The CYP17A1 -34T > C polymorphism and breast cancer risk in BRCA1 and BRCA2 mutation carriers.

Exposure to estrogen has a major effect on breast cancer risk. A polymorphism (-34 T > C; rs743572) in the cytochrome P450c17alpha gene (CYP17A1) encoding an enzyme which controls estrogen levels was reportedly associated with breast cancer risk in average risk populations. The effect of this polymorphism on breast or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers has not been thoroughly investigated. With this aim, 2,221 BRCA1 and BRCA2 mutation carriers (1,313 with breast cancer, 279 with ovarian cancer, and 695 asymptomatic carriers), with either BRCA1 (n = 1693) or BRCA2 (n = 528) germline mutations from seven centers were genotyped for the -34 T > C CYP17 polymorphism. Genotyping was accomplished using Taqman allelic discrimination, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) or PCR-based restriction-fragment length polymorphism analysis, and limited sequencing. Data were analyzed using Cox proportional hazards models. The hazard ratios (HRs) for breast cancer was 1.02 (95% CI 0.89-1.17, p = 0.74) and 1.10 (95% CI 0.72-1.67, p = 0.66) for BRCA1 and BRCA2 mutation carriers, respectively. The HRs for ovarian cancer were 1.17 (0.94-1.46, p = 0.17) and 0.91 (0.31-2.67, p = 0.86) for BRCA1 and BRCA2 mutation carriers, respectively. Results remained unaltered when the Israeli cohort (primarily Ashkenazim) was evaluated separately. In conclusion, there was no overall evidence for an association of the -34 T > C CYP17 polymorphism with either breast or ovarian cancer risk in BRCA1 or BRCA2 mutation carriers.

Germline CHEK2 mutations in Jewish Ashkenazi women at high risk for breast cancer.

BACKGROUND: Germline mutations in BRCA1 and BRCA2 genes account for only 20-40% of familial breast cancer cases. The CHEK2 gene encodes a checkpoint kinase, involved in response to DNA damage, and hence is a candidate gene for breast cancer susceptibility. Indeed, the CHEK2*1100delC truncating mutation was reported in a subset of mostly North European breast cancer families. The rate of the CHEK2*1100delC variant in the Ashkenazi Jewish population was reported to be 0.3%. OBJECTIVES: To evaluate whether CHEK2 germline mutations contribute to a breast cancer predisposition in Ashkenazi** Jewish high risk families. METHODS: High risk Ashkenazi Jewish women, none of whom was a carrier of the predominant Jewish mutations in BRCA1/BRCA2, were genotyped for germline mutations in the CHEK2 gene by exon-specific polymerase chain reaction followed by denaturing gradient gel electrophoresis and sequencing of abnormally migrating fragments. RESULTS: Overall, 172 high risk women were genotyped: 75 (43.6%) with breast cancer (average age at diagnosis 49.6 +/- 9.6 years, mean +/- SD) and 97 asymptomatic individuals (age at counseling 48.3 +/- 8.2 years). No truncating mutations were noted and four previously described missense mutations were detected (R3W 1.2%, 1157T 1.2%, R180C 0.6% and S428F 5%), one silent polymorphism (E84E 20.5%) and one novel missense mutation (Y424H 1.2%). Segregation analysis of the 1157T and S428F mutations (shown to affect protein function) with the cancer phenotype showed concordance for the CHK2*1157T mutation, as did two of three families with the CHK2*S428F mutation. CONCLUSIONS: CHEK2 missense mutations may contribute to breast cancer susceptibility in Ashkenazi Jews.