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PubMed1982

Differential synchronization of leukemic cells in vivo by hydroxyurea.

Flow cytometry (FCM) was used to monitor the cell cycle changes which occurred in the bone marrow cells of a patient with acute myeloblastic leukemia following pre-induction treatment with hydroxyurea. Flow cytometric and cytogenetic analysis showed two populations of cells; one hypertetraploid and presumably leukemic, and the other diploid and possibly normal. Sequential FCM monitoring of bone marrow cells after hydroxyurea demonstrated an early rise (after 24 h) in the S-phase component of diploid cells and a rise in the S-phase component of hypertetraploid cells 48-72 h later. Conventional induction therapy timed to coincide with this latter peak resulted in early remission.

Cell Cycle↗

PubMed1982

Effects of hydroxyurea on DNA synthesis in mouse L-cells.

The effect of the anti-metabolite hydroxyurea on DNA synthesis in mouse L-cells has been examined. It was shown previously that when DNA synthesis was diminished to very low levels by treatment with the drug there was preferential incorporation of added [3H]dThd into low molecular weight fragments (Martin, R.F., Radford, I. And Pardee, M. (1977) Biochem. Biophys. Res. Commun. 74, 9-15). On the basis of several criteria it is concluded here that these fragments are a product of semi-conservative nuclear DNA replication. The preferential labelling of DNA fragments, but not their size, is shown to be dependent on the hydroxyurea concentration used. These DNA fragments are also shown, by comparison with normal DNA replication intermediates, to comprise a heterogeneous population of 'larger-than-normal' fragments. Different models to account for these findings are considered and it is concluded that the results are compatible with a loss of coordination of DNA synthesis following drug treatment.

Animals↗

PubMed1984

Hydroxyurea treatment does not prevent initiation of DNA synthesis in Ehrlich ascites tumour cells and leads to the accumulation of short DNA fragments containing the replication origins.

The ability of EAT cells to initiate DNA synthesis in the presence of high doses of hydroxyurea was examined using the recently developed method for crosslinking DNA in vivo. Since crosslinking blocks elongation but has little effect on initiation (Russev and Vassilev (1982) J. Mol. Biol. 161, 77-87), this approach permits a separate study of the two stages of the DNA replication. We found out that hydroxyurea did not greatly affect the initiation of DNA replication but strongly inhibited the elongation of the already initiated new DNA chains. This resulted in the formation of short fragments enriched in sequences synthesized at and around the sites where DNA initiation began. These fragments were not ligated to the high molecular weight chromosomal DNA and could be released under denaturing conditions in single-stranded form. The reassociation and electrophoretic analysis showed that they contained about 200 nucleotides long interspersed DNA sequences repeated approx. 10(4) times per haploid genome, that probably served as replication origins.

Animals↗

PubMed1985

DNA repair synthesis induced by N-hydroxyurea, acetohydroxamic acid, and N-hydroxyurethane in primary rat hepatocyte cultures: comparative evaluation using the autoradiographic and the bromodeoxyuridine density-shift method.

N-Hydroxyurea and two structurally related compounds, acetohydroxamic acid and N-hydroxyurethane, were investigated for their potential to induce DNA repair synthesis in primary rat hepatocyte cultures. Repair was determined as repair replication by means of the bromodeoxyuridine density-shift method and, in the same cell preparations, as unscheduled DNA synthesis (UDS) by autoradiography. For all 3 compounds, a clear concentration-dependent induction of DNA repair replication could be demonstrated. Interpretation of the UDS data, however, depended on the mode whereby the results were evaluated. Expression of the results as net grains per nucleus after subtraction of cytoplasmic from nuclear grain counts yielded statistically significant increases over the control values for all compounds. In contrast, no significant changes of the nuclear labeling were obtained when nuclear and cytoplasmic grain counts were plotted separately. These findings demonstrate that the two modes to present UDS data may lead to different conclusions, a consequence of the uncertainty regarding the origin and importance of the cytoplasmic background. The observation that both hydroxyurea and the structurally related compounds acetohydroxamic acid and N-hydroxyurethane induce DNA repair in primary hepatocyte cultures suggests that metabolism-dependent genotoxicity may be a common property of aliphatic hydroxamic acids.

Animals↗

PubMed1987

A randomized study of methotrexate, bleomycin, hydroxyurea with versus without cisplatin in patients with previously untreated and recurrent squamous cell carcinoma of the head and neck.

The value of a combination of methotrexate, bleomycin and hydroxyurea with vs. without cisplatin was randomly examined in 62 evaluable patients with previously untreated (44 patients) and recurrent (18 patients) squamous cell carcinoma of the head and neck. Methotrexate (30 mg/m2) and bleomycin (15 mg) were given intravenously weekly, hydroxyurea (1000 mg/m2) per os 3 times per week for 4 weeks. Cisplatin (60 mg/m2) was added on Day 1 every month. A higher overall response rate was observed with the cisplatin-containing regimen (66%, included 17% complete) as compared with 27% (3% complete) with the 3-drug combination (P value 0.0025). The cisplatin-containing regimen was more active in both previously untreated patient group and in the group recurrent patients. Toxicity was more pronounced in the cisplatin regimen and necessitated frequently reduced drug dosages. No survival difference was observed between the treatment groups. Median survival in previously untreated patients was 16.2 months and 7.2 months in patients who failed conventional local treatment. It is concluded that a cisplatin-containing regimen is more effective in advanced head and neck carcinoma than the same combination without cisplatin.

Adult↗

PubMed1995

Induction of apoptosis in chronic myelogenous leukemia lymphocytes by hydroxyurea and adriamycin.

The nature of the cytotoxic effects of the anticancer drugs hydroxyurea, adriamycin, cisplatin and interferon, was studied on lymphocytes obtained from chronic myelogenous leukemia (CML) subjects prior to the commencement of chemotherapy. These drugs appeared to mediate their cytotoxic effects by the process of apoptosis as observed from the morphological changes, i.e., cell shrinkage, chromatin condensation, cell membrane blebbing, and also from the cellular damage and DNA fragmentation into oligonucleosomal ladder of 180-bp multiples, which are all characteristics of apoptotic cell death. The effect was much more marked by hydroxyurea and adriamycin. Maximum sensitivity was seen at 24 h post treatment. Untreated CML lymphocytes cultured for 24 h also showed some apoptosis.

Adult↗

PubMed1992

Treatment of recurrent head and neck cancer with 5-fluorouracil, hydroxyurea, and reirradiation.

Head and neck cancer locally recurrent after previous irradiation and surgery presents a difficult management problem. Conventional treatment alternatives include chemotherapy, reirradiation with interstitial implant, and hyperthermia. Reirradiation with external beam is generally not considered because of previous high radiation dose and limited tissue tolerance. In this study, 21 patients with recurrent and previously irradiated head and neck cancer were treated in a Phase I-II fashion. Patients received 5 days of 5-fluorouracil, 300 mg/m2/day IV bolus, Hydroxyurea 1.5 or 2 g/day by mouth and external beam radiation therapy every 2 weeks for up to four courses. Of 20 evaluable patients, 9 have attained a complete response (CR) and 6 a partial response (PR). Fifteen patients completed all planned therapy, eight on time, seven patients with delays. With a median follow-up of 7 months, 13 patients are alive, 7 disease-free (3 after salvage surgery) and 6 with recurrence. Eight patients have died. The 1-year survival is 56%. Treatment toxicity was mainly neutropenia. No major early or late radiation related side effects have been observed at a median follow-up of 7 months. Neither previous radiation dose, time since first radiation, prior chemotherapy, or site of recurrence was predictive of response or treatment tolerance. Patients with a performance status of at least 80 had a significant higher CR rate, with 7/10 patients in this group, as compared to 2/10 patients in patients with a performance status less than 80, achieving a CR. Reirradiation with 5-fluorouracil and hydroxyurea is a well tolerated outpatient treatment program for patients with recurrent and previous irradiated head and neck cancer that produces a high response rate and can provide significant palliation of symptoms.

Adult↗

PubMed1987

Ribonucleotide reductase M2 subunit sequences mapped to four different chromosomal sites in humans and mice: functional locus identified by its amplification in hydroxyurea-resistant cell lines.

The sites of sequences homologous to a murine cDNA for ribonucleotide reductase (RR) subunit M2 were determined on human and murine chromosomes by Southern blot analysis of interspecies somatic cell hybrid lines and by in situ hybridization. In the human genome, four chromosomal sites carrying RRM2-related sequences were identified at 1p31----p33, 1q21----q23, 2p24----p25, and Xp11----p21. In the mouse, M2 sequences were found on chromosomes 4, 7, 12, and 13 by somatic cell hybrid studies. By Southern analysis of human hydroxyurea-resistant cells that overproduce M2 because of gene amplification, we have identified the amplified restriction fragments as those that map to chromosome 2. To further confirm the site of the functional RRM2 locus, two other cDNA clones, p5-8 and S7 (coding for ornithine decarboxylase; ODC), which are coamplified with RRM2 sequences in human and rodent hydroxyurea-resistant cell lines, were mapped by Southern and in situ hybridization. Their chromosomal map positions coincided with the region of human chromosome 2 (p24----p25) that also contains one of the four RRM2-like sequences. Since this RRM2 sequence and p5-8 and ODC are most likely part of the same amplification unit, the RRM2 structural gene can be assigned to human chromosome 2p24----p25. This region is homologous to a region of mouse chromosome 12 that also carries one of numerous ODC-like sequences. In an RRM2-overproducing mouse cell line, we found amplification of the chromosome 12-specific restriction fragments. Thus, we conclude that mouse chromosome 12 carries the functional locus for RRM2.

Animals↗

PubMed1996

[Treatment with hydroxyurea of polycythemia vera in a 11 year-old child].

BACKGROUND: Polycythemia vera is a very rare disease in childhood; its treatment for this reason is not well established. CASE REPORT: An 11-year-old boy was admitted for polycythemia vera. The three classical major criteria for this condition were present and no cause for secondary polyglobulia could be recognized. The patient was given hydroxyurea. Three years later, he is well with hematocrit below 50%. CONCLUSIONS: Oral continuous myelosuppressive therapy with hydroxyurea may be proposed in children if there is no HLA-matched family member. Long-term follow-up is nevertheless necessary in order to detect relapse or side-effects of the treatment.

Antineoplastic Agents↗

PubMed2005

N-Hydroxyurea as zinc binding group in matrix metalloproteinase inhibition: mode of binding in a complex with MMP-8.

The first crystallographic structure of an N-hydroxyurea inhibitor bound into the active site of a matrix metalloproteinase is reported. The ligand and three other analogues were prepared and studied as inhibitors of MMP-2, MMP-3, and MMP-8. The crystal structure of the complex with MMP-8 shows that the N-hydroxyurea, contrary to the analogous hydroxamate, binds the catalytic zinc ion in a monodentate rather than bidentate mode and with high out-of-plane distortion of the amide bonds.

Animals↗

PubMed2005

Synthesis and NMR characterization of hydroxyurea and mesylglycol glycoconjugates as drug candidates for targeted cancer chemotherapy.

Tumor targeting of glycoconjugated antineoplastic agents is a strategy currently under investigation for cancer chemotherapy. We have synthesized the glucosides and galactosides of the clinically established drug hydroxyurea and of mesylglycol, the reactive moiety of the anticancer drug busulfan. Glycosides of hydroxyurea were obtained by carbamoylation of hydroxylamine glycosides. The glycosides of mesylglycol were synthesized by mesylation of protected glycol glycosides. All compounds were characterized by detailed 1H and 13C NMR analysis.

Antineoplastic Agents↗

PubMed2005

Quantitative analysis of trimethylsilyl derivative of hydroxyurea in plasma by gas chromatography-mass spectrometry.

Hydroxyurea is an antitumor drug widely used in the treatment of sickle cell disease. The drug has been analyzed in biological fluids by a number of high-performance liquid chromatography (HPLC) methods. This paper describes a fast and highly reliable capillary gas chromatography-mass spectrometry (GC-MS) procedure that was developed for the detection and quantitation of hydroxyurea in plasma. The compound and its labeled internal standard were liquid extracted from plasma and derivatized with BSTFA before analysis. The detection limit of the assay was 0.078 microg/ml and the limit of quantitation was 0.313 microg/ml with linearity up to 500 microg/ml. Intra-day variation, as coefficient of variation (C.V., %) over the selected concentration range, was 0.3-8.7% and inter-day variation was 0.4-9.6%.

Gas Chromatography-Mass Spectrometry↗

PubMed1975

Hydroxyurea in stage D carcinoma of the prostate: a pilot study.

There was 13 patinets with histologically metastatic prostatic adenocarcinoma treated with a single oral dose of 80 mg. per kg. hydroxyurea every third day (based on ideal or actual weight, whichever is less) and 12.5 mg. chlorotrianisene per day. Toxicity was mild. The most common manifestations were nausea, occasional vomiting leukopenia. A definite attempt was made to depress the white blood count to approximately 2,000 cells per cu. mm. Hydroxyurea was not discontinued unless the white blood count decreased to less that 2,000 cells per cu. mm., after which a single dose was usually omitted. Omission of a single dose would allow the white blood count to return promptly to more than 2,000 cells per cu. mm. Objective tumor regression was demonstrated in 6 of the 13 patients and all patients had a definite improvement in the quality of life.

Adenocarcinoma↗

PubMed2002

Coexistence of independent myelodysplastic and Philadelphia chromosome positive clones in a patient treated with hydroxyurea.

We report a patient with Philadelphia chromosome positive (Ph +ve) chronic myelogenous leukemia (CML), treated with hydroxyurea alone, who upon disease progression developed an additional Ph - ve clone containing chromosomal abnormalities typical of myelodysplastic syndrome (MDS). Retrospective analysis of a cryopreserved stem cell specimen from diagnosis confirmed that this second clone developed during the course of treatment. The development of a clone with additional cytogenetic abnormalities in CML has only been reported after leukemogenic treatment, stem cell transplantation or interferon. We report a case of secondary Ph - ve MDS/AML during blast crisis in a patient treated with hydroxyurea for CML.

Aged↗

PubMed1997

Achievement of a complete cytogenetic response with hydroxyurea in a patient with chronic myelogenous leukemia.

Hydroxyurea rarely produces a complete cytogenetic remission in patients with chronic myelogenous leukemia (CML). In this report, we describe one case of the CML patient who achieved complete cytogenetic remission (no Ph chromosome in 20-25 metaphase cells) by treatment with hydroxyurea alone. By the fluorescent in situ hybridization (FISH) methodology using bcr/abl specific translocation probe, sequential bone marrow specimens from the patient showed the characteristic 9;22 translocation at a higher rate (9-10%) than the normal control range (2.49-4.88%) at the time of complete cytogenetic remission. Thus, it is suggested that FISH is a more sensitive method to detect the bcr/abl fusion gene than conventional cytogenetic analysis for the detection of minimal residual disease in CML.

Antineoplastic Agents↗

PubMed1999

Longitudinal, transverse, and diffuse nail hyperpigmentation induced by hydroxyurea.

Hydroxyurea is a cytostatic agent used in patients with myeloproliferative disorders that may produce nail hyperpigmentation, most frequently longitudinal melanonychia. We present a patient treated with hydroxyurea whose nails showed several patterns of nail hyperpigmentation, including longitudinal and transverse bands, and a diffuse darkening of the nail matrix.

Aged↗

PubMed1997

An extension of stochastic curtailment for incompletely reported and classified recurrent events: the Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH).

The Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH), a double-blind randomized clinical trial, compared the frequency of acute vaso-occlusive (painful) crises during 2 yr of follow-up in 299 patients randomly assigned to hydroxyurea or placebo. Most patients had more than one crisis; all crises reported were included in the primary outcome analysis. A total of 7,229 follow-up medical contact reports were classified as crises/not crises by a Crisis Review Committee. Because of the time required to report, document, and classify contacts, interim analyses were prepared with incomplete data. If a stopping boundary were crossed, early termination could be advised only after assessing the potential impact of the incomplete data. In an extension of stochastic curtailment methods, simulation procedures were used to estimate the probability of detecting differences when group crisis rates projected to the end of the study were compared using a rank test. To account for medical contacts not yet reported and the future occurrence of crises, Poisson process models assuming no treatment effect on crisis rates were used for these simulations. The number of unclassified contacts that would be classified as crises was simulated as a binomial random variable. These methods may be useful for interim monitoring in other studies of recurrent events with ongoing event reporting and classification.

Anemia, Sickle Cell↗

PubMed1981

The influence of hydroxyurea on the incorporation of exogenous DNA into host cells.

The incorporation of exogenous isologous DNA into nuclei was studied in L-cells of replicating and non-replicating DNA. Hydroxyurea was used to inhibit DNA replication. The amount of exogenous DNA incorporated into cells decreased after the application of hydroxyurea by about a third. In the course of a 60-minute incubation exogenous DNA was incorporated into 75% of non-replicating DNA cells.

Animals↗