Saturday, May 3, 2008

Do vitamin D receptors influence the risk of breast cancer?

Certain vitamin D receptor (VDR) gene polymorphisms could affect the risk of breast cancer, as well as the estrogen receptor status of tumours in postmenopausal women, according to findings from a German study.

In Breast Cancer Research, Dr. Jenny Chang-Claude of the German Cancer Research Center, Heidelberg and colleagues note that VDR polymorphisms may influence cancer risk by altering the potentially anti-carcinogenic effects of vitamin D. Epidemiological studies have, however, previously yielded inconsistent results.

The researchers conducted a study of 1408 women with breast cancer and 2612 age-matched controls. They found no differences in serum 25-hydroxyvitamin D by VDR genotype. Overall, there was no association between the four individual polymorphisms analyzed and the risk of breast cancer.

What was interesting was that the Taql polymorphism was associated with the estrogen receptor status of tumours. Specifically, for t allele carriers compared to noncarriers among the breast cancer cases, the odds ratio was 1.18 for estrogen receptor-positive tumors and 0.88 for estrogen receptor-negative tumors.

Further analysis showed that the haplotype FtCA, which contains the Taql t allele, was associated with a significantly greater cancer risk (odds ratio, 1.43) than was FTCG, the most frequent haplotype.

It was concluded that the results support the potential effects of VDR polymorphisms on postmenopausal breast cancer risk. Future epidemiological studies assessing the association of vitamin D and breast cancer risk should therefore take the receptor status of the tumour and other gene variants of oestrogen metabolism into account.

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