Green tea and its extracts have been widely touted as potential treatments for cancer, as well as several other diseases. But scientists have struggled to explain how the green tea and its extracts may work to reduce the risk of cancer or to slow the growth of cancer cells.
A study recently published online by the journal, Metabolomics, offers an explanation that researchers say could open a new area of cancer-fighting research. The study reports that EGCG, the active biologic constituent in green tea, changed the metabolism of pancreatic cancer cells by suppressing the expression of an enzyme associated with cancer, LDHA.
The researchers also found an enzyme inhibitor, oxamate, which is known to reduce LDHA activity, operated in the same manner: It also disrupted the pancreatic cancer cells metabolic system.
“Scientists had believed they needed a molecular mechanism to treat cancer, but this study shows that they can change the metabolic system and have an impact on cancer,” said Wai-Nang Lee, MD, corresponding author of the study and a Los Angeles Biomedical Research Institute (LA BioMed) lead researcher. “By explaining how green tea’s active component could prevent cancer, this study will open the door to a whole new area of cancer research and help us understand how other foods can prevent cancer or slow the growth of cancerous cells.”
Using sophisticated metabolic profiling methods, the researchers found EGCG disrupted the balance of “flux” throughout the cellular metabolic network. Flux is the rate of turnover of molecules through a metabolic pathway. The researchers found the EGCG disrupted this balance in the same manner that oxamate, a known LDHA inhibitor, did.
Based on this finding, they concluded that both EGCG and oxamate reduced the risk of cancer by suppressing the activity of LDHA, a critical enzyme in cancer metabolism, thereby disrupting the balance in the cancer cells metabolic functions.
“This is an entirely new way of looking at metabolism,” said Dr. Lee. “It is no longer a case of glucose goes in and energy comes out. Now we understand how cancer cell metabolism can be disrupted, and we can examine how we can use this knowledge to try to alter the course of cancer or prevent cancer.
In content, this new study explains how green tea changed the metabolism of pancreatic cancer cells, opening a new area in cancer-fighting research. Green tea and its extracts have been widely touted as potential treatments for cancer, as well as several other diseases. But scientists have struggled to explain how the green tea and its extracts may work to reduce the risk of cancer or to slow the growth of cancer cells.
Green tea could modify the effect of cigarette smoking on lung cancer risk
Drinking green tea could modulate the effect of smoking on lung cancer.
Results of this hospital-based, randomized study conducted in Taiwan were presented at the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer, held here from Jan. 11-14, 2010.
“Lung cancer is the leading cause of all cancer deaths in Taiwan,” said I-Hsin Lin, M.S., a student at Chung Shan Medical University in Taiwan. “Tea, particularly green tea, has received a great deal of attention because tea polyphenols are strong antioxidants, and tea preparations have shown inhibitory activity against tumorigenesis.”
However, previous studies of green tea have been inhibited by the flaws of the epidemiologic model with its inherent biases.
Lin and colleagues enrolled 170 patients with lung cancer and 340 healthy patients as controls. The researchers administered questionnaires to obtain demographic characteristics, cigarette smoking habits, green tea consumption, dietary intake of fruits and vegetables, cooking practices and family history of lung cancer. They also performed genotyping on insulin-like growth factors as polymorphisms on the following insulin-like growth factors: IGF1, IGF2 and IGFBP3, which have all been reported to be associated with cancer risk.
Among smokers and non-smokers, those who did not drink green tea had a 5.16-fold increased risk of lung cancer compared with those who drank at least one cup of green tea per day. Among smokers, those who did not drink green tea at all had a 12.71-fold increased risk of lung cancer compared with those who drank at least one cup of green tea per day.
Lin and colleagues suspect genetics may play a role in this risk differential. Green tea drinkers with non-susceptible IGF1 (CA)19/(CA)19 and (CA)19/X genotypes reported a 66 percent reduction in lung cancer risk as compared with green tea drinkers carrying the IGF1 X/X genotype.
Heavy smokers carrying susceptible IGF1, IGF2 and IGFBP3 genotypes also had a higher risk of lung cancer compared with nonsmokers carrying non-susceptible IGF1, IGF2 and IGFBP3 genotypes.
“Our study may represent a clue that in the case of lung cancer, smoking-induced carcinogenesis could be modulated by green tea consumption and the growth factor environment,” said Lin