循环肿瘤DNA的检测:从数字化到测序

The Detection of Circulating Tumor DNA: From Digitalization to Sequencing

液体活检的主要检测对象——循环肿瘤DNA(circulating tumor DNA,ctDNA)是人体血液循环系统中具有一定特征的(包括突变、缺失、插入、重排、拷贝数变异、甲基化等)来自肿瘤细胞基因组的DNA片段,其主要来源于凋亡或坏死的肿瘤细胞。ctDNA的检测和分析能够提供肿瘤中的基因组信息,例如,基因组中的拷贝数变异、突变和甲基化富集等。相较于其他的肿瘤标志物,ctDNA相对稳定,提取技术相对成熟,与肿瘤的大小和发展具有一定的相关性,是一种新兴的、有前景的肿瘤生物标志物,在精准医疗中发挥着越来越重要的作用。不过ctDNA含量极低,背景游离DNA(cell free DNA,cfDNA)含量高,个体间差异大,且需要提前预判检测的位点和突变,因此,利用新方法和新技术对它进行全面检测分析是必不可少的。目前,针对ctDNA的检测方法和平台种类繁多,在此,我们总结了从数字PCR到下一代测序的ctDNA检测的研究进展,包括一些商业化的仪器和一些仍在实验室发展中的设备并对利用这些新兴技术分析检测ctDNA的发展趋势做了展望。

Circulating tumor DNA(ctDNA),the main item of liquid biopsy,is DNA fragments from tumor genome that carries certain characteristics(including single nucleotide variation,deletion,insertion,rearrangement,copy number variation,and methylation)in the human blood circulation system.It mainly originates from apoptotic or necrotic tumor cells.The detection and analysis of ctDNA can provide genomic information in tumors,such as copy number variation,single nucleotide mutation,and methylation enrichment across the genome.It has a certain correlation with tumor size and development and considered as an emerging and promising tumor biomarker for cancer progression,reoccurrence,and routine monitoring after surgery.Compared with other tumor markers,the isolation method is relatively simple due to the stability of ctDNA.However,the extremely low abundance of ctDNA,the high content of background cell free DNA(cfDNA),the large difference between individuals,and the need of predicted detection sites in advance make it necessary to analyze ctDNA in a comprehensive way.Herein,we summarize the recent progress on ctDNA detection from digital PCR to next generation sequencing,including some commercialized apparatuses and certain methods that have recently been developed.