A human scFv antibody against TRAIL receptor 2 induces autophagic cell death in both TRAIL-sensitive and TRAIL-resistant cancer cells

TRAIL Triggers CRAC-Dependent Calcium Influx and Apoptosis through the Recruitment of Autophagy Proteins to Death-Inducing Signaling Complex

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively kills various cancer cell types, but also leads to the activation of signaling pathways that favor resistance to cell death. Here, we investigated the as yet unknown roles of calcium signaling and autophagy regulatory proteins during TRAIL-induced cell death in leukemia cells. Taking advantage of the Gene Expression Profiling Interactive Analysis (GEPIA) project, we first found that leukemia patients present a unique TRAIL receptor gene expression pattern that may reflect their resistance to TRAIL. The exposure of NB4 acute promyelocytic leukemia cells to TRAIL induces intracellular Ca²⁺ influx through a calcium release-activated channel (CRAC)-dependent mechanism, leading to an anti-apoptotic response. Mechanistically, we showed that upon TRAIL treatment, two autophagy proteins, ATG7 and p62/SQSTM1, are recruited to the death-inducing signaling complex (DISC) and are essential for TRAIL-induced Ca²⁺ influx and cell death. Importantly, the treatment of NB4 cells with all-trans retinoic acid (ATRA) led to the upregulation of p62/SQSTM1 and caspase-8 and, when added prior to TRAIL stimulation, significantly enhanced DISC formation and the apoptosis induced by TRAIL. In addition to uncovering new pleiotropic roles for autophagy proteins in controlling the calcium response and apoptosis triggered by TRAIL, our results point to novel therapeutic strategies for sensitizing leukemia cells to TRAIL.

Cell Survival and Cell Death at the Intersection of Autophagy and Apoptosis: Implications for Current and Future Cancer Therapeutics

Autophagy and apoptosis are functionally distinct mechanisms for cytoplasmic and cellular turnover. While these two pathways are distinct, they can also regulate each other, and central components of the apoptosis or autophagy pathway regulate both processes directly. Furthermore, several upstream stress-inducing signaling pathways can influence both autophagy and apoptosis. The crosstalk between autophagy and apoptosis has an integral role in pathological processes, including those related to cancer, homeostasis, and aging. Apoptosis is a form of programmed cell death, tightly regulated by various cellular and biochemical mechanisms, some of which have been the focus of drug discovery efforts targeting cancer therapeutics. Autophagy is a cellular degradation pathway whereby cells recycle macromolecules and organelles to generate energy when subjected to stress. Autophagy can act as either a prodeath or a prosurvival process and is both tissue and microenvironment specific. In this review we describe five groups of proteins that are integral to the apoptosis pathway and discuss their role in regulating autophagy. We highlight several apoptosis-inducing small molecules and biologics that have been developed and advanced into the clinic and discuss their effects on autophagy. For the most part, these apoptosis-inducing compounds appear to elevate autophagy activity. Under certain circumstances autophagy demonstrates cytoprotective functions and is overactivated in response to chemo- or radiotherapy which can lead to drug resistance, representing a clinical obstacle for successful cancer treatment. Thus, targeting the autophagy pathway in combination with apoptosis-inducing compounds may be a promising strategy for cancer therapy.

Perfluorotridecanoic acid inhibits fetal Leydig cell differentiation after in utero exposure in rats via increasing oxidative stress and autophagy

Perfluorotridecanoic acid (PFTrDA) is a long-chain perfluoroalkyl substance, and its effect on the differentiation of fetal Leydig cells remains unclear. The objective of this study is to explore the effect of in utero PFTrDA exposure on the differentiation of fetal Leydig cells and investigate its underlying mechanisms. Pregnant Sprague-Dawley female rats were daily administered by gavage of PFTrDA at doses of 0, 1, 5, and 10 mg/kg from gestational day 14 to 21. PFTrDA had no effect on the body weight of dams, but significantly reduced the body weight and anogenital distance of male pups at birth at a dose of 10 mg/kg. PFTrDA significantly decreased serum testosterone levels as low as 1 mg/kg. PFTrDA did not affect fetal Leydig cell number, but promoted abnormal aggregation of fetal Leydig cells at doses of 5 and 10 mg/kg. PFTrDA down-regulated the expression of Insl3, Lhcgr, Scarb1, Star, Hsd3b1, Cyp17a1, Nr5a1, and Dhh as well as their proteins. PFTrDA lowered the levels of antioxidants (SOD1, CAT, and GPX1), induced autophagy as shown by increased levels of LC3II and beclin1, and reduced the phosphorylation of mTOR. In conclusion, PFTrDA inhibits the differentiation of fetal Leydig cells in male pups after in utero exposure mainly through increasing oxidative stress and inducing autophagy.

Space-Dependent Glia-Neuron Interplay in the Hippocampus of Transgenic Models of β-Amyloid Deposition

This review is focused on the description and discussion of the alterations of astrocytes and microglia interplay in models of Alzheimer's disease (AD). AD is an age-related neurodegenerative pathology with a slowly progressive and irreversible decline of cognitive functions. One of AD's histopathological hallmarks is the deposition of amyloid beta (Aβ) plaques in the brain. Long regarded as a non-specific, mere consequence of AD pathology, activation of microglia and astrocytes is now considered a key factor in both initiation and progression of the disease, and suppression of astrogliosis exacerbates neuropathology. Reactive astrocytes and microglia overexpress many cytokines, chemokines, and signaling molecules that activate or damage neighboring cells and their mutual interplay can result in virtuous/vicious cycles which differ in different brain regions. Heterogeneity of glia, either between or within a particular brain region, is likely to be relevant in healthy conditions and disease processes. Differential crosstalk between astrocytes and microglia in CA1 and CA3 areas of the hippocampus can be responsible for the differential sensitivity of the two areas to insults. Understanding the spatial differences and roles of glia will allow us to assess how these interactions can influence the state and progression of the disease, and will be critical for identifying therapeutic strategies.

Targeting the 4-1BB costimulatory molecule through single chain antibodies promotes the human T-cell response

Background

Adoptive T-cell therapy (ACT) using autologous tumor-reactive T lymphocytes has considerable potential for cancer immunotherapy. In ACT, T cells are isolated from cancer patients and then stimulated and expanded in vitro by cytokines and costimulatory molecules. 4-1BB is an important costimulatory protein belonging to the TNF receptor superfamily. It is involved in T-cell survival, proliferation and activation. Agonistic anti-4-1BB monoclonal antibodies have been introduced as appropriate tools for ACT.

Methods

Here, various single-chain fragment variable (scFv) antibodies were used to activate T cells isolated from peripheral blood via immune magnetic isolation. The T cells were stimulated with IL-2 and anti-CD-3 mAb and then treated with agonistic anti-4-1BB scFvs. The results showed the remarkable effects of anti-41BB scFvs on the functional properties of T cells, including their activation, proliferation and cytokine production. The flow cytometry analysis revealed a considerable increase in the expression of the T-cell activation marker CD69. Moreover, T-cell proliferation was evidenced in treated cells by CFSE labeling compared to the control groups.

Result

Anti-4-1BB scFvs significantly increased IFN-γ and IL-2 mRNA and protein expression in T cells, but exhibited no stimulatory effect on IL-4 expression. These findings show that anti-4-1BB scFvs could evoke a Type I immune response.

Conclusions

Our results demonstrate that targeting the 4-1BB molecule using agonistic scFvs could be an effective strategy for T-cell stimulation as part of an ACT approach to cancer treatment.

Astaxanthin Modulation of Signaling Pathways That Regulate Autophagy

Autophagy is a lysosomal pathway that degrades and recycles unused or dysfunctional cell components as well as toxic cytosolic materials. Basal autophagy favors cell survival. However, the aberrant regulation of autophagy can promote pathological conditions. The autophagy pathway is regulated by several cell-stress and cell-survival signaling pathways that can be targeted for the purpose of disease control. In experimental models of disease, the carotenoid astaxanthin has been shown to modulate autophagy by regulating signaling pathways, including the AMP-activated protein kinase (AMPK), cellular homolog of murine thymoma virus akt8 oncogene (Akt), and mitogen-activated protein kinase (MAPK), such as c-Jun N-terminal kinase (JNK) and p38. Astaxanthin is a promising therapeutic agent for the treatment of a wide variety of diseases by regulating autophagy.

Molecular Mode of Action of TRAIL Receptor Agonists-Common Principles and Their Translational Exploitation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its death receptors TRAILR1/death receptor 4 (DR4) and TRAILR2/DR5 trigger cell death in many cancer cells but rarely exert cytotoxic activity on non-transformed cells. Against this background, a variety of recombinant TRAIL variants and anti-TRAIL death receptor antibodies have been developed and tested in preclinical and clinical studies. Despite promising results from mice tumor models, TRAIL death receptor targeting has failed so far in clinical studies to show satisfying anti-tumor efficacy. These disappointing results can largely be explained by two issues: First, tumor cells can acquire TRAIL resistance by several mechanisms defining a need for combination therapies with appropriate sensitizing drugs. Second, there is now growing preclinical evidence that soluble TRAIL variants but also bivalent anti-TRAIL death receptor antibodies typically require oligomerization or plasma membrane anchoring to achieve maximum activity. This review discusses the need for oligomerization and plasma membrane attachment for the activity of TRAIL death receptor agonists in view of what is known about the molecular mechanisms of how TRAIL death receptors trigger intracellular cell death signaling. In particular, it will be highlighted which consequences this has for the development of next generation TRAIL death receptor agonists and their potential clinical application.

Salvianolic acid B inhibits the development of diabetic peripheral neuropathy by suppressing autophagy and apoptosis

OBJECTIVES

The aim of this study was to evaluate the neuroprotective effects of SalB on high glucose (HG)-induced excessive autophagy and apoptosis in vitro.

METHODS

The proliferation and apoptosis of RSC96 cells were determined using the MTT assay and flow cytometry, respectively. Western blot analysis was performed to examine the expression of autophagy and apoptosis-related proteins. RT-PCR and flow cytometry were manipulated to examine the level of Bcl-2. The signals of autophagy markers were detected using immunofluorescence methods.

KEY FINDINGS

We found that HG significantly reduced RSC96 cell's proliferation and induced apoptosis. What's more, HG increased the level of autophagy and apoptosis-related proteins. However, these effects were reversed by SalB. In addition, we also found that 3-MA decreased the expression of LC3A/B and Beclin1, while the JNK inhibitor SP600125 reduced the levels of phosphorylated JNK, LC3A/B and Beclin1.

CONCLUSIONS

High glucose not only induced apoptosis but also caused autophagic cell death by activating the JNK pathway. These effects prevented by SalB in an opposite manner.

Autophagic and Apoptotic Pathways as Targets for Chemotherapy in Glioblastoma

Glioblastoma multiforme is the most malignant and aggressive type of brain tumor, with a mean life expectancy of less than 15 months. This is due in part to the high resistance to apoptosis and moderate resistant to autophagic cell death in glioblastoma cells, and to the poor therapeutic response to conventional therapies. Autophagic cell death represents an alternative mechanism to overcome the resistance of glioblastoma to pro-apoptosis-related therapies. Nevertheless, apoptosis induction plays a major conceptual role in several experimental studies to develop novel therapies against brain tumors. In this review, we outline the different components of the apoptotic and autophagic pathways and explore the mechanisms of resistance to these cell death pathways in glioblastoma cells. Finally, we discuss drugs with clinical and preclinical use that interfere with the mechanisms of survival, proliferation, angiogenesis, migration, invasion, and cell death of malignant cells, favoring the induction of apoptosis and autophagy, or the inhibition of the latter leading to cell death, as well as their therapeutic potential in glioma, and examine new perspectives in this promising research field.

Different Patterns of Neurodegeneration and Glia Activation in CA1 and CA3 Hippocampal Regions of TgCRND8 Mice

We investigated the different patterns of neurodegeneration and glia activation in CA1 and CA3 hippocampal areas of TgCRND8 mice. The main feature of this transgenic model is the rapid development of the amyloid pathology, which starts already at 3 months of age. We performed immunohistochemical analyses to compare the different sensibility of the two hippocampal regions to neurodegeneration. We performed qualitative and quantitative evaluations by fluorescence immunohistochemistry with double or triple staining, followed by confocal microscopy and digital image analysis in stratum pyramidale (SP) and stratum radiatum (SR) of CA1 and CA3, separately. We evaluated time-dependent Aβ plaques deposition, expression of inflammatory markers, as well as quantitative and morphological alterations of neurons and glia in transgenic mice at 3 (Tg 3M) and 6 (Tg 6M) months of age, compared to WT mice. In CA1 SR of Tg 6M mice, we found significantly more Medium and Large plaques than in CA3. The pattern of neurodegeneration and astrocytes activation was different in the two areas, indicating higher sensitivity of CA1. In the CA1 SP of Tg 6M mice, we found signs of reactive astrogliosis, such as increase of astrocytes density in SP, increase of GFAP expression in SR, and elongation of astrocytes branches. We found also common patterns of glia activation and neurodegenerative processes in CA1 and CA3 of Tg 6M mice: significant increase of total and reactive microglia density in SP and SR, increased expression of TNFα, of iNOS, and IL1β in astrocytes and increased density of neurons-astrocytes-microglia triads. In CA1 SP, we found decrease of volume and number of pyramidal neurons, paralleled by increase of apoptosis, and, consequently, shrinkage of CA1 SP. These data demonstrate that in TgCRND8 mice, the responses of neurons and glia to neurodegenerative patterns induced by Aβ plaques deposition is not uniform in the two hippocampal areas, and in CA1 pyramidal neurons, the higher sensitivity may be related to the different plaque distribution in this area. All these modifications may be at the basis of memory loss, the peculiar symptom of AD, which was demonstrated in this transgenic mouse model of Aβ deposition, even at early stages.

Anticancer activity study of A3 adenosine receptor agonists

AIMS

A₃ adenosine receptor (A₃AR) signalling activation seems to mediate anticancer effect, and it has been targeted for drug development. The identification of potent and selective A₃AR agonists could be crucial for cancer drug development.

MATERIALS AND METHODS

In the present study was determined the in vitro activity of known 1-3 and newly 4-6 synthesized compounds with high A₃AR affinity and selectivity (K_i in the low nanomolar range) in binding studies. Effect of known and novel A₃AR agonists on human prostate cancer (PC3), hepatocellular carcinoma (Hep G2), and epithelial colorectal carcinoma (Caco-2) cells were analysed by cytotoxicity assay, dose and time dependent inhibitor assay, migration, apoptosis, autophagy and reactive oxygen species (ROS) assays.

KEY FINDINGS

Results show that the anticancer effect is not due to A₃AR activation alone. In fact, the more active and selective agonist versus A₃AR, compound 1, results inactive on cancer cells such as compounds 2-4. Moreover, results show that the novel compound 5, at micromolar concentration range (IC₅₀ = 28.0 μM), inhibits the growth of PC3, Hep G2, and Caco-2 cells and their migration in time- and dose- dependent manner. The mechanism involved in cell death is attributable to apoptosis. At the same time compound 5 promotes autophagy, which induce apoptosis producing autophagic cell death. Further investigation revealed that compound 5 elevates the level of ROS in all cancer cells tested, suggesting the involvement of ROS in cell death.

SIGNIFICANCE

These results show that the new compound 5 exerts inhibitory effect on cancer cells through differential effect and may serve as a potential anticancer agent.

Autophagy and multidrug resistance in cancer

Multidrug resistance (MDR) occurs frequently after long-term chemotherapy, resulting in refractory cancer and tumor recurrence. Therefore, combatting MDR is an important issue. Autophagy, a self-degradative system, universally arises during the treatment of sensitive and MDR cancer. Autophagy can be a double-edged sword for MDR tumors: it participates in the development of MDR and protects cancer cells from chemotherapeutics but can also kill MDR cancer cells in which apoptosis pathways are inactive. Autophagy induced by anticancer drugs could also activate apoptosis signaling pathways in MDR cells, facilitating MDR reversal. Therefore, research on the regulation of autophagy to combat MDR is expanding and is becoming increasingly important. We summarize advanced studies of autophagy in MDR tumors, including the variable role of autophagy in MDR cancer cells.

Journey of TRAIL from Bench to Bedside and its Potential Role in Immuno-Oncology

Induction of apoptosis in cancer cells has increasingly been the focus of many therapeutic approaches in oncology field. Since its identification as a TNF family member, TRAIL (TNF-related apoptosis-inducing ligand) paved a new path in apoptosis inducing cancer therapies. Its selective ability to activate extrinsic and intrinsic cell death pathways in cancer cells only, independently from p53 mutations responsible for conventional therapeutics resistance, spotted TRAIL as a potent cancer apoptotic agent. Many recombinant preparations of TRAIL and death receptor targeting monoclonal antibodies have been developed and being tested pre-clinically and clinically both as a single agent and in combinations. Of note, the monoclonal antibodies were not the only type of antibodies developed to target TRAIL receptors. Recent technology has brought forth several single chain variable domains (scFv) designs fused recombinantly to TRAIL as well. Also, it is becoming progressively more understandable that field of nanotechnology has revolutionized cancer diagnosis and therapy. The recent breakthroughs in materials science and protein engineering have helped considerably in strategically loading drugs into nanoparticles or conjugating drugs to their surface. In this review we aim to comprehensively highlight the molecular knowledge of TRAIL in the context of its pathway, receptors and resistance factors. We also aim to review the clinical trials that have been done using TRAIL based therapies and to review various scFv designs, the arsenal of nano-carriers and molecules available to selectively target tumor cells with TRAIL.

Autophagy is a regulator of TRAIL-induced apoptosis in NSCLC A549 cells

Autophagy, a catabolic process by which cytoplasmic components are degraded in lysosomes, plays an important role in the maintenance of cellular homeostasis. Dysregulation of autophagy is associated with several diseases. However, few studies have addressed the role of autophagy in the lung, and its role in lung diseases remains unclear. In the present study, we examined the effect of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on autophagy in A549 cells and explored the underlying mechanisms. We showed that TRAIL promoted autophagosome formation, as detected by the levels of LC3-II, and its effect on promoting autophagy was dependent on the expression of the autophagy related genes (ATGs) Atg5, Atg7, and beclin-1. TRAIL-induced ATG expression was attenuated by JNK silencing or treatment with the JNK inhibitor SP600125, indicating the involvement of the JNK pathway. Crosstalk between autophagy and apoptosis was demonstrated by silencing the autophagy related genes Atg5, Atg7, and beclin-1, and the dependence of TRAIL-induced apoptosis on autophagy-related gene expression. Taken together, our results indicate that TRAIL promotes autophagy in A549 cells via a mechanism involving the modulation of ATG expression through the JNK pathway. Inhibition of autophagy enhanced TRAIL-induced cell proliferative inhibition and apoptosis in A549 cells.

ERK-dependent mTOR pathway is involved in berberine-induced autophagy in hepatic steatosis

Non-alcoholic fatty liver disease (NAFLD) is a burgeoning health problem and is considered as a hepatic manifestation of metabolic syndrome. Increasing evidence demonstrates that berberine (BBR), a natural plant alkaloid, is beneficial for obesity-associated NAFLD. However, the mechanisms about how BBR improves hepatic steatosis remain uncertain. Recently, some reports revealed that enhanced autophagy could decrease hepatic lipid accumulation. In this study, we first established a high-fed diet (HFD) mice model and oleate-palmitate-induced lipotoxicity hepatocytes to explore the association among BBR, autophagy and hepatic steatosis. Our data demonstrated that BBR had profound effects on improving hepatic lipid accumulation both in vivo and in vitro, and led to high autophagy flux. The molecular alterations proceeding these changes were characterized by inhibition of the ERK/mTOR pathway. These findings suggest an important mechanism for the positive effects of BBR on hepatic steatosis, and may provide new evidence for the clinical use of BBR in NAFLD.

MAPK/JNK signalling: a potential autophagy regulation pathway

Autophagy refers to a lysosomal degradative pathway or a process of self-cannibalization. This pathway maintains nutrients levels for vital cellular functions during periods of starvation and it provides cells with survival advantages under various stress situations. However, the mechanisms responsible for the induction and regulation of autophagy are poorly understood. The c-Jun NH2-terminal kinase (JNK) signal transduction pathway functions to induce defence mechanisms that protect organisms against acute oxidative and xenobiotic insults. This pathway has also been repeatedly linked to the molecular events involved in autophagy regulation. The present review will focus on recent advances in understanding of the relationship between mitogen-activated protein kinase (MAPK)/JNK signalling and autophagic cell death.

Deferoxamine inhibits TRAIL-mediated apoptosis via regulation of autophagy in human colon cancer cells

Deferoxamine (DFO), an iron chelator, has numerous clinical applications for patients presenting with iron overload in regards to the improvement in the quality of life and overall survival. In addition, experimental iron chelators have demonstrated potent anticancer properties. The present study investigated the effects of DFO on TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in colon cancer cells and and the mechanism involved. The experimental results showed that DFO treatment inhibited TRAIL-mediated cancer cell apoptosis by increasing Akt activation and decreasing caspase activation in human colon cancer cells. Furthermore, DFO treatment induced autophagy flux, and chloroquine, an autophagy inhibitor, blocked DFO-mediated inhibition of TRAIL-induced apoptosis. The present study demonstrated that DFO inhibited TRAIL-mediated tumor cell death via the autophagy pathway, and the results suggest that potent anticancer agent, DFO, can be an inhibitor against antitumor therapy including TRAIL protein.

Vaccine for human contraception targeting sperm Izumo protein and YLP12 dodecamer peptide

There is an urgent need to develop a better method of contraception which is non-steroidal and reversible to control world population explosion and unintended pregnancies. Contraceptive vaccines (CV), especially targeting sperm-specific proteins, can provide an ideal contraceptive modality. Sperm-specific proteins can induce an immune response in women as well as men, thus can be used for CV development in both sexes. In this article, we will review two sperm-specific proteins, namely Izumo protein and YLP12 dodecamer peptide. Gene-knockout studies indicate that Izumo protein is essential for sperm-egg membrane fusion. Vaccination with Izumo protein or its cDNA causes a significant reduction in fertility of female mice. The antibodies to human Izumo inhibit human sperm penetration assay. Recently, our laboratory found that a significant percentage of infertile women have antibodies to Izumo protein. The second sperm-specific protein is YLP12 , a peptide mimetic sequence present on human sperm involved in recognition and binding to the human oocyte zona pellucida. Vaccination with YLP12 or its cDNA causes long-term, reversible contraception, without side effects, in female mice. Infertile, but not fertile, men and women have antibodies to YLP12 peptide. Our laboratory has isolated, cloned, and sequenced cDNA encoding human single chain variable fragment (scFv) antibody from infertile men which reacts with YLP12 peptide. The human YLP12 scFv antibody may provide a novel passive immunocontraceptive, the first of its kind. In conclusion, sperm-specific Izumo protein and YLP12 peptide can provide exciting candidates for antisperm CV development.

Novel anti-apoptotic microRNAs 582-5p and 363 promote human glioblastoma stem cell survival via direct inhibition of caspase 3, caspase 9, and Bim

Glioblastoma is the most common and lethal primary brain tumor. Tumor initiation and recurrence are likely caused by a sub-population of glioblastoma stem cells, which may derive from mutated neural stem and precursor cells. Since CD133 is a stem cell marker for both normal brain and glioblastoma, and to better understand glioblastoma formation and recurrence, we looked for dys-regulated microRNAs in human CD133+ glioblastoma stem cells as opposed to CD133+ neural stem cells isolated from normal human brain. Using FACS sorting of low-passage cell samples followed by microRNA microarray analysis, we found 43 microRNAs that were dys-regulated in common in three separate CD133+ human glioblastomas compared to CD133+ normal neural stem cells. Among these were several microRNAs not previously associated with cancer. We then verified the microRNAs dys-regulated in glioblastoma using quantitative real time PCR and Taqman analysis of the original samples, as well as human GBM stem cell and established cell lines and many human specimens. We show that two candidate oncogenic microRNAs, miR-363 and miR-582-5p, can positively influence glioblastoma survival, as shown by forced expression of the microRNAs and their inhibitors followed by cell number assay, Caspase 3/7 assay, Annexin V apoptosis/fluorescence activated cell sorting, siRNA rescue of microRNA inhibitor treatment, as well as 3′UTR mutagenesis to show luciferase reporter rescue of the most successful targets. miR-582-5p and miR-363 are shown to directly target Caspase 3, Caspase 9, and Bim.

Role of autophagy in the resistance to tumour necrosis factor-related apoptosis-inducing ligand-induced apoptosis in papillary and anaplastic thyroid cancer cells

Current alternative therapies for refractory thyroid cancer such as kinase inhibitors have limitations including incomplete response and toxicity. Although tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce cancer cell-specific apoptosis, various degrees of TRAIL resistance have been reported for different types of thyroid cancer cells. Here, we investigated if modulation of autophagy could improve sensitivity to TRAIL in papillary and anaplastic thyroid cancer cells. Human papillary thyroid cancer cells (TPC-1 cells) and human anaplastic thyroid cancer cells (FRO cells) were treated with TRAIL after transfection with ATG7 siRNA or control siRNA. Levels of autophagy and apoptosis were confirmed by Western blot of ATG7, LC3, caspase-3 and poly (ADP-ribose) polymerase. Viability index was determined by dimethyl-thiazole-diphenyltetrazolium bromide assay. Fraction of apoptotic cells was determined by flow cytometry. In TPC-1 cells, treatment with TRAIL increased the levels of autophagy. A low concentration (20 ng/ml) of TRAIL resulted in significantly decreased viability index and increased apoptosis. However, inhibition of autophagy with ATG7 siRNA desensitised the cells to TRAIL-induced apoptosis. In FRO cells, TRAIL did not increase the levels of autophagy. In contrast to TPC-1 cells, inhibition of autophagy with ATG7 siRNA sensitised FRO cells to TRAIL-induced apoptosis. Autophagy might contribute to the known sensitivity of papillary thyroid cancer cells to TRAIL-induced apoptosis. Inhibition of autophagy in anaplastic thyroid cancer cells could sensitise these cells to TRAIL-induced apoptosis.

Death receptor agonist therapies for cancer, which is the right TRAIL?

The activation of cell-surface death receptors represents an attractive therapeutic strategy to promote apoptosis of tumor cells. Several investigational therapeutics that target this extrinsic pathway, including recombinant human Apo2L/TRAIL and monoclonal agonist antibodies directed against death receptors-4 (DR4) or -5 (DR5), have been evaluated in the clinic. Although Phase 1/1b studies provided encouraging preliminary results, findings from randomized Phase 2 studies failed to demonstrate significant clinical benefit. This has raised multiple questions as to why pre-clinical data were not predictive of clinical response. Results from clinical studies and insight into why current agents have failed to yield robust responses are discussed. In addition, new strategies for the development of next generation death receptor agonists are reviewed.

Crosstalk between apoptosis and autophagy: molecular mechanisms and therapeutic strategies in cancer

Both apoptosis and autophagy are highly conserved processes that besides their role in the maintenance of the organismal and cellular homeostasis serve as a main target of tumor therapeutics. Although their important roles in the modulation of tumor therapeutic strategies have been widely reported, the molecular actions of both apoptosis and autophagy are counteracted by cancer protective mechanisms. While apoptosis is a tightly regulated process that is implicated in the removal of damaged or unwanted cells, autophagy is a cellular catabolic pathway that is involved in lysosomal degradation and recycling of proteins and organelles, and thereby is considered an important survival/protective mechanism for cancer cells in response to metabolic stress or chemotherapy. Although the relationship between autophagy and cell death is very complicated and has not been characterized in detail, the molecular mechanisms that control this relationship are considered to be a relevant target for the development of a therapeutic strategy for tumor treatment. In this review, we focus on the molecular mechanisms of apoptosis, autophagy, and those of the crosstalk between apoptosis and autophagy in order to provide insight into the molecular mechanisms that may be essential for the balance between cell survival and death as well as their role as targets for the development of novel therapeutic approaches.

Autophagy modulation as a target for anticancer drug discovery

Autophagy, an evolutionarily conserved catabolic process involving the engulfment and degradation of non-essential or abnormal cellular organelles and proteins, is crucial for homeostatic maintenance in living cells. This highly regulated, multi-step process has been implicated in diverse diseases including cancer. Autophagy can function as either a promoter or a suppressor of cancer, which makes it a promising and challenging therapeutic target. Herein, we overview the regulatory mechanisms and dual roles of autophagy in cancer. We also describe some of the representative agents that exert their anticancer effects by regulating autophagy. Additionally, some emerging strategies aimed at modulating autophagy are discussed as having the potential for future anticancer drug discovery. In summary, these findings will provide valuable information to better utilize autophagy in the future development of anticancer therapeutics that meet clinical requirements.

The role of TRAIL in mediating autophagy in myositis skeletal muscle: a potential nonimmune mechanism of muscle damage

OBJECTIVE

Multinucleated cells are relatively resistant to classic apoptosis, and the factors initiating cell death and damage in myositis are not well defined. We hypothesized that nonimmune autophagic cell death may play a role in muscle fiber damage. Recent reports indicate that TRAIL may induce both NF-κB activation and autophagic cell death in other systems. We undertook this study to investigate the role of TRAIL in cell death and pathogenesis in vitro and in vivo, using myositis muscle tissues from humans and mice.

METHODS

Gene expression profiling was performed in myositis patient and control muscle specimens. Immunohistochemistry analysis was performed to confirm the gene array findings. We also analyzed TRAIL-induced cell death (apoptosis and autophagy) and NF-κB activation in vitro in cultured cells.

RESULTS

TRAIL was expressed predominantly in myositis muscle fibers, but not in biopsy specimens from normal or other dystrophic-diseased muscle. Autophagy markers were up-regulated in humans with myositis and in mouse models of myositis. TRAIL expression was restricted to regenerating/atrophic areas of muscle fascicles, blood vessels, and infiltrating lymphocytes. TRAIL induced NF-κB activation and IκB degradation in cultured cells that are resistant to TRAIL-induced apoptosis but that undergo autophagic cell death.

CONCLUSION

Our data demonstrate that TRAIL is expressed in myositis muscle and may mediate both activation of NF-κB and autophagic cell death in myositis. Thus, this nonimmune pathway may be an attractive target for therapeutic intervention in myositis.

An anti-nucleic acid antibody delivers antigen to the cross-presentation pathway in dendritic cells and potentiates therapeutic antitumor effects

Cross-presentation is important for initiating CTL responses against tumors. Delivery of exogenous Ags to the cross-presentation pathway in dendritic cells (DCs), using a number of different carriers, has been attempted to further understand the mechanisms underlying cross-presentation and to develop therapeutic tumor vaccines. The present study reports a new antigenic carrier molecule: a single-chain V region fragment (scFv) of a nucleic acid-hydrolyzing Ab, 3D8. A fusion protein comprising 3D8 scFv and the CTL epitope OVA(250-264) (chicken OVA aa 250-264) was internalized by DC2.4 DCs and processed via a proteasome-dependent, brefeldin- and cycloheximide-sensitive, chloroquine- and primaquine-insensitive pathway, resulting in loading of the CTL epitope onto H-2K(b). In vivo cross-presentation and cross-priming were efficient, even without adjuvant; injection of mice with 3D8 scFv-OVA(250-264) induced cross-presentation of the CTL epitope by draining lymph node CD11c(+) B7.1(+) MHC class II(high) DCs, elicited a CTL response, and suppressed the growth of tumors expressing the OVA epitope. This report shows that an anti-nucleic acid Ab is used to deliver exogenous Ag to the cross-presentation pathway and inhibit in vivo tumor growth.

Programmable hydrogels for controlled cell catch and release using hybridized aptamers and complementary sequences

The ability to regulate cell-material interactions is important in various applications such as regenerative medicine and cell separation. This study successfully demonstrates that the binding states of cells on a hydrogel surface can be programmed by using hybridized aptamers and triggering complementary sequences (CSs). In the absence of the triggering CSs, the aptamers exhibit a stable, hybridized state in the hydrogel for cell-type-specific catch. In the presence of the triggering CSs, the aptamers are transformed into a new hybridized state that leads to the rapid dissociation of the aptamers from the hydrogel. As a result, the cells are released from the hydrogel. The entire procedure of cell catch and release during the transformation of the aptamers is biocompatible and does not involve any factor destructive to either the cells or the hydrogel. Thus, the programmable hydrogel is regenerable and can be applied to a new round of cell catch and release when needed.

Effects of Iron Oxide Nanoparticle Labeling on Human Endothelial Cells

Iron oxide nanoparticles (INOPS) are a potential contrast agent for magnetic resonance (MR) tracking of transplanted endothelial cells. The objective of this study was to examine the effect of INOPS labeling on endothelial cells. The mixture of INOPS and poly-l-lysine (PLL) was used to label human endothelial cells. Labeling efficiency was examined by Prussian blue staining, transmission electron microscopy, and atomic absorption spectrometry. The effect of iron oxide concentration on cell viability and proliferation were determined. The correlation of reactive oxygen species (ROS) and apoptosis was also examined. In vitro MRI scanning was carried out using a 1.5T MR system. INOPS-PLL could be readily taken up by endothelial cells and subsequently induce MRI signal intensity changes. However, higher labeling concentration (>50 μg/ml) and longer incubation (48 h) can affect cell viability and proliferation. Mitochondrial damage, apoptosis, and autolysosmes were observed under high INOPS-PLL concentrations, which were correlated to ROS production. INOPS-PLL nanoparticles can be used to label transplanted endothelial cells. However, high concentration of INOPS can impair cell viability, possibly through ROS-mediated apoptosis and autophagy.

Induction of autophagy in hepatocellular carcinoma cells by SB203580 requires activation of AMPK and DAPK but not p38 MAPK

SB203580 is a well-known inhibitor of p38 mitogen-activated protein kinase (MAPK). However, it can suppress cell proliferation in a p38 MAPK independent manner. The inhibitory mechanism remains unknown. Here, we showed that SB203580 induced autophagy in human hepatocellular carcinoma (HCC) cells. SB203580 increased GFP-LC3-positive cells with GFP-LC3 dots, induced accumulation of autophagosomes, and elevated the levels of microtubule-associated protein light chain 3 and Beclin 1. It stimulated the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and p53, but inhibited the phosphorylation of death-associated protein kinase (DAPK). Inhibition of AMPK, p53, or DAPK attenuated SB203580-induced autophagy. AMPK activation appeared to predate the DAPK signal. The activation of both AMPK and DAPK prompted the phosphorylation of p53 and enhanced Beclin 1 expression. Neither the downregulation of p38 MAPK by its siRNA or chemical inhibitor nor the upregulation of p38 MAPK by p38 MAPK DNA transfection affected B203580-induced autophagy. Collectively, the findings demonstrate a novel function of SB203580 to induce autophagy via activating AMPK and DAPK but independent of p38 MAPK. The induction of autophagy can thus account for the antiproliferative effect of SB203580 in HCC cells.

Mitochondrial therapeutics for cardioprotection

Mitochondria represent approximately one-third of the mass of the heart and play a critical role in maintaining cellular function-however, they are also a potent source of free radicals and pro-apoptotic factors. As such, maintaining mitochondrial homeostasis is essential to cell survival. As the dominant source of ATP, continuous quality control is mandatory to ensure their ongoing optimal function. Mitochondrial quality control is accomplished by the dynamic interplay of fusion, fission, autophagy, and mitochondrial biogenesis. This review examines these processes in the heart and considers their role in the context of ischemia-reperfusion injury. Interventions that modulate mitochondrial turnover, including pharmacologic agents, exercise, and caloric restriction are discussed as a means to improve mitochondrial quality control, ameliorate cardiovascular dysfunction, and enhance longevity.

Death receptors 4 and 5 activate Nox1 NADPH oxidase through riboflavin kinase to induce reactive oxygen species-mediated apoptotic cell death

Stimulation of the proapoptotic tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptors, death receptors 4 (DR4) and 5 (DR5), conventionally induces caspase-dependent apoptosis in tumor cells. Here we report that stimulation of DR4 and/or DR5 by the agonistic protein KD548-Fc, an Fc-fused DR4/DR5 dual-specific Kringle domain variant, activates plasma membrane-associated Nox1 NADPH oxidase to generate superoxide anion and subsequently accumulates intracellular reactive oxygen species (ROS), leading to sustained c-Jun N-terminal kinase activation and eventual apoptotic cell death in human HeLa and Jurkat tumor cells. KD548-Fc treatment induces the formation of a DR4/DR5 signaling complex containing riboflavin kinase (RFK), Nox1, the Nox1 subunits (Rac1, Noxo1, and Noxa1), TNF receptor-associated death domain (TRADD), and TNF receptor-associated factor 2 (TRAF2). Depletion of RFK, but not the Nox1 subunits, TRADD and TRAF2, failed to recruit Nox1 and Rac1 to DR4 and DR5, demonstrating that RFK plays an essential role in linking DR4/DR5 with Nox1. Knockdown studies also reveal that RFK, TRADD, and TRAF2 play critical, intermediate, and negligible roles, respectively, in the KD548-Fc-mediated ROS accumulation and downstream signaling. Binding assays using recombinantly expressed proteins suggest that DR4/DR5 directly interact with cytosolic RFK through RFK-binding regions within the intracellular death domains, and TRADD stabilizes the DR4/DR5-RFK complex. Our results suggest that DR4 and DR5 have a capability to activate Nox1 by recruiting RFK, resulting in ROS-mediated apoptotic cell death in tumor cells.

Aβ plaque-associated glial reaction as a determinant of apoptotic neuronal death and cortical gliogenesis: a study in APP mutant mice

The purpose of this study was to investigate the microglia-driven apoptosis and the Aβ deposits triggered generation of new microglial cells in the neocortex of TgCRND8 mice. Three- and seven-month-old TgCRND8 mice, displaying an early and widespread amyloid deposition, respectively, were used. In 7-month-old TgCRND8 mice the Aβ-associated glial reaction was accompanied by an intense immunoreactivity of both TNF-α and inducible nitric oxide synthase, increased immunoreactivity of the pro-apoptotic protein Bax and a decrease in levels of the anti-apoptotic protein Bcl-2.Cortical and hippocampal neurons of TgCRND8 mice displayed higher immunoreactivity and higher nuclear expression of the transcription factor NF-kB than controls. It is possible that such an increase could represent a defence/compensatory response to degeneration. These findings indicate that Aβ deposits activate brain-resident microglia population and astrocytes, and induce overproduction of inflammatory mediators that enhance pro- and anti-apoptotic cascades. In both 3- and 7-month-old TgCRND8 mice apparent gliogenesis was present in the vicinity of Aβ plaques in the neocortex, indicating that microglia have a high proliferative rate which might play a more complex role than previously acknowledge.

Generation of bivalent and bispecific kringle single domains by loop grafting as potent agonists against death receptors 4 and 5

Bivalent or bispecific binding activity of proteins has been mainly achieved by assembling two or more domains in a single molecule. Here we report bivalent/bispecific single-domain proteins based on the kringle domain (KD), which has a cystine knot structural motif and is highly tolerant of sequence modifications. KD has seven loops protruding from the core fold into two largely opposite directions, dubbed loop cluster regions (LCRs) 1 and 2. Mutational analysis of previously isolated agonistic KD variants against human death receptors (DRs) 4 and 5 revealed that they can simultaneously recognize two target molecules of DR4 and/or DR5 via the two independent binding sites of LCR1 and LCR2. Binding loop mapping of yeast-surface-displayed KD mutants identified high-affinity target binding loops in LCR2, which were then grafted into conformationally compatible loops located on the opposite side of LCR1 within the same or different KD variants to generate bivalent/bispecific KD variants against DR4 and/or DR5 with improved affinity. The loop-grafted bivalent/bispecific KD variants showed enhanced cell-death-inducing activity of tumor cells compared with their monovalent/monospecific and bivalent/monospecific counterparts, demonstrating an advantage of bispecific targeting to both DR4 and DR5 over the targeting of only one of the two pro-apoptotic receptors. Our results suggest that the KD with the two independent binding surfaces for target recognition is an appropriate scaffold for the development of bivalency and/or bispecificity by loop grafting on the single domain, which offers a distinct advantage over other protein scaffolds with a single binding surface.

β-Elemene-induced autophagy protects human gastric cancer cells from undergoing apoptosis

Background

β-Elemene, a compound found in an herb used in traditional Chinese medicine, has shown promising anti-cancer effects against a broad spectrum of tumors. The mechanism by which β-elemene kills cells remains unclear. The aim of the present study is to investigate the anti-tumor effect of β-elemene on human gastric cancer cells and the molecular mechanism involved.

Results

β-Elemene inhibited the viability of human gastric cancer MGC803 and SGC7901 cells in a dose-dependent manner. The suppression of cell viability was due to the induction of apoptosis. A robust autophagy was observed in the cells treated with β-elemene; it was characterized by the increase of punctate LC3 dots, the cellular morphology, and the increased levels of LC3-II protein. Further study showed that β-elemene treatment up-regulated Atg5-Atg12 conjugated protein but had little effect on other autophagy-related proteins. PI3K/Akt/mTOR/p70S6K1 activity was inhibited by β-elemene. Knockdown of Beclin 1 with small interfering RNA, or co-treatment with the autophagy inhibitor, 3-methyladenine or chlorochine enhanced significantly the antitumor effects of β-elemene.

Conclusions

Our data provides the first evidence that β-elemene induces protective autophagy and prevents human gastric cancer cells from undergoing apoptosis. A combination of β-elemene with autophagy inhibitor might thus be a useful therapeutic option for advanced gastric cancer.

Cancer targeting Gene-Viro-Therapy of liver carcinoma by dual-regulated oncolytic adenovirus armed with TRAIL gene

Liver cancer is a common and aggressive malignancy, but available treatment approaches remain suboptimal. Cancer targeting Gene-Viro-Therapy (CTGVT) has shown excellent anti-tumor effects in a preclinical study. CTGVT takes advantage of both gene therapy and virotherapy by incorporating an anti-tumor gene into an oncolytic virus vector. Potent anti-tumor activity is achieved by virus replication and exogenous expression of the anti-tumor gene. A dual-regulated oncolytic adenoviral vector designated Ad·AFP·E1A·E1B (Δ55) (Ad·AFP·D55 for short thereafter) was constructed by replacing the native viral E1A promoter with the simian virus 40 enhancer/α-fetoprotein (AFP) composite promoter (AFPep) based on an E1B-55K-deleted construct, ZD55. Ad·AFP·D55 showed specific replication and cytotoxicity in AFP-positive hepatoma cells. It also showed enhanced safety in normal cells when compared with the mono-regulated vector ZD55. To improve the anti-hepatoma activities of the virus, the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene was introduced into Ad·AFP·D55. Ad·AFP·D55-TRAIL exhibited remarkable anti-tumor activities in vitro and in vivo. Treatment with Ad·AFP·D55-TRAIL can induce both autophagy owing to the Ad·AFP·D55 vector and caspase-dependent apoptosis owing to the TRAIL protein. Therefore, Ad·AFP·D55-TRAIL could be a potential anti-hepatoma agent with anti-tumor activities due to AFP-specific replication and TRAIL-induced apoptosis.

The emerging role of autophagy in the pathophysiology of diabetes mellitus

An emerging body of evidence supports a role for autophagy in the pathophysiology of type 1 and type 2 diabetes mellitus. Persistent high concentrations of glucose lead to imbalances in the antioxidant capacity within the cell resulting in oxidative stress-mediated injury in both disorders. An anticipated consequence of impaired autophagy is the accumulation of dysfunctional organelles such as mitochondria within the cell. Mitochondria are the primary site of the production of reactive oxygen species (ROS), and an imbalance in ROS production relative to the cytoprotective action of autophagy may lead to the accumulation of ROS. Impaired mitochondrial function associated with increased ROS levels have been proposed as mechanisms contributing to insulin resistance. In this article we review and interpret the literature that implicates a role for autophagy in the pathophysiology of type 1 and type 2 diabetes mellitus as it applies to β-cell dysfunction, and more broadly to organ systems involved in complications of diabetes including the cardiovascular, renal and nervous systems.

Histone deacetylase inhibitors synergistically potentiate death receptor 4-mediated apoptotic cell death of human T-cell acute lymphoblastic leukemia cells

Cell-death signaling through the pro-apoptotic tumor necrosis factor-related apoptosis inducing ligand (TRAIL) receptors, death receptor 4 (DR4) and DR5, has shown tumor-selective apoptotic activity. Here, we examine susceptibility of various leukemia cell lines (HL-60, U937, K562, CCRF-CEM, CEM-CM3, and THP-1) to an anti-DR4 agonistic monoclonal antibody (mAb), AY4, in comparison with TRAIL. While most of the leukemia cell lines were intrinsically resistant to AY4 or TRAIL alone, the two T-cell acute lymphoblastic leukemia (T-ALL) lines, CEM-CM3 and CCRF-CEM cells, underwent synergistic caspase-dependent apoptotic cell death by combination of AY4 or TRAIL with a histone deacetylase inhibitor (HDACI), either suberoylanilide hydroxamic acid (SAHA) or valproic acid (VPA). All of the combined treatments synergistically downregulated several anti-apoptotic proteins (c-FLIP, Bcl-2, Bcl-X(L), XIAP, and survivin) without significant changing the expression levels of pro-apoptotic proteins (Bax and Bak) or the receptors (DR4 and DR5). Downregulation of c-FLIP to activate caspase-8 was a critical step for the synergistic apoptosis through both extrinsic and intrinsic apoptotic pathways. Our results demonstrate that the HDACIs have synergistic effects on DR4-specific mAb AY4-mediated cell death in the T-ALL cells with comparable competence to those exerted by TRAIL, providing a new strategy for the targeted treatment of human T-ALL cells.

A temperature-responsive antibody-like nanostructure

Antibodies play an essential role in various applications. However, antibodies exhibit considerable challenges in applications that require tunable binding capabilities and exposure to nonphysiological conditions such as chemical conjugation. This study is aimed to develop a novel antibody-like nanostructure with special features. The key components of the nanostructure are two DNA aptamers and a dendrimer. The aptamers are used to mimic the antigen-binding sites of an antibody; the dendrimer is used to provide a defined conjugation site for carrying molecules of interest. The results showed that the bivalent nanostructure exhibited a high binding affinity and specificity. Moreover, a temperature shift from 0 to 37 degrees C would trigger its rapid dissociation from the bound target cells, which is not possible in antibody-antigen complexes. Thus, an antibody-like nanostructure was successfully developed with novel features that natural antibodies do not possess.

Role of the urokinase plasminogen activator receptor in mediating impaired efferocytosis of anti-SSA/Ro-bound apoptotic cardiocytes: Implications in the pathogenesis of congenital heart block

RATIONALE

Binding of maternal anti-Ro/La antibodies to cognate antigen expressed on apoptotic cardiocytes decreases clearance by healthy cardiocytes, which may contribute to the development of autoimmune associated congenital heart block and fatal cardiomyopathy.

OBJECTIVE

Given recent evidence implicating the urokinase plasminogen activator receptor (uPAR) as a "don't eat me" signal during efferocytosis, experiments addressed whether surface bound anti-Ro antibodies inhibit apoptotic cell removal via an effect on the expression/function of the urokinase-type plasminogen activator protease uPA/uPAR system.

METHODS AND RESULTS

As assessed by flow cytometry and confocal microscopy, uPAR colocalizes and interacts with Ro60 on the surface of apoptotic human fetal cardiocytes. Blocking of uPAR enhances phagocytosis of apoptotic cardiocytes by healthy cardiocytes and reverses the anti-Ro60-dependent impaired clearance of apoptotic cardiocytes. Binding of anti-Ro60 antibodies to apoptotic cardiocytes results in increased uPAR expression, as well as enhanced uPA activity. The binding of anti-Ro60 did not alter other surface molecules involved in cell recognition (calreticulin, CD31, or CD47).

CONCLUSIONS

These data suggest that increased uPAR expression and uPA activity induced by anti-Ro60 binding to the apoptotic fetal cardiocyte provide a molecular basis by which these antibodies inhibit efferocytosis and ultimately lead to scar of the fetal conduction system and working myocardium.

Engineering of a human kringle domain into agonistic and antagonistic binding proteins functioning in vitro and in vivo

Here, we report the development of target-specific binding proteins based on the kringle domain (KD) ( approximately 80 residues), a ubiquitous modular structural unit occurring across eukaryotic species. By exploiting the highly conserved backbone folding by core residues, but using extensive sequence variations in the seven loop regions of naturally occurring human KDs, we generated a synthetic KD library on the yeast cell surface by randomizing 45 residues in the loops of a human KD template. We isolated KD variants that specifically bind to anticancer target proteins, such as human death receptor 4 (DR4) and/or DR5, and that function as agonists to induce apoptotic cell death in several cancer cell lines in vitro and inhibit tumor progression in mouse models. Combined treatments with KD variants possessing different recognition sites on the same target protein exerted synergisitic tumoricidal activities, compared to treatment with individual variants. In addition to the agonists, we isolated an antagonistic KD variant that binds human tumor necrosis factor-alpha (TNFalpha) and efficiently neutralizes TNFalpha-induced cytotoxicity in vitro and in vivo. The KD scaffold with seven flexible loops protruding from the central core was strongly sequence-tolerant to mutations in the loop regions, offering a potential advantage of distinct binding sites for target recognition on the single domain. Our results suggest that the KD scaffold can be used to develop target-specific binding proteins that function as agonists or antagonists toward given target molecules, indicative of their potential use as biotherapeutics.

Cyclophilin D is required for mitochondrial removal by autophagy in cardiac cells

Autophagy is a highly regulated intracellular degradation process by which cells remove cytosolic long-lived proteins and damaged organelles. The mitochondrial permeability transition (MPT) results in mitochondrial depolarization and increased reactive oxygen species production, which can trigger autophagy. Therefore, we hypothesized that the MPT may have a role in signaling autophagy in cardiac cells. Mitochondrial membrane potential was lower in HL-1 cells subjected to starvation compared to cells maintained in full medium. Mitochondrial membrane potential was preserved in starved cells treated with cyclosporin A (CsA), suggesting the MPT pore is associated with starvation-induced depolarization. Starvation-induced autophagy in HL-1 cells, neonatal rat cardiomyocytes and adult mouse cardiomyocytes was inhibited by CsA. Starvation failed to induce autophagy in CypD-deficient murine cardiomyocytes, whereas in myocytes from mice overexpressing CypD the levels of autophagy were enhanced even under fed conditions. Collectively, these results demonstrate a role for CypD and the MPT in the initiation of autophagy. We also analyzed the role of the MPT in the degradation of mitochondria by biochemical analysis and electron microscopy. HL-1 cells subjected to starvation in the presence of CsA had higher levels of mitochondrial proteins (by Western blot), more mitochondria and less autophagosomes (by electron microscopy) than cells starved in the absence of CsA. Our results suggest a physiologic function for CypD and the MPT in the regulation of starvation-induced autophagy. Starvation-induced autophagy regulated by CypD and the MPT may represent a homeostatic mechanism for cellular and mitochondrial quality control.

A novel anti-EGFR monoclonal antibody inhibiting tumor cell growth by recognizing different epitopes from cetuximab

The epidermal growth factor receptor (EGFR) overexpressed in many epithelial tumors is an attractive target for tumor therapy since numerous blocking agents of EGFR signaling have proven their anti-tumor activity. Here we report a novel monoclonal antibody (mAb), A13, which was generated from mice immunized with human cervical carcinoma A431 cells. In addition to binding to soluble EGFR with affinity of K(D) approximately 5.8nM, mAb A13 specifically bound to a variety of tumor cells and human placenta tissues expressing EGFR. A13 efficiently inhibited both EGF-dependant EGFR tyrosine phosphorylation in cervical and breast tumor cells and also in vitro colony formation of EGFR-overexpressing lung tumors. Competition and sandwich ELISAs, competitive surface plasmon resonance, and domain-level epitope mapping analyses demonstrated that mAb A13 competitively bound to the domain III (amino acids 302-503) of EGFR with EGF, but recognized distinct epitopes from those of cetuximab (Erbitux). Our results demonstrated that anti-EGFR mAb A13 interfered with EGFR proliferation signaling by blocking EGF binding to EGFR with different epitopes from those of cetuximab, suggesting that combination therapies of mAb A13 with cetuximab may prove beneficial for anti-tumor therapy.

Atg7 deficiency increases resistance of MCF-7 human breast cancer cells to photodynamic therapy

Photodynamic therapy (PDT) uses a photosensitizer, light and oxygen to produce extensive oxidative damage to organelles housing the photosensitizer. Although PDT is an efficient trigger of apoptosis, it also induces autophagy in many kinds of cells. Autophagy can serve as both a cell survival and a cell death mechanism. Our previous study indicates that autophagy contributes to cell death after PDT, especially in apoptosis-deficient cells. Here, we provide further evidence to support the role of autophagy in cell killing after PDT. Autophagy was blocked by knockdown of one essential factor, LC3 or Atg7, in MCF-7 cells. The cells were exposed to a range of doses of PDT sensitized by the phthalocyanine Pc 4; steps in autophagy were monitored by western blotting for LC3-II and by fluorescence microscopy for the uptake of monodansylcadaverine or for the distribution of transfected GFP-LC3; and overall cell death was monitored by MTT assay and by clonogenic assay. We find that blocking autophagy increased the survival of MCF-7 cells after PDT and increased the shoulder on the dose-response curve. In response to Pc 4-PDT, Atg7-deficient MCF-7 cells remained capable of robust accumulation of LC3-II, but were defective in comparison to Atg7(+) cells in the formation of autophagosomes. We conclude that apoptosis-deficient cells rely on autophagy for cell death after Pc 4-PDT and that the strong activation of LC3 maturation in response to PDT could occur even in cells with limited or no Atg7 expression.