title: Factors affecting cytochrome P-450 3A activity in cancer patients.
abstract: OBJECTIVE
  The purpose is to identify the demographic, physiologic, and inheritable factors that influence CYP3A activity in cancer patients.
  
  
  METHODS
  A total of 134 patients (62 females; age range, 26 to 83 years) underwent the erythromycin breath test as a phenotyping probe of CYP3A. Genomic DNA was screened for six variants of suspected functional relevance in CYP3A4 (CYP3A4*1B, CYP3A4*6, CYP3A4*17, and CYP3A4*18) and CYP3A5 (CYP3A5*3C and CYP3A5*6).
  
  
  RESULTS
  CYP3A activity (AUC(0-40 min)) varied up to 14-fold in this population. No variants in the CYP3A4 and CYP3A5 genes were a significant predictor of CYP3A activity (P > 0.2954). CYP3A activity was reduced by approximately 50% in patients with concurrent elevations in liver transaminases and alkaline phosphatase or elevated total bilirubin (P < 0.001). In a multivariate analysis, CYP3A activity was not significantly influenced by age, sex, and body size measures (P > 0.05), but liver function combined with the concentration of the acute-phase reactant, alpha-1 acid glycoprotein, explained approximately 18% of overall variation in CYP3A activity (P < 0.001).
  
  
  CONCLUSIONS
  These data suggest that baseline demographic, physiologic, and chosen genetic polymorphisms have a minor impact on phenotypic CYP3A activity in patients with cancer. Consideration of additional factors, including the inflammation marker C-reactive protein, as well as concomitant use of other drugs, food constituents, and complementary and alternative medicine with inhibitory and inducible effects on CYP3A, is needed to reduce variation in CYP3A and treatment outcome to anticancer therapy.
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231-1000, USA. sdbaker@jhmi.edu
authors.forename: Sharyn D
authors.initials: SD
authors.lastname: Baker
authors.forename: Ron H N
authors.initials: RH
authors.lastname: van Schaik
authors.forename: Laurent P
authors.initials: LP
authors.lastname: Rivory
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Ten Tije
authors.forename: Kimberly
authors.initials: K
authors.lastname: Dinh
authors.forename: Wilfried J
authors.initials: WJ
authors.lastname: Graveland
authors.forename: Paul W
authors.initials: PW
authors.lastname: Schenk
authors.forename: Kellie A
authors.initials: KA
authors.lastname: Charles
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Clarke
authors.forename: Michael A
authors.initials: MA
authors.lastname: Carducci
authors.forename: William P
authors.initials: WP
authors.lastname: McGuire
authors.forename: Fitzroy
authors.initials: F
authors.lastname: Dawkins
authors.forename: Hans
authors.initials: H
authors.lastname: Gelderblom
authors.forename: Jaap
authors.initials: J
authors.lastname: Verweij
authors.forename: Alex
authors.initials: A
authors.lastname: Sparreboom
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D049628:Body Size; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000235:genetics; D003710:Demography; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008111:Liver Function Tests; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D009961:Orosomucoid / Q000378:metabolism; D010641:Phenotype
chemical_list: D004273:DNA, Neoplasm; D007527:Isoenzymes; D009961:Orosomucoid; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human