Dissecting gastric cancer clonality with genomic analyses and patient xenografts

摘要 胃癌是全球第三大癌症死亡原因，有超过72万人 每年都会死于这种疾病。这种恶性肿瘤的存活率仍然很低：只有4%的患者患有 转移性胃癌在确诊后5年内仍存活。有趣的是，最近的胃癌基因组研究 已经表明这种恶性肿瘤是高度异质性的，每个肿瘤都有数百个突变。它是 然而，尚不清楚这些突变是如何组织成胃肿瘤亚克隆细胞群的。 了解胃肿瘤的亚克隆组织是很重要的，因为这些信息对于 设计优化的分子检测方法，指导精准医学。在本研究中，我们将 研究胃癌克隆性的区域和时间变化以了解肿瘤内的水平 异质性和亚克隆结构，并识别携带驱动突变的肿瘤亚克隆 有针对性地进行治疗。虽然亚克隆构筑研究尚未在胃癌中开展， 最近对其他癌症类型的研究，如肺癌和肾癌，产生了有趣而又不同的结果。 结果。虽然驱动突变倾向于出现在大多数肺癌亚克隆中，但多个和更年轻的 携带不同驱动因素的亚克隆是肾肿瘤的特征。因此，虽然肺癌和肾癌都是 显示广泛的肿瘤内异质性，这些结果表明有限的抽样(即一次活检)可能 适用于肺癌的分子引导治疗，但更广泛的多区域采样 肾癌的分子诊断需要进行分析。在这里，我们的目标是提高我们的 对胃癌克隆性及其与分子诊断相关性的研究 30例胃癌组织的区域测序及组织遗传学水平分析 将匹配的肿瘤移植到免疫抑制的NSG小鼠体内时的相似性。我们的导游 假设胃癌中广泛的肿瘤内异质性导致复杂的肿瘤类型 克隆建筑。本研究的目的如下：(1)研究胃癌的克隆多样性。 多区域测序和(2)评估组织学和基因组学上的相似性 肿瘤来源于患者来源的异种移植模型。这些实验对于阐明 胃癌克隆进化模式及其在精准医学中的影响和相关性。特别是， 我们将揭示驱动突变在胃癌亚克隆中的分布，并将提供非常强大的 为设计进一步的临床前研究和临床试验奠定基础，有效地针对这些突变，导致 亟需改善的胃癌存活率。我们的发现也将与癌症相关 由于胃癌对美国拉美裔美国人的影响不成比例，美国的差距很大。

Abstract Gastric cancer is the third leading cause of cancer mortality worldwide, with over 720,000 individuals succumbing to this disease each year. Survival to this malignancy remains dismal: only 4% of patients with metastatic gastric cancer are alive 5 years after diagnosis. Interestingly, recent gastric cancer genomic studies have shown that this malignancy is highly heterogeneous, with every tumor having hundreds of mutations. It is not known, however, how these mutations are organized into gastric tumor subclonal cell populations. Understanding the subclonal organization of gastric tumors is important as such information will be essential to design optimal molecular testing methods that guide precision medicine. In the present study, we will investigate regional and temporal changes in gastric cancer clonality to understand the levels of intra-tumor heterogeneity and subclonal architecture, and to identify tumor subclones carrying driver mutations that can be targeted for therapy. Although subclonal architecture studies have not yet been carried out in gastric cancer, recent studies in other cancer types, such as lung and renal tumors, have produced interesting, yet contrasting results. While driver mutations tend to be present in most lung tumor subclones, multiple and younger subclones carrying different drivers are characteristic of renal tumors. Thus, while both lung and renal cancer show extensive intra-tumor heterogeneity, these results suggest that limited sampling (i.e. a single biopsy) may be appropriate for molecularly-guided therapies in lung cancer but that more extensive multiregional sampling and analyses will be required for molecular diagnostics in renal cancer. Here we aim to improve our understanding of gastric cancer clonality and its relevance for molecular diagnostics by performing multi- regional sequencing of 30 gastric cancer tumors and by evaluating the levels of histological and genetic similarities of matching tumors when they are implanted into immunosuppressed NSG mice. Our guiding hypothesis is that extensive intra-tumor heterogeneity in gastric cancers leads to complex patters of tumor clonal architecture. Our aims in the study are as follows: (1) To investigate gastric cancer clonal diversity using multiregional sequencing and (2) To assess histological and genomic similarities between primary cancers and tumors derived from patient-derived xenograft models. These experiments will be crucial to elucidate the patterns of gastric cancer clonal evolution and their impact and relevance in precision medicine. In particular, we will uncover the distribution of driver mutations in gastric cancer subclones and will provide a very strong basis to design further preclinical studies and clinical trials that efficiently target such mutations, leading to much needed improvements in gastric cancer survival. Our findings will be also relevant to address cancer disparities in the country as gastric cancer disproportionally affects U.S. Hispanics.