Genetic Investigation On Obstructive Sleep Apnea Syndrome And Non-small Cell Lung Cancer

Obesity and inflammation has been well known to correlate with the pathogenesis of obstructive sleep apnea syndrome (OSAS). Interleukin (IL)-6, an important regulator of obesity and inflammation, was reported to increase phenotypically in patients with OSAS. This study aimed to investigate whether genetic variants in IL-6 could confer susceptibility to OSAS.The study population consisted of 151 patients with OSAS and 75 healthy controls from the southeast of China. Five haplotype-tagging single nucleotide polymorphisms (htSNPs) were selected across 21 kb of the IL-6 locus using Haploview software V4.1. They were rs1404008, rs1880242, rs10499563, rs1800796 and rs2069837. The htSNPs were amplified by polymerase chain reaction (PCR) and genotyped by restriction enzyme digestion followed by gelelectrophoresis. Linkage disequilibrium (LD) and haplotypes reconstruction were carried out by means of SHEsis program. Logistic regression was performed to assess odds ratios (OR) and 95% confidence intervals (CI), which were adjusted for gender, age and BMI.Our results suggested that: 1. No distribution difference of any of five htSNPs between OSAS patients and controls was observed. 2. In non-obese individuals (n = 117), the minor allele -572G decreased risk of OSAS compared with the major allele -572C [OR, 0.48; 95% CI, 0.26-0.86; P =0.014], and the genotype -572 (GG+CG) also decreased risk of OSAS compared with the the genotype -572 CC (OR, 0.38; 95%CI, 0.17-0.88, P =0.008). 3. The haplotype TG (rs1880242, rs1800796) carried by non-obese individuals conferred significantly decreased risk of OSAS than other haplotypes (OR, 0.39; 95% CI, 0.20-0.74; P =0.003). 4. The severity of sleep disordered breathing (measured by AHI, times/h) increased linearly in carriers of the C variant of IL-6 -572G/C polymorphism in non-obese individuals (14.3±5.1, 22.0±3.6 and 34.8±3.5 for GG, CG and CC, respectively; P = 0.012).The study indicated that genotype CC and allele C of -572G/C polymorphism of IL-6 gene in non-obese individuals could increase the risk of OSAS.Oppositely, genotype GG and allele G may have some protective effect to OSAS. Some haplotypes could play various roles in modifying the predisposition of OSAS in Chinese population. To the best of our knowledge, this is the first study to suggest that genetic variants in IL-6 could modify OSAS susceptibility. SNP genotyping of IL-6 gene could be a potential strategy to detect the risk of breathing disordered diseases in non-obese individuals.Part 2 Association of Genetic Variants in Interleukin-6 with Non-small Cell Lung CancerInterleukin (IL)-6 is a multifunctional cytokine that is important for immune responses, cell surcival, apoptosis, and proliferation. Early studies implicated IL-6 and its major effector STAT3 as protumorigenic agents in many cacners, including breast, lung, colon, prostate, ovarian, and hematological cancers as well as melanoma. Increasing evidences suggest that common genetic variants may modify the susceptibility of common disease. Three functional polymorphisms, rs1800795 (-174G/C), rs1800796 (-572C/G) and rs10499563 (-6331C/T), located in the promoter region of IL-6, could affect the transcription and plasma IL-6 levels, and associated with the risk of many diseases. The association of rs1800795 (-174G/C) and rs1800796 (-572C/G) with disease risk have been the most extensively studied in the past few years. However, whether IL-6 -6331C/T polymorphism is predisposed to cancer is unknown.Considering the notion that association studies based on haplotypes instead of genotypes, significantly improves the power of mapping and characterizing disease-causing genes. We hypothesized that genetic variants in IL-6, comprised of polymorphisms and haplotypes, confer susceptibility to non-small cell lung cancer (NSCLC). Therefore, we employed linkage disequilibrium (LD) and haplotype-based analyses to address the hypothesis using 4 haplotype-tagging SNPs (htSNPs) selected from 15 kb of IL-6 locus and haplotypes reconstructed with the htSNPs in 121 NSCLC patients and 112 healthy controls.After adjusted for age, gender and smoking history, no distribution difference of any of 4 htSNPs (rs1880242, rs10499563, rs1800796 and rs2069837) between NSCLC patients and controls was observed. The haplotype GTGA was significantly higher in NSCLC patients compared with controls (7.2% vs. 1.9%, P =0.004), suggesting that the haplotype is significantly associated with increased risk of NSCLC (OR, 4.50; 95% CI, 1.49-13.53). Our result indicated that genetic variants in IL-6 could modify NSCLC susceptibility.Part 3 Infrequently Methylated Event of E-Cadherin Promoter in Non-small Cell Lung Cancer.E-cadherin is one family member of transmembrane glycoproteins, which are involved in mediating adhesion between adjacent epithelial cells. E-cadherin is expressed predominantly on the cell surface in most epithelial tissues where it plays an important role in maintaining epithelial integrity and cellular differentiation. Epigenetic silencing of E-cadherin via aberrant methylation has been investigated in various human tumors, whereas evidence for elucidating mechanism underlying reduction of E-cadherin mRNA remains unclear in non-small cell lung cancer (NSCLC). We previously found that reduction of E-cadherin mRNA or protein expression has been frequently observed in NSCLC. In this study, we explore the contribution of E-cadherin methylation to the development and progression of NSCLC.We directly performed the bisulfite DNA sequencing to examine CpG methylation within the 5'CpG island of E-cadherin in 35 tumor and paired normal tissue specimens from patients with primary NSCLC. Then, we measured the level of E-cadherin mRNA by real-time quantitative PCR analysis. Despite of reduction in E-cadherin mRNA by 65.7% (23/35) and presence of methylation by 28.6% (10/35) in tumors, we found no association of reduction of E-cadherin mRNA level with methylation of 19 sites from -181 bp to -9 bp located upstream from the translation start of E-cadherin in NSCLC. In conclusion, we provide no evidence for the presence of aberrant methylation sites of E-cadherin in tumors from patients with NSCLC, which can explain decrease of E-cadherin mRNA. Decrease in E-cadherin mRNA may be regulated by methylation-independent pathways in NSCLC.