Spectrum and frequencies of BRCA1/2 mutations in Bulgarian high risk breast cancer patients

Founder vs. non-founder BRCA1/2 pathogenic alleles: the analysis of Belarusian breast and ovarian cancer patients and review of other studies on ethnically homogenous populations

The spectrum of BRCA1/2 mutations demonstrates significant interethnic variations. We analyzed for the first time the entire BRCA1/2 coding region in 340 Belarusian cancer patients with clinical signs of BRCA1/2-related disease, including 168 women with bilateral and/or early-onset breast cancer (BC), 104 patients with ovarian cancer and 68 subjects with multiple primary malignancies involving BC and/or OC. BRCA1/2 pathogenic alleles were detected in 98 (29%) women, with 67 (68%) of these being represented by founder alleles. Systematic comparison with other relevant studies revealed that the founder effect observed in Belarus is among the highest estimates observed worldwide. These findings are surprising, given that the population of Belarus did not experience geographic or cultural isolation throughout history.

Clinical application of artificial neural network (ANN) modeling to predict BRCA1/2 germline deleterious variants in Chinese bilateral primary breast cancer patients

BACKGROUND

Bilateral breast cancer (BBC), as well as ovarian cancer, are significantly associated with germline deleterious variants in BRCA1/2, while BRCA1/2 germline deleterious variants carriers can exquisitely benefit from poly (ADP-ribose) polymerase (PARP) inhibitors. However, formal genetic testing could not be carried out for all patients due to extensive use of healthcare resources, which in turn results in high medical costs. To date, existing BRCA1/2 deleterious variants prediction models have been developed in women of European or other descent who are quite genetically different from Asian population. Therefore, there is an urgent clinical need for tools to predict the frequency of BRCA1/2 deleterious variants in Asian BBC patients balancing the increased demand for and cost of cancer genetics services.

METHODS

The entire coding region of BRCA1/2 was screened for the presence of germline deleterious variants by the next generation sequencing in 123 Chinese BBC patients. Chi-square test, univariate and multivariate logistic regression were used to assess the relationship between BRCA1/2 germline deleterious variants and clinicopathological characteristics. The R software was utilized to develop artificial neural network (ANN) and nomogram modeling for BRCA1/2 germline deleterious variants prediction.

RESULTS

Among 123 BBC patients, we identified a total of 20 deleterious variants in BRCA1 (8; 6.5%) and BRCA2 (12; 9.8%). c.5485del in BRCA1 is novel frameshift deleterious variant. Deleterious variants carriers were younger at first diagnosis (P = 0.0003), with longer interval between two tumors (P = 0.015), at least one medullary carcinoma (P = 0.001), and more likely to be hormone receptor negative (P = 0.006) and HER2 negative (P = 0.001). Area under the receiver operating characteristic curve was 0.903 in ANN and 0.828 in nomogram modeling individually (P = 0.02).

CONCLUSION

This study shows the spectrum of the BRCA1/2 germline deleterious variants in Chinese BBC patients and indicates that the ANN can accurately predict BRCA deleterious variants than conventional statistical linear approach, which confirms the BRCA1/2 deleterious variants carriers at the lowest costs without adding any additional examinations.

Spectrum of BRCA1/2 Mutations in Romanian Breast and Ovarian Cancer Patients

Background: About 10,000 women are diagnosed with breast cancer and about 2000 women are diagnosed with ovarian cancer each year in Romania. There is an insufficient number of genetic studies in the Romanian population to identify patients at high risk of inherited breast and ovarian cancer. Methods: We evaluated 250 women of Romanian ethnicity with BC and 240 women of Romanian ethnicity with ovarian cancer for the presence of damaging germline mutations in breast cancer genes 1 and 2 (BRCA1 and BRCA2, respectively) using Next-Generation Sequencing (NGS) technology. Results: Of the 250 breast cancer patients, 47 carried a disease-predisposing BRCA mutation (30 patients (63.83%) with a BRCA1 mutation and 17 patients (36.17%) with a BRCA2 mutation). Of the 240 ovarian cancer patients, 60 carried a BRCA mutation (43 patients (72%) with a BRCA1 mutation and 17 patients (28%) with a BRCA2 mutation). In the BRCA1 gene, we identified 18 variants (4 in both patient groups (ovarian and breast cancer patients), 1 mutation variant in the BC patient group, and 13 mutation variants in the ovarian cancer patient group). In the BRCA2 gene, we identified 17 variants (1 variant in both ovarian and breast cancer patients, 6 distinct variants in BC patients, and 10 distinct variants in ovarian cancer patients). The prevailing mutation variants identified were c.3607C>T (BRCA1) (18 cases) followed by c.5266dupC (BRCA1) (17 cases) and c.9371A>T (BRCA2) (12 cases). The most prevalent mutation, BRCA1 c.3607C>T, which is less common in the Romanian population, was mainly associated with triple-negative BC and ovarian serous adenocarcinoma. Conclusion: The results of our analysis may help to establish specific variants of BRCA mutations in the Romanian population and identify individuals at high risk of hereditary breast and ovarian cancer syndrome by genetic testing.

High frequency of BRCA recurrent mutations in a consecutive series of unselected ovarian cancer patients

Hereditary predisposition to breast and ovarian cancer (HBOC) is diagnosed by molecular analysis of deleterious mutations in BRCA genes, allowing oncogenetic follow-up of patients and of their families. BRCA testing addresses only to HBOC families, using restrictive inclusion criteria based on familial history of cancer and age at diagnosis. Sporadic ovarian cancer has high incidence and mortality in Romania, with low median age of diagnosis and possibly a higher magnitude of hereditary contribution comparing to othe populations. However, sporadic ovarian cancers do not qualify for BRCA testing according to inclusion criteria, and a complete BRCA screening of all cancers is neither feasible nor recommended. Despite the large diversity of BRCA mutations worldwide, some recurrent mutations have higher frequencies in diverse populations. Precisely screening for recurrent mutations in a target population allows to rapidly identifying mutation carriers without sequencing the entire BRCA genes. In Romanian population and neighboring countries, several recurrent mutations have already been described. In a consecutive series of 50 sporadic ovarian cancer patients, not qualifying for BRCA complete testing, we screened for 9 most common BRCA mutations, by multiplex-PCR, RFLP and targeted Sanger sequencing. Our results revealed 6 different BRCA mutations in 8 unrelated patients, with a frequency of 16%, much higher than expected. We further recommend screening for the identified mutations in larger series of cancer patients. The results are highly beneficial to cancer patients, healthy relatives, and overall, considering prevention in cancer a priority, to public health system and future of oncogenetics in Romania

Hereditary Breast and Ovarian Cancer in Families from Southern Italy (Sicily)-Prevalence and Geographic Distribution of Pathogenic Variants in BRCA1/2 Genes

Recent advances in the detection of germline pathogenic variants (PVs) in BRCA1/2 genes have allowed a deeper understanding of the BRCA-related cancer risk. Several studies showed a significant heterogeneity in the prevalence of PVs across different populations. Because little is known about this in the Sicilian population, our study was aimed at investigating the prevalence and geographic distribution of inherited BRCA1/2 PVs in families from this specific geographical area of Southern Italy. We retrospectively collected and analyzed all clinical information of 1346 hereditary breast and/or ovarian cancer patients genetically tested for germline BRCA1/2 PVs at University Hospital Policlinico "P. Giaccone" of Palermo from January 1999 to October 2019. Thirty PVs were more frequently observed in the Sicilian population but only some of these showed a specific territorial prevalence, unlike other Italian and European regions. This difference could be attributed to the genetic heterogeneity of the Sicilian people and its historical background. Therefore hereditary breast and ovarian cancers could be predominantly due to BRCA1/2 PVs different from those usually detected in other geographical areas of Italy and Europe. Our investigation led us to hypothesize that a higher prevalence of some germline BRCA PVs in Sicily could be a population-specific genetic feature of BRCA-positive carriers.

Mutation analysis of BRCA1/2 mutations with special reference to polymorphic SNPs in Indian breast cancer patients

Background

Germline mutations BRCA1 and BRCA2 contribute almost equally in the causation of breast cancer (BC). The type of mutations in the Indian population that cause this condition is largely unknown.

Purpose

In this cohort, 79 randomized BC patients were screened for various types of BRCA1 and BRCA2 mutations including frameshift, nonsense, missense, in-frame and splice site types.

Materials and methods

The purified extracted DNA of each referral patient was subjected to Sanger gene sequencing using Codon Code Analyzer and Mutation Surveyor and next-generation sequencing (NGS) methods with Ion torrent software, after appropriate care.

Results

The data revealed that 35 cases were positive for BRCA1 or BRCA2 (35/79: 44.3%). BRCA2 mutations were higher (52.4%) than BRCA1 mutations (47.6%). Five novel mutations detected in this study were p.pro163 frameshift, p.asn997 frameshift, p.ser148 frameshift and two splice site single-nucleotide polymorphisms (SNPs). Additionally, four nonsense and one in-frame deletion were identified, which all seemed to be pathogenic. Polymorphic SNPs contributed the highest percentage of mutations (72/82: 87.8%) and contributed to pathogenic, likely pathogenic, likely benign, benign and variant of unknown significance (VUS). Young age groups (20–60 years) had a high frequency of germline mutations (62/82;75.6%) in the Indian population.

Conclusion

This study suggested that polymorphic SNPs contributed a high percentage of mutations along with five novel types. Younger age groups are prone to having BC with a higher mutational rate. Furthermore, the SNPs detected in exons 10, 11 and 16 of BRCA1 and BRCA2 were higher than those in other exons 2, 3 and 9 polymorphic sites in two germline genes. These may be contributory for BC although missense types are known to be susceptible for cancer depending on the type of amino acid replaced in the protein and associated with pathologic events. Accordingly, appropriate counseling and treatment may be suggested.

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.

Pre-examination factors affecting molecular diagnostic test results and interpretation: A case-based approach

BACKGROUND

Multiple organizations produce guidance documents that provide opportunities to harmonize quality practices for diagnostic testing. The International Organization for Standardization ISO 15189 standard addresses requirements for quality in management and technical aspects of the clinical laboratory. One technical aspect addresses the complexities of the pre-examination phase prior to diagnostic testing.

METHODS

The Committee for Molecular Diagnostics of the International Federation for Clinical Chemistry and Laboratory Medicine (also known as, IFCC C-MD) conducted a survey of international molecular laboratories and determined ISO 15189 to be the most referenced guidance document. In this review, the IFCC C-MD provides case-based examples illustrating the value of select pre-examination processes as these processes relate to molecular diagnostic testing. Case-based examples in infectious disease, oncology, inherited disease and pharmacogenomics address the utility of: 1) providing information to patients and users, 2) designing requisition forms, 3) obtaining informed consent and 4) maintaining sample integrity prior to testing.

CONCLUSIONS

The pre-examination phase requires extensive and consistent communication between the laboratory, the healthcare provider and the end user. The clinical vignettes presented in this paper illustrate the value of applying select ISO 15189 recommendations for general laboratory to the more specialized area of Molecular Diagnostics.