Targeting death and decoy receptors of the tumour-necrosis factor superfamily

Structural Insight for Roles of DR5 Death Domain Mutations on Oligomerization of DR5 Death Domain-FADD Complex in the Death-Inducing Signaling Complex Formation: A Computational Study

Death receptor 5 (DR5)-induced apoptosis that prioritizes the death of tumor cells has been proposed as one of the promising cancer therapies. In this process, oligomerized DR5 death domain (DD) binding to Fas-associated death domain (FADD) leads to FADD activating caspase-8, which marks the formation of the death-inducing signaling complex (DISC) that initiates apoptosis. DR5 DD mutations found in cancer cells have been suggested to play an important pathological role, the mechanism through which those mutants prevent the DR5-activated DISC formation is not clear yet. This study sought to provide structural and molecular insight for the roles of four selected DR5 DD mutations (E355K, E367K, K415N, and L363F) in the oligomerization of DR5 DD-FADD complex during the DISC formation. Results from the molecular dynamics simulations show that the simulated mutants induce conformational, dynamical motions and interactions changes in the DR5 DD-FADD tetramer complex, including changes in a protein's backbone flexibility, less exposure of FADD DED's caspase-8 binding site, reduced H-bonding and hydrophobic contacts at the DR5 DD-FADD DD binding, altered distribution of the electrostatic potentials and correlated motions of residues, and reduced binding affinity of DR5 DD binding to FADD. This study provides structural and molecular insight for the influence of DR5 DD mutations on oligomerization of DR5 DD-FADD complex, which is expected to foster understanding of the DR5 DD mutants' resistance mechanism against DR5-activated DISC formation.

2'-Hydroxy-4-methylsulfonylchalcone enhances TRAIL-induced apoptosis in prostate cancer cells

Prostate cancer is the most common malignant cancer in men and the second leading cause of cancer deaths. Previously, we have shown that 2'-hydroxy-4-methylsulfonylchalcone (RG003) induced apoptosis in prostate cancer cell lines PC-3 and DU145. Although tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent, some cancer cells are resistant to TRAIL treatment. PC-3 and LNCaP prostatic cancer cell lines have been reported to be resistant to TRAIL-induced apoptosis. Here, we show for the first time that RG003 overcomes TRAIL resistance in prostate cancer cells. RG003 can enhance TRAIL-induced apoptosis through DR5 upregulation and downregulation of Bcl-2, PI3K/Akt, NF-κB, and cyclooxygenase-2 (COX-2) survival pathways. When used in combined treatment, RG003 and TRAIL amplified TRAIL-induced activation of apoptosis effectors and particularly activation of caspase-8 and the executioner caspase-3, leading to increased poly-ADP-ribose polymerase cleavage and DNA fragmentation in prostate cancer cells. Furthermore, we showed that RG003 reduced COX-2 expression in cells. Previously, we showed that COX-2 was involved in resistance to an apoptosis mechanism; then, its inhibition by RG003 could render cells more sensitive to TRAIL treatment. We showed that nuclear factor-κB activation was inhibited after RG003 treatment. This inhibition was correlated with reduction in COX-2 expression and induction of apoptosis. Overall, we conclude, for the first time, that RG003 can enhance TRAIL-induced apoptosis in human prostate cancer cells. The significance of our in-vitro study with RG003 and TRAIL combined is very encouraging, suggesting the relevance of testing this combined treatment in xenograft animal models.

A bispecific fusion protein and a bifunctional enediyne-energized fusion protein consisting of TRAIL, EGFR peptide ligand, and apoprotein of lidamycin against EGFR and DR4/5 show potent antitumor activity

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mainly induces apoptosis through the extrinsic death receptor-induced pathway by ligation with death receptor 4 (DR4) and death receptor 5 (DR5). On the basis of the antitumor activity to cancer cells and no cytotoxity to normal cells of TRAIL and the target of the epidermal growth factor receptor (EGFR) ligand peptide, the study constructed a new bispecific fusion protein and a new bifunctional enediyne-energized fusion protein and investigated their antitumor efficacy. Bispecific fusion protein Ec-LDP-TRAIL showed potent binding activity to cancer cell lines with a high expression of EGFR or DR4/DR5 such as A431 and H460 cells, whereas poor binding activity to NIH/3T3 cells with low expressing EGFR and DR4/DR5. Ec-LDP-TRAIL also showed more potent cytotoxicity to A431 and H460 cells than Ec-LDP, which could result from the TRAIL-inducing apoptosis. Results of an in-vivo efficacy study showed that Ec-LDP-TRAIL at a dose of 10 mg/kg decreased the growth of epidermoid carcinoma A431 xenografts by 80.19% (P < 0.01) on day 26. Immunohistochemical detection of nuclear antigen factor Ki-67 suggested that Ec-LDP-TRAIL effectively induced cell necrosis and inhibited cell proliferation of tumor. From IC50 values, bispecific and bifunctional energized fusion protein Ec-LDP-TRAIL-AE was more potent and selective in its cytotoxicity against different carcinoma cell lines than corresponding lidamycin in vitro and induction of the cleavage of poly(ADP-ribose)polymerase was observed in A431 cells treated with Ec-LDP-TRAIL-AE and lidamycin, respectively. Ec-LDP-TRAIL-AE also significantly inhibited the growth of A431 xenografts in a nude mouse model. These properties suggested that Ec-LDP-TRAIL and Ec-LDP-TRAIL-AE may be promising candidates for targeted cancer therapy.

Death receptor-based enrichment of Cas9-expressing cells

Background

The CRISPR/Cas9 genome editing system has greatly facilitated and expanded our capacity to engineer mammalian genomes, including targeted gene knock-outs. However, the phenotyping of the knock-out effect requires a high DNA editing efficiency.

Results

Here, we report a user-friendly strategy based on the extrinsic apoptosis pathway that allows enrichment of a polyclonal gene-edited cell population, by selecting Cas9-transfected cells that co-express dominant-negative mutants of death receptors. The extrinsic apoptosis pathway can be triggered in many mammalian cell types, and ligands are easy to produce, do not require purification and kill much faster than the state-of-the-art selection drug puromycin. Stringent assessment of our advanced selection strategy via Sanger sequencing, T7 endonuclease I (T7E1) assay and direct phenotyping confirmed a strong and rapid enrichment of Cas9-expressing cell populations, in some cases reaching up to 100 % within one hour. Notably, the efficiency of target DNA cleavage in these enriched cells reached high levels that exceeded the reliable range of the T7E1 assay, a conclusion that can be generalized for editing efficiencies above 30 %. Moreover, our data emphasize that the insertion and deletion pattern induced by a specific gRNA is reproducible across different cell lines.

Conclusions

The workflow and the findings reported here should streamline a wide array of future low- or high-throughput gene knock-out screens, and should largely improve data interpretation from CRISPR experiments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12896-016-0250-4) contains supplementary material, which is available to authorized users.

Tumor Microenvironment-Mediated Construction and Deconstruction of Extracellular Drug-Delivery Depots

Protein therapy has been considered the most direct and safe approach to treat cancer. Targeting delivery of extracellularly active protein without internalization barriers, such as membrane permeation and endosome escape, is efficient and holds vast promise for anticancer treatment. Herein, we describe a "transformable" core-shell based nanocarrier (designated CS-NG), which can enzymatically assemble into microsized extracellular depots at the tumor site with assistance of hyaluronidase (HAase), an overexpressed enzyme at the tumor microenvironment. Equipped with an acid-degradable modality, the resulting CS-NG can substantially release combinational anticancer drugs-tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) and antiangiogenic cilengitide toward the membrane of cancer cells and endothelial cells at the acidic tumor microenvironment, respectively. Enhanced cytotoxicity on MDA-MB-231 cells and improved antitumor efficacy were observed using CS-NG, which was attributed to the inhibition of cellular internalization and prolonged retention time in vivo.

ABL kinases promote breast cancer osteolytic metastasis by modulating tumor-bone interactions through TAZ and STAT5 signaling

Bone metastases occur in up to 70% of advanced breast cancer. For most patients with breast cancer, bone metastases are predominantly osteolytic. Interactions between tumor cells and stromal cells in the bone microenvironment drive osteolytic bone metastasis, a process that requires the activation of osteoclasts, cells that break down bone. We report that ABL kinases promoted metastasis of breast cancer cells to bone by regulating the crosstalk between tumor cells and the bone microenvironment. ABL kinases protected tumor cells from apoptosis induced by TRAIL (TNF-related apoptosis-inducing ligand), activated the transcription factor STAT5, and promoted osteolysis through the STAT5-dependent expression of genes encoding the osteoclast-activating factors interleukin-6 (IL-6) and matrix metalloproteinase 1 (MMP1). Furthermore, in breast cancer cells, ABL kinases increased the abundance of the Hippo pathway mediator TAZ and the expression of TAZ-dependent target genes that promote bone metastasis. Knockdown of ABL kinases or treatment with ABL-specific allosteric inhibitor impaired osteolytic metastasis of breast cancer cells in mice. These findings revealed a role for ABL kinases in regulating tumor-bone interactions and provide a rationale for using ABL-specific inhibitors to limit breast cancer metastasis to bone.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

The TRAIL receptor agonist drozitumab targets basal B triple-negative breast cancer cells that express vimentin and Axl

Previously, we found that GST-tagged tumor necrosis factor-related apoptosis inducing ligand preferentially killed triple-negative breast cancer (TNBC) cells with a mesenchymal phenotype by activating death receptor 5 (DR5). The purpose of this study was to explore the sensitivity of breast cancer cell lines to drozitumab, a clinically tested DR5-specific agonist; identify potential biomarkers of drozitumab-sensitive breast cancer cells; and determine if those biomarkers were present in tumors from patients with TNBC. We evaluated viability, caspase activity, and sub-G1 DNA content in drozitumab-treated breast cancer cell lines and we characterized expression of potential biomarkers by immunoblot. Expression levels of vimentin and Axl were then explored in 177 TNBC samples from a publically available cDNA microarray dataset and by immunohistochemistry (IHC) in tumor tissue samples obtained from 53 African-American women with TNBC. Drozitumab-induced apoptosis in mesenchymal TNBC cell lines but not in cell lines from other breast cancer subtypes. The drozitumab-sensitive TNBC cell lines expressed the mesenchymal markers vimentin and Axl. Vimentin and Axl mRNA and protein were expressed in a subset of human TNBC tumors. By IHC, ~15 % of TNBC tumors had vimentin and Axl expression in the top quartile for both. These findings indicate that drozitumab-sensitive mesenchymal TNBC cells express vimentin and Axl, which can be identified in a subset of human TNBC tumors. Thus, vimentin and Axl may be useful to identify TNBC patients who would be most likely to benefit from a DR5 agonist.

Maslinic Acid, a Natural Triterpene, Induces a Death Receptor-Mediated Apoptotic Mechanism in Caco-2 p53-Deficient Colon Adenocarcinoma Cells

Maslinic acid (MA) is a natural triterpene present in high concentrations in the waxy skin of olives. We have previously reported that MA induces apoptotic cell death via the mitochondrial apoptotic pathway in HT29 colon cancer cells. Here, we show that MA induces apoptosis in Caco-2 colon cancer cells via the extrinsic apoptotic pathway in a dose-dependent manner. MA triggered a series of effects associated with apoptosis, including the cleavage of caspases -8 and -3, and increased the levels of t-Bid within a few hours of its addition to the culture medium. MA had no effect on the expression of the Bax protein, release of cytochrome-c or on the mitochondrial membrane potential. This suggests that MA triggered the extrinsic apoptotic pathway in this cell type, as opposed to the intrinsic pathway found in the HT29 colon-cancer cell line. Our results suggest that the apoptotic mechanism induced in Caco-2 may be different from that found in HT29 colon-cancer cells, and that in Caco-2 cells MA seems to work independently of p53. Natural antitumoral agents capable of activating both the extrinsic and intrinsic apoptotic pathways could be of great use in treating colon-cancer of whatever origin.

Molecular mechanisms of apoptosis and roles in cancer development and treatment

Programmed cell death (PCD) or apoptosis is a mechanism which is crucial for all multicellular organisms to control cell proliferation and maintain tissue homeostasis as well as eliminate harmful or unnecessary cells from an organism. Defects in the physiological mechanisms of apoptosis may contribute to different human diseases like cancer. Identification of the mechanisms of apoptosis and its effector proteins as well as the genes responsible for apoptosis has provided a new opportunity to discover and develop novel agents that can increase the sensitivity of cancer cells to undergo apoptosis or reset their apoptotic threshold. These novel targeted therapies include those targeting anti-apoptotic Bcl-2 family members, p53, the extrinsic pathway, FLICE-inhibitory protein (c-FLIP), inhibitor of apoptosis (IAP) proteins, and the caspases. In recent years a number of these novel agents have been assessed in preclinical and clinical trials. In this review, we introduce some of the key regulatory molecules that control the apoptotic pathways, extrinsic and intrinsic death receptors, discuss how defects in apoptotic pathways contribute to cancer, and list several agents being developed to target apoptosis.

The dual role of autophagy under hypoxia-involvement of interaction between autophagy and apoptosis

Hypoxia is one of severe cellular stress and it is well known to be associated with a worse outcome since a lack of oxygen accelerates the induction of apoptosis. Autophagy, an important and evolutionarily conserved mechanism for maintaining cellular homeostasis, is closely related to the apoptosis caused by hypoxia. Generally autophagy blocks the induction of apoptosis and inhibits the activation of apoptosis-associated caspase which could reduce cellular injury. However, in special cases, autophagy or autophagy-relevant proteins may help to induce apoptosis, which could aggravate cell damage under hypoxia condition. In addition, the activation of apoptosis-related proteins-caspase can also degrade autophagy-related proteins, such as Atg3, Atg4, Beclin1 protein, inhibiting autophagy. Although the relationship between autophagy and apoptosis has been known for rather complex for more than a decade, the underlying regulatory mechanisms have not been clearly understood. This short review discusses and summarizes the dual role of autophagy and the interaction and molecular regulatory mechanisms between autophagy and apoptosis under hypoxia.

In vitro toxicity, apoptosis and antimicrobial effects of phyto-mediated copper oxide nanoparticles

Herein, copper oxide nanoparticles (CuONPs) are proposed for widespread use in emerging biomedical applications.

Fluorinated dendrimer for TRAIL gene therapy in cancer treatment

The transfection of tumor necrosis factor-related apoptosis-inducing ligand gene by using fluorinated dendrimer is highly efficient and low toxic, resulting in efficient killing of cancer cells in vitro and suppressing tumor growth in vivo.

Isoproterenol Enhances Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand-Induced Apoptosis in Human Embryonic Kidney Cells through Death Receptor 5 up-Regulation

BACKGROUND AND OBJECTIVES

Chronic impairment of β-adrenergic receptor signaling increases cardiac apoptosis, hypertrophy and fibrosis. The aim of this study was to investigate whether isoproterenol (ISO), an agonist of the adrenergic receptor, can enhance tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in human embryonic kidney (HEK) 293 cells.

MATERIALS AND METHODS

HEK 293 cells were treated with ISO and/or TRAIL for 24 hours. Cell viability was evaluated by microscopy and an established viability assay, and apoptotic cell death was analyzed by staining with fluorescein isothiocynate-annexin-V/propidium iodide (PI) and caspase activation. To confirm the mechanism of cell death induced by co-treatment with ISO and TRAIL, expression of TRAIL receptor 2 (death receptor 5, DR5) was evaluated by immunoblotting.

RESULTS

Although ISO or TRAIL treatment decreased HEK 293 cell viability by 13% and 17%, respectively, co-treatment with ISO and TRAIL resulted in a markedly higher death rate of 35% after 24 hours. Increases were evident in early apoptotic cells (i.e., annexin-V positive/PI negative; 19.4%), late apoptotic cells (i.e., annexin-V positive/PI positive; 6.3%) and dead cells (i.e., annexin-V negative/PI positive; 1.1%) when cells were co-treated with ISO and TRAIL, compared to cells treated with either ISO or TRAIL. In addition, marked increases of cleaved cas-3, cleaved poly (adenosine diphosphate-ribose) polymerase and DR5 were observed in HEK 293 cells co-treated with ISO and TRAIL.

CONCLUSION

Treatments combining ISO with TRAIL may be responsible for death of HEK 293 cells through DR5 up-regulation. Activation of adrenergic receptors is responsible for the synergistic cell death observed with TRAIL.

TRAIL-R2 Superoligomerization Induced by Human Monoclonal Agonistic Antibody KMTR2

The fully human monoclonal antibody KMTR2 acts as a strong direct agonist for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor 2 (TRAIL-R2), which is capable of inducing apoptotic cell death without cross-linking. To investigate the mechanism of direct agonistic activity induced by KMTR2, the crystal structure of the extracellular region of TRAIL-R2 and a Fab fragment derived from KMTR2 (KMTR2-Fab) was determined to 2.1 Å resolution. Two KMTR2-Fabs assembled with the complementarity-determining region 2 of the light chain via two-fold crystallographic symmetry, suggesting that the KMTR2-Fab assembly tended to enhance TRAIL-R2 oligomerization. A single mutation at Asn53 to Arg located at the two-fold interface in the KMTR2 resulted in a loss of its apoptotic activity, although it retained its antigen-binding activity. These results indicate that the strong agonistic activity, such as apoptotic signaling and tumor regression, induced by KMTR2 is attributed to TRAIL-R2 superoligomerization induced by the interdimerization of KMTR2.

Targeting apoptosis is the major battle field for killing cancers

Targeting apoptosis is one of the major strategies for cancer therapy. Essentially, most of the conventional cancer therapeutic drugs that are in the clinical use induce apoptosis and in part necrosis of malignant cells and therefore prevent cancer progression and metastasis. Although these cytotoxic anticancer drugs are important weapons for killing cancers, their toxic side effects limited their application. The molecularly targeted therapeutics that are based on the deeper understanding of the defects in the apoptotic signaling in cancers are emerging and have shown promising anticancer activity in selectively killing cancers but not normal cells. The examples of molecular targets that are under exploration for cancer therapy include the cell surface receptors such as TNFR family death receptors, the intrinsic Bcl-2 family members and some other intracellular molecules like p53, MDM2, IAP, and Smac. The advance in the high-throughput bio-technologies has greatly accelerated the progress of cancer drug discovery.

Nanoparticle-Mediated Target Delivery of TRAIL as Gene Therapy for Glioblastoma

Human tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL) is an attractive cancer therapeutic because of its ability to induce apoptosis in tumor cells while having a negligible effect on normal cells. However, the short serum half-life of TRAIL and lack of efficient in vivo administration approaches have largely hindered its clinical use. Using nanoparticles (NPs) as carriers in gene therapy is considered as an alternative approach to increase TRAIL delivery to tumors as transfected cells would be induced to secrete TRAIL into the tumor microenvironment. To enable effective delivery of plasmid DNA encoding TRAIL into glioblastoma (GBM), we developed a targeted iron oxide NP coated with chitosan-polyethylene glycol-polyethyleneimine copolymer and chlorotoxin (CTX) and evaluated its effect in delivering TRAIL in vitro and in vivo. NP-TRAIL successfully delivers TRAIL into human T98G GBM cells and induces secretion of 40 pg mL(-1) of TRAIL in vitro. Transfected cells show threefold increased apoptosis as compared to the control DNA bound NPs. Systemic administration of NP-TRAIL-CTX to mice bearing T98G-derived flank xenografts results in near-zero tumor growth and induces apoptosis in tumor tissue. Our results suggest that NP-TRAIL-CTX can potentially serve as a targeted anticancer therapeutic for more efficient TRAIL delivery to GBM.

The alkyllysophospholipid edelfosine enhances TRAIL-mediated apoptosis in gastric cancer cells through death receptor 5 and the mitochondrial pathway

The ether phospholipid edelfosine is the prototype of a group of synthetic antitumor alkyllysophospholipid (ALP) compounds that exert pro-apoptotic effects in various types of cancer cells through cell type-dependent mechanisms. In this study, we examined the antitumor effect of edelfosine in human gastric cancer cells. Edelfosine decreased cell viability and induced autophagic death at a moderate concentration (~30 μM), whereas it induced apoptotic cell death at concentrations over 30 μM. Interestingly, low concentrations of edelfosine (5-10 μM) effectively enhanced recombinant human tumor necrosis factor (TNF)-related apoptosis-inducing ligand (rhTRAIL/TNFSF10)-induced apoptosis and clonogenicity in gastric cancer cells, including TRAIL-resistant AGS cells. Edelfosine upregulated the protein level of death receptor 5 (DR5/TNFRSF10B) and/or increased DR5 upregulation in lipid rafts. In addition, edelfosine-mediated rhTRAIL sensitization was regulated by the DR5 pathway. Edelfosine also activated p38MAPK (MAPK14), and edelfosine-mediated rhTRAIL sensitization was partially regulated by a p38-mediated decrease in mitochondrial membrane potential. This study suggests a novel therapeutic strategy targeting gastric cancer cells by using the combination of edelfosine and TRAIL.

The angular structure of ONC201, a TRAIL pathway-inducing compound, determines its potent anti-cancer activity

We previously identified TRAIL-inducing compound 10 (TIC10), also known as NSC350625 or ONC201, from a NCI chemical library screen as a small molecule that has potent anti-tumor efficacy and a benign safety profile in preclinical cancer models. The chemical structure that was originally published by Stahle, et. al. in the patent literature was described as an imidazo[1,2-a]pyrido[4,3-d]pyrimidine derivative. The NCI and others generally accepted this as the correct structure, which was consistent with the mass spectrometry analysis outlined in the publication by Allen et. al. that first reported the molecule's anticancer properties. A recent publication demonstrated that the chemical structure of ONC201 material from the NCI is an angular [3,4-e] isomer of the originally disclosed, linear [4,3-d] structure. Here we confirm by NMR and X-ray structural analysis of the dihydrochloride salt form that the ONC201 material produced by Oncoceutics is the angular [3,4-e] structure and not the linear structure originally depicted in the patent literature and by the NCI. Similarly, in accordance with our biological evaluation, the previously disclosed anti-cancer activity is associated with the angular structure and not the linear isomer. Together these studies confirm that ONC201, produced by Oncoceutics or obtained from the NCI, possesses an angular [3,4-e] structure that represents the highly active anti-cancer compound utilized in prior preclinical studies and now entering clinical trials in advanced cancers.

Hetero-modification of TRAIL trimer for improved drug delivery and in vivo antitumor activities

Poor pharmacokinetics and resistance within some tumor cell lines have been the major obstacles during the preclinical or clinical application of TRAIL (tumor-necrosis-factor (TNF)-related apoptosis-inducing ligand). The half-life of TRAIL_114-281 (114 to 281 amino acids) was revealed to be no more than 30 minutes across species. Therefore maleimido activated PEG (polyethylene glycol) and MMAE (Monomethyl Auristatin E) were applied to site-specifically conjugate with the mutated cysteines from different monomers of TRAIL successively, taking advantage of steric effects involved within TRAIL mutant conjugations. As a result, TRAIL trimer was hetero-modified for different purposes. And the resulting PEG-TRAIL-vcMMAE conjugate exhibited dramatically improved half-life (11.54 h), favourable in vivo targeting capability and antitumor activities while no sign of toxicity in xenograft models, suggesting it’s a viable therapeutic and drug delivery strategy.

Membrane display and functional analysis of juxtacrine ligand-receptor signaling

We developed a strategy for identifying modulators of juxtacrine signaling, triggered by a cell-surface ligand displayed on synthetic lipid bilayers, via cognate receptors on apposed cells. Using readouts for receptor lateral transport and intracellular signaling, we screened a small interfering RNA (siRNA) library and identified specific receptor tyrosine kinases (RTKs) that directly or indirectly modulate apoptosis signaling by a model death ligand through its cognate death receptors. This approach may be broadly useful for studying juxtacrine cell–cell signaling systems.

MiR-140-3p suppressed cell growth and invasion by downregulating the expression of ATP8A1 in non-small cell lung cancer

MicroRNAs (miRNAs) as a class of small noncoding RNA molecules regulate the expression of targeted gene. The dysregulation of microRNAs is reported to be involved in carcinogenesis and tumor progression. Here, we identified miR-140-3p as a downregulated microRNA in most cancer tissues including lung cancer tissues, compared with their normal counterparts. MiR-140-3p was observed to perform its tumor suppressor function via its inhibition on cell growth, migration and invasion but its induction of cell apoptosis. Furthermore, the growth of non-small-cell lung cancer (NSCLC) cells in nude mouse models were suppressed by overexpression of miR-140-3p. ATP8A1 was demonstrated as a novel direct target of miR-140-3p using a luciferase assay. The increased level of intracellular ATP8A1 protein attenuated the inhibitor role of miR-140-3p in the growth and mobility of NSCLC cell. A regulation mechanism of miR-140-3p for the development and progression of NSCLC through downregulating the ATP8A1 expression was first discovered in the present study.

Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of Al_xZn_1-xO nanocrystals with the size range of 33–55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

NaHS Protects Cochlear Hair Cells from Gentamicin-Induced Ototoxicity by Inhibiting the Mitochondrial Apoptosis Pathway

Aminoglycoside antibiotics such as gentamicin could cause ototoxicity in mammalians, by inducing oxidative stress and apoptosis in sensory hair cells of the cochlea. Sodium hydrosulfide (NaHS) is reported to alleviate oxidative stress and apoptosis, but its role in protecting aminoglycoside-induced hearing loss is unclear. In this study, we investigated the anti-oxidant and anti-apoptosis effect of NaHS in in vitro cultured House Ear Institute-Organ of Corti 1 (HEI-OC1) cells and isolated mouse cochlea. Results from cultured HEI-OC1 cells and cochlea consistently indicated that NaHS exhibited protective effects from gentamicin-induced ototoxicity, evident by maintained cell viability, hair cell number and cochlear morphology, reduced reactive oxygen species production and mitochondrial depolarization, as well as apoptosis activation of the intrinsic pathway. Moreover, in the isolated cochlear culture, NaHS was also demonstrated to protect the explant from gentamicin-induced mechanotransduction loss. Our study using multiple in vitro models revealed for the first time, the potential of NaHS as a therapeutic agent in protecting against aminoglycoside-induced hearing loss.

Redesigning a Monospecific Anti-FGFR3 Antibody to Add Selectivity for FGFR2 and Expand Antitumor Activity

FGF receptors (FGFR) are attractive candidate targets for cancer therapy because they are dysregulated in several human malignancies. FGFR2 and FGFR3 can be inhibited potentially without disrupting adult tissue homeostasis. In contrast, blocking the closely related FGFR1 and FGFR4, which regulate specific metabolic functions, carries a greater safety risk. An anti-FGFR3 antibody was redesigned here to create function-blocking antibodies that bind with dual specificity to FGFR3 and FGFR2 but spare FGFR1 and FGFR4. R3Mab, a previously developed monospecific anti-FGFR3 antibody, was modified via structure-guided phage display and acquired additional binding to FGFR2. The initial variant was trispecific, binding tightly to FGFR3 and FGFR2 and moderately to FGFR4, while sparing FGFR1. The X-ray crystallographic structure indicated that the antibody variant was bound to a similar epitope on FGFR2 as R3Mab on FGFR3. The antibody was further engineered to decrease FGFR4-binding affinity while retaining affinity for FGFR3 and FGFR2. The resulting dual-specific antibodies blocked FGF binding to FGFR3 and FGFR2 and inhibited downstream signaling. Moreover, they displayed efficacy in mice against human tumor xenografts overexpressing FGFR3 or FGFR2. Thus, a monospecific antibody can be exquisitely tailored to confer or remove binding to closely related targets to expand and refine therapeutic potential.

Expression, purification and characterization of heterotrimeric forms of sTRAIL using a polycistronic expression vector

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), which is capable of selectively inducing apoptosis of cancer cells, is a potential targeted drug for cancer therapy. The TRAIL protein induces apoptosis only in trimeric form. However, the recombinant soluble TRAIL (sTRAIL) trimer has low stability and a short half-life, which is a major obstacle for its advancement into clinical trials. Moreover, a percentage of engineered sTRAIL proteins are produced as dimers which may be toxic to normal human hepatocytes. In this study, we inserted three copies of the same subunit fragment of sTRAIL with a His tag into a polycistronic expression vector (pST39) to explore whether it would increase the proportion of trimers. We also constructed a heterozygous vector containing three subunit fragments of sTRAIL each with a different tag (His, HA, and Cmyc). Hybrid sTRAIL proteins (P-dTags) mainly as heterologous trimers were obtained by elution with a low concentration of imidazole based on different binding affinities of His with a nickel column. Functional analysis demonstrated that heterotrimeric forms of sTRAIL showed more stable activity compared to the P-3H at 4°C but not at 37°C without alteration in the native killing capacity. In addition, the heterologous trimers showed decreased toxicity to hepatocytes. These results suggest that the polycistronic expression system may be useful for expression of recombinant sTRAIL and improving its potential in cancer therapeutic applications.

Selenocysteine derivative overcomes TRAIL resistance in melanoma cells: evidence for ROS-dependent synergism and signaling crosstalk

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), as one of the most promising targeted drug for new cancer therapeutics, is limited in clinical application by the evolution of resistance in many cancer cell lines, especially in malignant melanoma. Thus, it is urgently needed to identify chemosensitizers to enhance the apoptotic inducing efficacy of TRAIL and overcome resistance of malignant melanoma cells. Herein, we reported that 3,3'-diselenodipropionic acid (DSeA), a Selenocysteine derivative, could synergistically enhance the growth inhibitory effect of TRAIL on A375 melanoma cells though induction of ROS-dependent apoptosis with involvement of PTEN-mediated Akt inactivation and DNA damage-mediated p53 phosphorylation, which subsequently activated mitochondrial and death receptor apoptotic pathways. Moreover, silencing of p53 down-regulated the expression levels of p53-inducible genes, and effectively blocked the cell apoptosis. Suppression of PI3K significantly increased the apoptotic cell death. In contrast, antioxidants effectively reversed the cell apoptosis through regulation of Akt and p53 signaling pathways. Taken together, the combination of DSeA and TRAIL could be a novel strategy to overcome TRAIL resistance in malignant melanoma, and DSeA may be candidates for further evaluation as a chemosensitizer in clinical trails.

Tumor Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL)-Troglitazone-induced Apoptosis in Prostate Cancer Cells Involve AMP-activated Protein Kinase

Prostate cancer (PCa) is one of the most frequently diagnosed cancers in men with limited treatment options for the hormone-resistant forms. Development of novel therapeutic options is critically needed to target advanced forms. Here we demonstrate that combinatorial treatment with the thiazolidinedione troglitazone (TZD) and TNF-related apoptosis-inducing ligand (TRAIL) can induce significant apoptosis in various PCa cells independent of androgen receptor status. Because TZD is known to activate AMP-activated protein kinase (AMPK), we determined whether AMPK is a molecular target mediating this apoptotic cascade by utilizing PCa cell lines stably overexpressing AMPKα1 dominant negative (C4-2-DN) or empty vector (C4-2-EV). Our results indicated a significantly higher degree of apoptosis with TRAIL-TZD combination in C4-2-EV cells compared with C4-2-DN cells. Similarly, results from a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a larger reduction of viability of C4-2-EV cells compared with C4-2-DN cells when treated with TRAIL-TZD, thus suggesting that C4-2-DN cells were more apoptosis-resistant. Additionally, siRNA-mediated knockdown of endogenous AMPKα1 expression showed a reduction of TRAIL-TZD-induced apoptosis, further confirming the participation of AMPK in mediating this apoptosis. Apoptosis induction by this combinatorial treatment was also associated with a cleavage of β-catenin that was inhibited in both C4-2-DN cells and those cells in which AMPKα1 was knocked down. In addition, time course studies showed an increase in pACC(S79) (AMPK target) levels coinciding with the time of apoptosis. These studies indicate the involvement of AMPK in TRAIL-TZD-mediated apoptosis and β-catenin cleavage and suggest the possibility of utilizing AMPK as a therapeutic target in apoptosis-resistant prostate cancer.

Enhancing tumor-targeting monoclonal antibodies therapy by PARP inhibitors

Monoclonal antibodies (mAbs) have become a successful therapeutic approach in cancer. However, some patients do not achieve long-term clinical benefit and most mAbs only exert modest effects as monotherapies. Therefore, combinations with chemotherapy are currently being investigated. Emerging studies have shown a synergistic therapeutic effect of PARP inhibitors and mAbs in cancer. PARP enzymes catalytically cleave β-NAD⁺ and transfer the ADP-ribose moiety to acceptor proteins, modifying their function. In here, we update recent data about the therapeutic effect of the combination of PARP inhibitors with mAbs in cancer treatment and discuss the molecular mechanisms involved in this synergy.

H3K9 Trimethylation Silences Fas Expression To Confer Colon Carcinoma Immune Escape and 5-Fluorouracil Chemoresistance

The Fas-FasL effector mechanism plays a key role in cancer immune surveillance by host T cells, but metastatic human colon carcinoma often uses silencing Fas expression as a mechanism of immune evasion. The molecular mechanism under FAS transcriptional silencing in human colon carcinoma is unknown. We performed genome-wide chromatin immunoprecipitation sequencing analysis and identified that the FAS promoter is enriched with H3K9me3 in metastatic human colon carcinoma cells. The H3K9me3 level in the FAS promoter region is significantly higher in metastatic than in primary cancer cells, and it is inversely correlated with Fas expression level. We discovered that verticillin A is a selective inhibitor of histone methyltransferases SUV39H1, SUV39H2, and G9a/GLP that exhibit redundant functions in H3K9 trimethylation and FAS transcriptional silencing. Genome-wide gene expression analysis identified FAS as one of the verticillin A target genes. Verticillin A treatment decreased H3K9me3 levels in the FAS promoter and restored Fas expression. Furthermore, verticillin A exhibited greater efficacy than decitabine and vorinostat in overcoming colon carcinoma resistance to FasL-induced apoptosis. Verticillin A also increased DR5 expression and overcame colon carcinoma resistance to DR5 agonist drozitumab-induced apoptosis. Interestingly, verticillin A overcame metastatic colon carcinoma resistance to 5-fluorouracil in vitro and in vivo. Using an orthotopic colon cancer mouse model, we demonstrated that tumor-infiltrating cytotoxic T lymphocytes are FasL(+) and that FasL-mediated cancer immune surveillance is essential for colon carcinoma growth control in vivo. Our findings determine that H3K9me3 of the FAS promoter is a dominant mechanism underlying FAS silencing and resultant colon carcinoma immune evasion and progression.

RAD001 (everolimus) enhances TRAIL cytotoxicity in human leukemic Jurkat T cells by upregulating DR5

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), either alone or in combination with other anti-cancer agents, is a promising new strategy for the treatment of cancer. However, aberrant PI3K/Akt/mTOR survival signaling may confer TRAIL resistance by altering the balance between pro- and anti-apoptotic proteins. In the present study, we showed that the Akt/mTOR inhibitor RAD001 (everolimus) induced cell death in a dose-dependent manner and enhanced TRAIL-induced apoptosis in human leukemic Jurkat T cells, which show PI3K/Akt/mTOR pathway activation and basal expression levels of death receptor (DR) 5 (TRAIL-R2). Investigation of the effect of RAD001 treatment on the expression of TRAIL receptors (TRAIL-Rs) in Jurkat T cells showed that RAD001 significantly upregulated DR5 by up to 51.22%, but not other TRAIL-Rs such as DR4 (TRAIL-R1), decoy receptor (DcR) 1 (TRAIL-R3), and DcR2 (TRAIL-R4). Pretreatment with DR5:Fc chimera abrogated the RAD001-induced increase of TRAIL cytotoxicity, indicating that the upregulation of DR5 by RAD001 plays a role in enhancing the susceptibility of Jurkat T cells to TRAIL. Our results indicate that combination treatment with RAD001 and TRAIL may be a novel therapeutic strategy in leukemia.

Mechanism of Arctigenin-Induced Specific Cytotoxicity against Human Hepatocellular Carcinoma Cell Lines: Hep G2 and SMMC7721

Arctigenin (ARG) has been previously reported to exert high biological activities including anti-inflammatory, antiviral and anticancer. In this study, the anti-tumor mechanism of ARG towards human hepatocellular carcinoma (HCC) was firstly investigated. We demonstrated that ARG could induce apoptosis in Hep G2 and SMMC7721 cells but not in normal hepatic cells, and its apoptotic effect on Hep G2 was stronger than that on SMMC7721. Furthermore, the following study showed that ARG treatment led to a loss in the mitochondrial out membrane potential, up-regulation of Bax, down-regulation of Bcl-2, a release of cytochrome c, caspase-9 and caspase-3 activation and a cleavage of poly (ADP-ribose) polymerase in both Hep G2 and SMMC7721 cells, suggesting ARG-induced apoptosis was associated with the mitochondria mediated pathway. Moreover, the activation of caspase-8 and the increased expression levels of Fas/FasL and TNF-α revealed that the Fas/FasL-related pathway was also involved in this process. Additionally, ARG induced apoptosis was accompanied by a deactivation of PI3K/p-Akt pathway, an accumulation of p53 protein and an inhibition of NF-κB nuclear translocation especially in Hep G2 cells, which might be the reason that Hep G2 was more sensitive than SMMC7721 cells to ARG treatment.

Identification of TRAIL-inducing compounds highlights small molecule ONC201/TIC10 as a unique anti-cancer agent that activates the TRAIL pathway

Background

We previously reported the identification of ONC201/TIC10, a novel small molecule inducer of the human TRAIL gene that improves efficacy-limiting properties of recombinant TRAIL and is in clinical trials in advanced cancers based on its promising safety and antitumor efficacy in several preclinical models.

Methods

We performed a high throughput luciferase reporter screen using the NCI Diversity Set II to identify TRAIL-inducing compounds.

Results

Small molecule-mediated induction of TRAIL reporter activity was relatively modest and the majority of the hit compounds induced low levels of TRAIL upregulation. Among the candidate TRAIL-inducing compounds, TIC9 and ONC201/TIC10 induced sustained TRAIL upregulation and apoptosis in tumor cells in vitro and in vivo. However, ONC201/TIC10 potentiated tumor cell death while sparing normal cells, unlike TIC9, and lacked genotoxicity in normal fibroblasts. Investigating the effects of TRAIL-inducing compounds on cell signaling pathways revealed that TIC9 and ONC201/TIC10, which are the most potent inducers of cell death, exclusively activate Foxo3a through inactivation of Akt/ERK to upregulate TRAIL and its pro-apoptotic death receptor DR5.

Conclusion

These studies reveal the selective activity of ONC201/TIC10 that led to its selection as a lead compound for this novel class of antitumor agents and suggest that ONC201/TIC10 is a unique inducer of the TRAIL pathway through its concomitant regulation of the TRAIL ligand and its death receptor DR5.

Enhancing the antitumor efficacy of a cell-surface death ligand by covalent membrane display

TNF superfamily death ligands are expressed on the surface of immune cells and can trigger apoptosis in susceptible cancer cells by engaging cognate death receptors. A recombinant soluble protein comprising the ectodomain of Apo2 ligand/TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) has shown remarkable preclinical anticancer activity but lacked broad efficacy in patients, possibly owing to insufficient exposure or potency. We observed that antibody cross-linking substantially enhanced cytotoxicity of soluble Apo2L/TRAIL against diverse cancer cell lines. Presentation of the ligand on glass-supported lipid bilayers enhanced its ability to drive receptor microclustering and apoptotic signaling. Furthermore, covalent surface attachment of Apo2L/TRAIL onto liposomes--synthetic lipid-bilayer nanospheres--similarly augmented activity. In vivo, liposome-displayed Apo2L/TRAIL achieved markedly better exposure and antitumor activity. Thus, covalent synthetic-membrane attachment of a cell-surface ligand enhances efficacy, increasing therapeutic potential. These findings have translational implications for liposomal approaches as well as for Apo2L/TRAIL and other clinically relevant TNF ligands.

The flavonoid morin from Moraceae induces apoptosis by modulation of Bcl-2 family members and Fas receptor in HCT 116 cells

It is evident based on literature that flavonoids from fruit can safely modulate cancer cell biology and induce apoptosis. Therefore, we investigated the anticancer activity of morin, a flavonoid which is plentiful in twigs of mulberry focusing on apoptosis, and its mechanisms. Morin upregulated the Fas receptor, and activates caspase-8, -9 and -3 in HCT-116 cells. Morin also activates Bid, and induced the loss of mitochondrial membrane potential (MMP, ∆Ψm) with Bax protein activation and cytochrome c release. In addition, morin induced ROS generation which was not blocked by N-acetylcysteine. Morin also suppressed Bcl-2 and cIAP-1, anti-apoptotic proteins, which may contribute to augmentation of morin-triggered apoptosis. As an upstream signaling pathway, suppressed Akt activity by morin was associated to apoptosis. This study suggests that morin induces caspase-dependent apoptosis through extrinsic pathway by upregulating Fas receptor as well as through the intrinsic pathway by modulating Bcl-2 and IAP family members, and ROS generation, and that Akt is the critical upstream signaling that regulates the apoptotic effect of morin in human colon cancer HCT-116 cells.

A humanized leucine zipper-TRAIL hybrid induces apoptosis of tumors both in vitro and in vivo

Evidence suggests that stimulating apoptosis in malignant cells without inflicting collateral damage to the host's normal tissues is a promising cancer therapy. Chemo- and radiation therapies that, especially if combined, induce apoptosis in tumor cells have been used for treating cancer patients for decades. These treatments, however, are limited in their ability to discriminate between malignant and non-malignant cells and, therefore, produce substantial healthy tissue damage and subsequent toxic side-effects. In addition, as a result of these therapies, many tumor types acquire an apoptosis-resistant phenotype and become more aggressive and metastatic. Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL) has been considered a promising and reliable selective inducer of apoptosis in cancerous cells. TRAIL, however, is not uniformly effective in cancer and multiple cancer cell types are considered resistant to natural TRAIL. To overcome this deficiency of TRAIL, we have earlier constructed a yeast-human hybrid leucine zipper-TRAIL in which the yeast GCN4-pII leucine zipper was fused to human TRAIL (GCN4-TRAIL). This construct exhibited a significantly improved anti-tumor apoptotic activity and safety, but is potentially immunogenic in humans. Here, we report a novel, potent, and fully human ATF7 leucine zipper-TRAIL (ATF7-TRAIL) fusion construct that is expected to have substantially lower immunogenicity. In solution, ATF7-TRAIL exists solely as a trimer with a Tm of 80°C and is active against cancer cells both in vitro and in vivo, in a mouse tumor xenograft model. Our data suggest that our re-engineered TRAIL is a promising candidate for further evaluation as an antitumor agent.

Dulanermin with rituximab in patients with relapsed indolent B-cell lymphoma: an open-label phase 1b/2 randomised study

BACKGROUND

Dulanermin-a non-polyhistidine-tagged soluble recombinant human apoptosis ligand 2 (Apo2L) or tumour-necrosis-factor-related apoptosis-inducing-ligand (TRAIL)-has pro-apoptotic activity in a range of cancers and synergistic preclinical activity with rituximab against lymphoma in vivo. We aimed to assess the safety, pharmacokinetics, and efficacy of dulanermin and rituximab in patients with relapsed indolent B-cell non-Hodgkin lymphoma.

METHODS

We did an open-label phase 1b/2 randomised study. Four study centres in the USA enrolled patients into phase 1b, and 27 study centres in the USA, Italy, Australia, France, Czech Republic, New Zealand, and Poland enrolled patients into phase 2. In phase 1b, patients (age ≥18 years) with indolent B-cell non-Hodgkin lymphoma with stable disease or better lasting at least 6 months after the most recent rituximab-containing regimen were included. In phase 2, patients (age ≥18 years) with follicular lymphoma grades 1-3a were included. In phase 1b, patients received 4 mg/kg or 8 mg/kg intravenous dulanermin on days 1-5 of up to four 21-day cycles and intravenous rituximab 375 mg/m(2) weekly for up to eight doses. In phase 2, patients were randomly assigned (1:1:1) centrally by an interactive voice response system to dulanermin (8 mg/kg for a maximum of four 21-day cycles), rituximab (375 mg/m(2) weekly for up to eight doses), or both in combination, stratified by baseline follicular lymphoma International Prognostic Index (0-3 vs 4-5) and geographic site (USA vs non-USA). The primary endpoints of the phase 1b study were the safety, tolerability, and pharmacokinetics of dulanermin with rituximab. The primary endpoint of phase 2 was the proportion of patients who achieved an objective response. All patients who received any dose of study drug were included in safety analyses. Efficacy analyses were per protocol. Treatment was open label; all patients and investigators were unmasked to treatment allocation. This study is registered with ClinicalTrials.gov, NCT00400764.

FINDINGS

Between June 6, 2006, and Feb 15, 2007, 12 patients were enrolled in phase 1b, and between April 4, 2007, and April 20, 2009, 60 patients were enrolled in phase 2, of whom 59 were included in safety analyses and 58 in efficacy analyses. No dose-limiting toxic effects were noted in phase 1b. The most common grade 1-2 adverse events in phase 1b were fatigue (nine; 75%), rash (five; 42%), and chills, decreased appetite, diarrhoea, and nausea (four each; 33%). 19 grade 3 or higher adverse effects were noted in five (42%) patients, with 14 occurring in one patient. After treatment with 8 mg/kg of dulanermin, in six patients the mean serum peak concentration was 80 μg/mL, dropping below the minimum detectable concentration (2 ng/mL) within 24 h after the dose. The mean steady state peak and trough concentrations of rituximab were 461 μg/mL (SD 97.5) and 303 μg/mL (92.8), respectively. In phase 2, eight (14%) of 59 patients experienced 12 grade 3 or higher adverse events. In phase 2, objective responses were noted in 14 of 22 (63.6%, 95% CI 41.8-81.3) patients treated with rituximab only, 16 of 25 (64.0%, 43.1-81.5) treated with dulanermin and rituximab, and one of 11 (9.1%, 0.5-39.0) treated with dulanermin only. The study was terminated early, on May 5, 2010, because of an absence of efficacy in the combination group.

INTERPRETATION

The addition of dulanermin to rituximab in patients with indolent B-cell non-Hodgkin lymphoma was tolerable but did not lead to increased objective responses. This combination is not being developed further in non-Hodgkin lymphoma.

FUNDING

Genentech and Amgen.

Different apoptotic pathways activated by oxaliplatin in primary astrocytes vs. colo-rectal cancer cells

Oxaliplatin-based chemotherapy improves the outcomes of metastatic colorectal cancer patients. Its most significant and dose-limiting side effect is the development of a neuropathic syndrome. The mechanism of the neurotoxicity is unclear. The limited knowledge about differences existing between neurotoxic and antitumor effects hinders the discovery of effective and safe adjuvant therapies. In vitro, we suggested cell-specific activation apoptotic pathways in normal nervous cells (astrocytes) vs. colon-cancer cells (HT-29). In the present research we compared the apoptotic signals evoked by oxaliplatin in astrocytes and HT-29 analyzing the intrinsic and extrinsic apoptotic pathways. In astrocytes, oxaliplatin induced a mitochondrial derangement measured as cytosolic release of cytochrome C, increase in superoxide anion levels and decreased expression of the antiapoptotic protein Bcl-2. Caspase-8, a main initiator of the extrinsic process remained unaltered. On the contrary, in HT-29 oxaliplatin increased caspase-8 activity and Bid expression, thus activating the extrinsic apoptosis, while the Bcl-2 increased expression blocked the mitochondrial damage. Data suggest the preferred activation of the intrinsic apoptosis as oxaliplatin damage signaling in normal nervous cells. The extrinsic pathway prevails in tumor cells indicating a possible strategy for planning new molecules to treat oxaliplatin-dependent neurotoxicity without negatively influence chemotherapy.

Histone Deacetylase Inhibitors (HDACi) Cause the Selective Depletion of Bromodomain Containing Proteins (BCPs)

Histone deacetylases (HDACs) and acetyltransferases control the epigenetic regulation of gene expression through modification of histone marks. Histone deacetylase inhibitors (HDACi) are small molecules that interfere with histone tail modification, thus altering chromatin structure and epigenetically controlled pathways. They promote apoptosis in proliferating cells and are promising anticancer drugs. While some HDACi have already been approved for therapy and others are in different phases of clinical trials, the exact mechanism of action of this drug class remains elusive. Previous studies have shown that HDACis cause massive changes in chromatin structure but only moderate changes in gene expression. To what extent these changes manifest at the protein level has never been investigated on a proteome-wide scale. Here, we have studied HDACi-treated cells by large-scale mass spectrometry based proteomics. We show that HDACi treatment affects primarily the nuclear proteome and induces a selective decrease of bromodomain-containing proteins (BCPs), the main readers of acetylated histone marks. By combining time-resolved proteome and transcriptome profiling, we show that BCPs are affected at the protein level as early as 12 h after HDACi treatment and that their abundance is regulated by a combination of transcriptional and post-transcriptional mechanisms. Using gene silencing, we demonstrate that the decreased abundance of BCPs is sufficient to mediate important transcriptional changes induced by HDACi. Our data reveal a new aspect of the mechanism of action of HDACi that is mediated by an interplay between histone acetylation and the abundance of BCPs. Data are available via ProteomeXchange with identifier PXD001660 and NCBI Gene Expression Omnibus with identifier GSE64689.