RESUMO
Tissue factor (TF), the cellular initiator of the protease blood coagulation cascade, has been shown to be expressed in a variety of solid tumors, particularly those of epithelial origin. However, the mechanisms that mediate TF expression in tumors, as well as the clinical implications of this expression, remain largely unknown. In this study, we examined the cytological distribution of TF in normal human breast tissue and breast carcinomas. Epithelial cells exhibited TF immunoreactivity with little obvious correlation with malignant progression from in situ lesions to invasive cancer. However, there was a strong correlation between progression to invasive cancer and the expression of TF antigen in cellular components of the stroma. TF-positive cells were particularly abundant in close proximity to infiltrating tumor cells and included both macrophages and myofibroblasts, as determined by double-immunofluorescent staining for TF and cell type-specific marker proteins. Double-immunofluorescent staining for TF and transforming growth factor beta (TGF-beta) revealed TGF-beta immunoreactivity both in tumor cells and in the extracellular matrix surrounding TF-positive stromal cells. To test the role of carcinoma cell-derived growth factors in the regulation of stromal cell TF activity, we examined the ability of conditioned media (CM) from breast carcinoma cell lines to stimulate TF activity in myofibroblast-like cells in vitro. Extracts from myofibroblasts exposed to CM displayed strong TF procoagulant activity. However, extracts from cells exposed to unconditioned media or CM pretreated with anti-TGF-beta antibodies did not. The induction of TF activity was also observed upon treatment of indicator cells with recombinant TGF-beta isoforms. Collectively, these data indicate that the recruitment and/or activation of TF-expressing stromal cells is an early event in progression to invasive breast cancer and likely occurs, in part, as a paracrine response to tumor cell-derived members of the TGF-beta family of growth factors.
Assuntos
Neoplasias da Mama/química , Tromboplastina/análise , Fator de Crescimento Transformador beta/fisiologia , Actinas/análise , Animais , Mama/química , Neoplasias da Mama/patologia , Feminino , Humanos , Camundongos , Camundongos Endogâmicos AKR , Tromboplastina/fisiologia , Fator de Crescimento Transformador beta/análise , Células Tumorais CultivadasRESUMO
Determinants of differentiation and apoptosis in myelomonocytic leukemia cells (U937) exposed to the novel hybrid polar compound SAHA (suberoylanilide hydroxamic acid) have been examined. In contrast to hexamethylenbisacetamide (HMBA), SAHA-related maturation was limited and accompanied by marked cytoxicity. SAHA-mediated apoptosis occurred within the G0G1 and S phase populations, and was associated with decreased mitochondrial membrane potential, caspase-3 activation, PARP degradation, hypophosphorylation/cleavage of pRB, and down-regulation of c-Myc, c-Myb, and B-Myb. Enforced expression of Bcl-2 or Bcl-XL inhibited SAHA-induced apoptosis, but only modestly potentiated differentiation. While SAHA induced the cyclin-dependent kinase inhibitor p21CIP1, antisense ablation of this CDKI increased, rather than decreased, SAHA-related lethality. In contrast, conditional expression of wild-type p53 failed to modify SAHA actions, but markedly potentiated HMBA-induced apoptosis. Finally, SAHA modestly increased expression/activation of the stress-activated protein kinase (SAPK/JNK); moreover, SAHA-related lethality was partially attenuated by a dominant-negative c-Jun mutant protein (TAM67). SAHA did not stimulate mitogen-activated protein kinase (MAPK), nor was lethality diminished by the specific MEK/MAPK inhibitor PD98059. These findings indicate that SAHA potently induces apoptosis in human leukemia cells via a pathway that is p53-independent but at least partially regulated by Bcl-2/Bcl-XL, p21CIP1, and the c-Jun/AP-1 signaling cascade.
Assuntos
Apoptose/efeitos dos fármacos , Ciclinas/metabolismo , Ácidos Hidroxâmicos/farmacologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas Proto-Oncogênicas c-jun/metabolismo , Inibidor de Quinase Dependente de Ciclina p21 , Regulação para Baixo , Humanos , Leucemia/metabolismo , Leucemia/patologia , Proteínas Proto-Oncogênicas c-myb/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Células U937 , Vorinostat , Proteína bcl-XRESUMO
We have previously reported that pretreatment of HL-60 human promyelocytic leukemia cells with the non-tumor-promoting protein kinase C (PKC) activator bryostatin 1 potentiates induction of apoptosis by the antimetabolite 1-[beta-D-arabinofuranosyl]cytosine (ara-C) (Biochem Pharmacol 47:839,1994). To determine whether this phenomenon results from altered expression of Bcl-2 or related proteins, Northern and Western analysis was employed to assess the effects of bryostatin 1 and other PKC activators on steady-state levels of Bcl-2, Bax, Bcl-x, and Mcl-1 mRNA and protein. Pretreatment of cells for 24 h with 10 nM bryostatin 1, or, to a lesser extent, the stage-1 tumor-promoter phorbol dibutyrate (PDB) significantly potentiated apoptosis induced by ara-C (100 microM; 6 h); in contrast, equivalent exposure to the stage-2 tumor promoter, mezerein (MZN), which, unlike bryostatin 1, is a potent inducer of differentiation in this cell line, failed to modify ara-C-related cell death. Neither bryostatin 1 nor PDB altered expression of bcl-2/Bcl-2 over this time frame. In contrast, MZN down-regulated bcl-2 mRNA levels, but this effect was not accompanied by altered expression of Bcl-2 protein. None of the PKC activators modified expression of Bax or Bcl-x(L) mRNA or protein; levels of Bcl-x(S) were undetectable in both treated and untreated cells. However, expression of Mcl-1 mRNA and protein increased modestly after treatment with either bryostatin 1 or PDB, and to a greater extent following exposure to MZN. Combined treatment of cells with bryostatin 1 and MZN resulted in undiminished potentiation of ara-C-mediated apoptosis and by antagonism of cellular maturation. These effects were accompanied by unaltered expression of Bcl-2, Bax, and Bcl-x(L), and by a further increase in Mcl-1 protein levels. When cells were co-incubated with bryostatin 1 and calcium ionophore (A23187), an identical pattern of expression of Bcl-2 family members was observed, despite the loss of bryostatin 1's capacity to potentiate apoptosis, and the restoration of its ability to induce differentiation. Finally, treatment of cells with bryostatin 1+/-ara-C (but not ara-C alone) resulted in a diffuse broadening of the Bcl-2 protein band, whereas exposure of cells to taxol (250 nM, 6 h) led to the appearance of a distinct Bcl-2 species with reduced mobility, phenomena compatible with protein phosphorylation. Together, these findings indicate that the ability of bryostatin 1 to facilitate drug-induced apoptosis in human myeloid leukemia cells involves factors other than quantitative changes in the expression of Bcl-2 family members, and raise the possibility that qualitative alterations in the Bcl-2 protein, such as phosphorylation status, may contribute to this capacity. They also suggest that increased expression of Mcl-1 occurs early in the pre-commitment stage of myeloid cell differentiation, and that this event does not protect cells from drug-induced apoptosis.
RESUMO
In Drosophila melanogaster males, X-Y meiotic chromosome pairing is mediated by the nucleolus organizers (NOs) which are located in the X heterochromatin (Xh) and near the Y centromere. Deficiencies for Xh disrupt X-Y meiotic pairing and cause high frequencies of X-Y nondisjunction. Insertion of cloned rRNA genes on an Xh- chromosome partially restores normal X-Y pairing and disjunction. To map the sequences within an inserted, X-linked rRNA gene responsible for stimulating X-Y pairing, partial deletions were generated by P element-mediated destabilization of the insert. Complete deletions of the rRNA transcription unit did not interfere with the ability to stimulate X-Y pairing as long as most of the intergenic spacer (IGS) remained. Within groups of deletions that lacked the entire transcription unit and differed only in length of residual IGS material, pairing ability was proportional to the dose of 240-bp intergenic spacer repeats. Deletions of the complete rRNA transcription unit or the 28S sequences alone blocked nucleolus formation, as determined by binding of an antinucleolar antibody, yet did not interfere with pairing ability, suggesting that X-Y pairing may not be mechanistically related to nucleolus formation. A model for achiasmatic pairing in Drosophila males based upon the combined action of topoisomerase I and a strand transferase is proposed.
Assuntos
Drosophila melanogaster/genética , Meiose/genética , RNA de Transferência/genética , Sequências Repetitivas de Ácido Nucleico , Animais , Sequência de Bases , Nucléolo Celular/ultraestrutura , Elementos de DNA Transponíveis , DNA Ribossômico/genética , Deleção de Genes , Íntrons , Masculino , Modelos Genéticos , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Fenótipo , Cromossomo X , Cromossomo YRESUMO
The p21MDA6 gene product induces cell cycle arrest in p53-null human leukemic cells exposed to differentiation stimuli. We employed an HL-60 cell line stably transfected with a p21MDA6 antisense construct to compare the effects of p21MDA6 dysregulation on the response of myeloid leukemia cells to differentiating and cytotoxic agents. Antisense-expressing cells (HL-60/AS5) treated with 5 nM PMA for 24 h exhibited attenuated induction of p21MDA6 compared to empty vector controls (HL-60/V2). This phenomenon was accompanied by a reduction in the percentage of cells undergoing G1 arrest (67.6 +/- 4.7 vs 82.9 +/- 1.3; P < or = 0.01) and expressing the monocytic maturation marker cd11b (35.5 +/- 2.8 vs 50.5 +/- 2.4; P < or = 0.005). Although HL-AS5 and HL-60/V2 cells did not exhibit obvious differences in the phosphorylation status of the retinoblastoma protein (pRB), in E2F complex formation, or in p27klp1 induction following PMA exposure, inhibition of activity of cyclin-dependent kinase-2 was attenuated in the antisense-expressing line. A 24-h exposure to 5 nM PMA also reduced the cloning efficiency of HL-60/V2 cells to a significantly greater extent than HL-60/AS5 cells (ie to 30.1 +/- 7.0 vs 57.2 +/- 5.6 of controls; P < or = 0.01). In contrast to the disparate responses to PMA, HL-60/AS5 and HL-60/V2 cells treated with the antimetabolite 1-beta-D-arabinofurano-sylcytosine (Ara-C; 10 microM for 6 h) displayed equal susceptibility to G1 arrest, apoptosis, and inhibition of clonogenicity, phenomena unaccompanied by p21MDA6 and p27klp1 induction, or pRB dephosphorylation. These observations indicate that dysregulation of p21MDA6 in p53-null human myeloid leukemia cells interferes with PMA-related G1 arrest, CDK-2 inhibition, differentiation, and loss of clonogenic survival in the absence of obvious alterations in pRB phosphorylation status or E2F complex formation. They also provide functional evidence that p21MDA6 induction does not appear to be required for Ara-C-induced apoptosis, G1 arrest, or the resulting reduction in the self-renewal capacity of HL-60 cells.
Assuntos
Apoptose/efeitos dos fármacos , Proteínas de Transporte , Proteínas de Ciclo Celular , Diferenciação Celular/efeitos dos fármacos , Ciclinas/farmacologia , Proteínas de Ligação a DNA , Antígenos CD11/análise , Inibidor de Quinase Dependente de Ciclina p21 , Ciclinas/biossíntese , Ciclinas/genética , Citarabina/farmacologia , Fatores de Transcrição E2F , Vetores Genéticos , Células HL-60 , Humanos , Proteína 1 de Ligação ao Retinoblastoma , Acetato de Tetradecanoilforbol/farmacologia , Fator de Transcrição DP1 , Fatores de Transcrição/metabolismo , TransfecçãoRESUMO
We have examined interactions between the purine nucleoside analog fludarabine (9-beta-arabinofuranosyl-2-fluoroadenine) and the macrocyclic lactone bryostatin 1 in the human monocytic leukemic cell line U937. Fludarabine exerted dose-dependent effects on U937 cell viability and growth which were associated with both induction of apoptosis, as well as cellular maturation. Incubation of cells with bryostatin 1 (10 nM; 24 h) after, but not before a 6-h exposure to 10 microM fludarabine resulted in a modest but significant increase in apoptosis, and was associated with greater than a 1 log reduction in clonogenicity. Subsequent exposure to bryostatin 1 also increased the percentage of fludarabine-treated cells displaying differentiation-related features (eg plastic adherence, CD11b positivity) compared to cells exposed to fludarabine alone. Bryostatin 1 did not increase the retention of the active fludarabine metabolite, F-ara-ATP, nor did it increase 3H-F-ara-A incorporation into DNA. Despite its capacity to trigger cellular maturation, fludarabine exposure (either with or without bryostatin 1) failed to induce the cyclin-dependent kinase inhibitors (CDKls) p21WAF1/CIP1 and p27KIP1. Nevertheless, dysregulation of p21 (resulting from stable transfection of cells with a p2lWAF1/CIP1 antisense construct) reduced fludarabine-mediated differentiation, while inducing a corresponding increase in apoptosis. Enforced expression of Bcl-2 partially protected cells from fludarabine-related apoptosis, an effect that was overcome, in part, by subsequent exposure of cells to bryostatin 1. Interestingly, Bcl-2-overexpressing cells were as or in some cases, more susceptible to differentiation induction by fludarabine (+/- bryostatin 1) than their empty vector-containing counterparts. Collectively, these results indicate that the antiproliferative effects of fludarabine toward U937 leukemic cells involve both induction of apoptosis and cellular maturation, and that each of these processes may be enhanced by bryostatin 1.
Assuntos
Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Lactonas/uso terapêutico , Leucemia Mielomonocítica Aguda/tratamento farmacológico , Vidarabina/análogos & derivados , Briostatinas , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Interações Medicamentosas , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Macrolídeos , Células U937 , Vidarabina/uso terapêuticoRESUMO
Current methods of localization of chromosomal antigens on polytene chromosomes of Drosophila melanogaster salivary glands by indirect immunofluorescence require comparison of two microscopic images of the same nucleus--a phase contrast or bright field image to visualize the chromosomes and a fluorescent image to locate the antibody. We have found that inclusion of the DNA-intercalating agent ethidium bromide in the mounting medium makes banded polytene chromosomes visible under epifluorescent illumination, eliminating the need for two images. The banding of the polytene chromosomes is clear enough to locate specific bands.
Assuntos
Bandeamento Cromossômico/métodos , Animais , Biotecnologia , Drosophila melanogaster/genética , Etídio , Estudos de Avaliação como Assunto , Feminino , Fluoresceína , Fluoresceínas , Microscopia de Fluorescência , Coloração e RotulagemRESUMO
Events accompanying sequential exposure of U937 leukemic cells to the deoxycytidine (dCyd) analogs 1-[beta-D-arabinofuranosyl]cytosine (ara-C) or 2',2'-difluorodeoxycytidine (gemcitabine; dFdC) followed by two protein kinase C (PKC) activators [bryostatin 1 (BRY) or phorbol 12'-myristate 13'-acetate (PMA)] exhibiting disparate differentiation-inducing abilities were characterized. A 24-hr exposure to 10 nM BRY or PMA after a 6-hr incubation with 1 microM ara-C or 100 nM dFdC resulted in equivalent increases in apoptosis, caspase-3 activation, and polyADP-ribose polymerase degradation, as well as identical DNA cleavage patterns. BRY and PMA did not modify retention of the lethal ara-C metabolite ara-CTP or alter ara-CTP/dCTP ratios. Unexpectedly, pretreatment of cells with ara-C or dFdC opposed BRY- and PMA-related induction of the cyclin-dependent kinase inhibitors (CDKIs) p21CIP1 and/or p27KIP1. These effects were not mimicked by the DNA polymerase inhibitor aphidicolin or by VP-16, a potent inducer of apoptosis. Inhibition of PKC activator-induced CDKI expression by ara-C and dFdC did not lead to redistribution of proliferating cell nuclear antigen but was accompanied by sub-additive or antagonistic effects on leukemic cell differentiation. Sequential exposure of cells to ara-C followed by BRY or PMA led to substantial reductions in clonogenicity that could not be attributed solely to apoptosis. Finally, pretreatment of cells with ara-C attenuated PMA- and BRY-mediated activation of mitogen-activated protein kinase, an enzyme implicated in CDKI induction. Collectively, these findings suggest that pretreatment of leukemic cells with certain dCyd analogs interferes with CDKI induction by the PKC activators PMA and BRY, and that this action may contribute to modulation of apoptosis and differentiation in cells exposed sequentially to these agents.
Assuntos
Proteínas de Ciclo Celular , Ciclinas/biossíntese , Citarabina/farmacologia , Desoxicitidina/análogos & derivados , Lactonas/farmacologia , Leucemia/metabolismo , Proteínas Associadas aos Microtúbulos/biossíntese , Proteína Quinase C/metabolismo , Acetato de Tetradecanoilforbol/farmacologia , Proteínas Supressoras de Tumor , Antimetabólitos Antineoplásicos/farmacologia , Apoptose , Briostatinas , Diferenciação Celular/efeitos dos fármacos , Inibidor de Quinase Dependente de Ciclina p21 , Inibidor de Quinase Dependente de Ciclina p27 , Desoxicitidina/farmacologia , Interações Medicamentosas , Ativação Enzimática , Humanos , Lactonas/antagonistas & inibidores , Leucemia/tratamento farmacológico , Leucemia/patologia , Macrolídeos , Mitógenos/farmacologia , Acetato de Tetradecanoilforbol/antagonistas & inibidores , Células U937 , GencitabinaRESUMO
The goal of the present study was to determine whether partial restoration of the differentiation-inducing capacity of the PKC activator bryostatin 1 by the calcium ionophore A23187 is accompanied by enhancement of apoptosis in ara-C-pretreated human leukemia cells. When HL-60 cells were exposed to ara-C (10 or 100 microM;6 h) followed by bryostatin 1 alone (10 nM; 24 h), no increase in apoptosis was noted. In contrast, subsequent exposure of ara-C-pretreated cells to A23187 (250 nM; 24 h) increased apoptosis by approximately 100%. When ara-C-pretreated cells were incubated with A23187 and bryostatin 1, no further potentiation of cell death (compared to cells exposed to A23187 alone) was observed. Nevertheless, the combination of bryostatin 1 and A23187 substantially increased inhibition of clonogenicity in cells preincubated with ara-C (e.g., by > or = 2 logs). This effect was associated with morphological and functional evidence (i.e., plastic adherence) of enhanced leukemic cell maturation. The differentiating capacity of the combination of bryostatin 1 and A23187 was significantly weaker than that of the phorbol diester, PMA (10 nM), and unaccompanied (at 24 h) by induction of the cyclin-dependent kinase inhibitors (CDKIs) p21WAF1/CIP1 and p27KIP1. However, the extent of apoptosis was comparable in cells exposed to ara-C followed by PMA or bryostatin 1 + A23187, suggesting that differentiation per se is not solely responsible for enhancement of cell death in ara-C-pretreated cells. Coadministration of bryostatin 1 and the organotellurium compound AS101, which mimics the actions of A23187 in some systems, after ara-C also led to enhanced antiproliferative effects which were unaccompanied by an increase in apoptosis. Finally, exposure of cells to ara-C followed by other differentiation-inducing agents, including dimethylsulfoxide and sodium butyrate also resulted in increases in cell death in this cell line. These findings indicate that the inability of bryostatin 1 to potentiate apoptosis in ara-C-pretreated HL-60 cells may involve factors other than an inadequate differentiation stimulus. They also suggest that loss of leukemic self-renewal capacity following exposure to cytotoxic and differentiation-inducing agents may involve mechanisms other than, or in addition to, potentiation of apoptosis, particularly cellular maturation.
Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Calcimicina/farmacologia , Citarabina/farmacologia , Lactonas/farmacologia , Acetamidas/farmacologia , Briostatinas , Cálcio/metabolismo , Diferenciação Celular/efeitos dos fármacos , Fragmentação do DNA , Células HL-60 , Humanos , Macrolídeos , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
The ability of low dose ionizing radiation (2 Gy) to modulate the activities of the mitogen activated protein kinase (MAPK) and c-Jun NH2-terminal kinase (JNK1) cascades in human monocytic leukemia (U937/pREP4) cells and in cells over-expressing dominant negative c-Jun (TAM67) (U937/TAM67) was investigated. Radiation exposure caused prolonged ( approximately 1 h) MAPK activations in U937 cells. In contrast, low dose irradiation weakly modulated JNK1 activity in these cells. Inhibition of the MAPK pathway by use of the specific MEK1/2 inhibitor (10 microM PD98059) in both U937/pREP4 and U937/TAM67 cells prior to radiation exposure permitted strong prolonged radiation-induced activations of JNK1. Expression of TAM67 decreased the ability of radiation to cause apoptosis compared to control transfected cells. However, combined MEK1/2 inhibition and radiation exposure in both cell types caused a large decrease in suspension culture growth and a large increase in apoptosis, when compared to either treatment alone. Reduced proliferation after combined irradiation and PD98059 treatment in both cell types correlated with prolonged cell cycle arrest in G2/M phase. Prolonged growth arrest was abolished when MEK1/2 inhibitor was removed 6 h following irradiation, which was associated with a reduction in apoptosis. The ability of MEK1/2 inhibition to cause prolonged G2/M growth arrest was reduced in U937 cells stably transfected with a p21Cip-1/WAF1 antisense construct (U937/p21AS). This data correlated with an enhancement of radiation-induced apoptosis and a reduced ability of MEK1/2 inhibition to potentiate apoptosis. Collectively our data demonstrate that inhibition of MEK1/2 function increases the radiation sensitivity of U937 cells, independently of c-Jun function, and decreases the ability of these cells to recover from the radiation-induced G2/M cell cycle checkpoint arrest. In addition, our data also demonstrate that the ability of MEK1/2 inhibition to potentiate radiation-induced cell death in U937 cells in part requires an ability of cells to express low levels of p21Cip-1/WAF1.
Assuntos
Apoptose/efeitos da radiação , Fase G2/efeitos da radiação , Quinases de Proteína Quinase Ativadas por Mitógeno/efeitos da radiação , Proteínas Quinases Ativadas por Mitógeno/efeitos da radiação , Mitose/efeitos da radiação , Apoptose/fisiologia , Ciclo Celular/fisiologia , Ciclo Celular/efeitos da radiação , Fase G2/fisiologia , Humanos , Proteínas Quinases JNK Ativadas por Mitógeno , Leucemia Mieloide/metabolismo , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Mitose/fisiologia , Células U937/efeitos da radiaçãoRESUMO
The ability of low-dose ionizing radiation (1 Gy) to modulate the activities of the mitogen-activated protein kinase (MAPK) and Jun NH2-terminal kinase (JNK1) cascades in human myeloid leukemia (HL60/pCEP4) cells and in cells overexpressing the anti-apoptosis protein BCL2 (HL60/Bcl-2) was investigated. Radiation exposure caused prolonged (3-4 h) activation of MAPK in HL60 cells. The ability of radiation to activate the MAPK pathway was attenuated by 30% in cells overexpressing BCL2. In contrast, low-dose irradiation of HL60/pCEP4 and HL60/Bcl-2 cells failed to modulate JNK1 activity. Inhibition of the MAPK pathway by use of the specific MEK1/2 inhibitor (10 microM PD98059) in both HL60/pCEP4 and HL60/Bcl-2 cells prior to irradiation permitted a similar prolonged radiation-induced activation of JNK1. Furthermore, combined treatment with PD98059 and radiation in both cell types caused a large decrease in growth of cells in suspension culture, a large increase in apoptosis, and a 90% decline in clonogenicity when compared to either treatment alone. Reduced proliferation after combined irradiation and PD98059 treatment in both cell types correlated with reduced Cdc2 activity and arrest in G2/M phase of the cell cycle. These data demonstrate that inhibition of MEK1/2 leading to blockade of the MAPK activation increases the radiation sensitivity of HL60 cells and decreases the ability of these cells to recover from the radiation-induced arrest at the G2/M-phase cell cycle checkpoint. In addition, our data demonstrate that elevated expression of BCL2 does not abrogate the ability of inhibition of MAPK to potentiate radiation-induced cell death in HL60 cells.
Assuntos
Proteínas Quinases Dependentes de Cálcio-Calmodulina/antagonistas & inibidores , Sobrevivência Celular/efeitos da radiação , Proteínas Quinases Ativadas por Mitógeno , Proteínas Proto-Oncogênicas c-bcl-2/fisiologia , Tolerância a Radiação , Apoptose/efeitos da radiação , Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Divisão Celular/efeitos da radiação , Flavonoides/farmacologia , Fase G2 , Células HL-60 , Humanos , Proteínas Quinases JNK Ativadas por Mitógeno , Mitose , Células U937RESUMO
Peripheral T-cell lymphomas (PTCLs) are fatal in the majority of patients and novel treatments, such as protein tyrosine kinase (PTK) inhibition, are needed. The recent finding of SYK/ITK translocations in rare PTCLs led us to examine the expression of Syk PTK in 141 PTCLs. Syk was positive by immunohistochemistry (IHC) in 133 PTCLs (94%), whereas normal T cells were negative. Western blot on frozen tissue (n=6) and flow cytometry on cell suspensions (n=4) correlated with IHC results in paraffin. Additionally, western blot demonstrated that Syk-positive PTCLs show tyrosine (525/526) phosphorylation, known to be required for Syk activation. Fluorescence in situ hybridization showed no SYK/ITK translocation in 86 cases. Overexpression of Syk, phosphorylation of its Y525/526 residues and the availability of orally available Syk inhibitors suggest that Syk merits further evaluation as a candidate target for pharmacologic PTK inhibition in patients with PTCL.
Assuntos
Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Linfoma de Células T Periférico/enzimologia , Proteínas Tirosina Quinases/metabolismo , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Western Blotting , Criança , Pré-Escolar , Cromossomos Humanos Par 5/genética , Cromossomos Humanos Par 9/genética , Feminino , Citometria de Fluxo , Humanos , Técnicas Imunoenzimáticas , Imunofenotipagem , Hibridização in Situ Fluorescente , Peptídeos e Proteínas de Sinalização Intracelular/genética , Linfoma Extranodal de Células T-NK/enzimologia , Linfoma Extranodal de Células T-NK/genética , Linfoma Extranodal de Células T-NK/patologia , Linfoma Anaplásico de Células Grandes/enzimologia , Linfoma Anaplásico de Células Grandes/genética , Linfoma Anaplásico de Células Grandes/patologia , Linfoma Cutâneo de Células T/enzimologia , Linfoma Cutâneo de Células T/genética , Linfoma Cutâneo de Células T/patologia , Linfoma de Células T Periférico/genética , Linfoma de Células T Periférico/patologia , Masculino , Pessoa de Meia-Idade , Fosforilação , Proteínas Tirosina Quinases/genética , Quinase Syk , Translocação Genética , Tirosina/metabolismoRESUMO
Cotreatment with a minimally toxic concentration of the protein kinase C (PKC) activator (and down-regulator) bryostatin 1 (BRY) induced a marked increase in mitochondrial dysfunction and apoptosis in U937 monocytic leukemia cells exposed to the proteasome inhibitor lactacystin (LC). This effect was blocked by cycloheximide, but not by alpha-amanitin or actinomycin D. Qualitatively similar interactions were observed with other PKC activators (eg, phorbol 12-myristate 13-acetate and mezerein), but not phospholipase C, which does not down-regulate the enzyme. These events were examined in relationship to functional alterations in stress (eg, SAPK, JNK) and survival (eg, MAPK, ERK) signaling pathways. The observations that LC/BRY treatment failed to trigger JNK activation and that cell death was unaffected by a dominant-interfering form of c-JUN (TAM67) or by pretreatment with either curcumin or the p38/RK inhibitor, SB203580, suggested that the SAPK pathway was not involved in potentiation of apoptosis. In marked contrast, perturbations in the PKC/Raf/MAPK pathway played an integral role in LC/BRY-mediated cell death based on evidence that pretreatment of cells with bisindolylmaleimide I, a selective PKC inhibitor, or geldanamycin, a benzoquinone ansamycin, which destabilizes and depletes Raf-1, markedly suppressed apoptosis. Furthermore, ERK phosphorylation was substantially prolonged in LC/BRY-treated cells compared to those exposed to BRY alone, and pretreatment with the highly specific MEK inhibitors, PD98059, U0126, and SL327, opposed ERK activation while protecting cells from LC/BRY-induced lethality. Together, these findings suggest a role for activation and/or dysregulation of the PKC/MAPK cascade in modulation of leukemic cell apoptosis following exposure to the proteasome inhibitor LC. (Blood. 2001;97:2105-2114)
Assuntos
Acetilcisteína/análogos & derivados , Acetilcisteína/farmacologia , Apoptose/efeitos dos fármacos , Diterpenos , Proteínas Quinases JNK Ativadas por Mitógeno , Lactonas/farmacologia , Sistema de Sinalização das MAP Quinases/fisiologia , Complexos Multienzimáticos/antagonistas & inibidores , Proteínas de Neoplasias/antagonistas & inibidores , Inibidores de Proteases/farmacologia , Proteína Quinase C/fisiologia , Células U937/efeitos dos fármacos , Amanitinas/farmacologia , Aminoacetonitrila/análogos & derivados , Benzoquinonas , Briostatinas , Butadienos/farmacologia , Curcumina/farmacologia , Cisteína Endopeptidases , Dactinomicina/farmacologia , Sinergismo Farmacológico , Ativação Enzimática/efeitos dos fármacos , Flavonoides/farmacologia , Humanos , Imidazóis/farmacologia , Indóis/farmacologia , Lactamas Macrocíclicas , MAP Quinase Quinase 4 , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Macrolídeos , Maleimidas/farmacologia , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno , Quinases de Proteína Quinase Ativadas por Mitógeno/antagonistas & inibidores , Quinases de Proteína Quinase Ativadas por Mitógeno/fisiologia , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/fisiologia , Proteínas de Neoplasias/metabolismo , Nitrilas/farmacologia , Inibidores da Síntese de Ácido Nucleico/farmacologia , Complexo de Endopeptidases do Proteassoma , Proteína Quinase C/antagonistas & inibidores , Inibidores da Síntese de Proteínas/farmacologia , Proteínas Proto-Oncogênicas c-raf/metabolismo , Piridinas/farmacologia , Quinonas/farmacologia , Terpenos/farmacologia , Acetato de Tetradecanoilforbol/farmacologia , Fator de Transcrição AP-1/fisiologia , Fosfolipases Tipo C/farmacologia , Células U937/enzimologia , Ubiquitinas/metabolismo , Proteínas Quinases p38 Ativadas por MitógenoRESUMO
Bryostatin 1 and the phorbol ester, phorbol myristate acetate (PMA), both bind to and activate protein kinase C (PKC) but exhibit divergent biological actions. Bryostatin 1 exerts variable effects on leukemic cell differentiation, and has been reported by some investigators to inhibit the proliferation of the monocytic leukemic cell line U937. In this study, we have compared the efficacy of bryostatin 1 and PMA with respect to U937 cell maturation, with a major emphasis on differential actions on the cell cycle arrest machinery. At equimolar concentrations (10 nM), PMA, in contrast to bryostatin 1, induced cellular differentiation of U937 cells, reflected by growth inhibition, increased plastic adhesion, and expression of the monocytic differentiation marker, CD11b. Consistent with these results, bryostatin 1 was less effective in inducing G0/G1 arrest and inhibiting cyclin-dependent kinase 2 (CDK2) activity. Bryostatin 1, unlike PMA, failed to induce expression of the cyclin-dependent kinase inhibitor (CDKI), p21CIP1/WAF1, and blocked the ability of PMA to induce this protein. Bryostatin 1 exposure resulted in increased expression of the CDKI p27KIP1 in these cells, although the kinetics differed from PMA. In addition, bryostatin 1 was less effective than PMA in dephosphorylating pRb, modifying E2F complexes, and downregulating c-Myc. Co-administration of bryostatin 1 with PMA antagonized the latter's differentiation-inducing capacity and anti-proliferative effects, actions that were accompanied by a reduction in PMA-mediated p21CIP1/WAF1 induction, CDK2 inhibition, pRb dephosphorylation, and c-Myc downregulation. Antagonistic effects of bryostatin 1 on PMA-related cell cycle events were mimicked by the specific PKC inhibitor GF109203X. Together, these studies indicate that bryostatin 1 is a considerably weaker stimulus than PMA for U937 cell differentiation, and raise the possibility that this deficiency arises from its failure to induce p21CIP1/WAF1 and trigger cell cycle arrest.
Assuntos
Quinases relacionadas a CDC2 e CDC28 , Proteínas de Transporte , Proteínas de Ciclo Celular , Ciclo Celular/efeitos dos fármacos , Proteínas de Ligação a DNA , Regulação da Expressão Gênica , Lactonas/farmacologia , Linfoma Difuso de Grandes Células B/metabolismo , Acetato de Tetradecanoilforbol/farmacologia , Antineoplásicos/farmacologia , Western Blotting , Briostatinas , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Quinase 2 Dependente de Ciclina , Quinases Ciclina-Dependentes/antagonistas & inibidores , Quinases Ciclina-Dependentes/metabolismo , Ciclinas/efeitos dos fármacos , Ciclinas/metabolismo , Fatores de Transcrição E2F , Humanos , Macrolídeos , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Proteína do Retinoblastoma/metabolismo , Proteína 1 de Ligação ao Retinoblastoma , Fatores de Tempo , Fator de Transcrição DP1 , Fatores de Transcrição/metabolismo , Células Tumorais CultivadasRESUMO
Stimulation of quiescent AKR-2B mouse fibroblasts with transforming growth factor beta1 results in uniform conversion to a myofibroblast-like phenotype as judged by a rapid accumulation of smooth muscle alpha-actin mRNA and protein. Because transcriptional regulation of the smooth muscle alpha-actin gene in these cells might be mediated by single-stranded DNA-binding proteins, we have examined the sensitivity of genomic DNA to chemical reagents with specificity for unpaired bases in a region of the promoter previously implicated in Puralpha, Purbeta, and MSY1 binding in vitro (Kelm, R. J., Jr., Cogan, J. G., Elder, P. K., Strauch, A. R., and Getz, M. J. (1999) J. Biol. Chem. 274, 14238-14245). Our data reveal specific differences between purified DNA treated in vitro and nucleoprotein complexes treated in living cells. Although some differences were observed in quiescent cells, treatment with transforming growth factor beta1 resulted in the development of additional sensitivity within 1 h. This enhancement was most pronounced in bases immediately upstream of an MCAT enhancer element-containing polypurine-polypyrimidine tract. A TATA-proximal element of similar base distribution showed no such hyperreactivities. These results suggest that activation of the endogenous smooth muscle alpha-actin gene during myofibroblast conversion is accompanied by specific structural changes in the promoter that are consistent with a decline in single-stranded DNA repressor protein binding.
Assuntos
Actinas/genética , DNA de Cadeia Simples/efeitos dos fármacos , Fibroblastos/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Regiões Promotoras Genéticas , Fator de Crescimento Transformador beta/farmacologia , Animais , Sequência de Bases , Becaplermina , Diferenciação Celular/efeitos dos fármacos , Elementos Facilitadores Genéticos , Fator de Crescimento Epidérmico/farmacologia , Fibroblastos/citologia , Fibroblastos/metabolismo , Insulina/farmacologia , Cinética , Camundongos , Dados de Sequência Molecular , Fator de Crescimento Derivado de Plaquetas/farmacologia , Proteínas Proto-Oncogênicas c-sis , TATA BoxRESUMO
The effects of the non-tumor-promoting protein kinase C (PKC) activator bryostatin 1 and the PKC inhibitors staurosporine and UCN-01 were examined with respect to modulation of 1-[beta-D-arabinofuranosyl]cytosine (ara-C)-induced apoptosis in human myeloid leukemia cells (HL-60) overexpressing the antiapoptotic protein Bcl-2. HL-60/Bcl-2 cells displayed a 5-fold increase in Bcl-2 protein compared with empty-vector counter-parts (HL-60/pCEP4) but comparable levels of Bax, Mcl-1, and Bcl-xL. After exposure to an equimolar concentration of ara-C (10 microM for 6 hr), HL-60/Bcl-2 cells were significantly less susceptible to apoptosis, DNA fragmentation, and loss of clonogenicity than HL-60/pCEP4 cells. The protective effect of increased Bcl-2 expression was manifested by a failure of ara-C to induce activation/cleavage of the Yama protease (CPP32; caspase-3) and degradation of one of its substrates, poly(ADP-ribose)polymerase to an 85-kDa cleavage product. When HL-60/Bcl-2 cells were preincubated with bryostatin 1 (10 nM; 24 hr) or coincubated with either staurosporine (50 nM; 6 hr) or UCN-01 (300 nM; 6 hr) after a 1-hr preincubation, exposures that exerted minimal effects alone, ara-C-induced apoptosis and DNA fragmentation were restored to levels equivalent to, or greater than, those observed in empty-vector controls. These events were accompanied by restoration of the ability of ara-C to induce CPP32 cleavage and activation, poly(ADP-ribose) polymerase degradation, and inhibition of colony formation. Western analysis of Bcl-2 protein obtained from overexpressing cells treated with bryostatin 1, staurosporine, or UCN-01 revealed the appearance of a slowly migrating species and a general broadening of the protein band, effects that were insensitive to the protein synthesis inhibitor cycloheximide. Alterations in Bcl-2 protein mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis were reversed by treatment of lysates with alkaline phosphatase or protein phosphatase 2A; actions of the latter were blocked by the specific phosphatase inhibitor okadaic acid. In vivo labeling studies of Bcl-2 protein demonstrated increased incorporation of [32PO4]orthophosphate in drug-treated cells. Last, phosphorylated Bcl-2 failed to display decreased binding to the proapoptotic protein Bax. Collectively, these findings indicate that bryostatin 1, which down-regulates PKC, and staurosporine and UCN-01, which directly inhibit the enzyme, circumvent resistance of Bcl-2-overexpressing leukemic cells to ara-C-induced apoptosis and activation of the protease cascade. They also raise the possibility that modulation of Bcl-2 phosphorylation status contributes to this effect.