A Study About The Expression Of SOX2 And OCT4 In Gastric Cancer Tissues And The Impact Of Overpression Of SOX2 In The Biological Characteristics Of Gastric Cancer Cells

Objective: Differentiation of tumor tissue is an important factor determining the prognosis of gastric cancer. This study focuses on not only the expression of sex determining region Y-box 2(SOX2)gene and Octamer binding factor 4(OCT4) gene in gastric cancer tissues but also the relationship and significance between the expression of SOX2,OCT4 and clinic pathological factors and prognosis of gastric cancer patients. Produced the overexpression SOX2 gene of gastric cancer cell lines. Studied the mechanism and impact of the overexpression of SOX2 to the biological characteristics of gastric cancer cells.Methods: 1. The m RNA and protein Expression level of SOX2, OCT4 gene in 60 cases of gastric cancer tissues and normal mucosa are detected respectively by the fluorescent quantitative polymerase chain reaction(PCR) and Westerbloting,immunohistochemistry. and the 60 cases are in differentiated degree. 2. The relationship between the Expression level of SOX2,OCT4 gene and clinic pathological parameters of patients are also analyzed in this study. 3. Construction of recombinant plasmid carrying with the gene SOX2, infected SGC-7901 cell with lentivirus vector and obtained stable expression stem cell SOX2 gene of gastric cancer cell lines. 4. A variety of cell function experimental, Such as Transwell cell invasion and migration assay, cell scratch assay, Nude mice tumorigenicity experiments in vivo, respectively was used to detect the impact of biological characteristics in overpression SOX2 gene of gastric cancer cell. 5. Fluorescence quantitative PCR, wester-bloting were finded that the expression of regulation gene in PI3K/Akt signaling pathway and gastric cancer stem cell marker gene in overexpression of SOX2 gene of gastric cancer cellsResults: 1. The fluorescent quantitative-PCR, Wester-bloting detection showed that the expression of SOX2 m RNA and protein have no statistically significant between the well-differentiated gastric cancer tissues and normal gastric mucosa(t=0.1033,P>0.05,t=0.116,P>0.05), However, the detection shows that the expression of SOX2 m RNA and protein in the well-differentiated gastric cancer tissues is significant higher not only than moderately differentiated gastric carcinoma(t=12.48, P<0.05, t = 22.78, P<0.05) but also than poorly differentiated gastric carcinoma(t =17.56, P<0.05, t =30.00, P<0.05), so a statistically significant exsits in difference. Compared with SOX2, the expression of OCT4 m RNA and protein also has no statistically significant between the well-differentiated gastric cancer tissues and normal gastric mucosa(t=2.436,P>0.05,t=1.064,P>0.05),but it is significantly lower than moderately differentiated gastric carcinoma(t=13.23,P<0.05,t=25.56,P<0.05), and poorly differentiated gastric carcinoma(t=12.10,P<0.05,t=69.48,P<0.05), so a statistically significant exists in difference.2. Immunohistochemical shows that the positive expression rate of SOX2 in well-differentiated gastric cancer tissues(10/21)is higher than not only moderately differentiated gastric carcinoma( 7/20) but also poorly differentiated gastric carcinoma( 2/19)(P < 0.05), and the positive expression rate of OCT4 in well-differentiated gastric cancer tissues(2/21)is lower than not only moderately differentiated gastric carcinoma(6/20)but also the poorly differentiated gastric carcinoma(12/19)(P<0.05).3. Compared with the clinical pathological parameters, the expression of SOX2,OCT4 protein in gastric cancer has nothing to do with the patient’s sex, age, as there is no statistically significance(P>0.05),but it is connect with the pathological staging, the degree of infiltration, lymph node metastasis(P < 0.05).4. Successfully produced the SGC7901-hsox2 in gastric cancer cell lines, Transwell assay showed that the ability of migration of SGC7901-hsox2 was significantly weaker compared with the SGC7901 and SGC7901-ZPP group(P <0.05). MTs resistance assay suggested that the IC50 to chemotherapeutic drugs L-OHP and 5-FU of SGC7901-hsox2 was decrease, compared with the blank group and negative control group(P <0.05). Nude mice tumorigenicity experiments in vivo, suggested that the tumorigenicity ability of the SGC7901-hsox2 was significantly lower than the blank group and negative control group(P <0.05).5. Fluorescence quantitative PCR, wester-bloting experimental results showed: The regulation gene PTEN expression levels of the PI3K/Akt signaling pathway in SGC7901-hsox2 were significantly increased, Compared to the blank group and negative control group(P <0.05). However, the Oct4、C-myc、CD44 gene relative expression levels of the cells overexpressing of SOX2 gene in SGC7901-hsox2 was suggested no significant change contrasted to the blank group and negative control group(P> 0.05).Conclusion: 1.The expression level of SOX2 in the different degree of differentiation of gastric cancer tissue is different. The higher degree of differentiation, the higher expression level of SOX2. SOX2 plays an important role in the process of gastric epithelial cells differentiation. SOX2 is the anti-oncogene in the process of the evolution in the gastric cancer.2. The lower degree of differentiation, the higher expression level of OCT4 mRNA and protein, the expression level of OCT4 in the poorly differentiated gastric carcinoma is significant higher than not only moderately differentiated gastric carcinoma,but also the well-differentiated gastric cancer tissues.It is closely related to gastric cancer cell differentiation.3. The low expression level of SOX2 and high expression level of OCT4 can promote the occurrence, development and invasion of gastric cancer. They are expected to become a target in the diagnosis, treatment and prognosis judgement of gastric cancer.4. The ability of invasion and migration, proliferation, and tumorigenicity of SOX2 gene overexpressed in gastric cancer cell were significantly decreased5. SOX2 gene changed biological characteristics of gastric cancer cells that may through PTEN regulated PI3K/Akt pathway.