By Joanna Lyford, Senior medwireNews Reporter
Bisphenol A (BPA), an organic compound that is ubiquitous in plastic products, may have a direct tumourigenic effect in the prostate, US researchers have shown.
The study, by Shuk-Mei Ho (University of Cincinnati, Ohio) and team, also showed that urinary levels of BPA are a marker of prostate cancer and may be linked with levels of prostate-specific antigen (PSA).
The findings “reveal a previously unknown relationship between BPA exposure and prostate cancer and suggest a mechanism underlying the role of BPA in cellular transformation and disease progression,” said Ho in a press statement.
“With this insight, we hope to further investigate ways we can decrease exposures to potentially cancerous-causing chemicals in everyday products and substances.”
Exposure to BPA exceeds 90% in the general population, entering the body through the skin, inhalation and ingestion of food and water. It mimics oestrogen and thyroid hormone and acts as a metabolic and immune disruptor; it is not, however, a recognised carcinogen.
In this study, Ho and team studied 60 male patients (mean age 70.0 years) from a urology clinic, 27 of whom had prostate cancer.
Urinary BPA levels (creatinine-adjusted) were significantly higher in men with prostate cancer than in men without, at 5.74 versus 1.43 µg/g. The difference was even more pronounced in men aged under 65 years, at 8.08 versus 0.90 µg/g.
In men with prostate cancer but not in cancer-free men, there was a signal of an inverse correlation between urinary BPA levels and PSA levels; the correlation failed to reach significance because of the small sample size, the authors say.
To investigate the molecular basis of these observations, Ho et al studied normal prostate epithelial cells and prostate cancer cells in vitro.
In all cell lines, exposure to low doses of BPA caused the proportion of cells with centrosome amplification to increase two- to eightfold. Centrosomes are often aberrant in cancer and are emerging as a potential therapeutic target in prostate cancer, note the authors.
In normal prostate epithelium, low doses of BPA promoted nucleation of microtubules and regrowth at centrosomes, whereas in one of the prostate cancer cell lines BPA encouraged anchorage-independent growth. These effects support a role for BPA in neoplastic transformation and disease progression, say the researchers.
They conclude: “[O]ur findings provide the first evidence that urinary BPA level may have prognostic value for [prostate cancer] and that disruption of the centrosome duplication cycle by low-dose BPA is a previously unknown mechanism underlying neoplastic transformation and cancer progression in the prostate.”
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