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Bisphenol A exposure linked to prostate cancer

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Evidence is continuing to accumulate that the industrial chemical bisphenol A (BPA) is a health hazard. The latest study of its toxicity was published on March 3 in the journal PLOS ONE by researchers at the University of Cincinnati College of Medicine (Cincinnati, Ohio). The researchers have found a link between BPA and prostate cancer.

BPA is an organic compound that is used to make polycarbonate plastic and epoxy resins; it is present in thousands of consumer products, including cans, receipts, and plastic water bottles. BPA exposure is widespread in the US—comprising more than 90% of the population. The substance can be absorbed through the skin, inhaled, and ingested from contaminated food and water. Last January, the state of California announced that it intends to ban BPA because it is a reproductive health hazard. It is an endocrine disruptor that mimics estrogen and thyroid hormone; in addition, the chemical is a metabolic and immune system disruptor. Higher levels of BPA exposure have been linked with an increased risk of cardiovascular disease, obesity, diabetes, immune disorders, and numerous reproductive dysfunctions.

The researchers note that laboratory and animal studies have found that BPA exposure can increase the risk of breast, brain, and prostate cancers; however, human studies connecting BPA exposure to heightened cancer risk are rare. Therefore, the investigators conducted as study to examine the association between urinary BPA levels and prostate cancer; they evaluated the effects of BPA on induction of centrosome abnormalities, which could serve as an underlying mechanism promoting the development of prostate cancer. (Centrosomes are small structures located next to the cell nucleus; centrosome abnormalities are a frequent finding in various malignant tumors.)

The study group comprised 60 urology patients; the investigators found higher levels of urinary BPA in prostate cancer patients than in patients without prostate cancer (5.74 µg/g vs. 1.43 µg/g). The difference was even greater in patients younger than 65 years of age. The researchers also found a trend toward a negative association between urinary BPA and serum PSA in prostate cancer patients but not in patients without prostate cancer. A laboratory study of four prostate cancer lines involved examination for centrosome. The findings were compared to two normal prostate cancer cell lines. Samples from both cell lines were exposed to low but increasing levels of BPA. The researchers found that increased levels of BPA increased the percentage of cells with centrosome abnormalities.

The investigators concluded that their findings provide the first evidence that urinary BPA level may predict the risk of prostate cancer and that disruption of the centrosome duplication cycle by low-dose BPA is a previously unknown mechanism underlying malignant transformation and cancer progression in the prostate. Prostate cancer is primarily a disease of men beyond the age of 65; however, the study found the presence of prostate cancer in men younger than 65 who had high BPA levels.

Prostate cancer is most successfully treated when found early. The American Cancer Society (ACS) reports the following statistics:

  • More than 90% of all prostate cancers are discovered while they are either localized (confined to the prostate) or regional (nearby). The five-year survival rate for men diagnosed with prostate tumors discovered at these stages is almost 100%.
  • In the past 25 years, the five-year survival rate for all stages combined has increased from 68% to almost 100%.
  • Prostate cancer is the most common cancer among men, excluding skin cancer.

At the early stage, there are usually no specific signs or symptoms of thee cancer. A prostate-specific antigen (PSA) blood test and digital rectal exam (DRE) can provide the best chance of identifying prostate cancer in its earliest stages; however, these tests can have some limitations; thus, it is prudent for a man to discuss prostate screening with a physician.

The following are the most common symptoms of prostate cancer. However, each individual may experience symptoms differently. Symptoms may include:

  • Weak or interrupted flow of urine
  • Urinating often (especially at night)
  • Difficulty urinating or holding back urine
  • Inability to urinate
  • Pain or burning when urinating
  • Blood in the urine or semen
  • Nagging pain in the back, hips, or pelvis if cancer has spread to the bones
  • Painful ejaculation

As a man ages, his prostate may enlarge and obstruct the flow of urine, or interfere with sexual function. An enlarged prostate gland, a condition called benign prostate hyperplasia, may require treatment with medicine or surgery to relieve symptoms. This common benign prostate condition, which is not cancer, can cause many of the same symptoms as prostate cancer.

  • In general, all men are at risk for prostate cancer. However, there are specific risk factors that increase the likelihood that certain men will develop the disease, including the following:
  • Age. Age is a risk factor for prostate cancer, especially for men 50 and older. Nearly two-thirds of all prostate cancers are diagnosed in men over the age of 65.
  • Race. Prostate cancer is more common among African-American men than it is among white American men. Japanese and Chinese men native to their country have the lowest rates of prostate cancer. However, when Chinese and Japanese men immigrate to the U.S., they have an increased risk of and mortality rate from prostate cancer when compared to their native populations. In Japan, the incidence of prostate cancer has increased as Western diets and lifestyles have been adopted.
  • Diet. Epidemiological data suggest that the diet consumed in Western industrialized nations may be a factor in developing prostate cancer. Consider the following information regarding diet and its effect on the risk for prostate cancer:
    • Fat. Some studies suggest that men who eat a high-fat diet, especially if it is high in red meat or high-fat dairy products, may have a greater chance of developing prostate cancer.
    • Fruits and vegetables. Diets high in fruits and vegetables may lower prostate cancer risk, although it is not clear which nutrient(s) may be responsible for this.
    • Vitamin E and selenium. The antioxidant Vitamin E, combined with selenium, has been shown to inhibit tumor growth in laboratory animals. But a large study found that supplements of these substances did not lower the risk of prostate cancer in men. In fact, the men taking vitamin E had a slightly higher risk of prostate cancer.
    • Carotenoids. Carotenoids, such as lycopenes, have been shown to inhibit the growth of human prostate cancer cells in tissue cultures (cells grown in the laboratory). The primary source of lycopenes is processed tomatoes. Again, however, it is not clear if lycopenes affect prostate cancer risk in men, as not all studies have found a benefit.
  • Obesity. Most studies have not found obesity to affect the risk of getting prostate cancer, but obese men may be more likely to develop more aggressive forms of prostate cancer.
  • Environmental exposures. Some studies show an increased risk of prostate cancer in men who are farmers, or those exposed to the metal cadmium while making batteries, welding, or electroplating. Additional research is needed in this area to confirm whether this is a true association.
  • Having a vasectomy, BPH (benign prostatic hyperplasia), or an STD (sexually transmitted disease). Researchers have looked at whether men who have had a vasectomy, BPH, or those who have been exposed to a sexually transmitted disease are at increased risk for prostate cancer. Some studies suggest a link, while others do not support these claims.
  • Family history of prostate cancer. Having a father or brother with prostate cancer more than doubles a man's risk of developing this disease. The risk is even higher for men with several affected relatives, particularly if the relatives were young at the time of diagnosis. Geneticists (doctors and scientists who study inheritance and the causes of genetic disease) divide families into three groups, depending on the number of men with prostate cancer and their ages of onset, including the following:
    • Sporadic. A family with prostate cancer present in one man, at a typical age of onset; sporadic means occurs by chance.
    • Familial. A family with prostate cancer present in more than one person, but with no definitive pattern of inheritance and usually an older age of onset.
    • Hereditary. A family with a cluster of three or more affected relatives within any nuclear family (parents and their children), a family with prostate cancer in each of three generations on either the mother or father's side, or a cluster of two relatives affected at a young age (55 or younger). Five to 10 percent of prostate cancer cases are considered hereditary.
  • Genetic factors. In the center of each cell of the human body, our genetic material—chromosomes—are found. Normally, cells contain 46 chromosomes, or 23 pairs, half of which are inherited from our mother, half from our father. The chromosomes contain genes—the body's blueprint. Genes code for traits, such as eye color and blood type, and also control important regulatory functions in the body such as the rate of cell growth. Some genes, when altered or mutated, give a higher risk for uncontrolled cell growth, which, in turn, can lead to tumor development. These genes have various names, but overall are referred to as cancer susceptibility genes. Approximately 5-10% of all prostate cancers are known to be attributed to an inherited DNA change.
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