Researchers have discovered that green tea inactivates the anti-cancer properties of Velcade (bor­tez­o­mib), a promising and frequently used drug for treating multiple myeloma.

In recent years, green tea prod­ucts have become a popular health supple­ment after studies dem­onstrated that one of its active com­­pounds, EGCG polyphenol, can act as a potent anti-cancer agent. “Cancer patients look to green tea extracts among other natural supple­ments to complement their thera­peutic regi­mens,” said Axel Schonthal, Ph.D., of the University of Southern California Keck School of Medicine.

With this in­­for­ma­tion in mind, a recent study in­ves­ti­gated whether exposing multiple myeloma cells to green tea extract in addi­tion to Velcade would im­prove treat­ment out­come. Unexpectedly, tumor cells treated with a green tea-Velcade com­bi­na­tion ex­peri­enced near 100 per­cent survival. Effectively, the green tea prevented cancer cell destruction by blocking Velcade activity.

In cells, the pro­te­a­some acts as a “garbage disposal” by breaking down used and unnecessary proteins, and Velcade functions as a pro­te­a­some inhibitor. By shutting off the pro­te­a­some function, Velcade disrupts cancerous cells’ life cycles, leading to chaos and eventual cell death.

Unlike several other pro­te­a­some inhibitors, the Velcade molecule con­tains a boronic acid component. Researchers determined that this boronic acid enables EGCG to bind directly to Velcade, thereby inactivating each com­­pound and canceling out the effects of both green tea and Velcade ther­apy on multiple myeloma cells. Follow-up tests with Viracept dem­onstrated that green tea did not block its activity.

These study findings have important implications for multiple myeloma patients undergoing treat­ment. Firstly, EGCG blocked Velcade function at levels easily attainable with over-the-counter green tea supple­ments (as few as two to three extract capsules).

“The current evi­dence is sufficient enough to strongly urge patients undergoing [Velcade] ther­apy to abstain from consuming green tea prod­ucts, in particular the widely avail­able, highly concentrated green tea and EGCG prod­ucts that are sold in liquid or capsule form,” said Dr. Schonthal.

Yet, researchers emphasize that these findings only apply to Velcade. For other, non-boronic acid-based multiple myeloma ther­a­pies, there is no evi­dence that green tea negates their effects. "Although the study has exposed detrimental effects of green tea in specific com­bi­na­tion with Velcade, this should not minimize the pre­vi­ously reported poten­tially beneficial effect of this herb," said Dr. Schonthal.

For more in­­for­ma­tion, please see the full study in the journal Blood.