Consumption of green tea may be contraindicated for patients who are receiving treatment with Velcade® (bortezomib), as the polyphenols in green tea may actually negate the therapeutic benefits of the drug, according to the results of a study published in Blood.
Velcade is a proteosome inhibitor that is used in the treatment of multiple myeloma. Proteosomes are proteins found in virtually all cells. They are responsible for the breakdown and reuse of a cell’s other proteins. Proteosomes regulate several aspects of cellular activity, including survival. By inhibiting proteosomes, Velcade has demonstrated an ability to reduce cellular survival.
Green tea has often been lauded as a “miracle herb,” and many holistic healthcare practitioners advocate for heavy use of it. Green tea contains a polyphenol called epigallocatechin gallate (EGCG) that has been shown to prevent cancer cells by changing the way normal cells react to potential carcinogens entering the body. EGCG also appears to create chemical changes that kill active cancer cells in multiple myeloma, breast, cervical, and colon cancer tumors. As a result, many cancer patients turn to green tea with the hopes that it will help in the fight against cancer. However, recent research indicates that green tea may have its drawbacks.
Because of the apparent anti-tumor effects of green tea, researchers conducted a study to determine whether a combination of green tea and Velcade would provide increased anti-tumor activity in multiple myeloma and glioblastoma. On the contrary, the results indicated that the EGCG in green tea prevented the tumor cell death induced by Velcade. This unexpected effect of EGCG only occurred with boronic acid-based proteosome inhibitors (Velcade, MG-262, PS-IX) and not with several non-boronic acid-based proteosome inhibitors (Viracept, MG-132, PS-I). The researchers stated: “EGCG directly reacted with Velcade and blocked its proteosome inhibitory function.” As a result, Velcade could not induce tumor cell death.
The researchers concluded that green tea polyphenols may inhibit the anti-tumor activity of Velcade and suggest that green tea products may be contraindicated for patients receiving therapy with Velcade.
 Golden EB, Lam PY, Kardosh A, et al. Green tea polyphenols block the anticancer effects of bortezomib and other boronic acid-based proteasome inhibitors. Blood [early online publication]. February 3, 2009.
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