TRAIL and its receptors in the colonic epithelium: a putative role in the defense of viral infections

Death receptor 5 is required for intestinal stem cell activity during intestinal epithelial renewal at homoeostasis

Intestinal epithelial renewal, which depends on the proliferation and differentiation of intestinal stem cells (ISCs), is essential for epithelial homoeostasis. Understanding the mechanism controlling ISC activity is important. We found that death receptor 5 (DR5) gene deletion (DR5-/-) mice had impaired epithelial absorption and barrier function, resulting in delayed weight gain, which might be related to the general reduction of differentiated epithelial cells. In DR5-/- mice, the expression of ISC marker genes, the number of Olfm4+ ISCs, and the number of Ki67+ and BrdU+ cells in crypt were reduced. Furthermore, DR5 deletion inhibited the expression of lineage differentiation genes driving ISC differentiation into enterocytes, goblet cells, enteroendocrine cells, and Paneth cells. Therefore, DR5 gene loss may inhibit the intestinal epithelial renewal by dampening ISC activity. The ability of crypts from DR5-/- mice to form organoids decreased, and selective DR5 activation by Bioymifi promoted organoid growth and the expression of ISC and intestinal epithelial cell marker genes. Silencing of endogenous DR5 ligand TRAIL in organoids down-regulated the expression of ISC and intestinal epithelial cell marker genes. So, DR5 expressed in intestinal crypts was involved in the regulation of ISC activity. DR5 deletion in vivo or activation in organoids inhibited or enhanced the activity of Wnt, Notch, and BMP signalling through regulating the production of Paneth cell-derived ISC niche factors. DR5 gene deletion caused apoptosis and DNA damage in transit amplifying cells by inhibiting ERK1/2 activity in intestinal crypts. Inhibition of ERK1/2 with PD0325901 dampened the ISC activity and epithelial regeneration. In organoids, when Bioymifi's effect in activating ERK1/2 activity was completely blocked by PD0325901, its role in stimulating ISC activity and promoting epithelial regeneration was also eliminated. In summary, DR5 in intestinal crypts is essential for ISC activity during epithelial renewal under homoeostasis.

Escaping cell death via TRAIL decoy receptors: a systematic review of their roles and expressions in colorectal cancer

The development of targeted therapy such as tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-based therapy has gained increasing attention as a promising new approach in cancer therapy. TRAIL specifically targets cancer cells while sparing the normal cells, thus, limiting the known side effects of the majority anti-cancer therapies. As more extensive research and clinical trials are conducted, resistance to TRAIL molecule has become one of the significant issues associated with the failure of TRAIL in treating colorectal cancer (CRC). To date, the exact mechanism by which TRAIL resistance may have occurred remains unknown. Interestingly, recent studies have revealed the critical role of the TRAIL decoy receptor family; consisting of decoy receptor 1 (DcR1; also known as TRAIL-R3), decoy receptor 2 (DcR2; also known as TRAIL-R4), and osteoprotegerin (OPG) in driving TRAIL resistance. This review highlights the expression of the decoy receptors in CRC and its possible association with the reduction in sensitivity towards TRAIL treatment based on the currently available in vitro, in vivo, and human studies. Additionally, discrepancies between the outcomes from different research groups are discussed, and essential areas are highlighted for future investigation of the roles of decoy receptors in modulating TRAIL-induced apoptosis. Overcoming TRAIL resistance through modulating the expression(s) and elucidating the role(s) of TRAIL decoy receptors hold great promise for TRAIL-based therapies to be extensively explored in treating human cancers including CRC.

Signaling pathways in intestinal homeostasis and colorectal cancer: KRAS at centre stage

The intestinal epithelium acts as a physical barrier that separates the intestinal microbiota from the host and is critical for preserving intestinal homeostasis. The barrier is formed by tightly linked intestinal epithelial cells (IECs) (i.e. enterocytes, goblet cells, neuroendocrine cells, tuft cells, Paneth cells, and M cells), which constantly self-renew and shed. IECs also communicate with microbiota, coordinate innate and adaptive effector cell functions. In this review, we summarize the signaling pathways contributing to intestinal cell fates and homeostasis functions. We focus especially on intestinal stem cell proliferation, cell junction formation, remodelling, hypoxia, the impact of intestinal microbiota, the immune system, inflammation, and metabolism. Recognizing the critical role of KRAS mutants in colorectal cancer, we highlight the connections of KRAS signaling pathways in coordinating these functions. Furthermore, we review the impact of KRAS colorectal cancer mutants on pathway rewiring associated with disruption and dysfunction of the normal intestinal homeostasis. Given that KRAS is still considered undruggable and the development of treatments that directly target KRAS are unlikely, we discuss the suitability of targeting pathways downstream of KRAS as well as alterations of cell extrinsic/microenvironmental factors as possible targets for modulating signaling pathways in colorectal cancer.

Gastrointestinal involvement attenuates COVID-19 severity and mortality

Given that gastrointestinal (GI) symptoms are a prominent extrapulmonary manifestation of coronavirus disease 2019 (COVID-19), we investigated intestinal infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its effect on disease pathogenesis. SARS-CoV-2 was detected in small intestinal enterocytes by immunofluorescence staining or electron microscopy, in 13 of 15 patients studied. High dimensional analyses of GI tissues revealed low levels of inflammation in general, including active downregulation of key inflammatory genes such as IFNG, CXCL8, CXCL2 and IL1B and reduced frequencies of proinflammatory dendritic cell subsets. To evaluate the clinical significance of these findings, examination of two large, independent cohorts of hospitalized patients in the United States and Europe revealed a significant reduction in disease severity and mortality that was independent of gender, age, and examined co-morbid illnesses. The observed mortality reduction in COVID-19 patients with GI symptoms was associated with reduced levels of key inflammatory proteins including IL-6, CXCL8, IL-17A and CCL28 in circulation but was not associated with significant differences in nasopharyngeal viral loads. These data draw attention to organ-level heterogeneity in disease pathogenesis and highlight the role of the GI tract in attenuating SARS-CoV-2-associated inflammation with related mortality benefit.

ONE SENTENCE SUMMARY

Intestinal infection with SARS-CoV-2 is associated with a mild inflammatory response and improved clinical outcomes.

Selective Tumor Cell Apoptosis and Tumor Regression in CDH17-Positive Colorectal Cancer Models using BI 905711, a Novel Liver-Sparing TRAILR2 Agonist

Activation of TRAILR2 has emerged as an important therapeutic concept in cancer treatment. TRAILR2 agonistic molecules have only had limited clinical success, to date, due either to lack of efficacy or hepatotoxicity. BI 905711 is a novel tetravalent bispecific antibody targeting both TRAILR2 and CDH17 and represents a novel liver-sparing TRAILR2 agonist specifically designed to overcome the disadvantages of previous strategies. Here, we show that BI 905711 effectively triggered apoptosis in a broad panel of CDH17-positive colorectal cancer tumor cells in vitro. Efficient induction of apoptosis was dependent on the presence of CDH17, as exemplified by the greater than 1,000-fold drop in potency in CDH17-negative cells. BI 905711 demonstrated single-agent tumor regressions in CDH17-positive colorectal cancer xenografts, an effect that was further enhanced upon combination with irinotecan. Antitumor efficacy correlated with induction of caspase activation, as measured in both the tumor and plasma. Effective tumor growth inhibition was further demonstrated across a series of different colorectal cancer PDX models. BI 905711 induced apoptosis in both a cis (same cell) as well as trans (adjacent cell) fashion, translating into significant antitumor activity even in xenograft models with heterogeneous CDH17 expression. In summary, we demonstrate that BI 905711 has potent and selective antitumor activity in CDH17-positive colorectal cancer models both in vitro and in vivo. The high prevalence of over 95% CDH17-positive tumors in patients with colorectal cancer, the molecule preclinical efficacy together with its potential for a favorable safety profile, support the ongoing BI 905711 phase I trial in colorectal cancer and additional CDH17-positive cancer types (NCT04137289).

TRAIL-R1 and TRAIL-R2 Mediate TRAIL-Dependent Apoptosis in Activated Primary Human B Lymphocytes

The maintenance of B cell homeostasis requires a tight control of B cell generation, survival, activation, and maturation. In lymphocytes upon activation, increased sensitivity to apoptotic signals helps controlling differentiation and proliferation. The death receptor Fas is important in this context because genetic Fas mutations in humans lead to an autoimmune lymphoproliferative syndrome that is similar to lymphoproliferation observed in Fas-deficient mice. In contrast, the physiological role of TNF-related apoptosis-inducing ligand receptors (TRAIL-Rs) in humans has been poorly studied so far. Indeed, most studies have focused on tumor cell lines and on mouse models whose results are difficult to transpose to primary human B cells. In the present work, the expression of apoptosis-inducing TRAIL-R1 and TRAIL-R2 and of the decoy receptors TRAIL-R3 and TRAIL-R4 was systematically studied in all developmental stages of peripheral B cells isolated from the blood and secondary lymphoid organs. Expression of TRAIL-Rs is modulated along development, with highest levels observed in germinal center B cells. In addition, T-dependent and T-independent signals elicited induction of TRAIL-Rs with distinct kinetics, which differed among B cell subpopulations: switched memory cells rapidly upregulated TRAIL-R1 and -2 upon activation while naïve B cells only reached similar expression levels at later time points in culture. Increased expression of TRAIL-R1 and -2 coincided with a caspase-3-dependent sensitivity to TRAIL-induced apoptosis in activated B cells but not in freshly isolated resting B cells. Finally, both TRAIL-R1 and TRAIL-R2 could signal actively and both contributed to TRAIL-induced apoptosis. In conclusion, this study provides a systematic analysis of the expression of TRAIL-Rs in human primary B cells and of their capacity to signal and induce apoptosis. This dataset forms a basis to further study and understand the dysregulation of TRAIL-Rs and TRAIL expression observed in autoimmune diseases. Additionally, it will be important to foresee potential bystander immunomodulation when TRAIL-R agonists are used in cancer treatment.

Immunopathogenesis of Liver Injury During Hepatitis C Virus Infection

The present report describes current concepts about the mechanism of liver cell injury caused by host immune response against hepatitis C virus (HCV) infection in human beings. This report is based on the observations from experimental studies and follow-up actions on human liver diseases. The results from different investigations suggest that liver injury depends on the presentation of viral antigen and the level of host immune response raised against HCV-related peptides. Both innate and adaptive immunity are triggered to counter the viral onset. During development of host immunity, the cell-mediated immune response involving CD4⁺ Th1 cells and CD8⁺ cytotoxic T-lymphocyte (CTL) cells were found to play a major role in causing liver damage. The hepatic Innate lymphoid cells (ILCs) subsets are involved in the immune regulation of different liver diseases: viral hepatitis, mechanical liver injury, and fibrosis. Humoral immunity and natural killer (NK) cell action also contributed in liver cell injury by antibody-dependent cellular cytotoxicity (ADCC). In fact, immunopathogenesis of HCV infection is a complex phenomenon where regulation of immune response at several steps decides the possibility of viral elimination or persistence. Regulation of immune response was noted starting from viral-host interaction to immune reaction cascade engaged in cell damage. The activation or suppression of interferon-stimulated genes, NK cell action, CTL inducement by regulatory T cells (Treg), B cell proliferation, and so on was demonstrated during HCV infection. Involvement of HLA in antigen presentation, as well as types of viral genotypes, also influenced host immune response against HCV peptides. The combined effect of all these effector mechanisms ultimately decides the progression of viral onset to acute or chronic infection. In conclusion, immunopathogenesis of liver injury after HCV infection may be ascribed mainly to host immune response. Second, it is cell-mediated immunity that plays a predominant role in liver cell damage.

Mesothelin's minimal MUC16 binding moiety converts TR3 into a potent cancer therapeutic via hierarchical binding events at the plasma membrane

TRAIL has been extensively explored as a cancer drug based on its tumor-selective activity profile but it is incapable per se of discriminating between death receptors expressed by normal host cells and transformed cancer cells. Furthermore, it is well documented that surface tethering substantially increases its biologic activity. We have previously reported on Meso-TR3, a constitutive TRAIL trimer targeted to the biomarker MUC16 (CA125), in which the entire ectodomain of human mesothelin was genetically fused to the TR3 platform, facilitating attachment to the cancer cells via the MUC16 receptor. Here, we designed a truncation variant, in which the minimal 64 amino acid MUC16 binding domain of mesothelin was incorporated into TR3. It turned out that the dual-domain biologic Meso64-TR3 retained its high MUC16 affinity and bound to the cancer cells quickly, independent of the TR3/death receptor interaction. Furthermore, it was substantially more potent than Meso-TR3 and TR3 in vitro and in a preclinical xenograft model of MUC16-dependent ovarian cancer. Phenotypically, Meso64-TR3 is more closely related to non-targeted TR3, evident by indistinguishable activity profiles on MUC16-deficient cancers and similar thermal stability characteristics. Overall, Meso64-TR3 represents a fully human, MUC16-targetd TRAIL-based biologic, ideally suited for exploring preclinical and clinical evaluation studies in MUC16-dependent malignancies.

The probiotic Propionibacterium freudenreichii as a new adjuvant for TRAIL-based therapy in colorectal cancer

TNF-Related Apoptosis-Inducing Ligand (TRAIL) is a well-known apoptosis inducer, which activates the extrinsic death pathway. TRAIL is pro-apoptotic on colon cancer cells, while not cytotoxic towards normal healthy cells. However, its clinical use is limited by cell resistance to cell death which occurs in approximately 50% of cancer cells. Short Chain Fatty Acids (SCFA) are also known to specifically induce apoptosis of cancer cells. In accordance, we have shown that food grade dairy propionibacteria induce intrinsic apoptosis of colon cancer cells, via the production and release of SCFA (propionate and acetate) acting on mitochondria. Here, we investigated possible synergistic effect between Propionibacterium freudenreichii and TRAIL. Indeed, we hypothesized that acting on both extrinsic and intrinsic death pathways may exert a synergistic pro-apoptotic effect. Whole transcriptomic analysis demonstrated that propionibacterial supernatant or propionibacterial metabolites (propionate and acetate), in combination with TRAIL, increased pro-apoptotic gene expression (TRAIL-R2/DR5) and decreased anti-apoptotic gene expression (FLIP, XIAP) in HT29 human colon cancer cells. The revealed synergistic pro-apoptotic effect, depending on both death receptors (TRAIL-R1/DR4, TRAIL-R2/DR5) and caspases (caspase-8, -9 and -3) activation, was lethal on cancer cells but not on normal human intestinal epithelial cells (HIEC), and was inhibited by Bcl-2 expression. Finally, milk fermented by P. freudenreichii induced HT29 cells apoptosis and enhanced TRAIL cytotoxic activity, as did P. freudenreichii DMEM culture supernatants or its SCFA metabolites. These results open new perspectives for food grade P. freudenreichii-containing products in order to potentiate TRAIL-based cancer therapy in colorectal cancer.

Osteoprotegerin: A novel biomarker for inflammatory bowel disease and gastrointestinal carcinoma

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily of proteins. Although initial data illustrated the key role that OPG plays in bone turnover, numerous recent reports indicate that OPG is also an important factor in inflammatory pathways and tumor cell survival. OPG contributes directly to inflammatory processes and has been evaluated as a novel non-invasive biomarker of gut inflammation. Furthermore, OPG affects cell turn-over, differentiation, death, and survival via extracellular pathways, correlating with worse prognosis in inflammatory bowel diseases and several gastrointestinal carcinomas. It is now clear that OPG has multiple functions and characteristics. This review gives an overview of OPG, highlights its roles in different extracellular pathways, and outlines how OPG could be used as a novel non-invasive biological marker in inflammatory bowel diseases and gastrointestinal carcinomas.

TRAIL-receptor 1 IgM antibodies strongly induce apoptosis in human cancer cells in vitro and in vivo

Agonistic tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-receptor-specific antibodies are attractive antitumor therapeutics. Recently, our group has generated several human monoclonal antibodies (mAbs) to TRAIL-receptor-1 (TRAIL-R1) (TR1-IgGs) using ISAAC technology. However, these TR1-IgGs did not demonstrate ideal apoptosis-inducing capacity in the absence of additional antibodies. To overcome this limitation, we class-switched the TR1-IgGs to TRAIL-R1 IgM antibodies (TR1-IgMs); TR1-IgMs might possess high valency and facilitate the crosslinking of the cell surface receptors. We showed that the TR1-IgMs bound TRAIL-R1, activated the caspase signal, and induced strong apoptosis (100-fold higher compared with the IgG form in one case) in human tumor cell lines without any additional crosslinking in vitro. We further demonstrated that these TR1-IgMs dramatically inhibited tumor growth in a xenograft model through the caspase activation cascade. These data suggest that TR1-IgMs may become potential immunotherapeutic agents for cancer therapy.

Onto better TRAILs for cancer treatment

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of the TNF cytokine superfamily. By cross-linking TRAIL-Receptor (TRAIL-R) 1 or TRAIL-R2, also known as death receptors 4 and 5 (DR4 and DR5), TRAIL has the capability to induce apoptosis in a wide variety of tumor cells while sparing vital normal cells. The discovery of this unique property among TNF superfamily members laid the foundation for testing the clinical potential of TRAIL-R-targeting therapies in the cancer clinic. To date, two of these therapeutic strategies have been tested clinically: (i) recombinant human TRAIL and (ii) antibodies directed against TRAIL-R1 or TRAIL-R2. Unfortunately, however, these TRAIL-R agonists have basically failed as most human tumors are resistant to apoptosis induction by them. It recently emerged that this is largely due to the poor agonistic activity of these agents. Consequently, novel TRAIL-R-targeting agents with increased bioactivity are currently being developed with the aim of rendering TRAIL-based therapies more active. This review summarizes these second-generation novel formulations of TRAIL and other TRAIL-R agonists, which exhibit enhanced cytotoxic capacity toward cancer cells, thereby providing the potential of being more effective when applied clinically than first-generation TRAIL-R agonists.

Cell death at the intestinal epithelial front line

The intestinal epithelium represents the largest epithelial surface in our body. This single-cell-layer epithelium mediates important functions in the absorption of nutrients and in the maintenance of barrier function, preventing luminal microorganisms from invading the body. Due to its constant regeneration the intestinal epithelium is a tissue not only with very high proliferation rates but also with very prominent physiological and pathophysiological cell death induction. The normal physiological differentiation and maturation of intestinal epithelial cells leads to their shedding and apoptotic cell death within a few days, without disturbing the epithelial barrier integrity. In contrast excessive intestinal epithelial cell death induced by irradiation, drugs and inflammation severely impairs the vital functions of this tissue. In this review we discuss cell death processes in the intestinal epithelium in health and disease, with special emphasis on cell death triggered by the tumour necrosis factor receptor family.

Interferon-Mediated Cytokine Induction Determines Sustained Virus Control in Chronic Hepatitis C Virus Infection

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and associated complications such as liver cirrhosis and hepatocellular carcinoma. Interferons (IFNs) are crucial for HCV clearance and a sustained virological response (SVR), but a significant proportion of patients do not respond to IFNα. The underlying mechanisms of an insufficient IFN response remain largely unknown. In this study, we found that patients responding to IFNα with viral clearance had significantly higher serum levels of TNF-related apoptosis inducing ligand (TRAIL), compared with patients who failed to control HCV. In addition, upon direct IFNα exposure, peripheral blood mononuclear cells (PBMCs) from patients with SVR upregulated TRAIL, as well as IFN-γ and the chemokines CXCL9 and CXCL10, much more strongly than cells from patients with antiviral treatment failure. As a possible mechanism of the stronger IFNα-induced cytokine response, we identified higher levels of expression and phosphorylation of the transcription factor STAT1 in PBMCs from patients with SVR. Increased TRAIL expression additionally involved the NF-κB and JNK signaling pathways. Thus, SVR in chronic HCV infection is associated with a strong IFNα-induced cytokine response, which might allow for the early prediction of treatment efficacy in HCV infection.

TRAIL receptor deficiency sensitizes mice to dextran sodium sulphate-induced colitis and colitis-associated carcinogenesis

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptor (TRAIL-R) play important roles in immune regulation and cancer cell death. Although TRAIL has been shown to induce chemokine release in various tumour cells, the function of TRAIL-R in the development of colitis and colitis-associated carcinogenesis has not been explored. In this study, we found that TRAIL-R-deficient mice exhibited a higher incidence of colitis and colitis-associated cancer than that of wild-type (WT) mice, and TRAIL-R expression was down-regulated in WT mice that were fed dextran sulphate sodium. Chemokines, including CCL2 and CXCL1, were highly expressed in the serum and inflammatory colon tissues of TRAIL-R(-/-) mice compared with WT mice, and TRAIL-R(-/-) mice showed a marked infiltration of immune cells during colitis. Hyperactivation of Janus kinase and nuclear factor-κB in colon epithelial cells was also observed, which correlated with the severity of colonic inflammation in TRAIL-R(-/-) mice. These data suggest that TRAIL-R plays a protective role in chemical-induced colon injury and negatively regulates mucosal immune responses.

Molecular profiling of chordoma

The molecular basis of chordoma is still poorly understood, particularly with respect to differentially expressed genes involved in the primary origin of chordoma. In this study, therefore, we compared the transcriptional expression profile of one sacral chordoma recurrence, two chordoma cell lines (U-CH1 and U-CH2) and one chondrosarcoma cell line (U-CS2) with vertebral disc using a high-density oligonucleotide array. The expression of 65 genes whose mRNA levels differed significantly (p<0.001; ≥6-fold change) between chordoma and control (vertebral disc) was identified. Genes with increased expression in chordoma compared to control and chondrosarcoma were most frequently located on chromosomes 2 (11%), 5 (8%), 1 and 7 (each 6%), whereas interphase cytogenetics of 33 chordomas demonstrated gains of chromosomal material most prevalent on 7q (42%), 12q (21%), 17q (21%), 20q (27%) and 22q (21%). The microarray data were confirmed for selected genes by quantitative polymerase chain reaction analysis. As in other studies, we showed the expression of brachyury. We demonstrate the expression of new potential candidates for chordoma tumorigenesis, such as CD24, ECRG4, RARRES2, IGFBP2, RAP1, HAI2, RAB38, osteopontin, GalNAc-T3, VAMP8 and others. Thus, we identified and validated a set of interesting candidate genes whose differential expression likely plays a role in chordoma.

Novel treatment option for MUC16-positive malignancies with the targeted TRAIL-based fusion protein Meso-TR3

Background

The targeted delivery of cancer therapeutics represents an ongoing challenge in the field of drug development. TRAIL is a promising cancer drug but its activity profile could benefit from a cancer-selective delivery mechanism, which would reduce potential side effects and increase treatment efficiencies. We recently developed the novel TRAIL-based drug platform TR3, a genetically fused trimer with the capacity for further molecular modifications such as the addition of tumor-directed targeting moieties. MUC16 (CA125) is a well characterized biomarker in several human malignancies including ovarian, pancreatic and breast cancer. Mesothelin is known to interact with MUC16 with high affinity. In order to deliver TR3 selectively to MUC16-expressing cancers, we investigated the possibility of targeted TR3 delivery employing the high affinity mesothelin/MUC16 ligand/receptor interaction.

Methods

Using genetic engineering, we designed the novel cancer drug Meso-TR3, a fusion protein between native mesothelin and TR3. The recombinant proteins were produced with mammalian HEK293T cells. Meso-TR3 was characterized for binding selectivity and killing efficacy against MUC16-positive cancer cells and controls that lack MUC16 expression. Drug efficacy experiments were performed in vitro and in vivo employing an intraperitoneal xenograft mouse model of ovarian cancer.

Results

Similar to soluble mesothelin itself, the strong MUC16 binding property was retained in the Meso-TR3 fusion protein. The high affinity ligand/receptor interaction was associated with a selective accumulation of the cancer drug on MUC16-expressing cancer targets and directly correlated with increased killing activity in vitro and in a xenograft mouse model of ovarian cancer. The relevance of the mesothelin/MUC16 interaction for attaching Meso-TR3 to the cancer cells was verified by competitive blocking experiments using soluble mesothelin. Mechanistic studies using soluble DR5-Fc and caspase blocking assays confirmed engagement of the extrinsic death receptor pathway. Compared to non-targeted TR3, Meso-TR3 displayed a much reduced killing potency on cells that lack MUC16.

Conclusions

Soluble Meso-TR3 targets the cancer biomarker MUC16 in vitro and in vivo. Following attachment to the tumor via surface bound MUC16, Meso-TR3 acquires full activation with superior killing profiles compared to non-targeted TR3, while its bioactivity is substantially reduced on cells that lack the tumor marker. This prodrug phenomenon represents a highly desirable property because it has the potential to enhance cancer killing with fewer side-effects than non-targeted TRAIL-based therapeutics. Thus, further exploration of this novel fusion protein is warranted as a possible therapeutic for patients with MUC16-positive malignancies.

Levels of TNF-related apoptosis-inducing ligand (TRAIL) show a long-term stability in the breast milk of mothers of preterm infants

BACKGROUND

The immune modulator TNF-related apoptosis-inducing ligand (TRAIL) has been found at extremely high levels in human milk of women with normal gestation at day 5 after delivery.

OBJECTIVE

To investigate the presence and the levels of soluble TRAIL in human milk of women with preterm delivery at different time points post-partum (32, 34, and 36 weeks from conception).

METHODS

The levels of soluble TRAIL were analyzed by ELISA in the breast milk of a group of 25 women with preterm delivery at different gestational ages.

RESULTS

Soluble TRAIL was present at high levels in human milk since early post-conceptional ages (32 weeks). No significant differences in TRAIL levels were noticed with respect to different gestational ages, or with respect to time of collection when comparing, in a selected group of patients, samples obtained between 15 and 26 days with those obtained 27 and 40 days after birth.

CONCLUSION

Due to the key immunoregulatory role of human soluble TRAIL, the presence of high levels of TRAIL in the milk of women with preterm delivery and its maintenance at high levels up to 72 days after birth support the importance of breastfeeding the preterm newborn.

Expression of TRAIL in liver tissue from patients with different outcomes of HBV infection

OBJECTIVES

Hepatitis B virus (HBV) infection triggers the production of TRAIL, suggesting that TRAIL may play a role in liver injury after HBV infection. However, it remains unclear whether TRAIL expression in liver tissue correlates with the extent of liver injury caused by HBV infection. The aim of this article was to investigate the correlation of TRAIL expression and disease severity.

METHODS

Liver biopsy specimens were collected from 71 patients with different outcomes of HBV infection, including 25 cases of chronic hepatitis B (CHB), 18 cases of severe hepatitis B (SHB), and 28 cases of liver cirrhosis (LC). Besides, specimens from 33 healthy individuals without detectable liver diseases were used as negative control (NC). The expression of TRAIL was measured by immunohistochemistry.

RESULTS

Expression of TRAIL in the HBV-infected patients was higher than that in the NC (P<0.001). Among the patients, TRAIL expression in the ones with CHB was significantly higher than that in NC (P<0.001). However, there was no statistically significant difference between patients with SHB and NC or between the ones with LC and NC (P=0.067 and P=0.178, respectively). Moreover, TRAIL expression in patients with CHB was higher than that in patients with SHB or LC (P<0.001 for both), whereas no statistically significant difference was observed between patients with SHB and the ones with LC (P=0.511).

CONCLUSION

TRAIL is involved in the inflammatory and immunoregulatory response after HBV infection. However, there was no significant correlation between expression of TRAIL and the extent of liver injury.

TRAIL up-regulation must be accompanied by a reciprocal PKCε down-regulation during differentiation of colonic epithelial cell: implications for colorectal cancer cell differentiation

PKC isoenzymes play central roles in various cellular signalling pathways, participating in a variety of protein phosphorylation cascades that regulate/modulate cellular structure and gene expression. It has been firmly established that several isoforms of PKC have a role in the regulation of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) activity. Our interest in probing the role of the epsilon isoform of PKC in the colonic cell differentiation stems from the discovery that PKCε and TRAIL are involved in the differentiation of other cell types like hematopoietic stem cells. Although the role of PKCε and TRAIL in the gastrointestinal system is unclear, it has been observed that PKCε has oncogenic activity in colon epithelial cells (CEC), while TRAIL increases the death of intestinal epithelial cells during inflammation. Here we demonstrate a reciprocal expression of PKCε and TRAIL in human colon mucosa: CECs at the bottom of the colonic crypts show high levels of PKCε, being negative for TRAIL expression. On the contrary, luminal CECs are positive for TRAIL, while negative for PKCε. Indeed, TRAIL- and butyrate-induced differentiation of the human colorectal cancer cell line HT29 requires the decrease of PKCε expression, whose absence in turn increases cell sensitivity to TRAIL-induced apoptosis. Moreover, TRAIL preferentially promotes HT29 differentiation into goblet cells. Taken together, this data demonstrate that TRAIL and PKCε must be reciprocally regulated to ensure physiological CEC differentiation starting from the stem cell pool, and that the down-regulation of PKCε is however critical for the differentiation and apoptosis of cancer cells.

Role of individual caspases induced by astrovirus on the processing of its structural protein and its release from the cell through a non-lytic mechanism

Caspases (Casp) activity has been associated with the intracellular proteolytic processing of the structural protein to yield the mature capsid formed by VP70 and with the cell release of human astrovirus (HAstV). This work describes the role of individual Casp on these events. The activity of initiator (-8, -9) and executioner (-3/7) Casp was clearly detected at 12h post-infection. All these proteases were able to cleave VP90 in an in vitro assay, but this processing was blocked in cells transfected with siRNA against Casp-3, -9, but not against Casp-8. In contrast, virus release, observed in the absence of cell lysis, was more drastically affected by either silencing Casp-3 or in the presence of the inhibitor Ac-DEVD-CHO. Cleavage of VP90 to yield VP70 was mapped at motif TYVD(657). These data indicate that the processing of VP90 and the release of HAstV from the cell are two Casp-related, but apparently independent, events.

The TRAIL to viral pathogenesis: the good, the bad and the ugly

Since the discovery of Tumor Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL) in 1995, much has been learned about the protein, its receptors and signaling cascade to induce apoptosis and the regulation of its expression. However, the physiologic role or roles that TRAIL may play in vivo are still being explored. The expression of TRAIL on effector T cells and the ability of TRAIL to induce apoptosis in virally infected cells provided early clues that TRAIL may play an active role in the immune defense against viral infections. However, increasing evidence is emerging that TRAIL may have a dual function in the immune system, both as a means to kill virally infected cells and in the regulation of cytokine production. TRAIL has been implicated in the immune response to viral infections (good), and in the pathogenesis of multiple viral infections (bad). Furthermore, several viruses have evolved mechanisms to manipulate TRAIL signaling to increase viral replication (ugly). It is likely that whether TRAIL ultimately has a proviral or antiviral effect will be dependent on the specific virus and the overall cytokine milieu of the host. Knowledge of the factors that determine whether TRAIL is proviral or antiviral is important because the TRAIL system may become a target for development of novel antiviral therapies.

Hypoxia/reoxygenation up-regulates death receptor expression and enhances apoptosis in human biliary epithelial cells

AIMS

To investigate whether ischemia/reperfusion (I/R)-induced apoptosis in the bile duct epithelium could be mediated by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors in biliary epithelial cells, we examined the effects of hypoxia/reoxygenation (H/R) on TRAIL cytotoxicity.

MAIN METHODS

Using an H/R model, normal primary human intrahepatic biliary epithelial cells were exposed to hypoxia for 1 h, and then reoxygenated. Expressions of death receptor 4 (DR4) and DR5 mRNA and protein were measured. After 1 h of hypoxia, biliary epithelial cells were treated with TRAIL in different concentrations for 4 h. The death of biliary epithelial cells was confirmed by analysis of apoptosis and methylthiazolyl tetrazolium. The activities of caspase-3 and caspase-8 were determined by fluorometric assay.

KEY FINDINGS

Compared with normoxic-cultured cells, the mRNA expressions of DR4 and DR5 were up-regulated from 0 min after reoxygenation, reaching a peak value at 60 min after reoxygenation. The protein expression of DR4 was most intense at 90 min after reoxygenation; the most intense expression of DR5 came at 120 min after reoxygenation. The apoptosis rate increased in the TRAIL treatment group and further increased in the TRAIL plus H/R group, and the effect of concentration-dependent TRAIL-mediated cell killing was more pronounced. Caspase-3 and caspase-8 enzymatic activities after H/R also increased with increased TRAIL concentration.

SIGNIFICANCE

H/R up-regulated the expression of DR4 and DR5, and enhanced TRAIL-mediated apoptosis in normal human intrahepatic biliary epithelial cells.

A single-nucleotide polymorphism in the gene encoding osteoprotegerin, an anti-inflammatory protein produced in response to infection with diarrheagenic Escherichia coli, is associated with an increased risk of nonsecretory bacterial diarrhea in North American travelers to Mexico

BACKGROUND

Osteoprotegerin (OPG), an immunoregulatory member of the TNF receptor superfamily, is expressed in inflamed intestinal mucosa. We investigated whether OPG is produced by intestinal epithelial cells and tested the hypothesis that single-nucleotide polymorphisms (SNPs) in the gene encoding OPG (TNFRSF11B) are associated with traveler's diarrhea (TD) among North American travelers to Mexico.

METHODS

OPG concentration was measured in the supernatants of T84 cells infected with various diarrheagenic Escherichia coli pathotypes. Genotyping was performed for 4 SNPs in the OPG gene for 968 North American travelers with or without TD. Stool samples from travelers with TD were evaluated for the presence of enteric pathogens.

RESULTS

T84 cells produced higher OPG levels in response to infection with various diarrheagenic E. coli pathotypes than with E. coli controls (P<.05). A SNP in the exon 1 region of the OPG gene (OPG+1181G>C) was associated with TD in white travelers who stayed in Mexico for >1 week during the summer (P=.009) and for TD due to nonsecretory pathogens (P=.001).

CONCLUSIONS

Our study suggests that OPG is secreted by intestinal epithelial cells in response to enteropathogens and that a polymorphism in the OPG gene is associated with an increased susceptibility to TD.

The Biology of TRAIL and the Role of TRAIL-Based Therapeutics in Infectious Diseases

TNF-related apoptosis inducing ligand (TRAIL) is a key mediator of the innate immune response to infection. While TRAIL-mediated apoptosis plays an essential role in the clearance of virus-infected cells, its physiologic role also includes immunosurveilance for cancer cells. Therapeutics that induce TRAIL-mediated apoptosis in cancer cells remain a focus of ongoing investigation in clinical trials, and much has been learned from these studies regarding the efficacy and toxicity of these interventions. These data, combined with data from numerous preclinical studies that detail the important and multifaceted role of TRAIL during infection with human immunodeficiency virus and other viruses, suggest that therapeutic exploitation of TRAIL signaling offers a novel and efficacious strategy for the management of infectious diseases.

Sensitivity of intestinal fibroblasts to TNF-related apoptosis-inducing ligand-mediated apoptosis in Crohn's disease

OBJECTIVE

Strictures and fistulas are common complications of Crohn's disease (CD). Collagen deposit and fibroblast proliferation can contribute to their development. Tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) binds two pro-apoptotic (TRAIL-R1, TRAIL-R2) and three anti-apoptotic (TRAIL-R3, TRAIL-R4, osteoprotegerin (OPG)) receptors. The aim of this work was to study TRAIL expression and the effects on intestinal fibroblasts (IFs) in CD.

MATERIAL AND METHODS

Intestinal samples from 25 CD (with or without fibrostenosing areas) and 38 control patients (with or without inflammation) were used. TRAIL, TRAIL R2 and TRAIL R3 expression in the intestine and in human IFs was studied by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and immunostaining in IF and intestinal samples. TRAIL-induced IF cell death was studied in the presence or absence of OPG and cytokines. Western blots for poly ADP-ribose polymerase (PARP) and caspase-8 were performed to confirm apoptosis in IFs.

RESULTS

Transcripts for TRAIL and its receptors were confirmed in the intestine. Immunostaining showed intestinal expression of TRAIL, TRAIL-R2 and TRAIL-R3 in fibroblasts, immune cells and epithelial cells, mainly in fibrostenosing areas. TRAIL-R3 mRNA expression was lower in IFs from fibrostenosing CD. The sensitivity of IFs to TRAIL-mediated apoptosis was higher in the fibrostenosing areas of CD. The effect of TRAIL was decreased by IL-6 and its soluble receptor and almost completely reversed by OPG in the CD patients involved.

CONCLUSIONS

TRAIL is expressed in the intestine and influences fibroblast survival. Variations in TRAIL expression and in TRAIL-mediated apoptosis could be involved in the tissue remodelling associated with CD.

Hepatitis C virus infection sensitizes human hepatocytes to TRAIL-induced apoptosis in a caspase 9-dependent manner

Apoptosis of infected cells represents a key host defense mechanism against viral infections. The impact of apoptosis on the elimination of hepatitis C virus (HCV)-infected cells is poorly understood. The TRAIL has been implicated in the death of liver cells in hepatitis-infected but not in normal liver cells. To determine the impact of TRAIL on apoptosis of virus-infected host cells, we studied TRAIL-induced apoptosis in a tissue culture model system for HCV infection. We demonstrated that HCV infection sensitizes primary human hepatocytes and Huh7.5 hepatoma cells to TRAIL induced apoptosis in a dose- and time-dependent manner. Mapping studies identified the HCV nonstructural proteins as key mediators of sensitization to TRAIL. Using a panel of inhibitors targeting different apoptosis pathways, we demonstrate that sensitization to TRAIL is caspase-9 dependent and mediated in part via the mitochondrial pathway. Sensitization of hepatocytes to TRAIL-induced apoptosis by HCV infection represents a novel antiviral host defense mechanism that may have important implications for the pathogenesis of HCV infection and may contribute to the elimination of virus-infected hepatocytes.

CD8 T cells utilize TRAIL to control influenza virus infection

Elimination of influenza virus-infected cells during primary influenza virus infections is thought to be mediated by CD8(+) T cells though perforin- and FasL-mediated mechanisms. However, recent studies suggest that CD8(+) T cells can also utilize TRAIL to kill virally infected cells. Therefore, we herein examined the importance of TRAIL to influenza-specific CD8(+) T cell immunity and to the control of influenza virus infections. Our results show that TRAIL deficiency increases influenza-associated morbidity and influenza virus titers, and that these changes in disease severity are coupled to decreased influenza-specific CD8(+) T cell cytotoxicity in TRAIL(-/-) mice, a decrease that occurs despite equivalent numbers of pulmonary influenza-specific CD8(+) T cells. Furthermore, TRAIL expression occurs selectively on influenza-specific CD8(+) T cells, and high TRAIL receptor (DR5) expression occurs selectively on influenza virus-infected pulmonary epithelial cells. Finally, we show that adoptive transfer of TRAIL(+/+) but not TRAIL(-/-) CD8(+) effector T cells alters the mortality associated with lethal dose influenza virus infections. Collectively, our results suggest that TRAIL is an important component of immunity to influenza infections and that TRAIL deficiency decreases CD8(+) T cell-mediated cytotoxicity, leading to more severe influenza infections.

Impaired TRAIL-dependent cytotoxicity of CD1c-positive dendritic cells in chronic hepatitis C virus infection

Dendritic cells (DCs) play a central role in antiviral immunity. Conflicting data on DC function have been reported for hepatitis C virus (HCV) infection. In addition to antigen presentation and cytokine secretion, a subset of human DCs displays direct cytotoxic activity. It has been suggested that measles virus and human immunodeficiency virus (HIV) may enhance cytotoxicity of DCs potentially leading to apoptosis of activated T cells and subsequent down-regulation of antiviral immune responses. We demonstrate that CD1c-positive myeloid DCs, but not BDCA-4-positive plasmacytoid DCs, are able to kill different target cells mainly via tumour necrosis factor-related apoptosis-inducing ligand. The ability of CD1c+ DCs to lyze target cells was found to be completely impaired in patients with chronic hepatitis C (10 chronic HCV patients vs 10 healthy controls; P < 0.001) but not in patients with primary biliary cirrhosis. Successful antiviral therapy of chronic hepatitis C rescued the cytotoxicity of DCs. Myeloid DCs of HCV patients and healthy controls had a similar phenotype and endocytotic activity, however, the frequency of mDCs in the peripheral blood was lower (P = 0.004) and the allostimulatory function was weaker (P < 0.001) in chronic hepatitis C. Thus, in contrast to HIV and measles virus studies on monocyte-derived DCs, freshly isolated myeloid DCs of patients with hepatitis C do not show an increased but a completely abolished cytotoxic activity. The impaired DC cytotoxicity could represent a novel mechanism for the increased prevalence of autoimmunity in HCV infection.

Expression of tumour necrosis factor-related apoptosis-inducing ligand and caspase-3 in relation to grade of inflammation and stage of fibrosis in chronic hepatitis C

AIM

To assess whether the distribution of the recently described proapoptotic ligand, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), and the apoptosis effector, caspase-3 alters with the degree of inflammation and fibrosis present in liver biopsy specimens from patients with chronic hepatitis C virus infection.

METHODS AND RESULTS

Expression of TRAIL and caspase-3 was assessed immunohistochemically in liver biopsy specimens obtained from 89 adults with chronic hepatitis C. Expression of TRAIL in hepatocytes correlated inversely with stage of fibrosis (P = 0.001), classified according to the Scheuer score; expression of caspase-3 in hepatocytes correlated with grade of inflammation (P = 0.012). Expression of TRAIL in hepatocytes was not correlated with grade of inflammation (P > 0.05); expression of caspase-3 was not correlated with stage of fibrosis (P > 0.05). Maximum expression of proapoptotic TRAIL protein was observed in cases with low grade inflammation (G0) and low stage fibrosis (S1). Maximum expression of caspase-3 in hepatocytes was observed in cases with high grade inflammation (G3-4) and high stage fibrosis (S3), but not with liver cirrhosis (S4).

CONCLUSIONS

There is a significant decrease in TRAIL expression with increasing grade of inflammation, whereas caspase-3 expression is significantly increased with advanced fibrosis, short of cirrhosis.

Hepatitis C virus infection and apoptosis

Apoptosis is central for the control and elimination of viral infections. In chronic hepatitis C virus (HCV) infection, enhanced hepatocyte apoptosis and upregulation of the death inducing ligands CD95/Fas, TRAIL and TNFα occur. Nevertheless, HCV infection persists in the majority of patients. The impact of apoptosis in chronic HCV infection is not well understood. It may be harmful by triggering liver fibrosis, or essential in interferon (IFN) induced HCV elimination. For virtually all HCV proteins, pro- and anti-apoptotic effects have been described, especially for the core and NS5A protein. To date, it is not known which HCV protein affects apoptosis in vivo and whether the infectious virions act pro- or anti-apoptotic. With the availability of an infectious tissue culture system, we now can address pathophysiologically relevant issues. This review focuses on the effect of HCV infection and different HCV proteins on apoptosis and of the corresponding signaling cascades.

Regulation of enterocyte apoptosis by acyl-CoA synthetase 5 splicing

BACKGROUND AND AIMS

The constant renewal of enterocytes along the crypt-villus axis (CVA) of human small intestine is due to cell-inherent changes resulting in the apoptotic cell death of senescent enterocytes. The aim of the present study was to examine underlying molecular mechanisms of the cell death at the villus tip.

METHODS

Characterization of human acyl-coenzyme A (CoA) synthetase 5 (ACSL5) was performed by cloning, recombinant protein expression, biochemical approaches, and several functional and in situ analyses.

RESULTS

Our data show that different amounts of acyl-CoA synthetase 5-full length (ACSL5-fl) and a so far unknown splice variant lacking exon 20 (ACSL5-Delta 20) are found in human enterocytes. In contrast with the splice variant ACSL5-Delta 20, recombinant and purified ACSL5-fl protein is active at a highly alkaline pH. Over expression of ACSL5-fl protein is associated with a decrease of the anti-apoptotic FLIP protein in a ceramide-dependent manner and an increased cell-surface expression of the death receptor TRAIL-R1. Expression analyses revealed that the ACSL5-fl/ACSL5-Delta 20 ratio increases along the CVA, thereby sensitizing ACSL5-fl-dominated cells at the villus tip to the death ligand TRAIL, which is corroborated by functional studies with human small intestinal mucosal samples and an immortalized human small intestinal cell line.

CONCLUSIONS

Our results suggest an ACSL5-dependent regulatory mechanism that contributes to the cellular renewal along the CVA in human small intestine. Deregulation of the ACSL5-fl/ACSL5-Delta 20 homeostasis in the maturation and shedding of cells along the CVA might also be of relevance for the development of intestinal neoplasia.

Newly established tumourigenic primary human colon cancer cell lines are sensitive to TRAIL-induced apoptosis in vitro and in vivo

Most data on the therapeutic potential of tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) as well as resistance to FAS ligand (FASL) in colorectal cancer have come from in vitro studies using cell lines. To gain a clearer understanding about the susceptibility of patient tumours to TRAIL and FASL, we derived primary human cancer epithelial cells from colon cancer patients. Characterisation of primary cultures PAP60 and MIH55 determined their highly proliferating advantage, transforming capability and tumorigenicity in vitro and in vivo. Although FASL treatment appeared to cause little apoptosis only in the PAP60 primary culture, increased apoptosis independent of p53 was observed in both primary PAP60 and MIH55 and control cell lines Caco-2, HT29 and DLD-1 after treatment with SuperKiller TRAIL. Expression analysis of death receptors (DR) in the original parental tumours, the primary cultures before and after engraftment as well as the mouse xenografts, revealed a significant upregulation of both DR4 and DR5, which correlated to differences in sensitivity of the cells to TRAIL-induced apoptosis. Treating patient tumour xenograft/SCID mouse models with Killer TRAIL in vivo suppressed tumour growth. This is the first demonstration of TRAIL-induced apoptosis in characterised tumorigenic primary human cultures (in vitro) and antitumour activity in xenograft models (in vivo).

The promise of TRAIL—potential and risks of a novel anticancer therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising new anticancer biotherapeutic. As shown by many preclinical studies, TRAIL efficiently induces apoptosis in numerous tumor cell lines but not in the majority of normal cells. However, an increasing number of publications report on a predominance of TRAIL resistance in primary human tumor cells, which require sensitization for TRAIL-induced apoptosis. Sensitization of cancer cells by treatment with chemotherapeutic drugs and irradiation has been shown to restore TRAIL sensitivity in many TRAIL-resistant tumor cells. Accordingly TRAIL treatment has been successfully used in different in vivo models for the treatment of tumors also in combination with chemotherapeutics without significant toxicity. However, some reports demonstrated toxicity of TRAIL alone or in combination with chemotherapeutic drugs in normal cells. This review summarizes data concerning the apoptosis-inducing pathways and efficacy of TRAIL, alone or in combination with chemotherapeutic drugs, in primary cancer cells compared to the unwanted effects of TRAIL treatment on normal tissue. We discuss the different in vitro tumor cell models and the potential of different recombinant forms of TRAIL or agonistic antibodies to TRAIL death receptors. Most preclinical studies show a high efficiency of a combinatorial TRAIL-based therapy in animal models and in primary human ex vivo tumor cells with a low toxicity in normal cells. Accordingly clinical phase I/II studies have begun and will be developed further with caution.

Immunopathogenesis in hepatitis C virus cirrhosis

HCV (hepatitis C virus) has a high propensity to persist and to cause chronic hepatitis C, eventually leading to cirrhosis. Since HCV itself is not cytopathic, liver damage in chronic hepatitis C is commonly attributed to immune-mediated mechanisms. HCV proteins interact with several pathways in the host's immune response and disrupt pathogen-associated pattern recognition pathways, interfere with cellular immunoregulation via CD81 binding and subvert the activity of NK (natural killer) cells as well as CD4(+) and CD8(+) T-cells. Finally, HCV-specific T-cells become increasingly unresponsive and apparently disappear, owing to several possible mechanisms, such as escape mutations in critical viral epitopes, lack of sufficient help, clonal anergy or expansion of regulatory T-cells. The role of neutralizing antibodies remains uncertain, although it is still possible that humoral immunity contributes to bystander damage of virally coated cells via antibody-dependent cellular cytotoxicity. Cytotoxic lymphocytes kill HCV-infected cells via the perforin/granzyme pathway, but also release Fas ligand and inflammatory cytokines such as IFNgamma (interferon gamma). Release of soluble effector molecules helps to control HCV infection, but may also destroy uninfected liver cells and can attract further lymphocytes without HCV specificity to invade the liver. Bystander damage of these non-specific inflammatory cells will expand the tissue damage triggered by HCV infection and ultimately activate fibrogenesis. A clear understanding of these processes will eventually help to develop novel treatment strategies for HCV liver disease, independent from direct inhibition of HCV replication.

TRAIL induces apoptosis in human colorectal adenoma cell lines and human colorectal adenomas

PURPOSE

Recombinant human (rh) tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potential new anticancer drug which can induce apoptosis in colorectal cancer cell lines. The aim of this study was to investigate whether it is possible to induce apoptosis in human adenoma cell lines and human adenomas using rhTRAIL.

EXPERIMENTAL DESIGN

Two human adenoma cell lines were exposed to 0.1 microg/mL of rhTRAIL for 5 hours. Apoptosis and caspase activation in cell lines were evaluated using immunocytochemistry, fluorimetric caspase assays, and Western blotting. Short-term explant cultures were established from freshly removed human adenomas (n = 38) and biopsies of normal colon epithelium (n = 15), and these were incubated for 5 hours in the presence or absence of 1 microg/mL of rhTRAIL. Apoptosis was determined in paraffin-embedded tissue using morphologic criteria and cleaved caspase-3 staining.

RESULTS

In the adenoma cell lines, rhTRAIL induced up to 55% apoptosis. This coincided with caspase-8 and caspase-3 activation and could be inhibited by a pan-caspase inhibitor. rhTRAIL induced caspase-dependent apoptosis in adenomas with high-grade dysplasia (n = 21) compared with the paired untreated counterparts (apoptotic index, 34 +/- 5% versus 17 +/- 2%, mean +/- SE; P = 0.002), but not in adenomas with low-grade dysplasia (n = 17) or in normal colon epithelium (n = 15).

CONCLUSIONS

Colorectal adenoma cell lines and adenomas with high-grade dysplasia are sensitive to rhTRAIL-induced apoptosis, whereas normal colon epithelium is not. This suggests the potential application of rhTRAIL in the treatment of adenomas with high-grade dysplasia.

Hypoxia/reoxygenation up-regulated the expression of death receptor 5 and enhanced apoptosis in human hepatocyte line

OBJECTIVES

Ischemia-reperfusion injury (IRI) is a key factor that contributes to early and late dysfunction of liver graft. Although we have known that hepatocytes express death receptors for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), the effects of TRAIL on hypoxia/reoxygenation (H/R)-mediated apoptosis are unclear. This study sought to examine the effects of H/R on TRAIL cytotoxicity, as a cause of primary hepatic graft dysfunction, delayed graft refunction, and chronic graft dysfunction.

METHODS

Using an hepatocyte H/R model in vitro to mimic IRI in the grafted liver, normal human hepatocytes HL-7702 were exposed to hypoxia for 5 hours then reoxygenated for 0, 2, 4, 6, or 20 hours. In another experiment, hepatocytes were exposed to hypoxia for 0, 2, 4, 8, or 20 hours. Expressions of TRAIL-R2/Death receptor 5 (DR5) mRNA were measured by semiquantitative reverse-transcriptase polymerase chain reactions. After 16 hours of hypoxia, human hepatocytes were treated with TRAIL in different concentrations for 5 hours. The death of hepatocytes was confirmed by flow cytometer and methyl thiazolyl tetrazolium analysis.

RESULT

After 5-hour hypoxia, the expressions of DR5 mRNA increased at all times of reoxygenation. DR5 mRNA was up-regulated from 0 hour after reoxygenation, reaching a peak value at 2 hours after reoxygenation compared with the normoxia cultured cells. Moreover, DR5 mRNA was up-regulated gradually following prolonged hypoxia. TRAIL-mediated cell killing was concentration-dependent being greater in the hypoxia treatment group compared to the normoxia group.

CONCLUSIONS

H/R up-regulated the expression of DR5 and enhanced TRAIL-mediated apoptosis in an human hepatocyte line. The TRAIL pathway might play a critical role in hepatocyte apoptosis induced by IRI.

Expression profiling of apoptosis-related genes in enterocytes isolated from patients with ulcerative colitis

Apoptosis regulation has been implicated as a main cause of epithelial dysfunction in patients with ulcerative colitis. Apoptosis can be divided into distinct pathways, which depend on the expression of a large number of apoptosis-related genes. The aim was to elucidate which pathways are dominant in normal and inflamed colonic epithelial cells. An apoptosis-specific gene array expression profiling system of 96 genes was used to determine the expression profile of apoptosis-related genes. Epithelial cells isolated from three patients with active ulcerative colitis were pooled and compared to pooled epithelial cells isolated from three control subjects. Genes found to be three-fold or more overexpressed in ulcerative colitis were subsequently analysed by PCR in a larger population (10 patients with ulcerative colitis, 8 control subjects). Selected genes found not to be regulated were additionally tested by PCR in the same population. Six genes were found to be highly expressed in epithelial cells from both controls and ulcerative colitis patients. These included Bcl-2 antagonist/killer, B lymphoid tyrosine kinase, caspase 14, Harakiri, tumour necrosis factor (TNF) receptor 2, and TNF receptor-associated factor 1 (TRAF1). Three genes were found to be upregulated in ulcerative colitis (p<0.01): caspase 1 and 5, and inhibitor of apoptosis protein 2 (c-IAP2). Both receptor- and mitochondrion-dependent apoptosis pathways are well expressed in enterocytes. Mainly activation-dependent and cytoprotective genes were upregulated in ulcerative colitis.

Interferon regulatory factor-5-regulated pathways as a target for colorectal cancer therapeutics

Colorectal cancer is the second most common cause of cancer-related death. A significant obstacle to successful management of patients with colorectal cancer is intrinsic drug resistance or, in patients who initially responded to chemotherapy, acquired drug resistance. Failure in normal apoptotic pathways often contributes to resistance to anticancer drugs or radiotherapy. As a result, the identification of genes that control cell death and apoptosis has come to the forefront of cancer research, leading to new targets and novel therapeutic strategies in the treatment of colorectal cancer. To this effect, the authors have recently identified a new apoptotic signaling pathway that occurs through the transcription factor interferon regulatory factor-5. Here, the different strategies for targeting the interferon regulatory factor-5 signaling pathway in colorectal cancer are discussed. These strategies can be applied to a new generation of cytotoxic agents, as well as to novel biological compounds that are directed at inducing and/or activating interferon regulatory factor-5 or key components of this pathway.

Implication of TNF-related apoptosis-inducing ligand in inflammatory intestinal epithelial lesions

BACKGROUND & AIMS

Few data exist on the molecular events causing intestinal epithelial destruction during inflammatory processes, such as inflammatory bowel disease (IBD). In this work, we analyzed the potential implication of tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) in these inflammatory lesions.

METHODS

TRAIL and TRAIL-receptor expression were analyzed in normal, inflammatory ileum/colon and human intestinal epithelial cell (IEC) lines (HIEC), Caco-2, and HT-29 using RNase protection assay, real-time and reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blot analysis. TRAIL-induced activation of NF-kappaB was determined by electrophoretic mobility shift assay. Caspase-recruitment domain (CARD)15 expression and interleukin-(IL)8 production were studied by RT-PCR and enzyme-linked immunosorbent assay. Apoptosis was monitored using Annexin-V/caspase-3 assays.

RESULTS

Normal mature IEC expressed low TRAIL levels, whereas, in inflammatory lesions, TRAIL messenger RNA and protein were markedly up-regulated in IEC and lamina propria lymphocytes at levels comparable with trinitrobenzene sulfonic acid-induced colitis. Interferon-gamma and TNF-alpha potently induced TRAIL in IEC. In vitro analyses revealed a dual biologic effect of TRAIL on HIEC: Under noninflammatory conditions, TRAIL up-regulated via nuclear factor-kappaB CARD15 and IL-8, whereas, under inflammatory conditions, TRAIL became a potent inducer of apoptosis in HIEC, which was confirmed ex vivo using ileal organ cultures. TNF-alpha markedly increased the expression of the proapoptotic receptor TRAIL-R2. TRAIL-induced IEC apoptosis required a functional caspase cascade.

CONCLUSIONS

TRAIL is a new inflammatory mediator implicated in the homeostasis of intestinal epithelial barrier functions. TRAIL is highly up-regulated in IEC in inflammatory ileum and colon. It may augment in an auto-/paracrine fashion the elimination of IEC via apoptosis.

Downregulation of TNF-Related Apoptosis-Inducing Ligand (TRAIL)/Apo2L in Barrett's Esophagus With Dysplasia and Adenocarcinoma

TRAIL/Apo2L is a CD95 ligand-related member of the TNF family that initiates apoptosis in immune and neoplastic cells after binding to specific surface receptors. The authors previously reported a specific topographic pattern of TRAIL expression in the normal colonic mucosa and the loss of TRAIL expression in tubular adenomas as well as in most colon carcinomas. Therefore, they hypothesized that similar changes may occur during the malignant transformation of Barrett's esophagus. The aim of this study was to compare TRAIL/Apo2L expression in normal gastroesophageal (GE) junction, Barrett's esophagus with and without dysplasia, and associated adenocarcinoma. Immunohistochemical evaluation of TRAIL expression was performed on formalin-fixed paraffin-embedded sections from 29 GE junction/esophageal biopsies, 20 gastric biopsies, 6 esophagectomies, 2 small bowel resection specimens, and 5 colon biopsies. The expression was graded semiquantitatively on a 4-point scale (0-3). TRAIL was expressed in the foveolar epithelium of the histologically normal GE junctional mucosa and stomach as well as in the normal intestinal epithelium, with maximal expression in the surface epithelium. TRAIL was always detected in Barrett's metaplasia (21/21, 100%), and the overall expression was similar to that of the columnar portion of the normal GE junction (8/8, 100%). TRAIL was rarely and weakly (1+) expressed in Barrett's esophagus with dysplasia (3/18, 16.7%) and adenocarcinoma (1/10, 10.0%) (P<0.001). Similarities in the topographic pattern of TRAIL expression in the normal GE junction, stomach, small intestine, and colon suggest a common function of TRAIL throughout the gastrointestinal tract. These results show that the downregulation of TRAIL is associated with development of dysplasia in Barrett's esophagus. Thus, the immunohistochemically detected downregulation of TRAIL expression appears to be a promising indicator of dysplasia in Barrett's esophagus.

Apoptosis of viral-infected airway epithelial cells limit viral production and is altered by corticosteroid exposure

Background

Effects of respiratory viral infection on airway epithelium include airway hyper-responsiveness and inflammation. Both features may contribute to the development of asthma. Excessive damage and loss of epithelial cells are characteristic in asthma and may result from viral infection.

Objective

To investigate apoptosis in Adenoviral-infected Guinea pigs and determine the role of death receptor and ligand expression in the airway epithelial response to limit viral infection.

Methods

Animal models included both an Acute and a Chronic Adeno-infection with ovalbumin-induced airway inflammation with/without corticosteroid treatment. Isolated airway epithelial cells were cultured to study viral production after infection under similar conditions. Immunohistochemistry, western blots and viral DNA detection were used to assess apoptosis, death receptor and TRAIL expression and viral release.

Results

In vivo and in vitro Adeno-infection demonstrated different apoptotic and death receptors (DR) 4 and 5 expression in response to corticosteroid exposure. In the Acute Adeno-infection model, apoptosis and DR4/5 expression was coordinated and were time-dependent. However, in vitro Acute viral infection in the presence of corticosteroids demonstrated delayed apoptosis and prolonged viral particle production. This reduction in apoptosis in Adeno-infected epithelial cells by corticosteroids exposure induced a prolonged virus production via both DR4 and TRAIL protein suppression. In the Chronic model where animals were ovalbumin-sensitized/challenged and were treated with corticosteroids, apoptosis was reduced relative to adenovirus-infected or corticosteroid alone.

Conclusion

Our data suggests that apoptosis of infected cells limits viral production and may be mediated by DR4/5 and TRAIL expression. In the Acute model of Adeno-infection, corticosteroid exposure may prolong viral particle production by altering this apoptotic response of the infected cells. This results from decreased DR4 and TRAIL expression. In the Chronic model treated with corticosteroids, a similar decreased apoptosis was observed. This data suggests that DR and TRAIL modulation by corticosteroids may be important in viral infection of airway epithelium. The prolonged virus release in the setting of corticosteroids may result from reduced apoptosis and suppressed DR4/TRAIL expression by the infected cells.

Colon cancer and apoptosis

BACKGROUND

The implementation of new therapeutic options for the management of metastatic colon cancer mandates a revisit to apoptosis and its role in colon cancer tumorigenesis with an emphasis on the mechanisms leading to chemotherapeutic resistance and immune system evasion of colon cancer cells.

DATA SOURCES

Literature regarding molecular apoptosis mechanisms and the role of apoptosis in colon cancer progression are reviewed by this article.

CONCLUSION

Programmed cell death has rapidly emerged as a potential target for cancer treatment at various stages of tumor progression. Chemoprevention, immuno-regulation, and metastasis are prospective targets by which apoptotic mechanisms could be utilized in the prevention and management of tumorigenesis. Understanding how defects in the death receptor pathway of apoptosis permit colon cancer cells to escape the immune system would allow for treatment options whereby the body's immune system could again recognize and eliminate unwanted cells.

Involvement of TRAIL/TRAIL-receptors in human intestinal cell differentiation

Despite the fact that tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) and its receptors (TRAIL-Rs) are expressed in intestinal mucosa, little is known about the biological role of this system in intestinal cell physiology. The expression of surface TRAIL and TRAIL-R1, -R2, -R3, -R4 were examined by flow cytometry in the immortalized human cell line tsFHI under culture conditions promoting growth or growth arrest and expression of differentiated traits. A progressive increase of surface TRAIL expression paralleled tsFHI differentiation, consistently with immunohistochemistry analysis showing an increase of TRAIL immunostaining along the crypt-villus axis in normal jejuneal mucosa. In spite of the presence of TRAIL-R1 and TRAIL-R2 "death receptors," recombinant TRAIL was not cytotoxic for tsFHI cells. Exposure of tsFHI to recombinant TRAIL rather increased/anticipated the expression levels of the cyclin-dependent kinase inhibitors p21 and p27, which mediate the induction of growth arrest and the stabilization of differentiated traits, respectively, as well as of the canonical differentiation marker DPPIV. The differentiation inducing activity of TRAIL was abolished by pre-incubation with a Fc-TRAIL-R2 chimera. On the other hand, TRAIL did not significantly modulate the levels of osteoprotegerin (OPG), CXCL8/IL-8, CXCL9/MIG, and CXCL10/IP10 spontaneously released or induced by inflammatory cytokines. Taken together, these data suggest that TRAIL might act as a paracrine trophic cytokine on intestinal epithelium, promoting intestinal cell differentiation.