Tamoxifen inhibits particulate-associated protein kinase C activity, and sensitises cultured human glioblastoma cells not to etoposide but to γ-radiation and BCNU

Rocha, Adriana Brondani da; Mans, Dennis R.A.; Bernard, Elena Aida; Ruschel, Carla Felippi Chiella; Logullo, Ângela Flávia; Wetmore, Lori; Leyva, A.; Schwartsmann, Gilberto

doi:10.1016/s0959-8049(99)00003-9

Cited by 23 publications

(6 citation statements)

References 21 publications

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“…In agreement with previous reports [25][26][27], a histone phosphorylation assay indicated that the three cell lines also contained relatively high levels of PKC that were in the same order of magnitude (table 1). Because of the presumed importance of PKC in the invasive phenotype of gliomas [3-7, 12, 28], this finding led us to hypothesise that the baseline PKC activity in the presently used glioma cell lines might account, at least in part, for their invasiveness under non-stimulated conditions (180 B 13, 160 B 11 and 145 B 21 cells invading per filter, for A-172, U-87 and U-373 cell lines, respectively).…”

Section: Regulation By Pkc Of Mt1-mmp Expression Mmp-2 Activity and supporting

confidence: 92%

“…PKC activity was determined in 4-Ìl fractions of known protein content as described [25,27], by assessing the degree of phosphorylation of lysine-rich type IIIS histone by [Á-32 P]ATP. Thus, enzyme preparations were pre-incubated for 2 min at 30°C with 40 Ìl of 50 mM Tris-HCl pH 7.4, 250 Ìg/ml of histone, 100 mM free Ca 2+ , 500 Ìg/ml of phosphatidylserine, and 25 Ìg/ml of diacylglycerol.…”

Section: Assay For Pkc Activitymentioning

confidence: 99%

“…Another important distinctive of high-grade CNS tumours is the presence of massively upregulated protein kinase C (PKC) when compared to normal glia [25][26][27]. This property has been suggested to be critical to the hyperproliferative state and the resistance to apoptosisinducing agents of these tumour types, as well as to glioma invasion.…”

Section: Introductionmentioning

confidence: 99%

“…However, the efficacy of such therapies may be compromised by overexpressed PKC activity, the lack of specificity of current PKC-interfering agents [21,27,55,56], and the availability of PKC-independent pathways for tumour spread [2,20]. Additionally to targeting PKC, anti-invasive strategies may be based on interference with the ERK cascade or with ODC.…”

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confidence: 99%

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Protein Kinase C-Mediated in vitro Invasion of Human Glioma Cells through Extracellular-Signal-Regulated Kinase and Ornithine Decarboxylase

et al. 2000

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We investigated the involvement of protein kinase C (PKC) in the in vitro invasiveness of the A-172, U-87 and U-373 human glioma cell lines, as well as the role of ornithine decarboxylase (ODC) and/or extracellular-signal-regulated kinase (ERK) in the actions of PKC. Thus, cells were treated under serum-free conditions with the PKC activator phorbol 12-myristate 13-acetate (PMA), or with the PKC inhibitors bisindolylmaleimide I (GF 109203X) or calphostin C in the absence or presence of the ODC inhibitor D,L-α-difluoromethylornithine (DFMO), and/or the mitogen-activated protein kinase/extracellular-signal-regulated kinase inhibitor 2′-amino-3′-methoxyflavone (PD 098059). Subsequently, cells were assessed for membrane-type 1 matrix metalloproteinase (MT1-MMP) mRNA contents, 72-kD latent, and 59/62-kD activated matrix metalloproteinase 2 (MMP-2) in conditioned media, as well as invasiveness. For these purposes, we used Northern blot analysis, gelatine zymography, and an in vitro filter invasion assay, respectively. Data were related to those found with untreated cells. PKC activity was 2- to 3-fold stimulated by PMA (100 nM for 30 min), and about 2-fold inhibited by calphostin C (40 nM for 2 h) or GF 109203X (5 µM for 20 min). This was accompanied by a similar increase or decrease, respectively, in MT1-MMP mRNA expression, 59/62-kD MMP-2 activity, and in vitro invasion. Inhibition of ODC activity (about 2-fold by 24 h DFMO 5 mM), ERK activation (almost completely by 20 min PD 098059 50 µM), or both these enzymes simultaneously led to a reduction by about half in levels of MT1-MMP mRNA, 59/62-kD MMP-2 activity, and invasion in untreated as well as PMA-stimulated cells. The use of these compounds did not significantly alter the inhibitory effects of GF 109203X or calphostin C. Modulation of PKC and/or ERK activity resulted in corresponding changes in ERK and/or ODC activities, but interference with ODC affected neither ERK nor PKC. Our data suggest a regulatory role for PKC, in co-operation with ERK and ODC, in glioma cell invasion, by modulation of MT1-MMP mRNA expression and MMP-2 activation.

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Section: Regulation By Pkc Of Mt1-mmp Expression Mmp-2 Activity and supporting

confidence: 92%

Section: Assay For Pkc Activitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Protein Kinase C-Mediated in vitro Invasion of Human Glioma Cells through Extracellular-Signal-Regulated Kinase and Ornithine Decarboxylase

et al. 2000

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“…This family of enzymes was found to be overexpressed or hyperactive in malignant CNS tumors [14]and is involved in processes associated with glioma cell proliferation, invasion and metastasis [15, 16, 17, 18]. …”

Section: Introductionmentioning

confidence: 99%

ERK, PKC and PI3K/Akt Pathways Mediate Extracellular ATP and Adenosine-Induced Proliferation of U138-MG Human Glioma Cell Line

Jacques-Silva¹,

Bernardi²,

Rodnight³

et al. 2004

Oncology

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Objective: Extracellular nucleotides and nucleosides induce proliferation in a set of human glioma cell lines. In this study we investigate the signal transduction pathways involved in ATP and adenosine-mediated proliferation in U138-MG human glioma cells. Methods: Cell proliferation was accessed through [³H]thymidine incorporation, cell counting and flow cytometry. Protein phosphorylation was detected through Western blotting. Results: ATP or adenosine (100 µM) induced extracellular signal-regulated protein kinase (ERK), Akt and GSK3β phosphorylation. The increase in [³H]thymidine incorporation induced by ATP or adenosine was decreased when cells were incubated with LY 294002 (by ±90%), GF 109203X (by ±76%) or PD 098059 (by ±63%). The increase in cell numbers with ATP or adenosine was less after a 48-hour treatment of cells with ATP or adenosine plus GF 109203X (by ±66%) or LY 294002 (by ±83%). Percentage of cells in S phase was decreased in cells treated with LY 294002 plus ATP when compared to ATP- treated cells. Conclusion: Stimulation of purinergic receptors in U138-MG cells leads to cell proliferation mediated by PI3K/Akt, ERK and PKC signaling. It may be clinically important for pharmacological intervention in gliomas to associate purinergic receptor antagonists and signal transduction pathways blockers.

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Combination therapy with irinotecan and protein kinase C inhibitors in malignant glioma

Chen

Fry

et al. 2003

Cancer

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The topoisomerase-I inhibitor irinotecan (CPT-11) is currently used in Phase I/II trials for the treatment of patients with recurrent malignant gliomas. Protein kinase C (PKC) inhibitors such as high-dose tamoxifen and hypericin also have been used in the treatment of malignant gliomas. The current study examined the role of PKC inhibitors as chemosensitizers for CPT-11 and their proposed mechanism of action. Two glioma cell lines (A-172 and U-87) and one primary glioma cell culture (LA-567) were used.Proliferation ( 3 H-thymidine) and cytotoxicity (methylthiotetrazole) studies were performed using CPT-11 (0 -100 M) alone, 7-ethyl-10-hydroxy camptothecin (SN-38) (0 -1000 nM) alone or in the presence of a PKC inhibitor, tamoxifen (10 M), hypericin (10 M), calphositin C (400 nM), or staurosporine (10 nM). The terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling(TUNEL) assay was used to determine apoptosis as the mechanism of cytotoxicity; alterations in bcl-2 and bax expression were determined using Western blot analysis. Conversion of CPT-11 to SN-38 by glioma cells was determined using high-performance liquid chromatography

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Tamoxifen inhibits particulate-associated protein kinase C activity, and sensitises cultured human glioblastoma cells not to etoposide but to γ-radiation and BCNU

Cited by 23 publications

References 21 publications

Protein Kinase C-Mediated in vitro Invasion of Human Glioma Cells through Extracellular-Signal-Regulated Kinase and Ornithine Decarboxylase

Protein Kinase C-Mediated in vitro Invasion of Human Glioma Cells through Extracellular-Signal-Regulated Kinase and Ornithine Decarboxylase

ERK, PKC and PI3K/Akt Pathways Mediate Extracellular ATP and Adenosine-Induced Proliferation of U138-MG Human Glioma Cell Line

Combination therapy with irinotecan and protein kinase C inhibitors in malignant glioma

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