Quantitative comparison of expression of nicotinic acetylcholine receptor (nAChR) subunits between non-small cell lung cancer (NSCLC) arising in life-time never-smokers in Chinese patients

Abstract

BACKGROUND: Nicotinic acetylcholine receptors (nAChR) are known to mediate the effects of nicotine in the human central nervous system resulting in smoking addiction. nAChRs also are expressed in bronchial epithelium and lung cancer where they may play a role in lung cancer pathogenesis, for example through nicotine acting via nAChRs to block apoptosis. OBJECTIVE: Our aim was to compare the level of expression of nAChR genes (CHRNJ in NSCLCs arising in lifetime never-smokers vs. those in smokers in Chinese patients. Twenty-four NSCLC tumor samples were analyzed using quantitative real time PCR methodology on tumour cDNA for the various nAChR subunits (CHRNAI, 2, 3, 4, 5, 6, 7, 9, 70, and CHRNBZ, 3, 4). Real-time PCR was performed with SYBR Green I mix. TATA-binding protein (TBP) was used as the endogenous reference for estimation of relative amount of CORN mRNA expression. RESULTS: Twelve tumours were from smokers and twelve were from lifetime non-smokers. 14 tumours came from men and 10 were from women. The mean age was 57.9 & 9.0 years for men and 61.8 * 9.8 for women. There were 19 adenocarcinomas and 5 squamous cell carcinomas, The TNM staging (I/II/III/IV) was 15/3/5/i. The mean relative amount of CHRN a/pha7(CHRNA7) mRNA was 0.17 f 0.05 in lifetime non-smokers compared to 0.89 f 1.12 in smokers (Student t-test P = 0.047, two-tailed with unequal variance). By comparative cycle method, the estimated relative amount (2”-AACt) for lifetime nonsmokers was 1.91 f 0.62 compared to 10.06 + 12.68 (Student t-test P= 0.048, two-tailed with unequal variance) for smokers. No statistically significant difference for CHRNA7 expression was found between genders and between adenocarcinomas and squamous cell carcinoma in the same 24 samples. Other CHRNsubunits are being studied. CONCLUSION: There is significant difference in the expression level of CHRNA7 between lifetime never-smokers and smokers in Chinese NSCLC tumours suggesting both that nicotine plays a role in and may also up regulate nAChR expression as part of the pathogenetic process. Further study is warranted to evaluate the potential role of expression of CHRNA7 as well as of other nAChR subunits in mediating the effects of nicotine in lung cancer pathogenesis.