Centrosome Aberrations in Chronic Myeloid Leukemia (CML) Are Correlated with Disease Progression and Chromosome Instability.

Purpose: Numerical and structural centrosome abnormalities are hallmarks of a variety of cancers and have been implicated in chromosome missegregation, chromosomal instability, and aneuploidy. These phenomena already occur in preneoplastic lesions like oral leukoplakia, early cervical neoplasias, and small benign tumors of colon and breast. Moreover, deviations from normal karyotype seem to increase as tumors enlarge and become malignant. Genetic instability is a common feature in chronic myeloid leukemia (CML). We sought to establish a relationship between centrosome abnormalities and cytogenetic aberrations in CD34+ cells from CML patients at diagnosis (chronic phase - CP) and in blast crisis (BC).

Methods: Diagnosis of CML was established by hematologic, cytogenetic and molecular parameters. Treatment was performed according to the protocols of the German CML study group (www.kompetenznetz-leukaemie.de). CD34+ cells from ten umbilical cord blood specimens served as negative controls. Centrosome number and morphology were analyzed by immunofluorescence microscopy. In brief, CD34+ cells from ficollized peripheral blood samples were concentrated by magnetic cell sorting (MACS) and cytospun onto coated slides. After methanol fixation cells were incubated with antibodies directed to centrosomal proteins Pericentrin and gamma-Tubulin. Antibody-antigen complexes were stained by incubation with FITC- and Cy3-conjugated secondary antibodies.

Results: CML CP samples tested at initial diagnosis (n=20) already displayed numerical and structural centrosome aberrations (30.0% +/−2.3) as compared with corresponding normal control cells (n=10) (2.3% +/−1.1). In BC samples (n=10) an increase of centrosome aberrations was observed (58.0% +/−2.0).

Conclusion: The findings suggest that centrosome defects in CML occur early and are already present at primary diagnosis. Centrosome defects may contribute to disease progression by generation of further chromosome instability leading to accumulation of alleles carrying pro-oncogenic mutations and loss of alleles containing normal tumor suppressor genes and thus accelerating complex genomic changes associated with CML BC.