Nutlin-3 up-regulates the expression of Notch1 in both myeloid and lymphoid leukemic cells, as part of a negative feedback antiapoptotic mechanism.
The small molecule inhibitor of the MDM2/p53 interaction Nutlin-3 significantly up-regulated the steady-state mRNA and protein levels of Notch1 in TP53(wild-type) (OCI, SKW6.4) but not in TP53(deleted) (HL-60) or TP53(mutated) (BJAB) leukemic cell lines. A direct demonstration that NOTCH1 was a transcriptional target of p53 in leukemic cells was obtained in experiments carried out with siRNA for p53. Moreover, inhibition of Notch1 expression using Notch1-specific siRNA significantly increased cytotoxicity in TP53(wild-type) leukemic cells. Of note, Nutlin-3 up-regulated Notch1 expression also in primary TP53(wild-type) B-chronic lymphocytic leukemia (B-CLL) cells and the combined use of Nutlin-3 plus pharmacological gamma-secretase inhibitors of the Notch signaling showed a synergistic cytotoxicity in both TP53(wild-type) leukemic cell lines and primary B-CLL cells. A potential drawback of gamma-secretase inhibitors was their ability to enhance osteoclastic maturation of normal circulating preosteoclasts induced by RANKL + M-CSF. Notwithstanding, Nutlin-3 completely suppressed osteoclastogenesis irrespective of the presence of gamma-secretase inhibitors. Taken together, these data indicate that the p53-dependent up-regulation of Notch1 in response to Nutlin-3 represents an antiapoptotic feedback mechanism able to restrain the potential therapeutic efficacy of Nutlin-3 in hematologic malignancies. Therefore, therapeutic combinations of Nutlin-3 + gamma-secretase inhibitors might potentiate the cytotoxicity of Nutlin-3 in p53(wild-type) leukemic cells.
Secchiero
Paola
P
Department of Morphology and Embryology, University of Ferrara, Ferrara, Italy. paola.secchiero@unife.it
Melloni
Elisabetta
E
di Iasio
Maria Grazia
MG
Tiribelli
Mario
M
Rimondi
Erika
E
Corallini
Federica
F
Gattei
Valter
V
Zauli
Giorgio
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017209:Apoptosis; D015153:Blotting, Western; D002219:Carbamates / Q000494:pharmacology; D002454:Cell Differentiation; D004151:Dipeptides / Q000494:pharmacology; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D025461:Feedback, Physiological; D005260:Female; D018922:HL-60 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013237:Stereoisomerism; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D002219:Carbamates; D004151:Dipeptides; D007093:Imidazoles; C410009:L 685458; C497761:NOTCH1 protein, human; D010879:Piperazines; D012333:RNA, Messenger; D051881:Receptor, Notch1; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C482205:nutlin 3; D053829:Amyloid Precursor Protein Secretases