title: FLT3 mutation incidence and timing of origin in a population case series of pediatric leukemia.
abstract: BACKGROUND
  Mutations in FLT3 result in activated tyrosine kinase activity, cell growth stimulation, and a poor prognosis among various subtypes of leukemia. The causes and timing of the mutations are not currently known. We evaluated the prevalence and timing of origin of FLT3 mutations in a population series of childhood leukemia patients from Northern California.
  
  
  METHODS
  We screened and sequenced FLT3 mutations (point mutations and internal tandem duplications, ITDs) among 517 childhood leukemia patients, and assessed whether these mutations occurred before or after birth using sensitive "backtracking" methods.
  
  
  RESULTS
  We determined a mutation prevalence of 9 of 73 acute myeloid leukemias (AMLs, 12%) and 9 of 441 acute lymphocytic leukemias (ALLs, 2%). Among AMLs, FLT3 mutations were more common in older patients, and among ALLs, FLT3 mutations were more common in patients with high hyperdiploidy (3.7%) than those without this cytogenetic feature (1.4%). Five FLT3 ITDs, one deletion mutation, and 3 point mutations were assessed for their presence in neonatal Guthrie spots using sensitive real-time PCR techniques, and no patients were found to harbor FLT3 mutations at birth.
  
  
  CONCLUSIONS
  FLT3 mutations were not common in our population-based patient series in California, and patients who harbor FLT3 mutations most likely acquire them after they are born.
authors.affiliation: Department of Epidemiology and Biostatistics, UCSF, Helen Diller Cancer Research Building, San Francisco, CA 94158, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Chang
authors.forename: Michelle
authors.initials: M
authors.lastname: Kang
authors.forename: Anny
authors.initials: A
authors.lastname: Xiao
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Chang
authors.forename: James
authors.initials: J
authors.lastname: Feusner
authors.forename: Patricia
authors.initials: P
authors.lastname: Buffler
authors.forename: Joseph
authors.initials: J
authors.lastname: Wiemels
mesh_terms: D000293:Adolescent; D002140:California; D002648:Child; D002675:Child, Preschool; D003582:Cytogenetics; D004252:DNA Mutational Analysis; D004171:Diploidy; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D009154:Mutation; D016133:Polymerase Chain Reaction; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000378:metabolism*; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics*
chemical_list: C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3