CLEVELAND, Ohio - In continuing studies of cancer preventing compounds in green tea, researchers at the Case Western Reserve University School of Medicine have found an ingredient that kills cancer cells, while sparing healthy cells.
Investigators tested the ingredient, called epigallocatechin-3-gallate, on cancerous human and mouse cells of the skin, lymph system, and prostate, and on normal human skin cells. In the test tube, it led to apoptosis, or programmed cell death, in the cancer cells, but left the healthy cells unharmed.
Findings appear in the December 17 issue of the Journal of the National Cancer Institute.
Epigallocatechin-3-gallate is a major constituent of the polyphenols found in green tea. This compound has been shown in previous studies from CWRU and elsewhere to prevent cancer in laboratory animals.
"We found that this particular compound, which is present in the amount of about 200 mg in one cup of green tea, can kill a variety of cancer cells through apoptosis without affecting the normal cells," said Hasan Mukhtar, a professor of dermatology at CWRU and senior author of the paper. The polyphenol broke the DNA of the cancer cells into fragments, a characteristic of apoptosis.
"The killing of cancer cells and the sparing of normal cells is very interesting because apoptosis is a programmed cell death which is a normal process going on in the body all the time. It is a preferential way of elimination of unwanted cells from the body," said Mukhtar.
Polyphenols induce the demise of cancer cells, but scientists do not yet know why this happens, said Mukhtar. "It is likely that this compound conveys a message to cancer cells through a highly ordered and well-regulated signal transduction pathway that says, 'You must commit suicide (programmed cell death) or I am going to kill you.' The cells then decide that instead of being murdered, they will commit suicide," said Mukhtar.
He feels that this finding leads investigators to a greater understanding of the mechanism involved in the process. If they can decipher the molecular mechanism by which green tea imparts protective effects, the knowledge may provide opportunities to interfere with cancer development through administration of purified polyphenolic derivatives, said Mukhtar. "Green tea appears to be potentially an ideal agent for chemoprevention."
The investigators feel that the chemoprevention properties of green tea need to be evaluated in human trials.
Tea consumption in the world ranks second only to water consumption. Approximately 20 percent of tea consumed is green; the rest is black tea.
Other authors on the paper are Nihal Ahmad, Denise K. Feyes, Anna-Liisa Nieminen, and Rajesh Agarwal, all with the CWRU School of Medicine.
Journal
JNCI Journal of the National Cancer Institute