循环miRNAs作为胃癌潜在生物标志物的研究及其机制探讨

Studis have revealed that specific-miRNAs abnormally expressed in both many tumor tissues and peripheral blood of malignancies, and the circulating miRNAs owned the features of the abundance, stability and easy detection. Thus, circulating miRNAs have drawn many researchers' attention for their potential as cancer biomarkers. In our previous study, we performed miRNAs profiles in both gastric cancer tissues and plasmas, and further validated in an independent samples as the first stage. We screened four miRNAs with better sensitivity and specificity for gastric cancer diagnosis. In this project, based on our previous study, by the method of molecular epidemiology, we will conduct a second stage validation with big samples from multi-center and multiple populations to evaluate the diagnostic value of plasma cancdiate miRNAs for early-stage and specificity of gastric cancer. Moreover, we will explore the regulatory effects of miRNAs to targets, and further focus on key biological functions of miRNAs to cell lines. In this study, the integration of high-throughput marker screening, multiple-center validations and functional evaluation will provide the population- and experiment-based evidences that circulating miRNAs could be potential biomarkers for gastric cancer, and further indicate the biological mechanism of miRNAs involved in the development and progression of gastric cancer, which will lay the foundation of prevention, intervention, early diagnosis and treatment for gastric cancer.

研究表明，多数肿瘤组织和循环miRNAs表达异常且趋势一致；加之循环miRNAs含量丰富、稳定性高、易于检测，因此循环miRNAs作为肿瘤潜在生物标志物备受关注。本课题组前期基于胃癌组织和血浆miRNAs表达谱分析和第一阶段独立样本验证，筛选出呈现较好敏感性和特异性的4个候选miRNAs。本项目基于前期结果，拟采用分子流行病学研究方法，在第二阶段大样本人群验证基础上，在多中心不同人群中验证并评估血浆miRNAs对胃癌早期和特异性的诊断价值；并采用一系列细胞分子生物学方法，探讨目标miRNAs的靶向调控作用以及对细胞生物学功能的影响。该研究将高通量标志物筛选、临床应用价值验证和多中心人群验证和功能学鉴定有机结合，为循环miRNAs作为胃癌潜在生物标志物提供人群和实验室证据，同时为阐释miRNAs参与胃癌发生发展作用及其可能生物学机制以及今后胃癌的预防、干预、早期诊断和治疗理论依据。

微小RNA（microRNA，miRNA）可参与降解或阻遏靶mRNAs的翻译，从而发挥癌基因或抑癌基因样作用，影响胃癌的发生发展。而外周血循环miRNAs因其含量丰富、稳定性高、易于检测等优点，可能成为未来理想的肿瘤生物标志物。本研究基于对胃癌组织及血浆miRNAs表达谱的检测分析，确定了在胃癌患者组织和血浆中表达均下调的miR-148a、miR-142-3p、miR-26a和miR-195。通过两阶段大样本验证，绘制受试者工作特征曲线（ROC）并计算曲线下面积（AUC），发现miR-26a对胃癌的诊断效能最大，提示miRNA-26a可作为潜在生物标志物用于胃癌诊断。本研究依托南通和宜兴临床队列进一步探讨miR-148a、miR-142-3p、miR-26a和miR-195在胃癌临床预后中的作用，并在细胞水平探讨其对胃癌细胞恶性生物学行为的影响。分层分析结果显示，miR-26a在小于60岁、女性、贲门癌以及TNM早期等的胃癌患者中显示出明显的预测价值；miR-148a的分析结果也提示在大于60岁、女性患者、TNM分期等分层中可能有潜在的预测胃癌患者预后的价值（P < 0.05）; 联合预测效应统计发现，同时高表达的miR-26a和miR-148a对胃癌患者的预后有明显的保护价值（HR = 0.71, 95%CI = 0.56-0.91，P = 0.007）。功能学研究结果发现，胃癌细胞中miR-26a表达水平显著低于正常胃细胞；miR-26a过表达后可明显抑制胃癌细胞的增殖能力、克隆形成能力以及侵袭与迁移能力，且能明显促进肿瘤细胞的凋亡。上述结果提示，miR-26a可作为预测胃癌患者预后的潜在生物标志物，可为今后胃癌的临床治疗和预后判断提供重要参考。