Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The processing and intracellular transport of myeloperoxidase were studied in the human promyelocytic leukaemia cell line HL-60 and in normal marrow cells labelled with [35S]methionine or [14C]leucine. Myeloperoxidase was precipitated with antimyeloperoxidase serum; the immunoprecipitates were subjected to sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and radiolabelled myeloperoxidase visualized by fluorography. During a 1 h pulse, myeloperoxidase was labelled in a chain of apparent Mr 90 000. With a subsequent chase, the Mr 90 000 polypeptide disappeared and was replaced by chains of Mr 62 000 and 12 400 corresponding roughly to the size of neutrophil myeloperoxidase subunits. The identification of the radioactive polypeptides as different forms of myeloperoxidase was established also by the similarity in patterns generated by partial proteolysis with V8 proteinase from Staphylococcus aureus. Processing of myeloperoxidase in HL-60 was slow; mature polypeptides were significantly increased only after 6 h. Another myeloperoxidase chain of apparent Mr 82 000 was an intermediate precursor or degradation form. Pulse-chase experiments in combination with sucrose-density-gradient separations of homogenates showed that the Mr 90 000 precursor was located in light density organelles only and not in granule fractions, whereas the Mr 82 000 precursor was located only in intermediate density organelles, suggesting that the latter is a product of the former. Processed mature myeloperoxidase was concentrated in the granule fraction, but some occurred in lower density organelles, which may indicate processing during intracellular transport. Only the Mr 90 000 polypeptide was secreted into the culture medium; this was also the only form found in the cytosol fraction.
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PMID:Biosynthesis, transport and processing of myeloperoxidase in the human leukaemic promyelocytic cell line HL-60 and normal marrow cells. 609 12

Lactoperoxidase iodination and two-dimensional electrophoresis of the labeled proteins have demonstrated well-characterized cytoskeletal proteins (actin and tubulins) on the surface of human lymphocytes undergoing blastogenic transformation and of certain malignant human cells. Such proteins could not be detected on the surface of normal resting human lymphocytes. The most prominent cytoskeletal protein identified on the surface membrane of mitogen-transformed T and B lymphocytes was actin. In Epstein-Barr virus genome-positive Burkitt's lymphoma and lymphoblastoid cell lines and in two leukemia cells, the major iodinated membrane protein components were actin and alpha 1-, alpha 2-, and beta-tubulins. These proteins were firmly connected to the cytoplasmic skeleton and could not be removed by Triton X-100. Concurrent immunofluorescence studies with specific antibodies and F(ab')2 fragments confirmed the appearance of cytoskeletal components on the biochemical data, and indicated that such cytoskeletal proteins formed distinctive patterns on the cell surface, ranging from small patches to large projections. Five-hour labeling with [35S]methionine indicates that all such cells released large quantities of labeled actin and tubulins into the culture medium. These materials were not readsorbed to the membrane surfaces of the cells.
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PMID:Appearance of cytoskeletal components on the surface of leukemia cells and of lymphocytes transformed by mitogens and Epstein-Barr virus. 625 49

Myeloperoxidase staining methods for classification of leukemias have traditionally employed benzidine dihydrochloride as the chromogen. Recent Occupational Safety and Health Administration regulations have classified benzidine as a carcinogen, which severely restricts its use in the clinical laboratory. Twenty-two specimens from normal control subjects and leukemia patients, previously classified by FAB criteria, were stained with benzidine and two alternate chromogens, diaminobenzidine and Hanker-Yates reagent (p-phenylenediamine and pyrocatechol). In a random, blind fashion, three experienced observers scored the stains from each case according to quality of smear, degree of peroxidase positivity, tinctorial distinction between nucleus and cytoplasm, and overall acceptability of the stain. All three observers rated the substitute chromogens as adequate for routine myeloperoxidase cytochemical staining. It is concluded that either of the methods studied would have clinical utility and can substitute for benzidine as a myeloperoxidase chromogen.
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PMID:Alternate chromogens as substitutes for benzidine for myeloperoxidase cytochemistry. 625 29

A 70-year-old male was admitted to our hospital because of leukocytosis. The laboratory examination revealed leukocytosis (44,500/microliters) with blasts (99%) in the peripheral blood. Myeloperoxidase staining of the leukemia cells was negative, but the surface phenotype was CD13- and CD33-positive, and negative for all lymphoid antigens. Peroxidase staining using the electron microscope was positive. Thus, the patient was diagnosed as acute myeloblastic leukemia (M0), according to the FAB classification. Although the therapy regimens commonly used for ANLL were effective for some cases with M0, the regimens mainly for ALL were more effective for the others. Thus we cannot determine what is the most effective regimen for M0. Since the patient had many complications, he was treated with low-dose AraC instead of combination chemotherapy. After the beginning of treatment, he became febrile and we added G-CSF to Ara-C. One month later, the patient achieved complete remission without severe infection. After four courses of consolidation therapy, the patient was discharged. He has been maintained in remission for more than 3 years and 8 months with only 5-day oral administration of cytarabine ocfosfate every four weeks.
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PMID:[Continuation of complete remission by oral administration of cytarabine ocfosfate in a patient with M0, who achieved remission by small doses of cytosine arabinoside with G-CSF]. 753 75

This study assesses the value of immunologic and ultrastructural methods in disclosing the lineage commitment of cells from acute leukemias (ALs). Two hundred and fifty-one ALs were characterized morphologically, cytochemically, and immunologically. Myeloperoxidase (MPO) positivity in > 3% of blasts was regarded as evidence of the myeloid origin of leukemic cells, cytoplasmic CD22 (cCD22) expression was taken as an indication for B-lineage acute lymphoblastic leukemia (ALL), and CD3+ (membrane or cytoplasmic) cases were classified as T-ALL. Diagnosis of minimally differentiated acute myeloid leukemia (AML-M0) was made when blast cells had undifferentiated features by light microscopy, reacted with at least one of the antibodies to myeloid-specific antigens (CD13, CD33, MPO), and lacked CD19, cCD22, and c/mCD3. Megakaryoblastic differentiation was demonstrated by the expression of CD41 and/or CD61. Following these criteria, 209 cases were classified as acute myeloid leukemia (AML) and 39 as ALL. Expression of lymphoid antigens was detected in 45% of AML cases and 30% of ALLs showed myeloid antigens. One case was regarded as a true biphenotypic leukemia because of the combined expression of MPO and CD33 for the myeloid lineage, and cCD3, CD2, and CD5 for the T-cell lineage. Two cases lacked signs of myeloid or lymphoid differentiation and were studied by electron microscopy methods. One displayed platelet peroxidase (PPO) activity and was classified as a megakaryoblastic variant, one other reacted with anti-CD33 and was considered AML-M0. We conclude that light microscopy and standard immunologic methods can accurately demonstrate the lineage orientation in greater than 99% of ALs. Integration with ultrastructural analysis can define the cell nature of virtually all cases of AL.
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PMID:Lineage identification of acute leukemias: relevance of immunologic and ultrastructural techniques. 755 58

Myeloperoxidase (MPO) mRNA is an early myeloid marker; its detection in the morphologically and immunophenotypically primitive blasts of acute undifferentiated leukemia (AUL) establishes myeloid lineage and allows reclassification as acute myelogenous leukemia with minimal differentiation (AML-MO). We have previously reported a procedure for MPO mRNA detection by RT-PCR (reverse transcription-polymerase chain reaction) and an adaptation for use of routine hematology smears. This variant procedure allows retrospective analysis of mRNA and is used in the present study to evaluate the lineage of leukemic blasts in seven cases with morphology and cytochemistry consistent with AUL. All hematology smears used in this study were air-dried, unstained or Wright-stained and stored at room temperature for periods varying between 3 days and 2 years. MPO mRNA was detected in six cases, establishing the myeloid lineage of the blasts and the diagnosis of AML-MO. In the remaining case, the blasts were MPO mRNA negative, confirming the diagnosis of AUL. The RT-PCR procedure for retrospective mRNA analysis is useful in the clinical setting, due to its high specificity and sensitivity, speed (less than 24 h), safety (no radioactivity) and convenient use of routine hematology smears; it is particularly attractive in clinical situations when fresh or frozen specimens are no longer available at the time when the need for molecular diagnostics becomes apparent.
Leukemia 1995 Jul
PMID:Myeloperoxidase mRNA detection for lineage determination of leukemic blasts: retrospective analysis. 763 Feb 2

A 51-year-old female was who admitted complaining of cough and slight fever and lower limb petechia. The laboratory examinations revealed leukocytosis (49,400/microliters) with blasts (71%) in the peripheral blood. The NCC was 30 x 10(4)/microliters with 84.8% blasts in the bone marrow. Myeloperoxidase staining was positive for 6% of blasts. Auer rods were not seen in some blasts. Thus, acute myeloblastic leukemia (M1) was diagnosed according to FAB classification. In the peripheral blood, 43.3% of blasts expressed CD19, 10.3% of blasts expressed CD20 and 55.6% of blasts expressed CD33 on admission. Though she received two courses of DCMP according to the DCMP-85 protocol, and one combined course of mitoxantrone, etoposide, and Ara-C. The NCC was 20.0 x 10(4)/microliters with 70% blasts in the bone marrow. CD19 was expressed by 72.4% of blasts and 35.0% expressed CD20. The ALL-90 protocol was started, but remission was not achieved. Thus this case was considered to be acute mixed lineage leukemia.
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PMID:[Acute mixed lineage leukemia showing resistance to AML and ALL therapy]. 768 36

Myeloperoxidase (MPO) is a microbicidal protein present in the primary granules of myeloid cells. Transcription of the MPO gene is turned on only during the late myeloblast and promyelocyte stages of myeloid maturation. Identification of cis-regulatory elements and transcription factors which regulate the MPO gene should, therefore, shed light on myeloid maturation. We report transfection and in vitro transcription experiments which demonstrate promoter activity in the proximal 5'-flanking region of the human MPO gene. Using a chloramphenicol acetyl transferase (CAT) reporter vector system, and segments of the 5'-flanking MPO DNA, we constructed a series of MPO promoter-CAT expression vectors. By electroporation and lipofectin-mediated transient transfection assays, as well as by in vitro transcription studies, a 594-bp MPO DNA sequence (bp -583 to +11) showed promoter activity in a variety of MPO-expressing and non-MPO-expressing cell lines. Compared with the SV40 early promoter, the MPO promoter had greater relative activity in MPO-expressing than in non-MPO-expressing cell lines, suggesting slight tissue specificity. However, a CAT reporter plasmid containing 1099-bp of 5'-flanking MPO DNA showed greater specificity for MPO expressing cell lines. Analysis of a group of promoter deletion mutants showed that the minimal promoter was contained in a DNA fragment extending from bp-128 to +11. The remainder of the promoter region contained several segments which appeared to enhance the activity of the minimal promoter. One such enhancer sequence was homologous to an enhancer previously described in the human elastase promoter. Activity of the 594-bp MPO promoter in HL-60 was reduced by only approximately 30% following treatment of the cells with chemical inducers of maturation, but the 1099-bp MPO promoter showed 60% reduction in activity after DMSO treatment. A previously described enhancer region in intron 9 of the MPO gene had little or no effect on activity of the 594-bp MPO promoter. The availability of the MPO promoter will facilitate determination of other factors involved in the regulation of this myeloid-specific gene.
Leukemia 1995 May
PMID:Identification and characterization of the human myeloperoxidase promoter. 776 48

Myeloperoxidase (MPO), a heme-peroxidase found in the HL-60 myeloblastic cell line, is involved in vincristine (VCR) metabolism and the inactivation of this drug. We have examined whether decreased MPO activity correlated with increased sensitivity to VCR toxicity in myeloid leukemia cells. We have used MPO antisense RNA to reduce 60% of the MPO activity in the HL-60 cells. The MPO-deficient HL-60 cell line, C15, was significantly more sensitive to VCR than the parental MPO-positive cell line. Both cell lines were negative for P170-glycoprotein expression. Conversely, an MPO-positive C15 subclone was more resistant to VCR than the MPO-deficient C15 cell line. No significant differences in cytotoxic effects were observed between MPO-positive and MPO-deficient cells, following treatment with either daunorubicin or actinomycin D, two multidrug resistance-related drugs. These results strongly support an important role for MPO in VCR resistance in HL-60 cells. Antisense manipulation of the MPO content of myeloid cells could be of potential interest in leukemia treatment.
Leukemia 1994 Feb
PMID:Antisense inhibition of myeloperoxidase increases the sensitivity of the HL-60 cell line to vincristine. 790 41

Myeloperoxidase (MPO) has recently been shown in an in vitro, cell-free system to catalyze the peroxidative degradation of vincristine (VCR). Oxidation of VCR involves a ring fission between positions 20' and 21', and is thought to be facilitated by the presence of an hydroxyl (-OH) group at position 20'. We report here two different approaches, both with potential clinical application, to decrease MPO-catalyzed vinca degradation. Firstly, we tested the hypothesis that -OH substitution at position 20' increases vinca susceptibility to peroxidation by comparing the relative extent of degradation of vinorelbine (Navelbine or NVB), which lacks a 20' hydroxyl substitution, with that of VCR. As anticipated, NVB was significantly less susceptible to MPO-catalyzed peroxidation than was VCR (p < 0.01). Secondly, we screened an array of compounds that are in current clinical use for their ability to inhibit MPO. Acetaminophen, N-acetylcysteine, propylthiouracil, D-penicillamine, mefenamic acid, dapsone, and methimazole all inhibited MPO at clinically achievable concentrations. Insofar as increased MPO activity has been observed in patients with acute myeloid leukemia, these findings suggest potential strategies for improving the activity of vinca alkaloids in this disease.
Leukemia 1994 Apr
PMID:Potential strategies for circumventing myeloperoxidase-catalyzed degradation of vinca alkaloids. 815 63


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