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Soy Isoflavones and Lignans Reduce Risk of Endometrial Cancer

High consumption of isoflavones, which are found in soy, and lignans, found in foods such as flaxseeds, reduce the risk of developing endometrial cancer, according to an August 2003 study.

The researchers undertook the study because the development of endometrial cancer is related to prolonged exposure to unopposed estrogens. Phytoestrogens, which are weak estrogens found in plant foods, may have antiestrogenic effects.

The researchers evaluated the link between dietary intake of phytoestrogens, including isoflavones and lignans, and the risk of endometrial cancer. The study, conducted in the San Francisco Bay Area, evaluated dietary information from 500 African American, Latina, and white women aged 35-79 years who were diagnosed with endometrial cancer between 1996 and 1999. The researchers compared these women to 470 age- and ethnicity-matched control women.

After comparing the two groups of women, the researchers discovered that the more isoflavones and lignans the women consumed, the less likely they were to develop endometrial cancer, particularly in postmenopausal women.  Soy is a source of isoflavones and Flaxseed is a rich source of lignans.  The researchers concluded, 'Some phytoestrogenic compounds, at the levels consumed in the typical American-style diet, are associated with reduced risk of endometrial cancer.'

Source: Horn-Ross PL, John EM, Canchola AJ, Stewart SL, Lee MM. Phytoestrogen intake and endometrial cancer risk. J Natl Cancer Inst. 2003 Aug 6;95(15):1158-64.  

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Vitamin B6 Stops Pancreatic Cancer Growth

A study published in the May 2003 issue of the journal Nutrition Research showed that vitamin B6 significantly inhibited the growth of pancreatic cancer in a human cell line. Researches from Brigham and Women’s Hospital / Harvard Medical School in Boston tested a human pancreatic carcinoma cell line with six different concentrations of pyridoxine, the most well known form of vitamin B6, and six varying concentrations of pyridoxal, another form of the vitamin. Control groups of cells did not receive the vitamin. Each experiment was carried out three times.

At concentrations of 2.5 micromoles and greater, pyridoxine inhibited pancreatic cell growth in a dose dependent manner, meaning the greater the dose, the greater the cancer inhibition. Concentrations of pyridoxine below 2.5 micromoles did not product this effect. From the second day of treatment, pyridoxal inhibited cancer growth at concentrations of 0.5 micromoles and greater but not at 0.1 micromoles.

The authors note that similar findings have been obtained with melanoma and liver cancer cells. They also noted that vitamin B6 added to the diet of mice suppressed tumors, and that the vitamin may inhibit colon cancer in some models of the disease. Additionally, supplementation with a multivitamin that included 100 milligrams pyridoxine per day reduced the risk of bladder cancer in one double-blind clinical trial.

The relatively high amounts of vitamin B6 needed in this study to inhibit cancer cell growth may raise some questions concerning safety, however, the authors cite a study in which 400 milligrams vitamin B6 per day was given to physically active men for twelve weeks during which no side effects were reported. Further studies are needed to determine the effect of megadose vitamin B6 treatment for cancer of the pancreas in human subjects.

Source: Nutrition Research, May 2003

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Melatonin Lowers Occurrence and Spread of Tumors in Mice

A study published in the January 2003 issue of the International Journal of Cancer further confirmed researchers' suspicions that low levels of the hormone melatonin may play a role in the development of cancer.

In the study, researchers examined the effects of melatonin treatment on mice genetically bred to have a greater risk of developing breast cancer. The mice were divided into three groups. One group was given melatonin five times monthly during the night with tap water (interrupted treatments). Another group received melatonin continuously until they died naturally. A third group served as controls, receiving no melatonin.

The results indicated the group receiving melatonin continuously experienced a decreased incidence of breast tumors and the tumors that did occur were smaller compared to controls. In addition, the group treated with continuous melatonin were less likely to have their cancer spread to the lungs. Also in this group of animals, the number of mice with four or more tumors was reduced.

Reference: Anisimov VN, Alimova IN, Baturin DA, Popovich IG, Zabezhinski MA, Manton KG, Semenchenko AV, Yashin AI. The effect of melatonin treatment regimen on mammary adenocarcinoma development in HER-2/neu transgenic mice. Int J Cancer. 2003 Jan 20;103(3):300-5.  

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Green Tea May Prevent Esophageal and Stomach Cancer

The 2002 annual meeting of the American Association for Cancer Research was the site of a presentation demonstrating that green tea drinkers in China have approximately half the rate of cancer of the esophagus and stomach as those who drink little tea. 

Researchers at the Keck School of Medicine at the University of Southern California analyzed data collected from 18,244 Chinese men ages 45 to 64 during which 42 men were diagnosed with esophageal cancer and 190 with stomach cancer. The men were followed from 1986 to 2002. Participants diagnosed with cancer were compared to 772 men who did not have cancer. Green tea polyphenols, the ingredients believed to be responsible for the benefits conferred by drinking tea and which include epigallocatechin and epicatechin and polyphenol breakdown products were measured in the urine of both groups.

The researchers found that epigallocatechin's presence in the urine was associated with a lowered incidence of esophageal and gastric cancer, after adjustment for other factors such as smoking and alcohol drinking. It is believed that the powerful antioxidant properties of green tea polyphenols are responsible for their anticancer effect, by protecting proteins DNA from oxidative damage.

Research team member and professor of preventive medicine at Keck School of Medicine Mimi C. Yu, PhD, summarized, "This study provides direct evidence that tea polyphenols may act as chemopreventive agents against gastric and esophageal cancer development."

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Resveratrol from Grapes May Fight Cancer

Resveratrol, the component of grapes best known for its cholesterol-lowering effects, may have another claim to fame: the ability to prevent cancer.

A study reported in the March 2002 British Journal of Cancer shows that the body converts resveratrol into an anticancer agent that can target and kill cancer cells. Previous studies have determined that resveratrol has anti-cancer abilities, but this was the first study to show the mechanism behind resveratrol's anticancer actions.

The researchers discovered that the cytochrome P450 enzyme known as CYP1B1, found in a number of different tumors, metabolizes resveratrol into a phytoestrogen known as piceatannol, which has anticancer activity. The cell death triggered by piceatannol /resveratrol was limited to cancer cells and did not harm normal cells.

According to the researchers, the study demonstrates "that a natural dietary cancer preventative agent can be converted to a compound with known anticancer activity by an enzyme that is found in human tumors." Research team leader and coauthor Professor Gerry Potter, of De Montfort University's School of Pharmacy commented, "We suspected that resveratrol might be beneficial for health and have cancer preventative properties. This research shows just how it could prevent tumors developing by producing these anticancer molecules within the cancer cells themselves."

Resveratrol's responsibility in grapes is mainly to protect the fruit against fungus. But over the years research indicated that in humans it has a number of beneficial effects. Resveratrol is found in red wine and is thought to be the reason why this beverage is so beneficial for the heart. This new study adds to the mounting evidence that resveratrol's abilities may reach beyond protecting the heart.

Reference: Potter GA, Patterson LH, Wanogho E, Perry PJ, Butler PC, Ijaz T, Ruparelia KC, Lamb JH, Farmer PB, Stanley LA, Burke MD. The cancer preventative agent resveratrol is converted to the anticancer agent piceatannol by the cytochrome P450 enzyme CYP1B1. Br J Cancer. 2002 Mar 4;86(5):774-8.

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St John's Wort Extract Fights Cancer

Researchers from the University of Freiburg, in Germany, have discovered that hyperforin, a natural antibiotic found in the herb St John's Wort, inhibits tumor cell growth. The research was published in the February 14 2002 issue of the journal Oncogene http://www.naturesj.com/onc/index.html, one of the top five cancer research journals in the world. 

The scientists found that the compound induced apoptosis, or programmed cell death in sixteen human and rat tumor cell lines. Although many of the cell lines were resistant to such common chemotherapeutic drugs as camptothecin, paclitaxel and vincristine, hyperforin arrested tumor growth in all but one line. In vivo, hyperforin was able to inhibit the growth of breast cancer cells injected into rats as well as paclitaxel, however, hyperforin did not produce any signs of toxicity, as is common when using chemotherapeutic drugs.

The researchers, led by Dr. C M Schempp of the University of Freiburg's Department of Dematology, believe that their investigations demonstrate that hyperforin's mechanism of action is that of activating a mitochondrial-mediated apoptosis pathway. Mitochondria are the cell's energy-producing organelles. Mitochondria of cells treated with hyperforin were observed to rapidly lose membrane potential as well as release cytochrome c, which is necessary for apoptosis. The authors conclude, "Owing to the combination of significant antitumour activity, low toxicity in vivo and natural abundance of the compound, hyperforin holds the promise of being an interesting novel antineoplastic (anti-cancer) agent that deserves further laboratory and in vivo exploration."

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