Inactivating mutations of the caspase-10 gene in gastric cancer

Comprehensive Pan-cancer Analysis Revealed CASP10 As a Promising Biomarker For Diverse Tumor Types

We aimed to explore the comprehensive cancer landscape of Caspase-10 (CASP10). CASP10, a member of the caspase family, is located at the human chromosome locus 2q33-34. Studies have suggested its potential role in the development of certain cancers. To evaluate CASP10 expression in normal and pan-cancer tissues, we integrated data from The Cancer Genome Atlas (TCGA), GEO, Human Protein Atlas (HPA), and UALCAN databases. The diagnostic and prognostic significance of CASP10 was analyzed using Receiver Operating Characteristic (ROC), Cox regression, and Kaplan-Meier analysis. Correlations of CASP10 with clinical parameters were assessed via the Wilcoxon test, Kruskal-Wallis test, and logistic regression analysis. Genomic variations were explored with cBioPortal, GSCALite database, and UALCAN databases. LinkedOmics database was used to detect the function of CASP10 in pan-cancer. Interactions between CASP10 and the Tumor Immune Microenvironment (TIME) were investigated using TISIDB, TIMER2, and TISCH databases. The GSCALite database was utilized to assess the sensitivity of CASP10 to small-molecule drugs. In addition, Western Blotting (WB) was employed to detect the expression of the CASP10 in our clinical Liver Hepatocellular Carcinoma (LIHC) and Stomach Adenocarcinoma (STAD) cohorts. The transcription and protein expression of CASP10 significantly differ across cancer types, marking it as a biomarker for diagnosis and prognosis. Its expression correlated with certain clinical characteristics such as histological types and Alpha-Fetoprotein (AFP) levels. CASP10 gene exhibited a 2% alteration frequency across pan-cancer patients, with significant SNV and CNV profiles, and decreased methylation levels. CASP10 was closely related to the Nuclear Factor-κappa B (NF-κB), TNF, cell cycle, and JAK-STAT signal pathways. CASP10 showed correlation with immune components in the tumor microenvironment, including lymphocytes, immune stimulators, immune inhibitors, MHC molecules, chemokines, receptors, and Cancer-Associated Fibroblasts (CAFs). Importantly, CASP10 could predict the sensitivity of diverse anti-cancer drugs. Finally, WB analysis validated the overexpression of CASP10 in LIHC and STAD tissues. Our comprehensive bioinformatic analysis reveal the function of CASP10 on the diagnosis, prognosis, and progression of diverse cancer types.

Clinicopathologic Analysis and Molecular Profiling of Ovarian Steroid Cell Tumors

Ovarian steroid and Leydig cell tumors (SCT and LCT, respectively) are rare stromal tumors, with aggressive behavior described in approximately one third of SCTs. Previously reported features potentially predictive of malignancy include size ≥7 cm, gross hemorrhage, necrosis, grade 2 or 3 nuclear atypia, and mitoses ≥2/10 HPFs; however, no subsequent studies have corroborated these findings. Herein, we evaluated a series of 25 tumors (21 SCT, 4 LCT) to explore their clinicopathologic and molecular features. Patients ranged from 16 to 79 years (median: 53 y) and all tumors were FIGO stage I. Recurrences occurred in 3 patients, all of whom died from disease. At least 1 atypical feature was identified in 63% of SCT/LCT and included hemorrhage (n=9), grade 2 or 3 atypia (n=7), mitoses≥2/10 HPFs (n=7), size≥7.0 cm (n=6), and necrosis (n=2); only malignant SCTs demonstrated 4 or 5 atypical features. Next-generation sequencing revealed malignant SCTs were genomically unstable, with uncommon and nonrecurring gene-level alterations ( MDM2/CDK4 coamplification, ATRX rearrangement, BAP1 mutation). One SCT with limited follow-up harbored FH and TP53 mutations and occasional arm-level copy number alterations, while all other sequenced tumors (n=7) were genomically stable; 1 had a CTNNB1 mutation and another a CASP10 mutation. In summary, the presence of at least 1 atypical feature is common in SCT/LCT, but most patients demonstrate a benign clinical course. Genomic alterations are infrequent but occur in malignant SCTs as well as a subset of benign SCTs. Molecular analysis of additional malignant SCTs is necessary to identify recurring and/or potentially actionable targets.

A Review on Caspases: Key Regulators of Biological Activities and Apoptosis

Caspases are proteolytic enzymes that belong to the cysteine protease family and play a crucial role in homeostasis and programmed cell death. Caspases have been broadly classified by their known roles in apoptosis (caspase-3, caspase-6, caspase-7, caspase-8, and caspase-9 in mammals) and in inflammation (caspase-1, caspase-4, caspase-5, and caspase-12 in humans, and caspase-1, caspase-11, and caspase-12 in mice). Caspases involved in apoptosis have been subclassified by their mechanism of action as either initiator caspases (caspase-8 and caspase-9) or executioner caspases (caspase-3, caspase-6, and caspase-7). Caspases that participate in apoptosis are inhibited by proteins known as inhibitors of apoptosis (IAPs). In addition to apoptosis, caspases play a role in necroptosis, pyroptosis, and autophagy, which are non-apoptotic cell death processes. Dysregulation of caspases features prominently in many human diseases, including cancer, autoimmunity, and neurodegenerative disorders, and increasing evidence shows that altering caspase activity can confer therapeutic benefits. This review covers the different types of caspases, their functions, and their physiological and biological activities and roles in different organisms.

Caspase-10 affects the pathogenesis of primary biliary cholangitis by regulating inflammatory cell death

Primary biliary cholangitis (PBC) is an autoimmune disease that involves chronic inflammation and injury to biliary epithelial cells. To identify critical genetic factor(s) in PBC patients, we performed whole-exome sequencing of five female siblings, including one unaffected and four affected sisters, in a multi-PBC family, and identified 61 rare heterozygote variants that segregated only within the affected sisters. Among them, we were particularly interested in caspase-10, for although several caspases are involved in cell death, inflammation and autoimmunity, caspase-10 is little known from this perspective. We generated caspase-10 knockout macrophages, and then investigated the obtained phenotypes in comparison to those of its structurally similar protein, caspase-8. Unlike caspase-8, caspase-10 does not play a role during differentiation into macrophages, but after differentiation, it regulates the process of inflammatory cell deaths such as necroptosis and pyroptosis more strongly. Interestingly, caspase-10 displays better protease activity than caspase-8 in the process of RIPK1 cleavage, and an enhanced ability to form a complex with RIPK1 and FADD in human macrophages. Higher inflammatory cell death affected the fibrotic response of hepatic stellate cells; this effect could be recovered by treatment with UDCA and OCA, which are currently approved for PBC patients. Our findings strongly indicate that the defective roles of caspase-10 in macrophages contribute to the pathogenesis of PBC, thereby suggesting a new therapeutic strategy for PBC treatment.

Differential Expression of Proteins in an Atypical Presentation of Autoimmune Lymphoproliferative Syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is a rare disease defined as a defect in the lymphocyte apoptotic pathway. Currently, the diagnosis of ALPS is based on clinical aspects, defective lymphocyte apoptosis and mutations in Fas, FasL and Casp 10 genes. Despite this, ALPS has been misdiagnosed. The aim of this work was to go one step further in the knowledge of the disease, through a molecular and proteomic analysis of peripheral blood mononuclear cells (PBMCs) from two children, a 13-year-old girl and a 6-year-old boy, called patient 1 and patient 2, respectively, with clinical data supporting the diagnosis of ALPS. Fas, FasL and Casp10 genes from both patients were sequenced, and a sample of the total proteins from patient 1 was analyzed by label-free proteomics. Pathway analysis of deregulated proteins from PBMCs was performed on the STRING and PANTHER bioinformatics databases. A mutation resulting in an in-frame premature stop codon and protein truncation was detected in the Fas gene from patient 2. From patient 1, the proteomic analysis showed differences in the level of expression of proteins involved in, among other processes, cell cycle, regulation of cell cycle arrest and immune response. Noticeably, the most down-regulated protein is an important regulator of the cell cycle process. This could be an explanation of the disease in patient 1.

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.

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.

Caspase-10 inhibits ATP-citrate lyase-mediated metabolic and epigenetic reprogramming to suppress tumorigenesis

Caspase-10 belongs to the class of initiator caspases and is a close homolog of caspase-8. However, the lack of caspase-10 in mice and limited substrate repertoire restricts the understanding of its physiological functions. Here, we report that ATP-citrate lyase (ACLY) is a caspase-10 substrate. Caspase-10 cleaves ACLY at the conserved Asp1026 site under conditions of altered metabolic homeostasis. Cleavage of ACLY abrogates its enzymatic activity and suppresses the generation of acetyl-CoA, which is critical for lipogenesis and histone acetylation. Thus, caspase-10-mediated ACLY cleavage results in reduced intracellular lipid levels and represses GCN5-mediated histone H3 and H4 acetylation. Furthermore, decline in GCN5 activity alters the epigenetic profile, resulting in downregulation of proliferative and metastatic genes. Thus caspase-10 suppresses ACLY-promoted malignant phenotype. These findings expand the substrate repertoire of caspase-10 and highlight its pivotal role in inhibiting tumorigenesis through metabolic and epigenetic mechanisms.

Caspases are most closely associated with cell death, but many have other cellular functions. Here, Das et al. find that upon metabolic stress, caspase-10 cleaves ACLY to regulate metabolic homeostasis and epigenetic reprogramming by altering Acetyl-CoA levels.

Reversine, a substituted purine, exerts an inhibitive effect on human renal carcinoma cells via induction of cell apoptosis and polyploidy

Background

Human renal cell carcinoma (RCC) is the most common type of kidney cancer that arises from the renal epithelium. Up to 33.3% of RCC patients treated with local tumor resections will subsequently develop recurrence or metastases. Thus, optimized therapeutic regimes are urgently needed to improve the prognosis of RCC. Reversine was recently reported to exert critical roles in cancer therapy.

Materials and methods

This study evaluated the anti-tumor effects of reversine on cell viability, colony formation, apoptosis, and cell cycle in 786-O and ACHN cell lines.

Results

It was demonstrated that reversine significantly inhibited the proliferation of both cell lines in time- and dose-dependent manners. Polyploidy formation was observed under high-concentration reversine treatment. In addition, reversine induced cell death via caspase-dependent apoptotic pathways, which could be partially inhibited by Z-VAD-FMK, a pan-caspase inhibitor.

Conclusion

Reversine could effectively suppress the proliferation of human RCC cells, and may serve as a novel therapeutic regimen for RCC in clinical practice.

Copy number variation in archival melanoma biopsies versus benign melanocytic lesions

BACKGROUND

Skin melanocytes can give rise to benign and malignant neoplasms. Discrimination of an early melanoma from an unusual/atypical benign nevus can represent a significant challenge. However, previous studies have shown that in contrast to benign nevi, melanoma demonstrates pervasive chromosomal aberrations.

OBJECTIVE

This substantial difference between melanoma and benign nevi can be exploited to discriminate between melanoma and benign nevi.

METHODS

Array-comparative genomic hybridization (aCGH) is an approach that can be used on DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues to assess the entire genome for the presence of changes in DNA copy number. In this study, high resolution, genome-wide single-nucleotide polymorphism (SNP) arrays were utilized to perform comprehensive and detailed analyses of recurrent copy number aberrations in 41 melanoma samples in comparison with 21 benign nevi.

RESULTS

We found statistically significant copy number gains and losses within melanoma samples. Some of the identified aberrations are previously implicated in melanoma. Moreover, novel regions of copy number alterations were identified, revealing new candidate genes potentially involved in melanoma pathogenesis.

CONCLUSIONS

Taken together, these findings can help improve melanoma diagnosis and introduce novel melanoma therapeutic targets.

SUMO-Modified FADD Recruits Cytosolic Drp1 and Caspase-10 to Mitochondria for Regulated Necrosis

Fas-associated protein with death domain (FADD) plays a key role in extrinsic apoptosis. Here, we show that FADD is SUMOylated as an essential step during intrinsic necrosis. FADD was modified at multiple lysine residues (K120/125/149) by small ubiquitin-related modifier 2 (SUMO2) during necrosis caused by calcium ionophore A23187 and by ischemic damage. SUMOylated FADD bound to dynamin-related protein 1 (Drp1) in cells both in vitro and in ischemic tissue damage cores, thus promoting Drp1 recruitment by mitochondrial fission factor (Mff) to accomplish mitochondrial fragmentation. Mitochondrial-fragmentation-associated necrosis was blocked by FADD or Drp1 deficiency and SUMO-defective FADD expression. Interestingly, caspase-10, but not caspase-8, formed a ternary protein complex with SUMO-FADD/Drp1 on the mitochondria upon exposure to A23187 and potentiated Drp1 oligomerization for necrosis. Moreover, the caspase-10 L285F and A414V mutants, found in autoimmune lymphoproliferative syndrome and non-Hodgkin lymphoma, respectively, regulated this necrosis. Our study reveals an essential role of SUMOylated FADD in Drp1- and caspase-10-dependent necrosis, providing insights into the mechanism of regulated necrosis by calcium overload and ischemic injury.

Genetic characterization of two gain-of-function alleles of the effector caspase DrICE in Drosophila

Caspases are the executioners of apoptosis. Although much is known about their physiological roles and structures, detailed analyses of missense mutations of caspases are lacking. As mutations within caspases are identified in various human diseases, the study of caspase mutants will help to elucidate how caspases interact with other components of the apoptosis pathway and how they may contribute to disease. DrICE is the major effector caspase in Drosophila required for developmental and stress-induced cell death. Here, we report the isolation and characterization of six de novo drICE mutants, all of which carry point mutations affecting amino acids conserved among caspases in various species. These six mutants behave as recessive loss-of-function mutants in a homozygous condition. Surprisingly, however, two of the newly isolated drICE alleles are gain-of-function mutants in a heterozygous condition, although they are loss-of-function mutants homozygously. Interestingly, they only behave as gain-of-function mutants in the presence of an apoptotic signal. These two alleles carry missense mutations affecting conserved amino acids in close proximity to the catalytic cysteine residue. This is the first time that viable gain-of-function alleles of caspases are described in any intact organism and provides a significant exception to the expectation that mutations of conserved amino acids always abolish the pro-apoptotic activity of caspases. We discuss models about how these mutations cause the gain-of-function character of these alleles.

New basal cell carcinoma susceptibility loci

In an ongoing screen for DNA sequence variants that confer risk of cutaneous basal cell carcinoma (BCC), we conduct a genome-wide association study (GWAS) of 24,988,228 SNPs and small indels detected through whole-genome sequencing of 2,636 Icelanders and imputed into 4,572 BCC patients and 266,358 controls. Here we show the discovery of four new BCC susceptibility loci: 2p24 MYCN (rs57244888[C], OR=0.76, P=4.7 × 10(-12)), 2q33 CASP8-ALS2CR12 (rs13014235[C], OR=1.15, P=1.5 × 10(-9)), 8q21 ZFHX4 (rs28727938[G], OR=0.70, P=3.5 × 10(-12)) and 10p14 GATA3 (rs73635312[A], OR=0.74, P=2.4 × 10(-16)). Fine mapping reveals that two variants correlated with rs73635312[A] occur in conserved binding sites for the GATA3 transcription factor. In addition, expression microarrays and RNA-seq show that rs13014235[C] and a related SNP rs700635[C] are associated with expression of CASP8 splice variants in which sequences from intron 8 are retained.

Old, new and emerging functions of caspases

Caspases are proteases with a well-defined role in apoptosis. However, increasing evidence indicates multiple functions of caspases outside apoptosis. Caspase-1 and caspase-11 have roles in inflammation and mediating inflammatory cell death by pyroptosis. Similarly, caspase-8 has dual role in cell death, mediating both receptor-mediated apoptosis and in its absence, necroptosis. Caspase-8 also functions in maintenance and homeostasis of the adult T-cell population. Caspase-3 has important roles in tissue differentiation, regeneration and neural development in ways that are distinct and do not involve any apoptotic activity. Several other caspases have demonstrated anti-tumor roles. Notable among them are caspase-2, -8 and -14. However, increased caspase-2 and -8 expression in certain types of tumor has also been linked to promoting tumorigenesis. Increased levels of caspase-3 in tumor cells causes apoptosis and secretion of paracrine factors that promotes compensatory proliferation in surrounding normal tissues, tumor cell repopulation and presents a barrier for effective therapeutic strategies. Besides this caspase-2 has emerged as a unique caspase with potential roles in maintaining genomic stability, metabolism, autophagy and aging. The present review focuses on some of these less studied and emerging functions of mammalian caspases.

New roles for old enzymes: killer caspases as the engine of cell behavior changes

It has become increasingly clear that caspases, far from being merely cell death effectors, have a much wider range of functions within the cell. These functions are as diverse as signal transduction and cytoskeletal remodeling, and caspases are now known to have an essential role in cell proliferation, migration, and differentiation. There is also evidence that apoptotic cells themselves can direct the behavior of nearby cells through the caspase-dependent secretion of paracrine signaling factors. In some processes, including the differentiation of skeletal muscle myoblasts, both caspase activation in differentiating cells as well as signaling from apoptotic cells has been reported. Here, we review the non-apoptotic outcomes of caspase activity in a range of different model systems and attempt to integrate this knowledge.

Caspase functions in cell death and disease

Caspases are a family of endoproteases that provide critical links in cell regulatory networks controlling inflammation and cell death. The activation of these enzymes is tightly controlled by their production as inactive zymogens that gain catalytic activity following signaling events promoting their aggregation into dimers or macromolecular complexes. Activation of apoptotic caspases results in inactivation or activation of substrates, and the generation of a cascade of signaling events permitting the controlled demolition of cellular components. Activation of inflammatory caspases results in the production of active proinflammatory cytokines and the promotion of innate immune responses to various internal and external insults. Dysregulation of caspases underlies human diseases including cancer and inflammatory disorders, and major efforts to design better therapies for these diseases seek to understand how these enzymes work and how they can be controlled.

Reversine suppresses oral squamous cell carcinoma via cell cycle arrest and concomitantly apoptosis and autophagy

BACKGROUND

The effective therapies for oral cancer patients of stage III and IV are generally surgical excision and radiation combined with adjuvant chemotherapy using 5-Fu and Cisplatin. However, the five-year survival rate is still less than 30% in Taiwan. Therefore, evaluation of effective drugs for oral cancer treatment is an important issue. Many studies indicated that aurora kinases (A, B and C) were potential targets for cancer therapies. Reversine was proved to be a novel aurora kinases inhibitor with lower toxicity recently. In this study, the potentiality for reversine as an anticancer agent in oral squamous cell carcinoma (OSCC) was evaluated.

METHODS

Effects of reversine on cell growth, cell cycle progress, apoptosis, and autophagy were evaluated mainly by cell counting, flow cytometry, immunoblot, and immunofluorescence.

RESULTS

The results demonstrated that reversine significantly suppressed the proliferation of two OSCC cell lines (OC2 and OCSL) and markedly rendered cell cycle arrest at G2/M stage. Reversine also induced cell death via both caspase-dependent and -independent apoptosis. In addition, reversine could inhibit Akt/mTORC1 signaling pathway, accounting for its ability to induce autophagy.

CONCLUSIONS

Taken together, reversine suppresses growth of OSCC via multiple mechanisms, which may be a unique advantage for developing novel therapeutic regimens for treatment of oral cancer in the future.

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.

Caspases and cancer

Evasion of apoptosis is considered to be one of the hallmarks of human cancers. This cell death modality is executed by caspases and several upstream regulatory factors, which direct their proteolytic activity, have been defined as either tumor suppressors or oncogenes. Often these regulatory factors, in addition to being potent apoptosis inducers, function in cell survival or repair signaling pathways in response to cellular stress. Thus, loss of function in a distinct regulatory mechanism does not necessarily mean that tumor formation is due to apoptosis malfunction resulting from insufficient caspase activation. Although each caspase has been assigned a distinct role in apoptosis, some redundancy with respect to their regulatory functions and substrate recognition is evident. Jointly, these proteases could be considered to possess solid tumor suppressor function, but what is the evidence that deregulation of specific caspases per se induces inappropriate cell survival, leading to enhanced tumorigenic potential? This question will be addressed in this review, which covers basic molecular mechanisms derived from in vitro analyses and emphasizes new insights that have emerged from in vivo and clinical studies.

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.

Functional comparison of innate immune signaling pathways in primates

Humans respond differently than other primates to a large number of infections. Differences in susceptibility to infectious agents between humans and other primates are probably due to inter-species differences in immune response to infection. Consistent with that notion, genes involved in immunity-related processes are strongly enriched among recent targets of positive selection in primates, suggesting that immune responses evolve rapidly, yet providing only indirect evidence for possible inter-species functional differences. To directly compare immune responses among primates, we stimulated primary monocytes from humans, chimpanzees, and rhesus macaques with lipopolysaccharide (LPS) and studied the ensuing time-course regulatory responses. We find that, while the universal Toll-like receptor response is mostly conserved across primates, the regulatory response associated with viral infections is often lineage-specific, probably reflecting rapid host–virus mutual adaptation cycles. Additionally, human-specific immune responses are enriched for genes involved in apoptosis, as well as for genes associated with cancer and with susceptibility to infectious diseases or immune-related disorders. Finally, we find that chimpanzee-specific immune signaling pathways are enriched for HIV–interacting genes. Put together, our observations lend strong support to the notion that lineage-specific immune responses may help explain known inter-species differences in susceptibility to infectious diseases.

We know of a large number of diseases or medical conditions that affect humans more severely than non-human primates, such as AIDS, malaria, hepatitis B, and cancer. These differences likely arise from different immune responses to infection among species. However, due to the lack of comparative functional data across species, it remains unclear how the immune system of humans and other primates differ. In this work, we present the first genome-wide characterization of functional differences in innate immune responses between humans and our closest evolutionary relatives. Our results indicate that “core” immune responses, those that are critical to fight any invading pathogen, are the most conserved across primates and that much of the divergence in immune responses is observed in genes that are involved in response to specific microbial and viral agents. In addition, we show that human-specific immune responses are enriched for genes involved in apoptosis and cancer biology, as well as with genes previously associated with susceptibility to infectious diseases or immune-related disorders. Finally, we find that chimpanzee-specific immune signaling pathways are enriched for HIV–interacting genes. Our observations may therefore help explain known inter-species differences in susceptibility to infectious diseases.

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.

Association of the variants CASP8 D302H and CASP10 V410I with breast and ovarian cancer risk in BRCA1 and BRCA2 mutation carriers

BACKGROUND

The genes caspase-8 (CASP8) and caspase-10 (CASP10) functionally cooperate and play a key role in the initiation of apoptosis. Suppression of apoptosis is one of the major mechanisms underlying the origin and progression of cancer. Previous case-control studies have indicated that the polymorphisms CASP8 D302H and CASP10 V410I are associated with a reduced risk of breast cancer in the general population.

METHODS

To evaluate whether the CASP8 D302H (CASP10 V410I) polymorphisms modify breast or ovarian cancer risk in BRCA1 and BRCA2 mutation carriers, we analyzed 7,353 (7,227) subjects of white European origin provided by 19 (18) study groups that participate in the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). A weighted cohort approach was used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI).

RESULTS

The minor allele of CASP8 D302H was significantly associated with a reduced risk of breast cancer (per-allele HR, 0.85; 95% CI, 0.76-0.97; P(trend) = 0.011) and ovarian cancer (per-allele HR, 0.69; 95% CI, 0.53-0.89; P(trend) = 0.004) for BRCA1 but not for BRCA2 mutation carriers. The CASP10 V410I polymorphism was not associated with breast or ovarian cancer risk for BRCA1 or BRCA2 mutation carriers.

CONCLUSIONS

CASP8 D302H decreases breast and ovarian cancer risk for BRCA1 mutation carriers but not for BRCA2 mutation carriers.

IMPACT

The combined application of these and other recently identified genetic risk modifiers could in the future allow better individual risk calculation and could aid in the individualized counseling and decision making with respect to preventive options in BRCA1 mutation carriers.

Mutational analysis of CASP10 gene in colon, breast, lung and hepatocellular carcinomas

AIMS

Evasion of apoptosis is a feature of cancer cells. As a mechanism of apoptosis inactivation in cancer cells, somatic mutations of pro-apoptotic genes have been reported in many cancers. Caspase-10 is an initiation-phase caspase, and somatic mutation of CASP10 that encodes caspase-10 has been found in non-Hodgkin's lymphoma and gastric carcinoma.

METHODS

The aim of this study was to explore whether CASP10 gene is somatically mutated in colon, breast, lung, and hepatocellular carcinomas. We analysed the entire coding region and all splice sites of CASP10 in 47 colon, 47 breast, 47 lung, and 47 hepatocellular carcinomas by a single-strand conformation polymorphism (SSCP) assay.

RESULTS

We found two CASP10 mutations in the colon cancers (2/47; 4.3%), but none in breast, lung or hepatocellular carcinomas. One mutation [c.41A > C (p.Lys14Thr)] was a missense mutation, while the other was a substitution mutation in a splice site (c.684 + 4G > A). The colon cancer with the CASP10 missense mutation harboured additional CASP gene mutations (CASP3, 7 and 8).

CONCLUSION

Our data indicate that somatic mutation of CASP10 is rare in colon, breast, lung, and hepatocellular carcinomas. However, the data also suggest that CASP10 mutation might contribute to the pathogenesis of some colon carcinomas together with other CASP gene mutations.

Preparation of the caspase-3/7 substrate Ac-DEVD-pNA by solution-phase peptide synthesis

This protocol describes the gram-scale solution-phase synthesis of the colorimetric caspase-3/7 substrate Ac-DEVD-pNA. The caspase enzymes are integral to cellular inflammation and apoptotic cascades, and are commonly studied by cell biologists, medicinal chemists and chemical biologists. In particular, the assessment of caspase enzymatic activity is a standard method to evaluate cell death pathways and new apoptosis-modulating agents. Caspase enzymatic activity can be conveniently monitored with peptidic chromogenic or fluorogenic substrates, with certain peptide sequences imparting selectivity for certain caspases. The synthesis of these peptide substrates is typically carried out by solid-phase synthesis, a method that is not ideal for production of the gram quantities needed for high-throughput screening. Described herein is a facile method for the synthesis of the Ac-DEVD-pNA caspase-3/7 substrate using solution-phase peptide synthesis. This protocol, involving iterative PyBOP-mediated couplings and Fmoc deprotections, is rapid (about 5 d), operationally simple and can be used to generate over 1 g of product at a fraction of the cost of the commercial substrate.

Emerging roles of proteases in tumour suppression

Proteases have long been associated with cancer progression because of their ability to degrade extracellular matrices, which facilitates invasion and metastasis. However, recent studies have shown that these enzymes target a diversity of substrates and favour all steps of tumour evolution. Unexpectedly, the post-trial studies have also revealed proteases with tumour-suppressive effects. These effects are associated with more than 30 different enzymes that belong to three distinct protease classes. What are the clinical implications of these findings?

Cloning and characterization of a novel caspase-10 isoform that activates NF-kappa B activity

Caspase-10 (also known as Mch4 and FLICE2) is an initiator caspase in the death receptor (DR)-dependent apoptotic pathway. So far six splice variants (caspase-10a-f) have been identified. Here we describe a novel isoform of the caspase-10 family named caspase-10g that is widely expressed in normal human tissues and various cell lines. Caspase-10g consists of 247 amino acids and does not contain the large or small subunit. A caspase-10g-specific exon is present between exon 5 and exon 6, which results in a protein product truncated shortly after the death-effector domain (DED)-containing prodomain. We further show that overexpression of caspase-10g dramatically enhances NF-kappaB activity in a dose- and time-dependent manner. Moreover, caspase-10g, unlike the protease-active caspase-10a, only promotes slight apoptosis when overexpressed in mammalian cells and it has no effect on caspase-10a-mediated apoptosis. Taken together, these results suggest that caspase-10g, as a novel prodomain-only isoform of caspase-10, may play a regulatory role preferentially in the NF-kappaB pathways.

Expression of phosphorylated caspase-9 in gastric carcinomas

Alterations of caspases, the main executioners of apoptosis, have been described in human cancers. Caspase-9 plays a crucial role in the initiation phase of the intrinsic apoptosis pathway. Caspase-9 is phosphorylated at Thr125 through the mitogen-activated protein kinase (MAPK) pathway, and this phosphorylation is associated with inhibition of caspase-9 activation. The aim of this study was to explore whether phosphorylated caspase-9 (p-caspase-9) expression could be a characteristic of gastric carcinomas. We analyzed expression of p-caspase-9 protein in 60 gastric adenocarcinomas by immunohistochemistry using a tissue microarray approach. p-caspase-9 was detected in 33 of the 60 carcinomas (55%). Both early and advanced gastric carcinomas expressed p-caspase-9. There was no significant association of p-caspase-9 expression with clinocopathological characteristics, including invasion, metastasis and stage. In contrast to gastric cancer cells, epithelial cells in normal gastric mucosa showed no or only weak expression of p-caspase-9. Taken together, these results indicate that caspase-9 is frequently phosphorylated in gastric carcinomas, and that the phosphorylation of caspase-9 might be an inhibitory mechanism of caspase-9-mediated apoptosis in gastric carcinomas. Increased expression of p-caspase-9 in malignant gastric epithelial cells compared to normal mucosal epithelial cells suggests that p-caspase-9 expression might play a role in gastric carcinoma development.

Caspase function in programmed cell death

The first proapoptotic caspase, CED-3, was cloned from Caenorhabditis elegans in 1993 and shown to be essential for the developmental death of all somatic cells. Following the discovery of CED-3, caspases have been cloned from several vertebrate and invertebrate species. As reviewed in other articles in this issue of Cell Death and Differentiation, many caspases function in nonapoptotic pathways. However, as is clear from the worm studies, the evolutionarily conserved role of caspases is to execute programmed cell death. In this article, I will specifically focus on caspases that function primarily in cell death execution. In particular, the physiological function of caspases in apoptosis is discussed using examples from the worm, fly and mammals.

Fine deletion mapping of chromosome 2q21-37 shows three preferentially deleted regions in oral cancer

We analysed the loss of heterozygosity (LOH) of long arm of chromosome 2 by using 16 polymorphic microsatellite markers in 39 matched oral normal and cancer tissues, and defined the deletional mapping of the region with putative tumor suppressor genes. LOH was detected at least one location in 33 of 39 (85%) tumor tissues. Frequent deletions were detected at the locations of microsatellite markers, D2S2304 (35%), D2S111 (40%), D2S155 (35%), D2S1327 (29%), D2S164 (29%), D2S125 (68%) and D2S140 (32%). Three preferentially deleted regions at 2q21-24, 2q33-35 and 2q37.3 were observed. Several candidate tumor suppressor genes in these regions such as LRP1B, CASP8, CASP10, BARD1, ILKAP, PPP1R7, and ING5, are located. Further molecular analysis of each gene should be performed to clarify their roles in oral carcinogenesis.

Genetic disorders of programmed cell death in the immune system

Human genetics offers new possibilities for understanding physiological regulatory mechanisms and disorders of the immune system. Genetic abnormalities of lymphocyte cell death programs have provided insights into mechanisms of receptor biology and principles of immune homeostasis and tolerance. Thus far, there are two major diseases of programmed cell death associated with inherited human mutations: the autoimmune lymphoproliferative syndrome and the caspase-eight deficiency state. We describe the details of their molecular pathogenesis and discuss how these diseases illustrate important concepts in immune regulation and genetics.

Caspase-10 involvement in cytotoxic drug-induced apoptosis of tumor cells

Anticancer drugs can induce tumor cell death by caspase-dependent apoptosis. The observation that procaspase-10 expression decreased in leukemic cells from acute myeloblastic leukemia patients at first relapse led us to explore the role of caspase-10 in cytotoxic drug-induced apoptosis. We show that caspase-10 is activated in etoposide-treated cells in a dose- and time-dependent manner. A caspase-10 peptide inhibitor, a caspase-10 dominant-negative mutant or a small interfering RNA (siRNA)-mediated downregulation of the enzyme negatively interfere with drug-induced cell death and caspase-2, -3, -8 and -9 activation. The extrinsic pathway to apoptosis is not involved in drug-induced caspase-10 activation that occurs downstream of Bax redistribution to mitochondria and cytochrome c release from this organelle. siRNA-mediated downregulation of Apaf-1 prevents etoposide-mediated activation of caspase-10. In a cell-free assay, cytochrome c and dATP treatment of cell extracts after immunodepletion of either caspase-3 or caspase-9 indicates that caspase-10 is activated downstream of caspase-9. Then, caspase-10 is involved in a feedback amplification loop that amplifies caspase-9 and -3 activities. Altogether, these data indicate an active role for caspase-10 in cytotoxic drug-induced tumor cell death, downstream of the mitochondria.

Genetics, pathology, and clinics of familial gastric cancer

Gastric cancer is relatively common worldwide, mainly in its sporadic form, but familial aggregation of the disease may be seen in approximately 10% of the cases. This suggests a genetic cause for the cancer in those families that has not been identified in most cases. Despite all efforts to determine its genetic basis, a single syndrome has been characterized-the hereditary diffuse gastric cancer (HDGC)-which is specifically associated with CDH1 (E-cadherin) germline mutations in one third of the families. The other two thirds and all the gastric cancer families not fulfilling the HDGC criteria remain without molecular diagnosis. In this article we review the state of the art of familial gastric cancer regarding the molecular aspects, the clinical criteria, the pathology features, and the management recommendations described so far to be associated with this cancer disease.

Genetic alterations in caspase-10 may be causative or protective in autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by lymphadenopathy, elevated numbers of T cells with alphabeta-T cell receptors but neither CD4 nor CD8 co-receptors, and impaired lymphocyte apoptosis in vitro. Defects in the Fas receptor are the most common cause of ALPS (ALPS Ia), but in rare cases other apoptosis proteins have been implicated, including caspase-10 (ALPS II). We investigated the role of variants of caspase-10 in ALPS. Of 32 unrelated probands with ALPS who did not have Fas defects, two were heterozygous for the caspase-10 missense mutation I406L. Like the previously reported ALPS II-associated mutation L285F, I406L impaired apoptosis when transfected alone and dominantly inhibited apoptosis mediated by wild type caspase-10 in a co-transfection assay. Other variants in caspase-10, V410I and Y446C, were found in 3.4 and 1.6% of chromosomes in Caucasians, and in 0.5 and <0.5% of African Americans, respectively. In contrast to L285F and I406L, these variants had no dominant negative effect in co-transfection assays into the H9 lymphocytic cell line. We found healthy individuals homozygous for V410I, challenging the earlier suggestion that homozygosity for V410I alone causes ALPS. Moreover, an association analysis suggested protection from severe disease by caspase-10 V410I in 63 families with ALPS Ia due to dominant Fas mutations (P<0.05). Thus, different genetic variations in caspase-10 can produce contrasting phenotypic effects.

Association of the CASP10 V410I variant with reduced familial breast cancer risk and interaction with the CASP8 D302H variant

Dysregulation of apoptosis plays a crucial role in carcinogenesis. As part of death receptor- and mitochondrion-mediated apoptosis, the homologues caspases 10 and 8 may act as low-penetrance breast cancer (BC) susceptibility genes. In death receptor-mediated apoptosis, engagement of death receptors by their ligands involves the assembly of the death-inducing signalling complex (DISC). In mitochondrion-mediated apoptosis, the release of cytochrome c into the cytosol results in apoptosome formation. Recruitment of both caspases 10 and 8 (CASP10 and CASP8, respectively) to DISC and apoptosome leads to their activation by dimerization. We investigated the influence of the coding CASP10 variant V410I (G1228A) by performing a case-control study - using 511 familial BC cases and 547 control subjects - on BC risk and revealed a significant association of V410I with a reduced risk (OR = 0.62, 95% CI = 0.43-0.88, P = 0.0076) related to the number of variant alleles (P(trend) = 0.0039). As CASP10 and CASP8 functionally co-operate during apoptosis, we analysed the mutual effect of both CASP10 V410I and CASP8 D302H, resulting in a significant association between the number of the variant alleles I410 and H302 and a highly decreased familial BC risk (OR = 0.35, P(trend) = 0.007), pointing to the interaction between the CASP10 and CASP8 polymorphisms in breast carcinogenesis.

Aberrant expression of caspase-14 in epithelial tumors

Cysteine-dependent aspartate-specific proteases (caspases) are the cellular executors of apoptosis. Caspase-14 is the most divergent member of the family of mammalian caspases and displays a variety of unique characteristics. It is expressed in a limited number of tissues and has the shortest amino acid sequence within the caspase protein family. During induction of apoptosis, it is not processed, whereas terminal differentiation in skin leads to cleavage of caspase-14. Here we show that 40% of lung squamous cell carcinomas, 22% of breast cancers, and about 80% of cervical carcinomas express caspase-14. Immunohistochemistry reveals that caspase-14 is localized in areas of ongoing differentiation close to necrotic sites but is not strictly associated with the differentiation markers keratin-1/-10. Caspase-14 is neither mutated nor alternatively spliced in the tumors analyzed. Furthermore, caspase-14 is not processed into a small and large subunit, a process critical for the proteolytic activation of known effector caspases. We conclude that conditions exist in tumors leading to re-expression of this normally silent gene.

Gene deregulation in gastric cancer

Despite its decreasing frequency in the Western world during recent decades, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Due to the oligosymptomatic course of early gastric cancer, most cases are diagnosed in the advanced stages of the disease. The curative potential of current standard treatment continues to be unsatisfactory, despite multimodal approaches involving surgery, chemotherapy and radiotherapy. Novel therapeutics including small molecules and monoclonal antibodies are being developed and have been partially introduced into clinical use in connection with neoplastic diseases such as chronic myeloid leukemia, non-Hodgkin's lymphoma and colorectal cancer. Thorough understanding of the changes in gene expression occurring during gastric carcinogenesis may help to develop targeted therapies and improve the treatment of this disease. Novel molecular biology techniques have generated a wealth of data on up- and down-regulation, activation and inhibition of specific pathways in gastric cancer. Here, we provide an overview of the different aspects of aberrant gene expression patterns in gastric cancer.

HIV-1 Tat protein concomitantly down-regulates apical caspase-10 and up-regulates c-FLIP in lymphoid T cells: a potential molecular mechanism to escape TRAIL cytotoxicity

In this study, we showed the existence of a positive correlation between the amount of human immunodeficiency virus-type 1 (HIV-1) RNA in HIV-1 seropositive subjects and the plasma levels of TRAIL. Since it has been previously demonstrated that HIV-1 Tat protein up-regulates the expression of TRAIL in monocytic cells whereas tat-expressing lymphoid cells are more resistant to TRAIL cytotoxicity, we next investigated the effect of Tat on the expression/activity of both apical caspase-8 and -10, which play a key role in mediating the initial phases of apoptosis by TRAIL, and c-FLIP. Jurkat lymphoblastoid human T cell lines stably transfected with a plasmid expressing wild-type (HIV-1) tat gene showed normal levels of caspase-8 but significantly decreased levels of caspase-10 at both mRNA and protein levels with respect to Jurkat transfected with the control plasmid or with a mutated (cys22) non-functional tat cDNA. A significant decrease of caspase-10 expression/activity was also observed in transient transfection experiments with plasmid carrying tat cDNA. Moreover, c-FLIP(L) and c-FLIP(S) isoforms were up-regulated in tat-expressing cells at both mRNA and protein level in comparison with control cells. Taken together, these results provide a molecular basis to explain the resistance of tat-expressing Jurkat cells to apoptosis induced by TRAIL and, possibly, to other death-inducing ligands.

Gastric cancer: new genetic developments

Gastric cancer's (GC) incidence shows large geographic differences worldwide with the lowest rates occurring in most Western industrialized countries including the United States and the United Kingdom; in contrast, relatively high rates of GC occur in Japan, Korea, China, and South America, particularly Chile. The Laurén classification system classifies GC under two major histopathological variants: 1) an intestinal type and 2) a diffuse type. The intestinal type is more common in the general population, more likely to be sporadic and related to environmental factors such as diet, particularly salted fish and meat as well as smoked foods, cigarette smoking, and alcohol use. It exhibits components of glandular, solid, or intestinal architecture, as well as tubular structures. On the other hand, the diffuse type is more likely to have a primary genetic etiology, a subset of which, known as hereditary diffuse gastric cancer (HDGC), is due to the E-cadherin (CDH1) germline mutation. The diffuse type pathology is characterized by poorly cohesive clusters of cells which infiltrate the gastric wall, leading to its widespread thickening and rigidity of the gastric wall, known as linitis plastica. Helicobacter pylori infection is associated with risk for both the intestinal and diffuse varieties of gastric cancer. Germline truncating mutations of the CDH1 gene, which codes for the E-cadherin protein, were initially identified in three Maori families from New Zealand that were predisposed to diffuse GC. Since then, similar mutations have been described in more than 40 additional HDGC families of diverse ethnic backgrounds. It is noteworthy that two-thirds of HDGC families reported to date have proved negative for the CDH1 germline mutation. A number of candidate genes have been identified through analysis of the molecular biology of E-cadherin. Patients with evidence of the CDH1 germline mutation in the context of a family history of HDGC must be considered as candidates for prophylactic gastrectomy, given the extreme difficulty in its early diagnosis and its exceedingly poor prognosis when there is regional or distant spread. Specifically, the E-cadherin cytoplasmic tail interacts with catenins, assembling the cell-adhesion complex involved with E-cadherin mediated cell:cell adhesion. Beta-catenin and gamma-catenin compete for the same binding site on the E-cadherin cytoplasmic tail, directly linking the adhesion complex to the cytoskeleton through alpha-catenin. Beta-catenin gene (CTNNB1) mutations have been described predominantly in intestinal-type gastric cancers and CTNNB1 gene amplification and overexpression have recently been described in a mixed-type gastric cancer. This paper reviews the genetics of both intestinal and diffuse types of gastric carcinoma, their differential diagnosis, molecular genetics, pathology, and, when known, their mode of genetic transmission within families.

Caspase-10 sensitizes breast carcinoma cells to TRAIL-induced but not tumor necrosis factor-induced apoptosis in a caspase-3-dependent manner

Although signaling by death receptors involves the recruitment of common components into their death-inducing signaling complexes (DISCs), apoptosis susceptibility of various tumor cells to each individual receptor differs quite dramatically. Recently it was shown that, besides caspase-8, caspase-10 is also recruited to the DISCs, but its function in death receptor signaling remains unknown. Here we show that expression of caspase-10 sensitizes MCF-7 breast carcinoma cells to TRAIL- but not tumor necrosis factor (TNF)-induced apoptosis. This sensitization is most obvious at low TRAIL concentrations or when apoptosis is assessed at early time points. Caspase-10-mediated sensitization for TRAIL-induced apoptosis appears to be dependent on caspase-3, as expression of caspase-10 in MCF-7/casp-3 cells but not in caspase-3-deficient MCF-7 cells overcomes TRAIL resistance. Interestingly, neutralization of TRAIL receptor 2 (TRAIL-R2), but not TRAIL-R1, impaired apoptosis in a caspase-10-dependent manner, indicating that caspase-10 enhances TRAIL-R2-induced cell death. Furthermore, whereas processing of caspase-10 was delayed in TNF-treated cells, TRAIL triggered a very rapid activation of caspase-10 and -3. Therefore, we propose a model in which caspase-10 is a crucial component during TRAIL-mediated apoptosis that in addition actively requires caspase-3. This might be especially important in systems where only low TRAIL concentrations are supplied that are not sufficient for the fast recruitment of caspase-8 to the DISC.

Characterization of gene expression in major types of salivary gland carcinomas with epithelial differentiation

Gene expression profiles were studied in 13 cases of salivary gland carcinoma including mucoepidermoid carcinoma (MEC), acinic cell carcinoma (ACC), and salivary duct carcinoma (SDC) using a cDNA array. A total of 162 genes were deregulated. Only 5 genes were overexpressed in all carcinomas including fibronectin 1 (FN1), tissue metalloproteinase inhibitor 1 (TIMP1), biglycan (BGN), tenascin-C (HXB), and insulin-like growth factor binding protein 5 (IGFBP5), whereas 16 genes were underexpressed. The small number of similarly deregulated genes in these carcinoma entities suggests an extensive genetic variation between them. This result agrees with the great histopathological diversity of different entities of salivary gland carcinoma. Furthermore, diversity in gene expression between the carcinoma types was identified also by hierarchical clustering. Each carcinoma entity was clustered together but MEC, SDC, and ACC were separated from each other. Significance analysis of microarrays identified 27 genes expressed differently between the groups. In MEC, overexpressed genes included those of cell proliferation (IL-6 and SFN) and cell adhesion (SEMA3F and COL6A3), whereas many underexpressed genes were related to DNA modification (NTHL1 and RBBP4). Apoptosis-related genes CASP10 and MMP11 were overexpressed in SDC, in accordance with the typical tumor necrosis seen in this entity. An intermediate filament protein of basal epithelial cells, cytokeratin 14 (KRT14) was clearly differently expressed between the 3 types of carcinoma, and can be used as an aid in their differential diagnosis. The array results were validated by RT-PCR and immunohistochemistry.

Increased expression of histone deacetylase 2 is found in human gastric cancer

Accumulated evidence has established that aberrant regulation of histone deacetylases (HDACs) is one of the major causes of the development of human malignancies. Among different iso-enzymes of HDAC and sirtuins grouped as the HDAC super family, little is known as to how histone deacetylase 2 (HDAC2) causes carcinogenesis in solid tumors. Here, in order to investigate the possible role of HDAC2 in gastric carcinogenesis, we analyzed the expression of HDAC2 in 71 gastric adenocarcinomas by immunohistochemistry. Moderate to strong expression of HDAC2 was found in 44 (62%) out of a total of 71 tumors. The majority of positive tumors, which were detected in the nucleus but not in normal gastric epithelium, did not express HDAC2 or showed only weak positive staining. Interestingly, we also noted that HDAC2 expression appeared to be associated with tumor aggressiveness as HDAC2 expression was observed to be statistically significant in advanced gastric cancer (P=0.0023, Chi-square test) and in positive lymph node metastasis (P=0.0713, Chi-square test). Taken together, these results suggest that HDAC2 may play an important role in the aggressiveness of gastric cancer.

Lessons from TRAIL-resistance mechanisms in colorectal cancer cells: paving the road to patient-tailored therapy

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Intrinsic, as well as acquired, resistance to chemotherapy remains a major problem in the treatment of this disease. It is, therefore, of great importance to develop new, patient-tailored, treatment strategies for colorectal cancer patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) acts through the pro-apoptotic DR4 and DR5 receptors in tumor cells without harming normal cells and will soon be tested in clinical trials as a novel anti-cancer agent. However, not all human colon cancer cell lines are sensitive to TRAIL due to intrinsic or acquired TRAIL-resistance. This review discusses the mechanisms and modulation of TRAIL-resistance in colon cancer cells. Cell sensitivity to TRAIL can be affected by TRAIL-receptor expression at the cell membrane, DR4/DR5 ratio and functionality of TRAIL-receptors. Additional intracellular factors leading to TRAIL-resistance affect the caspase 8/c-FLIP ratio, such as loss of caspase 8 and caspase 10 due to mutations or gene methylation, CARP-dependent degradation of active caspase 8 and changes in caspase 8 or c-FLIP expression levels. Further downstream in the TRAIL apoptotic pathway, Bax mutations, or increased expression of IAP family members, in particularly XIAP and survivin, also cause resistance. Chemotherapeutic drugs, NSAIDs, interferon-gamma and proteasome inhibitors can overcome TRAIL-resistance by acting on TRAIL-receptor expression or changing the expression of pro- or anti-apoptotic proteins.