Methylation of the DPYD promoter: an alternative mechanism for dihydropyrimidine dehydrogenase deficiency in cancer patients

Clin Cancer Res. 2005 Dec 15;11(24 Pt 1):8699-705. doi: 10.1158/1078-0432.CCR-05-1520.


Purpose: Dihydropyrimidine dehydrogenase (DPD) deficiency, a known pharmacogenetic syndrome associated with 5-fluorouracil (5-FU) toxicity, has been detected in 3% to 5% of the population. Genotypic studies have identified >32 sequence variants in the DPYD gene; however, in a number of cases, sequence variants could not explain the molecular basis of DPD deficiency. Recent studies in cell lines indicate that hypermethylation of the DPYD promoter might down-regulate DPD expression. The current study investigates the role of methylation in cancer patients with an unexplained molecular basis of DPD deficiency.

Experimental design: DPD deficiency was identified phenotypically by both enzyme assay and uracil breath test, and genotypically by denaturing high-performance liquid chromatography. The methylation status was evaluated in PCR products (209 bp) of bisulfite-modified DPYD promoter, using a novel denaturing high-performance liquid chromatography method that distinguishes between methylated and unmethylated alleles. Clinical samples included five volunteers with normal DPD enzyme activity, five DPD-deficient volunteers, and five DPD-deficient cancer patients with a history of 5-FU toxicity.

Results: No evidence of methylation was detected in samples from volunteers with normal DPD. Methylation was detected in five of five DPD-deficient volunteers and in three of five of the DPD-deficient cancer patient samples. Of note, one of the two samples from patients with DPD-deficient cancer with no evidence of methylation had the mutation DPYD*2A, whereas the other had DPYD*13.

Discussion: Methylation of the DPYD promoter region is associated with down-regulation of DPD activity in clinical samples and should be considered as a potentially important regulatory mechanism of DPD activity and basis for 5-FU toxicity in cancer patients.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Antimetabolites, Antineoplastic / toxicity
  • Chromatography, High Pressure Liquid
  • CpG Islands / genetics
  • DNA Methylation*
  • Dihydropyrimidine Dehydrogenase Deficiency*
  • Dihydrouracil Dehydrogenase (NADP) / genetics*
  • Down-Regulation
  • Female
  • Fluorouracil / toxicity
  • Genotype
  • Humans
  • Male
  • Middle Aged
  • Mutation
  • Neoplasms / enzymology*
  • Nucleic Acid Denaturation
  • Phenotype
  • Promoter Regions, Genetic / genetics*


  • Antimetabolites, Antineoplastic
  • Dihydrouracil Dehydrogenase (NADP)
  • Fluorouracil