Original Article
Copyright ©2011 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Jul 28, 2011; 17(28): 3330-3334
Published online Jul 28, 2011. doi: 10.3748/wjg.v17.i28.3330
Interactions between CagA and smoking in gastric cancer
Xiao-Qin Wang, Hong Yan, Paul D Terry, Jian-Sheng Wang, Li Cheng, Wen-An Wu, Sen-Ke Hu
Xiao-Qin Wang, Hong Yan, Department of Statistics and Epidemiology, School of Medicine, Xi’an Jiaotong University, Xi’an 710061, Shaanxi Province, China
Paul D Terry, Department of Public Health, University of Tennessee, HPER 390, Knoxville, TN 37996, United States
Jian-Sheng Wang, Department of Thoracic Oncosurgery, First Affiliated Hospital of Medical School, Xi’an Jiaotong University, Xi’an 710061, Shaanxi Province, China
Li Cheng, Department of Nursing, School of Medicine, Xi’an Jiaotong University, Xi’an 710061, Shaanxi Province, China
Wen-An Wu, Department of Radiation Oncology Cancer Hospital of Shaanxi Province, Xi’an 710061, Shaanxi Province, China
Sen-Ke Hu, Lab Center of Public Health Department, School of Medicine, Xi’an Jiaotong University, Xi’an 710061, Shaanxi Province, China
Author contributions: Wang XQ collected the data, did data entry and wrote the manuscript; Yan H designed the research and revised the manuscript; Terry PD assisted in the revision of this manuscript; Wang JS, Cheng L and Wu WA performed the research and did data entry; Hu SK performed the lab tests.
Supported by Health department of Shaanxi Province, China, No. 2009K12-022
Correspondence to: Hong Yan, Professor, Department of Statistics and Epidemiology, School of Medicine, Xi’an Jiaotong University, 76# West Yanta Road, Xi’an 710061, Shaanxi Province, China. xjtu_yh.paper@yahoo.com.cn
Telephone: +86-29-82655001 Fax: +86-29-82655032
Received: September 28, 2010
Revised: February 15, 2011
Accepted: February 22, 2011
Published online: July 28, 2011
Abstract

AIM: To examine the interactions between cytotoxin-associated gene (CagA) positive Helicobacter pylori infection and smoking in non-cardiac gastric cancer.

METHODS: A case-control study (257 cases and 514 frequency-matched controls) was conducted from September 2008 to July 2010 in Xi’an, China. Cases were newly diagnosed, histologically confirmed non-cardiac cancer. Controls were randomly selected from similar communities to the cases and were further matched by sex and age (± 5 years). A face-to-face interview was performed by the investigators for each participant. Data were obtained using a standardized questionnaire that included questions regarding known or suspected lifestyle and environmental risk factors of gastric cancer. A 5 mL sample of fasting venous blood was taken. CagA infection was serologically detected by enzyme-linked immunosorbent assays.

RESULTS: Smoking and CagA infection were statistically significant risk factors of non-cardiac cancer. CagA was categorized in tertiles, and the odds ratio (OR) was 12.4 (95% CI: 6.1-20.3, P = 0.003) for CagA after being adjusted for confounding factors when the high-exposure category was compared with the low-exposure category. Smokers had an OR of 5.4 compared with subjects who never smoked (95% CI: 2.3-9.0, P = 0.002). The OR of non-cardiac cancer was 3.5 (95% CI: 1.8-5.3) for non-smokers with CagA infection, 3.5 (95% CI: 1.9-5.1) for smokers without CagA infection, and 8.7 (95% CI: 5.1-11.9) for smokers with CagA infection compared with subjects without these risk factors. After adjusting for confounding factors, the corresponding ORs of non-cardiac cancer were 3.2 (95% CI: 1.5-6.8), 2.7 (95% CI: 1.3-4.9) and 19.5 (95% CI: 10.3-42.2), respectively. There was a multiplicative interaction between smoking and CagA, with a synergistic factor of 2.257 (Z = 2.315, P = 0.021).

CONCLUSION: These findings support a meaningful interaction between CagA and smoking for the risk of gastric cancer which may have implications for its early detection.

Keywords: Non-cardia cancer; Cytotoxin-associated gene; Helicobacter pylori; Interaction; Smoking