Clinical Significance Of MK, Ang-2 And VEGF Expression In Gastric Carcinoma

Background and ObjectivesGastric carcinoma (GC) is the most common malignant neoplasms in the digestive system. Like other tumors, gastric carcinoma has the characteristics such as invasion and metastasis in the process of the occurrence and development. The main reason for death in patients with gastric carcinoma is due to invasion and metastasis of tumor. Its clinical symptoms are not obvious at early stage. So it usually develops invasion and metastasis when the patient comes to see a doctor, and it's difficult to be treated and has a poor prognosis. It is necessary and important to study the mechanisms of tumor's invasion and metastasis.The mechanisms of tumor's invasion and metastasis are very complex. Occurance of the tumor is a multistage progress. Many genes' variation devote to its progression and aggressiveness. In 1970s, Folkman argued that the growth of tumor was dependent on neovascularization. The neovascularization is necessary for the growth and metastasis of tumor. The neonatal blood vessel network provides nourishment and oxygen to tumors, takes away metabolism garbage, activates tumor growth in a paracrine way, helps tumor cells enter into blood circulation, and makes invasion and metastasis to other tissues and organs. If the neovascularization was broken off, tumor cells would die out. Tumor neovascularization is controlled by both activators and inhibitors.Microvessel density(MVD) is a quantitative indicator of angiogenesis. CD34, one of the most differential markers of vascular endothelial, is used to detect MVD usually.To investigate the expression of midkine (MK), Angiopoietin-2 (Ang-2) and vascular endothelialgrowth factor (VEGF) in gastric carcinoma and normal mucosa and the roles in carcinogenesis,invasion and metastasis of gastric carcinoma as well as their relationship with angiogenesis and the significance of clinicopathology, provide new reference for forecasting the carcinogenesis,invasion and metastasis of gastric carcinoma and judge prognosis.Materials and methods(1) Sixty-four surgical specimens of gastric carcinoma and 20 normal mucosa specimens which were 5cm far from carcinoma loci, and confirmed pathologically. All the specimens were fixed in 10% neutral formalin and embedded in paraffin.(2) SABC immunohistochemical staining technique was used to exmine the expression of MK, Ang-2, VEGF and CD34 in gastric normal mucosa and carcinoma.(3) The data were analyzed by software SPSS 13.0. x~2-test, t-test, ANOVA and Spearman correlation were used to analysize the expression difference. Differencewas considered as statistically significant when P <0.05.Results(1) MK protein expressionThe positive staining of MK was mainly located homogeneously in cytoplasm of cells, occasionally in vascular endothelial cells. No specific positivity was detected in normal mucosa tissue, while the positive rate of MK was 76.6% in gastric carcinoma. There was significant difference between the two groups (P<0.01).(2) Ang-2 protein expressionThe positive staining of Ang-2 was mainly located in cytoplasm of tumor cells. The positive rate of Ang-2 was 0 and 84.4% in normal mucosa and gastric carcinoma , respectively (P<0.01). Furthermore, it was also stained homogeneously in vascular endothelial cells and vessel wall.(3) VEGF protein expression VEGF protein expression was detected in normal mucosa cells and gastric carcinoma cells, mainly in the cytoplasm of cells. It was also stained homogeneously in vascular endothelial cells and vessel wall. The positive rate of VEGF was 15.0% and 68.8% in normal mucosa and gastric carcinoma, respectively (P<0.01).(4)MVDMVD in gastric carcinoma tissues was higher than that in normal mucosa tissues, and it was heterogeneously distributed in gastric carcinoma tissues, with abnormal appearance. Some of the vessels had no cavities or just was budding. MVD was fewer and homogeneously distributed in normal mucosa. The mean of MVD was 30.089±8.294 and 15.012±7.134 in gastric carcinoma and normal mucosa, respectively (P<0.01).(5) Relationship between four protein's expression and the degree of differentiation of gastric carcinoma.The positive rate of MK was 68.8%, 76.9% and 81.8% in well, moderately and poorly differentiated gastric carcinoma, respectively. A descending trend was shown according to the descending of tissue differentiation, but there were no significant differences among them (P>0.05). The positive rate of Ang-2 was 68.8%, 84.6% and 95.5% in well, moderately and poorly differentiated gastric carcinoma, respectively. There were significant differences among these three groups (P<0.01). The positive rate of VEGF were 56.3%, 80.8% and 63.6% in well, moderately and poorly differentiated gastric carcinoma, respectively. But there were no significant differences among them(P>0.05). The mean of MVD was 28.728±7.627, 29.817±6.716 and 31.400±5.041 in well, moderately and poorly differentiated gastric carcinoma, respectively. There were no significant differences among them(P>0.05), too.(6) Relationship between four protein exoression and the infiltrating depth of tumorAccording to the infiltrating depth, 64 cases of gastric carcinoma were divided into negative and positive serosal invasion groups. The mean of MVD in two groups was 26.700±7.598 and 32.123±7.844, and an ascending trend with the deeper infiltrating of tumor cells could be also found (P<0.01).The positive rate of MK in two groups was 58.3% and 87.5%, showing a ascending trend with the deeper infiltrating of tumor cells into the mucosa (P<0.01).The positive rate of Ang-2 in two groups was 75.0% and 90.0%. A ascending trend was shown according to the ascending of tissue infiltrating depth, but there were no significant differences among them(P>0.05).The positive rate of VEGF in two groups was 50.0% and 80.0%. There was significant difference between the two groups (P<0.01), too.(7) Relationship between four protein expression and the status of lymphnode metastasis of gastric carcinomaAccording to the status of metastasis, all cases were divided into negative and positive lymphnode metastasis groups. The mean of MVD in two groups was 24.700±8.677 and 34.022±7.305, respectively. There was significant difference between the two groups (P<0.01).The positive rate of MK in two groups was 63.0% and 86.5%, It was lower in negative lymphnode metastasis group than positive lymphnode metastasis group (P<0.05).The positive rate of Ang-2 in two groups was 81.5% and 86.5%. There were no significant differences among them (P>0.05).The positive rate of VEGF in two groups was 51.9% and 81.1%. There was significant difference between the two groups (P<0.05), too.(8) Relationship between four protein expression and the clinical stage of gastric carcinomaAccording to clinical stage, the patients with gastric carcinoma were divided into group I a+ I b, group II+IIIa and group IIIb+IV.The mean of MVD in group I a+ I b, II+IIIa and Illb+IV was 22.422±5.483, 28.242±8.284 and 34.121±6.797, respectively. A ascending trend was present according to the progress of the clinical stage and There were significant differences among these three groups (P<0.01).The positive rate of MK in three groups was 33.3%, 73.1% and 93.1%. It was lower in group I a+ I b than that in group II +IIIa and lower in group II +IIIa than that in group IIIb+IV(P<0.01).The positive rate of Ang-2 in three groups were 88.9%, 84.6% and 82.8% and There were no significant differences among these three groups (P>0.05).The positive rate of VEGF in three groups was 22.2%, 57.5% and 93.1%.There was significant difference among these three groups (P<0.01), too.(9) Relationship between MK/Ang-2/VEGF and MVDThe MVD was 31.745±8.592 and 24.680+8.938 in the MK-positive group and MK-negative group, respectively, and the difference between them was significant (P<0.01). The MVD was 31.306±9.046 and 23.520±6.554 in the Ang-2-positive group and Ang-2-negative group, respectively, and the difference between them was significant (P<0.05). The MVD was 32.595±7.942 and 24.575±9.287 in the VEGF-positive group and VEGF-negative group,respectively, and the difference between them was significant (P<0.01).There was a positive correlation between MK and VEGF according to Spearman correlation analysis(r=0.264, P=0.035). The MVD in gastric carcinoma with both MK and VEGF positive was higher than that in patients with one of them positive (F=11.116, P=0.000). When both of them were negative expression, the MVD was the low (22.300±6.347).There was no correlation between Ang-2 and VEGF according to Spearman correlation analysis (r=0.174, P =0.169). But the MVD in gastric carcinoma with both Ang-2 and VEGF positive was higher than that in patients with one of them was positive (F= 10.483, P=0.000). When both of them were negative expression, the MVD was the low (18.260±4.564).Conclusions(1) The expression of MK, Ang-2, VEGF proteins and MVD was significantly higher in gastric carcinoma than that in normal mucosa.(2) Both MK and VEGF are associated with clinical stage, depth of gastricl carcinoma invasion, metastasis. In gastric carcinoma, the positive expression of MK and VEGF is correlated significantly. There may be some coordination of them in regulating mechanism of tumor angiogenesis. MK and VEGF are involved in the process of the development and metastasis of gastric carcinoma.(3) There is a significant positive correlation between Ang-2 and the degree of tumor differentiation.(4) Angiogenesis plays an important role in the progression of gastric carcinoma. Inhibiting the function of MK, Ang-2 and VEGF might block the regression vasculogenisis of gastric carcinoma on which invasion and metastasis depend.