MTHFR C667T Polymorphism and Lung Cancer Risk in Henan Province

Lung cancer is one of the most common malignancies and is the leading cause of cancer-related death worldwide (Jemal et al., 2010). Although epidemiologic studies have proved multiple risk factors such as age, gender, smoking, environmental pollution related to the occurrence of lung cancer, there are significant variations between individuals when exposed to same risk factors, for instance cigarette smoking, which is the primary risk factor for lung cancer, induces only 10-20% of lifetime smokers to develop lung cancer (Shields, 2002), this observation suggests that other factors, such as genetic susceptibility resulted from polymorphisms of genes involving chemical metabolism, DNA repair, cell cycle regulation and immunity may influence risk of lung cancer (Dong et al., 2008). Single nucleotide polymorphisms (SNPs), which represents an alternate nucleotide in a given and defined genetic location and occurs on average every 100 to 1000 base pairs in vertebrates, is used to establish differences between individuals (Gill, 2001) and is a useful markers for propensity to disease (Amos et al., 2008), disease states (Poehlmann et al., 2007), as well as evidence of the genetic basis of adaptation (Hoekstra et al., 2006). Methylene tetrahydrofolate reductase (MTHFR) is a key enzyme in metabolism of folate and nucleotides to maintain DNA stability and prevent cancers through catalyzing irreversible conversion of 5, 10-methylenetetrahydrofolate (5, 10-methyleneTHF) to 5-methyl tetrahydrofolate (5-methyl THF) (Botto and Yang, 2000). MTHFR C677T,