CD40 ligand protects from TRAIL-induced apoptosis in follicular lymphomas through NF-kappaB activation and up-regulation of c-FLIP and Bcl-xL

Role of decoy molecules in neuronal ischemic preconditioning

AIMS

Decoy receptors bind with TNF related apoptosis inducing ligands (TRAIL) but do not contain the cytoplasmic domains necessary to transduce apoptotic signals. We hypothesized that decoy receptors may confer neuronal protection against lethal ischemia after ischemic preconditioning (IPC).

MAIN METHOD

Mixed cortical neurons were exposed to IPC one day prior to TRAIL treatment or lethal ischemia.

KEY FINDINGS

IPC increased decoy receptor but reduced death receptor expression compared to lethal ischemia. IPC-induced increase in decoy receptor expression was reduced by prior treatment with CAPE, a nuclear factor-kappa B inhibitor (NFκB).

SIGNIFICANCE

Expression of decoy molecules, dependent on NFκB, may mediate neuronal survival induced by IPC.

Differential B-lymphocyte regulation by CD40 and its viral mimic, latent membrane protein 1

CD40 plays a vital role in humoral immunity, via its potent and multifaceted function as an activating receptor of various immune cells, most notably B lymphocytes. The Epstein-Barr virus-encoded transforming protein latent membrane protein 1 (LMP1) serves as a functional mimic of CD40 signals to B cells but lacks key regulatory controls that restrain CD40 signaling. This allows LMP1 to activate B cells in an abnormal manner that can contribute to the pathogenesis of human B-cell lymphoma and autoimmune disease. This review focuses upon a comparative analysis of CD40 versus LMP1 functions and mechanisms of action in B lymphocytes, discussing how this comparison can provide valuable information on both how CD40 signaling is normally regulated and how LMP1 disrupts the normal CD40 pathways, which can provide information of value to therapeutic design.

CD40·FasL and CTLA-4·FasL fusion proteins induce apoptosis in malignant cell lines by dual signaling

Evolution of apoptosis resistance in both lymphoma and leukemia cells is well documented, and induction of apoptosis in malignant cells is a major goal of cancer therapy. Up-regulation of anti-apoptotic signals is one of the mechanisms whereby resistance to apoptosis emerges. We have previously described the fusion proteins CD40·FasL and CTLA-4·FasL, which are formed from two functional membrane proteins and induce apoptosis of activated T cells. The present study explores the potential use of CD40·FasL and CTLA-4·FasL for the killing of malignant cells of lymphatic origin. Using malignant B and T cell lines that differ in surface expression of costimulatory molecules, we found that CTLA-4·FasL induces effective apoptosis of cells expressing CD95 and activates caspases 3, 8, and 9. Only B7-expressing B cells responded to CTLA-4·FasL with rapid abrogation of cFLIP expression. CD40·FasL effectively killed only the T cells that express high levels of CD40L in addition to CD95. In these cells, CD40·FasL significantly diminished cFLIP expression. Importantly, each of the fusion proteins is more potent than its respective components parts, alone or in combination. Thus, the proteins with their two functional ends deliver a pro-apoptotic signal and, in parallel, inhibit an anti-apoptotic signal, thus optimizing the wanted, death-inducing effect. Therefore, these proteins emerge as promising agents to be used for targeted and specific tumor cell killing.

Chemotherapy overcomes TRAIL-R4-mediated TRAIL resistance at the DISC level

TNF-related apoptosis-inducing ligand or Apo2L (Apo2L/TRAIL) is a promising anti-cancer drug owing to its ability to trigger apoptosis by binding to TRAIL-R1 or TRAIL-R2, two membrane-bound receptors that are often expressed by tumor cells. TRAIL can also bind non-functional receptors such as TRAIL-R4, but controversies still exist regarding their potential to inhibit TRAIL-induced apoptosis. We show here that TRAIL-R4, expressed either endogenously or ectopically, inhibits TRAIL-induced apoptosis. Interestingly, the combination of chemotherapeutic drugs with TRAIL restores tumor cell sensitivity to apoptosis in TRAIL-R4-expressing cells. This sensitization, which mainly occurs at the death-inducing signaling complex (DISC) level, through enhanced caspase-8 recruitment and activation, is compromised by c-FLIP expression and is independent of the mitochondria. Importantly, TRAIL-R4 expression prevents TRAIL-induced tumor regression in nude mice, but tumor regression induced by TRAIL can be restored with chemotherapy. Our results clearly support a negative regulatory function for TRAIL-R4 in controlling TRAIL signaling, and unveil the ability of TRAIL-R4 to cooperate with c-FLIP to inhibit TRAIL-induced cell death.

Targeting c-FLIP in cancer

Cellular-FLICE inhibitory protein (c-FLIP) is a key anti-apoptotic regulator that inhibits cell death mediated by the death receptors Fas, DR4, DR5, and TNF-R1. Three splice variants of c-FLIP function at the DISC level by blocking the processing and activation of procaspase-8 and -10. Overexpression of c-FLIP has been identified in many different tumour types, and its downregulation in vitro has been shown to restore apoptosis mediated by CD95L and TRAIL. c-FLIP therefore represents a promising target for cancer therapy. This review focuses on the molecular mechanisms that control c-FLIP expression and current research into inhibitors of the protein. Increasing evidence supports the investigation of c-FLIP as a therapeutic target to restore an apoptotic response in cancer cells.

Follicular lymphoma cell niche: identification of a preeminent IL-4-dependent T(FH)-B cell axis

Follicular lymphoma (FL) B cells contract tight connections with their microenvironment, which governs the pathogenesis and progression of the disease. Indeed, specific immune response gene signatures, obtained from whole biopsy samples, have been associated with patient survival. In this study, we performed gene expression profiling of purified B cell and non-B cell compartments obtained from FL and reactive lymph nodes. We identified 677 non-redundant genes defining the FL interface and involving 26 FL-specific functional networks. This approach highlighted an interleukin-4 (IL-4)-centered pathway associated with an activation of signal transducer and activator of transcription 6 (STAT6), which favors overexpression of IL-4-target genes. In addition, FL microenvironment was characterized by a strong enrichment in follicular helper T cells (T(FH)), as demonstrated through transcriptomic and flow cytometry analyses. The majority of phospho-STAT6(pos) B cells were located at the vicinity of cells expressing the programmed death 1 (PD-1) T(FH) marker. Moreover, purified FL-derived T(FH), expressed IL4 at very high levels compared with purified tonsil-derived T(FH) or non-T(FH) microenvironment. Altogether, our study demonstrated that tumor-infiltrating T(FH) specifically express functional IL-4 in FL, creating an IL-4-dependent T(FH)-B cell axis. This cross talk could sustain FL pathogenesis and represent a new potential therapeutic target.

B cell receptor triggering sensitizes human B cells to TRAIL-induced apoptosis

TRAIL is known to cause death in tumor cells, but physiological regulation of its activity remains poorly characterized. We demonstrate that BCR triggering sensitizes transformed centroblast-like BL cells and peripheral blood memory B cells to TRAIL-mediated apoptosis. The sensitization correlated with surface down-regulation and intracellular retention of TRAIL-R4, along with changes in the expression of several Bcl-2 protein family members. Although enhancing FAS-mediated cell death, CD40 activation protected B cells from TRAIL-induced apoptosis. Combination of Ig cross-linking with CD40 ligation did not prevent TRAIL-R4 down-regulation but induced changes in the mitochondria-regulated pathway of apoptosis that are known to be associated with resistance to TRAIL. Human CD5(+) B cells, presumably stimulated by reactivity to self without immunological help, exhibited very high ex vivo sensitivity to TRAIL. Our results define the first B-lymphocyte-specific physiological signal that increases cellular sensitivity to TRAIL. This may be important for our understanding of TRAIL involvement in the control of B cell responses and aid in designing TRAIL-based therapies for B cell lymphomas.

Pigment epithelium-derived factor is an intrinsic antifibrosis factor targeting hepatic stellate cells

The liver is the major site of pigment epithelium-derived factor (PEDF) synthesis. Recent evidence suggests a protective role of PEDF in liver cirrhosis. In the present study, immunohistochemical analyses revealed lower PEDF levels in liver tissues of patients with cirrhosis and in animals with chemically induced liver fibrosis. Delivery of the PEDF gene into liver cells produced local PEDF synthesis and ameliorated liver fibrosis in animals treated with either carbon tetrachloride or thioacetamide. In addition, suppression of peroxisome proliferator-activated receptor gamma expression, as well as nuclear translocation of nuclear factor-kappa B was found in hepatic stellate cells (HSCs) from fibrotic livers, and both changes were reversed by PEDF gene delivery. In culture-activated HSCs, PEDF, through the induction of peroxisome proliferator-activated receptor gamma, reduced the activity of nuclear factor-kappa B and prevented the nuclear localization of JunD. In conclusion, our observations that PEDF levels are reduced during liver cirrhosis and that PEDF gene delivery ameliorates cirrhosis suggest that PEDF is an intrinsic protector against liver cirrhosis. Direct inactivation of HSCs and the induction of apoptosis of activated HSCs may be two of the mechanisms by which PEDF suppresses liver cirrhosis.

The host-tumor interface in B-cell non-Hodgkin lymphoma: a new world to investigate

Research on B-cell non-Hodgkin lymphoma focuses mainly on oncogenic events occurring in lymphoma cells, but recently a new component has appeared that may be crucial in lymphomagenesis: the tumor microenvironment. Indeed, compelling evidence demonstrates the key role played by nonmalignant bystander cells in the establishment and proliferation of the tumor. Among these cells, stromal cells, monocytes/macrophages, and T cells in lymphoid organs have all been described as contributing to tumor progression. Interactions linked to cell-cell intimate contacts-but also mediated through soluble mediators such as cytokines and chemokines-do form a specific network. All these interrelations directed by the tumor create a friendly environment for lymphoma cells that permits them to proliferate. Blocking the cross-talk between the tumor microenvironment and lymphoma cells may thus represent a promising new strategy for treating B-cell malignancies.

[Evaluation of percentage of lymphocytes B with expression of co-receptors CD 40, CD22 and CD72 in hypertrophied adenoid at children with otitis media with effusion]

INTRODUCTION

In hypertrophied adenoid lymphocytes B make up about 60% all lymphocytes. When the lymphocytes B come in interaction with antigens this membranes signal be passed through their receptor (BCR) to interior of cell. This signal affect modulation on gene expression, activation from which depends activation, anergy or apoptosis of lymphocyte B. Accompany BCR co-receptors regulate his functions influence stimulate or inhibitive. To the most important co-receptors stepping out on lymphocyte B belong: CD40, CD22, CD72.

AIM OF STUDY

The aim of study was evaluation of lymphocytes B (CD19) with co-expression with CD72 and CD40 receptors in hypertrophied adenoid with at children with otitis media with effusion.

MATERIAL

An investigation was executed in hypertrophied adenoids with or without otitis media with effusion.

METHODS

By flow cytometry percentage of lymphocytes B with co-receptors CD 40, CD22 and CD72 in was analyzed.

RESULTS

The percentages of CD19+CD72+ lymphocytes in the group of children with adenoid hypertrophy and exudative otitis media were lower as compared to the reference group. However, the percentages of CD19+CD22+, CD19+CD40+ in the study group was approximate to the reference group.

CONCLUSIONS

The lower percentage of lymphocytes B CD72 + near approximate percentages of lymphocytes B CD40+ and BCD22+ at children with otitis media with effusion can be the cause of incorrect humoral response in hypertrophied adenoid at children. Maybe it is cause reduced spontaneous production IgA and IgG through lymphocyte at children with otitis media with effusion.

A unifying microenvironment model in follicular lymphoma: outcome is predicted by programmed death-1--positive, regulatory, cytotoxic, and helper T cells and macrophages

PURPOSE

The microenvironment influences outcome in follicular lymphoma. Our hypothesis was that several immune cell subsets are important for disease outcome and their individual prognostic importance should be demonstrable in the same analysis and in competition with clinical factors.

EXPERIMENTAL DESIGN

Seventy follicular lymphoma patients with extreme clinical outcome ("poor" and "good" cases) were selected in a population-based cohort of 197. None of the 37 good-outcome patients died from lymphoma, whereas all the 33 poor-outcome patients succumbed in <or=5 years. Furthermore, the good-outcome patients were followed for a long time and needed no or little treatment. A tissue microarray was constructed from diagnostic, pretreatment biopsies. Cellular subsets were quantified after immunostaining, using computerized image analysis, separating cells inside and outside the follicles (follicular and interfollicular compartments). Flow cytometry data from the same samples were also used.

RESULTS

Independently of the Follicular Lymphoma International Prognostic Index, CD4(+) cells were associated with poor outcome and programmed death-1-positive and CD8(+) cells were associated with good outcome. The prognostic values of CD4(+) and programmed death-1-positive cells were accentuated when they were follicular and that of CD8(+) cells were accentuated when they were interfollicular. Follicular FOXP3(+) cells were associated with good outcome and interfollicular CD68(+) cells were associated with poor outcome. Additionally, high CD4/CD8 and CD4 follicular/interfollicular ratios correlated with poor outcome.

CONCLUSION

There are many important immune cell subsets in the microenvironment of follicular lymphoma. Each of these is independently associated with outcome. This is the first study showing the effect of the balance of the entire microenvironment, not only of individual subsets.

New targets for the treatment of follicular lymphoma

The last two decades have witnessed striking advances in our understanding of the biological factors underlying the development of Follicular lymphoma (FL). Development of newer treatment approaches have improved the outlook for many individuals with these disorders; however, with these advances come new questions. Given the long-term survival of patients with FL, drugs with favourable side-effect profile and minimal long-term risks are desired. FL is incurable with current treatment modalities. It often runs an indolent course with multiple relapses and progressively shorter intervals of remission. The identification of new targets and development of novel targeted therapies is imperative to exploit the biology of FL while inherently preventing relapse and prolonging survival. This review summarizes the growing body of knowledge regarding novel therapeutic targets, enabling the concept of individualized targeted therapy for the treatment of FL.

Gene expression profiling identifies emerging oncogenic pathways operating in extranodal NK/T-cell lymphoma, nasal type

Biopsies and cell lines of natural killer/T-cell lymphoma, nasal type (NKTCL) were subject to combined gene expression profiling and array-based comparative genomic hybridization analyses. Compared with peripheral T-cell lymphoma, not otherwise specified, NKTCL had greater transcript levels for NK-cell and cytotoxic molecules, especially granzyme H. Compared with normal NKcells, tumors were closer to activated than resting cells and overexpressed several genes related to vascular biology, Epstein-Barr Virus-induced genes, and PDGFRA. Notably, platelet-derived growth factor receptor alpha and its phosphorylated form were confirmed at the protein level, and in vitro the MEC04 NKTCL cell line was sensitive to imatinib. Deregulation of the AKT, Janus kinase-signal transducers and activators of transcription, and nuclear factor-kappaB pathways was corroborated by nuclear expression of phosphorylated AKT, signal transducers and activators of transcription 3, and RelA in NKTCL, and several deregulated genes in these pathways mapped to regions of recurrent copy number aberrations (AKT3 [1q44], IL6R [1q21.3], CCL2 [17q12], TNFRSF21 [6p12.3]). Several features of NKTCL uncovered by this analysis suggest perturbation of angiogenic pathways. Integrative analysis also evidenced deregulation of the tumor suppressor HACE1 in the frequently deleted 6q21 region. This study highlights emerging oncogenic pathways in NKTCL and identifies novel diagnostic and therapeutic targets.

IFN regulatory factor 8 sensitizes soft tissue sarcoma cells to death receptor-initiated apoptosis via repression of FLICE-like protein expression

IFN regulatory factor 8 (IRF8) has been shown to suppress tumor development at least partly through regulating apoptosis of tumor cells; however, the molecular mechanisms underlying IRF8 regulation of apoptosis are still not fully understood. Here, we showed that disrupting IRF8 function resulted in inhibition of cytochrome c release, caspase-9 and caspase-3 activation, and poly(ADP-ribose) polymerase cleavage in soft tissue sarcoma (STS) cells. Inhibition of the mitochondrion-dependent apoptosis signaling cascade is apparently due to blockage of caspase-8 and Bid activation. Analysis of signaling events upstream of caspase-8 revealed that disrupting IRF8 function dramatically increases FLIP mRNA stability, resulting in increased IRF8 protein level. Furthermore, primary myeloid cells isolated from IRF8-null mice also exhibited increased FLIP protein level, suggesting that IRF8 might be a general repressor of FLIP. Nuclear IRF8 protein was absent in 92% (55 of 60) of human STS specimens, and 99% (59 of 60) of human STS specimens exhibited FLIP expression, suggesting that the nuclear IRF8 protein level is inversely correlated with FLIP level in vivo. Silencing FLIP expression significantly increased human sarcoma cells to both FasL-induced and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, and ectopic expression of IRF8 also significantly increased the sensitivity of these human sarcoma cells to FasL- and TRAIL-induced apoptosis. Taken together, our data suggest that IRF8 mediates FLIP expression level to regulate apoptosis and targeting IRF8 expression is a potentially effective therapeutic strategy to sensitize apoptosis-resistant human STS to apoptosis, thereby possibly overcoming chemoresistance of STS, currently a major obstacle in human STS therapy.

Transcriptional and apoptotic responses of THP-1 cells to challenge with toxigenic, and non-toxigenic Bacillus anthracis

Background

Bacillus anthracis secretes several virulence factors targeting different host organs and cell types during inhalational anthrax infection. The bacterial expression of a key virulence factor, lethal toxin (LeTx) is closely tied to another factor, edema toxin (EdTx). Both are transcribed on the same virulence plasmid (pXO1) and both have been the subject of much individual study. Their combined effect during virulent anthrax likely modulates both the global transcriptional and the phenotypic response of macrophages and phagocytes. In fact, responses brought about by the toxins may be different than each of their individual effects.

Results

Here we report the transcriptional and apoptotic responses of the macrophage-like phagocytic cell line THP-1 exposed to B. anthracis Sterne (pXO1⁺) spores, and B. anthracis Δ Sterne (pXO1^-) spores. These cells are resistant to LeTx-induced cytolysis, a phenotype seen in macrophages from several mouse strains which are sensitive to toxigenic anthrax infection. Our results indicate that the pXO1-containing strain induces higher pro-inflammatory transcriptional responses during the first 4 hours of interaction with bacterium, evident in the upregulation of several genes relevant to Nf-κB, phosphatases, prostaglandins, and TNF-α, along with decreases in expression levels of genes for mitochondrial components. Both bacterial strains induce apoptosis, but in the toxigenic strain-challenged cells, apoptosis is delayed.

Conclusion

This delay in apoptosis occurs despite the much higher level of TNF-α secretion induced by the toxigenic-strain challenge. Interestingly, CFLAR, an important apoptotic inhibitor which blocks apoptosis induced by large amounts of extracellular TNF-α, is upregulated significantly during toxigenic-strain infection, but not at all during non-toxigenic-strain infection, indicating that it may play a role in blocking or delaying TNF-α-mediated apoptosis. The suppression of apoptosis by the toxigenic anthrax strain is consistent with the notion that apoptosis itself may represent a protective host cell response.