The Study Of The Expression And Significance Of Oct-4 In Colorectal Cancer

Background and aims :Colorectal cancer is one of the common malignant tumors that is the leading cause of death in men and women. In China, the incidence of colorectal cancer are recently on the riseing, in the malignant tumor has been ranked fourth .Its morbidity rates is the second of cancer in western countries. Recurrence and metastasis is the leading cause of death in patients with colorectal cancer; Pathogenesis of colorectal cancer is not entirely clear. Many researchers believe that a small number of cancer stem cells (cancer stem cells, CSC) exist in tumor tissue, CSC and embryo embryonic stem cells (embroynic stem cells, ESC) have the same self-renewal, unlimited proliferation, multilineage differentiation potential, CSC are malignant starting cells and maintain tumor growth. A small number of dormant cancer stem cells for the radiotherapy and chemotherapy is not sensitive to become the root cause of tumor recurrence and metastasis. With the concept of cancer stem cells suggested, embryonic stem cell factor Oct-4, Sox-2, become the research focus in the field of malignant tumors in recent years. Study has suggested cancer stem cells exist in the colorectal cancer, which is the occurrence of colorectal cancer and the root causes of recurrence and metastasis.Oct-4(octamer binding factor 4) is a transcription factor that is specifically expressed in the totipotencial cells or the stem cells, which also is a special transcription factor for an early developmental of embryo and participates in the self-renewal of stem cells. Oct-4 is kown as a mark for totipotencial cell or multipotencial cell.In pluripotent cells and germ cells, the initiation process of normal development, maintenance and differentiation are involved in the role of Oct-4, the study shows that Oct-4 is expressed in mammalian embryonic stem cells and embryonic germ cells, further study found that adult stem cells also express the Oct-4. in the differentiation or mature tissues to lower or disappear. In embryos and germ cell tumors, the Oct-4 expression was significantly higher. Moreover, somatic tumor cells also express Oct-4,but the cells differentiate after the disappearance of Oct-4 expression..Therefore,via the Oct-4 protein expression of colorectal cancer in immunohistochemicy, this study is to explore the expression and the correlation of its expression and clinicopathological factors in colorectal cancer;to explore the relevance of its expression and efficacy of chemotherapy in colorectal cancer, the relationship of the Oct-4 expression with the prognosis and recurrence in colorectal cancer.this will provide the basis for evaluation of prognosis and clinical diagnosis and treatment.MethodsWe use immunohistochemistry method to determine oct-4 expressed in colorectal cancer, immunohistochemistry use streptavidin-biotin - peroxidase method. Steps are summarized below: Biopsies conventional paraffin-embedded, Sections cut at 4μm thickness were stained with hematoxylin and eosin.The sections were obtained and deparaffinized for immunohistochemical studies.Antigen retrieval was carried out by heating sections in natrium citricurn buffer solution of natrium citrieum (PH8.0) for 15 minutes.The endogenous peroxidase was blocked by 3%H₂O₂ in methanol for 30 minutes.Protein block was applied for 30 minutes for blocking of nonspecific background staining.A polyclonal goat anti-Oct4 antibody (Santa Cruz Biotechnology Santa Cru-z, CA), raised against the 2COOH terminus of the protein was used.The primary antibody was diluted(1:50) and incubated for 30 minutes at room temperature. The second antibody was used for 30 minutes at room temperature.And then, use DAB to colour and fix. The cell nucleus of positive cells was dyed into brown. Statistical analysis was carried out using the Statistical Package for Social Sciences(SPSS), version 10.0 for windows.Theχ² test was used to test the stain of Oct-4. P-values<0.05 were considered to be statistically significant.Results1. Oct-4 expression was dark brown, concentrated in the nucleus。There is a wide range of positive Oct-4 expression cells and the Oct-4 positive expression rate of 30.63%(49/160) in colorectal cancer patients which show a clear dark brown nuclei. In normal colorectal mucosa epithelium Oct-4 positive expression was not found ,the difference was statistically significant (P <0.05);2. In poorly differentiated colorectal cancer, the expression of Oct-4-positive rate was 44.12% (30/68), in the differentiation of group, expression of Oct-4-positive rate was 27.98% (17/63), the Oct-4 positive expression rate of well-differentiated colorectal cancer was 6.89% (2/29). Poorly differentiated group of Oct-4 positive expression rate > differentiated group> well-differentiated group, the difference was statistically significant (P <0.05).3. Oct-4 positive expression rate of Dukes'D is 61.9% (13/21) ,the highest, Oct-4 positive expression rate of Dukes'C is 41.67% (25/60), Oct-4 positive expression rate of Dukes' B is 20.41% (10/49) , Oct-4 positive expression rate of Dukes' A is 3.33% (1/30) .the difference was statistically significant.(P <0.05).4. Oct-4 expression was no significant correlation with age, gender, pathological type, the difference was not statistically significant.5. Oct-4 expression in the colorectal cancer with lymph node metastasis positive group was 43.38% (34/79) , Oct-4 positive expression in the colorectal cancer with absence of lymph node metastasis positive group was 18.52% (15/81) .the difference was statistically significant, (P <0.05).6. In all patients of Dukes'C period with Oct-4 positive expression,the 2-year recurrence and metastasis rate is 92%(23/25), which was significantly higher than the patients of Oct-4 negative expression group, the difference was statistical significance (P <0.05).Conclusion1 .Oct-4 has the relationship with colorectal cancer, which may be responsible for the occurrence of colorectal cancer.2.The study suggests the protein expression and the expression extent of Oct4 are positively correlated with the degree of malignancy of colorectal cancer. The expression of Oct-4 has a positive correlation with the pathological stage and lymph node metastasis. Which may reflect the biological behavior of colorectal cancer.3. Oct-4 protein expression is positively correlated with the recurrence and metastasis of colorectal cancer, which would probably have a certain clinical significance for the prognosis evaluation of colorectal cancer.