Identification and Functional Testing of ERCC2 Mutations in a Multi-national Cohort of Patients with Familial Breast- and Ovarian Cancer

Abstract

The increasing application of gene panels for familial cancer susceptibility disorders will probably lead to an increased proposal of susceptibility gene candidates. Using ERCC2 DNA repair gene as an example, we show that proof of a possible role in cancer susceptibility requires a detailed dissection and characterization of the underlying mutations for genes with diverse cellular functions (in this case mainly DNA repair and basic cellular transcription). In case of ERCC2, panel sequencing of 1345 index cases from 587 German, 405 Lithuanian and 353 Czech families with breast and ovarian cancer (BC/OC) predisposition revealed 25 mutations (3 frameshift, 2 splice-affecting, 20 missense), all absent or very rare in the ExAC database. While 16 mutations were unique, 9 mutations showed up repeatedly with population-specific appearance. Ten out of eleven mutations that were tested exemplarily in cell-based functional assays exert diminished excision repair efficiency and/or decreased transcriptional activation capability. In order to provide evidence for BC/OC predisposition, we performed familial segregation analyses and screened ethnically matching controls. However, unlike the recently published RECQL example, none of our recurrent ERCC2 mutations showed convincing co-segregation with BC/OC or significant overrepresentation in the BC/OC cohort. Interestingly, we detected that some deleterious founder mutations had an unexpectedly high frequency of > 1% in the corresponding populations, suggesting that either homozygous carriers are not clinically recognized or homozygosity for these mutations is embryonically lethal. In conclusion, we provide a useful resource on the mutational landscape of ERCC2 mutations in hereditary BC/OC patients and, as our key finding, we demonstrate the complexity of correct interpretation for the discovery of “bonafide” breast cancer susceptibility genes.

Targeted capture-based NGS is superior to multiplex PCR-based NGS for hereditary BRCA1 and BRCA2 gene analysis in FFPE tumor samples

“…Additionally, the drug is currently being tested in several clinical trials in different tumor entities with underlying mutations in BRCA1/2 and other genes involved in DDR. Therefore reliable diagnostic tests for the detection of BRCA1/2 mutations and variants in other genes involved in DDR in tumor tissues are crucial for treatment decision making [1,7,8].…”

“…Families with a high risk for HBOC are commonly tested for BRCA1 and BRCA2 germline variants by next-generation sequencing (NGS) complemented by array CGH or MLPA for copy number variation (CNV) detection using blood samples, saliva samples, or buccal smear in order to obtain high-quality DNA [1,[7][8][9]. Even in HBOC-families, however, tumor analysis can be necessary, e.g.…”

Risks of Solid Tumors in Heterozygous Carriers of Recessive Syndromes

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