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Inflammation-associated cell cycle-independent block of apoptosis by survivin in terminally differentiated neutrophils.

Altznauer F, Martinelli S, Yousefi S, Thürig C, Schmid I, Conway EM, Schöni MH, Vogt P, Mueller C, Fey MF, Zangemeister-Wittke U, Simon HU - J. Exp. Med. (2004)

Bottom Line: Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo.Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner.Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Pharmacology, University of Bern, Friedbühlstrasse 49, CH-3010 Bern, Switzerland.

ABSTRACT
Survivin has received great attention due to its expression in many human tumors and its potential as a therapeutic target in cancer. Survivin expression has been described to be cell cycle-dependent and restricted to the G2-M checkpoint, where it inhibits apoptosis in proliferating cells. In agreement with this current view, we found that survivin expression was high in immature neutrophils, which proliferate during differentiation. In contrast with immature cells, mature neutrophils contained only little or no survivin protein. Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo. Moreover, survivin-deficient mature neutrophils were unable to increase their lifespan after survival factor exposure. Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner. Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells. These data provide new insights into the regulation and function of survivin and have important implications for the pathogenesis, diagnosis, and treatment of inflammatory diseases and cancer.

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Antisense oligonucleotide treatment specifically prevents increases in survivin gene expression and antiapoptosis mediated by GM-CSF or G-CSF in mature neutrophils. (A) Real-time PCR. The lung cancer cell line A549 served as a standard (100%). Oligonucleotides (as and ms) had no effect on survivin mRNA expression in the absence of survival cytokines after a 4-h transfection period (top). Survivin-antisense (as), in contrast with mismatch control oligonucleotides (ms), prevented increases in survivin mRNA expression upon GM-CSF (middle) or G-CSF (bottom) stimulation in a dose-dependent manner. Values are means ± SEM of three independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (B) Immunoblotting. Protein expression of survivin in normal neutrophils was not affected by incubation with as or ms (not depicted). However, survivin-as, in contrast with ms, partially (GM-CSF) or completely (G-CSF) prevented cytokine-induced increases in survivin expression. To demonstrate the specificity of the survivin-as effects, we also measured XIAP and Mcl-1 levels in the experiments using G-CSF. The filters were reprobed with an anti–β-actin mAb to ensure equal loading of the gels, and results of the densitometry analysis in terms of percentage are presented below the immunoblots. Results are representative of three independent experiments. (C) DNA fragmentation assay. Targeting survivin expression by survivin-as increased spontaneous apoptosis (left). GM-CSF (middle) and G-CSF (right) prevented apoptosis, and survivin-as blocked cytokine-mediated survival in a dose-dependent manner. Neutrophils were cultured for 10 h. Values are means ± SEM of four independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (D) Viability assay. Neutrophils from survivin+/− mice demonstrated reduced IL-3–mediated survival. Neutrophils were isolated from blood and cultured in the presence of IL-3 for 24 h before viability was measured. No difference in spontaneous cell death was noticed between survivin+/+ and survivin+/− mice (not depicted). Values are means ± SEM of four independent experiments. *, P < 0.05.
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fig7: Antisense oligonucleotide treatment specifically prevents increases in survivin gene expression and antiapoptosis mediated by GM-CSF or G-CSF in mature neutrophils. (A) Real-time PCR. The lung cancer cell line A549 served as a standard (100%). Oligonucleotides (as and ms) had no effect on survivin mRNA expression in the absence of survival cytokines after a 4-h transfection period (top). Survivin-antisense (as), in contrast with mismatch control oligonucleotides (ms), prevented increases in survivin mRNA expression upon GM-CSF (middle) or G-CSF (bottom) stimulation in a dose-dependent manner. Values are means ± SEM of three independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (B) Immunoblotting. Protein expression of survivin in normal neutrophils was not affected by incubation with as or ms (not depicted). However, survivin-as, in contrast with ms, partially (GM-CSF) or completely (G-CSF) prevented cytokine-induced increases in survivin expression. To demonstrate the specificity of the survivin-as effects, we also measured XIAP and Mcl-1 levels in the experiments using G-CSF. The filters were reprobed with an anti–β-actin mAb to ensure equal loading of the gels, and results of the densitometry analysis in terms of percentage are presented below the immunoblots. Results are representative of three independent experiments. (C) DNA fragmentation assay. Targeting survivin expression by survivin-as increased spontaneous apoptosis (left). GM-CSF (middle) and G-CSF (right) prevented apoptosis, and survivin-as blocked cytokine-mediated survival in a dose-dependent manner. Neutrophils were cultured for 10 h. Values are means ± SEM of four independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (D) Viability assay. Neutrophils from survivin+/− mice demonstrated reduced IL-3–mediated survival. Neutrophils were isolated from blood and cultured in the presence of IL-3 for 24 h before viability was measured. No difference in spontaneous cell death was noticed between survivin+/+ and survivin+/− mice (not depicted). Values are means ± SEM of four independent experiments. *, P < 0.05.

Mentions: Survivin Delays Apoptosis in a Cell Cycle–independent Manner. The role of survivin as an antiapoptotic protein is still a matter of debate. Some authors concluded that survivin is less important for apoptosis regulation (30), whereas others suggested a significant role of this molecule in protecting cells from apoptosis in a cell cycle–dependent manner (3, 4). Mature neutrophils are terminally differentiated cells unable to proliferate (Fig. 4 C). Thus, this system not only represents an ideal tool to answer the question whether increased survivin levels prevent or reduce apoptosis, it also provides the unique possibility to test whether survivin exhibits antiapoptotic activity in a cell cycle–independent manner and beyond the G2-M checkpoint (5). The role of survivin in the apoptosis regulation of mature neutrophils was characterized by preventing its cytokine-mediated expression. Specific antisense but not mismatch oligonucleotides blocked the production of high levels of survivin mRNA (Fig. 7 A) and protein (Fig. 7 B) upon GM-CSF or G-CSF stimulation. Although antisense oligonucleotides partially inhibited GM-CSF–induced survivin protein expression (Fig. 7 B, top), the effects of G-CSF were completely blocked in this cell culture system at a dose of 5.0 μM (Fig. 7 B, bottom). To further prove the specificity of the survivin antisense oligonucleotides, we also analyzed XIAP and Mcl-1 protein levels. Both proteins were selected because of their potential antiapoptotic activities in neutrophils (31, 32). Although Mcl-1 levels were slightly affected at 5.0 μM antisense, no significant effects on the expression levels of these two control proteins were observed (Fig. 7 B, bottom). This suggests that reduction of survivin levels was an antisense-specific effect and not due to off-target effects mediated by nonantisense related toxicity of the oligonucleotides.


Inflammation-associated cell cycle-independent block of apoptosis by survivin in terminally differentiated neutrophils.

Altznauer F, Martinelli S, Yousefi S, Thürig C, Schmid I, Conway EM, Schöni MH, Vogt P, Mueller C, Fey MF, Zangemeister-Wittke U, Simon HU - J. Exp. Med. (2004)

Antisense oligonucleotide treatment specifically prevents increases in survivin gene expression and antiapoptosis mediated by GM-CSF or G-CSF in mature neutrophils. (A) Real-time PCR. The lung cancer cell line A549 served as a standard (100%). Oligonucleotides (as and ms) had no effect on survivin mRNA expression in the absence of survival cytokines after a 4-h transfection period (top). Survivin-antisense (as), in contrast with mismatch control oligonucleotides (ms), prevented increases in survivin mRNA expression upon GM-CSF (middle) or G-CSF (bottom) stimulation in a dose-dependent manner. Values are means ± SEM of three independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (B) Immunoblotting. Protein expression of survivin in normal neutrophils was not affected by incubation with as or ms (not depicted). However, survivin-as, in contrast with ms, partially (GM-CSF) or completely (G-CSF) prevented cytokine-induced increases in survivin expression. To demonstrate the specificity of the survivin-as effects, we also measured XIAP and Mcl-1 levels in the experiments using G-CSF. The filters were reprobed with an anti–β-actin mAb to ensure equal loading of the gels, and results of the densitometry analysis in terms of percentage are presented below the immunoblots. Results are representative of three independent experiments. (C) DNA fragmentation assay. Targeting survivin expression by survivin-as increased spontaneous apoptosis (left). GM-CSF (middle) and G-CSF (right) prevented apoptosis, and survivin-as blocked cytokine-mediated survival in a dose-dependent manner. Neutrophils were cultured for 10 h. Values are means ± SEM of four independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (D) Viability assay. Neutrophils from survivin+/− mice demonstrated reduced IL-3–mediated survival. Neutrophils were isolated from blood and cultured in the presence of IL-3 for 24 h before viability was measured. No difference in spontaneous cell death was noticed between survivin+/+ and survivin+/− mice (not depicted). Values are means ± SEM of four independent experiments. *, P < 0.05.
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fig7: Antisense oligonucleotide treatment specifically prevents increases in survivin gene expression and antiapoptosis mediated by GM-CSF or G-CSF in mature neutrophils. (A) Real-time PCR. The lung cancer cell line A549 served as a standard (100%). Oligonucleotides (as and ms) had no effect on survivin mRNA expression in the absence of survival cytokines after a 4-h transfection period (top). Survivin-antisense (as), in contrast with mismatch control oligonucleotides (ms), prevented increases in survivin mRNA expression upon GM-CSF (middle) or G-CSF (bottom) stimulation in a dose-dependent manner. Values are means ± SEM of three independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (B) Immunoblotting. Protein expression of survivin in normal neutrophils was not affected by incubation with as or ms (not depicted). However, survivin-as, in contrast with ms, partially (GM-CSF) or completely (G-CSF) prevented cytokine-induced increases in survivin expression. To demonstrate the specificity of the survivin-as effects, we also measured XIAP and Mcl-1 levels in the experiments using G-CSF. The filters were reprobed with an anti–β-actin mAb to ensure equal loading of the gels, and results of the densitometry analysis in terms of percentage are presented below the immunoblots. Results are representative of three independent experiments. (C) DNA fragmentation assay. Targeting survivin expression by survivin-as increased spontaneous apoptosis (left). GM-CSF (middle) and G-CSF (right) prevented apoptosis, and survivin-as blocked cytokine-mediated survival in a dose-dependent manner. Neutrophils were cultured for 10 h. Values are means ± SEM of four independent experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001. (D) Viability assay. Neutrophils from survivin+/− mice demonstrated reduced IL-3–mediated survival. Neutrophils were isolated from blood and cultured in the presence of IL-3 for 24 h before viability was measured. No difference in spontaneous cell death was noticed between survivin+/+ and survivin+/− mice (not depicted). Values are means ± SEM of four independent experiments. *, P < 0.05.
Mentions: Survivin Delays Apoptosis in a Cell Cycle–independent Manner. The role of survivin as an antiapoptotic protein is still a matter of debate. Some authors concluded that survivin is less important for apoptosis regulation (30), whereas others suggested a significant role of this molecule in protecting cells from apoptosis in a cell cycle–dependent manner (3, 4). Mature neutrophils are terminally differentiated cells unable to proliferate (Fig. 4 C). Thus, this system not only represents an ideal tool to answer the question whether increased survivin levels prevent or reduce apoptosis, it also provides the unique possibility to test whether survivin exhibits antiapoptotic activity in a cell cycle–independent manner and beyond the G2-M checkpoint (5). The role of survivin in the apoptosis regulation of mature neutrophils was characterized by preventing its cytokine-mediated expression. Specific antisense but not mismatch oligonucleotides blocked the production of high levels of survivin mRNA (Fig. 7 A) and protein (Fig. 7 B) upon GM-CSF or G-CSF stimulation. Although antisense oligonucleotides partially inhibited GM-CSF–induced survivin protein expression (Fig. 7 B, top), the effects of G-CSF were completely blocked in this cell culture system at a dose of 5.0 μM (Fig. 7 B, bottom). To further prove the specificity of the survivin antisense oligonucleotides, we also analyzed XIAP and Mcl-1 protein levels. Both proteins were selected because of their potential antiapoptotic activities in neutrophils (31, 32). Although Mcl-1 levels were slightly affected at 5.0 μM antisense, no significant effects on the expression levels of these two control proteins were observed (Fig. 7 B, bottom). This suggests that reduction of survivin levels was an antisense-specific effect and not due to off-target effects mediated by nonantisense related toxicity of the oligonucleotides.

Bottom Line: Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo.Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner.Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Pharmacology, University of Bern, Friedbühlstrasse 49, CH-3010 Bern, Switzerland.

ABSTRACT
Survivin has received great attention due to its expression in many human tumors and its potential as a therapeutic target in cancer. Survivin expression has been described to be cell cycle-dependent and restricted to the G2-M checkpoint, where it inhibits apoptosis in proliferating cells. In agreement with this current view, we found that survivin expression was high in immature neutrophils, which proliferate during differentiation. In contrast with immature cells, mature neutrophils contained only little or no survivin protein. Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo. Moreover, survivin-deficient mature neutrophils were unable to increase their lifespan after survival factor exposure. Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner. Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells. These data provide new insights into the regulation and function of survivin and have important implications for the pathogenesis, diagnosis, and treatment of inflammatory diseases and cancer.

Show MeSH
Related in: MedlinePlus