Ph-Negative Chronic Myeloid Leukemia: Molecular Analysis of ABL Insertion Into M-BCR on Chromosome

Leukemic cells f rom a patient with Ph-negative chronic myeloid leukemia (CML) had a normal karyotype. M-BCR was rearranged and chromosome in si tu hybridization showed a n ABL insertion be tween 5’ and 3’ M-BCR on a n apparently normal chromosome 22. T h e association of 5’ BCR and 3’ ABL at t h e 5’ junction of t h e chromosome 9 insert was typical of t h a t found for t h e BCR-ABL fusion g e n e in o the r patients with t h e standard t(9;22) and CML. With a n M-bcr-3’ probe, we cloned and characterized a 3’ junction fragment. Field inversion gel electrophoresis and chromosome in si tu hybridization studies using a probe isolated from genomic DNA 5’ of t h e junction showed tha t