质子NMR指纹谱结合模式识别筛寻大肠癌特征性粪便标志物组

Colorectal cancer (CRC) is the most commonly malignant tumour in digestive tract. Accurate diagnosis at an early stage of CRC is of great importance for optimum treatment and prognosis. Colonoscopy has a high sensitivity, and remains the gold standard for visualization of the colon and the detection of neoplastic abnormalities. However, it is invasive, exposes the subject to risks, and can only detect the stage with visible morphologic changes. High resolution Proton Nuclear Magnetic Resonance （1H-NMR）Spectroscopy has been shown to be particularly useful for identifying metabolic profiles in the fecal extracts, and disturbances in these profiles compared with the basal metabolic state may reveal potential biomarkers of CRC. Our previous work showed the metabolic differences of fecal extracts between healthy controls, and patients with ulcerative colitis (UC) and CRC. The fecal extracts in both UC and CRC patients were characterized by reduced levels of short-chain fatty acids (SCFA) in comparison with the healthy controls. We therefore hypothesized that metabolic changes in fecal extracts might reflect the early event of CRC development. This project is a NMR-based metabolomics coupled with pattern recognition to investigate the screening and diagnostic metabolic "fingerprint" from fecal specimens for CRC early detection. Stool specimens from healthy subjects, from patients with CRC (before and after operation) and with colorectal precancerous (including UC、Crohn`s disease and adenomatous polyp ) will be examined using the optimized NMR technique. This is to characterize possible differences between these groups and to identify potential diagnosis markers. The results from metabolomic fecal analysis of this screening cohort will be compared with results from colonoscopy, to assess the accuracy of fecal metabolomics in identifying patients with colorectal precancerous and malignancies. Additionally, fecal samples from gastric cancer (before and after operation) will be collected to validate that the CRC signature is unique. Successful application of this project can help us to develop a new screening and diagnostic method, which is non-invasive, inexpensive, simple, and has high sensitivity and specificity to screen CRC during the early stages. This would have a significant impact on the success of therapeutic interventions for CRC patients in China.

大肠癌是最常见的消化道恶性肿瘤，早诊早治有利于预后。纤维内镜只能发现已进展至形态学改变的病变，且存在有创、依从性差等缺陷。质子NMR结合模式识别分析粪便代谢谱有独特优势。预实验发现：溃疡性结肠炎的粪便代谢物谱类似于大肠癌但迥异于正常人。我们提出假说：伴随大肠上皮恶性转化过程发生了与其相适应的代谢改变，粪便代谢物谱可反映上述改变，是大肠癌发生的早期事件，质子NMR结合模式识别筛寻大肠癌特征性粪便代谢物组可能成为早期筛查手段。本项目将NMR参数优化、数据处理优化及人粪样检测试验相结合，通过比较正常人群、大肠癌癌前病变、大肠癌术前后、胃癌术前后粪样代谢物，明确粪样中低含量短链脂肪酸等代谢物在大肠癌早期发病的特异性和敏感性，并结合结肠镜检查加以验证。该项目如成功实施，有助于理解大肠癌发生早期所伴随的与其相适应的代谢变化，并可能为我国大肠癌的早期筛查提供无创、人群依从性高、筛检窗口前移的检测新手段。

大肠癌（Colorectal Cancer, CRC）是最常见的消化道恶性肿瘤，早诊早治有利于预后。纤维内镜只能发现已进展至形态学改变的病变，且存在有创、依从性差等缺陷。质子核磁共振谱（1H NMR）结合模式识别分析粪便代谢谱有独特优势。本项目联合质子NMR和模式识别,分别检测正常人群、CRC癌前病变、CRC术前/术后粪样代谢物，明确粪样中低含量短链脂肪酸等代谢物在CRC早期发病的特异性和敏感性，并且绘制受试者工作曲线(ROC)以评估其临床价值。主要研究结果如下：（1）通过对比分析健康者和CRC的粪便上清液，发现CRC粪便代谢轮廓较健康者发生了明显改变，且能区分早期癌及晚期癌：CRC的短链脂肪酸（丁酸、醋酸、丙酸）、葡萄糖及谷氨酰胺含量较健康者显著降低（p<0.05），而甘油、脯氨酸、丙氨酸、天冬酰胺、缬氨酸、谷氨酸、亮氨酸、异亮氨酸及乳酸含量较健康者显著升高（p<0.05），反映了肠道菌群失调、营养物质吸收障碍及机体糖代谢增强；其中短链脂肪酸对于诊断CRC具有>90%的诊断准确性。（2）通过对比分析健康者、肠腺瘤（CRC癌前病变）及早期CRC（I/II期）的粪便代谢组，发现大肠癌特征性粪便代谢如醋酸和琥珀酸能区分早期大肠癌和其癌前病变, 曲线下面积、敏感性及特异性均大于85%。(3)通过配对检测CRC的术前/术后粪便上清代谢物、CRC组织及其癌旁1cm和癌旁5cm肠组织代谢物，发现CRC粪便代谢轮廓的改变能反映癌组织的代谢改变：CRC粪便和癌组织的代谢物如短链脂肪酸、乳酸、丁酸、谷氨酸、琥珀酸及丙氨酸均较正常对照存在明显差异，提示了癌组织与粪便存在共代谢网络，以提供癌细胞增殖所需大量营养底物，如葡萄糖和谷氨酰胺等产生三磷酸腺苷（ATP）为肿瘤生长提供能量。本项目的实施提示伴随大肠上皮恶性转化过程发生了与其相适应的代谢改变，粪便代谢物谱可反映上述改变，是大肠癌发生的早期事件，质子NMR结合模式识别筛寻大肠癌特征性粪便代谢物组可能成为早期筛查手段。