title: All-trans retinoic acid pharmacokinetics and bioavailability in acute promyelocytic leukemia: intracellular concentrations and biologic response relationship.
abstract: OBJECTIVE
  This study investigated the in vitro pharmacologic behavior and disposition kinetics of all-trans retinoic acid (ATRA) in acute myeloid leukemic (AML) cells, their sensitivity to its differentiating effect, and the in vivo response of acute promyelocytic leukemia (APL) patients after therapy.
  
  
  METHODS
  Fresh leukemic cells from 14 AML patients (nine APL and five non-APL), were incubated in suspension culture in the absence or presence of 10(-6) mol/L ATRA. Intracellular ATRA concentration and ATRA metabolism was determined by high-performance liquid chromatography (HPLC).
  
  
  RESULTS
  Immediate uptake is observed with maximal intracellular levels (Cmax) achieved after 24 hours of incubation. At this time, ATRA levels were variable, ranging from 20 to 230 pmol/10(6) cells (median, 100 pmol/10(6) cells). Comparison of ATRA intracellular levels with the in vitro response of patients' cell samples as measured by the percentage of nitro blue tetrazolium (NBT)-positive cells after a 3-day incubation period allowed us to discriminate a group of APL patients (n = 6) with high Cmax (group A; median, 200 pmol/10(6) cells) and maximal differentiation at day 3 (median, 80%), and a group of patients (n = 8, three APL and five non-APL) with low Cmax (group B; median, 35 pmol/10(6) cells) and poor in vitro response (median, 40%; APL cases only). Interestingly, all APL patients, except one included in group A (rapid in vitro ATRA uptakers), achieved a complete remission.
  
  
  CONCLUSIONS
  These findings suggest that intracellular ATRA concentrations are determinant for ATRA response and should be taken into account when monitoring the efficacy of ATRA differentiation therapeutic trials in malignant disorders.
authors.affiliation: Laboratoire de Biologie Cellulaire Hématopoïétique, Hôpital Saint-Louis, Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Agadir
authors.forename: M
authors.initials: M
authors.lastname: Cornic
authors.forename: P
authors.initials: P
authors.lastname: Lefebvre
authors.forename: B
authors.initials: B
authors.lastname: Gourmel
authors.forename: M
authors.initials: M
authors.lastname: Jérôme
authors.forename: L
authors.initials: L
authors.lastname: Degos
authors.forename: P
authors.initials: P
authors.lastname: Fenaux
authors.forename: C
authors.initials: C
authors.lastname: Chomienne
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D004354:Drug Screening Assays, Antitumor; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D066298:In Vitro Techniques; D015473:Leukemia, Promyelocytic, Acute / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012074:Remission Induction; D016896:Treatment Outcome; D014212:Tretinoin / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D014212:Tretinoin