Duan Qingke, Tang Chao, Ma Zhao, Chen Chuangui, Shang Xiaobin, Yue Jie, Jiang Hongjing, Gao Yan, Xu Bo
Department of Biochemistry and Molecular Biology, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China.
Tianjin's Clinical Research Center for Cancer, Key Laboratory of Breast Cancer Prevention and Therapy, Tianjin Medical University, Ministry of Education, Tianjin, China.
Front Oncol. 2021 May 11;11:672020. doi: 10.3389/fonc.2021.672020. eCollection 2021.
Gastroesophageal junction (GEJ) cancer is a tumor that occurs at the junction of stomach and esophagus anatomically. GEJ cancer frequently metastasizes to lymph nodes, however the heterogeneity and clonal evolution process are unclear. This study is the first of this kind to use single cell DNA sequencing to determine genomic variations and clonal evolution related to lymph node metastasis. Multiple Annealing and Looping Based Amplification Cycles (MALBAC) and bulk exome sequencing were performed to detect single cell copy number variations (CNVs) and single nucleotide variations (SNVs) respectively. Four GEJ cancer patients were enrolled with two (Pt.3, Pt.4) having metastatic lymph nodes. The most common mutation we found happened in the TTN gene, which was reported to be related with the tumor mutation burden in cancers. Significant intra-patient heterogeneity in SNVs and CNVs were found. We identified the SNV subclonal architecture in each tumor. To study the heterogeneity of CNVs, the single cells were sequenced. The number of subclones in the primary tumor was larger than that in lymph nodes, indicating the heterogeneity of primary site was higher. We observed two patterns of multi-station lymph node metastasis: one was skip metastasis and the other was to follow the lymphatic drainage. Taken together, our single cell genomic analysis has revealed the heterogeneity and clonal evolution in GEJ cancer.
胃食管交界（GEJ）癌是一种发生在胃和食管解剖学交界处的肿瘤。GEJ癌常转移至淋巴结，但其异质性和克隆进化过程尚不清楚。本研究首次使用单细胞DNA测序来确定与淋巴结转移相关的基因组变异和克隆进化。分别采用多次退火环状循环扩增法（MALBAC）和外显子组测序检测单细胞拷贝数变异（CNV）和单核苷酸变异（SNV）。纳入了4例GEJ癌患者，其中2例（患者3、患者4）有转移性淋巴结。我们发现最常见的突变发生在TTN基因，据报道该基因与癌症中的肿瘤突变负荷有关。在SNV和CNV中发现了显著的患者内异质性。我们在每个肿瘤中鉴定了SNV亚克隆结构。为研究CNV的异质性，对单细胞进行了测序。原发肿瘤中的亚克隆数量多于淋巴结中的亚克隆数量，表明原发部位的异质性更高。我们观察到两种多站淋巴结转移模式：一种是跳跃转移，另一种是沿淋巴引流转移。综上所述，我们的单细胞基因组分析揭示了GEJ癌的异质性和克隆进化。
