Roxanne Nelson

January 20, 2010

January 19, 2010 (Coronado, California) — Consumption of green tea might reduce the risk for lung cancer, especially for individuals who smoke, according to a Taiwanese study presented here at the American Association for Cancer Research-International Association for the Study of Lung Cancer Joint Conference on Molecular Origins of Lung Cancer: Prospects for Personalized Prevention and Therapy.

Researchers found that individuals who did not drink green tea had a 5.16-fold increased risk for lung cancer, compared with those who drank at least 1 cup of green tea per day. When they narrowed the analysis to smokers, those who did not drink green tea at all had a 12.71-fold increased risk for lung cancer, compared with those who consumed at least 1 cup per day.

"Our results suggest that both smokers and nonsmokers could benefit by drinking green tea," lead author I-Hsin Lin, MS, a student at Chung Shan Medical University in Taiwan, told Medscape Oncology. "Green tea contains strong antioxidants called tea polyphenols, which have inhibitory effects of tumorgenesis, tumor proliferation, and tumor growth."

This is particularly true for smokers, she added. "Drinking green tea may provide a chance to lower the lung cancer risk in smokers, but it cannot reverse the toxic [effects] or carcinogenesis caused by smoking," said Ms. Lin. "Of course, we don't want smokers to use this as an excuse to keep smoking and thinking that they have a lower risk by drinking a cup of green tea every day."

Experimental studies have shown that tea polyphenols are potent antioxidants and can inhibit the development of a variety of malignancies, including lung cancer, but epidemiologic studies examining tea consumption and cancer are limited, and results have been inconclusive, according to the researchers.

Insulin-Like Growth Factor Might Play a Role

Previous experimental research has found that green tea might reduce cancer risk by decreasing the level of insulin-like growth factor (IGF)1 or increasing IGF-binding protein (IGFBP)3, said Ms. Lin.

The IGF signaling pathway plays a role in regulating cellular proliferation and apoptosis. The authors note that a high expression level of IGFBP3 suppresses the mitogenic action of IGFs and has been inversely associated with cancer risk. But there is only limited information available on the molecular role of IGF1, IGF2, and IGFBP3 in lung cancer.

"In our study, we analyzed the IGF1, IGF2, and IGFBP3 genotypes," Ms. Lin told Medscape Oncology. "Previous experimental research has shown that green tea might reduce cancer risk by decreasing IGF1 levels or increasing IGFBP3 levels."

"Also, previous studies and reviews have suggested that individuals who are carrying the cytosine-adenine (CA)19 allele might have lower IGF1 levels, so we confirmed our results based on those studies," she added.

Ms. Lin and colleagues designed a hospital-based case–control study to evaluate the effects of smoking, green tea consumption, and IGF1 (CA)n repeat, IGF2 820, and IGFBP3 –202 polymorphisms on the risk for lung cancer, and also examined the association between IGF1, IGF2, and IGFBP3 polymorphisms and lung cancer survival.

Highest-Risk Modulation in Smokers and Some Genotypes

The cohort consisted of 170 primary lung cancer patients and 340 healthy individuals who completed a questionnaire regarding cigarette-smoking habits, green tea consumption, dietary intake of fruits and vegetables, cooking practices, and family history of lung cancer.

The data for overall lung cancer survival was calculated from 136 lung cancer patients, and genotypes for IGF1 (CA)n repeat, IGF2 820, and IGFBP3 –202 were identified by polymerase chain reaction.

They found that smoking, consuming less than 1 cup of green tea per day, and exposure to cooking fumes for more than 3 hours per week were associated with an elevated risk for lung cancer. But after adjustment for the effects of exposure to cooking fumes, a significantly higher risk was observed in people who never drank green tea, particularly smokers.

Genotypes also played a role in modulating the risk. A 66% reduction in lung cancer risk was observed in green-tea drinkers with nonsusceptible IGF1 (CA)19/(CA)19 and (CA)19/X genotypes, compared with green-tea drinkers carrying the IGF1 X/X genotype (odds ratio, 0.34; 95% confidence interval, 0.17 - 0.69).

However, when looking at lung cancer survival, they did not find an association between the IGF1 (CA)n repeat, IGF2 820, and IGFBP3 –202 genotypes and overall survival.

"Our study [suggests] that, in the case of lung cancer, smoking-induced carcinogenesis could be modulated by green-tea consumption and the growth-factor environment," said Ms. Lin.

American Association for Cancer Research-International Association for the Study of Lung Cancer (AACR-IASLC) Joint Conference on Molecular Origins of Lung Cancer: Prospects for Personalized Prevention and Therapy: Abstract A21. Presented January 12, 2010.

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