Targeting of PML/RARalpha is lethal to retinoic acid-resistant promyelocytic leukemia cells.
Acute promyelocytic leukemia (APL) cells, containing the t(15;17) rearrangement, express the fusion protein, PML/RARalpha. Clinically, patients respond to all-trans retinoic acid (ATRA) through complete remissions associated with myeloid maturation of leukemic cells. This clinical ATRA response of APL is linked to PML/RARalpha expression. Unfortunately, these remissions are transient and relapsed APL is often ATRA-resistant. The role PML/RARalpha plays in the growth and maturation of these APL cells with acquired ATRA resistance has not been fully explored. This study uses an ATRA-resistant NB4 cell line (NB4-R1) to investigate the contribution of PML/RARalpha expression to ATRA resistance. Targeting of PML/RARalpha in NB4-R1 cells was undertaken using two approaches: homologous recombination and hammerhead ribozyme-mediated cleavage. Reducing PML/RARalpha protein in NB4-R1 cells rendered these cells more sensitive to ATRA. These cells were growth-inhibited in ATRA, apoptosis was induced, and there was no apparent signaling of differentiation. Sequence analysis identified a mutation in the ligand binding domain (LBD) of the RARalpha portion of PML/RARalpha. Results show that these retinoid-resistant NB4 cells require persistent PML/RARalpha expression for leukemic cell growth. Taken together, these findings can account for why these cells do not respond to ATRA and how reduction of PML/RARalpha abrogates the antiapoptotic effect it confers to these leukemic cells.
Laboratory of Molecular Medicine, Department of Medicine and Molecular Pharmacology and Therapeutics Program, Memorial Sloan-Kettering Cancer Center, New York, NY, USA. k-nason-burchenal@ski.mskcc.org
K
K
Nason-Burchenal
J
J
Allopenna
A
A
Bègue
D
D
Stéhelin
E
E
Dmitrovsky
P
P
Martin
D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002884:Chromosomes, Human, Pair 15; D002886:Chromosomes, Human, Pair 17; D004252:DNA Mutational Analysis; D004351:Drug Resistance / Q000235:genetics; D015870:Gene Expression; D018390:Gene Targeting; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000188:drug therapy / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D000071156:Promyelocytic Leukemia Protein; D016337:RNA, Catalytic / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018168:Receptors, Retinoic Acid / Q000235:genetics*; D011994:Recombinant Proteins; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection; D014178:Translocation, Genetic; D014212:Tretinoin / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D000071156:Promyelocytic Leukemia Protein; D016337:RNA, Catalytic; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D011994:Recombinant Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D014212:Tretinoin