miR-27a基因遗传变异促结直肠癌发生的分子机制

Colorectal cancer (CRC) is the most common digestive malignant tumor in developed countries and its morbidity and mortality rates kept rising in the past decades worldwide. Tumorigenesis of CRC is a multi-step process and could be affected by various factors including dietary intake, lifestyle-related factors and genetic factors, but the real mechanism is unclear. As a class of non-coding RNAs, miRNA was found to play key roles on regulation of gene expression and implicated in colorectal carcinogenesis. The single nucleotide polymorphisms (SNPs) in miRNA were found to be involved in miRNA expression and modified biological functions. Previously, we have found that SNP in pri-miR-27a (rs895819) was associated with increased CRC risk (OR=1.52, 95%CI: 1.02-2.06). However, the role of rs895819 in CRC development and its underlying mechanism remains to be elucidated. In the present study, we will 1) evaluate if rs895819 is associated with serum miR-27a in CRC patients, and 2) investigate if the single nucleotide muatation in the loop of miR-27a gene transcript (pri-miR-27a/pre-miR-27a) affects processing of mature miR-27a and its underlying molecular mechanism. This study may shed light on the role of miR-27a genetic variant in CRC development and provide novel strategy of development biomarker for CRC prediction, diagnosis and personal therapeutic targets.

结直肠癌是一种严重威胁人类健康的消化道恶性肿瘤，探索结直肠癌发生机制是当前结直肠癌基础研究和临床实践的关键科学问题。miR-27a在结直肠癌组织中高表达，被认为是个癌基因。研究显示miR-27a基因的SNP（rs895819）位于pri-miR-27a/pre-miR-27a基因转录本茎环结构的环上，不同rs895819基因型与多种肿瘤的发生危险度相关。本课题组先前采用大样本的自然人群为基础的病例对照研究，发现rs895819与结直肠癌发生危险增加相关，但该遗传变异促结直肠癌发生的机制还不清楚。为此，本项目拟1）纳入临床结直肠病例，分析其miR-27a基因多态性与血清miR-27a水平的相关性，2）利用分子细胞生物学技术，分析rs895819单核苷酸突变对miR-27a加工成熟的影响及机制。本项目的研究成果将为阐明结直肠癌的发病机制以及发展结直肠癌早期诊断、个体化治疗等的分子标记提供依据。

癌基因miR-27a在结直肠癌组织中高表达，然而，miR-27a基因的遗传变异rs895819与结直肠癌发生危险关系一直未明确。本课题采用结直肠癌患者、对照人群为基础开展病例-对照研究和结直肠细胞系实验研究，取得以下研究进展和成果。1）建立结直肠癌患者的研究队列，纳入病例组175例和对照组350例。通过分析直肠癌患者和对照人群miR-27a基因遗传变异rs895819，我们发现，rs895819与结直肠癌发病风险不相关；但在年龄低于55岁人群rs895819的AG、GG、AG+GG基因型与结直肠癌发病风险相关，OR分别为3.82（95%CI:1.17-12.40）、5.03（95%CI:0.91-27.99）和4.02（95%CI:1.29-12.58），提示rs895819的A→G变异增加结直肠癌风险。2）通过系统分析国内外有关rs895819和结直肠癌发病风险的8篇研究报道，并将2556例和3408对照人群进行分析，结果显示rs895819的纯合子模型、隐性模型和等位基因加性模型与结直肠癌发病风险相关。3）分析了结直肠癌患者的miR-27a基因rs895819与血清miR-27a水平相关性，研究结果显示，以AA基因型人群为对照，AG或GG基因型人群血清miR-27a的水平未见显著性差异，提示miR-27a基因rs895819与血清miR-27a水平不相关。4）进一步分析了14种结直肠癌细胞株miR-27a基因rs895819基因型与miR-27a的表达水平，结果显示，以AA基因型的4种结直肠癌细胞株为对照，10种AG基因型结直肠癌细胞株miR-27a的表达水平未见差异。此外，我们还对rs895819和不同肿瘤发病风险关联进行分析，结果显示，rs895819的A→G变异与肿瘤发生风险具有肿瘤依赖性，如增加结直肠癌、肺癌等风险但对乳腺癌有保护作用等。综上，项目研究明确了rs895819的A→G变异增加结直肠癌风险，但miR-27a基因rs895819与血清miR-27a水平不相关；rs895819的A→G变异与肿瘤发生风险具有肿瘤依赖性，其作用机制还有待于进一步探索。项目研究成果发表SCI论文1篇，SCI收录的会议论文2篇、其他会议论文1篇；培养毕业博士后出站1人、博士研究生4人；晋升教授1人、副教授（副主任技师）3人。