Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Scanty information is available on acute promyelocytic leukemia (APL) in children, and whether differences are present with respect to the adult form. The experience of the Italian Pediatric Hematology and Oncology Group (AIEOP) will be presented with respect to the following aspects: 1. Incidence of APL. The incidence of APL is generally considered to account for 3-9% of acute myelogenous leukemia (AML) in children and approximately 10-15% in adults. Recently a single Italian pediatric institution reported that APL constituted one third of observed acute nonlymphocytic leukemia (AnLL) cases. Data from the AIEOP cooperative study group have confirmed that APL in Italy is more frequently observed in children as compared to other countries. Environmental and/or genetic factors should be considered to explain such differences. 2. Diagnosis of M3v. The clinical and biological features of the largest series of childhood M3v will be presented and the problems encountered in the proper separation of 'classic' M3 and M3v in children will be discussed. 3. Clinical Aspects. The clinical features of the APL patients enrolled in the AIEOP study groups since 1989, will be presented with emphasis on the recent experience with the use of all-trans retinoic acid. 4. Analysis of PML/RAR alpha Fusion Transcripts. An RT-PCR analysis of 32 pediatric APL cases from cryopreserved bone marrow samples has been performed. It is concluded that APL in children did not differ significantly from the adult form, with the exception of a higher incidence of PML bcr3 breakpoint.
Leukemia 1994 Aug
PMID:Acute promyelocytic leukemia in children: experience of the Italian Pediatric Hematology and Oncology Group (AIEOP). 805 59

Acute promyelocytic leukemia (APML) almost always involves a chromosomal translocation t(15:17) that results in the fusion of the retinoic acid receptor alpha (RAR alpha) gene with a transcription factor gene called PML. Several cases of APML with t(11;17) have recently been described, involving fusion of the RAR alpha gene with a new zinc finger gene named PLZF. We report here a second non-classical translocation, t(5;17), with a rearranged RAR alpha gene in a child with APML. Based on restriction endonuclease analysis, the rearrangement of RAR alpha occurred within the second intron, the common breakpoint site for t(15;17). The leukemic cells in the bone marrow aspirate were a mixture of hypergranular and hypogranular bilobed promyelocytes. Although less than 1% abnormal promyelocytes were identified after induction therapy, cytogenetics revealed persistent t(5;17). Therefore, the child was treated with all-trans-retinoic acid (ATRA). There was no disease progression, and one marrow was interpreted as remission, with confirmation by cytogenetics which failed to reveal the translocation. However, disease reoccurred shortly after completion of ATRA. This poor response to ATRA may be an additional characteristic associated with non-classical translocations in APML. The identification of a second variant translocation involving the RAR alpha gene in APML suggests yet another RAR alpha rearrangement related to neoplastic myelopoiesis.
Leukemia 1994 Aug
PMID:A non-classical translocation involving 17q12 (retinoic acid receptor alpha) in acute promyelocytic leukemia (APML) with atypical features. 805 72

Nuclear bodies (NBs) are ultrastructurally defined granules predominantly found in dividing cells. Here we show that PML, a protein involved in the t(15;17) translocation of acute promyelocytic leukaemia (APL), is specifically bound to a NB. PML and several NB-associated proteins, found as auto-antigens in primary biliary cirrhosis (PBC), are co-localized and co-regulated. The APL-derived PML-RAR alpha fusion protein is shown to be predominantly localized in the cytoplasm, whereas a fraction is nuclear and delocalizes the NB antigens to multiple smaller nuclear clusters devoid of ultrastructural organization. RA administration (which in APL patients induces blast differentiation and consequently complete remissions) causes the re-aggregation of PML and PBC auto-antigens onto the NB, while PML-RAR alpha remains mainly cytoplasmic. Thus, PML-RAR alpha expression leads to a RA-reversible alteration of a nuclear domain. These results shed a new light on the pathogenesis of APL and provide a molecular link between NBs and oncogenesis.
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PMID:The t(15;17) translocation alters a nuclear body in a retinoic acid-reversible fashion. 813 41

The characteristic balanced 15;17 translocation, t(15;17), of acute promyelocytic leukemia (APL) fuses the retinoic acid receptor alpha (RAR alpha) gene on chromosome 17 to PML, a recently described gene of unknown function, on chromosome 15. It is this fusion gene and consequent fusion protein that is thought to be responsible for both the block in normal myelocyte differentiation as well as the dramatic in vitro and in vivo response to the differentiating effects of all-trans retinoic acid (RA). The t(15;17) also provides a genetic marker for the presence of leukemic cells. PML/RAR alpha fusion mRNA's can be detected by a reverse transcription polymerase chain reaction (RT-PCR) assay. Using this assay, at least three distinct patterns, differing in the 3' region of the PML breakpoint, can be identified. The detection of abnormal mRNA's by the RT-PCR assay has proven to be an important aid in the diagnosis of APL as well as the best predictor of an initial clinical response to RA. The results of an ongoing, longitudinal evaluation of patients with APL show that the RT-PCR assay may also be a useful indicator of minimal residual disease (MRD). Negative RT-PCR assays following completion of all therapy are associated with prolonged disease free survival, whereas persistence or return of a positive test is highly correlated with subsequent relapse. Further studies will determine whether patients who test positive may benefit from the introduction of additional antileukemic therapy.
Leukemia 1994 Apr
PMID:Molecular diagnosis and monitoring of acute promyelocytic leukemia treated with retinoic acid. 815 76

We performed clonality studies of hemopoietic reconstitution in 24 female patients (pts) with leukemias characterized by specific tumor markers. Thirteen pts had Acute Promyelocytic Leukemia (APL) with rearrangements of the RAR-a and PML genes, 8 BCR rearranged (BCR+)/Ph+ Chronic Myeloid Leukemia (CML) and 3 BCR+/Ph+ Acute Lymphoid Leukemia (ALL). Bone marrow (BM) DNA samples were obtained at diagnosis and at remission after Southern blot documented suppression of specific markers. The clonal or non-clonal nature of hemopoietic reconstitution was assessed by hybridizing the same DNAs with the M27 beta probe, in order to detect methylation differences at the X-linked DXS255 locus. Twenty four pts showed a polyclonal methylation pattern at remission, whereas in 3 cases an apparently clonal pattern was observed despite no evidence of specific gene rearrangement. In 2 of these 3 cases, however, DNAs derived from non-affected tissues (T lymphocytes, skin and BM fibroblasts) revealed the presence of the same DXS255 unmethylated allele detected at diagnosis, while in the third case we found the same apparently clonal pattern in blood mononuclear cells obtained from her healthy female BM donor. These data indicate that polyclonal hematopoiesis occur in APL and CML pts after therapy induced suppression of specific tumor markers, and that unbalanced or aberrant X chromosome methylation patterns are observed in some cases, most likely reflecting constitutional features.
Leukemia 1994 Apr
PMID:Polyclonal hemopoiesis in leukemia patients following molecularly documented remission. 815 81

Acute promyelocytic leukaemia is characterized by an expansion of haematopoietic precursors arrested at the promyelocytic stage (1). The differentiation block can be reversed by retinoic acid, which induces blast differentiation both in vitro (2) and in vivo (3-4). Acute promyelocytic leukaemia is also characterized by a 15;17 chromosome translocation (5) with breakpoints within the retinoic acid alpha receptor (RAR alpha) gene on 17 and within the PML gene, that encodes a putative transcription factor of unknown function (6-7), on 15 (8-10). As a consequence of the translocation a PML/RAR alpha gene is formed. It is transcriptionally active and encodes a PML/RAR alpha fusion protein detectable in all APL cases (11-14). We expressed the PML/RAR alpha protein in U937 myeloid precursor cell line and show that they: 1) lose the capacity to differentiate under the action of different stimuli (vitamin D3, transforming growth factor beta 1); ii) acquire enhanced sensitivity to retinoic acid; iii) exhibit a higher growth rate that is due to a reduction in apoptotic cell death. These results provide the first evidence of biological activity of PML/RAR alpha and recapitulate critical features of the promyelocytic leukemia phenotype.
Leukemia 1994 Apr
PMID:Effect of the acute promyelocytic leukemia PML/RAR alpha protein on differentiation and survival of myeloid precursors. 815 8

The molecular mechanisms underlying the t(15;17) cytogenetic translocation of acute promyelocytic leukaemia (APL) have been recently elucidated. Together with new insights into the understanding of APL pathogenesis, such investigations also provided the availability of a novel leukemia-specific marker to be used for both diagnostic and monitoring studies. The chromosome breakpoints of the t(15;17) have been shown to involve the retinoic acid receptor alpha (RAR-a) gene and the newly described PML gene on chromosomes 17 and 15, respectively. Rearrangements of these loci are found in virtually 100% of APLs, including the microgranular variant subtype and cases displaying apparently normal karyotypes. In cases with ambiguous morphology, molecular diagnosis may therefore enable the prompt administration of APL-specific therapies, such as all-trans retinoic acid. Significantly, clinical response to this differentiating agent is predictable based on the presence of the specific PML/RAR-a rearrangement. Appropriate oligoprimers complementary to PML and RAR-a sequences nearby the DNA breakpoints may be successfully used in PCR experiments to amplify the PML/RAR-a hybrid gene and sensitively detect minimal residual disease. Preliminary PCR studies indicate that this approach might indeed prove a very important and reliable prognostic indicator in the follow up monitoring of APL patients. Early identification of impending relapse by PCR may suggest the use of additional treatment in patients at risk and significantly increase the probability of cure of the disease.
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PMID:Clinical relevance of the PML/RAR-a gene rearrangement in acute promyelocytic leukaemia. 818 May 96

The current treatment of acute promyelocytic leukemia (APL, also called AML3 subtype) is focused on differentiating agents such as the vitamin A derivative all-trans retinoic acid (ATRA). This agent is a novel and very promising therapy for this disease characterized cytogenetically by a translocation t(15;17)(q21;q22) involving the alpha retinoic acid receptor on chromosome 17 and the PML gene on chromosome 15. Clinical trials have demonstrated that ATRA followed by or combined with conventional chemotherapy may be more beneficial than chemotherapy for inducing complete remission. Unfortunately, ATRA as a single agent, does not appear able to maintain patients in remission (median 5 months), and when relapse occurs resistance to a second induction of ATRA therapy is observed in almost all cases. Recently our laboratory investigated whether specific features of the AML3 cells at relapse could explain the in vivo resistance observed. We have demonstrated that AML3 patients' cells (from four patients) at relapse show high levels of CRABP, a cytosolic retinoic acid binding protein and this protein was not detected prior to ATRA therapy. Relapse-AML3 cells (n = 12) showed reduced differentiation induction when compared with 'virgin'-AML3 cells. Results from this study suggest that CRABP could modulate ATRA cellular concentrations reaching the nucleus. This induced ATRA hypercatabolytic state should be monitored during consolidation therapy and at relapse by evaluating CRABP and RA metabolite levels, in order to detect ATRA resistance in patients with AML3.
Leukemia 1994 Jun
PMID:In vitro all-trans retinoic acid (ATRA) sensitivity and cellular retinoic acid binding protein (CRABP) levels in relapse leukemic cells after remission induction by ATRA in acute promyelocytic leukemia. 820 83

In an ongoing study, we treated 79 patients with a molecular diagnosis of acute promyelocytic leukemia (APL) using all-trans retinoic acid (RA) for remission induction. Newly diagnosed patients received cytotoxic chemotherapy for consolidation, and previously treated patients received extended all-trans RA therapy, or a radionuclide-conjugated monoclonal antibody as post-remission treatment. Unlike studies in Europe, full-dose chemotherapy was not given during induction for patients who developed leukocytosis. Overall, 43 of 49 newly diagnosed patients (88%) and 25 of 30 previously treated patients (83%) achieved complete remission. We did not encounter de novo resistance to all-trans RA in any patient who was positive for PML/RAR-alpha rearrangements by reverse transcription polymerase chain reaction analysis. Ten patients died during induction from intracranial or pulmonary hemorrhage (six patients) or the 'retinoic acid syndrome' (four patients). The use of leukapheresis or low-dose chemotherapy (hydroxyurea or cytosine arabinoside) for drug-induced leukocytosis did not decrease early mortality. Compared to historical controls, early mortality was not affected by treatment with all-trans RA; however, both relapse-free and overall survival were significantly increased. Maintenance therapy with all-trans RA was associated with short remission duration, and relapses while taking the drug were universally associated with resistance to further retinoid treatment. We conclude that the use of all-trans RA for remission induction, with or without full-dose chemotherapy, has significantly increased the survival of patients with APL. While early mortality has not yet been reduced, the avoidance of full-dose chemotherapy during induction has significantly reduced early morbidity. The major outstanding clinical issue is the development of strategies that maximize safety in high-risk patients for whom intracranial hemorrhage remains the major cause of death.
Leukemia 1994 Jun
PMID:Treatment of acute promyelocytic leukemia with all-trans retinoic acid: an update of the New York experience. 820 86

While a great deal has been learned about APL over the last few years, many important questions remain unanswered. It has become clear that the PML/RAR-alpha fusion protein is expressed in most cases of APL, and this protein presumably contributes to leukaemia initiation and/or progression. PML/RAR-alpha appears to specifically block the further differentiation of myeloid progenitor cells, although the mechanism of its action is not known. It may inhibit the transcription of RAR- or PML-regulated genes, in which case expression must be restored in the presence of therapeutic RA concentrations. However, the possibility remains that PML/RAR-alpha may have a novel function. In order to elucidate the molecular pathogenesis of APL, several important questions remain to be answered. These include whether PML is a transcription factor; the identification of its target genes and response elements, and the role of PML/RAR-alpha and RA in their regulation. Also whether the expression of PML/RAR-alpha in bone marrow cells (either by itself or in combination with other oncogenes) alters their tumourigenicity or differentiation potential. It is also important to determine the function(s) of PLZF and PLZF/RAR-alpha, and determine whether other APL patients with mutations involving PML or RAR-alpha (but not both) respond to therapy with all-trans-RA. Finally, it is important both for the understanding of the molecular biology of APL and its therapy, to determine the effects of other regulatory factors involved in the control of myeloid cell differentiation such as granulocyte colony stimulation factor (G-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF) on APL cells in vitro and in vivo, both at presentation and in the RA-resistant patients in relapse.
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PMID:Retinoid receptors and acute promyelocytic leukaemia. 828 May


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