New strategies to direct therapeutic targeting of PML to treat cancers (original) (raw)
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Blood, 2018
A hallmark of acute promyelocytic leukemia (APL) is altered nuclear architecture, with disruption of promyelocytic leukemia (PML) nuclear bodies (NBs) mediated by the PML-retinoic acid receptor α (RARα) oncoprotein. To address whether this phenomenon plays a role in disease pathogenesis, we generated a knock-in mouse model with NB disruption mediated by 2 point mutations (C62A/C65A) in the Pml RING domain. Although no leukemias developed in Pml mice, these transgenic mice also expressing RARα linked to a dimerization domain (p50-RARα model) exhibited a doubling in the rate of leukemia, with a reduced latency period. Additionally, we found that response to targeted therapy with all- retinoic acid in vivo was dependent on NB integrity. PML-RARα is recognized to be insufficient for development of APL, requiring acquisition of cooperating mutations. We therefore investigated whether NB disruption might be mutagenic. Compared with wild-type cells, primary Pml cells exhibited increased si...
Journal of Experimental Medicine, 2013
Acute promyelocytic leukemia (APL) is a hematological malignancy driven by a chimeric oncoprotein containing the C terminus of the retinoic acid receptor-a (RARa) fused to an N-terminal partner, most commonly promyelocytic leukemia protein (PML). Mechanistically, PML-RARa acts as a transcriptional repressor of RARa and non-RARa target genes and antagonizes the formation and function of PML nuclear bodies that regulate numerous signaling pathways. The empirical discoveries that PML-RARa–associated APL is sensitive to both all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO), and the subsequent understanding of the mechanisms of action of these drugs, have led to efforts to understand the contribution of molecular events to APL cell differentiation, leukemia-initiating cell (LIC) clearance, and disease eradication in vitro and in vivo. Critically, the mechanistic insights gleaned from these studies have resulted not only in a better understanding of APL itself, but also carry val...
The PML gene encodes a phosphoprotein associated with the nuclear matrix
Blood, 1995
The t(15;17)(q22;q12) translocation is the cytogenetic hallmark of acute promyelocytic leukemia (APL). The PML and retinoic acid receptor-& (RA&) transcription factor genes are involved at the translocation breakpoint. To elucidate the biologic function of PML, antipeptide antibody against PML protein was raised in rabbits. This antibody was able to detect a 90-kD PML protein and a 110-kD PML-RARa fusion protein by Western blotting and a nuclear speckled pattern in all cell lines by immunofluorescent staining. In K562 and NIH/3T3 cells transfected with a PML expression plasmid, we found PML to be associated with the nuclear matrix. Our results also showed that PML is a phosphoprotein. A weak signal was detected in a Western blot containing the immunoprecipitated PML protein using the phosphotyrosine-specific monoclonal antibody. Therefore, at least one of the sites B ECAUSE THE NONRANDOM chromosome translocation t(15; 17)(q22;q12) can be found in over 95% of patients with acute promyelocytic leukemia (APL),'.' one can infer that genes involved in this unique translocation event play a role in its pathogenesis. Studies from several laboratories have confirmed that the t(15; 17) translocation occurs within the zinc finger transcription factor gene, PML, and the retinoic acid receptor-a (RARa) gene."' Because an extremely high number of APL patients can be induced to complete clinical remission by all-trans retinoic acid (ATRA),'"' it is believed that disruption of the RARa gene by the translocation plays a role in the leukemogenesis. However, evidence indicates that, when the myeloid leukemia cell line HL-60 loses its RA inducibility, this inducibility can be completely restored by other forms of RAR or retinoic X receptor (RXR)," suggesting that the loss of RARa function by APL cells may not be a critical event in leukemogenesis. Recent reports showed that the fusion protein PML-RARa encoded from the t(15; 17) breakpoint is responsible for RA inducibility in APL, because transfection of the PML-RARa cDNA into the human myeloid leukemia cell line U937 conferred RA inducibility." Furthermore, APL-derived NB4 cells that lose their RA inducibility also lose expression of the PML-RARa protein."
Finding a role for PML in APL pathogenesis: a critical assessment of potential PML activities
Leukemia, 2002
In normal mammalian cells the promyelocytic leukemia protein (PML) is primarily localized in multiprotein nuclear complexes called PML nuclear bodies. However, both PML and PML nuclear bodies are disrupted in acute promyelocytic leukemia (APL). The treatment of APL patients with all-trans retinoic acid (ATRA) results in clinical remission associated with blast cell differentiation and reformation of the PML nuclear bodies. These observations imply that the structural integrity of the PML nuclear body is critically important for normal cellular functions. Indeed, PML protein is a negative growth regulator capable of causing growth arrest in the G 1 phase of the cell cycle, transformation suppression, senescence and apoptosis. These PML-mediated, physiological effects can be readily demonstrated. However, a discrete biochemical and molecular model of PML function has yet to be defined. Upon first assessment of the current PML literature there appears to be a seemingly endless list of potential PML partner proteins implicating PML in a variety of regulatory mechanisms at every level of gene expression. The purpose of this review is to simplify this confusing field of research by using strict criteria to deduce which models of PML body function are well supported.
Journal of Structural Biology, 2007
Promyelocytic leukemia protein (PML), a tumor suppressor, forms in most human cell types discrete multiprotein complexes termed PML nuclear bodies. Here, we have used indirect immunofluorescence and confocal microscopy to describe various forms of a novel nuclear PML compartment associated with nucleoli that is found under growth-permitting conditions in human mesenchymal stem cells (hMSC) and skin fibroblasts but not in several immortal cell lines with defects in the p53 and pRb pathways. In addition, we found that shut-off of rRNA synthesis induced by actinomycin D causes PML translocation to the surface of segregated nucleoli. This translocation is dynamic and reversible, following changes in nucleolar activity. Intriguingly, treatment causing premature senescence restores PML binding to nucleoli-derived structures and to the surface of segregated nucleoli in HeLa cells. These findings indicate that PML may be involved in nucleolar functions of normal non-transformed or senescent cells. The absence of nucleolar PML compartment in rapidly growing tumor-derived cells suggests that PML association with the nucleolus might be important for cell-cycle regulation.