Gastric cancer is one of the common gastrointestinal malignancies in China and has a high incidence and mortality rate worldwide. Because of its rapid development, low early detection rate, middle and late stage after symptoms appear, and poor treatment effect, it is a serious threat to human health. In-depth study of the mechanism of gastric cancer development is of great clinical significance to guide the treatment of gastric cancer.
Paxillin, an important cell adhesion factor discovered in recent years, is a substrate of tumorigenic tyrosine kinase, which is associated with integrins and constitutes a key site of local adhesion between cells and extracellular matrix, regulating cell movement and dissemination, thus enhancing the ability of tumor cells to metastasize and invade.
Vascular endothelial growth factor (VEGF) is a strong pro-angiogenic factor, a highly specific mitogenic factor for vascular endothelial cells, and a glycosylated secretory peptide factor that promotes the formation of neovascularization in tumor tissues, thus facilitating tumor growth and progression. To understand the expression of Paxillin and VEGF in nodular gastric cancer tissues and their relationship with the clinicopathological features of gastric cancer, we used immunohistochemistry to detect the protein expression levels of Paxillin and VEGF in gastric cancer tissues and to explore their relationship with the biological behavior of gastric cancer.
1. Materials and methods
1.1 Materials Fifty-five cases of surgically resected gastric cancer specimens were collected from 2009-01 to 2009-07 at the First Clinical Medical College of Shanxi Medical University. Among them, 38 cases were male and 17 cases were female, with a male to female ratio of 2.24:1; age ranged from 39 to 81 years, with a mean age of 63.56±10.58 years; pathological grading: 49 cases of adenocarcinoma, 6 cases of indolent cell carcinoma; 38 cases of low differentiation, 11 cases of intermediate differentiation, and 6 cases of high differentiation; PTNM staging (international UICC 1997 staging standard): 10 cases of stage I, 13 cases of stage II, 16 cases of stage III, and 16 cases of stage IV. Stage I, Stage II, Stage III, Stage III, Stage IV, and Stage IV.
None of the above cases had been treated with antitumor therapy such as radiotherapy and chemotherapy before surgery. From the above 55 patients with gastric cancer, 20 cases were randomly selected from the normal gastric marginal tissues as the control group. All specimens were pathologically confirmed and embedded in 10% (neutral) formaldehyde (fixed), (paraffin) and sectioned 4 μm thick.
1.2 Methods Immunohistochemical two-step staining was used, and the first antibodies Paxillin and VEGF were purchased from Fuzhou Maixin Biotechnology Development Co. Sections were subjected to high-temperature and high-pressure tissue antigen repair. The staining procedure was performed according to the kit instructions. Known positive slices were used as positive control, and PBS was used instead of primary antibody as negative control.
1.3 Judgment of results Positive expression of Paxillin and VEGF was defined as the appearance of brownish-yellow granular material in the cytoplasm. Five representative high magnification fields were counted in each section, and 100 cells were counted in each field, and the percentage of positive cells and staining intensity were scored separately. Specific judgment criteria were as follows.
(1) Scoring according to the degree of staining: 0 points for no staining, 1 point for weak staining intensity (yellowish or yellow to brownish staining of only individual cells), 3 points for strong staining intensity (yellow to brownish staining), and 2 points for moderate staining intensity (staining intensity in between the previous two);
(2) Scoring according to the percentage of stained cells: 0 points for stained cells <5% of the counted cells, 1 point for 5-25%, 2 points for 26-50%, 3 points for 51%-75%, and 4 points for >75%. (1)+(2) is the total score, and the total score is 0 to 7. A score of 0 is negative (-), a score of 1 to 2 is weakly positive (+), a score of 3 to 5 is positive (++), and a score of 6 to 7 is strongly positive (++++).
1.4 Statistics All data were analyzed using the SPSS17.0 statistical package. Qualitative data were compared using the χ2 test and Fisher’s exact probability method.
2, Results
2.1 Expression of Paxillin in gastric cancer tissues and normal cutting edge tissues
The positive expression of Paxillin protein was the appearance of yellow granular material in the cytoplasm, which was mainly localized in the cytoplasm. Among 55 cases of gastric cancer tissues, 37 cases were positive, with a positive rate of 67.27%, including 5 strong positive cases, 13 positive cases, 19 weak positive cases and 18 negative cases. Among 20 cases of normal gastric cutting edge tissues, 4 cases were positively expressed, including 1 strong positive, 1 positive and 2 weak positive cases, with a positivity rate of 20.00%. The expression of Paxillin protein in gastric cancer tissues was significantly higher than that in the normal cutting edge group, and the difference was significant (P<0.01).
2.2 Expression of VEGF in gastric cancer tissues and normal cutting edge tissues
The positive expression of VEGF was the appearance of yellow granular material in the cytoplasm, which was mainly localized in the cytoplasm. Among the 55 cases of gastric cancer tissues, 40 cases were positive, with a positive rate of 72.72%, including 5 strong positive cases, 13 positive cases, 22 weak positive cases and 15 negative cases. Among 20 cases of normal gastric cutting edge tissues, there were 7 cases with positive expression, including 1 strong positive, 2 positive and 4 weak positive cases, with a positive rate of 35.00%. The expression of VEGF in gastric cancer tissues was significantly higher than that in the normal cutting edge group, and the difference was significant (P<0.01).
2.3 Relationship between the expression of Paxillin protein and clinical features and pathological parameters
Paxillin positive expression was related to tumor size, tissue differentiation, infiltration depth of gastric cancer, TNM stage and lymph node metastasis, and the difference was significant between groups (P<0.05), but not with gender and age. 0.05), but not with gender, age and tumor size.
3. Discussion
The relationship between cell adhesion and tumor is one of the popular topics of life science research in recent years. The development and metastasis of malignant tumors is not only due to the abnormal proliferation of tissue cells, but also due to the abnormal cell-cell and cell-matrix specific adhesion and cell migration process. It is also an important site for cell signaling.
In the early stage of integrin activation, tyrosine phosphorylation of several integrin-associated proteins, including Paxillin, is observed. There is a certain connection between paxillin and tumor cell infiltration and metastasis.
The expression of paxillin was significantly higher in medium and low differentiated adenocarcinoma tissues than in high differentiated adenocarcinoma tissues of the stomach, significantly higher in progressive gastric cancer tissues than in early gastric cancer tissues, and significantly higher in primary gastric cancer tissues than in lymph node metastases. paxillin was significantly higher in esophageal cancer tissues and was associated with clinical stage and lymph node metastases. Paxillin was also highly expressed in colorectal cancer and closely correlated with the depth of cancer infiltration into the intestinal wall and lymph node metastasis.
In patients with hepatocellular carcinoma, the positive rate of paxillin was higher in the group with low differentiation than in the group with high differentiation, higher in the group with portal vein thrombosis than in the group without thrombosis, and higher in the group with extrahepatic metastasis than in the group without extrahepatic metastasis; in lung cancer tissues, more than half of those with positive expression of paxillin had lymph node metastasis, while less than one fifth of those with negative expression of paxillin had lymph node metastasis. The expression of Paxillin is likely to be related to the development and metastasis of gastric cancer, and can be used as a predictor of tumor infiltration and metastasis and poor patient prognosis.
The present experimental study showed that:high expression of Paxillin protein in gastric cancer tissues was significantly (P<0.01) different compared with normal gastric cutting edge tissues.Positive expression of Paxillin was associated with tumor size, tissue differentiation, depth of gastric cancer infiltration, TNM stage, and lymph node metastasis, and the difference was significant (P<0.05) between all groups. This shows that Paxillin is involved in the occurrence and development of gastric cancer and is an influential factor in the poor prognosis of gastric cancer.
Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), is a growth factor that acts specifically on vascular endothelial cells. In recent years, the relationship between VEGF and malignant tumors has been emphasized and more studies have been conducted. It has been found that upregulation of VEGF expression in malignant tumor tissues can promote tumor blood vessel formation, which is an extremely critical step in the process of tumor generation, development and metastasis.
The abundant tumor neovascularization, on the one hand, transports oxygen, nutrition and metabolites to meet the needs of unlimited growth of tumor tissues; on the other hand, the incomplete basement membrane of neovascularization and the increase of vascular permeability also provide convenient conditions for tumor infiltration and metastasis.
It has been shown that VEGF gene is highly expressed in gastric cancer tissues, and it has significant correlation with the depth of tumor infiltration, clinical stage and lymphatic metastasis. The expression of VEGF in gastric cancer tissues was related to the degree of tissue differentiation, the depth of gastric cancer infiltration, TNM stage and lymph node metastasis, suggesting that it is a poor prognostic factor for gastric cancer.
In conclusion, Paxillin and VEGF are involved in the occurrence and development of gastric cancer and are influential factors in poor prognosis of gastric cancer. Moreover, the expression of both is closely related to the degree of tissue differentiation, the depth of gastric cancer infiltration, TNM stage, and lymph node metastasis, suggesting that the combined detection of Paxillin and VEGF expression in gastric cancer tissues is more accurate than a single index to determine the prognosis. In cases with regional lymph node metastasis, the positive expression rates of Paxillin and VEGF were significantly higher, suggesting an increased risk of regional lymph node metastasis in gastric cancer, which has certain guiding significance for the radical scope of gastric cancer surgery and postoperative chemotherapy.
In addition, Paxillin and VEGF interact with each other in the development of gastric cancer, and VEGF promotes the migration and infiltration of tumor cells by tyrosine phosphorylation of Paxillin, which in turn enhances the expression of paxillin, and treatment targeting Paxillin can not only stop the occurrence and development of tumor, but also inhibit the angiogenesis of tumor and increase the sensitivity of tumor to chemotherapy. It is expected to be an important target for antitumor therapy.