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 higher prevalence of M-bcr than acute lymphoblastic leukemia (ALL) patients, which show a higher prevalence of m-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) patients and 72 ALL patients before treatment with BCR-ABL positive were recruited for blood routine examination and bone marrow smear cytology. Some 80 CML-CP and 32 ALL patients after imatinib (IM) treatment were followed-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 higher proportion of M-bcr (42.7%) compared to CML-BP and ALL patients while ALL patients had a higher BCR-ABL relative concentration with high expression of m-bcr (51.4%). Patients with M-bcr demonstrated higher WBC counts than those with m-bcr and the mixed group and higher PLT counts were noted in the CML-CP and ALL groups. After imatinib (IM) treatment, patients with m-bcr showed higher BCR-ABL relative concentrations in both CML-CP and ALL groups.

CONCLUSIONS: This study identified the BCR-ABL gene as an important factor in CML and ALL cases. The M-bcr subtype was associated more with CML while the m-bcr subtype was associated more with ALL. Patients with m-bcr seem to have a poorer response to IM in either CML or ALL patients compared to M-bcr patients.