From procaspase-8 to caspase-8: revisiting structural functions of caspase-8

Houttuynia cordata Thunb. Hexane fraction induces MDA-MB-231 cell apoptosis via caspases, ER stress, cell cycle arrest and attenuated Akt/ERK signaling

Houttuynia cordata Thunb. (HCT) is a perennial plant used in traditional Thai medicine for many centuries. This study aimed to investigate the antiproliferative effect of the hexane fraction, which has not been explored before. HCT ethanol extract (crude extract) was sequentially fractionated to obtain a hexane (H) fraction. GC-MS was used to determine the phytochemicals. The H fraction consisted of lipids, mainly α-linolenic acid and some terpenoids. MTT assay was used to determine the cytotoxic effects of H fraction in MCF-7, MDA-MB-231, NIH3T3 and PBMCs. The mode of cell death and cell cycle analysis were determined by flow cytometry. The mechanisms of cell death were defined by mitochondrial transmembrane potential (MTP) reduction and activation of caspase-3, -8 and -9. The expression levels of the Bcl-2 family, cell cycle-related, endoplasmic reticulum (ER) stress-associated proteins; and Akt/ERK signaling molecules were investigated by immunoblotting. The H fraction was toxic to MDA-MB-231 more than MCF-7 cells but not to NIH3T3 and PBMCs. The growth of MDA-MB-231 cells was inhibited through apoptosis. MTP was disrupted whereas caspase-3, -8 and -9 were activated. The expression of pro-apoptotic Bax and Bak was upregulated, while Bid and anti-apoptotic Bcl-xL proteins were downregulated. Cyclin D1 and CDK4 levels were downregulated. The cell cycle was arrested at G1. Moreover, GRP78 and CHOP elevation indicated ER stress-mediated pathway. The expression ratio of pAkt/Akt and pERK/ERK were reduced. Taken together, the molecular mechanisms of MDA-MB-231 cell apoptosis were via intrinsic/extrinsic pathways, cell cycle arrest, ER stress and abrogation of Akt/ERK survival pathways. According to the most current research, the H fraction may be used as an adjuvant in the BC treatment; however, before the anticancer strategy can be applied to patients, it is important to determine each active compound's effects in cell lines and in vivo when compared with a combined mixture.

Multi-dimensional visualization of ingestion, biological effects and interactions of microplastics and a representative POP in edible jellyfish

Due to their ubiquity and potential risks, microplastics (MPs) and nanoplastics (NPs) are concerning environmental issues. Yet there are still significant knowledge gaps in understanding the tissue-specific accumulation and dynamic change of MPs and NPs in the aquatic organism and how these micro/nano-scale emerging contaminants interact with other environmental pollutants such as persistent organic pollutants (POPs). Here, in vivo imaging systems (IVIS), radioisotope tracing, and histological staining were innovatively used to reveal the fate and toxicity of fluorescently-labeled MPs/NPs and 14C-labeled 2,4,4'-trichlorobiphenyl (PCB28) in edible jellyfish Rhopilema esculentum. These contaminants' ingestion, biological effects, and interactions were visualized at cellular, tissue, and whole-body multidimensional levels. Both MPs and NPs were shown to be preferentially accumulated in the mouthlets of oral arms, and most ingested MPs/NPs were present in the extracellular environment instead of being internalized into the mesoglea. Moreover, the presence of MPs or NPs in the seawater significantly inhibited the bioaccumulation of PCB28 in the jellyfish tissue, thus alleviating physiological alteration, gastric damage, and apoptosis caused by PCB28. This study provides a multi-dimensional visualization strategy to display the distribution and biological effects of typical pollutants in marine organisms and offers new insights for understanding the impacts of MPs/NPs and POPs on marine ecosystems.

Transcriptome and computational approaches highlighting the molecular regulation of Zacco platypus induced by mesocosm exposure to common disinfectant chlorine

Chlorine (Cl₂) is a disinfectant often used in swimming pools and water treatment facilities. However, it is released into aquatic ecosystems, where it may harm non-targeted organisms. Here, we performed a mesocosm experiment exposing Zacco platypus (Z. platypus) to biocide Cl₂ for 30 days (30 d) at two days' time points 15 days (15 d) and 30 d samples were collected. Here, Z. platypus was exposed to a sublethal concentration (0.1 mg/L) of Cl₂, and comparative transcriptomics analyses were performed to determine their response mechanisms at the molecular level. According to RNA sequencing of the whole-body transcriptome, 860 and 1189 differentially expressed genes (DEGs) were identified from the 15 d and 30 d responses to Cl₂, respectively. After enrichment analysis of GO (Gene Ontology) functions and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, identified DEGs were demonstrated to be associated with a variety of functions, including "ion binding and transmembrane transporters". Cl₂ also induced oxidative stress in Z. platypus by increasing the levels of reactive oxygen species (ROS) while decreasing the catalase (CAT) content and the levels of solute carrier family 22 member 11 (slc22a11), Caspase-8 (casp-8), inducible nitric oxide synthase (NOS2), cytosolic phospholipase A2 gamma (PLA2G4). However, Z. platypus still allows recovery during stress suspension by increasing the expression levels of solute carrier family proteins. The GO and KEGG annotation results revealed that the expression of DEGs were related to the detoxification process, immune response, and antioxidant mechanism. Additionally, protein-protein interaction networks (PPI) and cytoHubba analyses identified sixteen hub genes and their interaction. These findings elucidate the regulation of various DEGs and signaling pathways in response to Cl₂ exposure, which will improve our knowledge and laid foundation for further investigation of the toxicity of Cl₂ to Z. platypus.

Expression profile of the proapoptotic protein Bax in the human brain

Bax is a well-known universal proapoptotic protein. Bax protein is detected in almost all human organs, and its expression levels can be correlated with disease progression and therapeutic efficacy in certain settings. Interestingly, increasing evidence has shown that mature neuronal cell death is often not typical apoptosis. Most results on the expression of Bax proteins (predominantly Baxα) in the human brain come from disease-oriented studies, and the data on Bax protein expression in the normal brain are limited and lack consistency due to many variable factors. Here, we analyzed Bax RNA and protein expression data from multiple databases and performed immunostaining of over 80 samples from 25 healthy subjects across 7 different brain regions. We found that Bax protein expression was heterogeneous across brain regions and individual subjects. Both neurons and glial cells, such as astrocytes, could be Bax positive, but Bax positivity appeared to be highly selective, even within the same cell type in the same region. Furthermore, Bax proteins could be localized in the cytosol (evenly spread or concentrated to one region), nucleus or nucleolus depending on the cell type. Such variation and distribution in Bax expression suggest that Bax may function differently in the human brain than in other organs.

Life-Saver or Undertaker: The Relationship between Primary Cilia and Cell Death in Vertebrate Embryonic Development

The development of multicellular organisms requires a tightly coordinated network of cellular processes and intercellular signalling. For more than 20 years, it has been known that primary cilia are deeply involved in the mediation of intercellular signalling and that ciliary dysfunction results in severe developmental defects. Cilia-mediated signalling regulates cellular processes such as proliferation, differentiation, migration, etc. Another cellular process ensuring proper embryonic development is cell death. While the effect of cilia-mediated signalling on many cellular processes has been extensively studied, the relationship between primary cilia and cell death remains largely unknown. This article provides a short review on the current knowledge about this relationship.

Baculoviral inhibitor of apoptosis protein repeat-containing protein 3 delays early Wallerian degeneration after sciatic nerve injury

Wallerian degeneration is a complex biological process that occurs after nerve injury, and involves nerve degeneration and regeneration. Schwann cells play a crucial role in the cellular and molecular events of Wallerian degeneration of the peripheral nervous system. However, Wallerian degeneration regulating nerve injury and repair remains largely unknown, especially the early response. We have previously reported some key regulators of Wallerian degeneration after sciatic nerve injury. Baculoviral inhibitor of apoptosis protein repeat-containing protein 3 (BIRC3) is an important factor that regulates apoptosis-inhibiting protein. In this study, we established rat models of right sciatic nerve injury. In vitro Schwann cell models were also established and subjected to gene transfection to inhibit and overexpress BIRC3. The data indicated that BIRC3 expression was significantly up-regulated after sciatic nerve injury. Both BIRC3 upregulation and downregulation affected the migration, proliferation and apoptosis of Schwan cells and affected the expression of related factors through activating c-fos and ERK signal pathway. Inhibition of BIRC3 delayed early Wallerian degeneration through inhibiting the apoptosis of Schwann cells after sciatic nerve injury. These findings suggest that BIRC3 plays an important role in peripheral nerve injury repair and regeneration. The study was approved by the Institutional Animal Care and Use Committee of Nantong University, China (approval No. 2019-nsfc004) on March 1, 2019.

c-Src Increases the Sensitivity to TKIs in the EGFR-Mutant Lung Adenocarcinoma

c-Src and the epidermal growth factor receptor (EGFR) are key apical kinases that govern cell responses to microenvironmental cues. How c-Src affects EGFR-related signaling and targeted therapy remains elusive. Initially, caspase-8 phosphorylated at tyrosine 380 by c-Src predominantly enhancing c-Src activation to facilitate metastasis through attaining epithelial-mesenchymal transition (EMT) phenotype in lung adenocarcinoma. Mechanistically, the linkage of c-Src SH2 domain with phosphotyrosine 380 of caspase-8 and SH3 domain with “PDEP” motif of caspase-8 overactivates c-Src as compared with other c-Src-partner proteins. c-Src is incapable of triggering EGFR-related signaling. This is reflected by the levels of phosphotyrosine 1068, 1086, and 1145, which have no impact on c-Src activation. Tyrosine kinase inhibitors (TKIs) suppress EGFR-related signaling to yield cell deaths of lung adenocarcinoma by both necroptosis and intrinsic apoptosis. Given that c-Src activation is frequent in lung adenocarcinoma, blocking c-Src activation through dasatinib can seal the survival-signaling-related phosphotyrosines of EGFR by its SH2 domain, which in turn increases the antitumor activity of TKIs in EGFR-mutant lung adenocarcinoma. Collectively, c-Src inactivation by dasatinib administration sensitizes EGFR-mutant lung adenocarcinoma to TKIs.

Honokiol inhibits the growth of SKBR3 cells

BACKGROUND

Breast cancer is one of the most malignant tumors in the reproductive system and has a poor prognosis. Finding drugs with high efficiency, low side-effects, and low cost has become a research hotspot.

METHODS

In the present study, we treated SK-BR-3 cells with different doses of honokiol. Crystal violet staining method was used to detect changes in the total number of living cells; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to detect the effect of honokiol on SK-BR-3 cell proliferation. Cell migration ability change was determined by wound healing assay. Cell invasion ability change was determined by Transwell migration assay. Flow cytometry was used to detect the apoptotic rate of SK-BR-3 cells, and Western blot was used to detect the expression levels of proliferation-associated protein (PCNA); migration- and invasion-related protein matrix metalloproteinase-2 (MMP-2); vimentin; apoptosis-related proteins Bcl-xl, caspase 3, and cleaved caspase 3 (CC3); and β-catenin and its downstream target molecule c-Myc.

RESULTS

Compared with the control group, different doses of honokiol have different degrees of inhibitory effects on cells, including proliferation and invasion and migration (P<0.01). After treatment with 50 or 60 µmol·L-1 honokiol, the apoptotic rate of SK-BR-3 cells increased (both P<0.01); PCNA expression was significantly downregulated (P<0.01). Intracellular accumulation of apoptosis-related proteins Bcl-xl and caspase-3 decreased but C-C3 increased. We also found downregulation of MMP-2 expression, a protein related to invasion and migration (P<0.01), and a decrease in the expression levels of the Wnt/β-catenin signaling pathway-related proteins β-catenin and c-Myc (P<0.01).

CONCLUSIONS

Honokiol can promote the apoptosis of SK-BR-3 cells and can inhibit the proliferation, migration, and invasion of human breast cancer SK-BR-3 cells. The underlying mechanism may be through inhibiting the activation of the Wnt signaling pathway.

Study of the common activating mechanism of apoptosis and epithelial-to-mesenchymal transition in alveolar type II epithelial cells

Infection and severe trauma can result in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and eventually pulmonary fibrosis. Epithelial-to-mesenchymal transition (EMT) is related to pulmonary fibrosis. Our study found that pyocyanin (PCN) could promote apoptosis and EMT in alveolar type II epithelial A549 cells. We hypothesized that there might be a common mechanism related to both apoptosis and EMT in A549 cells. The aim of this study was to determine whether reactive oxygen species (ROS) induced by PCN is the common stimulus upstream of apoptosis and EMT as well as the relevant signalling pathways. A549 cells were challenged with PCN; ROS was then detected by immunofluorescence, and apoptosis was measured by flow cytometry. Caspases, EMT markers and the TGF-β/Smad pathway were assessed by Western blot, qPCR or ELISA. The results showed that PCN promoted ROS production, and the apoptosis rate was clearly increased. E-cadherin downregulation, vimentin and α-SMA upregulation in A549 cells, cleaved caspase-9 and caspase-3, TGF-β1 and activated Smad2/3 were also detected. Interestingly, the protein expression of cleaved caspase-3 and vimentin was highly positively correlated. Inhibition of ROS could partially reverse PCN-induced EMT and apoptosis in A549 cells, and EMT could also be reversed by TGF-β1 inhibitors. In conclusion, ROS may be a common activating mechanism of apoptosis and EMT in alveolar epithelial cells, during which the degree of apoptosis is positively related to EMT. ROS may induce alveolar epithelial cell apoptosis through the mitochondrial pathway or endoplasmic reticulum pathway. ROS activates TGF-β1, followed by SMADs, eventually inducing EMT.

A Structural Model for Bax∆2-Mediated Activation of Caspase 8-Dependent Apoptosis

Bax∆2 is a pro-apoptotic anti-tumor protein in the Bax family. While most of the Bax family causes cell death by targeting mitochondria, Bax∆2 forms cytosolic aggregates and activates caspase 8-dependent cell death. We previously showed that the Bax∆2 helix α9 is critical for caspase 8 recruitment. However, the interaction between these two proteins at the structural level is unknown. In this in silico study, we performed molecular dynamics (MD) simulations and protein-protein docking on Bax∆2 variants. The results suggest that the Bax∆2 variants have different stable states. Mutating the Baxα mitochondria-targeting signal [L26P/L27P] appears to introduce a kink into helix α1. Protein-protein docking suggests that helices α9 of both wild-type Bax∆2 and Bax∆2 caspase 8 binding-deficient mutant [L164P] can fit in the same caspase 8 binding site, but the mutant is unable to fit as well as wild-type Bax∆2. Together, these data point to a structural basis for explaining Bax∆2 function in caspase 8-dependent cell death.

The Effects of Houttuynia cordata Thunb and Piper ribesioides Wall Extracts on Breast Carcinoma Cell Proliferation, Migration, Invasion and Apoptosis

Houttuynia cordata Thunb. (HCT) and Piper ribesioides Wall. (PR) are common herbs that are widely distributed throughout East Asia and possess various biological properties including anti-cancer effects. However, in breast cancer, their mechanisms responsible for anti-carcinogenic effects have not been clarified yet. In this study, the inhibitory effects of HCT and PR ethanolic extracts on breast cancer cell proliferation, migration, invasion and apoptosis were examined. In MCF-7 and MDA-MB-231 cells, HCT and PR extracts at low concentrations can inhibit colony formation and induce G1 cell cycle arrest by downregulating cyclinD1 and CDK4 expression. Additionally, HCT and PR extracts also decreased the migration and invasion of both breast cancer cell lines through inhibition of MMP-2 and MMP-9 secretion. Moreover, the induction of apoptosis was observed in breast cancer cells treated with high concentrations of HCT and PR extracts. Not only stimulated caspases activity, but HCT and PR extracts also upregulated the expression of caspases and pro-apoptotic Bcl-2 family proteins in breast cancer cells. Altogether, these findings provide the rationale to further investigate the potential actions of HCT and PR extracts against breast cancer in vivo.

Caspase-8: The double-edged sword

Caspase-8 is a cysteine - aspartate specific protease that classically triggers the extrinsic apoptotic pathway, in response to the activation of cell surface Death Receptors (DRs) like FAS, TRAIL-R and TNF-R. Besides it's roles in triggering death receptor-mediated apoptosis, Caspase-8 has also been implicated in the onsets of anoikis, autophagy and pyroptosis. Furthermore, Caspase-8 also plays a crucial pro-survival function by inhibiting an alternative form of programmed cell death called necroptosis. Low expression levels of pro-Caspase-8 is therefore associated with the malignant transformation of cancers. However, the long-held notion that pro-Caspase-8 expression/activity is generally lost in most cancers, thereby contributing to apoptotic escape and enhanced resistance to anti-cancer therapeutics, has been found to be true for only a minority of cancers types. In the majority of cases, pro-Caspase-8 expression is maintained and sometimes elevated, while it's apoptotic activity is regulated through different mechanisms. This supports the notion that the non-apoptotic functions of Caspase-8 offer growth advantage in these cancer types and have, therefore, gained renewed interest in the recent years. In light of these reasons, a number of therapeutic approaches have been employed, with the intent of targeting pro-Caspase-8 in cancer cells. In this review, we would attempt to discuss - the classic roles of Caspase-8 in initiating apoptosis; it's non-apoptotic functions; it's the clinical significance in different cancer types; and the therapeutic applications exploiting the ability of pro-Caspase-8 to regulate various cellular functions.

Molecular characterization of caspase-8-like and its expression induced by microcystin-LR in grass carp (Ctenopharygodon idella)

Caspase-8, an initiator caspase, plays a vital role in apoptosis. In this study, caspase-8-like (named as Cicaspase-8-like), a homologue of caspase-8, was identified in grass carp (Ctenopharygodon idella). The full-length cDNA sequence of CiCaspase-8-like was 1409 bp and contained a 162 bp 5'-UTR, a 239 bp 3'-UTR and a 1008 bp coding sequence. The putative amino acids sequence was 335 residues long, including a large subunit (P20) and a small subunit (P10), but lacking conserved death effector domains. A histidine active site DHSQMDAFVCCVLSHG and a cysteine active-site motif KPKLFFIQACQG were found in P20. Phylogenetic analysis showed that Cicaspase-8-like clustered with the caspase-8 and caspase-8-like of other fish and grouped closely with Carassius auratus caspase-8-like. Quantitative real-time PCR revealed that the Cicaspase-8-like mRNA were expressed constitutively in all tested tissues from healthy grass carp, with high expression level in the blood, spleen, liver and gill, indicating its role in immune reaction. The expression of Cicaspase-8-like mRNA was decreased significantly in the liver because of the stress caused by microcystin-LR (MC-LR) (75 and 100 μg MC-LR/kg BW) at 24 h and 96 h post injection (P < 0.05), but it was increased significantly in grass carp treated with 25 μg MC-LR/kg BW at 24 h (P < 0.05) post injection. Cleaved fragments of Cicaspase-8-like were observed using western blot analysis, and the expression of Cicaspase-8-like protein was increased after MC-LR treatments. Moreover, the expression of both caspase-9 and caspase-3 mRNA increased significantly after treatment with the three doses of MC-LR. TUNEL assay results showed remarkable changes in apoptosis after the MC-LR treatment. These results suggest that Cicaspase-8-like is an important caspase and plays an essential role in MC-LR-induced apoptosis.

Cucurbit[8]uril Reactivation of an Inactivated Caspase-8 Mutant Reveals Differentiated Enzymatic Substrate Processing

Caspase‐8 constructs featuring an N‐terminal FGG sequence allow for selective twofold recognition by cucurbit[8]uril, which leads to an increase of the enzymatic activity in a cucurbit[8]uril dose‐dependent manner. This supramolecular switching has enabled for the first time the study of the same caspase‐8 in its two extreme states; as full monomer and as cucurbit[8]uril induced dimer. A mutated, fully monomeric caspase‐8 (D384A), which is enzymatically inactive towards its natural substrate caspase‐3, could be fully reactivated upon addition of cucurbit[8]uril. In its monomeric state caspase‐8 (D384A) still processes a small synthetic substrate, but not the natural caspase‐3 substrate, highlighting the close interplay between protein dimerization and active site rearrangement for substrate selectivity. The ability to switch the caspase‐8 activity by a supramolecular system thus provides a flexible approach to studying the activity of a protein at different oligomerization states.

Fas Ligand Gene (Faslg) Plays an Important Role in Nerve Degeneration and Regeneration After Rat Sciatic Nerve Injury

Wallerian degeneration (WD) is associated with changes in the expression levels of a large number of genes. However, the effects of these up- or down-regulated genes are poorly understood. We have reported some key factors that are differentially regulated during WD in our previous research. Here, we explored the roles of Fas ligand gene (Faslg) in WD after rat sciatic nerve injury. The data showed that Faslg was up-regulated in injured nerves. Expression changed of Faslg in Schwann cells (SCs) resulted in alterations in the release of related factors. Silencing or overexpression of Faslg affected SC proliferation, migration, and apoptosis through β-catenin, nuclear factor-κB (NF-κB), and caspase-3 pathways in vivo and in vitro. Our data suggest that Faslg is a key regulatory gene that affects nerve repair and regeneration in peripheral nerve injury. This study sheds new light on the effects of Faslg on peripheral nerve degeneration and/or regeneration.

Cypermethrin toxication leads to histopathological lesions and induces inflammation and apoptosis in common carp (Cyprinus carpio L.)

Cypermethrin (Cyp), a known neurotoxic pesticide, is widely used in agricultural applications. In the present study, the aim was to determine the histopathological effects of Cyp toxication and evaluate the activation of inducible nitric oxide synthetase (iNOS) and 8-hydroxy-2-deoxyguanosine (8-OHdG) using an immunofluorescence assay. Thereafter, we identified the expressions of caspase 3, capsase 8, iNOS, and metallothionein 1 (MT1) genes in common carp using quantitative reverse transcription polymerase chain reaction (qRT-PCR). High and low doses of Cyp were administered to experimental groups for 24, 48, 72, and 96 h. As a result, necrotic neurons in different stages and desquamation of ependymal cells due to necrosis were detected in the brain. Histopathological changes, including hyperplasia of lamellar cells, telangiectasia of lamellae and thickening due to cellular infiltration in gills, hemorrhage, diffuse hydropic degeneration, and focal necrosis in the liver were observed in the experimental groups. Immunopositive reactions of 8-OHdG were clearly observed in the nuclei and cytoplasm of neurons, and positive reactions for iNOS were detected in the cytoplasm of neurons and in the glial cells of the experimental groups. Furthermore, we found that caspase 3, capsase 8, iNOS, and MT1 genes were up-regulated in the brain when exposed to both high and low doses of Cyp. In conclusion, our findings revealed that Cyp toxication harms the organs of common carp, particularly the brain, and also gives rise to inflammation, DNA damage, and apoptosis. Therefore, the use of Cyp should be restricted to protect the health of aquatic animals.

Caspase involvement in autophagy

Caspases are a family of cysteine proteases widely known as the principal mediators of the apoptotic cell death response, but considerably less so as the contributors to the regulation of pathways outside cellular demise. In regards to autophagy, the modulatory roles of caspases have only recently begun to be adequately described. In contrast to apoptosis, autophagy promotes cell survival by providing energy and nutrients through the lysosomal degradation of cytoplasmic constituents. Under basal conditions autophagy and apoptosis cross-regulate each other through an elaborate network of interconnections which also includes the interplay between autophagy-related proteins (ATGs) and caspases. In this review we focus on the effects of this crosstalk at the cellular level, as we aim to concentrate the main observations from research conducted so far on the fine-tuning of autophagy by caspases. Several members of this protease-family have been found to directly interact with key ATGs involved in different tiers across the autophagic cascade. Therefore, we firstly outline the core mechanism of macroautophagy in brief. In an effort to emphasize the importance of the intricate cross-regulation of ATGs and caspases, we also present examples of autophagy's contribution to apoptotic cell death during development.

Shared susceptibility loci at 2q33 region for lung and esophageal cancers in high-incidence areas of esophageal cancer in northern China

Background

Cancers from lung and esophagus are the leading causes of cancer-related deaths in China and share many similarities in terms of histological type, risk factors and genetic variants. Recent genome-wide association studies (GWAS) in Chinese esophageal cancer patients have demonstrated six high-risk candidate single nucleotide polymorphisms (SNPs). Thus, the present study aimed to determine the risk of these SNPs predisposing to lung cancer in Chinese population.

Methods

A total of 1170 lung cancer patients and 1530 normal subjects were enrolled in this study from high-incidence areas for esophageal cancer in Henan, northern China. Five milliliters of blood were collected from all subjects for genotyping. Genotyping of 20 high-risk SNP loci identified from genome-wide association studies (GWAS) on esophageal, lung and gastric cancers was performed using TaqMan allelic discrimination assays. Polymorphisms were examined for deviation from Hardy-Weinberg equilibrium (HWE) using Х² test. Bonferroni correction was performed to correct the statistical significance of 20 SNPs with the risk of lung cancer. The Pearson’s Х² test was used to compare the distributions of gender, TNM stage, histopathological type, smoking and family history by lung susceptibility genotypes. Kaplan-Meier and Cox regression analyses were carried out to evaluate the associations between genetic variants and overall survival.

Results

Four of the 20 SNPs identified as high-risk SNPs in Chinese esophageal cancer showed increased risk for Chinese lung cancer, which included rs3769823 (OR = 1.26; 95% CI = 1.107–1.509; P = 0.02), rs10931936 (OR = 1.283; 95% CI = 1.100–1.495; P = 0.04), rs2244438 (OR = 1.294; 95% CI = 1.098–1.525; P = 0.04) and rs13016963 (OR = 1.268; 95% CI = 1.089–1.447; P = 0.04). All these SNPs were located at 2q33 region harboringgenes of CASP8, ALS2CR12 and TRAK2. However, none of these susceptibility SNPs was observed to be significantly associated with gender, TNM stage, histopathological type, smoking, family history and overall survival.

Conclusions

The present study identified four high-risk SNPs at 2q33 locus for Chinese lung cancer and demonstrated the shared susceptibility loci at 2q33 region for Chinese lung and esophageal cancers.

Mitochondrial DNA oxidation induces imbalanced activity of NLRP3/NLRP6 inflammasomes by activation of caspase-8 and BRCC36 in dry eye

The concept of innate immunity has been expanded to recognize environmental pathogens other than microbial components. However, whether and how the innate immunity is initiated by epithelium in response to environmental physical challenges such as low humidity and high osmolarity in an autoimmune disease, dry eye, is still largely unknown. Using two experimental dry eye models, primary human corneal epithelial cultures exposed to hyperosmolarity and mouse ocular surface facing desiccating stress, we uncovered novel innate immunity pathway by ocular surface epithelium, where oxidized mitochondrial DNA induces imbalanced activation of NLRP3/NLRP6 inflammasomes via stimulation of caspase-8 and BRCC36 in response to environmental stress. Activated NLRP3 with suppressed NLRP6 stimulates caspase-1 activation that leads to IL-1β and IL-18 maturation and secretion. NLRP3-independent caspase-8 noncanonically activates caspase-1 via reciprocal regulation of NLRP3/NLRP6-mediated inflammasomes. Reactive oxygen species-induced mitochondrial DNA oxidative damage and BRCC36 deubiquitinating activity provide a missing link and mechanism by which innate immunity responds to environmental stress via caspase-8-involved NLRP3/NLRP6 inflammasomes.

Fibronectin protects lung cancer cells against docetaxel-induced apoptosis by promoting Src and caspase-8 phosphorylation

Fibronectin is involved in orchestrating many diverse cellular behaviors, including adhesion, invasion, differentiation, and proliferation and recently has also been shown to participate in the development of chemoresistance. In this study, we found that fibronectin expression was inversely correlated with clinical responses to docetaxel treatment in non-small cell lung cancer patients. Subsequently, we showed that fibronectin pretreatment could enhance cell viability and reduce apoptosis in docetaxel-treated lung cancer cells because fibronectin induced phosphorylated Src and caspase-8, rendering the later inactive, thus inhibiting docetaxel-induced apoptosis. The inhibition of apoptosis by fibronectin was found to be enhanced by Src overexpression and reversed by Src knockdown in lung cancer cells. Further investigation revealed that a downregulation of phospho-Src via treatment with a Src kinase inhibitor could also abolish fibronectin activity and recover docetaxel-induced apoptosis. Molecular studies revealed that this reversion was due to decreased phospho-Src levels rather than a reduction in total Src expression. Inhibition of phospho-Src reduced phospho-caspase-8 and promoted caspase-8 activity, restoring apoptosis following docetaxel and fibronectin co-treatment. Finally, xenografts experiments demonstrated that fibronectin promoted lung cancer cell proliferation during docetaxel treatment in vivo. Our findings indicate that fibronectin promotes Src and caspase-8 phosphorylation in lung cancer cells, which decreases caspase-8 activation and protects tumor cells from docetaxel-induced apoptosis. Therefore, the fibronectin/Src/caspase-8 pathway may play a crucial role in docetaxel resistance in lung cancer.

Caspase-8 functions as a key mediator of inflammation and pro-IL-1β processing via both canonical and non-canonical pathways

Caspase-8 is an apical component of cell death pathways. Activated caspase-8 can drive classical caspase-dependent apoptosis and actively inhibits cell death mediated by RIPK3-driven necroptosis. Genetic deletion of Casp8 results in embryonic lethality as a result of uncontrolled necroptosis. This lethality can be rescued by simultaneous deletion of Ripk3. Recently, caspase-8 has been additionally connected to inflammatory pathways within the cell. In particular, caspase-8 has been shown to be crucially involved in the induction of pro-IL-1β synthesis and processing via both non-canonical and canonical pathways. In this review, we bring together current knowledge regarding the role of caspase-8 in cellular inflammation with a particular emphasis on the interplay between caspase-8 and the classical and non-canonical inflammasomes.

New Insights into the Role of Ubiquitin Networks in the Regulation of Antiapoptosis Pathways

Ubiquitin is a small modifier protein that conjugates on lysine (Lys) residues of substrates, and it can be targeted by another ubiquitin molecule to form chains through conjugation on the intrinsic Lys residues and methionine (Met) 1 residue. Ubiquitination of substrates by such chains determines the fate of substrates, thereby influencing various biological processes. In this chapter, we focus on apoptosis with an emphasis on the regulation by ubiquitination. The signal transduction of apoptosis is governed not only by the classical function of ubiquitin, which is proteasome-dependent degradation of substrates, but also by the apoptosis signaling complex formation guided by different types of ubiquitin chains. Ubiquitinations of pro- and antiapoptotic proteins are tightly regulated by particular sets of enzymes, such as ubiquitin E3 ligases and deubiquitinases (DUBs). We further discuss ubiquitination in the tumor necrosis factor (TNF) signaling pathway as an example for the ubiquitin-dependent regulation of apoptosis and cell survival.

Enhancement of the proapoptotic properties of newcastle disease virus promotes tumor remission in syngeneic murine cancer models

Newcastle disease virus (NDV) is considered a promising agent for cancer therapy due to its oncolytic properties. These include preferential replication in transformed cells, induction of innate and adaptive immune responses within tumors, and cytopathic effects in infected tumor cells due to the activation of apoptosis. To enhance the latter and thus possibly enhance the overall oncolytic activity of NDV, we generated a recombinant NDV encoding the human TNF receptor Fas (rNDV-B1/Fas). rNDV-B1/Fas replicates to similar titers as its wild-type (rNDV-B1) counterpart; however, overexpression of Fas in infected cells leads to higher levels of cytotoxicity correlated with faster and increased apoptosis responses, in which both the intrinsic and extrinsic pathways are activated earlier. Furthermore, in vivo studies in syngeneic murine melanoma models show an enhancement of the oncolytic properties of rNDV-B1/Fas, with major improvements in survival and tumor remission. Altogether, our data suggest that upregulation of the proapoptotic function of NDV is a viable approach to enhance its antitumor properties and adds to the currently known, rationally based strategies to design optimized therapeutic viral vectors for the treatment of cancer.

The endocannabinoid anandamide induces apoptosis in cytotrophoblast cells: involvement of both mitochondrial and death receptor pathways

INTRODUCTION

A balanced proliferation, apoptosis and differentiation in trophoblast cells of the human placenta is crucial for a proper placental development. Alteration in trophoblast apoptosis and differentiation are associated with gestational-related complications, such as preeclampsia, intrauterine growth restriction or miscarriages. The endocannabinoids (eCBs) have been recognized as new interveners in pregnancy events such as implantation and decidualization. However, their importance in placentation is poorly understood. We hypothesise that these novel lipid mediators may intervene in cytotrophoblast apoptosis and, concomitantly, have a role during placental development.

METHODS

primary human cytotrophoblasts (hCTs) and the human trophoblast-like choriocarcinoma cell line BeWo cells were exposed to Anandamide (AEA). It was investigated the cellular pathways involved in cell death, by the assessment of cell morphology, caspases activity, mitochondrial membrane potential (Δψm), reactive oxygen/nitrogen species (ROS/RNS) and western blot of cleaved Poly (ADP-ribose) polymerase 1 (PARP-1), truncated Bid (t-Bid) and IκB-α.

RESULTS

AEA decreased hCTs viability and induced morphological features of apoptosis (chromatin condensation and fragmentation), caspase-3/7 activation and PARP-1 cleavage. In BeWo, AEA also increased the activities of caspase-3/7 and 9, induced loss in Δψm and production of ROS/RNS. These effects were reversed by either CB1 or CB2 antagonists, whereas the increase in caspase-3/7 activity was only reversed with CB2 blockage. AEA-treated cells showed increased caspase-8 activation and formation of t-Bid, suggesting the interplay between intrinsic and extrinsic apoptotic pathways. AEA also increased IκB-α expression, a NF-κB regulatory protein.

CONCLUSION

Our results highlight the importance of eCBs in cytotrophoblast cell apoptosis and indicate that a crosstalk between intrinsic and extrinsic apoptotic pathways is involved in AEA-induced effects.

Caspases: a molecular switch node in the crosstalk between autophagy and apoptosis

Autophagy and apoptosis are two important catabolic processes contributing to the maintenance of cellular and tissue homeostasis. Autophagy controls the turnover of protein aggregates and damaged organelles within cells, while apoptosis is the principal mechanism by which unwanted cells are dismantled and eliminated from organisms. Despite marked differences between these two pathways, they are highly interconnected in determining the fate of cells. Intriguingly, caspases, the primary drivers of apoptotic cell death, play a critical role in mediating the complex crosstalk between autophagy and apoptosis. Pro-apoptotic signals can converge to activate caspases to execute apoptotic cell death. In addition, activated caspases can degrade autophagy proteins (i.e., Beclin-1, Atg5, and Atg7) to shut down the autophagic response. Moreover, caspases can convert pro-autophagic proteins into pro-apoptotic proteints to trigger apoptotic cell death instead. It is clear that caspases are important in both apoptosis and autophagy, thus a detailed deciphering of the role of caspases in these two processes is still required to clarify the functional relationship between them. In this article, we provide a current overview of caspases in its interplay between autophagy and apoptosis. We emphasized that defining the role of caspases in autophagy-apoptosis crosstalk will provide a framework for more precise manipulation of these two processes during cell death.

Cartilage polysaccharide induces apoptosis in K562 cells through a reactive oxygen species-mediated caspase pathway

In this study, a polysaccharide (PS) was successfully extracted from porcine cartilage and its effect on chronic myeloid leukemia was examined using human K562 cells. The results of cell proliferation assays indicated that the PS inhibited cancer cell growth at different concentrations. Morphological and biochemical changes characteristic of apoptosis were observed and confirmed by PI staining and TUNEL assay. The nuclear DNA, RNA and proteins of the cancer cells subjected to PS treatment were irreversibly destroyed by reactive oxygen species (ROS), additionally, the ROS effected on the cells directly. The apoptotic signals altered the permeability of the mitochondrial outer membrane, thereby resulted in the release of apoptotic factors into the cytoplasm that induced apoptosis. As caspase-3/7, 8 and 9 were expressed, it was speculated that both intrinsic and extrinsic pathways were involved in the PS-induced apoptosis.

Caspase-8 mutations in head and neck cancer confer resistance to death receptor-mediated apoptosis and enhance migration, invasion, and tumor growth

Little is known regarding molecular markers in head and neck squamous cell carcinoma (HNSCC) that predict responsiveness to different therapeutic regimens or predict HNSCC progression. Mutations in procaspase-8 occur in 9% of HNSCC primary tumors, but the functional consequences of these mutations are poorly understood. In this study, we examined the impact of four, representative, HNSCC-associated procaspase-8 mutations on activation of the extrinsic apoptosis pathway, as well as cellular migration and invasion, and in vivo tumor growth. All four mutant proteins acted to potently inhibit activation of apoptosis following treatment with TRAIL or agonistic anti-Fas. In contrast to wild-type procaspase-8, the mutant proteins were not recruited to FADD following treatment with TRAIL or anti-Fas, but may be constitutively bound by FADD. Three of the four procaspase-8 mutants promoted enhanced cellular migration and invasion through matrigel, relative to that seen with the wild-type procaspase-8 protein. Procaspase-8 mutation also stimulated the growth of HNSCC xenograft tumors. These findings indicate that HNSCC-associated procaspase-8 mutations inhibit activation of the extrinsic apoptosis pathway and are likely to represent markers for resistance to therapeutic regimens incorporating death receptor activators. Moreover, procaspase-8 mutations may serve as markers of HNSCC tumor progression, as exemplified by enhanced migration, invasion, and tumor growth.

Activated neutrophils induce epithelial cell apoptosis through oxidant-dependent tyrosine dephosphorylation of caspase-8

Activated neutrophils can injure host cells through direct effects of oxidants on membrane phospholipids, but an ability to induce apoptotic cell death has not previously been reported. We show that neutrophils activated in vivo in patients who have sustained multiple trauma or in vitro by exposure to bacterial lipopolysaccharide promote epithelial cell apoptosis through SHP-1-mediated dephosphorylation of epithelial cell caspase-8. Epithelial cell apoptosis induced by circulating neutrophils from patients who had sustained serious injury depended on the generation of neutrophil-derived reactive oxygen intermediates and was blocked by inhibition of NADPH oxidase or restoration of intracellular glutathione. Caspase-8 was constitutively tyrosine phosphorylated in a panel of resting epithelial cells, but underwent SHP-1-dependent dephosphorylation in response to hydrogen peroxide, activated neutrophils, or inhibition of Src kinases. Cells transfected with a mutant caspase-8 in which tyrosine residues at Tyr397 or Tyr465 are replaced by nonphosphorylatable phenylalanine underwent accelerated apoptosis, whereas either mutation of these residues to phosphomimetic glutamic acid or transfection with the Src kinases Lyn or c-Src inhibited hydrogen peroxide-induced apoptosis. Exposure to either hydrogen peroxide or lipopolysaccharide-stimulated neutrophils increased phosphorylation and activity of the phosphatase SHP-1, increased activity of caspases 8 and 3, and accelerated epithelial cell apoptosis. These observations reveal a novel mechanism for neutrophil-mediated tissue injury through oxidant-dependent, SHP-1-mediated dephosphorylation of caspase-8 resulting in enhanced epithelial cell apoptosis.

Lyn-mediated procaspase 8 dimerization blocks apoptotic signaling in B-cell chronic lymphocytic leukemia

Lyn’s overexpression mediates resistance to apoptosis by promoting phosphorylation and dimerization of procaspase 8 in B-CLL cells.

Cadmium triggers kidney cell apoptosis of purse red common carp (Cyprinus carpio) without caspase-8 activation

Caspase-8, the essential initiator caspase, is believed to play a pivotal role in death receptor-mediated apoptotic pathway. It also participates in mitochondria-mediated apoptosis via cleavage of proapoptotic Bid in mammals. However, its role in fish remains elusive in Cadmium-induced apoptotic pathway. In this study, we isolated the caspase-8 gene from common carp, one of the most important industrial aquatic animals in China using rapid amplification of cDNA ends (RACE). The deduced amino acid sequence of caspase-8 comprised 475 amino acids, which showed approximately 64.1% identity and 79.8% similarity to zebrafish (Danio rerio) caspase-8, possessed two conserved death effector domains, a large subunit and a small subunit. Phylogenetic analysis demonstrated that caspase-8 formed a clade with zebrafish caspase-8. In kidney, cadmium (Cd) exposure triggered apoptosis and increased caspase-3 and -9 activities, whereas it did not affect caspase-8 activity. Real-time quantitative PCR analysis revealed that caspase-8 transcriptional level was not significantly increased in kidney after exposure to Cd. Using Western blot analysis, no caspase-8 cleaved fragment was detected and no significant alteration of procaspase-8 level was found with the same Cd-treated condition. Moreover, the immunopositive staining was predominantly limited to the cytoplasm of renal tubular epithelial cells and no remarkable changes of immunoreactivities were observed using immunohistochemical detection after Cd treatment. The results reveal that Cd can trigger apoptosis, while it cannot activate caspase-8 in purse red common carp.

Salmonella infection induces recruitment of Caspase-8 to the inflammasome to modulate IL-1β production

Nucleotide-binding oligomerization domain-like receptors (NLRs) detect pathogens and danger-associated signals within the cell. Salmonella enterica serovar Typhimurium, an intracellular pathogen, activates caspase-1 required for the processing of the proinflammatory cytokines, pro-IL-1β and pro-IL-18, and pyroptosis. In this study, we show that Salmonella infection induces the formation of an apoptosis-associated specklike protein containing a CARD (ASC)-Caspase-8-Caspase-1 inflammasome in macrophages. Caspase-8 and caspase-1 are recruited to the ASC focus independently of one other. Salmonella infection initiates caspase-8 proteolysis in a manner dependent on NLRC4 and ASC, but not NLRP3, caspase-1 or caspase-11. Caspase-8 primarily mediates the synthesis of pro-IL-1β, but is dispensable for Salmonella-induced cell death. Overall, our findings highlight that the ASC inflammasome can recruit different members of the caspase family to induce distinct effector functions in response to Salmonella infection.

TRAIL negatively regulates VEGF-induced angiogenesis via caspase-8-mediated enzymatic and non-enzymatic functions

Solid tumors supply oxygen and nutrients required for angiogenesis by producing vascular endothelial growth factor (VEGF). Thus, inhibitors of VEGF signaling abrogate tumor angiogenesis, resulting in the suppression of tumor growth and metastasis. We here investigated the effects of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on VEGF-induced angiogenesis. TRAIL inhibited VEGF-induced in vitro angiogenesis of human umbilical vein endothelial cells (HUVECs) and in vivo neovascularization in chicken embryos and mice. TRAIL blocked VEGF-induced angiogenic signaling by inhibiting ERK, Src, FAK, paxillin, Akt, and eNOS. Further, TRAIL blocked intracellular Ca(2+) elevation and actin reorganization in HUVECs stimulated with VEGF, without inhibiting VEGF receptor-2 tyrosine phosphorylation. TRAIL increased caspase-8 activity, without inducing caspase-9/-3 activation and apoptosis. Moreover, TRAIL resulted in cleavage of FAK into FAK-related non-kinase-like fragments in VEGF-stimulated HUVECs, which was blocked by a caspase-8 inhibitor and cellular caspase-8-like inhibitory protein. Biochemical and pharmacological inhibition of caspase-8 and FAK blocked the inhibitory effects of TRAIL on VEGF-stimulated anti-angiogenic signaling and events. In addition, caspase-8 knockdown also suppressed VEGF-mediated signaling and angiogenesis, suggesting that procaspase-8 plays a role of a non-apoptotic modulator in VEGF-induced angiogenic signaling. These results suggest that TRAIL inhibits VEGF-induced angiogenesis by increasing caspase-8 activity and subsequently decreasing non-apoptotic signaling functions of procaspase-8, without inducing caspase-3 activation and endothelial cell cytotoxicity. These data indicate that caspase-8 may be used as an anti-angiogenic drug for solid tumors resistant to TRAIL and anti-tumor drugs.

Study on Apoptosis of Human Promyelocytic Leukemia HL-60 Cells Induced by Fucosterol via Death Receptor Pathway

The purpose of this study is to investigate the effect of fucosterol on the induction of apoptosis and the molecular mechanism involved in Human promyelocytic leukemia HL-60 Cells. HL-60 Cells were treated with different concentrations of fucosterol at different time. MTT method was used to study fucosterol anti-tumor activity. Morphology observation was performed to determine the effects of fucosterol on apoptosis of HL-60 cells. Flow cytometry (FCM) was used to detect the cell cycle. Laser scanning confocal microscope (LSCM) was used to analyze the expressions of Fas, FasL, Fadd and Caspase-8. Caspase activity kits were used to determine the activity of Caspase-8 and Caspase-3. The results showed fucosterol could inhibit the growth of HL-60 cells, and the apoptosis morphology for 48 h treatment was obvious, which showed cell protuberance, cytoplasm concentrated and apoptotic body. Fucosterol treatment for 24 h increased the protein expression of Fas, FasL, Fadd and Caspase-8. It also showed that the activity of Caspase-3 and Caspase-8 has increased significantly. In conclusion, Fucosterol could induce HL-60 cells apoptosis via death receptor pathway.

Regulation of tumor necrosis factor-α-induced microvascular endothelial cell hyperpermeability by recombinant B-cell lymphoma-extra large

BACKGROUND

Tumor necrosis factor-α (TNF-α), a cytotoxic cytokine, induces endothelial cell barrier dysfunction and microvascular hyperpermeability, leading to tissue edema, a hallmark of traumatic injuries. The objective of the present study was to determine whether B-cell lymphoma-extra large (Bcl-xL), an antiapoptotic protein, would regulate and protect against TNF-α-mediated endothelial cell barrier dysfunction and microvascular hyperpermeability.

METHODS

Rat lung microvascular endothelial cells were grown as monolayers on Transwell membranes, and fluorescein isothiocyanate-bovine albumin flux (5 mg/mL) across the monolayer was measured fluorometrically to indicate changes in monolayer permeability. The rat lung microvascular endothelial cell adherens junctional integrity and actin cytoskeleton was studied using β-catenin immunofluorescence and rhodamine phalloidin dye, respectively. Pretreatment of caspase-8 inhibitor (Z-IETD-FMK, 100 μM) for 1 hour and transfection of Bcl-2-homology domain 3-interacting domain death agonist small interfering RNA (10 μM) for 48 hours were performed to study their respective effects on TNF-α-induced (10 ng/mL; 1-hour treatment) monolayer permeability. Recombinant Bcl-xL protein (2.5 μg/ml) was transfected in rat lung microvascular endothelial cells for 1 hour, and its effect on permeability was demonstrated using a permeability assay. Caspase-3 activity was assayed fluorometrically.

RESULTS

Z-IETD-FMK pretreatment protected the adherens junctions and decreased TNF-α-induced monolayer hyperpermeability. Bcl-2-homology domain 3-interacting domain death agonist small interfering RNA transfection attenuated the TNF-α-induced increase in monolayer permeability. Recombinant Bcl-xL protein showed protection against TNF-α-induced actin stress fiber formation, an increase in caspase-3 activity, and monolayer hyperpermeability.

CONCLUSIONS

Our results have demonstrated the protective effects of recombinant Bcl-xL protein against TNF-α-induced endothelial cell adherens junction damage and microvascular endothelial cell hyperpermeability. These findings support the potential for Bcl-xL-based drug development against microvascular hyperpermeability and tissue edema.

PARP-1 regulates resistance of pancreatic cancer to TRAIL therapy

PURPOSE

Activating extrinsic apoptotic pathways targeting death receptors (DR) using agonistic antibodies or TNF-related apoptosis-inducing ligand (TRAIL) is promising for cancer therapy. However, most pancreatic cancers are resistant to TRAIL therapy. The present studies aimed to identify combination therapies that enhance the efficacy of TRAIL therapy and to investigate the underlying mechanisms.

EXPERIMENTAL DESIGN

A xenograft model in nude mice was used to determine pancreatic cancer tumorigenesis and therapeutic efficacy of TRA-8, a monoclonal agonistic antibody for DR5. Pancreatic cancer cells were used to characterize mechanisms underlying PARP-1 regulation of TRA-8-induced apoptosis in vitro.

RESULTS

PARP-1 was found highly expressed in the TRA-8-resistant PANC-1 and Suit-2 cells, compared with TRA-8-sensitive BxPc-3 and MiaPaca-2. Inhibition of PARP-1 with a pharmacologic inhibitor sensitized PANC-1 and Suit2 cells to TRA-8-induced apoptosis in a dose-dependent manner. Furthermore, siRNAs specifically knocking down PARP-1 markedly enhanced TRA-8-induced apoptosis in vitro and augmented the efficacy of TRA-8 therapy on tumorigenesis in vivo. PARP-1 knockdown increased TRA-8-induced activation of caspase-8 in the death-induced signaling complex (DISC). Immunoprecipitation with DR5 antibody identified the recruitment of PARP-1 and PARP-1-mediated protein poly-ADP-ribosylation (pADPr) modification in the DR5-associated DISC. Further characterization revealed that PARP-1-mediated pADPr modification of caspase-8 inhibited caspase-8 activation, which may contribute to its function in regulating TRA-8 resistance.

CONCLUSIONS

Our studies provide molecular insights into a novel function of PARP-1 in regulating the extrinsic apoptosis machinery and also support interventions combining PARP-1 inhibitors with DR agonists for pancreatic cancer therapy.

Cancer immunogenicity, danger signals, and DAMPs: what, when, and how?

Cancer immunosurvelliance usually leads to formation of cancer cells that have been "immunoedited" to resist anti-tumor immunity. One of the consequences of immunoediting that is, reduced immunogenicity, is an important roadblock in revival of stable and long-lasting anti-tumor immune responses. Research done during the last decade has shown that emission by the dying cancer cells of immunomodulatory factors or damage-associated molecular patterns (DAMPs), which can act as danger signals, is a critical event in accentuating the immunogenicity of cancer cells, in response to a subset of anticancer treatments. Recent evidence has defined that an apoptotic cell death subroutine and its underlying biochemistry, which has been termed as "immunogenic cell death (ICD)" or "immunogenic apoptosis," is required for the efficient emission of DAMPs and inciting anti-tumor immunity. Here, we review the basic concepts of ICD, like cancer immunogenicity, danger signals, and DAMPs. Moreover, we discuss the emerging molecular links between endoplasmic reticulum (ER) stress, induction of a viral response-like gene expression, danger signals, and anti-tumor immunity. We envisage that along with ER stress-based trafficking of DAMPs (which is a "short-range communicator" of danger), the accompanying induction of a viral response-like gene expression and the secretion of anti-tumorigenic cytokines may become a crucial signature of ICD induction by anticancer therapy.

A coupled protein and probe engineering approach for selective inhibition and activity-based probe labeling of the caspases

Caspases are cysteine proteases that play essential roles in apoptosis and inflammation. Unfortunately, their highly conserved active sites and overlapping substrate specificities make it difficult to use inhibitors or activity-based probes to study the function, activation, localization, and regulation of individual members of this family. Here we describe a strategy to engineer a caspase to contain a latent nucleophile that can be targeted by a probe containing a suitably placed electrophile, thereby allowing specific, irreversible inhibition and labeling of only the engineered protease. To accomplish this, we have identified a non-conserved residue on the small subunit of all caspases that is near the substrate-binding pocket and that can be mutated to a non-catalytic cysteine residue. We demonstrate that an active-site probe containing an irreversible binding acrylamide electrophile can specifically target this cysteine residue. Here we validate the approach using the apoptotic mediator, caspase-8, and the inflammasome effector, caspase-1. We show that the engineered enzymes are functionally identical to the wild-type enzymes and that the approach allows specific inhibition and direct imaging of the engineered targets in cells. Therefore, this method can be used to image localization and activation as well as the functional contributions of individual caspase proteases to the process of cell death or inflammation.

Resveratrol induces long-lasting IL-8 expression and peculiar EGFR activation/distribution in human keratinocytes: mechanisms and implications for skin administration

Anti-inflammatory and skin tumour preventing effects of resveratrol have been extensively studied pre-clinically and resveratrol has been proposed for clinical investigations. To provide a basis or/and limitations for topical administration to human skin, molecular mechanisms underlying resveratrol effects towards normal human epidermal keratinocytes (NHEK) were evaluated. NHEK were challenged by either resveratrol alone or by its combination with TNFalpha or TGFalpha, and time-dependent molecular events were monitored. Interleukin 8 (IL-8) expression and its mRNA stability, ERK1/2, p65/RelA, and EGFR phosphorylation were determined. Intracellular distribution of EGFR/P-EGFR was measured in the membrane, cytoplasmic, and nuclear fractions. Specific DNA binding activity of NFκB (p65/RelA) and AP-1(c-Fos), NHEK proliferation, and molecular markers of apoptosis/cell cycle were detected. Resveratrol induced delayed, long-lasting and steadily growing IL-8 gene and protein over-expression as well as enhanced EGFR phosphorylation, both abrogated by the EGFR kinase inhibitor PD168393. However, resveratrol did not act as a phosphatase inhibitor. ERK phosphorylation was transiently inhibited at early time-points and activated at 6–24 h. Accordingly, c-Fos-specific DNA binding was increased by resveratrol. Cellular distribution of EGFR/P-EGFR was shifted to membrane and nucleus while cytosolic levels were reduced concomitant with enhanced degradation. Notwithstanding high nuclear levels of EGFR/P-EGFR, spontaneous and TGFalpha-triggered cell proliferation was strongly suppressed by resveratrol mainly through cell cycle arrest.

Mechanisms for ribotoxin-induced ribosomal RNA cleavage

The Type B trichothecene deoxynivalenol (DON), a ribotoxic mycotoxin known to contaminate cereal-based foods, induces ribosomal RNA (rRNA) cleavage in the macrophage via p38-directed activation of caspases. Here we employed the RAW 264.7 murine macrophage model to test the hypothesis that this rRNA cleavage pathway is similarly induced by other ribotoxins. Capillary electrophoresis confirmed that the antibiotic anisomycin (≥25ng/ml), the macrocylic trichothecene satratoxin G (SG) (≥10ng/ml) and ribosome-inactivating protein ricin (≥300ng/ml) induced 18s and 28s rRNA fragmentation patterns identical to that observed for DON. Also, as found for DON, inhibition of p38, double-stranded RNA-activated kinase (PKR) and hematopoietic cell kinase (Hck) suppressed MAPK anisomycin-induced rRNA cleavage, while, in contrast, their inhibition did not affect SG- and ricin-induced rRNA fragmentation. The p53 inhibitor pifithrin-μ and pan caspase inhibitor Z-VAD-FMK suppressed rRNA cleavage induced by anisomycin, SG and ricin, indicating that these ribotoxins shared with DON a conserved downstream pathway. Activation of caspases 8, 9 and 3 concurrently with apoptosis further suggested that rRNA cleavage occurred in parallel with both extrinsic and intrinsic pathways of programmed cell death. When specific inhibitors of cathepsins L and B (lysosomal cysteine cathepsins active at cytosolic neutral pH) were tested, only the former impaired anisomycin-, SG-, ricin- and DON-induced rRNA cleavage. Taken together, the data suggest that (1) all four ribotoxins induced p53-dependent rRNA cleavage via activation of cathepsin L and caspase 3, and (2) activation of p53 by DON and anisomycin involved p38 whereas SG and ricin activated p53 by an alternative mechanism.

Artichoke polyphenols induce apoptosis and decrease the invasive potential of the human breast cancer cell line MDA-MB231

The human breast cancer cell line, estrogen receptor negative, MDA-MB231, was used to evaluate the antitumor effect of polyphenolic extracts from the edible part of artichokes (AEs). Treatment of cancer cells reduced cell viability and inhibited cell growth in a dose-dependent manner. Importantly, AEs did not have any effect on normal breast epithelial cell line, MCF10A. Chlorogenic acid (ChA), the most representative component of the polyphenolic fraction of artichoke, had no prominent effects on the cell death rate of MDA-MB231 cells. The addition of AEs to the cells, rather than ChA, triggered apoptosis via a mitochondrial and a death-receptor pathway, as shown by the activation of caspase-9 and caspase-8, respectively. Furthermore, an increase of the Bax:Bcl2 ratio and up-regulation of cyclin-dependent kinase inhibitor, p21(WAF1), crucial apoptotic players, were documented. According to our data on activation of caspase-9, a loss of mitochondrial transmembrane potential (Ψ(m)) was shown. Cell motility and invasion capabilities were remarkably inhibited by AEs-treatment in highly invasive MDA-MB231 cells. In addition, a significant decrease of proteolytic activity of metalloproteinase-2 protein (MMP-2), involved in degrading components of the extracellular matrix, was detected. Our findings indicate that AEs reduced cell viability, inhibited cell growth, triggered apoptotic mechanisms, and showed inhibitory properties against the invasive behavior of MDA-MB231 cancer cell line. Altogether, these data indicate the potential chemopreventive activity of artichoke polyphenolic extracts.

Mulberry leaf polyphenol extract induced apoptosis involving regulation of adenosine monophosphate-activated protein kinase/fatty acid synthase in a p53-negative hepatocellular carcinoma cell

The polyphenols in mulberry leaf possess the ability to inhibit cell proliferation, invasion, and metastasis of tumors. It was reported that the p53 status plays an important role in switching apoptosis and the cell cycle following adenosine monophosphate-activated protein kinase (AMPK) activation. In this study, we aimed to detect the effect of the mulberry leaf polyphenol extract (MLPE) on inducing cell death in p53-negative (Hep3B) and p53-positive (Hep3B with transfected p53) hepatocellular carcinoma cells and also to clarify the role of p53 in MLPE-treated cells. After treatment of the Hep3B cells with MLPE, apoptosis was induced via the AMPK/PI3K/Akt and Bcl-2 family pathways. Transient transfection of p53 into Hep3B cells led to switching autophagy instead of apoptosis by MLPE treatment. We demonstrated that acridine orange staining and protein expressions of LC-3 and beclin-1 were increased in p53-transfected cells. These results implied induction of apoptosis or autophagy in MLPE-treated hepatocellular carcinoma cells can be due to the p53 status. We also found MLPE can not only activate AMPK but also diminish fatty acid synthase, a molecular target for cancer inhibition. At present, our results indicate MLPE can play an active role in mediating the cell death of hepatocellular carcinoma cells and the p53 might play an important role in regulating the death mechanisms.

Demethoxycurcumin Retards Cell Growth and Induces Apoptosis in Human Brain Malignant Glioma GBM 8401 Cells

Demethoxycurcumin (DMC; a curcumin-related demethoxy compound) has been recently shown to display antioxidant and antitumor activities. It has also produced a potent chemopreventive action against cancer. In the present study, the antiproliferation (using the MTT assay, DMC was found to have cytotoxic activities against GBM 8401 cell with IC₅₀ values at 22.71 μM) and induced apoptosis effects of DMC have been investigated in human brain malignant glioma GBM 8401 cells. We have studied the mitochondrial membrane potential (MMP), DNA fragmentation, caspase activation, and NF-κB transcriptional factor activity. By these approaches, our results indicated that DMC has produced an inhibition of cell proliferation as well as the activation of apoptosis in GBM 8401 cells. Both effects were observed to increase in proportion with the dosage of DMC treatment, and the apoptosis was induced by DMC in human brain malignant glioma GBM 8401 cells via mitochondria- and caspase-dependent pathways.

Genotypic variants at 2q33 and risk of esophageal squamous cell carcinoma in China: a meta-analysis of genome-wide association studies

Genome-wide association studies have identified susceptibility loci for esophageal squamous cell carcinoma (ESCC). We conducted a meta-analysis of all single-nucleotide polymorphisms (SNPs) that showed nominally significant P-values in two previously published genome-wide scans that included a total of 2961 ESCC cases and 3400 controls. The meta-analysis revealed five SNPs at 2q33 with P< 5 × 10(-8), and the strongest signal was rs13016963, with a combined odds ratio (95% confidence interval) of 1.29 (1.19-1.40) and P= 7.63 × 10(-10). An imputation analysis of 4304 SNPs at 2q33 suggested a single association signal, and the strongest imputed SNP associations were similar to those from the genotyped SNPs. We conducted an ancestral recombination graph analysis with 53 SNPs to identify one or more haplotypes that harbor the variants directly responsible for the detected association signal. This showed that the five SNPs exist in a single haplotype along with 45 imputed SNPs in strong linkage disequilibrium, and the strongest candidate was rs10201587, one of the genotyped SNPs. Our meta-analysis found genome-wide significant SNPs at 2q33 that map to the CASP8/ALS2CR12/TRAK2 gene region. Variants in CASP8 have been extensively studied across a spectrum of cancers with mixed results. The locus we identified appears to be distinct from the widely studied rs3834129 and rs1045485 SNPs in CASP8. Future studies of esophageal and other cancers should focus on comprehensive sequencing of this 2q33 locus and functional analysis of rs13016963 and rs10201587 and other strongly correlated variants.

Characterization of Cholix toxin-induced apoptosis in HeLa cells

Cholix toxin (Cholix) is a novel ADP-ribosylating cytotoxin produced by Vibrio cholerae, which utilizes eukaryotic elongation factor 2 as a substrate and acts by a mechanism similar to that of diphtheria toxin and Pseudomonas exotoxin A. First it was found that Cholix-treated HeLa cells exhibited caspase-dependent apoptosis, whereas intestinal cells such as Caco-2, HCT116, and RKO did not. Here we investigated Cholix-induced cell death signaling pathways in HeLa cells. Cholix-induced cytochrome c release into cytosol was initiated by specific conformational changes of pro-apoptotic Bak associated with Bax. Silencing of bak/bax genes or bak gene alone using siRNA significantly suppressed cytochrome c release and caspase-7 activation, but not activation of caspases-3 and -9. Although pretreatment with a caspase-8 inhibitor (Z-IETD-FMK) reduced Cholix-induced cytochrome c release and activation of caspases-3, -7, and -9, cytotoxicity was not decreased. Pretreatment with Z-YVAD-FMK, which inhibits caspase-1, -4, and -5, suppressed not only cytochrome c release, activation of caspase-3, -7, -8, or -9, and PARP cleavage, but also cytotoxicity, indicating that caspase-1, -4, and -5 activation is initiated at an early stage of Cholix-induced apoptosis and promotes caspase-8 activation. These results show that the inflammatory caspases (caspase-1, -4, and -5) and caspase-8 are responsible for both mitochondrial signals and other caspase activation. In conclusion, we showed that Cholix-induced caspase activation plays an essential role in generation of apoptotic signals, which are mediated by both mitochondria-dependent and -independent pathways.

Integrin signaling, cell survival, and anoikis: distinctions, differences, and differentiation

Cell survival and apoptosis implicate an increasing complexity of players and signaling pathways which regulate not only the decision-making process of surviving (or dying), but as well the execution of cell death proper. The same complex nature applies to anoikis, a form of caspase-dependent apoptosis that is largely regulated by integrin-mediated, cell-extracellular matrix interactions. Not surprisingly, the regulation of cell survival, apoptosis, and anoikis furthermore implicates additional mechanistic distinctions according to the specific tissue, cell type, and species. Incidentally, studies in recent years have unearthed yet another layer of complexity in the regulation of these cell processes, namely, the implication of cell differentiation state-specific mechanisms. Further analyses of such differentiation state-distinct mechanisms, either under normal or physiopathological contexts, should increase our understanding of diseases which implicate a deregulation of integrin function, cell survival, and anoikis.

Reversion of gene expression alterations in hearts of mice with chronic chagasic cardiomyopathy after transplantation of bone marrow cells

Chronic chagasic cardiomyopathy is a leading cause of heart failure in Latin American countries, being associated with intense inflammatory response and fibrosis. We have previously shown that bone marrow mononuclear cell (BMC) transplantation improves inflammation, fibrosis, and ventricular diameter in hearts of mice with chronic Chagas disease. Here we investigated the transcriptomic recovery induced by BMC therapy by comparing the heart transcriptomes of control, chagasic, and BMC transplanted mice. Out of the 9390 unique genes quantified in all samples, 1702 had their expression altered in chronic chagasic hearts compared to those of normal mice. Major categories of significantly upregulated genes were related to inflammation, fibrosis and immune responses, while genes involved in mitochondrion function were downregulated. When BMC-treated chagasic hearts were compared to infected mice, 96% of the alterations detected in infected hearts were restored to normal levels, although an additional 109 genes were altered by treatment. Transcriptomic recovery, a new measure that considers both resotrative and side effects of treatment, was remarkably high (84%). Immunofluorescence and morphometric analyses confirmed the effects of BMC therapy in the pattern of inflammatory-immune response and expression of adhesion molecules. In conclusion, by using large-scale gene profiling for unbiased assessment of therapeutic efficacy we demonstrate immunomodulatory effects of BMC therapy in chronic chagasic cardiomyopathy and identify potentially relevant factors involved in the pathogenesis of the disease that may provide new therapeutic targets.

zVAD-induced autophagic cell death requires c-Src-dependent ERK and JNK activation and reactive oxygen species generation

The treatment of L929 fibrosarcoma cells with zVAD has been shown to induce necroptosis. However, whether autophagy is involved or not in this event remains controversial. In this study, we re-examined the role of autophagy in zVAD-induced cell death in L929 cells and further elucidated the signaling pathways triggered by caspase inhibition and contributing to autophagic death. First, we found that zVAD can stimulate LC3-II formation, autophagosome and autolysosome formation, and ROS accumulation. Antioxidants, beclin 1 or Atg5 silencing, and class III PtdIns3K inhibitors all effectively blocked ROS production and cell death, suggesting ROS accumulation downstream of autophagy contributes to cell necrosis. zVAD also stimulated PARP activation, and the PARP inhibitor DPQ can reduce zVAD-induced cell death, but did not affect ROS production, suggesting the increased ROS leads to PARP activation and cell death. Notably, our data also indicated the involvement of Src-dependent JNK and ERK in zVAD-induced ROS production and autophagic death. We found caspase 8 is associated with c-Src at the resting state, and upon zVAD treatment this association was decreased and accompanied by c-Src activation. In conclusion, we confirm the autophagic death in zVAD-treated L929 cells, and define a new molecular pathway in which Src-dependent ERK and JNK activation can link a signal from caspase inhibition to autophagy, which in turn induce ROS production and PARP activation, eventually leading to necroptosis. Thus, in addition to initiating proteolytic activity for cell apoptosis, inactivated caspase 8 also functions as a signaling molecule for autophagic death.