TRAIL-induced apoptosis in gliomas is enhanced by Akt-inhibition and is independent of JNK activation

The Role of Curcumin in Cancer: A Focus on the PI3K/Akt Pathway

Cancer is a life-threatening disease and one of the leading causes of death worldwide. Despite significant advancements in therapeutic options, most available anti-cancer agents have limited efficacy. In this context, natural compounds with diverse chemical structures have been investigated for their multimodal anti-cancer properties. Curcumin is a polyphenol isolated from the rhizomes of Curcuma longa and has been widely studied for its anti-inflammatory, anti-oxidant, and anti-cancer effects. Curcumin acts on the regulation of different aspects of cancer development, including initiation, metastasis, angiogenesis, and progression. The phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) pathway is a key target in cancer therapy, since it is implicated in initiation, proliferation, and cancer cell survival. Curcumin has been found to inhibit the PI3K/Akt pathway in tumor cells, primarily via the regulation of different key mediators, including growth factors, protein kinases, and cytokines. This review presents the therapeutic potential of curcumin in different malignancies, such as glioblastoma, prostate and breast cancer, and head and neck cancers, through the targeting of the PI3K/Akt signaling pathway.

Suppression of TBCK enhances TRAIL-mediated apoptosis by causing the inactivation of the akt signaling pathway in human renal carcinoma Caki-1 cells

BACKGROUND

TBC1 domain-containing kinase (TBCK) protein functions as a growth suppressor in certain cell types and as a tumor promoter in others. Although TBCK knockdown increases the responsiveness of cancer cells to anticancer drugs, the detailed mechanisms by which TBCK knockdown increases susceptibility to anticancer drugs remain unknown.

OBJECTIVE

This study analyzed the role of TBCK in sensitivities to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and doxorubicin in human renal cancer cells.

METHODS

Flow cytometry was employed to evaluate the extent of apoptosis. Western blotting, transient transfection, and lentiviral infection techniques were conducted to investigate the impact of TBCK on apoptosis-related protein expression and mitogen-activated protein kinase (MAPK).

RESULTS

TBCK knockdown in renal cancer cells inhibits ERK and Akt signaling pathways and increases TRAIL and doxorubicin sensitivity. In TBCK-knockdown Caki-1 cells, ERK and Akt phosphorylation was suppressed compared to control cell lines, and TRAIL and doxorubicin sensitivities were increased in these cells. In addition, the phosphorylation of PDK1 was suppressed in TBCK-suppressed cells, indicating that TBCK may be involved in the PDK1 and Akt signaling pathways. The introduction of dominantly active Akt into TBCK-suppressed cells restored their sensitivity to TRAIL. In addition, TBCK downregulation enhanced TRAIL sensitivity in different renal cancer cell lines.

CONCLUSIONS

These data suggest that TBCK could potentially have a crucial function in influencing the effects of anti-cancer drugs including TRAIL by modulating the signaling pathway involving Akt and PDK1 in human renal cancer cells.

Fate and Efficacy of Engineered Allogeneic Stem Cells Targeting Cell Death and Proliferation Pathways in Primary and Brain Metastatic Lung Cancer

Primary and metastatic lung cancer is a leading cause of cancer-related death and novel therapies are urgently needed. Epidermal growth factor receptor (EGFR) and death receptor (DR) 4/5 are both highly expressed in primary and metastatic non-small cell lung cancer (NSCLC); however, targeting these receptors individually has demonstrated limited therapeutic benefit in patients. In this study, we created and characterized diagnostic and therapeutic stem cells (SC), expressing EGFR-targeted nanobody (EV) fused to the extracellular domain of death DR4/5 ligand (DRL) (EVDRL) that simultaneously targets EGFR and DR4/5, in primary and metastatic NSCLC tumor models. We show that EVDRL targets both cell surface receptors, and induces caspase-mediated apoptosis in a broad spectrum of NSCLC cell lines. Utilizing real-time dual imaging and correlative immunohistochemistry, we show that allogeneic SCs home to tumors and when engineered to express EVDRL, alleviate tumor burden and significantly increase survival in primary and brain metastatic NSCLC. This study reports mechanistic insights into simultaneous targeting of EGFR- and DR4/5 in lung tumors and presents a promising approach for translation into the clinical setting.

Harnessing TRAIL-Induced Apoptosis Pathway for Cancer Immunotherapy and Associated Challenges

The immune cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has attracted rapidly evolving attention as a cancer treatment modality because of its competence to selectively eliminate tumor cells without instigating toxicity in vivo. TRAIL has revealed encouraging promise in preclinical reports in animal models as a cancer treatment option; however, the foremost constraint of the TRAIL therapy is the advancement of TRAIL resistance through a myriad of mechanisms in tumor cells. Investigations have documented that improvement of the expression of anti-apoptotic proteins and survival or proliferation involved signaling pathways concurrently suppressing the expression of pro-apoptotic proteins along with down-regulation of expression of TRAILR1 and TRAILR2, also known as death receptor 4 and 5 (DR4/5) are reliable for tumor cells resistance to TRAIL. Therefore, it seems that the development of a therapeutic approach for overcoming TRAIL resistance is of paramount importance. Studies currently have shown that combined treatment with anti-tumor agents, ranging from synthetic agents to natural products, and TRAIL could result in induction of apoptosis in TRAIL-resistant cells. Also, human mesenchymal stem/stromal cells (MSCs) engineered to generate and deliver TRAIL can provide both targeted and continued delivery of this apoptosis-inducing cytokine. Similarly, nanoparticle (NPs)-based TRAIL delivery offers novel platforms to defeat barricades to TRAIL therapeutic delivery. In the current review, we will focus on underlying mechanisms contributed to inducing resistance to TRAIL in tumor cells, and also discuss recent findings concerning the therapeutic efficacy of combined treatment of TRAIL with other antitumor compounds, and also TRAIL-delivery using human MSCs and NPs to overcome tumor cells resistance to TRAIL.

TRAIL of Hope Meeting Resistance in Cancer

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis selectively via its interaction with the death receptors TRAILR1/DR4 and TRAILR2/DR5 in a wide range of cancers, while sparing normal cells. Despite its tremendous potential for cancer therapeutics, the translation of TRAIL into the clinic has been confounded by TRAIL-resistant cancer populations. We discuss different molecular mechanisms underlying TRAIL-mediated apoptosis and resistance to TRAIL. We also discuss the successes and failures of recent preclinical and clinical studies of TRAIL-induced apoptosis, and current attempts to overcome TRAIL resistance, and we provide a perspective for improving the prospects of future clinical implementation.

Elaeagnus angustifolia Plant Extract Inhibits Epithelial-Mesenchymal Transition and Induces Apoptosis via HER2 Inactivation and JNK Pathway in HER2-Positive Breast Cancer Cells

Elaeagnus angustifolia (EA) is a medicinal plant used for treating several human diseases in the Middle East. Meanwhile, the outcome of EA extract on HER2-positive breast cancer remains nascent. Thus, we herein investigated the effects of the aqueous EA extract obtained from the flowers of EA on two HER2-positive breast cancer cell lines, SKBR3 and ZR75-1. Our data revealed that EA extract inhibits cell proliferation and deregulates cell-cycle progression of these two cancer cell lines. EA extract also prevents the progression of epithelial-mesenchymal transition (EMT), an important event for cancer invasion and metastasis; this is accompanied by upregulations of E-cadherin and β-catenin, in addition to downregulations of vimentin and fascin, which are major markers of EMT. Thus, EA extract causes a drastic decrease in cell invasion ability of SKBR3 and ZR75-1 cancer cells. Additionally, we found that EA extract inhibits colony formation of both cell lines in comparison with their matched control. The molecular pathway analysis of HER2 and JNK1/2/3 of EA extract exposed cells revealed that it can block HER2 and JNK1/2/3 activities, which could be the major molecular pathway behind these events. Our findings implicate that EA extract may possess chemo-preventive effects against HER2-positive breast cancer via HER2 inactivation and specifically JNK1/2/3 signaling pathways.

Tumoricidal stem cell therapy enables killing in novel hybrid models of heterogeneous glioblastoma

BACKGROUND

Tumor-homing tumoricidal neural stem cell (tNSC) therapy is a promising new strategy that recently entered human patient testing for glioblastoma (GBM). Developing strategies for tNSC therapy to overcome intratumoral heterogeneity, variable cancer cell invasiveness, and differential drug response of GBM will be essential for efficacious treatment response in the clinical setting. The aim of this study was to create novel hybrid tumor models and investigate the impact of GBM heterogeneity on tNSC therapies.

METHODS

We used organotypic brain slice explants and distinct human GBM cell types to generate heterogeneous models ex vivo and in vivo. We then tested the efficacy of mono- and combination therapy with primary NSCs and fibroblast-derived human induced neural stem cells (iNSCs) engineered with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or enzyme-prodrug therapy.

RESULTS

Optical imaging, molecular assays, and immunohistochemistry revealed that the hybrid models recapitulated key aspects of patient GBM, including heterogeneity in TRAIL sensitivity, proliferation, migration patterns, hypoxia, blood vessel structure, cancer stem cell populations, and immune infiltration. To explore the impact of heterogeneity on tNSC therapy, testing in multiple in vivo models showed that tNSC-TRAIL therapy potently inhibited tumor growth and significantly increased survival across all paradigms. Patterns of tumor recurrence varied with therapeutic (tNSC-TRAIL and/or tNSC-thymidine kinase), dose, and route of administration.

CONCLUSIONS

These studies report new hybrid models that accurately capture key aspects of GBM heterogeneity which markedly impact treatment response while demonstrating the ability of tNSC mono- and combination therapy to overcome certain aspects of heterogeneity for robust tumor kill.

Development of acquired resistance to lapatinib may sensitise HER2-positive breast cancer cells to apoptosis induction by obatoclax and TRAIL

Background

Lapatinib has clinical efficacy in the treatment of trastuzumab-refractory HER2-positive breast cancer. However, a significant proportion of patients develop progressive disease due to acquired resistance to the drug. Induction of apoptotic cell death is a key mechanism of action of lapatinib in HER2-positive breast cancer cells.

Methods

We examined alterations in regulation of the intrinsic and extrinsic apoptosis pathways in cell line models of acquired lapatinib resistance both in vitro and in patient samples from the NCT01485926 clinical trial, and investigated potential strategies to exploit alterations in apoptosis signalling to overcome lapatinib resistance in HER2-positive breast cancer.

Results

In this study, we examined two cell lines models of acquired lapatinib resistance (SKBR3-L and HCC1954-L) and showed that lapatinib does not induce apoptosis in these cells. We identified alterations in members of the BCL-2 family of proteins, in particular MCL-1 and BAX, which may play a role in resistance to lapatinib. We tested the therapeutic inhibitor obatoclax, which targets MCL-1. Both SKBR3-L and HCC1954-L cells showed greater sensitivity to obatoclax-induced apoptosis than parental cells. Interestingly, we also found that the development of acquired resistance to lapatinib resulted in acquired sensitivity to TRAIL in SKBR3-L cells. Sensitivity to TRAIL in the SKBR3-L cells was associated with reduced phosphorylation of AKT, increased expression of FOXO3a and decreased expression of c-FLIP. In SKBR3-L cells, TRAIL treatment caused activation of caspase 8, caspase 9 and caspase 3/7. In a second resistant model, HCC1954-L cells, p-AKT levels were not decreased and these cells did not show enhanced sensitivity to TRAIL. Furthermore, combining obatoclax with TRAIL improved response in SKBR3-L cells but not in HCC1954-L cells.

Conclusions

Our findings highlight the possibility of targeting altered apoptotic signalling to overcome acquired lapatinib resistance, and identify potential novel treatment strategies, with potential biomarkers, for HER2-positive breast cancer that is resistant to HER2 targeted therapies.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4852-1) contains supplementary material, which is available to authorized users.

Delivery of mitoxantrone using a plant virus-based nanoparticle for the treatment of glioblastomas

Mitoxatrone (MTO), an antineoplastic chemotherapeutic, has potent activity against the most common and agressive type of primary brain tumor, glioblastoma multiforme (GBM). However, its poor penetration through the blood brain barrier, and cardiotoxic side effects from systemic delivery limit its effectiveness for clinical treatment. To address these limitations, we utilize a plant virus-based nanoparticle, cowpea mosaic virus (CPMV), to deliver MTO to treat GBM. In this work, we loaded MTO into the interior cavity of CPMV (CPMV-MTO) through diffusion through its pores. We report the uptake of CPMV-MTO in glioma cells and demonstrate its cytotoxic effects in vitro as a solo therapy, and in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). These results reveal the potential for this plant virus-based nanoparticle platform for the treatment of GBM.

Inhibition of mTORC2 enhances UVB-induced apoptosis in keratinocytes through a mechanism dependent on the FOXO3a transcriptional target NOXA but independent of TRAIL

The primary cause of non-melanoma skin cancer (NMSC) is ultraviolet B (UVB) radiation. We have shown previously that mTORC2 inhibition sensitizes keratinocytes to UVB-induced apoptosis mediated by the transcription factor FOXO3a. FOXO3a is a key regulator of apoptosis and a tumor suppressor in several cancer types. Activation of FOXO3a promotes apoptosis through the coordinated expression of a variety of target genes, including TRAIL and NOXA. We hypothesized that in the setting of mTORC2 inhibition, the UVB-induced expression of these factors would lead to apoptosis in a FOXO3a-dependent manner. Using spontaneously immortalized human keratinocytes (HaCaT cells), we observed that both TRAIL and NOXA expression increased in cells exposed to UVB and the TOR kinase inhibitor Torin 2. Similar to knockdown of FOXO3a, NOXA knockdown reversed the sensitization to UVB-induced apoptosis caused by mTORC2 inhibition. In contrast, loss of TRAIL by either knockdown or knockout actually enhanced expression of nuclear FOXO3a, which maintained apoptosis. These surprising results are not due to faulty death receptor signaling in HaCaT cells, as we found that the cells undergo extrinsic apoptosis in response to treatment with recombinant TRAIL. Even more striking, TRAIL knockout cells were sensitized to recombinant TRAIL-induced apoptosis compared to wild-type HaCaT cells, with the largest increase occurring in the presence of mTORC2 inhibition. Taken together, these studies provide strong evidence that mTORC2 controls UVB-induced apoptosis by regulating NOXA expression downstream of FOXO3a. Moreover, FOXO3a transcriptional activation by mTORC2 inhibitors may be a valuable target for prevention or therapy of NMSC, especially in cases with low endogenous TRAIL.

TRAIL pathway targeting therapeutics

Introduction

Despite decades of focused research efforts, cancer remains a significant cause of morbidity and mortality. Tumor necrosis factor(TNF)-related apoptosis-inducing ligand (TRAIL) is capable of inducing cell death selectively in cancer cells while sparing normal cells.

Areas covered

In this review, the authors cover TRA therapy and strategies that have been undertaken to improve their efficacy, as well as unconventional approaches to TRAIL pathway activation including TRAIL-inducing small molecules. They also discuss mechanisms of resistance to TRAIL and the use of combination strategies to overcome it.

Expert commentary

Targeting the TRAIL pathway has been of interest in oncology, and although initial clinical trials of TRAIL receptor agonists (TRAs) showed limitations, novel approaches represent the future of TRAIL-based therapy.

microRNA-7 upregulates death receptor 5 and primes resistant brain tumors to caspase-mediated apoptosis

Background

MicroRNAs (miRs) are known to play a pivotal role in tumorigenesis, controlling cell proliferation and apoptosis. In this study, we investigated the potential of miR-7 to prime resistant tumor cells to apoptosis in glioblastoma (GBM).

Methods

We created constitutive and regulatable miR-7 expression vectors and utilized pharmacological inhibition of caspases and genetic loss of function to study the effect of forced expression of miR-7 on death receptor (DR) pathways in a cohort of GBM with established resistance to tumor necrosis factor apoptosis inducing ligand (TRAIL) and in patient-derived primary GBM stem cell (GSC) lines. We engineered adeno-associated virus (AAV)-miR-7 and stem cell (SC) releasing secretable (S)-TRAIL and utilized real time in vivo imaging and neuropathology to understand the effect of the combined treatment of AAV-miR-7 and SC-S-TRAIL in vitro and in mouse models of GBM from TRAIL-resistant GSC.

Results

We show that expression of miR-7 in GBM cells results in downregulation of epidermal growth factor receptor and phosphorylated Akt and activation of nuclear factor-kappaB signaling. This leads to an upregulation of DR5, ultimately priming resistant GBM cells to DR-ligand, TRAIL-induced apoptotic cell death. In vivo, a single administration of AAV-miR-7 significantly decreases tumor volumes, upregulates DR5, and enables SC-delivered S-TRAIL to eradicate GBM xenografts generated from patient-derived TRAIL-resistant GSC, significantly improving survival of mice.

Conclusions

This study identifies the unique role of miR-7 in linking cell proliferation to death pathways that can be targeted simultaneously to effectively eliminate GBM, thus presenting a promising strategy for treating GBM.

A DR4 capturer with AKT siRNA for the synergetic enhancement of death receptor-mediated apoptosis

A DR4 capturer with AKT siRNA was developed for the synergetic enhancement of death receptor-mediated apoptosis.

N-terminal gelsolin fragment potentiates TRAIL mediated death in resistant hepatoma cells

TNF-α related apoptosis-inducing ligand (TRAIL) selectively kills tumor cells, without damaging normal cells. TRAIL receptors facilitate induction of apoptosis for selective elimination of malignant cells. However, some cancer cells have developed resistances to TRAIL which limits anticancer potential. Gelsolin, a multifunctional actin-binding protein, mediates cell death involving the TRAIL receptors in the hepatic stellate cell line, LX2. Here, we have shown that conditioned medium (CM) containing gelsolin fragments or an N-terminal gelsolin fragment (amino acid residues 1-70) in the presence of TRAIL impairs cell viability of TRAIL resistant transformed human hepatocytes (HepG2). Cell growth regulation by CM and TRAIL was associated with the modulation of p53/Mdm2, Erk and Akt phosphorylation status. The use of N-terminal gelsolin peptide1-70 alone or in combination with TRAIL, induced inhibition of Akt phosphorylation and key survival factors, Mdm2 and Survivin. Treatment of cells with an Akt activator SC79 or p53 siRNA reduced the effects of the N-terminal gelsolin fragment and TRAIL. Together, our study suggests that the N-terminal gelsolin fragment enhances TRAIL-induced loss of cell viability by inhibiting phosphorylation of Akt and promoting p53 function, effecting cell survival.

Bi-specific molecule against EGFR and death receptors simultaneously targets proliferation and death pathways in tumors

Developing therapeutics that target multiple receptor signaling pathways in tumors is critical as therapies targeting single specific biomarker/pathway have shown limited efficacy in patients with cancer. In this study, we extensively characterized a bi-functional molecule comprising of epidermal growth factor receptor (EGFR) targeted nanobody (ENb) and death receptor (DR) targeted ligand TRAIL (ENb-TRAIL). We show that ENb-TRAIL has therapeutic efficacy in tumor cells from different cancer types which do not respond to either EGFR antagonist or DR agonist monotherapies. Utilizing pharmacological inhibition, genetic loss of function and FRET studies, we show that ENb-TRAIL blocks EGFR signalling via the binding of ENb to EGFR which in turn induces DR5 clustering at the plasma membrane and thereby primes tumor cells to caspase-mediated apoptosis. In vivo, using a clinically relevant orthotopic resection model of primary glioblastoma and engineered stem cells (SC) expressing ENb-TRAIL, we show that the treatment with synthetic extracellular matrix (sECM) encapsulated SC-ENb-TRAIL alleviates tumor burden and significantly increases survival. This study is the first to report novel mechanistic insights into simultaneous targeting of receptor-mediated proliferation and cell death signaling pathways in different tumor types and presents a promising approach for translation into the clinical setting.

Genomic instability in human cancer: Molecular insights and opportunities for therapeutic attack and prevention through diet and nutrition

Genomic instability can initiate cancer, augment progression, and influence the overall prognosis of the affected patient. Genomic instability arises from many different pathways, such as telomere damage, centrosome amplification, epigenetic modifications, and DNA damage from endogenous and exogenous sources, and can be perpetuating, or limiting, through the induction of mutations or aneuploidy, both enabling and catastrophic. Many cancer treatments induce DNA damage to impair cell division on a global scale but it is accepted that personalized treatments, those that are tailored to the particular patient and type of cancer, must also be developed. In this review, we detail the mechanisms from which genomic instability arises and can lead to cancer, as well as treatments and measures that prevent genomic instability or take advantage of the cellular defects caused by genomic instability. In particular, we identify and discuss five priority targets against genomic instability: (1) prevention of DNA damage; (2) enhancement of DNA repair; (3) targeting deficient DNA repair; (4) impairing centrosome clustering; and, (5) inhibition of telomerase activity. Moreover, we highlight vitamin D and B, selenium, carotenoids, PARP inhibitors, resveratrol, and isothiocyanates as priority approaches against genomic instability. The prioritized target sites and approaches were cross validated to identify potential synergistic effects on a number of important areas of cancer biology.

Combination treatment of TRAIL, DFMO and radiation for malignant glioma cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown potent and cancer-selective killing activity and drawn considerable attention as a promising therapy for cancer. Another promising cancer therapy is difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, which is oraly administered and well tolerated. Nevertheless, many types of cancer, including gliomas, have exhibited resistance to TRAIL-induced apoptosis and similarly the potency of DFMO should be enhanced to optimize therapeutic efficacy. In this study we sought to determine whether DFMO, in combination with TRAIL and radiation, could result in an enhanced anti-glioma effect in vitro. We investigated the effect of DFMO, TRAIL and radiation in various combinations on a panel of glioblastoma cell lines (A172, T98G, D54, U251MG). Viability and proliferation of the cells were examined with trypan blue exclusion assay, crystal violet and xCELLigence system. Apoptosis (Annexin-PI), cell cycle and activation of caspase-8 were tested with flow cytometry. BAD protein levels were determined by Western blot analysis. DFMO induced BAD overexpression. Combination treatment with DFMO, TRAIL and radiation significantly reduced cell viability in all cell lines tested. Increased induction of cell death and cell cycle arrest was confirmed with flow cytometry in A172 and D54 cell lines, while enhanced activation of annexin and caspase-8 was revealed in U251MG and T98G cells. The treatment of glioblastoma cell lines with combination of DFMO, TRAIL and radiation showed an enhanced effect. This combination treatment may represent a novel strategy for targeting glioblastoma.

Targeting Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL): A Promising Therapeutic Strategy in Gliomas

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been increasingly studied for the treatment of gliomas. TRAIL has the ability to specifically target cancer cells, without any harmful effects on normal cells, and induces apoptosis by interacting with specific receptors. Nevertheless, resistance mechanisms to TRAIL may occur at different points in the signaling pathways of TRAIL-induced apoptosis. Various approaches have been developed to overcome TRAIL resistance. Here, we have reviewed the known molecular pathways by which TRAIL exerts anticancer activity, possible resistance mechanisms, ways to sensitize resistant cancer cells, and finally the current clinical successes or limitations of TRAIL-based therapies.

BAFF, APRIL, TWEAK, BCMA, TACI and Fn14 proteins are related to human glioma tumor grade: immunohistochemistry and public microarray data meta-analysis

Gliomas are common and lethal tumors of the central nervous system (CNS). Genetic alterations, inflammatory and angiogenic processes have been identified throughout tumor progression; however, treatment still remains palliative for most cases. Biological research on parameters influencing cell survival, invasion and tumor heterogeneity identified several cytokines interfering in CNS inflammation, oxidative stress and malignant transformation, including TNF-superfamily (TNFSF) members. In this report we performed a meta-analysis of public gene-array data on the expression of a group of TNFSF ligands (BAFF, APRIL, TWEAK) and their receptors (BAFF-R, TACI, BCMA, Fn14) in gliomas. In addition, we investigated by immunohistochemistry (IHC) the tumor cells' expression of these ligands and receptors in a series of 56 gliomas of different grade. We show that in IHC, BAFF and APRIL as well as their cognate receptors (BCMA, TACI) and Fn14 expression correlate with tumor grade. This result was not evidenced in micro-arrays meta-analysis. Finally, we detected for the first time Fn14, BAFF, BCMA and TACI in glioma-related vascular endothelium. Our data, combined with our previous report in glioma cell lines, suggest a role for these receptors and ligands in glioma biology and advance these molecules as potential markers for the classification of these tumors to the proliferative, angiogenic or stem-like molecular subtype.

Combination treatment for glioblastoma cells with tumor necrosis factor-related apoptosis-inducing ligand and oncolytic adenovirus delta-24

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exhibits cancer-selective killing activity representing a promising anticancer therapeutic strategy. Adenovirus Delta-24 is another interested anticancer agent selectively killing cells with a defective p16/Rb/E2F pathway. However, many types of cancer, including gliomas, could develop resistance to Delta-24 or TRAIL-induced apoptosis. In this study, we investigated whether TRAIL, in combination with adenovirus Delta-24, could result in an enhanced antiglioma effect in vitro in a panel of glioblastoma cell lines (U87MG, U251MG, D54, and T98G). The treatment of glioblastoma cell lines with TRAIL and Delta-24 adenovirus in combination showed markedly enhanced effect, compared to each agent alone.

Therapeutic targeting of EGFR-activated metabolic pathways in glioblastoma

INTRODUCTION

The highly divergent histological heterogeneities, aggressive invasion and extremely poor response to treatment make glioblastoma (GBM) one of the most lethal and difficult cancers in humans. Among key elements driving its behavior is epidermal growth factor receptor (EGFR), however, neither traditional therapy including neurosurgery, radiation, temozolomide, nor targeted EGFR therapeutics in clinic has generated promising results to date. Strategies are now focusing on blocking the downstream EGFR-activated metabolic pathways and the key phosphorylated kinases.

AREAS COVERED

Here, we review two major EGFR-activated downstream metabolic pathways including the PI3K/AKT/mTOR and RAS/RAF/MAPK pathways and their key phosphorylated kinase alterations in GBMs. This review also discusses potential pharmacological progress from bench work to clinical trials in order to evaluate specific inhibitors as well as therapeutics targeting PI3K and RAS signaling pathways.

EXPERT OPINION

Several factors impede clinical progress in targeting GBM, including the high rates of acquired resistance, heterogeneity within and across the tumors, complexity of signaling pathways and difficulty in traversing the blood-brain barrier (BBB). Substantial insight into genetic and molecular pathways and strategies to better tap the potential of these agents include rational combinatorial regimens and molecular phenotype-based patient enrichment, each of which will undoubtedly generate new therapeutic approaches to combat these devastating disabilities in the near future.

Bortezomib sensitizes malignant human glioma cells to TRAIL, mediated by inhibition of the NF-{kappa}B signaling pathway

Previous studies have shown that the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has significant apoptosis-inducing activity in some glioma cell lines, although many lines are either moderately or completely resistant, which has limited the therapeutic applicability of this agent. Because our recent studies showed that inhibition of proteasomal function may be independently active as an apoptosis-inducing stimulus in these tumors, we investigated the sensitivity of a panel of glioma cell lines (U87, T98G, U373, A172, LN18, LN229, LNZ308, and LNZ428) to TRAIL alone and in combination with the proteasome inhibitor bortezomib. Analysis of these cell lines revealed marked differences in their sensitivity to these treatments, with two (LNZ308 and U373) of the eight cell lines revealing no significant induction of cell death in response to TRAIL alone. No correlation was found between sensitivity of cells to TRAIL and expression of TRAIL receptors DR4, DR5, and decoy receptor DcR1, caspase 8, apoptosis inhibitory proteins XIAP, survivin, Mcl-1, Bcl-2, Bcl-Xl, and cFLIP. However, TRAIL-resistant cell lines exhibited a high level of basal NF-κB activity. Bortezomib was capable of potentiating TRAIL-induced apoptosis in TRAIL-resistant cells in a caspase-dependent fashion. Bortezomib abolished p65/NF-κB DNA-binding activity, supporting the hypothesis that inhibition of the NF-κB pathway is critical for the enhancement of TRAIL sensitization in glioma cells. Moreover, knockdown of p65/NF-κB by shRNA also enhanced TRAIL-induced apoptosis, indicating that p65/NF-κB may be important in mediating TRAIL sensitivity and the effect of bortezomib in promoting TRAIL sensitization and apoptosis induction.

Vorinostat modulates cell cycle regulatory proteins in glioma cells and human glioma slice cultures

Chromatin modification through histone deacetylase inhibition has shown evidence of activity against malignancies. The mechanism of action of such agents are pleiotropic and potentially tumor specific. In this study, we studied the mechanisms of vorinostat-induced cellular effects in gliomas. The effects of vorinostat on proliferation, induction of apoptosis and cell cycle effects were studied in vitro (D54, U87 and U373 glioma cell lines). To gain additional insights into its effects on human gliomas, vorinostat-induced changes were examined ex vivo using a novel organotypic human glioma slice model. Vorinostat treatment resulted in increased p21 levels in all glioma cells tested in a p53 independent manner. In addition, cyclin B1 levels were transcriptionally downregulated and resulted in reduced kinase activity of the cyclin B1/cdk1 complex causing a G2 arrest. These effects were associated with a dose- and time-dependent inhibition of cellular proliferation and anchorage-independent growth in association with hyperacetylation of core histones and induction of apoptosis. Of particular significance, we demonstrate histone hyperacetylation and increased p21 levels in freshly resected human glioma specimens maintained as organotypic slice cultures and exposed to vorinostat similar to cell lines suggesting that human glioma can be targeted by this agent. Our data suggest that the effects of vorinostat are associated with modulation of cell cycle related proteins and activation of a G2 checkpoint along with induction of apoptosis. These effects are mediated by both transcriptional and post-translational mechanisms which provide potential options that can be exploited to develop new therapeutic approaches against gliomas.

High susceptibility of metastatic cells derived from human prostate and colon cancer cells to TRAIL and sensitization of TRAIL-insensitive primary cells to TRAIL by 4,5-dimethoxy-2-nitrobenzaldehyde

BACKGROUND

Tumor recurrence and metastasis develop as a result of tumors' acquisition of anti-apoptotic mechanisms and therefore, it is necessary to develop novel effective therapeutics against metastatic cancers. In this study, we showed the differential TRAIL responsiveness of human prostate adenocarcinoma PC3 and human colon carcinoma KM12 cells and their respective highly metastatic PC3-MM2 and KM12L4A sublines and investigated the mechanism underlying high susceptibility of human metastatic cancer cells to TRAIL.

RESULTS

PC3-MM2 and KM12L4A cells with high level of c-Myc and DNA-PKcs were more susceptible to TRAIL than their poorly metastatic primary PC3 and KM12 cells, which was associated with down-regulation of c-FLIPL/S and Mcl-1 and up-regulation of the TRAIL receptor DR5 but not DR4 in both metastatic cells. Moreover, high susceptibility of these metastatic cells to TRAIL was resulted from TRAIL-induced potent activation of caspase-8, -9, and -3 in comparison with their primary cells, which led to cleavage and down-regulation of DNA-PKcs. Knockdown of c-Myc gene in TRAIL-treated PC3-MM2 cells prevented the increase of DR5 cell surface expression, caspase activation and DNA-PKcs cleavage and attenuated the apoptotic effects of TRAIL. Moreover, the suppression of DNA-PKcs level with siRNA in the cells induced the up-regulation of DR5 and active caspase-8, -9, and -3. We also found that 4,5-dimethoxy-2-nitrobenzaldehyde (DMNB), a specific inhibitor of DNA-PK, potentiated TRAIL-induced cytotoxicity and apoptosis in relatively TRAIL-insensitive PC3 and KM12 cells and therefore functioned as a TRAIL sensitizer.

CONCLUSION

This study showed the positive relationship between c-Myc expression in highly metastatic human prostate and colon cancer cells and susceptibility to TRAIL-induced apoptosis and therefore indicated that TRAIL might be used as an effective therapeutic modality for advanced metastatic cancers overexpressing c-Myc and combination of TRAIL therapy with agent that inhibits the DNA-PKcs/Akt signaling pathway might be clinically useful for the treatment of relatively TRAIL-insensitive human cancers.

Efficacy of adenovirally expressed soluble TRAIL in human glioma organotypic slice culture and glioma xenografts

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in malignant cells, including gliomas, and is currently in anticancer clinical trials. However, the full-length and tagged forms of TRAIL, unlike the untagged ligand (soluble TRAIL (sTRAIL)), exhibits toxicity against normal cells. Here, we report the generation and testing of an adenovirus (AdsTRAIL) that expresses untagged sTRAIL in an intracranial xenograft model and a human glioma organotypic slice culture model. AdsTRAIL efficiently induced apoptosis in glioma cell lines, including those resistant to sTRAIL, but not in normal human astrocytes (NHAs). It inhibited anchorage-independent glioma growth and exerted a bystander effect in transwell assays. Intratumoral injections of AdsTRAIL in a rodent intracranial glioma model resulted in reduced tumor growth and improved survival compared with Ad-enhanced green fluorescent protein (EGFP)- or vehicle-treated controls without toxicity. Human glioma organotypic slices treated with AdsTRAIL demonstrated apoptosis induction and caspase activation.

A dual PI3K/mTOR inhibitor, PI-103, cooperates with stem cell-delivered TRAIL in experimental glioma models

The resistance of glioma cells to a number of antitumor agents and the highly invasive nature of glioma cells that escape the primary tumor mass are key impediments to the eradication of tumors in glioma patients. In this study, we evaluated the therapeutic efficacy of a novel PI3-kinase/mTOR inhibitor, PI-103, in established glioma lines and primary CD133(+) glioma-initiating cells and explored the potential of combining PI-103 with stem cell-delivered secretable tumor necrosis factor apoptosis-inducing ligand (S-TRAIL) both in vitro and in orthotopic mouse models of gliomas. We show that PI-103 inhibits proliferation and invasion, causes G(0)-G(1) arrest in cell cycle, and results in significant attenuation of orthotopic tumor growth in vivo. Establishing cocultures of neural stem cells (NSC) and glioma cells, we show that PI-103 augments the response of glioma cells to stem cell-delivered S-TRAIL. Using bimodal optical imaging, we show that when different regimens of systemic PI-103 delivery are combined with NSC-derived S-TRAIL, a significant reduction in tumor volumes is observed compared with PI-103 treatment alone. To our knowledge, this is the first study that reveals the antitumor effect of PI-103 in intracranial gliomas. Our findings offer a preclinical rationale for application of mechanism-based systemically delivered antiproliferative agents and novel stem cell-based proapoptotic therapies to improve treatment of malignant gliomas.

Potent synergistic interaction between the Nampt inhibitor APO866 and the apoptosis activator TRAIL in human leukemia cells

OBJECTIVE

The nicotinamide phosphoribosyltransferase (Nampt) inhibitor APO866 depletes intracellular nicotinamide adenine dinucleotide (NAD(+)) and shows promising anticancer activity in preclinical studies. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) binds to plasma membrane receptors DR4 and DR5 and induces apoptosis via caspase-8 and -10. Here we have explored the interaction between APO866 and TRAIL in leukemia cell lines and in primary B-cell chronic lymphocytic leukemia cells.

MATERIALS AND METHODS

Cells were treated with APO866, TRAIL, or their combination. Viability and mitochondrial transmembrane potential (ΔΨ(m)) were determined by cell staining with propidium iodide and tetramethylrhodamine ethyl ester, respectively, and flow cytometry. Nampt and γ-tubulin levels, as well as caspase-3 cleavage were detected by immunoblotting. DR4 and DR5 expression were assessed by immunostaining and flow cytometry. Caspases were inhibited with zVAD-FMK and zDEVD-FMK; autophagy with 3-methyladenine, LY294002, and wortmannin. Intracellular NAD(+) and adenosine triphosphate (ATP) were measured by cycling assays and high-performance liquid chromatography (HPLC), respectively.

RESULTS

APO866 induced NAD(+) depletion, ΔΨ(m) dissipation, and ATP shortage in leukemia cells, thereby leading to autophagic cell death. TRAIL induced caspase-dependent apoptosis. TRAIL addition to APO866 synergistically increased its activity in leukemia cells by enhancing NAD(+) depletion, ΔΨ(m) dissipation, and ATP shortage. No DR5 upregulation at the cell surface in response to APO866 was observed. Remarkably, in healthy leukocytes APO866 and TRAIL were poorly active and failed to show any cooperation.

CONCLUSIONS

Activation of the extrinsic apoptotic cascade with TRAIL selectively amplifies the sequelae of Nampt inhibition in leukemia cells, and appears as a promising strategy to enhance APO866 activity in hematological malignancies.

TRAIL-induced apoptosis of hepatocellular carcinoma cells is augmented by targeted therapies

AIM: To analyze the effect of chemotherapeutic drugs and specific kinase inhibitors, in combination with the death receptor ligand tumor necrosis factor-related apoptosis inducing ligand (TRAIL), on overcoming TRAIL resistance in hepatocellular carcinoma (HCC) and to study the efficacy of agonistic TRAIL antibodies, as well as the commitment of antiapoptotic BCL-2 proteins, in TRAIL-induced apoptosis.

METHODS: Surface expression of TRAIL receptors (TRAIL-R1-4) and expression levels of the antiapoptotic BCL-2 proteins MCL-1 and BCL-x_L were analyzed by flow cytometry and Western blotting, respectively. Knock-down of MCL-1 and BCL-x_L was performed by transfecting specific small interfering RNAs. HCC cells were treated with kinase inhibitors and chemotherapeutic drugs. Apoptosis induction and cell viability were analyzed via flow cytometry and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

RESULTS: TRAIL-R1 and -R2 were profoundly expressed on the HCC cell lines Huh7 and Hep-G2. However, treatment of Huh7 and Hep-G2 with TRAIL and agonistic antibodies only induced minor apoptosis rates. Apoptosis resistance towards TRAIL could be considerably reduced by adding the chemotherapeutic drugs 5-fluorouracil and doxorubicin as well as the kinase inhibitors LY294002 [inhibition of phosphoinositol-3-kinase (PI3K)], AG1478 (epidermal growth factor receptor kinase), PD98059 (MEK1), rapamycin (mammalian target of rapamycin) and the multi-kinase inhibitor Sorafenib. Furthermore, the antiapoptotic BCL-2 proteins MCL-1 and BCL-x_L play a major role in TRAIL resistance: knock-down by RNA interference increased TRAIL-induced apoptosis of HCC cells. Additionally, knock-down of MCL-1 and BCL-x_L led to a significant sensitization of HCC cells towards inhibition of both c-Jun N-terminal kinase and PI3K.

CONCLUSION: Our data identify the blockage of survival kinases, combination with chemotherapeutic drugs and targeting of antiapoptotic BCL-2 proteins as promising ways to overcome TRAIL resistance in HCC.

In vivo gene delivery by embryonic-stem-cell-derived astrocytes for malignant gliomas

The treatment of malignant gliomas with current therapies remains a challenge in neurooncology. Our recent work showed that embryonic stem cell (ESC)-derived astrocytes conditionally expressing genes can be used to induce apoptosis in malignant glioma cells in vitro. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene has been shown to induce apoptosis in a variety of tumor cells, including gliomas. The aim of this study was to assess the proapoptotic effects of transgenic TRAIL delivered by ESC-derived astrocytes on malignant gliomas in vivo. Malignant glioma A172 cells were used to induce heterotopic xenografts in nude mice. ESC-derived astrocytes conditionally expressing TRAIL were injected into the xenografts. TRAIL expression was documented in the malignant glioma xenografts by reverse transcription PCR and immunohistochemistry after external gene induction. A significant reduction in tumor volume occurred 48 h after a single injection (14%) and double injections (31%) in the experimental groups. Terminal dUTP nick end labeling (TUNEL) revealed abundant apoptotic tumor cells in the experimental groups. Seven days after injection, the tumor had undergone severe necrosis, with only scattered residual tumor cells at the periphery. Death receptor DR4 expression increased significantly in the experimental groups compared with controls. Our data suggest that ESC-derived astrocytes conditionally expressing TRAIL should be considered as vectors to deliver gene therapy for malignant gliomas.

Bone marrow stroma confers resistance to Apo2 ligand/TRAIL in multiple myeloma in part by regulating c-FLIP

Apo2 ligand (Apo2L)/TRAIL induces apoptosis of cancer cells that express the specific receptors while sparing normal cells. Because the tumor microenvironment protects myeloma from chemotherapy, we investigated whether hemopoietic stroma induces resistance to Apo2L/TRAIL apoptosis in this disease. Apo2L/TRAIL-induced death was diminished in myeloma cell lines (RPMI 8226, U266, and MM1s) directly adhered to a human immortalized HS5 stroma cell line but not adhered to fibronectin. In a Transwell assay, with myeloma in the upper well and HS5 cells in the lower well, Apo2L/TRAIL apoptosis was reduced when compared with cells exposed to medium in the lower well. Using HS5 and myeloma patients' stroma-conditioned medium, we determined that soluble factor(s) produced by stroma-myeloma interactions are responsible for a reversible Apo2/TRAIL apoptosis resistance. Soluble factor(s) attenuated procaspase-8, procaspase-3, and poly(ADP-ribose) polymerase cleavage and diminished mitochondrial membrane potential changes without affecting Bcl-2 family proteins and/or Apo2L/TRAIL receptors. Soluble factor(s) increased the baseline levels of the anti-apoptotic protein c-FLIP in all cell lines tested. Inhibition of c-FLIP by means of RNA interference increased Apo2/TRAIL sensitivity in RPMI 8226 cells. Unlike direct adhesion to fibronectin, soluble factor(s) have no impact on c-FLIP redistribution within cellular compartments. Cyclohexamide restored Apo2L/TRAIL sensitivity in association with down-regulation of c-FLIP, suggesting that c-FLIP synthesis, not intracellular traffic, is essential for soluble factor(s) to regulate c-FLIP. Additionally, IL-6 conferred resistance to Apo2L/TRAIL-mediated apoptosis in association with increased c-FLIP levels. In conclusion, the immune cytotoxic effect of Apo2L/TRAIL can be restored at least in part by c-FLIP pathway inhibitors.

Targeting the PI3K/Akt/mTOR pathway: effective combinations and clinical considerations

The PI3K/Akt/mTOR pathway is a prototypic survival pathway that is constitutively activated in many types of cancer. Mechanisms for pathway activation include loss of tumor suppressor PTEN function, amplification or mutation of PI3K, amplification or mutation of Akt, activation of growth factor receptors, and exposure to carcinogens. Once activated, signaling through Akt can be propagated to a diverse array of substrates, including mTOR, a key regulator of protein translation. This pathway is an attractive therapeutic target in cancer because it serves as a convergence point for many growth stimuli, and through its downstream substrates, controls cellular processes that contribute to the initiation and maintenance of cancer. Moreover, activation of the Akt/mTOR pathway confers resistance to many types of cancer therapy, and is a poor prognostic factor for many types of cancers. This review will provide an update on the clinical progress of various agents that target the pathway, such as the Akt inhibitors perifosine and PX-866 and mTOR inhibitors (rapamycin, CCI-779, RAD-001) and discuss strategies to combine these pathway inhibitors with conventional chemotherapy, radiotherapy, as well as newer targeted agents. We will also discuss how the complex regulation of the PI3K/Akt/mTOR pathway poses practical issues concerning the design of clinical trials, potential toxicities and criteria for patient selection.

Anti-Apoptosis Mechanisms in Malignant Gliomas

Malignant gliomas are characterized by an intrinsic resistance to apoptosis. Increasing evidence suggests that this is a fundamental mechanism by which gliomas evade elimination when treated with both conventional and targeted therapies. In this review, we describe the multiple anti-apoptotic signals that have been demonstrated to be active in malignant gliomas. We describe the preclinical evidence that suggests that targeting those signaling anomalies can increase tumor responsiveness and enhance the elimination of gliomas in preclinical models. We discuss recent advances in translating pro-apoptotic compounds to clinical trial, and the potential for implementing agents that target the apoptotic pathway as a strategy for improving the outcomes for patients with high-grade gliomas.

TRAIL in cancer therapy: present and future challenges

Since its identification in 1995, TNF-related apoptosis-inducing ligand (TRAIL) has sparked growing interest in oncology due to its reported ability to selectively trigger cancer cell death. In contrast to other members of the TNF superfamily, TRAIL administration in vivo is safe. The relative absence of toxic side effects of this naturally occurring cytokine, in addition to its antitumoural properties, has led to its preclinical evaluation. However, despite intensive investigations, little is known in regards to the mechanisms underlying TRAIL selectivity or efficiency. An appropriate understanding of its physiological relevance, and of the mechanisms controlling cancer cells escape from TRAIL-induced cell death, will be required to optimally use the cytokine in clinics. The present review focuses on recent advances in the understanding of TRAIL signal transduction and discusses the existing and future challenges of TRAIL-based cancer therapy development.

MCL-1 as a Buffer for Proapoptotic BCL-2 Family Members during TRAIL-induced Apoptosis

Previous studies have suggested that Mcl-1, an antiapoptotic Bcl-2 homolog that does not exhibit appreciable affinity for the caspase 8-generated C-terminal Bid fragment (tBid), diminishes sensitivity to tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL). This study was performed to determine the mechanism by which Mcl-1 confers TRAIL resistance and to evaluate methods for overcoming this resistance. Affinity purification/immunoblotting assays using K562 human leukemia cells, which contain Mcl-1 and Bcl-x(L) as the predominant antiapoptotic Bcl-2 homologs, demonstrated that TRAIL treatment resulted in binding of tBid to Bcl-x(L) but not Mcl-1. In contrast, TRAIL caused increased binding between Mcl-1 and Bak that was diminished by treatment with the caspase 8 inhibitor N-(N(alpha)-acetylisoleucylglutamylthreonyl) aspartic acid (O-methyl ester)-fluoromethyl ketone (IETD(OMe)-fmk) or the c-Jun N-terminal kinase inhibitor SP600125. In addition, TRAIL caused increased binding of Bim and Puma to Mcl-1 that was inhibited by IETD(OMe)-fmk but not SP600125. Further experiments demonstrated that down-regulation of Mcl-1 by short hairpin RNA or the kinase inhibitor sorafenib increased TRAIL-induced Bak activation and death ligand-induced apoptosis in a wide variety of neoplastic cell lines as well as clinical acute myelogenous leukemia specimens. Collectively, these observations not only suggest a model in which Mcl-1 confers TRAIL resistance by serving as a buffer for Bak, Bim, and Puma, but also identify sorafenib as a potential modulator of TRAIL sensitivity.

TRAIL-mediated apoptosis in HIV-1-infected macrophages is dependent on the inhibition of Akt-1 phosphorylation

HIV-1 uses mononuclear phagocytes (monocytes, tissue macrophages, and dendritic cells) as a vehicle for its own dissemination and as a reservoir for continuous viral replication. The mechanism by which the host immune system clears HIV-1-infected macrophages is not understood. TRAIL may play a role in this process. TRAIL is expressed on the cell membrane of peripheral immune cells and can be cleaved into a soluble, secreted form. The plasma level of TRAIL is increased in HIV-1-infected patients, particularly those with high viral loads. To study the effect of elevated TRAIL on mononuclear phagocytes, we used recombinant human (rh) TRAIL and human monocyte-derived macrophages (MDM) as an in vitro model. Our results demonstrated rhTRAIL-induced apoptosis in HIV-1-infected MDM and inhibited viral replication, while having a reduced effect on uninfected MDM. HIV-1 infection significantly decreased Akt-1 phosphorylation; rhTRAIL exposure further decreased Akt-1 phosphorylation. Infection with a dominant-negative Akt-1 adenovirus potentiated rhTRAIL-induced apoptosis, while constitutively active Akt-1 blocked rhTRAIL-induced apoptosis in HIV-1-infected MDM. From this data we conclude the death ligand TRAIL preferentially provokes apoptosis of HIV-1-infected MDM, and the mechanism is reliant upon the inhibition of Akt-1 phosphorylation. Understanding this mechanism may facilitate the elimination of HIV-1-infected macrophages and lead to new therapeutic avenues for treatment of HIV-1 infection.

TRAIL inhibits angiogenesis stimulated by VEGF expression in human glioblastoma cells

Tumour growth is tightly related to new blood vessel formation, tissue remodelling and invasiveness capacity. A number of tissular factors fuel the growth of glioblastoma multiforme, the most aggressive brain neoplasm. In fact, gene array analyses demonstrated that the proapoptotic cytokine tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) inhibited mRNA expression of VEGF, along with those of matrix metalloproteinase-2 (MMP-2), its inhibitor tissue inhibitor of matrix metalloproteinases-2 (TIMP-2), as well as the tumour invasiveness-related gene secreted protein acid rich in cysteine (SPARC) in different human glioblastoma cell lines. Particularly, VEGF mRNA and protein expression and release from glioblastoma cells were also inhibited by TRAIL. The latter also exerted antimitogenic effects on human umbilical vein endothelial cells (HUVECs). With the same cells, TRAIL inhibited new vessel formation in the in vitro matrigel model, as well as it exerted powerful inhibition of blood vessel formation induced by an angiogenic cocktail administered in subcutaneous pellets in vivo in the C57 mouse. Moreover, the expression of MMP-2, its inhibitor TIMP-2 and the tumour invasiveness-related protein SPARC were effectively inhibited by TRAIL in glioblastoma cell lines. In conclusion, our data indicate that TRAIL inhibits the orchestra of factors contributing to glioblastoma biological aggressiveness. Thus, the TRAIL system could be regarded as a molecular target to exploit for innovative therapy of this type of tumour.

TNF-related apoptosis-inducing ligand as a therapeutic agent in autoimmunity and cancer

Recombinant, soluble TNF-related apoptosis-inducing ligand (TRAIL) is currently being developed as a promising natural immune molecule for trial in cancer patients because it selectively induces apoptosis in transformed or stressed cells but not in most normal cells. In cancer patients, phase 1 and 2 clinical trials using agonistic mAbs that engage the human TRAIL receptors DR4 and DR5 have also provided encouraging results. It is now evident that TRAIL suppresses autoimmune disease in various experimental animal models, suggesting that the therapeutic value of recombinant TRAIL and agonistic DR4 and DR5 mAbs might also extend to the suppression of autoimmune disease. This review provides an insight into our current understanding of the role(s) of TRAIL in disease, with a specific focus on cancer and autoimmunity. We also emphasize biological agents and drugs that sensitize tumour cells to TRAIL-mediated apoptosis and discuss the potential molecular basis for their sensitization.

Quantitative PCR on 5 genes reliably identifies CTCL patients with 5% to 99% circulating tumor cells with 90% accuracy

We previously identified a small number of genes using cDNA arrays that accurately diagnosed patients with Sézary Syndrome (SS), the erythrodermic and leukemic form of cutaneous T-cell lymphoma (CTCL). We now report the development of a quantitative real-time polymerase chain reaction (qRT-PCR) assay that uses expression values for just 5 of those genes: STAT4, GATA-3, PLS3, CD1D, and TRAIL. qRT-PCR data from peripheral blood mononuclear cells (PBMCs) accurately classified 88% of 17 patients with high blood tumor burden and 100% of 12 healthy controls in the training set using Fisher linear discriminant analysis (FLDA). The same 5 genes were then assayed on 56 new samples from 49 SS patients with blood tumor burdens of 5% to 99% and 69 samples from 65 new healthy controls. The average accuracy over 1000 resamplings was 90% using FLDA and 88% using support vector machine (SVM). We also tested the classifier on 14 samples from patients with CTCL with no detectable peripheral involvement and 3 patients with atopic dermatitis with severe erythroderma. The accuracy was 100% in identifying these samples as non-SS patients. These results are the first to demonstrate that gene expression profiling by quantitative PCR on a selected number of critical genes can be employed to molecularly diagnosis SS.

Synergistic enhancement of TRAIL- and tumor necrosis factor alpha-induced cell death by a phenoxazine derivative

2-Amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1) has been developed as a novel phenoxazine derivative having an anticancer activity on a variety of cancer cell lines as well as transplanted tumors in mice with minimal toxicity to normal cells. We examined the effects of Phx-1 on Jurkat cells, a human T cell line. Phx-1 inhibited proliferation of the cells in a dose-dependent manner but hardly induced cell death, suggesting that Phx-1 acts primarily as an antiproliferative reagent but not as a cytocidal drug. Phx-1 enhanced tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptotic cell death about 100-fold. Tumor necrosis factor alpha, which alone does not induce cell death of Jurkat cells, caused apoptosis in combination with Phx-1. These enhancements of cell death were not due to up-regulation of the death receptors. Phx-1 decreased serum-induced phosphorylation of Akt, a kinase involved in cell proliferation and survival, and inhibited complex III of mitochondrial respiratory chain. Considering that both TRAIL and Phx-1 have only marginal cytotoxicity to most normal cells, Phx-1 may provide an ideal combination for cancer therapy with TRAIL.