Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interactions between the protein kinase C (PKC) activator/down-regulator bryostatin 1 and paclitaxel have been examined in human myeloid leukemia cells (U937) and in highly paclitaxel-resistant cells ectopically expressing a Bcl-2 phosphorylation loop-deleted protein (Delta Bcl-2). Treatment (24 hours) of wild-type cells with paclitaxel (eg, 5 to 20 nM) in combination with 10 nM bryostatin 1 induced a marked increase in mitochondrial damage (eg, cytochrome c and Smac/DIABLO [second mitochondria-derived activator of caspases/direct IAP binding protein with low pI] release), caspase activation, Bid cleavage, and apoptosis; moreover, bryostatin 1 circumvented the block to paclitaxel-induced mitochondrial injury and apoptosis conferred by ectopic expression of the loop-deleted protein. Coadministration of tumor necrosis factor (TNF) soluble receptors, or ectopic expression of CrmA or dominant-negative caspase-8, abrogated potentiation of paclitaxel-induced mitochondrial injury and apoptosis by bryostatin 1, implicating the extrinsic apoptotic pathway in this process. Similar events occurred in HL-60 leukemia cells. Potentiation of paclitaxel-induced apoptosis in wild-type and mutant cells by bryostatin 1 was associated with increases in TNF-alpha mRNA and protein and was mimicked by exogenous TNF-alpha. Coadministration of the selective PKC inhibitor GFX (1 microM) blocked the increase in TNF-alpha mRNA levels and apoptosis in bryostatin 1/paclitaxel-treated cells. Lastly, synchronization of cells in G(2)M increased their sensitivity to TNF-alpha-associated lethality. Collectively, these findings indicate that in U937 cells, bryostatin 1 promotes paclitaxel-mediated mitochondrial injury and apoptosis, and circumvents resistance to cell death conferred by loss of the Bcl-2 phosphorylation domain, through the PKC-dependent induction of TNF-alpha. They further suggest that this process is amplified by paclitaxel-mediated arrest of cells in G(2)M, where they are more susceptible to TNF-alpha-induced lethality.
 ...
PMID:Induction of tumor necrosis factor by bryostatin 1 is involved in synergistic interactions with paclitaxel in human myeloid leukemia cells. 1252 1

Interactions between the protein kinase C activator bryostatin 1 and the cyclin-dependent kinase (CDK) inhibitor flavopiridol (FP) have been examined in human myeloid leukemia cells (U937 and HL-60). Previous studies have demonstrated synergistic induction of apoptosis in leukemic cells exposed to the potent differentiation-inducer phorbol 12-myristate 13-acetate (PMA) in conjunction with FP [L. Cartee et al., Cancer Res., 61: 2583-2591, 2001]. Although bryostatin 1 (10 nM) is a very weak inducer of differentiation compared with PMA in these cells, coadministration of a minimally toxic concentration of FP (100 nM) did not promote bryostatin 1-related maturation but instead caused a marked increase in mitochondrial damage (e.g., cytochrome c release; loss of Deltapsi(m)), caspase activation, poly(ADP-ribose) polymerase cleavage, and apoptosis. Bryostatin 1/FP-induced apoptosis was significantly diminished in cells ectopically expressing dominant-negative Fas-associated death domain or by coadministration of tumor necrosis factor (TNF)-alpha soluble receptors, implicating the extrinsic pathway in bryostatin 1/FP actions. Enhanced apoptosis in bryostatin 1/FP-treated cells was accompanied by down-regulation of Mcl-1 and a sustained increase in TNF-alpha release. The selective protein kinase C inhibitor GFX blocked TNF-alpha and cytochrome c release in bryostatin 1/FP-treated cells and attenuated apoptosis. Finally, coadministration of bryostatin 1 (or PMA) with FP induced a marked increase in apoptosis in U937 cells ectopically expressing an NH(2)-terminal phosphorylation loop-deleted Bcl-2 protein, which are otherwise highly resistant to FP-mediated lethality. Taken together, these findings suggest that synergistic induction of apoptosis by bryostatin 1 and FP does not stem from disruption of the leukemic cell maturation process but instead results from enhanced release of TNF-alpha and activation of the extrinsic apoptotic cascade, culminating in cell death.
 ...
PMID:Protein kinase C-dependent activation of the tumor necrosis factor receptor-mediated extrinsic cell death pathway underlies enhanced apoptosis in human myeloid leukemia cells exposed to bryostatin 1 and flavopiridol. 1253 76

Phorbol 12-myristate 13-acetate (PMA) is a protein kinase C (PKC) activator and tumor promoter that induces terminal differentiation in human myeloid leukemia cells. We undertook to characterize phorbol ester-activated PKC-mediated cell cycle arrest and apoptosis. In the present studies, we determined the effect of high intracellular levels of the anti-apoptosis Bcl-2 protein on caspase 3 activation and cyctochrome c release during phorbol ester 12-myristate 13-acetate (PMA)-induced apoptosis. For this, we used the U937 cells, Bcl-2 overexpressed U937 cells (U937/Bcl-2) and the PMA-resistant derivative cell line R-U937. The G1 arrest of U937 cells and U937/Bcl-2 cells induced by treatment with 20 nM PMA is associated with cyclin A down-regulation and accumulation of p21, cdks inhibitor. However, PMA had no effect on the levels of cyclin A expression and p21 expression under the same conditions of time and concentration of PMA in the R-U937 cells. Treatment with 20 nM PMA for 24 h produced morphological features of apoptosis and DNA fragmentation in U937 and U937/Bcl-2 cells, but not in R-U937 cells. This was associated with the caspase 3 activation and cyctochrome c release. R-U937 cells exhibited less cytochrome c release and sustained phosphorylation level of Akt during PMA-induced apoptosis. These findings indicate that R-U937 cells are resistant to PMA-induced apoptosis by a mechanism of the signaling defect in the activation of the caspase 3 that is involved in the execution of apoptosis.
 ...
PMID:Inactive caspase 3 activates Akt in human leukemia cells susceptible or resistant to apoptosis induced by phorbol ester. 1268 78

Daunorubicin (DNR) induces apoptosis in the human myeloid leukemia cells by activation of neutral sphingomyelinease and ceramide production. In the present study, we determined the effect of the antiapoptosis protein Bcl-2 on caspase-3 activation, phospholipase C-gamma 1 (PLC-gamma 1) degradation and cytochrome c release during the DNR-induced apoptosis. Treatment with 3 microM DNR for 12 hr produced morphological features of apoptosis and DNA fragmentation in U937 cells, which was associated with caspase-3 activation and PLC-gamma 1 degradation. Induction of apoptosis was also accompanied by release of cytochrome c, down-regulation of X-linked inhibitor of apoptosis protein (XIAP), and inactivation of Akt, which was blocked by the pan-caspase inhibitor z-VAD-fmk. DNR-induced caspase-3 activation, PLC-gamma 1 degradation and apoptosis were significantly attenuated in Bcl-2 overexpressing U937/Bcl-2 cells. Ectopic expression of Bcl-2 appeared to inhibit DNR-induced apoptosis by interfering with inhibition of XIAP and Akt degradation.
 ...
PMID:Bcl-2 overexpression prevents daunorubicin-induced apoptosis through inhibition of XIAP and Akt degradation. 1456 88

In past studies, we showed that T cells transduced with retroviral diphtheria immunotoxin (IT) target genes could serve as vehicles for delivering IT to tumors in vivo. We took advantage of the observation that antigen-specific T cells are able to penetrate tumors to design an approach delivering combined cellular and humoral therapy directly to the tumor site. To improve tumor specificity, we selected interleukin (IL)-3 as a ligand because its receptor is selectively overexpressed on myeloid leukemia progenitors. Because Bcl-2 family proteins show structural similarity to diphtheria toxin (DT), we constructed a unique retroviral IT using Bax, a proapoptotic member of the Bcl-2 family, in place of DT. Bax was chosen because several studies showed that its transduction induces lethal apoptosis in different cancers. The retroviral construct for gene therapy included IL-3 positioned downstream of its 80 amino acid leader, and permitted cotranslational protein synthesis of hybrid IL-3/human Bax fusion protein. Other vectors were constructed with IL-3 fused to DT or Pseudomonas exotoxin. Retroviral vectors were used to transiently transduce C8, a CD4(+) T cell clone that specifically recognized FBL-3, a lethal myeloid leukemia. Supernatants collected from transduced cells showed proapoptotic activity and selectively inhibited FBL-3 cells in vitro. Intraperitoneal injection of transduced but not nontransduced C8 into mice with subcutaneous tumors or systemic cancer significantly inhibited tumor growth. These results indicate that retroviral IT made with IL-3 and various toxic proteins may be useful in patients with acute myelogenous leukemia (AML). Furthermore, the Bax construct may be particularly useful as a nonimmunogenic substitute for bacterial toxins in retIT.
 ...
PMID:Retroviral immunotoxin gene therapy of leukemia in mice using leukemia-specific T cells transduced with an interleukin-3/Bax fusion protein gene. 1467 Jan 29

Interactions between histone deacetylase (HDAC) inhibitors and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), also known as Apo2 ligand, were examined in human leukemia cells (e.g., U937, Jurkat, and HL-60). Simultaneous exposure of cells to 100-ng/ml TRAIL with either 1-mM sodium butyrate or 2- micro M suberoylanilide hydroxamic acid resulted in a striking increase in leukemic cell mitochondrial damage, caspase activation, and apoptosis. Lethal effects were significantly diminished in U937 cells ectopically expressing dominant-negative caspase-8, dominant-negative Fas-associated death domain, CrmA (receptor pathway), or Bcl-2 or Bcl-X(L) (mitochondrial pathway). Analysis of mitochondrial events in U937 cells exposed to TRAIL/HDAC inhibitors revealed enhanced Bid activation and Bax translocation, loss of mitochondrial membrane potential, and cytoplasmic release of cytochrome c, Smac/DIABLO, and apoptosis-inducing factor. No changes were observed in expression of FLICE-like inhibitory protein, TRAIL receptors, or reactive oxygen species generation. TRAIL/HDAC inhibitor-induced apoptosis triggered caspase-dependent cleavage of p21(WAF1/CIP1); moreover, enforced expression of a nuclear localization signal deletant form of p21(WAF1/CIP1) significantly diminished lethality. Lastly, p27(KIP1), pRb, X-linked inhibitor of apoptosis, and Bcl-2 displayed extensive proteolysis. These findings indicate that coadministration of TRAIL with HDAC inhibitors synergistically induces apoptosis in human myeloid leukemia cells and provide further evidence that simultaneous activation of the extrinsic and intrinsic pathways in such cells leads to a dramatic increase in mitochondrial injury and activation of the caspase cascade.
 ...
PMID:Simultaneous activation of the intrinsic and extrinsic pathways by histone deacetylase (HDAC) inhibitors and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) synergistically induces mitochondrial damage and apoptosis in human leukemia cells. 1470 68

Hydroxyurea (HU) is an inhibitor of nucleotide synthesis extensively used to control the chronic phase of myeloid leukemia. This antimetabolite has been employed in the clinic for several decades but in recent years the leukemogenic potential of HU has been suspected. In the present study, a B-lymphoblastoid cell line transformed by the Epstein-Barr virus was used to investigate the apoptotic effects of HU and delineate some of the molecular pathways implicated in the cytotoxic action. The cell line, characterized by immunophenotyping, cytogenetic and fluorescence in situ hybridization (FISH) studies, showed no chromosomal abnormalities, even after a prolonged exposure to HU. Different flow cytometry assays were used to measure HU-induced impairment of the cell cycle, inhibition of DNA synthesis, and the occurrence of apoptosis. The treatment with HU leads to the appearance of a hypo-diploid DNA content peak (sub-G1) characteristic of the apoptotic cell population. The drug also induces a cell block in S phase as measured by 5-bromo-2'-deoxyuridine (BrdU) incorporation. Inhibition of DNA synthesis precedes induction of apoptosis by HU. A drug-induced loss of plasma membrane asymmetry was characterized by flow cytometry using annexin V-FITC to stain phosphatidylserine residues. The implication of the antiapoptotic protein Bcl-2 and the tumor suppressor p53 in the development of HU-mediated apoptosis was also evidenced. The drug appears to promote cell death by regulating the expression levels of these two proteins. Different criteria define the apoptotic response of the lymphoblastoid cells to the treatment with HU. However, the extent of drug-induced cell death is limited, and no DNA fragmentation and no activation of the caspase cascade was observed in this model. Beyond the specific interest in HU-induced apoptosis, the work reported here illustrates the utility of the EBV immortalization process to investigate the pharmacological activity of specific drugs from clinical samples.
 ...
PMID:Hydroxyurea-induced apoptosis in an EBV-immortalized lymphoblastoid cell line. 1497 55

Phyllanthus urinaria (P. urinaria), a widely used herb medicine, was tested for the anticancer effect on human myeloid leukemia cells in this study. The water extract of P. urinaria induced the apoptosis of HL-60 cells as demonstrated by morphological change, DNA fragmentation and increased caspase-3 activity. However, normal human peripheral mononuclear cells remained viable under the same treatment. The P. urinaria-induced apoptosis of HL-60 cells was associated with the increased Bax gene expression and decreased Bcl-2 gene expression. In addition, the gene expressions of Fas receptor and Fas ligand, but not p53, were also induced in HL-60 cells dose- and time-dependently. The inhibitor of ceramide synthase, fumonisin B1, completely suppressed the apoptosis induced by P. urinaria and this inhibitory effect of fumonisin B1 could be eliminated by the addition of ceramide. It indicated that the activity of ceramide synthase is critical for the P. urinaria-induced apoptosis in HL-60 cells. The P. urinaria-induced apoptosis in HL-60 cells is mediated through a ceramide-related pathway.
 ...
PMID:Phyllanthus urinaria induces the Fas receptor/ligand expression and ceramide-mediated apoptosis in HL-60 cells. 1513 54

Treatment for 14 to 24 hours with low concentrations of arsenic trioxide (As2O3, 1-4 microM) caused apoptosis in U-937 promonocytes and other human myeloid leukemia cell lines (HL-60, NB4). This effect was potentiated by cotreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 and wortmannin, and the Akt inhibitor Akt(i)5. However, the inhibitors did not increase the toxicity of the mitochondria-targeting drug lonidamine, and the DNA-specific drugs camptothecin and cisplatin, when used under similar experimental conditions as As2O3. The potentiation of As2O3-provoked apoptosis involved the increased disruption of mitochondrial transmembrane potential, increased caspase-3 activation and cytochrome c release from mitochondria, increased Bax and Bid activation, and attenuation of 27-kDa heat shock protein (HSP27) expression; the potentiation was prevented by Bcl-2 overexpression. The PI3K/Akt inhibitors decreased the intracellular glutathione content, and caused intracellular oxidation, as measured by peroxide accumulation. Cotreatment with subcytotoxic concentrations of hydrogen peroxide increased apoptosis induction by As2O3. On the other hand, the treatments did not significantly affect glutathione S-transferase pi expression and activity. These results, which indicate that glutathione is a target of PI3K/Akt in myeloid leukemia cells, may partially explain the selective increase of As2O3 toxicity by PI3K/Akt inhibitors, and may provide a rationale to improve the efficacy of these inhibitors as therapeutic agents.
 ...
PMID:Pharmacologic inhibitors of PI3K/Akt potentiate the apoptotic action of the antileukemic drug arsenic trioxide via glutathione depletion and increased peroxide accumulation in myeloid leukemia cells. 1566 16

Ponicidin, an extract from the Chinese herb Rabdosia rubescens, is currently one of the most important traditional Chinese herbal medicines. Ponicidin has been reported to have anti-tumor effects on a large variety of malignant diseases. In this study, we investigated the anti-proliferation effects of ponicidin on human myeloid K562 and HL-60 cells. Cell viability was measured by MTT assay; cell apoptosis was assessed by flow cytometry, DNA fragmentation analysis and Hoechst 33258 staining. Caspase-3 and poly(ADP-ribose) polymerase (PARP) activation and Bax and Bcl-2 expression were detected by Western blot analysis. The results revealed that ponicidin could significantly inhibit the growth of K562 and HL-60 cells by induction of apoptosis. The suppression was both time- and dose-dependent. Cell apoptosis was observed clearly after the cells were treated with ponicidin for 48-72 h. Western blotting showed cleavage of the caspase-3 zymogen protein (32 kDa) with the appearance of its 17 kDa subunit, together with a cleaved 89-kDa fragment of 116 kDa PARP when apoptosis occurred. Bcl-2 expression was down-regulated while Bax expression up-regulated concurrently when the cells were treated with ponicidin for 24-48 h. Therefore, we conclude that ponicidin has significant anti-proliferation effects by induction of apoptosis on myeloid leukemia cells in vitro, down-regulation of Bcl-2, and up-regulation of Bax, and that activation of caspase-3 and PARP may be an important apoptosis-inducing mechanism. The results suggest that ponicidin may serve as a potential therapeutic agent for leukemia.
 ...
PMID:Antiproliferation effects of ponicidin on human myeloid leukemia cells in vitro. 1575 38


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