Clinically Significant Unclassified Variants in BRCA1 and BRCA2 Genes Among Korean Breast Cancer Patients.

Unclassified variants (UVs) of BRCA1 and BRCA2 genes are not defined as pathogenic for breast cancer, and their clinical significance currently remains undefined. Therefore, this study was conducted to identify potentially pathogenic unclassified variants by comparing their prevalence between breast cancer patients and controls. ,A total of 328 breast cancer patients underwent BRCA1/2 genetic screening at the National Cancer Center of Korea. Genetic variants of BRCA genes that were categorized as unclassified according to the Breast Cancer Information Core database were selected based on allelic frequency, after which candidate variants were genotyped in 421 healthy controls. We also examined family members of the study participants. Finally, the effects of amino acid substitutions on protein structure and function were predicted in silico.,Genetic tests revealed 33 unclassified variants in BRCA1 and 47 in BRCA2. Among 15 candidates genotyped in healthy controls, c.5339T>C in BRCA1 and c.6029T>G, c.7522G>A in BRCA2 were not detected. Moreover, the c.5339T>C variant in the BRCA1 gene was detected in four patients with a family history of breast cancer. This nonsynonymous variant (Leu1780Pro) in the BRCA1 C-terminal (BRCT) domain was predicted to have an effect on BRCA1 protein structure/function. ,This study showed that comparison of genotype frequency between cases and controls could help identify unclassified variants of BRCA genes that are potentially pathogenic. Moreover, our findings suggest that c.5339T>C in BRCA1 might be a pathogenic variant for patients and their families.