Functional Characterization of Variants of Unknown Significance in Familial Breast Cancer

• Autor(a) principal: Lourenço, Rita Adubeiro
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/56683
• topic: Familial Breast Cancer; Variants of Unknown Significance; VUS; Homologous Recombination; Ionizing Radiation; Functional Assays; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Familial breast cancer (BC) cases account for 5-10 % of all BC cases and are mainly associated with inherited mutations in BRCA1 and BRCA2 genes. Many other genes related with BC development have already been identified and are mostly related with Homologous Recombination (HR) repair system, one of the main pathways that repair DNA double-strand breaks (DSBs). Genetic testing for BC has become standard and with more widespread genetic testing, an increased detection of variants of unknown significance (VUS) as either benign or pathogenic will occur. Functional analyses on VUS may identify pathogenicity, and clearly categorize their mutational status. We carried-out a proof-of concept in vitro functional analysis in peripheral blood lymphocytes of VUS-harboring individuals and controls assessing the cellular response to -radiation. Six samples were collected, two BC patient with a pathogenic ATM mutation, two BRCA1 VUS carriers, and two controls. Several methodologies were selected to evaluate the cellular response to genetic lesions induced by -radiation (2Gy): chromosomal aberrations (CA), micronuclei (MN) and comet assay. The CA assay results present no statistical difference between samples. In the MN assay the carriers show lower amount of binucleated cells with MN when compared to control samples, which is possibly due to cellular death events. The comet assay results show a clear increase in sensitivity to ionizing radiation, possibly associated with deficiency in repair, of samples from carrying a pathogenic mutation in the ATM gene and those with the BRCA1 VUS. Overall, except for the CA assay, the results show an increased susceptibility to ionizing radiation in pathogenic ATM mutation carriers and BRCA1 VUS carriers. However, some additional studies should be performed to completely understand the results obtained, and the impact of alterations in cancer risk.