The researchers found that EGCG interrupts the communication signals needed by cancer cells to survive, prompting them to die in eight of 10 patient samples tested in the laboratory.
The cells came from patients with B-cell chronic lymphocytic leukaemia (CLL), most often diagnosed in patients in their mid-to-late 60s and currently without cure. While chemotherapy is administered in the most severe cases, doctors have tended to stall use of this treatment in early stage patients, some of whom may live with it for decades and not require treatment. Green tea could however offer a less harmful, but effective alternative for this category of patients.
"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," said Neil Kay from the Mayo Clinic. "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."
The findings are reported in an early electronic article in the journal Blood.
"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," said author Yean K. Lee.
"Our research goal is to identify new treatments for CLL that have a favourable side effect profile and can be used in patients with early stage disease to prevent progression. I think we're getting there," added Mayo Clinic researcher Tait D. Shanafelt.
Since the 1970s, epidemiological studies of cancer have shown that in parts of the world where green tea is consumed, the incidence of solid tumour cancers such as breast, lung and gastrointestinal cancers is lower. Mouse-model testing of green tea's cancer-prevention properties and lab tests on EGCG have confirmed that they protect against solid tumours and induce death in cancer cells from solid tumours.
The Mayo Clinic research suggests EGCG works by inhibiting a pathway in the leukaemia cells related to angiogenesis -- the complex process that maintains nourishing blood flow to a biological structure, in this case a cancer cell.
Chronic lymphocytic leukaemia affects 2,750 new people in the UK every year.