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 administration of sodium butyrate at 0.75 mM induced the functional differentiation of U-937 human promonocytic leukemia cells with negligible cell mortality. However, the drug rapidly caused cell death with characteristics of apoptosis when used at concentrations of 5 mM and above. In addition, butyrate stimulated the expression of the stress-responsive heat-shock protein 70 (HSP70) gene when applied at both differentiation-inducing and apoptosis-inducing concentrations. The induction of HSP70 by butyrate was inhibited by the simultaneous addition of cAMP-increasing agents (dibutyryl cAMP or the combination of forskolin plus theophylline). However, these agents did not prevent differentiation and only partially reduced apoptosis. Moreover, the DNA topoisomerase II inhibitor etoposide, which provoked U-937 cell differentiation and apoptosis with the same or greater efficiency than butyrate, failed to stimulate HSP70 expression. Finally, it was observed that cAMP-increasing agents also abrogated the induction of HSP70 and reduced the apoptosis caused by cadmium chloride, a typical inducer of the stress response. Taken together, these results indicate that HSP70 expression is not required for differentiation of promonocytic cells, as earlier proposed, and that butyrate probably triggers the stress response in these cells.
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PMID:Modulation of heat-shock protein 70 (HSP70) gene expression by sodium butyrate in U-937 promonocytic cells: relationships with differentiation and apoptosis. 934 7

The c-Myb proto-oncogene is preferentially expressed in hematopoietic lineages, and highly expressed in several leukemia types. The Human T-cell Leukemia Virus Type I (HTLV-I) is the etiological agent of Adult T-cell Leukemia/Lymphoma (ATLL). A previous report suggested that Tax, the viral transactivator, is able to suppress the transactivation potential of c-Myb protein by competing for recruitment of CBP. We tested whether such a competition could affect transcription from the c-Myb promoter in Tax expressing T-cells. Using several c-Myb promoter reporter constructs carrying mutations in various regions, we demonstrate that Tax suppression of c-Myb transactivation results in transrepression of the c-Myb promoter through the Myb responsive elements in Jurkat T-cells. The ability of Tax mutants M22, M47 and V89A to interact with the full-length CBP and p300 proteins in vitro, and their ability to repress the c-Myb promoter, was then evaluated. Although both M47 and M22 bind to CBP and p300 to a similar extent, only M47 was able to repress the c-Myb promoter, suggesting that competition for CBP/p300 binding was not the mechanism underlying Tax's effect. This concept was further supported by the fact that the Tax mutant V89A transrepresses the c-Myb promoter efficiently in spite of an impaired binding to CBP and p300. Therefore, Tax-mediated repression of the c-Myb promoter appears to be independent from a direct competition between c-Myb and Tax for recruitment of CBP/p300. Interestingly, a decreased transcription from the endogenous c-Myb promoter was observed in several HTLV-I transformed T-cell lines. Finally, the ability of Tax to directly repress the endogenous c-Myb promoter was demonstrated in a Jurkat cell line stably transfected with a tax gene driven by a cadmium-inducible promoter.
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PMID:HTLV-I Tax transrepresses the human c-Myb promoter independently of its interaction with CBP or p300. 1081 7

The B-myb gene was identified on the basis of its homology with the protooncogene c-myb, homolog of the avian myeloblastosis virus (AMV) and avian leukemia virus (E26) transforming genes. Several studies using antisense constructs or antisense oligonucleotides as well as overexpression experiments suggest that B-Myb plays an important role in the transition from G(1) to S phase of the cell cycle and that B-Myb expression is cell cycle regulated. We have previously demonstrated that the human T cell lymphotropic virus type 1 (HTLV1) trans-activator Tax is able to repress transcription from c-myb promoter reporter constructs as well as from the endogenous c-myb promoter in human T cells and that this effect is mediated through inhibition of the c-Myb trans-activating functions. Here we report that both HTLV-1 as well as HTLV-2 Tax proteins inhibit c-Myb trans-activation in mouse embryo fibroblasts (MEFs). In addition to c-Myb, B-Myb expression is also markedly downregulated in HTLV-1-transformed cells at both RNA and protein levels. Furthermore, by using a Jurkat T cell line stably transfected with a tax gene driven by a cadmium-inducible promoter (JPX9), we were able to demonstrate that Tax directly represses the endogenous B-myb promoter in T cells. Because c-Myb and B-Myb have been involved in cell cycle progression, our results suggest that Tax, by repressing both c-Myb and B-Myb endogenous promoters, may bypass their requirement for cell cycle progression in HTLV-1-transformed T cells.
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PMID:Tax oncoprotein trans-represses endogenous B-myb promoter activity in human T cells. 1108 Aug 2

In this study we have examined the antitumor effect of combined administrations of indomethacin (IND) with doxorubicin (DOX) on growth of K-562 leukemia cells. Although, as single drug treatment, only high concentrations of IND reduced growth (>200 microM) and induced apoptosis (>800 microM) of the K-562 cells, a synergistic effects on DOX-induced cell growth inhibition, apoptosis and differentiation were observed during the co-administration of DOX with 10 microM IND. Cells treated with this combination had elevated GSHt level compare to DOX-treated cells. Modulation of GSHt level of DOX-treated cells with Cd2+ ions or BSO confirmed its important role in processes of DOX-induced differentiation. Results of this study showed that IND has a positive effect on therapeutic efficacy of DOX, and could be a perspective modulator in cancer chemotherapy.
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PMID:Potentiation of doxorubicin-induced apoptosis and differentiation by indomethacin in K-562 leukemia cells. 1525 71

The hematopoietic system, due to intensive cells proliferation, is very sensitive to toxic substances. Many chemicals, including benzene, pesticides (dithiocarbamines), ethylene oxide and metals (mercury, cadmium, chrome, cobalt, lead, aluminum) exert their toxic effect on the hematopoietic system. Exposure to each of these substances may occur in the work place due to environmental pollution and in municipal or residential areas. Exposure to lead, aluminum, cadmium, and benzene results in the incidence of anemia. In addition, exposure to benzene and its metabolites leads to myelodysplastic syndromes, leukemia, lymphomas and bone marrow aplasia. Ethylene oxide induces neoplasm of the hematopoietic system and lymphomas, especially non-Hodgkin lymphoma. Arsenic compounds act like immunosuppressants. Mercury and chrome affect the immune system by immunosuppression and by evoking autoimmune reactions. Dithiocarbamates are suspected to induce leukemia. An analysis of the pathophysiology of individual substances reveal universal toxic mechanisms. In this paper, the authors discuss the pathomechanism of toxic effects of the aforesaid chemicals on the haematopoietic system and peripheral blood cells from the viewpoint of mutagenesis, apoptosis, myelotoxicity, anemia, immunomodulation, and individual sensitivity.
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PMID:[Effect of metals, benzene, pesticides and ethylene oxide on the haematopoietic system]. 1621 39

L1 and Alu elements are among the most active retroposons (mobile elements) in the human genome. Several human diseases, including certain forms of breast cancer and leukemia, are associated with L1 and Alu insertions in functionally important areas of the genome. We present data demonstrating that environmental pollutants, such as heavy metals, can stimulate L1 retrotransposition in a tissue culture system using two different types of assays. The response to these agents was equivalent when using a cell line with a stably integrated L1 vector (genomic) or a by introducing the L1 vector by transient transfection (episomal) of the cell. Reproducible results showed that mercury (HgS), cadmium (CdS), and nickel (NiO) increase the activity of L1 by an average of three (3) fold p<0.001. This observation is the first to link several carcinogenic agents with the increased retrotransposition activity of L1 as an alternate mechanism of generating genomic instability contributing to the process of carcinogenesis. Our results demonstrate that mobile element activation must be considered as one of the mechanisms when evaluating genomic damage/instability in response to environmental agents.
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PMID:Heavy metals stimulate human LINE-1 retrotransposition. 1670 97

Risk assessment derives its confidence from toxicology research that is based on relevancy to human health. This article focuses on two highly topical areas of current scientific research, stem cells and chromatin biology, which present new avenues for preclinical and clinical applications, and the frontier role of tissue engineering and regeneration. Appreciating the utility and necessity of chromatin and human somatic stem cells as research tools and looking toward tissue engineering may close the uncertainty gaps between animal and human cross-species toxicology evaluations. The focus will be on developmental toxicology applications, but appropriate extrapolation to any other areas of toxicology can be made. We further provide background on basic biology of these three areas and examples of how early life exposure to known and potential environmental toxicants induce malformations, childhood and adult-onset diseases, through aberrant chromatin modification of critical gene expressions (acute lymphocyte leukemia, heavy-metal nickel and cadmium-associated defects, and reproductive tract malformations and carcinomas induced by the synthetic estrogen, diethylstilbestrol).
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PMID:Human stem cells, chromatin, and tissue engineering: boosting relevancy in developmental toxicity testing. 1753 11

Despite arsenic's (As) toxic potential, arsenic trioxide (As2O3) is used as a safe and effective treatment in acute promyelocytic leukaemia. However, it is unknown whether such therapy influences the balance of other trace elements in the body. In this study, mice were treated intraperitoneally daily with 1.0 mg As2O3/kg bw for 3, 5 or 7 days. As, and seven essential and nonessential trace elements with the potential to interact with As, were measured through inductively coupled plasma-mass spectrometry in serum, heart, lung, liver, pancreas, kidney, intestine and brain. As2O3 supplementation increased As in all target tissues on day 3, thereafter reaching an almost steady state. The major findings in other elements were a sequential decrease in serum zinc (on day 7 by 64%; P<0.001), and a decrease in selenium in the pancreas on day 3 (9%; P<0.05), in the intestine on day 3 (30%; P<0.001) and finally, in the brain on days 5 (12%; P<0.05) and 7 (15%; P<0.01). Changes in magnesium, iron, copper, cadmium and mercury were minor and inconsistent. This study suggests that supplementation with other trace elements may be beneficial when As2O3 treatment regimens are used in the clinic.
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PMID:Sequential effects of daily arsenic trioxide treatment on essential and nonessential trace elements in tissues in mice. 1869 93

In the present investigation, the effect of Spirulina platensis (Sp) was undertaken on rats fed with lead and cadmium including diet by using physiological, enzymehistochemical and stereological methods. For this aim, 50 rats were equally divided into five groups as control (C), lead (Pb), Spirulina+lead (Sp+Pb), cadmium (Cd), and Spirulina+cadmium (Sp+Cd). Red blood cell (RBC) and white blood cell (WBC) counts, packed cell volume (PCV), and haemoglobine (Hb) concentrations were determined by haemocytometric methods in blood samples collected on 30th day. Population of T lymphocyte was counted by the alpha-naphthyl acetate esterase (ANAE) staining method, and reticulocytes were counted by stereological method. The counts of RBC, WBC, and ANAE positive T lymphocyte, and the values of Hb, PCV, and MCHC were decreased in the Pb and Cd groups compared to control group. Also, the number of reticulocytes (polychromatofilic erythrocyte) increased in the Pb groups, whereas it decreased in the Cd group. On the other hand, these values were ceased by S. platensis in the treated groups. These results suggest that S. platensis supplementation may be useful in adjuvant treatment of leukemia and anemia caused by lead and cadmium toxication.
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PMID:Spirulina platensis feeding inhibited the anemia- and leucopenia-induced lead and cadmium in rats. 1897 56

Phenoxyl radicals are inevitable intermediates in the oxidative enzymatic metabolism of a phenolic antitumour drug, etoposide (VP-16), by peroxidases, cytochrome P-450, prostaglandin synthetase and tyrosinase, as well as in its interactions with oxygen and peroxyl radicals. It has been shown that one-electron reduction of the VP-16 phenoxyl radical by ascorbate and thiols prevents/delays its oxidative metabolism by tyrosinase both in model systems and in cell homogenates. To elucidate the role of endogenous thiols in the reduction of VP-16 phenoxyl radicals, K562 human leukaemia cells grown in Dulbecco's modified Eagle's medium which does not contain vitamin C (ascorbate) were used, thus excluding the ascorbate-dependent reduction of VP-16 phenoxyl radicals. VP-16 phenoxyl radicals were reduced by endogenous reductants in K562 cell homogenates, intracellular thiols mainly being responsible. Depletion of endogenous thiols by mersalyl acid resulted in almost complete inhibition of the ability of cell homogenates to reduce VP-16 phenoxyl radicals. Three systems were used to evaluate the contribution of thiol-dependent reduction of VP-16 phenoxyl radicals: (1) K562 cell homogenates depleted or supplemented with glutathione (GSH) in vitro; (2) homogenates derived from K562 cells with a decreased level of endogenous thiols and GSH (using a specific inhibitor of gamma-glutamyl cysteine synthetase, buthionine-S,R-sulfoximine; BSO) and (3) homogenates derived from K562 cells with increased content of endogenous thiols as a result of treatment with cadmium chloride. Depletion of thiols in K562 cells or cell homogenates proportionally decreased the ability of homogenates to reduce VP-16 phenoxyl radicals. Similarly, depletion or supplementation of K562 cells or cell homogenates with GSH proportionally decreased or increased the ability to reduce VP-16 phenoxyl radicals. Reduction of VP-16 phenoxyl radicals by K562 cell homogenates was similar to that obtained from cell homogenates isolated from K/VP.5 cells, a VP-16 resistant cell line derived from K562 cells. Elevation of endogenous thiols by cadmium chloride increased the ability of homogenates to reduce VP-16 phenoxyl radicals but did not reveal any significant difference in the ability of the two types of cells to interact with VP-16 radicals. Finally, BSO treatment of K562 cells led to potentiation of VP-16-induced DNA damage and to an increase in VP-16-induced growth inhibition, suggesting that, in the absence of ascorbate, modulation of endogenous thiols may be an important factor determining the oxidative metabolism and cytotoxic activity of VP-16 in tumour cells.
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PMID:Reduction of phenoxyl radicals of the antitumour agent etoposide (VP-16) by glutathione and protein sulfhydryls in human leukaemia cells: Implications for cytotoxicity. 2065 Jan 83


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