I always hear about people drinking green tea all the time to lose weight but according to Katiyar's article, Green tea prevents non-melanoma skin cancer by enhancing DNA repair, green tea can help protect against non-melanoma skin cancer! Katiyar used an experiment conduced
with hairless mice to draw conclusions about green tea. He gave them water
extract of green tea leaves and then exposed them to UVB waves. It was
concluded that tumor incidences decreased in the mice exposed to green tea. The
important fact involved here is that green tea is a polyphenol.
A
strategy to prevent skin cancer is the use of dietary phytochemicals,
specifically polyphenols. Polyphenols are also present in
green tea and the major ones are: epicatechin, epigallocatechin,
epicatechin-3-gallate and epigallocatechin-3-gallate. These have antioxidant
and anti-inflammatory characteristics.
As we all know, skin exposure to UV
radiation can cause skin cancer. There are 3 types of UV waves: UVA, UVB and
UVC. UVA waves can cause the generation of singlet oxygen and hydroxyl free
radicals, which in turn can damage proteins, lipids and DNA. UVB waves can
induce oxidative stress, immunosuppression, and DNA damange. UVC waves are
usually blocked by the ozone layer. CITE
Exposure to UV light can lead to
errors in DNA repair and in turn, oncogenic mutations. Polyphenols can protect
against non-melanoma cancer through enhancing DNA repair. This is through
stimulation of IL-12, which is an immunoregulatory cytokine. IL-12 is known for
it’s antitumor activity and can induce DNA repair.
It is hard for the polyphenols to
be absorbed through the gut barrier since they are large molecules. So topical
treatments seem to be more efficient even though both can still work. Based on
Katiyar’s article, about 5-6 cups of green tea a day can provide the same
protection as it did for the mouse in his study. This can differ from individual
to individual depending on factors like race and exposure time to UV radiation.
Discussion:
I think this was a very interesting
study. Scientists continue to discover new ways in which various molecules can
help fight cancer. In this case polyphenols may help prevent non-melanoma skin
cancer. In class, Dr. Islas
provided a slide with a chart about where in the world certain cancers are
prevalent. I noticed that skin cancer is prevalent in Australia and least
likely in Japan. Green tea is very common in Japan and not as prevalent in Australia.
Perhaps this can be an underlying factor why Japan does not have many cases of
skin cancer.
I am taking Medical Microbiology right now and we are
learning about the immune system so I would be curious to research what role
the immune system plays in preventing skin cancer. The article briefly
mentioned how DNA damage by UV waves triggers immunosuppression and I am
curious as to how it does this on a molecular level. I know that there is a
group researching cancer and the immune system this for their project and I am
excited and eager to hear their presentation.
References:
Katiyar, Santosh K. “Green tea prevents non-melanoma skin
cancer by enhancing DNA repair.” Pubmed. 15 April 2011. Accessed 19 April 2012.
Web.
