title: Dynamics of BCR-ABL mutated clones prior to hematologic or cytogenetic resistance to imatinib.
abstract: background: Mutations of the BCR-ABL tyrosine kinase domain constitute a major cause of resistance to tyrosine kinase inhibitors in patients with chronic myeloid leukemia. We sought to improve the diagnostic armamentarium by screening and to analyze the dynamics of mutated clones in chronic myeloid leukemia patients who experienced hematologic or cytogenetic relapse.
  
  
  METHODS
  Ninety-five patients who relapsed during imatinib therapy were screened for BCR-ABL kinase domain mutations using sensitive denaturing high-performance liquid chromatography (D-HPLC) and direct sequencing. To investigate the dynamics of mutated clones D-HPLC was applied to 453 cDNA samples tracking back from relapse towards the start of imatinib therapy.
  
  
  RESULTS
  Twenty-two different point mutations affecting 18 amino acids were detectable in 46/79 (58%) and in 7/16 patients (44%) with hematologic or cytogenetic relapse, respectively. A deletion of 81 nucleotides (del248-274) of ABL exon 4 was observed in two patients. Three patients had exclusively single nucleotide polymorphisms (K247R, T315T, E499E, n=1 each) within the BCR-ABL kinase domain. In patients harboring mutations, hematologic relapse occurred after a median of 12.9 months (range, 0.9-44.2), and BCR-ABL mutations first became detectable at a median of 5.8 months (range, 0-30.5) after starting imatinib therapy (p<0.0001). Nine patients showed evidence of BCR-ABL mutations prior to imatinib therapy (T315I, n=4; M351T, n=3; M244V and Y253H, n=1 each).
  
  
  CONCLUSIONS
  We conclude that: (i) D-HPLC is a sensitive method for screening for BCR-ABL mutations before and during therapy with tyrosine kinase inhibitors; (ii) the occurrence of BCR-ABL mutations during imatinib therapy is predictive of relapse; (iii) mutations may be detectable several months before relapse, and (iv) the sensitive detection of small numbers of mutated clones could provide clinical benefit by triggering early therapeutic interventions.
authors.affiliation: III. Medizinische Klinik, Medizinische, Fakultät Mannheim der Universität Heidelberg, Mannheim, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ernst
authors.forename: Philipp
authors.initials: P
authors.lastname: Erben
authors.forename: Martin C
authors.initials: MC
authors.lastname: Müller
authors.forename: Peter
authors.initials: P
authors.lastname: Paschka
authors.forename: Thomas
authors.initials: T
authors.lastname: Schenk
authors.forename: Jana
authors.initials: J
authors.lastname: Hoffmann
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kreil
authors.forename: Paul
authors.initials: P
authors.lastname: La Rosée
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Hehlmann
authors.forename: Andreas
authors.initials: A
authors.lastname: Hochhaus
mesh_terms: D000328:Adult; D000368:Aged; D019943:Amino Acid Substitution; D001549:Benzamides; D002851:Chromatography, High Pressure Liquid; D002986:Clinical Trials as Topic; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D005260:Female; D016044:Fusion Proteins, bcr-abl; D016313:Genes, abl / Q000235:genetics*; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000008:administration & dosage*; D017354:Point Mutation; D011237:Predictive Value of Tests; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage*; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D011743:Pyrimidines / Q000008:administration & dosage*; D012008:Recurrence; D012189:Retrospective Studies
chemical_list: D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl