title: Dihydropyrimidine dehydrogenase activity in human peripheral blood mononuclear cells and liver: population characteristics, newly identified deficient patients, and clinical implication in 5-fluorouracil chemotherapy.
abstract: Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (FUra), one of the most widely used anticancer drugs. Previous studies from our laboratory demonstrated the clinical importance of DPD in cancer patients (G. D. Heggie, J-P. Sommadossi, D. S. Cross, W. J. Huster, and R. B. Diasio. Cancer Res., 47: 2203-2206, 1987; B. E. Harris, R. Song, S-j. Soong, and R. B. Diasio. Cancer Res., 50: 197-201, 1990), particularly in those with DPD deficiency who experience severe FUra toxicity (including death) following FUra treatment [R. B. Diasio, T. L. Beavers, and J. T. Carpenter. J. Clin. Invest., 81: 47-51, 1988; B. E. Harris, J. T. Carpenter, and R. B. Diasio. Cancer (Phila.), 68: 499-501, 1991]. We now suggest that measurement of DPD activity may be useful in routine screening of cancer patients prior to FUra treatment. In this paper, we describe the following serial studies: (a) we developed a sensitive, accurate, and precise DPD assay and a storage method to stabilize DPD activity, permitting large scale DPD screening in cancer patients; (b) we demonstrated a normal distribution (Gaussian distribution) of human DPD activity from peripheral blood mononuclear cells (PBM-DPD) in a population study. Baselines for PBM-DPD with fresh and frozen samples were 0.425 +/- 0.124 (SD) and 0.189 +/- 0.064 nmol/min/mg protein, respectively. The 95% and 99% distribution ranges for both fresh and frozen samples were also determined, providing criteria for detection of DPD-deficient patients; (c) we identified nine new patients with profound or partial DPD deficiency; (d) we determined a baseline for human liver DPD activity, which was shown to be 0.360 +/- 0.182 nmol/min/mg protein (frozen samples); (e) we did a preliminary evaluation of liver DPD from deficient patients. Low liver DPD activity in two deficient patients correlated with low PBM-DPD activity. Using a polyclonal antibody raised against human liver DPD in our laboratory (Z. Lu, R. Zhang, and R. B. Diasio. J. Biol. Chem., 267: 17102-17109, 1992), Western blot analysis demonstrated decreased DPD protein in the liver cytosol from DPD-deficient patients compared to normal subjects. These results may be useful in improving the effectiveness and/or lessening the toxicity of FUra chemotherapy.
authors.affiliation: Department of Pharmacology, University of Alabama at Birmingham 35294.
authors.forename: Z
authors.initials: Z
authors.lastname: Lu
authors.forename: R
authors.initials: R
authors.lastname: Zhang
authors.forename: R B
authors.initials: RB
authors.lastname: Diasio
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000201:enzymology; D003110:Colonic Neoplasms / Q000201:enzymology; D042943:Dihydrouracil Dehydrogenase (NADP); D005260:Female; D005472:Fluorouracil / Q000009:adverse effects / Q000627:therapeutic use; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D010088:Oxidoreductases / Q000032:analysis* / Q000097:blood / Q000172:deficiency; D012004:Rectal Neoplasms / Q000201:enzymology; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D010088:Oxidoreductases; D042943:Dihydrouracil Dehydrogenase (NADP); D005472:Fluorouracil