An investigation of mammographic density and gene variants in healthy women

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Abstract
This cross-sectional study examined if polymorphisms in genes that code for enzymes involved in the production and metabolism of estrogens are associated with mammographic density, a strong predictor of breast cancer risk. The study included 328 healthy women of different ethnicities who underwent mammographic screening and donated a blood or mouthwash sample for DNA analysis. After digitizing cranio-caudal views of the mammograms, we performed computer-assisted mammographic density assessment. Following DNA extraction, samples were analyzed for polymorphisms in the COMT (Val158Met), CYP1A1 (Ile462Val), CYP1B1 (Val432Leu), CYP1A2 (*1F) and CYP17 (T27C) genes using PCR-RFLP. Breast density was lower in Caucasians than in Asians. Caucasian women were less likely to carry the CYP1A1 variant allele and more likely to carry the variant alleles for CYP1B1 and COMT than women with Asian or Hawaiian ancestry. The low-activity COMT and CYP1A2 variant alleles were weakly related to lower percent mammographic density after adjustment for age, ethnicity, body mass index and reproductive variables (p for gene-dosage effect = 0.08 and 0.05, respectively). These relations were observed in premenopausal women only and were similar in direction and magnitude after stratification by ethnicity. We found no significant associations between breast density and the variant alleles for CYP1A1, CYP1B1 and CYP17. Our data suggest lower mammographic density for women carrying the COMT and CYP1A2 variant alleles than for women carrying the common alleles, though this is the opposite of what is commonly hypothesized from the enzyme function.

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