EGCg (epigallocatechin-3-gallate), the polyphenol found in green tea, may cause apoptosis in oral cancer cells while leaving normal cells alone, according to researchers at Penn State. Previous studies had shown that EGCg destroyed oral cancer cells without harming healthy ones, but researchers did not understand the mechanism of action behind this. This study, published online in Molecular Nutrition and Food Research, demonstrates that EGCg may trigger apoptosis in the mitochondria, leading 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 Josh 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."
In this study, the EGCg did not cause this reaction in normal cells, but rather actually increased the protective capabilities of the cell. The researchers examined normal human oral cells side-by-side with human oral cancer cells to determine how EGCg was affecting cancer cells as opposed to normal cells. They did this by growing both types of cells on petri dishes and then exposing them to EGCg. The researchers collected the cells and checked for oxidative stress and antioxidant responses.
The researchers determined that the protein known as sirtuin 3 is critical to the process. Sirtuin 3 plays an essential role in antioxidant activity and in mitochondrial function in many tissues throughout the body. They conclude that EGCg’s potential ability to selectively regulate the activity of sirtuin 3 (to turn it off in cancer cells and to turn it on in normal cells) is a key factor, and may be relevant to many kinds of cancers.
For Related Resource Material, Please Listen to Our Clinical Rounds Call:
Source: Ling Tao, Jong-Yung Park, Joshua D. Lambert. Differential prooxidative effects of the green tea polyphenol, (-)-epigallocatechin-3-gallate, in normal and oral cancer cells are related to differences in sirtuin 3 signaling. Molecular Nutrition & Food Research, 2014; DOI: 10.1002/mnfr.201400485