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1.  PERK-dependent regulation of MDA-7/IL-24-induced autophagy in primary human glioma cells 
Autophagy  2008;4(4):513-515.
Melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The studies by further defines the mechanism(s) by which a GST-MDA-7 fusion protein inhibits cell survival of primary human glioma cells in vitro. GST-MDA-7 killed glioma cells with diverse genetic characteristics that were dependent on activation of JNK1-3 with subsequent activation of BAX and the induction of mitochondrial dysfunction. Activation of JNK1-3 was dependent upon protein kinase R-like endoplasmic reticulum kinase (PERK) and GST-MDA-7 lethality was suppressed in PERK-/- cells. GST-MDA-7 caused PERK-dependent vacuolization of LC3-expressing endosomes whose formation was suppressed by incubation with 3-methyladenine, expression of HSP70 or of BiP/GRP78, or by knockdown of ATG5 or Beclin 1 expression, but not by inhibition of the JNK1-3 pathway. Knockdown of ATG5 or Beclin 1 expression or overexpression of HSP70 reduced GST-MDA-7 lethality. Our data demonstrate that GST-MDA-7 induces an ER stress response that, via the induction of autophagy, is causal in the activation of pro-apoptotic pathways that converge on the mitochondrion and ultimately culminate in decreased glioma cell survival.
PMCID: PMC2674579  PMID: 18299661
autophagy; caspase; ER stress; cell death
2.  MDA-7/IL-24–induced cell killing in malignant renal carcinoma cells occurs by a ceramide/CD95/PERK–dependent mechanism 
Molecular cancer therapeutics  2009;8(5):1280-1291.
Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The present studies focused on clarifying the mechanism(s) by which glutathione S-transferase (GST)-MDA-7 altered cell survival of human renal carcinoma cells in vitro. GST-MDA-7 caused plasma membrane clustering of CD95 and the association of CD95 with procaspase-8. GST-MDA-7 lethality was suppressed by inhibition of caspase-8 or by overexpression of short-form cellular FLICE inhibitory protein, but only weakly by inhibition of cathepsin proteases. GST-MDA-7–induced CD95 clustering (and apoptosis) was blocked by knockdown of acidic sphingomyelinase or, to a greater extent, ceramide synthase-6 expression. GST-MDA-7 killing was, in parallel, dependent on inactivation of extracellular signal–regulated kinase 1/2 and on CD95-induced p38 mitogen-activated protein kinase and c-jun NH2-terminal kinase-1/2 signaling. Knockdown of CD95 expression abolished GST-MDA-7–induced phosphorylation of protein kinase R–like endoplasmic reticulum kinase. GST-MDA-7 lethality was suppressed by knockout or expression of a dominant negative protein kinase R–like endoplasmic reticulum kinase that correlated with reduced c-jun NH2-terminal kinase-1/2 and p38 mitogen-activated protein kinase signaling and maintained extracellular signal–regulated kinase-1/2 phosphorylation. GST-MDA-7 caused vacuolization of LC3 through a mechanism that was largely CD95 dependent and whose formation was suppressed by knockdown of ATG5 expression. Knockdown of ATG5 suppressed GST-MDA-7 toxicity. Our data show that in kidney cancer cells GST-MDA-7 induces ceramide-dependent activation of CD95, which is causal in promoting an endoplasmic reticulum stress response that activates multiple proapoptotic pathways to decrease survival.
doi:10.1158/1535-7163.MCT-09-0073
PMCID: PMC2889018  PMID: 19417161
3.  OSU-03012 Stimulates PKR-Like Endoplasmic Reticulum-Dependent Increases in 70-kDa Heat Shock Protein Expression, Attenuating Its Lethal Actions in Transformed Cells 
Molecular pharmacology  2008;73(4):1168-1184.
We have further defined mechanism(s) by which 2-amino-N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl}acetamide [OSU-03012 (OSU)], a derivative of the cyclooxygenase-2 (COX2) inhibitor celecoxib but lacking COX2 inhibitory activity, kills transformed cells. In cells lacking expression of protein kinase R-like endoplasmic reticulum kinase (PERK-/-), the lethality of OSU was attenuated. OSU enhanced the expression of Beclin 1 and ATG5 and cleavage of pro-caspase 4 in a PERK-dependent fashion and promoted the Beclin 1- and ATG5-dependent formation of vacuoles containing LC3, followed by a subsequent caspase 4-dependent cleavage of cathepsin B and a cathepsin B-dependent formation of low pH intracellular vesicles; cathepsin B was activated and released into the cytosol and genetic suppression of caspase 4, cathepsin B, or apoptosis-inducing factor function significantly suppressed cell killing. In parallel, OSU caused PERK-dependent increases in 70-kDa heat shock protein (HSP70) expression and decreases in 90-kDa heat shock protein (HSP90) and Grp78/BiP expression. Changes in HSP70 expression were post-transcriptional. Knockdown or small-molecule inhibition of HSP70 expression enhanced OSU toxicity, and overexpression of HSP70 suppressed OSU-induced low pH vesicle formation and lethality. Our data demonstrate that OSU-03012 causes cell killing that is dependent on PERK-induced activation of multiple toxic proteases. OSU-03012 also increased expression of HSP70 in a PERK-dependent fashion, providing support for the contention that OSU-03012-induced PERK signaling promotes both cell survival and cell death processes.
doi:10.1124/mol.107.042697
PMCID: PMC2674576  PMID: 18182481
4.  OSU-03012 enhances Ad.mda-7-induced GBM cell killing via ER stress and autophagy and by decreasing expression of mitochondrial protective proteins 
Cancer biology & therapy  2010;9(7):526-536.
The present studies focused on determining whether the autophagy-inducing drug OSU-03012 (AR-12) could enhance the toxicity of recombinant adenoviral delivery of melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) in glioblastoma multiforme (GBM) cells. The toxicity of a recombinant adenovirus to express MDA-7/IL-24 (Ad.mda-7) was enhanced by OSU-03012 in a diverse panel of primary human GBM cells. The enhanced toxicity correlated with reduced ERK1/2 phosphorylation and expression of MCL-1 and BCL-XL, and was blocked by molecular activation of ERK1/2 and by inhibition of the intrinsic, but not the extrinsic, apoptosis pathway. Both OSU-03012 and expression of MDA-7/IL-24 increased phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) that correlated with increased levels of autophagy and expression of dominant negative PERK blocked autophagy induction and tumor cell death. Knockdown of ATG5 or Beclin1 suppressed OSU-03012 enhanced MDA-7/IL-24-induced autophagy and blocked the lethal interaction between the two agents. Ad.mda-7-infected GBM cells secreted MDA-7/IL-24 into the growth media and this conditioned media induced expression of MDA-7/IL-24 in uninfected GBM cells. OSU-03012 interacted with conditioned media to kill GBM cells and knockdown of MDA-7/IL-24 in these cells suppressed tumor cell killing. Collectively, our data demonstrate that the induction of autophagy and mitochondrial dysfunction by a combinatorial treatment approach represents a potentially viable strategy to kill primary human GBM cells.
PMCID: PMC2888700  PMID: 20107314
ROS; caspase; ER stress; CD95; cell death
5.  Adenoviral ER-targeted mda-7/IL-24 vector enhances human cancer cell killing 
Molecular cancer therapeutics  2008;7(8):2528-2535.
We developed several adenoviral vectors designed to target MDA-7 expression to different subcellular compartments (ie, ER, mitochondria, nucleus, and cytosol) and evaluated their ability to enhance apoptosis. Adenoviral ER-targeted mda-7/IL-24 vector (Ad-ER-mda7) selectively and effectively inhibited the growth and proliferation of lung (A549 and H1299) and esophageal (Seg1 and Bic1) cancer cells by enhancing cell killing. Both Ad-mda7 and Ad-ER-mda7 activated a novel pathway of ER stress-induced apoptosis characterized by unregulated expression of phosphorylated JNK (p-JNK), phosphorylated cJun (p-cJun), and phosphorylated RNA-dependent protein kinase (p-PKR). Caspase-4 activation mediated Ad-mda7- and Ad-ER-mda7-induced cell death. In addition, Ad-mda7- and Ad-ER-mda7-mediated growth inhibition correlated with activation of ER molecular markers PKR and JNK both in vitro (in Ad-mda7- or Ad-ER-mda7-treated lung cancer cells) and in vivo. These findings suggest that vectors targeting the endoplasmic reticulum (Ad-ER-mda7) may be more effective in cancer gene therapy possibly through more effective induction or ER stress pathways.
doi:10.1158/1535-7163.MCT-08-0083
PMCID: PMC2597048  PMID: 18723497
Apoptosis; MDA-7; adenovirus; gene therapy
6.  PERK–Dependent Regulation of Ceramide Synthase 6 and Thioredoxin Play a Key Role in mda-7/IL-24–Induced Killing of Primary Human Glioblastoma Multiforme Cells 
Cancer research  2010;70(3):1120-1129.
Melanoma differentiation associated gene-7(mda-7) encodes IL-24, a cytokine that can selectively trigger apoptosis in transformed cells. Recombinant mda-7 adenovirus (Ad.mda-7) effectively kills glioma cells, offering a novel gene therapy strategy to address deadly brain tumors. In this study, we defined the proximal mechanisms by which Ad-mda-7 kills glioma cells. Key factors implicated included activation of the endoplasmic reticulum stress kinase protein kinase R–like endoplasmic reticulum kinase (PERK), Ca++ elevation, ceramide generation and reactive oxygen species (ROS) production. PERK inhibition blocked ceramide or dihydroceramide generation, which were critical for Ca++ induction and subsequent ROS formation. Activation of autophagy and cell death relied upon ROS formation, the inhibition of which ablated Ad.mda-7–killing activity. In contrast, inhibiting TRX induced by Ad.MDA-7 enhanced tumor cytotoxicity and improved animal survival in an orthotopic tumor model. Our findings indicate that mda-7/IL-24 induces an endoplasmic reticulum stress response that triggers production of ceramide, Ca2+, and ROS, which in turn promote glioma cell autophagy and cell death.
doi:10.1158/0008-5472.CAN-09-4043
PMCID: PMC2890071  PMID: 20103619
7.  Vorinostat and sorafenib increase ER stress, autophagy and apoptosis via ceramide-dependent CD95 and PERK activation 
Cancer biology & therapy  2008;7(10):1648-1662.
We recently noted that low doses of sorafenib and vorinostat interact in a synergistic fashion to kill carcinoma cells by activating CD95, and this drug combination is entering phase I trials. The present studies mechanistically extended our initial observations. Low doses of sorafenib and vorinostat, but not the individual agents, caused an acidic sphingomyelinase and fumonisin B1-dependent increase in CD95 surface levels and CD95 association with caspase 8. Knock down of CD95 or FADD expression reduced sorafenib/vorinostat lethality. Signaling by CD95 caused PERK activation that was responsible for both promoting caspase 8 association with CD95 and for increased eIF2α phosphorylation; suppression of eIF2α function abolished drug combination lethality. Cell killing was paralleled by PERK- and eIF2α-dependent lowering of c-FLIP-s protein levels and over-expression of c-FLIP-s maintained cell viability. In a CD95-, FADD- and PERK-dependent fashion, sorafenib and vorinostat increased expression of ATG5 that was responsible for enhanced autophagy. Expression of PDGFRβ and FLT3 were essential for high dose single agent sorafenib treatment to promote autophagy. Suppression of PERK function reduced sorafenib and vorinostat lethality whereas suppression of ATG5 levels elevated sorafenib and vorinostat lethality. Over-expression of c-FLIP-s blocked apoptosis and enhanced drug-induced autophagy. Thus sorafenib and vorinostat promote ceramide-dependent CD95 activation followed by induction of multiple downstream survival regulatory signals: ceramide-CD95-PERK-FADD-pro-caspase 8 (death); ceramide-CD95-PERK-eIF2α -↓c-FLIP-s (death); ceramide-CD95-PERK-ATG5-autophagy (survival).
PMCID: PMC2674577  PMID: 18787411
Vorinostat; Sorafenib; CD95; c-FLIP-s; PDGFRβ; FLT3; autophagy; ceramide; cell death; ASMase
8.  Enhancing mda-7/IL-24 therapy in renal carcinoma cells by inhibiting multiple protective signaling pathways using sorafenib and by Ad.5/3 gene delivery 
Cancer Biology & Therapy  2010;10(12):1290-1305.
We have determined whether an adenovirus that comprises the tail and shaft domains of a serotype 5 virus and the knob domain of a serotype 3 virus expressing MDA-7/IL-24, Ad.5/3-mda-7, more effectively infects and kills renal carcinoma cells (RCCs) compared to a serotype 5 virus, Ad.5-mda-7. RCCs are a tumor cell type that generally does not express the receptor for the type 5 adenovirus; the coxsakie and adenovirus receptor (CAR). Ad.5/3-mda-7 infected RCCs to a much greater degree than Ad.5-mda-7. MDA-7/IL-24 protein secreted from Ad.5/3-mda-7-infected RCCs induced MDA-7/IL-24 expression and promoted apoptosis in uninfected “bystander” RCCs. MDA-7/IL-24 killed both infected and bystander RCCs via CD95 activation. Knockdown of intracellular MDA-7/IL-24 in uninfected RCCs blocked the lethal effects of conditioned media. Infection of RCC tumors in one flank, with Ad.5/3-mda-7, suppressed growth of infected tumors and reduced the growth rate of uninfected tumors implanted on the opposite flank. The toxicity of the serotype 5/3 recombinant adenovirus to express MDA-7/IL-24 was enhanced by combined molecular or small molecule inhibition of MEK1/2 and PI3K; inhibition of mTOR, PI3K and MEK1/2; or use of the multi-kinase inhibitor sorafenib. In RCCs, combined inhibition of cytoprotective cell signaling pathways enhanced the MDA-7/IL-24-induction of CD95 activation, with greater mitochondrial dysfunction due to loss of MCL-1 and BCL-XL expression and tumor cell death. Treatment of RCC tumors in vivo with sorafenib also enhanced Ad.5/3-mda-7 toxicity and prolonged animal survival. Future combinations of these approaches hold promise for developing a more effective therapy for kidney cancer.
doi:10.4161/cbt.10.12.13497
PMCID: PMC3047088  PMID: 20948318
ERK; JNK; PI3K; AKT; MDA-7/IL-24; sorafenib; PERK; MAPK; interleukin; RCC; kidney
9.  Regulation of Subtilase Cytotoxin-Induced Cell Death by an RNA-Dependent Protein Kinase-Like Endoplasmic Reticulum Kinase-Dependent Proteasome Pathway in HeLa Cells 
Infection and Immunity  2012;80(5):1803-1814.
Shiga-toxigenic Escherichia coli (STEC) produces subtilase cytotoxin (SubAB), which cleaves the molecular chaperone BiP in the endoplasmic reticulum (ER), leading to an ER stress response and then activation of apoptotic signaling pathways. Here, we show that an early event in SubAB-induced apoptosis in HeLa cells is mediated by RNA-dependent protein kinase (PKR)-like ER kinase (PERK), not activating transcription factor 6 (ATF6) or inositol-requiring enzyme 1(Ire1), two other ER stress sensors. PERK knockdown suppressed SubAB-induced eIF2α phosphorylation, activating transcription factor 4 (ATF4) expression, caspase activation, and cytotoxicity. Knockdown of eIF2α by small interfering RNA (siRNA) or inhibition of eIF2α dephosphorylation by Sal003 enhanced SubAB-induced caspase activation. Treatment with proteasome inhibitors (i.e., MG132 and lactacystin), but not a general caspase inhibitor (Z-VAD) or a lysosome inhibitor (chloroquine), suppressed SubAB-induced caspase activation and poly(ADP-ribose) polymerase (PARP) cleavage, suggesting that the ubiquitin-proteasome system controls events leading to caspase activation, i.e., Bax/Bak conformational changes, followed by cytochrome c release from mitochondria. Levels of ubiquitinated proteins in HeLa cells were significantly decreased by SubAB treatment. Further, in an early event, some antiapoptotic proteins, which normally turn over rapidly, have their synthesis inhibited, and show enhanced degradation via the proteasome, resulting in apoptosis. In PERK knockdown cells, SubAB-induced loss of ubiquitinated proteins was inhibited. Thus, SubAB-induced ER stress is caused by BiP cleavage, leading to PERK activation, not by accumulation of ubiquitinated proteins, which undergo PERK-dependent degradation via the ubiquitin-proteasome system.
doi:10.1128/IAI.06164-11
PMCID: PMC3347452  PMID: 22354021
10.  Evaluation of Wuchereria bancrofti GST as a Vaccine Candidate for Lymphatic Filariasis 
Background
Lymphatic filarial parasites survive within the lymphatic vessels for years despite the complex immune environment surrounding them. Parasites possibly accomplish this by adopting various immunomodulatory strategies, which include release of glutathione-S-transferases (GSTs) that counteract the oxidative free radicals produced by the host. Since GSTs produced by parasites appear to be critical for the survival of parasites in the host, several studies evaluated the potential of parasite GSTs as vaccine candidates especially against schistosomiasis, fascioliasis and Seteria cervi. However, vaccine potential of GSTs of lymphatic filarial parasites has not been evaluated before.
Methods/Principal Findings
In the present study, the GST gene was cloned from the third stage larval (L3) cDNA libraries of Wuchereria bancrofti, and recombinant GST (WbGST) was expressed and purified. Serum samples from individuals living in an endemic area were analyzed for their reactivity with rWbGST. These findings showed that sera from endemic normal individuals (EN) carry significant levels of anti-WbGST IgG antibodies compared to subjects who are microfilaraemic (Mf) or show symptoms of clinical pathology (CP). Isotype analysis of the anti-WbGST IgG antibodies showed a predominance of IgG1 and IgG3 antibodies in EN individuals. Subsequent functional analysis of the rWbGST showed that the rWbGST protein retained the enzymatic activity of GST and the antibodies in EN sera could inhibit this enzymatic activity. Similar results were obtained when anti-rWbGST antibodies raised in mice were used in the neutralization assay. Brugia malayi GST and WbGST show significant sequence similarity. Therefore, to evaluate the vaccine potential of rWbGST, we used B. malayi L3 as challenge parasites. Vaccine potential of rWbGST was initially evaluated by confirming the role of human and mice WbGST antibodies in an antibody dependent cellular cytotoxicity (ADCC) assay. Subsequent vaccination studies in a jird model showed that approximately 61% protection could be achieved against a B. malayi L3 challenge infection in jirds immunized with rWbGST.
Conclusions
Results of this study show that rWbGST is a potential vaccine candidate against lymphatic filariasis. Nearly 61% protection can be achieved against a B. malayi challenge infection in a jird model. The study also showed that the WbGST protein retained the enzymatic activity of GST and this enzymatic activity appears to be critical for the survival of the parasite in the host.
Author Summary
Lymphatic parasites survive for years in a complex immune environment by adopting various strategies of immune modulation, which includes counteracting the oxidative free radical damage caused by the host. We now know that the filarial parasites secrete antioxidant enzymes. Among these, the glutathione-S-transferases (GSTs) have the potent ability to effectively neutralize cytotoxic products arising from reactive oxygen species (ROS) that attack cell membranes. Thus, GSTs have the potential to protect the parasite against host oxidative stress. GSTs of several helminthes, including schistosomes, fasciola and the filarial parasite Seteria cervi, are also involved in inducing protective immunity in the host. The schistosome 28 kDa GST has been successfully developed into a vaccine and is currently in Phase II clinical trials. Thus, GST appears to be a potential target for vaccine development. Therefore, in the present study, we cloned W. bancrofti GST, and expressed and purified the recombinant protein. Immunization and challenge experiments showed that 61% of protection could be achieved against B. malayi infections in a jird model. In vitro studies confirm that the anti-WbGST antibodies participate in the killing of B. malayi L3 through an ADCC mechanism and enzymatic activity of WbGST appears to be critical for this larvicidal function.
doi:10.1371/journal.pntd.0000457
PMCID: PMC2685978  PMID: 19513102
11.  Regulation of autophagy by ceramide-CD95-PERK signaling 
Autophagy  2008;4(7):929-931.
The manuscripts by Park et al.1 and Zhang et al.2 were initially planned as studies to understand the regulation of cell survival in transformed cells treated with sorafenib and vorinostat, and in primary hepatocytes treated with a bile acid+MEK1/2 inhibitor. In both cell systems we discovered that the toxicity of sorafenib and vorinostat or bile acid+MEK1/2 inhibitor exposure depended on the generation of ceramide and the ligand-independent activation of the CD95 death receptor, with subsequent activation of pro-caspase 8. We noted, however, in these systems that, in parallel with death receptor–induced activation of the extrinsic pathway, CD95 signaling also promoted increased phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) and eIF2α, increased expression of ATG5, and increased processing of LC3 and vesicularization of a GFP-LC3 construct. The knockdown of ATG5 expression blocked GFP-LC3 vesicularization and enhanced cell killing. Thus ceramide-CD95 signaling promoted cell death via activation of pro-caspase 8 and cell survival via autophagy. PERK was shown to signal in a switch-hitting fashion; PERK promoted CD95-DISC formation and an eIF2α-dependent reduction in c-FLIP-s levels that were essential for cell killing to proceed, but in parallel it also promoted autophagy that was protective. The death receptor-induced apoptosis and autophagy occur proximal to the receptor rather than the mitochondrion, and the relative flow of death receptor signaling into either pathway may determine cell fate. Finally, death receptor induced apoptosis and autophagy could be potential targets for therapeutic intervention.
PMCID: PMC3292039  PMID: 18719356
Vorinostat; Sorafenib; bile acid; CD95; autophagy; ceramide; cell death; ASMase
12.  Copper compound induces autophagy and apoptosis of glioma cells by reactive oxygen species and jnk activation 
BMC Cancer  2012;12:156.
Background
Glioblastoma multiforme (GBM) is the most aggressive of the primary brain tumors, with a grim prognosis despite intensive treatment. In the past decades, progress in research has not significantly increased overall survival rate.
Methods
The in vitro antineoplastic effect and mechanism of action of Casiopeina III-ia (Cas III-ia), a copper compound, on rat malignant glioma C6 cells was investigated.
Results
Cas III-ia significantly inhibited cell proliferation, inducing autophagy and apoptosis, which correlated with the formation of autophagic vacuoles, overexpression of LC3, Beclin 1, Atg 7, Bax and Bid proteins. A decrease was detected in the mitochondrial membrane potential and in the activity of caspase 3 and 8, together with the generation of intracellular reactive oxygen species (ROS) and increased activity of c-jun NH2-terminal kinase (JNK). The presence of 3-methyladenine (as selective autophagy inhibitor) increased the antineoplastic effect of Cas III-ia, while Z-VAD-FMK only showed partial protection from the antineoplastic effect induced by Cas III-ia, and ROS antioxidants (N-acetylcysteine) decreased apoptosis, autophagy and JNK activity. Moreover, the JNK –specific inhibitor SP600125 prevented Cas III-ia-induced cell death.
Conclusions
Our data suggest that Cas III-ia induces cell death by autophagy and apoptosis, in part due to the activation of ROS –dependent JNK signaling. These findings support further studies of Cas III-ia as candidate for treatment of human malignant glioma.
doi:10.1186/1471-2407-12-156
PMCID: PMC3404907  PMID: 22540380
Copper compounds; Autophagy; Apoptosis; ROS; NK; Casiopeinas
13.  Endoplasmic Reticulum Stress-Induced JNK Activation Is a Critical Event Leading to Mitochondria-Mediated Cell Death Caused by β-Lapachone Treatment 
PLoS ONE  2011;6(6):e21533.
Background
β-lapachone (β-lap) is a bioreductive agent that is activated by the two-electron reductase NAD(P)H quinone oxidoreductase 1 (NQO1). Although β-lap has been reported to induce apoptosis in various cancer types in an NQO1-dependent manner, the signaling pathways by which β-lap causes apoptosis are poorly understood.
Methodology/Principal Findings
β-lap-induced apoptosis and related molecular signaling pathways in NQO1-negative and NQO1-overexpressing MDA-MB-231 cells were investigated. Pharmacological inhibitors or siRNAs against factors involved in β-lap-induced apoptosis were used to clarify the roles played by such factors in β-lap-activated apoptotic signaling pathways. β-lap leads to clonogenic cell death and apoptosis in an NQO1- dependent manner. Treatment of NQO1-overexpressing MDA-MB-231 cells with β-lap causes rapid disruption of mitochondrial membrane potential, nuclear translocation of AIF and Endo G from mitochondria, and subsequent caspase-independent apoptotic cell death. siRNAs targeting AIF and Endo G effectively attenuate β-lap-induced clonogenic and apoptotic cell death. Moreover, β-lap induces cleavage of Bax, which accumulates in mitochondria, coinciding with the observed changes in mitochondria membrane potential. Pretreatment with Salubrinal (Sal), an endoplasmic reticulum (ER) stress inhibitor, efficiently attenuates JNK activation caused by β-lap, and subsequent mitochondria-mediated cell death. In addition, β-lap-induced generation and mitochondrial translocation of cleaved Bax are efficiently blocked by JNK inhibition.
Conclusions/Significance
Our results indicate that β-lap triggers induction of endoplasmic reticulum (ER) stress, thereby leading to JNK activation and mitochondria-mediated apoptosis. The signaling pathways that we revealed in this study may significantly contribute to an improvement of NQO1-directed tumor therapies.
doi:10.1371/journal.pone.0021533
PMCID: PMC3127577  PMID: 21738692
14.  α-TEA cooperates with chemotherapeutic agents to induce apoptosis of p53 mutant, triple-negative human breast cancer cells via activating p73 
Introduction
Successful treatment of p53 mutant, triple-negative breast cancers (TNBC) remains a daunting challenge. Doxorubicin (DOXO) and cisplatin (CDDP) are standard-of-care treatments for TNBC, but eventually fail due to acquired drug resistance and toxicity. New treatments for overcoming drug resistance and toxicity in p53 mutant, TNBC are therefore badly needed. Unlike p53, p73 - a member of the p53 family - is usually not mutated in cancers and has been shown to regulate p53-mediated apoptotic signaling in p53-deficient cancers. Therefore, identification of anticancer agents that can activate p73 in p53-deficient cancers may provide a chemotherapeutic approach for treatment of p53 mutant cancers. Here we report on the reconstitution of the p53 tumor suppressor pathway in a p53-independent manner via p73 with combination treatments of α-TEA, a small bioactive lipid, plus DOXO or CDDP.
Methods
p53 mutant, TNBC cell lines MDA-MB-231, BT-20 and MDA-MB-468 were used to evaluate the anticancer effect of chemotherapeutic drugs and α-TEA using annexin V (FITC)/PI staining, western blot analyses, RT-PCR and siRNA knockdown techniques.
Results
Combination treatments of α-TEA plus DOXO or CDDP act cooperatively to induce apoptosis, caspase-8 and caspase-9 cleavage, p73, phospho-c-Ab1 and phospho-JNK protein expression, and increase expression of p53 downstream mediators; namely, death receptor-5, CD95/APO-1 (Fas), Bax and Noxa, as well as Yap nuclear translocation - plus reduce expression of Bcl-2. Knockdown of p73, c-Abl, JNK or Yap using siRNAs shows that p73 plays a critical role in combination treatment-enhanced apoptosis and the expression of pro-apoptotic and anti-apoptotic mediators, and that c-Abl, JNK and Yap are upstream mediators of p73 in combination treatment responses.
Conclusions
Data show that α-TEA in combination with DOXO or CDDP synergistically enhances apoptosis in TNBC via targeting p53-mediated genes in a p73-dependent manner, and that p73 responses are downstream of c-Abl, JNK and Yap.
doi:10.1186/bcr2801
PMCID: PMC3109563  PMID: 21214929
15.  Transcriptional Regulation of VEGF-A by the Unfolded Protein Response Pathway 
PLoS ONE  2010;5(3):e9575.
Background
Angiogenesis is crucial to many physiological and pathological processes including development and cancer cell survival. Vascular endothelial growth factor-A (VEGFA) is the predominant mediator of angiogenesis in the VEGF family. During development, adverse environmental conditions like nutrient deprivation, hypoxia and increased protein secretion occur. IRE1α, PERK, and ATF6α, master regulators of the unfolded protein response (UPR), are activated under these conditions and are proposed to have a role in mediating angiogenesis.
Principal Findings
Here we show that IRE1α, PERK, and ATF6α powerfully regulate VEGFA mRNA expression under various stress conditions. In Ire1α−/− and Perk−/− mouse embryonic fibroblasts and ATF6α-knockdown HepG2 cells, induction of VEGFA mRNA by endoplasmic reticulum stress is attenuated as compared to control cells. Embryonic lethality of Ire1α−/− mice is due to the lack of VEGFA induction in labyrinthine trophoblast cells of the developing placenta. Rescue of IRE1α and PERK in Ire1α−/− and Perk−/− cells respectively, prevents VEGFA mRNA attenuation. We further report that the induction of VEGFA by IRE1α, PERK and ATF6 involves activation of transcription factors, spliced-XBP-1, ATF4 and cleaved ATF6 respectively.
Conclusions/Significance
Our results reveal that the IRE1α-XBP-1, PERK-ATF4, and ATF6α pathways constitute novel upstream regulatory pathways of angiogenesis by modulating VEGF transcription. Activation of these pathways helps the rapidly growing cells to obtain sufficient nutrients and growth factors for their survival under the prevailing hostile environmental conditions. These results establish an important role of the UPR in angiogenesis.
doi:10.1371/journal.pone.0009575
PMCID: PMC2833197  PMID: 20221394
16.  Flavonoids Activated Caspases for Apoptosis in Human Glioblastoma T98G and U87MG Cells But Not in Human Normal Astrocytes 
Cancer  2010;116(1):164-176.
BACKGROUND
Human glioblastoma is a deadly brain cancer that continues to defy all current therapeutic strategies. We induced apoptosis in human glioblastoma T98G and U87MG cells following treatment with apigenin (APG), (−)-epigallocatechin (EGC), (−)-epigallocatechin-3-gallate (EGCG), and genistein (GST) that did not induce apoptosis in human normal astrocytes (HNA).
METHODS
Induction of apoptosis was examined using Wright staining and ApopTag assay. Production of reactive oxygen species (ROS) and increase in intracellular free [Ca2+] were measured by fluoresent probes. Analysis of mRNA and Western blotting indicated increases in expression and activities of the stress kinases and cysteine proteases for apoptosis. JC-1 showed changes in mitochondrial membrane potential (ΔΨm) and use of specific inhibitors confirmed activation of kinases and proteases in apoptosis.
RESULTS
Treatment of glioblastoma cells with APG, EGC, EGCG, or GST triggered ROS production that induced apoptosis with phosphorylation of p38 MAPK and activation of the redox-sensitive JNK1 pathway. Pretreatment of cells with ascorbic acid attenuated ROS production and p38 MAPK phosphorylation. Increases in intracellular free [Ca2+] and activation of caspase-4 indicated involvement of endoplasmic reticulum stress in apoptosis. Other events in apoptosis included overexpression of Bax, loss of ΔΨm, mitochondrial release of cytochrome c and Smac into the cytosol, down regulation of baculoviral inhibitor-of-apoptosis repeat containing proteins, and activation of calpain, caspase-9, and caspase-3. EGC and EGCG also induced caspase-8 activity. APG, EGC, EGCG, or GST did not induce apoptosis in HNA.
CONCLUSION
Results strongly suggest that flavonoids are potential therapeutic agents for induction of apoptosis in human glioblastoma cells.
doi:10.1002/cncr.24699
PMCID: PMC3159962  PMID: 19894226
apoptosis; flavonoids; glioblastoma; T98G; U87MG
17.  Regulation of Autophagy Via PERK-eIF2α Effectively Relieve the Radiation Myelitis Induced by Iodine-125 
PLoS ONE  2013;8(11):e76819.
Radiation myelitis is the most serious complication in clinical radiotherapy for spinal metastases. We previously showed that 125I brachytherapy induced apoptosis of spinal cord neurons accompanied by autophagy. In this study, we further investigated the mechanism by which 125I radiation triggered autophagy in neural cells. We found that autophagy induced by 125I radiation was involved in endoplasmic reticulum (ER) stress and mainly dependent on PERK-eIF2α pathway. The expressions of LC3II, ATG12 and PI3K were significantly suppressed in PERK knockout neural cells. Meanwhile, the expressions of phosphorylated-Akt s473 and caspase3/8 all significantly increased in neural cells transfected with a PERK siRNA and which enhanced apoptosis of neurons after 125I radiation. The results were consistent with that by MTT and Annexin-FITC/PT staining. In annimal model of banna pigs with radiation myelitis caused by 125I brachytherapy, we have successfully decreased PERK expression by intrathecal administration of the lentivirus vector. The apoptosis rate was significantly higher than that in control group and which deteriorated radiation myelitis of banna pigs. Thus, autophagy caused by 125I radiation was mainly as an attempt of cell survival at an early stage, but it would be a self-destructive process and promoted the process of apoptosis and necrosis radiated by 125I for more than 72 hours. The study would be useful and helpful to maximize efficiency of radiation therapy in clinical therapy.
doi:10.1371/journal.pone.0076819
PMCID: PMC3818370  PMID: 24223705
18.  PERK-dependent regulation of IAP translation during ER stress 
Oncogene  2008;28(6):910-920.
Exposure of cells to Endoplasmic Reticulum (ER) stress leads to activation of phosphatidylinositol 3-kinase (PI3K)–Akt signaling pathway and transcriptional induction of the inhibitor of apoptosis family of proteins. One of the proximal effectors of the ER stress response, the PKR-like ER kinase (PERK), leads to cellular adaptation to stress by multiple mechanisms, including attenuation of protein synthesis, and transcriptional induction of pro-survival genes. While PERK activity leads to cellular adaptation to ER stress, we now demonstrate that PERK activity also inhibits the ER stress-induced apoptotic program through induction of cellular inhibitor of apoptosis (cIAP1 and cIAP2) proteins. This induction of IAPs occurs through both transcriptional and translational responses that are PERK-dependent. Reintroduction of cIAP1 or cIAP2 expression into PERK−/− MEFs during ER stress delays the early onset of ER stress-induced caspase activation and apoptosis observed in these cells. Furthermore, we demonstrate that activation of the PI3K-Akt pathway by ER stress is dependent on PERK, suggesting additional ways in which PERK activity protects cells from ER stress-induced apoptosis.
doi:10.1038/onc.2008.428
PMCID: PMC2642534  PMID: 19029953
PERK; ER Stress; Apoptosis; IAP
19.  Targeting breast cancer-initiating/stem cells with melanoma differentiation-associated gene-7/interleukin-24 
Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) displays a broad range of antitumor properties including cancer-specific induction of apoptosis, inhibition of tumor angiogenesis and modulation of antitumor immune responses. In our study, we elucidated the role of MDA-7/IL-24 in inhibiting growth of breast cancer-initiating/stem cells. Ad.mda-7 infection decreased proliferation of breast cancer-initiating/stem cells without affecting normal breast stem cells. Ad.mda-7 induced apoptosis and endoplasmic reticulum stress in breast cancer-initiating/stem cells similar to unsorted breast cancer cells and inhibited the self-renewal property of breast cancer-initiating/stem cells by suppressing Wnt/β-catenin signaling. Prevention of inhibition of Wnt signaling by LiCl increased cell survival upon Ad.mda-7 treatment, suggesting that Wnt signaling inhibition might play a key role in MDA-7/IL-24-mediated death of breast cancer-initiating/stem cells. In a nude mouse subcutaneous xenograft model, Ad.mda-7 injection profoundly inhibited growth of tumors generated from breast cancer-initiating/stem cells and also exerted a potent “bystander” activity inhibiting growth of distant uninjected tumors. Further studies revealed that tumor growth inhibition by Ad.mda-7 was associated with a decrease in proliferation and angiogenesis, two intrinsic features of MDA-7/IL-24, and a reduction in vivo in the percentage of breast cancer-initiating/stem cells. Our findings demonstrate that MDA-7/IL-24 is not only nontoxic to normal cells and normal stem cells but also can kill both unsorted cancer cells and enriched populations of cancer-initiating/stem cells, providing further documentation that MDA-7/IL-24 might be a safe and effective way to eradicate cancers and also potentially establish disease-free survival.
doi:10.1002/ijc.28289
PMCID: PMC4334374  PMID: 23720015
MDA-7/IL-24; apoptosis; Wnt signaling; cancer-initiating/stem cells; breast cancer
20.  Gamma-Tocotrienol induced Apoptosis is Associated with Unfolded Protein Response in Human Breast Cancer Cells 
Gamma-Tocotrienol (γ-T3) is a member of the vitamin E family. Tocotrienols (T3) are powerful antioxidants and possess anti-cancer, neuroprotective and cholesterol lowering properties. T3s inhibit the growth of various cancer cell lines without affecting normal cells. Less is known about the exact mechanisms of action of T3s on cell death and other growth inhibitory pathways. In the present study we demonstrate that γ-T3 induces apoptosis in MDA-MB 231 and MCF-7 breast cancer cells as evident by PARP cleavage and caspase-7 activation. Gene expression analysis of MCF-7 cells treated with γ-T3 revealed alterations in the expression of multiple genes involved in cell growth and proliferation, cell death, cell cycle, cellular development, cellular movement and Gene expression. Further analysis of differentially modulated genes using Ingenuity Pathway Analysis software suggested modulation of canonical signal transduction or metabolic pathways such as NRF-2 mediated oxidative stress response, TGF-β signaling and Endoplasmic Reticulum (ER) stress response. Analysis of ER stress related proteins in MCF-7 and MDA-MB 231 cells treated with γ-T3 demonstrated activation of PERK and pIRE1α pathway to induce ER stress. Activating transcription factor 3 (ATF3) was identified as the most upregulated gene (16.8 folds) in response to γ-T3. ATF3 knockdown using siRNA suggested essential role of ATF3 in γ-T3 induced apoptosis. In summary, we demonstrate that γ-T3 modulates ER stress signaling and have identified ATF3 as a molecular target for γ-T3 in breast cancer cells.
doi:10.1016/j.jnutbio.2010.11.012
PMCID: PMC3123668  PMID: 21429729
Vitamin E; Tocotrienol; Breast Cancer; ER Stress; Unfolded Protein Response (UPR); Apoptosis
21.  Attenuation of endoplasmic reticulum stress and mitochondrial injury in kidney with ischemic postconditioning application and trimetazidine treatment 
Background
Endoplasmic reticulum (ER) and mitochondria have been implicated in the pathology of renal ischemia/reperfusion (I/R). In the present study, we investigated whether the use of ischemic postconditioning (IPostC) and trimetazidine (TMZ) separately or combined could reduce ER stress and mitochondria damage after renal ischemia.
Methods
Kidneys of Wistar rats were subjected to 60-min of warm ischemia followed by 120-min of reperfusion (I/R group, n = 6), or to 6 cycles of ischemia/reperfusion (10-s each cycle) just after 60-min of warm ischemia (IPostC group, n = 6), or to i.p. injection of TMZ (3 mg/kg) 30-min before ischemia (TMZ group, n = 6), or to the combination of both treatments (IPostC+TMZ group, n = 6). The results of these experimental groups were compared to those of a sham-operated group in which rat renal pedicles were only dissected. Sodium reabsorption rate, creatinine clearance lactate deshydrogenase (LDH) activity in plasma, and concentration of malonedialdehyde (MDA) in tissue were determined. In addition, Western blot analysis was performed to identify the amounts of cytochrome c, c-JunNH2-terminal kinase (JNK), voltage-dependent anion channel (VDAC), glycogen synthase kinase 3-beta (GSK3-β), and ER stress parameters.
Results
IPostC or/and TMZ significantly decreased cytolysis, oxidative stress and improved renal function in comparison to I/R group. IPostC but not TMZ significantly attenuated ER stress parameters versus I/R group. Indeed, it down-regulated the glucose-regulated protein 78 (GRP78), the activating transcription factor 4 (ATF4), the RNA activated protein kinase (PKR)-like ER kinas (PERK), the X box binding protein-1 (XBP-1) and the caspase12 protein levels. TMZ treatment significantly augmented GSK3-β phosphorylation and reduced levels of cytochrome c and VDAC phosphorylation in comparison to IPostC application. The combination of both treatments gave a synergetic effect. It significantly improved the survival rate, attenuated cytolysis, oxidative stress and improved renal function.
Conclusion
This study revealed that IPostC protects kidney from I/R injury by suppressing ER stress while the beneficial effects of TMZ are mediated by mitochondria protection. The combination of both treatments ameliorated functional recovery.
doi:10.1186/1423-0127-19-71
PMCID: PMC3431271  PMID: 22853733
Kidney; Ischemia-reperfusion; Ischemic postconditioning; Trimetazidine; Endoplasmic reticulum stress; Mitochondria
22.  ABL-N-induced apoptosis in human breast cancer cells is partially mediated by c-Jun NH2-terminal kinase activation 
Introduction
The present study was designed to determine the possibility of acetylbritannilactone (ABL) derivative 5-(5-(ethylperoxy)pentan-2-yl)-6-methyl-3-methylene-2-oxo-2,3,3a,4,7,7a-hexahydrobenzofuran-4-yl 2-(6-methoxynaphthalen-2-yl)propanoate (ABL-N) as a novel therapeutic agent in human breast cancers.
Methods
We investigated the effects of ABL-N on the induction of apoptosis in human breast cancer cells and further examined the underlying mechanisms. Moreover, tumor growth inhibition of ABL-N was done in xenograft models.
Results
ABL-N induced the activation of caspase-3 in estrogen receptor (ER)-negative cell lines MDA-MB-231 and MDA-MB-468, as evidenced by the cleavage of endogenous substrate Poly (ADP-ribose) polymerase (PARP). Pretreatment of cells with pan-caspase inhibitor z-VAD-fmk or caspase-3-specific inhibitor z-DEVD-fmk inhibited ABL-N-induced apoptosis. ABL-N treatment also resulted in an increase in the expression of pro-apoptotic members (Bax and Bad) with a concomitant decrease in Bcl-2. Furthermore, c-Jun-NH2-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinase (p38) were activated in the apoptosis induced by ABL-N and JNK-specific inhibitor SP600125 and JNK small interfering RNA (siRNA) antagonized ABL-N-mediated apoptosis. However, the p38-specific inhibitor SB203580 had no effect upon these processes. Moreover, neither of the caspase inhibitors prevented ABL-N-induced JNK activation, indicating that JNK is upstream of caspases in ABL-N-initiated apoptosis. Additionally, in a nude mice xenograft experiment, ABL-N significantly inhibited the tumor growth of MDA-MB-231 cells.
Conclusions
ABL-N induces apoptosis in breast cancer cells through the activation of caspases and JNK signaling pathways. Moreover, ABL-N treatment causes a significant inhibition of tumor growth in vivo. Therefore, it is thought that ABL-N might be a potential drug for use in breast cancer prevention and intervention.
doi:10.1186/bcr2475
PMCID: PMC2880430  PMID: 20096139
23.  The activation of c-Jun NH2-terminal kinase is required for dihydroartemisinin-induced autophagy in pancreatic cancer cells 
Background
c-Jun NH2-terminal kinases (JNKs) are strongly activated by a stressful cellular environment, such as chemotherapy and oxidative stress. Autophagy is a protein-degradation system in which double-membrane vacuoles called autophagosomes are formed. The autophagy-related gene Beclin 1 plays a key role in this process. We previously found that autophagy was induced by dihydroartemisinin (DHA) in pancreatic cancer cells. However, little is known about the complex relationship between ROS, JNK activation, autophagy induction, and Beclin 1 expression.
Methods
Cell viability and CCK-8 assays were carried out to determine the cell proliferation; small interfering RNAs (siRNAs) were used to knockdown c-Jun NH2-terminal kinases (JNK1/2) genes; western blot was performed to detect the protein expression of LC3, JNK, Beclin 1, caspase 3 and β-actin; production of intracellular ROS was analyzed using FACS flow cytometry; autophagy induction was confirmed by electron microscopy.
Results
In the present study, we explored the role of DHA and Beclin 1 expression in autophagy. DHA-treated cells showed autophagy characteristics, and DHA also activated the JNK pathway and up-regulated the expression of Beclin 1. Conversely, blocking JNK signaling inhibited Beclin 1 up-regulation. JNK activation was found to primarily depend on reactive oxygen species (ROS) resulting from the DHA treatment. Moreover, JNK pathway inhibition and Beclin 1 silencing prevented the induction of DHA-induced autophagy.
Conclusions
These results suggest that the induction of autophagy by DHA is required for JNK-mediated Beclin 1 expression.
doi:10.1186/1756-9966-33-8
PMCID: PMC3901759  PMID: 24438216
c-Jun NH2-terminal kinase; Beclin 1; Apoptosis; LC3; Autophagy; Pancreatic cancer; Dihydroartemisinin
24.  Synthetic Triterpenoid Cyano Enone of Methyl Boswellate (CEMB) activates intrinsic, extrinsic, & endoplasmic reticulum stress cell death pathways in tumor cell lines 
Molecular cancer therapeutics  2011;10(9):1635-1643.
We explored the effect of a novel synthetic triterpenoid compound Cyano Enone of Methyl Boswellates (CEMB) on various prostate cancer and glioma cancer cell lines. CEMB displayed concentration-dependent cytotoxic activity with submicromolar lethal dose 50% (LD50) values in ten of ten tumor cell lines tested. CEMB-induced cytotoxicity is accompanied by activation of downstream effector caspases (caspases 3 and 7) and by upstream initiator caspases involved in both the extrinsic (caspase 8) and intrinsic (caspase 9) apoptotic pathways. By using small interfering RNAs (siRNAs), we show evidence that knock down of caspase 8, death receptor 4 (DR4), Apaf-1, and Bid impairs CEMB-induced cell death. Similar to other proapoptotic synthetic triterpenoid compounds, CEMB-induced apoptosis involved endoplasmic reticulum (ER) stress, as demonstrated by partial rescue of tumor cells by siRNA-mediated knock-down of expression of genes involve in the unfolded protein response such as Ire1, Perk, and ATF6. Altogether our results suggest that CEMB stimulates several apoptotic pathways in cancer cells, suggesting that this compound should be evaluated further as a potential agent for cancer therapy.
doi:10.1158/1535-7163.MCT-10-0887
PMCID: PMC4174562  PMID: 21746806
Triterpenoid; Apoptosis; ER stress
25.  JNK1/2 regulate Bid by direct phosphorylation at Thr59 in response to ALDH1L1 
Cell Death & Disease  2014;5(7):e1358-.
BH3 interacting-domain death agonist (Bid) is a BH3-only pro-apoptotic member of the Bcl-2 family of proteins. Its function in apoptosis is associated with the proteolytic cleavage to the truncated form tBid, mainly by caspase-8. tBid translocates to mitochondria and assists Bax and Bak in induction of apoptosis. c-Jun N-terminal kinase (JNK)-dependent alternative processing of Bid to jBid was also reported. We have previously shown that the folate stress enzyme 10-formyltetrahydrofolate dehydrogenase (ALDH1L1) activates JNK1 and JNK2 in cancer cells as a pro-apoptotic response. Here we report that in PC-3 prostate cancer cells, JNK1/2 phosphorylate Bid at Thr59 within the caspase cleavage site in response to ALDH1L1. In vitro, all three JNK isoforms, JNK 1–3, phosphorylated Thr59 of Bid with JNK1 being the least active. Thr59 phosphorylation protected Bid from cleavage by caspase-8, resulting in strong accumulation of the full-length protein and its translocation to mitochondria. Interestingly, although we did not observe jBid in response to ALDH1L1 in PC-3 cells, transient expression of Bid mutants lacking the caspase-8 cleavage site resulted in strong accumulation of jBid. Of note, a T59D mutant mimicking constitutive phosphorylation revealed more profound cleavage of Bid to jBid. JNK-driven Bid accumulation had a pro-apoptotic effect in our study: small interfering RNA silencing of either JNK1/2 or Bid prevented Bid phosphorylation and accumulation, and rescued ALDH1L1-expressing cells. As full-length Bid is a weaker apoptogen than tBid, we propose that the phosphorylation of Bid by JNKs, followed by the accumulation of the full-length protein, delays attainment of apoptosis, and allows the cell to evaluate the stress and make a decision regarding the response strategy. This mechanism perhaps can be modified by the alternative cleavage of phospho-T59 Bid to jBid at some conditions.
doi:10.1038/cddis.2014.316
PMCID: PMC4123105  PMID: 25077544

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