|Unique Grape Skin Extract Inhibits Prostate
Cancer Cell Growth in the Laboratory
Laboratory experiments show that an extract of the skin of muscadine
grapes can inhibit growth of prostate cancer cells in the laboratory.
Investigators from the National Cancer Institute (NCI), part of
the National Institutes of Health, and their research partners
also show that muscadine grape skin extract (MSKE) does not contain
significant amounts of resveratrol, another grape skin component
that has been widely studied and shown to be of potential benefit
in preventing prostate cancer growth. The results appear in the
September 1, 2007, issue of Cancer Research.
Using a series of human prostate cancer cells, representing different
stages of prostate cancer progression, the researchers showed that
MSKE significantly inhibits the growth of cancerous, but not normal,
prostate cells, primarily by inducing a process called apoptosis,
or programmed cell death. Programmed cell death is one of the mechanisms
the body uses to rid itself of cells with unrepaired genetic damage
before those cells can duplicate themselves. In contrast, resveratrol
seems to act by blocking the cell cycle, a sequence of steps that
a cell passes through when it grows and divides into two identical
cells. Both mechanisms are used by the body to prevent the development
According to Jeffrey E. Green, M.D., chief of the Transgenic Oncogenesis
and Genomics Section in NCI's Center for Cancer Research (CCR), "These
results show that MSKE may have potent antitumor activities in
the lab that differ from the effects of resveratrol. Further studies
of MSKE will be necessary to determine if this extract has potential
as a chemopreventive or therapeutic agent."
The fact that all of the cells studied, which cover the different
stages of prostate cancer tumor progression, responded to MSKE
suggests that the active compounds in this extract may inhibit
tumor development at very early stages.
The muscadine grape (Vitis rotundifolia) is distinct
from the more common red grapes used to produce red wines, a major
source of resveratrol. The chemical constituents of muscadine grapes
differ from most other grape varieties, as they are richer in chemicals
called anthocyanins. Anthocyanins, which produce the red and purple
colors of the grapes, have strong antioxidant activity and have
shown several antitumor effects, including inhibition of DNA synthesis
in breast cancer cells, of blood vessel growth in some tumors,
and of enzymes involved in tumor spread. Muscadine grapes can be
found growing wild from Delaware to the Gulf of Mexico and westward
from Missouri to Texas.
While previous studies suggested that anthocyanins might suppress
the cancer process, no rigorous study of the mechanisms underlying
these effects has yet been done. Resveratrol, by contrast, has
been widely examined. Although earlier studies showed that it can
induce programmed cell death in prostate cancer cells, resveratrol
did not significantly induce cell death in the prostate cell model
system used for this muscadine study. The results of this study
suggest that resveratrol may activate different antitumor mechanisms
Even though MSKE had significant inhibitory effects on the prostate
cancer cells studied, it did not alter the growth rate of the normal
human prostate cells in the lab, which served as controls. Ongoing
studies of MSKE in animals will help to determine the underlying
mechanisms of MSKE's inhibitory effects in prostate cancer cells.
The researchers hope that the lab effects of MSKE will be reproducible
in testing on cancerous and normal prostate cells in animals. Should
MSKE move on to trials in humans, Green says that since "muscadine
grape products, including grape juice and grape wine, have been
used in human studies without reported side effects, they may be
relatively safe for use in clinical trials."
For more information about cancer, please visit the NCI website
at www.cancer.gov, or call
NCI's Cancer Information Service at 1-800-4 CANCER (1-800-422-6237).
For more information on Dr. Green's research at NCI, please go
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