| Backgrounds and PurposeEsophageal cancer is one of the most common gastrointestinal cancers in the world. According to the data of IARC (International Agency for Research on Cancer), in2008, esophageal cancer is the eighth most common cancer in the world, and there were482300newly diagnosed cases; esophageal cancer is also the sixth most deadly cancer worldwide, and about406800people died from esophageal cancer. China is a high-risk area of esophageal cancer, and the mortality of esophageal cancer is the fourth among all malignant tumors in our country, only behind lung cancer, gastric cancer and liver cancer. Of the two major histological types, esophageal squamous cell carcinoma (ESCC) rather than adenocarcinoma is common worldwide. The main high-risk area of esophageal adenocarcinoma is the area inhabited by people of European descent, while ESCC is relatively more prevalent among the East Asian population, including the Chinese.Although the exact etiology of ESCC remains to be identified, cigarette smoking and alcohol drinking have been demonstrated as the major factors that contribute to the development of ESCC in accumulating epidemiological and clinical studies. Tobacco smoking and alcohol consumption have been categorized into group I carcinogens, confirmed human carcinogens, by the working group of IARC. Carcinogens in tobacco and alcohol can be metabolized in vivo, and polymorphisms in these carcinogen-related genes in vivo may affect the metabolism of these carcinogens and further modify the susceptibility to ESCC. In2009, a genome-wide association (GWA) study by Cui et al. in a Japanese population showed that two SNPs in the ALDH2and ADH1B, which encode dehydrogenases involved in alcohol metabolism, were strongly associated with ESCC risk.Polymorphisms mean two or more variants, genotypes or alleles in one biological population at the same time. According to the chronological order of studies, polymorphisms may be grouped into three main categories:Restriction Fragment Length Polymorphism (RFLP), Repeated Sequence Polymorphism (RSP) and Single-nucleotide polymorphism (SNP). All three kinds of polymorphisms can reflect the differences of genetic susceptibility in individuals with genetic diseases and offer the help for basic research and clinical diagnosis. SNP, a polymorphism from the variation of a Single Nucleotide (A, T, C or G) in the genome, plays a significant role in identifying genetic susceptibility to the disease due to its advantages of high density, good stability and easy accessibility.The nicotinic acetylcholine receptor (nAChR) belongs to the superfamily of ligand-gated ion channels, and it is activated by acetylcholine (Ach), choline and nicotine. It is involved in the regulation of nicotine and nitrosamines. Nitrosamines are important carcinogens in tobacco that contribute to the development of many smoking-related cancers, and N’-nitrosonornicotine (NNN) which have a high affinity for nAChR can affect carcinogensis of esophagus in human; while nicotine in tobacco triggers the psychological and neurobiological effects that are associated with smoking consumption and addiction,. Furthermore, the nAChR pathway is related to tumor cell proliferation, apoptosis, survival, migration, invasion, and angiogenesis, which can affect the progression of cancer patients. Consequently, nAChR may have effects on ESCC risk, ESCC progression and smoking behaviors.CHRNA5-CHRNA3-CHRNB4(CHRNA5-A3-B4) gene cluster encodes the a5and α3and β4subunits of nAchR. Recently, GWA studies have shown several polymorphisms in the CHRNA5-A3-B4gene cluster to be related to lung cancer risk and smoking behaviors, such as nicotine addiction (ND), cigarettes smoked per day (CPD) and pack-years, in people of European descent. Because these three variants are extremely rare in the Asian population, according to the HapMap database, they play little roles, if any, in the risk of smoking-related cancers and smoking behaviors in Chinese people. Then investigators in China screened polymorphisms in the CHRNA5-A3-B4gene cluster and found that variants rs667282and rs3743073in CHRNA5-A3-B4can also affect lung cancer risk in Chinese populations.In this case-control study, we investigated the impact of the variants rs667282and rs3743073in CHRNA5-A3-B4on the risk and progression of ESCC, as well as smoking behaviors, in a Chinese population.Materials and MethodsThis study consisted of866ESCC patients and952healthy controls. All subjects were biologically unrelated ethnic Han Chinese from Shandong Province in China. Patients who were newly diagnosed with histologically confirmed primary ESCC were recruited from Qilu Hospital of Shandong University, Shandong Tumor Hospital and Institute and the Second Hospital of Shandong University. Controls, the healthy individuals excluding history of malignancy, were selected from the physical examination center of Qilu Hospital. Whole-blood samples were collected from all study participants. We extracted genomic DNA from the blood samples and collected subject data through face-to-face interviews conducted by trained medical students or clinical doctors with a pre-tested standardized questionnaire regarding age, gender, drinking status, smoking status, smoking dose, and smoking exposure.Then we genotyped rs667282and rs3743073using the TaqMan method and further confirmed it with sequencing assay. The effect of CHRNA5-A3-B4variation on ESCC risk was estimated using a logistic regression model. Associations between the2SNP genotype groups with the histological grade and clinical stage of ESCC were evaluated using the chi-square test. The Kruskal-Wallis test was used to compare the difference of cigarettes per day (CPD) and pack-years of smoking.Results(1)Impact of CHRNA5-A3-B4variation on ESCC riskThe genotypes of rs667282were markedly distinct in cases and controls, and the frequencies of TT and TC genotypes in cases were obviously higher than those in controls, whereas the allele distribution of rs3743073was similar between cases and controls. We calculated the odds ratios adjusted by age, sex, drinking status and smoking status using a logistic regression model. The TT/TC genotypes of rs667282exhibited an increased association with ESCC risk (adjusted OR=1.32,95%CI=1.03to1.69, P=0.029), which suggested that T allele of rs667282in CHRNA5-A3-B4gene cluster is a risk factor for ESCC. Rs3743073did not show a significant association with the risk of ESCC (P>0.05).We further examined the impact of rs667282on ESCC risk, stratified by age, gender, drinking status and smoking status. The increased cancer risk accompanied by rs667282TT/TC genotypes was more notable in younger subjects (≤60years)(OR=1.44,95%CI=1.04to1.98, P=0.024).(2)Impact of CHRNA5-A3-B4variation on ESCC progressionThere was a weak association between the TT/TC genotypes of rs667282and advanced clinical stage (OR=1.30,95%CI=0.78to1.85, P=0.137), however no relationship between rs667282and the histological grade of ESCC was observed. In this study rs3743073did not show a significant association with histological grade and clinical stage of ESCC patients.(3) Impact of CHRNA5-A3-B4variation on ESCC progressionSubjects with rs667282TT/TC genotypes exhibited a tendency to smoke more CPD than those with the CC genotype (mean=23.1CPD,95%CI=22.3to24.0CPD; mean=21.5CPD,95%CI=19.9to23.2CPD, respectively), and more pack-years (mean=36.3pack-years,95%CI=34.7to47.8pack-years; mean=34.6pack-years,95%CI=31.6to37.6pack-years, respectively). However, this difference did not reach statistical significance (P>0.05). Subjects with rs3743073GG/TG genotypes showed similar smoking behaviors on CPD with those with the TT genotype (mean=23.1CPD,95%CI=22.2to24.0CPD; mean=22.0CPD,95%CI=20.6to23.2CPD, respectively), and on pack-years (mean=36.0pack-years,95%CI=34.4to37.5pack-years; mean=35.7pack-years,95%CI=32.9to38.4pack-years, respectively).ConclusionsThe TT/TC genotypes of CHRNA5-A3-B4rs667282are the risk factors for ESCC, and it might affect clinical stage of ESCC. The relationship between CHRNA5-A3-B4and smoking behaviors in a Chinese population needs further investigation. ObjectiveLung cancer is the most common cause of cancer-related deaths all over the world. Approximately1.6million lung cancer cases and1.4million lung cancer deaths occurred in2008globally. Non-small cell lung cancer (NSCLC) accounts for about80%of primary lung cancers, with most of the patients diagnosed at the advanced stage (stage Ⅲ or Ⅳ). Despite chemotherapy and radiotherapy, prognosis of advanced NSCLC patients is still unsatisfactory with a5-year survival rates less than15%. Prognosis prediction for these patients was usually based on clinical characteristics, such as smoking behaviors, performance status (PS) and tumor, lymph node and metastasis (TNM) staging system. However, recent studies have shown that genetic factors may also influence the survival of advanced NSCLC patientsnicotinic acetylcholine receptors (nAChRs) play a key role in carcinogenesis and progression of lung cancer. Polymorphisms in CHRNA5-A3-B4and CHRNB3-A6, two gene clusters encoding nAChR subunits, have been associated with lung cancer risk by GWAS. In this study, we investigated whether variants in the two gene clusters were associated with prognosis of advanced non-small cell lung cancer (NSCLC).MethodsA total of165stage IIIB-IV NSCLC patients were enrolled in this study. Clinicopathological characteristics and survival data were collected, and overall survival (OS) was defined as the interval between the date of first treatment and the date of last follow-up or death from any cause. Three polymorphisms (rs667282and rs3743073in CHRNA5-A3-B4and rs13280604in CHRNB3-A6) were genotyped using the TaqMan method. OS curves were drawn with the Kaplan-Meier product limit method for each of the different genotype groups. Comparisons were made with the log-rank test. Hazard ratios (HRs) of risk genotypes were estimated by fitting the Cox model while adjusting for confounding factors.ResultsOur results showed that patients with CHRNA5-A3-B4rs667282TT or TC genotypes had a significantly shorter OS time than those carrying the CC genotype (median survival time=11.7and18.2months, respectively; P=0.043). Multivariate Cox regression analysis showed that rs667282TT/TC genotypes are significantly associated with poorer survival (adjusted hazard ratio=1.64;95%confidence interval1.03-2.61; P=0.038). These impacts were not observed in the other two polymorphisms. No evident association was found between variants and dlinicopathologic features of advanced NSCLC.ConclusionOur present study suggested that rs667282in CHRNA5-A3-B4may influence the prognosis of advanced NSCLC patients, however, the association of rs3743073in CHRNA5-A3-B4and rs13280604in CHRNB3-A6with the prognosis of advanced NSCLC patients needs further investigation. |
PDF Full Text Request