Fas Receptor Clustering and Involvement of the Death Receptor Pathway in Rituximab-Mediated Apoptosis with Concomitant Sensitization of Lymphoma B Cells to Fas-Induced Apoptosis

Serum miR-146a level is a potential biomarker in predicting the outcome of diffuse large B-cell lymphoma

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma with heterogenicity in clinical manifestation and prognosis. Some microRNAs can influence the development of tumors and may be related to the response of therapy or prognosis. This study aims to explore the role of serum miR-146a in predicting the prognosis of DLBCL.

METHODS

A total of 72 de novo DLBCL patients received 6 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or rituximab combined CHOP (R-CHOP) regimen, and their serum samples were collected before treatment and after 4 cycles of chemotherapy.

RESULTS

The results show that a high level of miR-146a is significantly associated with a good outcome in baseline and is more obvious in post-chemotherapy. In addition, a high level of miR-146a was associated with better progression-free survival and overall survival in patients treated with R-CHOP but has not been related to a superior outcome in patients treated with CHOP. Rituximab may improve the efficacy of therapy, especially in patients with high miR-146a levels. The level of miR-146a decreased in more patients after chemotherapy, and it seems patients with a decreased expression of miR-146a after chemotherapy tended a better outcome, but it is not statistically significant.

CONCLUSION

Our results suggest that the level of serum miR-146a can serve as a potential prognostic biomarker for DLBCL patients.

Clusters of apoptotic signaling molecule-enriched rafts, CASMERs: membrane platforms for protein assembly in Fas/CD95 signaling and targets in cancer therapy

Mammalian cells show the ability to commit suicide through the activation of death receptors at the cell surface. Death receptors, among which Fas/CD95 is one of their most representative members, lack enzymatic activity, and depend on protein-protein interactions to signal apoptosis. Fas/CD95 death receptor-mediated apoptosis requires the formation of the so-called death-inducing signaling complex (DISC), bringing together Fas/CD95, Fas-associated death domain-containing protein and procaspase-8. In the last two decades, cholesterol-rich lipid raft platforms have emerged as scaffolds where Fas/CD95 can be recruited and clustered. The co-clustering of Fas/CD95 and rafts facilitates DISC formation, bringing procaspase-8 molecules to be bunched together in a limited membrane region, and leading to their autoproteolytic activation by oligomerization. Lipid raft platforms serve as a specific region for the clustering of Fas/CD95 and DISC, as well as for the recruitment of additional downstream signaling molecules, thus forming the so-called cluster of apoptotic signaling molecule-enriched rafts, or CASMER. These raft/CASMER structures float in the membrane like icebergs, in which the larger portion lies inside the cell and communicates with other subcellular structures to facilitate apoptotic signal transmission. This allows an efficient spatiotemporal compartmentalization of apoptosis signaling machinery during the triggering of cell death. This concept of proapoptotic raft platforms as a basic chemical-biological structure in the regulation of cell death has wide-ranging implications in human biology and disease, as well as in cancer therapy. Here, we discuss how these raft-centered proapoptotic hubs operate as a major linchpin for apoptosis signaling and as a promising target in cancer therapy.

Lipid raft involvement in signal transduction in cancer cell survival, cell death and metastasis

Lipid rafts are cholesterol‐ and sphingolipid‐enriched specialized membrane domains within the plasma membrane. Lipid rafts regulate the density and activity of signal receptors by compartmentalizing them, promoting signalling cascades that play important roles in the survival, death and metastasis of cancer cells. In this review, we emphasize the current concept initially postulated by F. Mollinedo and C. Gajate on the importance of lipid rafts in cancer survival, death and metastasis by describing representative signalling pathways, including the IGF system and the PI3K/AKT, Fas/CD95, VEGF/VEGFR2 and CD44 signalling pathways, and we also discuss the concept of CASMER (cluster of apoptotic signalling molecule‐enriched rafts), coined, originally introduced and further advanced by F. Mollinedo and C. Gajate in the period 2005–2010. Then, we summarize relevant research progress and suggest that lipid rafts play important roles in the survival, death and metastasis of cancer cells, making them promising targets for cancer therapy.

Geranylgeranylacetone promotes human osteosarcoma cell apoptosis by inducing the degradation of PRMT1 through the E3 ubiquitin ligase CHIP

Geranylgeranylacetone (GGA), an inducer of heat shock proteins, exerts anticancer activity in some tumours. However, the effect of GGA on human osteosarcoma (OS) has not been reported. This work is designed to evaluate the effect of GGA on the proliferation and apoptosis of human OS cells and to explore the underlying mechanisms. It was found that GGA markedly inhibited the proliferation and induced apoptosis of U-2 OS cells in a dose-dependent manner and also up-regulated the expression of heat shock protein 70 (Hsp70). The degradation and ubiquitination of protein arginine N-methyltransferase 1 (PRMT1) were obviously enhanced in U-2 OS cells with CHIP overexpression and GGA treatment. The expression of PRMT1 was reversed in GGA-treated cell after CHIP knockdown. The turnover of PRMT1 was obviously faster in cells overexpressing CHIP than that in control cells. The methylation and activity of STAT3 were induced by PRMT1, resulting in the inhibition of FAS transcription. Overexpression of PRMT1 reversed the effect of GGA on activation of apoptosis-related proteins and U-2 OS cell apoptosis. The expressions of PRMT1 were significantly up-regulated in OS tissues compared with the adjacent normal tissues and benign bone tumours. In conclusion, GGA promotes the degradation of PRMT1 through the Hsp70-CHIP-mediated proteasome pathway, thereby inducing the FAS-triggered cell apoptosis. Inhibition of PRMT1 may be a potential therapeutic strategy for OS patients.

Induction of apoptosis in SSN-1cells by Snakehead Fish Vesiculovirus (SHVV) via Matrix protein dependent intrinsic pathway

An increasing important area in immunology is the process cell death mechanism, enabling the immune system triggered thru extrinsic or intrinsic signals to effectively remove unwanted or virus infected cells called apoptosis. A recently isolated infectious Snakehead fish vesiculovirus (SHVV), comprising negative strand RNA and encoded viral matrix (M) proteins, is responsible for causing cytopathic effects in infected fish cells. However, the mechanism by which viral M protein mediates apoptosis has not been elucidated. Therefore, in the present experiments, it was investigated the regulatory potential of apoptosis signals during SHVV infection. By employing the model of SHVV infection in SSN-1 cells, the accelerated apoptosis pathway involves an intrinsic pathway requiring the activation of caspase-9 but not caspase-3 or -8. In the groups of infection (SHVV) or treatment (hydrogen peroxide) were induced apoptotic morphological changes and indicated the activation of the main caspases, i.e.; executioner caspase-3, initiators caspase-8 and caspase-9 using colorimetric assays. Turning to the role of viral M protein when it was overexpressed in SSN-1 cells, it was indicated that the viral M gene alone has the ability to induce apoptosis. To elucidate the mechanism of apoptosis in SSN-1 cells, the activation inhibitors of main caspases were used showing that inhibiting of caspase-3 or caspase-8 activation did not seize induction of apoptosis in virus-infected SSN-1 cells. However, the inhibiting of caspase-9 activation reduced significantly the apoptosis initiation process and sharply the expression of viral M gene, suggesting that SHVV plays a major role in the early induction of apoptosis by caspase-9. Interestingly, there were also differences in the mitochondrial membrane potential after the apoptotic induction of caspases, which confirm that caspase-9 is primarily responsible for the cleavage of caspases during apoptosis. Taken together, these findings can therefore be assumed that viral M protein induces apoptosis via the intrinsic apoptotic pathway in SHVV infecting SSN-1 cells.

Rutin-protected BisGMA-induced cytotoxicity, genotoxicity, and apoptosis in macrophages through the reduction of the mitochondrial apoptotic pathway and induction of antioxidant enzymes

Bisphenol-A-glycidyldimethacrylate (BisGMA) is a resin monomer frequently used in dentin restorative treatments. The leakage of BisGMA monomer from BisGMA-based polymeric resins can lead to cytotoxicity in macrophages. Rutin has various beneficial bioeffects, including antioxidation and antiinflammation. In this study, we found that pretreatment of RAW264.7 macrophages with rutin-inhibited cytotoxicity induced by BisGMA in a concentration-dependent manner. BisGMA-induced apoptosis, which was detected by levels of phosphatidylserine from the internal to the external membrane and formation of sub-G1, and genotoxicity, which was detected by cytokinesis-blocked micronucleus and single-cell gel electrophoresis assays, were inhibited by rutin in a concentration-dependent manner. Rutin suppressed the BisGMA-induced activation of caspase-3 and -9 rather than caspase-8. Rutin inhibited the activation of the mitochondrial apoptotic pathway, including cytochrome C release and mitochondria disruption, after macrophages were treated with BisGMA. Finally, BisGMA-induced reactive oxygen species (ROS) generation and antioxidant enzyme (AOE) deactivation could be reversed by rutin. Parallel trends were observed in the elevation of AOE activation and inhibition of ROS generation, caspase-3 activity, mitochondrial apoptotic pathway activation, and genotoxicity. These results suggested that rutin suppressed BisGMA-induced cytotoxicity through genotoxicity, the mitochondrial apoptotic pathway, and relatively upstream factors, including reduction of ROS generation and induction of AOE.

Mechanisms of Apoptosis Resistance to NK Cell-Mediated Cytotoxicity in Cancer

Natural killer (NK) cells are major contributors to immunosurveillance and control of tumor development by inducing apoptosis of malignant cells. Among the main mechanisms involved in NK cell-mediated cytotoxicity, the death receptor pathway and the release of granules containing perforin/granzymes stand out due to their efficacy in eliminating tumor cells. However, accumulated evidence suggest a profound immune suppression in the context of tumor progression affecting effector cells, such as NK cells, leading to decreased cytotoxicity. This diminished capability, together with the development of resistance to apoptosis by cancer cells, favor the loss of immunogenicity and promote immunosuppression, thus partially inducing NK cell-mediated killing resistance. Altered expression patterns of pro- and anti-apoptotic proteins along with genetic background comprise the main mechanisms of resistance to NK cell-related apoptosis. Herein, we summarize the main effector cytotoxic mechanisms against tumor cells, as well as the major resistance strategies acquired by tumor cells that hamper the extrinsic and intrinsic apoptotic pathways related to NK cell-mediated killing.

Lipid rafts as signaling hubs in cancer cell survival/death and invasion: implications in tumor progression and therapy: Thematic Review Series: Biology of Lipid Rafts

Cholesterol/sphingolipid-rich membrane domains, known as lipid rafts or membrane rafts, play a critical role in the compartmentalization of signaling pathways. Physical segregation of proteins in lipid rafts may modulate the accessibility of proteins to regulatory or effector molecules. Thus, lipid rafts serve as sorting platforms and hubs for signal transduction proteins. Cancer cells contain higher levels of intracellular cholesterol and lipid rafts than their normal non-tumorigenic counterparts. Many signal transduction processes involved in cancer development (insulin-like growth factor system and phosphatidylinositol 3-kinase-AKT) and metastasis [cluster of differentiation (CD)44] are dependent on or modulated by lipid rafts. Additional proteins playing an important role in several malignant cancers (e.g., transmembrane glycoprotein mucin 1) are also being detected in association with lipid rafts, suggesting a major role of lipid rafts in tumor progression. Conversely, lipid rafts also serve as scaffolds for the recruitment and clustering of Fas/CD95 death receptors and downstream signaling molecules leading to cell death-promoting raft platforms. The partition of death receptors and downstream signaling molecules in aggregated lipid rafts has led to the formation of the so-called cluster of apoptotic signaling molecule-enriched rafts, or CASMER, which leads to apoptosis amplification and can be pharmacologically modulated. These death-promoting rafts can be viewed as a linchpin from which apoptotic signals are launched. In this review, we discuss the involvement of lipid rafts in major signaling processes in cancer cells, including cell survival, cell death, and metastasis, and we consider the potential of lipid raft modulation as a promising target in cancer therapy.

Astragaloside IV protects retinal pigment epithelial cells from apoptosis by upregulating miR‑128 expression in diabetic rats

The present study aimed to investigate the protective effects exerted by astragaloside‑IV (AIV) on retinal pigment epithelial (RPE) cells of rats with diabetes mellitus (DM), and to explore the underlying molecular mechanisms. For this purpose, a rat model of DM was established by injecting rats with an intraperitoneal injection of streptozotocin. AIV was then intragastrically administered. An electroretinogram (ERG) was used to assess retinopathy and TUNEL staining was used to detect the level of apoptosis of RPE cells. Western blot analysis was used to determine protein expression in RPE cells in vitro and in vivo. AIV was found to be able to significantly increase body weight and decrease blood glucose levels in rats with DM in a dose‑dependent manner. Compared with the rats with DM, the rat rod cell response a wave, b wave, maximum response b wave, photopic (photo)‑ERG b wave and oscillatory potential (OP) p4 wave latency significantly decreased and the amplitude of OP Os1 wave increased significantly in the rats with DM treated with AIV for 11 weeks. In addition, AIV significantly decreased the apoptotic levels of RPE cells from rats with DM and significantly decreased the protein expression levels of Bax/Bcl‑2, Fas/FasL, active caspase‑3, active caspase‑8, active caspase‑9, homeobox B3 (HOXB3), p‑phosphoinositide 3‑kinase (PI3K)/PI3K, p‑AKT/AKT and p‑p70S6K1/p70S6K1, whereas it significantly increased miR‑128 expression in the RPE cells from rats with DM. In vitro, AIV significantly inhibited the high glucose (HG)‑induced apoptosis of RPE cells by increasing miR‑128 expression and Bcl‑2 and FasL protein expression in vivo. On the whole, the findings of the present study demonstrate that AIV treatment protects RPE cells of diabetic rats from apoptosis, and that these effects may be associated with the upregulation of miR‑128 expression.

Granulysin- and granzyme-dependent elimination of myeloid cells by therapeutic ova-specific type 1 regulatory T cells

The intrinsic immunosuppressive properties of regulatory T (Treg) cells can be harnessed for therapeutic approaches aiming at down-modulating harmful immune reactions. In this context, expanded type 1 Treg cells (Tr1 cells) specific for ovalbumin (ova-Tr1 cells) have been tested for clinical efficacy in the treatment of autoimmune disorders such as refractory Crohn's disease (CD). The clinical use of these therapeutic products warrants exploration of their mechanism of action. Here, we identified a relationship between the CD activity index and the expression of lytic molecules by the ova-Tr1 cells administered in the previously reported First-in-Man study [Crohn's And Treg cells Study 1 (CATS1) study]. Accordingly, ova-Tr1 cells were found to carry granules containing high levels of lytic molecules, including multiple granzymes and granulysin. These cells displayed a T-cell receptor (TCR)-independent cytotoxic activity, which was preferentially directed toward myeloid cell lines and monocyte-derived dendritic cells. Upon contact with myeloid cells, ova-Tr1 cells induced their apoptosis via a perforin-independent and a granulysin/granzyme-dependent mechanism. As compared to CD8+ cytotoxic T cells, ova-Tr1 cells required more time to lyse target cells and displayed a more gradual lytic activity over time. Notably, this activity was sustained over days resulting in the control of myeloid cell populations at a relatively low ratio. Our study reveals that ova-Tr1 cells are endowed with a sustained cytotoxic activity that relies on a unique combination of granulysin and granzymes and that preferentially eliminates myeloid target cells in a TCR-independent manner.

Molecular mechanism of C-phycocyanin induced apoptosis in LNCaP cells

The usefulness of Marine-derived products as the source of anticancer agents has been explored for many decades. The objective of our study was to investigate the molecular mechanism by which C-PC induces apoptosis in monotherapy as well as in combination treatment with a known chemotherapeutic drug named Topotecan (TPT) using prostate cancer cells (LNCaP). To determine the intracellular mechanism of action, we analyzed the gene expression profile of C-PC treated cells using human apoptosis RT² profiler PCR array, which indicated that C-PC was able to regulate both anti- and pro-apoptotic genes significantly. Detailed analysis revealed increases in the levels of Bax, Apaf-1 (pro-apoptotic proteins) along with the activation of the key apoptotic proteases such as caspase-8, caspase-9, and caspase-3. Similarly, analysis of anti-apoptotic proteins demonstrated a decrease in the expression of Bcl-2, Mcl-1, and survivin. Results from the whole-cell incubation studies indicated that C-PC was only binding to the plasma membrane-associated receptor proteins. LNCaP cells treated with C-PC alone and in combination with TPT showed increased expression of the death receptor FAS (also known as FAS or CD95) along with cleaved PARP, confirming its importance. Our study is significant since it is providing greater insight into the apoptotic mechanisms triggered by C-PC as well as emphasizing the involvement of FAS in mediating its effects. Furthermore, our results with combination treatments suggest that-PC could improve the anticancer effects of drugs such as TPT that are currently used for cancer treatments. In addition, use of C-PC in combination can also diminish the side effects resulting from conventional chemotherapeutic agents such as TPT.

Rs217727 polymorphism in H19 promotes cell apoptosis by regulating the expressions of H19 and the activation of its downstream signaling pathway

BACKGROUND

The objective of the current study was to explore the role of H19 rs217727 polymorphism in the control of hepatocellular carcinoma (HCC).

METHOD

The Student's t test, Cox regression, and Kaplan-Meier analyses were used to clarify whether the H19 rs217727 polymorphism played an important role in the development of HCC. Real-time polymerase chain reaction (PCR) and western-blot analysis were carried out to measure the levels of H19, microRNA (miR)-675, FAS-associated death domain (FADD), caspase-8, and caspase-3 among H19 CC, CT, and TT groups, as well as in cells transfected with H19/si-H19, or miR-675 mimic/inhibitor. The MTT assay, colony formation assay, and flow cytometry assay were performed to detect the effect of H19/miR-675 on cell viability, cell colony formation, and cell apoptosis.

RESULT

T allele of H19 rs217727 polymorphism apparently increased the survival rate of patients with HCC. Meanwhile, H19 enhanced miR-675 expression but reduced the mRNA and protein levels of FADD, caspase-3, and caspase-8. The T allele of H19 rs217727 polymorphism apparently increased the apoptotic rate of HCC cells. Furthermore, FADD was a virtual target gene of miR-675 with a potential "hit" located in the 3'-untranslated region (UTR) of FADD, whereas H19 inhibited FADD expression via increasing the expression of miR-675. Moreover, H19 upregulated the expression of miR-675 whereas reducing the expression of FADD, caspase-3, and caspase-8. Finally, H19 and miR-675 promoted cell proliferation and cell colony formation but repressed cell apoptosis.

CONCLUSION

In summary, the above findings demonstrated that the polymorphism of rs217727 in H19 was associated with HCC via the H19/miR-675/FADD/caspase-8/caspase-3/apoptosis signaling pathway.

Lupus nephritis and B-cell targeting therapy

INTRODUCTION

Lupus Nephritis (LN) is a severe manifestation of Systemic Lupus Erythematosus (SLE) with a significant prognostic impact. Over a prolonged course, an exhaustion of treatment alternatives may occur and further therapeutic options are needed. B cells play a pivotal role in disease pathogenesis and represent an attractive therapeutic target. Areas covered: This review provides an update regarding targeting B cells in LN. The rational for this approach, as well as currently available and future targets are discussed. Expert commentary: Despite its wide clinical use and the encouraging results from retrospective studies, a role of rituximab in LN has not been prospectively confirmed. Trial design methodologies as well as intrinsic limitations of this approach may be responsible and rituximab use is currently limited as a rescue treatment or in settings where a strong steroid sparing effect is warranted. Despite belimumab now being licensed for use in SLE, the evidence in LN is weak although prospective trials are on-going. The combination of different targeted approaches as well as a focus on new clinical end-points may be strategies to identify new therapeutic options.

Caspase-8 and Caspase-9 Functioned Differently at Different Stages of the Cyclic Stretch-Induced Apoptosis in Human Periodontal Ligament Cells

Background

Human periodontal ligament (PDL) cells underwent apoptosis after mechanical stretch loading. However, the exact signalling pathway remains unknown. This study aimed to elucidate how the apoptotic caspases functioned in the cyclic stretch-induced apoptosis in human PDL cells.

Materials and Methods

In the present study, 20% cyclic stretch was selected to load the cells for 6 or 24 h. The following parameters were analyzed: apoptotic rates, the protein levels of caspase-3, -7, -8 and -9 and the activities of caspase-8 and -9. Subsequently, the influences of caspase-8 and caspase-9 inhibitors on the apoptotic rate and the protein level of the activated caspase-3 were assessed as well.

Results

The apoptotic rates increased in response to cyclic stretch, but the cells entered different apoptotic stages after 6 and 24 h stretches. Caspase-3, -7, -8 and -9 were all activated after stretch loading. The stretch-induced apoptosis and the protein level of the activated caspase-3 were inhibited after inhibiting both caspase-8 and caspase-9 in both 6 and 24 h stretched cells and after inhibiting caspase-9 in 24 h stretched cells.

Conclusion

Caspase-8 and -9 functioned differently at different apoptotic stages in human PDL cells after cyclic stretch.

Crocetin exploits p53-induced death domain (PIDD) and FAS-associated death domain (FADD) proteins to induce apoptosis in colorectal cancer

Tumor suppressor p53 preserves the genomic integrity by restricting anomaly at the gene level. The hotspots for mutation in half of all colon cancers reside in p53. Hence, in a p53-mutated cellular milieu targeting cancer cells may be achievable by targeting the paralogue(s) of p53. Here we have shown the effectiveness of crocetin, a dietary component, in inducing apoptosis of colon cancer cells with varying p53 status. In wild-type p53-expressing cancer cells, p53 in one hand transactivates BAX and in parallel up-regulates p53-induced death domain protein (PIDD) that in turn cleaves and activates BID through caspase-2. Both BAX and t-BID converge at mitochondria to alter the transmembrane potential thereby leading to caspase-9 and caspase-3-mediated apoptosis. In contrast, in functional p53-impaired cells, this phytochemical exploits p53-paralogue p73, which up-regulates FAS to cleave BID through FAS-FADD-caspase-8-pathway. These findings not only underline the phenomenon of functional switch-over from p53 to p73 in p53-impaired condition, but also validate p73 as a promising and potential target for cancer therapy in absence of functional p53.

Ceramide mediates FasL-induced caspase 8 activation in colon carcinoma cells to enhance FasL-induced cytotoxicity by tumor-specific cytotoxic T lymphocytes

FasL-mediated cytotoxicity is one of the mechanisms that CTLs use to kill tumor cells. However, human colon carcinoma often deregulates the Fas signaling pathway to evade host cancer immune surveillance. We aimed at testing the hypothesis that novel ceramide analogs effectively modulate Fas function to sensitize colon carcinoma cells to FasL-induced apoptosis. We used rational design and synthesized twenty ceramide analogs as Fas function modulators. Five ceramide analogs, IG4, IG7, IG14, IG17, and IG19, exhibit low toxicity and potent activity in sensitization of human colon carcinoma cells to FasL-induced apoptosis. Functional deficiency of Fas limits both FasL and ceramide analogs in the induction of apoptosis. Ceramide enhances FasL-induced activation of the MAPK, NF-κB, and caspase 8 despite induction of potent tumor cell death. Finally, a sublethal dose of several ceramide analogs significantly increased CTL-mediated and FasL-induced apoptosis of colon carcinoma cells. We have therefore developed five novel ceramide analogs that act at a sublethal dose to enhance the efficacy of tumor-specific CTLs, and these ceramide analogs hold great promise for further development as adjunct agents in CTL-based colon cancer immunotherapy.

Novel drug targets for personalized precision medicine in relapsed/refractory diffuse large B-cell lymphoma: a comprehensive review

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy and the most common subtype of non-Hodgkin's lymphoma in adults, with one of the highest mortality rates in most developed areas of the world. More than half of DLBLC patients can be cured with standard R-CHOP regimens, however approximately 30 to 40 % of patients will develop relapsed/refractory disease that remains a major cause of morbidity and mortality due to the limited therapeutic options.Recent advances in gene expression profiling have led to the identification of at least three distinct molecular subtypes of DLBCL: a germinal center B cell-like subtype, an activated B cell-like subtype, and a primary mediastinal B-cell lymphoma subtype. Moreover, recent findings have not only increased our understanding of the molecular basis of chemotherapy resistance but have also helped identify molecular subsets of DLBCL and rational targets for drug interventions that may allow for subtype/subset-specific molecularly targeted precision medicine and personalized combinations to both prevent and treat relapsed/refractory DLBCL. Novel agents such as lenalidomide, ibrutinib, bortezomib, CC-122, epratuzumab or pidilizumab used as single-agent or in combination with (rituximab-based) chemotherapy have already demonstrated promising activity in patients with relapsed/refractory DLBCL. Several novel potential drug targets have been recently identified such as the BET bromodomain protein (BRD)-4, phosphoribosyl-pyrophosphate synthetase (PRPS)-2, macrodomain-containing mono-ADP-ribosyltransferase (ARTD)-9 (also known as PARP9), deltex-3-like E3 ubiquitin ligase (DTX3L) (also known as BBAP), NF-kappaB inducing kinase (NIK) and transforming growth factor beta receptor (TGFβR).This review highlights the new insights into the molecular basis of relapsed/refractory DLBCL and summarizes the most promising drug targets and experimental treatments for relapsed/refractory DLBCL, including the use of novel agents such as lenalidomide, ibrutinib, bortezomib, pidilizumab, epratuzumab, brentuximab-vedotin or CAR T cells, dual inhibitors, as well as mechanism-based combinatorial experimental therapies. We also provide a comprehensive and updated list of current drugs, drug targets and preclinical and clinical experimental studies in DLBCL. A special focus is given on STAT1, ARTD9, DTX3L and ARTD8 (also known as PARP14) as novel potential drug targets in distinct molecular subsets of DLBCL.

Rituximab: modes of action, remaining dispute and future perspective

Less than two decades ago, immunotherapy joined chemotherapy and radiotherapy as an effective approach for the treatment of cancer. The anti-CD20 monoclonal antibody, rituximab, is now used to treat almost all types of non-Hodgkin's B-cell lymphomas, and it could be useful in the treatment of other diseases with B-cell involvement. Upon binding, rituximab induces death of the target cells. It seems to act not only by activating immune system defense mechanisms such as complement-dependent and antibody-dependent cellular cytotoxicity, but also by inducing direct cell death. In this paper, we review current knowledge on rituximab mechanisms of action, with particular attention to its direct effects, and also highlight potential future avenues of research.

Localized Store-Operated Calcium Influx Represses CD95-Dependent Apoptotic Effects of Rituximab in Non-Hodgkin B Lymphomas

The anti-CD20 mAb, rituximab, is routinely used to treat B cell malignancies. However, a majority of patients relapse. An improvement in the complete response was obtained by combining rituximab with chemotherapy, at the cost of increased toxicity. We reported that rituximab induced the colocalization of both the Orai1 Ca(2+) release-activated Ca(2+) channel (CRAC) and the endoplasmic reticulum Ca(2+) sensor stromal interaction molecule 1 with CD20 and CD95 into a cluster, eliciting a polarized store-operated Ca(2+) entry (SOCE). We observed that blocking this Ca(2+) entry with downregulation of Orai1, pharmacological inhibitors, or reducing calcemia with hypocalcemic drugs sensitized human B lymphoma cell lines and primary human lymphoma cells to rituximab-induced apoptosis in vitro, and improved the antitumoral effect of rituximab in xenografted mice. This revealed that Ca(2+) entry exerted a negative feedback loop on rituximab-induced apoptosis, suggesting that associating CRAC channel inhibitors or hypocalcemic agents with rituximab may improve the treatment of patients with B cell malignancies. The calcium-dependent proteins involved in this process appear to vary according to the B lymphoma cell type, suggesting that CRAC-channel targeting is likely to be more efficient than calcium-dependent protein targeting.

Action and resistance of monoclonal CD20 antibodies therapy in B-cell Non-Hodgkin Lymphomas

Anti-CD20 monoclonal antibodies (mAbs) have improved patient's survival with Non-Hodgkin Lymphoma, when combined with chemotherapy. Several mechanisms of action have been reported, including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity and induction of apoptosis. Despite the large amount of studies and published data, the role each mechanism played in vivo is not fully understood. Furthermore, the reason why a significant percentage of patients are refractory or resistant remains unknown. Several activated intracellular signaling pathways have been implicated in the mechanisms of resistance of rituximab. In the present manuscript, we review those mechanisms and new anti-CD20 mAbs, as well as the efforts being accomplished to overcome it, focusing on new drugs targeting pathways implicated in resistance to rituximab.

Rituximab increases the cytotoxicities of vincristine and hydroxyurea through caspase-dependent and caspase-independent cell death, respectively

In the treatment of B cell non-Hodgkin's lymphoma, rituximab is used in combination with different chemotherapeutics to improve its efficacy, but the mechanisms involved are not fully understood. The authors examined the mechanism by which rituximab combined with hydroxyurea or vincristine induces cell death in the human Burkitt's lymphoma Ramos cell line. Cell death was analyzed by phosphatidylserine exposure, caspase activation, and mitochondrial membrane changes. Their results indicate that the cell death initiated by the combination of rituximab and hydroxyurea is caspase-independent. In contrast, preincubation of the cells with the same concentrations of caspase inhibitors used with hydroxyurea eliminated the synergistic effect of the rituximab and vincristine combination. This was confirmed by the presence of the active fragment of caspase-3 in vincristine-treated cells. These preliminary results demonstrate that rituximab can activate different downstream signals to induce direct cell effects. Furthermore, the findings support the important role of mitochondria in the regulation of both pathways.

Lipid rafts as major platforms for signaling regulation in cancer

Cell signaling does not apparently occur randomly over the cell surface, but it seems to be integrated very often into cholesterol-rich membrane domains, termed lipid rafts. Membrane lipid rafts are highly ordered membrane domains that are enriched in cholesterol, sphingolipids and gangliosides, and behave as major modulators of membrane geometry, lateral movement of molecules, traffic and signal transduction. Because the lipid and protein composition of membrane rafts differs from that of the surrounding membrane, they provide an additional level of compartmentalization, serving as sorting platforms and hubs for signal transduction proteins. A wide number of signal transduction processes related to cell adhesion, migration, as well as to cell survival and proliferation, which play major roles in cancer development and progression, are dependent on lipid rafts. Despite lipid rafts harbor mainly critical survival signaling pathways, including insulin-like growth factor I (IGF-I)/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, recent evidence suggests that these membrane domains can also house death receptor-mediated apoptotic signaling. Recruitment of this death receptor signaling pathway in membrane rafts can be pharmacologically modulated, thus opening up the possibility to regulate cell demise with a therapeutic use. The synthetic ether phospholipid edelfosine shows a high affinity for cholesterol and accumulates in lipid rafts in a number of malignant hematological cells, leading to an efficient in vitro and in vivo antitumor activity by inducing translocation of death receptors and downstream signaling molecules to these membrane domains. Additional antitumor drugs have also been shown to act, at least in part, by recruiting death receptors in lipid rafts. The partition of death receptors together with downstream apoptotic signaling molecules in membrane rafts has led us to postulate the concept of a special liquid-ordered membrane platform coined as "cluster of apoptotic signaling molecule-enriched rafts" (CASMER), referring to raft platforms enriched in apoptotic molecules. CASMERs act as scaffolds for apoptosis signaling compartmentalization, facilitating and stabilizing protein-protein interactions by local assembly of cross-interacting molecules, which leads to apoptosis amplification and a decrease in apoptotic signal threshold. Edelfosine also displaced survival PI3K/Akt signaling from lipid rafts, leading to Akt inhibition, in mantle cell lymphoma cells. Thus, membrane rafts could act as scaffold structures where segregation of pro- from anti-apoptotic molecules could take place. In this review, we summarize our view of how reorganization of the protein composition of lipid raft membrane domains regulates cell death and therefore it might be envisaged as a novel target in the treatment of cancer.

CD74 interferes with the expression of fas receptor on the surface of lymphoma cells

BACKGROUND

Resistance to Fas-mediated apoptosis limits the efficacy of currently available chemotherapy regimens. We identified CD74, which is known to be overexpressed in hematological malignancies, as one of the factors interfering with Fas-mediated apoptosis.

METHODS

CD74 expression was suppressed in human B-lymphoma cell lines, BJAB and Raji, by either transduction with lentivirus particles or transfection with episomal vector, both encoding CD74-specific shRNAs or non-target shRNA. Effect of CD74 expression on Fas signaling was evaluated by comparing survival of mice hydrodynamically transfected with vector encoding full-length CD74 or empty vector. Sensitivity of cells with suppressed CD74 expression to FasL, edelfosine, doxorubicin, and a humanized CD74-specific antibody, milatuzumab, was evaluated by flow cytometry and compared to control cells. Fas signaling in response to FasL stimulation and the expression of Fas signaling components were evaluated by Western blot. Surface expression of Fas was detected by flow cytometry.

RESULTS

We determined that cells with suppressed CD74 are more sensitive to FasL-induced apoptosis and Fas signaling-dependent chemotherapies, edelfosine and doxorubicin, than control CD74-expressing cells. On the other hand, expression of full-length CD74 in livers protected the mice from a lethal challenge with agonistic anti-Fas antibody Jo2. A detailed analysis of Fas signaling in cells lacking CD74 and control cells revealed increased cleavage/activation of pro-caspase-8 and corresponding enhancement of caspase-3 activation in the absence of CD74, suggesting that CD74 affects the immediate early steps in Fas signaling at the plasma membrane. Cells with suppressed CD74 expression showed increased staining of Fas receptor on their surface. Pre-treatment with milatuzumab sensitized BJAB cells to Fas-mediated apoptosis.

CONCLUSION

We anticipate that specific targeting of the CD74 on the cell surface will sensitize CD74-expressing cancer cells to Fas-mediated apoptosis, and thus will increase effectiveness of chemotherapy regimens for hematological malignancies.

Enhancement of Rituximab-induced cell death by the physical association of CD20 with CD40 molecules on the cell surface

CD20 is an attractive therapeutic target given the success of its monoclonal antibody, Rituximab, in the treatment of B-cell malignancies and B-cell-mediated autoimmune diseases. Treatment with Rituximab causes a rapid depletion of B cells and a decrease in disease symptoms. Despite the clinical efficiency of Rituximab, its mechanism of action is not completely understood. In this study, we aimed at further investigating the Rituximab-induced cell death and the factors affecting such responses. Our results indicate that Rituximab-induced cell death depends on the nature of the cells and levels of CD20 expression on the cell surface. Coexpression of CD20 with CD40, a member of the TNF receptor family that is known to be physically associated with CD20 on the cell surface, enhances the apoptotic response induced by Rituximab. Inhibiting the formation of CD40 disulfide-bound-homodimers, a process required for some CD40 signaling, further enhances Rituximab-induced cell death. Cell death induced by anti-CD40 mAb is also upregulated by the presence of CD20, suggesting a bidirectional influence of the CD20/CD40 association. Moreover, treating cells with both anti-CD20 and anti-CD40 antibodies improves the cell death response induced by a single-agent treatment. These results highlight the role of the CD20/CD40 association in triggering B-cell depletion and may pave the way for an alternative more efficient therapeutic strategy in treating B-cell-mediated disorders.

The CD95/CD95L signaling pathway: a role in carcinogenesis

Apoptosis is a fundamental process that contributes to tissue homeostasis, immune responses, and development. The receptor CD95, also called Fas, is a member of the tumor necrosis factor receptor (TNF-R) superfamily. Its cognate ligand, CD95L, is implicated in immune homeostasis and immune surveillance, and various lineages of malignant cells exhibit loss-of-function mutations in this pathway; therefore, CD95 was initially classified as a tumor suppressor gene. However, more recent data indicate that in different pathophysiological contexts, this receptor can transmit non-apoptotic signals, promote inflammation, and contribute to carcinogenesis. A comparison with the initial molecular events of the TNF-R signaling pathway leading to non-apoptotic, apoptotic, and necrotic pathways reveals that CD95 is probably using different molecular mechanisms to transmit its non-apoptotic signals (NF-κB, MAPK, and PI3K). As discussed in this review, the molecular process by which the receptor switches from an apoptotic function to an inflammatory role is unknown. More importantly, the biological functions of these signals remain elusive.

Importance of the difference in surface pressures of the cell membrane in doxorubicin resistant cells that do not express Pgp and ABCG2

P-glycoprotein (Pgp) represents the archetypal mechanism of drug resistance. But Pgp alone cannot expel drugs. A small but growing body of works has demonstrated that the membrane biophysical properties are central to Pgp-mediated drug resistance. For example, a change in the membrane surface pressure is expected to support drug–Pgp interaction. An interesting aspect from these models is that under specific conditions, the membrane is predicted to take over Pgp concerning the mechanism of drug resistance especially when the surface pressure is high enough, at which point drugs remain physically blocked at the membrane level. However it remains to be determined experimentally whether the membrane itself could, on its own, affect drug entry into cells that have been selected by a low concentration of drug and that do not express transporters. We demonstrate here that in the case of the drug doxorubicin, alteration of the surface pressure of membrane leaflets drive drug resistance.

Fas ligand-mediated immune surveillance by T cells is essential for the control of spontaneous B cell lymphomas

Loss of function of the tumor suppressor gene PRDM1 (also known as BLIMP1) or deregulated expression of the oncogene BCL6 occurs in a large proportion of diffuse large B cell lymphoma (DLBCL) cases. However, targeted mutation of either gene in mice leads to only slow and infrequent development of malignant lymphoma, and despite frequent mutation of BCL6 in activated B cells of healthy individuals, lymphoma development is rare. Here we show that T cells prevent the development of overt lymphoma in mice caused by Blimp1 deficiency or overexpression of Bcl6 in the B cell lineage. Impairment of T cell control results in rapid development of DLBCL-like disease, which can be eradicated by polyclonal CD8(+) T cells in a T cell receptor-, CD28- and Fas ligand-dependent manner. Thus, malignant transformation of mature B cells requires mutations that impair intrinsic differentiation processes and permit escape from T cell-mediated tumor surveillance.

Targeting of the tumor necrosis factor receptor superfamily for cancer immunotherapy

The tumor necrosis factor (TNF) ligand and cognate TNF receptor superfamilies constitute an important regulatory axis that is pivotal for immune homeostasis and correct execution of immune responses. TNF ligands and receptors are involved in diverse biological processes ranging from the selective induction of cell death in potentially dangerous and superfluous cells to providing costimulatory signals that help mount an effective immune response. This diverse and important regulatory role in immunity has sparked great interest in the development of TNFL/TNFR-targeted cancer immunotherapeutics. In this review, I will discuss the biology of the most prominent proapoptotic and co-stimulatory TNF ligands and review their current status in cancer immunotherapy.

Nucleolin inhibits Fas ligand binding and suppresses Fas-mediated apoptosis in vivo via a surface nucleolin-Fas complex

Resistance to Fas-mediated apoptosis is associated with poor cancer outcomes and chemoresistance. To elucidate potential mechanisms of defective Fas signaling, we screened primary lymphoma cell extracts for Fas-associated proteins that would have the potential to regulate Fas signaling. An activation-resistant Fas complex selectively included nucleolin. We confirmed the presence of nucleolin-Fas complexes in B-cell lymphoma cells and primary tissues, and the absence of such complexes in B-lymphocytes from healthy donors. RNA-binding domain 4 and the glycine/arginine-rich domain of nucleolin were essential for its association with Fas. Nucleolin colocalized with Fas on the surface of B-cell lymphoma cells. Nucleolin knockdown sensitized BJAB cells to Fas ligand (FasL)-induced and Fas agonistic antibody-induced apoptosis through enhanced binding, suggesting that nucleolin blocks the FasL-Fas interaction. Mice transfected with nucleolin were protected from the lethal effects of agonistic anti-mouse Fas antibody (Jo2) and had lower rates of hepatocyte apoptosis, compared with vector and a non-Fas-binding mutant of nucleolin. Our results show that cell surface nucleolin binds Fas, inhibits ligand binding, and thus prevents induction of Fas-mediated apoptosis in B-cell lymphomas and may serve as a new therapeutic target.

Construction and characterization of a camelized, human, VH-based peptide vaccine against CD20 antigen

AIM

The purpose of this study was to construct and characterize a camelized, human, heavy-chain variable (VH) fragment-based peptide vaccine against CD20 antigen.

MATERIALS & METHODS

Camelized, human VH with improved solubility and stability was used as a vaccine scaffold. A CD20 B-cell epitope was introduced into the complementarity determining region 3 of the engineered VH and a measles virus-derived T-helper epitope was grafted into the complementarity determining region 3. The chimeric VH fragment was synthesized in bacteria and purified for immunization of mice. The titers and antigen-binding specificity of the antibody elicited by the chimeric peptide vaccine were assessed in vitro.

RESULTS

Notably, the CD20 epitope within the chimeric VH peptide elicited high-titered anti-CD20 antibody. Besides binding to GST-CD20 fusion protein, the antibody was cross-reactive with the native CD20 antigen on Raji cells.

CONCLUSION

In conclusion, the chimeric VH peptide vaccine consisting of the CD20 epitope can induce the production of the CD20-specific antibody, likely having potential implications in preventing CD20 overexpression cancers.

Combined administration of rituximab and on 013105 induces apoptosis in mantle cell lymphoma cells and reduces tumor burden in a mouse model of mantle cell lymphoma

PURPOSE

Mantle cell lymphoma (MCL) is an incurable B-cell lymphoma, and new therapeutic strategies are urgently needed.

EXPERIMENTAL DESIGN

The effects of ON 013105, a novel benzylstyryl sulfone kinase inhibitor, alone or with doxorubicin or rituximab, were examined in Granta 519 and Z138C cells. For in vivo studies, CB17/SCID mice were implanted subcutaneously with Z138C cells and treated with various combinations of ON 013105, doxorubicin, and rituximab. Tumor burden and body weight were monitored for 28 days.

RESULTS

ON 013105 induced mitochondria-mediated apoptosis in MCL cells. Death was preceded by translocation of tBid to the mitochondria and cytochrome c release. In addition, ON 013105-treated cells exhibited reduced levels of cyclin D1, c-Myc, Mcl-1, and Bcl-xL. Using nuclear magnetic resonance (NMR) spectroscopy, we showed specific binding of ON 013105 to eIF4E, a critical factor for the initiation of protein translation. We proffer that this drug-protein interaction preferentially prevents the translation of the aforementioned proteins and may be the mechanism by which ON 013105 induces apoptosis in MCL cells. Efficacy studies in a mouse xenograft model showed that ON 013105 inhibited MCL tumor growth and that combining ON 013105 with rituximab reduced tumor burden further with negligible unwanted effects.

CONCLUSIONS

Our findings suggest that ON 013105, alone or in combination with rituximab, may be a potent therapeutic agent to treat MCLs.

Galectin-3 binds to CD45 on diffuse large B-cell lymphoma cells to regulate susceptibility to cell death

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma and an aggressive malignancy. Galectin-3 (gal-3), the only antiapoptotic member of the galectin family, is overexpressed in DLBCL. While gal-3 can localize to intracellular sites, gal-3 is secreted by DLBCL cells and binds back to the cell surface in a carbohydrate-dependent manner. The major counterreceptor for gal-3 on DLBCL cells was identified as the transmembrane tyrosine phosphatase CD45. Removal of cell-surface gal-3 from CD45 with the polyvalent glycan inhibitor GCS-100 rendered DLBCL cells susceptible to chemotherapeutic agents. Binding of gal-3 to CD45 modulated tyrosine phosphatase activity; removal of endogenous cell-surface gal-3 from CD45 with GCS-100 increased phosphatase activity, while addition of exogenous gal-3 reduced phosphatase activity. Moreover, the increased susceptibility of DLBCL cells to chemotherapeutic agents after removal of gal-3 by GCS-100 required CD45 phosphatase activity. Gal-3 binding to a subset of highly glycosylated CD45 glycoforms was regulated by the C2GnT-1 glycosyltransferase, indicating that specific glycosylation of CD45 is important for regulation of gal-3-mediated signaling. These data identify a novel role for cell-surface gal-3 and CD45 in DLBCL survival and suggest novel therapeutic targets to sensitize DLBCL cells to death.

CD95-mediated cell signaling in cancer: mutations and post-translational modulations

Apoptosis has emerged as a fundamental process important in tissue homeostasis, immune response, and during development. CD95 (also known as Fas), a member of the tumor necrosis factor receptor (TNF-R) superfamily, has been initially cloned as a death receptor. Its cognate ligand, CD95L, is mainly found at the plasma membrane of activated T-lymphocytes and natural killer cells where it contributes to the elimination of transformed and infected cells. According to its implication in the immune homeostasis and immune surveillance, and since several malignant cells of various histological origins exhibit loss-of-function mutations, which cause resistance towards the CD95-mediated apoptotic signal, CD95 has been classified as a tumor suppressor gene. Nevertheless, this assumption has been recently challenged, as in certain pathophysiological contexts, CD95 engagement transmits non-apoptotic signals that promote inflammation, carcinogenesis or liver/peripheral nerve regeneration. The focus of this review is to discuss these apparent contradictions of the known function(s) of CD95.

Targeting the Fas/FasL signaling pathway in cancer therapy

INTRODUCTION

The Fas/FasL system plays a significant role in tumorigenesis. Research has shown that its impairment in cancer cells may lead to apoptosis resistance and contribute to tumor progression. Thus, the development of effective therapies targeting the Fas/FasL system may play an important role in the fight against cancer.

AREAS COVERED

In this review the recent literature on targeting the Fas/FasL system for therapeutic exploitation at different levels is reviewed. Promising pre-clinical approaches and various exceptions are highlighted. The potential of combined therapies is also explored, whereby tumor sensitivity to Fas-mediated apoptosis is restored, before an effective targeted therapy is employed.

EXPERT OPINION

The success of the Fas/FasL system targeting for therapeutics will require a better understanding of the alterations conferring resistance, in order to use the most appropriate sensitizing chemotherapeutic or radiotherapeutic agents in combination with effective targeted therapies.

Frequency of Th17 CD20+ cells in the peripheral blood of rheumatoid arthritis patients is higher compared to healthy subjects

Introduction

Rheumatoid arthritis (RA) is considered a T cell driven autoimmune disease, therefore, the ability of B cell depleting biologics, e.g., anti-CD20 antibodies, to alleviate RA is unclear. This study examined the proportions of IL-17-secreting lymphocytes in the blood of healthy subjects and RA patients and determined if Th17 cells belong to a CD20+ subset of T cells.

Methods

Fluorescence-activated cell sorting and confocal microscopy verified CD3, CD4/CD8 and CD20-staining of T cells. IL-17 secretion was determined using a commercial assay.

Results

In healthy subjects and RA patients blood, the median percentage of total CD20+ lymphocytes was similar (7.5%; n = 6 and 10.3%; n = 9, respectively) and comprised predominantly of B cells (~ 86%). However, 2-4% of CD3+ T cells from both healthy subjects (n = 7) and RA (n = 8) individuals co-expressed CD20. The peripheral blood of healthy subjects contained few IL-17-secreting CD20+ T cells (< 0.1%; n = 6). In contrast, in RA blood a median and interquartile range % of, 24.2%; IQR 28.5 of IL-17-secreting T cells were CD20+ (n = 9; p = 0.02).

Conclusions

In the blood of RA patients, a greater proportion of Th17 cells are of a CD20+ phenotype compared to healthy individuals. These cells may represent an additional target for anti-CD20 therapies.

Direct Effect of Rituximab in B-Cell–Derived Lymphoid Neoplasias: Mechanism, Regulation, and Perspectives

The anti-CD20 monoclonal antibody rituximab is the backbone of treatment for the B-cell malignancies non-Hodgkin lymphoma and chronic lymphocytic leukemia. However, there is a wide variability in response to rituximab treatment, and some patients are refractory to current standard therapies. Rituximab kills B cells by multiple mechanisms of action, including complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity, which are immune-mediated mechanisms, as well as by direct effects on cell signaling pathways and cell membranes following CD20 binding. A large number of events that are affected by rituximab binding have been identified, including lipid raft modifications, kinase and caspase activation, and effects on transcription factors and apoptotic/antiapoptotic molecules. Studies on cell lines and isolated tumor cells have shown that by targeting these pathways, it may be possible to increase or decrease susceptibility to rituximab cell killing. An increased understanding of the direct effects of rituximab may therefore aid in the design of new, rational combinations to improve the outcome of CD20-based therapy for patients who currently have suboptimal outcome following standard treatments. Mol Cancer Res; 9(11); 1435–42. ©2011 AACR.

Multivalent rituximab lipid nanoparticles as improved lymphoma therapies: indirect mechanisms of action and in vivo activity

AIMS

The activity of therapeutic antibodies can be enhanced by creating multivalent constructs, such as antibody lipid nanoparticles (LNPs). Here, we examine differences between rituximab (Ritux) and Ritux-LNPs in terms of their indirect mechanisms of action: complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC).

MATERIALS & METHODS

We employed two mantle-cell lymphoma cell lines, Z138 and JVM2, which exhibit different in vivo sensitivities to Ritux along with variable expression levels of cell-surface proteins that regulate ADCC and CDC.

RESULTS

In both cell lines, CDC and ADCC were found to be significantly enhanced after treatment with Ritux-LNPs compared with Ritux. In vivo efficacy studies, however, suggested that the therapeutic activities of Ritux and Ritux-LNPs were equivalent, which was subsequently explained in part by pharmacokinetic studies indicating rapid elimination of Ritux-LNP.

CONCLUSION

Although indirect and direct mechanisms of multivalent Ritux are enhanced, its further development requires methods to improve its circulation lifetime.

Actin-independent exclusion of CD95 by PI3K/AKT signalling: implications for apoptosis

The immune system eliminates infected or transformed cells through the activation of the death receptor CD95. CD95 engagement drives the recruitment of the adaptor protein Fas-associated death domain protein (FADD), which in turn aggregates and activates initiator caspases-8 and -10. The CD95-mediated apoptotic signal relies on the capacity to form the CD95/FADD/caspases complex termed the death-inducing signalling complex (DISC). Cells are classified according to the magnitude of DISC formation as either type I (efficient DISC formation) or type II (inefficient). CD95 localised to lipid rafts in type I cells, whereas the death receptor was excluded from these domains in type II cells. Here, we show that inhibition of both PI3K class IA and serine-threonine kinase Akt in type II cells promoted the redistribution of CD95 into lipid rafts, DISC formation and the initiation of the apoptotic signal. Strikingly, these molecular events took place independently of CD95L and the actin cytoskeleton. Overall, these findings highlight that the oncogenic PI3K/Akt signalling pathway participates in maintaining cells in a type II phenotype by excluding CD95 from lipid rafts.

Anti-tumor and anti-inflammatory properties of ankaflavin and monaphilone A from monascus purpureus NTU 568

An azaphilonidal derivative monaphilone A (MA) was recently isolated from the fermented products of Monascus purpureus NTU 568 by our laboratory. We report here the exploration of apoptosis-related and anti-inflammatory properties of MA and ankaflavin (AK) by some experiments about inducing death of human laryngeal carcinoma cell line HEp-2 and reducing inflammatory responses on murine macrophage RAW 264.7 cells. We employed a ssDNA enzyme-linked immunosorbent assay (ELISA) kit to investigate the nuclear changes of early apoptosis induced by AK and MA on HEp-2 cells and used a western blot and an enzyme activity assay to demonstrate the activation of caspase-3, caspase-8, and caspase-9 by MA and AK. Our studies revealed that AK and MA may decrease lipopolysaccharide (LPS)-induced inflammatory responses, including nitrite productions and expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) in RAW 264.7 cells. All evidence support that azaphilonidal derivatives from M. purpureus NTU 568, such as AK and MA, are suitable for the development of chemotherapy or chemopreventive agents.

Antibody-based fusion proteins to target death receptors in cancer

Ideally, an immunotoxin should be inactive 'en route', acquire activity only after tumor cell surface binding and have no off-target effects towards normal cells. In this respect, antibody-based fusion proteins that exploit the tumor-selective pro-apoptotic death ligands sFasL and sTRAIL appear promising. Soluble FasL largely lacks receptor-activating potential, whereas sTRAIL is inactive towards normal cells. Fusion proteins in which an anti-tumor antibody fragment (scFv) is fused to sFasL or sTRAIL prove to be essentially inactive when soluble, while gaining potent anti-tumor activity after selective binding to a predefined tumor-associated cell surface antigen. Importantly, off-target binding by scFv:sTRAIL to normal cells showed no signs of toxicity. In this review, we highlight the rationale and perspectives of scFv:TRAIL/scFv:sFasL based fusion proteins for cancer therapy.

Strategies to enhance rituximab anti-tumor activity in the treatment of CD20-positive B-cell neoplasms

Rituximab is a chimeric monoclonal anti-CD20 antibody and was the first monoclonal antibody (mAb) therapy approved by FDA (Food and Drug Administration) for the treatment of B-cell lymphoma. It has revolutionized the treatment of patients with CD20-positive non-Hodgkin's lymphoma and CLL. Rituximab is currently being used in virtually all patients with B-cell lymphomas either alone or in combination with chemotherapy. Despite its excellent safety and efficacy profile, only a small portion of B-cell lymphoma patients treated with rituximab as a single agent have sustained complete remissions. Combining rituximab with standard chemotherapy regimens is associated with higher response rates, and improved survival in a subset of patients. Unfortunately, a significant percentage of patients who initially respond to rituximab eventually relapse, and there are patients that demonstrate intrinsic resistance to initial therapy. In the last decade, ongoing scientific research has led to a better understanding of rituximab-associated cytotoxic mechanisms against lymphoma target cells. Scientific efforts are increasingly being focused in developing new strategies to improve mAb activity. Various strategies include the following: combining rituximab with different biologic agents (e.g. cytokines, immunomodulatory drugs); developing novel antibody constructs (including bi-specific antibodies); and/or inhibiting signaling pathways associated with lymphomagenesis and immuno-chemotherapy resistance. In this review article, we will provide an overview of various rituximab-associated cytotoxic mechanisms and novel strategies to improve mAb activity against B-cell lymphoma.

Epstein-Barr virus in bone marrow of rheumatoid arthritis patients predicts response to rituximab treatment

Objectives. Viruses may contribute to RA. This prompted us to monitor viral load and response to anti-CD20 therapy in RA patients.

Methods. Blood and bone marrow from 35 RA patients were analysed for CMV, EBV, HSV-1, HSV-2, parvovirus B19 and polyomavirus using real-time PCR before and 3 months after rituximab (RTX) treatment and related to the levels of autoantibodies and B-cell depletion. Clinical response to RTX was defined as decrease in the 28-joint disease activity score (DAS-28) >1.3 at 6 months.

Results. Before RTX treatment, EBV was identified in 15 out of 35 patients (EBV-positive group), of which 4 expressed parvovirus. Parvovirus was further detected in eight patients (parvo-positive group). Twelve patients were negative for the analysed viruses. Following RTX, EBV was cleared, whereas parvovirus was unaffected. Eighteen patients were responders, of which 12 were EBV positive. The decrease in the DAS-28 was significantly higher in EBV-positive group compared with parvo-positive group (P = 0.002) and virus-negative patients (P = 0.04). Most of EBV-negative patients that responded to RTX (75%) required retreatment within the following 11 months compared with only 8% of responding EBV-positive patients. A decrease of RF, Ig-producing cells and CD19⁺ B cells was observed following RTX but did not distinguish between viral infections. However, EBV-infected patients had significantly higher levels of Fas-expressing B cells at baseline as compared with EBV-negative groups.

Conclusions. EBV and parvovirus genomes are frequently found in bone marrow of RA patients. The presence of EBV genome was associated with a better clinical response to RTX. Thus, presence of EBV genome may predict clinical response to RTX.

Lipid rafts and clusters of apoptotic signaling molecule-enriched rafts in cancer therapy

There is an imperative need to overcome the rather poor outcomes of current cancer chemotherapy with further development of novel targets and drugs. Direct activation of the cancer cell apoptotic machinery constitutes an appealing approach. Recent findings have shown that apoptosis can be triggered by co-aggregation of lipid rafts with death receptors and downstream signaling molecules, thus facilitating their interactions to convey apoptotic signals. We postulate this cluster of apoptotic signaling molecule-enriched rafts (CASMER) as a novel supramolecular entity that modulates apoptosis, representing a new target in cancer therapy. The development of drugs that target lipid rafts leading to the formation of clusters of apoptotic signaling molecule-enriched rafts offers new opportunities for therapeutic intervention in cancer therapy.