A compound found in green tea can kill oral cancer cells without harming healthy cells, scientists have found.
Previous research has shown that a compound found in green tea, epigallocatechin-3-gallate (EGCG), killed oral cancer cells without harming normal cells, but the reasons for its ability to target the cancer cells were not understood.
The new study found 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 Joshua Lambert, associate professor of food science and co-director of Penn State’s Center for Plant and Mushroom Foods for Health.
“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,” he said.
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.
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 the process.
“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 is published in the journal Molecular Nutrition and Food Research.