Ridge S A, Sludden J, Brown O, Robertson L, Wei X, Sapone A, Fernandez-Salguero P M, Gonzalez F J, Vreken P, van Kuilenburg A B, van Gennip A H, McLeod H L
Department of Medicine & Therapeutics, Institute of Medical Sciences, University of Aberdeen, Foresterhill, United Kingdom.
Br J Clin Pharmacol. 1998 Aug;46(2):151-6. doi: 10.1046/j.1365-2125.1998.00751.x.
Dihydropyrimidine dehydrogenase (DPD) catalyses the reduction of pyrimidines, including the anticancer agent 5-fluorouracil (5FU). Impaired 5FU degradation, through low DPD activity, has led to severe, life-threatening or fatal toxicity after administration of 5FU. Complete DPD deficiency is associated with the inherited metabolic disease thymine uraciluria. Several mutations in the gene encoding DPD have recently been identified, but the phenotype-genotype concordance of these alterations in the general population has not been reported.
Mononuclear cells were isolated from whole blood and DPD activity was determined after ex vivo incubation with 14C-5FU followed by h.p.1.c. analysis of 5FU metabolites. Analysis of mutations in the DPD gene at an exon splice site, codons 534, 543, and 732, and a deletion at base 1897 (deltaC1897) were performed in 30 subjects with the lowest and 30 subjects with the highest enzyme activity using PCR-RFLP.
DPD activity was measured in 226 Caucasian subjects and was highly variable (range 19.1-401.4 pmol min(-1)mg(-1) protein). Mutations were frequently observed at codons 543 (allele frequency 28%), 732 (allele frequency 5.8%), and 534 (allele frequency 0.8%), but were not associated with low DPD activity. There were no splice site or deltaC1897 mutations found in this population.
The five mutations analysed in this study are insufficient for identification of patients at risk for 5FU toxicity or thymine uraciluria. Both the splice site mutation and deltaC1897 are relatively rare in the general Caucasian population. Therefore, identification of further molecular alterations is required to facilitate the use of DPD analysis in genetic diagnosis and cancer therapeutics.
二氢嘧啶脱氢酶（DPD）催化嘧啶的还原反应，包括抗癌药物5-氟尿嘧啶（5FU）。由于DPD活性低下导致5FU降解受损，已致使患者在使用5FU后出现严重、危及生命或致命的毒性反应。完全性DPD缺乏与遗传性代谢疾病胸腺嘧啶尿症相关。最近已鉴定出编码DPD的基因中的若干突变，但尚未报道这些改变在普通人群中的表型-基因型一致性。
从全血中分离出单核细胞，在与14C-5FU进行体外孵育后测定DPD活性，随后通过高效液相色谱法分析5FU代谢产物。使用聚合酶链反应-限制性片段长度多态性（PCR-RFLP）对30名酶活性最低和30名酶活性最高的受试者进行DPD基因外显子剪接位点、密码子534、543和732处的突变分析以及1897位碱基缺失（deltaC1897）分析。
对226名白种人受试者测定了DPD活性，其活性变化很大（范围为19.1 - 401.4 pmol min(-1)mg(-1)蛋白质）。在密码子543（等位基因频率28%）、732（等位基因频率5.8%）和534（等位基因频率0.8%）处频繁观察到突变，但这些突变与低DPD活性无关。在该人群中未发现剪接位点或deltaC1897突变。
本研究中分析的5种突变不足以识别有5FU毒性或胸腺嘧啶尿症风险的患者。剪接位点突变和deltaC1897在普通白种人群中相对罕见。因此，需要鉴定更多的分子改变，以便在基因诊断和癌症治疗中更好地应用DPD分析。
