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Comparative Functional Analysis of DPYD Variants of Potential Clinical Relevance to Dihydropyrimidine Dehydrogenase Activity
Journal article   Open access   Peer reviewed

Comparative Functional Analysis of DPYD Variants of Potential Clinical Relevance to Dihydropyrimidine Dehydrogenase Activity

Steven M. Offer, Croix C. Fossum, Natalie J. Wegner, Alexander J. Stuflesser, Gabriel L. Butterfield and Robert B. Diasio
Cancer research (Chicago, Ill.), Vol.74(9), pp.2545-2554
05/01/2014
DOI: 10.1158/0008-5472.CAN-13-2482
PMCID: PMC4012613
PMID: 24648345
url
https://doi.org/10.1158/0008-5472.CAN-13-2482View
Published (Version of record) Open Access

Abstract

Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme of the uracil catabolic pathway, being critically important for inactivation of the commonly prescribed anti-cancer drug 5-fluorouracil (5-FU). DPD impairment leads to increased exposure to 5-FU and, in turn, increased anabolism of 5-FU to cytotoxic nucleotides, resulting in more severe clinical adverse effects. Numerous variants within the gene coding for DPD, DPYD, have been described, although only a few have been demonstrated to reduce DPD enzyme activity. To identify DPYD variants that alter enzyme function, we expressed 80 protein-coding variants in an isogenic mammalian system and measured their capacities to convert 5-FU to dihydro-fluorouracil, the product of DPD catabolism. The M166V, E828K, K861R, and P1023T variants exhibited significantly higher enzyme activity than wild-type DPD (120%, P = 0.025; 116%, P = 0.049; 130%, P = 0.0077; 138%, P = 0.048, respectively). Consistent with clinical association studies of 5-FU toxicity, the D949V substitution reduced enzyme activity by 41% (P = 0.0031). Enzyme activity was also significantly reduced for 30 additional variants, 19 of which had < 25% activity. None of those 30 variants have been previously reported to associate with 5-FU toxicity in clinical association studies, which have been conducted primarily in populations of European ancestry. Using publicly available genotype databases, we confirmed the rarity of these variants in European populations but showed that they are detected at appreciable frequencies in other populations. These data strongly suggest that testing for the reported deficient DPYD variations could dramatically improve predictive genetic tests for 5-FU sensitivity, especially in individuals of non-European descent.
Life Sciences & Biomedicine Oncology Science & Technology

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