title: The mutational burdens and evolutionary ages of early gastric cancers are comparable to those of advanced gastric cancers.
abstract: Early gastric cancers (EGCs) precede advanced gastric cancers (AGCs), with a favourable prognosis compared to AGC. To understand the progression mechanism of EGC to AGC, it is required to disclose EGC and AGC genomes in mutational and evolutionary perspectives. We performed whole-exome sequencing and copy number profiling of nine microsatellite (MS)-unstable (MSI-H) (five EGCs and four AGCs) and eight MS-stable (MSS) gastric cancers (four EGCs and four AGCs). In the cancers, we observed well-known driver mutations (TP53, APC, PIK3CA, ARID1A, and KRAS) that were enriched in cancer-related pathways, including chromatin remodelling and tyrosine kinase activity. The MSI-H genomes harboured ten times more mutations, but were largely depleted of copy number alterations (CNAs) compared to the MSS cancers. Interestingly, EGC genomes showed a comparable level of mutations to AGC in terms of the number, sequence composition, and functional consequences (potential driver mutations and affected pathways) of mutations. Furthermore, the CNAs between EGC and AGC genomes were not significantly different in either MSI-H and MSS. Evolutionary analyses using somatic mutations and MSI as molecular clocks further identified that EGC genomes were as old as AGC genomes in both MSS and MSI-H cancers. Our results suggest that the genetic makeup for gastric cancer may already be achieved in EGC genomes and that the time required for transition to AGC may be relatively short. Also, the data suggest a possibility that the mutational profiles obtained from early biopsies may be useful in the clinical settings for the molecular diagnosis and therapeutics of gastric cancer patients.
authors.affiliation: Department of Medical Informatics, College of Medicine, The Catholic University of Korea, Seoul, 137-701, Republic of Korea.
authors.forename: Tae-Min
authors.initials: TM
authors.lastname: Kim
authors.forename: Seung-Hyun
authors.initials: SH
authors.lastname: Jung
authors.forename: Min Sung
authors.initials: MS
authors.lastname: Kim
authors.forename: In-Pyo
authors.initials: IP
authors.lastname: Baek
authors.forename: Sung-Won
authors.initials: SW
authors.lastname: Park
authors.forename: Sung Hak
authors.initials: SH
authors.lastname: Lee
authors.forename: Han Hong
authors.initials: HH
authors.lastname: Lee
authors.forename: Sung Soo
authors.initials: SS
authors.lastname: Kim
authors.forename: Yeun-Jun
authors.initials: YJ
authors.lastname: Chung
authors.forename: Sug Hyung
authors.initials: SH
authors.lastname: Lee
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D000368:Aged; D004252:DNA Mutational Analysis; D018450:Disease Progression; D005260:Female; D018628:Gene Dosage; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology*
keywords: cancer progression; gastric cancer; microsatellite instability; mutations