Reclassification of Five BRCA1/2 Variants with Unknown Significance Using Complex Functional Study

Cancer Res Treat. 2022 Oct;54(4):970-984. doi: 10.4143/crt.2021.1078. Epub 2022 Feb 8.


Purpose: While BRCA1/2 genes are commonly investigated, variants of unknown significance (VUS) and variants with potential splice effect are still being detected and they represent a substantial challenge in genetic counseling and therapy.

Materials and methods: Out of genetically tested 3,568 hereditary breast and ovarian cancer probands five, functionally not investigated variants with potential splice-modifying effect were subjected to functional characterization. Transcript-level analysis on peripheral blood-derived RNA of the carriers was performed to test aberrant splicing. The completeness of the aberrant splicing event was also studied, existence and extent of nonsense-mediated decay was even addressed. Clinical and phenotype data, pedigree and co-segregation analyses were also done. Locus-specific loss of heterozygosity (LOH) in tumor tissues was additionally tested.

Results: In case of the BRCA1:c.4484+4dupA and the BRCA1:c.5407-10G>A variants functional results allowed us to reclassify them from VUS into likely pathogenic category. BRCA1:c.4358-31A>C, by producing incomplete aberrant splicing, was highlighted as strong VUS, but in lack of other supporting evidence, re-categorization was not possible. The likely pathogenic assertion of previously not reported BRCA2:c.8487G>T was reinforced based on its spliceogenic property and tumor LOH, while BRCA2:c.793G>A failed to present aberrant splicing in spite of suggestive predictions, which altered its original VUS evaluation into likely benign class.

Conclusion: We presented molecular and clinical evidence for reclassification of four out of five BRCA1/2 variants. Both up- and down-classification harbour important clinical significance. Patients carrying re-classified pathogenic variants in the future will not be dropped out from medical surveillance, preventive measures, treatment and predictive family screening in relatives at risk.

Keywords: BRCA1; BRCA2; Breast neoplasms; Reclassification; Splicing; Variants of unknown significance.

MeSH terms

  • BRCA1 Protein / genetics
  • Breast Neoplasms* / genetics
  • Female
  • Genes, BRCA1
  • Genes, BRCA2
  • Humans
  • Mutation
  • Ovarian Neoplasms* / genetics
  • Ovarian Neoplasms* / pathology
  • RNA


  • BRCA1 Protein
  • BRCA1 protein, human
  • RNA