title: [A clinical and laboratory study of chronic myeloid leukemia with atypical BCR-ABL fusion gene subtypes].
abstract: OBJECTIVE
  To explore the clinical and laboratory features of chronic myeloid leukemia (CML) with atypical e14a3 and e19a2 BCR-ABL fusion gene subtypes.
  
  
  METHODS
  We retrospectively analyzed a cohort of CML patients with Ph chromosome positive confirmed by cytogenetic and FISH but classical e13a3(b2a2), e14a2(b3a2)and e1a2 fusion transcripts negative identified by conventional real-time quantification RT-PCR (RQ-PCR). Further RQ-PCR was done with the forward primer and reverse primer designed to detect rare atypical BCR-ABL fusion genes including e14a3 and e19a2 transcripts. Direct sequencing analysis was performed on the PCR products and mutations in the BCR-ABL kinase domain were detected. The clinical data of patients were retrospectively analyzed.
  
  
  RESULTS
  Six CML patients were found to carry t(9;22) abnormality and BCR-ABL rearrangement confirmed by FISH but classical BCR-ABL fusion genes negative detected by RQ-PCR. Further RQ-PCR and sequencing analysis confirmed the fusion of BCR exon 14 and ABL exon 3 in five CML patients (case 1-5) and the fusion of BCR exon 19 and ABL exon 2 in one CML patient (case 6). E255K and I293T IM-resistant mutations were detected in case 1 and 2, respectively. Among five cases with e14a3 transcripts, four were CML-CP, one CML-AP. Four patients were male and one was female. The median age was 48 years. The patient (case 6) with e19a2 transcripts was 40-year-old female with a diagnosis of CML-CP and PLT count was more than 1 000×10⁹/L. Imatinib (IM) therapy was administer in case 1, 2, 3, 4 and hematopoietic stem cell transplantation (HSCT) was undergone in case 5 after hydroxyurea (Hu) or interferon failure. Case 1 who had E255K IM resistant mutation, responded poorly to IM but obtained a complete cytogenetic remission (CCyR) after a substitution of dasatinib for IM. Case 2 and 3 achieved CCyR 6 months later after IM treatment and had been maintained well with IM despite I293T mutation in case 2. Case 4 attained CCyR 3 months later after IM treatment but relapsed and died soon. Case 5 was still in CCyR after HSCT. Case 6 with e19a2 transcripts got complete hematologic response after Hu treatment and CCyR was achieved soon after IM therapy.
  
  
  CONCLUSIONS
  Incidence of CML with atypical transcripts is extremely low. They could benefit from tyrosine kinase inhibitors or HSCT. Rare and atypical BCR- ABL fusion gene subtypes could be missed by conventional RQ-PCR.
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Gui
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Jinlan
authors.initials: J
authors.lastname: Pan
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Huiying
authors.initials: H
authors.lastname: Qiu
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Jiannong
authors.initials: J
authors.lastname: Cen
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Yongquan
authors.initials: Y
authors.lastname: Xue
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Suning
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Shen
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yao
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Yafang
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Hematology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000328:Adult; D005260:Female; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000145:classification / Q000175:diagnosis / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
chemical_list: D016044:Fusion Proteins, bcr-abl