Cancer cells and normal cells are known
to respond differently to nutrients and drugs that affect glutathione
status.
Numerous studies have shown that tumor
cells have elevated levels of glutathione levels, which confers
resistance to chemotherapy drugs.
One of the challenges of cancer therapy
is how to deplete tumor cells of glutathione, so as to make them
more vulnerable to the effects of chemotherapy drugs, while at the
same time allowing normal cells to remain relatively unaffected
by chemotherapeutic drugs.
A number of new findings have emerged
that take into consideration the role of glutathione in pathways
that promote programmed cell death (apoptosis) in cancer cells.
A German study has reported that glutathione
(GSH) plays a critical role in cellular mechanisms that result in
cell death. The study found that cancer cells resistant to apoptosis
had higher intracellular GSH levels.
Depletion of glutathione in these tumor
cells made them more vulnerable to the effects of anticancer drugs
or the gene that promotes apoptosis (CD95 or APO-1/Fas). The researchers
concluded that apoptosis resistance in tumor cells depends, at least
in part, on intracellular GSH levels. (1)
In another study conducted in Spain,
researchers found that lowering GSH concentration may be convenient
not only for the efficiency of chemotherapy, but also to induce
a rather fast and direct apoptosis mechanism in tumor cells. (2)
Based on that premise that the glutathione-S-transferase
enzyme is expressed at high levels in many tumors, researchers at
the Fox Chase Cancer Center in Pennsylvania, went on to design a
novel prodrug (PABA/NO).
The glutathione-s-transferase in tumor
cells converts PABA/NO to lethal nitric oxide, resulting in death
of the tumor cell. The prodrug was shown to have antitumor effects
in an animal model for human ovarian cancer. (3)
In the fourth study, Polish researchers
found that ingesting a selenium supplement is beneficial, as a supportive
element in chemotherapy. (4)
Selenium is a co-factor of the enzyme
glutathione peroxidase [GSH-P(x)] and was found to significantly
increase the activity of GSH-P(x) in patients reciving the supplement.
A previous clinical study by the same
researchers recommended the administration of selenium in patients
with ovarian cancer undergoing multi-drug chemotherapy. (5)
Another interesting study by researchers
in Texas showed that your chances of surviving a type of brain cancer,
called primary malignant glioma, could depend on the type of glutathione-s-transferase
(GST) gene you were born with.
Having a combination of a two specific
variants of GST (germ-line GSTP1*A/*A and GSTM1 null genotype) confers
a survival advantage in some types of brain cancers, but also comes
with an increased risk of adverse events related to chemotherapy.
(6)
There is compelling evidence to suggest
a crucial role for glutathione and substances that target glutathione
metabolism in the prevention and treatment of cancer.
Undenatured whey protein is one of
the natural foods known to selectively deplete cancer cells of their
glutathione, thus making them more susceptible to such cancer treatments
as radiation and chemotherapy.
For a complete report on the research
on undenatured whey protein and cancer see the report Glutathione
(GSH) and Whey Protein in Cancer.
Disclaimer: The information here
is not provided by medical professionals and is not intended as
a substitute for medical advice. Please consult your physician before
beginning any course of treatment.
References:
1. Friesen C et al. [Cell Death and
Differentiation advance online publication, 23 April 2004]
2. Tormos C et al. [Cancer Lett. 2004 May 10;208(1):103-13.]
3. Findlay VJ et al. [Mol Pharmacol. 2004 May;65(5):1070-9.]
4. Sieja K et al. [Gynecol Oncol. 2004 May;93(2):320-327.]
5. Sieja K. [Pharmazie. 1998 Jul;53(7):473-6.]
6. Okcu MF et. al. [Clin Cancer Res. 2004 Apr 15;10(8):2618-25.]
This article was first published
in the April 2004 issue of The
Glutathione Report, a newsletter featuring regular updates on
the health benefits of glutathione. Get a Free
report on Glutathione in Health and Disease
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