BRCA1/2 mutations, including large genomic rearrangements, among unselected ovarian cancer patients in Korea

Abstract

Objective: We performed small-scale mutation and large genomic rearrangement (LGR) analysis of BRCA1/2 in ovarian cancer patients to determine the prevalence and the characteristics of the mutations.

Methods: All ovarian cancer patients who visited a single institution between September 2015 and April 2017 were included. Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and long-range polymerase chain reaction (PCR) were performed to comprehensively study BRCA1/2. The genetic risk models BRCAPRO, Myriad, and BOADICEA were used to evaluate the mutation analysis.

Results: In total, 131 patients were enrolled. Of the 131 patients, Sanger sequencing identified 16 different BRCA1/2 small-scale mutations in 20 patients (15.3%). Two novel nonsense mutations were detected in 2 patients with a serous borderline tumor and a large-cell neuroendocrine carcinoma. MLPA analysis of BRCA1/2 in Sanger-negative patients revealed 2 LGRs. The LGRs accounted for 14.3% of all identified BRCA1 mutations, and the prevalence of LGRs identified in this study was 1.8% in 111 Sanger-negative patients. The genetic risk models showed statistically significant differences between mutation carriers and non-carriers. The 2 patients with LGRs had at least one blood relative with breast or ovarian cancer.

Conclusion: Twenty-two (16.8%) of the unselected ovarian cancer patients had BRCA1/2 mutations that were detected through comprehensive BRCA1/2 genetic testing. Ovarian cancer patients with Sanger-negative results should be considered for LGR detection if they have one blood relative with breast or ovarian cancer. The detection of more BRCA1/2 mutations in patients is important for efforts to provide targeted therapy to ovarian cancer patients.

Keywords: Genes; Korea; Mutation; Neoplasms; Ovary.

Fig. 1. MLPA analysis of patient A (A) and B (B). The red squares indicate the deleted BRCA1 probes. (C) Long-range PCR results for patient B showing an 11.7 kb-sized deletion of the BRCA1 gene. (D) Sanger sequencing of the abnormal band revealed the LGR breakpoint: NG_005905.2:g.167479_179115del11637. This LGR fuses the AluY sequence with the AluSq sequence.

MLPA, multiplex ligation-dependent probe amplification; PCR, polymerase chain reaction; LGR, large genomic rearrangement; HC, healthy control; L, DNA extension ladder; P, patient B; UTR, untranslated region.

Fig. 2. Pedigree of the 2 patients with LGR mutations in this study. (A) Family pedigree of patient A with a deletion of BRCA1 exons 1–2. (B) Family pedigree of patient B with a deletion of BRCA1 exons 21–23.

LGR, large genomic rearrangement; Ca, cancer; Dx, diagnosed.