Background
In the majority of familial breast cancer (BC) families, the etiology of the disease remains unresolved. To identify missing BC heritability resulting from relatively rare variants (minor allele frequency ≤ 1%), we have performed whole exome sequencing followed by variant analysis in a virtual panel of 492 cancer-associated genes on BC patients from
BRCA1
and
BRCA2
negative families with elevated BC risk.
Methods
BC patients from 54
BRCA1
and
BRCA2
-negative families with elevated BC risk and 120 matched controls were considered for germline DNA whole exome sequencing. Rare variants identified in the exome and in a virtual panel of cancer-associated genes [492 genes associated with different types of (hereditary) cancer] were compared between BC patients and controls. Nonsense, frame-shift indels and splice-site variants (strong protein-damaging variants, called PDAVs later on) observed in BC patients within the genes of the panel, which we estimated to possess the highest probability to predispose to BC, were further validated using an alternative sequencing procedure.
Results
Exome- and cancer-associated gene panel-wide variant analysis show that there is no significant difference in the average number of rare variants found in BC patients compared to controls. However, the genes in the cancer-associated gene panel with nonsense variants were more than two-fold over-represented in women with BC and commonly involved in the DNA double-strand break repair process. Approximately 44% (24 of 54) of BC patients harbored 31 PDAVs, of which 11 were novel. These variants were found in genes associated with known or suspected BC predisposition (
PALB2, BARD1, CHEK2, RAD51C
and
FANCA
) or in predisposing genes linked to other cancer types but not well-studied in the context of familial BC (
EXO1, RECQL4, CCNH, MUS81, TDP1, DCLRE1A, DCLRE1C, PDE11A
and
RINT1
) and genes associated with different hereditary syndromes but not yet clearly associated with familial cancer syndromes (
ABCC11, BBS10, CD96, CYP1A1, DHCR7, DNAH11, ESCO2, FLT4, HPS6, MYH8, NME8
and
TTC8
). Exome-wide, only a few genes appeared to be enriched for PDAVs in the familial BC patients compared to controls.
Conclusions
We have identified a series of novel candidate BC predisposition variants/genes. These variants/genes should be further investigated in larger cohorts/case-control studies. Other studies including co-segregation analyses in affected families, locus-specific loss of heterozygosity and functional studies should shed further light on their relevance for BC risk.
Electronic supplementary material
The online version of this article (10.1186...
