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Dihydropyrimidine dehydrogenase polymorphisms and fluoropyrimidine toxicity: ready for routine clinical application within personalized medicine?

Del Re M, Di Paolo A, van Schaik RH, Bocci G, Simi P, Falcone A, Danesi R - EPMA J (2010)

Bottom Line: Fluoropyrimidines, including 5-fluorouracil (5-FU), are widely used in the treatment of solid tumors and remain the backbone of many combination regimens.Despite their clinical benefit, fluoropyrimidines are associated with gastrointestinal and hematologic toxicities, which often lead to treatment discontinuation. 5-FU undergoes complex metabolism, dihydropyrimidine dehydrogenase (DPD) being the rate-limiting enzyme of inactivation of 5-FU and its prodrugs.To date, more than 30 SNPs and deletions have been identified within DPD, the majority of these variants having no functional consequences on enzymatic activity.

View Article: PubMed Central - PubMed

Affiliation: Division of Pharmacology, Department of Internal Medicine, University of Pisa, 55, Via Roma, 56126 Pisa, Italy.

ABSTRACT
Fluoropyrimidines, including 5-fluorouracil (5-FU), are widely used in the treatment of solid tumors and remain the backbone of many combination regimens. Despite their clinical benefit, fluoropyrimidines are associated with gastrointestinal and hematologic toxicities, which often lead to treatment discontinuation. 5-FU undergoes complex metabolism, dihydropyrimidine dehydrogenase (DPD) being the rate-limiting enzyme of inactivation of 5-FU and its prodrugs. Several studies have demonstrated significant associations between severe toxicities by fluoropyrimidines and germline polymorphisms of DPD gene. To date, more than 30 SNPs and deletions have been identified within DPD, the majority of these variants having no functional consequences on enzymatic activity. However, the identification of deficient DPD genotypes may help identify poor-metabolizer patients at risk of developing potentially life-threatening toxicities after standard doses of fluoropyrimidines.

No MeSH data available.


Related in: MedlinePlus

Schematic representation of DPD gene structure and polymorphisms
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Fig4: Schematic representation of DPD gene structure and polymorphisms

Mentions: The search for genetic variants of DPD and their association with enzyme activity represents a clinically useful approach to investigate DPD deficiency. The advantage over other methods consists in the requirement of a small blood sample for DNA extraction that can be stored at room temperature and it does not require the precautions necessary for an enzymatic test. The detection of DPD sequence variants is mainly carried out by denaturing HPLC analysis and then by automatic sequencing [41]. The gene encoding DPD is located in human chromosomal region 1p22 and is formed by 23 exons of approximately 950 kb [42, 43]. Over 30 single nucleotide polymorphisms (SNPs) and deletion/insertion mutations have been identified within DPD (Fig. 4, Tables 1 and 2), although most of these variants have no functional consequences on enzymatic activity. The most important variant associated with substantially reduced enzyme activity in heterozygous patients and lack of detectable activity in homozygous subjects is the IVS14 + 1G > A (DPYD*2A), which has been found in up to 40–50% of subjects with partial or complete DPD deficiency [20, 44, 45] (Table 2). This mutation changes the invariant splice donor site from GT to AT, leading to the skipping of exon 14 immediately upstream of the mutated splice donor site in the process of DPD pre-mRNA splicing. As a result, the mature DPD mRNA lacks a 165-bp segment encoding the amino acids 581–635 and the mutant DPD protein has no residual enzymatic activity, as no significant DPD-dependent metabolism is measured in patients with this polymorphism. A toxic death after the administration of capecitabine was described by Largillier et al. in a breast cancer patient who displayed a deficient phenotype and was demonstrated to be heterozygous for the IVS14 + 1G > A polymorphism [46]. Many other polymorphisms have been reported as responsible of the severe toxicity after 5-FU administration (Table 1). van Kuilenburg et al. analyzed the DPD gene of 14 patients with a reduced DPD activity and the analysis revealed the presence of mutations in 11 out of 14 patients and five patients showed multiple mutations in the coding region of the DPD gene. In four patients it was detected the missense mutation 85 T > C, whereas the splice site mutation IVS14 + 1G > A was detected in six subjects. One patient was homozygous for the 2194G > A mutation, whereas three patients were heterozygous for the 1627A > G mutation and two patients were homozygous for the 496A > G and 2846A > T. The 2846A > T variant has also been detected in a patient with a complete DPD deficiency [47, 48]. Gross et al. analyzed four individuals with symptoms of 5-FU-related toxicity and detected six sequence variants in the DPD. Among them, 775A > G was found in a breast cancer patient who had received CMF polychemotherapy and displayed severe toxicity. None of a control cohort of 157 healthy individuals displayed this variant, suggesting that the base pair change might be a deleterious mutation and the novel mutation was present together with the known 85 T > C. Another patient, treated with CMF due to invasive breast carcinoma, carried four missense mutations 85 T > C, 496A > G, 1601G > A, and 1627A > G. The compound heterozygote genotype did not occur in any of the 157 control samples and had not been described previously. The combination of 496A > G and 1601G > A was demonstrated in a colon cancer patient showing unexpected toxicity upon 5-FU administration. In the third patient, with invasive breast carcinoma given 5-FU, epirubicin and cyclophosphamide, 85 T > C and the silent mutation 1896 T > C were found in the coding area of DPD [41]. A meta-analysis of over 1200 patients suggested that more than 30% of patients treated with 5-FU experienced substantial drug-related toxicity [49]. However, genetic variants of DPD are not always associated with severe 5-FU toxicity. Table 1 and 2 report some of the more common SNPs identified in the DPD. While some mutations are directly responsible for severe 5-FU side effects, for example the IVS14 + 1G > A which is always associated with high toxicity in cancer patients, others, like the 1601G > A polymorphism, result in 5-FU related toxicity only in combination with other genetic variants such as the 496A > G [41]. Recent studies have also suggested that epigenetic factors may influence DPD activity, such as an aberrant methylation of the DPD promoter gene, which was found to cause a partially DPD deficient phenotype [50–52].Fig. 4


Dihydropyrimidine dehydrogenase polymorphisms and fluoropyrimidine toxicity: ready for routine clinical application within personalized medicine?

Del Re M, Di Paolo A, van Schaik RH, Bocci G, Simi P, Falcone A, Danesi R - EPMA J (2010)

Schematic representation of DPD gene structure and polymorphisms
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3405332&req=5

Fig4: Schematic representation of DPD gene structure and polymorphisms
Mentions: The search for genetic variants of DPD and their association with enzyme activity represents a clinically useful approach to investigate DPD deficiency. The advantage over other methods consists in the requirement of a small blood sample for DNA extraction that can be stored at room temperature and it does not require the precautions necessary for an enzymatic test. The detection of DPD sequence variants is mainly carried out by denaturing HPLC analysis and then by automatic sequencing [41]. The gene encoding DPD is located in human chromosomal region 1p22 and is formed by 23 exons of approximately 950 kb [42, 43]. Over 30 single nucleotide polymorphisms (SNPs) and deletion/insertion mutations have been identified within DPD (Fig. 4, Tables 1 and 2), although most of these variants have no functional consequences on enzymatic activity. The most important variant associated with substantially reduced enzyme activity in heterozygous patients and lack of detectable activity in homozygous subjects is the IVS14 + 1G > A (DPYD*2A), which has been found in up to 40–50% of subjects with partial or complete DPD deficiency [20, 44, 45] (Table 2). This mutation changes the invariant splice donor site from GT to AT, leading to the skipping of exon 14 immediately upstream of the mutated splice donor site in the process of DPD pre-mRNA splicing. As a result, the mature DPD mRNA lacks a 165-bp segment encoding the amino acids 581–635 and the mutant DPD protein has no residual enzymatic activity, as no significant DPD-dependent metabolism is measured in patients with this polymorphism. A toxic death after the administration of capecitabine was described by Largillier et al. in a breast cancer patient who displayed a deficient phenotype and was demonstrated to be heterozygous for the IVS14 + 1G > A polymorphism [46]. Many other polymorphisms have been reported as responsible of the severe toxicity after 5-FU administration (Table 1). van Kuilenburg et al. analyzed the DPD gene of 14 patients with a reduced DPD activity and the analysis revealed the presence of mutations in 11 out of 14 patients and five patients showed multiple mutations in the coding region of the DPD gene. In four patients it was detected the missense mutation 85 T > C, whereas the splice site mutation IVS14 + 1G > A was detected in six subjects. One patient was homozygous for the 2194G > A mutation, whereas three patients were heterozygous for the 1627A > G mutation and two patients were homozygous for the 496A > G and 2846A > T. The 2846A > T variant has also been detected in a patient with a complete DPD deficiency [47, 48]. Gross et al. analyzed four individuals with symptoms of 5-FU-related toxicity and detected six sequence variants in the DPD. Among them, 775A > G was found in a breast cancer patient who had received CMF polychemotherapy and displayed severe toxicity. None of a control cohort of 157 healthy individuals displayed this variant, suggesting that the base pair change might be a deleterious mutation and the novel mutation was present together with the known 85 T > C. Another patient, treated with CMF due to invasive breast carcinoma, carried four missense mutations 85 T > C, 496A > G, 1601G > A, and 1627A > G. The compound heterozygote genotype did not occur in any of the 157 control samples and had not been described previously. The combination of 496A > G and 1601G > A was demonstrated in a colon cancer patient showing unexpected toxicity upon 5-FU administration. In the third patient, with invasive breast carcinoma given 5-FU, epirubicin and cyclophosphamide, 85 T > C and the silent mutation 1896 T > C were found in the coding area of DPD [41]. A meta-analysis of over 1200 patients suggested that more than 30% of patients treated with 5-FU experienced substantial drug-related toxicity [49]. However, genetic variants of DPD are not always associated with severe 5-FU toxicity. Table 1 and 2 report some of the more common SNPs identified in the DPD. While some mutations are directly responsible for severe 5-FU side effects, for example the IVS14 + 1G > A which is always associated with high toxicity in cancer patients, others, like the 1601G > A polymorphism, result in 5-FU related toxicity only in combination with other genetic variants such as the 496A > G [41]. Recent studies have also suggested that epigenetic factors may influence DPD activity, such as an aberrant methylation of the DPD promoter gene, which was found to cause a partially DPD deficient phenotype [50–52].Fig. 4

Bottom Line: Fluoropyrimidines, including 5-fluorouracil (5-FU), are widely used in the treatment of solid tumors and remain the backbone of many combination regimens.Despite their clinical benefit, fluoropyrimidines are associated with gastrointestinal and hematologic toxicities, which often lead to treatment discontinuation. 5-FU undergoes complex metabolism, dihydropyrimidine dehydrogenase (DPD) being the rate-limiting enzyme of inactivation of 5-FU and its prodrugs.To date, more than 30 SNPs and deletions have been identified within DPD, the majority of these variants having no functional consequences on enzymatic activity.

View Article: PubMed Central - PubMed

Affiliation: Division of Pharmacology, Department of Internal Medicine, University of Pisa, 55, Via Roma, 56126 Pisa, Italy.

ABSTRACT
Fluoropyrimidines, including 5-fluorouracil (5-FU), are widely used in the treatment of solid tumors and remain the backbone of many combination regimens. Despite their clinical benefit, fluoropyrimidines are associated with gastrointestinal and hematologic toxicities, which often lead to treatment discontinuation. 5-FU undergoes complex metabolism, dihydropyrimidine dehydrogenase (DPD) being the rate-limiting enzyme of inactivation of 5-FU and its prodrugs. Several studies have demonstrated significant associations between severe toxicities by fluoropyrimidines and germline polymorphisms of DPD gene. To date, more than 30 SNPs and deletions have been identified within DPD, the majority of these variants having no functional consequences on enzymatic activity. However, the identification of deficient DPD genotypes may help identify poor-metabolizer patients at risk of developing potentially life-threatening toxicities after standard doses of fluoropyrimidines.

No MeSH data available.


Related in: MedlinePlus