结直肠癌中miRNA基因及其靶基因多态性位点的研究进展

结直肠癌是最常见的消化系统肿瘤之一。近年来的研究表明,miRNA在结直肠癌的发病过程起着重要的作用。由于单核苷酸多态性（SNPs）的存在,miRNA的结构和功能可能发生变化,从而影响结直肠癌的发病率。目前国内外对miRNA及其靶基因多态性与结直肠癌的关系研究不多。在本文中,我们将对结直肠癌中miRNA表达谱的改变、miRNA基因及其靶基因多态性与结直肠癌的关系及miRNA基因多态性对于结直肠癌的诊断、预后判断、预测疗效的应用前景等内容进行综述。     

microRNA在结直肠癌中的研究进展

结直肠癌是我国常见的恶性肿瘤之一,其发病率较高,相关发病机制的研究日益增多。MicroRNA （miRNA）广泛参与肿瘤的发生、发展及转归,探讨其在结直肠癌发生、发展、转归、预后中的作用及将其作为结直肠癌早期诊断和预后评估肿瘤标志物的可能性,对结直肠癌的诊疗实践均具有重要的意义。     

粪便miRNA标志物在结直肠癌筛选和诊断中的应用研究进展

摘 要：结直肠癌是一个受多种因素影响的病理过程,缺乏理想的无创诊断方法。结直肠癌患者死亡率偏高的主要原因之一是中晚期才表现出临床症状,因此,临床上急需可靠的用于结直肠癌筛选和诊断的生物标志物。MicroRNAs是一类小分子非编码RNA,在肿瘤的发生、转移等机制中具有重要作用。随着检测技术的发展,粪便microRNA作为无创分子生物标志物得到深入的研究,并用于结直肠癌的筛选和诊断。全文对粪便miRNA在结直肠癌筛选和诊断中的应用及检测进展作一综述,重点介绍可用于结直肠癌早期诊断的miRNA。     

散发性结直肠癌发病分子机制研究进展

结直肠癌是最常见的消化系统恶性肿瘤之一,其病因和发病机制十分复杂。自1974年Morson提出结直肠腺瘤癌变序贯学说以来,随着现代分子生物学技术的飞速发展,研究者对结直肠癌发病的分子机制进行了深入研究。目前认为,结直肠癌的发生是一个多因素、多步骤、内外因交互作用的结果,且具有鲜明的分子特征,主要包括癌基因的激活、抑癌基因的失活及基因组不稳定现象等。全文主要围绕结直肠癌发病分子机制的最新研究进展作一综述。     

肥胖与结直肠癌发病机制的研究进展

肥胖是由于机体能量长期供过于求,过多的脂肪在体内堆积所致。近年来,随着人们物质水平的提高以及生活习惯的改变,肥胖人群所占的比例越来越多,并成为结直肠癌发生发展的高危因素。肥胖所致结直肠癌发病机制有多种,包括瘦素、脂联素和炎症因子等脂肪因子的作用,以及胰岛素抵抗、miRNA、微量元素、维生素、氧化应激反应和肠道微生态紊乱等方面的原因。本文对其作用机制的研究进展加以综述,以期对结直肠癌的预防和治疗起到积极的指导作用。     

钙-基因与结直肠腺瘤发病风险关联的研究进展

结直肠癌是胃肠道中常见的恶性肿瘤,近几年,结直肠癌的发病率和死亡率保持着上升趋势,居高不下。而结直肠腺瘤是结直肠癌最重要的癌前病变,其发病机制对于结直肠癌早期诊疗至关重要。结直肠腺瘤的发病机制较为复杂,一般涉及多个基因的相互作用和信号通路。且钙剂与结直肠腺瘤的关联研究在近年来也引起广泛关注。因此,本文对钙与基因的相互作用和结直肠腺瘤发病风险的关系进行综述,为结直肠癌的早期筛查、诊断和早期治疗提供参考。      

microRNA在结直肠癌中的研究进展

microRNA(miRNA)是一类长21-25nt核苷酸的内源性非编码调控RNA,通过与靶细胞mRNA的3’UTR完全互补导致mRNA降解,或不完全互补结合阻断mRNA翻译,参与细胞发育、增殖、分化和凋亡。miRNA具有癌基因和抑癌基因的作用,若干miRNA直接或间接参与结直肠癌的发生和发展,miRNA表达谱与结直肠癌的诊断、分期、进展和预后密切相关。     

microRNA在结直肠癌中的研究进展

microRNA（miRNA）是一类长21-25nt核苷酸的内源性非编码调控RNA,通过与靶细胞mRNA的3＇UTR完全互补导致mRNA降解,或不完全互补结合阻断mRNA翻译,参与细胞发育、增殖、分化和凋亡。miRNA具有癌基因和抑癌基因的作用,若干miRNA直接或间接参与结直肠癌的发生和发展,miRNA表达谱与结直肠癌的诊断、分期、进展和预后密切相关。     

血清miRNA作为结直肠癌患者诊断标志物的价值研究

[目的]探讨特征性血液miRNA作为结直肠癌诊断标志物的可行性.[方法]用miRNA的定量PCR芯片,从结直肠癌患者和健康对照者血清中筛选出候选的特征性miR-NA.再以线虫cel-39作为外参,采用相对定量法分析36例结直肠癌患者及25名健康对照者血清中候选miRNA表达情况.[结果]9条miRNA呈特征性表达,其中5条miRNA明显上调,4条明显下调;9条特征性表达的miRNA均得以验证.将9条特征性血清miRNA进行聚类分析,可见其能够清晰地将结直肠癌患者与健康对照者分为两类.采用ROC曲线分析发现被检测结直肠癌样本的曲线下面积(AUC)达0.934 (95％CI:0.877～0.992)(P＜0.001).[结论]miR-21等9条miRNA组合检测可作为结直肠癌诊断的生物标志物.     

结直肠癌miRNA相关基因单核苷酸多态性与预后相关性研究现状

目的:总结microRNA(miRNA)相关基因单核苷酸多态性(single nucleotide polymorphism,SNP)与结直肠癌患者预后的相关性研究,探讨miRNA相关基因SNPs在结直肠癌患者中的预后价值。方法:应用Medline及PubMed全文数据库检索系统,以"miRNA、单核苷酸多态性、癌症和预后"等为关键词,检索2008-07-2013-10的相关文献。纳入标准:1)miRNA相关基因SNP在癌症中的研究现状;2)miRNA相关基因SNP与结直肠癌患者预后的相关性研究。符合要求并纳入分析的文献39篇。结果:miRNAs是一类非编码小RNAs,可以与靶基因mRNA分子3′非翻译区域特异性结合来负调控蛋白表达。miRNA的突变、缺失或表达水平异常与肿瘤的发生发展密切相关。miRNAs表达水平的异常可作为结直肠癌预后相关的标志。编码miRNA的基因及相关的靶基因结合位点中也存在SNP,其可能通过miRNA转录、miRNA前体形成以及miRNA与mRNA的结合这3种不同的机制影响miRNA的调控,从而来影响结直肠癌患者的预后。miRNA相关基因SNPs(pre-miR-423的rs6505162、pre-miR-608的rs4919510、mir608的rs4919510、mir219-1的rs213210以及let-7f-2的rs17276588),在结直肠癌患者中的预后价值可能与肿瘤分期及治疗有关。结论:miRNA相关基因SNPs可作为预测结直肠癌患者预后的替代标志。     

Ten-eleven translocation 1 (TET1) gene is a potential target of miR-21-5p in human colorectal cancer

DNA 5-methylcytosine (5-mC) methylation, a key epigenetic mark, is critical for biological and pathological processes. Aberrant DNA methylation occurs in all tumor types and correlates with tumor suppressor gene silencing. DNA methylation is thought to be very stable, and active DNA demethylation remains a long-standing enigma. Recently, the ten-eleven translocation (TET) family of oxygenases are found to oxidize 5-mC to 5-hydroxymethylcytosine (5-hmC), which is prerequisite for active DNA demethylation. Both TET1 expression and global 5-hmC content are significantly reduced in colorectal cancer (CRC), the top leading cause of cancer-related death in the world. However, the involving molecular mechanisms are still unclear. The oncogenic microRNA (miRNA) miR-21-5p has recently identified as a diagnostic and prognostic biomarker in CRC. In this study, TET1 was predicted as a novel target of miR-21-5p by using a web-based predictive software starBase v2.0. We found that the 3′-UTR region of TET1 gene contains a miR-21-5p-binding site. Examination of tumor tissues from CRC patients found that loss of TET1 was associated with the progression of CRC to advance stages. In addition, negative correlation of miR-21-5p and TET1 expression was also observed. Transfection of the synthetic miR-21-5p mimic or inhibitor into the colorectal cancer cells could inhibit or increase the TET1-3′-UTR luciferase activity, respectively. Our results demonstrate that TET1 is a potential target of miR-21-5p in CRC.     

MiR-429 is an independent prognostic factor in colorectal cancer and exerts its anti-apoptotic function by targeting SOX2

Emerging evidence has demonstrated that microRNAs (miRNAs) can act as oncogenes or tumor suppressors to participate in cancer development. In this study, we found that miR-429 expression was up-regulated in human colorectal cancer (CRC) tissues, and the high miR-429 expression was significantly associated with tumor size, lymph node metastasis and poor prognosis. Functionally, miR-429 overexpression suppressed cell apoptosis by directly targeting SOX2 in HT-29 cells. Taken together, our data suggest for the first time that miR-429 could play an oncogenic role in the cellular processes of CRC and represent a novel prognostic biomarker for CRC.     

MiR-4500 is epigenetically downregulated in colorectal cancer and functions as a novel tumor suppressor by regulating HMGA2

This study aimed to understand the exact function and potential mechanism of miR-4500 in colorectal cancer (CRC). In this study, the expression of miR-4500 was decreased in both CRC cells and tissues, and downregulated miR-4500 indicated advanced tumor stage and poor survival. By bisulfite sequencing analysis, we found that the CpG island in the promoter region of miR-4500 was hypermethylated in CRC cells and tissues compared with normal control cells and non-tumor tissues, respectively. Functionally, gain- and loss-of-function analyses indicated the tumor suppressor role of miR-4500: it suppressed cell proliferation, cell cycle progression, migration, and invasion. Predictive algorithms and experimental analyses identified HMGA2 as a direct target of miR-4500. Reintroducing HMGA2 impaired the inhibitory effects of miR-4500 on cell growth and motility. Clinically, higher HMGA2 protein expression in CRC tissues was associated with advanced tumor stage and poor survival. An inverse correlation was found between miR-4500 levels and HMGA2 protein expression. Taken together, this study provides the first evidence that miR-4500 functions as a novel tumor suppressor in the miR-4500/HMGA2 axis in colorectal carcinogenesis, and restoring miR-4500 expression might represent a promising therapeutic strategy for CRC.     

MiR-18b-5p对大肠癌PTEN/PI3K/Akt2信号通路的调控

目的:探讨miR-18b-5p对大肠癌PTEN/PI3K/Akt2信号转导通路的调控。方法:qRT-PCR方法检测33例大肠癌患者癌组织中miR-18b-5p表达水平,将患者临床病理特征与癌组织miR-18b-5p表达水平进行独立样本t检验和多元线性回归分析。应用microrna.org预测miR-18b-5p靶基因,miR-18b-5p 类似物、抑制物转染肠癌细胞SW480及HCT116,qRT-PCR检测细胞PTEN、PI3K、Akt2 mRNA表达水平。结果:在大肠癌患者癌组织中,miR-18b-5p表达水平显著增高,为癌旁组织的3.6倍(P<0.01 ),其表达水平与肿瘤分化程度、淋巴结转移及TNM分期相关。Microrna.org预测PTEN可能是miR-18b-5p的靶基因,大肠癌细胞转染类似物后PTEN含量明显降低,其下游基因PI3K、Akt2表达增高。结论:miR-18b-5p下调抑癌基因PTEN表达,诱导PI3K/Akt2信号转导通路持续活化,促进了大肠癌的发生发展。     

microRNA-320a inhibits tumor invasion by targeting neuropilin 1 and is associated with liver metastasis in colorectal cancer

MicroRNAs (miRNAs) have been implicated in regulating diverse cellular pathways. Although there is emerging evidence that various miRNAs function as oncogenes or tumor suppressors in colorectal cancer (CRC), the role of miRNAs in mediating liver metastasis remains unexplored. The expression profile of miRNAs in liver metastasis and primary CRC tissues was analyzed by miRNA microarrays and verified by real-time polymerase chain reaction (PCR). In 62 CRC patients, the expression levels of miR-320a were determined by real-time PCR, and the effects on migration and invasion of miR-320a were determined using a transwell assay. miR-320a target genes were confirmed by luciferase assay, real-time PCR and western blot analysis. A set of miRNAs was found to be dysregulated in the liver metastasis tissues compared to matched primary CRC tissues, and the expression levels of miR-320a were significantly decreased in the liver metastasis tissues examined. miR-320a was correlated with tumor progression in CRC. miR-320a was downregulated in liver metastatic colon cancer cells and inhibited liver metastatic colon cancer cell migration and invasion. miR-320a directly binds to the 3'UTR of neuropilin 1 (NRP-1), a protein that functions as a co-receptor of vascular epithelial growth factor. miR-320a downregulated the expression of NRP-1 at both the mRNA and protein levels. These data demonstrated that miR-320a may be useful for identifying CRC patients that are at an elevated risk for developing liver metastasis. Our findings suggest that miR-320a may be a novel therapeutic candidate for the treatment of colorectal cancer.     

Detection of circulating microRNAs with Ago2 complexes to monitor the tumor dynamics of colorectal cancer patients during chemotherapy

Because of the different forms of circulating miRNAs in plasma, Argonaute2 (Ago2)-miRNAs and extracellular vesicles (EV-miRNAs), we examined the two forms of extracellular miRNAs in vitro and developed a unique methodology to detect circulating Ago2-miRNAs in small volumes of plasma. We demonstrated that Ago2-miR-21 could be released into the extracellular fluid by active export from viable cancer cells and cytolysis in vitro. As miR-21 and miR-200c were abundantly expressed in both metastatic liver sites and primary lesions, we evaluated Ago2-miR-21 as a candidate biomarker of both active export and cytolysis while Ago2-miR-200c as a biomarker of cytolysis in plasma obtained from colorectal cancer (CRC) patients before treatment and in a series of plasma obtained from CRC patients with liver metastasis who received systemic chemotherapy. The measurement of Ago2-miR-21 allowed us to distinguish CRC patients from subjects without CRC. The trend in ΔCt values for Ago2-miR-21 and -200c during chemotherapy could predict tumor response to ongoing treatment. Thus, capturing circulating Ago2-miRNAs from active export can screen patients with tumor burdens, while capturing them from passive release by cytolysis can monitor tumor dynamics during chemotherapy treatment.     

Prognostic significance of PDCD4 expression and association with microRNA-21 in each Dukes' stage of colorectal cancer patients

Down-regulation of the novel tumor suppressor gene programmed cell death 4 (PDCD4) was demonstrated in several types of cancer and regulation by micro-RNA is gaining attention. However, the clinical significance of the PDCD4 gene in colorectal cancer (CRC) patients still remains unclear. In particular, the significance of PDCD4 mRNA expression in each tumor stage has not been reported. In this study, we evaluated the prognostic value of PDCD4 expression in each Dukes' stage of CRC patients. Furthermore, relationships between the PDCD4 mRNA and microRNA-21 (miR-21) were evaluated. Tumor tissues and normal adjacent tumor tissues from 326 patients with CRC (Dukes' stage A, 44 cases; Dukes' B, 118 cases; Dukes' C, 100 cases; Dukes' D, 64 cases) were examined. The PDCD4 mRNA was investigated by the quantitative real-time RT-PCR method and miR-21 was examined by TaqMan microRNA assays. The overall survival rates (OS) and disease-free survival rates (DFS) of low PDCD4 patients were significantly worse than those of patients with high expression. In analysis of each tumor stage, OS and DFS of patients with low PDCD4 levels were significantly worse than those with high PDCD4 levels in Dukes' stage B and C. In Dukes' stage D, patients with low PDCD4 expression showed a significant worse OS compared to those of patients with high PDCD4 expression. In contrast, no significant differences were seen between these groups in patients with Dukes' stage A. PDCD4 expression in CRC tissues was an independent prognostic factor in Dukes' stage B, C and D. Significant inverse correlations were demonstrated between PDCD4 and miR-21. The reduced PDCD4 mRNA expression is associated with poor prognosis in CRC patients with Dukes' stage B, C and D. Furthermore, PDCD4 mRNA levels were negatively regulated by miR-21in each tumor stage of CRC.     

MicroRNA expression profiling of exfoliated colonocytes isolated from feces for colorectal cancer screening

To reduce the colorectal cancer (CRC) mortality rate, we have reported several CRC screening methods using colonocytes isolated from feces. Expression analysis of oncogenic microRNA (miRNA) in peripheral blood was recently reported for CRC detection. In the present study, we conducted miRNA expression analysis of exfoliated colonocytes isolated from feces for CRC screening. Two hundred six CRC patients and 134 healthy volunteers were enrolled in the study. miRNA expression of the miR-17-92 cluster, miR-21, and miR-135 in colonocytes isolated from feces as well as frozen tissues was analyzed by quantitative real-time PCR. The expression of the miR-17-92 cluster, miR-21, and miR-135 was significantly higher in CRC tissues compared with normal tissues. The exfoliated colonocytes of 197 CRC patients and 119 healthy volunteers were analyzed because of the presence of sufficient miRNA concentration. miR-21 expression did not differ significantly between CRC patients and healthy volunteers (P = 0.6). The expression of miR-17-92 cluster and miR-135 was significantly higher in CRC patients than in healthy volunteers (P < 0.0001). The overall sensitivity and specificity by using miRNA expression was 74.1% (146/197; 95% confidence interval, 67.4-80.1) and 79.0% (94/119; 95% confidence interval, 70.6-85.9), respectively. Sensitivity was dependent only on tumor location (P = 0.0001). miRNA was relatively well conserved in exfoliated colonocytes from feces both of CRC patients and healthy volunteers. miRNA expression analysis of the isolated colonocytes may be a useful method for CRC screening. Furthermore, oncogenic miRNA highly expressed in CRC should be investigated for CRC screening tests in the future.