foodconsumer.org: Vegetable-based drug could suppress melanoma

Vegetable-based drug could suppress melanoma
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admin on 03/01/2009 17:37:00
 
March 1, 2009 (foodconsumer.org) -- Compounds extracted from green vegetables,
when used along with selenium, could be a potent treatment for melanoma, a
deadly skin cancer, according to a new study published in the March 2009 issue
of Clinical Cancer Research.
The study, led by researchers at Penn State College of Medicine, showed that the
treatment of targeted tumors was safer and more effective than conventional
therapy.
"There are currently no drugs to target the proteins that trigger melanoma,"
said Dr. Gavin Robertson.  "We have developed drugs from naturally occurring
compounds that can inhibit the growth of tumors in mice by 50 to 60 percent with
a very low dose."
In previous studies, Robertson and his colleagues found targeting the Akt3
protein may potentially inhibit the development of melanoma.  The finding led
them to a class of compounds called isothiocyanates, which are commonly found in
cruciferous vegetables such as broccoli.
Isothiocyanates have been known to have certain chemo-preventative properties. 
The problem is that the potency of these compounds is too low to be used as
therapeutic agents to treat cancer.
In the current study, the researchers compared the therapeutic efficacy of
isothiocyanates and isoselenocyanates in tumor-bearing mice.  Isoselenocyanate
is a drug in which the sulfur bonds have been replaced with selenium, according
to a press release by Penn State.
"Selenium deficiency is common in cancer patients, including those diagnosed
with metastatic melanoma," explained Robertson.  "Besides, selenium is known to
destabilize Akt proteins in prostate cancer cells."
For the study, the researchers injected mice with 10 million cancer cells and
six days later when large tumors developed in the mice, they treated the animals
either with isothiocyanates or isoselenocyanates.
"We found that the selenium-enhanced compounds significantly reduced the
production of Akt3 protein and shut down its signaling network," explained
Robertson.
In addition, isoselenocyanates also reduced the growth of tumors by 60 percent,
compared to the isothiocyanates alone.
Different human melanoma cell lines responded to the selenium enhanced drug
differently with the efficiency ranging from 30 to 70 percent, depending on the
cell lines.
The mechanism behind the therapeutic effect of isoselenocyanates remains
unknown, but the researchers believe that the use of naturally occurring
compounds that target cancer-causing proteins may lead to the discovery of more
effective ways to treat melanoma.
The National Cancer Institute estimated that melanoma was found in 62,480 people
in the U.S. and killed 8,420 in 2008.
Rich sources of selenium include Brazil nuts, shrimp, crab meat, salmon,
halibut, brown rice, chicken, port, and whole wheat bread.
Isothiocyanates are found in vegetables including broccoli, Brussels sprouts,
cabbage, horseradish, mustard, radish, watercress, garden cress, and Indian
cress. The common isothiocyanates include allyl isothiocyanate, benzyl
isothiocyanate, phenethyl isothiocyanate, and sulforaphane, according to the
Linus Pauling Institute.
By Sue Mueller, and edited by Heather Kelley.