Previous studies have found that a chemical commonly found in plastic products contributes to prostate cancer in animals. Does it have a role in human prostate cancer?
Prostate cancer is the second most common cancer in men in North America, yet its cause is unknown.
A team of researchers recently studied the association between urinary bisphenol A (BPA), a chemical used to make certain plastics and other products, and prostate cancer.
These researchers found that BPA in the urine was higher in men with prostate cancer compared to men without prostate cancer and even higher in men under age 65 with prostate cancer.
Shuk-Mei Ho, PhD, from the Department of Environmental Health and Center for Environmental Genetics at the University of Cincinnati and Cincinnati Veterans Affairs Hospital Medical Center in Cincinnati, Ohio, was the lead researcher on this study.
The study enrolled 60 men, 27 with prostate cancer and 33 without prostate cancer. The average age of the men was 70 years old.
The researchers measured levels of urinary BPA in the men.
Polycarbonate plastic may be found in some food and drink packaging, particularly water and infant bottles, although more manufacturers are now making BPA free packaging. Epoxy resins are used as protective coatings on metal products such as bottle tops, food cans and some water supply pipes.
In the lab, the researchers exposed prostate cancer cells in petri dishes to BPA to test its effects on normal cell division.
Results of the analyses showed that men with prostate cancer had higher levels of BPA in their urine than men without prostate cancer. The average amount of BPA in the urine of men with prostate cancer was 5.7 μg/g, compared with an average of 1.4 μg/g in the urine of men without prostate cancer.
The urinary BPA was even higher in the younger men with prostate cancer than in those without prostate cancer. In the men younger than 65, the average urinary BPA was 8.1 μg/g versus 0.9 μg/g in men without prostate cancer.
A possible explanation provided by the research team for higher BPA in younger prostate cancer patients was that BPA was first used in the US in 1957. Younger patients could have been exposed to BPA their whole lives, but older patients might not have contacted BPA until the age of 11 or older.
BPA treatment of prostate cells in the lab showed that BPA caused abnormal changes in the regular cell division processes.
Changes in centrosome amplification inside the prostate cells were increased two to eight times after exposure to low amounts of BPA. Centrosome function is needed for proper cell division, and centrosome abnormalities are often seen in cancers.
"BPA is not a recognized carcinogen," the authors of this study wrote.
“[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,” these authors wrote.
This study was published in the March issue of PLoS ONE.
Some of the funding for the research was provided by grants form the National Institutes of Health.