Monday, February 23, 2009

Tea-drinker beware ....


As a general rule, I support the concurrent use of antioxidant-rich foods and food supplements along with anticancer drugs. There is a considerable amount of documentation on the benefit of doing so and very little indication of harm. However, I am also committed to informing my readers if and when situations arise in which such concurrent usage appears unwise. Such a situation has now arisen.

Velcade (bortezomib) is a drug used in the treatment of multiple myeloma. It is also indicated for the treatment of patients with mantle cell lymphoma who have previously received one other therapy.

Velcade is classified as a proteasome inhibitor. Green tea (Camilla sinensis), on the other hand, is a widely used beverage, an unfermented form of the beverage, which many people also take for proposed medicinal purposes. Millions of people drink it with no problem. It was heartening to see many people from the countryside sipping their thermoses of green tea. It seemed like a healthier alternative to another elixir that is growing in popularity, Coca Cola.

But should green tea – which most people agree is a very healthful beverage – be used when one is also taking Velcade? At first sight, you might think that these two agents would go well together. But when scientists at the University of Southern California (USC) studied the combination they got a shock. An extract of green tea, including its very active ingredient, EGCG, did not enhance the effects of Velcade in either multiple myeloma or brain cancer (glioblastoma) cells. Instead, it effectively prevented tumor cell death induced by Velcade in both test tube and animal studies (Golden 2009).

Essentially, EGCG blocked the proteasome inhibiting effect of Velcade, so that it could not trigger stress in the cancer cell or activate a compound called caspase-7 that was necessary for its action. This negative effect may be limited to Velcade. In this experiment, it was only seen in boronic acid-based proteasome inhibitors but not in the slightly different non-boronic acid based agents (such as the drug Viracept).

Conclusion: "Green tea polyphenols may have the potential to negate the therapeutic efficacy of bortezomib [i.e. Velcade] and suggest that consumption of green tea products may be contraindicated during cancer therapy with bortezomib" (Golden 2009).

It bears repeating that these were in vitro and in vivo experiments (not human clinical trials). Nonetheless, the results are disturbing. They are also confusing, since researchers at the University of Florida had previously shown that EGCG in green tea was also a proteasome inhibitor (Smith 2002). However, I think that the latest results should be taken seriously. If you are taking Velcade (bortezomib).

If you are not taking Velcade there is no indication that green tea or EGCG are anything but healthful.

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