Epidemiological and ES cell-based functional evaluation of BRCA2 variants identified in families with breast cancer

Sequencing-based functional assays for classification of BRCA2 variants in mouse ESCs

Sequencing of genes, such as BRCA1 and BRCA2, is recommended for individuals with a personal or family history of early onset and/or bilateral breast and/or ovarian cancer or a history of male breast cancer. Such sequencing efforts have resulted in the identification of more than 17,000 BRCA2 variants. The functional significance of most variants remains unknown; consequently, they are called variants of uncertain clinical significance (VUSs). We have previously developed mouse embryonic stem cell (mESC)-based assays for functional classification of BRCA2 variants. We now developed a next-generation sequencing (NGS)-based approach for functional evaluation of BRCA2 variants using pools of mESCs expressing 10-25 BRCA2 variants from a given exon. We use this approach for functional evaluation of 223 variants listed in ClinVar. Our functional classification of BRCA2 variants is concordant with the classification reported in ClinVar or those reported by other orthogonal assays.

Fatalism and metaphor in Confucianism: A qualitative study of barriers to genetic testing among first-degree relatives of hereditary cancer patients from China

OBJECTIVE

Despite the benefits, the rate of genetic testing among first-degree relatives (FDRs; parents, children, and siblings) remains low, and the barriers to undergoing testing among FDRs in China are not clear. We explored the reasons why FDRs refused genetic testing.

METHODS

Semi-structured face-to-face interviews were conducted with 22 patients and 27 FDRs. Participants were recruited at an urban tertiary hospital in Guangzhou, South China. We used qualitative content analysis to analyse the transcripts of audio recordings and identify major themes and subthemes.

RESULTS

Three major themes emerged related to FDRs' low rate of participation in genetic testing. First, there is cognitive distance from genetic testing/cancer and a lack of knowledge of preventive medicine that deepens the 'fatalistic' attitude towards cancer among FDRs, which leads to an enormous gap between their knowledge and understanding of genetic testing. Second, medical consultation is not valued in Confucianism, and the view of cancer as 'bad news' and the risk of cancer as a curse makes cancer a metaphor, which leads to exhausting arguments when persuading FDRs to undergo genetic testing. Third, physical distance from the hospital, loss of privacy, possible discrimination in many social activities and genetic testing as a source of stress and anxiety lead FDRs to fear the disruption of their daily lives.

CONCLUSIONS

There are many barriers to genetic testing among the FDRs of hereditary cancer patients originating from the national social and cultural context. Healthcare professionals should develop interventions rooted in culture and promote cancer risk communication between hereditary cancer patients and FDRs.

Identification of the core motif of the BRCA2 C-terminal RAD51-binding domain by comparing canine and human BRCA2

Mammary tumors are the most common tumors in women and non-spayed female dogs. One of the reasons for mammary tumors is mutations of the tumor suppressor gene, BRCA2. BRCA2 participates in homologous recombination repair by interacting with the RAD51 recombinase. BRCA2 has two RAD51-binding domains, consisting of BRC repeats and the C-terminal RAD51-binding domain, respectively. Although several studies have addressed the function of the C-terminal RAD51-binding domain of human BRCA2, the amino acid sequences required for the RAD51-interaction activity remain unclear. In this study, the C-terminal RAD51-binding domains of canine and human BRCA2 were compared; the canine domain displayed a weaker interaction with RAD51. This difference was attributed to the C-terminal portion of the domain via a comparison between canine and human domains. Furthermore, peptides shorter than those previously reported displayed RAD51-interacting activity, and a core motif of this domain consisting of 25 amino acids was identified. Since a mutation (S3323N) was reported in the core motif of this domain, the effect of this mutation was evaluated. The mutant exhibited similar RAD51-binding activity as that of the wild-type protein, suggesting that the mutation was functionally neutral. These data suggested that the C-terminal portion of the BRCA2 C-terminal RAD51-binding domain influenced its RAD51-interaction activity, and a minimum core motif of 25 amino acids was identified in this domain. These data may help clarify BRCA2 function, as well as the tumorigenic effects of BRCA2 mutation.