A tetranucleotide repeat polymorphism in CYP19 and breast cancer risk

Area of Science:

• Genetics and Molecular Biology
• Endocrinology
• Cancer Research

Background:

• The CYP19 gene encodes aromatase, crucial for converting androgens to estrogens.
• A tetranucleotide (TTTA) repeat polymorphism in CYP19 intron 4 has been linked to breast cancer risk in prior studies.
• Previous research suggests specific CYP19 alleles may be more frequent in women with breast cancer.

Purpose of the Study:

• To investigate the association between CYP19 repeat alleles and breast cancer risk.
• To explore the relationship between CYP19 alleles and hormone levels in women.
• To evaluate the frequency of different CYP19 alleles in breast cancer cases and controls.

Main Methods:

• A case-control study nested within the Nurses' Health Study cohort.
• Genotyping of CYP19 tetranucleotide (TTTA) repeat polymorphism in 462 cases and 618 controls.
• Analysis of associations between CYP19 alleles, breast cancer risk, and hormone levels (estrone sulfate, estrone, estradiol).

Main Results:

• A statistically significant higher frequency of the (TTTA)10 allele was observed in breast cancer cases compared to controls (p=0.005).
• The (TTTA)10 allele was more frequent in advanced cancer cases (4+ nodes or distant metastasis, p=0.02).
• The 7-repeat allele was associated with decreased estrone sulfate levels, while the 8-repeat allele was linked to higher estrone/androstenedione ratios and elevated estrogen levels in controls.

Conclusions:

• While the (TTTA)10 allele showed increased frequency in breast cancer cases, no direct association with breast cancer risk was found.
• Polymorphisms in CYP19 may influence hormone levels, but the functional impact of the 10 allele on breast cancer risk remains unclear.
• Linkage disequilibrium with other functional polymorphisms in CYP19 might explain the observed associations, warranting cautious interpretation.