13 Genes Associated with Apoptosis Resistance in CLL

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Blood First Edition Paper

prepublished online February 13, 2003

Submitted June 27, 2002

Accepted January 28, 2003

The resistance of B-CLL cells to DNA damage-induced apoptosis defined

by DNA microarrays

t Vallat, Henri Magdelenat, Helene Merle-Beral, Peggy

Masdehors, le Potocki de Montalk, Frederic Davi, Mogens

Kruhoffer, Laure Sabatier, F Orntoft, and Jozo Delic*

Laboratoire de Radiobiologie et Oncologie, CEA, DSV/DRR, Fontenay aux

Roses, France; Hematology/Biology, Hospital Pitie-Salpetriere, Paris,

France

Laboratoire de Physiopathology, Institute Curie, Paris, France

Hematology/Biology, Hospital Pitie-Salpetriere, Paris, France

Laboratoire de Radiobiologie et Oncologie, CEA, DSV/DRR, Fontenay aux

Roses, France

Clinical Biochemistry, Universitethospital, Aarhus, Denmark

* Corresponding author; email: delic@....

B-cell chronic lymphoid leukemia (B-CLL) is a highly heterogeneous

human malignancy, presumably reflecting specific molecular

alterations in gene expression and protein activity which are thought

to underlie the variable disease outcome. The majority of B-CLL cell

samples undergo apoptotic death in response to DNA damage. However, a

clinically distinct aggressive subset of B-CLL is completely

resistant to in vitro activation of the apoptotic death pathway. We

therefore compared gene expression patterns in resistant and

sensitive B-CLL cell subsets. DNA microarray analysis was performed

for four sensitive and three resistant B-CLL cell samples, before and

after apoptotic stimuli, and the specific expression patterns of the

selected genes were confirmed by quantitative real-time PCR.

We selected 16 genes whose expression varied at least two-fold

specifically in resistant cells. Furthermore, we confirmed the

expression of these selected genes by real-time PCR on 15 additional

B-CLL cell samples not included in the microarray analysis.

In this manner, 13 genes were found to be specific for all resistant

B-CLL cell samples tested: nuclear orphan receptor TR3, MHC class II

glycoprotein HLA-DQA1, mtmr6, c-myc, c-rel, c-IAP1, mat2A and fmod

were upregulated while MIP1/GOS19-1 homolog, stat1, blk, hsp27 and

ech1 were downregulated. In some cases, the expression profile was

dependent on the status of p53. Some of these genes encode general

apoptotic factors but also exhibit lymphoid cell specificities which

could potentially be linked to the development of lymphoid

malignancies (MIP1, blk, TR3, mtmr6).

Taken together, our data define new molecular markers specific to

resistant B-CLLs which might be of clinical relevance.