Identified potential pathogenic variants of BARD1 in 1449 Chinese high-risk breast cancer patients.

Abstract

e22525 Background: BARD1 (BRCA1-associated ring domain 1), nuclear partner of BRCA1, has been recognized as a breast cancer predisposition gene. Recently, two large-scale population-based case–control studies confirmed that germline loss-of-function mutations in BARD1 were associated with a risk of breast cancer. Since the germline mutation frequency of BARD1 is much less than that of BRCA1/2, the distinct mutation spectrum of BARD1 is still obscure, especially in Chinese breast cancer patients. To verify the utility of BARD1 genetic testing in Chinese population, we assessed the mutational frequency and spectrum of BARD1 in a sequential series of Chinese high-risk breast cancer patients. Methods: A cohort of high-risk breast cancer patients (n = 1449) were collected in Zhejiang Cancer Hospital from 2008 through 2020, including 608 familial breast cancer (BC) cases, 173 bilateral BC cases, 222 triple negative BC cases, 436 early-onset BC cases (≤40 years) and 10 male BC cases. The complete coding sequence and intron–exon boundaries of BARD1 were screened by a 98-gene panel sequencing assay. The SIFT, Polyphen2 and MutationTaster prediction programs were used for analyzing the effect of the variants of unknown significance (VUS) on the BARD1 protein function. Results: A total of three BARD1 pathogenic mutations (c.1348_1349delinsCAT, c.70_71insGT and c.373G > T) were identified, which had been all reported, and accounting for 0.2% (3/1449) in Chinese high-risk breast cancer patients. The frequencies were 0.33% (2/608) and 0.12% (1/841) in familial and non-familial breast cancer patients, respectively. In total, 19 VUSs including 17 missenses, one inframe deletion and one inframe insertion of BARD1 were identified in this study. Based on in silico analysis, nine BARD1 missense variants (c.76A > G, c.1912G > A, c.1693C > T, c.2191C > T, c.127C > A, c.1601C > T, c.443G > A, c.233G > A and c.1972C > T) were classified as potentially damaging. However, the two newly variants c.420_422del and c.68_69insTCCGGGAACGAGCCTCGTTCC still remain VUS, and the other eight variants were classified as benign. Conclusions: Our data presented the germline mutations of BARD1 in a large-scale Chinese high-risk breast cancer population, which accounted for 0.2% in our cohort. Moreover nine potential pathogenic variants were found based on in silico analysis. Clinically, these data may be helpful in genetic counseling of breast cancer patients with BARD1 germline mutation. While the further research on the VUS are needed.