Expression And Correlation Of SIRT3、HIF-lα And VEGF Protein In Colorectal Cancer

Colorectal cancer(CRC) is a common cancer of digestive system. According to the incidence and mortality, CRC ranks the forefront of cancer both worldwide and in China, with an increasing trend. It is immense important for the prevention and treatment of CRC to explore the mechanism of molecular biology which promotes its occurrence and development. SIRT3, the primary mitochondrial deacetylase, has been established not only regulating the energy metabolism of mitochondrial, steady state of the intracellular reactive oxygen species(ROS) but also affecting aging, cell’s apoptosis and tumor phenotype, etc. SIRT3 which performances high expression in oral and esophageal squamous cell carcinoma promotes the growth of tumor. While in lung, liver, breast cancer, low expression of SIRT3 acts as tumor suppressor. The function may vary with different types of tumor pathology. At present, it has been shown by a large number of researches that SIRT3, as a michondrial tumor suppressor, is closely related to some malignant tumor’s development and prognosis. Genetic loss of the deacetylase SIRT3 leads to the generation of ROS increasing that amplifies HIF-1α stabilization and HIF dependent gene expression, thereby driving the tumor phenotype. There are 200 kinds of HIF-1α dependent genes involved in tumor metabolism, angiogenesis, invasion and metastasis. Some HIF-dependent genes such as glucose transporters, glycolytic enzymes, and Vascular Endothelial Growth Factor(VEGF) are critical for cell survival when chronically exposed to a hypoxic microenvironment in the tumor.However, what role the SIRT3 plays in CRC is still not clear. In our study we will detect the protein expression of SIRT3, HIF-1α and VEGF in CRC tissues and the normal colorectal muscoia tissues, explore the possible role of SIRT3 in CRC, analyse the relationship between their protein expression and CRC clinic-pathology features, new target may be provided for the clinical treatment of CRC.Objective:By detecting the protein expression of SIRT3, HIF-1α and VEGF in CRC tissues and the normal colorectal muscoia tissues to analyze the relationship between the protein expression and clinic-pathological features,and their pairwise correlations, to investigate the effect of the above protein on the occurrence and development of CRC.Methods:Collecting 66 cases of CRC tissues and 45 cases of normal colorectal mucosa tissues paraffin specimens which were surgically removed and pathologically confirmed in the first hospital of Qinhuangdao from September, 2013 to January, 2014. Preparation for Immunohistochemical Staining PV6001 two step method to respectively detect the protein expression in tissues. 20 cases of fresh tissues were collected during operation both the CRC tissues and the corresponding normal colorectal mucosa tissues. Western-blotting technology was carried out to quantitatively detect protein. Statistical analysis were adopted by combined clinic-pathological features with experimental data.Results:1 The results of Immunohistochemical Staining1.1 Protein expression level: The positive expression rate of SIRT3 in CRC tissues was 51.5%(34/66), which was significantly lower than 86.7%(39/45) that in normal colorectal mucosa tissues, with significant statistically difference(P<0.05); The positive expression rates of HIF-1α and VEGF protein in CRC tissues was 71.2%(47/66) and 74.2%(49/66) respectively, which was significantly higher than 0%(0/45) and 22.2%(10/35) that in the normal colorectal mucosa tissues, with significant statistically difference(P<0.05).1.2 The relationship between proteins expression and the clinic- pathological features: The positive expression rate of SIRT3 in CRC tissues had no relation with age, sex, differentiation, tumor size, without statistically significant(P>0.05), and it was related with the depth of tumor invasion, lymph node metastasis, metastasis and TNM stages, the difference was statistically significant(P<0.05); The expression rate of HIF-1α and VEGF protein in CRC tissues had nothing to do with age, sex, differentiation, without statistically significant difference(P>0.05),and it was related with the tumor size, invasion depth, lymph node metastasis, metastasis and TNM stages, the difference is statistically significant(P<0.05).1.3 Correlation coefficient of three kind of proteins: there was a negative correlation between SIRT3 and HIF-1α protein, r=-0.617(P<0.05); also, there was a negative correlation between SIRT3 and VEGF protein: r =-0.502(P<0.05); positive correlation existed in HIF-1α and VEGF protein: r =0.538(P<0.05).2 Western-blotting results2.1 Protein expression level: SIRT3 protein in CRC tissues(SIRT3/ GAPDH) protein expression quantity for(0.624±0.066) was lower than(0.783±0.038) that in the normal colorectal mucosa tissues, HIF-1α protein in CRC tissues(HIF-1α/GAPDH) protein expression quantity for(0.373±0.049) was higher than(0.142±0.030) that in the normal colorectal mucosa tissues, VEGF protein in CRC tissues(VEGF/GAPDH) protein expression quantity for(0.320 ± 0.040) was higer than(0.139 ± 0.035) that in the normal colorectal mucosa tissues, all the differences were statistically significant(P < 0.05).2.2 Correlation coefficient of three kind of proteins: there was a negative correlation between SIRT3 and HIF-1α protein, r=-0.621(P<0.05); there was the same correlation between SIRT3 and VEGF protein: r =-0.695(P<0.05); conversely, there was a positive correlation between HIF-1α and VEGF protein: r =0.486(P<0.05).Conclusion:1 The expression of SIRT3 protein in the CRC is lower than that in normal colorectal tissues, SIRT3 may have an inhibitory effect on CRC process of occurrence and development; Both HIF-1α and VEGF protein expression in the CRC are higher than that in normal colorectal tissues, prompting HIF-1α and VEGF protein promote the occurrence and development of CRC process.2 In the CRC, SIRT3 protein has a negative effect on regulating HIF-1α and VEGF.3 The protein expression of SIRT3 in CRC is related with tumor occurrence, hypoxia microenvironment and angiogenesis of tumor, and possibly through HIF-1α dependent upregulation of VEGF proteins affects the occurrence and development of CRC.