BRCA1/BRCA2 founder mutations and cancer risks: impact in the western Danish population

Germline variants profiling of BRCA1 and BRCA2 in Chinese Hakka breast and ovarian cancer patients

Objective

To investigate the prevalence and spectrum of BRCA1 and BRCA2 mutations in Chinese Hakka patients with breast and ovarian cancer.

Methods

A total of 1,664 breast or ovarian cancer patients were enrolled for genetic testing at our hospital. Germline mutations of the BRCA gene were analysed by next-generation sequencing, including the coding regions and exon intron boundary regions.

Results

The 1,664 patients included 1,415 (85.04%) breast cancer patients and 245 (14.72%) ovarian cancer patients, while four (0.24%) patients had both the breast and ovarian cancers. A total of 151 variants, including 71 BRCA1 variants and 80 BRCA2 variants, were detected in the 234 (14.06%) patients. The 151 variants included 58 pathogenic variants, 8 likely pathogenic variants, and 85 variants of unknown significance (VUS). A total of 56.25% (18/32) and 65.38% (17/26) of pathogenic variants (likely pathogenic variants are not included) were distributed in exon 14 of BRCA1 and exon 11 of BRCA2, respectively. The most common pathogenic variants among this Hakka population are c.2635G > T (p.Glu879*) (n = 7) in the BRCA1 gene and c.5164_5165del (p.Ser1722Tyrfs*4) (n = 7) in the BRCA2 gene among the Hakka population. A hotspot mutation in the Chinese population, the BRCA1 c.5470_5477del variant was not found in this Hakka population. The prevalence and spectrum of variants in the BRCA genes in the Hakka patients are different from that in other ethnic groups.

Conclusions

The most common pathogenic variant in this population is c.2635G > T in the BRCA1 gene, and c.5164_5165delAG in the BRCA2 gene in this population. The prevalence and spectrum of variants in the BRCA1 and BRCA2 genes in the Hakka patients from southern China are different from those in other ethnic groups.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09943-0.

The Features of BRCA1 and BRCA2 Germline Mutations in Hakka Ovarian Cancer Patients: BRCA1 C.536 A>T Maybe a Founder Mutation in This Population

Objective

To investigate the frequencies of BRCA1 and BRCA2 mutations in Chinese Hakka patients with ovarian cancer.

Methods

The protein coding regions and exon intron boundary regions of the BRCA gene were sequenced using genomic DNA isolated from the lymphocytes of patients with next-generation sequencing. The patients’ family history and clinical records were collected.

Results

A total of 195 patients with ovarian cancer were included in the study, and 52 distinct variants of the BRCA gene were identified. It was found that 64 patients (64/195, 32.8%) had BRCA gene mutations, including 32 patients (50.0%) with BRCA1 mutation, 27 patients (42.2%) with BRCA2 mutation, and 5 patients (7.8%) with both mutations. Furthermore, 22 pathogenic mutations were detected in 26 patients, 2 likely pathogenic variants in 2 patients, 12 variants of uncertain significance in 20 patients, and 16 likely benign variants in 24 patients. The mutations were mainly found to occur in exons 8, 14, and 17 of BRCA1 and exons 10, 11, 14, and 15 of BRCA2. The results showed that the BRCA genes possess different mutation hotspots in different ethnic groups. In addition, recurrent mutations were noted in many patients. BRCA1 c.536 A>T, considered a founder mutation, was identified in 10 patients (15.63%, 10/64), followed by BRCA1 c.2635 G>T (6.25%, 4/64) and BRCA2 c.2566 T>C (6.25%, 4/64).

Conclusion

The BRCA1 c.536 A>T could be considered to be a founder mutation in this ovarian cancer population. This recurrent BRCA1 mutation has rarely been observed in other ethnic groups. Our findings are expected to provide valuable data for clinical consultation and for designing individualized treatment for ovarian cancer.

BRCA1 and VDR gene polymorphisms are associated with prostate cancer risk in Mexican men

Prostate cancer (PC) is a polygenic disease with broad differences across ethnicities. BRCA1/2 and VDR have exhibited a featured genetic contribution to PC development in European populations. Nonetheless, its contribution in Latino populations specifically among Mexican men, where 70% of PC cases are detected in advanced stages, is still unknown. The contribution of seven polymorphisms in BRCA1/2 and VDR genes to PC susceptibility was evaluated in 370 incident PC cases and 759 age-matched (±5 years) controls belonging to the Mexican population. Based on Gleason score at diagnosis, PC cases were classified as well-differentiated PC (Gleason <7) and moderate or poorly differentiated PC (Gleason ≥7). Age at diagnosis was used to divided PC cases in earlier (<60 years) and late-onset PC (≥60 years). Prostate and breast cancer family histories were obtained through interview. Our results provided evidences about the contribution of BRCA1-rs1799966 (OR_{CC genotype}  = 2.30; 95% confidence interval [CI] = 1.36-3.91) to the moderate or poorly differentiated PC risk, independently of the family history of prostate, breast or ovary cancer. Further, VDR-rs2238135-G allele was associated with early-onset PC (OR_{G allele}  = 2.05; 95% CI = 1.06-3.95), and marginally with moderate or poorly differentiated PC risk. The present study revealed the crucial role of BRCA1 in PC aggressiveness risk, outstanding the gender imbalance regarding the breast cancer risk in women.

Novel BRCA2 pathogenic genotype and breast cancer phenotype discordance in monozygotic triplets

BRCA1/2 genes with high-penetrance are tumor suppressor and tumor susceptibility genes that play important roles in the homologous recombination mechanism in DNA repair and increase breast cancer risk. Variants in BRCA1 or BRCA2 are the main causes of familial and early-onset breast cancer. This study investigated pathogenic variant belonging to the BRCA2 gene splice region in monozygotic triplets. A 44-year-old woman was diagnosed with breast cancer when she was 32 years old. Her monozygotic sister had a history of breast cancer. No malignancy was detected in the third one of the monozygotic triplets. Sanger sequencing was used to evaluate the BRCA1/2 gene status of the patient and family members. It was figured out that they had the same genetic variant, a heterozygous germ-line splice region variant (c.7008-1G > C) in the BRCA2 gene. This novel splice region variant may be a new pathogenic variant of the BRCA2 gene. Its association with breast cancers needs to be further verified in more patient cases.

BRCA1 and BRCA2 mutation spectrum - an update on mutation distribution in a large cancer genetics clinic in Norway

Background

Founder mutations in the two breast cancer genes, BRCA1 and BRCA2, have been described in many populations, among these are Ashkenazi-Jewish, Polish, Norwegian and Icelandic. Founder mutation testing in patients with relevant ancestry has been a cost-efficient approach in such populations. Four Norwegian BRCA1 founder mutations were defined by haplotyping in 2001, and accounted for 68% of BRCA1 mutation carriers at the time. After 15 more years of genetic testing, updated knowledge on the mutation spectrum of both BRCA1 and BRCA2 in Norway is needed. In this study, we aim at describing the mutation spectrum and frequencies in the BRCA1/2 carrier population of the largest clinic of hereditary cancer in Norway.

Methods

A total of 2430 BRCA1 carriers from 669 different families, and 1092 BRCA2 carriers from 312 different families were included in a quality of care study. All variants were evaluated regarding pathogenicity following ACMG/ENIGMA criteria. The variants were assessed in AlaMut and supplementary databases to determine whether they were known to be founder mutations in other populations.

Results

There were 120 different BRCA1 and 87 different BRCA2 variants among the mutation carriers. Forty-six per cent of the registered BRCA1/2 families (454/981) had a previously reported Norwegian founder mutation. The majority of BRCA1/2 mutations (71%) were rare, each found in only one or two families. Fifteen per cent of BRCA1 families and 25% of BRCA2 families had one of these rare variants. The four well-known Norwegian BRCA1 founder mutations previously confirmed through haplotyping were still the four most frequent mutations in BRCA1 carriers, but the proportion of BRCA1 mutation carriers accounted for by these mutations had fallen from 68 to 52%, and hence the founder effect was weaker than previously described.

Conclusions

The spectrum of BRCA1 and BRCA2 mutations in the carrier population at Norway’s largest cancer genetics clinic is diverse, and with a weaker founder effect than previously described. As a consequence, retesting the families that previously have been tested with specific tests/founder mutation tests should be a prioritised strategy to find more mutation positive families and possibly prevent cancer in healthy relatives.

No evidence of increased breast cancer risk for proven noncarriers from BRCA1 and BRCA2 families

In families screened for mutations in the BRCA1 or BRCA2 genes and found to have a segregating mutation the breast cancer risk for women shown not to carry the family-specific mutation might be at above "average" risk. We assessed the risk of breast cancer in a clinic based cohort of 725 female proven noncarriers in 239 BRCA1 and BRCA2 families compared with birth-matched controls from the Danish Civil Registration System. Prospective analysis showed no significantly increased risk for breast cancer in noncarriers with a hazard ratio of 0.67 [95 % confidence interval (CI) 0.32-1.42, p = 0.29] for all family members who tested negative and 0.87 (95 % CI 0.38-1.97, p = 0.73) for non-carries who were first-degree relatives of mutation carriers. Proven noncarriers from BRCA1 and BRCA2 families have no markedly increased risk for breast cancer compared to the general population, and our data do not suggest targeted breast cancer surveillance for noncarriers from BRCA1 and BRCA2 families.

Impact of germline and somatic BRCA1/2 mutations: tumor spectrum and detection platforms

The BRCA1/2 genes are long and complex and mutation carriers are at risk of developing malignancies, mainly of gynecological origin. Various mutations arise in these genes and their characterization is a time-consuming, cost intensive, complicated process. Tumors of BRCA1/2 origin have distinct molecular and histological features that can impact responses to therapy. Therefore, detection of these mutations constitutes an important step in the risk assessment, prevention strategy and treatment of subjects. Although Sanger sequencing is the gold standard for the detection of genetic mutations, several next generation sequencing-based high throughput platforms have been developed and adapted for the detection of BRCA1/2 mutations. This review provides a comprehensive overview of the sequencing platforms available for the screening and identification of these mutations. We also summarize what is known about the different types of mutations that arise in these genes and the tumor spectra they result in. Finally, we present a short discussion on existing clinical guidelines which assist physicians in the decision-making process. These parameters have important consequences for the management of patients and an urgent need exists for the development of detection platforms that are cost effective and can provide clinicians with conclusive results within a significantly shorter time.

Spectrum of genetic variants of BRCA1 and BRCA2 in a German single center study

BACKGROUND

Determination of mutation status of BRCA1 and BRCA2 has become part of the clinical routine. However, the spectrum of genetic variants differs between populations. The aim of this study was to deliver a comprehensive description of all detected variants.

METHODS

In families fulfilling one of the German Consortium for Hereditary Breast and Ovarian Cancer (GC-HBOC) criteria for genetic testing, one affected was chosen for analysis. DNA of blood lymphocytes was amplified by PCR and prescreened by DHPLC. Aberrant fragments were sequenced. All coding exons and splice sites of BRCA1 and BRCA2 were analyzed. Screening for large rearrangements in both genes was performed by MLPA.

RESULTS

Of 523 index patients, 121 (23.1%) were found to carry a pathogenic or likely pathogenic (class 4/5) mutation. A variant of unknown significance (VUS) was detected in 73/523 patients (13.9%). Two mutations p.Gln1756Profs*74 and p.Cys61Gly comprised 42.3% (n = 33/78) of all detected pathogenic mutations in BRCA1. Most of the other mutations were unique mutations. The most frequently detected mutation in BRCA2 was p.Val1283Lys (13.9%; n = 6/43). Altogether, 101 different neutral genetic variants were counted in BRCA1 (n = 35) and in BRCA2 (n = 66).

CONCLUSION

The two most frequently detected mutations are founder mutations in Poland and Czech Republic. More similarities seem to be shared with our direct neighbor countries compared to other European countries. For comparison of the extended genotype, a shared database is needed.