Abstract:         Background and purpose: Differentiation of tumor tissue is an important factor on determining the prognosis of gastric cancer. This study aimed to investigate the expression levels and clinical significance of gender determining region Y-box 2 (SOX2) gene and octamer binding factor 4 (OCT4) gene in gastric cancer tissues varying different differentiation degrees. Methods: Sixty cases with gastric cancer were recruited in this study. The gastric cancer tissues and corresponding normal mucosa of the 60 cases were obtained. The mRNA and protein level of SOX2, OCT4 gene are evaluated by the quantitative real-time PCR (qRT-PCR), Western blot and immunohistochemistry, respectively. The relationship between the expression levels of SOX2, OCT4 gene and clinical pathological parameters were also analyzed in this study. Results: The expression of SOX2 in both mRNA and protein levels had no significant difference between the well-differentiated gastric cancer tissues and normal gastric mucosa (mRNA levels: t=0.1033, P>0.05; protein levels: t=0.116, P>0.05). However, both the mRNA and protein expression of SOX2 in patients with well-differentiated gastric cancer tissues were significant higher than not only in patients with moderately differentiated gastric carcinoma (mRNA levels: t=12.48, P<0.05; protein levels: t=22.78, P<0.05) but also in patients with than poorly differentiated gastric carcinoma (mRNA levels: t=17.56, P<0.05; protein levels: t=30.00, P<0.05). In contrast to SOX2, both the mRNA and protein expression of OCT4 in patients with well-differentiated gastric cancer tissues were significant lower than not only in patients with moderately differentiated gastric carcinoma (mRNA levels: t=13.23, P<0.05; protein levels: t=25.56, P<0.05) but also in patients with poorly differentiated gastric carcinoma (mRNA levels: t=12.10, P<0.05; protein levels: t=69.48, P<0.05). There was no significance of OCT4 mRNA and protein expression between the well-differentiated gastric cancer tissues and normal gastric mucosa (mRNA levels: t=2.436, P>0.05; protein levels: t=1.064, P>0.05). Immunohistochemical study demonstrated that the positive rate of SOX2 in patients with well-differentiated gastric cancer tissues (10/21) were higher than in patients with not only moderately differentiated gastric carcinoma (7/20) but also poorly differentiated gastric carcinoma (2/19, P<0.05), while the positive rate of OCT4 in cases with well-differentiated gastric cancer tissues (2/21) were lower than in cases with not only moderately differentiated gastric carcinoma (6/20) but also the poorly differentiated gastric carcinoma (12/19, P<0.05). There was no correlation between the expression of SOX2, OCT4 in gastric cancer and gender or age (P>0.05). Nevertheless, the expression of SOX2, OCT4 were positive or negative correlated with the pathological staging, the degree of infiltration and lymph node metastasis (P<0.05). Conclusion: Decreased SOX2 expression and increased expression level of OCT4 can promote the formation, development and invasion of gastric cancer and they may become biomarkers or the diagnosis, treatment and prognosis evaluation in gastric carcinoma.

Key words: Stomach neoplasms, Sex determining region Y-box 2, Octamer binding factor 4, Cell differentiation