| [OBJECTIVE] Gastric cancer is one of the most common malignant tumors in China. Because of the onset delitescence and difficulty to detect in the early stage, now gastric cancer is threatening the human's health seriously. The search for a novel tumor marker for the early detection of gastric cancer is one of the critical subjects in the study of gastric cancer. The kallikrein gene family (KLKs) is one lately discovered secreted serine protease family that seriously associated with malignancy. The human kallikrein gene 6 (KLK6), which encodes for human kallikrein 6 protein (hK6), is one member of the gene family. The hK6 protein consists of a 223-amino acid serine proteinase with trypsinlike activity, and has close relationship with gastric cancer. One purpose of this research is to initially investigate the expression and clinicopathological significance of hK6 in gastric cancer, using streptavidin-peroxidase (SP). The other is to develop a sandwich ELISA for quantifying hK6 concentrations in serum of gastric cancer and explore whether hK6 is a serum biomarker for gastric cancer.[METHODS]1. Through immunohistochemistry to examine the expression of hK6 in 120 cases with gastric cancer,45 cases with gastric ulcer and 41 cases with normal gastric mucosa, and statistically analyzed whether the expression of hK6 correlated with the clinicopathologic variables in patients with gastric cancer.2. A sandwich ELISA method was developed for quantifying hK6 in serum. The chessboard titrations were applied for selection of optimal concentration of coating antibody and enzyme-linked antibody. The hK6 serum concentrations in 146 samples of malignant gastric neoplasm,50 samples of gastric ulcer and 46 samples of normal gastric mucosa were measured using the established ELISA condition. Furthermore, the result of hK6 was compared with CEA in order to investigate whether hK6 is a serum biomarker for gastric cancer. [RESULTS] 1. HK6 was mainly expressed in cytoplasm. The positive rate of hK6 was significantly higher in gastric cancer than that in gastric ulcer and normal gastric mucosa(69.17% vs.31.11% and 19.51%, P<0.01). Accompanied with depth of invasion increasing, stage of TNM upgrading and lymph node metastasis happening, the positive straining rate of hK6 in gastric cancer significantly ascended (P<0.05,P<0.01). But there was no obvious correlation between its expression and the sex, age of patient, tumor diameter and differentiation or primary pathological location of gastric cancer (P>0.05).2. A sandwich ELISA method was established for quantifying hK6 in serum, and the optimal concentration of coating antibody and enzyme-linked antibody were 5μg/mL and 1:2000, respectively. The hK6 concentrations in individuals with gastric cancer (5.32±1.65) ng/mL were significantly higher than those in gastric ulcer (3.51±1.02) ng/mL and healthy individuals (3.11±0.64) ng/mL (P<0.05). Furthermore, the concentration of hK6 in the late-stage was higher than that in the early-stage (P<0.05). No significant difference was observed in serum hK6 concentrations between individuals with gastric ulcer and healthy individuals (P>0.05). The hK6 and CEA positive rate of gastric cancer were 61.64% and 41.10%, respectively. And the positive rate of the combined assay of them was 76.71%.[CONCLUSION] HK6 might play an important role in the carcinogenesis and progression of gastric cancer. Serum results suggest that hK6 is a favorable serum biomarker for gastric cancer, and the established sandwich ELISA is simple and convenient for application. |
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