title: Clonal evolution as the limiting factor in the detection of minimal residual disease by polymerase chain reaction in children in Brazil with acute lymphoid leukemia.
abstract: BACKGROUND
  The purpose of this investigation was to analyze the incidence of clonal evolution in children in Brazil children with acute lymphoblastic leukemia and its interference with the detection of minimal residual disease by polymerase chain reaction using clone-specific primers.
  
  
  METHODS
  The authors analyzed DNA samples from 12 children with acute lymphoblastic leukemia at diagnosis and after relapse using polymerase chain reaction and automatic sequencing to determine the presence of T-cell receptor gamma (TCRgamma) gene rearrangements. A clone-specific primer was synthesized based on the sequence obtained at diagnosis for each patient and at relapse for those with clonal evolution for the study of minimal residual disease.
  
  
  RESULTS
  A change of the original clone was detected in 3 of 12 patients (25%), involving the same rearrangement detected at diagnosis, suggesting the development of subclones. Minimal residual disease was detected at the end of treatment or before the relapse in all patients who had maintained the same rearrangements detected at diagnosis. Minimal residual disease was investigated at the end of treatment in two of the three patients with clonal evolution and was not detected with the use of clone-specific primers.
  
  
  CONCLUSIONS
  These data suggest that clonal evolution for TCRgamma gene rearrangements was not a rare event among children in Brazil and, when present, interfered with the detection of minimal residual disease.
authors.affiliation: Department of Pediatrics and Puericulture, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Scrideli
authors.forename: Simone
authors.initials: S
authors.lastname: Kashima
authors.forename: Rosana
authors.initials: R
authors.lastname: Cipolloti
authors.forename: Ricardo
authors.initials: R
authors.lastname: Defavery
authors.forename: Luiz G
authors.initials: LG
authors.lastname: Tone
mesh_terms: D000208:Acute Disease; D001938:Brazil; D002648:Child; D002675:Child, Preschool; D017931:DNA Primers / Q000737:chemistry; D004273:DNA, Neoplasm / Q000032:analysis*; D005260:Female; D015334:Gene Rearrangement, gamma-Chain T-Cell Antigen Receptor / Q000235:genetics*; D019675:Genes, T-Cell Receptor gamma / Q000235:genetics; D006801:Humans; D016130:Immunophenotyping; D007223:Infant; D007945:Leukemia, Lymphoid / Q000175:diagnosis* / Q000235:genetics*; D018365:Neoplasm, Residual; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D004273:DNA, Neoplasm