The Research On Relationship Between PAQR3 Gene Methylation And Colorectal Cancer

Objective The incidence and mortality rate of colorectal cancer have increased year by year,colorectal cancer ranks the third in the malignant tumors, which has seriously affected the life and health of human beings. The occurrence of colorectal cancer is the joint result of multiple factors,multiple genes and steps.Images,endoscopy and refers to the anus,are currently the main ways for diagnosis of colorectal cancer, but there are still many patients experienced misdiagnosis and waste treatment of diseases, and even have missed the best treatment opportunities. Genetic studies to explore the occurrence and development of colorectal cancer mechanism provides a new train of thought. The increasing maturity of genetic testing technology for early colorectal cancer diagnosis provides a great convenience. Despite some genes are served as tumor markers of colorectal cancer and have also been widely used in clinical, but as we known,the mechanism is complex, we need to understand more mechanisms of colorectal cancer to achieve the purpose of early diagnosis, early treatment.In recent years, gene methylation is a a hot area of tumor research, DNA methylation is an early event in tumor, on the process is under the role of the DNA methyltransferase(DNMT), the methylgroup provided by the S- adenosylmethionine(SAM),was covalently bound to the Cp G dinucleotide cytosine 5-carbon position(5m-c). The Cp G island abnormal methylation of gene promoter is a heteromorphism changes,which is a epigenetic changes process without gene structure changes, this process is reversible, the aim is to protect against DNA specific enzyme degradation and to regulate gene expression, Gene promoter methylation is closely related with transcription, hypermethylation and hypomethylation of state co-exist in normal tissues, gene promoter methylation inhibits the transcription of genes; promoter hypomethylation of the gene promotes gene transcription,therefore gene promoter methylation abnormalities will lead to tumor formation. Some scholars have found that methylation levels in cancer patients are generally higher than healthy people, the body is in microsatellite instability status, genes are likely occur mutation.Some genes methylation level is age-related and will be increased along with the age increases.In recent years, more and more researchsof tumor suppressor gene methylation as detection index have been launched, aberrant methylation occurs in the early stages of tumor formation,along with the tumor progress, methylation rates increases. At home and abroad,reports on singled and combined detection of gene methylation to the early diagnosis of colorectal cancer provide much more specific diagnosis.PAQR3 is a member of progesterone and adiponectin receptors(PAQR) family, PAQR3 is a new tumor suppressor gene which plays a role in colorectal cancer, the fuction of PAQR3 refers to cell transduction, energy metabolism, cell proliferation, differentiation, maturation of germ cells and other biological processes. PAQR3 is also named as PKTG, which can encode37 k D membrane protein, PAQR3 protein is a seven transmembrane protein that located in Golgi complex, the N-terminal faces cytoplasmic, C-terminal towards to organelle cavity.PAQR3 can negatively regulate the Ras / Raf / MEK / ERK signaling pathway, the signaling pathway is one of the classical mitogen-activated protein kinase cascade pathway(mitogenactivated proteinkinases cascade, MAPKs cascade), whose role is to feel the extracellular signals to intracellμlar signal transduction,then further regulate cell proliferation, differentiation,signal transduction, apoptosis and cell malignant transformation processes, such as the development of cancer. There are two mechanisms by PAQR3 that can negatively regulate the AKT signaling pathway, on the one hand, PAQR3 binds to and alters the subcellular localization of p110ɑ in cytoplasm PI3 K complex, then to prevent from binding to p85 sites,it finally leads to the phosphorylation of PI3 K and the inactivation of AKT; on the other hand,PAQR3 blocks the GPCR Gβ sites to inhibit the role of AKT in GRCR activated Gβ/γ site. In gastric cancers, PAQR3 negatively regulate of ERK and phosphorylates AKT,which draws a conclusion that PAQR3 exerts a negative regulator of EMT process by inhibiting ERK and AKT signaling pathways.The aims are to analyze PAQR3 m RNA,protein and gene methylation levels in cellulars and moleular levels,and the relationships with colorectal cancers, for providing further new targets for more effective diagnosis and treatment of colorectal cancer.Methods 54 cases of colorectal cancer tissues and adjacent tissues were collected in surgery,q RT-PCR was used for PAQR3 m RNA analysis; MSP was used to analyze the methylation levels of PAQR3 gene;protein Western blot was used for the analysis the expression levels of PAQR3 protein.Statistical Methods: SPSS16.0 statistical software for data processing, all the data are presented as percentage, mean ± Standard Deviation,Fisher’s exact and χ2 test, P <0.05 was considered statistically significant.Results(1)There are 31 colorectal cancers with low expression levels of PAQR3 m RNA in54 patients and 10 normal tissues with low expression levels of PAQR3 m RNA,the rate of low expression is 57.4%(31/54),The Dct of PAQR3 m RNA is 9.32± 1.97 in cancers tissues and 8.44 ± 2.42 in normal tissues,the differences are statistically significant(p<0.05).(2)PAQR3 m RNA were detected with lower expression in 31 colorectal cancer tissues, in which12 colorectal cancers PAQR3 with part gene methylation and 6 colorectal cancers wtih complete methylation were detected, 13 cancer tissues were not detected with methylation.compared to normal tissues, PAQR3 in cancer tissues were detected with high methylation, in others 23 tissues which m RNA expression of PAQR3 were not significantly lower in patients with colorectal cancer, there are only 3 tissues with PAQR3 gene methylation and 20 tissues without methylation, the difference was statistically significant(p<0.05).The Rate of PAQR3 gene methylation was 33.3%(18/54) in colorectal cancer tissues and 5.6%(3/54) in tissues adjacent to carcinoma, PAQR3 gene methylation rate in colorectal cancer tissues was significantly higher than the corresponding tissues adjacent to carcinoma(p < 0.05).(3) 25 cases of colorectal cancer tissues PAQR3 protein expression levels were decreased and even didn’t express, 29 cases of colorectal cancer tissues didn’t siginificantly decrease.The lower rate of PAQR3 protein was 46.3%(25/54).(4) PAQR3 gene methylation level is related with age, differentiation degree, infiltration depth, lymph node metastasis, the older, low differentiation, lymph node metastases, deep infiltration depth of methylation rate is higher;on the other hand,is lower. But not with gender, tumor site and clinical stage. The methylation in normal tissues adjacent to carcinoma is not related with gender, age, tumor site,the degree of differentiation, lymph node metastases, infiltration depth and clinical stage.Conclusions(1) The level of PAQR3 m RNA expression decreases in colorectal cancer tissues.(2) The level of PAQR3 PAQR3 expression increases in colorectal cancer tissues.(3) The level of PAQR3 protein expression decreases in colorectal cancer tissues.(4)PAQR3 gene promoter methylation is associated with the occurrence of colorectal cancer,the PAQR3 gene methylation rate in patients that older, low differentiation,lymph node metastases, deep infiltrating depth is higher; on the contrary,the methylation rate is lower.