Early and advanced gastric cancer genomes

Early gastric cancers (EGC) precede advanced gastric cancers (AGC) with a favorable clinical outcome compared to advanced gastric cancers (AGC). To understand the progression mechanisms of EGC to AGC, it is required to disclose the EGC and AGC genomes in terms of the the mutational and evolutionary perspectives. In this study, we performed whole-exome sequencing and copy number profiling of nine microsatellite (MS)-unstable (MSI-H) (5 EGC and 4 AGC) and eight MS-stable (MSS) gastric cancers (4 EGC and 4 AGC). Unexpectedly, we observed no substantial differences in the number, sequence composition and functional consequences (potential driver mutations and affected pathways) of the mutations and CNAs between EGC and AGC genomes in both MSI-H and MSS cases. Gastrectomy tissues from 17 GC patients were used for this study. The hospital pathology department confirmed pathologic features of the GC (e.g., EGC vs. AGC, differentiation, lymph node metastasis and TNM stage). All of the picked areas from tumor and normal areas were frozen, cut, and stained with hematoxylin & eosin (H&E). Two pathologists selected cases with rich tumor cell population (at least 60%), which were subsequently used in the study. Copy number profiling was performed using Agilent 180K platform according to the manufacturer's protocol.