11 results on '"Ponnathpur V"'
Search Results
2. Effects of modulators of protein kinases on taxol-induced apoptosis of human leukemic cells possessing disparate levels of p26BCL-2 protein
- Author
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Ponnathpur V, Am, Ibrado, Jc, Reed, Ray S, Huang Y, Self S, Bullock G, Nawabi A, and Kapil Bhalla
- Subjects
G2 Phase ,Paclitaxel ,Apoptosis ,DNA Fragmentation ,Staurosporine ,Antineoplastic Agents, Phytogenic ,Genistein ,Neoplasm Proteins ,S Phase ,Proto-Oncogene Proteins c-bcl-2 ,Carcinogens ,Tumor Cells, Cultured ,Humans ,Enzyme Inhibitors ,Phorbol 12,13-Dibutyrate - Abstract
Taxol-induced polymerization of tubulin into stable microtubules and cell cycle metaphase arrest have been demonstrated to result in internucleosomal DNA fragmentation and morphological features of apoptosis in human leukemia cells. Recent studies have also shown that Taxol-induced apoptosis, but not Taxol-induced microtubular bundling or mitotic arrest, is significantly inhibited in cells that overexpress the bcl-2 gene product p26BCL-2. In the present studies we examined the effects of several modulators of activities of protein kinases on Taxol-induced DNA fragmentation and apoptosis in human pre-B leukemia 697 cells transfected with the cDNA of the bcl-2 gene and expressing high intracellular levels of p26BCL-2 (697/BCL-2 cells). Treatment with 0.1-1.0 microM MTaxol for 24 h produced prolonged mitotic arrest of control 697/neo cells, which had been transfected with the neomycin resistance gene. This resulted in apoptosis-associated large DNA fragments ranging between 5 and 200 kb and internucleosomal DNA fragmentation. Cotreatment with the phorbol ester phorbol dibutyrate (PdBU) significantly reduced Taxol-induced internucleosomal and large DNA fragmentation and inhibited apoptosis of 697/neo cells. In contrast, a combined exposure to Taxol and staurosporine (ST; 5 or 50 ng/ml), a potent inhibitor of protein kinase C and other kinases, significantly increased DNA fragmentation and apoptosis of 697/neo cells. Additionally, in 697/BCL-2 cells, ST partially overcame the suppressive effects of high p26BCL-2 levels on Taxol-induced apoptosis. Cotreatment with the tyrosine kinase inhibitor Genistein (30 microM) markedly inhibited Taxol-induced DNA fragmentation and apoptosis of 697/neo cells. However, it is noteworthy that the modulations of Taxol-induced DNA fragmentation and apoptosis by PdBU, ST, and Genistein occurred without significant effects on Taxol-mediated mitotic arrest of 697/neo cells. These agents also did not affect intracellular p26BCL-2 levels in 697/neo or 697/BCL-2 cells. These findings indicate that Taxol-induced apoptosis can be modulated by agents that affect the activities of protein kinases, and these effects are not mediated by modulations of Taxol-induced mitotic arrest or by alterations of intracellular p26BCL-2 levels. more...
- Published
- 1995
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3. Characterization of a human myeloid leukemia cell line highly resistant to taxol
- Author
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Kapil Bhalla, Huang Y, Tang C, Self S, Ray S, Me, Mahoney, Ponnathpur V, Tourkina E, Am, Ibrado, and Bullock G
- Subjects
Membrane Glycoproteins ,Paclitaxel ,Daunorubicin ,Drug Resistance ,Apoptosis ,DNA, Neoplasm ,Microtubules ,Verapamil ,Leukemia, Myeloid ,Cyclosporine ,Tumor Cells, Cultured ,Humans ,ATP Binding Cassette Transporter, Subfamily B, Member 1 ,Carrier Proteins ,Cell Division - Abstract
Taxol-resistant sublines of HL-60 myeloid leukemia cells (HL-60/TAX100 and HL-60/TAX1000) have been isolated in vitro by subculturing in progressively higher concentrations of taxol. HL-60/TAX100 and HL-60/TAX1000 cells are capable of continuous growth in the presence of 0.1 microM and 1.0 microM taxol, respectively, and the IC50 (50% growth inhibitory dose) values for taxol for the two sublines are 0.34 and 2.44 microM as compared to 3.1 nM for the parent HL-60 cells. HL-60/TAX100 and HL-60/TAX1000 cells display a variable degree of cross-resistance to taxotere, vincristine and doxorubicin, but are sensitive to the antimetabolite Ara-C. Both HL-60/TAX100 and HL-60/TAX1000 cells over-express MDR-1 m-RNA and the membrane efflux multidrug transporter P-glycoprotein (PGP), as determined by Western blot and immunofluorescence labeling with anti-PGP antibodies. Consequently, exposure of the taxol-resistant cells to [3H]taxol or daunomycin results in the accumulation of significantly lower levels of the two drugs. Co-treatment with cyclosporine (0.5 microgram/ml) or verapamil (10 microM) partially overcomes taxol resistance in HL-60/TAX1000 cells. Following treatment with clinically relevant concentration of taxol (1.0 microM for 24 h), HL-60 but not HL-60/TAX1000 cells display intracellular microtubular bundling, markedly enhanced accumulation of the cells in G2/M phase of cell-cycle and internucleosomal DNA fragmentation associated with apoptosis which is independent of bcl-2 gene expression. These taxol-resistant myeloid leukemia cells may serve as in vitro experimental models for examinating strategies which may have potential applicability for overcoming taxol resistance. more...
- Published
- 1994
4. High-dose mitoxantrone induces programmed cell death or apoptosis in human myeloid leukemia cells
- Author
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Bhalla, K, primary, Ibrado, AM, additional, Tourkina, E, additional, Tang, C, additional, Grant, S, additional, Bullock, G, additional, Huang, Y, additional, Ponnathpur, V, additional, and Mahoney, ME, additional more...
- Published
- 1993
- Full Text
- View/download PDF
5. 1-beta-D-arabinofuranosylcytosine-, mitoxantrone-, and paclitaxel-induced apoptosis in HL-60 cells: improved method for detection of internucleosomal DNA fragmentation.
- Author
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Ray, S, Ponnathpur, V, Huang, Y, Tang, C, Mahoney, M E, Ibrado, A M, Bullock, G, and Bhalla, K
- Subjects
AGAR ,ANTINEOPLASTIC agents ,APOPTOSIS ,COMPARATIVE studies ,DNA ,DRUG administration ,DOSE-effect relationship in pharmacology ,ELECTROPHORESIS ,HUMAN genome ,RESEARCH methodology ,MEDICAL cooperation ,PACLITAXEL ,RESEARCH ,EVALUATION research ,ACUTE myeloid leukemia ,CYTARABINE ,MITOXANTRONE ,CANCER cell culture ,PHARMACODYNAMICS - Abstract
We investigated the ability of different doses and durations of exposure to the chemotherapeutic drugs 1-beta-D-arabinofuranosylcytosine (Ara-C), mitoxantrone (MTN), and paclitaxel (taxol, TXL) to induce internucleosomal DNA fragmentation and apoptosis in human acute myeloid leukemia (AML) HL-60 cells in suspension culture. At clinically achievable concentrations, all three drugs have been shown to induce apoptosis in HL-60 cells. An improved method was developed for the isolation of pure genomic DNA and the detection of drug-induced internucleosomal DNA fragmentation in < 1.0 microgram of DNA sample by agarose gel electrophoresis. Morphologic evidence for apoptosis was determined by light microscopy following Wright staining, and cell viability was assessed by trypan blue dye exclusion. Internucleosomal DNA fragmentation was observed following exposure to 1.0 microM Ara-C for 4 h, which increased with 10 and 50 microM Ara-C. Incubation with 100 microM Ara-C produced internucleosomal DNA fragmentation starting at 3 h, which increased with longer periods of exposure to Ara-C. Utilizing a schedule of 1-h exposure followed by 3-h suspension in drug-free medium, 0.25 microM MTN was found to initiate DNA fragmentation, which increased with exposure to 1.0 and 5.0 microM MTN. However, identical treatment with higher concentrations of MTN resulted in random DNA degradation. Alternatively, continuous exposure to 1.0 microM MTN for 3 h was necessary to initiate internucleosomal DNA fragmentation. This increased with exposure intervals of up to 6 h. Exposure to TXL concentrations as low as 0.01 microM for 24 h caused internucleosomal DNA fragmentation, which increased with dose escalation (0.05, 0.1, 0.5, and 1.0 microM) of TXL. Although continuous exposure to 1.0 microM TXL for a period as short as 8 h produced internucleosomal DNA fragmentation, this increased significantly with longer exposure intervals. In general there appears to be a threshold concentration and duration of exposure below which none of these three drugs activates endonucleolytic internucleosomal DNA fragmentation and apoptosis. This threshold is lower for the DNA-interactive drugs MTN and Ara-C but higher for the non-DNA-interactive drug TXL. Higher doses or prolonged treatments with the drugs produce random DNA fragmentation associated with necrotic cell death. These in vitro results may further improve our understanding of the antileukemic cytotoxic effects of these drugs, which may enable a more rational design of drug regimens for optimal treatment of AML. [ABSTRACT FROM AUTHOR] more...
- Published
- 1994
6. High levels of p26BCL-2 oncoprotein retard taxol-induced apoptosis in human pre-B leukemia cells
- Author
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Tang C, Mc, Willingham, Jc, Reed, Miyashita T, Ray S, Ponnathpur V, Huang Y, Me, Mahoney, Bullock G, and Kapil Bhalla
- Subjects
Paclitaxel ,Apoptosis ,DNA, Neoplasm ,In Vitro Techniques ,Protein-Tyrosine Kinases ,Phosphoproteins ,Microtubules ,Proto-Oncogene Proteins c-bcl-2 ,Tubulin ,Precursor B-Cell Lymphoblastic Leukemia-Lymphoma ,Proto-Oncogene Proteins ,Tumor Cells, Cultured ,Tyrosine ,ATP Binding Cassette Transporter, Subfamily B, Member 1 ,Phosphotyrosine ,Cell Division ,DNA Damage - Abstract
In human leukemic cells clinically relevant concentrations of taxol have been demonstrated to induce the biochemical and morphologic hallmarks of apoptosis (Leukemia 1993;7:563-568). Since overexpression of the bcl-2 gene has been reported to retard apoptosis due to a variety of anticancer agents, we examined and compared taxol-induced intracellular microtubular bundling and apoptosis in pre-B human leukemia 697 cells and their counterparts which have been transfected with and overexpress cDNA derived from the bcl-2 gene. Treatment with 0.1 or 1.0 mumol/l taxol for 24 h resulted in internucleosomal DNA fragmentation and morphologic features of apoptosis in 697 cells, but not in 697/BCL-2 cells. However, indirect immunofluorescent staining with anti-tubulin antibody revealed that taxol treatment produces stable microtubule bundles resistant to calcium-mediated disassembly in 697, as well as 697/BCL-2 cells. In addition, taxol-induced microtubule bundling was associated with a marked accumulation of the two cell types in the G2/M phase of the cell cycle. Following exposure to taxol, when 697 cells were washed and kept in drug-free medium, they showed rapid onset of apoptosis followed by loss of cell viability and a decline in cell numbers. In contrast, identically treated 697/BCL-2 cells kept in drug-free medium remained in a growth arrested state, but showed little evidence of apoptosis for up to 4 days. They eventually demonstrated features of apoptotic cell death and loss of viability between 5 and 7 days. This was not accompanied by a decrease in p26BCL-2 levels. Anti-phosphotyrosine or anti-MAP kinase immunoblot analyses of proteins isolated from taxol-treated 697 and 697/BCL-2 cells failed to show any difference in tyrosine phosphorylation of cellular proteins. Therefore, our findings indicate that in 697/BCL-2 cells, high levels of p26BCL-2 significantly delay taxol-induced endonucleolytic internucleosomal DNA fragmentation and apoptosis, but do not affect taxol-induced microtubule bundling or cell cycle growth arrest. The delayed onset of taxol-induced DNA fragmentation and apoptosis in 697/BCL-2 cells without down-regulation of p26BCL-2 levels suggests that an alternative mechanism of taxol-mediated apoptosis might be triggered which is unimpeded by high p26BCL-2 levels, or taxol-induced prolongation of mitotic arrest may lead to the inactivation or inhibition of that mechanism by which p26BCL-2 is able to block apoptosis. more...
7. Mechanisms of resistance to Taxol induced apoptosis in human leukemic cells
- Author
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Ponnathpur, V., Tang, C., Reed, J.C., Huang, Y., Willingham, M.C., Rav, S., Bullock, G., and Bhalla, K.
- Subjects
Drug resistance -- Physiological aspects ,Business ,Health care industry ,Taxol (Medication) -- Physiological aspects - Abstract
AUTHORS: V. Ponnathpur, C. Tang, J.C. Reed, Y. Huang, M.C. Willingham, S. Rav, G. Bullock and K. Bhalla. Division of Hematology/Oncology, Department of Medicine, and Department of Pathology and Laboratory [...] more...
- Published
- 1994
8. Echocardiographic atrioventricular interval optimization in patients with dual-chamber pacemakers and symptomatic left ventricular systolic dysfunction.
- Author
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Gilligan DM, Sargent D, Ponnathpur V, Dan D, Zakaib JS, and Ellenbogen KA
- Subjects
- Aged, Cardiac Output, Low, Cross-Over Studies, Double-Blind Method, Echocardiography, Doppler, Exercise Tolerance, Heart Block diagnostic imaging, Heart Failure diagnostic imaging, Hemodynamics physiology, Humans, Male, Prognosis, Quality of Life, Risk Assessment, Severity of Illness Index, Treatment Outcome, Ventricular Dysfunction, Left mortality, Echocardiography, Transesophageal, Heart Block therapy, Heart Failure therapy, Pacemaker, Artificial, Ventricular Dysfunction, Left diagnostic imaging, Ventricular Dysfunction, Left therapy
- Published
- 2003
- Full Text
- View/download PDF
9. High levels of p26BCL-2 oncoprotein retard taxol-induced apoptosis in human pre-B leukemia cells.
- Author
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Tang C, Willingham MC, Reed JC, Miyashita T, Ray S, Ponnathpur V, Huang Y, Mahoney ME, Bullock G, and Bhalla K
- Subjects
- ATP Binding Cassette Transporter, Subfamily B, Member 1 metabolism, Cell Division drug effects, DNA Damage, DNA, Neoplasm analysis, In Vitro Techniques, Microtubules drug effects, Microtubules ultrastructure, Phosphoproteins metabolism, Phosphotyrosine, Protein-Tyrosine Kinases metabolism, Proto-Oncogene Proteins c-bcl-2, Tubulin metabolism, Tumor Cells, Cultured, Tyrosine analogs & derivatives, Tyrosine metabolism, Apoptosis drug effects, Paclitaxel antagonists & inhibitors, Precursor B-Cell Lymphoblastic Leukemia-Lymphoma pathology, Proto-Oncogene Proteins pharmacology
- Abstract
In human leukemic cells clinically relevant concentrations of taxol have been demonstrated to induce the biochemical and morphologic hallmarks of apoptosis (Leukemia 1993;7:563-568). Since overexpression of the bcl-2 gene has been reported to retard apoptosis due to a variety of anticancer agents, we examined and compared taxol-induced intracellular microtubular bundling and apoptosis in pre-B human leukemia 697 cells and their counterparts which have been transfected with and overexpress cDNA derived from the bcl-2 gene. Treatment with 0.1 or 1.0 mumol/l taxol for 24 h resulted in internucleosomal DNA fragmentation and morphologic features of apoptosis in 697 cells, but not in 697/BCL-2 cells. However, indirect immunofluorescent staining with anti-tubulin antibody revealed that taxol treatment produces stable microtubule bundles resistant to calcium-mediated disassembly in 697, as well as 697/BCL-2 cells. In addition, taxol-induced microtubule bundling was associated with a marked accumulation of the two cell types in the G2/M phase of the cell cycle. Following exposure to taxol, when 697 cells were washed and kept in drug-free medium, they showed rapid onset of apoptosis followed by loss of cell viability and a decline in cell numbers. In contrast, identically treated 697/BCL-2 cells kept in drug-free medium remained in a growth arrested state, but showed little evidence of apoptosis for up to 4 days. They eventually demonstrated features of apoptotic cell death and loss of viability between 5 and 7 days. This was not accompanied by a decrease in p26BCL-2 levels. Anti-phosphotyrosine or anti-MAP kinase immunoblot analyses of proteins isolated from taxol-treated 697 and 697/BCL-2 cells failed to show any difference in tyrosine phosphorylation of cellular proteins. Therefore, our findings indicate that in 697/BCL-2 cells, high levels of p26BCL-2 significantly delay taxol-induced endonucleolytic internucleosomal DNA fragmentation and apoptosis, but do not affect taxol-induced microtubule bundling or cell cycle growth arrest. The delayed onset of taxol-induced DNA fragmentation and apoptosis in 697/BCL-2 cells without down-regulation of p26BCL-2 levels suggests that an alternative mechanism of taxol-mediated apoptosis might be triggered which is unimpeded by high p26BCL-2 levels, or taxol-induced prolongation of mitotic arrest may lead to the inactivation or inhibition of that mechanism by which p26BCL-2 is able to block apoptosis. more...
- Published
- 1994
10. Combined antileukemic activity of pIXY 321 and Ara-C against human acute myeloid leukemia cells.
- Author
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Tang C, Huang Y, Ponnathpur VS, Ray S, Mahoney ME, Bullock G, Ibrado AM, and Bhalla K
- Subjects
- Acute Disease, Apoptosis drug effects, Blotting, Northern, Blotting, Western, DNA, Neoplasm drug effects, Humans, Nucleosomes genetics, Tumor Cells, Cultured, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Cytarabine administration & dosage, Granulocyte-Macrophage Colony-Stimulating Factor administration & dosage, Interleukin-3 administration & dosage, Leukemia, Myeloid drug therapy, Recombinant Fusion Proteins administration & dosage
- Abstract
Prolonged administration of conventional (100 mg/m2/day) or low dose Ara-C (20 mg/m2/day) has been associated with significant clinical antileukemic effects in AML and myelodysplastic syndromes. These doses and schedules of Ara-C yield plasma Ara-C concentrations in the range of 10 to 100 nM. Utilizing concentrations and a schedule of Ara-C treatment, representative of Ara-C exposures in these clinical situations, we performed in vitro studies to examine the effects of co-treatment with pIXY 321 on Ara-C induced apoptosis and Ara-C-mediated colony growth inhibition of human myeloid leukemia HL-60 cells. Significantly greater internucleosomal DNA fragmentation, higher percentage of morphologically recognizable apoptotic cells and increased colony growth inhibition were observed following treatment with 100 versus 10 nM Ara-C for 5 days. Simultaneous exposure to 10 ng/ml pIXY 321 resulted in significantly increased colony growth inhibition as well as DNA fragmentation and apoptosis due to 10 nM but not 100 nM Ara-C. These concentrations of Ara-C inhibited c-myc and did not induce c-jun mRNA expression. These effects of Ara-C on c-myc and c-jun expressions were not influenced by co-treatment with pIXY 321. Neither treatment with pIXY 321 or Ara-C alone, nor co-treatment with pIXY 321 and Ara-C, significantly altered the intracellular p26BCL-2 levels in HL-60 cells. These results indicate that co-treatment with pIXY 321 significantly increases low dose Ara-C-induced apoptosis and thereby its antileukemic activity. more...
- Published
- 1994
- Full Text
- View/download PDF
11. Characterization of a human myeloid leukemia cell line highly resistant to taxol.
- Author
-
Bhalla K, Huang Y, Tang C, Self S, Ray S, Mahoney ME, Ponnathpur V, Tourkina E, Ibrado AM, and Bullock G
- Subjects
- ATP Binding Cassette Transporter, Subfamily B, Member 1, Apoptosis drug effects, Carrier Proteins analysis, Carrier Proteins genetics, Cell Division drug effects, Cyclosporine pharmacology, DNA, Neoplasm analysis, DNA, Neoplasm drug effects, Daunorubicin pharmacokinetics, Drug Resistance genetics, Humans, Leukemia, Myeloid drug therapy, Leukemia, Myeloid genetics, Leukemia, Myeloid metabolism, Membrane Glycoproteins analysis, Membrane Glycoproteins genetics, Microtubules drug effects, Microtubules ultrastructure, Paclitaxel pharmacokinetics, Tumor Cells, Cultured, Verapamil pharmacology, Leukemia, Myeloid pathology, Paclitaxel pharmacology
- Abstract
Taxol-resistant sublines of HL-60 myeloid leukemia cells (HL-60/TAX100 and HL-60/TAX1000) have been isolated in vitro by subculturing in progressively higher concentrations of taxol. HL-60/TAX100 and HL-60/TAX1000 cells are capable of continuous growth in the presence of 0.1 microM and 1.0 microM taxol, respectively, and the IC50 (50% growth inhibitory dose) values for taxol for the two sublines are 0.34 and 2.44 microM as compared to 3.1 nM for the parent HL-60 cells. HL-60/TAX100 and HL-60/TAX1000 cells display a variable degree of cross-resistance to taxotere, vincristine and doxorubicin, but are sensitive to the antimetabolite Ara-C. Both HL-60/TAX100 and HL-60/TAX1000 cells over-express MDR-1 m-RNA and the membrane efflux multidrug transporter P-glycoprotein (PGP), as determined by Western blot and immunofluorescence labeling with anti-PGP antibodies. Consequently, exposure of the taxol-resistant cells to [3H]taxol or daunomycin results in the accumulation of significantly lower levels of the two drugs. Co-treatment with cyclosporine (0.5 microgram/ml) or verapamil (10 microM) partially overcomes taxol resistance in HL-60/TAX1000 cells. Following treatment with clinically relevant concentration of taxol (1.0 microM for 24 h), HL-60 but not HL-60/TAX1000 cells display intracellular microtubular bundling, markedly enhanced accumulation of the cells in G2/M phase of cell-cycle and internucleosomal DNA fragmentation associated with apoptosis which is independent of bcl-2 gene expression. These taxol-resistant myeloid leukemia cells may serve as in vitro experimental models for examinating strategies which may have potential applicability for overcoming taxol resistance. more...
- Published
- 1994
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