Molecular characteristics of Asian male BRCA-related cancers

PURPOSE

Germline mutations of BRCA1 or BRCA2 predispose men to develop various cancers, including breast cancers and prostate cancers. Male breast cancer (MBC) is a rare disease while prostate cancer (PRC) is uncommon in young men at the age of less than 40. The prevalence of BRCA genes in Asian male patients has to be elevated.

METHODS

Germline mutations screening was performed in 98 high-risk Chinese MBC and PRC patients.

RESULT

We have identified 16 pathogenic BRCA2 mutation carriers, 12 were MBC patients, 2 were PRC patients and 2 were patients with both MBC and PRC. The mutation percentages were 18.8%, 6.7% and 50% for MBC, PRC and both MBC and PRC patients, respectively. BRCA2 gene mutations confer a significantly higher risk of breast/prostate cancers in men than those with BRCA1 mutations. BRCA mutated MBC patients had a younger age of diagnosis and strong family histories of breast cancers while BRCA mutated PRC patients had strong family histories of ovarian cancers.

CONCLUSION

Male BRCA carriers with breast cancers or prostate cancers showed distinct clinical and molecular characteristics, a male-specific genetic screening model would be useful to identify male cancer patients who have a high risk of BRCA mutation.

How does re-classification of variants of unknown significance (VUS) impact the management of patients at risk for hereditary breast cancer?

Background

The popularity of multigene testing increases the probability of identifying variants of uncertain significance (VUS). While accurate variant interpretation enables clinicians to be better informed of the genetic risk of their patients, currently, there is a lack of consensus management guidelines for clinicians on VUS.

Methods

Among the BRCA1 and BRCA2 mutations screening in 3,544 subjects, 236 unique variants (BRCA1: 86; BRCA2: 150) identified in 459 patients were being reviewed. These variants consist of 231 VUS and 5 likely benign variants at the initial classification.

Results

The variants in 31.8% (146/459) patients were reclassified during the review, which involved 26 unique variants (11.0%). Also, 31 probands (6.8%) and their family members were offered high-risk surveillance and related management after these variants were reclassified to pathogenic or likely pathogenic. At the same time, 69 probands (15%) had their VUS downgraded to cancer risk equivalent to the general population level.

Conclusion

A review of archival variants from BRCA1 and BRCA2 genetic testing changed the management for 31.8% of the families due to increased or reduced risk. We encourage regular updates of variant databases, reference to normal population and collaboration between research laboratories on functional studies to define the clinical significances of VUS better.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01270-4.

Germline mutations in Chinese ovarian cancer with or without breast cancer

BACKGROUND

Ovarian and breast cancers are known to have significant genetic components. Considering the differences in the mutation spectrum across ethnicity, it is important to identify hereditary breast and ovarian cancer (HBOC) genes mutation in Chinese for clinical management.

METHODS

Two cohorts of 451 patients with ovarian cancer only (OV) and 93 patients with both breast and ovarian (BROV) cancers were initially screened for BRCA1, BRCA2, TP53, and PTEN. 109 OV and 43 BROV patients with extensive clinical risk and were being tested negative, were then further characterized by 30-gene panel analysis.

RESULTS

Pathogenic BRCA1/2 variants were identified in 45 OV patients and 33 BROV patients, giving a prevalence of 10% and 35.5%, respectively. After the extended screening, mutations in other HBOC genes were identified in an additional 12.8% (14/109) of the OV cohort and 14% (6/43) in the BROV cohort. The most commonly mutated genes in the OV cohort were MSH2 (4.6%) while in the BROV cohort were MSH2 (4.7%) and PALB2 (4.7%). With this extended multigene testing strategy, pathogenic mutations were detected in 12.8% of OV patients (BRCAs: 10%; additional genes: 12.8%) and 40.9% (BRCAs: 35.5%; additional genes: 14%) of BROV patients.

CONCLUSION

Extended characterization of the contributions of HBOC genes to OV and BROV patients has significant impacts on further management in patients and their families, expanding the screening net for more asymptomatic individuals.

Telomeres acquire distinct heterochromatin characteristics during siRNA-induced RNA interference in mouse cells

Telomeres are protective structures present at the ends of linear chromosomes and consist of simple repeating-DNA sequences and specialized proteins [1, 2]. Integrity of the telomeres is important in maintaining genome stability[1-6]. RNA interference(RNAi) involves short double-stranded RNA (21-23 nucleotides long), termed short interference RNA(siRNA), resulting in the downregulation of genes with cognate sequences [7-9]. During transient siRNA-induced RNAi in mouse fibroblast cultures, we found significant reversible changes related to the telomeres. Telomeres acquired distinct heterochromatin features. There were increased bindings of Argonaute-1 (AGO1), telomeric repeat-binding factor 1(TERF1), and heterochromatin protein 1beta (HP1beta) on the telomeres. Histone H3 (lysine 9) was hypermethylated at the telomeres. The chromosome ends also were associated with an unidentified RNA. During RNAi, expression of a transgene inserted adjacent to the telomere was downregulated. In addition, the concentration of a group of heterogeneous high-molecular-weight RNA containing telomeric repeat sequences was increased, and this RNA formed a small number of transient, discrete nuclear foci. Our findings suggest that telomeres participate actively in the siRNA-induced RNAi process. These responses of telomeres to the RNAi process might partially account for the off-target effects of RNAi.

Specific epitopes of the structural and hypothetical proteins elicit variable humoral responses in SARS patients

BACKGROUND

Severe acute respiratory syndrome (SARS) is an infectious disease which was caused by a novel coronavirus (SARS-CoV). SARS has caused an outbreak in the world during 2003 and 2004, with 8098 individuals being infected and a death toll of 774 in 28 regions around the world. Specific humoral responses to viral infection remain unclear.

OBJECTIVE

To analyse the antigenicity of the SARS-CoV genome and identify potential antigenic epitopes in the structural proteins.

METHODS

Potential antigenic epitopes were identified in the structural proteins (nucleocapsid, membrane, spike, and small envelope proteins) and hypothetical proteins (SARS3a, 3b, 6, 7a, and 9b) that are specific for SARS-CoV. A peptide chip platform was created and the profiles of antibodies to these epitopes were investigated in 59 different SARS patients' sera obtained 6-103 days after the onset of the illness. Serial sera from five additional patients were also studied.

RESULTS

Epitopes at the N-terminus of the membrane protein and the C-terminus of nucleocapsid protein elicited strong antibody responses. Epitopes on the spike protein were only moderately immunogenic but the effects were persistent. Antibodies were also detected for some putative proteins, noticeably the C-termini of SARS3a and SARS6.

CONCLUSIONS

Important epitopes of the SARS-CoV genome that may serve as potential markers for the viral infection are identified. These specific antigenic sites may also be important for vaccine development against this new fatal infectious disease.