Protein expression analysis of chromosome 12 candidate genes in chronic lymphocytic leukemia (CLL)

Abstract

The pathogenic role of trisomy 12 in chronic lymphocytic leukemia (CLL) remains unresolved, but recently an upregulated RNA expression level has been observed for chromosome 12 candidate genes. In the current study, the protein expression of chromosome 12 candidate genes was characterized by comparing CLL cases with (n ¼ 58) or without (n ¼ 16) trisomy 12, CD19 þ -B-cells and cell lines (JVM-2, EHEB, JURKAT). Immunoblotting was performed to quantify the levels of AID, APAF-1, ARF3, CCND2, CDK2, CKD4, GLI, MDM-2, p27, Smac/ DIABLO and STAT6 (signal transducer and activator of transcription 6). The cell lines showed distinct expression patterns for CCND2, MDM-2, p27, Smac/DIABLO and STAT6, and displayed higher levels of CDK2 and CDK4 than the CLL cases. JURKAT and the CLL cases expressed uniformly high levels of p27, but low levels of CCND2. AID expression in the CLL cases was weak with slight variations regardless of the subgroup affiliation. The expression of the investigated proteins was independent of the trisomy 12 status as well as of the VH mutation status. The comparison of CD19 þ -B-cells with CLL revealed higher protein levels in CLL for CDK4, p27, Smac/ DIABLO and STAT6. Further studies including protein expression experiments in genetic high-risk subgroups of CLL have to elucidate whether these proteins qualify as candidates for targeted CLL therapies.

Identification of a gene on chromosome 12q22 uniquely overexpressed in chronic lymphocytic leukemia

“…It is unclear which genes play a role in the trisomy 12 phenotype; microarray 5 and QRT-PCR 28 studies have suggested a number of candidate genes; however, analysis of protein levels of some of these genes did not reveal any difference in protein expression levels between CLL patients with and without the trisomy 12 aberration. 29 The identification of CLLU1 again implicates chromosome 12 in CLL; however, CLLU1 up-regulation seems to occur independently of large chromosome 12 aberrations.…”

Frequent DAP kinase but not p14 or Apaf-1 hypermethylation in B-cell chronic lymphocytic leukemia

“…(Roman-Gomez et al 2004) As yet, there is no data on Apaf-1 methylation in CLL, and our study is the first report of the absence of Apaf-1 hypermethylation in CLL, consistent with the finding of Apaf-1 protein expression in CLL. (Winkler et al 2005) In summary, DAP kinase but not p14 or Apaf-1 is frequently targeted by methylation, suggesting an important role of DAP kinase dysregulation in the DAP kinase/p14/HDM2/p53/Apaf-1 apoptosis pathway. The clinical behavior of CLL in Orientals is similar to Caucasian CLL patients.…”

CD49d is overexpressed by trisomy 12 chronic lymphocytic leukemia cells: evidence for a methylation-dependent regulation mechanism

“…5,6 Despite the recent demonstration of a relative enrichment in NOTCH1 mutations in CLL carrying trisomy 12, [7][8][9] no specific genetic and/or biological features have so far been identified in trisomy 12 CLL to explain the peculiar clinical behavior of this CLL subset. 10,11 Patients and methods This study, approved by the Internal Review Boards of the Centro di Riferimento Oncologico of Aviano (Approval n. IRB-05-2010) and Salzburg Medical University (Approval n. 415-E/1287/4-2011), included peripheral blood samples from 1200 patients with typical CLL according to the current guidelines. 12 Informed consent was obtained from the participants in accordance with the Declaration of Helsinki.…”