目前临床缺乏早期预警肝癌转移复发及疗效监测有效手段，肿瘤时间和空间异质性是造成该困局主因。作为“液体活检”代表，循环肿瘤DNA（circulating tumor DNA, ctDNA）是肿瘤释放到外周血的突变DNA，能克服肿瘤异质性局限，而肝癌ctDNA研究罕有报道。我们前期研究发现血浆DNA能预测肝癌复发；肝癌患者血浆存在ctDNA，但单基因突变频率低，单位点突变检测阳性率更低。本课题拟通过全外显子测序比较肝癌患者肿瘤及ctDNA突变信息，探讨ctDNA反映肿瘤异质性的可靠性并绘制肝癌ctDNA特征谱；进一步构建DNA捕获芯片、靶向深度测序检测肝癌切除和索拉菲尼治疗患者不同时间点ctDNA，建立转移复发和耐药相关ctDNA特征谱，探寻转移复发及耐药关键基因，并进行体内外验证。本研究将从ctDNA这个新视点为揭示肝癌转移复发及耐药机制奠定基础，为早期预警肝癌转移复发及疗效监测提供新思路。

Currently, there is an urgent need for a reliable method that integrates the prediction and surveillance of metastasis and recurrence, and monitoring antitumor treatment response of hepatocellular carcinoma (HCC) in a real-time manner. Temporal and spatial heterogeneities of malignant tumor are proposed to cause this dilemma. As the representative of liquid biopsy, circulating tumor DNA (ctDNA) is the mutant DNA fragment released to blood by tumor cells, which could dynamically and comprehensively reflect the whole genomic landscape of cancer and break through the restriction of tumor heterogeneity. Up to now, few studies on HCC ctDNA have been reported. Our former work found circulating DNA could predict postoperative recurrence of HCC patients, and ctDNA was detectable in HCC patients whereas single mutation rate was very low and the positive rate was even lower by detecting the single-site mutation. This study aims to explore the possibility of detecting ctDNA to overcome heterogeneity of HCC by comparing the mutational profile of HCC tumor tissues with that of ctDNA through whole exome sequencing. Then, ctDNA specific mutation panel will be created to customize a DNA fragment capture chip for detecting ctDNA with targeted deep sequencing at multiple time points from HCC patients undergoing tumor resection or sorafenib therapy, respectively. Subsequently, metastasis and recurrence-associated or drug resistance-associated ctDNA profiles are constructed to search for differentially expressed mutant genes, and the biological functions and molecular mechanisms are further explored in vitro and in vivo. Conclusively, this study focuses on ctDNA to establish the foundation for deciphering the molecular mechanisms involved in HCC metastasis/recurrence and drug resistance, and provide a novel method for the prediction and surveillance of HCC metastasis/recurrence and treatment response.