Five studies presented today during the American Association for Cancer
Research's 4th annual Frontiers in Cancer Prevention Research meeting in
Baltimore, Md., add to the arsenal of research that shows adding certain
vegetables and herbs to the diet can prevent or, in some cases, halt the growth
of cancer.
Moreover, it is not just a matter of mechanical prevention, such as adding
fiber to the diet to maintain digestive health. This research deals with the
chemical interactions between compounds found in foods and the body's cells and
DNA, and it shows that the addition of these foods to the diet can reap benefits
at any stage of life.
Broccoli Sprouts Relieve Gastritis in H. pylori Patients; May Help
Prevent Gastric Cancer (Abstract #3442)
Broccoli sprouts may not be a culinary favorite for some, but their chemical
properties are becoming increasingly popular among those interested in
preventing cancer.
In the latest series of studies, a team from Japan has found that a diet rich
in broccoli sprouts significantly reduced Helicobacteri pylori (H. pylori)
infection among a group of 20 individuals. H. pylori is known to cause gastritis
and is believed to be a major factor in peptic ulcer and stomach cancer.
"Even though we were unable to eradicate H. pylori, to be able suppress it
and relieve the accompanying gastritis by means as simple as eating more
broccoli sprouts is good news for the many people who are infected," said
Akinori Yanaka from the University of Tsukuba, Japan, lead investigator of the
study.
Scientists are focusing on the anti-cancer properties of a chemical derived
from broccoli sprouts called sulforaphane. Among other things, this chemical has
the ability to help cells defend against oxidants, the highly reactive and toxic
molecules that damage DNA and kill cells, leading potentially to cancer.
Previously, researchers working with H. pylori discovered that sulforaphane acts
against the bacterium in vitro, alleviating gastritis in H. pylori-infected mice
through its antioxidant activity.
None of these findings had been tested in people, however, until the Yanaka-led
team added broccoli sprouts (the plant at its youngest and most sulforaphane-rich,
just two or three days old) to the diet of 20 individuals infected with H.
pylori. Another group of 20 infected with the bacterium received alfalfa spouts
instead of broccoli sprouts. Each received 100 grams of fresh sprouts daily for
two months.
"We wanted to test alfalfa spouts together with broccoli sprouts," Yanaka
explained, "because the chemical constituents of the two plants are almost
identical."
However, the way in which they differ is significant. Broccoli sprouts
contain 250 milligrams of sulforaphane glucosinolate per 100 grams per serving,
whereas alfalfa sprouts contain neither sulforaphane nor sulforaphane
glucosinolate.
Glucosinolates occur in cruciferous vegetables, like broccoli and cabbage,
and are broken down enzymatically into sulforaphane and a variety of other,
biologically active compounds when damage occurs to the plant--that is, by
cutting or chewing it.
The presence of H. pylori was assessed by performing urea breath tests and
evaluating H. pylori-specific stool antigen. The degree of gastritis was
evaluated by measuring the level of pepsinogen in the blood. Pepsinogen is also
an indicator of gastric atrophy. These tests were performed just before adding
broccoli and alfalfa sprouts to the diet, and at one and two months after
starting the dietary regimen. Following two months' consumption of 100 grams of
broccoli sprouts per day, patients showed significantly less H. pylori and
markedly decreased pepsinogen. Alfalfa sprouts had no effect, and the broccoli
failed to eliminate H. pylori completely. Two months after eliminating broccoli
sprouts from the diet, H. pylori and pepsinogen returned to pre-test levels in
the subjects.
"The data suggest strongly that a diet rich in sulforaphane glucosinolate may
help protect against gastric cancer, presumably by activating gastric mucosal
anti-oxidant enzymes that can protect the cells from H. pylori-induced DNA
damage," Yanaka concluded.
Broccoli Sprout-extract Protects Against Skin Cancer from UV Light in
High-risk Mice (Abstract #2597)
Eat it or wear it? That is the question.
If you ask Albena T. Dinkova-Kostova, Ph.D., of Johns Hopkins University in
Baltimore, she will likely answer "both."
In the laboratory of Paul Talalay, M.D., who first reported the indirect
antioxidant properties of sulforaphane, the compound derived from cruciferous
vegetables like broccoli, Dinkova-Kostova and her colleagues applied broccoli
sprout extract to the skin of hairless mice, and found it counteracted the
carcinogenic response to ultraviolet light exposure.
Mice from a strain characterized by post-weaning hair loss were exposed to a
dose of UV light comparable to what a person would get sunbathing at the beach
on a clear day, twice a week for 20 weeks. After irradiation, broccoli sprout
extracts containing either a low or high dose of sulforaphane were applied to
the backs of the mice, five days a week for 11 weeks. Acetone (known commonly as
the ingredient in nail polish remover) was used as the vehicle for delivering
the sulforaphane, and it alone was applied on the control group. At the
conclusion of the study period, 100 percent of the control mice had developed
cancerous skin tumors.
The incidence and number of tumors was reduced by half, however, in the mice
receiving the high dose of broccoli sprout extract. The rate of tumor reduction
was less among the low-dose recipients, but even in their case, some benefit was
observed.
"We weren't looking for a sunscreen effect," Dinkova-Kostova is quick to
point out. "The sulforaphane-containing extract was applied after the period of
regular exposure to ultra-violet light. That's more relevant, since most people
receive some sun damage to their skin in childhood, particularly adults who grew
up before effective sunscreen lotions were developed."
Previous research has shown that sulforaphane boosts protective and
detoxifying reactions in cells, inactivating carcinogens and reactive oxygen
intermediates that contribute to the disease by damaging DNA. As in other
studies involving the anti-cancer potential of sulforaphane, Dinkova-Kostova's
group notes that broccoli sprouts contain much more of the compound than adult
broccoli.
"Our findings suggest a promising strategy for skin cancer prevention after
exposure to UV light," Dinkova-Kostova said.
Change in Diet at Any Age May Help Protect Against Breast Cancer
(Abstract #3697)
Many find it to be the perfect companion to hot dogs and sausage, but new
studies suggest that sauerkraut may have another beneficial side effect -- it
may protect women from breast cancer.
Results from the U.S. component of the Polish Women's Health Study are
showing an association between cabbage and sauerkraut consumption, and a
constituent called glucosinolate, and a lower risk of breast cancer. The
influence seemed to be highest among women who consumed high amounts beginning
in adolescence and throughout adulthood.
"The observed pattern of risk reduction indicates that the breakdown products
of glucosinolates in cabbage may affect both the initiation phase of
carcinogenesis--by decreasing the amount of DNA damage and cell mutation--and
the promotion phase--by blocking the processes that inhibit programmed cell
death and stimulate unregulated cell growth," said Dorothy Rybaczyk- Pathak,
Ph.D., from the University of New Mexico.
Pathak, along with colleagues from Michigan State University and the National
Food and Nutrition Institute of Warsaw, Poland, evaluated the diet of Polish
immigrants to the United States, living in Chicago and surrounding Cook County,
Ill., and the Detroit, Mich., metropolitan area. Women with higher rates of raw-
or short-cooked cabbage and sauerkraut consumption, three or more servings per
week, compared to those who consumed less than one serving a week, had a
significantly reduced breast cancer risk.
Like broccoli, cabbage is a cruciferous vegetable--its flowers are in the
shape of a cross--and a member of the Brassica family, which includes broccoli,
Brussels sprouts, kale, collard greens and cauliflower. These plants contain
glucosinolates and the enzyme myrosinase which, when broken down by chewing or
cutting, release several biologically active products which previous studies
have shown to possess anti-carcinogenic properties.
Pathak began the study by wondering why the breast cancer risk of Polish
women rose three-fold after they immigrated to the United States. She
hypothesized that dietary changes were among the environmental factors
contributing to this rapid increase in risk. In Poland, where abundance of food
is a recent phenomenon, women traditionally eat an average of 30 pounds of
cabbage and sauerkraut per year, as opposed to just 10 pounds per year among
American women. Moreover, Polish women traditionally eat more raw cabbage and
sauerkraut, in salads, or short-cooked, as a side dish.
She observed the lowest rate of breast cancer among women who consumed high
amounts of raw- or short-cooked cabbage during adolescence, but found that high
consumption during adulthood provided a significant protective effect for women
who had eaten smaller quantities of this vegetable during adolescence. Cabbage
cooked a long time, such as in hunter's stew, cabbage rolls and pierogi, had no
bearing on breast cancer risk.
Possible Chemoprevention of Ovarian Cancer by the Herbal, Ginkgo
Biloba (Abstract #3654)
Researchers in Boston, led by Drs. Bin Ye and Daniel Cramer of Brigham and
Women's Hospital, have developed new laboratory and epidemiological evidence
that demonstrates, for the first time, that ginkgo biloba appears to lower the
risk of developing ovarian cancer.
In a population-based study which involved more than 600 ovarian cancer cases
and 640 healthy, matched controls, women who took ginkgo supplements for six
months or longer were shown to have a 60 percent lower risk for ovarian cancer.
Ye and his colleagues found that ginkgo, echinacea, St. John's Wort, ginseng,
and chondroitin were the most commonly used herbals among study participants. A
further analysis of the data showed that ginkgo was the only herb linked to
ovarian cancer prevention. The preventive effect was more pronounced in women
with non-muncious ovarian cancers, with data showing that ginkgo may reduce the
risk of this type of ovarian cancer by 65-70 percent. "Among the mixture of
ginkgo chemicals," said Ye, "we found laboratory evidence that ginkgolide A and
B--terpene compounds--are the most active components contributing to this
protective effect."
Ye's team, which included scientists from Dana-Farber Cancer Institute at
Harvard Medical School, Boston University and Linden Bioscience, next took the
evidence demonstrated by their population studies to the laboratory. In vitro
experiments showed that a low dosage of ginkgolide caused ovarian cancer cells
to stop growing. They observed significant cell cycle blockage in non-mucinous
ovarian cancer cells. Ginkgolides appeared to be less effective against the
mucinous type of ovarian cancer cells.
"While the detailed mechanism of ginkgo action on ovarian cancer cells is not
yet well understood," Ye explained, "from the existing literature it most likely
that ginkgo and ginkgolides are involved in anti-inflammation and
anti-angiogenesis processes via many extra- and intra-cellular signal pathways.
In the future, these findings could potentially offer a new strategy for ovarian
cancer prevention and therapy, using the active forms of ginkgolides."
Ovarian cancer is the most deadly of all gynecological cancers. It is called
a "silent killer" because most cases are discovered only in very advanced
stages.
Changing Genes: Garlic Shown to Inhibit DNA Damaging Chemical in
Breast Cancer (Abstract #2543)
Legend suggests that garlic may ward off evil spirits, such as vampires. Now
scientists are finding that garlic, or a flavor component of pungent herb, may
help ward off carcinogens produced by meat cooked at high temperatures.
Cooking protein-rich foods like meats and eggs at high temperatures releases
a chemical called PhIP, a suspected carcinogen. Epidemiological studies have
shown that the incidence of breast cancer is higher among women who eat large
quantities of meat, although fat and caloric intake and hormone exposure may
contribute to this increased risk.
Diallyl sulfide (DAS), a flavor component of garlic, has been shown to
inhibit the effects of PhIP that, when biologically active, can cause DNA damage
or transform substances in the body into carcinogens.
Ronald D. Thomas, Ph.D., and a team of researchers at Florida A&M University
in Tallahassee hypothesized that PhIP enhances the metabolism of the enzymes
linked to carcinogenesis. They further suggested that the diallyl sulfide
derived from garlic might counter this activity.
"We treated human breast epithelial cells with equal amounts of PhIP and DAS
separately, and the two together, for periods ranging from three to 24 hours,"
said Thomas. "PhIP induced expression of the cancer-causing enzyme at every
stage, up to 40-fold, while DAS completely inhibited the PhIP enzyme from
becoming carcinogenic."
The finding demonstrates for the first time that DAS triggers a gene
alteration in PhIP that may play a significant role in preventing cancer,
notably breast cancer, induced by PhIP in well-done meats.
Thomas noted that no studies have shown a link between cooking vegetables and
fruits and PhIP, regardless of the method used.
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Founded in 1907, the American Association for Cancer Research is a
professional society of more than 24,000 laboratory, translational, and clinical
scientists engaged in all areas of cancer research in the United States and in
more than 60 other countries. AACR's mission is to accelerate the prevention and
cure of cancer through research, education, communication, and advocacy. Its
principal activities include the publication of five major peer-reviewed
scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer
Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers &
Prevention. AACR's Annual Meetings attract nearly 16,000 participants who share
new and significant discoveries in the cancer field. Specialty meetings, held
throughout the year, focus on the latest developments in all areas of cancer
research.