Background: The BRCA1 gene is an important breast-cancer susceptibility gene. Promoter polymorphisms can alter the binding affinity of transcription factors, changing transcriptional activity and may affect susceptibility to disease.
Methods and Results: Using direct sequencing of the BRCA1 promoter region, we identified four polymorphisms c.-2804T→C (rs799908:T→C), c.-2265C→T (rs11655505:C→T), c.-2004A→G (rs799906:A→G) and c.-1896(ACA)1→(ACA)2 (rs8176071:(ACA)1→(ACA)2) present in Hong Kong Chinese. Each polymorphism was studied independently and in combination by functional assays. Although all four variants significantly altered promoter activity, the c.-2265T allele had stronger binding than the C allele, and the most common mutant haplotype, which contains the c.-2265T allele, increased promoter activity by 70%. Risk association first tested in Hong Kong Chinese women with breast cancer and age-matched controls and replicated in a large population-based study of Shanghai Chinese, together totalling >3000 participants, showed that carriers of the c.-2265T allele had a reduced risk for breast cancer (combined odd ratio (OR) = 0.80, 95% CI 0.69 to 0.93; p = 0.003) which was more evident among women aged ⩾45 years at first diagnosis of breast cancer and without a family history of breast cancer (combined OR = 0.75, 95% CI 0.61 to 0.91; p = 0.004). The most common haplotype containing the c.-2265T allele also showed significant risk association for women aged ⩾45 years without a family history of breast cancer (OR = 0.64, 95% CI 0.46 to 0.89; p = 0.008).
Conclusion: This comprehensive study of BRCA1 promoter polymorphisms found four variants that altered promoter activity and with the most significant contribution from c.-2265C→T, which could affect susceptibility to breast cancer in the Chinese population. Its significance in other populations remains to be investigated.
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▸ Supplementary tables and figure are published online only at http://jmg.bmj.com/content/vol46/issue1
The first two authors contributed equally to this work
Funding: This study was funded by the Research Grant Council, Hong Kong SAR, China, (project code HKU 7520/05M) and the Committee on Research and Conference Grants from the University of Hong Kong (project code 200711159018). The Shanghai Breast Cancer Study is supported by RO1CA64277 and RO1CA90899 from the National Cancer Institute.
Competing interests: None.