Effects Of Cigarette Smoking, Green Tea Consumption, MicroRNA-29b, And Its Target DNMT3B On Lung Cancer Development

Ruey-Hong WONG, ,Chung Shan Medical University, Taiwan (ROC)
HUANG C. 1 , LAI C. 2,4 , LAM K. 1 , TSAI C. 5,6 , WANG J. 2,7

1 Department of Public Health, Chung Shan Medical University, Taichung, Taiwan
2 Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan
3 Department of Family and Community Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan
4 Thoracic Surgery, Cheng Ching General Hospital, Taichung, Taiwan
5 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan
6 Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
7 Department of Family Medicine, Cheng Ching General Hospital, Taichung, Taiwan

Green tea can prevent cancer. However, its inhibitory mechanisms on smoking-induced lung cancer are unclear. In the tumor development, the increased expression of DNA methyltransferase (DNMT) was observed, and this expression was downregulated by increased micro (miR)-29b expression. Especially, cigarette smoke and tea polyphenols might influence the DNMT3B expression by regulating the miR-29b expression. Therefore, we designed a case-control study to evaluate the effects of cigarette smoking, green tea consumption, and expressions of miR-29b and DNMT3B in the development of lung cancer. A total of 71 lung cancer patients and 71 healthy controls were recruited to measure expressions of miR-29b and DNMT3B mRNA in whole blood by real-time polymerase chain reaction in the present study. Questionnaires were administered to obtain the epidemiological and clinical characteristics. Results revealed, among healthy controls, smokers had a significantly lower miR-29b expression than nonsmokers. After adjusting the effects of confounding factors, compared to the subjects with the combination of higher miR-29b expression/lower DNMT3B mRNA expression, subjects with other combinations of miR-29b and DNMT3B mRNA expression had a 3.36-fold (95% C.I. = 1.11-10.17) increased risk for lung cancer development. Significant interactions of smoking with miR-29b and with DNMT3B mRNA expression on lung cancer development were observed; respectively. Significant interaction of green tea consumption and DNMT3B mRNA expression on lung cancer development was also observed. Our study suggested smoking might reduce the miR-29b expression. Smokers with lower miR-29b expression and higher DNMT3B mRNA expression, and green tea nondrinkers with higher DNMT3B mRNA expression were susceptible for lung cancer development.
Keywords: green tea, smoking, lung cancer, miR-29b, DNMT3B