Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023467 (acute myeloid leukemia)
 35,200 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acute myeloid leukemia (AML) is not a single disease but a group of malignancies in which the clonal expansion of various types of hematopoietic precursor cells in the bone marrow leads to perturbation of the delicate balance between self-renewal and differentiation that is characteristic of normal hematopoiesis. An increasing number of genetic aberrations, such as chromosomal translocations that alter the function of transcription regulatory factors, has been identified as the cause of AML and shown to act by deregulating gene programming at both the genetic and epigenetic level. While the genetic aberrations occurring in acute myeloid leukemia are fairly well understood, we have only recently become aware of the epigenetic deregulation associated with leukemia, in particular with myeloid leukemias. The deposition of epigenetic "marks" on chromatin - post-translational modifications of nucleosomal proteins and methylation of particular DNA sequences - is accomplished by enzymes, which are often embedded in multi-subunit "machineries" that have acquired aberrant functionalities during leukemogenesis. These enzymes are targets for so-called "epi-drugs". Indeed, recent results indicate that epi-drugs may constitute an entirely novel type of anti-cancer drugs with unanticipated potential. Proof-of-principle comes from studies with histone deacetylase inhibitors, promising novel anti-cancer drugs. In this review we focus on the epigenetic mechanisms associated with acute myeloid leukemogenesis and discuss the therapeutic potential of epigenetic modulators such as histone deacetylase and DNA methyltransferase inhibitors.
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PMID:Acute myeloid leukemia: therapeutic impact of epigenetic drugs. 1596 34

Apaf-1 is important for tumor suppression and drug resistance because it plays a central role in DNA damage-induced apoptosis. Inactivation of the Apaf-1 gene is implicated in disease progression and chemoresistance of some malignancies. In this study, we attempted to clarify the role of Apaf-1 in leukemogenesis. Apaf-1 mRNA levels were below the detection limit or very low in 5 of 20 human leukemia cell lines (25%) and 5 of 12 primary acute myeloblastic leukemia cells (42%). There were no gross structural abnormalities in the Apaf-1 gene in these samples. Expression of factors regulating Apaf-1 transcription, such as E2F-1, p53, and Sp-1, did not differ between Apaf-1-positive and Apaf-1-negative cells. Methylation of CpG in the region between +87 and +128 of the Apaf-1 gene was almost exclusively observed in Apaf-1-defective cell lines. Treatment of these cells with 5-aza-2'-deoxycytidine, a specific inhibitor of DNA methylation, restored the expression of Apaf-1. Furthermore, we showed that the region between +87 and +128 could act as a repressor element by recruiting corepressors such as methylated DNA-binding domain 2 and histone deacetylase 1 upon methylation. Overexpression of Dnmt1, a mammalian maintenance DNA methyltransferase, was associated with Apaf-1 gene methylation. DNAs from Dnmt1-overexpressing cells were more resistant to digestion with methylation-sensitive enzyme HpaII than those from cells with low Dnmt1 expression, suggesting that Dnmt1 mediates aberrant methylation of multiple genes. In conclusion, methylation silencing is a mechanism of the inactivation of Apaf-1 in acute leukemia, and Dnmt1 overexpression may underlie hypermethylation of the Apaf-1 gene.
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PMID:Methylation silencing of the Apaf-1 gene in acute leukemia. 1597 51

Myelodysplastic syndromes (MDS) are a heterogenous group of hematopoietic stem cell disorders that are multifactorial in their etiology. Aberrant DNA hypermethylation is now thought to be involved in MDS, as numerous tumor-suppressor genes have been identified that are silenced in these patients. Thus, the use of DNA methyltransferase inhibitors, such as 5-aza-2'-deoxycytidine (decitabine, Dacogen, MGI Pharma Inc, Bloomington, MN), for reversal of this process appears to be a rational intervention that may influence the course of the disease. Several phase I/II studies have been conducted using a low-dose schedule of decitabine in MDS patients. Based on these studies, decitabine appears to be effective and generally well tolerated, especially in those patients with worse prognostic indicators. Recent results of a phase III study also confirmed that patients treated with decitabine compared to standard supportive care had higher overall response rates and longer time to AML transformation. Decitabine appears to be a promising new therapy for the treatment of MDS; however, defining the optimal dosing schedule and exploring the possible use in combination with other agents such as the histone deacetylase inhibitors need further evaluation.
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PMID:Decitabine in myelodysplastic syndromes. 1601 1

Decitabine, a potent DNA methyltransferase inhibitor, which was originally under development by Pharmachemie, is being developed by SuperGen. Pharmachemie had been studying decitabine in phase II clinical trials for several leukemia indications in Europe and the US. Preliminary results indicated that the compound was active in the treatment of myelodysplasia, relapsed leukemia, acute myeloid leukemia and postallogeneic progenitor cell transplant relapse. The compound is in phase II clinical trials with phase III trials scheduled to begin shortly. Decitabine has been used to treat myelodysplastic syndrome in a total of 125 patients, with an overall response rate of 49%. In a study using decitabine to treat chronic myelogenous leukemia in 81 patients, a response rate of 62% among patients in chronic phase of the disease was achieved. In a phase I/II trial designed to establish safety and efficacy in the treatment of sickle cell anemias treatment with decitabine generated a response in 100% of the patients tested: a total of eight patients were enrolled, each experienced elevated levels of fetal hemoglobin. Side effects were minimal and the drug was well tolerated. Plans for additional clinical studies of decitabine as a treatment for sickle cell anemia are underway. A phase II trial using a low dose of decitabine in patients with myelodysplastic syndrome has been completed. Of 66 patients entered, 62 were evaluable. The response rate was 48%, with a median response duration of 40 weeks. The mean survival from the start of therapy was 13 months. In a study with 37 CML patients, a 25% overall response rate was seen in those patients in the blastic phase of the disease, and a 52% response rate was observed in the accelerated phase patients. The most significant side effect was prolonged myelosuppression. The drug suppresses cellular growth in seven human tumor cell lines, possibly by reactivation of certain growth suppressor genes.
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PMID:Decitabine (SuperGen). 1603 61

Azanucleoside drugs such as 5-azacytidine (Vidaza) and 5-aza-2'-deoxycytidine (decitabine, Dacogen) function as DNA methyltransferase inhibitors in vitro and represent promising new drugs for the treatment of myelodysplastic syndrome (MDS) and acute myeloid leukemia. In this study, we aimed to determine the effect of decitabine on the genomic methylation level in MDS patients. Comparison of different assays established micellar electrokinetic chromatography as a reliable method for the analysis of genomic methylation levels. When used for the determination of DNA methylation levels in bone marrow DNA from MDS patients during various time points of decitabine treatment, the results revealed a significant (up to 70%) demethylation in five of seven patients. Interestingly, genome-wide demethylation appeared after karyotype normalization, which suggests demethylation of nonclonal cells. Drug-induced demethylation dynamics were also confirmed by bisulfite sequencing of pericentromeric satellite elements. Our results are the first to show a genome-wide demethylating activity of decitabine in tumor material. In addition, our data uncovers novel targets of decitabine-mediated demethylation that are important for the refinement of treatment schedules with demethylating drugs.
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PMID:Characterization of DNA demethylation effects induced by 5-Aza-2'-deoxycytidine in patients with myelodysplastic syndrome. 1610 56

Hypermethylation of CpG islands near gene promoter regions is associated with transcriptional inactivation and represents an important mechanism of gene silencing in carcinogenesis. Such epigenetic phenomena can act alongside DNA mutations and deletions to disrupt tumor-suppressor gene function. The methylation status of the promoter-associated CpG islands from 11 well-characterized cancer-related genes was analyzed by methylation-specific polymerase chain reaction in 60 adult patients with acute myelogenous leukemia (AML) at diagnosis. The frequency of aberrant methylation among the patient samples was 45.0% (27/60) for suppressor of cytokine signaling-1, 31.7% (19/60) for p15, 20.0% (12/60) for retinoic acid receptor beta2, 13.3% (8/60) for p73 and E-cadherin, 5.0% (3/60) for O(6)-methylguanine DNA methyltransferase, 3.3% (2/60) for death-associated protein kinase 1 and hMLH1, 1.7% (1/60) for p16, and 0% (0/60) for the tissue inhibitor of matrix metalloproteinases-3 and Ras association domain family 1A. Aberrant DNA methylation was found in AML of all French-American-British subtypes and throughout all cytogenetic risk groups. There appeared to be a trend towards a higher methylation frequency in AML patients with an unfavorable karyotype, but this difference was not statistically significant. Our data indicate that hypermethylation of multiple genes involving fundamental cellular pathways is a common event in AML, which varies greatly in frequency among the genes examined. The accumulation of epigenetic events affecting genes which are involved in regulating cell cycle inhibition, cell adhesion, growth factor signaling, and apoptosis may contribute to the malignant AML phenotype. The growing knowledge of the role of epigenetics in the aberrant silencing of cancer-related genes provides a rationale and molecular basis for targeted therapeutic approaches with demethylating agents in AML.
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PMID:Clinical implications of aberrant DNA methylation patterns in acute myelogenous leukemia. 1623 Nov 40

A variety of epigenetic changes contribute to transcriptional dysregulation in myelodysplastic syndromes (MDSs) and acute myeloid leukemia (AML). DNA methyltransferase (DNMT) inhibitors--azacitidine and decitabine--have significant activity in the treatment of MDS. Despite marked activity in myeloid malignancy, monotherapy with DNMT inhibitors is limited by low complete and partial response rates (7-20%) and median response durations of 15 months. As with classical cytotoxic therapy, the targeting of biologic pathways and mechanisms may best be accomplished using a combination of agents offering complementary mechanisms and synergistic pharmacodynamic interactions. The goal of this approach is to improve response rates, quality, and duration, and to minimize adverse events. There are a number of new therapies under development for the management of MDS and AML. This review article touches on some of the more promising combination regimens in various phases of investigation. The treatment of MDS and AML is undergoing rapid evolution. Cytogenetic complete remission and prolonged survival represent important goals. Incremental improvements in disease state and quality-of-life issues are also important for patients. Given the overall failure of cytotoxic chemotherapy in the achievement of cures in MDS and MDS-related AML, the application of less toxic, biologically directed agents may represent a more promising approach to treatment. Combination therapies with DNMT inhibitors using optimal dosing regimens to focus on methylation reversal with lower doses over longer periods of time, rather than direct cytotoxic effects, are beginning to suggest promising results in MDS and AML.
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PMID:Combination therapy with DNA methyltransferase inhibitors in hematologic malignancies. 1634 Dec 38

DNA methyltransferase (DNMT) inhibitors, azacitidine (Vidaza, Pharmion, Boulder, CO, USA) and decitabine (Dacogen; SuperGen Inc, Dublin, CA, USA, and MGI Pharma Inc, Bloomington, MN, USA), have had a significant impact on the treatment paradigm of myelodysplastic syndromes (MDSs), previously managed mainly by supportive care and hematopoietic-stem-cell transplantation. The positive clinical experience seen in MDS to date coupled with the persistent challenges faced in the treatment of other hematologic malignancies has served as the impetus for further exploration of the therapeutic value of DNMT inhibitors beyond MDS. In that respect, the majority of data for these agents are in the setting of acute myelogenous leukemia (AML). Experience with these agents in patients with refractory anemia with excess blasts in transformation (reclassified by the World Health Organization as AML) was also reported in the clinical trials submitted to the FDA for approval of azacitidine for MDS. Some use has also been described in chronic myelogenous leukemia and acute lymphocytic leukemia. Further studies are needed to clarify the appropriate dose and the number and duration of cycles in the treatment of leukemias, and to identify ideal candidates for therapy, explore the role of DNMT inhibitors in combination with other agents, especially histone deacetylase inhibitors, delineate differences between the commercially available agents, and establish the long-term safety of these agents. To this end, experience with DNMT inhibitors in hematologic malignancies other than MDS is reviewed in an effort to better understand the therapeutic potential of these agents and to define areas of future exploration in these settings.
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PMID:Inhibitors of DNA methylation: beyond myelodysplastic syndromes. 1634 Dec 39

Myelodysplastic syndrome (MDS) is a disorder of hematopoietic stem cells characterized by ineffective hematopoiesis. The result is pancytopenia leading to transfusion-dependent anemia, an increased risk of infection or bleeding, and a potential to progress to acute myeloid leukemia (AML). MDS is most prevalent among older individuals, many of whom also suffer from other medical conditions. MDS is classified according to World Health Organization criteria and the International Prognostic Scoring System. Supportive care remains the mainstay of therapy. Those with low-risk MDS can often be monitored for an extended period of time without specific therapy, whereas those with intermediate- or high-risk MDS benefit from treatment. Currently, only azacitidine is approved for the treatment of MDS. Several new agents are being tested, including inhibitors of angiogenesis (thalidomide, lenalidomide), farnesyl transferase inhibitors (lonafarnib, tipifarnib), and DNA methyltransferase inhibitors (azacitidine, decitabine). Lenalidomide appears particularly effective in patients with low-risk MDS with the deletion of chromosome 5q31. Allogeneic stem cell transplantation is an alternative for high-risk MDS. With advances in transplantation techniques, this treatment can be offered to an increasing number of patients. However, it is necessary to assess each patient's disease individually and to evaluate prognostic factors, other treatment options, and the appropriateness and timing of transplantation.
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PMID:Myelodysplasia: when to treat and how. 1651 26

Therapeutic options for patients with relapse of MDS or high risk AML after allogeneic stem cell transplantation are limited. We here present the case of a 64-year-old female patient with MDS, who received peripheral blood stem cells from her HLA-identical brother after a non-myeloablative conditioning regimen. Two months after allogeneic transplantation she suffered from a relapse, now fulfilling WHO criteria for AML with a bone marrow blast count of 91%. We then decided to treat her with azacitidine, a DNA methyltransferase inhibitor with proven antileukemic activity. The patient achieved a complete haematological response after two cycles and full donor chimerism after a single dose of donor lymphocytes. We postulate that azacitidine acts through a direct reduction of malignant cells and may in addition augment the immunologic effects of donor lymphocyte infusions.
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PMID:Successful treatment of relapsed AML after allogeneic stem cell transplantation with azacitidine. 1662 Sep 71


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