Hyperdiploidy associated with T315I mutation in BCR-ABL kinase domain in an accelerated phase-chronic myeloid leukemia case.

Background: Chronic myeloid leukemia (CML) is genetically characterized by the occurrence of a reciprocal translocation t(9;22)(q34;q11), resulting in a BCR/ABL gene fusion on the derivative chromosome 22, i.e. the Philadelphia (Ph) chromosome. During CML progression 60-80% of the cases acquire additional genetic changes. Even though hyperdiploidy is not a rare finding in advanced phase-CML, hyperdiploidy together with a T315I kinase domain (KD) mutation in the BCR-ABL gene has not yet been reported.

Results: A complete cytogenetic and molecular cytogenetic analysis; molecular biology methods such as quantitative reverse transcription polymerase chain reaction (RQ-PCR) and allele-specific oligonucleotide (ASO)-PCR; and immunophenotypically confirmed CML in acceleration phase (AP). Our case revealed the presence of hyperdiploidy including multiple copies of the Ph chromosome, presence of b3a2 fusion transcript,T315I mutation in BCR-ABL KD in pre imatinib mesylate (IM) treatment. The ratio of BCR-ABL/ABL expression in post nilotinib treatment was 0.07% on international scale.

Conclusions: The patient demonstrated a good response to nilotinib after imatinib failure; while the hyperdiploid clone disappeared the T315I mutation remained during follow-up. The underlying mechanisms and prognostic implications of these cytogenetic abnormalities are discussed.