Submitted February 22, 2006
Accepted June 26, 2006
Immunostimulatory oligonucleotide-induced metaphase cytogenetics detects chromosomal aberrations in 80% of CLL patients: A study of 132 CLL cases with correlation to FISH, IgVH status and CD38 expression
Frank Dicker*, Susanne Schnittger, Torsten Haferlach, Wolfgang Kern, and Claudia Schoch
MLL Munich Leukemia Diagnostics GmbH, Munich, Germany
* Corresponding author; email: frank.dicker{at}mll-online.com.
Compared to fluorescence in situ hybridization (FISH) conventional metaphase cytogenetics plays only a minor prognostic role in chronic lymphocytic leukemia (CLL) so far due to technical problems resulting from limited proliferation of CLL cells in vitro. Here we present a simple method for in vitro stimulation of CLL cells which overcomes this limitation. In our unselected patient population 125/132 cases could be successfully stimulated for metaphase generation by culture with the immunostimulatory CpG-oligonucleotide DSP30 plus interleukin 2. 101/125 cases showed chromosomal aberrations. The aberration rate is comparable to the rate detected by parallel interphase FISH. Conventional cytogenetics detected additional aberrations in 47 patients compared to FISH analysis. A complex aberrant karyotype, defined as 
3 aberrations, was detected in 30/125 patients compared to only one such case as defined by FISH. Conventional cytogenetics frequently detected balanced and unbalanced translocations. A significant correlation of the poor prognosis unmutated IgVH status with unbalanced translocations and of the likewise poor prognosis CD38 expression to balanced translocations and complex aberrant karyotype was found. We demonstrate that FISH analysis underestimates the complexity of chromosomal aberrations in CLL. Therefore, conventional cytogenetics may define subgroups of patients with high risk of progression.
