The Role of the BCR-ABL Fusion Gene in the Pathogenesis of Chronic Myeloid Leukemia: A Review of the Foundational Molecular and Clinical Evidence

Abstract

Introduction: Chronic Myeloid Leukemia (CML), a once fatal myeloproliferative neoplasm, became the archetype of successful molecularly targeted therapy in oncology. This transformation was entirely dependent on the identification of a single, causative genetic abnormality. This review synthesises the foundational literature published before 2010 that established the causal role of the BCR-ABL fusion gene in the pathogenesis of CML and chronicled the development of therapy directed against it.

Literature Review: The scientific narrative began with the discovery of a consistent cytogenetic marker, the Philadelphia chromosome, which was later identified as a reciprocal translocation between chromosomes 9 and 22. Research in the 1980s pinpointed the molecular consequence: the creation of the BCR-ABL fusion gene. This oncogene was proven to encode a constitutively active tyrosine kinase protein, which drives the uncontrolled proliferation and anti-apoptotic signaling that define CML. This precise molecular understanding spurred the rational design of Imatinib mesylate, a specific BCR-ABL kinase inhibitor. Landmark clinical trials in the early 2000s demonstrated that Imatinib produced unprecedented rates of complete and durable remissions, transforming the disease's natural history.

Conclusion: The pre-2010 literature provides a complete and triumphant arc from a descriptive cytogenetic discovery to a life-saving molecular therapy. It confirms that the BCR-ABL oncogene is the necessary and sufficient driver of CML, and that its targeted inhibition represents one of the most successful applications of molecular medicine in history.