Green Tea Ingredient May Target
Protein To Kill Oral Cancer Cells
UNIVERSITY PARK, Pa. -- A compound found in green tea may trigger a cycle that kills
oral cancer cells while leaving healthy cells alone, according to Penn State
food scientists. The research could lead to
treatments for oral cancer, as well as other types of cancer.
Earlier studies had shown that
epigallocatechin-3-gallate -- EGCG -- a compound found in green tea, killed
oral cancer cells without harming normal cells, but researchers did not
understand the reasons for its ability to target the cancer cells, said Joshua Lambert, associate professor offood
scienceand co-director of Penn State'sCenter for Plant and Mushroom
Foods for Health. The
current study shows that EGCG may trigger a process in the mitochondria that
leads to cell death.
"EGCG is doing something to damage the mitochondria and that mitochondrial
damage sets up a cycle causing more damage and it spirals out, until the cell
undergoes programmed cell death," said Lambert. "It looks like EGCG
causes the formation of reactive oxygen species in cancer cells, which damages
the mitochondria, and the mitochondria responds by making more reactive oxygen
As this mitochondrial demise continues, the cancer cell also reduces the
expression of anti-oxidant genes, further lowering its defenses."So, it's turning off its mechanism of protection at the same
time that EGCG is causing this oxidative stress," Lambert added.The EGCG did not cause this reaction in normal cells. In fact, it
appeared to increase the protective capabilities of the cell, according to the
researchers, who report their findings in the online issue of Molecular
Nutrition and Food Research.
The researchers studied normal human oral cells side-by-side with human oral
cancer cells to determine how EGCG was affecting cancer cells differently than
normal cells. They grew the normal and cancer cells on petri dishes and then
exposed them to EGCG, the major polyphenol found in green tea, at
concentrations typically found in the saliva after chewing green-tea chewing
gum. At various times, the researchers would collect the cells and check for
oxidative stress and signs of antioxidant response.
"We also took a lot of pictures, so we could use fluorescent dyes that
measure mitochondrial function and oxidative stress and actually see these
things develop," said Lambert, who worked with Jong-Yung Park, a research
technician and Ling Tao, a doctoral candidate in food science.
The researchers said that a protein called sirtuin 3 -- SIRT3 -- is critical to
"It plays an important role in mitochondrial function and in anti-oxidant
response in lots of tissues in the body, so the idea that EGCG might
selectively affect the activity of sirtuin 3 in cancer cells -- to turn it off
-- and in normal cells -- to turn it on -- is probably applicable in multiple
kinds of cancers," Lambert said.
The study builds on earlier research on how EGCG affected oral cancer, a
disease that is expected to kill more than 8,000 people in the United States
"We've published one paper previously just looking at the effect of these
green tea polyphenols on oral cancer cells in cultures, and there have been
other papers published using oral cancer cells and at least a couple of animal
model studies that have looked at oral cancer and prevention of oral
cancer," said Lambert.
He said the next step would be to study the mechanism in animals. If those
tests and human trials are successful, the researchers then hope to create
anti-cancer treatments that are as effective as current treatments without the
harmful side effects. "The problem with a lot of
chemotherapy drugs -- especially early chemotherapy drugs -- is that they
really just target rapidly dividing cells, so cancer divides rapidly, but so do
cells in your hair follicles and cells in your intestines, so you have a lot of
side effects," said Lambert. "But you don't see these sorts of side
effects with green tea consumption."
The American Institute for Cancer Research supported this work.