Analysis of BRCA1/2 mutation spectrum and prevalence in unselected Chinese breast cancer patients by next-generation sequencing

Abstract

Purpose: BRCA1 and BRCA2 (BRCA1/2) are two major high-penetrance breast cancer predisposition genes, mutations in which can lead to high risks and early onset of breast cancer. This study was performed to comprehensively investigate the spectrum and prevalence of BRCA1/2 mutations in unselected Chinese breast cancer patients and evaluate the associations of BRCA1/2 mutations with related clinicopathological characteristics of the tumors.

Methods: By integrating microfluidic PCR-based target enrichment and next-generation sequencing, paired tumor and normal tissues from 313 unselected breast cancer patients were analyzed for both germline and somatic mutations of BRCA1/2 genes in Chinese Han population.

Results: Total 5 BRCA1 and 8 BRCA2 deleterious germline mutations were detected in 5 (1.60%) and 12 (3.83%) of the 313 patients, respectively. The entire frequency of deleterious germline mutations of BRCA1/2 was 5.43%. Among them, c.1069A > T and c.3418_3419insTGACTACT in BRCA1, c.8474_8487delCATACCCTATACAG and c.6547delG in BRCA2 were novel. In addition, 32 germline variants of unknown significance in 31 (9.90%) of the 313 patients were identified. We also detected 13 somatic mutations in ten patients (3.19%), including 4 (1.28%) deleterious mutations (c.1575delT, c.2677C > T, c.7024C > T, and c.7672G > T in BRCA2) and 5 novel mutations (c.4728A > G and c.4820T > C in BRCA1; c.2527G > A, c.4069C > G and c.7672G > T in BRCA2). Notably, BRCA1 mutation carriers were significantly younger, and more likely to be ER negative and basal-like breast cancers.

Conclusions: Our study provided a reliable and effective platform for BRCA1/2 genetic testing, and suggested that there was a relatively high prevalence and special spectrum of BRCA1/2 mutations in unselected Chinese breast cancer patients.

Keywords: BRCA1; BRCA2; Breast cancer; Microfluidic PCR; Mutation; Next-generation sequencing.

Fig. 1

Schematic representation of BRCA1 and BRCA2 deleterious germline mutations in functional domains and protein binding regions. Single-nucleotide variants and small indels mapped to the BRCA1/2 protein sequences are shown. Arrows point to amino acid mutation position and height of the arrows indicates the number of cases. Protein domains are shown as colored bars, RING RING domain, NLS nuclear localization sequence, SCD serine containing domain, BRCT BRCA1 C-terminus, T tower domain, OB oligonucleotide/oligosaccharide-binding. Horizontal solid black lines indicate protein binding domains for the listed binding partners. Red circles with letter P mark phosphorylation sites