Biomedical Pioneering Innovation Center (BIOPIC), Integrated Research Building Room 330, School of Life Sciences, Peking University, Yiheyuan Road No.5, Haidian District, Beijing, 100871, China.
State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, 510060, China.
Genome Med. 2021 Sep 7;13(1):146. doi: 10.1186/s13073-021-00963-2.
Epstein-Barr virus (EBV)-associated gastric carcinomas (EBVaGCs) present unique molecular signatures, but the tumorigenesis of EBVaGCs and the role EBV plays during this process remain poorly understood.
We applied whole-exome sequencing, EBV genome sequencing, and whole-genome bisulfite sequencing to multiple samples (n = 123) derived from the same patients (n = 25), which covered saliva samples and different histological stages from morphologically normal epithelial tissues to dysplasia and EBVaGCs. We compared the genomic landscape between EBVaGCs and their precursor lesions and traced the clonal evolution for each patient. We also analyzed genome sequences of EBV from samples of different histological types. Finally, the key molecular events promoting the tumor evolution were demonstrated by MTT, IC50, and colony formation assay in vitro experiments and in vivo xenograft experiments.
Our analysis revealed increasing mutational burden and EBV load from normal tissues and low-grade dysplasia (LD) to high-grade dysplasia (HD) and EBVaGCs, and oncogenic amplifications occurred late in EBVaGCs. Interestingly, within each patient, EBVaGCs and HDs were monoclonal and harbored single-strain-originated EBV, but saliva or normal tissues/LDs had different EBV strains from that in EBVaGCs. Compared with precursor lesions, tumor cells showed incremental methylation in promotor regions, whereas EBV presented consistent hypermethylation. Dominant alterations targeting the PI3K-Akt and Wnt pathways were found in EBV-infected cells. The combinational inhibition of these two pathways in EBV-positive tumor cells confirmed their synergistic function.
We portrayed the (epi) genomic evolution process of EBVaGCs, revealed the extensive genomic diversity of EBV between tumors and normal tissue sites, and demonstrated the synergistic activation of the PI3K and Wnt pathways in EBVaGCs, offering a new potential treatment strategy for this disease.
Epstein-Barr 病毒（EBV）相关胃癌（EBVaGC）具有独特的分子特征，但 EBVaGC 的肿瘤发生机制以及 EBV 在这一过程中的作用仍知之甚少。
我们应用全外显子组测序、EBV 基因组测序和全基因组亚硫酸氢盐测序对来自同一患者（n=25）的多个样本（n=123）进行分析，这些样本涵盖了从形态正常的上皮组织到异型增生和 EBVaGC 的唾液样本和不同的组织学阶段。我们比较了 EBVaGC 与其前体病变之间的基因组图谱，并追踪了每个患者的克隆进化。我们还分析了不同组织学类型样本中的 EBV 基因组序列。最后，通过体外 MTT、IC50 和集落形成实验以及体内异种移植实验，证实了促进肿瘤进化的关键分子事件。
我们的分析表明，从正常组织和低级别异型增生（LD）到高级别异型增生（HD）和 EBVaGC，突变负荷和 EBV 载量逐渐增加，而致癌扩增则在 EBVaGC 中晚期发生。有趣的是，在每个患者中，EBVaGC 和 HD 均为单克隆，并且携带单株起源的 EBV，但唾液或正常组织/LD 具有与 EBVaGC 不同的 EBV 株。与前体病变相比，肿瘤细胞在启动子区域表现出递增的甲基化，而 EBV 则表现出一致的超甲基化。在 EBV 感染的细胞中发现了针对 PI3K-Akt 和 Wnt 通路的优势改变。在 EBV 阳性肿瘤细胞中联合抑制这两条通路证实了它们的协同作用。
我们描绘了 EBVaGC 的（ epi ）基因组进化过程，揭示了肿瘤和正常组织部位之间 EBV 的广泛基因组多样性，并证实了 PI3K 和 Wnt 通路在 EBVaGC 中的协同激活，为该疾病提供了新的潜在治疗策略。
