Bcr-Abl

BCR-ABL1 is a Philadelphia chromosome-derived fusion oncogene that encodes a constitutively active tyrosine kinase and drives chronic myeloid leukemia (CML) pathophysiology^[1]. Mechanistically, BCR-ABL1 coordinates malignant signaling with pathways linked to proliferation, apoptosis resistance, hematopoietic stem cell alteration, and leukemia stem cell persistence^[2][3]. In disease models and clinical monitoring, CML is defined by BCR-ABL1 transcripts, most commonly e13a2 and e14a2, which encode p210 BCR-ABL1^[4]. Compared with these common isoforms, rare transcripts such as e1a2, e19a2, e6a2, e8a2, e13a3, and e14a3 show structural divergence that can alter leukemogenic activity, diagnostic detection, and tyrosine kinase inhibitor response^[5][6]. Transcript subtype also has practical research value, because e14a2 showed faster or deeper molecular responses than e13a2 in imatinib- or nilotinib-treated cohorts, while survival did not differ between transcripts^[4]. For experimental applications, imatinib targets ABL kinase activity, whereas nilotinib and dasatinib show stronger BCR-ABL inhibition and retain activity against multiple imatinib-resistant mutants^[1].