Some common mutations of RAD50 and NBS1 in western populations do not contribute significantly to Chinese non-BRCA1/2 hereditary breast cancer

Familial/inherited cancer syndrome: a focus on the highly consanguineous Arab population

The study of hereditary cancer, which accounts for ~10% of cancer cases worldwide is an important subfield of oncology. Our understanding of hereditary cancers has greatly advanced with recent advances in sequencing technology, but as with any genetic trait, gene frequencies of cancer-associated mutations vary across populations, and most studies that have located hereditary cancer genes have been conducted on European or Asian populations. There is an urgent need to trace hereditary cancer genes across the Arab world. Hereditary disease is particularly prevalent among members of consanguineous populations, and consanguineous marriages are particularly common in the Arab world. There are also cultural and educational idiosyncrasies that differentiate Arab populations from other more thoroughly studied groups with respect to cancer awareness and treatment. Therefore, a review of the literature on hereditary cancers in this understudied population was undertaken. We report that BRCA mutations are not as prevalent among Arab breast cancer patients as they are among other ethnic groups, and therefore, other genes may play a more important role. A wide variety of germline inherited mutations that are associated with cancer are discussed, with particular attention to breast, ovarian, colorectal, prostate, and brain cancers. Finally, we describe the state of the profession of familial cancer genetic counselling in the Arab world, and the clinics and societies dedicated to its advances. We describe the complexities of genetic counselling that are specific to the Arab world. Understanding hereditary cancer is heavily dependent on understanding population-specific variations in cancer-associated gene frequencies.

Association of Single-Nucleotide Polymorphisms in Monoubiquitinated FANCD2-DNA Damage Repair Pathway Genes With Breast Cancer in the Chinese Population

Objective:

The aim of the study was to estimate breast cancer risk conferred by individual single-nucleotide polymorphisms of breast cancer susceptibility genes.

Methods:

We analyzed the 48 tagging single-nucleotide polymorphisms of 8 breast cancer susceptibility genes involved in the monoubiquitinated FANCD2–DNA damage repair pathway in 734 Chinese women with breast cancer and 672 age-matched healthy controls.

Results:

Forty-five tagging single-nucleotide polymorphisms were successfully genotyped by SNPscan, and the call rates for each tagging single-nucleotide polymorphisms were above 98.9%. We found that 13 tagging single-nucleotide polymorphisms of 5 genes (Parter and localizer of Breast cancer gene2 (PALB2), Tumour protein 53 (TP53), Nijmegen breakage syndrome 1, Phosphatase and tensin homolog deleted from chromosome 10 (PTEN), and Breast cancer gene 1 (BRCA1-interacting protein 1)) were significantly associated with breast cancer risk. A total of 5 tagging single-nucleotide polymorphisms (rs2299941 of PTEN, rs2735385, rs6999227, rs1805812, and rs1061302 of Nijmegen breakage syndrome 1) were tightly associated with breast cancer risk in sporadic cases, and 5 other tagging single-nucleotide polymorphisms (rs1042522 of TP53, rs2735343 of PTEN, rs7220719, rs16945628, and rs11871753 of BRCA1-interacting protein 1) were tightly associated with breast cancer risk in familial and early-onset cases.

Conclusions:

Some of the tagging single-nucleotide polymorphisms of 5 genes (PALB2, TP53, Nijmegen breakage syndrome 1, PTEN, and BRCA1-interacting protein 1) involved in the monoubiquitinated FANCD2–DNA damage repair pathway were significantly associated with breast cancer risk.

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.

Heterozygous germline mutations in NBS1 among Korean patients with high-risk breast cancer negative for BRCA1/2 mutation

The purpose of the present study was to analyze genetic variations in the NBS1 gene and to evaluate the contribution of heterozygous NBS1 mutation to the risk of breast cancer among Korean patients with high-risk breast cancer negative for BRCA1/2 mutation. We screened 235 non-BRCA1/2 Korean patients with high-risk breast cancer for NBS1 mutations. The entire NBS1 gene was sequenced using fluorescent conformation-sensitive capillary electrophoresis. In silico analysis of the NBS1 variants was performed using PolyPhen-2 and SIFT. The frequency of variants predicted to be deleterious by in silico analysis was compared between breast cancer patients and controls. Twenty-eight sequence variants in the NBS1 gene were identified: 9 exonic variants, including 5 missense mutations (p.R169C, p.I171V, p.E185Q, p.E564K, and p.F603L) and 4 silent mutations, and 19 variants within introns. Among the five missense variants, p.I171V (c.511A > G) was the only variant predicted to be deleterious by in silico analysis. Heterozygosity for p.I171V was found in 4/235 patients with breast cancer and 3/281 individuals in the control group. The frequency of p.I171V was not significantly different between the patient and control groups (1.7 vs. 1.06%, p = 0.7). Heterozygosity of p.I171V in the NBS1 gene was found in a small proportion of Korean patients with high-risk breast cancer. The contribution of the p.I171V variant to the development of breast cancer among Korean patients was not significant.

Functional variants in NBS1 and cancer risk: evidence from a meta-analysis of 60 publications with 111 individual studies

Several potentially functional variants of Nijmegen breakage syndrome 1 (NBS1) have been implicated in cancer risk, but individually studies showed inconclusive results. In this study, a meta-analysis based on 60 publications with a total of 39 731 cancer cases and 64 957 controls was performed. The multivariate method and the model-free method were adopted to determine the best genetic model. It was found that rs2735383 variant genotypes were associated with significantly increased overall risk of cancer under the recessive genetic model [odds ratio (OR) =1.12, 95% confidence interval (CI): 1.02-1.22, P = 0.013]. Similar results were found for rs1063054 under the dominant model effect (OR = 1.12, 95% CI: 1.01-1.23, P = 0.024). The I171V mutation, 657del5 mutation and R215W mutation also contribute to the development of cancer (for I171V, OR = 3.93, 95% CI: 1.68-9.20, P = 0.002; for 657del5, OR = 2.79, 95% CI: 2.17-3.68, P < 0.001; for R215W, OR = 1.77, 95% CI: 1.07-2.91, P = 0.025). From stratification analyses, an effect modification of cancer risks was found in the subgroups of tumour site and ethnicity for rs2735383, whereas the I171V, 657del5 and R215W showed a deleterious effect of cancer susceptibility in the subgroups of tumour site. However, rs1805794, D95N and P266L did not appear to have an effect on cancer risk. These results suggest that rs2735383, rs1063054, I171V, 657del5 and R215W are low-penetrance risk factors for cancer development.

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.

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.