Genomic DNA was extracted from white blood cells (PAXgene-RNA tubes) using the PAXgene blood RNA kit (QIAGEN, Hilden, Germany) according to the manufacturer's instructions (PAXgene blood RNA kit handbook version 2, April 2008). Taget gene and adjacent DNA exons and SNP analyses were conducted using PRISM3730 DNA Analyzer (Applied Biosystems, Foster City, CA, USA) and TaqMan SNP Genotyping Assay (Applied Biosystems) according to the manufacturer's instructions. (Hokkaido System Science, Sapporo, Japan).