Clinical Significance of BCR-ABL Fusion Gene Subtypes in Chronic Myelogenous and Acute Lymphoblastic Leukemias

Background: Some reports have suggested that chronic myeloid leukemia (CML) patients have a higherprevalence of M-bcr than acute lymphoblastic leukemia (ALL) patients, which show a higher prevalence ofm-bcr. However, the relationship between BCR-ABL subtypes and progression of CML and ALL remains unclear.Materials and
Methods: 354 CML chronic phase (CML-CP) patients, 26 CML blastic phase (CML-BP) patientsand 72 ALL patients before treatment with BCR-ABL positive were recruited for blood routine examinationand bone marrow smear cytology. Some 80 CML-CP and 32 ALL patients after imatinib (IM) treatment werefollowed-up for BCR-ABL relative concentrations detected after treatment for 3, 6 and 9 months and 1 year.
Results: Before treatment, CML-CP patients showed lower BCR-ABL relative concentrations with a higherproportion of M-bcr (42.7%) compared to CML-BP and ALL patients while ALL patients had a higher BCR-ABLrelative concentration with high expression of m-bcr (51.4%). Patients with M-bcr demonstrated higher WBCcounts than those with m-bcr and the mixed group and higher PLT counts were noted in the CML-CP and ALLgroups. After imatinib (IM) treatment, patients with m-bcr showed higher BCR-ABL relative concentrations inboth CML-CP and ALL groups.
Conclusions: This study identified the BCR-ABL gene as an important factor inCML and ALL cases. The M-bcr subtype was associated more with CML while the m-bcr subtype was associatedmore with ALL. Patients with m-bcr seem to have a poorer response to IM in either CML or ALL patientscompared to M-bcr patients.