Rare key functional domain missense substitutions in MRE11A, RAD50, and NBNcontribute to breast cancer susceptibility: results from a Breast Cancer Family Registry case-control mutation-screening study

Abstract

IntroductionThe MRE11A-RAD50-Nibrin (MRN) complex plays several critical roles related to repair of DNA double-strand breaks. Inherited mutations in the three components predispose to genetic instability disorders and the MRN genes have been implicated in breast cancer susceptibility, but the underlying data are not entirely convincing. Here, we address two related questions: (1) are some rare MRN variants intermediate-risk breast cancer susceptibility alleles, and if so (2) do the MRN genes follow a BRCA1/BRCA2 pattern wherein most susceptibility alleles are protein-truncating variants, or do they follow an ATM/CHEK2 pattern wherein half or more of the susceptibility alleles are missense substitutions?MethodsUsing high-resolution melt curve analysis followed by Sanger sequencing, we mutation screened the coding exons and proximal splice junction regions of the MRN genes in 1,313 early-onset breast cancer cases and 1,123 population controls. Rare variants in the three genes were pooled using bioinformatics methods similar to those previously applied to ATM, BRCA1, BRCA2, and CHEK2, and then assessed by logistic regression.ResultsRe-analysis of our ATM, BRCA1, and BRCA2 mutation screening data revealed that these genes do not harbor pathogenic alleles (other than modest-risk SNPs) with minor allele frequencies >0.1% in Caucasian Americans, African Americans, or East Asians. Limiting our MRN analyses to variants with allele frequencies of <0.1% and combining protein-truncating variants, likely spliceogenic variants, and key functional domain rare missense substitutions, we found significant evidence that the MRN genes are indeed intermediate-risk breast cancer susceptibility genes (odds ratio (OR) = 2.88, P = 0.0090). Key domain missense substitutions were more frequent than the truncating variants (24 versus 12 observations) and conferred a slightly higher OR (3.07 versus 2.61) with a lower P value (0.029 versus 0.14).ConclusionsThese data establish that MRE11A, RAD50, and NBN are intermediate-risk breast cancer susceptibility genes. Like ATM and CHEK2, their spectrum of pathogenic variants includes a relatively high proportion of missense substitutions. However, the data neither establish whether variants in each of the three genes are best evaluated under the same analysis model nor achieve clinically actionable classification of individual variants observed in this study.

No evidence that protein truncating variants inBRIP1are associated with breast cancer risk: implications for gene panel testing

“…The laboratory process has been described in detail for our recent studies of ATM, 22 CHEK2, 23 XRCC2, 24 RAD51, 25 RINT1 26 and MRN genes 27. The semi-automated approach relies on mutation scanning by high-resolution melt curve (HRM) analysis followed by direct Sanger sequencing of the individual samples for which an aberrant melt curve profile is indicative of the presence of a sequence variant.…”

Gene-Panel Sequencing and the Prediction of Breast-Cancer Risk

“…34 More limited evidence is available for two other DNA-repair genes, MRE11A and RAD50 , which encode proteins that form an evolutionarily conserved complex with NBN . 43–48 …”

Molecular Biology In Young Women With Breast Cancer: From Tumor Gene Expression To Dna Mutations

“…Deleterious mutations have been identified in all three genes of the MRN complex. The study done by Damiola et al, which included 1313 women < 45 years old with BC, found that rare MRN gene variants significantly contribute to early-onset BC susceptibility 112 . NBN has the strongest evidence of acting as a BC risk gene 113,114 .…”