Brett Smith for redOrbit.com – Your Universe Online
Researchers from Penn State have identified an ingredient in green tea known as epigallocatechin-3-gallate (EGCG) that destroys oral cancer cells while leaving healthy cells untouched, according to a new report in the journal Molecular Nutrition and Food Research.
In particular, the study found that EGCG sets off a process in cancer cell mitochondria that leads to the cell’s destruction.
“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 study author Joshua Lambert, associate professor of food science at Penn State. “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 species.”
This destructive cycle also leads to a lower expression of anti-oxidant genes in the cancer cell, lowering its defenses further.
“So, it’s turning off its mechanism of protection at the same time that EGCG is causing this oxidative stress,” Lambert added.
To reach their conclusion, scientists analyzed healthy oral cells along with oral cancer cells to figure out how EGCG was impacting cancer cells, but not the healthy ones. The team also cultivated both kinds of cells on petri dishes and then subjected them to EGCG at concentrations normally seen in the saliva after chewing green-tea gum. At numerous times, the scientists would gather the cells and look for oxidative stress and indications 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,” Lambert said.
The study also revealed that a protein called sirtuin 3 is essential to the observed effect.
“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 new study expands on previous research by the same team that focused on how green tea could be used as a potential treatment for cancer.
“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,” Lambert said.
The study team said their future work will focus on the effect of EGCG in animal models and in humans. This next stage is being performed with the intention of developing new cancer drugs.
“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,” Lambert said. “But you don’t see these sorts of side effects with green tea consumption.”
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