the expression of NKG2D, this may impair NKG2D-mediated immune surveillance of gastric cancer and lead to the tumor escaping.3. In the patients with gastric cancer, both the expression of NKG2D and the serum levels of sMICA correlate with cancer stage and metastasis, but show no correlation with cell differentiation.4. The significance of detecting NKG2D and sMICA is the observation and analysis immune state and development of disease, this may be of some clinical value in the prognosis estimating on gastric cancer.