Recurrent genetic variants and prioritization of variants of uncertain clinical significance associated with hereditary breast and ovarian cancer in families from the Region of Murcia.

Objectives: Hereditary breast and ovarian cancer (HBOC) follows an autosomal dominant inheritance pattern of cancer susceptibility genes. The risk of developing this disease is primarily associated with germline mutations in the BRCA1 and BRCA2 genes. The advent of massive genetic sequencing technologies has expanded the mutational spectrum of this hereditary syndrome, thereby increasing the number of variants of uncertain clinical significance (VUS) detected by genetic testing. Methods: A prevalence study of HBOC was performed within 2,928 families from the Region of Murcia, in southeastern Spain. Genetic testing enabled the identification of recurrent pathogenic variants and founder mutations, which were mainly related to the BRCA1 and BRCA2 genes. VUS testing was performed using a prioritization algorithm designed by our working group. Results: Variants c.68_69del, c.212+1G>A, and c.5123C>A were detected in 30 % of BRCA1 carriers, whereas exon 2 deletion concurrent with c.3264dupT, c.3455T>G and c.9117G>A variants were found in 30 % of BRCA2 carriers. A total of 16 VUS (15 %) were prioritized. Conclusions: The genotype-phenotype correlation observed in our study is consistent with the scientific literature. Furthermore, the founder effect of c.1918C>T (BRCA1) and c.8251_8254del (ATM) was verified in the Murcian population, whereas exon 2 deletion (BRCA2) was proven to be a Spanish founder mutation. Our algorithm enabled us to prioritize potentially pathogenic VUS that required further testing to determine their clinical significance and potential role in HBOC.

Next step in molecular genetics of hereditary breast/ovarian cancer: Multigene panel testing in clinical actionably genes and prioritization algorithms in the study of variants of uncertain significance.

INTRODUCTION: BRCA1 and BRCA2 are the two main genes causing hereditary breast and ovarian cancer (HBOC). However, thanks to the development of Next Generation Sequencing (NGS), other genes linked to this syndrome (CHEK2, BRIP1, ATM and PALB2 among others) can be analysed. MATERIAL AND METHODS: an analysis by multigene panel testing was performed in 138 index cases (ICs) from HBOC Spanish families with a previous non-informative result for BRCA1/2. The BRCA Hereditary Cancer Master™ Plus kit, including 26 actionable and candidate genes related to HBOC was employed. Once classified, an algorithm was employed to prioritized those variants of unknown significance with a higher risk of having a deleterious effect. Moreover, a mRNA splicing assay was performed for the prioritized VUS c.3402+3A > C in ATM, located at intron 23. RESULTS: A total of 82 variants were found: 70 VUS and 12 pathogenic or probably pathogenic variants. The diagnostic yield in actionable genes non-BRCA was 7.97% of the total tested ICs. Overall, 19 VUS were prioritized, which meant 27% of the 70 total VUS. RNA analysis of the variant 3402+3A > C confirmed a deleterious impact on splicing. DISCUSSION: The implementation of a multigene panel in HBOC studied families improved the diagnostic yield, concordant with results obtained in previous publications. Due to the important number of VUS obtained in NGS, the application of a prioritization algorithm is needed in order to select those variants in which it is necessary to conduct further studies.