Showing papers on "Promyelocytic leukemia protein published in 2000"

PML regulates p53 acetylation and premature senescence induced by oncogenic Ras

Abstract: The tumour suppressor p53 induces cellular senescence in response to oncogenic signals p53 activity is modulated by protein stability and post-translational modification, including phosphorylation and acetylation The mechanism of p53 activation by oncogenes remains largely unknown Here we report that the tumour suppressor PML regulates the p53 response to oncogenic signals We found that oncogenic Ras upregulates PML expression, and overexpression of PML induces senescence in a p53-dependent manner p53 is acetylated at lysine 382 upon Ras expression, an event that is essential for its biological function Ras induces re-localization of p53 and the CBP acetyltransferase within the PML nuclear bodies and induces the formation of a trimeric p53-PML-CBP complex Lastly, Ras-induced p53 acetylation, p53-CBP complex stabilization and senescence are lost in PML-/- fibroblasts Our data establish a link between PML and p53 and indicate that integrity of the PML bodies is required for p53 acetylation and senescence upon oncogene expression

The transcriptional role of PML and the nuclear body

Abstract: The PML gene encodes a tumour suppressor protein associated with a distinct subnuclear domain, the nuclear body. Various functions have been attributed to the PML nuclear body, but its main biochemical role is still unclear. Recent findings indicate that PML is essential for the proper formation of the nuclear body and can act as a transcriptional co-factor. Here we summarize the current understanding of the biological functions of PML and the nuclear body, and discuss a role for these intra-nuclear structures in the regulation of transcription.

PML is induced by oncogenic ras and promotes premature senescence

Abstract: Oncogenic ras provokes a senescent-like arrest in human diploid fibroblasts involving the Rb and p53 tumor suppressor pathways To further characterize this response, we compared gene expression patterns between ras-arrested and quiescent IMR90 fibroblasts One of the genes up-regulated during ras-induced arrest was promyelocytic leukemia (PML) protein, a potential tumor suppressor that encodes a component of nuclear structures known as promyelocytic oncogenic domains (PODs) PML levels increased during both ras-induced arrest and replicative senescence, leading to a dramatic increase in the size and number of PODs Forced PML expression was sufficient to promote premature senescence Like oncogenic ras, PML increased the levels of p16, hypophosphorylated Rb, phosphoserine-15 p53, and expression of p53 transcriptional targets The fraction of Rb and p53 that colocalized with PML markedly increased during ras-induced arrest, and expression of PML alone forced p53 to the PODs E1A abolished PML-induced arrest and prevented PML induction and p53 phosphorylation in response to oncogenic ras These results imply that PML acts with Rb and p53 to promote ras-induced senescence and provide new insights into PML regulation and activity

The function of PML in p53-dependent apoptosis.

Abstract: The PML gene of acute promyelocytic leukaemia (APL) encodes a growth- and tumour-suppresor protein that is essential for several apoptotic signals. The mechanisms by which PML exerts its pro-apoptotic function are still unknown. Here we show that PML acts as a transcriptional co-activator with p53. PML physically interacts with p53 both in vitro and in vivo and co-localizes with p53 in the PML nuclear body (PML-NB). The co-activatory role of PML depends on its ability to localize in the PML-NB. p53-dependent, DNA-damage-induced apoptosis, transcriptional activation by p53, the DNA-binding ability of p53, and the induction of p53 target genes such as Bax and p21 upon gamma-irradiation are all impaired in PML-/- primary cells. These results define a new PML-dependent, p53-regulatory pathway for apoptosis and shed new light on the function of PML in tumour suppression.

Regulation of p53 activity in nuclear bodies by a specific PML isoform

Abstract: Covalent modification of the promyelocytic leukaemia protein (PML) by SUMO-1 is a prerequisite for the assembly of nuclear bodies (NBs), subnuclear structures disrupted in various human diseases and linked to transcriptional and growth control. Here we demonstrate that p53 is recruited into NBs by a specific PML isoform (PML3) or by coexpression of SUMO-1 and hUbc9. NB targeting depends on the direct association of p53, through its core domain, with a C-terminal region of PML3. The relocalization of p53 into NBs enhances p53 transactivation in a promoter-specific manner and affects cell survival. Our results indicate the existence of a cross-talk between PML- and p53-dependent growth suppression pathways, implying an important role for NBs and their resident proteins as modulators of p53 functions.

Promyelocytic leukemia protein (PML) and Daxx participate in a novel nuclear pathway for apoptosis

Abstract: The promyelocytic leukemia protein (PML) gene of acute promyelocytic leukemia (APL) encodes a cell growth and tumor suppressor essential for multiple apoptotic signals. Daxx was identified as a molecule important for the cytoplasmic transduction of the Fas proapoptotic stimulus. Here, we show that upon mitogenic activation of mature splenic lymphocytes, Daxx is dramatically upregulated and accumulates in the PML nuclear body (NB) where PML and Daxx physically interact. In the absence of PML, Daxx acquires a dispersed nuclear pattern, and activation-induced cell death of splenocytes is profoundly impaired. PML inactivation results in the complete abrogation of the Daxx proapoptotic ability. In APL cells, Daxx is delocalized from the NB. Upon retinoic acid treatment, which induces disease remission in APL, Daxx relocalizes to the PML NBs. These results indicate that PML and Daxx cooperate in a novel NB-dependent pathway for apoptosis and shed new light in the role of PML in tumor suppression.

Association of the Bloom Syndrome Protein with Topoisomerase IIIα in Somatic and Meiotic Cells

Abstract: Bloom syndrome (BS) is characterized by genomic instability and cancer susceptibility caused by defects in BLM, a DNA helicase of the RecQ-family (J. German and N. A. Ellis, The Genetic Basis of Human Cancer, pp. 301–316, 1998). RecQ helicases and topoisomerase III proteins interact physically and functionally in yeast (S. Gangloff et al., Mol. Cell. Biol., 14: 8391–8398, 1994) and in Escherichia coli can function together to enable passage of double-stranded DNA (F. G. Harmon et al., Mol. Cell, 3: 611–620, 1999). We demonstrate in somatic and meiotic human cells an association between BLM and topoisomerase IIIα. These proteins colocalize in promyelocytic leukemia protein nuclear bodies, and this localization is disrupted in BS cells. Thus, mechanisms by which RecQ helicases and topoisomerase III proteins cooperate to maintain genomic stability in model organisms likely apply to humans.

Sp110 Localizes to the PML-Sp100 Nuclear Body and May Function as a Nuclear Hormone Receptor Transcriptional Coactivator

Abstract: The nuclear body is a multiprotein complex that may have a role in the regulation of gene transcription. This structure is disrupted in a variety of human disorders including acute promyelocytic leukemia and viral infections, suggesting that alterations in the nuclear body may have an important role in the pathogenesis of these diseases. In this study, we identified a cDNA encoding a leukocyte-specific nuclear body component designated Sp110. The N-terminal portion of Sp110 was homologous to two previously characterized components of the nuclear body (Sp100 and Sp140). The C-terminal region of Sp110 was homologous to the transcription intermediary factor 1 (TIF1) family of proteins. High levels of Sp110 mRNA were detected in human peripheral blood leukocytes and spleen but not in other tissues. The levels of Sp110 mRNA and protein in the human promyelocytic leukemia cell line NB4 increased following treatment with all-trans retinoic acid (ATRA), and Sp110 localized to PML-Sp100 nuclear bodies in ATRA-treated NB4 cells. Because of the structural similarities between Sp110 and TIF1 proteins, the effect of Sp110 on gene transcription was examined. An Sp110 DNA-binding domain fusion protein activated transcription of a reporter gene in transfected mammalian cells. In addition, Sp110 produced a marked increase in ATRA-mediated expression of a reporter gene containing a retinoic acid response element. Taken together, the results of this study demonstrate that Sp110 is a member of the Sp100/Sp140 family of nuclear body components and that Sp110 may function as a nuclear hormone receptor transcriptional coactivator. The predominant expression of Sp110 in leukocytes and the enhanced expression of Sp110 in NB4 cells treated with ATRA raise the possibility that Sp110 has a role in inducing differentiation of myeloid cells.

The lymphocytic choriomeningitis virus RING protein Z associates with eukaryotic initiation factor 4E and selectively represses translation in a RING-dependent manner.

Abstract: Only a few host cell proteins that associate with arenaviruses have been identified. To date, the arenavirus Z protein associates with the promyelocytic leukemia protein PML and the ribosomal P proteins. The majority of PML is present in nuclear bodies which are translocated to the cytoplasm by infection with the arenavirus, lymphocytic choriomeningitis virus (LCMV). The Z protein is a small zinc-binding RING protein with an unknown function which is required for the viral life cycle. Here, we demonstrate an association between Z and the host cell translation factor, eukaryotic initiation factor 4E (eIF-4E) in infected and transfected cells. Z's association with both ribosomal proteins and this translation factor led us to investigate whether Z could modulate host cell translation. In cell culture, Z selectively represses protein production in an eIF-4E-dependent manner. Specifically, we see reduction in cyclin D1 protein production with no effect on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in cells transfected with Z. Previous reports indicate that cyclin D1 is sensitive to eIF-4E levels, whereas GAPDH is not. Consistent with this, we observe preferential downregulation of cyclin D1 during infection and no effect on GAPDH. Further, no changes in RNA levels were observed for cyclin D1 or GAPDH transcripts. The interaction between eIF-4E and Z may provide a mechanism for slower growth observed in infected cells and a viral strategy for establishing chronic infection.

The promyelocytic leukemia (PML) protein suppresses cyclin D1 protein production by altering the nuclear cytoplasmic distribution of cyclin D1 mRNA

Abstract: The majority of the promyelocytic leukemia (PML) protein is present in nuclear bodies which are altered in several pathogenic conditions including acute promyelocytic leukemia. PML nuclear bodies are found in nearly all cells yet their function remains unknown. Here, we demonstrate that PML and the eukaryotic initiation factor 4E (eIF-4E) co-localize and co-immunopurify. eIF-4E is involved in nucleocytoplasmic transport of specific mRNAs including cyclin D1. eIF-4E overexpression leads to increased cyclin D1 protein levels; whereas, overexpression of PML leads to decreased cyclin D1 levels. Neither PML nor eIF-4E cause significant changes in cyclin D1 mRNA levels. The association with eIF-4E led us to investigate if PML could alter mRNA distribution as a possible post-transcriptional mechanism for suppressing cyclin D1 production. We show that overexpression of PML results in nuclear retention of cyclin D1 mRNA and that intact PML nuclear bodies are required. Addition of eIF-4E overcomes PML induced retention and alters the morphology of PML bodies suggesting a mechanism by which eIF-4E can modulate PML function. These results raise the possibility that PML nuclear bodies may participate in the regulation of nucleocytoplasmic transport of specific mRNAs.

BCR-ABL mediates arsenic trioxide-induced apoptosis independently of its aberrant kinase activity.

Abstract: In the prechemotherapy era arsenic derivatives were used for treatment of chronic myelogenous leukemia, a myeloproliferative disorder characterized by the t(9;22) translocation, the Philadelphia chromosome (Ph+). In acute promyelocytic leukemia response to arsenic trioxide (As2O3) has been shown to be genetically determined by the acute promyelocytic leukemia-specific t(15;17) translocation product PML/RARalpha. Hence, we reasoned that As2O3 might have a selective inhibitory effect on proliferation of BCR-ABL-expressing cells. Here, we report that: (a) As2O3 induced apoptosis in Ph+ but not in Ph- lymphoblasts; (b) enforced expression of BCR-ABL in U937 cells dramatically increased the sensitivity to As2O3; (c) the effect of As2O3 was independent of BCR-ABL kinase activity; and (d) As2O3 reduced proliferation of chronic myelogenous leukemia blasts but not of peripheral CD34+ progenitors. In summary, these data establish As2O3 as a tumor cell-specific agent, making its clinical application in Ph+ leukemia feasible.

Identification of B94 (TNFAIP2) as a potential retinoic acid target gene in acute promyelocytic leukemia.

Abstract: Acute promyelocytic leukemia (APL) is characterized by a block to myeloid differentiation caused by expression of the fusion oncoprotein promyelocytic leukemia-retinoic acid receptor α (PML-RARα). The purpose of this study was to identify genes that are regulated in a PML-RARα-dependent fashion by retinoic acid (RA), because such genes may be integrally involved in APL pathogenesis and/or myeloid differentiation. A cDNA microarray approach was used to identify genes induced in response to RA in TF1 myeloid leukemia cells expressing PML-RARα (TF1-PR cells). The B94 gene (TNFAIP2; Unigene Hs.101382), originally identified as a tumor necrosis factorα -inducible gene in endothelial cells, was one of several genes found to be induced by RA specifically in TF1-PR cells, but not in TF1-neo (control) cells. The induction of B94 was most pronounced in cells expressing the PML-RARα short isoform and was negligible in cells that expressed a mutant PML-RARα protein containing a deletion of the PML coiled-coil domain. B94 induction by RA occurred within 1 h, did not require new protein synthesis, and was inhibited by actinomycin D, suggesting rapid transcriptional activation. B94 was also induced by RA in NB4, UF1, and HL-60 cells, but not in other hematopoietic cell lines tested, suggesting that its up-regulation by RA may be specific to cells that express PML-RARα or are at the late myeloblast or promyelocyte stage of myeloid development. A screen of bone marrow cells from normal donors or patients with acute myelogenous leukemia showed that B94 was highly expressed in normal marrow and in marrow from patients with acute myelogenous leukemia French-American-British subtypes M 0 -M 2 , but was repressed in marrow cells from APL patients. Treatment of APL blasts in vitro with all- trans -RA resulted in up-regulation of B94 mRNA. These results suggest that B94 plays a role in myeloid development and support the hypothesis that B94 is a target gene of PML-RARα in APL.

Potentiation of GATA-2 Activity through Interactions with the Promyelocytic Leukemia Protein (PML) and the t(15;17)-Generated PML-Retinoic Acid Receptor α Oncoprotein

Abstract: The hematopoietically expressed GATA family of transcription factors function as key regulators of blood cell fate. Among these, GATA-2 is implicated in the survival and growth of multipotential progenitors. Here we report that the promyelocytic leukemia protein (PML) can complex with GATA-2 and potentiate its transactivation capacity. The binding is mediated through interaction of the zinc finger region of GATA-2 and the B-box domain of PML. The B-box region of PML is retained in the PML-RARalpha (retinoic acid receptor alpha) fusion protein generated by the t(15;17) translocation characteristic of acute promyelocytic leukemia (APL). Consistent with this, we provide evidence that GATA-2 can physically associate with PML-RARalpha. Functional experiments further demonstrated that this interaction has the capacity to render GATA-dependent transcription inducible by retinoic acid, raising the possibility that GATA target genes may be involved in the molecular pathogenesis of APL.

Mechanisms of all-trans retinoic acid-induced differentiation of acute promyelocytic leukemia cells.

Abstract: Retinoic acids (RA) play a key role in myeloid differentiation through their agonistic nuclear receptors (RARα/RXR) to modulate the expression of target genes. In acute promyelocytic leukemia (APL) cells with rearrangement of retinoic acid receptor α (RARα) (including: PML-RARα, PLZF-RARα, NPM-RARα, NuMA-RARα or STAT5b-RARα) as a result of chromosomal translocations, the RA signal pathway is disrupted and myeloid differentiation is arrested at the promyelocytic stage. Pharmacologic dosage ofall-trans retinoic acid (ATRA) directly modulates PML-RARα and its interaction with the nuclear receptor co-repressor complex, which restores the wild-type RARα/RXR regulatory pathway and induces the transcriptional expression of downstream genes. Analysing gene expression profiles in APL cells before and after ATRA treatment represents a useful approach to identify genes whose functions are involved in this new cancer treatment. A chronologically well coordinated modulation of ATRA-regulated genes has thus been revealed which seems to constitute a balanced functional network underlying decreased cellular proliferation, initiation and progression of maturation, and maintenance of cell survival before terminal differentiation.

The puzzling multiple lives of PML and its role in the genesis of cancer.

Abstract: PML, the gene associated with acute promyelocytic leukemia (APL); PML, the target of numerous viral agents; PML, the growth suppressor; PML, the mediator of multiple apoptotic pathways; PML, the tumor suppressor; PML, the protein which epitomizes a novel nuclear structure, the nuclear body; PML, the transcription co-factor. Despite the recent flurry of reports attributing multiple biological roles to the PML protein, PML still lacks a definitive biochemical function. This is probably the reason why PML is so attractive to many investigators. Here, we will summarize the facts and speculations on this puzzling protein.

BLM, the Bloom’s syndrome protein, varies during the cell cycle in its amount, distribution, and co-localization with other nuclear proteins

Abstract: BLM, the protein encoded by the gene mutated in Bloom's syndrome (BS), is a phylogenetically highly conserved DNA helicase that varies in amount and distribution in the nucleus during the cell-division cycle. It is undetectable in many cells as they emerge from mitosis but becomes abundant during G(1) and remains so throughout S, G(2), and mitosis. BLM is widely distributed throughout the nucleus but at certain times also becomes concentrated in foci that vary in number and size. It co-localizes transitorily with replication protein A (RPA) and promyelocytic leukemia protein (PML) nuclear bodies, and at times it enters the nucleolus. The observations support the hypothesis that BLM is distributed variously about the nucleus to manipulate DNA in some, very possibly several, nucleic acid transactions, when and where they take place. The specific transaction(s) remain to be identified. Although absence from the nucleus of functional BLM - the situation in BS - obviously is not lethal in the human, other helicases would appear to be unable to substitute for it completely, witness the hypermutability and hyperrecombinability of BS cells.

Lack of expression for the suppressor PML in human small cell lung carcinoma.

Abstract: The promyelocytic leukemia (PML) gene, which encodes a transformation and growth suppressor, was first identified at the chromosomal translocation break point t(15;17) in acute promyelocytic leukemia (PML). To determine if the PML gene might be involved in other neoplasias such as lung cancer, PML expression was analyzed by immunohistochemical staining and in situ hybridization. Considerable PML protein expression in the PML-oncogenic domain (POD) structure was found in adenocarcinomas (ADC) and squamous cell carcinomas (SCC) of the lung, but was almost completely absent in all the small cell lung carcinomas (SCLC) examined. In situ hybridization showed that both mRNA and DNA of PML were present in SCLC and in normal lung, suggesting that the decreased protein expression was due to either a defect in translation or protein instability, rather than the consequence of decreased transcription or gene deletion. Double staining showed that PML expression was inversely correlated with the proliferation marker Ki-67 and positively correlated with levels of apoptotic cells in these tumors. To determine if the precursor cells of SCLC, the neuroendocrine-producing cells, express PML, double labeling was performed with PML and chromogranin A, a bio-marker for neuroendocrine cells. Neuroendocrine cells from normal tissues were found to be PML positive, indicating that the lack of PML protein in SCLC is associated with the tumorigenic phenotype and is not the result of cell-lineage specificity. Thus, the decreased PML expression may play an important role in SCLC development.

Potential mechanisms of resistance to TRAIL/Apo2L-induced apoptosis in human promyelocytic leukemia HL-60 cells during granulocytic differentiation

Abstract: Human promyelocytic leukemia HL-60 cells are well known to differentiate into granulocytes or monocytes in the presence of some agents such as DMSO or PMA, respectively. Differentiated HL-60 cells become resistant to some apoptotic stimuli including anticancer drugs or irradiation though undifferentiated cells significantly respond to these stimuli. TRAIL (TNF-related apoptosis-inducing ligand) which is also known as Apo2 ligand (Apo2L), a new member of TNF family, can induce apoptosis in some tumor cells but not in many normal cells. We show here that apoptosis is well induced in HL-60 cells by TRAIL, but susceptibility to TRAIL is reduced during granulocytic differentiation by DMSO. We also suggest some possible mechanisms by which granulocytic differentiated cells become resistant to TRAIL-induced apoptosis. First, in granulocytic differentiated cells, expression of antagonistic decoy receptors for TRAIL (TRAIL-R3/TRID/DcR1/LIT and TRAIL-R4/TRUNDD/DcR2) were enhanced. In addition, expression of Toso, a cell surface apoptosis regulator, seemed to block activation of caspase-8 by TRAIL via enhanced expression of FLIPL in granulocytic differentiated cells. These findings suggest that differentiated cells are resistant using plural mechanisms against various apoptosis-inducing stimuli rather than undifferentiated cells.

Differentiating agents in pediatric malignancies: all-trans-retinoic acid and arsenic in acute promyelocytic leukemia.

Abstract: Acute promyelocytic leukemia (APL) is the most potentially curable type of acute myeloid leukemia. It is characterized by the chromosomal translocation t(15;17), which results in the fusion gene PML-RAR-alpha. The introduction of all-trans- retinoic acid (ATRA) was a major advance in treatment of this disease. This agent induces terminal differentiation of malignant myeloid cells to mature neutrophils, and its side effects are usually well tolerated in children. ATRA does not eradicate the malignant myeloid clone in APL and, eventually, resistance develops. Arsenic trioxide induces nonterminal differentiation of malignant promyelocytes and promotes apoptosis. APL patients treated with ATRA or arsenic trioxide have rapid resolution of their coagulopathy. Because both of these drugs are well tolerated in children and their synergy has been shown in animal models, the possibility of combining ATRA and arsenic trioxide in front-line therapy for children with APL is being considered.

Interferon beta induces S-phase slowing via up-regulated expression of PML in squamous carcinoma cells

Abstract: Type I Interferon (IFN) and all-trans retinoic acid (RA) inhibit cell proliferation of squamous carcinoma cell lines (SCC). Examinations of growth-affected cell populations show that SCC lines ME-180 and SiHa treated with IFN-beta undergo a specific slower progression through the S phase that seems to trigger cellular death. In combination treatment RA potentiates IFN-beta effect in SCC ME-180 but not in SiHa cell line, partially resistant to RA antiproliferative action. RA added as single agent affects cell proliferation differently by inducing a slight G1 accumulation. The IFN-beta-induced S phase lengthening parallels the increased expression of PML, a nuclear phosphoprotein specifically up-regulated at transcriptional level by IFN, whose overexpression induces cell growth inhibition and tumor suppression. We report that PML up-regulation may account for the alteration of cell cycle progression induced by IFN-beta in SCC by infecting cells with PML-PINCO recombinant retrovirus carrying the PML-3 cDNA under the control of the 5' LTR. In fact PML overexpression reproduces the IFN-beta-induced S phase lengthening. These findings provide important insight into the mechanism of tumor suppressing function of PML and could allow PML to be included in the pathways responsible for IFN-induced cell growth suppression.

Translocation (15;17)(q22;q21) not associated with acute promyelocytic leukemia and negative for PML/RARa rearrangement.

Abstract: Sir, A 44-year old Chinese man presented with a twoweek history of bone pain and myalgia. Complete blood counts showed: hemoglobin (Hb) 6.3 g/dL, white cell count (WBC) 1.1×109/L (blasts 21%), and platelet count (Plt) 159×109/L. The clotting profile was normal. Bone marrow aspiration revealed a morphologic diagnosis of acute myeloid leukemia-M2 (Figure 1A). Cytochemically, the blast cells were negative for myeloperoxidase and showed a low level of Sudan black B positivity (10%). Immunophenotyping showed multilineage antigen expression (CD13, CD33, CD7 and surface CD22) in addition to CD34 and HLA-DR. Cytogenetic studies performed on synchronized and non-synchronized short term cultures of bone marrow cells supplemented by direct harvest1 showed: 46,XY, t(15;17) (q22;q21)[3]/46,XY[5] (Figure 2). All-trans retinoic acid was started empirically at the dose of 45 mg/m2/day in view of the t(15;17) (q22;q21), but was discontinued after two weeks when molecular studies showed no evidence of the PML/RARα rearrangement. A complete remission was attained by induction chemotherapy followed by two courses of consolidation. The patient relapsed one year later and died of the disease. Southern blot hybridization of RARα gene configuration was performed with a 5.5 kb RARα probe (covering intron 2 to exon 4) on BglII and HindIII DNA digests.2 No rearrangement of the RARα gene could be defined in our patient (data not shown). Similarly, no PML/RARα fusion transcript could be detected at diagnosis by polymerase chain reaction as described.3 Fluorescence in situ hybridization, performed on interphase nuclei using a PML/RARα dual color translocation probe (Vysis, Downers Grove, IL, USA), showed two separate PML and RARα signals (Figure 1B) in 300 interphase nuclei and all metaphases analyzed. No PML/RARα fusion signal was identified.

Rapid Diagnosis of Acute Promyelocytic Leukemia by Analyzing the Immunocytochemical Pattern of the PML Protein With the Monoclonal Antibody PG-M3

Abstract: The fusion protein, promyelocytic leukemia–retinoic acid receptor (PML-RAR)alpha, generated by the t(15;17) translocation has an abnormal cellular distribution with colocalization of RARalpha and PML proteins. We analyzed the immunostaining pattern of PML protein using the PGM3 monoclonal antibody directed against the amino terminal portion of PML (retained in wild-type PML and PML-RARalpha fusion protein) in the diagnosis of acute promyelocytic leukemia (APL). In addition, we compared this test with other methods for detecting the PML-RARalpha fusion gene. A normal immunostaining pattern was observed in nonmyeloid disorders and in 78 of 111 acute myeloid leukemias (AMLs). A microgranular pattern was observed in 25 AMLs, all corresponding to APL. These results were concordant with the reverse transcriptase–polymerase chain reaction results for PML-RARalpha fusion gene. Only 1 case positive for the PML-RARalpha transcript showed a normal protein pattern by immunocytochemistry. PML immunostaining was helpful to rapidly differentiate 7 cases with borderline characteristics and to obtain the diagnosis in 2 cases with scarce material. The effectiveness and low cost of this technique support its routine use as a first-line procedure in the differential diagnosis of AML.

Transcriptional regulation of cellular transformation.

Abstract: Structurally and functionally altered transcription factors have been associated with many human neoplasms. A better understanding of these transcriptional defects has revealed new therapeutic opportunities.