The research using laboratory cell cultures shows that a component of green tea known as epigallocatechin-3-gallate (EGCG) [epi-gallo-cat-ekin-3-gal-ate] helps kill leukemia cells by interrupting the communication signals they need to survive. The findings are reported in an early electronic article in the journal Blood (http://www.bloodjournal.org/cgi/reprint/2003-08-2763v1).
The leukemia cells studied were from patients with B-cell chronic lymphocytic leukemia (CLL) -- most often diagnosed in patients in their mid-to-late 60s. Currently, there is no cure for CLL, though chemotherapy is administered in the most severe cases. The Mayo Clinic study, led by Neil E. Kay, M.D., shows that green tea's EGCG interrupted survival signals, prompting leukemia cells to die in eight of 10 patient samples tested in the laboratory.
Says Dr. Kay: "We're continuing to look for therapeutic agents that are nontoxic to the patient but kill cancer cells, and this finding with EGCG is an excellent start. Understanding this mechanism and getting these positive early results gives us a lot to work with in terms of offering patients with this disease more effective, easily tolerated therapies earlier."
About the Leukemia called CLL
CLL affects individuals differently in the pace at which it progresses. Some patients may live with it for decades and not require treatment, while others need immediate treatment, and some die within months despite therapy.
Because the course of the CLL is so individualistic and unpredictable, physicians have historically adopted an attitude of "watchful waiting" with early-stage CLL patients. This rationale -- to spare elderly patients exposure to toxic chemotherapy -- has been challenged recently as new tests have improved physicians' ability to identify early stage patients who have a more aggressive form of the cancer.
As a result, much CLL research is focused on identifying which initial-stage patients should be treated earlier in the course of their disease -- the topic of another recent article by Mayo Clinic researchers (Blood, Feb 2004; 103: 1202 - 1210.)
Significance of the Mayo Clinic Finding
The CLL characteristics make this finding even more important, as it suggests a new, nontoxic treatment. First author Yean K. Lee comments, "With these findings we may be able to pursue the idea of culling out early-stage patients who have historically not been treated and perhaps use an EGCG-based treatment. That's our next step with our research."
Mayo Clinic CLL researcher Tait D. Shanafelt, M.D., is likewise encouraged. "Our research goal is to identify new treatments for CLL that have a favorable side effect profile and can be used in patients with early stage disease to prevent progression. I think we're getting there."
Why Green Tea?
Mayo Clinic researchers focused on green tea for at least three reasons. One, since the 1970s, epidemiological studies of cancer have shown that in parts of the world where green tea is consumed, the incidence of solid tumor cancers such as breast, lung and gastrointestinal cancers is lower. Secondly, mouse-model testing of green tea's cancer-prevention properties has shown they protect against solid tumors. And three, in the laboratory, the EGCG component of green tea has been proven to induce death in cancer cells from solid tumors.
The Mayo Clinic research suggests EGCG works by inhibiting a pathway in the leukemia cells related to angiogenesis -- the complex process that maintains nourishing blood flow to a biological structure, in this case a cancer cell.