Phase I Single-Dose Study of Intracavitary-Administered Iodine-131-TM-601 in Adults With Recurrent High-Grade Glioma

Chlorotoxin peptide-functionalized polyethylenimine-entrapped gold nanoparticles for glioma SPECT/CT imaging and radionuclide therapy

BACKGROUND

Malignant glioma is the most common and deadliest brain cancer due to the obstacle from indistinct tumor margins for surgical excision and blood brain barrier (BBB) for chemotherapy. Here, we designed and prepared multifunctional polyethylenimine-entrapped gold nanoparticles (Au PENPs) for targeted SPECT/CT imaging and radionuclide therapy of glioma.

RESULTS

Polyethylenimine was selected as a template for sequential modification with polyethylene glycol (PEG), glioma-specific peptide (chlorotoxin, CTX) and 3-(4-hydroxyphenyl)propionic acid-OSu (HPAO), and were then used to entrap gold nanoparticles (Au NPs). After 131I radiolabeling via HPAO, the 131I-labeded CTX-functionalized Au PENPs as a multifunctional glioma-targeting nanoprobe were generated. Before 131I radiolabeling, the CTX-functionalized Au PENPs exhibited a uniform size distribution, favorable X-ray attenuation property, desired water solubility, and cytocompatibility in the given Au concentration range. The 131I-labeled CTX-functionalized Au PENPs showed high radiochemical purity and stability, and could be used as a nanoprobe for the targeted SPECT/CT imaging and radionuclide therapy of glioma cells in vitro and in vivo in a subcutaneous tumor model. Owing to the unique biological properties of CTX, the developed nanoprobe was able to cross the BBB and specifically target glioma cells in a rat intracranial glioma model.

CONCLUSIONS

Our results indicated that the formed nanosystem had the significant potential to be applied for glioma targeted diagnosis and therapy.

Radiosynthesis and Preliminary Biological Evaluation of 18F-Fluoropropionyl-Chlorotoxin as a Potential PET Tracer for Glioma Imaging

PURPOSES

Chlorotoxin can specifically bind to matrix metalloproteinase 2 (MMP-2), which are overexpressed in the glioma. In this work, radiosynthesis of [18F]-fluoropropionyl-chlorotoxin ([18F]-FP-chlorotoxin) as a novel PET tracer was investigated, and biodistribution in vivo and PET imaging were performed in the C6 glioma model.

PROCEDURES

[18F]-FP-chlorotoxin was prepared from the reaction of chlorotoxin with [18F]-NFB (4-nitrophenyl 2-[18F]-fluoropropionate), which was synthesized from multistep reactions. Biodistribution was determined in 20 normal Kunming mice. Small-animal PET imaging with [18F]-FP-chlorotoxin was performed on the same rats bearing orthotopic C6 glioma at different time points (60 min, 90 min, and 120 min) after injection and compared with 2-deoxy-2-[18F] fluoro-D-glucose ([18F]-FDG).

RESULTS

[18F]-FP-Chlorotoxin was successfully synthesized in the radiochemical yield of 41% and the radiochemical purity of more than 98%. Among all the organs, the brain had the lowest and stable uptake of [18F]-FP-chlorotoxin, while the kidney showed the highest uptake. Compared with [18F]-FDG, a low uptake of [18F]-FP-chlorotoxin was detected in normal brain parenchyma and a high accumulation of [18F]-FP-chlorotoxin was found in the gliomas tissue. The glioma to normal brain uptake ratio of [18F]-FP-chlorotoxin was higher than that of [18F]-FDG. Furthermore, the uptake of [18F]-FP-chlorotoxin at 90 min after injection was better than that at 60 min after injection.

CONCLUSIONS

Compared with [18F]-FDG, [18F]-FP-chlorotoxin has a low and stable uptake in normal brain parenchyma. [18F]-FP-Chlorotoxin seems to be a potential PET tracer with a good performance in diagnosis of the glioma.

Chlorotoxin-A Multimodal Imaging Platform for Targeting Glioma Tumors

Chlorotoxin (CTX) is a 36-amino-acid disulfide-containing peptide derived from the venom of the scorpion Leiurus quinquestriatus. CTX alters physiology in numerous ways. It interacts with voltage gated chloride channels, Annexin-2, and matrix metalloproteinase-2 (MMP-2). CTX-based bioconjugates have been widely subjected to phase I/II clinical trials and have shown substantial promise. Many studies have demonstrated that CTX preferentially binds to neuroectodermal tumors, such as glioblastoma, without cross-reactivity to normal brain cells. With its ability to penetrate the blood-brain-barrier (BBB) and its tyrosine residue allows covalent conjugation with functional moieties, CTX is an attractive platform to explore development of diagnostic and therapeutic agents for gliomas. In this review, we outline CTX structure and its molecular targets, summarize molecular variations of CTX developed for glioma imaging, and discuss future trends and perspectives for CTX conjugates as a theranostic agent.

Targeting central nervous system pathologies with nanomedicines

One of the major challenges in drug development is the delivery of therapeutics to the central nervous system (CNS). The blood-brain barrier (BBB), which modulates the passage of molecules from the CNS, presents a formidable obstacle that limits brain uptake of therapeutics and, therefore, impedes the treatment of multiple neurological pathologies. Targeted nanocarriers present an excellent opportunity for drug delivery into the brain leveraging on endogenous receptors to transport therapeutics across the BBB endothelium. Receptor-mediated transport endows multiple benefits over other conventional delivery methods such as the transient permeabilization of the BBB or the direct depositioning of intracranial depots. Herein, different strategies for nanocarrier targeting to the CNS are discussed, highlighting the challenges and recent developments.

Anti-metastatic effect of 131I-labeled Buthus martensii Karsch chlorotoxin in gliomas

The present study investigated the underlying molecular mechanism by which Buthus martensii Karsch chlorotoxin (BmK CT) inhibits the invasion and metastasis of glioma cells and the possibility of 131I‑labeled BmK CT (131I‑BmK CT) as a novel targeted agent for the treatment of glioma. The impact of BmK CT with and without 131I radiolabeling on the invasion and metastasis of glioma cells in vitro was studied. Cell viability was assessed using Cell Counting Kit‑8 and plate colony formation assays in order to confirm the cytotoxicity of BmK CT and 131I‑BmK CT at different concentrations. Transwell invasion and wound‑healing assays were conducted in order to investigate the inhibitory effects BmK CT and 131I‑BmK CT on cell migration and invasion. Furthermore, western blotting, ELISA immunofluorescence and a gelatin zymography assay were performed to evaluate changes in the protein expression levels of glioma cells following treatment with BmK CT or 131I‑BmK CT. The results indicated that BmK CT inhibits the invasion and metastasis of glioma cells via regulation of tissue inhibitor of metalloproteinase‑2 expression and that 131I‑BmK CT has the potential to be a novel targeted therapeutic drug for glioma.

Glioblastoma quo vadis: Will migration and invasiveness reemerge as therapeutic targets?

PURPOSE

The purpose of the current review is to highlight, on one hand, the fact that the migratory pattern of glioma cells is the major obstacle to combat them with chemotherapy, and on the other one, the new treatment strategies to overcome this obstacle.

METHODS

This review surveys several membrane and extracellular molecules involved in glioma cell migration, invasiveness and resistance to apoptosis.

RESULTS

This review focuses on signaling pathways implicated in the positive regulation of glioblastoma cell migration, including glutamate and ion channel networks, microtubes and membrane-derived extracellular vesicles (EV) containing microRNAs. Glioma cells release glutamate to the extracellular matrix, inducing neuronal cell death, which may facilitate glioma growth and invasion. Glioma cell migration and invasion are further facilitated through ion channels and transporters that modify cellular volume. Microtubes and EV promote connections and communication among glioma cells and with the microenvironment and are associated with progression and resistance to therapy. Potential therapies linked to these pathways for glioblastoma are being developed.

CONCLUSION

Our view is evolving from an intracellular view of the complex intracellular signaling pathways to one of orchestral machinery, including connections between heterogeneous tumoral and nontumoral cells and with the microenvironment through channels, microtubes, and extracellular miRNA, generating different signals at different times. All of these elements give rise to a new perspective for the treatment of glioblastoma.

Evidence and context of use for contrast enhancement as a surrogate of disease burden and treatment response in malignant glioma

The use of contrast enhancement within the brain on CT or MRI has been the gold standard for diagnosis and therapeutic response assessment in malignant gliomas for decades. The use of contrast enhancing tumor size, however, remains controversial as a tool for accurately diagnosing and assessing treatment efficacy in malignant gliomas, particularly in the current, quickly evolving therapeutic landscape. The current article consolidates overwhelming evidence from hundreds of studies in the field of neuro-oncology, providing the necessary evidence base and specific contexts of use for consideration of contrast enhancing tumor size as an appropriate surrogate biomarker for disease burden and as a tool for measuring treatment response in malignant glioma, including glioblastoma.

From venoms to BBB-shuttles. MiniCTX3: a molecular vector derived from scorpion venom

A monocyclic peptidomimetic version of chlorotoxin, MiniCTX3, was developed as a BBB-shuttle being able to transport nanoparticles across endothelial cells. Our results reveal animal venoms as an outstanding source of BBB-shuttles.

Venom-based peptide therapy: insights into anti-cancer mechanism

The 5-year relative survival rate of all types of cancer has increased significantly over the past three decades partly due to the targeted therapy. However, still there are many targeted therapy drugs could play a role only in a portion of cancer patients with specific molecular alternation. It is necessary to continue to develop new biological agents which could be used alone and/or in combination with current FDA approved drugs to treat complex cancer diseases. Venom-based drugs have been used for hundreds of years in human history. Nevertheless, the venom-origin of the anti-cancer drug do rarely appear in the pharmaceutical market; and this is due to the fact that the mechanism of action for a large number of the venom drug such as venom-based peptide is not clearly understood. In this review, we focus on discussing some identified venom-based peptides and their anti-cancer mechanisms including the blockade of cancer cell proliferation, invasion, angiogenesis, and metastasis (hallmarks of cancer) to fulfill the gap which is hindering their use in cancer therapy. Furthermore, it also highlights the importance of immunotherapy based on venom peptide. Overall, this review provides readers for further understanding the mechanism of venom peptide and elaborates on the need to explore peptide-based therapeutic strategies.

Peptide therapeutics from venom: Current status and potential

Peptides are recognized as being highly selective, potent and relatively safe as potential therapeutics. Peptides isolated from the venom of different animals satisfy most of these criteria with the possible exception of safety, but when isolated as single compounds and used at appropriate concentrations, venom-derived peptides can become useful drugs. Although the number of venom-derived peptides that have successfully progressed to the clinic is currently limited, the prospects for venom-derived peptides look very optimistic. As proteomic and transcriptomic approaches continue to identify new sequences, the potential of venom-derived peptides to find applications as therapeutics, cosmetics and insecticides grows accordingly.

SPECT imaging and radionuclide therapy of glioma using 131I labeled Buthus martensii Karsch chlorotoxin

Gliomas, the most prevalent type of brain tumor in adults, are associated with high rates of morbidity and mortality. Recent studies on ¹³¹I labeled scorpion toxins suggest they can be developed as tumor-specific agents for glioma diagnosis and treatment. This study investigated the potential of ¹³¹I labeled Buthus martensii Karsch chlorotoxin (¹³¹I-BmK CT) as a new approach for targeted imaging and therapy of glioma. The results showed that ¹³¹I can be successfully linked to BmK CT with satisfactory radiochemical purity and stability and that ¹³¹I-BmK CT markedly inhibited glioma cell growth in a dose and time dependent manner, with significant accumulation in glioma cells in vitro. Persistent intratumoral radioiodine retention and specific accumulation of ¹³¹I-BmK CT were observed in C6 glioma tumor, which was clearly visualized by SPECT imaging. Both intratumoral and intravenous injections of ¹³¹I-BmK CT could result in significant tumor inhibition efficacy and prolonging the lifetime of tumor-bearing mice. Based on these promising results, it is concluded that ¹³¹I-BmK CT has the potential to be explored as a novel tool for SPECT imaging and radionuclide therapy of glioma.

Nonclinical Profile of BLZ-100, a Tumor-Targeting Fluorescent Imaging Agent

BLZ-100 is a single intravenous use, fluorescent imaging agent that labels tumor tissue to enable more complete and precise surgical resection. It is composed of a chlorotoxin peptide covalently bound to the near-infrared fluorophore indocyanine green. BLZ-100 is in clinical development for intraoperative visualization of human tumors. The nonclinical safety and pharmacokinetic (PK) profile of BLZ-100 was evaluated in mice, rats, canines, and nonhuman primates (NHP). Single bolus intravenous administration of BLZ-100 was well tolerated, and no adverse changes were observed in cardiovascular safety pharmacology, PK, and toxicology studies in rats and NHP. The single-dose no-observed-adverse-effect-levels (NOAELs) were 7 mg (28 mg/kg) in rats and 60 mg (20 mg/kg) in NHP, corresponding to peak concentration values of 89 400 and 436 000 ng/mL and area-under-the-curve exposure values of 130 000 and 1 240 000 h·ng/mL, respectively. Based on a human imaging dose of 3 mg, dose safety margins are >100 for rat and monkey. BLZ-100 produced hypersensitivity reactions in canine imaging studies (lethargy, pruritus, swollen muzzle, etc). The severity of the reactions was not dose related. In a follow-up study in dogs, plasma histamine concentrations were increased 5 to 60 minutes after BLZ-100 injection; this coincided with signs of hypersensitivity, supporting the conclusion that the reactions were histamine based. Hypersensitivity reactions were not observed in other species or in BLZ-100 human clinical studies conducted to date. The combined imaging, safety pharmacology, PK, and toxicology studies contributed to an extensive initial nonclinical profile for BLZ-100, supporting first-in-human clinical trials.

The Molecular Basis of Toxins' Interactions with Intracellular Signaling via Discrete Portals

An understanding of the molecular mechanisms by which microbial, plant or animal-secreted toxins exert their action provides the most important element for assessment of human health risks and opens new insights into therapies addressing a plethora of pathologies, ranging from neurological disorders to cancer, using toxinomimetic agents. Recently, molecular and cellular biology dissecting tools have provided a wealth of information on the action of these diverse toxins, yet, an integrated framework to explain their selective toxicity is still lacking. In this review, specific examples of different toxins are emphasized to illustrate the fundamental mechanisms of toxicity at different biochemical, molecular and cellular- levels with particular consideration for the nervous system. The target of primary action has been highlighted and operationally classified into 13 sub-categories. Selected examples of toxins were assigned to each target category, denominated as portal, and the modulation of the different portal’s signaling was featured. The first portal encompasses the plasma membrane lipid domains, which give rise to pores when challenged for example with pardaxin, a fish toxin, or is subject to degradation when enzymes of lipid metabolism such as phospholipases A₂ (PLA₂) or phospholipase C (PLC) act upon it. Several major portals consist of ion channels, pumps, transporters and ligand gated ionotropic receptors which many toxins act on, disturbing the intracellular ion homeostasis. Another group of portals consists of G-protein-coupled and tyrosine kinase receptors that, upon interaction with discrete toxins, alter second messengers towards pathological levels. Lastly, subcellular organelles such as mitochondria, nucleus, protein- and RNA-synthesis machineries, cytoskeletal networks and exocytic vesicles are also portals targeted and deregulated by other diverse group of toxins. A fundamental concept can be drawn from these seemingly different toxins with respect to the site of action and the secondary messengers and signaling cascades they trigger in the host. While the interaction with the initial portal is largely determined by the chemical nature of the toxin, once inside the cell, several ubiquitous second messengers and protein kinases/ phosphatases pathways are impaired, to attain toxicity. Therefore, toxins represent one of the most promising natural molecules for developing novel therapeutics that selectively target the major cellular portals involved in human physiology and diseases.

Scorpion venoms in gastric cancer

Venom secretions from snakes, scorpions, spiders and bees, have been widely applied in traditional medicine and current biopharmaceutical research. Possession of anticancer potential is another novel discovery for animal venoms and toxins. An increasing number of studies have shown the anticancer effects of venoms and toxins of snakes, and scorpions in vitro and in vivo, which were achieved mainly through the inhibition of cancer growth, arrest of cell cycle, induction of apoptosis and suppression of cancer metastasis. However, more evidence is needed to support this concept and the mechanisms of anticancer actions are not clearly understood. The present review is focused on the recant updates on anticancer venom research.

Re-irradiation alternatives for recurrent high-grade glioma

Despite advances in the fields of surgery, chemotherapy and radiotherapy, the prognosis for high-grade glioma (HGG) remains unsatisfactory. The majority of HGG patients experience disease recurrence. To date, no standard treatments have been established for recurrent HGG. Repeat surgery and chemotherapy demonstrate moderate efficacy. As recurrent lesions are usually located within the previously irradiated field, a second course of irradiation was once considered controversial, as it was considered to exhibit unsatisfactory efficacy and radiation-related toxicities. However, an increasing number of studies have indicated that re-irradiation may present an efficacious treatment for recurrent HGG. Re-irradiation may be delivered via conventionally fractionated stereotactic radiotherapy, hypofractionated stereotactic radiation therapy, stereotactic radiosurgery and brachytherapy techniques. In the present review, the current literature regarding re-irradiation treatment for recurrent HGG is summarized with regard to survival outcome and side effects.

A role for ion channels in perivascular glioma invasion

Malignant gliomas are devastating tumors, frequently killing those diagnosed in little over a year. The profuse infiltration of glioma cells into healthy tissue surrounding the main tumor mass is one of the major obstacles limiting the improvement of patient survival. Migration along the abluminal side of blood vessels is one of the salient features of glioma cell invasion. Invading glioma cells are attracted to the vascular network, in part by the neuropeptide bradykinin, where glioma cells actively modify the gliovascular interface and undergo volumetric alterations to navigate the confined space. Critical to these volume modifications is a proposed hydrodynamic model that involves the flux of ions in and out of the cell, followed by osmotically obligated water. Ion and water channels expressed by the glioma cell are essential in this model of invasion and make opportune therapeutic targets. Lastly, there is growing evidence that vascular-associated glioma cells are able to control the vascular tone, presumably to free up space for invasion and growth. The unique mechanisms that enable perivascular glioma invasion may offer critical targets for therapeutic intervention in this devastating disease. Indeed, a chloride channel-blocking peptide has already been successfully tested in human clinical trials.

131I-labeled multifunctional dendrimers modified with BmK CT for targeted SPECT imaging and radiotherapy of gliomas

Aim: The poly(amidoamine) dendrimers modified with Buthus martensii Karsch chlorotoxin (BmK CT) were developed as a 131I delivery system for glioma-targeted imaging and therapy. Materials & methods: Dendrimers before and after labeling 131I were synthetized and their physicochemical properties were tested. The targeting and therapeutic efficacy of 131I-G5.NHAc-HPAO-(PEG-BmK CT)-(mPEG) dendrimer against glioma was evaluated in vitro and in vivo. Results: All the dendrimers were stable under different conditions. BmK CT modification increased the cellular uptake of dendrimers in C6 glioma cells, but not in the normal RLE-6TN cells. 131I-G5.NHAc-HPAO-(PEG-BmK CT)-(mPEG) dendrimer was radiochemically pure and could be applied in glioma-targeting single-photon emission CT (SPECT) imaging and radiotherapy. Conclusion: 131I-G5.NHAc-HPAO-(PEG-BmK CT)-(mPEG) complex is a promising multifunctional nanoplatform for glioma-specific nuclear imaging and radiotherapy.

Image-Guided Tumor Resection

Each year, millions of individuals undergo cancer surgery that is intended to be curative or at least a necessary component of a curative regimen. Particularly for those patients whose cancer harbors cells that are resistant to chemotherapy or radiation, the extent of surgery often defines whether they will be a survivor or casualty of the disease. For many solid tumor types, the difference in survival between patients who undergo gross total resection and those who have residual bulky disease is often profound. With surgery being central to cancer survivorship, it is stunning how few resources have been invested in improving surgical outcomes, particularly in comparison to chemotherapeutic research and discovery. This article reviews recent advances related to developing targeted fluorescent agents to guide surgeons during cancer removal. The goal of these drugs and devices is to clearly distinguish cancer from normal tissue to improve surgical outcome for cancer patients.

Preclinical Validation of the Utility of BLZ-100 in Providing Fluorescence Contrast for Imaging Spontaneous Solid Tumors

There is a need in surgical oncology for contrast agents that can enable real-time intraoperative visualization of solid tumors that can enable complete resections while sparing normal surrounding tissues. The Tumor Paint agent BLZ-100 is a peptide-fluorophore conjugate that can specifically bind solid tumors and fluoresce in the near-infrared range, minimizing light scatter and signal attenuation. In this study, we provide a preclinical proof of concept for use of this imaging contrast agent as administered before surgery to dogs with a variety of naturally occurring spontaneous tumors. Imaging was performed on excised tissues as well as intraoperatively in a subset of cases. Actionable contrast was achieved between tumor tissue and surrounding normal tissues in adenocarcinomas, squamous cell carcinomas, mast cell tumors, and soft tissue sarcomas. Subcutaneous soft tissue sarcomas were labeled with the highest fluorescence intensity and greatest tumor-to-background signal ratio. Our results establish a foundation that rationalizes clinical studies in humans with soft tissue sarcoma, an indication with a notably high unmet need.

Structure-Activity Relationship of Chlorotoxin-Like Peptides

Animal venom (e.g., scorpion) is a rich source of various protein and peptide toxins with diverse physio-/pharmaco-logical activities, which generally exert their action via target-specific modulation of different ion channel functions. Scorpion venoms are among the most widely-known source of peptidyl neurotoxins used for callipering different ion channels, such as; Na⁺, K⁺, Ca⁺, Cl(-), etc. A new peptide of the chlorotoxin family (i.e., Bs-Tx7) has been isolated, sequenced and synthesized from scorpion Buthus sindicus (family Buthidae) venom. This peptide demonstrates 66% with chlorotoxin (ClTx) and 82% with CFTR channel inhibitor (GaTx1) sequence identities reported from Leiurus quinquestriatus hebraeus venom. The toxin has a molecular mass of 3821 Da and possesses four intra-chain disulphide bonds. Amino acid sequence analysis of Bs-Tx7 revealed the presence of a scissile peptide bond (i.e., Gly-Ile) for human MMP2, whose activity is increased in the case of tumour malignancy. The effect of hMMP2 on Bs-Tx7, or vice versa, observed using the FRET peptide substrate with methoxycoumarin (Mca)/dinitrophenyl (Dnp) as fluorophore/quencher, designed and synthesized to obtain the lowest Km value for this substrate, showed approximately a 60% increase in the activity of hMMP2 upon incubation of Bs-Tx7 with the enzyme at a micromolar concentration (4 µM), indicating the importance of this toxin in diseases associated with decreased MMP2 activity.

Polymeric drug delivery for the treatment of glioblastoma

Glioblastoma (GBM) remains an almost universally fatal diagnosis. The current therapeutic mainstay consists of maximal safe surgical resection followed by radiation therapy (RT) with concomitant temozolomide (TMZ), followed by monthly TMZ (the "Stupp regimen"). Several chemotherapeutic agents have been shown to have modest efficacy in the treatment of high-grade glioma (HGG), but blood-brain barrier impermeability remains a major delivery obstacle. Polymeric drug-delivery systems, developed to allow controlled local release of biologically active substances for a variety of conditions, can achieve high local concentrations of active agents while limiting systemic toxicities. Polymerically delivered carmustine (BCNU) wafers, placed on the surface of the tumor-resection cavity, can potentially provide immediate chemotherapy to residual tumor cells during the standard delay between surgery and chemoradiotherapy. BCNU wafer implantation as monochemotherapy (with RT) in newly diagnosed HGG has been investigated in 2 phase III studies that reported significant increases in median overall survival. A number of studies have investigated the tumoricidal synergies of combination chemotherapy with BCNU wafers in newly diagnosed or recurrent HGG, and a primary research focus has been the integration of BCNU wafers into multimodality therapy with the standard Stupp regimen. Overall, the results of these studies have been encouraging in terms of safety and efficacy. However, the data must be qualified by the nature of the studies conducted. Currently, there are no phase III studies of BCNU wafers with the standard Stupp regimen. We review the rationale, biochemistry, pharmacokinetics, and research history (including toxicity profile) of this modality.

Arachnids of medical importance in Brazil: main active compounds present in scorpion and spider venoms and tick saliva

Arachnida is the largest class among the arthropods, constituting over 60,000 described species (spiders, mites, ticks, scorpions, palpigrades, pseudoscorpions, solpugids and harvestmen). Many accidents are caused by arachnids, especially spiders and scorpions, while some diseases can be transmitted by mites and ticks. These animals are widely dispersed in urban centers due to the large availability of shelter and food, increasing the incidence of accidents. Several protein and non-protein compounds present in the venom and saliva of these animals are responsible for symptoms observed in envenoming, exhibiting neurotoxic, dermonecrotic and hemorrhagic activities. The phylogenomic analysis from the complementary DNA of single-copy nuclear protein-coding genes shows that these animals share some common protein families known as neurotoxins, defensins, hyaluronidase, antimicrobial peptides, phospholipases and proteinases. This indicates that the venoms from these animals may present components with functional and structural similarities. Therefore, we described in this review the main components present in spider and scorpion venom as well as in tick saliva, since they have similar components. These three arachnids are responsible for many accidents of medical relevance in Brazil. Additionally, this study shows potential biotechnological applications of some components with important biological activities, which may motivate the conducting of further research studies on their action mechanisms.

Toxins and derivatives in molecular pharmaceutics: Drug delivery and targeted therapy

Protein and peptide toxins offer an invaluable source for the development of actively targeted drug delivery systems. They avidly bind to a variety of cognate receptors, some of which are expressed or even up-regulated in diseased tissues and biological barriers. Protein and peptide toxins or their derivatives can act as ligands to facilitate tissue- or organ-specific accumulation of therapeutics. Some toxins have evolved from a relatively small number of structural frameworks that are particularly suitable for addressing the crucial issues of potency and stability, making them an instrumental source of leads and templates for targeted therapy. The focus of this review is on protein and peptide toxins for the development of targeted drug delivery systems and molecular therapies. We summarize disease- and biological barrier-related toxin receptors, as well as targeted drug delivery strategies inspired by those receptors. The design of new therapeutics based on protein and peptide toxins is also discussed.

The role of disulfide bonds in structure and activity of chlorotoxin

BACKGROUND

Chlorotoxin is a small scorpion peptide that inhibits glioma cell migration. We investigated the importance of a major component of chlorotoxin's chemical structure - four disulfide bonds - to its tertiary structure and biological function.

RESULTS

Five disulfide bond analogs of chlorotoxin were synthesized, with l-α-aminobutyric acid residues replacing each or all of the disulfide bonds. Chemical oxidation and circular dichroism experiments revealed that Cys III-VII and Cys V-VIII were essential for native structure formation. Cys I-IV and Cys II-VI were important for stability of enzymatic proteolysis but not for the inhibition of human umbilical vein endothelial cell migration.

CONCLUSION

The disulfide bonds of chlorotoxin are important for its structure and stability and have a minor role in its activity against cell migration.

Combination treatment with theranostic nanoparticles for glioblastoma sensitization to TMZ

PURPOSE

Tumor resistance to chemotherapeutic drugs is one of the major obstacles in the treatment of glioblastoma multiforme (GBM). In this study, we attempted to modulate tumor response to chemotherapy by combination treatment that included experimental (small interference RNA (siRNA), chlorotoxin) and conventional (temozolomide, TMZ) therapeutics.

PROCEDURES

siRNA therapy was used to silence O(6)-methylguanine methyltransferase (MGMT), a key factor in brain tumor resistance to TMZ. For targeting of tumor cells, we used chlorotoxin (CTX), a peptide with antitumoral properties. siRNA and CTX were conjugated to iron oxide nanoparticles (NP) that served as the drug carrier and allowed the means to monitor the changes in tumor volume by magnetic resonance imaging (MRI).

RESULTS

Theranostic nanoparticles (termed CTX-NP-siMGMT) were internalized by T98G glioblastoma cells in vitro leading to enhancement of TMZ toxicity. Combination treatment of mice bearing orthotopic tumors with CTX-NP-siMGMT and TMZ led to significant retardation of tumor growth, which was monitored by MRI.

CONCLUSIONS

While our results demonstrate that siRNA delivery by targeted nanoparticles resulted in modulating tumor response to chemotherapy in GBM, they also point to a significant contribution of CTX to tumor cell death.

Targeting ion channels for cancer therapy by repurposing the approved drugs

Ion channels have been shown to be involved in oncogenesis and efforts are being poured in to target the ion channels. There are many clinically approved drugs with ion channels as "off" targets. The question is, can these drugs be repurposed to inhibit ion channels for cancer treatment? Repurposing of drugs will not only save investors' money but also result in safer drugs for cancer patients. Advanced bioinformatics techniques and availability of a plethora of open access data on FDA approved drugs for various indications and omics data of large number of cancer types give a ray of hope to look for possibility of repurposing those drugs for cancer treatment. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Current strategies for targeted delivery of bio-active drug molecules in the treatment of brain tumor

Brain tumor is one of the most challenging diseases to treat. The major obstacle in the specific drug delivery to brain is blood-brain barrier (BBB). Mostly available anti-cancer drugs are large hydrophobic molecules which have limited permeability via BBB. Therefore, it is clear that the protective barriers confining the passage of the foreign particles into the brain are the main impediment for the brain drug delivery. Hence, the major challenge in drug development and delivery for the neurological diseases is to design non-invasive nanocarrier systems that can assist controlled and targeted drug delivery to the specific regions of the brain. In this review article, our major focus to treat brain tumor by study numerous strategies includes intracerebral implants, BBB disruption, intraventricular infusion, convection-enhanced delivery, intra-arterial drug delivery, intrathecal drug delivery, injection, catheters, pumps, microdialysis, RNA interference, antisense therapy, gene therapy, monoclonal/cationic antibodies conjugate, endogenous transporters, lipophilic analogues, prodrugs, efflux transporters, direct conjugation of antitumor drugs, direct targeting of liposomes, nanoparticles, solid-lipid nanoparticles, polymeric micelles, dendrimers and albumin-based drug carriers.

Chlorotoxin: a helpful natural scorpion peptide to diagnose glioma and fight tumor invasion

Chlorotoxin is a small 36 amino-acid peptide identified from the venom of the scorpion Leiurus quinquestriatus. Initially, chlorotoxin was used as a pharmacological tool to characterize chloride channels. While studying glioma-specific chloride currents, it was soon discovered that chlorotoxin possesses targeting properties towards cancer cells including glioma, melanoma, small cell lung carcinoma, neuroblastoma and medulloblastoma. The investigation of the mechanism of action of chlorotoxin has been challenging because its cell surface receptor target remains under questioning since two other receptors have been claimed besides chloride channels. Efforts on chlorotoxin-based applications focused on producing analogues helpful for glioma diagnosis, imaging and treatment. These efforts are welcome since gliomas are very aggressive brain cancers, close to impossible to cure with the current therapeutic arsenal. Among all the chlorotoxin-based strategies, the most promising one to enhance patient mean survival time appears to be the use of chlorotoxin as a targeting agent for the delivery of anti-tumor agents. Finally, the discovery of chlorotoxin has led to the screening of other scorpion venoms to identify chlorotoxin-like peptides. So far several new candidates have been identified. Only detailed research and clinical investigations will tell us if they share the same anti-tumor potential as chlorotoxin.

Radiosurgery reirradiation for high-grade glioma recurrence: a retrospective analysis

Despite various treatment strategies being available, recurrent high-grade gliomas (r-HGG) are difficult to manage. To obtain local control, radiosurgery (SRS) reirradiation has been considered as potential treatment. In the present study, a retrospective analysis was performed on r-HGG patients treated with salvage single- (s-SRS) or multi-fraction SRS (m-SRS). The aim of this study was to evaluate the effectiveness of salvage SRS in terms of overall survival (OS); toxicity was analyzed as well. Between 2004 May and 2011 December, 128 r-HGG patients (161 lesions) treated with CyberKnife(®) SRS reirradiation were retrospectively analyzed. Toxicity was graded according to Radiation Therapy Oncology Group and by Common Terminology Criteria for Adverse Events v.3 criteria. OS from the diagnosis date and OS from reirradiation were estimated using the Kaplan-Meier method. Median follow-up was 9 months (range 15 days-82 months). All patients completed SRS without high-grade toxicity. Radiation necrosis was observed in seven patients (6 %) with large volume lesions. The median survival from initial diagnosis was 32 months. The 1-, 2-, and 3-years survival rates from diagnosis were 95, 62, and 45 % respectively. Median survival following SRS was 11.5 months. The 1-, 2-, and 3-years survival rate following SRS was 48, 20, and 17 % respectively. On multivariate analysis, age <40 years, salvage surgery before SRS, and other post-SRS therapies (second-line chemotherapy and/or surgery) were found to significantly improve survival (p = 0.03). SRS represents a safe and feasible option to treat r-HGG patients with low complication rates and potential survival benefit.

Scorpion venom components as potential candidates for drug development

Scorpions are well known for their dangerous stings that can result in severe consequences for human beings, including death. Neurotoxins present in their venoms are responsible for their toxicity. Due to their medical relevance, toxins have been the driving force in the scorpion natural compounds research field. On the other hand, for thousands of years, scorpions and their venoms have been applied in traditional medicine, mainly in Asia and Africa. With the remarkable growth in the number of characterized scorpion venom components, several drug candidates have been found with the potential to tackle many of the emerging global medical threats. Scorpions have become a valuable source of biologically active molecules, from novel antibiotics to potential anticancer therapeutics. Other venom components have drawn attention as useful scaffolds for the development of drugs. This review summarizes the most promising candidates for drug development that have been isolated from scorpion venoms.

Neurotoxin-directed synthesis and in vitro evaluation of Au nanoclusters

A glioma-specific theranostic agent is prepared by using Chlorotoxin fusion protein to direct the synthesis of Au nanoclusters, which exhibit bright fluorescence and high specificity to target and treat glioma cells.

Chloride channels in cancer: Focus on chloride intracellular channel 1 and 4 (CLIC1 AND CLIC4) proteins in tumor development and as novel therapeutic targets

In recent decades, growing scientific evidence supports the role of ion channels in the development of different cancers. Both potassium selective pores and chloride permeabilities are considered the most active channels during tumorigenesis. High rate of proliferation, active migration, and invasiveness into non-neoplastic tissues are specific properties of neoplastic transformation. All these actions require partial or total involvement of chloride channel activity. In this context, this class of membrane proteins could represent valuable therapeutic targets for the treatment of resistant tumors. However, this encouraging premise has not so far produced any valid new channel-targeted antitumoral molecule for cancer treatment. Problematic for drug design targeting ion channels is their vital role in normal cells for essential physiological functions. By targeting these membrane proteins involved in pathological conditions, it is inevitable to cause relevant side effects in healthy organs. In light of this, a new protein family, the chloride intracellular channels (CLICs), could be a promising class of therapeutic targets for its intrinsic individualities: CLIC1 and CLIC4, in particular, not only are overexpressed in specific tumor types or their corresponding stroma but also change localization and function from hydrophilic cytosolic to integral transmembrane proteins as active ionic channels or signal transducers during cell cycle progression in certain cases. These changes in intracellular localization, tissue compartments, and channel function, uniquely associated with malignant transformation, may offer a unique target for cancer therapy, likely able to spare normal cells. This article is part of a special issue itled "Membrane Channels and Transporters in Cancers."

CLC-3 channels in cancer (review)

Ion channels are involved in regulating cell proliferation and apoptosis (programed cell death). Since increased cellular proliferation and inhibition of apoptosis are characteristic features of tumorigenesis, targeting ion channels is a promising strategy for treating cancer. CLC-3 is a member of the voltage-gated chloride channel superfamily and is expressed in many cancer cells. In the plasma membrane, CLC-3 functions as a chloride channel and is associated with cell proliferation and apoptosis. CLC-3 is also located in intracellular compartments, contributing to their acidity, which increases sequestration of drugs and leads to chemotherapy drug resistance. In this review, we summarize the recent findings concerning the involvement of CLC-3 in cancer and explore its potential in cancer therapy.

A Bioengineered Peptide that Localizes to and Illuminates Medulloblastoma: A New Tool with Potential for Fluorescence-Guided Surgical Resection

Tumors of the central nervous system are challenging to treat due to the limited effectiveness and associated toxicities of chemotherapy and radiation therapy. For tumors that can be removed surgically, extent of malignant tissue resection has been shown to correlate with disease progression, recurrence, and survival. Thus, improved technologies for real-time brain tumor imaging are critically needed as tools for guided surgical resection. We previously engineered a novel peptide that binds with high affinity and unique specificity to αVβ3, αVβ5, and α5β1 integrins, which are present on tumor cells, and the vasculature of many cancers, including brain tumors. In the current study, we conjugated this engineered peptide to a near infrared fluorescent dye (Alexa Fluor 680), and used the resulting molecular probe for non-invasive whole body imaging of patient-derived medulloblastoma xenograft tumors implanted in the cerebellum of mice. The engineered peptide exhibited robust targeting and illumination of intracranial medulloblastoma following both intravenous and intraperitoneal injection routes. In contrast, a variant of the engineered peptide containing a scrambled integrin-binding sequence did not localize to brain tumors, demonstrating that tumor-targeting is driven by specific integrin interactions. Ex vivo imaging was used to confirm the presence of tumor and molecular probe localization to the cerebellar region. These results warrant further clinical development of the engineered peptide as a tool for image-guided resection of central nervous system tumors.

Pathogen-inspired drug delivery to the central nervous system

For as long as the human blood-brain barrier (BBB) has been evolving to exclude bloodborne agents from the central nervous system (CNS), pathogens have adopted a multitude of strategies to bypass it. Some pathogens, notably viruses and certain bacteria, enter the CNS in whole form, achieving direct physical passage through endothelial or neuronal cells to infect the brain. Other pathogens, including bacteria and multicellular eukaryotic organisms, secrete toxins that preferentially interact with specific cell types to exert a broad range of biological effects on peripheral and central neurons. In this review, we will discuss the directed mechanisms that viruses, bacteria, and the toxins secreted by higher order organisms use to enter the CNS. Our goal is to identify ligand-mediated strategies that could be used to improve the brain-specific delivery of engineered nanocarriers, including polymers, lipids, biologically sourced materials, and imaging agents.

Scorpions: a presentation

Scorpions, at least the species of the family Buthidæ whose venoms are better known, appear as animals that have evolved very little over time. The composition of their venoms is relatively simple as most toxins have a common structural motif that is found in other venoms from primitive species. Moreover, all the scorpion venom toxins principally act on membrane ionic channels of excitable cells. The results of recent works lead to the conclusion that in scorpions there is a close relationship between venomous function and innate immune function both remarkably efficient.

A neurocentric perspective on glioma invasion

Malignant gliomas are devastating tumours that frequently kill patients within 1 year of diagnosis. The major obstacle to a cure is diffuse invasion, which enables tumours to escape complete surgical resection and chemo- and radiation therapy. Gliomas use the same tortuous extracellular routes of migration that are travelled by immature neurons and stem cells, frequently using blood vessels as guides. They repurpose ion channels to dynamically adjust their cell volume to accommodate to narrow spaces and breach the blood-brain barrier through disruption of astrocytic endfeet, which envelop blood vessels. The unique biology of glioma invasion provides hitherto unexplored brain-specific therapeutic targets for this devastating disease.

Nanomedicine for drug targeting: strategies beyond the enhanced permeability and retention effect

The growing research interest in nanomedicine for the treatment of cancer and inflammatory-related pathologies is yielding encouraging results. Unfortunately, enthusiasm is tempered by the limited specificity of the enhanced permeability and retention effect. Factors such as lack of cellular specificity, low vascular density, and early release of active agents prior to reaching their target contribute to the limitations of the enhanced permeability and retention effect. However, improved nanomedicine designs are creating opportunities to overcome these problems. In this review, we present examples of the advances made in this field and endeavor to highlight the potential of these emerging technologies to improve targeting of nanomedicine to specific pathological cells and tissues.

The genome of Mesobuthus martensii reveals a unique adaptation model of arthropods

Representing a basal branch of arachnids, scorpions are known as ‘living fossils’ that maintain an ancient anatomy and are adapted to have survived extreme climate changes. Here we report the genome sequence of Mesobuthus martensii, containing 32,016 protein-coding genes, the most among sequenced arthropods. Although M. martensii appears to evolve conservatively, it has a greater gene family turnover than the insects that have undergone diverse morphological and physiological changes, suggesting the decoupling of the molecular and morphological evolution in scorpions. Underlying the long-term adaptation of scorpions is the expansion of the gene families enriched in basic metabolic pathways, signalling pathways, neurotoxins and cytochrome P450, and the different dynamics of expansion between the shared and the scorpion lineage-specific gene families. Genomic and transcriptomic analyses further illustrate the important genetic features associated with prey, nocturnal behaviour, feeding and detoxification. The M. martensii genome reveals a unique adaptation model of arthropods, offering new insights into the genetic bases of the living fossils.

Scorpions have maintained the primary anatomical features of their Paleozoic arthropod ancestors. Here, the authors report the genome sequence of Mesobuthus martensii and highlight evidence of genetic and morphological evolution that represents a unique adaptation model of arthropods.

Scorpion venoms as a potential source of novel cancer therapeutic compounds

Scorpions and their venoms have been used in traditional medicine for thousands of years in China, India and Africa. The scorpion venom is a highly complex mixture of salts, nucleotides, biogenic amines, enzymes, mucoproteins, as well as peptides and proteins (e.g. neurotoxins). One of the recently observed biological properties of animal venoms and toxins is that they possess anticancer potential. An increasing number of studies have shown that scorpion venoms and toxins can decrease cancer growth, induce apoptosis and inhibit cancer progression and metastasis in vitro and in vivo. Several active molecules with anticancer activities, ranging from inhibition of proliferation and cell cycle arrest to induction of apoptosis and decreasing cell migration and invasion, have been isolated from scorpion venoms. These observations have shed light on the application of scorpion venoms and toxins as potential novel cancer therapeutics. This mini-review focuses on the anticancer potential of scorpion venoms and toxins and the possible mechanisms for their antitumor activities.

Overview of scorpion species from China and their toxins

Scorpions are one of the most ancient groups of terrestrial animals. They have maintained a steady morphology over more than 400 million years of evolution. Their venom arsenals for capturing prey and defending against predators may play a critical role in their ancient and conservative appearance. In the current review, we present the scorpion fauna of China: 53 species covering five families and 12 genera. We also systematically list toxins or genes from Chinese scorpion species, involving eight species covering four families. Furthermore, we review the diverse functions of typical toxins from Chinese scorpion species, involving Na⁺ channel modulators, K⁺ channel blockers, antimicrobial peptides and protease inhibitors. Using scorpion species and their toxins from China as an example, we build the bridge between scorpion species and their toxins, which helps us to understand the molecular and functional diversity of scorpion venom arsenal, the dynamic and functional evolution of scorpion toxins, and the potential relationships of scorpion species and their toxins.