title: Phenotypic and clinical implications of variants in the dihydropyrimidine dehydrogenase gene.
abstract: Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of the pyrimidine bases uracil, thymine and the antineoplastic agent 5-fluorouracil. Genetic variations in the gene encoding DPD (DPYD) have emerged as predictive risk alleles for 5FU-associated toxicity. Here we report an in-depth analysis of genetic variants in DPYD and their consequences for DPD activity and pyrimidine metabolites in 100 Dutch healthy volunteers. 34 SNPs were detected in DPYD and 15 SNPs were associated with altered plasma concentrations of pyrimidine metabolites. DPD activity was significantly associated with the plasma concentrations of uracil, the presence of a specific DPYD mutation (c.1905+1G>A) and the combined presence of three risk variants in DPYD (c.1905+1G>A, c.1129-5923C>G, c.2846A>T), but not with an altered uracil/dihydrouracil (U/UH2) ratio. Various haplotypes were associated with different DPD activities (haplotype D3, a decreased DPD activity; haplotype F2, an increased DPD activity). Functional analysis of eight recombinant mutant DPD enzymes showed a reduced DPD activity, ranging from 35% to 84% of the wild-type enzyme. Analysis of a DPD homology model indicated that the structural effect of the novel p.G401R mutation is most likely minor. The clinical relevance of the p.D949V mutation was demonstrated in a cancer patient heterozygous for the c.2846A>T mutation and a novel nonsense mutation c.1681C>T (p.R561X), experiencing severe grade IV toxicity. Our studies showed that the endogenous levels of uracil and the U/UH2 ratio are poor predictors of an impaired DPD activity. Loading studies with uracil to identify patients with a DPD deficiency warrants further investigation.
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: a.b.vankuilenburg@amc.uva.nl.
authors.forename: André B P van
authors.initials: ABPV
authors.lastname: Kuilenburg
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Judith
authors.initials: J
authors.lastname: Meijer
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Michael W T
authors.initials: MWT
authors.lastname: Tanck
authors.affiliation: Department of Chemistry, Biomedical Center, Uppsala University, S-751 24 Uppsala, Sweden.
authors.forename: Doreen
authors.initials: D
authors.lastname: Dobritzsch
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Lida
authors.initials: L
authors.lastname: Zoetekouw
authors.affiliation: Trinity College Dublin, Dublin, Ireland.
authors.forename: Lois-Lee
authors.initials: LL
authors.lastname: Dekkers
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Roelofsen
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Rutger
authors.initials: R
authors.lastname: Meinsma
authors.affiliation: Department of Oncology, Medisch Spectrum Twente, Enschede, The Netherlands.
authors.forename: Machteld
authors.initials: M
authors.lastname: Wymenga
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Wim
authors.initials: W
authors.lastname: Kulik
authors.affiliation: Department of Clinical Chemistry, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Büchel
authors.affiliation: Departments of Clinical Chemistry, Pediatrics, Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Raoul C M
authors.initials: RCM
authors.lastname: Hennekam
authors.affiliation: Department of Clinical Chemistry, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
authors.forename: Carlo R
authors.initials: CR
authors.lastname: Largiadèr
mesh_terms: D019943:Amino Acid Substitution; D018389:Codon, Nonsense; D054067:Dihydropyrimidine Dehydrogenase Deficiency / Q000097:blood / Q000235:genetics*; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000235:genetics*; D005260:Female; D057809:HEK293 Cells; D006239:Haplotypes; D006801:Humans; D008875:Middle Aged; D020125:Mutation, Missense; D020641:Polymorphism, Single Nucleotide; D014498:Uracil / Q000097:blood
chemical_list: D018389:Codon, Nonsense; D014498:Uracil; D042943:Dihydrouracil Dehydrogenase (NADP)
keywords: 5-Fluorouracil; DPYD; Dihydropyrimidine dehydrogenase; Pharmacogenetics; Pyrimidine metabolism