Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:A9QXG9 (bcl-2)
 7,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined the effects of high intracellular levels of Bcl-2 on the metabolism and DNA incorporation of high-dose Ara-C (HIDAC) as well as on Ara-C-induced DNA strand breaks and apoptosis of human AML HL-60 cells. HL-60/Bcl-2 and HL-60/neo cells were created by retrovirally transfecting the human AML HL-60 cells with the pZip-bcl-2 and pZip-neo plasmids, respectively. As compared to HL-60/neo, HL-60/Bcl-2 cells contained significantly higher (approximately 10-fold) p26Bcl-2, but equivalent levels of Bax and undetectable levels of Bcl-xL. HIDAC (10 or 100 microM for 4 h) produced the kilobase size and internucleosomal DNA fragmentation associated with apoptosis in HL-60/neo but not in HL-60/Bcl-2 cells. Significantly greater loss of survival (by MTT assay) and flowcytometric and morphologically recognizable apoptosis were observed in HL-60/neo cells. HIDAC did not affect Bcl-2 levels in either cell type. The intracellular accumulation of Ara-CTP relative to dCTP, Ara-C DNA incorporation and Ara-C-induced early DNA damage in the form of strand breaks (detected by alkaline elution assay) were not significantly different between HL-60/Bcl-2 and HL-60/neo cells. In addition, HIDAC treatment caused similar DNA synthesis inhibition in the two cell types. These results indicate that high intracellular levels of Bcl-2 operate distally to inhibit the final apototic cell death pathway by preventing the conversion of HIDAC-induced early DNA damage into lethal DNA fragmentation associated with apoptosis.
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PMID:Intracellular metabolism of Ara-C and resulting DNA fragmentation and apoptosis of human AML HL-60 cells possessing disparate levels of Bcl-2 protein. 889 76

The cytotoxic effect of the new potential intercalating anticancer drug oracin was studied on Burkitt's lymphoma cell line that overexpressed bcl-2 (BL bcl-2) and a control transfectant without the bcl-2 gene (BL SV2). Oracin showed a marked cytostatic effect on both BL SV2 and BL bcl-2 cells. IC50, as measured by the MTT assay, was approx. 5-times greater for BL bcl-2 cells (5.0 micromol/l) than for BL SV2 cells (1.0 micromol/l). There was no significant increase in apoptosis after 24 h of treatment with oracin (1.0 micromol/l) in both cell lines. However, after 48 h from the removal of oracin in BL SV2 culture the levels of apoptotic and secondary necrotic cells increased to 20 and 37%, respectively. In contrast, BL bcl-2 cells treated in a similar manner showed only basal levels of apoptotic and secondary necrotic cells. Analysis of the cell cycle profiles showed a significant increase of S and G2/M phases of the cell cycle in both cell lines after 6 h of drug treatment (1.0 micromol/l). The cells were arrested in G2/M phase of the cell cycle after 24 h, with no significant changes in cell viability. After 72 h, the viable BL SV2 cells were still in G2/M, however, the viability of this culture had fallen to approx. 5%. Flow cytometry analysis of the DNA content revealed the presence of a 'sub-G2' region, which represented the apoptotic cells. The BL SV2 cells died after 72 h while they were in the G2/M phase. Although the treated BL bcl-2 cells were similarly arrested in the G2/M phase, they nevertheless remained with a relatively high viability (68%).
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PMID:G2 cell cycle arrest and apoptosis are induced in Burkitt's lymphoma cells by the anticancer agent oracin. 900 May 27

Overexpression of P-glycoprotein (PGP), MRP or LRP has been characterized as the 'proximal', while overexpression of the anti-apoptosis Bcl-2 or Bcl-xL relative to the pro-apoptosis Bax protein has been recognized as the 'distal' mechanism of multidrug resistance in human AML cells. In the present studies, we examined whether these mechanisms can co-exist in human AML HL-60 cells. We also determined how these mechanisms would affect the accumulation and cytotoxicity of a PGP substrate, such as Taxol (paclitaxel). For this, immunoblot analyses were performed to determine the expression of PGP, MRP, Myc, Bcl-2, Bcl-xL and Bax on either the multidrug-resistant HL-60 sublines created under the selection pressure of doxorubicin (HL-60/AR), paclitaxel (HL-60/TAX1000) or vincristine (HL-60/VCR), or sublines created by transfection and overexpression of the bcl-2 (HL-60/Bcl-2) or bcl-xL gene (HL-60/Bcl-xL). As compared to the control HL-60, HL-60/AR cells possess high MRP while HL-60/TAX1000 and HL-60/VCR cells express high levels of the mdr-1 encoded PGP. In addition, these multidrug-resistant cells possess 1.5- to 2.5-fold higher Bcl-2, while their Bax and Myc levels are similar to those in the control HL-60 cells. HL-60/TAX1000 and HL-60/VCR cells also express three- and 2.5-fold higher Bcl-xL levels. PGP, but not MRP, overexpression significantly impaired paclitaxel accumulation and paclitaxel-induced apoptosis, as well as reduced its cytotoxic effects as determined by the MTT assay. In contrast, enforced and much higher expression of Bcl-2 in HL-60/Bcl-2 (five-fold) or Bcl-xL in HL-60/Bcl-xL cells (10-fold) significantly reduced paclitaxel-induced apoptosis and the loss of cell viability, without affecting its intracellular accumulation. These results confirm the possibility of co-expression of multiple mechanisms of multidrug resistance in human leukemic cells which had been selected by exposure to a single drug. The results also indicate that MRP overexpression does not confer resistance against paclitaxel. In addition, these findings suggest that, for Bcl-2 and Bcl-xL, enforced overexpression to high levels is necessary to induce paclitaxel resistance in HL-60 cells.
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PMID:Co-expression of several molecular mechanisms of multidrug resistance and their significance for paclitaxel cytotoxicity in human AML HL-60 cells. 900 89

Recent studies have demonstrated that following estrogen ablation, estrogen responsive breast cancer cells undergo apoptosis. In addition, estrogen receptor (ER) expression has been strongly correlated with the expression of the bcl-2 gene product, p26Bcl-2 protein, which is known to inhibit apoptosis. In the present studies, we investigated whether estrogen affects the intracellular levels of p26Bcl-2 and thereby modulates taxol-induced apoptosis of estrogen responsive human breast cancer MCF-7 cells. Transfer of MCF-7 cells to a culture-medium without estrogens reduced their intracellular p26Bcl-2 levels by 50%. Inclusion of 0.1 microM estradiol in the medium produced approximately a four-fold increase in p26Bcl-2, but not p29Bcl-x1, or p21Bax levels; the expression of the c-myc and mdr-1 genes remained unchanged. Estradiol-induced four-fold increase in the ratio of the p26Bcl-2 to p21Bax levels caused a significant decline in the lethal, kilobase size DNA fragments of apoptosis, which had resulted when MCF-7 cells were cultured in a medium without estrogen. In addition, in MCF-7 cells, estradiol-induced increase in the intracellular p26Bcl-2 to p21Bax ratios was associated with a significant reduction in the large-sized DNA fragmentation induced by treatment with taxol. The increased ratios also protected MCF-7 cells against taxol-mediated cytotoxicity as assessed by the MTT assay. These results suggest that by modulating p26Bcl-2 levels, estrogens may affect the antitumor activity of taxol and potentially of other anti-breast cancer drugs against estrogen responsive human breast cancer cells.
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PMID:Estrogen increases intracellular p26Bcl-2 to p21Bax ratios and inhibits taxol-induced apoptosis of human breast cancer MCF-7 cells. 911 21

In the present study it was investigated whether and by which mechanisms the co-administration of interleukin-3 (IL-3) and the P-glycoprotein blocker PSC 833 can augment mitoxantrone (MX) and daunorubicin (DAU) cytotoxicity in two human growth factor dependent P-glycoprotein (P-gp) positive myeloid leukemic cell lines, Mo-7 and GF-D8. Cytotoxicity was determined in MTT assay. Increased cytotoxicity occurred in Mo-7 cells preincubated with 24h IL-3 followed by 1 h MX (cell survival: 85% +/- 6 vs 68% +/- 2, at 0.05 microM MX, P < 0.005) or DAU (79% +/- 8 vs 62% +/- 9 at 0.8 microg/ml DAU, P < 0.05). Similar results were obtained for the GF-D8 cell line. In this cell line, at 0.5 microM MX the cell survival decreased from 84% +/- 13 to 61% +/- 19 (P < 0.05) and at 5.0 microg/ml DAU from 102% +/- 8 to 69% +/- 5, (P < 0.002). The IL-3 administration did not affect the P-gp and bcl-2 protein expression, cellular MX concentration or MX efflux but coincided with an increased percentage of cells in S-phase and topoisomerase II (topo II)-alpha mRNA and topo II activity especially in the Mo-7 cell line. PSC 833 enhanced DAU cytotoxicity in both cell lines. The administration of IL-3 plus PSC 833 in the Mo-7 cell line resulted in an additive effect on DAU cytotoxicity. At 0.8 microg/ml DAU and 2 microg/ml PSC 833, the percentage surviving cells decreased from 62% +/- 9 in the absence of IL-3 to 37% +/- 3 in the presence of IL-3 (P < 0.01). The additive effect of combined treatment was most pronounced in GF-D8 cells which also had the highest P-gp expression. In contrast, PSC 833 did not modulate the MX effects, irrespective of the presence of IL-3. In summary, the results demonstrate that the combined administration of IL-3 and PSC 833 can enhance the cytotoxic effects of DAU but not MX in these P-gp positive cell lines whereas the effects of MX could be modulated by factors which influence topo II activity.
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PMID:The combined effects of IL-3 and PSC 833 on daunorubicin- and mitoxantrone cytotoxicity in two growth factor-dependent leukemic cell lines. 918 Feb 92

Most antitumor agents exert their cytotoxic effect through the induction of apoptosis, and this process may be mediated through an elevation in p53 protein, with a subsequent increase in bax and decrease in bcl-2. p53 also increases mdm-2 expression and mdm-2 may then bind and inactivate p53. Cells from 31 patients with chronic lymphocytic leukemia (CLL) were treated in vitro with 2-chlorodeoxyadenosine (CdA), arabinosyl-2-fluoroadenine (F-ara-A), or chlorambucil (CLB) and drug sensitivity measured using the MTT assay. The protein levels of bax and bcl-2 were measured in CLL cells from 25 patients, and were found to be higher in leukemic cells than in normal B cells. The bcl-2 levels varied three-fold, the bax levels fifteen-fold, and the bax:bcl-2 ratios ranged from 0.44 to 2.91. The expression of mdm-2 mRNA was measured in CLL cells from 28 patients and was found to vary twenty-fold. However, no correlation was observed between drug sensitivity to CdA, F-ara-A, or CLB and the cellular levels of mdm-2 mRNA, or the protein levels of bax or bcl-2, or the bax:bcl-2 ratio. Treatment of CLL cells having wild type p53 with CdA, F-ara-A or CLB produced an increase in p53 protein and mdm-2 mRNA. This was not observed in cells having a p53 mutation, and these cells were highly resistant to both CLB and the nucleoside analogs. In contrast to the nucleoside analogs and CLB, dexamethasone and vincristine had no effect on mdm-2 mRNA levels. Treatment of CLL cells containing a wild type p53 gene with CdA, F-ara-A, or CLB, did not produce any consistent changes in bax or bcl-2. Thus, CdA, F-ara-A and CLB appear to act in CLL cells through a p53-dependent pathway, whereas this does not occur with dexamethasone or vincristine. The cellular levels of mdm-2, bcl-2, bax or the bax:bcl-2 ratios are not predictive indicators of clinical sensitivity in CLL, but an increase in mdm-2 levels after drug treatment is indicative of p53 function in these cells.
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PMID:P53, MDM-2, BAX and BCL-2 and drug resistance in chronic lymphocytic leukemia. 938 52

To characterize the pattern of cell death and to investigate the potential role of bcl-2 in a death paradigm of corneal endothelial cells, primary cultures of bovine corneal endothelial (BCEN) cells were first established and treated with 0.01-1 microM staurosporine, a nonspecific protein kinase inhibitor. The pattern of BCEN cell death induced by staurosporine was apoptotic in nature, characterized by shrinkage of the cytoplasmic membrane, nuclear condensation and DNA fragmentation. Cotreatment of BCEN cells with Z-VAD-fmk (a caspase inhibitor) but not cycloheximide (a protein synthesis inhibitor) prevented staurosporine-induced cell death. To investigate the potential role of bcl-2, BCEN cells were transferred with a eukaryotic expression vector containing anti-apoptotic bcl-2 cDNA and characterized by reverse transcription-polymerase chain reaction (RT-PCR; BCEN/bcl-2). As measured by the MTT reduction assay after treatment with staurosporine, the survival rate of BCEN/bcl-2 cells was 48.0 +/- 4.8% compared to 7.4 +/- 2.1% in control BCEN cells. As determined by light microscopy, apoptotic changes such as nuclear condensation and apoptotic bodies were largely attenuated in BCEN/bcl-2 cells after staurosporine treatment although arborization of processes and rounding up of the cell body were not affected by overexpression of bcl-2. These results suggest that staurosporine induces apoptosis in a cycloheximide-independent but caspase-dependent manner and bcl-2 acts as a negative regulator in staurosporine-induced apoptosis of BCEN cells.
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PMID:Protective role for bcl-2 in experimentally induced cell death of bovine corneal endothelial cells. 1032 44

In an attempt to understand the roles of the tumour suppressor gene p53 and the proto-oncogene bcl-2 in cell death and survival in pituitary adenomas, we investigated the relationship of their expression to the apoptotic response of two pituitary adenoma cell lines (GH3 and AtT-20) to bromocriptine. An MTT (3-4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrasolium bromide) assay was performed after treatment with bromocriptine for various periods of time over a range of concentrations to determine the effect of this drug on cell growth. Bromocriptine inhibited growth of GH3 and AtT-20 cells in a dose dependent manner. DNA fragmentation was assessed in GH3 and AtT-20 cells exposed to 10 ug/ml bromocriptine- for 48 h and 72 h. The DNA of GH3 and AtT-20 cells showed nucleosomal fragmentation, indicative of apoptosis. When assayed 2 days after adding bromocriptine, approximately 60% of GH3 and 58% of AtT-20 cells treated with bromocriptine displayed typical apoptotic morphology, including condensed chromatin and fragmented nuclei. There was a time dependent increase in the proportion of all tumour cells undergoing apoptosis. Decreased expression of bcl-2 and accumulation of wild-type p53 were associated with bromocriptine induced apoptosis in pituitary adenoma cells. DNA analysis confirmed the results obtained by the protein study. Different expression of p53 and bcl-2 genes is consistent with the expression of these gene products. These findings show that bromocriptine activated wild-type p53 and suppressed bcl-2 favouring occurrence of apoptosis in pituitary adenoma cells. Copyright 1999 Harcourt Publishers Ltd.
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PMID:Bromocriptine-induced apoptosis in pituitary adenoma cells: relationship to p53 and bcl-2 expression. 1084 57

More than 50% of patients with aggressive B lymphomas and the majority of patients with low grade lymphomas are not cured by current therapeutic strategies. The lymphomas express the B cell antigen CD20 on the cell surface and this antigen serves as target for antibody-directed therapies. Clinical studies with encouraging results have been underway with the use of a chimeric anti-CD20 antibody (IDEC-C2B8), consisting of human IgG1-6 constant regions and variable regions from the murine monoclonal anti-CD20 antibody IDEC-2B8. This study investigated the potential anti-tumor therapeutic value of combination treatment with anti-C2B8 and cytotoxic drugs. The in vitro study examined the sensitizing effect of C2B8 antibody on the DHL-4 B lymphoma line to various cytotoxic agents. Cytotoxicity was determined by the MTT assay. Surface and cytoplasmic proteins were determined by flow cytometry. Pretreatment of DHL-4 with C2B8 resulted in inhibition of cell proliferation and cell death and a fraction of the cells underwent apoptosis. While the DHL-4 tumor cells were relatively resistant to several cytotoxic drugs, pretreatment with C2B8 rendered the cells sensitive to TNF-alpha, ricin, diphtheria toxin (DTX), adriamycin and cisplatin but not to VP-16. Chemosensitization of DHL-4 tumor cells was not due to downmodulation of either the MDR-1 or bcl-2 gene products. However, treatment of DHL-4 with C2B8 inhibited TNF-alpha secretion. These findings demonstrate that C2B8 antibody potentiates the sensitivity of DHL-4 tumor cells to several cytotoxic agents. Further, the findings suggest that combination treatments with C2B8 antibody and drugs may be of clinical benefit in the treatment of patients with resistant aggressive B lymphomas.
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PMID:Chimeric anti-CD20 (IDEC-C2B8) monoclonal antibody sensitizes a B cell lymphoma cell line to cell killing by cytotoxic drugs. 1085 64

We have developed an in vitro model of 38 T-lymphoblastic leukemia lines resistant to cytosine arabinoside (ara-C) and L-asparaginase (ASNase). Of these, 26 cell lines resistant to both drugs, 6 resistant to ara-C, and 6 resistant to ASNase were isolated. In 18 of these cell lines, all randomly selected, resistance to ara-C, ASNase and gamma radiation was documented by the MTT and trypan blue assays, as well as flow cytometry with Annexin V and propidium iodide (PI) staining. In these lines, p53, p21WAF1, and bcl-2 levels were measured by ELISA. Results show that P21WAF1 upregulation following p53 induction did not occur, suggesting that p53 function may be lost. Moreover, the data imply that upregulation of bcl-2 is critical in the development of resistance to ara-C and ASNase in these leukemic lines. In the CEM/0 parent line, p53 maintained its ability to interact with its DNA binding site as documented by the electrophoretic mobility shift assay (EMSA). But in one single- and one double-resistant leukemic cell line examined, p53 was not shown to maintain this ability. We conclude that double-resistant clones to ara-C and ASNase are refractory to both drugs, providing an excellent leukemic model to investigate the multiple-drug resistance.
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PMID:Development of a double-drug-resistant human leukemia model to cytosine arabinoside and L-asparaginase: evaluation of cross-resistance to other treatment modalities. 1129 23


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