Analysis of isodicentric Ph chromosomes in chronic myeloid leukemia blast crisis

Objective To explore the genetic and clinical characteristics of isodicentric Ph chromosomes [idic(Ph)] in lymphoid blast crisis of chronic myeloid leukemia (CML-BLC). Methods Bone marrow aspirates of 2 patients with CML-BLC were analyzed by R banding after 24 hours of culturing. Genomic copy number variations (CNV) were analyzed by single nucleotide polymorphism array (SNP array) in case 1. The results were confirmed with fluorescence in situ hybridization (FISH). Variations of acute lymphoblastic leukemia-related genes including CDKN2A/AB and PAX5 were detected by multiplex ligation-dependent probe amplication (MLPA). Results Deletions and duplications on derivative chromosome 9 detected by FISH were confirmed by SNP array analysis. The distances between the BCR/ABL fusion signals on the idic(Ph) chromosomes in the two patients have differed greatly. The idic(Ph) in the second patient was supposed to be formed by two Ph chromosomes joined at their q terminals, where as the idic(Ph) in the first patient have been shown to be fused at the satellite regions of their p arms. Conclusion The idic(Ph) chromosomes presented in CML-BLC may predict resistance to Imatinib and response to Dasatinib. Key words: Isodicentric Ph chromosomes; Lymphoid blast crisis of chronic myeloid leukemia; Single nucleotide polymorphism array; Multiplex ligation-dependent probe amplification; Florescence in situ hybridization