Abstract A41: Harnessing neural stem cell tumor tropism for targeted nanoparticle delivery: Potential for ovarian cancer therapy

Intraperitoneal as compared to intravenous administration of chemotherapy has shown improved survival rates for stage III ovarian cancer. While this demonstrates that concentrating chemotherapy at the tumors has therapeutic benefit, intraperitoneal therapy was also accompanied by significantly increased toxic side effects. There is thus an urgent need for a targeted delivery system that could localize therapy at the tumors and decrease the side-effects. Here we show that stem cell/nanoparticle hybrids may be used for such targeted therapy. In pre-clinical brain and other invasive and metastatic tumor models, neural stem cells have been shown to overcome a variety of biological barriers and migrate selectively to invasive tumor foci, even penetrating hypoxic tumor regions. Here we present data confirming that neural stem cells also migrate selectively to ovarian cancer. Moreover, the neural stem cells can engineered to transport to the tumors nanoparticles that either contain chemotherapy drugs or can be induced to heat. The combination of neural stem cells and nanoparticles that can either be used for thermal ablation or slowly release chemotherapy drugs offers the potential to realize a modular and general drug targeting system for the treatment of stage III ovarian cancer.

Citation Format: Rachael Mooney, Megan Gilchrist, Yiming Weng, Alexander Annala, Sukhada Bhojane, Elizabeth Garcia, Luella Roma, Kenna Schnarr, Thanh Dellinger, Ernest Han, Aboody S. Karen, Jacob M. Berlin. Harnessing neural stem cell tumor tropism for targeted nanoparticle delivery: Potential for ovarian cancer therapy. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A41.

Biocompatibility of pristine graphene for neuronal interface

OBJECT

Graphene possesses unique electrical, physical, and chemical properties that may offer significant potential as a bioscaffold for neuronal regeneration after spinal cord injury. The purpose of this investigation was to establish the in vitro biocompatibility of pristine graphene for interface with primary rat cortical neurons.

METHODS

Graphene films were prepared by chemical vapor deposition on a copper foil catalytic substrate and subsequent apposition on bare Permanox plastic polymer dishes. Rat neuronal cell culture was grown on graphene-coated surfaces, and cell growth and attachment were compared with those on uncoated and poly-d-lysine (PDL)-coated controls; the latter surface is highly favorable for neuronal attachment and growth. Live/dead cell analysis was conducted with flow cytometry using ethidium homodimer-1 and calcein AM dyes. Lactate dehydrogenase (LDH) levels-indicative of cytotoxicity-were measured as markers of cell death. Phase contrast microscopy of active cell culture was conducted to assess neuronal attachment and morphology.

RESULTS

Statistically significant differences in the percentage of live or dead neurons were noted between graphene and PDL surfaces, as well as between the PDL-coated and bare surfaces, but there was little difference in cell viability between graphene-coated and bare surfaces. There were significantly lower LDH levels in the graphene-coated samples compared with the uncoated ones, indicating that graphene was not more cytotoxic than the bare control surface. According to phase contrast microscopy, neurons attached to the graphene-coated surface and were able to elaborate long, neuritic processes suggestive of normal neuronal metabolism and morphology.

CONCLUSIONS

Further use of graphene as a bioscaffold will require surface modification that enhances hydrophilicity to increase cellular attachment and growth. Graphene is a nanomaterial that is biocompatible with neurons and may have significant biomedical applications.

Antioxidant carbon particles improve cerebrovascular dysfunction following traumatic brain injury

Injury to the neurovasculature is a feature of brain injury and must be addressed to maximize opportunity for improvement. Cerebrovascular dysfunction, manifested by reduction in cerebral blood flow (CBF), is a key factor that worsens outcome after traumatic brain injury (TBI), most notably under conditions of hypotension. We report here that a new class of antioxidants, poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), which are nontoxic carbon particles, rapidly restore CBF in a mild TBI/hypotension/resuscitation rat model when administered during resuscitation--a clinically relevant time point. Along with restoration of CBF, there is a concomitant normalization of superoxide and nitric oxide levels. Given the role of poor CBF in determining outcome, this finding is of major importance for improving patient health under clinically relevant conditions during resuscitative care, and it has direct implications for the current TBI/hypotension war-fighter victims in the Afghanistan and Middle East theaters. The results also have relevancy in other related acute circumstances such as stroke and organ transplantation.

Antibody-targeted nanovectors for the treatment of brain cancers

Introduced here is the hydrophilic carbon clusters (HCCs) antibody drug enhancement system (HADES), a methodology for cell-specific drug delivery. Antigen-targeted, drug-delivering nanovectors are manufactured by combining specific antibodies with drug-loaded poly(ethylene glycol)-HCCs (PEG-HCCs). We show that HADES is highly modular, as both the drug and antibody component can be varied for selective killing of a range of cultured human primary glioblastoma multiforme. Using three different chemotherapeutics and three different antibodies, without the need for covalent bonding to the nanovector, we demonstrate extreme lethality toward glioma, but minimal toxicity toward human astrocytes and neurons.

Noncovalent assembly of targeted carbon nanovectors enables synergistic drug and radiation cancer therapy in vivo

Current chemotherapeutics are characterized by efficient tumor cell-killing and severe side effects mostly derived from off-target toxicity. Hence targeted delivery of these drugs to tumor cells is actively sought. In an in vitro system, we previously demonstrated that targeted drug delivery to cancer cells overexpressing epidermal growth factor receptor (EGFR+) can be achieved by poly(ethylene glycol)-functionalized carbon nanovectors simply mixed with a drug, paclitaxel, and an antibody that binds to the epidermal growth factor receptor, cetuximab. This construct is unusual in that all three components are assembled through noncovalent interactions. Here we show that this same construct is effective in vivo, enhancing radiotherapy of EGFR+ tumors. This targeted nanovector system has the potential to be a new therapy for head and neck squamous cell carcinomas, deserving of further preclinical development.

Competitive activity-based protein profiling identifies aza-β-lactams as a versatile chemotype for serine hydrolase inhibition

Serine hydrolases are one of the largest and most diverse enzyme classes in Nature. Most serine hydrolases lack selective inhibitors, which are valuable probes for assigning functions to these enzymes. We recently discovered a set of aza-β-lactams (ABLs) that act as potent and selective inhibitors of the mammalian serine hydrolase protein-phosphatase methylesterase-1 (PME-1). The ABLs inactivate PME-1 by covalent acylation of the enzyme's serine nucleophile, suggesting that they could offer a general scaffold for serine hydrolase inhibitor discovery. Here, we have tested this hypothesis by screening ABLs more broadly against cell and tissue proteomes by competitive activity-based protein profiling (ABPP), leading to the discovery of lead inhibitors for several serine hydrolases, including the uncharacterized enzyme α,β-hydrolase domain-containing 10 (ABHD10). ABPP-guided medicinal chemistry yielded a compound ABL303 that potently (IC(50) ≈ 30 nM) and selectively inactivated ABHD10 in vitro and in living cells. A comparison of optimized inhibitors for PME-1 and ABHD10 indicates that modest structural changes that alter steric bulk can tailor the ABL to selectively react with distinct, distantly related serine hydrolases. Our findings, taken together, designate the ABL as a versatile reactive group for creating first-in-class serine hydrolase inhibitors.

Abstract 27: Antioxidant Carbon-based Nanomaterials: In-vitro Protection and In- vivo Effects on the Neurovascular Unit

Introduction: Dysfunction of the cerebrovasculature, manifested by poor reperfusion and loss of autoregulation, is a feature of ischemia and traumatic brain injury (TBI). Oxidative stress is implicated in this effect. Conventional antioxidants have not proven clinically effective. Nanomaterials are an emerging class of antioxidants with potential advantages including quenching of oxidative radicals without need for enzymatic transformation.

Objectives: We tested whether the carbon nanomaterials, poly(ethylene gylcol)-functionalized hydrophilic carbon clusters (PEG-HCCs) are antioxidants and determined their effect on the cerebrovasculature following mild experimental TBI and hypotension.

Methods: HCCs were generated by treating single wall carbon nanotubes with oleum and nitric acid. HCCs were functionalized with PEG via coupling to carboxcylic acids. The ability to quench superoxide anion (SO) was determined in solution and b.End3 cultured brain endothelial cells after administering the electron chain transport inhibitor Antimycin A (AntA) using dihydroethidium (DHE) fluorescence flow cytometry. In-vivo studies were performed in Long Evans rats following mild TBI (3m/s; 2.5 mm deformation; 80 ms duration) and 50 mins. hemorrhagic hypotension followed by resuscitation with Lactated Ringers ( Figure : Resus ) then by shed blood ( Hospital ). Treatment with 2 mg/kg PEG-HCCs in 1 mL or PBS was initiated prior to the “Hospital” phase. Laser Doppler perfusion (LDF) was measured to 6 hours post-TBI.

Results: DHE fluorescence induced by AntA was eliminated by post-treatment with PEG-HCCs (2-4 mg/L; 15 min post-AntA). At that concentration, there was no innate toxicity in cells determined by clonogenic and trypan blue assay. Only pre-treatment with a 10X excess of SO dismutase (SOD) achieved comparable DHE effect. PEG-HCC post-treatment improved cell survival after a higher dose of AntA, to 65% of baseline compared to 23% for SOD. In-vivo following TBI, hypotension reduced relative LDF to approximately 30% ( Fig ). Administered just prior to shed blood nanotubes restored LDF to 100% of baseline while the vehicle group remained significantly lower at 56%. LDF declined in all groups over time.

Conclusions: PEG-HCCs are biocompatible with b.End3 cells and rapidly protected these cells from oxidative stress. PEG-HCCs at a clinically realistic time point improved cerebrovasculature dysfunction post-TBI/hypotension. The duration of effect is consistent with blood half life after a single dose. Longer term dosing studies are underway to establish the effect on outcome and reperfusion injury.

Abstract A145: EGFR-targeting of carbon nanovectors loaded with paclitaxel improves their antitumor efficacy and radiosensitization of head and neck squamous cell carcinoma in vivo

Nanoparticels have been researched broadly as new generation of diagnostics, imaging agents, and drugs for detecting and treating cancer. We previously developed PEGylated small hydrophilic carbon clusters (PEG-HCCs) and reported that PEG-HCCs conjugated with paclitaxel (PTX/PEG-HCCs) is a stable effective drug delivery system with minimal toxicity. Here, we describe the establishment of targeted nanovectors by simply mixing PTX/PEG-HCCs with cetuximab (ImClone Systems), an anti-epidermal growth factor receptor (EGFR) monoclonal antibody. The specificity of this EGFR targeted method of delivery of PTX/PEG-HCCs was demonstrated in mice implanted subcutaneously on opposing flanks with EGFR expressing, OSC-19 (head and neck squamous cell carcinoma: HNSCC) cells and non-EGFR-expressing MCF-7 cells in a nude mouse. The targeted nanovector system, Cet/PTX/PEG-HCCs, showed greater efficacy superior than PTX/PEG-HCCs on OSC-19 tumor growth, but not on MCF-7 tumors. Cet/PTX/PEG-HCCs also showed greater growth inhibition prolonged survival compared to PTX or PTX/PEG-HCCs in an orthotopic nude mouse model of human HNSCC. These results suggested that Cet/PTX/PEG-HCCs can targeted to HNSCC overexpressing EGFR cells. In addition, Cet/PTX/PEG-HCCs were found to radiosensitize HNSCC cells both in vitro and in vivo. Cet/PTX/PEG-HCCs plus radiation inhibited tumor growth and prolonged survival in vivo. This work is highly significant as success would allow for targeted chemotherapy for HNSCC by simply mixing commercially available drugs and antibodies with a nanovector solution.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A145.

Abstract C3: Selective denuding of nanoparticles for tumor targeting

Targeted delivery of therapeutics to tumors is highly desired both to deliver fragile compounds that cannot reach the tumor on their own and to limit off-target toxicity. Nanovectors, nanoparticles capable of transporting and delivering one or more bioactive molecules, are an emerging class of targeted drug delivery platforms. Targeting of nanovectors to tumors is conventionally achieved both by designing them to be approximately 50–200 nm in diameter in order to take advantage of the enhanced permeation and retention (EPR) effect common to tumors and/or functionalizing the nanovectors with ligands that bind specifically in the tumor environment. In order for these strategies to be successful, the nanovectors must have an extended circulation time in the blood. One result of this is accumulation and prolonged retention of many nanovectors in the liver and spleen, which raises toxicity concerns. Here we demonstrate a dramatically different strategy making use of nanovectors composed of insoluble ultrasmall nanoparticles cores functionalized with responsive solubilizing polymer shells. The responsive polymers are designed to be cleaved from the insoluble nanoparticles core in the tumor microenvironment, which results in the deposition of the insoluble nanoparticles at the tumor site. On the other hand, because the particles are ultrasmall, if they remain unchanged they are rapidly cleared from the body, dramatically reducing potential side effects.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr C3.

Noncovalent functionalization of carbon nanovectors with an antibody enables targeted drug delivery

Current chemotherapeutics are characterized by efficient tumor cell-killing and severe side effects mostly derived from off-target toxicity. Hence targeted delivery of these drugs to tumor cells is actively sought. We previously demonstrated that poly(ethylene glycol)-functionalized carbon nanovectors are able to sequester paclitaxel, a widely used hydrophobic cancer drug, by simple physisorption and thereby deliver the drug for killing of cancer cells. The cell-killing when these drug-loaded carbon nanoparticles were used was equivalent to when a commercial formulation of paclitaxel was used. Here we show that by further mixing the drug-loaded nanoparticles with Cetuximab, a monoclonal antibody that recognizes the epidermal growth factor receptor (EGFR), paclitaxel is preferentially targeted to EGFR+ tumor cells in vitro. This supports progressing to in vivo studies. Moreover, the construct is unusual in that all three components are assembled through noncovalent interactions. Such noncovalent assembly could enable high-throughput screening of drug/antibody combinations.

Improved synthesis of graphene oxide

An improved method for the preparation of graphene oxide (GO) is described. Currently, Hummers' method (KMnO(4), NaNO(3), H(2)SO(4)) is the most common method used for preparing graphene oxide. We have found that excluding the NaNO(3), increasing the amount of KMnO(4), and performing the reaction in a 9:1 mixture of H(2)SO(4)/H(3)PO(4) improves the efficiency of the oxidation process. This improved method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers' method or Hummers' method with additional KMnO(4). Moreover, even though the GO produced by our method is more oxidized than that prepared by Hummers' method, when both are reduced in the same chamber with hydrazine, chemically converted graphene (CCG) produced from this new method is equivalent in its electrical conductivity. In contrast to Hummers' method, the new method does not generate toxic gas and the temperature is easily controlled. This improved synthesis of GO may be important for large-scale production of GO as well as the construction of devices composed of the subsequent CCG.

Effective drug delivery, in vitro and in vivo, by carbon-based nanovectors noncovalently loaded with unmodified Paclitaxel

Many new drugs have low aqueous solubility and high therapeutic efficacy. Paclitaxel (PTX) is a classic example of this type of compound. Here we show that extremely small (<40 nm) hydrophilic carbon clusters (HCCs) that are PEGylated (PEG-HCCs) are effective drug delivery vehicles when simply mixed with paclitaxel. This formulation of PTX sequestered in PEG-HCCs (PTX/PEG-HCCs) is stable for at least 20 weeks. The PTX/PEG-HCCs formulation was as effective as PTX in a clinical formulation in reducing tumor volumes in an orthotopic murine model of oral squamous cell carcinoma. Preliminary toxicity and biodistribution studies suggest that the PEG-HCCs are not acutely toxic and, like many other nanomaterials, are primarily accumulated in the liver and spleen. This work demonstrates that carbon nanomaterials are effective drug delivery vehicles in vivo when noncovalently loaded with an unmodified drug.

Highly Efficient Ruthenium Catalysts for the Formation of Tetrasubstituted Olefins via Ring-Closing Metathesis

[reaction: see text] A series of ruthenium-based metathesis catalysts with N-heterocyclic carbene (NHC) ligands have been prepared in which the N-aryl groups have been changed from mesityl to mono-ortho-substituted phenyl (e.g., tolyl). These new catalysts offer an exceptional increase in activity for the formation of tetrasubstituted olefins via ring-closing metathesis (RCM), while maintaining high levels of activity in ring-closing metathesis (RCM) reactions that generate di- and trisubstituted olefins.

Ruthenium-Catalyzed Ring-Closing Metathesis to Form Tetrasubstituted Olefins

[structure: see text]. Increased efficiency for ring-closing metathesis to form tetrasubstituted olefins using N-heterocyclic carbene ligated ruthenium catalysts was achieved by reducing the size of the substituents at the ortho positions of the N-bound aryl rings.

Highly active chiral ruthenium catalysts for asymmetric ring-closing olefin metathesis

The synthesis of olefin metathesis catalysts containing chiral, monodentate N-heterocyclic carbenes and their application to asymmetric ring-closing metathesis (ARCM) are reported. These catalysts retain the high levels of reactivity found in the related achiral variants (1a and 1b). Using the parent chiral catalysts 2a and 2b and derivatives that contain steric bulk in the meta positions of the N-bound aryl rings (catalysts 3-5), five- through seven-membered rings were formed in up to 92% ee. The addition of sodium iodide to catalysts 2a-4a (to form 2b-4b in situ) caused a dramatic increase in enantioselectivity for many substrates. Catalyst 5a, which gave high enantiomeric excesses for certain substrates without the addition of NaI, could be used in loadings of < or =1 mol %. Mechanistic explanations for the large sodium iodide effect as well as possible mechanistic pathways leading to the observed products are discussed.