Germline Genetic Findings Which May Impact Therapeutic Decisions in Families with a Presumed Predisposition for Hereditary Breast and Ovarian Cancer.

In this study, we aim to gain insight in the germline mutation spectrum of ATM, BARD1, BRIP1, ERCC4, PALB2, RAD51C and RAD51D in breast and ovarian cancer families from Spain. We have selected 180 index cases in whom a germline mutation in BRCA1 and BRCA2 was previously ruled out. The importance of disease-causing variants in these genes lies in the fact that they may have possible therapeutic implications according to clinical guidelines. All variants were assessed by combined annotation dependent depletion (CADD) for scoring their deleteriousness. In addition, we used the cancer genome interpreter to explore the implications of some variants in drug response. Finally, we compiled and evaluated the family history to assess whether carrying a pathogenic mutation was associated with age at diagnosis, tumour diversity of the pedigree and total number of cancer cases in the family. Eight unequivocal pathogenic mutations were found and another fourteen were prioritized as possible causal variants. Some of these molecular results could contribute to cancer diagnosis, treatment selection and prevention. We found a statistically significant association between tumour diversity in the family and carrying a variant with a high score predicting pathogenicity (p = 0.0003).

A PALB2 truncating mutation: Implication in cancer prevention and therapy of Hereditary Breast and Ovarian Cancer.

Explaining genetic predisposition in Hereditary Breast and Ovarian Cancer (HBOC) families without BRCA mutations is crucial. Germline PALB2 inactivating mutations were associated with an increased risk of HBOC due to its role in DNA repair through cooperation with BRCA proteins. The prevalence and penetrance of PALB2 mutations in Spanish HBOC patients remains unexplained. PALB2 mutation screening has been conducted in 160 high-risk BRCA-negative patients and 320 controls. We evaluated four predicted splicing disruption variants and large genomic rearrangements by multiplex ligation-dependent probe amplification. We have found a frameshift mutation which segregates in an early onset cancer family; and four rare missense variants. None of the variants tested for a predicted splicing disruption showed an aberrant transcript pattern. No large genomic rearrangements were detected. Although PALB2 truncating mutations are rarely identified, segregation analysis and early onset cancer suggest a significant contribution to HBOC susceptibility in the Spanish population. PALB2 screening may improve genetic counselling through prevention measures, pedigree management and PARP inhibitor therapy selection.

Unraveling the molecular effect of a rare missense mutation in BRIP1 associated with inherited breast cancer.

BRIP1 is a component of the Fanconi Anemia/BRCA pathway responsible for DNA reparation via helicase activity. Some heterozygous variants in BRIP1 could contribute to Hereditary Breast Cancer through a defective DNA repair. The clinical utility of BRIP1 mutations in a familial cancer context is compromised by the conflicting interpretation of "variants of uncertain significance" (VUS). Defining the clinical significance of variants identified in genetic tests is a major challenge; therefore, studies that evaluate the biological effect of these variants are definitely necessary. To contribute to this purpose, we have characterized the variant c.550G>T of BRIP1, a missense mutation with little evidence about its pathogenicity. Since Human Splicing FinderTM predicts the creation of a new exonic splicing enhancer site we decided to perform cDNA analysis revealing that the c.550G>T mutation located in exon 6 led to an aberrant transcript causing exon 5 skipping. Our results demonstrate that the c.550G>T BRIP1 variant disrupts normal splicing, causing exon 5 skipping. Considering that the exon 5 encodes the helicase domain of BRIP1, it is expected an alteration of the function. This finding enhances the interpretation of this VUS, suggesting a potential pathogenic effect.