Inhibition of autophagy and induction of glioblastoma cell death by NEO214, a perillyl alcohol-rolipram conjugate

Glioblastoma (GBM) is the most aggressive primary brain tumor, exhibiting a high rate of recurrence and poor prognosis. Surgery and chemoradiation with temozolomide (TMZ) represent the standard of care, but, in most cases, the tumor develops resistance to further treatment and the patients succumb to disease. Therefore, there is a great need for the development of well-tolerated, effective drugs that specifically target chemoresistant gliomas. NEO214 was generated by covalently conjugating rolipram, a PDE4 (phosphodiesterase 4) inhibitor, to perillyl alcohol, a naturally occurring monoterpene related to limonene. Our previous studies in preclinical models showed that NEO214 harbors anticancer activity, is able to cross the blood-brain barrier (BBB), and is remarkably well tolerated. In the present study, we investigated its mechanism of action and discovered inhibition of macroautophagy/autophagy as a key component of its anticancer effect in glioblastoma cells. We show that NEO214 prevents autophagy-lysosome fusion, thereby blocking autophagic flux and triggering glioma cell death. This process involves activation of MTOR (mechanistic target of rapamycin kinase) activity, which leads to cytoplasmic accumulation of TFEB (transcription factor EB), a critical regulator of genes involved in the autophagy-lysosomal pathway, and consequently reduced expression of autophagy-lysosome genes. When combined with chloroquine and TMZ, the anticancer impact of NEO214 is further potentiated and unfolds against TMZ-resistant cells as well. Taken together, our findings characterize NEO214 as a novel autophagy inhibitor that could become useful for overcoming chemoresistance in glioblastoma.Abbreviations: ATG: autophagy related; BAFA1: bafilomycin A1; BBB: blood brain barrier; CQ: chloroquine; GBM: glioblastoma; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MGMT: O-6-methylguanine-DNA methyltransferase; MTOR: mechanistic target of rapamycin kinase; MTORC: MTOR complex; POH: perillyl alcohol; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TMZ: temozolomide.

NEO100 enables brain delivery of blood‒brain barrier impermeable therapeutics

BACKGROUND

Intracarotid injection of mannitol has been applied for decades to support brain entry of therapeutics that otherwise do not effectively cross the blood-brain barrier (BBB). However, the elaborate and high-risk nature of this procedure has kept its use restricted to well-equipped medical centers. We are developing a more straightforward approach to safely open the BBB, based on the intra-arterial (IA) injection of NEO100, a highly purified version of the natural monoterpene perillyl alcohol.

METHODS

In vitro barrier permeability with NEO100 was evaluated by transepithelial/transendothelial electrical resistance and antibody diffusion assays. Its mechanism of action was studied by western blot, microarray analysis, and electron microscopy. In mouse models, we performed ultrasound-guided intracardiac administration of NEO100, followed by intravenous application of Evan's blue, methotrexate, checkpoint-inhibitory antibodies, or chimeric antigen receptor (CAR) T cells.

RESULTS

NEO100 opened the BBB in a reversible and nontoxic fashion in vitro and in vivo. It enabled greatly increased brain entry of all tested therapeutics and was well tolerated by animals. Mechanistic studies revealed effects of NEO100 on different BBB transport pathways, along with translocation of tight junction proteins from the membrane to the cytoplasm in brain endothelial cells.

CONCLUSION

We envision that this procedure can be translated to patients in the form of transfemoral arterial catheterization and cannulation to the cerebral arteries, which represents a low-risk procedure commonly used in a variety of clinical settings. Combined with NEO100, it is expected to provide a safe, widely available approach to enhance brain entry of any therapeutic.

Development of immune memory to glial brain tumors after tumor regression induced by immunotherapeutic Toll-like receptor 7/8 activation

The efficacy of immunotherapeutic TLR7/8 activation by resiquimod (R848) was evaluated in vivo, in the CNS-1 rat glioma model syngeneic to Lewis rats. The immune treatment was compared with cytotoxic cyclophosphamide chemotherapy, and as well, was compared with the combination cytotoxic and immunotherapeutic treatments. We found that parenteral treatment with the TLR7/8 agonist, resiquimod, eventually induced complete tumor regression of CNS-1 glioblastoma tumors in Lewis rats. Cyclophosphamide (CY) treatment also resulted in dramatic CNS-1 remission, while the combined treatment showed similar antitumor effects. The resiquimod efficacy appeared not to be associated with direct injury to CNS-1 growth, while CY proved to exert tumoricidal cytotoxicity to the tumor cells. Rats that were cured by treatment with the innate immune response modifier resiquimod proved to be fully immune to secondary CNS-1 tumor rechallenge. They all remained tumor-free and survived. In contrast, rats that controlled CNS-1 tumor growth as a result of CY treatment did not develop immune memory, as demonstrated by their failure to reject a secondary CNS-1 tumor challenge; they showed a concomittant outgrowth of the primary tumor upon secondary tumor exposure. Rechallenge of rats that initially contained tumor growth by combination chemo-immunotherapy also failed to reject secondary tumor challenge, indicating that the cytotoxic effect of the CY likely extended to the endogenous memory immune cells as well as to the tumor. These data demonstrate strong therapeutic antitumor efficacy for the immune response modifier resiquimod leading to immunological memory, and suggest that CY treatment, although effective as chemotherapeutic agent, may be deleterious to maintenance of long-term antitumor immune memory. These data also highlight the importance of the sequence in which a multi-modal therapy is administered.

Pharmacokinetic properties of the temozolomide perillyl alcohol conjugate (NEO212) in mice

Background

NEO212 is a novel small-molecule anticancer agent that was generated by covalent conjugation of the natural monoterpene perillyl alcohol (POH) to the alkylating agent temozolomide (TMZ). It is undergoing preclinical development as a therapeutic for brain-localized malignancies. The aim of this study was to characterize metabolism and pharmacokinetic (PK) properties of NEO212 in preclinical models.

Methods

We used mass spectrometry (MS) and modified high-performance liquid chromatography to identify and quantitate NEO212 and its metabolites in cultured glioblastoma cells, in mouse plasma, brain, and excreta after oral gavage.

Results

Our methods allowed identification and quantitation of NEO212, POH, TMZ, as well as primary metabolites 5-aminoimidazole-4-carboxamide (AIC) and perillic acid (PA). Intracellular concentrations of TMZ were greater after treatment of U251TR cells with NEO212 than after treatment with TMZ. The half-life of NEO212 in mouse plasma was 94 min. In mice harboring syngeneic GL261 brain tumors, the amount of NEO212 was greater in the tumor-bearing hemisphere than in the contralateral normal hemisphere. The brain:plasma ratio of NEO212 was greater than that of TMZ. Excretion of unaltered NEO212 was through feces, whereas its AIC metabolite was excreted via urine.

Conclusions

NEO212 preferentially concentrates in brain tumor tissue over normal brain tissue, and compared to TMZ has a higher brain:plasma ratio, altogether revealing favorable features to encourage its further development as a brain-targeted therapeutic. Its breakdown into well-characterized, long-lived metabolites, in particular AIC and PA, will provide useful equivalents for PK studies during further drug development and clinical trials with NEO212.

Developing a clinically relevant radiosensitizer for temozolomide-resistant gliomas

The prognosis for patients with glioblastoma (GB) remains grim. Concurrent temozolomide (TMZ) radiation—the cornerstone of glioma control—extends the overall median survival of GB patients by only a few months over radiotherapy alone. While these survival gains could be partly attributed to radiosensitization, this benefit is greatly minimized in tumors expressing O⁶-methylguanine DNA methyltransferase (MGMT), which specifically reverses O⁶-methylguanine lesions. Theoretically, non-O⁶-methylguanine lesions (i.e., the N-methylpurine adducts), which represent up to 90% of TMZ-generated DNA adducts, could also contribute to radiosensitization. Unfortunately, at concentrations attainable in clinical practice, the alkylation capacity of TMZ cannot overwhelm the repair of N-methylpurine adducts to efficiently exploit these lesions. The current therapeutic application of TMZ therefore faces two main obstacles: (i) the stochastic presence of MGMT and (ii) a blunted radiosensitization potential at physiologic concentrations. To circumvent these limitations, we are developing a novel molecule called NEO212—a derivatization of TMZ generated by coupling TMZ to perillyl alcohol. Based on gas chromatography/mass spectrometry and high-performance liquid chromatography analyses, we determined that NEO212 had greater tumor cell uptake than TMZ. In mouse models, NEO212 was more efficient than TMZ at crossing the blood-brain barrier, preferentially accumulating in tumoral over normal brain tissue. Moreover, in vitro analyses with GB cell lines, including TMZ-resistant isogenic variants, revealed more potent cytotoxic and radiosensitizing activities for NEO212 at physiologic concentrations. Mechanistically, these advantages of NEO212 over TMZ could be attributed to its enhanced tumor uptake presumably leading to more extensive DNA alkylation at equivalent dosages which, ultimately, allows for N-methylpurine lesions to be better exploited for radiosensitization. This effect cannot be achieved with TMZ at clinically relevant concentrations and is independent of MGMT. Our findings establish NEO212 as a superior radiosensitizer and a potentially better alternative to TMZ for newly diagnosed GB patients, irrespective of their MGMT status.

miR-18a Inhibits BMP4 and HIF-1α Normalizing Brain Arteriovenous Malformations

RATIONALE

Brain arteriovenous malformations (AVMs) are abnormal tangles of vessels where arteries and veins directly connect without intervening capillary nets, increasing the risk of intracerebral hemorrhage and stroke. Current treatments are highly invasive and often not feasible. Thus, effective noninvasive treatments are needed. We previously showed that AVM-brain endothelial cells (BECs) secreted higher VEGF (vascular endothelial growth factor) and lower TSP-1 (thrombospondin-1) levels than control BEC; and that microRNA-18a (miR-18a) normalized AVM-BEC function and phenotype, although its mechanism remained unclear.

OBJECTIVE

To elucidate the mechanism of action and potential clinical application of miR-18a as an effective noninvasive treatment to selectively restore the phenotype and functionality of AVM vasculature.

METHODS AND RESULTS

The molecular pathways affected by miR-18a in patient-derived BECs and AVM-BECs were determined by Western blot, RT-qPCR (quantitative reverse transcription polymerase chain reaction), ELISA, co-IP, immunostaining, knockdown and overexpression studies, flow cytometry, and luciferase reporter assays. miR-18a was shown to increase TSP-1 and decrease VEGF by reducing PAI-1 (plasminogen activator inhibitor-1/SERPINE1) levels. Furthermore, miR-18a decreased the expression of BMP4 (bone morphogenetic protein 4) and HIF-1α (hypoxia-inducible factor 1α), blocking the BMP4/ALK (activin-like kinase) 2/ALK1/ALK5 and Notch signaling pathways. As determined by Boyden chamber assays, miR-18a also reduced the abnormal AVM-BEC invasiveness, which correlated with a decrease in MMP2 (matrix metalloproteinase 2), MMP9, and ADAM10 (ADAM metallopeptidase domain 10) levels. In vivo pharmacokinetic studies showed that miR-18a reaches the brain following intravenous and intranasal administration. Intranasal co-delivery of miR-18a and NEO100, a good manufacturing practices-quality form of perillyl alcohol, improved the pharmacokinetic profile of miR-18a in the brain without affecting its pharmacological properties. Ultra-high-resolution computed tomography angiography and immunostaining studies in an Mgp^-/- AVM mouse model showed that miR-18a decreased abnormal cerebral vasculature and restored the functionality of the bone marrow, lungs, spleen, and liver.

CONCLUSIONS

miR-18a may have significant clinical value in preventing, reducing, and potentially reversing AVM.

Intravenous delivery of microRNA-133b along with Argonaute-2 enhances spinal cord recovery following cervical contusion in mice

BACKGROUND CONTEXT

Acute spinal cord injury (SCI) is a devastating condition for which spine decompression and stabilization of injury remains the only therapy available in the clinical setup. However, fibrous scar formation during the healing process significantly impairs full recovery. MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression by binding to target mRNA(s) and initiating translational repression or mRNA degradation. It has been reported that microRNA-133b (miR133b) is highly expressed in regenerating neurons following a SCI in zebrafish, and lentiviral delivery of miR133b at the time of SCI in mice resulted in improved functional recovery.

PURPOSE

The aim of this study was to investigate whether intravenous delivery of miR133b enhances spinal cord recovery when administered 24 hours following a cervical contusion injury in mice.

STUDY DESIGN

This is an experimental animal study of acute SCI, investigating the effect of miR133b on spinal cord recovery by targeting scar lesion formation. The approach involved setting an acute SCI in mice, which was followed 24 hours later by intravenous co-delivery of miR133b and Argonaute 2 (Ago2), a protein involved in miRNA stabilization. Readouts of the impact of this intervention included analysis of RNA and protein expression at the lesion site, in particular with regard to markers of scar tissue formation, and determination of motor function recovery by the grip strength meter task.

METHODS

C57BL6 female mice between 6 and 8 weeks of age were tested. The injury model employed was a unilateral moderate contusion at the cervical fifth level. Twenty-four hours following the injury, the authors co-delivered miR133b, or scrambled miRNA as negative control, along with Ago2 for 3 consecutive days, one dose per day via tail-vein injection. They first investigated the level of miR133b in the spinal cord and in spinal cord lesion after a single dose of injection. Next, they determined the efficacy of miR133b and/or Ago2 delivery in regulating gene and protein expression at the lesion site. Finally, they established the role of miR133b and/or Ago2 in enhancing forelimb gripping recovery as assessed by the grip strength meter task for 8 weeks post-SCI.

RESULTS

Intravenous delivery of miR133b and/or Ago2 targeted the microenvironment at the lesion site and prevented the increased expression of certain extracellular matrix proteins (ECM), in particular collagen type 1 alpha 1 and tenascin N, which are known to have a key role in scar formation. It also reduced microglia and/or macrophage recruitment to the lesion site. Functional recovery in mice treated with miR133b and/or Ago2 started around 2 weeks postinjury and continued to improve over time, whereas mice in the control group displayed significantly poorer recovery.

CONCLUSIONS

Our data indicate therapeutic activity of intravenous miR133b and/or Ago2 treatment, possibly via decreasing ECM protein expression and macrophage recruitment at the lesion site, thereby minimizing detrimental fibrous scar formation.

CLINICAL SIGNIFICANCE

There is an urgent medical need for better treatments of SCIs. Based on our findings in a preclinical model, the miR133b and/or Ago2 system specifically targets fibrous scar formation, a barrier in neuronal regrowth, by remodeling ECM molecules at the injury site. Prevention of scar formation is critical to improved outcomes of treatment. Of note, delivery of miR133b and/or Ago2 was initiated 24 hours after traumatic impact, thus indicating a fairly long window of opportunity providing more time and flexibility for therapeutic intervention. Intravenous miR133b may become a beneficial therapeutic strategy to treat patients with acute SCI.

Efficient brain targeting and therapeutic intracranial activity of bortezomib through intranasal co-delivery with NEO100 in rodent glioblastoma models

OBJECTIVE

Many pharmaceutical agents are highly potent but are unable to exert therapeutic activity against disorders of the central nervous system (CNS), because the blood-brain barrier (BBB) impedes their brain entry. One such agent is bortezomib (BZM), a proteasome inhibitor that is approved for the treatment of multiple myeloma. Preclinical studies established that BZM can be effective against glioblastoma (GBM), but only when the drug is delivered via catheter directly into the brain lesion, not after intravenous systemic delivery. The authors therefore explored alternative options of BZM delivery to the brain that would avoid invasive procedures and minimize systemic exposure.

METHODS

Using mouse and rat GBM models, the authors applied intranasal drug delivery, where they co-administered BZM together with NEO100, a highly purified, GMP-manufactured version of perillyl alcohol that is used in clinical trials for intranasal therapy of GBM patients.

RESULTS

The authors found that intranasal delivery of BZM combined with NEO100 significantly prolonged survival of tumor-bearing animals over those that received vehicle alone and also over those that received BZM alone or NEO100 alone. Moreover, BZM concentrations in the brain were higher after intranasal co-delivery with NEO100 as compared to delivery in the absence of NEO100.

CONCLUSIONS

This study demonstrates that intranasal delivery with a NEO100-based formulation enables noninvasive, therapeutically effective brain delivery of a pharmaceutical agent that otherwise does not efficiently cross the BBB.

Inhibition of motility by NEO100 through the calpain-1/RhoA pathway

OBJECTIVE

Glioblastoma (GBM) is the most aggressive type of brain tumor with a high rate of tumor recurrence, and it often develops resistance over time to current standard of care chemotherapy. Its highly invasive nature plays an essential role in tumor progression and recurrence. Glioma stem cells (GSCs) are a subpopulation of glioma cells highly resistant to treatments and are considered responsible for tumor recurrence.

METHODS

Patient-derived populations of GSCs were analyzed by western blot, MTT, and cytoplasmic calcium labeling to determine the cytotoxicity of NEO100. High-performance liquid chromatography was used to evaluate the levels of NEO100 in the cell culture supernatants. The effects of the compound on GSC motility were studied using Boyden chamber migration, 3D spheroid migration and invasion assays, and an mRNA expression PCR array. A RhoA activation assay, western blot, and immunofluorescence techniques were employed to confirm the signaling pathways involved. Intracranial implantation of GSCs in athymic mice was used to evaluate the effects of NEO100 in vivo on tumor progression and overall survival.

RESULTS

Here, the authors show how NEO100, a highly purified good manufacturing practices-quality form of perillyl alcohol, is cytotoxic for different subtypes of GSCs, regardless of the mechanisms of DNA repair present. At doses similar to the IC50 (half maximal inhibitory concentration) values, NEO100 induces ER stress and activates apoptotic pathways in all GSC populations tested. At subcytotoxic doses in the micromolar range, NEO100 blocks migration and invasion of GSCs. These results correlate with a decrease in calpain-1 expression and an increase in RhoA activation, leading to enhanced contractility of the GSCs. In addition, NEO100 blocks the activation of the kinases Src, p42/44 MAPK, Akt, and Stat3, all related to cell proliferation and migration. Intranasal administration of NEO100 in mice with GSC-derived intracranial tumors led to a decrease in tumor progression and a 32% increase in overall survival. Immunostaining studies showed that NEO100 induces apoptosis and reduces GSC invasion in vivo.

CONCLUSIONS

NEO100 could have significant value targeting GSCs and could be used for GBM therapy as either monotherapy or a coadjuvant therapy during temozolomide rest cycles.

The Rolipram-Perillyl Alcohol Conjugate (NEO214) Is A Mediator of Cell Death through the Death Receptor Pathway

Glioblastoma (GBM) is a highly aggressive primary brain tumor with a poor prognosis. Treatment with temozolomide, standard of care for gliomas, usually results in drug resistance and tumor recurrence. Therefore, there is a great need for drugs that target GBM. NEO214 was generated by covalently linking rolipram to perillyl alcohol (POH) via a carbamate bond to form the rolipram-perillyl alcohol conjugate. We show here that NEO214 is effective against both temozolomide-sensitive and temozolomide-resistant glioma cells. Furthermore, NEO214 is effective for different mechanisms of temozolomide resistance: overexpression of MGMT (O⁶-methylguanine methyl-transferase); deficiency in specific mismatch repair proteins; and overexpression of base excision repair (BER) proteins. NEO214-induced cytotoxicity involves apoptosis triggered by endoplasmic reticulum (ER) stress, as well as activating the Death Receptor 5 (DR5)/TNF-related apoptosis-inducing ligand (TRAIL/Apo2L) pathway. In vitro studies show that glioma cells treated with NEO214 express DR5 and exhibit cell death in the presence of recombinant TRAIL, a growth factor constitutively produced by astrocytes. Our in vitro 3D coculture data show that induction of DR5 in glioma cells with NEO214 and TRAIL cause tumor cell death very effectively and specifically for glioma cells. In vivo studies show that NEO214 has antitumor efficacy in orthotropic syngeneic rodent tumor models. Furthermore, NEO214 has therapeutic potential especially for brain tumors because this drug can cross the blood-brain barrier (BBB), and is effective in the TRAIL-rich astrocyte microenvironment. NEO214 is a strong candidate for use in the treatment of GBMs.

NEO212, a conjugate of temozolomide and perillyl alcohol, blocks the endothelial-to-mesenchymal transition in tumor-associated brain endothelial cells in glioblastoma

As the endothelial-to-mesenchymal transition (EndMT) supports the pro-angiogenic and invasive characteristics of glioblastoma multiforme (GBM), blocking this process would be a promising approach to inhibit tumor progression and recurrence. Here, we demonstrate that glioma stem cells (GSC) induce EndMT in brain endothelial cells (BEC). TGF-β signaling is necessary, but not sufficient to induce this EndMT process. Cell-to-cell contact and the contribution of Notch signaling are also required. NEO212, a conjugate of temozolomide and perillyl alcohol, blocks EndMT induction and reverts the mesenchymal phenotype of tumor-associated BEC (TuBEC) by blocking TGF-β and Notch pathways. Consequently, NEO212 reduces the invasiveness and pro-angiogenic properties associated with TuBEC, without affecting control BEC. Intracranial co-implantation of BEC and GSC in athymic mice showed that EndMT occurs in vivo, and can be blocked by NEO212, supporting the potential clinical value of NEO212 for the treatment of GBM.

Phase II study of ERC1671 plus bevacizumab versus bevacizumab plus placebo in recurrent glioblastoma: interim results and correlations with CD4+ T-lymphocyte counts

Aim:

ERC1671 is an allogeneic/autologous therapeutic glioblastoma (GBM) vaccine – composed of whole, inactivated tumor cells mixed with tumor cell lysates derived from the patient and three GBM donors.

Methods:

In this double-blinded, randomized, Phase II study bevacizumab-naive patients with recurrent GBM were randomized to receive either ERC1671 in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) (Leukine^® or sargramostim) and cyclophosphamide plus bevacizumab, or placebo plus bevacizumab.

Interim results:

Median overall survival (OS) of patients treated with ERC1671 plus bevacizumab was 12 months. In the placebo plus bevacizumab group, median OS was 7.5 months. The maximal CD4⁺ T-lymphocyte count correlated with OS in the ERC1671 but not in the placebo group.

Conclusion:

The addition of ERC1671/GM-CSF/cyclophosphamide to bevacizumab resulted in a clinically meaningful survival benefit with minimal additional toxicity.

NEO212 Inhibits Migration and Invasion of Glioma Stem Cells

Glioblastoma multiforme is a malignant brain tumor noted for its extensive vascularity, aggressiveness, and highly invasive nature, suggesting that cell migration plays an important role in tumor progression. The poor prognosis in GBM is associated with a high rate of tumor recurrence, and resistance to the standard of care chemotherapy, temozolomide (TMZ). The novel compound NEO212, a conjugate of TMZ and perillyl alcohol (POH), has proven to be 10-fold more cytotoxic to glioma stem cells (GSC) than TMZ, and is active against TMZ-resistant tumor cells. In this study, we show that NEO212 decreases migration and invasion of primary cultures of patient-derived GSCs, in both mesenchymal USC02 and proneural USC04 populations. The mechanism by which NEO212 reduces migration and invasion appears to be independent of its DNA alkylating effects, which cause cytotoxicity during the first hours of treatment, and is associated with a decrease in the FAK/Src signaling pathway, an effect not exhibited by TMZ. NEO212 also decreases the production of matrix metalloproteinases MMP2 and MMP9, crucial for GSC invasion. Gene expression analysis of epithelial and mesenchymal markers suggests that NEO212 increases the expression of epithelial-like characteristics, suggesting a reversion of the epithelial-to-mesenchymal transition process. Furthermore, in an in vivo orthotopic glioma model, NEO212 decreases tumor progression by reducing invasion of GSCs, thereby increasing survival time of mice. These studies indicate that NEO212, in addition to cytotoxicity, can effectively reduce migration and invasion in GSCs, thus exhibiting significant clinical value in the reduction of invasion and malignant glioma progression. Mol Cancer Ther; 17(3); 625-37. ©2018 AACR.

Induction of Pro-Apoptotic Endoplasmic Reticulum Stress in Multiple Myeloma Cells by NEO214, Perillyl Alcohol Conjugated to Rolipram

Despite the introduction of new therapies for multiple myeloma (MM), many patients are still dying from this disease and novel treatments are urgently needed. We have designed a novel hybrid molecule, called NEO214, that was generated by covalent conjugation of the natural monoterpene perillyl alcohol (POH), an inducer of endoplasmic reticulum (ER) stress, to rolipram (Rp), an inhibitor of phosphodiesterase-4 (PDE4). Its potential anticancer effects were investigated in a panel of MM cell lines. We found that NEO214 effectively killed MM cells in vitro with a potency that was over an order of magnitude stronger than that of its individual components, either alone or in combination. The cytotoxic mechanism of NEO214 involved severe ER stress and prolonged induction of CCAAT/enhancer-binding protein homologous protein (CHOP), a key pro-apoptotic component of the ER stress response. These effects were prevented by salubrinal, a pharmacologic inhibitor of ER stress, and by CHOP gene knockout. Conversely, combination of NEO214 with bortezomib, a drug in clinical use for patients with MM, resulted in synergistic enhancement of MM cell death. Combination with the adenylate cyclase stimulant forskolin did not enhance NEO214 impact, indicating that cyclic adenosine 3',5'-monophosphate (AMP) pathways might play a lesser role. Our study introduces the novel agent NEO214 as a potent inducer of ER stress with significant anti-MM activity in vitro. It should be further investigated as a potential MM therapy aimed at exploiting this tumor's distinct sensitivity to ER stress.

A perillyl alcohol-conjugated analog of 3-bromopyruvate without cellular uptake dependency on monocarboxylate transporter 1 and with activity in 3-BP-resistant tumor cells

The anticancer agent 3-bromopyruvate (3-BP) is viewed as a glycolytic inhibitor that preferentially kills glycolytic cancer cells through energy depletion. However, its cytotoxic activity is dependent on cellular drug import through transmembrane monocarboxylate transporter 1 (MCT-1), which restricts its anticancer potential to MCT-1-positive tumor cells. We created and characterized an MCT-1-independent analog of 3-BP, called NEO218. NEO218 was synthesized by covalently conjugating 3-BP to perillyl alcohol (POH), a natural monoterpene. The responses of various tumor cell lines to treatment with either compound were characterized in the presence or absence of supplemental pyruvate or antioxidants N-acetyl-cysteine (NAC) and glutathione (GSH). Drug effects on glyceraldehyde 3-phosphate dehydrogenase (GAPDH) enzyme activity were investigated by mass spectrometric analysis. The development of 3-BP resistance was investigated in MCT-1-positive HCT116 colon carcinoma cells in vitro. Our results show that NEO218: (i) pyruvylated GAPDH on all 4 of its cysteine residues and shut down enzymatic activity; (ii) severely lowered cellular ATP content below life-sustaining levels, and (iii) triggered rapid necrosis. Intriguingly, supplemental antioxidants effectively prevented cytotoxic activity of NEO218 as well as 3-BP, but supplemental pyruvate powerfully protected cells only from 3-BP, not from NEO218. Unlike 3-BP, NEO218 exerted its potent cytotoxic activity irrespective of cellular MCT-1 status. Treatment of HCT116 cells with 3-BP resulted in prompt development of resistance, based on the emergence of MCT-1-negative cells. This was not the case with NEO218, and highly 3-BP-resistant cells remained exquisitely sensitive to NEO218. Thus, our study identifies a mechanism by which tumor cells develop rapid resistance to 3-BP, and presents NEO218 as a superior agent not subject to this cellular defense. Furthermore, our results offer alternative interpretations of previously published models on the role of supplemental antioxidants: Rather than quenching reactive oxygen species (ROS), supplemental NAC or GSH directly interact with 3-BP, thereby neutralizing the drug's cytotoxic potential before it can trigger ROS production. Altogether, our study introduces new aspects of the cytotoxic mechanism of 3-BP, and characterizes NEO218 as an analog able to overcome a key cellular defense mechanism towards this drug.

Intratumoral delivery of bortezomib: impact on survival in an intracranial glioma tumor model

OBJECTIVE Glioblastoma (GBM) is the most prevalent and the most aggressive of primary brain tumors. There is currently no effective treatment for this tumor. The proteasome inhibitor bortezomib is effective for a variety of tumors, but not for GBM. The authors' goal was to demonstrate that bortezomib can be effective in the orthotopic GBM murine model if the appropriate method of drug delivery is used. In this study the Alzet mini-osmotic pump was used to bring the drug directly to the tumor in the brain, circumventing the blood-brain barrier; thus making bortezomib an effective treatment for GBM. METHODS The 2 human glioma cell lines, U87 and U251, were labeled with luciferase and used in the subcutaneous and intracranial in vivo tumor models. Glioma cells were implanted subcutaneously into the right flank, or intracranially into the frontal cortex of athymic nude mice. Mice bearing intracranial glioma tumors were implanted with an Alzet mini-osmotic pump containing different doses of bortezomib. The Alzet pumps were introduced directly into the tumor bed in the brain. Survival was documented for mice with intracranial tumors. RESULTS Glioma cells were sensitive to bortezomib at nanomolar quantities in vitro. In the subcutaneous in vivo xenograft tumor model, bortezomib given intravenously was effective in reducing tumor progression. However, in the intracranial glioma model, bortezomib given systemically did not affect survival. By sharp contrast, animals treated with bortezomib intracranially at the tumor site exhibited significantly increased survival. CONCLUSIONS Bypassing the blood-brain barrier by using the osmotic pump resulted in an increase in the efficacy of bortezomib for the treatment of intracranial tumors. Thus, the intratumoral administration of bortezomib into the cranial cavity is an effective approach for glioma therapy.

Heterocellular Contacts with Mouse Brain Endothelial Cells Via Laminin and α6β1 Integrin Sustain Subventricular Zone (SVZ) Stem/Progenitor Cells Properties

Neurogenesis in the subventricular zone (SVZ) is regulated by diffusible factors and cell–cell contacts. In vivo, SVZ stem cells are associated with the abluminal surface of blood vessels and such interactions are thought to regulate their neurogenic capacity. SVZ neural stem cells (NSCs) have been described to contact endothelial-derived laminin via α6β1 integrin. To elucidate whether heterocellular contacts with brain endothelial cells (BEC) regulate SVZ cells neurogenic capacities, cocultures of SVZ neurospheres and primary BEC, both obtained from C57BL/6 mice, were performed. The involvement of laminin-integrin interactions in SVZ homeostasis was tested in three ways. Firstly, SVZ cells were analyzed following incubation of BEC with the protein synthesis inhibitor cycloheximide (CHX) prior to coculture, a treatment expected to decrease membrane proteins. Secondly, SVZ cells were cocultured with BEC in the presence of an anti-α6 integrin neutralizing antibody. Thirdly, BEC were cultured with β1^−/− SVZ cells. We showed that contact with BEC supports, at least in part, proliferation and stemness of SVZ cells, as evaluated by the number of BrdU positive (+) and Sox2+ cells in contact with BEC. These effects are dependent on BEC-derived laminin binding to α6β1 integrin and are decreased in cocultures incubated with anti-α6 integrin neutralizing antibody and in cocultures with SVZ β1^−/− cells. Moreover, BEC-derived laminin sustains stemness in SVZ cell cultures via activation of the Notch and mTOR signaling pathways. Our results show that BEC/SVZ interactions involving α6β1 integrin binding to laminin, contribute to SVZ cell proliferation and stemness.

Monoamine oxidase A (MAO A) inhibitors decrease glioma progression

Glioblastoma (GBM) is an aggressive brain tumor which is currently treated with temozolomide (TMZ). Tumors usually become resistant to TMZ and recur; no effective therapy is then available. Monoamine Oxidase A (MAO A) oxidizes monoamine neurotransmitters resulting in reactive oxygen species which cause cancer. This study shows that MAO A expression is increased in human glioma tissues and cell lines. MAO A inhibitors, clorgyline or the near-infrared-dye MHI-148 conjugated to clorgyline (NMI), were cytotoxic for glioma and decreased invasion in vitro. Using the intracranial TMZ-resistant glioma model, clorgyline or NMI alone or in combination with low-dose TMZ reduced tumor growth and increased animal survival. NMI was localized specifically to the tumor. Immunocytochemistry studies showed that the MAO A inhibitor reduced proliferation, microvessel density and invasion, and increased macrophage infiltration. In conclusion, we have identified MAO A inhibitors as potential novel stand-alone drugs or as combination therapy with low dose TMZ for drug-resistant gliomas. NMI can also be used as a non-invasive imaging tool. Thus has a dual function for both therapy and diagnosis.

A novel drug conjugate, NEO212, targeting proneural and mesenchymal subtypes of patient-derived glioma cancer stem cells

Glioblastoma multiforme (GBM), a highly malignant brain tumor, accounts for half of all gliomas. Despite surgery, radiation and chemotherapy, the median survival is between 12 and 15 months. The poor prognosis is due to tumor recurrence attributed to chemoresistant glioma cancer stem cells (GSCs). Here we examined the effects of a novel compound NEO212, which is composed of two covalently conjugated anti-cancer compounds - temozolomide (TMZ) and perillyl alcohol (POH), on GSCs expressing either the proneural or mesenchymal gene signatures. These GSCs were obtained from patient-derived tumor tissue. Our findings demonstrate that NEO212 is 10 fold more cytotoxic to GSCs than TMZ (standard-of-care). Furthermore, NEO212 is effective against both proneural and clinically aggressive mesenchymal GSC subtypes. The mechanism of NEO212 mediated-cytotoxicity is through double-strand DNA breaks and apoptosis. In vivo studies show that NEO212 significantly delays tumor growth of both proneural and mesenchymal tumor stem cell populations. Patient-derived GSCs and tumors derived from these cells are highly reflective of the heterogeneity in human GBM. The efficacy of NEO212 against both GSC subtypes indicates that NEO212 has great clinical potential to effectively target GBM.

Quinoline-based antimalarial drugs: a novel class of autophagy inhibitors

OBJECT

Chloroquine (CQ) is a quinoline-based drug widely used for the prevention and treatment of malaria. More recent studies have provided evidence that this drug may also harbor antitumor properties, whereby CQ possesses the ability to accumulate in lysosomes and blocks the cellular process of autophagy. Therefore, the authors of this study set out to investigate whether CQ analogs, in particular clinically established antimalaria drugs, would also be able to exert antitumor properties, with a specific focus on glioma cells.

METHODS

Toward this goal, the authors treated different glioma cell lines with quinine (QN), quinacrine (QNX), mefloquine (MFQ), and hydroxychloroquine (HCQ) and investigated endoplasmic reticulum (ER) stress-induced cell death, autophagy, and cell death.

RESULTS

All agents blocked cellular autophagy and exerted cytotoxic effects on drug-sensitive and drug-resistant glioma cells with varying degrees of potency (QNX > MFQ > HCQ > CQ > QN). Furthermore, all quinoline-based drugs killed glioma cells that were highly resistant to temozolomide (TMZ), the current standard of care for patients with glioma. The cytotoxic mechanism involved the induction of apoptosis and ER stress, as indicated by poly(ADP-ribose) polymerase (PARP) cleavage and CHOP/GADD153. The induction of ER stress and resulting apoptosis could be confirmed in the in vivo setting, in which tumor tissues from animals treated with quinoline-based drugs showed increased expression of CHOP/GADD153, along with elevated TUNEL staining, a measure of apoptosis.

CONCLUSIONS

Thus, the antimalarial compounds investigated in this study hold promise as a novel class of autophagy inhibitors for the treatment of newly diagnosed TMZ-sensitive and recurrent TMZ-resistant gliomas.

Nanoparticle biointerfacing by platelet membrane cloaking

Development of functional nanoparticles can be encumbered by unanticipated material properties and biological events, which can affect nanoparticle effectiveness in complex, physiologically relevant systems. Despite the advances in bottom-up nanoengineering and surface chemistry, reductionist functionalization approaches remain inadequate in replicating the complex interfaces present in nature and cannot avoid exposure of foreign materials. Here we report on the preparation of polymeric nanoparticles enclosed in the plasma membrane of human platelets, which are a unique population of cellular fragments that adhere to a variety of disease-relevant substrates. The resulting nanoparticles possess a right-side-out unilamellar membrane coating functionalized with immunomodulatory and adhesion antigens associated with platelets. Compared to uncoated particles, the platelet membrane-cloaked nanoparticles have reduced cellular uptake by macrophage-like cells and lack particle-induced complement activation in autologous human plasma. The cloaked nanoparticles also display platelet-mimicking properties such as selective adhesion to damaged human and rodent vasculatures as well as enhanced binding to platelet-adhering pathogens. In an experimental rat model of coronary restenosis and a mouse model of systemic bacterial infection, docetaxel and vancomycin, respectively, show enhanced therapeutic efficacy when delivered by the platelet-mimetic nanoparticles. The multifaceted biointerfacing enabled by the platelet membrane cloaking method provides a new approach in developing functional nanoparticles for disease-targeted delivery.

Chemotherapeutic effect of a novel temozolomide analog on nasopharyngeal carcinoma in vitro and in vivo

BACKGROUND

Many patients with nasopharyngeal carcinoma (NPC) face poor prognosis. Due to its hidden anatomical location, the tumor is usually diagnosed quite late, and despite initially successful treatment with radiation and cisplatin, many patients will relapse and succumb to the disease. New treatment options are urgently needed. We have performed preclinical studies to evaluate the potential NPC therapeutic activity of a newly developed analog of temozolomide (TMZ), an alkylating agent that is the current chemotherapeutic standard of care for patients with malignant glioma.

RESULTS

TMZ was covalently conjugated to the natural monoterpene perillyl alcohol (POH), creating the novel fusion compound NEO212. Its impact on two NPC cell lines was studied through colony formation assays, cell death ELISA, immunoblots, and in vivo testing in tumor-bearing mice. In vitro, NEO212 effectively triggered tumor cell death, and its potency was significantly greater than that of its individual components, TMZ or POH alone. Intriguingly, merely mixing TMZ with POH also was unable to achieve the superior potency of the conjugated compound NEO212. Treatment of NPC cells with NEO212 inactivated the chemoprotective DNA repair protein MGMT (O6-methylguanine methyltransferase), resulting in significant chemosensitization of cells to a second round of drug treatment. When tested in vivo, NEO212 reduced tumor growth in treated animals.

CONCLUSION

Our results demonstrate anticancer activity of NEO212 in preclinical NPC models, suggesting that this novel compound should be evaluated further for the treatment of patients with NPC.

First clinical results of a personalized immunotherapeutic vaccine against recurrent, incompletely resected, treatment-resistant glioblastoma multiforme (GBM) tumors, based on combined allo- and auto-immune tumor reactivity

Glioblastoma multiforme (GBM) patients have a poor prognosis. After tumor recurrence statistics suggest an imminent death within 1-4.5 months. Supportive preclinical data, from a rat model, provided the rational for a prototype clinical vaccine preparation, named Gliovac (or ERC 1671) composed of autologous antigens, derived from the patient's surgically removed tumor tissue, which is administered together with allogeneic antigens from glioma tissue resected from other GBM patients. We now report the first results of the Gliovac treatment for treatment-resistant GBM patients. Nine (9) recurrent GBM patients, after standard of care treatment, including surgery radio- and chemotherapy temozolomide, and for US patients, also bevacizumab (Avastin™), were treated under a compassionate use/hospital exemption protocol. Gliovac was given intradermally, together with human GM-CSF (Leukine(®)), and preceded by a regimen of regulatory T cell-depleting, low-dose cyclophosphamide. Gliovac administration in patients that have failed standard of care therapies showed minimal toxicity and enhanced overall survival (OS). Six-month (26 weeks) survival for the nine Gliovac patients was 100% versus 33% in control group. At week 40, the published overall survival was 10% if recurrent, reoperated patients were not treated. In the Gliovac treated group, the survival at 40 weeks was 77%. Our data suggest that Gliovac has low toxicity and a promising efficacy. A phase II trial has recently been initiated in recurrent, bevacizumab naïve GBM patients (NCT01903330).

Effects of convection-enhanced delivery of bevacizumab on survival of glioma-bearing animals

OBJECT

Bevacizumab (Avastin), an antibody to vascular endothelial growth factor (VEGF), alone or in combination with irinotecan (Camptosar [CPT-11]), is a promising treatment for recurrent glioblastoma. However, the intravenous (IV) administration of bevacizumab produces a number of systemic side effects, and the increase in survival it provides for patients with recurrent glioblastoma is still only a few months. Because bevacizumab is an antibody against VEGF, which is secreted into the extracellular milieu by glioma cells, the authors hypothesized that direct chronic intratumoral delivery techniques (i.e., convection-enhanced delivery [CED]) can be more effective than IV administration. To test this hypothesis, the authors compared outcomes for these routes of bevacizumab application with respect to animal survival, microvessel density (MVD), and inflammatory cell distribution.

METHODS

Two human glioma cell lines, U87 and U251, were used as sources of intracranial tumor cells. The glioma cell lines were implanted into the brains of mice in an orthotopic xenograft mouse tumor model. After 7 days, the mice were treated with one of the following: 1) vehicle, 2) CED bevacizumab, 3) IV bevacizumab, 4) intraperitoneal (IP) irinotecan, 5) CED bevacizumab plus IP irinotecan, or 6) IV bevacizumab plus IP irinotecan. Alzet micro-osmotic pumps were used to introduce bevacizumab directly into the tumor. Survival was monitored. Excised tumor tissue samples were immunostained to measure MVD and inflammatory cell and growth factor levels.

RESULTS

The results demonstrate that mice treated with CED of bevacizumab alone or in combination with irinotecan survived longer than those treated systemically; CED-treated animals survived 30% longer than IV-treated animals. In combination studies, CED bevacizumab plus CPT-11 increased survival by more than 90%, whereas IV bevacizumab plus CPT-11 increased survival by 40%. Furthermore, CED bevacizumab-treated tissues exhibited decreased MVD compared with that of IV-treated tissues. In additional studies, the infiltration of macrophages and dendritic cells into CED-treated animals were increased compared with those in IV-treated animals, suggesting a highly active inflammatory response taking place in CED-treated mice.

CONCLUSIONS

The administration of bevacizumab via CED increases survival over that of treatment with IV bevacizumab. Thus, CED of bevacizumab alone or in combination with chemotherapy can be an effective protocol for treating gliomas.

Use of ERC-1671 Vaccine in a Patient with Recurrent Glioblastoma Multiforme after Progression during Bevacizumab Therapy: First Published Report

Glioblastoma multiforme is a highy aggressive tumor that recurs despite resection, focal beam radiation, and temozolamide chemotherapy. ERC-1671 is an experimental treatment strategy that uses the patient's own immune system to attack the tumor cells. The authors report preliminary data on the first human administration of ERC-1671 vaccination under a single-patient, compassionate-use protocol. The patient survived for ten months after the vaccine administration without any other adjuvant therapy and died of complications related to his previous chemotherapies.

Intravenous administration of retroviral replicating vector, Toca 511, demonstrates therapeutic efficacy in orthotopic immune-competent mouse glioma model

Toca 511 (vocimagene amiretrorepvec), a nonlytic, amphotropic retroviral replicating vector (RRV), encodes and delivers a functionally optimized yeast cytosine deaminase (CD) gene to tumors. In orthotopic glioma models treated with Toca 511 and 5-fluorocytosine (5-FC) the CD enzyme within infected cells converts 5-FC to 5-fluorouracil (5-FU), resulting in tumor killing. Toca 511, delivered locally either by intratumoral injection or by injection into the resection bed, in combination with subsequent oral extended-release 5-FC (Toca FC), is under clinical investigation in patients with recurrent high-grade glioma (HGG). If feasible, intravenous administration of vectors is less invasive, can easily be repeated if desired, and may be applicable to other tumor types. Here, we present preclinical data that support the development of an intravenous administration protocol. First we show that intravenous administration of Toca 511 in a preclinical model did not lead to widespread or uncontrolled replication of the RVV. No, or low, viral DNA was found in the blood and most of the tissues examined 180 days after Toca 511 administration. We also show that RRV administered intravenously leads to efficient infection and spread of the vector carrying the green fluorescent protein (GFP)-encoding gene (Toca GFP) through tumors in both immune-competent and immune-compromised animal models. However, initial vector localization within the tumor appeared to depend on the mode of administration. Long-term survival was observed in immune-competent mice when Toca 511 was administered intravenously or intracranially in combination with 5-FC treatment, and this combination was well tolerated in the preclinical models. Enhanced survival could also be achieved in animals with preexisting immune response to vector, supporting the potential for repeated administration. On the basis of these and other supporting data, a clinical trial investigating intravenous administration of Toca 511 in patients with recurrent HGG is currently open and enrolling.

Tumor vasculature and glioma stem cells: Contributions to glioma progression

Glioblastoma multiforme (GBM), the most malignant of brain tumors, is characterized by extensive vascularization and a high degree of invasion. The current standard of care is not very effective, resulting in tumor recurrence with patients rarely surviving over 2 years. This tumor recurrence is attributed to the presence of chemo and radiation resistant glioma stem cells (GSCs). These cells are associated with vascular niches which regulate GSC self-renewal and survival. Recent studies suggest that while blood vessels support glioma stem cells, these tumor cells in turn may regulate and contribute to the tumor vasculature by transdifferentiating into endothelial cells directly or through the secretion of regulatory growth factors such as vascular endothelial growth factor (VEGF) and hepatoma derived growth factor (HDGF). The relationship between the tumor vasculature and the glioma stem cells is the subject of this review.

Chloroquine enhances temozolomide cytotoxicity in malignant gliomas by blocking autophagy

Object

In a recent clinical trial, patients with newly diagnosed glioblastoma multiforme benefited from chloroquine (CQ) in combination with conventional therapy (resection, temozolomide [TMZ], and radiation therapy). In the present study, the authors report the mechanism by which CQ enhances the therapeutic efficacy of TMZ to aid future studies aimed at improving this therapeutic regimen.

Methods

Using in vitro and in vivo experiments, the authors determined the mechanism by which CQ enhances TMZ cytotoxicity. They focused on the inhibition-of-autophagy mechanism of CQ by knockdown of the autophagy-associated proteins or treatment with autophagy inhibitors. This mechanism was tested using an in vivo model with subcutaneously implanted U87MG tumors from mice treated with CQ in combination with TMZ.

Results

Knockdown of the autophagy-associated proteins (GRP78 and Beclin) or treatment with the autophagy inhibitor, 3-methyl adenine (3-MA), blocked autophagosome formation and reduced CQ cytotoxicity, suggesting that autophagosome accumulation precedes CQ-induced cell death. In contrast, blocking autophagosome formation with knockdown of GRP78 or treatment with 3-MA enhanced TMZ cytotoxicity, suggesting that the autophagy pathway protects from TMZ-induced cytotoxicity. CQ in combination with TMZ significantly increased the amounts of LC3B-II (a marker for autophagosome levels), CHOP/GADD-153, and cleaved PARP (a marker for apoptosis) over those with untreated or individual drug-treated glioma cells. These molecular mechanisms seemed to take place in vivo as well. Subcutaneously implanted U87MG tumors from mice treated with CQ in combination with TMZ displayed higher levels of CHOP/GADD-153 than did untreated or individual drug-treated tumors.

Conclusions

Taken together, these results demonstrate that CQ blocks autophagy and triggers endoplasmic reticulum stress, thereby increasing the chemosensitivity of glioma cells to TMZ.

Sequential administration of carbon nanotubes and near-infrared radiation for the treatment of gliomas

The objective was to use carbon nanotubes (CNT) coupled with near-infrared radiation (NIR) to induce hyperthermia as a novel non-ionizing radiation treatment for primary brain tumors, glioblastoma multiforme (GBM). In this study, we report the therapeutic potential of hyperthermia-induced thermal ablation using the sequential administration of carbon nanotubes (CNT) and NIR. In vitro studies were performed using glioma tumor cell lines (U251, U87, LN229, T98G). Glioma cells were incubated with CNTs for 24 h followed by exposure to NIR for 10 min. Glioma cells preferentially internalized CNTs, which upon NIR exposure, generated heat, causing necrotic cell death. There were minimal effects to normal cells, which correlate to their minimal uptake of CNTs. Furthermore, this protocol caused cell death to glioma cancer stem cells, and drug-resistant as well as drug-sensitive glioma cells. This sequential hyperthermia therapy was effective in vivo in the rodent tumor model resulting in tumor shrinkage and no recurrence after only one treatment. In conclusion, this sequence of selective CNT administration followed by NIR activation provides a new approach to the treatment of glioma, particularly drug-resistant gliomas.

Argonaute-2 promotes miR-18a entry in human brain endothelial cells

BACKGROUND

Cerebral arteriovenous malformation (AVM) is a vascular disease exhibiting abnormal blood vessel morphology and function. miR-18a ameliorates the abnormal characteristics of AVM-derived brain endothelial cells (AVM-BEC) without the use of transfection reagents. Hence, our aim was to identify the mechanisms by which miR-18a is internalized by AVM-BEC. Since AVM-BEC overexpress RNA-binding protein Argonaute-2 (Ago-2) we explored the clinical potential of Ago-2 as a systemic miRNA carrier.

METHODS AND RESULTS

Primary cultures of AVM-BEC were isolated from surgical specimens and tested for endogenous miR-18a levels using qPCR. Conditioned media (CM) was derived from AVM-BEC cultures (AVM-BEC-CM). AVM-BEC-CM significantly enhanced miR-18a internalization. Ago-2 was detected using western blotting and immunostaining techniques. Ago-2 was highly expressed in AVM-BEC; and siAgo-2 decreased miR-18a entry into brain-derived endothelial cells. Only brain-derived endothelial cells were responsive to the Ago-2/miR-18a complex and not other cell types tested. Secreted products (eg, thrombospondin-1 [TSP-1]) were tested using ELISA. Brain endothelial cells treated with the Ago-2/miR-18a complex in vitro increased TSP-1 secretion. In the in vivo angiogenesis glioma model, animals were treated with miR-18a in combination with Ago-2. Plasma was obtained and tested for TSP-1 and vascular endothelial growth factor (VEGF)-A. In this angiogenesis model, the Ago-2/miR-18a complex caused a significant increase in TSP-1 and decrease in VEGF-A secretion in the plasma.

CONCLUSIONS

Ago-2 facilitates miR-18a entry into brain endothelial cells in vitro and in vivo. This study highlights the clinical potential of Ago-2 as a miRNA delivery platform for the treatment of brain vascular diseases.

MicroRNA-18a improves human cerebral arteriovenous malformation endothelial cell function

BACKGROUND AND PURPOSE

Cerebral arteriovenous malformation (AVM) is a vascular disease that disrupts normal blood flow and leads to serious neurological impairment or death. Aberrant functions of AVM-derived brain endothelial cells (AVM-BECs) are a disease hallmark. Our aim was to use microRNA-18a (miR-18a) as a therapeutic agent to improve AVM-BEC function.

METHODS

Human AVM-BECs were tested for growth factor production and proliferation under different shear flow conditions and evaluated for tubule formation. Thrombospondin-1, inhibitor of DNA-binding protein 1, and vascular endothelial growth factor (VEGF) isotype mRNA levels were quantified by quantitative real-time polymerase chain reaction. Thrombospondin-1, VEGF-A, and VEGF-D protein expression was measured using enzyme-linked immunosorbent assay. Proliferation and tubule formation were evaluated using bromodeoxyuridine incorporation and growth factor-reduced Matrigel assays, respectively.

RESULTS

miR-18a increased thrombospondin-1 production but decreased inhibitor of DNA-binding protein 1, a transcriptional repressor of thrombospondin-1. miR-18a reduced VEGF-A and VEGF-D levels, both overexpressed in untreated AVM-BECs. This is the first study reporting VEGF-D overexpression in AVM. These effects were most prominent under arterial shear flow conditions. miR-18a also reduced AVM-BEC proliferation, improved tubule formation, and was effectively internalized by AVM-BECs in the absence of extraneous transfection reagents.

CONCLUSIONS

We report VEGF-D overexpression in AVM and the capacity of miR-18a to induce AVM-BECs to function more normally. This highlights the clinical potential of microRNA as a treatment for AVM and other vascular diseases.

Repositioning of Verrucosidin, a purported inhibitor of chaperone protein GRP78, as an inhibitor of mitochondrial electron transport chain complex I

Verrucosidin (VCD) belongs to a group of fungal metabolites that were identified in screening programs to detect molecules that preferentially kill cancer cells under glucose-deprived conditions. Its mode of action was proposed to involve inhibition of increased GRP78 (glucose regulated protein 78) expression during hypoglycemia. Because GRP78 plays an important role in tumorigenesis, inhibitors such as VCD might harbor cancer therapeutic potential. We therefore sought to characterize VCD's anticancer activity in vitro. Triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468 were treated with VCD under different conditions known to trigger increased expression of GRP78, and a variety of cellular processes were analyzed. We show that VCD was highly cytotoxic only under hypoglycemic conditions, but not in the presence of normal glucose levels, and VCD blocked GRP78 expression only when glycolysis was impaired (due to hypoglycemia or the presence of the glycolysis inhibitor 2-deoxyglucose), but not when GRP78 was induced by other means (hypoxia, thapsigargin, tunicamycin). However, VCD's strictly hypoglycemia-specific toxicity was not due to the inhibition of GRP78. Rather, VCD blocked mitochondrial energy production via inhibition of complex I of the electron transport chain. As a result, cellular ATP levels were quickly depleted under hypoglycemic conditions, and common cellular functions, including general protein synthesis, deteriorated and resulted in cell death. Altogether, our study identifies mitochondria as the primary target of VCD. The possibility that other purported GRP78 inhibitors (arctigenin, biguanides, deoxyverrucosidin, efrapeptin, JBIR, piericidin, prunustatin, pyrvinium, rottlerin, valinomycin, versipelostatin) might act in a similar GRP78-independent fashion will be discussed.

Abstract 3740: Temozolomide-perillyl alcohol conjugate is cytotoxic for glioma cancer stem cells

Glioblastoma multiforme (GBM), the most malignant glioma, is a highly invasive tumor which is usually fatal within 2 years. The chemotherapeutic agent of choice is temozolomide (TMZ); however glioma patients inevitably become resistant to TMZ and tumors recur. Tumor recurrence has been associated with highly invasive, chemoresistant cancer stem cells (CSC) which is resistant to TMZ. We have constructed a new chemical entity by conjugating TMZ to perillyl alcohol (POH) via a carbamate bond. This compound, TMZ-POH, contains POH, a naturally occurring monoterpene that reduces tumor cell migration and has anti-tumor properties against gliomas as well as other cancers. In the studies presented here we demonstrate that TMZ-POH is cytotoxic to CSCs without affecting normal stem cells. The mechanism of TMZ-POH induced cytotoxicity is mediated in part through the DNA damage response pathway and apoptosis. Furthermore, the TMZ-POH conjugate is 5 to 10 fold more effective in inducing cell death compared to TMZ, POH or the mixture of these agents. Our data show that TMZ-POH is a promising novel compound directed against cancer stem cells and therefore important for the treatment of drug resistant, recurrent gliomas.

Citation Format: Niyati Jhaveri, Fabienne Agasse, Florence M. Hofman, Thomas C. Chen. Temozolomide-perillyl alcohol conjugate is cytotoxic for glioma cancer stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3740. doi:10.1158/1538-7445.AM2013-3740

Abstract C74: Temozolomide-perillyl alcohol conjugate is cytotoxic for glioma cancer stem cells

Glioblastoma multiforme (GBM), the most malignant glioma, is a highly invasive tumor which is usually fatal within 2 years. The chemotherapeutic agent of choice is temozolomide (TMZ); however glioma patients inevitably become resistant to TMZ and tumors recur. Tumor recurrence has been associated with highly invasive, chemoresistant cancer stem cells (CSC) which is resistant to TMZ. We have constructed a new chemical entity by conjugating TMZ to perillyl alcohol (POH) via a carbamate bond. This compound, TMZ-POH, contains POH, a naturally occurring monoterpene that reduces tumor cell migration and has anti-tumor properties against gliomas as well as other cancers. In the studies presented here we demonstrate that TMZ-POH is cytotoxic to CSCs without affecting normal stem cells. The mechanism of TMZ-POH induced cytotoxicity is mediated in part through the DNA damage response pathway and apoptosis. Furthermore, the TMZ-POH conjugate is 5 to 10 fold more effective in inducing cell death compared to TMZ, POH or the mixture of these agents. Our data show that TMZ-POH is a promising novel compound directed against cancer stem cells and therefore important for the treatment of drug resistant, recurrent gliomas.

Citation Format: Niyati Jhaveri, Fabienne Agasse, Florence M. Hofman, Thomas C. Chen. Temozolomide-perillyl alcohol conjugate is cytotoxic for glioma cancer stem cells. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C74.

Perillyl alcohol for the treatment of temozolomide-resistant gliomas

Perillyl alcohol (POH) is a monoterpene that has been used orally for the treatment of systemic cancer. However, when used orally significant gastrointestinal side effects and lack of overall efficacy were documented. Recently, in a phase II trial in Brazil for the treatment of temozolomide (TMZ)-resistant malignant gliomas, POH was well tolerated when administered intranasally. The present study explores the effects and mechanisms of POH on TMZ-sensitive and TMZ-resistant glioma cells. In vitro studies showed that POH was cytotoxic to TMZ-resistant as well as TMZ-sensitive glioma cells, and this effect was independent of O(6)-methylguanine-DNA methyltransferase expression. POH induced cytotoxicity, in part, through the endoplasmic reticulum (ER) stress pathway as shown by the increased expression of glucose-regulated protein-78 (GRP78), activating transcription factor 3, and C/EBP-homologous protein. In addition, POH impeded survival pathways, such as mTOR and Ras. As well, POH reduced the invasive capacity of sensitive and resistant glioma cells. POH alone and/or in combination with other ER stress-inducing cytotoxic drugs (i.e., 2, 5-dimethyl-celecoxib, nelfinavir) further induced apoptosis in TMZ-sensitive and TMZ-resistant glioma cells. To show whether intranasal delivery of POH was effective for the treatment of TMZ-resistant gliomas, animals bearing intracranial tumors were given POH intranasally. Animals treated through intranasal administration of POH exhibited a decrease in tumor growth and an increase in survival. Our data show that POH is an effective anti-glioma cytotoxic agent for TMZ-resistant gliomas when administered intranasally.

Preferential killing of triple-negative breast cancer cells in vitro and in vivo when pharmacological aggravators of endoplasmic reticulum stress are combined with autophagy inhibitors

The cellular processes of autophagy and endoplasmic reticulum stress (ERS) appear to be interconnected, and it has been proposed that autophagy may serve to reduce ERS via removal of terminally misfolded and aggregated proteins. Conversely, there are indications that blockage of autophagy may increase ERS. Based on earlier work demonstrating that pharmacologically aggravated ERS can result in tumor cell killing, we investigated whether blockage of autophagy would enhance this effect in a therapeutically useful manner. We therefore combined chloroquine (CQ), a pharmacological inhibitor of autophagy, with other drugs known to act as ERS aggravators (ERSA), namely nelfinavir (an HIV protease inhibitor) and celecoxib (a cyclooxygenase-2 inhibitor) or its non-coxib analog 2,5-dimethyl-celecoxib (DMC), and investigated combination drug effects in a variety of breast cancer cell lines. We found that the addition of CQ resulted in synergistic enhancement of tumor cell killing by ERSA compounds, particularly in triple-negative breast cancer (TNBC) cells. This combination effect could also be confirmed in an in vivo model, where CQ boosted low-dose ERSA effects, resulting in rapid deterioration of xenografted tumors in mice. Altogether, our results indicate that combinations of an autophagy inhibitor with pharmacological ERSA (i.e. compounds that lead to ER stress aggravation) should be further explored for potential therapy of otherwise difficult-to-treat TNBC.

Thrombospondin-1 modulates the angiogenic phenotype of human cerebral arteriovenous malformation endothelial cells

BACKGROUND

The management of cerebral arteriovenous malformation (AVM) is challenging, and invasive therapies place vital intracranial structures at risk of injury. The development of noninvasive, pharmacologic approaches relies on identifying factors that mediate key angiogenic processes. Previous studies indicate that endothelial cells (ECs) derived from cerebral AVM (AVM-ECs) are distinct from control brain ECs with regard to important angiogenic characteristics.

OBJECTIVE

To determine whether thrombospondin-1 (TSP-1), a potent angiostatic factor, regulates critical angiogenic features of AVM-ECs and to identify factors that modulate TSP-1 production in AVM-ECs.

METHODS

EC proliferation, migration, and tubule formation were evaluated with bromodeoxyuridine incorporation, Boyden chamber, and Matrigel studies, respectively. TSP-1 and inhibitor of DNA binding/differentiation 1 (Id1) mRNA levels were quantified with microarray and quantitative real-time polymerase chain reaction analyses. TSP-1 protein expression was measured using Western blotting, immunohistochemical, and enzyme-linked immunosorbent assay techniques. The mechanistic link between Id1 and TSP-1 was established through small interfering RNA-mediated knockdown of Id1 in AVM-ECs followed by Western blot and enzyme-linked immunosorbent assay experiments assessing TSP-1 production.

RESULTS

AVM-ECs proliferate faster, migrate more quickly, and form disorganized tubules compared with brain ECs. TSP-1 is significantly down-regulated in AVM-ECs. The addition of TSP-1 to AVM-EC cultures normalizes the rate of proliferation and migration and the efficiency of tubule formation, whereas brain ECs are unaffected. Id1 negatively regulates TSP-1 expression in AVM-ECs.

CONCLUSION

These data highlight a novel role for TSP-1 in the pathobiology of AVM angiogenesis and provide a context for its use in the clinical management of brain AVMs.

Preclinical development of novel anti-glioma drugs targeting the endoplasmic reticulum stress response

The endoplasmic reticulum (ER) stress response represents a cellular "yin-yang" process, where low to moderate activity is cell protective and supports chemoresistance (yang), but where more severe conditions will aggravate these mechanisms to the point where they abandon their protective efforts and instead turn on a cell death program (yin). Because tumor cells frequently experience chronic stress conditions (due to hypoxia, hypoglycemia, acidification, etc.), the protective yang components of their ER stress response are continuously engaged and thus less able to neutralize additional insults taxing the ER stress response. This tumor-specific situation may provide therapeutic opportunities for pharmacologic intervention, where further aggravation of ER stress would lead to the activation of pro-apoptotic yin components and result in tumor cell death. This review will describe the yin-yang principle of ER stress, and will present pharmacologic agents and combination strategies aimed at exploiting the ER stress response for improved therapeutic outcomes, particularly in the setting of difficult to treat tumor types such as glioblastoma.

Abstract 3820: Reduced migration and enhanced killing of glioblastoma multiforme by mefloquine via alteration of sphingolipid levels

Purpose: Glioblastoma multiforme (GBM) is one of the most aggressive and common brain tumors. Current therapy for GBM is limited to surgery, radiation therapy and chemotherapy using temozolomide (TMZ). However, the emergence of resistance to TMZ and the ability of malignant gliomas to migrate away from the primary tumor site often results in recurrence of the tumor and failure of the initial therapy. This dire scenario illustrates the urgent need to identify novel agents that will be effective in TMZ-resistant tumors. In this study, we investigated the anticancer potential of an FDA approved antimalarial drug, mefloquine (MQ), in the in vitro model of GBM. MQ's impact on glioma viability, proliferation and migration was studied in a number of wild type and TMZ-resistant cells lines. We also evaluated the effects of MQ on intracellular levels of sphingolipids, which are bioactive lipids and have been recognized as the mediators of cellular proliferation and invasion in GBM. Method: To study the effect of MQ on TMZ resistance in vitro, we generated TMZ-resistant cell lines from established GBM cells. We evaluated the effects of MQ on cellular viability and proliferation by MTT assay and colony formation assay. Moreover, cell death was determined by analyzing the effect of MQ on various markers of apoptosis (e.g. cleavage of caspase 7 and PARP) using western blot. The effect of MQ on the migration of both TMZ-sensitive and -resistant cells was evaluated using wound healing scratch assay and Boyden chamber. To evaluate the impact of MQ on sphingolipids, we employed a validated LC-MS lipidomic assay to quantify the levels of various sphingolipids. Results: MQ was able to reduce cellular viability and proliferation in both TMZ-sensitive and -resistant GBM cells. MQ exerted its antitumor activity through induction of apoptosis. Our results further demonstrate the ability of MQ to reduce the migration of both TMZ-sensitive and -resistant GBM cell lines. In addition MQ was able to reduce the intracellular levels of sphingosine-1-phosphate (S1P), a pro-survival and pro-migratory sphingolipid and increased the levels of ceramide, a pro-apoptotic sphingolipid. Conclusion: Altogether our results demonstrate the ability of MQ to reduce cellular viability and proliferation and to induce apoptotic cell death in both TMZ-sensitive and -resistant GBM cells. It is conceivable that MQ exerts these effects by altering sphingolipid metabolism. These preliminary data suggests that MQ should be further investigated for cancer therapeutic purposes for TMZ-resistant GBM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3820. doi:1538-7445.AM2012-3820

Exploring the Therapeutic Efficacy of Glioma Vaccines Based on Allo- and Syngeneic Antigens and Distinct Immunological Costimulation Activators

The efficacy of a various immunotherapeutic immunisation strategies for malignant glioma brain cancer was evaluated in the syngeneic CNS-1 Lewis rat glioma model. A prototype glioma cancer vaccine, which was composed of multivalent antigens derived from allogeneic and syngeneic cells and lysates, formed the prototype preparation of antigens. These antigens reflect the autologous antigens derived from the patient’s surgically removed tumor tissue, as well as allogeneic antigens form glioma tumor tissue surgically removed from donor patients. This antigen mixture provides a broad spectrum of tumor associated antigens (TAA) and helps to prevent escape of tumor immune surveillance when given as a vaccine. This antigen preparation was administered in a therapeutic setting with distinct single or multiple co-stimulation-favouring immunostimulants and evaluated for inhibition of tumor growth. Our prototype vaccine was able to arrest progression of tumor growth when co-delivered in a specific regimen together with the costimulating multi-TLR agonist, Bacille Calmette Guerin (BCG) and interleukin-2, or with the Toll-Like receptor (TLR) 7/8 activator resiquimod.

A critical role for GRP78/BiP in the tumor microenvironment for neovascularization during tumor growth and metastasis

Glucose-regulated protein 78 (GRP78)/BiP is a multifunctional protein which plays a major role in endoplasmic reticulum (ER) protein processing, protein quality control, maintaining ER homeostasis, and controlling cell signaling and viability. Previously, using a transgene-induced mammary tumor model, we showed that Grp78 heterozygosity impeded cancer growth through suppression of tumor cell proliferation and promotion of apoptosis and the Grp78(+/-) mice exhibited dramatic reduction (70%) in the microvessel density (MVD) of the endogenous mammary tumors, while having no effect on the MVD of normal organs. This observation suggests that GRP78 may critically regulate the function of the host vasculature within the tumor microenvironment. In this article, we interrogated the role of GRP78 in the tumor microenvironment. In mouse tumor models in which wild-type (WT), syngeneic mammary tumor cells were injected into the host, we showed that Grp78(+/-) mice suppressed tumor growth and angiogenesis during the early phase but not during the late phase of tumor growth. Growth of metastatic lesions of WT, syngeneic melanoma cells in the Grp78(+/-) mice was potently suppressed. We created conditional heterozygous knockout of GRP78 in the host endothelial cells and showed severe reduction of tumor angiogenesis and metastatic growth, with minimal effect on normal tissue MVD. Furthermore, knockdown of GRP78 expression in immortalized human endothelial cells showed that GRP78 is a critical mediator of angiogenesis by regulating cell proliferation, survival, and migration. Our findings suggest that concomitant use of current chemotherapeutic agents and novel therapies against GRP78 may offer a powerful dual approach to arrest cancer initiation, progression, and metastasis.

Green tea epigallocatechin gallate enhances therapeutic efficacy of temozolomide in orthotopic mouse glioblastoma models

The alkylating agent temozolomide, in combination with surgery and radiation, is the current standard of care for patients with glioblastoma. However, despite this extensive therapeutic effort, the inclusion of temozolomide extends survival only by a few short months. Among the factors contributing to chemoresistance is elevated expression of the endoplasmic reticulum (ER) chaperone GRP78 (glucose-regulated protein 78; BiP), a key pro-survival component of the ER stress response system. Because the green tea component EGCG (epigallocatechin 3-gallate) had been shown to inhibit GRP78 function, we investigated whether this polyphenolic agent would be able to increase the therapeutic efficacy of temozolomide in preclinical models of glioblastoma. Mice with intracranially implanted human U87 (p53 wild type) or U251 (p53 mutant) glioblastoma cells were treated with temozolomide and EGCG, alone and in combination. We found that EGCG alone did not provide survival benefit, but significantly improved the existing therapeutic effect of temozolomide, i.e., life extension was substantially greater under combination therapy as compared to temozolomide therapy alone. Immunohistochemical analysis of tumor tissue revealed increased expression levels of GRP78 in temozolomide-treated animals, which was diminished when temozolomide was combined with EGCG. Parallel in vitro experiments with siRNA targeting GRP78 or its major pro-apoptotic antagonist CHOP (CCAAT/enhancer binding protein homologous protein/GADD153) further established a critical role of the ER stress response system, where si-GRP78 sensitized cells to treatment with temozolomide, and si-CHOP provided protection from drug-induced toxicity. Thus, ER stress-regulatory components affect the chemotherapeutic response of glioblastoma cells to treatment with temozolomide, and inclusion of EGCG is able to increase the therapeutic efficacy of this DNA-damaging agent.