Haiyan Jiao^1,2, Chunlian Liu³, Weidong Guo⁴, Liang Peng^1,2, Yintao Chen^1,2 and Francis L. Martin⁵

¹Department of Medical Genetics and Cell Biology, Ningxia Medical University, Yinchuan, Ningxia, 750004, P. R. China. ²Key Laboratory of Reproduction and Genetics of Ningxia Hui Antonomous Region, Yinchuan, Ningxia, 750004, P. R. China. ³Department of Reproduction, Center of Gynaecology and Obstetrics, Affiliated Hospital of Ningxia Medical University, Yinchuan, Ningxia, 750004, P.R. China. ⁴Department of Surgical Oncology, Affiliated Hospital of Ningxia Medical University, Yinchuan, Ningxia, 750004, P. R. China. ⁵Centre for Biophotonics, Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, UK.

Abstract

Studies investigating possible associations between cytochrome P4501B1 (CYP1B1) polymorphisms and breast cancer risk have been inconsistent. We set out to ascertain whether there might be an association between polymorphisms in exon 2 (codon 119, G→T) and exon 3 (codon 432, G→C) of CYP1B1 and breast cancer in a Chinese Han population in the rural region of Ningxia. Using an allele-specific polymerase chain reaction method and direct DNA sequencing, the presence or absence of the two CYP1B1 polymorphisms was investigated. Genotype and allele frequencies were analyzed in breast cancer cases (n = 152) and healthy age-matched controls (n = 156). The odds ratio (OR) of 119G→T or 432G→C in breast cancer cases and controls was 3.3 (95% CI: 1.28 to 8.28) and 2.8 (95% CI: 1.04 to 7.51), respectively. In addition, the OR for people with both polymorphisms (119T and 432C) was 4.69 (95% CI: 1.97 to 11.19). Our results suggest that certain polymorphisms in the CYP1B1 gene might increase risk for breast cancer among Han Chinese, perhaps because they influence the efficiency of CYP1B1 bio-transformation of oestrogens or pro-carcinogens into DNA- reactive electrophiles that may act as cancer-initiating agents.