Impact of Polymorphisms in Casein Kinase 1 Epsilon and Environmental Factors in Oral Cancer Susceptibility

In Taiwan, the incidence rate of oral cancer is constantly increasing. Polymorphisms and lifestyle habits are major contributing factors to the development of oral cancer in such cases. Casein kinase 1 epsilon (CK1ε) gene expression plays a role in numerous cancers, and the knockdown of CK1ε induces tumor cell-selective cytotoxicity. The present study was designed to determine the effects of CK1ε gene polymorphisms combined with environmental carcinogens on susceptibility to developing oral squamous cell carcinoma and its clinicopathological status. Four single-nucleotide polymorphisms (SNPs) in CK1ε gene (rs135745, rs135764, rs1997644 and rs2075984) from 741 oral cancer patients and 462 healthy controls were analyzed using real-time polymerase chain reaction. Our results shown that variant types (GC) of CK1ε polymorphic rs135745 exhibited a significantly higher risk of 1.41 (95% confidence interval [CI]: 1.036-1.919) for oral cancer than did wild type alleles. Furthermore, these CK1ε gene SNPs along with betel-quid chewing and/or tobacco use further increased susceptibility to oral cancer. Moreover, variant genotypes (GC+CC) of CK1ε rs135745 were significantly associated with lymph node metastasis. These results suggested that the CK1ε gene polymorphism is associated with the clinicopathological development of oral cancer and increases individuals' susceptibility to environmental carcinogens (e.g., smoking and betel-quid chewing) in terms of developing oral cancer.