Dihydropyrimidine dehydrogenase pharmacogenetics in the Taiwanese population

5-Fluorouracil (5-FU) remains the most frequently used chemotherapy agent in various human cancers. Over 80% of the 5-FU administered is metabolized by dihydropyrimidine dehydrogenase (DPD) in the liver. However, mutations in the DPD gene have been found to be associated with low DPD activity causing severe complications. The aim of this study was to determine the frequency of 11 known mutations in Taiwanese subjects and the relationship between mutation and DPD level. Samples from a total of 300 subjects were investigated in this study. The PCR-RFLP method was used to identify 11 mutations of the DPYD gene, including 62G>A, 74A>G, 85T>C (DPYD*9A), 812delT, 1003G>T, 1156G>T, 1627A>G (DPYD*5), 1714C>G, 1897delC (DPYD*3), 2194G>A (DPYD*6), and IVS14+1G>A (DPYD*2A). DPD protein levels were determined using a DPD ELISA kit. Four mutations, including 74A>G, 85T>C (DPYD*9A), 1627A>G (DPYD*5), and 2194G>A (DPYD*6), were found in our 300 samples. The following mutations were not detected: 62G>A, 812delT, 1003G>T, 1156G>T, 1714C>G, 1897delC (DPYD*3), and IVS14+1G>A (DPYD*2A). The phenotype analysis by DPD protein level indicated that the 1627A>G (DPYD*5) mutation was not associated with the DPD protein level and might be a polymorphism in the DPD gene. The DPD level was also not correlated with gender. No significant correlations between these 11 mutations and DPD protein level were found indicating that examination of these mutations is insufficient to provide a high-value prediction of the 5-FU pharmacogenetic syndrome in Taiwanese. Genotype and phenotype analysis indicated the 1627A>G (DPYD*5) mutation to be a polymorphism.