Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

All-trans retinoic acid (ATRA) is an essential component of the treatment of acute promyelocytic leukemia (APL), but the optimal timing and duration remain to be determined. Molecular characterization of this disease can refine the diagnosis and could be potentially useful in monitoring response to treatment. Patients defined morphologically to have APL were randomized to receive a 5-day course of ATRA before commencing chemotherapy or to receive daily ATRA commencing with chemotherapy and continuing until complete remission (CR). The chemotherapy was that used in current MRC Leukaemia Trials. Outcome comparisons were by intention to treat with additional analysis for relevant risk factors. Patients were characterized by molecular techniques for the fusion products of the t(15;17) and monitored by reverse transcriptase-polymerase chain reaction (RT-PCR) during and after treatment. Two hundred thirty-nine patients were randomized. Treatment with extended ATRA resulted in a superior remission rate (87% v 70%, P <.001), due to fewer early and induction deaths (12% v 23%, P =.02), and less resistant disease (2% v 7%, P =.03), which was associated with a significantly more rapid recovery of neutrophils and platelets. Extended ATRA reduced relapse risk (20% v 36% at 4 years, P =.04) and resulted in superior survival (71% v 52% at 4 years, P =.005). Presenting white blood cell count (WBC) was a key determinant of outcome. The 70% of patients who presented with a WBC less than 10 x 10(9)/L had a better CR (85% v 62%, P =.0001) and reduced relapse risk (22% v 42%, P =.002) and superior survival (69% v 43%, P <. 0001). Within the low count group, extended ATRA resulted in a better CR (94% v 76%, P =.001), reduced relapse risk (13% v 35%, P =. 04), and improved survival (80% v 57%, P =.0009). There was no evidence of benefit in patients presenting with a higher WBC (>10 x 10(9)/L). Molecular monitoring after the third chemotherapy course had a correlation with risk of relapse. The relapse risk was 57% if the RT-PCR was positive versus 27% if the RT-PCR was negative (P =. 006). APL patients who present with a low WBC derive substantial benefit from combining ATRA with induction chemotherapy until remission is achieved, whereas patients with a higher WBC did not benefit. Molecular characterization of disease can improve diagnostic precision and a positive RT-PCR after consolidation identifies patients at a higher risk of relapse.
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PMID:Presenting white blood cell count and kinetics of molecular remission predict prognosis in acute promyelocytic leukemia treated with all-trans retinoic acid: result of the Randomized MRC Trial. 1036 Nov 10

Fourteen patients with PML/RARalpha-positive acute promyelocytic leukemia (APL) were given salvage therapy at the time of first molecular relapse. All patients had achieved first molecular remission after the AIDA protocol (all-trans retinoic acid [ATRA] + idarubicin) and were being prospectively monitored by reverse transcriptase-polymerase chain reaction (RT-PCR). Molecular relapse was defined as reappearance of RT-PCR-positivity for the PML/RARalpha fusion (sensitivity 10(-4)) in 2 successive marrow samples collected during postconsolidation monitoring. The median duration of first molecular remission was 7.5 months (range, 2 to 25). Salvage therapy consisted of oral ATRA for 30 days followed by 4 daily courses of chemotherapy (CHT) with cytarabine 1 g/m(2)/d and mitoxantrone 6 mg/m(2)/d. Second molecular remission was obtained in 12 of 14 patients (86%). Seven of these 12 attained molecular remission after ATRA alone. Of the 2 patients who persisted PCR(+) after CHT, 1 died in remission and 1 progressed to hematologic relapse. Of 12 patients PCR(-), 8 received consolidation with autologous bone marrow transplantation (ABMT), and 4 received ATRA-containing maintenance. Ten patients in this group are in sustained second molecular remission at a median time of 9.5+ months (range, 4 to 22+) and 2 underwent hematologic relapse 6 and 13 months, respectively, after transient second molecular remission. The 2-year Kaplan and Meier survival estimate from time of relapse was 92% (95% confidence interval [CI]: 61% to 98%) in this series, and 44% (95% CI: 35% to 52%) in a previous series of 37 patients who received the same treatment at the time of hematologic recurrence (P <.05, by log-rank test). This study suggests that early administration of salvage therapy is advantageous in APL and represents the first experience on therapy of molecular relapse in acute leukemia.
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PMID:Therapy of molecular relapse in acute promyelocytic leukemia. 1049 92

The Spanish PETHEMA group designed a protocol for newly diagnosed PML/RARalpha-positive acute promyelocytic leukemia (APL) in which induction and consolidation followed the original AIDA regimen, except for the omission of cytarabine and etoposide from consolidation. Induction consisted of 45 mg/m(2) all-trans retinoic acid (ATRA) daily until complete remission (CR) and 12 mg/m(2) idarubicin on days 2, 4, 6, and 8. Patients in CR received 3 monthly chemotherapy courses: idarubicin 5 mg/m(2)/d x 4 (course no. 1), mitoxantrone 10 mg/m(2)/d x 5 (course no. 2), and idarubicin 12 mg/m(2)/d x 1 (course no. 3). Maintenance therapy consisted of 90 mg/m(2)/d mercaptopurine orally, 15 mg/m(2)/wk methotrexate intramuscularly, and, intermittently, 45 mg/m(2)/d ATRA for 15 days every 3 months. Between November 1996 and December 1998, 123 patients with newly diagnosed PML/RARalpha-positive APL from 39 centers were enrolled. A total of 109 patients achieved CR (89%; 95% confidence interval [CI], 83 to 95), 12 died of early complications, and the remaining 2 were resistant. Consolidation treatment was associated with very low toxicity and no deaths in remission were recorded. Molecular assessment of response by reverse transcriptase-polymerase chain reaction (RT-PCR) showed conversion to PCR-negative in 48 of 99 (51%) and 82 of 88 patients (93%) after induction and consolidation, respectively. The 2-year Kaplan-Meier estimates of overall survival and event-free survival were 82% +/- 4% and 79% +/- 4%, respectively. For patients who achieved CR, the 2-year disease-free survival (DFS) was 92% +/- 3%. These data indicate that a significant reduction in toxicity might be obtained in APL using a less intensive consolidation without apparently compromising the antileukemic effect. These results also suggest a minor role for cytarabine and etoposide in the treatment of newly diagnosed PML/RARalpha-positive APL patients.
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PMID:A modified AIDA protocol with anthracycline-based consolidation results in high antileukemic efficacy and reduced toxicity in newly diagnosed PML/RARalpha-positive acute promyelocytic leukemia. PETHEMA group. 1055 84

Acute promyelocytic leukemia was diagnosed in a 48-year-old man; the karyotype was normal, whereas reverse transcriptase polymerase chain reaction (RT-PCR) analysis identified PML/RAR alpha chimeric transcripts of the bcr3 type. Rather unexpectedly, the patient did not respond to alltrans retinoic acid administration; he attained complete remission with conventional chemotherapy and became PML/RAR alpha negative. Two years later, while PML/RAR alpha negative on RT-PCR, he presented with thrombocytopenia. Bone marrow examination was compatible with myelodysplasia of the RAEB type; the karyotype was normal. Then, after 10 months, he developed overt acute myeloid leukemia with PML/RAR alpha negative, French-American-British M2 blasts; karyotypic analysis revealed mosaicism for trisomy 8.
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PMID:Acute promyelocytic leukemia relapsing into FAB-M2 acute myeloid leukemia with trisomy 8. 1070 Aug 73

CYP26 (P450RAI) catalyzes catabolic retinoic acid (RA) hydroxylation and thereby appears to play a critical role in retinoid signaling pathways during development. In this study, a quantitative competitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed for evaluation of CYP26 message levels in human prenatal tissues. Statistical analyses of transcription levels in 12 prenatal human brains and six prenatal human livers demonstrated good sensitivity and reproducibility. Quantitative profiles of CYP26 gene expression in early (gestational days 57-110) prenatal cephalic and hepatic tissues and comparisons with adult counterparts are reported for the first time. Prenatal cephalic tissues at days 57-67 exhibited values of 1950+/-420 (CYP26 molecules/10(6) GAPDH molecules) whereas prenatal cephalic tissues at days 105-110 exhibited values of 22300+/-4450 (CYP26 molecules/10(6) GAPDH molecules), indicating a sharp developmental increase (approximately 11-fold). Levels in human adult cephalic tissues were slightly less than the prenatal cephalic levels measured during the earliest stages of gestation and were approximately 3-fold lower than those measured in adult human hepatic tissues. Levels in human prenatal hepatic tissues at days 63-110 gestation were less than 800 (CYP26 molecules/10(6) GAPDH molecules) and did not exhibit developmental increases. Considered together, the data have strong implications for the importance of CYP26 in early development of the human brain.
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PMID:Patterns of CYP26 expression in human prenatal cephalic and hepatic tissues indicate an important role during early brain development. 1072 25

To examine the role of retinoids in hematopoietic cell growth in vivo, we studied female SENCAR mice made vitamin A deficient by dietary restriction. Deficient mice exhibited a dramatic increase in myeloid cells in bone marrow, spleen, and peripheral blood. The abnormal expansion of myeloid cells was detected from an early stage of vitamin A deficiency and contrasted with essentially normal profiles of T and B lymphocytes. This abnormality was reversed on addition of retinoic acid to the vitamin A-deficient diet, indicating that the myeloid cell expansion is a direct result of retinoic acid deficiency. TUNEL analysis indicated that spontaneous apoptosis, a normal process in the life cycle of myeloid cells, was impaired in vitamin A-deficient mice, which may play a role in the increased myeloid cell population. Quantitative reverse transcriptase-polymerase chain reaction analysis of purified granulocytes showed that expression of not only RAR, but RXRs, 2 nuclear receptors that mediate biologic activities of retinoids, was significantly reduced in cells of deficient mice. This work shows that retinoids critically control the homeostasis of myeloid cell population in vivo and suggests that deficiency in this signaling pathway may contribute to various myeloproliferative disorders.
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PMID:Vitamin A deficiency in mice causes a systemic expansion of myeloid cells. 1154 74

3'-Azido-2',3'-dideoxythymidine (AZT, 1, zidovudine, RetrovirTM) is used to treat patients with human immunodeficiency virus (HIV) infection. AZT, after conversion to AZT-5'-triphosphate (AZT-TP) by cellular enzymes, inhibits HIV-reverse transcriptase (HIV-RT). The major clinical limitations of AZT are due to clinical toxicities that include bone marrow suppression, hepatic abnormalities and myopathy, absolute dependence on host cell kinase-mediated activation which leads to low activity, limited brain uptake, a short half-life of about one hour in plasma that dictates frequent administration to maintain therapeutic drug levels, low potential for metabolic activation and/or high susceptibility to catabolism, and the rapid development of resistance by HIV-1. These limitations have prompted the development of strategies for designing prodrugs of AZT. A variety of 5'-O-substituted prodrugs of AZT constitute the subject of this review. The drug-design rationale on which these approaches are based is that the ester conjugate will be converted by hydrolysis and/or enzymatic cleavage to AZT or its 5&prime;-monophosphate (AZT-MP). Most prodrug derivatives of AZT have been prepared by derivatization of AZT at its 5'-O position to provide two prominent classes of compounds that encompass: A) 5'-O-carboxylic esters derived from 1) cyclic 5'-O-carboxylic acids such as steroidal 17b-carboxylic acids, 1-adamantanecarboxylic acid, bicyclam carboxylic acid derivatives, O-acetylsalicylic acid, and carbohydrate derivatives, 2) amino acids, 3) 1, 4-dihydro-1-methyl-3-pyridinylcarboxylic acid, 4) aliphatic fatty acid analogs such as myristic acid containing a heteroatom, or without a heteroatom such as stearic acid, and 5) long chain polyunsaturated fatty acid analogs such as retinoic acid, and B) masked phosphates such as 1) phosphodiesters that include monoalkyl or monoaryl phosphate, carbohydrate, ether lipid, ester lipid, and foscarnet derivatives, 2) a variety of phosphotriesters that include dialkylphosphotriesters, diarylphosphotriesters, glycolate and lactate phosphotriesters, phosphotriester approaches using simultaneous enzymatic and chemical hydrolysis of bis(4-acyloxybenzyl) esters, bis(S-acyl-2-thioethyl) (SATE) esters, cyclosaligenyl prodrugs, glycosyl phosphotriesters, and steroidal phosphotriesters, 3) phosphoramidate derivatives, 4) dinucleoside phosphate derivatives that possess a second anti-HIV moiety such as AZT-P-ddA, AZT-P-ddI, AZTP2AZT, AZTP2ACV), and 5) 5'-hydrogen phosphonate and 5'-methylene phosphonate derivatives of AZT. In these prodrugs, the conjugating moiety is linked to AZT via a 5'-O-ester or 5'-O-phosphate group. 5'-O-Substituted AZT prodrugs have been designed with the objectives of improving anti-HIV activity, enhancing blood-brain barrier penetration, modifying pharmacokinetic properties to increase plasma half-life and improving drug delivery with respect to site-specific targeting or drug localization. Bypassing the first phosphorylation step, regulating transport and conferring sustained release of AZT prolong its duration of action, decrease toxicity and improve patient acceptability. The properties of these prodrugs and their anti-HIV activities are now reviewed.
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PMID:Novel approaches for designing 5'-O-ester prodrugs of 3'-azido-2', 3'-dideoxythymidine (AZT). 1091 Oct 16

Although the occurrence of marrow fibrosis in acute myeloid leukemia has been described, there have been no reports of acute promyelocytic leukemia (APL) associated with marrow fibrosis. Here we describe an APL patient with severe marrow fibrosis at initial presentation. He had the typical manifestations of APL, except for marrow fibrosis. Complete remission was achieved by treatment with all-trans retinoic acid plus chemotherapy, and his marrow fibrosis gradually improved concomitantly with the decrease in leukemic cells. To clarify the mechanism of marrow fibrosis in this patient, we investigated the expression of genes for several cytokines promoting fibrosis by the reverse transcriptase polymerase chain reaction methods. An overexpression of transforming growth factor-beta(1) was noted in his leukemic cells at initial presentation, whereas no increase in expression was observed at the time of relapse when he no longer had marrow fibrosis. These findings suggest that overexpression of transforming growth factor-beta(1) was involved in the development of marrow fibrosis in this APL patient.
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PMID:Acute promyelocytic leukemia with marrow fibrosis at initial presentation: possible involvement of transforming growth factor-beta(1). 1218 33

A new synthetic retinoid, Am80, is effective in treating acute promyelocytic leukemia relapsed from all-trans-retinoic acid-induced complete remission (CR). We report here the long-term clinical outcomes of patients who achieved second CR with Am80. Of 24 evaluable patients, 14 achieved a second CR by Am80 therapy. Of those patients, 4 relapsed within 6 months, despite subsequent consolidation chemotherapy. Six patients underwent sibling or unrelated HLA-matched allogeneic bone marrow transplantation (BMT), and 4 are alive without relase for more than 49 months after achieving second CR. Four of 8 patients who did not receive BMT are alive without relapse for more than 49 months. Promyelocytic leukemia-retinoic acid receptor alpha (PML-RAR alpha) fusion transcript was undetectable by reverse transcriptase-polymerase chain reaction in all living patients. Therefore, if patients achieve second CR with Am80 and HLA-matched donors are available, BMT is the treatment of choice. However, it is noteworthy that CR was maintained for more than 49 months in half of the patients who did not receive BMT.
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PMID:Good prognosis of patients with acute promyelocytic leukemia who achieved second complete remission (CR) with a new retinoid, Am80, after relapse from CR induced by all-trans-retinoic acid. 1119 14

Peroxisome proliferator-activated receptors (PPARs), which belong to the nuclear hormone receptor superfamily, have recently been described as potent key regulators of epidermal development. As 1,25-dihydroxyvitamin D3, retinoic acid and triiodothyronine are known to exert effects on skin and hair follicle growth through similar receptors, we decided to investigate both the expression pattern of the PPAR alpha, -delta and -gamma subtypes and their role in human hair follicles. Using reverse transcriptase-polymerase chain reaction and immunohistochemistry, we established that PPAR alpha, -delta and -gamma were expressed in both dermal and epithelial human hair follicle cells. Additionally, we evaluated the dose effect of clofibrate, a PPAR alpha ligand, on the survival of human hair follicles in culture. A beneficial effect was observed within a narrow range of concentrations.
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PMID:Expression of peroxisome proliferator activated receptors (PPARs) in human hair follicles and PPAR alpha involvement in hair growth. 1120 Aug 28


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