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Andrepatrick Arrigo - One of the best experts on this subject based on the ideXlab platform.
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Hsp27 as a negative regulator of cytochrome c release
Molecular and Cellular Biology, 2002Co-Authors: Catherine Paul, Florence Manero, Sandrine Gonin, Carole Kretzremy, Sophie Virot, Andrepatrick ArrigoAbstract:We previously showed that Hsp27 protects against apoptosis through its interaction with cytosolic cytochrome c. We have revisited this protective activity in murine cell lines expressing different levels of Hsp27. We report that Hsp27 also interferes, in a manner dependent on level of expression, with the release of cytochrome c from mitochondria. Moreover, a decreased level of endogenous Hsp27, which sensitized HeLa cells to apoptosis, reduced the delay required for cytochrome c release and procaspase 3 activation. The molecular mechanism regulating this function of Hsp27 is unknown. In our cell systems, Hsp27 is mainly cytosolic and only a small fraction of this protein colocalized with mitochondria. Moreover, we show that only a very small fraction of cytochrome c interacts with Hsp27, hence excluding a role of this interaction in the retention of cytochrome c in mitochondria. We also report that Bid intracellular relocalization was altered by changes in Hsp27 level of expression, suggesting that Hsp27 interferes with apoptotic signals upstream of mitochondria. We therefore investigated if the ability of Hsp27 to act as an expression-dependent modulator of F-actin microfilaments integrity was linked to the retention of cytochrome c in mitochondria. We show here that the F-actin depolymerizing agent cytochalasin D rapidly induced the release of cytochrome c from mitochondria and caspase activation. This phenomenon was delayed in cells pretreated with the F-actin stabilizer phalloidin and in cells expressing a high level of Hsp27. This suggests the existence of an apoptotic signaling pathway linking cytoskeleton damages to mitochondria. This pathway, which induces Bid intracellular redistribution, is negatively regulated by the ability of Hsp27 to protect F-actin network integrity. However, this upstream pathway is probably not the only one to be regulated by Hsp27 since, in staurosporine-treated cells, phalloidin only partially inhibited cytochrome c release and caspase activation. Moreover, in etoposide-treated cells, Hsp27 still delayed the release of cytochrome c from mitochondria and Bid intracellular redistribution in conditions where F-actin was not altered.
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Hsp27 protects mitochondria of thermotolerant cells against apoptotic stimuli
Cell Stress & Chaperones, 2001Co-Authors: Afshin Samali, John D Robertson, Elisabeth Peterson, Florence Manero, Leone Van Zeijl, Catherine Paul, Ian A Cotgreave, Andrepatrick Arrigo, Sten OrreniusAbstract:Enhanced cell survival and resistance to apoptosis during thermotolerance correlates with an increased expression of heat shock proteins (Hsps). Here we present additional evidence in support of the hypothesis that the induction of Hsp27 and Hsp72 during acquired thermotolerance in Jurkat T-lymphocytes prevents apoptosis. In thermotolerant cells, Hsp27 was shown to associate with the mitochondrial fraction, and inhibition of Hsp27 induction during thermotolerance in cells transfected with Hsp27 antisense potentiated mitochondrial cytochrome c release after exposure to various apoptotic stimuli, despite the presence of elevated levels of Hsp72. Caspase activation and apoptosis were inhibited under these conditions. In vitro studies revealed that recombinant Hsp72 more efficiently blocked cytochrome c–mediated caspase activation than did recombinant Hsp27. A model is presented for the inhibition of apoptosis during thermotolerance in which Hsp27 preferentially blocks mitochondrial cytochrome c release, whereas Hsp72 interferes with apoptosomal caspase activation.
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Hsp27 inhibits cytochrome c dependent activation of procaspase 9
The FASEB Journal, 1999Co-Authors: Carmen Garrido, Andrepatrick Arrigo, Annie Fromentin, Arlette Hammann, Jeanmarie Bruey, Eric SolaryAbstract:We have previously shown that the small heat shock protein Hsp27 inhibited apoptotic pathways triggered by a variety of stimuli in mammalian cells. The present study demonstrates that Hsp27 overexpression decreases U937 human leukemic cell sensitivity to etoposide-induced cytotoxicity by preventing apoptosis. As observed for Bcl-2, Hsp27 overexpression delays poly(ADP-ribose)polymerase cleavage and procaspase-3 activation. In contrast with Bcl-2, Hsp27 overexpression does not prevent etoposide-induced cytochrome c release from the mitochondria. In a cell-free system, addition of cytochrome c and dATP to cytosolic extracts from untreated cells induces the proteolytic activation of procaspase-3 in both control and bcl-2-transfected U937 cells but fails to activate procaspase-3 in Hsp27-overexpressing cells. Immunodepletion of Hsp27 from cytosolic extracts increases cytochrome c/dATP-mediated activation of procaspase-3. Overexpression of Hsp27 also prevents procaspase-9 activation. In the cell-free system, i...
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regulation of Hsp27 oligomerization chaperone function and protective activity against oxidative stress tumor necrosis factor α by phosphorylation
Journal of Biological Chemistry, 1999Co-Authors: Thorsten Rogalla, Catherine Paul, Andrepatrick Arrigo, Monika Ehrnsperger, Xavier Preville, Alexey Kotlyarov, Gudrun Lutsch, Cecile Ducasse, Martin Wieske, Johannes BuchnerAbstract:The small heat shock proteins (sHsps) from human (Hsp27) and mouse (Hsp25) form large oligomers which can act as molecular chaperones in vitro and protect cells from heat shock and oxidative stress when overexpressed. In addition, mammalian sHsps are rapidly phosphorylated by MAPKAP kinase 2/3 at two or three serine residues in response to various extracellular stresses. Here we analyze the effect of sHsp phosphorylation on its quaternary structure, chaperone function, and protection against oxidative stress. We show that in vitro phosphorylation of recombinant sHsp as well as molecular mimicry of Hsp27 phosphorylation lead to a significant decrease of the oligomeric size. We demonstrate that both phosphorylated sHsps and the triple mutant Hsp27-S15D,S78D,S82D show significantly decreased abilities to act as molecular chaperones suppressing thermal denaturation and facilitating refolding of citrate synthase in vitro. In parallel, Hsp27 and its mutants were analyzed for their ability to confer resistance against oxidative stress when overexpressed in L929 and 13.S.1.24 cells. While wild type Hsp27 confers resistance, the triple mutant S15D,S78D,S82D cannot protect against oxidative stress effectively. These data indicate that large oligomers of sHsps are necessary for chaperone action and resistance against oxidative stress whereas phosphorylation down-regulates these activities by dissociation of sHsp complexes to tetramers.
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Hsp27 as a switch between differentiation and apoptosis in murine embryonic stem cells
Journal of Biological Chemistry, 1997Co-Authors: Patrick Mehlen, Anne Mehlen, J Godet, Andrepatrick ArrigoAbstract:Small stress proteins are developmentally regulated and linked to cell growth and differentiation. The early phase of murine embryonic stem (ES) cell differentiation, characterized by a gradual growth arrest, is accompanied with Hsp27 transient accumulation. This differentiation process also correlated with changes in Hsp27 phosphorylation and oligomerization. The role of Hsp27 was investigated in ES clones stably transfected with murine or human Hsp27 genes, placed in sense or antisense orientation. Several clones were obtained that either underexpressed endogenous murine Hsp27 or overexpressed murine or human Hsp27. Maintained undifferentiated, these clones showed similar growth rates. We report here that Hsp27 constitutive overexpression enhanced the differentiation-mediated decreased rate of ES cell proliferation but did not alter morphological changes. In contrast, Hsp27 underexpression, which attenuated cell growth arrest, induced differentiation abortion because of an overall cell death by apoptosis. Recently, we showed that Hsp27 interfered with cell death probably because of its ability to modulate intracellular glutathione. Hsp27 accumulation during ES cell differentiation was also correlated with an increase in glutathione, which was attenuated by Hsp27 down-expression. Hence, Hsp27 transient expression seems essential for preventing differentiating ES cells from undergoing apoptosis, a switch that may be redox regulated.
Jun Chen - One of the best experts on this subject based on the ideXlab platform.
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phosphorylation of Hsp27 by protein kinase d is essential for mediating neuroprotection against ischemic neuronal injury
The Journal of Neuroscience, 2012Co-Authors: R A Stetler, Lili Zhang, Zhongfang Weng, Feng Zhang, Xiaoming Hu, Suping Wang, Peter S Vosler, Steven H Graham, Jun ChenAbstract:Heat shock protein 27 (Hsp27) (or HSPB1) exerts cytoprotection against many cellular insults, including cerebral ischemia. We previously identified apoptosis signal-regulating kinase 1 (ASK1) as a critical downstream target of Hsp27 conferring the neuroprotective effects of Hsp27 against neuronal ischemia. However, the function of Hsp27 is highly influenced by posttranslational modification, with differential cellular effects based on phosphorylation at specific serine residues. The role of phosphorylation in neuronal ischemic neuroprotection is currently unknown. We have created transgenic mice and viral vectors containing Hsp27 mutated at three critical serine residues (Ser15, Ser78, and Ser82) to either alanine (Hsp27-A, nonphosphorylatable) or aspartate (Hsp27-D, phosphomimetic) residues. Under both in vitro and in vivo neuronal ischemic settings, overexpression of wild-type Hsp27 (Hsp27) and Hsp27-D, but not Hsp27-A, was neuroprotective and inhibited downstream ASK1 signaling pathways. Consistently, overexpressed Hsp27 was phosphorylated by endogenous mechanisms when neurons were under ischemic stress, and single-point mutations identified Ser15 and Ser82 as critical for neuroprotection. Using a panel of inhibitors and gene knockdown approaches, we identified the upstream kinase protein kinase D (PKD) as the primary kinase targeting Hsp27 directly for phosphorylation. PKD and Hsp27 coimmunoprecipitated, and inhibition or knockdown of PKD abrogated the neuroprotective effects of Hsp27 as well as the interaction with and inhibition of ASK1 signaling. Together, these data demonstrate that Hsp27 requires PKD-mediated phosphorylation for its suppression of ASK1 cell death signaling and neuroprotection against ischemic injury.
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Hsp27 protects against ischemic brain injury via attenuation of a novel stress response cascade upstream of mitochondrial cell death signaling
The Journal of Neuroscience, 2008Co-Authors: Anne R Stetler, Lili Zhang, Zhongfang Weng, Feng Zhang, Suping Wang, Peter S Vosler, Steven H Graham, Jun Chen, Armando P SignoreAbstract:Heat shock protein 27 (Hsp27), a recently discovered member of the heat shock protein family, is markedly induced in the brain after cerebral ischemia and other injury states. In non-neuronal systems, Hsp27 has potent cell death-suppressing functions. However, the mechanism of Hsp27-mediated neuroprotection has not yet been elucidated. Using transgenic and viral overexpression of Hsp27, we investigated the molecular mechanism by which Hsp27 exerts its neuroprotective effect. Overexpression of Hsp27 conferred long-lasting tissue preservation and neurobehavioral recovery, as measured by infarct volume, sensorimotor function, and cognitive tasks up to 3 weeks following focal cerebral ischemia. Examination of signaling pathways critical to neuronal death demonstrated that Hsp27 overexpression led to the suppression of the MKK4/JNK kinase cascade. While Hsp27 overexpression did not suppress activation of an upstream regulatory kinase of the MKK/JNK cascade, ASK1, Hsp27 effectively inhibited ASK1 activity via a physical association through its N-terminal domain and the kinase domain of ASK1. The N-terminal region of Hsp27 was required for neuroprotective function against in vitro ischemia. Moreover, knockdown of ASK1 or inhibition of the ASK1/MKK4 cascade effectively inhibited cell death following neuronal ischemia. This underscores the importance of this kinase cascade in the progression of ischemic neuronal death. Inhibition of PI3K had no effect on Hsp27-mediated neuroprotection, suggesting that Hsp27 does not promote cell survival via activation of PI3K/Akt. Based on these findings, we conclude that overexpression of Hsp27 confers long-lasting neuroprotection against ischemic brain injury via a previously unexplored association and inhibition of ASK1 kinase signaling.
Martin E Gleave - One of the best experts on this subject based on the ideXlab platform.
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Hsp27 promotes insulin like growth factor i survival signaling in prostate cancer via p90rsk dependent phosphorylation and inactivation of bad
Cancer Research, 2010Co-Authors: Amina Zoubeidi, Anousheh Zardan, Romina M Wiedmann, Jennifer A Locke, Eliana Beraldi, Ladan Fazli, Martin E GleaveAbstract:Hsp27 is highly expressed in castrate-resistant prostate cancer. Although its overexpression confers resistance to androgen ablation and chemotherapy, the mechanisms by which Hsp27 inhibits treatment-induced apoptosis are incompletely defined. Castrate-resistance often correlates with increased activity of autocrine and/or paracrine growth/survival stimulatory loops including the mitogen-activated protein kinase (MAPK) and Akt pathways and insulin-like growth factor (IGF) axis components. Because Hsp27 can be activated by both MAPK and Akt pathways, it is possible that interactions between IGF-I signaling and Hsp27 phosphoactivation function to promote castrate-resistant progression. Here, we report that Hsp27 expression and phosphorylation levels correlate with IGF-I signaling and castrate-resistant progression in human prostate cancer specimens and cell lines. IGF-I induces Hsp27 phosphorylation in a time- and dose-dependent manner via p90Rsk, which interacts directly with and phosphorylates Hsp27 in vitro and in vivo. Conversely, p90Rsk inhibition using short interfering RNA or a dominant negative mutant abolishes IGF-I-induced Hsp27 phosphorylation. Hsp27 overexpression increases IGF-I-induced phosphorylation of Erk, p90Rsk, and Akt. Conversely, Hsp27 knockdown abrogates IGF-I-induced phosphorylation of Erk, p90Rsk, and Akt, thereby destabilizing Bad/14-3-3 complexes and increasing apoptotic rates. These data elucidate the interactions between Hsp27 phosphorylation and the IGF-I receptor signaling pathway and support targeting Hsp27 as a therapeutic strategy for castrate-resistant prostate cancer.
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Hsp27 knockdown using nucleotide based therapies inhibit tumor growth and enhance chemotherapy in human bladder cancer cells
Molecular Cancer Therapeutics, 2007Co-Authors: Masayuki Kamada, Palma Rocchi, Eliana Beraldi, Alan So, Mototsugu Muramaki, Martin E GleaveAbstract:Heat shock protein 27 (Hsp27) is a cytoprotective chaperone that is phosphoactivated during cell stress that prevents aggregation and/or regulate activity and degradation of certain client proteins. Recent evidence suggests that Hsp27 may be involved in tumor progression and the development of treatment resistance in various tumors, including bladder cancer. The purpose of this study was to examine, both in vitro and in vivo , the effects of overexpression of Hsp27 and, correspondingly, the down-regulation of Hsp27 using small interfering (si) RNA and OGX-427, a second-generation antisense oligonucleotide targeting Hsp27. Hsp27 overexpression increased UMUC-3 cell growth and resistance to paclitaxel. Both OGX-427 and Hsp27 siRNA decreased Hsp27 protein and mRNA levels by >90% in a dose- and sequence-specific manner in human bladder cancer UMUC-3 cells. OGX-427 or Hsp27 siRNA treatment induced apoptosis and enhanced sensitivity to paclitaxel in UMUC-3 cells. In vivo , OGX-427 significantly inhibited tumor growth in mice, enhanced sensitivity to paclitaxel, and induced significantly higher levels of apoptosis compared with xenografts treated with control oligonucleotides. Collectively, these findings suggest that Hsp27 knockdown with OGX-427 and combined therapy with paclitaxel could be a novel strategy to inhibit the progression of bladder cancer. [Mol Cancer Ther 2007;6(1):299–308]
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increased Hsp27 after androgen ablation facilitates androgen independent progression in prostate cancer via signal transducers and activators of transcription 3 mediated suppression of apoptosis
Cancer Research, 2005Co-Authors: Palma Rocchi, Eliana Beraldi, Ladan Fazli, Susan Ettinger, Robert L Vessella, Colleen C Nelson, Martin E GleaveAbstract:One strategy to improve therapies in prostate cancer involves targeting cytoprotective genes activated by androgen withdrawal to delay the emergence of the androgen-independent (AI) phenotype. The objectives of this study were to define changes in Hsp27 levels after androgen ablation and to evaluate the functional relevance of these changes in AI progression. Using a tissue microarray of 232 specimens of hormone-naive and post-hormone ablation–treated prostate cancer, we found that Hsp27 levels increase after androgen ablation to become highly expressed (>4-fold, P ≤ 0.01) in AI tumors. Hsp27 overexpression rendered LNCaP cells highly resistant to androgen withdrawal both in vitro and in vivo . Tumor volume and serum prostate–specific antigen levels increased 4.3- and 10-fold faster after castration when Hsp27 was overexpressed. Treatment of LNCaP tumor cells in vitro with Hsp27 antisense oligonucleotides (ASO) or short-interfering RNA suppressed Hsp27 levels in a dose-dependent and sequence-specific manner increased the apoptotic sub–G-G1 fraction and caspase-3 cleavage >2-fold, as well as decreased signal transducers and activators of transcription 3 (Stat3) levels and its downstream genes, c- fos and sPLA-2. The cytoprotection afforded by Hsp27 overexpression was attenuated by Stat3 knockdown using specific Stat3 ASO. Coimmunoprecipitation and immunofluorescence confirmed that Hsp27 interacts with Stat3 and that Stat3 levels correlated directly with Hsp27 levels. Hsp27 ASO treatment in athymic mice bearing LNCaP tumors significantly delayed LNCaP tumor growth after castration, decreasing mean tumor volume and serum prostate–specific antigen levels by 57% and 69%, respectively. These findings identify Hsp27 as a modulator of Stat3-regulated apoptosis after androgen ablation and as a potential therapeutic target in advanced prostate cancer.
Patrick Mehlen - One of the best experts on this subject based on the ideXlab platform.
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Hsp27 as a switch between differentiation and apoptosis in murine embryonic stem cells
Journal of Biological Chemistry, 1997Co-Authors: Patrick Mehlen, Anne Mehlen, J Godet, Andrepatrick ArrigoAbstract:Small stress proteins are developmentally regulated and linked to cell growth and differentiation. The early phase of murine embryonic stem (ES) cell differentiation, characterized by a gradual growth arrest, is accompanied with Hsp27 transient accumulation. This differentiation process also correlated with changes in Hsp27 phosphorylation and oligomerization. The role of Hsp27 was investigated in ES clones stably transfected with murine or human Hsp27 genes, placed in sense or antisense orientation. Several clones were obtained that either underexpressed endogenous murine Hsp27 or overexpressed murine or human Hsp27. Maintained undifferentiated, these clones showed similar growth rates. We report here that Hsp27 constitutive overexpression enhanced the differentiation-mediated decreased rate of ES cell proliferation but did not alter morphological changes. In contrast, Hsp27 underexpression, which attenuated cell growth arrest, induced differentiation abortion because of an overall cell death by apoptosis. Recently, we showed that Hsp27 interfered with cell death probably because of its ability to modulate intracellular glutathione. Hsp27 accumulation during ES cell differentiation was also correlated with an increase in glutathione, which was attenuated by Hsp27 down-expression. Hence, Hsp27 transient expression seems essential for preventing differentiating ES cells from undergoing apoptosis, a switch that may be redox regulated.
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large unphosphorylated aggregates as the active form of Hsp27 which controls intracellular reactive oxygen species and glutathione levels and generates a protection against tnfα in nih 3t3 ras cells
Biochemical and Biophysical Research Communications, 1997Co-Authors: Patrick Mehlen, Eilen Hickey, Lee A Weber, Andrepatrick ArrigoAbstract:Abstract The mammalian small stress protein Hsp27 is an oligomeric phosphoprotein which interferes with the cell death induced by several stimuli. In that sense, we and others have recently shown that human Hsp27 expression induced cellular protection against tumor necrosis factor (TNFα), a protection which depends on the ability of Hsp27 to decrease the level of reactive oxygen species and increase that of glutathione. Here, we have analyzed unphosphorylatable mutants of human Hsp27 in which serines 15, 78, and 82 were replaced by alanines, glycines, or aspartic acids. Depending on the amino acid which was used to substitute the serine sites, a different pattern of Hsp27 structural organization was observed. Alanine substitution generated large Hsp27 aggregates while glycine and aspartic acid did the reverse. Hence, these phosphorylatable serine residues can be considered as key elements affecting Hsp27 structural organization. Only the large aggregates of Hsp27 were able to modulate reactive oxygen species and glutathione and generated cellular protection against TNFα. Moreover, using drugs that modulate the intracellular level of glutathione, we show that an increase in glutathione by itself was sufficient to generate large Hsp27 structures while the reverse was observed in the case of glutathione deprivation.
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Hsp27 as a mediator of confluence dependent resistance to cell death induced by anticancer drugs
Cancer Research, 1997Co-Authors: Carmen Garrido, Andrepatrick Arrigo, Patrick Ottavi, Annie Fromentin, Arlette Hammann, B Chauffert, Patrick MehlenAbstract:Abstract Resistance of colorectal cancer cells to chemotherapeutic drugs increases as cells reach confluence. Here we show that the small stress protein Hsp27, which has been described to block necrotic and apoptotic cell death, accumulates in confluent human colorectal cancer cell lines HT-29 and Caco2. Cell confluence also induces Hsp27 phosphorylation and changes in its intracellular distribution. We also show that overexpression of human Hsp27 by transfection of HT-29 cells increased the resistance of cells to doxorubicin or cisplatin and prevented drug-induced apoptosis. Interestingly, nonconfluent Hsp27-transfected cells and confluent control cells in which Hsp27 is expressed at the same level displayed a similar drug resistance. Hsp27-transfected cells did not exhibit an enhanced resistance when they reached confluence, nor was there an increased accumulation of Hsp27. We have previously shown that Hsp27 expression blocks tumor necrosis factor-induced cell death as a result of decreasing intracellular reactive oxygen species (ROS). Here we show that Hsp27 overexpression in HT-29 cells, obtained either by transfection or by growing the cells at high density, correlated with a significant ROS decrease. We conclude that cell confluent-dependent Hsp27 accumulation, probably due to its ability to decrease ROS levels, is essential for the establishment of the resistance of colorectal cancer cells when reaching confluence.
Palma Rocchi - One of the best experts on this subject based on the ideXlab platform.
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small heat shock proteins Hsp27 hspb1 αb crystallin hspb5 and hsp22 hspb8 as regulators of cell death
The International Journal of Biochemistry & Cell Biology, 2012Co-Authors: Julie Acunzo, Maria Katsogiannou, Palma RocchiAbstract:Abstract Hsp27, αB-crystallin and HSP22 are ubiquitous small heat shock proteins (sHsp) whose expression is induced in response to a wide variety of unfavorable physiological and environmental conditions. These sHsp protect cells from otherwise lethal conditions mainly by their involvement in cell death pathways such as necrosis, apoptosis or autophagy. At a molecular level, the mechanisms accounting for sHsp functions in cell death are (1) prevention of denatured proteins aggregation, (2) regulation of caspase activity, (3) regulation of the intracellular redox state, (4) function in actin polymerization and cytoskeleton integrity and (5) proteasome-mediated degradation of selected proteins. In cancer cells, these sHsp are often overexpressed and associated with increased tumorigenicity, cancer cells metastatic potential and resistance to chemotherapy. Altogether, these properties suggest that Hsp27, αB-crystallin and Hsp22 are appropriate targets for modulating cell death pathways. In the present, we briefly review recent reports showing molecular evidence of cell death regulation by these sHsp and co-chaperones. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.
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Hsp27 knockdown using nucleotide based therapies inhibit tumor growth and enhance chemotherapy in human bladder cancer cells
Molecular Cancer Therapeutics, 2007Co-Authors: Masayuki Kamada, Palma Rocchi, Eliana Beraldi, Alan So, Mototsugu Muramaki, Martin E GleaveAbstract:Heat shock protein 27 (Hsp27) is a cytoprotective chaperone that is phosphoactivated during cell stress that prevents aggregation and/or regulate activity and degradation of certain client proteins. Recent evidence suggests that Hsp27 may be involved in tumor progression and the development of treatment resistance in various tumors, including bladder cancer. The purpose of this study was to examine, both in vitro and in vivo , the effects of overexpression of Hsp27 and, correspondingly, the down-regulation of Hsp27 using small interfering (si) RNA and OGX-427, a second-generation antisense oligonucleotide targeting Hsp27. Hsp27 overexpression increased UMUC-3 cell growth and resistance to paclitaxel. Both OGX-427 and Hsp27 siRNA decreased Hsp27 protein and mRNA levels by >90% in a dose- and sequence-specific manner in human bladder cancer UMUC-3 cells. OGX-427 or Hsp27 siRNA treatment induced apoptosis and enhanced sensitivity to paclitaxel in UMUC-3 cells. In vivo , OGX-427 significantly inhibited tumor growth in mice, enhanced sensitivity to paclitaxel, and induced significantly higher levels of apoptosis compared with xenografts treated with control oligonucleotides. Collectively, these findings suggest that Hsp27 knockdown with OGX-427 and combined therapy with paclitaxel could be a novel strategy to inhibit the progression of bladder cancer. [Mol Cancer Ther 2007;6(1):299–308]
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increased Hsp27 after androgen ablation facilitates androgen independent progression in prostate cancer via signal transducers and activators of transcription 3 mediated suppression of apoptosis
Cancer Research, 2005Co-Authors: Palma Rocchi, Eliana Beraldi, Ladan Fazli, Susan Ettinger, Robert L Vessella, Colleen C Nelson, Martin E GleaveAbstract:One strategy to improve therapies in prostate cancer involves targeting cytoprotective genes activated by androgen withdrawal to delay the emergence of the androgen-independent (AI) phenotype. The objectives of this study were to define changes in Hsp27 levels after androgen ablation and to evaluate the functional relevance of these changes in AI progression. Using a tissue microarray of 232 specimens of hormone-naive and post-hormone ablation–treated prostate cancer, we found that Hsp27 levels increase after androgen ablation to become highly expressed (>4-fold, P ≤ 0.01) in AI tumors. Hsp27 overexpression rendered LNCaP cells highly resistant to androgen withdrawal both in vitro and in vivo . Tumor volume and serum prostate–specific antigen levels increased 4.3- and 10-fold faster after castration when Hsp27 was overexpressed. Treatment of LNCaP tumor cells in vitro with Hsp27 antisense oligonucleotides (ASO) or short-interfering RNA suppressed Hsp27 levels in a dose-dependent and sequence-specific manner increased the apoptotic sub–G-G1 fraction and caspase-3 cleavage >2-fold, as well as decreased signal transducers and activators of transcription 3 (Stat3) levels and its downstream genes, c- fos and sPLA-2. The cytoprotection afforded by Hsp27 overexpression was attenuated by Stat3 knockdown using specific Stat3 ASO. Coimmunoprecipitation and immunofluorescence confirmed that Hsp27 interacts with Stat3 and that Stat3 levels correlated directly with Hsp27 levels. Hsp27 ASO treatment in athymic mice bearing LNCaP tumors significantly delayed LNCaP tumor growth after castration, decreasing mean tumor volume and serum prostate–specific antigen levels by 57% and 69%, respectively. These findings identify Hsp27 as a modulator of Stat3-regulated apoptosis after androgen ablation and as a potential therapeutic target in advanced prostate cancer.