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

In 1992-1993, synergistic interaction of ribonucleotide reductase inhibitors (fludarabine, cladribine) and cytarabine (Ara-C) increasing Ara-CTP concentration in myeloblasts was proved. Based on these findings and encouraging results of the addition of cladribine to standard daunorubicin+Ara-C induction regimen (DAC) in acute myeloid leukemia (AML), the Polish Adult Leukemia Group (PALG) conducted a pilot study on the administration of cytarabine, daunorubicin, and fludarabine (DAF) as a reinduction treatment of AML to assess tolerance, toxicity, and early outcome. The DAF regimen consisted of daunorubicine 60 mg m(-2) day(-1) iv on days 1-3 and fludarabine 25 mg m(-2) day(-1) iv on days 1-5 given before cytarabine 200 mg m(-2) day(-1) in ci on days 1-7. Thirty-four AML patients with median age 39, 24% relapsed and 76% refractory, were included into the study between September 2003 and August 2004. Achieved response rate in the whole study population was 56%; n = 16 patients with complete remission (CR), and n = 3 patients with partial remission (PR). Fifteen of 16 patients achieved CR after the first course of therapy. Only 9% of total population died before the assessment of remission. All patients developed severe neutropenia. Serious infections were observed in 47% of the cases. Severe thrombocytopenia was observed in 72% of the patients. All patients required substitution of platelet concentrates (median 4), and PRBC (median 5). Severe alopecia, mucositis, vomiting were of low frequency. Liver, kidney, or circulatory failure, diarrhea, or polyneuropathy were not observed. The probability of overall survival (OS) for 1 year for the whole study population (34 patients) and the group of 16 patients in CR was: 44% (95% confidence interval [CI] 36-52%) and 69% (95% CI 55-83%), respectively. The probability of leukemia-free survival (LFS) for 1 year was 38% (95% CI 22-54%). Summarizing, DAF regimen used as the induction therapy in relapsed/refractory AML was well tolerated with acceptable toxicity and early efficacy.
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PMID:Daunorubicin, cytarabine and fludarabine (DAF) for remission induction in relapsed or refractory acute myeloid leukemia. Evaluation of safety, tolerance and early outcome--Polish Adult Leukemia Group (PALG) pilot study. 1807 33

Enzyme kinetics of GTI-2040 (5'-GGC TAA ATC GCT CCA CCA AG-3'), a phosphorothioate ribonucleotide reductase antisense, were investigated for the first time in 3' exonuclease solution and human liver microsomes (HLMs), using the ion-pair high-performance liquid chromatogram method for quantification of the parent drug and two major 3'N-1 and 3'N-2 metabolites. Enzyme kinetics of GTI-2040 in 3'-exonuclease solution were found to be well characterized by the Michaelis-Menten model, using the sum of formation rates of 3'N-1 and 3'N-2 (approximately total metabolism) because of sequential metabolism. In HLMs, a biphasic binding was observed for GTI-2040 with high- and low-affinity constants (K(d)s) of 0.03 and 3.8 microM, respectively. Enzyme kinetics of GTI-2040 in HLMs were found to deviate from Michaelis-Menten kinetics when the total GTI-2040 substrate was used. However, after correction for the unbound fractions, the formation rate of total metabolites could be described by Michaelis-Menten kinetics. Using the free substrate fraction, the K(m) and V(max) of GTI-2040 were determined to be 6.33 +/- 3.2 microM and 16.5 +/- 8.4 nmol/mg/h, respectively. Using these values, in vitro hepatic intrinsic clearance (CL(int)) in HLM was estimated to be 2.61 +/- 0.56 ml/h. The CL(int) was then used to predict GTI-2040's in vivo intrinsic clearance in humans by a microsomal protein scaling factor, which gave a mean value of 182.7 l/h, representing 24.1% of the observed in vivo mean scaled hepatic intrinsic clearance of 758.7 l/h in patients with acute myeloid leukemia. We concluded that the saturable nonspecific binding of GTI-2040 in HLMs complicated the interpretation of its enzyme kinetics, and scaled intrinsic clearance from HLMs only partially predicted the in vivo intrinsic clearance.
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PMID:Enzyme kinetics of GTI-2040, a phosphorothioate oligonucleotide targeting ribonucleotide reductase. 1865 46

Approximately 4000 children and adolescents under the age of 20 years develop acute leukemia per year in the US. Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. Despite impressive improvements in outcome, relapsed ALL is the fourth most common pediatric malignancy. Therapy for relapsed ALL remains unsatisfactory, and the majority of relapse patients still succumb to leukemia. Between one-third and one-half of patients with acute myelogenous leukemia (AML) relapse, and no standard therapy is recognized for patients with relapsed and/or refractory AML. Novel therapeutic agents are needed to improve the cure rate for relapsed ALL and AML. Clofarabine is a next-generation nucleoside analog, designed to incorporate the best features and improve the therapeutic index of cladribine and fludarabine. Clofarabine inhibits both DNA polymerase and ribonucleotide reductase, leading to impaired DNA synthesis and repair, and directly induces apoptosis. Phase I and II single-agent trials in children have shown that clofarabine is safe and active in both myeloid and lymphoid relapsed/refractory acute leukemias. Clofarabine has been approved by the FDA for pediatric patients with relapsed/refractory ALL after at least 2 prior therapeutic attempts. Rational combinations of clofarabine with other active agents in refractory leukemias are currently under investigation.
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PMID:Treating refractory leukemias in childhood, role of clofarabine. 1872 51

While the therapeutic activity of the deoxycytidine analogue decitabine is thought to reflect its ability to reactivate methylation-silenced genes, this agent is also known to trigger p53-dependent DNA damage responses. Here, we report that p53-inducible ribonucleotide reductase (p53R2/RRM2B) is a robust transcriptional target of decitabine. In cancer cells, decitabine treatment induces p53R2 mRNA expression, protein expression, and promoter activity in a p53-dependent manner. The mechanism of p53R2 gene induction by decitabine does not seem to be promoter DNA hypomethylation, as the p53R2 5' CpG island is hypomethylated before treatment. Small interfering RNA (siRNA) targeting of DNA methyltransferase 1 (DNMT1) in wild-type p53 cells leads to genomic DNA hypomethylation but does not induce p53R2, suggesting that DNMT/DNA adduct formation is the molecular trigger for p53R2 induction. Consistent with this idea, only nucleoside-based DNMT inhibitors that form covalent DNA adducts induce p53R2 expression. siRNA targeting of p53R2 reduces the extent of cell cycle arrest following decitabine treatment, supporting a functional role for p53R2 in decitabine-mediated cellular responses. To determine the clinical relevance of p53R2 induction, we measured p53R2 expression in bone marrow samples from 15 myelodysplastic syndrome/acute myelogenous leukemia (MDS/AML) patients undergoing decitabine therapy. p53R2 mRNA and protein were induced in 7 of 13 (54%) and 6 of 9 (67%) patients analyzed, respectively, despite a lack of methylation changes in the p53R2 promoter. Most notably, there was a significant association (P = 0.0047) between p53R2 mRNA induction and clinical response in MDS/AML. These data establish p53R2 as a novel hypomethylation-independent decitabine gene target associated with clinical response.
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PMID:p53-inducible ribonucleotide reductase (p53R2/RRM2B) is a DNA hypomethylation-independent decitabine gene target that correlates with clinical response in myelodysplastic syndrome/acute myelogenous leukemia. 1901 Sep 10

Off-patent drugs with previously unrecognized anticancer activity could be rapidly repurposed for this new indication. To identify such compounds, we conducted 2 independent cell-based chemical screens and identified the antimicrobial ciclopirox olamine (CPX) in both screens. CPX decreased cell growth and viability of malignant leukemia, myeloma, and solid tumor cell lines as well as primary AML patient samples at low-micromolar concentrations that appear pharmacologically achievable. Furthermore, oral CPX decreased tumor weight and volume in 3 mouse models of leukemia by up to 65% compared with control without evidence of weight loss or gross organ toxicity. In addition, oral CPX prevented the engraftment of primary AML cells in nonobese diabetic/severe combined immunodeficiency mouse models, thereby establishing its ability to target leukemia stem cells. Mechanistically, CPX bound intracellular iron, and this intracellular iron chelation was functionally important for its cytotoxicity. By electron paramagnetic resonance, CPX inhibited the iron-dependent enzyme ribonucleotide reductase at concentrations associated with cell death. Thus, in summary, CPX has previously unrecognized anticancer activity at concentrations that are pharmacologically achievable. Therefore, CPX could be rapidly repurposed for the treatment of malignancies, including leukemia and myeloma.
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PMID:Chelation of intracellular iron with the antifungal agent ciclopirox olamine induces cell death in leukemia and myeloma cells. 1979 31

Clofarabine is a second-generation purine nucleoside analogue. It works mainly by inhibiting ribonucleotide reductase and incorporating into DNA. Clofarabine has shown efficacy in selected pediatric leukemias. It has also shown significant efficacy alone and in combination with other drugs in treating adult myeloid leukemias and high-risk myelodysplastic syndromes. Further, there is significant promise for clofarabine in the treatment of older patients with acute myeloid leukemia who are unlikely to benefit from standard induction chemotherapy due to unfavorable baseline prognostic factors. An oral formulation of clofarabine is also currently under development.
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PMID:Clofarabine: emerging role in leukemias. 1971 46

The mainstay of acute myeloid leukemia chemotherapy is the nucleoside analog cytarabine (ara-C). Numerous studies suggest that the intracellular concentrations of the ara-C active metabolite, ara-CTP, vary widely among patients and, in turn, are associated with variability in clinical response to acute myeloid leukemia treatment. Thus, genetic variation in key genes in the ara-C metabolic pathway--specifically, deoxycytidine kinase (a rate-limiting activating enzyme), 5 nucleotidase, cytidine deaminase and deoxycytidylate deaminase (all three are inactivating enzymes), human equilibrative nucleoside transporter (ara-C uptake transporter) and ribonucleotide reductase (RRM1 and RRM2--enzymes regulating intracellular deoxycytidine triphosphate pools)--form the molecular basis of the interpatient variability observed in intracellular ara-CTP concentrations and response to ara-C. Understanding genetic variants in the key candidate genes involved in the metabolic activation of ara-C, as well as the pharmacodynamic targets of ara-C, will provide an opportunity to identify patients at an increased risk of adverse reactions or decreased likelihood of response, based upon their genetic profile, which in future could help in dose optimization to reduce drug toxicity without compromising efficacy. The pharmacogenetic studies on ara-C would also be equally applicable to other nucleoside analogs, such as gemcitabine, decitabine, clofarabine and so on, which are metabolized by the same pathway.
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PMID:Genetic factors influencing cytarabine therapy. 1984 38

Therapeutic use of oligodeoxynucleotides (ODNs) that hybridize to and downregulate target mRNAs encoding proteins that contribute to malignant transformation has a sound rationale, but has had an overall limited clinical success in cancer due to insufficient intracellular delivery. Here we report a development of formulations capable of promoting targeted delivery and enhanced pharmacologic activity of ODNs in acute myeloid leukemia (AML) cell lines and patient primary cells. In this study, transferrin (Tf) conjugated pH-sensitive lipopolyplex nanoparticles (LPs) were prepared to deliver GTI-2040, an antisense ODN against the R2 subunit of ribonucleotide reductase that has been shown to contribute to chemoresistance in AML. LPs had an average particle size around 110 nm and a moderately positive zeta potential at approximately 10 mV. The ODN encapsulation efficiency of LPs was >90%. These nanoparticles could release ODNs at acidic endosomal pH and facilitate the cytoplasmic delivery of ODNs after endocytosis. In addition, Tf-mediated targeted delivery of GTI-2040 was achieved. R2 downregulation at both mRNA and protein levels was improved by 8-fold in Kasumi-1 cells and 2- to 20-fold in AML patient primary cells treated with GTI-2040-Tf-LPs, compared to free GTI-2040 treatment. Moreover, Tf-LPs were more effective than nontargeted LPs, with 10 to 100% improvement at various concentrations in Kasumi-1 cells and an average of 45% improvement at 3 microM concentration in AML patient primary cells. Treatment with 1 microM GTI-2040-Tf-LPs sensitized AML cells to the chemotherapy agent cytarabine, by decreasing its IC(50) value from 47.69 nM to 9.05 nM. This study suggests that the combination of pH sensitive LP formulation and Tf mediated targeting is a promising strategy for antisense ODN delivery in leukemia therapy.
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PMID:Targeted delivery of antisense oligodeoxynucleotide by transferrin conjugated pH-sensitive lipopolyplex nanoparticles: a novel oligonucleotide-based therapeutic strategy in acute myeloid leukemia. 1985 11

GTI-2040 is a potent antisense to the M2 subunit of the ribonucleotide reductase (RNR), an enzyme involved in the de novo synthesis of nucleoside triphosphates. We hypothesized that combination of GTI-2040 with the cytarabine (Ara-C) could result in an enhanced cytotoxic effect with perturbed intracellular deoxynucleotide/nucleotide (dNTP/NTP) pools including Ara-C triphosphate (Ara-CTP). This study aims to provide a direct experimental support of this hypothesis by monitoring the biochemical modulation effects, intracellular levels of Ara-CTP, dNTPs/NTPs following the combination treatment of Ara-C, and GTI-2040 in K562 human leukemia cells. GTI-2040 was introduced into cells via electroporation. A hybridization-ligation ELISA was used to quantify intracellular GTI-2040 concentrations. Real-time PCR and Western blot methods were used to measure the RNR M2 mRNA and protein levels, respectively. 3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay was used to measure the cytotoxicity following various drug treatments. A non-radioactive HPLC-UV method was used for measuring the intracellular Ara-CTP, while a LC-MS/MS method was used to quantify intracellular dNTP/NTP pools. GTI-2040 was found to downregulate M2 mRNA and protein levels in a dose-dependent manner and showed significant decrease in dNTP but not NTP pool. When combining GTI-2040 with Ara-C, a synergistic cytotoxicity was observed with no further change in dNTP/NTP pools. Importantly, pretreatment of K562 cells with GTI-2040 was found to increase Ara-CTP level for the first time, and this effect may be due to inhibition of RNR by GTI-2040. This finding provides a laboratory justification for the current phase I/II evaluation of GTI-2040 in combination with Ara-C in patients with acute myeloid leukemia.
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PMID:Biochemical modulation of aracytidine (Ara-C) effects by GTI-2040, a ribonucleotide reductase inhibitor, in K562 human leukemia cells. 2119 77

Nucleoside analogs are widely used for treatment of various malignancies. Benchmark drugs are cytarabine for acute myeloid leukemia and gemcitabine for pancreatic and lung cancer. Sapacitabine is a novel cytidine analog currently in development. This editorial focuses on the potential of new nucleoside analogs and on novel possibilities of gemcitabine. Gemcitabine is a nucleoside analog with many faces, which shows a remarkable activity in a variety of cancers, most likely because it has a unique metabolism, a so-called self-potentiation. Gemcitabine is taken up by nucleoside transporters, is activated by deoxycytidine kinase and incorporated into both RNA and DNA. Inhibition of ribonucleotide reductase and dCMP deaminase enhances its activation, while cytidine deaminase converts gemcitabine to its presumably inactive metabolite 2',2'-difluorodeoxyuridine, which in its nucleotide form may inhibit thymidylate synthase. Gemcitabine is widely used in combination, predominantly with a platinum analog, with other combinations less frequently used or being explored. Standard administration of gemcitabine is with a 30-min weekly infusion at 1000 mg/m(2), but alternatives are being explored such as prodrugs (e.g., CO-1.01, which can bypass transport deficiency), the fixed-dose rate infusion (10 mg/m(2)/min), and local routes of administration by a 24-h hepatic artery infusion, by instillation in the bladder or by intraperitoneal administration to treat advanced ovarian cancer. Other alternatives for combinations of gemcitabine in ovarian cancer consist of increasing the inhibition of ribonucleotide reductase with triapine or hydroxyurea. Gemcitabine's action on signaling also provides a rational concept for combination with signal transduction pathways.
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PMID:Nucleoside and nucleobase analogs in cancer treatment: not only sapacitabine, but also gemcitabine. 2240 48


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