Gene Expression in CLL Cells Associated with Lymphadenopathy and Chromosome 11q23 Deletion.

Abstract

Previously we have demonstrated that peripheral blood samples with B-cell Chronic Lymphocytic Leukemia (CLL) have different gene expression profiles associated with chromosome aberrations detected by fluorescence in situ hybridization (FISH). In particular, the vast majority of differentially expressed genes were related to the presence of the 11q23 deletion. The 11q23 deletion has previously been shown to be correlated with shortened over-all survival and extensive/bulky lymphadenopathy. In this study we sought to identify genes whose expression may play role in the progression of CLL in patients that carry the 11q23 deletion. Gene expression from 10,700 human gene specific 50-mer oligos (MWG Biotech, Ebersberg, Germany) was compared between two groups of peripheral blood CLL samples. The first group consisted of CLL patients with the 11q23 deletion detected by FISH as well as with the presence of abdominal/mediastinal lymphadenopathy. The second group consisted of CLL patients without the 11q23 deletion and without the presence of known abdominal/mediastinal lymphadenopathy. The non-11q deletion group included CLL patients with the 13q14 deletion, trisomy 12, 17p13 deletion, as well as several without any detectable abnormality. Immunoglobulin heavy chain variable region (IgVH) mutational status was compared in CLL samples in both groups to ensure that resulting expression differences were not the result of this known prognostic marker. Median of ratios was compared between the two groups. Eighty-eight (87) genes had a p-value < 0.01. Gene function was classified at the European Molecular Biology Laboratory (EMBL) Bioinformatic Harvester website. Twenty of these differentially expressed genes were cell cycle/cell signaling related genes that were over-expressed in the 11q23 deletion group. Examples include: activating transcription factor 4, rho-associated coiled-coil containing protein kinase 2, fibroblast growth factor 21 precursor, signal transducing adaptor molecule 1, mad2-like 1, interferon receptor 1, pim-2 oncogene, and zw10 interactor. In comparison, using the same peripheral blood CLL samples, 78 genes were differentially expressed (p < 0.01) between those samples that had a mutated IgVH versus those that had an unmutated IgVH. Therefore, the presence of both the 11q23 deletion and bulky abdominal/mediastinal lymphadenopathy significantly alters the gene expression profile of peripheral blood CLL cells, particularly genes related to the cell cycle and cell signaling related processes. Biological roles of some of these genes may help further elucidate the basis of the clinical behavior of CLL patients