Association Of VEGF Genetic Polymorphisms With Primary Lung Cancer

Objective:Lung cancer,a severely threaten to the health and life,is one of the most common malignant tumors.Disease incidence is rising year by year.Many findings show that the incidence rate and death rate of lung cancer is very high in world wide.But the diagnosis do not have obvious improvement now.Many lung cancer patients have been in advanced stage, when diagnosed.The effect of treatment and survival rate was limited.So precaution and early diagnosis are the effective way to improve the survival rate of lung cancer.Previous studies have demonstrated that smoking,circumstance and life style were associated with the noset risk of lung cancer.Along with the developing of the molecular biology,the effect of hereditary susceptibility was focused on the research of lung cancer.Angiogenesis is an important step in the development of tumor and is necessary for primary tumor growth,invasiveness, and metastasis.Vascular endothelial growth factor(VEGF) is a specific mitogen for endothelial cells.High levels of VEGF can effectually promotes proliferation,differentiation and migration of endothelial cells;induces angiogenesis,and can promots establishment of conferted capillary network in tumors.Besides, it can increase the permeability of the capillaries and veinlet.It has been suggested that a high pathologic level of VEGF released from most tumors is associated with immune deficiencies in cancer.So VEGF is believed to play a central role in in the development,growth,invasiveness,and metastasis of tumor.It is now recognized as a kind of important angiogenic cytokine associated with tumorigenesis and development of tumor.Recently,studies show that some tumors may induce a higher serum,urinary or intratumoral VEGF level,for instance: breast cancer,gastric cancer,lung cancer,prostatic carcinoma, and esophageal carcinoma.DNA sequence variations in the vascular endothelial growth factor gene may lead to altered VEGF production and/or activity.It has been suggested that a few single nucleotide polymorphisms(SNP) are associated with differential VEGF expression.Consequently,the relevant researches between VEGF polymorphisms and the susceptibility of lung cancer will be beneficial to the precaution and early diagnosis of lung cancer.But,this kind of research was rare in China.VEGF gene has high incidence of polymorphism.At least 30 single nucleotide polymorphisms(SNP) have been identified in the VEGF gene.This study was designed to investigate the association between two single nucleotide polymorphisms [-460T/C and -1154G/A]in the promoter region of VEGF gene and the susceptibilitiy of lung cancer in North China.Methods:This hospital-based case-control study included 200 lung cancer patients(75 squamous cell carcinomas,84 adenocarcinomas,41 small cell lung carcinomas) and 204 healthy controls.Genomic DNA was extracted by using proteinase K digestion followed by a salting out procedure. Polymorphisms of VEGF gene were analyzed by PCR-restriction fragment length polymorphism analysis(RFLP) and primer-introduced restriction analysis PCR(PIRA-PCR).Statistical analysis was performed using SPSS11.5 software package.P<0.05 was considered significant for all statistical analyses.Hardy-Weinberg analysis was performed by comparing the observed and expected genotype frequencies in the control group using Chi-square test.The divergence of age and sex validated with t test.Comparison of the VEGF gene genotype,allelotype and haplotype distribution in cancer patients and healthy controls was performed by means of two-sided contingency tables using Chi-square test.The VEGF gene haplotype frequencies and linkage disequilibrium coefficient were estimated by using EH linkage software and 2LD software.The odds ratio(OR) and 95%confidence Interval (CI) were calculated using an unconditional logistic regression model and adjusted by age,gender and smoking status accordingly.Results:1 The frequency of smokers in lung cancer patients(58.0%) was significantly higher than that in healthy controls(42.0%) (χ~2=10.777,P=0.001).So smoking may increased the risk of developing lung cancer(age and gender adjusted OR=1.933, 95%CI=1.302-2.871,respectively).2 The distribution of the VEGF -460T/C SNP genotypes among healthy controls did not significantly deviate from that expected by Hardy-Weinberg equilibrium(P>0.05).In lung cancer patients,frequency of the T and C allele were 72.5%and 27.5%respectively;in healthy controls,the frequency were 79.9%and 20.1%respectively.The frequency of the C allele in lung cancer patients was significantly higher than that in healthy controls(χ~2=6.109,P=0.013).The frequencies of three genotypes(T/T,T/C and C/C) in healthy controls were 63.2%,33.3%and 3.4%respectively,and in lung cancer patients were 52.5%,40.0%and 7.5%respectively. (Because of the frequencies of C/C genotype was too low,so combined the T/C and C/C genotype).The frequencies of the two genotypes(T/T and T/C+C/C) in patients and healthy controls were 52.2%,47.5%and 63.2%,36.7%,respectively. There was significant difference between the two groups (χ~2=4.445,P=0.029).Compared with individuals with the T/T genotype,individuals with the T/C+C/C genotype had significantly higher risk to develop lung cancer(age,gender and smoking status adjusted OR=1.692,95%CI=1.123-2.549).When stratified by smoking status,compared with individuals with the T/T genotype,the T/C+C/C genotype increased the risk in developing lung cancer in non-smokers (age and gender adjusted OR=2.457,95%CI =1.357-4.450). When stratified by tumor histology,compared with individuals with the T/T genotype,individuals with the T/C+C/C genotype carried an increased risk of lung cancer in squamous cell carcinomas(SCC) and small cell lung carcinomas(SCLC)(age,gender smoking status adjusted OR= 1.867 and 2.092,95%CI=1.058-3.295 and 1.036-4.224).3 The distribution of the VEGF -1154 G/A SNP genotypes among healthy controls did not significantly deviate from that expected by Hardy-Weinberg equilibrium(P>0.05).When overall lung cancer cases were compared with the controls,no significant difference was found in the distributions of genotype and allele(P>0.05).When the overall lung cancer cases were categorized by smoking status,however,the G/A+A/A genotype was associated with a significantly reduced risk of non-smokers as compared with the G/G genotype(age and gender adjusted OR=0.412, 95%CI=0.228-0.746).When stratified by tumor histology,No significant association was found between the VEGF -1154G/A polymorphism and the risk of lung cancer.4 The combined effect of VEGF -460T/C and -1154G/A SNP on lung cancer was analyzed.It was shown that the two SNPs were not in linkage disequilibrium(D' = 0.370936).Conclusions:1 Smoking may increase the risk of developing lung cancer. 2 VEGF -460T/C SNP was associated with the risk of lung cancer.When stratified by smoking status,compared with individuals with the T/T genotype,the T/C+C/C genotype increased the risk of lung cancer in non-smokers.When stratified by tumor histology,compared with the T/T genotype, individuals with the T/C+C/C genotype carried an increased risk of lung cancer in squamous cell carcinomas(SCC) and small cell lung carcinomas(SCLC).3 The combined G/A+A/A genotype of VEGF -1154G/A SNP was associated with a significantly decreased risk of non-smokers,compared with the G/G genotype.