The oncogene DEK promotes leukemic cell survival and is downregulated by both Nutlin-3 and chlorambucil in B-chronic lymphocytic leukemic cells.
OBJECTIVE
To characterize the role of the oncogene DEK in modulating the response to either Nutlin-3, a small-molecule inhibitor of the MDM2/p53 interaction, or chlorambucil in primary B-chronic lymphocytic leukemia (B-CLL) cells.


METHODS
DEK mRNA and protein levels were evaluated in primary B-CLL samples (n = 21), p53(wild-type) SKW6.4, p53(mutated) BJAB lymphoblastoid cell lines, and normal CD19(+) B lymphocytes-treated Nutlin-3 or chlorambucil (10 micromol/L, each). Knocking down experiments with either p53 or DEK small interfering RNA (siRNA) were done to investigate the potential role of p53 in controlling the expression of DEK and the role of DEK in leukemic cell survival/apoptosis.


RESULTS
Both Nutlin-3 and chlorambucil downregulated DEK in primary B-CLL samples (n = 21) and SKW6.4 but not in BJAB cells. Knocking down p53 attenuated the effect of Nutlin-3 on DEK expression, whereas knocking down DEK significantly increased both spontaneous and Nutlin-3-induced apoptosis. Conversely, counteracting DEK downmodulation by using p53 small interfering RNA reduced Nutlin-3-mediated apoptosis. On the other hand, Nutlin-3 potently induced p53 accumulation, but it did not affect DEK levels in normal CD19(+) B lymphocytes.


CONCLUSIONS
These data show that the downregulation of DEK in response to either Nutlin-3 or chlorambucil represents an important molecular determinant in the cytotoxic response of leukemic cells, and suggest that strategies aimed to downregulate DEK might improve the therapeutic potential of these drugs.
Secchiero
Paola
P
Department of Morphology and Embryology, University of Ferrara, Ferrara, Italy.
Voltan
Rebecca
R
di Iasio
Maria Grazia
MG
Melloni
Elisabetta
E
Tiribelli
Mario
M
Zauli
Giorgio
G
D000368:Aged; D000369:Aged, 80 and over; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D017209:Apoptosis; D001402:B-Lymphocytes / Q000378:metabolism / Q000473:pathology*; D015153:Blotting, Western; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002699:Chlorambucil / Q000494:pharmacology*; D002868:Chromosomal Proteins, Non-Histone / Q000502:physiology*; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D015513:Oncogene Proteins / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology*; D000075223:Poly-ADP-Ribose Binding Proteins; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013237:Stereoisomerism; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
D018906:Antineoplastic Agents, Alkylating; D002868:Chromosomal Proteins, Non-Histone; C084738:DEK protein, human; D007093:Imidazoles; D015513:Oncogene Proteins; D010879:Piperazines; D000075223:Poly-ADP-Ribose Binding Proteins; D012333:RNA, Messenger; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D002699:Chlorambucil; C482205:nutlin 3