Use of APO2L/TRAIL with mTOR inhibitors in the treatment of glioblastoma multiforme

Resveratrol Derivative, Trans-3, 5, 4'-Trimethoxystilbene Sensitizes Osteosarcoma Cells to Apoptosis via ROS-Induced Caspases Activation

Numerous studies have shown that resveratrol can induce apoptosis in cancer cells. Trans-3, 5, 4'-trimethoxystilbene (TMS), a novel derivative of resveratrol, is a more potent anticancer compound than resveratrol and can induce apoptosis in cancer cells. Herein, we examined the mechanisms involved in TMS-mediated sensitization of human osteosarcoma (143B) cells to TNF-related apoptosis-inducing ligand- (TRAIL-) induced apoptosis. Our results showed that cotreatment with TSM and TRAIL activated caspases and increased PARP-1 cleavage in 143B cells. Decreasing cellular ROS levels using NAC reversed TSM- and TRAIL-induced apoptosis in 143B cells. NAC abolished the upregulated expression of PUMA and p53 induced by treatment with TRAIL and TSM. Silencing the expression of p53 or PUMA using RNA interference attenuated TSM-mediated sensitization of 143B cells to TRAIL-induced apoptosis. Knockdown of Bax also reversed TSM-induced sensitization of 143B cell to TRAIL-mediated apoptotic cell death. These results indicate that cotreatment with TRAIL and TSM evaluated intracellular ROS level, promoted DNA damage, and activated the Bax/PUMA/p53 pathway, leading to activation of both mitochondrial and caspase-mediated apoptosis in 143B cells. Orthotopic implantation of 143B cells in mice also demonstrated that cotreatment with TRAIL and TSM reversed resistance to apoptosis in cells without obvious adverse effects in normal cells.

Acetylshikonin Sensitizes Hepatocellular Carcinoma Cells to Apoptosis through ROS-Mediated Caspase Activation

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown strong and explicit cancer cell-selectivity, which results in little toxicity toward normal tissues, and has been recognized as a potential, relatively safe anticancer agent. However, several cancers are resistant to the apoptosis induced by TRAIL. A recent study found that shikonin b (alkannin, 5,8-dihydroxy-2-[(1S)-1-hydroxy-4-methylpent-3-en-1-yl]naphthalene-1,4-dione) might induce apoptosis in TRAIL-resistant cholangiocarcinoma cells through reactive oxygen species (ROS)-mediated caspases activation. However, the strong cytotoxic activity has limited its potential as an anticancer drug. Thus, the current study intends to discover novel shikonin derivatives which can sensitize the liver cancer cell to TRAIL-induced apoptosis while exhibiting little toxicity toward the normal hepatic cell. The trypan blue exclusion assay, western blot assay, 4′,6-diamidino-2-phenylindole (DAPI) staining and the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay as well as the ‘comet’ assay, were used to study the underlying mechanisms of cell death and to search for any mechanisms of an enhancement of TRAIL-mediated apoptosis in the presence of ASH. Herein, we demonstrated that non-cytotoxic doses of acetylshikonin (ASH), one of the shikonin derivatives, in combination with TRAIL, could promote apoptosis in HepG2 cells. Further studies showed that application of ASH in a non-cytotoxic dose (2.5 μM) could increase intracellular ROS production and induce DNA damage, which might trigger a cell intrinsic apoptosis pathway in the TRAIL-resistant HepG2 cell. Combination treatment with a non-cytotoxic dose of ASH and TRAIL activated caspase and increased the cleavage of PARP-1 in the HepG2 cell. However, when intracellular ROS production was suppressed by N-acetyl-l-cysteine (NAC), the synergistic effects of ASH and TRAIL on hepatocellular carcinoma (HCC) cell apoptosis was abolished. Furthermore, NAC could alleviate p53 and the p53 upregulated modulator of apoptosis (PUMA) expression induced by TRAIL and ASH. Small (or short) interfering RNA (siRNA) targeting PUMA or p53 significantly reversed ASH-mediated sensitization to TRAIL-induced apoptosis. In addition, Bax gene deficiency also abolished ASH-induced TRAIL sensitization. An orthotopical HCC implantation mice model further confirmed that co-treated ASH overcomes TRAIL resistance in HCC cells without exhibiting potent toxicity in vivo. In conclusion, the above data suggested that ROS could induce DNA damage and activating p53/PUMA/Bax signaling, and thus, this resulted in the permeabilization of mitochondrial outer membrane and activating caspases as well as sensitizing the HCC cell to apoptosis induced by TRAIL and ASH treatment.

Mesenchymal Stem Cell Expressing TRAIL as Targeted Therapy against Sensitised Tumour

Tapping into the ability of engineered mesenchymal stem cells (MSCs) to mobilise into the tumour has expanded the scope of cancer treatment. Engineered MSCs expressing tumour necrosis factor (TNF)-related apoptosis inducing ligand (MSC-TRAIL) could serve as a platform for an efficient and targeted form of therapy. However, the presence of cancer stem cells (CSCs) that are resistant to TRAIL and apoptosis may represent a challenge for effective treatment. Nonetheless, with the discovery of small molecular inhibitors that could target CSCs and tumour signalling pathways, a higher efficacy of MSC-TRAIL mediated tumour inhibition can be achieved. This might pave the way for a more effective form of combined therapy, which leads to a better treatment outcome. In this review, we first discuss the tumour-homing capacity of MSCs, its effect in tumour tropism, the different approach behind genetically-engineered MSCs, and the efficacy and safety of each agent delivered by these MSCs. Then, we focus on how sensitisation of CSCs and tumours using small molecular inhibitors can increase the effect of these cells to either TRAIL or MSC-TRAIL mediated inhibition. In the conclusion, we address a few questions and safety concerns regarding the utilization of engineered MSCs for future treatment in patients.

Icaritin Sensitizes Human Glioblastoma Cells to TRAIL-Induced Apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been considered to be one of the most promising candidates in research on treatments for cancer, because it induces apoptosis in a wide variety of cancer cells but not in most normal human cell types. However, many cells including glioblastoma (GBM) cells are resistant to TRAIL-induced apoptosis, which limits the potential application of TRAIL in cancer therapy. Icaritin, a hydrolytic product of icariin from Epimedium Genus, has been identified as a potential therapeutic and preventive agent in renal cell carcinoma and breast cancer. In this study, we investigated whether Icaritin treatment could modulate TRAIL-induced apoptosis in GBM. The effect of icaritin on TRAIL sensitivity was assessed in human GBM U87 and U373 cells. The underlying regulatory cascades were approached by biochemical and pharmacological strategies. We found that nontoxic concentration of icaritin alone had no significant effect on the level of apoptosis, but a combination treatment of TRAIL and icaritin caused a significantly more profound apoptosis. The sensitization was accompanied by c-FLIP down-regulation and inhibition of NF-κB activity. Studies have further demonstrated that silencing NF-κB alone was sufficient to down-regulate c-FLIP expression and sensitized both tested cells to TRAIL-induced apoptosis. These data suggest that icaritin sensitizes TRAIL-induced tumor cell apoptosis via suppression of NF-κB-dependent c-FLIP expression, providing in vitro evidence supporting the notion that icaritin is a potential sensitizer of TRAIL in anticancer therapy against human GBM.

Mammalian target of rapamycin inhibitor RAD001 sensitizes endometrial cancer cells to paclitaxel-induced apoptosis via the induction of autophagy

The aim of the present study was to investigate the effects of the mammalian target of rapamycin (mTOR) inhibitor, RAD001, on the growth of human endometrial cancer cells. The effects of RAD001 on human endometrial cancer Ishikawa and HEC-1A cell proliferation were determined by MTT assay. Green fluorescent protein microtubule-associated protein 1 light chain 3α (GFP-LC3) protein aggregates were observed under a confocal microscope, and Ishikawa and HEC-1A cell apoptosis was detected using flow cytometry. The expression levels of LC3-I, LC3-II and mTOR proteins were detected by western blot analysis. The results showed that RAD001 effectively inhibited human endometrial cancer Ishikawa and HEC-1A cell proliferation via downregulation of AKT/mTOR phosphorylation. Moreover, RAD001 induced autophagic cell death and a higher sensitivity to paclitaxel-induced apoptosis. These results indicate that RAD001 could have therapeutic potential in human endometrial cancer with hyperactivated AKT/mTOR signaling.

Shogaol overcomes TRAIL resistance in colon cancer cells via inhibiting of survivin

In this study, we showed the ability of representative shogaol, which as a major component of ginger, to overcome TRAIL resistance by increasing apoptosis in colon cancer cells. Shogaol increased death receptor 5 (DR5) levels. Furthermore, shogaol decreased the expression level of antiapoptotic proteins (survivin and Bcl-2) and increased pro-apoptotic protein, Bax. Shogaol treatment induced apoptosis and a robust reduction in the levels of the antiapoptotic protein survivin but did not affect the levels of many other apoptosis regulators. Moreover, knockdown of survivin sensitized colon cancer cells to resistant of TRAIL-induced apoptosis. Therefore, we showed the functions of shogaol as a sensitizing agent to induce cell death of TRAIL-resistant colon cancer cells. This study gives rise to the possibility of applying shogaol as an antitumor agent that can be used for the purpose of combination treatment with TRAIL in TRAIL-resistant colon tumor therapy.

Gingerol sensitizes TRAIL-induced apoptotic cell death of glioblastoma cells

Glioblastoma multiforme (GBM) is the most lethal and aggressive astrocytoma of primary brain tumors in adults. Although there are many clinical trials to induce the cell death of glioblastoma cells, most glioblastoma cells have been reported to be resistant to TRAIL-induced apoptosis. Here, we showed that gingerol as a major component of ginger can induce TRAIL-mediated apoptosis of glioblastoma. Gingerol increased death receptor (DR) 5 levels in a p53-dependent manner. Furthermore, gingerol decreased the expression level of anti-apoptotic proteins (survivin, c-FLIP, Bcl-2, and XIAP) and increased pro-apoptotic protein, Bax and truncate Bid, by generating reactive oxygen species (ROS). We also found that the sensitizing effects of gingerol in TRAIL-induced cell death were blocked by scavenging ROS or overexpressing anti-apoptotic protein (Bcl-2). Therefore, we showed the functions of gingerol as a sensitizing agent to induce cell death of TRAIL-resistant glioblastoma cells. This study gives rise to the possibility of applying gingerol as an anti-tumor agent that can be used for the purpose of combination treatment with TRAIL in TRAIL-resistant glioblastoma tumor therapy.

Targeted induction of apoptosis in glioblastoma multiforme cells by an MRP3-specific TRAIL fusion protein in vitro

Single-chain Fv fragments (scFvs) consist of the variable heavy-chain (VH) and variable light-chain (VL) domains, which are the smallest immunoglobulin fragments containing the whole antigen-binding site. Human soluble tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) proves to acquire a potent pro-apoptotic activity only after selective binding to a predefined tumor cell surface antigen and has no off-target effects towards normal cells. Glioblastoma multiforme (GBM) is the most frequent and aggressive type of brain tumor and overexpresses human multidrug resistance protein 3 (MRP3). In this study, we designed a novel fusion protein, termed scFvM58-sTRAIL, in which the MRP3-specific scFv antibody M58 was genetically fused to the N-terminus of human soluble TRAIL (sTRAIL). The recombinant scFvM58-sTRAIL fusion protein, expressed in Escherichia coli, was purified by chromatography and tested for cytotoxicity. scFvM58-sTRAIL showed a significant apoptosis-inducing activity towards MRP3-positive GBM cells in vitro. The pro-apoptotic activity of scFvM58-sTRAIL towards GBM cells was strongly inhibited in the presence of the parental scFvM58 antibody, suggesting that cytotoxic activity is MRP3-restricted. In a control experiment with MRP3-negative Jurkat cells, scFvM58-sTRAIL did not induce apparent apoptosis. In addition, through target antigen-restricted binding, scFvM58-sTRAIL was capable of activating not only TRAIL-R1 but also TRAIL-R2. In conclusion, our results suggest that fusion protein scFvM58-sTRAIL with specificity for MRP3 is a highly selective therapeutic agent and may provide an alternative therapy for human GBM.

Saquinavir-NO-targeted S6 protein mediates sensitivity of androgen-dependent prostate cancer cells to TRAIL

We previously reported that the NO-modified form of HIV protease inhibitor Saquinavir (Saq) is a potent antitumoral agent efficient against numerous tumor cell lines in vitro and in vivo. In acute toxicity studies, doses of Saq-NO equivalent to DL100 of the parental drug were completely nontoxic. Beside direct effect on malignant cell growth, Saq-NO sensitizes certain type of cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated cell death. In this study, we evaluated the effects of Saq-NO on androgen-dependent prostate cancer LNCaP. Saq-NO inhibited both the growth of LNCaP cells in vitro and in xenograft models. Suppression of tumor growth was accompanied with cell cycle arrest in G 0/G 1 phase and established a persistent inhibition of proliferation. Furthermore, Saq-NO reverted sensitivity of LNCaP cells to TRAIL but not to TNF. Treatment of cells with Saq-NO induced transient upregulation of Akt and ERK1/2. This, however, did not represent the primary mode of action of Saq-NO, as elimination with specific inhibitors did not compromise the chemotherapic efficacy of the drug. However, permanent abrogation of phosphorylation of the S6 protein, which is the downstream target of both signaling pathways, was observed. Diminished S6 phosphorylation was associated with re-established sensitivity to TRAIL and reduction of X-linked inhibitor of apoptosis protein (XIAP). In summary, NO modification of Saq led to a new chemical entity with stronger and more pleiotropic antitumor activity than the parental drug.

Lanatoside C sensitizes glioblastoma cells to tumor necrosis factor-related apoptosis-inducing ligand and induces an alternative cell death pathway

Human glioblastoma (GBM) cells are notorious for their resistance to apoptosis-inducing therapeutics. We have identified lanatoside C as a sensitizer of GBM cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced cell death partly by upregulation of the death receptor 5. We show that lanatoside C sensitizes GBM cells to TRAIL-induced apoptosis in a GBM xenograft model in vivo. Lanatoside C on its own serves as a therapeutic agent against GBM by activating a caspase-independent cell death pathway. Cells treated with lanatoside C showed necrotic cell morphology with absence of caspase activation, low mitochondrial membrane potential, and early intracellular ATP depletion. In conclusion, lanatoside C sensitizes GBM cells to TRAIL-induced cell death and mitigates apoptosis resistance of glioblastoma cells by inducing an alternative cell death pathway. To our knowledge, this is one of the first examples of use of caspase-independent cell death inducers to trigger tumor regression in vivo. Activation of such mechanism may be a useful strategy to counter resistance of cancer cells to apoptosis.

Cell surface delivery of TRAIL strongly augments the tumoricidal activity of T cells

PURPOSE

Adoptive T-cell therapy generally fails to induce meaningful anticancer responses in patients with solid tumors. Here, we present a novel strategy designed to selectively enhance the tumoricidal activity of T cells by targeted delivery of TNF-related apoptosis-inducing ligand (TRAIL) to the T-cell surface.

EXPERIMENTAL DESIGN

We constructed two recombinant fusion proteins, anti-CD3:TRAIL and K12:TRAIL. Tumoricidal activity of T cells in the presence of these fusion proteins was assessed in solid tumor cell lines, primary patient-derived malignant cells, and in a murine xenograft model.

RESULTS

When added to T cells, K12:TRAIL and anti-CD3:TRAIL selectively bind to the T-cell surface antigens CD3 and CD7, respectively, leading to cell surface accretion of TRAIL. Subsequently, anti-CD3:TRAIL and K12:TRAIL increased the tumoricidal activity of T cells toward cancer cell lines and primary patient-derived malignant cells by more than 500-fold. Furthermore, T-cell surface delivery of TRAIL strongly inhibited tumor growth and increased survival time of xenografted mice more than 6-fold.

CONCLUSIONS

Targeted delivery of TRAIL to cell surface antigens of T cells potently enhances the tumoricidal activity of T cells. This approach may be generally applicable to enhance the efficacy of adoptive T-cell therapy.

PI3Kinase signaling in glioblastoma

Glioblastoma (GBM) is the most common primary tumor of the CNS in the adult. It is characterized by exponential growth and diffuse invasiveness. Among many different genetic alterations in GBM, e.g., mutations of PTEN, EGFR, p16/p19 and p53 and their impact on aberrant signaling have been thoroughly characterized. A major barrier to develop a common therapeutic strategy is founded on the fact that each tumor has its individual genetic fingerprint. Nonetheless, the PI3K pathway may represent a common therapeutic target to most GBM due to its central position in the signaling cascade affecting proliferation, apoptosis and migration. The read-out of blocking PI3K alone or in combination with other cancer pathways should mainly focus, besides the cytostatic effect, on cell death induction since sublethal damage may induce selection of more malignant clones. Targeting more than one pathway instead of a single agent approach may be more promising to kill GBM cells.

Survival signalling and apoptosis resistance in glioblastomas: opportunities for targeted therapeutics

Glioblastoma multiforme (GBM) is the most common primary brain tumour in adults and one of the most aggressive cancers in man. Despite technological advances in surgical management, combined regimens of radiotherapy with new generation chemotherapy, the median survival for these patients is 14.6 months. This is largely due to a highly deregulated tumour genome with opportunistic deletion of tumour suppressor genes, amplification and/or mutational hyper-activation of receptor tyrosine kinase receptors. The net result of these genetic changes is augmented survival pathways and systematic defects in the apoptosis signalling machinery. The only randomised, controlled phase II trial conducted targeting the epidermal growth factor receptor (EGFR) signalling with the small molecule inhibitor, erlotinib, has showed no therapeutic benefit. Survival signalling and apoptosis resistance in GBMs can be viewed as two sides of the same coin. Targeting increased survival is unlikely to be efficacious without at the same time targeting apoptosis resistance. We have critically reviewed the literature regarding survival and apoptosis signalling in GBM, and highlighted experimental, preclinical and recent clinical trials attempting to target these pathways. Combined therapies simultaneously targeting apoptosis and survival signalling defects might shift the balance from tumour growth stasis to cytotoxic therapeutic responses that might be associated with greater therapeutic benefits.

Review: on TRAIL for malignant glioma therapy?

Glioblastoma (GBM) is a devastating cancer with a median survival of around 15 months. Significant advances in treatment have not been achieved yet, even with a host of new therapeutics under investigation. Therefore, the quest for a cure for GBM remains as intense as ever. Of particular interest for GBM therapy is the selective induction of apoptosis using the pro-apoptotic tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL signals apoptosis via its two agonistic receptors TRAIL-R1 and TRAIL-R2. TRAIL is normally present as homotrimeric transmembrane protein, but can also be processed into a soluble trimeric form (sTRAIL). Recombinant sTRAIL has strong tumouricidal activity towards GBM cells, with no or minimal toxicity towards normal human cells. Unfortunately, GBM is a very heterogeneous tumour, with multiple genetically aberrant clones within one tumour. Consequently, any single agent therapy is likely to be not effective enough. However, the anti-GBM activity of TRAIL can be synergistically enhanced by a variety of conventional and novel targeted therapies, making TRAIL an ideal candidate for combinatorial strategies. Here we will, after briefly detailing the biology of TRAIL/TRAIL receptor signalling, focus on the promises and pitfalls of recombinant TRAIL as a therapeutic agent alone and in combinatorial therapeutic approaches for GBM.

Emerging therapies for malignant glioma

The current standard of care for malignant gliomas consists of surgery, radiotherapy and conventional (DNA-damaging) chemotherapies. These treatments are relatively nonspecific and may be applied to all glioma subtypes. Developments in cancer medicine, however, now offer the opportunity to direct therapies to specific molecular pathways involved in tumorigenesis. This offers the potential to tailor treatments to tumor subtypes--perhaps with greater efficacy and less toxicity. Many of the so-called targeted therapies are under investigation in the treatment of malignant glioma. In this review, we will focus on the use of agents that affect signal transduction. In particular, we will review the potential role for inhibitors of: tyrosine kinases, targets of rapamycin, farnesyl transferase and histone deacetylase. Inhibitors of angiogenesis will also be discussed. Some 'targeted' therapies are less specific than others, working on more than one pathway or receptor, thus complex interactions are possible.

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.

Heat shock protein 90alpha recruits FLIPS to the death-inducing signaling complex and contributes to TRAIL resistance in human glioma

Heat shock protein 90 (HSP90) is a molecular chaperone that contributes to the proper folding and stability of target proteins. Because HSP90 has been suggested to interact with FLIP(S), the key regulator of tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in glioma cells, we examined the role HSP90 played in controlling TRAIL response. HSP90alpha was found to associate with FLIP(S) in resting cells in a manner dependent on the ATP-binding NH2-terminal domain of HSP90alpha. Following TRAIL exposure, HSP90alpha and the client FLIP(S) protein were recruited to the death-inducing signaling complex (DISC). Short interfering RNA-mediated suppression of HSP90alpha did not alter the total cellular levels of FLIP(S), but rather inhibited the recruitment of FLIP(S) and other antiapoptotic proteins such as RIP and FLIP(L) to the DISC, and sensitized otherwise resistant glioma cells to TRAIL-induced apoptosis. These results show that HSP90alpha, by localizing FLIP(S) to the DISC, plays a key role in the resistance of tumor cells to TRAIL, and perhaps other proapoptotic agents. The results also define a novel means of apoptotic control by a HSP90alpha that may in turn help explain the global antiapoptotic effects of this protein.