Analysis of the DPYD Gene Implicated in 5-Fluorouracil Catabolism in a Cohort of Caucasian Individuals

Abstract

Purpose: Complete or partial loss of dihydropyrimidine dehydrogenase (DPD) function has been described in cancer patients with intolerance to fluoropyrimidine drugs like 5-fluorouracil (5-FU) or Xeloda. The intention of this population study is to assess and to evaluate gene variations in the entire coding region of the dihydropyrimidine dehydrogenase gene (DPYD), which could be implicated in DPD malfunction. Experimental Design: A cohort of 157 individuals was genotyped by denaturing highperformance liquid chromatography; 100 of these genotypes were compared with functional studies on DPD activity and mRNA expression. Results: Twenty-three variants in coding and noncoding regions of the DPYD gene were detected, giving rise to15 common haplotypes with a frequency of >1%. Rare sequence alterations included a frameshift mutation (295-298delTCAT) and three novel point mutations, 1218G>A (Met Ser). DPD enzyme activity showed high variation in the analyzed population and correlated with DPD mRNA expression. In particular, the novel variants were not accompanied with decreased enzyme activity. However, a statistically significant deviation from the median DPD activity of the population was associated with the mutations 1601G>A (Ser Dihydropyrimidine dehydrogenase (DPD; EC 1.3.1.2) is the initial and rate-limiting enzyme in the catabolism of pyrimidines. The homodimeric protein catalyzes the reduction of uracil and thymine in an NADPH-dependent manner and, furthermore, plays a critical role in the pharmacokinetics of fluoropyrimidine-based anticancer drugs. Eighty percent to 85% of administered standard doses of the common chemotherapeutic agent 5-fluorouracil (5-FU) are rapidly degraded by DPD to inactive compounds followed by excretion of a-fluoroh-alanine within 24 hours (1 -3). The rationally designed orally administered fluoropyrimidine drug Xeloda (capecitabine) is converted in situ into 5-FU due to intracellular thymidine phosphorylase activity. Capecitabine has been shown to be safer and more effective than 5-FU and has greater patient convenience (4, 5).

Influence of dihydropyrimidine dehydrogenase gene (DPYD) coding sequence variants on the development of fluoropyrimidine-related toxicity in patients with high-grade toxicity and patients with excellent tolerance of fluoropyrimidine-based chemotherapy

“…Statistically significant difference between controls and the high-toxicity group was found in frequency of IVS14+1G>A carriers The DHPLC analysis performed in the low-toxicity and control groups revealed presence of five intronic variants flanking to analyzed exons (IVS9-51T>G, IVS10-15T>C, IVS12-11G>A, IVS13+39C>T, and IVS13+40A>G). All these variants of unknown significance were described previously in various populations and were not considered for further analysis in our study [12,24,25]. The strong association of IVS13+39C>T with c.1627A>G (I543V) reported in previous studies was also observed in our samples (data not shown) [16,26].…”

Genetic variations and haplotype structures of the DPYD gene encoding dihydropyrimidine dehydrogenase in Japanese and their ethnic differences

“…Its allele frequency in Japanese (0.029 in this study) and Taiwanese (0.022) (Hsiao et al 2004) was much lower than that in (Seck et al 2005;Morel et al 2006).…”

“…The SNP 496A[G (Met166Val) in block 1 is found at a lower allele frequency in Japanese (0.022) than in Caucasians (0.080) (Seck et al 2005). Seck et al (2005) inferred two haplotypes harboring 496A[G (Met166Val) from 157 Caucasians: hap5 ( # 9d in this study) harboring additional 85T[C (Cys29Arg) and IVS10-15T[C and hap11 concurrently harboring IVS10-15T[C alone with frequencies of 0.040 and 0.014, respectively.…”

“…To date, at least 30 variant DPYD alleles have been published, with or without deleterious impact upon DPD activity (Gross et al 2003;Ogura et al 2005;Seck et al 2005;van Kuilenburg 2004;Zhu et al 2004). Of these variations, a splice site polymorphism, IVS14 + 1G[A, which causes skipping of exon 14, is occasionally detected in North Europeans with allele frequencies of 0.01-0.02 (van Kuilenburg 2004).…”

Molecular biomarkers of colorectal cancer: prognostic and predictive tools for clinical practice

“…Studies have indicated that patients with DPD deficiency often experience severe 5-FU toxicity, including death in some cases (Milano et al, 1999;Coursier et al, 2010). Studies on the mechanistic link between DPD deficiency and 5-FU toxicity have identified more than 30 polymorphisms in DPYD, the gene encoding DPD (Raida et al, 2001;Mattison et al, 2002;Seck et al, 2005). Most of these polymorphisms have no functional effect on DPD activity except for DPYD*2A allele, a G>A splice site transition that results in the skipping of exon 14.…”