Relationship Between NAMPT Genetic Polymorphisms And The Susceptibility To ECSS

BackgroundAll over the word, the morbidity and mortality of esophageal cancer (EC) are relatively high, and China is one region with the highest incidence. The clinical manifestation of its early stage is not very typical. Hence, when the patients were diagnosed as EC, most of them had been in the advanced stage, had short lifetime and lived with low quality. If the patients are diagnosed in time, they could be cured once and for all, with endoscopic minimally invasive treatment. Therefore, early detection and early diagnosis are very important for high-risk groups and patients with EC. In addition, if one key link of its pathogenesis is intervened by some reasonable and effective methods, the risk of its high-risk groups to develop EC may be notably reduced, and maybe it will be a great breakthrough of its therapies.However, the exact pathogenesis of EC has been not known. Environments, unhealthy lifestyles (such as hot diet, smoking, drinking, oral hygiene, et al.), infection of human papilloma virus and so on, might influence the development of EC. Moreover, genetic factors are the research hotspots. Single nucleotide polymorphisms (SNPs) could influence the structures or expressions of proteins, thus elevate or reduce the genetic susceptibilities of diseases. In addition, haplotypes could integrate informations of linkage disequilibrium among several SNPs, and reflect more effectively the correlation of genetic polymorphisms and genetic susceptibilities to diseases. EC is known as the synthetic results of action and inaction of carcinogenic metabolisms, damage and repair of DNA and cell proliferation and apoptosis. Furthermore, the genetic polymorphisms involving in carcinogenic metabolisms, DNA repair, control of cell cycle, and folic acid metabolism have been related with the genetic susceptibilities of EC.Nicotinamide phosphoribosyl transferase (Nampt) discussed in this paper, is named as pre-B-cell colony enhancing factor (PBEF) or visfatin. Nampt shows a high degree of evolutionary conservation in amino acids sequence. Nampt acts as a rate-limiting enzyme in NAD biosynthesis, which involves in several cellular metabolisms, such as transcription regulation, DNA repair, cell cycle progression, apoptosis, calcium homeostasis, telomerase activity, antioxidation, energy metabolism, circadian rhythm maintenance and chromatin dynamics regulation, and regulatory factors of genomic stability and organismal metabolic homeostasis. Additionally, it exists intracellularly (iNampt) and extracellularly (eNampt). iNampt is involved in angiogenesis by activating the extracellular signal regulated kinase (ERK) 1/2 pathway and promoting the production of vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP) 2/9. The expression of iNampt is important for the maturation and differentiation, and eNampt may induce the expressions of multiple proinflammatory cytokines and chemotactic factors. Nampt as a few emerging adipokine, which could simulate the function of insulin, might be relative with the development of cancers. Some cancer patients had reportedly higher expression of iNampt and eNampt, compared with healthy population. According to reports, the level of its expression was in direct proportion to the grade malignancy of gastric cancer, malignant glioma cells and other cancers. Furthermore, Nampt might be a good biomarker for malignancies.NAMPT shows relatively evolutionary conservation, suggesting that only tiny mutation could profoundly change the structure or function of Nampt, even influence the development of diseases, such as bladder carcinoma, obesity and acute lung injury. rs61330082 is located in the promoter region, which could bind with transcription factor and start transcription with specificity. rs2505568 and rs9034 are in the 3’untranslated region, which has several TATA motifs needed by cell secretion. Therefore, the variations of three SNPs might influence the expression of Nampt, even vary the genetic susceptibilities of tumors.ObjectiveAnyang is a region with high incidence of EC in China. This case-control study was conducted there, to explore the relationship between NAMPT genetic polymorphisms at rs61330082, rs2505568 and rs9034 as well as the relevant haplotypes and the susceptibility to esophageal squamous cell carcinoma (ESCC).Methods405 ESCC patients were recruited from Anyang Tumor Hospital in Henan Province from February 2005 to July 2011. The control group was consisted of 405 gender-and age-matched, healthy and genetically unrelated individuals recruited, during the same time period from the same region. After each subject was required to sign an informed consent, blood sample was collected and genomic DNA was extracted. Genotypes at rs61330082, rs2505568 and rs9034 of NAMPT were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). To confirm the existence of polymorphisms,10% samples were randomly selected and directly sequenced. PHASE 2.1 software was used to construct haplotypes on the basis of the known genotypes, and estimate haplotype frequencies. Using STATA 11.2 software, the observed genotype frequencies were tested for Hardy-Weinberg equilibrium by the chi-square test, the distribution of age between the two groups was compared by the Mann-Whitney U test, and the differences of smoking and drinking were compared by the McNemar test. The possible effects of the genotypes, alleles and haplotypes on ESCC susceptibility were analyzed by odds ratio and 95% CI, in conditional Logistic regression models adjusted for age, gender, smoking and drinking.ResultsThree SNPs at rs61330082, rs2505568 and rs9034 of NAMPT were genetic polymorphic, and the distributions of genotypes were found to be in Hardy-Weinberg equilibrium (P> 0.05). A significantly smaller proportion of the cases possessed either genotype CT, TT or allele T at rs61330082 than the controls (48.89% vs.53.33%, P< 0.01; 18.52% vs.30.37%, P< 0.01; 42.96% vs.57.04%, P< 0.01, respectively). Thus, they were less susceptible to ESCC. On the contrary, individuals with genotype CC or allele C were more susceptible to ESCC. No subjects carried genotype AA at rs2505568 or genotype TT at rs9034, and the other genotypes and alleles were distributed without significant differences. Five haplotypes were constructed using PHASE 2.1 software. Haplotype CTC, CTT or CAC was more frequent in the cases than in the controls (P< 0.01, OR= 1.57,95% CI:1.16-2.12; P= 0.04,OR= 1.72,95% CI:1.03-2.85; P< 0.01, OR= 3.39,95% CI:1.99-5.75, respectively).ConclusionGenetic polymorphisms of NAMPT at rs61330082, rs2505568 and rs9034 were existed in Chinese population. Genotype CC and allele C at rs61330082 were risk factors for ESCC, and the genetic polymorphisms at rs2505568 and rs9034 were independent of developing to ESCC. The presence of haplotypes CTC (rs61330082 C-rs2505568 T-rs9034 C), CTT (rs61330082 C-rs2505568 T-rs9034 T) or CAC (rs61330082 C-rs2505568 A-rs9034 C) was positively correlated with the development of ESCC. In a word, genetic polymorphism at rs61330082, as well as haplotypes CTC, CTT and CAC, might be biomarkers for high-risk groups of ESCC, even targets of genetic therapies.