Experiments in rats have shown that exposure to low doses of the oestrogenic compound bisphenol A during prostate development leads to altered gene expression and a predisposition to precancerous lesions of the prostate in old age.
Previous studies have shown that bisphenol A, which is used in the manufacture of plastics and epoxy resins, can leach from food and drink containers and enter the human bloodstream. The compound has been found in foetal tissue at levels five times higher than in maternal blood.
The prostate gland develops just after birth in rats, equivalent to foetal development in the second and third trimesters of human pregnancy. The researchers therefore exposed rat pups to bisphenol A at levels similar to those found in human blood serum. The prostate glands of the rats developed normally.
Once the rats were adults, the researchers exposed them to oestradiol, to mimic the changing hormones of men as they age.
They found that the rats exposed to bisphenol A as pups were more than twice as likely to develop precancerous prostate lesions after exposure to oestradiol as rats who were not exposed.
Lead researcher Dr Gail Prins, from the University of Illinois at Chicago, said the rat studies showed that early exposure to oestrogens was associated with increased prostate cancer susceptibility in later life.
'It does bring up the question of whether human exposures might be involved in disease processes in humans,' she said.
'This is highly relevant because relative oestradiol levels increase in ageing men as a result of their increased body fat and declining testosterone levels.'
Early exposure to bisphenol A was associated with permanent changes to expression of certain genes in prostate cells, a phenomenon known as epigenetic reprogramming.
'We will see if we can determine a molecular fingerprint that may indicate these exposures have taken place,' said Dr Prin.
Cancer Research 2006; 66: 5,624-32
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