A Killer Green Tea Compound
A number of previous studies report that compounds in green tea, most notably epigallocatechin-3-gallate (EGCG), exert cancer preventative effects. Joshua Lambert, from Pennsylvania State University (Pennsylvania, USA), and colleagues elucidate the mechanism by which EGCG kills oral cancer cells while leaving normal cells unharmed. 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. The investigators posit that 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. As this mitochondrial demise continues, the cancer cell also reduces the expression of anti-oxidant genes, further lowering its defenses. The team notes that the protein known as sirtuin 3 (SIRT3) is critical to the process, as it plays an important role in mitochondrial function and in anti-oxidant response in the tissues in the body.