Targeting the extrinsic apoptosis pathway in cancer

Timosaponin AIII: A novel potential anti-tumor compound from Anemarrhena asphodeloides

Timosaponin AIII, a major steroidal saponin found in Anemarrhena asphodeloides Bge., which has been widely used as anti-pyretic, anti-diabetic, anti-inflammatory, anti-platelet aggregator and anti-depressant agents in traditional Chinese medicine. Recent pharmacological study showed that timosaponin AIII had potent cytotoxicity, which was potential to be developed as an anticancer agent, however the molecular mechanism underlying the anticancer activity has not been fully elucidated. This review aims to give a systematic summary of the study of timosaponin AIII to reveal its anti-tumor activities by investigating invasion and migration, apoptosis, autophagy and reversing multi-drug resistance. Furthermore, we also make an overview of the mechanisms identified till now. These meaningful findings may provide novel insights on exploiting timosaponin AIII as a new anti-tumor agent.

Spotlight on Bortezomib: potential in the treatment of hepatocellular carcinoma

INTRODUCTION

This study reviews the evidence for the use of Bortezomib (BZB), a first-in-class proteasome inhibitor in advanced Hepatocellular carcinoma (HCC). This review aims to delineate the role of BZB within the management of non-surgical and metastatic HCC, either as an alternative or as an adjunct to the current treatment paradigm.

AREAS COVERED

In addition to BZB pharmacology and mechanism of action, safety and tolerance profiles of the drug obtained from clinical trials are explored. The utility of BZB as a therapeutic agent either alone or in combination with other therapies against HCC, including its application in both preclinical and clinical settings has been reviewed. In particular, we highlight the importance of preclinical evaluation of BZB as a combinatorial agent in synergism with other therapies for the use in the management of HCC.

EXPERT OPINION

There has been much interest surrounding the use of BZB, a first-in-class proteasome inhibitor for HCC therapy. The discernment of outcomes of BZB clinical trials for HCC need to take into consideration the disease-specific factors that can affect survival outcomes including patient selection and aetiological differences. Further preclinical testing of BZB in combination with other therapeutic modalities can be important for eliciting enhanced anti-HCC effects.

Programmed Cell Death, from a Cancer Perspective: An Overview

Programmed cell death (PCD) is probably the most widely discussed subject among the topics of cancer therapy. Over the last 2 decades an astonishing boost in our perception of cell death has been seen, and its role in cancer and cancer therapy has been thoroughly investigated. A number of discoveries have clarified the molecular mechanism of PCD, thus expounding the link between PCD and therapeutic tools. Even though PCD is assumed to play a major role in anticancer therapy, the clinical relevance of its induction remains uncertain. Since PCD involves multiple death programs including programmed necrosis and autophagic cell death, it has contributed to our better understanding of cancer pathogenesis and therapeutics. In this review, we discuss a brief outline of PCD types as well as their role in cancer therapeutics. Since irregularities in the cell death process are frequently found in various cancers, key proteins governing cell death type could be used as therapeutic targets for a wide range of cancer.

Nanoparticles induce apoptosis via mediating diverse cellular pathways

With a special size and structure, nanoparticles (NPs) have excellent application prospects in various fields and are widely used in the biomedicine, cosmetics and chemical industries nowadays. However, there have been some reports on the biosafety of this new type of material, pointing out its cytotoxicity in inducing apoptosis. With different physicochemical properties in size, shape, surface charge, and ligand, NPs exhibit different biocompatibilities when interacting with different cells. Therefore, a comprehensive and deep study into the proapoptotic mechanism of NPs is necessary. In the present review, we summarize the NP-triggered apoptotic signal pathways in detail and highlight some important functional molecules involved. We hope our findings and perspectives provide a new direction for the sound development of nanotechnology in the future.

Host-based processes as therapeutic targets for Rift Valley fever virus

Rift Valley fever virus (RVFV) is an enveloped, segmented, negative sense RNA virus that replicates within the host's cytoplasm. To facilitate its replication, RVFV must utilize host cell processes and as such, these processes may serve as potential therapeutic targets. This review summarizes key host cell processes impacted by RVFV infection. Specifically the influence of RVFV on host transcriptional regulation, post-transcriptional regulation, protein half-life and availability, host signal transduction, trafficking and secretory pathways, cytoskeletal modulation, and mitochondrial processes and oxidative stress are discussed. Therapeutics targeted towards host processes that are essential for RVFV to thrive as well as their efficacy and importance to viral pathogenesis are highlighted.

The antipsychotic agent trifluoperazine hydrochloride suppresses triple-negative breast cancer tumor growth and brain metastasis by inducing G0/G1 arrest and apoptosis

Women with aggressive triple-negative breast cancer (TNBC) are at high risk of brain metastasis, which has no effective therapeutic option partially due to the poor penetration of drugs across the blood-brain barrier. Trifluoperazine (TFP) is an approved antipsychotic drug with good bioavailability in brain and had shown anticancer effect in several types of cancer. It drives us to investigate its activities to suppress TNBC, especially the brain metastasis. In this study, we chose three TNBC cell lines MDA-MB-468, MDA-MB-231, and 4T1 to assess its anticancer activities along with the possible mechanisms. In vitro, it induced G0/G1 cell cycle arrest via decreasing the expression of both cyclinD1/CDK4 and cyclinE/CDK2, and stimulated mitochondria-mediated apoptosis. In vivo, TFP suppressed the growth of subcutaneous xenograft tumor and brain metastasis without causing detectable side effects. Importantly, it prolonged the survival of mice bearing brain metastasis. Immunohistochemical analysis of Ki67 and cleaved caspase-3 indicated TFP could suppress the growth and induce apoptosis of cancer cells in vivo. Taken together, TFP might be a potential available drug for treating TNBC with brain metastasis, which urgently needs novel treatment options.

LipoxinA4 attenuates acute pancreatitis-associated acute lung injury by regulating AQP-5 and MMP-9 expression, anti-apoptosis and PKC/SSeCKS-mediated F-actin activation

An essential component of acute pancreatitis(AP)-induced acute lung injury(ALI) is the inflammation that is part of the body's systemic inflammatory response to a variety of systemic stimuli. Lipoxins(LXs) are considered important endogenous lipids that mediate the resolution of inflammation. In previous studies, we found that Lipoxin A4 (LXA4) reduced AP-induced pulmonary oedema and TNF-α production in lung. However, the underlying mechanism remains unclear. Due to the above studies, we investigated the aquaporin, matrix metalloprotein, apoptosis and PKC/SSeCKS signal pathway in cellular and animal models of AP-associated lung injury following LXA4 intervention. In this study, we first proved LXA4 could effectively promote F-actin reconstruction and regulate its expression in pulmonary microvascular endothelial cells both in vivo and vitro via suppressing PKC/SSeCKS signalling pathway. Next, we found that LXA4 attenuated cell growth inhibition and apoptosis in lung tissues of AP-ALI mice and HPMECs. Additionally, we demonstrated that LXA4 could regulate the expression of AQP-5 and MMP-9 to stabilize the permeability of pulmonary microvascular endothelial cell. In summary, our results suggest that the anti-inflammatory eff ;ects of LXA4 may be due to the inhibition of both the PKC/SSeCKS pathway and apoptosis to reduce alveolar fluid exudation and to the regulation of AQP-5 and MMP-9 expression to maintain the clearance of alveolar fluid. Thus, LXA4 is capable of exerting protective eff ;ects on AP-induced ALI.

Delphinidin induces apoptosis and inhibits epithelial-to-mesenchymal transition via the ERK/p38 MAPK-signaling pathway in human osteosarcoma cell lines

Delphinidin is major anthocyanidin that is extracted from many pigmented fruits and vegetables. This substance has anti-oxidant, anti-inflammatory, anti-angiogenic, and anti-cancer properties. In addition, delphinidin strongly suppresses the migration and invasion of various cancer cells during tumorigenesis. Although delphinidin has anti-cancer effects, little is known about its functional roles in osteosarcoma (OS). For these reasons, we have demonstrated the effects of delphinidin on OS cell lines. The effects of delphinidin on cell viability and growth of OS cells were assessed using the MTT assay and colony formation assays. Hoechst staining indicated that the delphinidin-treated OS cells were undergoing apoptosis. Flow cytometry, confocal microscopy, and a western blot analysis also indicated evidence of apoptosis. Inhibition of cell migration and invasion was found to be associated with epithelial-to-mesenchymal transition (EMT), observed by using a wound healing assay, an invasion assay, and a western blot analysis. Furthermore, delphinidin treatment resulted in a profound reduction of phosphorylated forms of ERK and p38. These findings demonstrate that delphinidin treatment suppressed EMT through the mitogen-activated protein kinase (MAPK) signaling pathway in OS cell lines. Taken together, our results suggest that delphinidin strongly inhibits cell proliferation and induces apoptosis. Delphinidin treatment also suppresses cell migration and prevents EMT via the MAPK-signaling pathway in OS cell lines. For these reasons, delphinidin has anti-cancer effects and can suppress metastasis in OS cell lines, and it might be worth using as an OS therapeutic agent.

Bax/Tubulin/Epithelial-Mesenchymal Pathways Determine the Efficacy of Silybin Analog HM015k in Colorectal Cancer Cell Growth and Metastasis

The inhibition of apoptosis, disruption of cellular microtubule dynamics, and over-activation of the epithelial mesenchymal transition (EMT), are involved in the progression, metastasis, and resistance of colorectal cancer (CRC) to chemotherapy. Therefore, the design of a molecule that can target these pathways could be an effective strategy to reverse CRC progression and metastasis. In this study, twelve novel silybin derivatives, HM015a-HM015k (15a−15k) and compound 17, were screened for cytotoxicity in CRC cell lines. Compounds HM015j and HM015k (15k and 15j) significantly decreased cell proliferation, inhibited colony formation, and produced cell cycle arrest in CRC cells. Furthermore, 15k significantly induced the formation of reactive oxygen species and apoptosis. It induced the cleavage of the intrinsic apoptotic protein (Bax p21) to its more efficacious fragment, p18. Compound 15k also inhibited tubulin expression and disrupted its structure. Compound 15k significantly decreased metastatic LOVO cell migration and invasion. Furthermore, 15k reversed mesenchymal morphology in HCT116 and LOVO cells. Additionally, 15k significantly inhibited the expression of the mesenchymal marker N-cadherin and upregulated the expression of the epithelial marker, E-cadherin. Compound 15k inhibited the expression of key proteins known to induce EMT (i.e., DVL3, β-catenin, c-Myc) and upregulated the anti-metastatic protein, cyclin B1. Overall, in vitro, 15k significantly inhibited CRC progression and metastasis by inhibiting apoptosis, tubulin activity and the EMT pathways. Overall, these data suggest that compound 15k should be tested in vivo in a CRC animal model for further development.

A survey of metastasis suppressors in Metazoa

Metastasis suppressors are genes/proteins involved in regulation of one or more steps of the metastatic cascade while having little or no effect on tumor growth. The list of putative metastasis suppressors is constantly increasing although thorough understanding of their biochemical mechanism(s) and evolutionary history is still lacking. Little is known about tumor-related genes in invertebrates, especially non-bilaterians and unicellular relatives of animals. However, in the last few years we have been witnessing a growing interest in this subject since it has been shown that many disease-related genes are already present in simple non-bilateral animals and even in their unicellular relatives. Studying human diseases using simpler organisms that may better represent the ancestral conditions in which the specific disease-related genes appeared could provide better understanding of how those genes function. This review represents a compilation of published literature and our bioinformatics analysis to gain a general insight into the evolutionary history of metastasis-suppressor genes in animals (Metazoa). Our survey suggests that metastasis-suppressor genes emerged in three different periods in the evolution of Metazoa: before the origin of metazoans, with the emergence of first animals and at the origin of vertebrates.

STAT5 inhibition induces TRAIL/DR4 dependent apoptosis in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a rare, aggressive, heterogeneous, Non-Hodgkin's lymphoma with poor prognosis and inadequate response to current therapies. Recent sequencing studies indicate a prevalence of activating mutations in the JAK/STAT signaling pathway. Oncogenic mutations in STAT5B, observed in approximately one third of cases of multiple different PTCL subtypes, correlate with inferior patient outcomes. Therefore, interest in the development of therapeutic strategies for targeting STAT5 in PTCL is warranted. In this study, we show that the drug pimozide inhibits STAT5 in PTCL, leading to apoptotic cell death by means of the TRAIL/DR4 dependent extrinsic apoptotic pathway. Pimozide induced PTCL cell death is caspase 8 dependent, increases the expression of the TRAIL receptor, DR4, on the surface of pre-apoptotic PTCL cells, and enhances TRAIL induced apoptosis in a TRAIL dependent manner. In parallel, we show that mRNA and protein levels of intrinsic pathway BCL-2 family members and mitochondrial membrane potential remain unaffected by STAT5 knockdown and/or inhibition. In primary PTCL patient samples, pimozide inhibits STAT5 activation and induces apoptosis. Our data support a role for STAT5 inhibition in PTCL and implicate potential utility for inhibition of STAT5 and activation of the extrinsic apoptotic pathway as combination therapy in PTCL.

Curcuzedoalide contributes to the cytotoxicity of Curcuma zedoaria rhizomes against human gastric cancer AGS cells through induction of apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Curcuma zedoaria Roscoe (Zingiberaceae), also known as white turmeric or zedoaria, has been used in Ayurveda and traditional Chinese medicine to treat various cancers, and it possesses several sesquiterpenoid compounds.

OBJECTIVE

This study aimed to evaluate the therapeutic effects of a methanolic (MeOH) extract of C. zedoaria rhizomes, as well as its active constituents, against gastric cancer, which is a frequently diagnosed cancer in South Korea.

MATERIALS AND METHODS

Repeated column chromatography, together with semi-preparative HPLC purification, was used to separate the bioactive constituents from the C. zedoaria MeOH extract. The cytotoxic effects of the C. zedoaria MeOH extract and its active compounds were measured in human gastric cancer AGS cells. Expression of proteins related to apoptosis was evaluated using Western blotting analysis.

RESULTS

The MeOH extract of C. zedoaria rhizomes exerted a cytotoxic effect on AGS cells (IC₅₀: 96.60 ± 4.87μg/mL). Based on the bioactivity-guided fractionation for antiproliferative activity, a chemical investigation of the MeOH extract led to the isolation of five sesquiterpenes including isoprocurcumenol (1), germacrone (2), curzerenone (3), curcumenol (4), and curcuzedoalide (5). Among these, curcuzedoalide demonstrated the strongest effect in suppressing gastric cancer cell proliferation in a dose-dependent manner with an IC₅₀ value of 125.11±2.77μM. Western blotting analysis showed that curcuzedoalide inhibited AGS human gastric cancer cell viability by activating caspase-8, caspase-9, caspase-3, and PARP, which contributed to apoptotic cell death in AGS human gastric cancer cells.

CONCLUSION

These data indicate that curcuzedoalide contributed to the cytotoxicity of C. zedoaria by activating the cleavage of caspases and PARP, which are representative markers for apoptosis. Therefore, curcuzedoalide is a positive candidate for the development of novel chemotherapeutics.

Graphene Oxide-Silver Nanocomposite Enhances Cytotoxic and Apoptotic Potential of Salinomycin in Human Ovarian Cancer Stem Cells (OvCSCs): A Novel Approach for Cancer Therapy

The use of graphene to target and eliminate cancer stem cells (CSCs) is an alternative approach to conventional chemotherapy. We show the biomolecule-mediated synthesis of reduced graphene oxide-silver nanoparticle nanocomposites (rGO-Ag) using R-phycoerythrin (RPE); the resulting RPE-rGO-Ag was evaluated in human ovarian cancer cells and ovarian cancer stem cells (OvCSCs). The synthesized RPE-rGO-Ag nanocomposite (referred to as rGO-Ag) was characterized using various analytical techniques. rGO-Ag showed significant toxicity towards both ovarian cancer cells and OvCSCs. After 3 weeks of incubating OvCSCs with rGO-Ag, the number of A2780 and ALDH⁺CD133⁺ colonies was significantly reduced. rGO-Ag was toxic to OvCSCs and reduced cell viability by mediating the generation of reactive oxygen species, leakage of lactate dehydrogenase, reduced mitochondrial membrane potential, and enhanced expression of apoptotic genes, leading to mitochondrial dysfunction and possibly triggering apoptosis. rGO-Ag showed significant cytotoxic potential towards highly tumorigenic ALDH⁺CD133⁺ cells. The combination of rGO-Ag and salinomycin induced 5-fold higher levels of apoptosis than each treatment alone. A combination of rGO-Ag and salinomycin at very low concentrations may be suitable for selectively killing OvCSCs and sensitizing tumor cells. rGO-Ag may be a novel nano-therapeutic molecule for specific targeting of highly tumorigenic ALDH⁺CD133⁺ cells and eliminating CSCs. This study highlights the potential for targeted therapy of tumor-initiating cells.

Lup-20(29)-en-3β,28-di-yl-nitrooxy acetate affects MCF-7 proliferation through the crosstalk between apoptosis and autophagy in mitochondria

Betulin (BT), a pentacyclic lupine-type triterpenoid natural product, possesses antitumor activity in various types of cancers. However, its clinical development was discouraged due to its low biological activities and poor solubility. We prepared lup-20(29)-en-3β,28-di-yl-nitrooxy acetate (NBT), a derivative of BT, that was chemically modified at position 3 of ring A and C-28 by introducing a NO-releasing moiety. This study mainly explored the mechanism of NBT in treating breast cancer through the crosstalk between apoptosis and autophagy in mitochondria. NBT possessed a potent antiproliferative activity in MCF-7 cells both in vitro and in vivo. Mechanically, NBT affected cell death through the mitochondrial apoptosis pathway and autophagy. NBT induced cell cycle arrest in the G₀/G₁ phase by decreasing the expression of cyclin D1. It also induced mitochondrial apoptosis by increasing the expression of Bax, caspase-9, and poly(ADP-ribose) polymerase and mitochondrial membrane potential loss and leaks of cytochrome c (Cyt C) from mitochondria in MCF-7 cells and decreasing the expression of mitochondrial Bcl-2. We further demonstrated whether chloroquine (CQ), which inhibits the degradation of autophagosome induced by NBT, affects the proliferation of MCF-7 cells compared with NBT. The experiments inferred that the combination of NBT and CQ significantly promoted MCF-7 cell mitochondria to divide and Cyt C to be released from mitochondria to the cytoplasm, resulting in an increased apoptosis rate. The in vivo experiments showed that NBT inhibited the growth of MCF-7 tumor via the apoptosis pathway, and its effect was similar to 5-fluorouracil.

Therapeutic opportunities based on caspase modulation

Caspases are a family of proteolytic enzymes that play a critical role in the regulation of programmed cell death via apoptosis. Activation of caspases is frequently impaired in human cancers, contributing to cancer formation, progression and therapy resistance. A better understanding of the molecular mechanisms regulating caspase activation in cancer cells is therefore highly important. Thus, targeted modulation of caspase activation and apoptosis represents a promising approach for the development of new therapeutic options to elucidate cancer cell death.

CGP57380 enhances efficacy of RAD001 in non-small cell lung cancer through abrogating mTOR inhibition-induced phosphorylation of eIF4E and activating mitochondrial apoptotic pathway

The mammalian target of rapamycin (mTOR) is a potentially important therapeutic target in a broad range of cancer types. mTOR inhibitors such as rapamycin and its analogs (rapalogs) have been proven effective as anticancer agents in non-small cell lung cancer (NSCLC), whereas they strongly enhance phosphorylation of eukaryotic translation initiation factor 4E (eIF4E) and activation of Akt, which cause resistance to mTOR-targeted therapy after an initial response. Rapamycin induces eIF4E phosphorylation by activating MAPK-interacting kinases (Mnks), and therefore targeting Mnk/eIF4E pathway represents a potential therapeutic strategy for the treatment of NSCLC. Here, our results showed that over-expression of p-Mnk1 and p-eIF4E was significantly associated with poor overall survival of NSCLC patients and high expression of p-Mnk1 might act as an independent prognostic biomarker for these patients. Meanwhile, inhibiting Mnk1 expression by Mnk inhibitor (CGP57380) could abrogate rapalogs (RAD001)-induced eIF4E phosphorylation and Akt activation. Furthermore, combination of CGP57380 and RAD001 could induce NSCLC cells apoptosis via activating intrinsic mitochondrial pathway, and exert synergistic antitumor efficacy both in vitro and in vivo. In conclusion, combination of targeting both mTOR and Mnk/eIF4E signaling pathways to enhance effectiveness of mTOR-targeted cancer therapy might be significant innovation for the personalized treatment of NSCLC.

4EGI-1 induces apoptosis and enhances radiotherapy sensitivity in nasopharyngeal carcinoma cells via DR5 induction on 4E-BP1 dephosphorylation

The eIF4F complex regulated by a various group of eIF4E-binding proteins (4E-BPs) can initial the protein synthesis. Small molecule compound 4EGI-1, an inhibitor of the cap-dependent translation initiation through disturbing the interaction between eIF4E and eIF4G which are main elements of the eIF4E complex, has been reported to suppress cell proliferation by inducing apoptosis in many types of cancer. And death receptor 5 (DR5) is a major component in the extrinsic apoptotic pathway. However, the correlation among 4EGI-1, DR5 and 4E-BPs have not been discovered in NPC now. Therefore, we intend to find out the effect of 4EGI-1 on the apoptosis process of NPC and the relationship among 4EGI-1, DR5 and 4E-BPs. Our results revealed a significant down regulation of DR5 expression in NPC tissues, which inversely correlated with lymph node metastasis status and clinical stages. Depressed DR5 expression was an independent biomarker for poor prognosis in NPC, and elevated DR5 expression showed longer overall survival time in 174 NPC patients. Besides, 4EGI-1 induced apoptosis in NPC cells through the DR5-caspase-8 axis on 4E-BP1 and eIF4E dephosphorylation exerting positive influence on their anti-tumor activities. The induction of DR5 also sensitized NPC cells to radiotherapy, and the SER was 1.195. These results establish the death receptor pathway as a novel anticancer mechanism of eIF4E/eIF4G interaction inhibitor in NPC.

The potential of brown-algae polysaccharides for the development of anticancer agents: An update on anticancer effects reported for fucoidan and laminaran

In recent decades, attention to cancer-preventive treatments and studies on the development of anticancer drugs have sharply increased owing to the increase in cancer-related death rates in every region of the world. However, due to the adverse effects of synthetic drugs, much attention has been given to the development of anticancer drugs from natural sources because of fewer side effects of natural compounds than those of synthetic drugs. Recent studies on compounds and crude extracts from marine algae have shown promising anticancer properties. Among those compounds, polysaccharides extracted from brown seaweeds play a principal role as anticancer agents. Especially, a number of studies have revealed that polysaccharides isolated from brown seaweeds, such as fucoidan and laminaran, have promising effects against different cancer cell types in vitro and in vivo. Herein, we reviewed in vitro and in vivo anticancer properties reported for fucoidan and laminaran toward various cancer cells from 2013 to 2016.

Down-regulation of CHERP inhibits neuroblastoma cell proliferation and induces apoptosis through ER stress induction

Neuroblastoma is a childhood tumor that is derived from the sympathetic nervous system. In recent years, great progress has been made in our understanding of neuroblastoma. However, applying theories to improve disease outcomes remains challenging. In this study, we observed that calcium homeostasis endoplasmic reticulum protein (CHERP) was involved in the maintenance of neuroblastoma cell proliferation and tumorigenicity. Moreover, elevated CHERP expression was positively correlated with poor patient survival, whereas low CHERP expression was predictive of better outcomes. Additional functional studies showed that CHERP knockdown inhibited neuroblastoma cell proliferation in vitro and resulted in defective tumorigenicity in vivo. Moreover, CHERP depletion suppressed neuroblastoma cell proliferation by inducing endoplasmic reticulum stress and cell apoptosis. Considering the functional roles of CHERP in neuroblastoma development and maintenance, CHERP might function as a novel therapeutic target for neuroblastoma patients.

Modulating lysosomal function through lysosome membrane permeabilization or autophagy suppression restores sensitivity to cisplatin in refractory non-small-cell lung cancer cells

Lung cancer is the leading cause of cancer-related deaths. Most patients develop resistance to platinum within several months of treatment. We investigated whether triggering lysosomal membrane permeabilization (LMP) or suppressing autophagy can restore cisplatin susceptibility in lung cancer with acquired chemoresistance. Cisplatin IC₅₀ in A549Pt (parental) and A549cisR (cisplatin resistant) cells was 13 μM and 47 μM, respectively. Following cisplatin exposure, A549cisR cells failed to elicit an apoptotic response. This was manifested by diminished Annexin–V staining, caspase 3 and 9, BAX and BAK activation in resistant but not in parental cells. Chloroquine preferentially promoted LMP in A549cisR cells, revealed by leakage of FITC-dextran into the cytosol as detected by immunofluorescence microscopy. This was confirmed by increased cytosolic cathepsin D signal on Immunoblot. Cell viability of cisplatin-treated A549cisR cells was decreased when co-treated with chloroquine, corresponding to a combination index below 0.8, suggesting synergism between the two drugs. Notably, chloroquine activated the mitochondrial cell death pathway as indicated by increase in caspase 9 activity. Interestingly, inhibition of lysosomal proteases using E64 conferred cytoprotection against cisplatin and chloroquine co-treatment, suggesting that chloroquine-induced cell death occurred in a cathepsin-mediated mechanism. Likewise, blockage of caspases partially rescued A549cisR cells against the cytotoxicity of cisplatin and chloroquine combination. Cisplatin promoted a dose-dependent autophagic flux induction preferentially in A549cisR cells, as evidenced by a surge in LC3-II/α-tubulin following pre-treatment with E64 and increase in p62 degradation. Compared to untreated cells, cisplatin induced an increase in cyto-ID-loaded autophagosomes in A549cisR cells that was further amplified by chloroquine, pointing toward autophagic flux activation by cisplatin. Interestingly, this effect was less pronounced in A549Pt cells. Blocking autophagy by ATG5 depletion using siRNA markedly enhances susceptibility to cisplatin in A549cisR cells. Taken together, our results underscore the utility of targeting lysosomal function in overcoming acquired cisplatin refractoriness in lung cancer.

Gedunin inhibits pancreatic cancer by altering sonic hedgehog signaling pathway

INTRODUCTION

The lack of efficient treatment options for pancreatic cancer highlights the critical need for the development of novel and effective chemotherapeutic agents. The medicinal properties found in plants have been used to treat many different illnesses including cancers. This study focuses on the anticancer effects of gedunin, a natural compound isolated from Azadirachta indica.

METHODS

Anti–proliferative effect of gedunin on pancreatic cancer cells was assessed using MTS assay. We used matrigel invasion assay, scratch assay, and soft agar colony formation assay to measure the anti–metastatic potential of gedunin. Immunoblotting was performed to analyze the effect of gedunin on the expression of key proteins involved in pancreatic cancer growth and metastasis. Gedunin induced apoptosis was measured using flow cytometric analysis. To further validate, xenograft studies with HPAC cells were performed.

RESULTS

Gedunin treatment is highly effective in inducing death of pancreatic cancer cells via intrinsic and extrinsic mediated apoptosis. Our data further indicates that gedunin inhibited metastasis of pancreatic cancer cells by decreasing their EMT, invasive, migratory and colony formation capabilities. Gedunin treatment also inhibited sonic hedgehog signaling pathways. Further, experiments with recombinant sonic hedgehog protein and Gli inhibitor (Gant-61) demonstrated that gedunin induces its anti–metastatic effect through inhibition of sonic hedgehog signaling. The anti–cancer effect of gedunin was further validated using xenograft mouse model.

CONCLUSION

Overall, our data suggests that gedunin could serve as a potent anticancer agent against pancreatic cancers.

Mitochondrial Ca2+ removal amplifies TRAIL cytotoxicity toward apoptosis-resistant tumor cells via promotion of multiple cell death modalities

Ca2+ has emerged as a new target for cancer treatment since tumor-specific traits in Ca2+ dynamics contributes to tumorigenesis, malignant phenotypes, drug resistance, and survival in different tumor types. However, Ca2+ has a dual (pro-death and pro-survival) function in tumor cells depending on the experimental conditions. Therefore, it is necessary to minimize the onset of the pro-survival Ca2+ signals caused by the therapy. For this purpose, a better understanding of pro-survival Ca2+ pathways in cancer cells is critical. Here we report that Ca2+ protects malignant melanoma (MM) and osteosarcoma (OS) cells from tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) cytotoxicity. Simultaneous measurements using the site-specific Ca2+ probes showed that acute TRAIL treatment rapidly and dose-dependently increased the cytosolic Ca2+ concentration ([Ca2+]cyt) and mitochondrial Ca2+ concentration ([Ca2+]mit) Pharmacological analyses revealed that the [Ca2+]mit remodeling was under control of mitochondrial Ca2+ uniporter (MCU), mitochondrial permeability transition pore (MPTP), and a Ca2+ transport pathway sensitive to capsazepine and AMG9810. Ca2+ chelators and the MCU inhibitor ruthenium 360, an MPTP opener atractyloside, capsazepine, and AMG9810 all decreased [Ca2+]mit and sensitized these tumor cells to TRAIL cytotoxicity. The Ca2+ modulation enhanced both apoptotic and non-apoptotic cell death. Although the [Ca2+]mit reduction potentiated TRAIL-induced caspase-3/7 activation and cell membrane damage within 24 h, this potentiation of cell death became pronounced at 72 h, and not blocked by caspase inhibition. Our findings suggest that in MM and OS cells mitochondrial Ca2+ removal can promote apoptosis and non-apoptotic cell death induction by TRAIL. Therefore, mitochondrial Ca2+ removal can be exploited to overcome the resistance of these cancers to TRAIL.

Preclinical evaluation of the imipridone family, analogs of clinical stage anti-cancer small molecule ONC201, reveals potent anti-cancer effects of ONC212

Anti-cancer small molecule ONC201 upregulates the integrated stress response (ISR) and acts as a dual inactivator of Akt/ERK, leading to TRAIL gene activation. ONC201 is under investigation in multiple clinical trials to treat patients with cancer. Given the unique imipridone core chemical structure of ONC201, we synthesized a series of analogs to identify additional compounds with distinct therapeutic properties. Several imipridones with a broad range of in vitro potencies were identified in an exploration of chemical derivatives. Based on in vitro potency in human cancer cell lines and lack of toxicity to normal human fibroblasts, imipridones ONC206 and ONC212 were prioritized for further study. Both analogs inhibited colony formation, and induced apoptosis and downstream signaling that involves the integrated stress response and Akt/ERK, similar to ONC201. Compared to ONC201, ONC206 demonstrated improved inhibition of cell migration while ONC212 exhibited rapid kinetics of activity. ONC212 was further tested in >1000 human cancer cell lines in vitro and evaluated for safety and anti-tumor efficacy in vivo. ONC212 exhibited broad-spectrum efficacy at nanomolar concentrations across solid tumors and hematological malignancies. Skin cancer emerged as a tumor type with improved efficacy relative to ONC201. Orally administered ONC212 displayed potent anti-tumor effects in vivo, a broad therapeutic window and a favorable PK profile. ONC212 was efficacious in vivo in BRAF V600E melanoma models that are less sensitive to ONC201. Based on these findings, ONC212 warrants further development as a drug candidate. It is clear that therapeutic utility extends beyond ONC201 to include additional imipridones.

DR5 suppression induces sphingosine-1-phosphate-dependent TRAF2 polyubiquitination, leading to activation of JNK/AP-1 and promotion of cancer cell invasion

BACKGROUND

Death receptor (DR5), a well-characterized death domain-containing cell surface pro-apoptotic protein, has been suggested to suppress cancer cell invasion and metastasis. However, the underlying mechanisms have not been fully elucidated. Our recent work demonstrates that DR5 suppression promotes cancer cell invasion and metastasis through caspase-8/TRAF2-mediated activation of ERK and JNK signaling and MMP1 elevation. The current study aimed at addressing the mechanism through which TRAF2 is activated in a caspase-8 dependent manner.

RESULTS

DR5 knockdown increased TRAF2 polyubiquitination, a critical event for TRAF2-mediated JNK/AP-1 activation. Suppression of sphingosine-1-phosphate (S1P) generation or depletion of casapse-8 inhibited not only enhancement of cell invasion, but also elevation and polyubiquitination of TRAF2, activation of JNK/AP-1 activation and increased expression of MMP1 induced by DR5 knockdown.

CONCLUSIONS

Both S1P and caspase-8 are critical for TRAF2 stabilization, polyubiquitination, subsequent activation of JNK/AP1 signaling and MMP1 expression and final promotion of cell invasion.

Brusatol inhibits growth and induces apoptosis in pancreatic cancer cells via JNK/p38 MAPK/NF-κb/Stat3/Bcl-2 signaling pathway

Brusatol, isolated from brucea, has been proved to exhibit anticancer influence on various kind of human malignancies. However, the role that brusatol plays in pancreatic cancer is seldom known by the public. Through researches brusatol was proved to inhibit growth and induce apoptosis in both PATU-8988 and PANC-1 cells by decreasing the expression level of Bcl-2 and increasing the expression levels of Bax, Cleaved Caspase-3. Then we found the activation of the JNK, p38 MAPK and inactivation of the NF-κb, Stat3 are related with the potential pro-apoptotic signaling pathways. However, SP600125 could not only abrogated the JNK activation caused by brusatol, but also reverse the p38 activation and the decrease of Bcl-2 as SB203580 did. Besides, SP600125 and SB203580 also reversed the inactivation of NF-κb and Stat3. Furthermore, BAY 11-7082 and S3I-201 indeed had the similar effect as brusatol had on the expression of Phospho-Stat3 and Bcl-2. To sum up, we came to a conclusion that in pancreatic cancer, brusatol do inhibit growth and induce apoptosis. And we inferred that brusatol illustrates anticancer attribution via JNK/p38 MAPK/NF-κb/Stat3/Bcl-2 signaling pathway.

The suppression of apoptosis by α-herpesvirus

Apoptosis, an important innate immune mechanism that eliminates pathogen-infected cells, is primarily triggered by two signalling pathways: the death receptor pathway and the mitochondria-mediated pathway. However, many viruses have evolved various strategies to suppress apoptosis by encoding anti-apoptotic factors or regulating apoptotic signalling pathways, which promote viral propagation and evasion of the host defence. During its life cycle, α-herpesvirus utilizes an elegant multifarious anti-apoptotic strategy to suppress programmed cell death. This progress article primarily focuses on the current understanding of the apoptosis-inhibition mechanisms of α-herpesvirus anti-apoptotic genes and their expression products and discusses future directions, including how the anti-apoptotic function of herpesvirus could be targeted therapeutically.

Phytochemical Modulation of Apoptosis and Autophagy: Strategies to Overcome Chemoresistance in Leukemic Stem Cells in the Bone Marrow Microenvironment

Advances in scientific research and targeted treatment regimes have improved survival rates for many cancers over the past few decades. However, for some types of leukemia, including acute lymphoblastic and acute myeloid leukemia, mortality rates have continued to rise, with chemoresistance in leukemic stem cells (LSCs) being a major contributing factor. Most cancer drug therapies act by inducing apoptosis in dividing cells but are ineffective in targeting quiescent LSCs. Niches in the bone marrow, known as leukemic niches, behave as "sanctuaries" where LSCs acquire drug resistance. This review explores the role of the bone marrow environment in the maintenance of LSCs and its contribution to chemoresistance and considers current research on the potential use of phytochemicals to overcome chemoresistance through the modulation of signaling pathways involved in the survival and death of leukemic clonal cells and/or leukemic stem cells. Phytochemicals from traditional Chinese medicine, namely baicalein, chrysin, wogonin (constituents of Scutellaria baicalensis; huáng qín; ), curcumin (a constituent of Curcuma longa, jiāng huáng, ), and resveratrol (a constituent of Polygonum cuspidatum; hŭ zhàng, ) have been shown to induce apoptosis in leukemic cell lines, with curcumin and resveratrol also causing cell death via the induction of autophagy (a nonapoptotic pathway). In order to be effective in eliminating LSCs, it is important to target signaling pathways (such as Wnt/β-catenin, Notch, and Hedgehog). Resveratrol has been reported to induce apoptosis in leukemic cells through the inhibition of the Notch and Sonic hedgehog signaling pathways, therefore showing potential to affect LSCs. While these findings are of interest, there is a lack of reported research on the modulatory effect of phytochemicals on the autophagic cell death pathway in leukemia, and on the signaling pathways involved in the maintenance of LSCs, highlighting the need for further work in these areas.

HLBT-100: a highly potent anti-cancer flavanone from Tillandsia recurvata (L.) L

BACKGROUND

The incidence and mortalities from cancers remain on the rise worldwide. Despite significant efforts to discover and develop novel anticancer agents, many cancers remain in the unmet need category. As such, efforts to discover and develop new and more effective and less toxic agents against cancer remain a top global priority. Our drug discovery approach is natural products based with a focus on plants. Tillandsia recurvata (L.) L. is one of the plants selected by our research team for further studies based on previous bioactivity findings on the anticancer activity of this plant.

METHODS

The plant biomass was extracted using supercritical fluid extraction technology with CO2 as the mobile phase. Bioactivity guided isolation was achieved by use of chromatographic technics combined with anti-proliferative assays to determine the active fraction and subsequently the pure compound. Following in house screening, the identified molecule was submitted to the US National Cancer Institute for screening on the NCI60 cell line panel using standard protocols. Effect of HLBT-100 on apoptosis, caspase 3/7, cell cycle and DNA fragmentation were assessed using standard protocols. Antiangiogenic activity was carried out using the ex vivo rat aortic ring assay.

RESULTS

A flavonoid of the flavanone class was isolated from T. recurvata (L.) L. with potent anticancer activity. The molecule was code named as HLBT-100 (also referred to as HLBT-001). The compound inhibited brain cancer (U87 MG), breast cancer (MDA-MB231), leukemia (MV4-11), melanoma (A375), and neuroblastoma (IMR-32) with IC50 concentrations of 0.054, 0.030, 0.024, 0.003 and 0.05 µM, respectively. The molecule also exhibited broad anticancer activity in the NCI60 panel inhibiting especially hematological, colon, CNS, melanoma, ovarian, breast and prostate cancers. Twenty-three of the NCI60 cell lines were inhibited with GI50 values <0.100 µM. In terms of potential mechanisms of action, the molecule demonstrated effect on the cell cycle as evidenced by the accumulation of cells with 

CONCLUSION

This paper describes for the first time the anticancer activity of HLBT-100 isolated from T. recurvate (L.) L. The broad and selective anticancer activity of HLBT-100 as evidenced by its potent activity against IMR-32, CNS cancer cell line while not active against neuro-2a, a normal CNS cell line. The activity demonstrated by HLBT-100 in these studies makes the molecule a potential candidate for further development targeting especially those cancers that remain in the unmet need category such as glioblastoma multiforme and acute myeloid leukemia in addition to other cancers.

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Key Words

• Angiogenesis
• Anticancer
• Ball Moss
• Flavanone
• Tillandsia recurvata

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MESH Headings Collapse

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Affiliation(s)

Henry I. C. Lowe Bio-Tech R&D Institute, University of the West Indies, 6 St. Johns Close, Mona, Jamaica Educational & Scientific LLC, 725 W Lombard St, Baltimore, MD 21201 USA Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA
Ngeh J. Toyang Educational & Scientific LLC, 725 W Lombard St, Baltimore, MD 21201 USA Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA
Charah T. Watson Bio-Tech R&D Institute, University of the West Indies, 6 St. Johns Close, Mona, Jamaica
Kenneth N. Ayeah Educational & Scientific LLC, 725 W Lombard St, Baltimore, MD 21201 USA Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA
Joseph Bryant Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA

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Co-targeting translation and proteasome rapidly kills colon cancer cells with mutant RAS/RAF via ER stress

Colorectal cancers with mutant RAS/RAF are therapy refractory. Deregulated mRNA translation has become an emerging target in cancer treatment. We recently reported that mTOR inhibitors induce apoptosis via ER stress and the extrinsic pathway upon acute inhibition of the eIF4F complex in colon cancer cells and xenografts, while mutant BRAF600E leads to therapeutic resistance via ERK-mediated Mcl-1 stabilization. In this study, we demonstrated that several other translation inhibitors also activate ER stress and the extrinsic apoptotic pathway. Co-targeting translation and proteasome using the combination of Episilvestrol and Bortezomib promoted strong ER stress and rapid killing of colon cancer cells with mutant RAS/RAF in culture and mice. This combination led to marked induction of ER stress and ATF4/CHOP, followed by DR5- and BAX-dependent apoptosis, but unexpectedly with maintained or even increased levels of prosurvival factors such as p-AKT, p-4E-BP1, Mcl-1, and eiF4E targets c-Myc and Bcl-xL. Our study supports that targeting deregulated proteostasis is a promising approach for treating advanced colon cancer via induction of destructive ER stress that overcomes multiple resistance mechanisms associated with translation inhibition.

Crude extract and solvent fractions of Calystegia soldanella induce G1 and S phase arrest of the cell cycle in HepG2 cells

The representative halophyte Calystegia soldanella (L) Roem. et Schult is a perennial vine herb that grows in coastal dunes throughout South Korea as well as in other regions around the world. This plant has long been used as an edible and medicinal herb to cure rheumatic arthritis, sore throat, dropsy, and scurvy. Some studies have also shown that this plant species exhibits various biological activities. However, there are few studies on cytotoxicity induced by C. soldanella treatment in HepG2 human hepatocellular carcinoma cells. In this study, we investigated the viability of HepG2 cells following treatment with crude extracts and four solvent-partitioned fractions of C. soldanella. Of the crude extract and four solvent fractions tested, treatment with the 85% aqueous methanol (aq. MeOH) fraction resulted in the greatest inhibition of HepG2 cell proliferation. Flow cytometry showed that the 85% aq. MeOH fraction induced a G0/G1 and S phase arrest of the cell cycle progression. The 85% aq. MeOH fraction arrested HepG2 cells at the G0/G1 phase in a concentration-dependent manner, and resulted in decreased expression of cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2, CDK4, CDK6, p21, and p27. Additionally, the 85% aq. MeOH fraction treatment also arrested HepG2 cells in the S phase, with decreased expression of cyclin A, CDK2, and CDC25A. Also, treatment with this fraction reduced the expression of retinoblastoma (RB) protein and the transcription factor E2F. These results suggest that the 85% aq. MeOH fraction exhibits potential anticancer activity in HepG2 cells by inducing G0/G1 and S phase arrest of the cell cycle.

Role of Apigenin in Cancer Prevention via the Induction of Apoptosis and Autophagy

Apigenin (4′,5,7-trihydroxyflavone) is a flavonoid commonly found in many fruits and vegetables such as parsley, chamomile, celery, and kumquats. In the last few decades, recognition of apigenin as a cancer chemopreventive agent has increased. Significant progress has been made in studying the chemopreventive aspects of apigenin both in vitro and in vivo. Several studies have demonstrated that the anticarcinogenic properties of apigenin occur through regulation of cellular response to oxidative stress and DNA damage, suppression of inflammation and angiogenesis, retardation of cell proliferation, and induction of autophagy and apoptosis. One of the most well-recognized mechanisms of apigenin is the capability to promote cell cycle arrest and induction of apoptosis through the p53-related pathway. A further role of apigenin in chemoprevention is the induction of autophagy in several human cancer cell lines. In this review, we discuss the details of apigenin, apoptosis, autophagy, and the role of apigenin in cancer chemoprevention via the induction of apoptosis and autophagy.

Apigenin induces both intrinsic and extrinsic pathways of apoptosis in human colon carcinoma HCT-116 cells

Apigenin is one of the plant-originated flavones with anticancer activities. In this study, apigenin was assessed for its in vitro effects on a human colon carcinoma line (HCT‑116 cells) in terms of anti-proliferation, cell cycle progression arrest, apoptosis and intracellular reactive oxygen species (ROS) generation, and then outlined its possible apoptotic mechanism for the cells. Apigenin exerted cytotoxic effect on the cells via inhibiting cell growth in a dose-time-dependent manner and causing morphological changes, arrested cell cycle progression at G0/G1 phase, and decreased mitochondrial membrane potential of the treated cells. Apigenin increased respective ROS generation and Ca2+ release and thereby, caused ER stress in the treated cells. Apigenin shows apoptosis induction towards the cells, resulting in enhanced portion of apoptotic cells. A mechanism involved ROS generation and endoplasmic reticulum stress was outlined for the apigenin-mediated apoptosis via both intrinsic mitochondrial and extrinsic pathways, based on the assayed mRNA and protein expression levels in the cells. With this mechanism, apigenin resulted in the HCT-116 cells with enhanced intracellular ROS generation and Ca2+ release together with damaged mitochondrial membrane, and upregulated protein expression of CHOP, DR5, cleaved BID, Bax, cytochrome c, cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9, which triggered apoptosis of the cells.

Regulation of Intrinsic and Extrinsic Apoptotic Pathways in Osteosarcoma Cells Following Oleandrin Treatment

Our previous study has reported the anti-tumor effect of oleandrin on osteosarcoma (OS) cells. In the current study, we mainly explored its potential regulation on intrinsic and extrinsic apoptotic pathway in OS cells. Cells apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were detected using fluorescence staining and flow cytometry. Caspase-3 activity was detected using a commercial kit. The levels of cytoplasmic cytochrome c, mitochondrial cytochrome c, bcl-2, bax, caspase-9, Fas, FasL, caspase-8 and caspase-3 were detected by Western blotting. z-VAD-fmk was applied to block both intrinsic and extrinsic apoptosis pathways, and cells apoptosis was also tested. Furthermore, we used z-LEHD-fmk and Fas blocking antibody to inhibit intrinsic and extrinsic pathways, separately, and the selectivity of oleandrin on these pathways was explored. Results showed that oleandrin induced the apoptosis of OS cells, which was accompanied by an increase in ROS and a decrease in MMP. Furthermore, cytochrome c level was reduced in mitochondria but elevated in the cytoplasm. Caspase-3 activity was enhanced by oleandrin in a concentration- and time-dependent manner. Oleandrin also down-regulated the expression of bcl-2, but up-regulated bax, caspase-9, Fas, FasL, caspase-8 and caspase-3. In addition, the suppression of both apoptotic pathways by z-VAD-fmk greatly reverted the oleandrin-induced apoptosis. Moreover, the suppression of one pathway by a corresponding inhibitor did not affect the regulation of oleandrin on another pathway. Taken together, we concluded that oleandrin induced apoptosis of OS cells via activating both intrinsic and extrinsic apoptotic pathways.

Death receptor 5 (DR5) and a 5-gene apoptotic biomarker panel with significant differential diagnostic potential in colorectal cancer

High expression of Inhibitor of apoptosis proteins (IAPs) has been related to colorectal cancer (CRC) progression, resistance to treatment and poor prognosis. TRAIL (TNF-related apoptosis-inducing ligand) through its receptors DR4 (TRAIL-R1) and DR5 (TRAIL-R2) can selectively induce cancer cell apoptosis. The mRNA expression of DR4, DR5, c-IAP1, c-IAP2, XIAP and BIRC5/Survivin genes was examined in 100 paired (cancerous-normal) colorectal tissue specimens by real-time PCR, 50 of which were KRAS wild-type and 50 KRAS-mutant. DR5, XIAP and BIRC5/Survivin genes are significantly up-regulated (p < 0.0001, p = 0.012 and p = 0.0003, respectively), whereas c-IAP1 and c-IAP2 genes are significantly down-regulated at mRNA and protein levels in CRC (p < 0.0001 for both). ROC analyses showed that DR5, cIAP1 and cIAP2 expression has discriminatory value between CRC and normal tissue (AUC = 0.700, p < 0.0001 for DR5; AUC = 0.628, p = 0.011 for cIAP1; AUC = 0.673, p < 0.0001 for cIAP2). Combinatorial ROC analysis revealed the marginally fair discriminatory value of 5 genes as a panel (AUC = 0.685, p < 0.0001). Kaplan-Meier survival curves revealed significant association of cIAP2 down-regulation in CRC with lower overall survival probability of CRC patients (p = 0.0098). DR5, BIRC5/Survivin, XIAP, c-IAP1 and c-IAP2 mRNA expression are significantly deregulated in CRC and could provide a panel of markers with significant discriminatory value between CRC and normal colorectal tissue.

A novel adamantane thiadiazole derivative induces mitochondria-mediated apoptosis in lung carcinoma cell line

The interaction of organic compounds with apoptosis regulatory proteins is an attractive field of research because of its relevance in the development of new chemotherapeutic agents for cancer treatment. Our group designed four new adamantane thiadiazole derivatives (ATDs). The four ATDs were theoretically tested for their binding affinities to a model of an apoptosis inhibitor protein using molecular modeling. ATD-4 which interacted with the highest binding affinity was synthesized and characterized. The in vitro cytotoxicity of ATD-4 against different cancer cell lines as well as normal cell line was determined and compared with 5-fluorouracil as a standard positive control. The lung carcinoma cell line that showed the highest cytotoxic activity due to ATD-4 treatment was chosen to further study if ATD-4 can perform its cytotoxic activity through the induction of apoptosis as expected from molecular modeling. Inducing apoptosis by ATD-4 in lung carcinoma cell line was assessed by various biochemical and morphological characteristics. Biochemically: The effect of ATD-4 on cell cycle and its ability to induce apoptosis were checked through flow cytometry. Caspase-3 activity was detected by a colorimetric method. Real time-polymerase chain reaction (q-PCR) was used to detect p53, caspase-3, bcl-2 and bax gene expression. Morphologically: Changes in cell surface morphology, granulation and average surface roughness were detected using atomic force microscopy (AFM). Cell shrinkage, increase in cytoplasmic organelles, changes in mitochondrial number and morphology, chromatin condensation, membrane blebbing and formation of apoptotic bodies were detected using transmission electron microscopy (TEM). The obtained results suggest that ATD-4 exerted its antitumor activity against A549 cells through the induction of the intrinsic (mitochondrial) apoptotic pathway.

Interferon α Induces the Apoptosis of Cervical Cancer HeLa Cells by Activating both the Intrinsic Mitochondrial Pathway and Endoplasmic Reticulum Stress-Induced Pathway

The interferon α (IFN-α) has been often used as a sensitizing agent for the treatment of various malignancies such as hepatocellular carcinoma, malignant melanoma, and renal cell cancer by promoting the apoptosis of thesetumor cell types. However, the effect of IFN-α on cervical cancer remains unknown. In this study, HeLa cells were used as a testing model for the treatment of IFN-α on cervical cancer. The results indicate that IFN-α markedly inhibits the proliferation and induces the apoptosis of HeLa cells. The activation of caspase 3, the up-regulation of both Bim and cleaved poly (ADP-ribose) polymerase (PARP) 1, the down-regulation of Bcl-xL, as well as the release of cytochrome c from mitochondria were significantly induced upon IFN-α treatment, indicating that the intrinsic apoptotic pathway could be activated by IFN-α treatment. In addition, caspase 4—which is involved in the endoplasmic reticulum (ER) stress-induced apoptosis—was activated in response to IFN-α treatment. Knocking down caspase 4 by small interfering RNA (siRNA) markedly reduced the IFN-α-mediated cell apoptosis. However, no significant changes in the expressions of caspases 8 and 10 were observed upon IFN-α treatment, indicating that the apoptosis caused by IFN-α might be independent of the extrinsic apoptotic pathway. These findings suggest that IFN-α may possess anti-cervical cancer capacity by activating cell apoptosis via the intrinsic mitochondrial pathway and caspase-4-related ER stress-induced pathway.

Molecular and functional characterization of caspase-8 from the big-belly seahorse (Hippocampus abdominalis)

Apoptosis is a physiological process that can also participate in host immune defense mechanisms, including tumor growth suppression along with homeostasis and maturation of immune cells. Caspases are known to be involved in cellular apoptotic signaling; among them, caspase-8 plays an important role in the initiation phase of the apoptotic death cascade. In the current study, we molecularly characterized a caspase-8 homolog (designated as HaCasp-8) from Hippocampus abdominalis. The HaCasp-8 gene harbors a 1476 bp open reading frame (ORF) that codes for a protein of 492 amino acids (aa) with a predicted molecular mass of 55 kDa. HaCasp-8 houses the typical domain architecture of known initiator caspases, including the death effector domain and the carboxyl-terminal catalytic domain. As expected, phylogenetic analysis reflected a closer evolutionary relationship of HaCasp-8 with its teleostean similitudes. The results of our qPCR assays confirmed the ubiquitous expression of HaCasp-8 in physiologically important tissues examined, with pronounced expression levels in ovary tissues, followed by blood cells. HaCasp-8 expression at the mRNA level was found to be significantly modulated by lipopolysaccharide, polyinosinic:polycytidylic acid, Streptococcus iniae, and Edwardsiella tarda injection. Overexpression of HaCasp-8 could trigger a significant level of cell death in HEK293T cells, suggesting its putative role in cell death. Taken together, our findings suggest that HaCasp-8 is an important component in the caspase cascade, and its expression can be significantly modulated under pathogen stress conditions in the big-belly seahorse.

A novel transgenic mouse model of lysosomal storage disorder

Knockout technology has proven useful for delineating functional roles of specific genes. Here we describe and provide an explanation for striking pathology that occurs in a subset of genetically engineered mice expressing a rat Ca_Vβ2a transgene under control of the cardiac α-myosin heavy chain promoter. Lesions were limited to mice homozygous for transgene and independent of native Cacnb2 genomic copy number. Gross findings included an atrophied pancreas; decreased adipose tissue; thickened, orange intestines; and enlarged liver, spleen, and abdominal lymph nodes. Immune cell infiltration and cell engulfment by macrophages were associated with loss of pancreatic acinar cells. Foamy macrophages diffusely infiltrated the small intestine's lamina propria, while similar macrophage aggregates packed liver and splenic red pulp sinusoids. Periodic acid-Schiff-positive, diastase-resistant, iron-negative, Oil Red O-positive, and autofluorescent cytoplasm was indicative of a lipid storage disorder. Electron microscopic analysis revealed liver sinusoids distended by clusters of macrophages containing intracellular myelin "swirls" and hepatocytes with enlarged lysosomes. Additionally, build up of cholesterol, cholesterol esters, and triglycerides, along with changes in liver metabolic enzyme levels, were consistent with a lipid processing defect. Because of this complex pathology, we examined the transgene insertion site. Multiple transgene copies inserted into chromosome 19; at this same site, an approximate 180,000 base pair deletion occurred, ablating cholesterol 25-hydroxylase and partially deleting lysosomal acid lipase and CD95 Loss of gene function can account for the altered lipid processing, along with hypertrophy of the immune system, which define this phenotype, and serendipitously provides a novel mouse model of lysosomal storage disorder.

Epothilone B induces apoptosis and enhances apoptotic effects of ABT-737 on human cancer cells via PI3K/AKT/mTOR pathway

PURPOSE

Epothilone B and its derivatives are tested in multiple clinical trials. Epothilone B induces neurotoxic effect in clinical trials; however, low-dose epothilone B regimen can promote neuroprotection and neurogenesis. Thus, the study of new combination chemotherapy regimen incorporating low-dose epothilone B with other chemotherapeutic agents might help to develop epothilone B-based approaches to cancer treatment and avoid the neurotoxicity of epothilone B.

METHODS

Cell proliferation was assessed by SRB cell viability assay. Apoptosis was analyzed by propidium iodide (PI) staining. Mitochondrial membrane depolarization was evaluated using JC-1 staining. The expression of proteins was detected by western blotting.

RESULTS

In this study, we demonstrated that the combination of ABT-737 and low-dose epothilone B showed synergistic anti-proliferation effects on human cancer cells. In addition, epothilone B + ABT-737 synergy was through mitochondria-mediated apoptosis pathway. Furthermore, combination treatment markedly induced the activation of caspase-3 and the cleavage of PARP. The activation of PI3K/Akt/mTOR pathway is associated with resistance to epothilone B. Our data showed that epothilone B plus ABT-737 resulted in a blockade of the PI3K/AKT/mTOR signaling pathway.

CONCLUSIONS

These data indicate that ABT-737 may be a pertinent sensitizer to epothilone B, and the strategy of combining epothilone B with ABT-737 appears to be an attractive option for overcoming the resistance and neurotoxicity of epothilone B.

(E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol inhibits growth of colon tumors in mice

In our previous study, we found that (E)-2,4-bis(p-hydroxyphenyl)-2-butenal showed anti-cancer effect, but it showed lack of stability and drug likeness. We have prepared several (E)-2,4-bis(p-hydroxyphenyl)-2-butenal analogues by Heck reaction. We selected two compounds which showed significant inhibitory effect of colon cancer cell growth. Thus, we evaluated the anti-cancer effects and possible mechanisms of one compound (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol in vitro and in vivo. In this study, we found that (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol induced apoptotic cell death in a dose dependent manner (0-15 μg/ml) through activation of Fas and death receptor (DR) 3 in HCT116 and SW480 colon cancer cell lines. Moreover, the combination treatment with (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol and nuclear factor κB (NF-κB) inhibitor, phenylarsine oxide (0.1 μM) or signal transducer and activator of transcription 3 (STAT3) inhibitor, Stattic (50 μM) increased the expression of Fas and DR3 more significantly. In addition, (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol suppressed the DNA binding activity of both STAT3 and NF-κB. Knock down of STAT3 or NF-κB p50 subunit by STAT3 small interfering RNA (siRNA) or p50 siRNA magnified (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol-induced inhibitory effect on colon cancer cell growth. Besides, the expression of Fas and DR3 was increased in STAT3 siRNA or p50 siRNA transfected cells. Moreover, docking model and pull-down assay showed that (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol directly bound to STAT3 and NF-κB p50 subunit. Furthermore, (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol inhibited colon tumor growth in a dose dependent manner (2.5 mg/kg-5 mg/kg) in mice. Therefore, these findings indicated that (E)-4-(3-(3,5-dimethoxyphenyl)allyl)-2-methoxyphenol may be a promising anti-cancer agent for colon cancer with more advanced research.

Suppression of death receptor 5 enhances cancer cell invasion and metastasis through activation of caspase-8/TRAF2-mediated signaling

The role of death receptor 5 (DR5), a well-known cell surface pro-apoptotic protein, in the negative regulation of invasion and metastasis of human cancer cells and the underlying mechanisms are largely unknown and were hence the focus of this study. In this report, we have demonstrated that DR5 functions to suppress invasion and metastasis of human cancer cells, as evidenced by enhanced cancer cell invasion and metastasis upon genetic suppression of DR5 either by gene knockdown or knockout. When DR5 is suppressed, FADD and caspase-8 may recruit and stabilize TRAF2 to form a metastasis and invasion signaling complex, resulting in activation of ERK and JNK/AP-1 signaling that mediate the elevation and activation of matrix metalloproteinase-1 (MMP1) and eventual promotion of cancer invasion and metastasis. Our findings thus highlight a novel non-apoptotic function of DR5 as a suppressor of human cancer cell invasion and metastasis and suggest a basic working model elucidating the underlying biology.

Apoptotic pathways as a therapeutic target for colorectal cancer treatment

Colorectal cancer is the second leading cause of death from cancer among adults. The disease begins as a benign adenomatous polyp, which develops into an advanced adenoma with high-grade dysplasia and then progresses to an invasive cancer. Appropriate apoptotic signaling is fundamentally important to preserve a healthy balance between cell death and cell survival and in maintaining genome integrity. Evasion of apoptotic pathway has been established as a prominent hallmark of several cancers. During colorectal cancer development, the balance between the rates of cell growth and apoptosis that maintains intestinal epithelial cell homeostasis gets progressively disturbed. Evidences are increasingly available to support the hypothesis that failure of apoptosis may be an important factor in the evolution of colorectal cancer and its poor response to chemotherapy and radiation. The other reason for targeting apoptotic pathway in the treatment of cancer is based on the observation that this process is deregulated in cancer cells but not in normal cells. As a result, colorectal cancer therapies designed to stimulate apoptosis in target cells would play a critical role in controlling its development and progression. A better understanding of the apoptotic signaling pathways, and the mechanisms by which cancer cells evade apoptotic death might lead to effective therapeutic strategies to inhibit cancer cell proliferation with minimal toxicity and high responses to chemotherapy. In this review, we analyzed the current understanding and future promises of apoptotic pathways as a therapeutic target in colorectal cancer treatment.

Molecular cloning and characterization of four caspases members in Apostichopus japonicus

The caspase family representing aspartate-specific cysteine proteases have been demonstrated to possess key roles in apoptosis and immune response. We previously demonstrated that LPS challenged Apostichopus japonicus coelomocyte could significantly induced apoptosis in vitro. However, apoptosis related molecules were scarcely investigated in this economic species. In the present work, we cloned and characterized four members caspase family from A. japonicus (designated as Ajcaspase-2, Ajcaspase-3, Ajcaspase-6, and Ajcaspase-8, respectively) by RACE. Multiple sequence alignment and structural analysis revealed that all Ajcaspases contained the conservative CASC domain at C terminal, in which some unique features for each Ajcaspase made them different from each other. These specific domains together with phylogenetic analysis supported that all these four identified proteins belonged to novel members of apoptotic signaling pathway in sea cucumber. Tissue distribution analysis revealed that four Ajcaspase genes were constitutively expressed in all examined tissues. The expression of Ajcaspase-2 was tightly correlated with that of Ajcaspase-8 in each detected tissues. Ajcaspase-3 and Ajcaspase-6 transcripts were both highly expressed in immune tissue of coelomocytes. Furthermore, the Vibrio splendidus challenged sea cucumber coelomocytes could significantly up-regulate the mRNA expressions of four genes. The expression levels of Ajcaspase-2 and Ajcaspase-8 were relative earlier than those of Ajcaspase-6 and Ajcaspase-3, respectively, which could be inferred that Ajcapase-2 might directly modulate Ajcaspase-6, and Ajcaspase-8 initiate the expression of Ajcaspase-3. The induce expressions differed among each Ajcaspase depending upon their roles such as initiator or effector caspase. All our results demonstrated that four Ajcaspases present diversified functions in apoptotic cascade signaling pathway of sea cucumber under immune response.

Functional TRAIL receptors in monocytes and tumor-associated macrophages: A possible targeting pathway in the tumor microenvironment

Despite the accepted dogma that TRAIL kills only tumor cells and spares normal ones, we show in this study that mononuclear phagocytes are susceptible to recombinant TRAIL via caspase-dependent apoptosis. Human resting monocytes and in vitro-differentiated macrophages expressed substantial levels of the functional TRAIL receptors (TRAIL-R1 and TRAIL-R2), while neutrophils and lymphocytes mostly expressed the non-signaling decoy receptor (TRAIL-R3). Accordingly, exclusively monocytes and macrophages activated caspase-8 and underwent apoptosis upon recombinant TRAIL treatment. TRAIL-Rs were up-regulated by anti-inflammatory agents (IL-10, glucocorticoids) and by natural compounds (Apigenin, Quercetin, Palmitate) and their treatment resulted in increased TRAIL-induced apoptosis. In mice, the only signaling TRAIL-R (DR5) was preferentially expressed by blood monocytes rather than neutrophils or lymphocytes. In both mice and humans, Tumor-Associated Macrophages (TAM) expressed functional TRAIL-R, while resident macrophages in normal tissues did not. As a proof of principle, we treated mice bearing a murine TRAIL-resistant fibrosarcoma with recombinant TRAIL. We observed significant decrease of circulating monocytes and infiltrating TAM, as well as reduced tumor growth and lower metastasis formation. Overall, these findings demonstrate that human and murine monocytes/macrophages are, among leukocytes, uniquely susceptible to TRAIL-mediated killing. This differential susceptibility to TRAIL could be exploited to selectively target macrophages in tumors.

Copper induced apoptosis in Caco-2 and Hep-G2 cells: Expression of caspases 3, 8 and 9, AIF and p53

Copper (Cu) is an essential trace metal needed to ensure cell function. However, when present at high concentrations it becomes toxic to organisms. Cell death, induced by toxic levels of copper, was previously observed in in vitro studies. However, there is no consensus about the cell death pathway induced by Cu and it is still not known whether this occurs as a result of the direct action of the metal or by indirect effects. In the present work, we intend to identify the influence of different Cu concentrations in the induction of apoptosis and to explore the potential signaling pathways, using two different in vitro cell culture models (Caco-2 and Hep-G2). Cells were exposed, during 6, 12, 24 and 48h, to Cu concentrations corresponding to IC50 and 1/8 of IC50, according to the viability assays. Then, considering the different apoptosis pathways, the expression of caspases 3, 8 and 9, apoptosis inducing factor (AIF) and p53 genes was analyzed by quantitative real time PCR. The results suggested that different Cu concentrations could trigger different apoptotic pathways, at different times of exposure. In both cell lines, apoptosis seems to be initiated by caspase independent pathway and intrinsic pathway, followed by extrinsic pathway. In conclusion, this study demonstrates that Cu induces the activation of apoptosis through caspase dependent and independent pathways, also suggesting that apoptosis activation mechanism is dependent on the concentration, time of exposure to Cu and cell type.

Ras-related associated with diabetes gene acts as a suppressor and inhibits Warburg effect in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is rapidly becoming one of the most prevalent cancers worldwide and is a prominent source of mortality. Ras-related associated with diabetes (RRAD), one of the first members of the 35–39 kDa class of novel Ras-related GTPases, is linked to several types of cancer, although its function in HCC remains unclear. In this study, we observed that RRAD was downregulated in HCC compared with adjacent normal tissues. This change was associated with a poor prognosis. Furthermore, knockdown of RRAD in SK-Hep-1 cells facilitated cell proliferation, accelerated the G1/S transition during the cell cycle, induced cell migration, and reduced apoptosis. In contrast, overexpression of RRAD in Huh7 cells had the opposite effects. Moreover, we demonstrated that RRAD induced cell proliferation through regulation of the cell cycle by downregulating cyclins and cyclin-dependent kinases. RRAD induced tumor cell apoptosis through the mitochondrial apoptosis pathway. In addition, we confirmed that knockdown of RRAD promoted aerobic glycolysis by upregulating glucose transporter 1, whereas overexpression of RRAD inhibited aerobic glycolysis. In conclusion, RRAD plays a pivotal role as a potential tumor suppressor in HCC. An improved understanding of the roles of RRAD in tumor metabolism may provide insights into its potential as a novel molecular target in HCC therapy.