Methionine and PI3K Metabolism Drive CIMP in EBV Epithelial Cancers

项目3 -项目概要 EB病毒（EBV）与多种上皮细胞疾病相关，包括胃癌和 鼻咽癌尽管它的B细胞嗜性，超过一半的200，000 EB病毒相关的癌症， 每年发生的癌症是胃癌和鼻咽癌。癌症基因组图谱项目确定了 EBV感染的胃癌是四种生物学上不同的亚型之一。极端肿瘤基因组CpG岛 甲基化表型（CIMP）和功能获得性PI 3 K突变是显著特征，表明 EBV+ GC中相互关联的驱动程序角色。事实上，EBV+胃癌的DNA甲基化水平最高 任何人类癌症。高甲基化和PI 3 K活性升高也是EBV+ NPC的特征， 伯基特淋巴瘤，进一步表明这些致癌特性与高度恶性淋巴瘤的发病密切相关。 EB病毒潜伏期受限。然而，关于潜伏的EBV突变如何与 肿瘤驱动突变导致上皮癌，以及如何通过精确方法靶向这些肿瘤。我们 因此使用EBV+上皮肿瘤细胞RNAseq和CRISPR/Cas9筛选来鉴定宿主因子， 敲除是合成致死的，通过低甲基化剂地西他滨逆转CIMP或在阻断CIMP后， 高选择性拮抗剂alpelisib引起的PI 3 K活性亢进。我们的中心假设是EBV+上皮细胞 癌症依赖于潜伏病毒基因组之间的相互作用，以及过度活跃的PI 3 K和CIMP， 可以作为合成致死方法的目标。我们的目的是（1）定义潜伏性EBV的作用， （2）确定EBV+上皮癌中过度活跃的PI 3 K信号传导在支持CIMP中的作用; (3)定义EBV+上皮癌CIMP逆转后的关键合成致命弱点。总的来说，这些 预计研究将确定EBV感染的上皮癌如何破坏宿主蛋氨酸和PI 3 K 代谢途径来支持CIMP，以及CIMP如何不仅沉默肿瘤抑制因子， 在防止DNA损伤中起着关键作用。因此，我们的研究可能会支持发展战略， EBV相关上皮癌的合理治疗方法。

PROJECT 3 – PROJECT SUMMARY Epstein-Barr virus (EBV) is associated with multiple epithelial cell diseases, including gastric cancer and nasopharyngeal carcinoma. Despite its B-cell tropism, more than half of the 200,000 EBV-associated cancers that occur annually are gastric and nasopharyngeal carcinomas. The Cancer Genome Atlas project identified EBV-infected gastric cancer as one of the four biologically distinct subtypes. Extreme tumor genome CpG island methylator phenotype (CIMP) and gain-of-function PI3K mutations are salient features, suggesting interconnected driver roles in EBV+ GC. In fact, EBV+ gastric cancer has the highest level of DNA methylation of any human cancer. Hypermethylation and elevated PI3K activity are also characteristic of EBV+ NPC and Burkitt lymphoma, further suggesting a close pathogenetic relationship of these oncogenic properties with highly restricted forms of EBV latency. Yet, much remains to be learned about how latent EBV mutation together with tumor driver mutations result in epithelial cancers, and how these can be targeted by precision approaches. We therefore used EBV+ epithelial tumor cell RNAseq and CRISPR/Cas9 screens to identify host factors whose knockout is synthetic lethal with reversal of CIMP by the hypomethylating agent decitabine or upon blockade of PI3K hyperactivity by the highly selective antagonist alpelisib. Our central hypothesis is that EBV+ epithelial cancers rely on cross-talk between latent viral genomes, and hyperactive PI3K and CIMP, disruption of which can be targeted in synthetic lethal approaches. Our Aims are to (1) Define the role of latent EBV in driving CIMP; (2) Define the role of hyperactive PI3K signaling in EBV+ epithelial cancers in support of CIMP; (3) Define key synthetic lethal vulnerabilities upon EBV+ epithelial cancer CIMP reversal. Collectively, these studies are expected to identify how EBV-infected epithelial cancers subvert host methionine and PI3K metabolism pathways to support CIMP, and how in turn CIMP not only silences tumor suppressors, but also plays key roles in guarding against DNA damage. Our studies may therefore support strategies to develop rational therapeutic approaches for EBV-associated epithelial cancers.