| Background Laryngeal cancer is one of the most common forms of malignant tumors in head and neck cancer, which accounts for about 1%～5% of all the malignant tumors in human beings. Over 90% laryngeal cancers is squamous cell carcinoma (SCC) that arises from the epithelium of the upper aerodigestive tract. Most patients were diagnosed at their early 60s, with a male predominance. However, more than 40% tumors had developed into advanced-stage when diagnosed resulting in poor prognosis for these patients. Until now, the mechanisms of laryngeal squamous cell carcinoma (LSCC) remain less understood. Although smoking and alcohol consumption are considered the main risk factors for LSCC, only fractions of individuals exposed develop cancer. Genetic variations, therefore, may play an important role in LSCC susceptibility.With the completion of Human Genome Project (HGP), association study of population based polymorphisms of functional DNA has recently been considered as the most efficient way to explore some complex diseases. It is known that genetic variations play an important role in gene structure and function, which could change the biological functions of genes. Single nucleotide polymorphisms (SNPs) are the most common types of genetic variations, which can impact the gene structure and repair enzyme function, leading to increased risk of cancer. SNPs have been widely used for gene mapping of molecular markers in the study of molecular epidemiology and genetics. By comparing the SNPs of cases and controls, we can locate and identify specific disease-related genes. Many studies have suggested that the genes in DNA repair, apoptosis, and folate metabolism were associated with laryngeal cancer risk. Most functional SNPs singly or jointly contribute to the risk of laryngeal cancer, and possibly have gene-gene and gene-environment interactions. However, there are no studies conducted in Chinese populations to replicate these findings. Our study would investigate the association between the single nucleotide polymorphisms of IL-13 gene and the susceptibility to laryngeal cancer in Chinese males.IL-13 is one of the Th2 cytokines that made by T cells, B cells, mast cells, basophils, NK cells and dendritic cells. Recently, a lot of studies indicate that this cytokine plays a critical role in many aspects of immune regulation, especially in the negative regulation of anti-tumor immunity. Therefore, we might speculate that the IL-13 might be implicated in the development of LSCC through negative regulation of anti-tumor immunity.IL-13 locates at 12 kbp upstream on the chromosome 5q31. Many epidemiological studies suggested that single-nucleotide polymorphisms (SNPs) in IL-13 gene confer to susceptibility to cancer. Genetic variations in 3’-untranslated region (3’-UTR) of gene have been reported to affect gene expression by interfering with microRNAs (miRNAs), which are thought to function as either tumor suppressors or oncogenes by binding to their target mRNA. The SNP rs1295685 we selected is located at the 3’-UTR of the IL-13 gene and it, might participate in the LSCC development. To date, few studies have investigated the effect of polymorphism in IL-13 3’-UTR on laryngeal cancer and the function remains unknown.In the present study, we hypothesized that the rs1295685 polymorphism is associated with LSCC. This hypothesis was tested in our ongoing, hospital-based, case-control study in Chinese males.Objective To investigate the association between the single nucleotide polymorphisms of IL-13 gene and the susceptibility to laryngeal cancer in Chinese males.Materials and Methods 1. Study subjects. A hospital-based case-control study of 111 histopathologically confirmed LSCC patients and 340 cancer-free control subjects was performed among males. All participants were consecutively recruited between November 2011 and September 2012 at the First Affiliated Hospital of Nanjing Medical University (Nanjing, China) and other hospitals in Jiangsu province and were genetically unrelated ethnic Han Chinese living in Jiangsu province and Anhui province of Eastern China. Patients who once had cancer, metastasised cancer from other or unknown origins and radiotherapy or chemotherapy were excluded. The cancer-free controls were recruited from individuals who were seeking health care in the out-patient departments at the hospital that frequently matched by age (±5 years) to the cases. Tumors were staged according to the Union for International Cancer Control (UICC). People who smoked daily up to one year were defined as smokers while the others were considered as nonsmokers. Those who consumed alcohol at least three times a week for a period lasting more than 6 months were classified as drinkers and the rest were considered as nondrinkers. We used face-to-face interviews by trained interviewers to obtain detailed information on demographic characteristics and related factors. After informed consent was signed, each participant donated 5 ml blood used for genomic DNA extraction. The research protocol was approved by the Institutional Review Board of the First Affiliated Hospital of Nanjing Medical University, Nanjing, China.2. DNA extraction and polymorphism genotyping. Genomic DNA was extracted from 150 ml EDTA-anticoagulated peripheral blood samples using a DNA extraction kit (Tiangen Biotech, Beijing, China) following the manufacturer’s instructions. The rs1295685 polymorphism in IL-13 3’-UTR was genotyped using TaqMan single nucleotide polymorphism Genotyping Assays (Applied Biosystems, Foster City, CA, USA). The sequences of primer and probe for the SNP were F: 5-GGGGCCCTGAGTCTCTGAA-3 and R:5-GTTTGTCACCGTTGGGGATT-3. Amplification was performed with ABI 7900HT Real Time PCR System (Applied Biosystems) under the following conditions:50℃ for 2 min,95℃ for 10 min followed by 40 cycles of 95℃ for 15 s and 60℃ for 1 min. The SDS 2.4 software (Applied Biosystems) was used for allelic discrimination. To ensure accuracy of the genotyping, negative controls were included in each plate and more than 10% samples were randomly selected for confirmation. Two persons conducted the genotyping independently in a blind fashion to make sure the results 100% concordant.3. Statistical analyses. Student’s t-test (for continuous variables) or Chi-square test (for categorical variables) was used to examine the frequency distributions of selected demographic variables and frequencies of genotypes between cases and controls. Hardy-Weinberg equilibrium was applied using a goodness-of-fit Chi-square test. The association between the IL-13 rs1295685 polymorphism and LSCC risk was estimated as odds ratios (ORs) and 95% confidence intervals (CIs) by using unconditional logistic regression analysis with the adjustment of possible confounders. Interaction was tested using a multiplicative interaction term included in the multivariate model. We assessed a multiplicative gene-environment interaction by logistic regression analysis to explore potential interactions between the polymorphism and tobacco smoking or drinking. A P value of less than 0.05 was considered as statistically significant and all statistical tests were two-sided. All analyses were performed with SPSS software package (version 13.0, SPSS Inc., Chicago, IL).Results Individuals with IL-13 rs 1295685 TT/CT genotypes had an increased risk of laryngeal cancer (adjusted OR=2.00,95%CI:1.23～3.27, P= 0.005). Particularly among younger patients (OR= 2.72 and 95%CI:1.40～5.28), smokers (OR= 2.07 and 95%CI:1.19～3.58), drinkers (OR= 1.96 and 95%CI:1.03～3.73) and those without a family history of cancer (OR= 2.01 and 95%CI:1.18～3.41). No significant relationship was observed between rs1295685 polymorphism and progression of laryngeal cancer.Conclusions 1. The polymorphism of IL-13 rs1295685 plays an important role in the etiology of laryngeal cancer in Chinese males;2. No significant interaction was observed between rs1295685 polymorphism and smoking or drinking;3. No significant relationship was observed between rs1295685 polymorphism and progression of laryngeal squamous cell carcinoma. |
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