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Results for “Azacitidine”

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At least 271 records · Page 15Linked to original sources

PubMed1991

Effect of myogenic determination on tumorigenicity of chemically transformed 10T1/2 cells.

Transforming agents have been postulated to interfere with cellular differentiation programs, thus causing uncontrolled growth. Inducing transformed cells to differentiate can result in loss of the transformed phenotype since many end-stage differentiated cells are unable to divide. We attempted to bypass or suppress the tumorigenic phenotype of 3-methylcholanthrene (MCA)-transformed 10T1/2 cells (MCA Cl 15C1) by induction of myogenic determination. MCA Cl 15C1 cells were either treated with the hypomethylating drug 5-azacytidine (5-aza-CR) or were transfected with the muscle determination gene MyoD1, both of which induce a myogenic phenotype in 10T1/2 cells. Colonies containing myoblast-like cells were isolated and examined. Muscle markers were detected both in 5-aza-CR-treated and in MyoD1-transfected myogenic clones by immunofluorescence and northern analyses. The myogenic clones did not show decreased tumorigenicities relative to that of the parental cells upon subcutaneous injection in nude mice. Some of the resulting tumors, however, were classified as rhabdomyosarcomas rather than fibrosarcomas. Although induction of myogenic determination was not sufficient to abolish the tumorigenic phenotype of MCA Cl 15C1 cells, several tumors showed decreased levels of MyoD1 mRNA, suggesting that growth in vivo either selected for or caused decreased determination gene expression.

Animals↗

PubMed1976

Inhibition of uridine-cytidine kinase by 5-azacytidine 5'-triphosphate.

5-Azacytidine 5'-triphosphate (5-aza-CTP) inhibited the phosphorylation of uridine, cytidine, and 5-azacytidine (5-aza-C) in a reaction catalyzed by uridine-cytidine kinase. The inhibition appeared to be competitive with respect to the adenosine 5'-triphosphate and noncompetitive with respect to nucleoside substrates. 5-aza-CTP was a potent inhibitor of 5-aza-C phosphorylation but a weak inhibitor of uridine and cytidine phosphorylation. These results suggest that the feedback inhibition of uridine-cytidine kinase by 5-aza-CTP may limit the amount of intracellular nucleotide analog formed in drug-treated cells.

Azacitidine↗

PubMed1976

A new hamster fibrosarcoma model for in vitro/in vivo evaluation of cancer chemotherapeutic agents.

A hamster fetal cell clone has been developed for in vitro chemotherapeutic studies as well as in an in vivo fibrosarcoma model system. Highly reproducible quantitative in vitro chemotherapeutic data can be obtained with this cell line within 5 days, and as few as 10(2) cells produce rapidly growing fibrosarcomas when injected subcutaneously into adult hamsters. We found using these cells in vitro that 1-beta-D-arabinofuranosylcytosine (ara-C) can antagonize the effect of 5-azacytidine (aza-C) if given simultaneously or if aza-C treatment is preceded by a 2-hr exposure to ara-c. Using the same cell line as in vivo model for chemotherapy it was also shown that ara-C and cyclocytidine significantly inhibited tumor growth. This hamster cell line may be quite useful as an in vitro/in vivo model system for the study of cancer chemotherapeutic agents.

Ancitabine↗

PubMed1978

Phase II study of subcutaneously administered 5-azacytidine (NSC-102816) in patients with metastatic malignant melanoma.

Thirty (30) patients with advanced metastatic malignant melanoma refractory to DTIC (NSC-45388) and a nitrosourea were treated with 5-azacytidine (NSC-102816). 5-Azacytidine was administered subcutaneously at a dosage of 100 mg/m2/day for 10 days. Twenty-six (26) patients were evaluable for toxicity and response. Major organ toxicities were hematologic, gastrointestinal, and cutaneous; no antitumor activity was noted.

Azacitidine↗

PubMed1986

Induction failures in childhood acute nonlymphocytic leukemia: etoposide/5-azacytidine for cases refractory to daunorubicin/cytarabine.

Treatment with a combination of daunorubicin (45 mg/m2 IV, days 1-3) and cytarabine (100 mg/m2 continuous IV infusion, days 4-10) failed to induce complete remission in 31 of 87 children (36%) with acute nonlymphocytic leukemia (ANLL). Six patients with monocytic or promyelocytic leukemia died before day 14 of therapy from complications of hyperleukocytosis and coagulopathy; an additional 10 failed because of fatal infections associated with drug-induced marrow hypoplasia, and the remaining 15 had residual leukemia despite receiving two courses of daunorubicin and cytarabine. Alternative therapy with etoposide (250 mg/m2, IV, days 1-3, 7-9) and 5-azacytidine (300 mg/m2 IV, days 4, 5, 9, 10) induced complete remission in nine (60%) of the 15 patients with resistant leukemia. Among the six children who failed to respond to either regimen, three had cytochemical and immunophenotypic features indicative of acute mixed-lineage leukemia, and one had monosomy 7 syndrome. Our findings suggest that the addition of etoposide and 5-azacytidine to a basic daunorubicin-cytarabine regimen would increase remission induction rates in childhood ANLL. Careful determination of pretreatment characteristics, including blast cell immunophenotype and cytogenetic properties, are needed to identify unusual cases of ANLL that may require selective therapy.

Acute Disease↗

PubMed2001

DNA hypomethylation of karyoplasts for bovine nuclear transplantation.

The objective of this research was to evaluate if DNA hypomethylation in cells used as karyoplasts would improve development of bovine nuclear transplantation (NT) embryos. DNA from serum-fed (SF), serum-starved (SS), and 1, or 5 microM 5-azacytidine (5-aza-CR) treated cells was digested with a methylation sensitive enzyme, and evaluated for DNA methylation. A significant reduction in DNA methylation was observed in cells cultured for 48 or 72 hr in SS medium as well as in cells cultured for 48 hr in the presence of 5 microM 5-aza-CR when compared to cells cultured in SF medium. All other comparisons contained no significant differences when compared to controls. When donor cells were cultured in 5-aza-CR, SF, or SS treatment media for 48 hr, no significant difference was observed (P = 0.06) in blastocyst development rates after NT. One embryo produced by donor cells treated with 5-aza-CR established a pregnancy. Four pregnancies resulted from embryos produced by SS donor cell NT and 3 resulted from embryos produced by SF donor cell NT. Supplementation of the donor cell culture medium with 5-aza-CR was not beneficial for increasing blastocyst rate or establishing pregnancy after NT.

Animals↗

PubMed1993

Transient expression of a human beta-actin promoter/lacZ gene introduced into mouse embryos correlates with a low degree of methylation.

We have analysed the correlation between expression and methylation for the human beta-actin promoter introduced into mouse embryos. The beta-actin promoter was fused to the reporter gene lacZ, and expression was analysed after pronuclear injection into fertilized mouse eggs. We analysed transient expression in in vitro cultured preimplantation embryos and expression after chromosomal integration in 5 independent lines of transgenic mice. The in vitro cultured preimplantation embryos expressed lacZ from the 2-cell to the blastocyst stages, and most abundantly at the morula stage. By increasing the amount of injected DNA, a larger proportion of embryos expressed lacZ. Embryos expressing lacZ in only a subset of the blastomeres were detected at all preimplantation stages. In contrast to the transient expression after injection, we have not detected lacZ expression in any of the 5 analysed lines of transgenic mice carrying the same construct. The lack of expression in transgenic mice correlates with hypermethylation of C residues in the vast majority of CG sequences in the integrated beta-actin/lacZ construct, whereas the injected construct was completely nonmethylated. We discuss methylation and other possible reasons for the observed differences in expression between injected and integrated copies of the beta-actin/lacZ construct and for lacZ expression in only a subset of blastomeres in preimplantation embryos.

Actins↗

PubMed1995

5-Aza deoxyCytidine-induced inhibition of differentiation of spermatogonia into spermatocytes in the mouse.

In order to explore the significance of DNA methylation in proliferation and differentiation of germ cells in testis, 5-aza,2'-deoxyCytidine (5-azaCdR), a hypomethylating agent, was administered in vivo to neonatal mice having only spermatogonial (premeiotic) cells. End-labeling of the MspI, HpaII, and HhaI digested DNA revealed considerable loss of methylation following the treatment. Cellular and histological preparations of the testis showed complete inhibition of differentiation into spermatocytic stage. Analysis of protein synthesis in the treated and control testis by growing the cells in 35S-Methionine medium and resolving the lysate by SDS-PAGE revealed that the programme of expression of at least 5 polypeptides (35.0, 31.5, 27.0, 22.5, and 18.0 KD) was altered as a result of 5-azaCdR incorporation. It appears that DNA methylation plays a critical role in the differentiation of gonia into primary spermatocytes.

Animals↗

PubMed1995

Myogenic cells derived from rat bone marrow mesenchymal stem cells exposed to 5-azacytidine.

The compound 5-azacytidine has been previously shown to convert cells of the rat embryonic fibroblastic cell line, C3H/10T1/2, into myoblasts, adipocytes, and chondrocytes. Rare, resident cells of bone marrow and periosteum, referred to as mesenchymal stem cells, have been shown to differentiate into a number of mesenchymal phenotypes including bone, cartilage, and adipocytes. Rat bone marrow-derived mesenchymal stem cells were exposed to 5-azacytidine beginning 24 h after seeding twice-passaged cells into culture dishes. After an exposure of 24 h, long, multinucleated myotubes were observed in some of the dishes 7-11 days later. Cells containing Sudan black-positive droplets in their cytoplasm were also observed. Thus, culture-propagated rat bone marrow mesenchymal stem cells appear to have the capacity to be induced to differentiate in vitro into myogenic and adipocytic phenotypes, although nonmesenchymal cells (rat brain fibroblasts) cannot be so induced. Taken together, these observations provide support for the suggestion that mesenchymal stem cells in the bone marrow of postnatal organisms may provide a source for myoprogenitor cells which could function in clinically relevant myogenic regeneration.

Adipocytes↗

PubMed2005

Differential properties of dentate gyrus and CA1 neural precursors.

In the present article we investigated the properties of CA1 and dentate gyrus cell precursors in adult rodents both in vivo and in vitro. Cell proliferation in situ was investigated by rating the number of cells incorporating BrdU after kainate-induced seizures. CA1 precursors displayed a greater proliferation capacity than dentate gyrus precursors. The majority of BrdU-labeled cells in CA1 expressed Nestin and Mash-1, two markers of neural precursors. BrdU-positive cells in the dentate gyrus expressed Nestin, but only a few expressed Mash-1. In animals pretreated with the antimitotic azacytidine, the capacity of kainate to enhance the proliferation was higher in CA1 than in the dentate gyrus. Differences in intrinsic progenitor cell activity could underlie these different expansion capacities. Thus, we compared the renewal- expansion and multipotency of dentate gyrus and CA1 precursors isolated in vitro. We found that the dissected CA1 region, including the periventricular zone, is enriched in neurosphere-forming cells (presumed stem cells), which respond to either EGF or FGF-2. Dentate gyrus contains fewer neurosphere-forming cells and none that respond to FGF-2 alone. Neurospheres generated from CA1 were multipotent and produced neurons, astrocytes, and oligodendrocytes, while dentate gyrus neurospheres mostly produced glial cells. The analysis of the effects of EGF on organotypic cultures of hippocampal slices depicted similar features: BrdU and Nestin immunoreactivities increased after EGF treatment in CA1 but not in the dentate gyrus. These results suggest that CA1 precursors are more stem-cell-like than granule cell precursors, which may represent a more restricted precursor cell.

Analysis of Variance↗

PubMed2003

Reduced expression of oestrogen receptor beta in invasive breast cancer and its re-expression using DNA methyl transferase inhibitors in a cell line model.

To gain insights into the possible role of oestrogen receptor (ER) beta in breast carcinogenesis, immunohistochemical analysis of ER beta was performed on 512 breast specimens encompassing normal (n = 138), pure ductal carcinoma in situ (n = 16), invasive cancers (n = 319), lymph node metastases (n = 31), and recurrences (n = 8). Real-time polymerase chain reaction (PCR) was used to investigate the methylation status of the ER beta gene in the ER beta negative breast cancer cell lines SkBr3 and MDA-MB-435. A gradual reduction in, but not a complete loss of, ER beta expression was observed during the transition from normal and pre-invasive lesions to invasive cancers, where ER beta was lost in 21% of cases. This was more pronounced in invasive ductal than in lobular carcinomas, a significantly higher proportion of which were ER beta-positive (74% compared with 91%, respectively, p = 0.0004). Examination of paired primary cancers with their axillary lymph node metastases showed that if ER beta was present in the primary tumour, it persisted in the metastasis. Treatment of ER beta-negative cell lines with DNA methyl transferase inhibitors restored ER beta expression, providing experimental evidence that silencing of ER beta in breast carcinomas could be due to promoter hypermethylation. These results suggest that loss of ER beta expression is one of the hallmarks of breast carcinogenesis and that it may be a reversible process involving methylation.

Age Factors↗

PubMed2003

Apoptosis of terminal hypertrophic chondrocytes in an in vitro model of endochondral ossification.

It is widely accepted that growth plate chondrocytes undergo apoptosis when they reach the terminal hypertrophic stage of their differentiation during the process of endochondral ossification in vivo. In this report, an established chondrocyte cell culture model of mammalian endochondral ossification was utilized to investigate the fate of chondrocytes after they had entered hypertrophy in vitro. Fetal bovine epiphyseal chondrocytes were treated with the demethylating agent, 5-azacytidine, for 48 h and then cultured under azacytidine-depleted conditions. There was evidence for apoptosis in azacytidine-treated cells, as demonstrated by nuclear condensation and fragmentation (days 27 and 35) using transmission electron microscopy, and the detection of exposed phosphatidylserine on the plasma membrane surface of apoptotic chondrocytes (day 27) using fluorescence-labelled annexin V. Treated cultures on days 10 and 20 and untreated cultures at all corresponding time-points showed no morphological characteristics of apoptosis. In situ hybridization studies of treated cultures revealed that expression of the apoptotic suppressor, bcl-2, remained consistently high throughout the culture period, whilst the apoptotic inducer, bax, was not expressed until day 23. Quantification of these data showed a gradual shift in the ratio of the expression level of bcl-2 and bax in favour of bax with time in culture, particularly from day 23 onwards. Taken together, the results indicate that azacytidine-treated epiphyseal chondrocytes entered terminal hypertrophy from day 23 onwards in culture and died by apoptosis. This study confirms this culture system as a successful recapitulation of the entire mammalian chondrocyte differentiation pathway, including apoptosis. The culture model will prove valuable for studies of the apoptotic fate of terminally differentiated chondrocytes in the growth plate with a view to providing a better understanding of the underlying mechanisms of skeletal malformations and other pathological disorders such as osteoarthritis.

Animals↗

PubMed2003

Altered expression of the septin gene, SEPT9, in ovarian neoplasia.

The septin family of genes has been implicated in a variety of cellular processes including cytokinesis, membrane transport and fusion, exocytosis, and apoptosis. One member of the septin family maps to chromosome 17q25.3, a region commonly deleted in sporadic ovarian and breast tumours, and has also been identified as a fusion partner of MLL in acute myeloid leukaemias. The present study demonstrates that the pattern of expression of multiple splice variants of this septin gene is altered in ovarian tumours and cell lines. In particular, expression of the zeta transcript is detectable in the majority of tumours and cell lines, but not in a range of non-malignant adult and fetal tissues. Zeta expression is accompanied by loss of the ubiquitous beta transcript. Somatic mutations of the gene were not detected in ovarian tumours, but it was demonstrated that beta expression in tumour cell lines can be reactivated by 5-azacytidine treatment, suggesting a role for methylation in the control of expression of this gene.

Adult↗

PubMed2007

Improved outcome in childhood acute myeloid leukemia in Singapore with the MRC AML 10 protocol.

BACKGROUND: The introduction of the United Kingdom Medical Research Council's 10th AML trial (MRC AML 10) protocol incorporating high-dose anthracycline therapy has improved outcome of children with acute myeloid leukemia (AML). In this study, we review the results of childhood AML therapy in a Singapore university hospital over the last 17 years emphasizing toxicity and outcome. PROCEDURE: Retrospective analysis revealed 34 children with AML between 1988 and 2003. Prior to September 1996, therapy consisted of: POG-8498 (n = 10), others (n = 9). From September 1996, all but one of 15 children received MRC AML 10 treatment. RESULTS: At the time of analysis, 17 had died from disease, and 17 patients were alive among whom 2 had relapsed. MRC AML 10-treated patients (n = 14) had significantly better 3-year overall, event-free, and disease-free survival (74% vs. 35%, 77% vs. 20%, 83% vs. 31%; P = 0.019, P = 0.002, and P = 0.010, respectively) and were likelier to achieve complete remission (CR) than non-MRC AML 10 patients (P = 0.102). Among patients who achieved CR, MRC AML 10-treated patients were significantly more likely to achieve CR after only one cycle of chemotherapy (P = 0.016). Hematologic toxicity was similar among the different regimens (P = 0.9). CONCLUSIONS: These findings suggest that MRC AML 10 treatment results in significantly superior survival, without excess toxicity. Future studies should attempt to elucidate the relative importance of individual MRC AML 10 components and reduce the high cumulative anthracycline dose without compromising outcome.

Acute Disease↗

PubMed2003

Proteomic analysis of a lymphoma-derived cell line (DG75) following treatment with a demethylating drug: modification of membrane-associated proteins.

5'-azacytidine (AZC) is a potent DNA demethylating agent used clinically for treatment of patients with malignant hemopathies. We have previously shown that AZC induces a halt in cell growth and a decrease of cell activity, without affecting cell viability. We have also shown using proteomics, that 35 polypeptides were differentially expressed in a cytoplasmic fraction. The aim of this study was to provide a more complete picture of modifications in AZC-treated cells using cell membrane preparations. Therefore the protein pattern changes following AZC treatment of the cell line DG75 were studied on a detergent-solubilized fraction obtained from these membranes. Results showed that 49 proteins were differentially expressed in the membrane fraction. Seven polypeptides were down-regulated, while 42 were up-regulated. The identity of most of these differentially expressed proteins was determined by mass spectrometry (liquid chromatography-tandem mass spectrometry or matrix-assisted laser desorption/ionization-time of flight), and the identified proteins were grouped based on cellular function and participation in biochemical and signaling pathways.

Antimetabolites, Antineoplastic↗

PubMed2006

Cytogenetic and expression profiles associated with transformation to androgen-resistant prostate cancer.

BACKGROUND: The mechanisms underlying the progression of prostate cancer to androgen-resistant cancer are still not fully understood. Here, we studied the genetic events associated with this transformation. METHODS: The androgen sensitive prostate cancer cells line LNCaP-FGC and its androgen resistant subline LNCaP-r were investigated using SKY, CGH, and cDNA microarray. RESULTS: Karyotypically, several additional chromosomal aberrations were seen in LNCaP-r as compared to the parental line. CGH also revealed unique net chromosomal alterations in LNCaP-r compared to LNCaP-FGC, including gain of 2p13-23, 2q21-32, and 13q and loss of 6p22-pter. cDNA microarray analysis identified several genes involved in DNA methylation, such as DNMT2, DNMT3a, and methyl-CpG binding domain protein 2 and 4 that were higher expressed in LNCaP-r. Interestingly, androgen responsiveness of LNCaP-r was restored after treated with DNA methyltransferase inhibitor. CONCLUSIONS: Our findings may serve as a basis for molecular dissection of the mechanisms involved in development of androgen resistant prostate cancer.

Androgens↗

PubMed2006

Characterization of decomposition products and preclinical and low dose clinical pharmacokinetics of decitabine (5-aza-2'-deoxycytidine) by a new liquid chromatography/tandem mass spectrometry quantification method.

Aberrant DNA methylation patterns resulting in gene transcriptional repression are observed in numerous cancers. Decitabine, a DNA methyltransferase inhibitor, is being clinically evaluated in patients with hematologic malignancies and solid tumors. Decitabine is rather unstable and decomposes to 1-beta-D-2'-deoxyribofuranosyl-3-guanylurea under basic conditions and several additional unknown products under neutral conditions. This has greatly limited application of pharmacokinetic assays to clinical development of decitabine. In this paper, a high-performance liquid chromatography/ultraviolet multi-stage mass spectrometry (HPLC-UV-MSn) study of the decomposition of decitabine in water and human plasma revealed that these previously unknown products are isomers of the intermediates formyl-1-beta-D-2'-deoxyribofuranosyl-3-guanylurea and 1-beta-D-2'-deoxyribofuranosyl-3-guanylurea. A HPLC tandem mass spectrometry (MS/MS) method for the determination of decitabine concentrations in human and rat plasma has been developed. This method was based on a specific fragmentation pathway of the molecular ion of decitabine at m/z 229 to generate a unique fragment ion at m/z 113 under collision-induced dissociation. Separation of decitabine and the stable internal standard dihydro-5-aza-cytidine from the endogenous interfering substance in plasma extract was carried out on a C18 Aquasil column under an isocratic elution with a mobile phase consisting of 5% water/acetonitrile and 10 mM ammonium formate. The detection of decitabine was via selected reaction monitoring (SRM, 229 > 113), and its ionization was enhanced by post-column addition of acetonitrile. Effects of sample preparation and handling parameters on the stability of decitabine were also evaluated in human plasma at various temperatures. The accuracy and precision of this assay showed a coefficient of variation of <15% over the range of 0.5-25 ng for rat plasma and 0.1-25 ng for human plasma injected on-column. Pharmacokinetics of decitabine in rats following intravenous doses of 1.0 and 5.0 mg/kg were characterized. In the rat, plasma concentration-time profiles were found to follow a biexponential decline and the pharmacokinetics was dose-independent. Application of this decitabine pharmacokinetic assay to human studies is therefore justified and ongoing.

Animals↗

PubMed1986

Effect of 5-azacytidine on the differentiation of human leukemia K-562 cells.

The treatment of K-562 cells with 10(-5) M to 10(-7) M 5-azacytidine induced a marked increase in benzidine-positive cells. Similarly, the exposure of K-562 cells to 2 X 10(-3) M butyric acid or 5 X 10(-7) M 1-beta-arabinofuranosylcytosine or 1 X 10(-3) M hydroxyurea induced an erythroid differentiation of K-562 cells. The activity of DNA-methyltransferase and the level of methylcytosine in newly synthesized DNA were significantly decreased when the cells were treated with 5-azacytidine or butyric acid, while 1-beta-arabinofuranosylcytosine or hydroxyurea had no inhibitory effect on DNA-methylation of K-562 cells. These results suggest that the inhibition of DNA-methylation is not necessarily a specific phenomenon for erythroid differentiation of K-562 cells.

Azacitidine↗