Mutational landscape of gastric adenocarcinoma in Chinese: Implications for prognosis and therapy
Proceedings of the National Academy of Sciences of the United States of America
Gastric cancer (GC) is a highly heterogeneous disease. To identify potential clinically actionable therapeutic targets that may inform individualized treatment strategies, we performed whole-exome sequencing on 78 GCs of differing histologies and anatomic locations, as well as whole-genome sequencing on two GC cases, each with three primary tumors and two matching lymph node metastases. The data showed two distinct GC subtypes with either high-clonality (HiC) or low-clonality (LoC). The HiC
... ype of intratumoral heterogeneity was associated with older age, TP53 (tumor protein P53) mutation, enriched C > G transition, and significantly shorter survival, whereas the LoC subtype was associated with younger age, ARID1A (AT rich interactive domain 1A) mutation, and significantly longer survival. Phylogenetic tree analysis of whole-genome sequencing data from multiple samples of two patients supported the clonal evolution of GC metastasis and revealed the accumulation of genetic defects that necessitate combination therapeutics. The most recurrently mutated genes, which were validated in a separate cohort of 216 cases by targeted sequencing, were members of the homologous recombination DNA repair, Wnt, and PI3K-ERBB pathways. Notably, the drugable NRG1 (neuregulin-1) and ERBB4 (V-Erb-B2 avian erythroblastic leukemia viral oncogene homolog 4) ligand-receptor pair were mutated in 10% of GC cases. Mutations of the BRCA2 (breast cancer 2, early onset) gene, found in 8% of our cohort and validated in The Cancer Genome Atlas GC cohort, were associated with significantly longer survivals. These data define distinct clinicogenetic forms of GC in the Chinese population that are characterized by specific mutation sets that can be investigated for efficacy of single and combination therapies. clonality | exome sequencing | mutation | ERBB | BRCA2 G astric cancer (GC) is the fourth most common cancer and the second leading cause of cancer death worldwide, accounting for 8% of all newly diagnosed cancers and 10% of cancer mortality(1). Environmental risk factors for GC include a high-salt diet, smoking, and infectious agents (1), including the bacterium Helicobacter pylori (2), and Epstein Barr Virus (3). Consistent with its complicated etiology (e.g., diet) and anatomical environment, GC is clinically and pathologically highly heterogeneous (4), with a large variation in 5-y survival rates in different countries, and even different cities in the same country (5, 6). This clinical heterogeneity is mirrored by concomitant heterogeneous molecular signatures in GC mRNA, protein, and miRNA expression profiles (7, 8) . Standard treatment strategies have largely ignored the heterogeneity and individuality of different subtypes of GC. The current approach entails surgical removal of the tumor followed by adjuvant fluoropyrimidine, taxane, and platinum-based chemotherapy doublets or triplets, especially for advanced GC, and this is exacerbated by the lack of reliable markers to predict response. Recently, the US Food and Drug Administration and the European Medicines Agency have approved Trastuzumab for patients with HER2-overexpressing metastatic GC, which represent less than 15% of the disease population. The high incidence of GC in Asian countries and its increasing incidence in Western countries point to a clear need for developing more effective therapies for GC as well as the discovery of markers that predict their therapeutic response. Genome sequencing has emerged as a powerful tool to identify potential driving oncogenic targets for therapeutic intervention. Wang et al. sequenced 22 samples from Hong Kong GC patients and identified mutations in genes involved in chromatin modification Significance We have identified a lethal subtype of gastric cancer (GC) that is characterized by high levels of clonal heterogeneity and TP53 (tumor protein P53) mutation. We have also uncovered key novel mutations in the targetable NRG1 (neuregulin-1) and ERBB4 (V-Erb-B2 avian erythroblastic leukemia viral oncogene homolog 4) ligand-receptor pair and identified BRCA2 (breast cancer 2, early onset) mutations as new genetic markers to predict better survival for GC. Our study represents a novel approach for GC personalized medicine and identified novel clinical actionable therapies for GC therapy.