[Major molecular response to imatinib in a patient with acute mixed lineage leukemia expressing a novel BCR/ABL transcript].

OBJECTIVE: To identify the novel BCR/ABL transcript in a patient with acute mixed lineage leukemia (AMLL), and to evaluate the imatinib treatment response by quantitatively monitoring the aberrant BCR/ABL. METHODS: Specimens of peripheral blood and bone marrow were obtained. By using several detect protocols, we found a novel BCR/ABL transcript in a patient with Ph-positive AMLL. The patient was treated with Imatinib and the aberrant BCR/ABL was quantitatively monitored to evaluate the clinical response. RESULTS: On admission, cytogenetic analysis showed Philadelphia-chromosome (Ph) positive in the specimens, but BCR/ABL e1a2, b2a2, and b3a2 were negative. Morphological analysis of the bone marrow showed the myeloid blast cells accounted for 66%, and immunophenotyping analysis showed 2 groups of aberrant blast cells: myeloid and B lineage. Chemical therapy and bone marrow transplantation failed to control the disease, and a novel BCR/ABL transcript (GenBank: EF423615) was found by using several detection protocols. The novel fusion protein showed a deletion of 10 amino acids and H893Q compared with the common BCR/ABL b2a2 fusion protein. The patient was then treated with imatinib and hematological remission was soon achieved, and 5 months after the imatinib treatment the quantity of the aberrant BCR/ABL was gradually decreased to negative. During the treatment the patient had discontinued the drug once and just then the aberrant BCR/ABL became positive soon. Imatinib was administered again and molecular remission was soon achieved for the second time. By continued therapy with imatinib, the patient got sustained and complete molecular remission lasting 12 months so far. CONCLUSION: The aberrant BCR/ABL may contribute to the clinical features of AMLL and the AMLL patients that have aberrant BCR/ABL may be sensitive to Imatinib.