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

The in-vitro activity of a group of antifungal compounds known to inhibit ergosterol synthesis was investigated against Leishmania donovani grown as intracellular amastigotes in the human leukaemia monocyte cell line, THP-1. Toxicity on the host cells was assessed using the colorimetric MTT assay. Compounds inhibiting 2,3 oxidosqualene lanosterol cyclase; RO 43-3815, RO 43-5955, RO 43-8208, RO 42-6589 and RO 43-0688 displayed high activity with a median effective dose (ED50) of 0.6, 0.9, 3.5, 2.2 and 0.7 mg/L respectively. Of the azole compounds, oxiconazole had an ED50 value of 3.3 mg/L while ketoconazole showed the least activity. The delta-14-reductase and delta-8-delta-7 isomerase inhibitor, amorolfine, gave the highest therapeutic index with an ED50 value of 1.6 mg/L. Most compounds tested had a lower ED50 value than the standard antileishmanial drugs, sodium stibogluconate (5.5 mg Sbv/L) and meglumine antimoniate (3.0 mg Sbv/L) indicating the clean potential of these antifungal compounds in treating leishmaniasis.
 ...
PMID:The in-vitro anti-leishmanial activity of inhibitors of ergosterol biosynthesis. 814 23

The nucleoside analog, 2'-deoxycoformycin (dCF), and the alkylating agents, chlorambucil (CLB) and cyclophosphamide, are effective agents in the treatment of chronic B cell leukemias and lymphomas. The cyclophosphamide analog, 4-hydroperoxycyclophosphamide (4-HC), generates the same active metabolite as cyclophosphamide in cells and has been used extensively for bone marrow purging in vitro. We have observed that deoxyadenosine (dAdo) plus dCF (dAdo/dCF) inhibit the repair of x-irradiation-induced and bleomycin-induced DNA damage in vitro, and that this results in either synergistic or additive cytotoxicity, respectively. In the present study we examined whether dAdo/dCF, can enhance the antitumor activity of CLB and 4-HC in chronic lymphocytic leukemia (CLL) cells in vitro. CLL cells were treated with CLB for 6 hr and then with dAdo/dCF for 18 hr and cytotoxicity was measured by the MTT assay. Synergy was observed between CLB and dAdo/dCF in CLL cells from 2 patients, with synergy increasing as the CLB dose was raised. In contrast, similar treatment of human bone marrow cells resulted in little or no synergistic cell kill. Treatment of CLL cells from 2 patients with 4-HC for 30 min followed by dAdo/dCF for 18 hr resulted in little synergistic cytotoxicity, although this drug combination did produce an additive cell kill. Thus, combination therapy with nucleoside analogs and alkylating agents may be useful for improving treatment of CLL.
Leukemia 1994 Apr
PMID:Combination therapy with nucleoside analogs and alkylating agents. 815 82

The natural isoflavone genistein inhibits the growth of a number of tumour cell lines in vitro. During investigations on the antiproliferative effects of genistein we observed that, with respect to direct cell counting, a tetrazolium (MTT) colorimetric assay consistently underestimated the growth inhibitory activity of the substance. Cell proliferation was markedly inhibited by genistein in three tumour cell lines (MCF-7, human breast tumour; Jurkat cells, human T-cell leukaemia; L-929, mouse transformed fibroblasts) when cell number was evaluated by direct counting, whereas a 72-h MTT assay failed to reveal any growth-inhibitory effect. Cell cycle analysis by propidium iodide staining and flow-cytometry revealed a G2/M cell cycle arrest after genistein treatment. Genistein-treated cells displayed an increase in cell volume and in mitochondrial number and/or activity, as revealed by enhanced formazan generation and increased uptake of the vital mitochondrial dye rhodamine 123. These results suggest that alterations in cell cycle phase redistribution of tumour cells by genistein may significantly influence mitochondrial number and/or function and, consequently, MTT reduction to formazan. This may constitute an important bias in analysing the effects of genistein, and possibly other drugs that block the G2/M transition, on growth and viability of cancer cells in vitro by MTT assay.
 ...
PMID:Genistein inhibits tumour cell growth in vitro but enhances mitochondrial reduction of tetrazolium salts: a further pitfall in the use of the MTT assay for evaluating cell growth and survival. 821 51

Little is known about the precise ways in which monocytes and macrophages recognize tumor cells and how they exert their cytolytic and/or cytostatic effects. By a functional, morphologic, and flow-cytometric approach, we have studied monocyte/macrophage- and cytokine-mediated cytotoxicity against U937 cells, a human histiocytic lymphoma cell line. A rapid decrease in cell viability of U937 cells (MTT assay) could be observed at an effector-to-target cell (E:T) ratio of 10 in the presence of interferon (IFN)-gamma-activated monocytes. Light and electron microscopic examination showed the characteristic features of apoptosis of U937 cells after incubation with either monocytes or tumor necrosis factor (TNF)-alpha. TNF-alpha-induced apoptosis (10(4) U/mL) as measured by multiparameter flow cytometry (propidium iodide [PI]) paralleled the functional decrease in cell viability (MTT assay) of 20 +/- 3% after 24 hours up to a maximum of 50 +/- 4% after 48 hours. Apoptosis could be confirmed by the detection of DNA degradation into multiples of 200-bp subunits by agarose gel electrophoresis. After prolonged incubation times, monocyte-mediated leukemic cell death could be quantified as apoptosis by flow cytometry, whereas no decrease in net cell viability of tumor cells relative to the initial cell number could be observed by MTT spectrophotometry. In conclusion, our data provide evidence that apoptosis is the major mode of TNF-alpha-dependent monocyte-mediated cytotoxicity against U937 cells. Furthermore, multiparameter flow-cytometric analysis offers a sensitive method to quantify cytokine- and cell-induced apoptosis in leukemia.
 ...
PMID:Apoptosis in tumor necrosis factor-alpha-dependent, monocyte-mediated leukemic cell death: a functional, morphologic, and flow-cytometric analysis. 824 65

Topoisomerase II (topo II) is a target for many cytotoxic agents. Two observations, however, warrant caution in their therapeutic use: first, these agents can inhibit differentiation and second, perturbations in function render the enzyme error-prone. Illegitimate recombination events occurring at sites where topo II acts in differentiation could be particularly important in the development of secondary malignancies (relatively frequent after therapy with agents that target topo II). Topo II inhibitors are heterogeneous in mechanisms of action; in site-specificity of cleavable complex 'entrapment' (where present) and in the relative potency against the two topo II isoforms, all potentially influencing the site of maximum DNA damage. The object of this study was to examine the effect of topo II inhibitors on human haemopoietic precursor cells, to determine which have most impact on differentiation. We selected two which act via cleavable complex entrapment, but with different site preferences (m-AMSA and VP-16), and two acting via other mechanisms (merbarone and fostriecin). VP-16 and m-AMSA showed similar patterns with low dose stimulation of granulocyte-macrophage colony formation and high dose inhibition of all colony types. The stimulation was accompanied by an increase in colony size and blast content, consistent with a low dose inhibition of differentiation. Forstriecin, in contrast, stimulated predominantly mixed and erythroid colonies. Merbarone failed to increase colony formation. Neither produced substantial inhibition of colony formation. The effects on granulocyte-macrophage progenitors were confirmed using 7-day suspension cultures, using nitroblue tetrazolium (NBT) reduction and 3-4,5,dimethylthiazol 2,5-diphenyl tetrazolium bromide (MTT) assays for differentiated cells and total cell mass, respectively. These results demonstrate that the effects of topo II inhibitors on haemopoietic cell proliferation and differentiation are agent-specific and can involve lineage-restricted partial inhibition of differentiation.
Leukemia 1994 Jan
PMID:Effects of DNA topoisomerase II inhibitors on human bone marrow progenitor cells. 828 77

Mitoxantrone (MIT) has not been studied as a single agent in children with untreated leukemia. The antileukemic activity of MIT in these patients and its activity in relation to clinical and cell biological features is unknown. We studied the in vitro cytotoxicity of MIT, daunorubicin (DNR) and doxorubicin (DOX) in untreated childhood acute lymphoblastic leukemia (ALL, n = 131) and acute nonlymphoblastic leukemia (ANLL, n = 20) samples, using the MTT assay. There were marked interindividual differences in resistance to all three drugs. A strong, significant cross-resistance was found in ALL between MIT, DNR and DOX. All samples of the T-lineage, a prognostically unfavorable immunophenotype, however, were significantly more resistant to DNR and DOX, but not to MIT, than common or pre-B ALL samples. ALL cells from children with a prognostically unfavorable age at diagnosis, especially those < 2 years, showed a relative resistance to all three drugs compared to the intermediate age-group. This was found within all patients, but also within the common or pre-B ALL cases only. Sex, white blood cell count, or FAB type was not related to in vitro drug resistance. None of the three drugs showed an overall preferential activity in ALL or ANLL. We conclude that the in vitro antileukemic activity of MIT, DNR and DOX is related to certain clinical and cell biological features. There were no major differences between the three drugs in antileukemic activity, except that T-ALL samples were more resistant than common or pre-B ALL samples to DNR and DOX, while MIT was equally active in these two immunophenotypes.
Leukemia 1994 Jan
PMID:In vitro cytotoxicity of mitoxantrone, daunorubicin and doxorubicin in untreated childhood acute leukemia. 828 94

The effects of resistance modifiers (RM) on the cytotoxicity of mafosfamide (MAF), bis-chloroethylnitrosourea (BCNU) and dacarbazine (DTIC) were evaluated by the MTT colorimetric assay in isolated lymphocytes and blast cells derived from patients with chronic lymphatic leukaemia (CLL; n = 28) and acute myeloid leukaemia (AML; n = 30), or from healthy donors (n = 19). Pentoxifylline (PTX) has been shown to restore sensitivity to alkylating drugs by interfering with DNA repair. PTX (10 microM) significantly sensitised leukaemic blasts to the cytotoxic effect of MAF. In 8 out of 30 AML samples, sensitisation ratios (SRs; i.e. cytotoxic drug ID50s in the presence or absence of RM) for MAF in the presence of PTX were > 2 ranging up to 4.2. Inhibition of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) by O6-benzylguanine (O6-BG; 50 microM) enhanced the cytotoxicity of DTIC in CLL lymphocytes. SRs > 2 for DTIC in the presence of O6-BG were observed in 7 out of 28 CLL specimens. Sensitisation was generally greater in the more chemo-resistant specimens. Ethacrynic acid (EA; 1 microM), an inhibitor of glutathione-S-transferases (GST), failed to influence the cytotoxicity of alkylating agents in any cell type. Also, all examined RMs did not sensitive leukaemic cells to the cytotoxic effect of BCNU. The data show significant chemosensitisation of leukaemic cells to alkylating agents by PTX and O6-BG, indicating a potential clinical use of these substances as RM in patients.
 ...
PMID:Chemosensitisation of alkylating agents by pentoxifylline, O6-benzylguanine and ethacrynic acid in haematological malignancies. 829 28

The current study was undertaken to compare two methods for the efficiency of measuring tumor necrosis factor (TNF-alpha) in biological fluids, which is species undependent, reliable, sensitive, simple and not expensive. We have compared the MTT tetrazolium cytotoxic assay [1,2] and the 3H-thymidine (3H-TdR) incorporation cytostatic assay for measuring the anti-tumor activity of human recombinant TNF-alpha, of human colonic tissue and of supernatants of in vitro stimulated human and rat peritoneal macrophages. Two target cell-lines, namely murine myelomonocytic leukaemia WEHI-164- and L-929-transformed murine fibroblast cell-lines, were used in the MTT assay. The L-929 line was also used in the 3H-TdR assay. WEHI-164 was more sensitive than the L-929 cell-line in the MTT cytotoxic assay. Furthermore, the MTT assay was more sensitive to TNF-alpha than the 3H-TdR assay. Both methods can be used for the detection of anti-tumor activity in biological fluids but the MTT cytotoxic method has the advantage of being more sensitive and more simple.
 ...
PMID:A comparison between two methods for measuring tumor necrosis factor in biological fluids. 831 31

A new and simple method for quantitating adhesion of leukemia cells, HL60, to endothelial cells was developed. HL60 cells were incubated with MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) which forms a blue dye of formazan in the cells. MTT did not inhibit shape change of HL60 cells induced on activated endothelial cells at 90 min. The expression of a cell adhesion molecule, LFA-1, in HL60 cells at 21 h was not inhibited by MTT. After incubation of the MTT-labeled cells and endothelial cells, non-adhered cells were washed out. Adhered cells were lysed with dimethylsulfoxide, and quantitated by measuring absorbance at 540 nm. The absorbance was well correlated with the adherent cell numbers measured by direct counting or by 51Cr-labeling method. U937 and Ramos cells were also quantitatively labeled by MTT. The method has the advantage of being easy, simple and applicable to various cell-cell adhesion assays.
 ...
PMID:Simple colorimetric cell-cell adhesion assay using MTT-stained leukemia cells. 837 Sep 31

To investigate the possibility of killing tumor cells by the expression of an exogenously introduced toxic gene, we have constructed a novel retroviral vector (LTRNL) which has the polyA signal deleted herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene. The vector becomes toxic by treating cells expressing HSV1-tk with the antiherpetic drugs acyclovir or ganciclovir (GCV). Cells of the human leukemia lines (K562, MEG-01) were infected with this vector and two transduced cell lines (K562/LTRNL, MEG-01/LTRNL) were established. Southern blot analysis confirmed the integration of the HSV1-tk transgene in these cells and Northern blot analysis exhibited the expression of 4.8-kb viral mRNA containing the HSV1-tk gene. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay for the in vitro cytotoxic effects of GCV to these cells demonstrated that concentrations of about 2.5 microM for K562/LTRNL and 1.25 microM for MEG-01/LTRNL cells resulted in 50% inhibition of cell growth after 72 hr. Subcutaneous tumors of MEG-01/LTRNL in KSN nude mice, but not those of uninfected MEG-01 cells, showed durable regressions after exposure of the mice to 40 mg/kg of GCV given subcutaneously once a day for 15 days. This study indicates that the LTRNL-infected human leukemia cells exhibit inducible susceptibility to GCV.
 ...
PMID:Transduction of a drug-sensitive toxic gene into human leukemia cell lines with a novel retroviral vector. 839 Jun 93


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>