The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal

16 May 2005 - Green tea’s much-touted health benefits now have more backing in biochemical research. Christine Palermo and Thomas Gasiewicz, both of the University of Rochester Medical Center, recently uncovered a novel anti-cancer pathway that depends on a component of green and white teas. The discovery of this pathway, presented in the April 5 issue of the journal Biochemistry, provides pharmaceutical companies with another target for drug-design in the fight against cancer.

Gasiewicz previously identified the anti-cancer compound of green tea, epigallocatechin gallate (EGCG). The chemical is known to inhibit cancer formation by interacting with proteins in a cell. Gasiewicz’s research on other carcinogenic compounds initially led him to believe that EGCG binds directly to a molecule responsible for activation of cancer-genes, the aryl hydrocarbon receptor (AhR). AhR ceases to perform its carcinogenic role when bound by a molecule that inhibits protein function.

"We initially hypothesized that EGCG would work in the same way as other AhR antagonists, by binding directly to it," says Gasiewicz, professor and chair of Environmental Medicine and director of Rochester's Environmental Health Science Center. “We were completely surprised that this isn't the case.” In fact, the research team found that EGCG’s chemoprotective effects target another component of the cell: the Hsp90 protein.

Hsp90 is a special protein that aids AhR by allowing it to maintain a specific three-dimensional structure. EGCG binds to Hsp90, preventing it from helping AhR keep its shape. Proper protein function is determined by proper structure and without Hsp90, AhR is useless in its carcinogenic role. Thus, although EGCG is not directly binding to AhR, it inhibits the molecules dangerous effects by acting through Hsp90.

"It's important to find out the source of green tea's protective effects," noted Gasiewicz, "What is exciting here is that a completely new mechanism has been found that very well could be responsible for its protective effects, and that could help us find a compound that is much more potent."

---