Rad50 c.687delT does not contribute significantly to familial breast cancer in a French population

Importance of Germline and Somatic Alterations in Human MRE11, RAD50, and NBN Genes Coding for MRN Complex

The MRE11, RAD50, and NBN genes encode for the nuclear MRN protein complex, which senses the DNA double strand breaks and initiates the DNA repair. The MRN complex also participates in the activation of ATM kinase, which coordinates DNA repair with the p53-dependent cell cycle checkpoint arrest. Carriers of homozygous germline pathogenic variants in the MRN complex genes or compound heterozygotes develop phenotypically distinct rare autosomal recessive syndromes characterized by chromosomal instability and neurological symptoms. Heterozygous germline alterations in the MRN complex genes have been associated with a poorly-specified predisposition to various cancer types. Somatic alterations in the MRN complex genes may represent valuable predictive and prognostic biomarkers in cancer patients. MRN complex genes have been targeted in several next-generation sequencing panels for cancer and neurological disorders, but interpretation of the identified alterations is challenging due to the complexity of MRN complex function in the DNA damage response. In this review, we outline the structural characteristics of the MRE11, RAD50 and NBN proteins, the assembly and functions of the MRN complex from the perspective of clinical interpretation of germline and somatic alterations in the MRE11, RAD50 and NBN genes.

RAD50 germline mutations are associated with poor survival in BRCA1/2-negative breast cancer patients

RAD50 is a highly conserved DNA double-strand break (DSB) repair gene. However, the associations between RAD50 germline mutations and the survival and risk of breast cancer have not been fully elucidated. Here, we aimed to investigate the clinical impact of RAD50 germline mutations in a large cohort of unselected breast cancer patients. In our study, RAD50 germline mutations were determined using next-generation sequencing in 7657 consecutive unselected breast cancer patients without BRCA1/2 mutations. We also screened for RAD50 recurrent mutations (L719fs, K994fs, and H1269fs) in 5000 healthy controls using Sanger sequencing. We found that 26 out of 7,657 (0.34%) patients had RAD50 pathogenic mutations, and 16 patients carried one of the three recurrent mutations (L719fs, n = 6 cases; K994fs, n = 5 cases; and H1269fs, n = 5 cases); the recurrent mutation rate was 0.21%. The frequency of the three recurrent mutations in the 5,000 healthy controls was 0.18% (9/5,000). These mutations did not confer an increased risk of breast cancer in the studied patients [odds ratios (OR), 1.16; 95% confidence interval (CI), 0.51-2.63; p = 0.72]. Nevertheless, multivariate analysis revealed that RAD50 pathogenic mutations were an independent unfavourable predictor of recurrence-free survival (RFS) [adjusted hazard ratio (HR) 2.66; 95% CI, 1.18-5.98; p = 0.018] and disease-specific survival (DSS; adjusted HR 4.36; 95% CI, 1.58-12.03; p = 0.004) in the entire study cohort. Our study suggested that RAD50 germline mutations are not associated with an increased risk of breast cancer, but patients with RAD50 germline mutations have unfavourable survival compared to patients without these mutations.

Frequency of pathogenic germline mutation in CHEK2, PALB2, MRE11, and RAD50 in patients at high risk for hereditary breast cancer

PURPOSE

This study was performed to evaluate the frequency of mutations in CHEK2, PALB2, MRE11, and RAD50 among Korean patients at high risk for hereditary breast cancer.

METHODS

A total of 235 Korean patients with hereditary breast cancer who tested negative for BRCA1/2 mutation were enrolled to this study. Entire coding regions of CHEK2, PALB2, MRE11, and RAD50 were analyzed using massively parallel sequencing (MPS). Sequence variants detected by MPS were confirmed by Sanger sequencing.

RESULTS

Six patients (2.5 %) were found to have pathogenic variants in CHEK2 (n = 1), PALB2 (n = 2), MRE11 (n = 1), and RAD50 (n = 2). Among the pathogenic variants, PALB2 c.2257C>T was previously reported in other studies, while CHEK2 c.1245dupC, PALB2 c.1048C>T, MRE11 c.1773_1774delAA, RAD50 c.1276C>T, and RAD50 c.3811_3813delGAA were newly identified in this study. A total of 15 missense variants were found in the four genes among 26 patients; 7 patients had a variant in CHEK2, 11 in PALB2, 2 in MRE11, and 6 in RAD50. When in silico analyses were performed to the 15 missense variants, six variants (CHEK2 c.686A>G, PALB2 c.1492G>T, PALB2 c.3054G>C, MRE11 c.140C>T, RAD50 c.1456C>T, and RAD50 c.3790C>T) were predicted to be deleterious.

CONCLUSIONS

Pathogenic variants in CHEK2, PALB2, MRE11, and RAD50 were detected in a small proportion of Korean patients with features of hereditary breast cancer.

Germline variants in MRE11/RAD50/NBN complex genes in childhood leukemia

BACKGROUND

The MRE11, RAD50, and NBN genes encode proteins of the MRE11-RAD50-NBN (MRN) complex involved in cellular response to DNA damage and the maintenance of genome stability. In our previous study we showed that the germline p.I171V mutation in NBN may be considered as a risk factor in the development of childhood acute lymphoblastic leukemia (ALL) and some specific haplotypes of that gene may be associated with childhood leukemia. These findings raise important questions about the role of mutations in others genes of the MRN complex in childhood leukemia. The aim of this study was to answer the question whether MRE11 and RAD50 alterations may be associated with childhood ALL or AML.

METHODS

We estimated the frequency of constitutional mutations and polymorphisms in selected regions of MRE11, RAD50, and NBN in the group of 220 children diagnosed with childhood leukemias and controls (n=504/2200). The analysis was performed by specific amplification of region of interest by PCR and followed by multi-temperature single-strand conformation polymorphism (PCR-MSSCP) technique. We performed two molecular tests to examine any potential function of the detected the c.551+19G>A SNP in RAD50 gene. To our knowledge, this is the first analysis of the MRE11, RAD50 and NBN genes in childhood leukemia.

RESULTS

The frequency of either the AA genotype or A allele of RAD50_rs17166050 were significantly different in controls compared to leukemia group (ALL+AML) (p<0.0019 and p<0.0019, respectively). The cDNA analysis of AA or GA genotypes carriers has not revealed evidence of splicing abnormality of RAD50 pre-mRNA. We measured the allelic-specific expression of G and A alleles at c.551+19G>A and the statistically significant overexpression of the G allele has been observed. Additionally we confirmed the higher incidence of the p.I171V mutation in the leukemia group (7/220) than among controls (12/2400) (p<0.0001).

CONCLUSION

The formerly reported sequence variants in the RAD50 and MRE11 gene may not constitute a risk factor of childhood ALL in Polish population. The RAD50_rs17166050 variant allele is linked to decreased ALL risk (p<0.0009, OR=0.6358 (95%CI: 0.4854-0.8327)). Despite the fact that there is no splicing abnormality in carriers of the variant allele but an excess of the G over the A allele was consistently observed. This data demonstrate that some specific alternations of the RAD50 gene may be associated with childhood ALL.

The MRN protein complex genes: MRE11 and RAD50 and susceptibility to head and neck cancers

BACKGROUND

The members of MRE11/RAD50/NBN (MRN) protein complex participates in DNA double-strand break repair and DNA-damage checkpoint activation. We have previously shown that the p.I171V NBN gene mutation may contribute to the development of laryngeal cancer. This study tested the hypothesis that variants of the MRE11 and RAD50 genes, previously described as cancer risk factors, predispose to increased susceptibility to head and neck cancer.

FINDINGS

In this study we analyzed the RAD50 and MRE11 genes in 358 patients: 175 with a single laryngeal cancer (LC), 115 with multiple primary tumors but one malignancy (primary or second) localized in the larynx (MPT-LC), 68 patients with multiple primary tumors localized in the head or neck (MPT) and 506 controls. No carriers of previously reported mutation in the MRE11 or RAD50 gene (particularly the pathogenic c.687delT) were detected in the present study. We identified the p.V127I variant (2/175 LC, 2/506 controls; OR=2.91; 95% CI 0.41-20.85) and p.V315L variant (2/115 MPT-LC, 1/506 controls; OR=8.96; 95% CI 0.81-99.68) of the RAD50 gene.

CONCLUSIONS

Our data indicated that previously described common genetic variations in the MRE11 and RAD50 genes do not contribute to an increased risk of laryngeal cancer and second primary tumors localized in the head and neck. Prospective studies with larger groups of patients may reveal the possible impact of these genes in tumor occurrence.

The impact of next generation sequencing on the analysis of breast cancer susceptibility: a role for extremely rare genetic variation?

Women with a family history of breast cancer have an approximately twofold elevated risk of the disease. Even though an array of genes has been associated with breast cancer risk the past two decades, variants within these genes jointly explain at most 40% of this familial risk. Many explanations for this 'missing heritability' have been proposed, including the existence of many very rare variants, interactions between genetic and environmental factors and structural genetic variation. In this review, we discuss how next generation sequencing will teach us more about the genetic architecture of breast cancer, with a specific focus on very rare genetic variants. While such variants potentially explain a substantial proportion of familial breast cancer, assessing the breast cancer risks conferred by them remains challenging, even if this risk is relatively high. To assess more moderate risks, epidemiological approaches will require very large patient cohorts to be genotyped for the variant, only achievable through international collaboration. How well we will be able to eventually resolve the missing heritability for breast cancer in a clinically meaningful way crucially depends on the underlying complexity of the genetic architecture.

RAD50 and NBS1 are not likely to be susceptibility genes in Chinese non-BRCA1/2 hereditary breast cancer

Deleterious mutations in several genes that are involved in repair of damage to DNA have been associated with an increased risk of breast cancer. Recent studies have shown sequence variants in two such genes, RAD50 and NBS1, which can be predisposed to breast cancer. The aim of this study is to elucidate the contribution of RAD50 and NBS1 germline mutations to the etiology of non-BRCA1/2 hereditary breast cancer in China. We conducted a mutational analysis of RAD50 and NBS1 in genomic DNA from 384 Chinese women with early-onset breast cancer and/or affected relatives. All the coding exons and adjacent intronic splice junction rejoins of RAD50 and NBS1 were screened using PCR-DHPLC and DNA sequencing analysis. Among all cases, no obviously deleterious mutations were observed in RAD50; one synonymous change c.102G>A at codon 34 and one single nucleotide polymorphism IVS9 + 19C>T were identified in NBS1. Furthermore, there was no remarkable difference in the allele frequency of NBS1 c.553G>C (E185Q) between cases (172/384) and controls (182/420). Our results exclude the possible role of RAD50 and NBS1 in familial breast cancer predisposition in Chinese women, and there is no evidence for the recommendation of RAD50 and NBS1 for genetic testing in China.