ABSTRACT
B-cell acute lymphoblastic leukemia (ALL; B-ALL) is the most common pediatric cancer, and high hyperdiploidy (HyperD) identifies the most common subtype of pediatric B-ALL. Despite HyperD being an initiating oncogenic event affiliated with childhood B-ALL, the mitotic and chromosomal defects associated with HyperD B-ALL (HyperD-ALL) remain poorly characterized. Here, we have used 54 primary pediatric B-ALL samples to characterize the cellular-molecular mechanisms underlying the mitotic/chromosome defects predicated to be early pathogenic contributors in HyperD-ALL. We report that HyperD-ALL blasts are low proliferative and show a delay in early mitosis at prometaphase, associated with chromosome-alignment defects at the metaphase plate leading to robust chromosome-segregation defects and nonmodal karyotypes. Mechanistically, biochemical, functional, and mass-spectrometry assays revealed that condensin complex is impaired in HyperD-ALL cells, leading to chromosome hypocondensation, loss of centromere stiffness, and mislocalization of the chromosome passenger complex proteins Aurora B kinase (AURKB) and Survivin in early mitosis. HyperD-ALL cells show chromatid cohesion defects and an impaired spindle assembly checkpoint (SAC), thus undergoing mitotic slippage due to defective AURKB and impaired SAC activity, downstream of condensin complex defects. Chromosome structure/condensation defects and hyperdiploidy were reproduced in healthy CD34+ stem/progenitor cells upon inhibition of AURKB and/or SAC. Collectively, hyperdiploid B-ALL is associated with a defective condensin complex, AURKB, and SAC.
Subject(s)
Adenosine Triphosphatases , Aurora Kinase B , Chromosome Aberrations , Chromosomes, Human , DNA-Binding Proteins , Metaphase/genetics , Multiprotein Complexes , Neoplasm Proteins , Ploidies , Precursor B-Cell Lymphoblastic Leukemia-Lymphoma , Adenosine Triphosphatases/genetics , Adenosine Triphosphatases/metabolism , Aurora Kinase B/genetics , Aurora Kinase B/metabolism , Chromosomes, Human/genetics , Chromosomes, Human/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Humans , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Neoplasm Proteins/genetics , Neoplasm Proteins/metabolism , Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/enzymology , Precursor B-Cell Lymphoblastic Leukemia-Lymphoma/geneticsABSTRACT
BACKGROUND: Phylloid hypomelanosis is a rare neurocutaneous syndrome characterized by a pattern of hypopigmentation consisting of leaflike or oblong macules reminiscent of floral ornaments. Associated extracutaneous anomalies include cerebral, ocular, and skeletal defects. Recently it has been suggested that this phenotype originates from mosaic partial or complete trisomy 13. We report clinical and cytogenetic data for 2 cases. OBSERVATIONS: A bizarre pattern of multiple leaflike macules was noted in 2 girls with mental deficiency. In patient 1, additional anomalies included syndactyly, clinodactyly, trichomegaly of the eyelashes, low frontal hairline, and several pale pink telangiectatic macules. In patient 2, epileptic seizures, dental malposition, oligodontia, preauricular fistulas, scoliosis, tethered cord, and syringomyelia were noted. A diagnosis of phylloid hypomelanosis was made in both patients. In both patients, blood lymphocytes showed a normal karyotype 46,XX; however, fibroblasts derived from lesional skin demonstrated tetrasomy of chromosome 13q21-qter in patient 1 and trisomy of 13q22-qter in patient 2. CONCLUSIONS: These 2 cases lend further support to the concept that phylloid hypomelanosis is a distinct clinicogenetic entity that should no longer be confused with pigmentary mosaicism of the Ito type. From a comparison of our cytogenetic findings with those documented in previous articles, we infer that phylloid hypomelanosis is most likely related to the 13q region.
