本项目针对肿瘤多样性形成和发展的历史过程中的进化驱动力，及其对肿瘤生长模式和转移的影响，拟以肝移植受者移植前原发性多结节性肝癌、完整的非肿瘤肝脏组织及其血液循环肿瘤DNA临床肿瘤样本为研究对象，采取三维多点微取样方式和基因组分析，基于群体遗传学理论和基因组学技术分析不同肿瘤之间及肿瘤内的细胞群体遗传多样性、群体结构和细胞支系演化关系。结合得到的基因组多样性数据，发展细胞群体生长模型，建立肿瘤内部生长模式。利用观察数据对中性进化模型进行检验，推断肿瘤内遗传多样性的进化驱动力量。根据肿瘤细胞群体遗传多样性，验证在多点密集取样的非肿瘤部分肝脏组织中不同肿瘤克隆的有无及其比例，动态追踪病人术前及术后不同时期血液循环DNA中肿瘤DNA的比例，推测肿瘤迁移、转移路径及扩散历史。

Cancer has been recognized as an evolutionary process driven by somatic mutations and natural selection. Recent large-scale genomic sequencing studies have revealed extensive genetic heterogeneity within a tumor which is believed to be driven by positive selection, thus retaining high frequency in the tumor. However, it lacks a set of empirical data with a precise estimation of low frequency mutations and a model to test the force of selection. Our previous study in a hepatocellular carcinoma indicates that neutral process inevitably results in rapid and extreme genetic diversification of tumor cells. We are applying population genetic theories to model the mutation process during tumor growth with aims to measure genetic heterogeneity driven by neutral forces. In the meanwhile, multiple tumors in each of the HCC case will be undertaken extensively three-dimensional sampling of hundreds of local cell populations with ~2,000 cells per sample. The whole-genome sequencing and genotyping will be carried out for discovering somatic mutations. The observed diversity within and between tumors will be used to infer the phylogenetic tree of tumor clones and to test the evolutionary forces. Fixed and polymorphic variations will be verified in multiple non-tumor samples and in blood ctDNA to speculate the number of migrating tumor populations, trace the path of tumor migration and monitor tumor recurrence.