Allelic Imbalance and Chromothripsis Lead to Diversity in Japanese Tumor Genomes With Whole‐Genome Duplication

ABSTRACT

Whole‐genome analyses have revealed that large‐scale structural variations (SVs) such as whole‐genome duplication (WGD) occur early in the development of many cancers. However, the diversity of chromosomal abnormalities within tumors before and after WGD remains poorly understood. Here, we analyzed various types of Japanese tumor genomes via whole‐genome sequencing and examined the diversity of WGD by focusing on large SVs at the chromosomal level. WGD was detected in 52% of cases, while the frequency of chromothripsis (CT) was 20%. Although aneuploidy via deletion of chromosome arms was common in many cancers, in rare ovarian cancers, all chromosomes were near‐haploidy before WGD. Minor allele analysis revealed that many non‐mutated ohnolog genes drifted down chromosome arms after WGD and returned to normal ploidy, but only 17p, including TP53, which is also an ohnolog, underwent loss of heterozygosity due to arm deletion before WGD in most cancers. TP53 mutations were frequently detected in WGD and CT‐positive tumors, and these SVs strongly correlated with homologous recombination deficiency scores. Furthermore, these tumors had many mutations that continued to generate neoantigens and resulted in worse survival outcomes. Diversity analysis of tumors with WGD will provide a new perspective on structural abnormalities in tumor genomes.