Structure and chromosome localization of the human CASP8 gene

Relationship Between CASP9 and CASP10 Gene Polymorphisms and Cancer Susceptibility: Evidence from an Updated Meta-analysis

Caspase-9 (CASP9) and caspase-10 (CASP10) polymorphisms were associated with human cancers; however, the results remain controversial. In this meta-analysis, we aimed to estimate the relationship among CASP9 (rs1052576, rs1052571, rs4645978, rs4645981, rs4645982, rs2308950) and CASP10 (rs13006529, rs13010627, rs3900115) polymorphisms and the overall risk of cancers. Relevant studies were obtained from Web of Science, MEDLINE, PubMed, Scopus, and Google scholar databases (updated January 1, 2021). Odds ratio (OR) and 95% confidence intervals (CIs) were measured to estimate the strength of association. Our meta-analysis included 40 studies. The rs4645981 significantly enhanced the risk of cancer under TT vs. CC (OR = 2.42), TC vs. CC (OR = 1.55), TT+ TC vs. CC (OR = 1.66), TT vs. TC + CC (OR = 1.91), and T vs. C (OR = 1.57) inheritance models. As for the rs1052571 variant, increased risk of cancer was observed under TT vs. CC (OR =1.22), TC vs. CC (OR = 1.17), and TT+ TC vs. CC (OR = 1.18) models. The stratified analysis showed a significant correlation between rs4645978 or rs4645981 polymorphisms and cancer risk, while in Asians rs4645978 conferred an increased risk of colorectal, lung, and prostate cancer. Both rs4645981 and rs1052576 polymorphisms were correlated with an enhanced risk of lung cancer. In conclusion, our meta-analysis suggested that CASP9 rs4645981 and rs1052571 polymorphisms are associated with overall cancer risk. More studies on larger populations are warranted to validate these associations.

Decoding Cell Death: From a Veritable Library of Babel to Vade Mecum?

Programmed cell death (PCD) is a requisite feature of development and homeostasis but can also be indicative of infections, injuries, and pathologies. In concordance with these heterogeneous contexts, an array of disparate effector responses occur downstream of cell death and its clearance-spanning tissue morphogenesis, homeostatic turnover, host defense, active dampening of inflammation, and tissue repair. This raises a fundamental question of how a single contextually appropriate response ensues after an event of PCD. To explore how complex inputs may together tailor the specificity of the resulting effector response, here we consider (a) the varying contexts during which different cell death modalities are observed, (b) the nature of the information that can be passed on by cell corpses, and (c) the ways by which efferocyte populations synthesize signals from dying cells with those from the surrounding microenvironment.

Polymorphisms in the Gene Encoding Caspase 8 May Predict the Response to First-Line Platinum-Based Chemotherapy in Locally Advanced or Advanced Non-Small-Cell Lung Cancer

Caspase 8 is a protein involved in the process of cell apoptosis, which may affect the efficacy of anti-cancer treatment. The aim of our study was to determine the impact of polymorphisms in the CASP-8 gene encoding caspase 8 on the prognosis in non-small-cell lung cancer (NSCLC). The study involved 99 patients with newly diagnosed locally advanced or metastatic NSCLC treated with platinum-based chemotherapy. The presence of the GG genotype was associated with distant metastases, smoking, and a family history of cancer. The higher risk of early progression was associated with weight loss and the CASP-8 genotype (GG vs. AG or AA: 20.51% vs. 2.86%). The higher risk of progression-free survival (PFS) shortening was associated with a higher stage of disease (hazard ratio (HR) = 2.50, 95% CI: 1.61–3.89, p < 0.0001), distant metastases (HR = 2.30, 95% CI: 1.42–3.72, p = 0.0016), and the GG genotype (HR = 1.68, 95% CI: 1.10–2.57, p = 0.0152). The influence of the GG genotype on the PFS was confirmed in a multivariate analysis (HR = 1.80, 95% CI: 1.06–3.05, p = 0.0317). We did not confirm the influence of CASP-8 genotypes on the overall survival (OS).

Genomic variants in Fas-mediated apoptosis pathway predict a poor response to Platinum-based Chemotherapy for Chinese Gastric Cancer Patients

Platinum-based adjuvant chemotherapy is very common for gastric cancer (GC) patients, but the chemotherapy sensitivity is very heterogeneous. The genomic variants and the gene-gene interactions involved in Fas-mediated apoptosis pathway including Fas (FAS 1377 G > A and 670 A > G), FasL (FASL 844 C > T) and caspase-8 (CASP8 -652 6N ins > del or I > D), may paly vital roles in the response to platinum-based treatment. In our investigation, 662 stage II-III postoperative GC patients were enrolled between 1998 and 2006. 261 patients accepted platinum-based regimens and the remaining 401 were not. The log rank tests, Kaplan Meier plots, Pearson chi-square tests, Student t-tests and Cox regression analyses were performed. For the chemotherapy cohort, FAS 1377 G > A or FAS 670 A > G variants alone was related with inferior survival, and a greater than additive effect was identified when patients simultaneously carrying FAS 1377 GA and FAS 670 GA genotypes. But the poor response was neutralized when patients simultaneously carrying FASL 844 C > T or CASP8 -652 6N ins > del mutations. Our study suggested that FAS 1377 G > A and FAS 670 A > G variants may serve as potential biomarkers to predict the response to platinum-based adjuvant chemotherapy, and the gene-gene interactions involved in Fas-mediated apoptosis pathway may enhance or neutralize the chemosensitivity.

FLIP(L): the pseudo-caspase

Possessing structural homology with their active enzyme counterparts but lacking catalytic activity, pseudoenzymes have been identified for all major enzyme groups. Caspases are a family of cysteine‐dependent aspartate‐directed proteases that play essential roles in regulating cell death and inflammation. Here, we discuss the only human pseudo‐caspase, FLIP(L), a paralog of the apoptosis‐initiating caspases, caspase‐8 and caspase‐10. FLIP(L) has been shown to play a key role in regulating the processing and activity of caspase‐8, thereby modulating apoptotic signaling mediated by death receptors (such as TRAIL‐R1/R2), TNF receptor‐1 (TNFR1), and Toll‐like receptors. In this review, these canonical roles of FLIP(L) are discussed. Additionally, a range of nonclassical pseudoenzyme roles are described, in which FLIP(L) functions independently of caspase‐8. These nonclassical pseudoenzyme functions enable FLIP(L) to play key roles in the regulation of a wide range of biological processes beyond its canonical roles as a modulator of cell death.

The Apoptosis Pathway and CASP8 Variants Conferring Risk for Acute and Overuse Musculoskeletal Injuries

Rotator cuff tendinopathy (RCT), anterior cruciate ligament (ACL) ruptures, and carpal tunnel syndrome (CTS), are examples of chronic (RCT and CTS) and acute (ACL ruptures) musculoskeletal soft tissue injuries. These injuries are multifactorial in nature, with several identified intrinsic and extrinsic risk factors. Previous studies have implicated specific sequence variants within genes encoding structural and regulatory components of the extracellular matrix of tendons and/ligaments to predispose individuals to these injuries. An example, includes the association of sequence variants within the apoptotic regulatory gene, caspase-8 (CASP8) with other musculoskeletal injury phenotypes, such as Achilles tendinopathy. The primary aim of this study was, therefore, to investigate previously implicated DNA sequence variants within CASP8: rs3834129 (ins/del) and rs1045485 (G/C), and the rs13113 (T/A) identified using a whole exome sequencing approach, with risk of musculoskeletal injury phenotypes (RCT, ACL ruptures, and CTS) in three independent studies. In addition, the aim was to implicate a CASP8 genomic interval in the modulation of risk of RCT, ACL ruptures, or CTS. It was found that the AA genotype of CASP8 rs13113 (T/A) was independently associated with increased risk for CTS. In addition, it was found that the del-C haplotype (rs3834129-rs1045485) was significantly associated with non-contact ACL ruptures, which is in alignment with previous research findings. Collectively, the results of this study implicate the apoptosis pathway as biologically significant in the underlying pathogenesis of musculoskeletal injury phenotypes. These findings should be repeated in larger sample cohorts and across different populations. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:680-688, 2020.

Differential roles of protease isoforms in the tumor microenvironment

Alternative splicing of precursor mRNA is a key mediator of gene expression regulation leading to greater diversity of the proteome in complex organisms. Systematic sequencing of the human genome and transcriptome has led to our understanding of how alternative splicing of critical genes leads to multiple pathological conditions such as cancer. For many years, proteases were known only for their roles as proteolytic enzymes, acting to regulate/process proteins associated with diverse cellular functions. However, the differential expression and altered function of various protease isoforms, such as (i) anti-apoptotic activities, (ii) mediating intercellular adhesion, and (iii) modifying the extracellular matrix, are evidence of their specific contribution towards shaping the tumor microenvironment. Revealing the alternative splicing of protease genes and characterization of their protein products/isoforms with distinct and opposing functions creates a platform to understand how protease isoforms contribute to specific cancer hallmarks. Here, in this review, we address cancer-specific isoforms produced by the alternative splicing of proteases and their distinctive roles in the tumor microenvironment.

A meta-analysis of caspase-8 -652 6N del polymorphism and digestive tract cancer risk

Caspase-8 (CASP8) is one key regulator of apoptosis of T lymphocytes and is encoded by the CASP8 gene. It has been reported that the six-nucleotide deletion polymorphism (-652 6N del) of the CASP8 gene had effect on some cancer risk. Few studies explored the association between CASP8 gene polymorphism and digestive tract cancer risk. To evaluate the association between the CASP8 -652 6N del polymorphism and the risk of digestive tract cancer, we conducted this meta-analysis. We found that CASP8-652 6N del polymorphism was associated with a significantly reduced risk of digestive tract cancer in the co-dominant model (del/del vs. ins/ins: OR= 0.82, 95%CI= 0.72-0.95; del/ins vs. ins/ins: OR= 0.92, 95%CI= 0.87-0.97; dominant model (del/ins+ del/del vs. ins/ins: OR= 0.91, 95%CI= 0.87-0.96, recessive model: del/del vs. del/ins+ ins/ins: OR= 0.85, 95%CI= 0.75-0.97). In the stratified analysis by cancer types, we found that all genetic models had protective effect on gastric cancer. Similar results were observed for colorectal cancer under heterozygote comparison and dominant model, but not under homozygote comparison or recessive model. In addition, a significantly decreased risk was found on esophageal cancer for most genetic models, except heterozygote comparison. When stratified by ethnicity and source of control, an evidently decreased risk was identified in the Asian populations and population-based studies. In conclusion, there exists an association between the CASP8 -652 6N del polymorphism and reduced digestive cancer risk, especially among Asians and population-based studies.

Genetic polymorphisms and gastric cancer risk: a comprehensive review synopsis from meta-analysis and genome-wide association studies

Objective

In the past few decades, more than 500 reports have been published on the relationship between single nucleotide polymorphisms (SNPs) on candidate genes and gastric cancer (GC) risk. Previous findings have been disputed and are controversial. Therefore, we performed this article to summarize and assess the credibility and strength of genetic polymorphisms on the risk of GC.

Methods

We used Web of Science, PubMed, and Medline to identify meta-analyses published before July 30th, 2018 that assessed associations between variants on candidate genes and the risk of GC. Cumulative epidemiological evidence of statistical associations was assessed combining Venice criteria and a false-positive report probability (FPRP) test.

Results

Sixty-one variants demonstrated a significant association with GC risk, whereas 29 demonstrated no association. Nine variants on nine genes were rated as presenting strong cumulative epidemiological evidence for a nominally significant association with GC risk, including APE1 (rs1760944), DNMT1 (rs16999593), ERCC5 (rs751402), GSTT1 (null/presence), MDM2 (rs2278744), PPARG (rs1801282), TLR4 (rs4986790), IL-17F (rs763780), and CASP8 (rs3834129). Eleven SNPs were rated as moderate, and 33 SNPs were rated as weak. We also used the FPRP test to identify 13 noteworthy SNPs in five genome-wide association studies.

Conclusions

Sixty-one variants are significantly associated with GC risk, and 29 variants are not associated with GC risk; however, five variants on five genes presented strong evidence for an association upgraded from moderate. Further study of these variants may be needed in the future. Our study also provides referenced information for the genetic predisposition to GC.

CASP8 -652 6N insertion/deletion polymorphism and overall cancer risk: evidence from 49 studies

The CASP8 -652 6N insertion/deletion (I/D) polymorphism reduces expression of caspase 8. We conducted a meta-analysis to clarify the relationship between this polymorphism and cancer risk. Eligible articles were retrieved from PubMed, EMBASE, CNKI, and WANFANG databases through February 2017. A total of 33 articles with 49 studies, including 33,494 cases and 36,397 controls, were analyzed. We found that the CASP8 -652 6N ins/del polymorphism was associated with decreased overall cancer risk in five genetic models [DD vs. II: odds ratio (OR)=0.76, 95% confidence interval (CI)=0.69–0.84, ID vs. II: OR=0.87, 95% CI=0.83–0.92, DD vs. ID/II: OR=0.82, 95% CI=0.75–0.89, ID/DD vs. II: OR=0.85, 95% CI=0.80–0.90, and D vs. I: OR=0.87, 95% CI=0.83–0.91]. Stratified analyses showed that the polymorphism was associated with decreased risk of colorectal, breast, esophageal, renal cell, lung, cervical, bladder, gastric, and other cancers. Overall cancer risk was reduced in Asian and Caucasian patients, both hospital- and population-based studies, and both high and low quality studies. Our results highlight the role of the CASP8 -652 6N ins/del polymorphism in decreasing cancer risk. Further studies with large-cohort populations, especially for specific cancer types and ethnic groups, are needed to confirm our findings.

Multifunctional murrel caspase 1, 2, 3, 8 and 9: Conservation, uniqueness and their pathogen-induced expression pattern

Caspases are evolutionarily conserved proteases which play fundamental role in apoptosis. Invasion of pathogen triggers the activation of caspases-mediated pro-inflammatory and pro-apoptotic pathways, where multifunctional caspases are involved. In striped murrel Channa striatus, epizootic ulcerative syndrome (EUS) causes endemics resulting in huge economic loss. Aphanomyces invadans, an oomycete is the primary causative agent of EUS which further induces secondary bacterial infections especially Aeromonas hydrophila. In order to get insights into the caspase gene family in C. striatus during EUS infection, we performed various physicochemical and structural analyses on the cDNA and protein sequences of five different murrel caspases namely CsCasp 1, 2, 3, 8 and 9. Sequence analysis of murrel caspase proteins showed that in spite of the conserved CASC domain, each caspase embraces some unique features which made them functionally different. Tissue distribution analysis showed that all the murrel caspases are highly expressed in one of the immune organs such as liver, kidney, spleen and blood cells. Further, to understand the role of caspase during EUS infection, modulation in expression of each caspase gene was analysed after inducing fungal and bacterial infection in C. striatus. Pathogen-induced gene expression pattern revealed an interesting fact that the expression of all the caspase genes reached a maximum level at 24 h post-infection (p.i) in case of bacteria, whereas it was 48 h in fungus. However, the initiation of elevated expression differed between each caspase based on their role such as pro-inflammatory, initiator and executioner caspase. Overall, the results suggested that the caspases in murrel are diverse in their structure and function. Here, we discuss the similarities and differences of five different murrel caspases.

Caspase-8 polymorphisms and risk of oral squamous cell carcinoma

Caspase-8 (CASP8) is a key controller of apoptosis, and its deregulation is crucially involved in carcinogenesis. The aim of the present study was to evaluate the function of CASP8 polymorphisms in oral squamous carcinoma (OSCC) by evaluating the risk associated with three single-nucleotide polymorphisms (SNPs) in a case-control study in a Han Chinese patient population. A total of 505 individuals with clinically diagnosed OSCC and 507 healthy controls were tested for the three SNPs rs3834129, rs13016963 and rs1045485, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing analysis. After adjusting for other confounders, the genotype frequencies of CASP8 -652 6N ins/del promoter polymorphism (rs3834129) were found to be lower in patients with OSCC compared with normal subjects. No significant difference was detected in the genotype frequencies of rs13016963 between the patients and control subjects. However, the AA genotype frequency of rs1306963 was associated with OSCC as a risk factor among non-smokers and non-drinkers. For CASP8, rs1045485 was not present in any of the patients with OSCC or control subjects. These results suggest that the del allele of rs3834129 may play a protective role in the tumorigenesis of OSCC and may be useful as a genetic susceptibility marker for OSCC in the population studied.

Targeting apoptosis in autoimmune hepatitis

Apoptosis is the predominant mechanism of liver cell death in autoimmune hepatitis, and interventions that can modulate this activity are emerging. The aim of this review was to describe the apoptotic mechanisms, possible aberrations, and opportunities for intervention in autoimmune hepatitis. Studies cited in PubMed from 1972 to 2014 for autoimmune hepatitis, apoptosis in liver disease, apoptosis mechanisms, and apoptosis treatment were examined. Apoptosis is overactive in autoimmune hepatitis, and the principal pathway of cell death is receptor mediated. Surface death receptors are activated by extrinsic factors including liver-infiltrating cytotoxic T cells and the cytokine milieu. The executioner caspases 3 and 7 cleave nuclear deoxyribonucleic acid, and the release of apoptotic bodies can stimulate inflammatory, immune, and fibrotic responses. Changes in mitochondrial membrane permeability can be initiated by caspase 8, and an intrinsic pathway of apoptosis can complement the extrinsic pathway. Defects in the apoptosis of activated effector cells can prolong their survival and sustain the immune response. Caspase inhibitors have been used in diverse experimental and human diseases to retard apoptosis. Oligonucleotides that inhibit the signaling of toll-like receptors can limit the presentation of auto-antigens, and inhibitors of apoptosis that extend the survival of effector cells can be blocked by antisense oligonucleotides. Mechanisms that enhance the clearance of apoptotic bodies and affect key signaling pathways are also feasible. Interventions that influence the survival of liver and effector cells by altering their apoptosis are candidates for study in autoimmune hepatitis.

CASP8 -652 6N del polymorphism contributes to colorectal cancer susceptibility: evidence from a meta-analysis

Objective

Caspase-8 (CASP8) plays a central role in the apoptotic pathway and aberrant regulation of this pathway may cause cancers. Previous studies investigating the association between CASP8 -652 6N ins/del polymorphism and colorectal cancer (CRC) risk showed inconclusive results. We performed a meta-analysis of all available studies to investigate this association.

Methods

All studies published up to October 2013 on the association between CASP8 -652 6N ins/del polymorphism and CRC risk were identified by searching electronic databases PubMed, EMBASE, and Cochrane library. The association between CASP8 -652 6N ins/del polymorphism and CRC risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

Results

Six studies with 6,325 cases and 6,842 controls were included in the meta-analysis. We observed that the CASP8 -652 6N ins/del polymorphism was significantly correlated with CRC risk when all studies were pooled into the meta-analysis (ins/del vs. ins/ins: OR = 0.890, 95%CI 0.821–0.964, P = 0.004; del/del + ins/del vs. ins/ins: OR = 0.899, 95%CI 0.833–0.970, P = 0.006). In stratified analyses by ethnicity, source of control, and quality score, significant association was observed in Asians (ins/del vs. ins/ins: OR = 0.862, 95%CI 0.761–0.977, P = 0.020; del/del + ins/del vs. ins/ins: OR = 0.845, 95%CI 0.749–0.953, P = 0.006), population-based studies (ins/del vs. ins/ins: OR = 0.890, 95%CI 0.813–0.975, P = 0.012; del/del + ins/del vs. ins/ins: OR = 0.901, 95%CI 0.827–0.982, P = 0.018), and high quality studies. However, in subgroup analysis according to cancer location, no significant association was detected.

Conclusions

The present meta-analysis suggests that the CASP8 is a candidate gene for CRC susceptibility. The CASP8 -652 6N ins/del polymorphism may play a protective role in CRC development especially among Asians. Further large and well-designed studies are needed to confirm this association.

Downregulation of caspase-10 predicting poor survival after resection of stage II colorectal cancer

PURPOSE

The aim of this study was to evaluate the prevalence and clinical significance of caspase-10 mRNA expression in stage II colorectal cancer.

METHODS

Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze caspase-10 expression in cancer tissue and corresponding normal mucosa from 120 patients with stage II colorectal cancer. Variables were analyzed by Chi-square test or Fisher's exact test. Survival was evaluated with method of Kaplan-Meier. Multivariate analysis was performed with Cox's proportional hazards model.

RESULTS

The expression of caspase-10 mRNA was found to be downregulated in cancer tissue compared to normal mucosa (P = 0.001). Poorly differentiated cancer showed lower mRNA expression than cancer with greater differentiation (P = 0.031). Univariate survival curves, estimated using the method of Kaplan-Meier, defined a significant association between caspase-10 expression and both overall survival (P = 0.012) and disease-free survival (P = 0.021). A multivariate analysis, performed by Cox's proportional hazards regression model, confirmed that a low caspase-10 expression was the only significant factor to predict poor prognosis in patients with stage II colorectal cancer.

CONCLUSION

Our data indicate that caspase-10 expression, measured by quantitative real-time RT-PCR, is a possible prognostic factor in patients with stage II colorectal cancer.

The connections between neural crest development and neuroblastoma

Neuroblastoma (NB), the most common extracranial solid tumor in childhood, is an extremely heterogeneous disease both biologically and clinically. Although significant progress has been made in identifying molecular and genetic markers for NB, this disease remains an enigmatic challenge. Since NB is thought to be an embryonal tumor that is derived from precursor cells of the peripheral (sympathetic) nervous system, understanding the development of normal sympathetic nervous system may highlight abnormal events that contribute to NB initiation. Therefore, this review focuses on the development of the peripheral trunk neural crest, the current understanding of how developmental factors may contribute to NB and on recent advances in the identification of important genetic lesions and signaling pathways involved in NB tumorigenesis and metastasis. Finally, we discuss how future advances in identification of molecular alterations in NB may lead to more effective, less toxic therapies, and improve the prognosis for NB patients.

Individual caspase-10 isoforms play distinct and opposing roles in the initiation of death receptor-mediated tumour cell apoptosis

The cysteine protease caspase-8 is an essential executioner of the death receptor (DR) apoptotic pathway. The physiological function of its homologue caspase-10 remains poorly understood, and the ability of caspase-10 to substitute for caspase-8 in the DR apoptotic pathway is still controversial. Here, we analysed the particular contribution of caspase-10 isoforms to DR-mediated apoptosis in neuroblastoma (NB) cells characterised by their resistance to DR signalling. Silencing of caspase-8 in tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-sensitive NB cells resulted in complete resistance to TRAIL, which could be reverted by overexpression of caspase-10A or -10D. Overexpression experiments in various caspase-8-expressing tumour cells also demonstrated that caspase-10A and -10D isoforms strongly increased TRAIL and FasL sensitivity, whereas caspase-10B or -10G had no effect or were weakly anti-apoptotic. Further investigations revealed that the unique C-terminal end of caspase-10B was responsible for its degradation by the ubiquitin-proteasome pathway and for its lack of pro-apoptotic activity compared with caspase-10A and -10D. These data highlight in several tumour cell types, a differential pro- or anti-apoptotic role for the distinct caspase-10 isoforms in DR signalling, which may be relevant for fine tuning of apoptosis initiation.

The enigmatic roles of caspases in tumor development

One function ascribed to apoptosis is the suicidal destruction of potentially harmful cells, such as cancerous cells. Hence, their growth depends on evasion of apoptosis, which is considered as one of the hallmarks of cancer. Apoptosis is ultimately carried out by the sequential activation of initiator and executioner caspases, which constitute a family of intracellular proteases involved in dismantling the cell in an ordered fashion. In cancer, therefore, one would anticipate caspases to be frequently rendered inactive, either by gene silencing or by somatic mutations. From clinical data, however, there is little evidence that caspase genes are impaired in cancer. Executioner caspases have only rarely been found mutated or silenced, and also initiator caspases are only affected in particular types of cancer. There is experimental evidence from transgenic mice that certain initiator caspases, such as caspase-8 and -2, might act as tumor suppressors. Loss of the initiator caspase of the intrinsic apoptotic pathway, caspase-9, however, did not promote cellular transformation. These data seem to question a general tumor-suppressive role of caspases. We discuss several possible ways how tumor cells might evade the need for alterations of caspase genes. First, alternative splicing in tumor cells might generate caspase variants that counteract apoptosis. Second, in tumor cells caspases might be kept in check by cellular caspase inhibitors such as c-FLIP or XIAP. Third, pathways upstream of caspase activation might be disrupted in tumor cells. Finally, caspase-independent cell death mechanisms might abrogate the selection pressure for caspase inactivation during tumor development. These scenarios, however, are hardly compatible with the considerable frequency of spontaneous apoptosis occurring in several cancer types. Therefore, alternative concepts might come into play, such as compensatory proliferation. Herein, apoptosis and/or non-apoptotic functions of caspases may even promote tumor development. Moreover, experimental evidence suggests that caspases might play non-apoptotic roles in processes that are crucial for tumorigenesis, such as cell proliferation, migration, or invasion. We thus propose a model wherein caspases are preserved in tumor cells due to their functional contributions to development and progression of tumors.

Activation and specificity of human caspase-10

Two apical caspases, caspase-8 and -10, are involved in the extrinsic death receptor pathway in humans, but it is mainly caspase-8 in its apoptotic and nonapoptotic functions that has been an intense research focus. In this study we concentrate on caspase-10, its mechanism of activation, and the role of the intersubunit cleavage. Our data obtained through in vitro dimerization assays strongly suggest that caspase-10 follows the proximity-induced dimerization model for apical caspases. Furthermore, we compare the specificity and activity of the wild-type protease with a mutant incapable of autoprocessing by using positional scanning substrate analysis and cleavage of natural protein substrates. These experiments reveal a striking difference between the wild type and the mutant, leading us to hypothesize that the single chain enzyme has restricted activity on most proteins but high activity on the proapoptotic protein Bid, potentially supporting a prodeath role for both cleaved and uncleaved caspase-10.

Molecular cloning of sea bass (Dicentrarchus labrax L.) caspase-8 gene and its involvement in Photobacterium damselae ssp. piscicida triggered apoptosis

Caspase-8 is an initiator caspase that plays a crucial role in some cases of apoptosis by extrinsic and intrinsic pathways. Caspase-8 structure and function have been extensively studied in mammals, but in fish the characterization of that initiator caspase is still scarce. In this work, the sea bass counterpart of mammalian caspase-8 was sequenced and characterized, and its involvement in the apoptogenic activity of a toxin from a fish pathogen was assessed. A 2472 bp cDNA of sea bass caspase-8 was obtained, consisting of 1455 bp open reading frame coding for 484 amino acids and with a predicted molecular weight of 55.2 kDa. The sea bass caspase-8 gene has 6639 bp and is organized in 11 introns and 12 exons. Several distinctive features of sea bass caspase-8 were identified, which include two death effector domains, the caspase family domains p20 and p10, the caspase-8 active-site pentapeptide and potential aspartic acid cleavage sites. The sea bass caspase-8 sequence revealed a significant degree of similarity to corresponding sequences from several vertebrate taxonomic groups. A low expression of sea bass caspase-8 was detected in various tissues of non-stimulated sea bass. Furthermore, it is shown that stimulation of sea bass with mid-exponential phase culture supernatants from Photobacterium damselae ssp. piscicida (Phdp), known to induce selective apoptosis of macrophages and neutrophils, resulted in an increased expression of caspase-8 in the spleen, one of the main affected organs by Phdp infection.

CASP8 polymorphisms contribute to cancer susceptibility: evidence from a meta-analysis of 23 publications with 55 individual studies

Several potentially functional polymorphisms of CASP8 encoding an apoptotic enzyme, caspase 8, have been implicated in cancer risk, but individually published studies showed inconclusive results. We performed a meta-analysis of 23 publications with a total of 55 174 cancer cases and 59 336 controls from 55 individual studies. We summarized the data on the associations between three studied CASP8 polymorphisms (G>C D302H, -652 6N del and Ex14-271A>T) and cancer risk and performed subgroup analysis by ethnicity, cancer type, study design and etiology. We found that D302H CC and CG variant genotypes were associated with significantly reduced overall risk of cancers using conservative random genetic models [homozygote comparison: odds ratios (OR) = 0.79; 95% confidence interval (CI): 0.69-0.92; dominant comparison: OR = 0.93, 95% CI: 0.89-0.98; recessive comparison: OR = 0.81, 95% CI: 0.71-0.93). In further stratified analyses, the reduced cancer risk remained for subgroups of Caucasians, breast or estrogen-related cancers, and hospital- or population-based studies, except for an elevated risk for brain tumors. Similarly, the -652 6N del polymorphism was also associated with significantly reduced overall risk of cancers (homozygote comparison: OR = 0.84, 95% CI: 0.75-0.94; dominant comparison: OR = 0.88, 95% CI: 0.81-0.96; recessive comparison: OR = 0.90, 95% CI: 0.82-0.99) and all subgroups analyzed. However, the Ex14-271A>T polymorphism did not appear to have an effect on cancer risk. These results suggest that CASP8 D302H and -652 6N del polymorphisms are potential biomarkers for cancer risk.

Rubella vaccine-induced cellular immunity: evidence of associations with polymorphisms in the Toll-like, vitamin A and D receptors, and innate immune response genes

Toll-like, vitamin A and D receptors and other innate proteins participate in various immune functions. We determined whether innate gene-sequence variations are associated with rubella vaccine-induced cytokine immune responses. We genotyped 714 healthy children (11-19 years of age) after two doses of rubella-containing vaccine for 148 candidate SNP markers. Rubella virus-induced cytokines were measured by ELISA. Twenty-two significant associations (range of P values 0.002-0.048) were found between SNPs in the vitamin A receptor family (RARA, RARB, TOP2B and RARG), vitamin D receptor and downstream mediator of vitamin D signaling (RXRA) genes and rubella virus-specific (IFN-gamma, IL-2, IL-10, TNF-alpha, and GM-CSF) cytokine immune responses. A TLR3 gene promoter region SNP (rs5743305, -8441A > T) was associated with rubella-specific GM-CSF secretion. Importantly, SNPs in the TRIM5 gene coding regions, rs3740996 (His43Tyr) and rs10838525 (Gln136Arg), were associated with an allele dose-related secretion of rubella virus-specific TNF-alpha and IL-2/GM-CSF, respectively, and have been previously shown to have functional consequences regarding the antiviral activity and susceptibility to HIV-1 infection. We identified associations between individual SNPs and haplotypes in, or involving, the RIG-I (DDX58) gene and rubella-specific TNF-alpha secretion. This is the first paper to present evidence that polymorphisms in the TLR, vitamin A, vitamin D receptor, and innate immunity genes can influence adaptive cytokine responses to rubella vaccination.

A new caspase-8 isoform caspase-8s increased sensitivity to apoptosis in Jurkat cells

Caspase-8 is a key initiator of death receptor-induced apoptosis. Here we report a novel short isoform of caspase-8 (caspase-8s), which encodes the first (Death Effector Domain) DED and part of the second DED, missing the C-terminal caspase domain. In vivo binding assays showed that transfected caspase-8s bound to (Fas-associated death domain protein) FADD, the adaptor protein in (death-induced signal complex) DISC. To investigate the potential effects of caspase-8s on cell apoptosis, Jurkat cells were stably transfected with caspase-8s. Overexpression of caspase-8s increased sensitivity to the apoptotic stimuli, Fas-agonistic antibody CH11. These results suggest that caspase-8s may act as a promoter of apoptosis through binding to FADD and is involved in the regulation of apoptosis. In addition, the results also indicate that the first DED was an important structure mediating combination between caspase-8 and FADD.

The six-nucleotide deletion/insertion variant in the CASP8 promoter region is inversely associated with risk of squamous cell carcinoma of the head and neck

Caspase 8 (CASP8) is an apoptosis-related cysteine peptidase involved in the death receptor pathway and likely in the mitochondrial pathway. A CASP8 promoter region six-nucleotide deletion/insertion (-652 6N ins/del) variant and a coding region D302H polymorphism are reportedly important in cancer development, but no reported study has assessed the associations of these genetic variations with risk of head and neck cancer. In a hospital-based study of non-Hispanic whites, we genotyped CASP8 -652 6N del and 302H variants in 1,023 patients with squamous cell carcinoma of the head and neck (SCCHN) and 1,052 cancer-free controls. Crude and adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using unconditional logistic regression models. The CASP8 -652 6N del variant genotypes or haplotypes were inversely associated with SCCHN risk (adjusted OR, 0.70; 95% CI, 0.57-0.85 for the ins/del + del/del genotypes compared with the ins/ins genotype; adjusted OR, 0.73; 95% CI, 0.55-0.97 for the del-D haplotype compared with the ins-D haplotype). Furthermore, the number of the CASP8 -652 6N del (but not 302H) variant allele tended to correlate with increased levels of camptothecin-induced p53-mediated apoptosis in T lymphocytes from 170 cancer-free controls. We concluded that the CASP8 -652 6N del variant allele may contribute to the risk of developing SCCHN in non-Hispanic white populations. Further validation by population-based case-control studies and rigorous mechanistic studies is warranted.

Alternative Fas-mediated cell death pathway is dependent on the different cleavage patterns of procaspase-8

It has been reported that mitochondria-independent or mitochondria-dependent (type I/II) Fas signaling pathways in leukemia cells depend on the amount of active caspase-8. However, Bid molecules, which could not be cleaved in type I cells, could be effectively cleaved by recombinant active caspase-8 in vitro. The cleavage of recombinant Bid by recombinant active caspase-8 could be blocked by anti-p10 and anti-p18 specific antibodies. Fas receptors could be similarly internalized into cytoplasm in type I and type II cells. Interestingly, p10 subunit of active caspase-8 could be detected in both type I and II cells, while p18 subunit of active caspase-8 could be detected only in type II cells but not in type I cells. These results demonstrated that p18 subunit was necessary for Bid cleavage and the mitochondria pathway might be dependent on the release of p18 subunit from active caspase-8.

Genetic variants and haplotypes of the caspase-8 and caspase-10 genes contribute to susceptibility to cutaneous melanoma

Caspase-8 (CASP8) and caspase-10 (CASP10) play key roles in regulating apoptosis, and their functional polymorphisms may alter apoptosis and cancer risk. However, no reported studies have investigated the association between such polymorphisms and the risk of cutaneous melanoma (CM). In a hospital-based study of 805 non-Hispanic white patients with CM and 835 cancer-free age-, sex-, and ethnicity-matched controls, we genotyped three reported putatively functional polymorphisms of CASP8 and CASP10-CASP8 D302 H (rs1045485:G>C), CASP8 -652 6N del (rs3834129:-/CTTACT), and CASP10 I522L (rs13006529:A>T)-and assessed their associations with risk of CM and interactions with known risk factors for CM. We also calculated the false-positive report probability (FPRP) for significant findings. CASP8 302 H variant genotypes (DH: adjusted odds ratio [OR], 0.70; 95% confidence interval [CI], 0.50-0.98; DH+HH: unadjusted OR, 0.78; 95% CI, 0.62-0.98; FPRP, 0.79) and CASP8 -652 6N del variant genotypes (ins/del: OR, 0.74; 95% CI, 0.57-0.97; ins/del+del/del: OR, 0.76; 95% CI, 0.61-0.95; FPRP, 0.61) were associated with significantly lower CM risk than were the DD and ins/ins genotypes, respectively. However, the CASP10 522L variant genotypes were not associated with significantly altered CM risk. Also, the D-del-I haplotype was associated with a significantly lower CM risk (OR, 0.52; 95% CI, 0.37-0.74; FPRP, 0.04) than was the most common haplotype, D-ins-I. Furthermore, multivariate logistic regression analysis revealed that CASP8 D302 H, CASP8 -652 6N del, and CASP10 I522L were independent risk factors for CM. Therefore, these CASP8 and CASP10 polymorphisms may be biomarkers for susceptibility to CM.

Association between CTLA-4 gene promoter (49 A/G) in exon 1 polymorphisms and inflammatory bowel disease in the Tunisian population

BACKGROUND/AIM

To investigate the possible association between the polymorphism of the CTLA-4 exon 1 +49 A/G and susceptibility to Crohn's disease (CD) and ulcerative colitis (UC) in the Tunisian population.

METHODS

The +49 A/G dimorphism was analyzed in 119 patients with CD, 65 patients with UC, and 100 controls by the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

Significantly higher frequencies of the CTLA-4 +49A allele and A/A homozygous individuals were observed in patients with CD when compared with controls (pc = 0.0023 and pc = 0.0003, respectively). Analysis of CTLA-4 A/G polymorphism with respect to sex in CD showed a significant difference in A/A genotypes between female patients and controls (pc = 0.0001 and pc = 0.038, respectively). There were no differences in the subgroups of patients with CD.

CONCLUSIONS

Forty-nine A alleles and AA genotype are associated with CD susceptibility in Tunisians. Other genes involved in the T-cell regulation remain strong candidates for IBD susceptibility and require further investigation.

Genetic susceptibility to cancer: the role of polymorphisms in candidate genes

CONTEXT

Continuing advances in genotyping technologies and the inclusion of DNA collection in observational studies have resulted in an increasing number of genetic association studies.

OBJECTIVE

To evaluate the overall progress and contribution of candidate gene association studies to current understanding of the genetic susceptibility to cancer.

DATA SOURCES

We systematically examined the results of meta-analyses and pooled analyses for genetic polymorphisms and cancer risk published through March 2008.

STUDY SELECTION

We identified 161 meta-analyses and pooled analyses, encompassing 18 cancer sites and 99 genes. Analyses had to meet the following criteria: include at least 500 cases, have cancer risk as outcome, not be focused on HLA antigen genetic markers, and be published in English.

DATA EXTRACTION

Information on cancer site, gene name, variant, point estimate and 95% confidence interval (CI), allelic frequency, number of studies and cases, tests of study heterogeneity, and publication bias were extracted by 1 investigator and reviewed by other investigators.

RESULTS

These 161 analyses evaluated 344 gene-variant cancer associations and included on average 7.3 studies and 3551 cases (range, 508-19 729 cases) per investigated association. The summary odds ratio (OR) for 98 (28%) statistically significant associations (P value <.05) were further evaluated by estimating the false-positive report probability (FPRP) at a given prior probability and statistical power. At a prior probability level of 0.001 and statistical power to detect an OR of 1.5, 13 gene-variant cancer associations remained noteworthy (FPRP <0.2). Assuming a very low prior probability of 0.000001, similar to a probability assumed for a randomly selected single-nucleotide polymorphism in a genome-wide association study, and statistical power to detect an OR of 1.5, 4 associations were considered noteworthy as denoted by an FPRP value <0.2: GSTM1 null and bladder cancer (OR, 1.5; 95% CI, 1.3-1.6; P = 1.9 x 10(-14)), NAT2 slow acetylator and bladder cancer (OR, 1.46; 95% CI, 1.26-1.68; P = 2.5 x 10(-7)), MTHFR C677T and gastric cancer (OR, 1.52; 95% CI, 1.31-1.77; P = 4.9 x 10(-8)), and GSTM1 null and acute leukemia (OR, 1.20; 95% CI, 1.14-1.25; P = 8.6 x 10(-15)). When the OR used to determine statistical power was lowered to 1.2, 2 of the 4 noteworthy associations remained so: GSTM1 null with bladder cancer and acute leukemia.

CONCLUSION

In this review of candidate gene association studies, nearly one-third of gene-variant cancer associations were statistically significant, with variants in genes encoding for metabolizing enzymes among the most consistent and highly significant associations.

CASP8 polymorphisms, estrogen and progesterone receptor status, and breast cancer risk

OBJECTIVES

This study was conducted to evaluate the potential role of CASP8 genetic polymorphisms in the etiology of breast cancer in a case-control study, Korea.

METHODS

Incident breast cancer cases confirmed histologically (n = 1,599) were recruited from two hospitals in Seoul during 2001-2005. Control subjects (n = 1,536) were selected from the Health Examinee Cohort from Seoul and Gyeonggi Province surrounding Seoul, Korea. Three SNPs (D302H D > H, 5'-UTR C > T, and K337K G > A) were genotyped by the primer extension assay. The CASP8 D302H, which was not polymorphic in 48 samples, was excluded in further genotyping. Odds ratios and 95% confidential intervals (95% CIs) were estimated by unconditional logistic regression model adjusted for age at enrollment, education, age at first full-term pregnancy, cigarette smoking, and family history of breast cancer.

RESULTS

The 5'-UTR T allele containing genotypes (CT/TT) were associated with an increased risk of breast cancer, compared with those with the CC genotype (OR = 1.13, 95% CI = 0.95-1.34; and OR = 1.48, 95% CI = 1.04-2.10, respectively; P-trend = 0.02). When stratified by the estrogen and progesterone receptor status, the association between the 5'-UTR T allele and breast cancer risk was prominent in ER(+) and PR(+) cases among pre-menopausal women (OR = 1.31, 95% CI = 1.00-1.72 and OR = 1.40, 95% CI = 1.06-1.85, respectively), whereas the association was found prominent in ER(-) or PR(-) cases (OR = 1.32, 95% CI = 0.93-1.87 and OR = 1.42, 95% CI = 1.04-1.94, respectively) among post-menopausal women.

CONCLUSION

Our results thus suggest that the CASP8 5'-UTR C > T are associated with breast cancer risks and the effect may be modified by estrogen and progesterone receptor status.

The evolutionary conservation of the core components necessary for the extrinsic apoptotic signaling pathway, in Medaka fish

Background

Death receptors on the cell surface and the interacting cytosolic molecules, adaptors and initiator caspases, are essential as core components of the extrinsic apoptotic signaling pathway. While the apoptotic machinery governing the extrinsic signaling pathway is well characterized in mammals, it is not fully understood in fish.

Results

We identified and characterized orthologs of mammalian Fas, FADD and caspase-8 that correspond to the death receptor, adaptor and initiator caspase, from the Medaka fish (Oryzias latipes). Medaka Fas, caspase-8 and FADD exhibited protein structures similar to that of their mammalian counterparts, containing a death domain (DD), a death effector domain (DED) or both. Functional analyses indicated that these molecules possess killing activity in mammalian cell lines upon overexpression or following activation by apoptotic stimuli, suggesting similar pro-apoptotic functions in the extrinsic pathway as those in mammals. Genomic sequence analysis revealed that the Medaka fas (tnfrsf6), fadd and caspase-8 (casp8) genes are organized in a similar genomic structure as the mammalian genes. Database search and phylogenetic analysis revealed that the fas gene, but not the fadd and casp8 genes, appear to be present only in vertebrates.

Conclusion

Our results indicate that the core components necessary for the extrinsic apoptotic pathway are evolutionarily conserved in function and structure across vertebrate species. Based on these results, we presume the mechanism of apoptosis induction via death receptors was evolutionarily established during the appearance of vertebrates.

Nitric oxide differentially regulates the gene expression of caspase genes but not some autophagic genes

Nitric oxide (NO) is fundamentally important molecule which produces a wide range of cellular effects with the most poorly understood one being alteration in the sensitivity to cell death. The objective of this study was to test the hypothesis that NO would differentially affect caspase or autophagy gene expression in a manner that might account for the disparate actions of NO to either enhance or protect against cell death. Neonatal mouse cardiomyocytes in culture were treated with the NO donor SIN-1 (3-morpholinosydnonimine hydrochloride) for up to 20 h. RNA was collected, after either 2, 4 or 20 h, labeled and hybridized to cDNA microarray slides The concentration of SIN-1 was selected after concentration response studies of SIN-1 on cell viability, assessed by the MTT assay. The cDNA microarrays were used that contained the mouse genome version 2.0 with genes for enzymes crucial to apoptosis, namely caspases-1, -2, -3, -6, -7, -8, -9, -11, -12 and -14, as well as for enzymes crucial to autophagy namely beclin-1, Apg5l and Apg12l. Considering the entire 20 h period, treatment with SIN-1 was associated with significant (p<0.05) changes in five caspases. In contrast, there were no changes in the three separate genes involved in autophagy. Time course experiments showed a consistent increase in caspase-8, -11 and -14, and a consistent decrease in caspase-1 and -6. Notably, caspase-1 showed a persistent and marked reduction so that after 20 h of treatment, caspase-1 was dramatically reduced, almost ten fold, to 0.14+/-0.11 of control. In conclusion, these results suggest that: (i) NO regulates the expression of genes involved in apoptotic but not some involved in autophagic cell death; (ii) the more recently discovered caspase-14 may have a role in the heart; (iii) NO-induced alteration of different caspases may explain the ability of NO to either enhance or protect against cell death depending on whether associated factors involve, respectively caspases-8, -11, and -14 or -1 and -6.

The initiator caspase, caspase-10β, and the BH-3-only molecule, Bid, demonstrate evolutionary conservation inXenopusof their pro-apoptotic activities in the extrinsic and intrinsic pathways

Two major apoptotic signaling pathways have been defined in mammals, the extrinsic pathway, initiated by ligation of death receptors, and the intrinsic pathway, triggered by cytochrome c release from mitochondria. Here, we identified and characterized the Xenopus homologs of caspase-10 (xCaspase-10beta), a novel initiator caspase, and Bid (xBid), a BH3-only molecule of the Bcl-2 family involved in both the extrinsic and intrinsic pathways. Exogenous expression of these molecules induced apoptosis of mammalian cells. By biochemical and cytological analyses, we clarified that xCaspase-10beta and xBid exhibit structural and functional similarities to their mammalian orthologues. We also detected xCaspase-10beta and xBid transcripts during embryogenesis by whole-mount in situ hybridization and RT-PCR analysis. Microinjection of mRNA encoding a protease-defect xCaspase-10beta mutant into embryos resulted in irregular development. Enforced expression of active xBid induced cell death in developing embryos. Using transgenic frogs established to allow monitoring of caspase activation in vivo, we confirmed that this form of cell death is caspase-dependent apoptosis. Thus, we demonstrated that the machinery governing the extrinsic and intrinsic apoptotic pathways are already established in Xenopus embryos. Additionally, we propose that the functions of the initiator caspase and BH3-only molecule are evolutionarily conserved in vertebrates, functioning during embryonic development.

Caspase 8 is absent or low in many ex vivo gliomas

BACKGROUND

Better treatments are required urgently for patients with malignant glioma, which currently is incurable. Death ligands, such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), may offer promise for the treatment high-grade glioma if such ligands induce apoptotic signaling in vivo in glioma cells. Caspase 8 is required for death ligand signaling, and its levels may influence the sensitivity of glioma cells to death ligands. It also may act as a tumor suppressor protein. The authors analyzed caspase 8 expression levels in ex vivo glioma specimens and explored potential mechanisms of its regulation.

METHODS

Eleven glioblastomas, 5 anaplastic astrocytomas, and 3 low-grade astrocytomas were studied. The levels of caspase 8, caspase 10, cellular FLICE inhibitory protein (c-FLIP), and signal transducer and activator of transcription (STAT)-1 were assayed using quantitative immunoblotting. Caspase 8 mRNA was measured by Northern blot analysis. The methylation status of the caspase 8 gene was determined by bisulfate modification of genomic DNA, cloning, and sequencing. Statistical analyses were performed using nonparametric (Spearman) correlations.

RESULTS

Some ex vivo glioma samples lacked detectable caspase 8, with many expressing barely detectable levels. No tumors expressed significant amounts of caspase 10 or c-FLIP. A strong association was found between caspase 8 mRNA and protein levels. Neither expression of the transcription factor STAT-1 nor caspase 8 gene methylation correlated with caspase 8 levels.

CONCLUSIONS

The absence of caspase 8 protein in many resected glioma samples implied that many patients with glioma may not benefit from death ligand-based treatments, unless caspase 8 (or caspase 10) protein expression can be elevated. Demethylating agents are unlikely to boost caspase 8 levels in glioma cells, but treatments that increase caspase 8 mRNA levels may up-regulate expression of the protein.

Development of autoimmune arthritis with aging via bystander T cell activation in the mouse model of Sjögren's syndrome

OBJECTIVE

A wide spectrum of extraglandular manifestations may occur in patients with Sjogren's syndrome (SS), but the mechanisms responsible for in vivo progression are still obscure. We undertook this study to evaluate the age-related changes during the development of extraglandular autoimmune lesions, including arthritis, in the murine model of primary SS, and to evaluate the possible relationship between age-related disturbance of activation-induced cell death and the in vivo kinetics against autoantigens.

METHODS

A total of 126 NFS/sld mice were investigated at ages 2, 4, 6, 10, 12, 18, 20, and 24 months. Cytokine production was tested using culture supernatants from anti-CD3 monoclonal antibody-stimulated T cells. Anti-single-stranded DNA (anti-ssDNA) antibodies, Ig isotypes (IgG1, IgG2a), rheumatoid factor (RF), and anti-type II collagen (anti-CII) antibodies were detected by enzyme-linked immunosorbent assay. Proliferative T cell responses against each of 3 recombinant alpha-fodrin proteins and against CII were analyzed.

RESULTS

Autoimmune arthritis developed in SS model mice until age 24 months. Significant elevations in serum levels of RF, anti-ssDNA antibodies, and anti-CII antibodies were found in aging SS model mice. A high titer of serum autoantibodies against alpha-fodrin fragments (containing different epitopes that were originally identified in primary SS model mice) was frequently detected in young and aged SS model mice. Moreover, we found that alpha-fodrin autoantigen induced Th1 immune responses and accelerated disturbance of Fas-mediated T cell apoptosis in aged SS model mice.

CONCLUSION

These results indicate that age-related disturbance of activation-induced cell death via bystander T cell activation may play a crucial role in the development of autoimmune arthritis in a murine model of SS.

Promoter methylation pattern of caspase-8, P16INK4A, MGMT, TIMP-3, and E-cadherin in medulloblastoma

Methylation of promoter regions of CpG-rich sites is an important mechanism for silencing of tumor suppressor genes (TSG). To evaluate the role of tumor suppressor genes caspase-8 (CASP8), TIMP-3, E-cadherin (CDH1), p16INK4A, and MGMT in medulloblastoma tumorigenesis, 51 medulloblastomas (46 primary tumor specimens, 5 cell lines) were screened for methylation of promoter linked CpG-islands. For CASP8, we examined the 5' UTR region that has been shown to be associated with expression of CASP8. As detected by methylation specific PCR, methylation rate was low for TIMP-3 (3% of tumor samples; 1/5 cell lines), for MGMT (0% of tumor samples; 1/5 cell lines), for p16INK4A (2% of tumor samples; 2/5 cell lines) and for CDH1 (8% of tumor samples; 1/4 cell lines). CASP8, however, was methylated in 90% of tumor samples and 4/5 cell lines examined. Screening other tumor entities for CASP8 methylation, we found a similarly high level in 6 neuroblastoma cell lines in contrast to 5 osteosarcoma-, 4 Ewing's sarcoma- and 6 non-embryonic tumor cell lines without any increased promoter methylation. From our results we conclude that methylation of the CASP8 5' UTR region may play a role in inactivation of CASP8 in neural crest tumors.

The up-regulation of human caspase-8 by interferon-gamma in breast tumor cells requires the induction and action of the transcription factor interferon regulatory factor-1

Treatment of human breast tumor cells with interferon-gamma (IFN-gamma) elevates caspase-8 expression and sensitizes these cells to death receptor-mediated apoptosis through the increased processing and activation of apical procaspase-8. We have characterized the human caspase-8 gene promoter and studied the transcriptional regulation of caspase-8 gene expression in MCF-7 breast tumor cells treated with IFN-gamma. Our findings show that IFN-gamma induces the up-regulation of caspase-8 mRNA expression through a protein synthesis-dependent mechanism involving the action of the IFN-gamma-inducible transcription factor interferon regulatory factor-1 (IRF-1) and without altering mRNA stability. The human caspase-8 gene promoter lacks recognizable TATA and CAAT boxes but contains a consensus Sp1 binding site. We have identified two major IFN-gamma-inducible transcriptional start sites in these cells by S1 nuclease mapping, confirmed by primer extension analysis. Deletion analysis of the promoter defined an 82-bp minimal region responsible for IFN-gamma-inducible promoter activity. In this region, we have identified an IFN-stimulated response element that is important for both the basal and IFN-gamma-enhanced transcriptional activities. Electrophoretic mobility shift assay analysis demonstrated that IFN-gamma induces a complex between an oligonucleotide probe containing the ISRE motif and IRF-1 over a similar time scale to the induction of caspase-8 mRNA. Exogenously expressed IRF-1 in MCF-7 cells up-regulated the activity of a luciferase reporter plasmid containing an 82-bp region of the caspase-8 promoter. These data define a new pathway through which IFN-gamma might control the sensitivity of tumor cell to death receptor-mediated apoptosis.

Inactivating mutations of caspase-8 gene in colorectal carcinomas

BACKGROUND & AIMS

There has been evidence that dysregulation of apoptosis is involved in the pathogenesis of cancer development. Caspase-8 is an initiation caspase that activates the caspase cascade during apoptosis. The aim of this study was to explore the possibility that mutation of the caspase-8 gene might be involved in the development of colorectal cancer.

METHODS

We analyzed the entire coding region of the caspase-8 gene for the detection of somatic mutations in 180 colorectal tumors (98 invasive carcinomas and 82 adenomas) by polymerase chain reaction, single-strand conformation polymorphism, and DNA sequencing.

RESULTS

Overall, we detected a total of 5 somatic mutations in 98 invasive carcinomas (5.1%), but no mutations were detected in 82 adenomas (0%). The frequency of caspase-8 mutation in the carcinomas was significantly higher than that in adenomas (P < 0.05). The 5 mutations consisted of 1 frameshift, 1 nonsense mutation, and 3 missense mutations. We expressed the 5 tumor-derived caspase-8 mutants and found that 3 of the 5 mutations markedly decreased apoptosis activity of caspase-8. Furthermore, expression of the inactivating caspase-8 mutants interfered with apoptosis by death receptor overexpression, indicating that these mutants have dominant-negative inhibition of the death receptor-induced apoptosis.

CONCLUSIONS

The presence of caspase-8 mutation in colon carcinomas suggests that caspase-8 gene mutation might lead to the loss of its apoptotic function and contribute to the pathogenesis of colorectal carcinomas, especially at the late stage of colorectal carcinogenesis.

The human caspase-8 promoter sustains basal activity through SP1 and ETS-like transcription factors and can be up-regulated by a p53-dependent mechanism

Caspase-8, also known as MACH/FLICE/Mch5, is the most upstream-located cysteine-aspartyl-protease (caspase) in a caspase cascade involved in apoptosis triggered by members of the tumor necrosis factor receptor superfamily or other stimuli such as chemotherapeutic agents. Regulation of caspase-8 expression on a post-translational level has been studied in detail, whereas only little information is available on its control by gene transcription. We identified and cloned the human caspase-8 promoter, determined the transcriptional start site of the caspase-8 gene, and examined the regulatory mechanisms of the promoter with respect to its basal activity as well as to its inducibility upon apoptotic stimuli in human hepatoma cells. We identified two minimal sequences essential for basal transcription of caspase-8 and demonstrate that a single SP1 and an ETS-like binding motif mediate this effect. We further show that the caspase-8 promoter is inducible and demonstrate that adenoviral infection increases caspase-8 mRNA levels. However, the increase in caspase-8 gene transcription after adenoviral infection absolutely depends on the p53 status of the hepatoma cell line, implying that caspase-8 is a target gene of p53. We show that delivery of exogenous p53 alone is sufficient to induce the caspase-8 promoter even in p53-deficient Hep3B hepatoma cells. Subsequent promoter deletion analysis in combination with luciferase reporter assays identified a p53-responsive element downstream of the transcriptional start site. We demonstrate that this p53-responsive sequence overlaps with the ETS-like binding site and suggest that an additional p53-inducible, yet unknown factor interacts with this region of the caspase-8 promoter. In summary, our study contributes to the understanding of the transcriptional regulation of the caspase-8 gene by basal (SP1- and ETS-dependent) and inducible (p53-dependent) mechanisms.

Expression of short-form caspase 8 correlates with decreased sensitivity to Fas-mediated apoptosis in neuroblastoma cells

Disruption of apoptotic death signal transduction pathways may be responsible for tumor formation, progression and resistance to treatment in neuroblastoma. Caspase 8, one of the initiator caspases, plays an important role in the Fas-Fas ligand pathway. This caspase signals through the formation of a death-inducing signaling complex in response to Fas activation by its ligand. In this study, we evaluated the sensitivity of a series of human neuroblastoma cell lines to membrane-bound Fas ligand induced-cell death, as well as the expression of Fas, caspase 3 and caspase 8. Sensitivity to Fas-mediated cell death did not correlate with the expression of Fas in neuroblastoma cells, but was directly associated with the pattern of caspase 8 protein expression. We found that the majority of neuroblastoma cell lines we evaluated lacked caspase 8 expression, and these cell lines were invariably resistant to Fas-mediated cell death. In contrast, cell lines expressing normal caspase 8 protein were quite sensitive to Fas-mediated cell death. More interestingly, a group of cell lines expressing a distinct short form of caspase 8 with splicing out of exon 3 consistently showed moderate sensitivity to Fas-mediated cell death. These results indicate that the profile of caspase 8 expression is an important determinant of the response of neuroblastoma cells to Fas-mediated cell death.

Upregulation of the apoptosis regulators cFLIP, CD95 and CD95 ligand in peripheral blood mononuclear cells in relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) is a chronic disease involving an inflammatory reaction within the white matter of the CNS, mediated by T cells, B cells and macrophages. The pathogenesis of MS may involve impaired activation-induced cell death of activated myelin-specific mature T cells. We investigated the mRNA expression of the apoptosis mediators cellular FLICE-inhibitory protein (cFLIP), caspase-8, CD95 and CD95L in peripheral blood mononuclear cells (PB MNCs) from MS patients using real-time PCR. The overall increased expression of the four key players in the CD95 pathway in relapsing-remitting MS suggests their involvement in the inflammatory process in this disease.

Potentiation of Fas- and TRAIL-mediated apoptosis by IFN-gamma in A549 lung epithelial cells: enhancement of caspase-8 expression through IFN-response element

Epithelial cell apoptosis triggered cooperatively by multiple cytokines contributes to the injury induced by inflammatory responses in the lung and elsewhere. Here we show that interferon-gamma (IFN-gamma) sensitizes A549 cells, human lung epithelial cells, to cytokine-mediated apoptosis by upregulating caspase-8 expression. Pretreating the cells with IFN-gamma potentiated Fas- and TNF-related apoptosis inducing ligand (TRAIL)-induced cell death, but other forms of apoptosis, not mediated via receptors, were unaffected. Western blotting and inhibitor assays showed that IFN-gamma selectively increased expression of caspases-7 and -8, but not caspases-2, -3, -9, or -10, as a necessary step leading to apoptosis. Assaying promoter activity using a luciferase reporter gene indicated that an IFN-gamma response element was located in the 5'-flanking region of the caspase-8 gene, spanning positions -227 to -219. Taken together, these findings suggest that IFN-gamma potentiates Fas- and TRAIL-mediated apoptosis by increasing caspase-8 expression via an IFN-gamma response element in A549 cells.

Intramolecular epitope spreading among anti-caspase-8 autoantibodies in patients with silicosis, systemic sclerosis and systemic lupus erythematosus, as well as in healthy individuals

Dysregulation of apoptosis through the Fas-Fas ligand pathway is relevant in autoimmune disease onset. We recently reported elevated serum levels of sFas in patients with silicosis, systemic sclerosis (SSC) and systemic lupus erythematosus (SLE), and proposed a block of apoptosis in the pathogenesis. The disturbance of apoptosis in lymphocytes including autoreactive clones could induce autoantibody production. Since autoantibodies directed against unknown antigens are present in the sera of these patients, the sera samples were examined for the presence of autoantibodies directed to caspase-8. Using Western blotting, autoantibodies against caspase-8 were detected in healthy individuals and in over 60% of patients. Using epitope mapping employing 12 amino acid polypeptides with SPOTs system, a minimum of 4 epitopes and a maximum of 13 were found, which implied that epitope spreading was in progress. It is noteworthy that two important catalytic cystein residues were included within the epitopes; firstly the active site cystein Cys287, and secondly Cys360 located in the unique pentapeptide motif QACQG. Using recombinant human caspase-8 linked protein chip array, autoantibodies were identified and molecular weight determined. The antibodies were mainly IgG; 80% were subclass IgG1(lambda); 20% were IgG4(kappa). Despite the ratio of human light chain kappa:lambda = 2:1, the predominance of IgG1(lambda) is noticeable. Anti-caspase-8 autoantibodies are detectable in healthy individuals and in patients suffering silicosis, SSc or SLE. A few epitopes were detected in healthy individuals compared to those suffering autoimmune diseases, indicating the intramolecular epitope spreading. Relationship of autoantibodies and the clinical background of the patients requires clarification.

Possible attenuation of fas-mediated signaling by dominant expression of caspase-8 aberrant isoform in adult T-cell leukemia cells

The Fas up-regulated in adult T-cell leukemia (ATL) cells is usually the wild-type protein and is usually functional, at least in vitro. However, primary ATL cells, in contrast to ATL cell lines, are not necessarily susceptible to anti-Fas-induced apoptosis. To clarify the mechanism tuning the apoptotic signal transduction initiated by the activation caspase-8 in ATL cells and ATL cell lines, we examined the expression profile of caspase-8, of which there are at least 8 isoforms at the messenger RNA (mRNA) level with the potential to finely tune the signal transduction. Reverse transcription polymerase chain reaction disclosed the 2 major mRNA bands of 815 bp (casp-8S) and 951 bp (casp-8L) with different expression profiles among normal CD4 T-cells, primary ATL cells, and ATL cell lines. Casp-8L was the predominant form in primary ATL cells, whereas casp-8S was predominant in ATL cell lines. Casp-8S was structurally intact as shown by nucleotide analysis, whereas casp-8L was shown to be generated by a 136-bp insertion between exons 8 and 9 and to carry a frame shift in the transcript, introducing a premature stop codon and probably resulting in a truncated protein of approximately 30 kd deduced for the casp-8L transcript. These results suggest that an imbalanced expression of casp-8 isoforms, especially the dominant casp-8L in primary ATL cells, is in part responsible for tumor pathology through the modulation of cell death via Fas-mediated signaling.

Inactivating mutations of CASP10 gene in non-Hodgkin lymphomas

Caspase 10 (Mch4/FLICE2) is a caspase homologous to caspase 8. A recent report described that inherited CASP10 gene mutations underlie defective lymphocyte and dendritic cell apoptosis in autoimmune lymphoproliferative syndrome (ALPS). In this study, to explore the possibility that mutation of this gene might be involved in the development of non-Hodgkin lymphoma (NHL), we have analyzed the entire coding region and all splice sites of the CASP10 gene for the detection of somatic mutations in 117 human NHLs. Overall, 17 NHLs (14.5%) were found to have CASP10 mutations, which were identified in the coding regions of the prodomain (n = 3), the p17 large protease subunit (n = 11), and the p12 small protease subunit (n = 3). We expressed the tumor-derived caspase 10 mutants in 293 cells and found that apoptosis was suppressed. These data suggest that the inactivating mutations of the CASP10 gene might lead to the loss of its apoptotic function and contribute to the pathogenesis of some human NHLs.

Activation of caspase-9 is required for UV-induced apoptosis of human keratinocytes

UV radiation from the sun activates both the membrane death receptor and the intrinsic or mitochondrial apoptotic signaling pathways in epidermal keratinocytes, triggering apoptosis and affording protection against skin cancer formation. We have investigated the involvement of caspase-9 in the UV death effector pathway in human keratinocytes, since this is the initiating caspase in the mitochondrial pathway required for UV-induced apoptosis in some, but not all, cell types. UV radiation triggered activation of caspase-3, caspase-9, and caspase-8 with similar kinetics, although the rank order of activation was caspase-3 > caspase-9 > caspase-8. Inhibition of caspase-9 with either the peptide inhibitor benzyloxycarbonyl-Leu-Glu(OCH(3))-His-Asp(OCH(3))-fluoromethyl ketone, or expression of a catalytically inactive caspase-9 by retroviral transduction, protected normal keratinocytes from UV-induced apoptosis. HaCaT keratinocytes harboring mutant p53 alleles were also protected from UV-induced apoptosis by the dominant negative caspase-9. The dominant negative caspase-9 blocked UV-induced activation of caspase-3, caspase-9, and caspase-8, and also protected cells from the loss of mitochondrial membrane potential. In contrast, the dominant negative caspase-9 did not protect from anti-Fas-induced apoptosis or caspase activation. These results identify caspase-9 as the critical upstream caspase initiating apoptosis by UV radiation in human keratinocytes, the relevant cell type for this important environmental carcinogen.