The results of multigene panel sequencing in Slovak HBOC families

Abstract

Hereditary breast and ovarian cancer (HBOC) is primarily associated with mutations in the BRCA1/2 genes. However, causal variants in other high, moderate, and low penetrance genes proportionally increase the risk of breast/ovarian cancer. This study aims to provide data about the mutation spectrum of HBOC-associated genes in Slovak HBOC families and estimate the ratio of BRCA versus non-BRCA causal variants. We used panel sequencing containing 22 high/moderaterisk susceptibility genes and parallel MLPA analysis of BRCA1/2, CHEK2 genes, to analyze 94 individuals with a strong family/personal history of breast and/or ovarian cancer. The analyzed group consisted of 80 patients diagnosed with cancer (85.1%) and 14 healthy individuals (14.9%) with a positive family history of HBOC syndrome. In total, we have identified 22 causal DNA variants (23.4%) showing 15 primary findings in BRCA1/2 genes (68.2%) and 7 positive secondary findings in CHEK2, PALB2, CDH1, and MUTYH genes (31.8%). The most frequent pathogenic alterations were BRCA1 mutations c.181T>G and CNV variant (c.5573-?_c.5701+?)del, known as deletion of exons 21-22. Besides known mutations, the BRCA1 variant c.2794del (p.Val932Leufs*68) and variant c.2480dup (p.Tyr827*) in the CDH1 gene represent the novel, previously unpublished variants that might be population-specific. In conclusion, we provide the first report of multigene panel testing in Slovak HBOC families demonstrating that almost one-third of pathogenic mutations are situated in susceptibility genes other than BRCA1/2. Although multigene panel testing requires precise data filtration and interpretation, it might bring the relevant data for clinical management of the patients. Key words: hereditary breast and ovarian cancer; BRCA1; BRCA2; panel sequencing; pathogenic variants; secondary findings According to 2018 GLOBOCAN statistics, breast cancer is the leading type of malignancy diagnosed in women worldwide, representing the most common cause of cancer death in the female population. Ovarian cancer is ranked at 8 th place of global cancer incidence in women [1], associated with one of the highest mortalities of all gynecological cancers in developed countries. In Slovakia, GLOBOCAN data show estimated cumulative risks of breast and ovarian cancer at 6.59%