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Concordance between somatic copy number loss and down-regulated expression: A pan-cancer study of cancer predisposition genes.

ABSTRACT: Cancer predisposition genes (CPGs) are a class of cancer genes in which germline variants lead to increased risk of cancer. Research has revealed that copy number variation (CNV) may be linked to cancer susceptibility in CPGs. In this pan-cancer analysis, we explored the relationship between somatic CNV and gene expression changes in CPGs. Based on curated 827 human CPGs from literature, we firstly identified 729 CPGs with precise CNV information from 5067 tumor samples using TCGA CNV data. Among them, 128 CPGs tended to have more frequent copy number losses (CNLs) compared with copy number gains (CNGs). Then by correlating these CNV data with TCGA gene expression data, we obtained 49 CPGs with concordant CNLs and gene down-regulation. Intriguingly, five CPGs showed concordance between CNL and down-regulation in 50 or more tumor samples: MTAP (216 samples), PTEN (143), MCPH1 (86), SMAD4 (63), and MINPP1 (51), which may represent the recurrent driving force for gene expression change during oncogenesis. Moreover, network analysis revealed that these 49 CPGs were tightly connected. In summary, this study provides the first observation of concordance between CNLs and down-regulation of CPGs in pan-cancer, which may help better understand the CPG biology in tumorigenesis and cancer progression.

SUBMITTER: Wei R

PROVIDER: S-EPMC5144096 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Somatic mosaicism denotes the presence of genetically distinct populations of somatic cells in one individual who has developed from a single fertilised oocyte. Mosaicism may result from a mutation that occurs during postzygotic development and is propagated to only a subset of the adult cells. Our aim was to investigate both somatic mosaicism for copy-neutral loss of heterozygosity (cn-LOH) events and DNA copy number variations (CNVs) in fully differentiated tissues.We studied panels of tissue samples (11-12 tissues per individual) from four autopsy subjects using high-resolution Illumina HumanOmniExpress-12 BeadChips to reveal the presence of possible intra-individual tissue-specific cn-LOH and CNV patterns. We detected five mosaic cn-LOH regions >5 Mb in some tissue samples in three out of four individuals. We also detected three CNVs that affected only a portion of the tissues studied in one out of four individuals. These three somatic CNVs range from 123 to 796 kb and are also found in the general population. An attempt was made to explain the succession of genomic events that led to the observed somatic genetic mosaicism under the assumption that the specific mosaic patterns of CNV and cn-LOH changes reflect their formation during the postzygotic embryonic development of germinal layers and organ systems.Our results give further support to the idea that somatic mosaicism for CNVs, and also cn-LOHs, is a common phenomenon in phenotypically normal humans. Thus, the examination of only a single tissue might not provide enough information to diagnose potentially deleterious CNVs within an individual. During routine CNV and cn-LOH analysis, DNA derived from a buccal swab can be used in addition to blood DNA to get information about the CNV/cn-LOH content in tissues of both mesodermal and ectodermal origin. Currently, the real frequency and possible phenotypic consequences of both CNVs and cn-LOHs that display somatic mosaicism remain largely unknown. To answer these questions, future studies should involve larger cohorts of individuals and a range of tissues.

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Concordance between somatic copy number loss and down-regulated expression: A pan-cancer study of cancer predisposition genes.

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