The cleavage product deltaPML-RARalpha contributes to all-trans retinoic acid-mediated differentiation in acute promyelocytic leukemia cells.
PML-RARalpha protein, the leukemogenic product of t(15,17) in acute promyelocytic leukemia, is cleaved into a truncated form termed deltaPML-RARalpha during all-trans retinoic acid (ATRA)-induced differentiation of NB4 cells. DeltaPML-RARalpha is not formed in ATRA differentiation resistant NB4 subclones. As(2)O(3) inhibits deltaPML-RARalpha formation and differentiation-induction when given in combination with ATRA. Treatment with hexamethylene bisacetamide (HMBA) combined with ATRA enhances ATRA-induced differentiation in ATRA-insensitive NB4-CI and arsenic-resistant NB4/As cells, and is associated with stabilization of PML-RARalpha protein and increased deltaPML-RARalpha formation. Unlike forced expression of PML-RARalpha, forced deltaPML-RARalpha expression based on an estimated deletion of the N-terminal PML portion does not repress RARE-tk-luc reporter activity mediated by endogenous retinoic acid receptors. The cleavage of PML-RARalpha is blocked by RARalpha antagonist Ro-41-5253 and cycloheximide and therefore requires a RARalpha transactivation-dependent pathway. Proteasome inhibitor MG-132 and caspase inhibitor Z-VAD-FMK do not block ATRA-induced PML-RARalpha cleavage and differentiation. These data suggest that (a) ATRA treatment induces PML-RARalpha cleavage by induction of unknown enzymes independent of proteasome- and caspase-mediated pathways; (b) deltaPML-RARalpha might function differently from both PML-RARalpha and RARalpha; (c) failure to cleave PML-RARalpha and form deltaPML-RARalpha after ATRA treatment may contribute to ATRA resistance in APL cells.
Jing
Yongkui
Y
Division of Hematology/Oncology, Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA. yongkui.jing@mssm.edu
Xia
Lijuan
L
Lu
Min
M
Waxman
Samuel
S
D000081:Acetamides / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D001151:Arsenic / Q000494:pharmacology; D015153:Blotting, Western; D002454:Cell Differentiation; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015533:Transcriptional Activation; D014162:Transfection; D014212:Tretinoin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000081:Acetamides; D000970:Antineoplastic Agents; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D015514:Oncogene Proteins, Fusion; D011500:Protein Synthesis Inhibitors; C093476:promyelocytic leukemia-retinoic acid receptor alpha fusion oncoprotein; D014212:Tretinoin; D003513:Cycloheximide; D008156:Luciferases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C014026:hexamethylene bisacetamide; D001151:Arsenic; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde