Objective: To investigate the role of disease associated germ line mutations in BRCA1 gene among Chinese early-onset breast cancer patients.
Methods: A total of 188 early-onset breast cancer patients, who were diagnosed with breast cancer before 41-year-old, were enrolled from four breast cancer clinical centers in China. Thirty-nine of them (20.7%) also had family history of breast/ovarian cancer. DNA extracted from lymphocytes was amplified by polymerase chain reaction (PCR) for the entire exons and the splicing sites of BRCA1. Twenty-two of the patients were screened by single strand conformation polymorphism (SSCP), and the other 166 of them were screened by denaturing high performance liquid chromatography (DHPLC). The abnormal fragments recognized were ascertained by DNA direct sequencing. For those samples with the same recurrent mutation, five BRCA1-linked markers (D17S855, D17S1322, D17S1323, D17S1326 and D17S1327) were used for the allelotype analysis.
Results: Twelve disease-associated mutations were identified in 15 (8.0%) patients, among which BRCA1 1100delAT and 5589del8 were identified in 3 and 2 patients respectively. Nine (23.1%) of them were identified in those with breast/ovarian cancer family history. The difference of BRCA1 mutation frequency between the patients with and without family history was statistically significant (P=0.001). Allelotype analysis showed the two BRCA1 5589del8 mutation carriers shared the same allelotype in all the 5 STR sites, and two of the three 1100delAT mutation carriers, who came from the northern China, also shared the same allelotype in all the 5 STR sites, which were different from those of the 5589del8 mutation carriers'.
Conclusion: This is a relatively very large scale multi-hospital-based study of BRCA1 mutations in Chinese early-onset breast cancer patients up to now. It seems reasonable to give genetic consultations and genetic test of BRCA1 gene to early-onset breast cancer patients in China, especially for those with breast/ovarian cancer family history. The two recurrent mutations might be founder mutations of Chinese population. It might be cost-effective to analyze these two mutations before whole gene analysis.