Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the uncontrolled proliferation of myeloid cells in the bone marrow and peripheral blood. It is defined by the BCR::ABL1 fusion gene resulting from a translocation of chromosomes 9 and 22 or t(9;22). This translocation results in an elongated chromosome 9 and a truncated chromosome 22, called the Philadelphia (Ph) chromosome, which is present in about 95% of CML cases. The oncogenic BCR::ABL1 fusion gene is located on the Ph chromosome.
The BCR::ABL1 gene produces a mutated tyrosine kinase. Tyrosine kinases are enzymes that play a crucial role in the regulation of various cellular processes, including cell growth, differentiation, metabolism, and apoptosis (programmed cell death). In CML, these mutated tyrosine kinases promote uncontrolled cell proliferation of myeloid cells.
