Chrna5 Gene Promoter Region Polymorphism And Lung Cancer Genetic Susceptibility Analysis And Functional Study

Objectives:To investigate the association between polymorphisms in the promoter region of the nicotine acetylcholine receptor subunits a5 (CHRNA5)gene and the susceptibility of lung cancer in Chinese Han population. And the molecular effects, including transcriptional effects and binding ability to transcriptional factors, of two haplotypes.Methods:This study was designed as a case-control study. Genotyping were performed using SNaPshot assay in 505 pathologically diagnosed lung cancer patients and 496 matched controls. The transcriptional effects were measured by dual-luciferase reporter assay. The SPR assay showed the binding affinity of the polymorphisms to nuclear extracts,.Results:In the genotype analysis, the TA of rs503464 in CHRNA5 was identified to protect carriers from lung cancer risk with the adjusted OR of 0.637 (95%CI:0.472-0.858)for TT+AA genotypes. Further stratified analyses revealed, compared with the homozygous, the protective effect of the TA gentoype was more evident in the subjects with age>60 or no family history of cancer(P<0.001). Furthermore, The haplotype analysis revealed that two lower frequent haplotypes (T-ins and C-del) were statistically protective to lung cancer (P=0.0002, OR=0.33 and P=0.0094, OR= 0.61 respectively). Unexpectedly, the luciferase result showed that the two protective haplotype constructs had the opposite promoter activity in various cells (A549, H1299, HELF and HELA):the T/ins of the highest-activity haplotype versus the C/del of the lowest-activity haplotype. Surface plasmon resonance demonstrated that both minor alleles (T and del) decreased DNA binding affinity to nuclear extracts, which was presumed responsible for the disparity on promoter activity.Conclusions:both the major haplotype C/ins and the minor haplotype T/del showing moderate promoter activity appeared not associated with lung cancer. It seemed that the CHRNA5 promoter with moderate activity was not advantageous; underactivited and overactivited of CHRNA5 promoter could be protective against lung cancer. These results indicate a new associated risk pattern of "U-shaped" between CHRNA5 promoter activity and susceptibility to lung cancer, which implies a complex role for CHRNA5 in lung cancer. Together, our findings confirmed CHRNA5 as a susceptible gene to lung cancer in Chinese populations.