title: Expression levels of TEL, AML1, and the fusion products TEL-AML1 and AML1-TEL versus drug sensitivity and clinical outcome in t(12;21)-positive pediatric acute lymphoblastic leukemia.
abstract: OBJECTIVE
  t(12;21)(p13; q22), present in approximately 25% of pediatric precursor B-ALL, is highly sensitivity to L-asparaginase and the prognosis depends on the intensity of the treatment protocol. This study analyzes the relationship between the mRNA expression of the genes and fusion products involved in t(12;21), in vitro sensitivity to prednisolone, vincristine, and L-asparaginase, and long-term clinical outcome in t(12;21)+ acute lymphoblastic leukemia (ALL) patients.
  
  
  METHODS
  Long-term clinical outcome in 45 t(12;21)+ ALL patients was related to mRNA expression of TEL, AML1, TEL-AML1, and AML1-TEL, determined by real-time quantitative PCR, and the in vitro sensitivity to prednisolone, vincristine, and L-asparaginase, using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays.
  
  
  RESULTS
  A significant approximately 3.5-fold lower TEL expression in t(12;21)+ compared with t(12;21)- ALL samples (P = 0.006) and normal controls (P = 0.004) was found. Expression of AML1 did not differ between t(12;21)+ and t(12;21)- ALL. However, AML1 expression in the leukemic cells was 2-fold higher compared with normal controls (P = 0.02). The TEL-AML1 fusion product was expressed in all t(12;21)+ cases, whereas the reciprocal fusion product AML1-TEL was expressed in only 76%. High expression levels of TEL-AML1 [hazard ratio (HR), 1.3; 95% confidence interval (95% CI), 1.10-1.57; P = 0.003], AML1-TEL (HR, 4.9; 95% CI, 1.99-12.40; P = 0.001) and AML1 (HR, 1.1; 95% CI, 1.03-1.22; P = 0.006) were associated with a poor long-term clinical outcome within t(12;21)+ ALL. Cellular drug resistance towards prednisolone, vincristine, and L-asparaginase could not explain this predictive value. Multivariate analysis including age and WBC showed that only high AML1-TEL expression is an independent poor prognostic factor in t(12;21)+ childhood ALL.
  
  
  CONCLUSIONS
  High AML1-TEL expression is an independent poor prognostic factor in t(12;21)+ childhood ALL.
authors.affiliation: Division of Pediatric Oncology/Hematology, Erasmus MC, Sophia Children's Hospital, Rotterdam, Netherlands.
authors.forename: Wendy A G
authors.initials: WA
authors.lastname: Stams
authors.forename: Monique L
authors.initials: ML
authors.lastname: den Boer
authors.forename: H Berna
authors.initials: HB
authors.lastname: Beverloo
authors.forename: Jules P P
authors.initials: JP
authors.lastname: Meijerink
authors.forename: Elisabeth R
authors.initials: ER
authors.lastname: van Wering
authors.forename: Gritta E
authors.initials: GE
authors.lastname: Janka-Schaub
authors.forename: Rob
authors.initials: R
authors.lastname: Pieters
mesh_terms: D001215:Asparaginase / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002648:Child; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins / Q000235:genetics; D018572:Disease-Free Survival; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000473:pathology*; D011239:Prednisolone / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics; D014178:Translocation, Genetic; D016896:Treatment Outcome; D014750:Vincristine / Q000494:pharmacology; D000097764:ETS Translocation Variant 6 Protein
chemical_list: D001215:Asparaginase; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D011239:Prednisolone; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D014750:Vincristine; D000097764:ETS Translocation Variant 6 Protein; C493728:RUNX1 protein, human; C102421:TEL-AML1 fusion protein