Dihydropyrimidine dehydrogenase pharmacogenetics in patients with colorectal cancer

Abstract

Summary Individuals with a deficiency in the enzyme dihydropyrimidine dehydrogenase (DPD) may experience severe life-threatening toxicity when treated with 5-fluorouracil (5-FU). As routine measurement of enzyme activity is not practical in many clinical centres, we have investigated the use of DNA mutation analysis to identify cancer patients with low enzyme levels. We have identified two new mutations at codons 534 and 543 in the DPD cDNA of a patient with low enzyme activity and screened the DNA from 75 colorectal cancer patients for these mutations and the previously reported splice site mutation (Vreken et al, 1996;Wei et al, 1996). In all cases, DPD enzyme activity was also measured. The splice site mutation was detected in a patient (1 out of 72) with low enzyme activity whereas mutations at codons 534 (2 out of 75) and 543 (11 out of 23) were not associated with low enzyme activity. These studies highlight the need to combine DPD genotype and phenotype analysis to identify mutations that result in reduced enzyme activity.Keywords: dihydropyrimidine dehydrogenase; 5-fluorouracil; polymorphism; colorectal cancer 5-Fluorouracil (5-FU) is widely used in the treatment of advanced solid tumours, including colorectal, breast and head/neck tumours. 5-FU is also frequently used in adjuvant chemotherapy for colorectal and breast cancers, in which its mild toxicity profile of mucositis and diarrhoea is well tolerated by patients who are at risk for tumour recurrence but have no current evidence of disease. 5-FU is a pyrimidine analogue and greater than 80% of a dose is degraded in a three-step pathway, initially catalysed by the enzyme dihydropyrimidine dehydrogenase (DPD; E.C. 1.3.1.2., Heggie et al, 1987). Deficiency in DPD enzyme activity is associated with a considerable delay in clearance of 5-FU from the plasma (Diasio et al, 1988;Fleming et al, 1992), leading to severe, life-threatening diarrhoea, neutropenia and in some cases neurotoxicity, incurring prolonged hospitalization . High concentrations of plasma and urine 5-FU, uracil and thymine may be detected along with low mononuclear cell DPD activity in these patients. The toxicity is thought to result from higher levels of 5-FU entering the anabolic pathway, resulting in an increased production of cytotoxic nucleotides. Although thymidine rescue has been attempted in one case (Takimoto et al, 1996), the majority of cases have been managed with supportive care after the cessation of 5-FU-based therapy. DPD activity is found in most human tissues, with the highest levels in the liver and lymphocytes. Population studies of peripheral blood mononuclear cell (PBMNC) DPD have shown that enzyme activity is variable with a seven-to 10-fold range observed (Lu et al, 1993;Etienne et al, 1994;McMurrough and McLeod, 1996). These studies suggest that although total deficiency is rare in adults, as many as 3% of the population may have low enzyme levels and thus be at One mutation in the DPYD gene has been reported to date in patients exhibiting severe toxicity after 5...

Mutations in exon 14 of dihydropyrimidine dehydrogenase and 5-Fluorouracil toxicity in Portuguese colorectal cancer patients

“…Exon 14 DPYD mutations showed a statistically significant association with grade 3-4 5-FU toxicity (P ϭ 0.01). The frequency of DPYD in our colorectal cancer population was not significantly different from that reported by Ridge et al 15 (2.7 vs. 4%).…”

“…10,22 It has subsequently been demonstrated that a number of these individuals were genotypically heterozygous for a mutant DPYD allele, [11][12][13][14][15][16] but data are scant on the frequency of mutations in DPYD among cancer patients. In this study, we showed that the prevalence of the mutation in exon 14 of DPYD in a CRC population treated with 5-FU was 2.7%.…”

“…This mutation was detected in one of eight patients with severe 5-FU toxicity, which is in line with other published studies. 7,8,[13][14][15][16] A few reports have recently described the prevalence of the exon 14 -skipping mutation in colorectal cancer and healthy populations. Van Kuilenburg et al 18 reported a frequency of 0.9% in 1357 Caucasian blood donors.…”

“…10 Several of these patients are genotypically heterozygous for a mutant DPYD allele. [11][12][13][14][15][16] To date, more than 30 variant DPYD alleles have been identified, some of which result in decreased activity of DPD enzyme. [17][18][19] Analysis of the prevalence of the various mutations has shown that the splice-site mutation IVS14ϩ1G3 A is by far the most common.…”

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

“…In our study, heterozygous 1003G[T (Val335Leu) was found from a patient On the other hand, Caucasians and Japanese share four variations: *5 (Ile543Val), *9 (Cys29Arg), Met166Val, and *6 (Val732Ile), although their allele frequencies were different, especially for *9 (Table 4). Because they have not necessarily correlated with phenotypic changes (e.g., differences in DPD enzyme activity, 5-FU pharmacokinetics and pharmacodynamics) (Collie-Duguid et al 2000;Johnson et al 2002;Zhu et al 2004;Seck et al 2005;Ridge et al 1998aRidge et al , 1998bHsiao et al 2004), all of these variations are generally accepted as common polymorphisms that result in unaltered function. Consistent with this, van Kuilenburg et al (2002) suggested that the Fig.…”