Glioblastoma-specific anti-TUFM nanobody for in-vitro immunoimaging and cancer stem cell targeting

ALOX5 contributes to glioma progression by promoting 5-HETE-mediated immunosuppressive M2 polarization and PD-L1 expression of glioma-associated microglia/macrophages

BACKGROUND

Oxylipin metabolism plays an essential role in glioma progression and immune modulation in the tumor microenvironment. Lipid metabolic reprogramming has been linked to macrophage remodeling, while the understanding of oxylipins and their catalyzed enzymes lipoxygenases in the regulation of glioma-associated microglia/macrophages (GAMs) remains largely unexplored.

METHODS

To explore the pathophysiological relevance of oxylipin in human glioma, we performed Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) analysis in human glioma and non-tumor brain tissues. To comprehensively investigate the role of arachidonate lipoxygenase 5 (ALOX5) in glioma, we performed in vivo bioluminescent imaging, immunofluorescence staining and flow cytometry analysis on tumors from orthotopic glioma-bearing mice. We developed an ALOX5-targeted nanobody, and tested its anti-glioma efficacy of combination therapy with α-programmed cell death protein-1 (PD-1).

RESULTS

In this study, we found that ALOX5 and its oxylipin 5-hydroxyeicosatetraenoic acid (5-HETE) are upregulated in glioma, accumulating programmed death-ligand 1 (PD-L1)+ M2-GAMs and orchestrating an immunosuppressive tumor microenvironment. Mechanistically, 5-HETE derived from ALOX5-overexpressing glioma cells, promotes GAMs migration, PD-L1 expression, and M2 polarization by facilitating nuclear translocation of nuclear factor erythroid 2-related factor 2. Additionally, a nanobody targeting ALOX5 is developed that markedly suppresses 5-HETE efflux from glioma cells, attenuates M2 polarization of GAMs, and consequently ameliorates glioma progression. Furthermore, the combination therapy of the ALOX5-targeted nanobody plus α-PD-1 exhibits superior anti-glioma efficacy.

CONCLUSIONS

Our findings reveal a pivotal role of the ALOX5/5-HETE axis in regulating GAMs and highlight the ALOX5-targeted nanobody as a potential therapeutic agent, which could potentiate immune checkpoint therapy for glioma.

Sonication is a suitable method for loading nanobody into glioblastoma small extracellular vesicles

Glioblastoma is one of the deadliest cancers, therefore novel efficient therapeutic approaches are urgently required. One of such are nanobodies, prospective nano-sized bio-drugs with advantageous characteristics. Nanobodies can target intracellular proteins, but to increase their efficiency, the delivery system should be applied. Here, we examined small extracellular vesicles as a delivery system for anti-vimentin nanobody Nb79. Nb79 was loaded in small extracellular vesicles either by incubation with glioblastoma cells, by passive loading into isolated small extracellular vesicles or by sonication of isolated small extracellular vesicles. Small extracellular vesicles secreted by glioblastoma cells were isolated by ultracentrifugation on sucrose cushion. The size distribution and average size of sonicated and non-sonicated small extracellular vesicles were determined by nanoparticle tracking analysis method. The loading of Nb79 into small extracellular vesicles by incubation with cells, passive loading or sonication was confirmed by Western blot and electron microscopy. The effect of small extracellular vesicles on cell survival was determined by WST-1 reagent. Loading of small extracellular vesicles by incubation of cells with Nb79 was unsuccessful and resulted in substantial cell death. On the other hand, as confirmed by Western blot and electron microscopy, sonication is a successful method for obtaining Nb79-loaded small extracellular vesicles. Small extracellular vesicles also had an effect on cell viability. Small extracellular vesicles without Nb79 increased survival of U251 and NCH644 cells for 20-25%, while the Nb79-loaded small extracellular vesicles decreased survival of NCH421k by 11%. We demonstrated that sonication is a suitable method to load nanobodies into exosome, and these small extracellular vesicles could in turn reduce cell survival. The method could be translated also to other applications, such as targeted delivery system of other protein-based drugs.

NANOBODIES®: A Review of Diagnostic and Therapeutic Applications

NANOBODY® (a registered trademark of Ablynx N.V) molecules (Nbs), also referred to as single domain-based VHHs, are antibody fragments derived from heavy-chain only IgG antibodies found in the Camelidae family. Due to their small size, simple structure, high antigen binding affinity, and remarkable stability in extreme conditions, nanobodies possess the potential to overcome several of the limitations of conventional monoclonal antibodies. For many years, nanobodies have been of great interest in a wide variety of research fields, particularly in the diagnosis and treatment of diseases. This culminated in the approval of the world's first nanobody based drug (Caplacizumab) in 2018 with others following soon thereafter. This review will provide an overview, with examples, of (i) the structure and advantages of nanobodies compared to conventional monoclonal antibodies, (ii) methods used to generate and produce antigen-specific nanobodies, (iii) applications for diagnostics, and (iv) ongoing clinical trials for nanobody therapeutics as well as promising candidates for clinical development.

Nanobodies targeting ABCC3 for immunotargeted applications in glioblastoma

The cancer "omics" reveal many clinically relevant alterations that are transforming the molecular characterization of glioblastomas. However, many of these findings are not yet translated into clinical practice due, in part, to the lack of non-invasive biomarkers and the limitations imposed by the blood-brain barrier. Nanobodies, camelid single-domain antibody fragments, emerge as a promising tool for immunotargeted applications for diagnosing and treating glioblastomas. Performing agnostic bioinformatic analysis from glioblastoma patient datasets, we identified ATP Binding Cassette subfamily C member 3 (ABCC3) as a suitable target for immunotargeted applications. The expression of ABCC3 is associated with poor survival and impaired response to temozolomide. Importantly, high expression of ABCC3 is restricted to glioblastoma, with negligible levels in healthy brain tissue, and further correlates with tumor grade and stemness markers. We identified three immunogenic epitopes of ABCC3 which were used to isolate nanobodies from a glioblastoma-specific phage-display nanobody library. Two nanobodies targeting ABCC3 (NbA42 and NbA213) were further characterized and demonstrated in vivo selective recognition of ABCC3 in glioblastoma xenograft mouse models upon systemic administration. We designate NbA42 and NbA213 as new candidates to implement immunotargeted applications guiding a more personalized and precise diagnosis, monitoring, and treatment of glioblastoma patients.

Diagnosis of Glioblastoma by Immuno-Positron Emission Tomography

Simple Summary

Neuroimaging has transformed the way brain tumors are diagnosed and treated. Although different non-invasive modalities provide very helpful information, in some situations, they present a limited value. By merging the specificity of antibodies with the resolution, sensitivity, and quantitative capabilities of positron emission tomography (PET), “Immuno-PET” allows us to conduct the non-invasive diagnosis and monitoring of patients over time using antibody-based probes as an in vivo, integrated, quantifiable, 3D, full-body “immunohistochemistry”, like a “virtual biopsy”. This review provides and focuses on immuno-PET applications and future perspectives of this promising imaging approach for glioblastoma.

Abstract

Neuroimaging has transformed neuro-oncology and the way that glioblastoma is diagnosed and treated. Magnetic Resonance Imaging (MRI) is the most widely used non-invasive technique in the primary diagnosis of glioblastoma. Although MRI provides very powerful anatomical information, it has proven to be of limited value for diagnosing glioblastomas in some situations. The final diagnosis requires a brain biopsy that may not depict the high intratumoral heterogeneity present in this tumor type. The revolution in “cancer-omics” is transforming the molecular classification of gliomas. However, many of the clinically relevant alterations revealed by these studies have not yet been integrated into the clinical management of patients, in part due to the lack of non-invasive biomarker-based imaging tools. An innovative option for biomarker identification in vivo is termed “immunotargeted imaging”. By merging the high target specificity of antibodies with the high spatial resolution, sensitivity, and quantitative capabilities of positron emission tomography (PET), “Immuno-PET” allows us to conduct the non-invasive diagnosis and monitoring of patients over time using antibody-based probes as an in vivo, integrated, quantifiable, 3D, full-body “immunohistochemistry” in patients. This review provides the state of the art of immuno-PET applications and future perspectives on this imaging approach for glioblastoma.

Novel Ion Channel Targets and Drug Delivery Tools for Controlling Glioblastoma Cell Invasiveness

Comprising more than half of all brain tumors, glioblastoma multiforme (GBM) is a leading cause of brain cancer-related deaths worldwide. A major clinical challenge is presented by the capacity of glioma cells to rapidly infiltrate healthy brain parenchyma, allowing the cancer to escape control by localized surgical resections and radiotherapies, and promoting recurrence in other brain regions. We propose that therapies which target cellular motility pathways could be used to slow tumor dispersal, providing a longer time window for administration of frontline treatments needed to directly eradicate the primary tumors. An array of signal transduction pathways are known to be involved in controlling cellular motility. Aquaporins (AQPs) and voltage-gated ion channels are prime candidates as pharmacological targets to restrain cell migration in glioblastoma. Published work has demonstrated AQPs 1, 4 and 9, as well as voltage-gated potassium, sodium and calcium channels, chloride channels, and acid-sensing ion channels are expressed in GBM and can influence processes of cell volume change, extracellular matrix degradation, cytoskeletal reorganization, lamellipodial and filopodial extension, and turnover of cell-cell adhesions and focal assembly sites. The current gap in knowledge is the identification of optimal combinations of targets, inhibitory agents, and drug delivery systems that will allow effective intervention with minimal side effects in the complex environment of the brain, without disrupting finely tuned activities of neuro-glial networks. Based on published literature, we propose that co-treatments using AQP inhibitors in addition to other therapies could increase effectiveness, overcoming some limitations inherent in current strategies that are focused on single mechanisms. An emerging interest in nanobodies as drug delivery systems could be instrumental for achieving the selective delivery of combinations of agents aimed at multiple key targets, which could enhance success in vivo.

Mitochondrial Protein Translation: Emerging Roles and Clinical Significance in Disease

Mitochondria are one of the most important organelles in cells. Mitochondria are semi-autonomous organelles with their own genetic system, and can independently replicate, transcribe, and translate mitochondrial DNA. Translation initiation, elongation, termination, and recycling of the ribosome are four stages in the process of mitochondrial protein translation. In this process, mitochondrial protein translation factors and translation activators, mitochondrial RNA, and other regulatory factors regulate mitochondrial protein translation. Mitochondrial protein translation abnormalities are associated with a variety of diseases, including cancer, cardiovascular diseases, and nervous system diseases. Mutation or deletion of various mitochondrial protein translation factors and translation activators leads to abnormal mitochondrial protein translation. Mitochondrial tRNAs and mitochondrial ribosomal proteins are essential players during translation and mutations in genes encoding them represent a large fraction of mitochondrial diseases. Moreover, there is crosstalk between mitochondrial protein translation and cytoplasmic translation, and the imbalance between mitochondrial protein translation and cytoplasmic translation can affect some physiological and pathological processes. This review summarizes the regulation of mitochondrial protein translation factors, mitochondrial ribosomal proteins, mitochondrial tRNAs, and mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) in the mitochondrial protein translation process and its relationship with diseases. The regulation of mitochondrial protein translation and cytoplasmic translation in multiple diseases is also summarized.

BEX2 suppresses mitochondrial activity and is required for dormant cancer stem cell maintenance in intrahepatic cholangiocarcinoma

Cancer stem cells (CSCs) define a subpopulation of cancer cells that are resistant to therapy. However, little is known of how CSC characteristics are regulated. We previously showed that dormant cancer stem cells are enriched with a CD274^low fraction of cholangiocarcinoma cells. Here we found that BEX2 was highly expressed in CD274^low cells, and that BEX2 knockdown decreased the tumorigenicity and G₀ phase of cholangiocarcinoma cells. BEX2 was found to be expressed predominantly in G₀ phase and starvation induced the USF2 transcriptional factor, which induced BEX2 transcription. Comprehensive screening of BEX2 binding proteins identified E3 ubiquitin ligase complex proteins, FEM1B and CUL2, and a mitochondrial protein TUFM, and further demonstrated that knockdown of BEX2 or TUFM increased mitochondria-related oxygen consumption and decreased tumorigenicity in cholangiocarcinoma cells. These results suggest that BEX2 is essential for maintaining dormant cancer stem cells through the suppression of mitochondrial activity in cholangiocarcinoma.

Nanobodies in cancer

For treatment and diagnosis of cancer, antibodies have proven their value and now serve as a first line of therapy for certain cancers. A unique class of antibody fragments called nanobodies, derived from camelid heavy chain-only antibodies, are gaining increasing acceptance as diagnostic tools and are considered also as building blocks for chimeric antigen receptors as well as for targeted drug delivery. The small size of nanobodies (∼15 kDa), their stability, ease of manufacture and modification for diverse formats, short circulatory half-life, and high tissue penetration, coupled with excellent specificity and affinity, account for their attractiveness. Here we review applications of nanobodies in the sphere of tumor biology.

Applications of Nanobodies

Unique, functional, homodimeric heavy chain-only antibodies, devoid of light chains, are circulating in the blood of Camelidae. These antibodies recognize their cognate antigen via one single domain, known as VHH or Nanobody. This serendipitous discovery made three decades ago has stimulated a growing number of researchers to generate highly specific Nanobodies against a myriad of targets. The small size, strict monomeric state, robustness, and easy tailoring of these Nanobodies have inspired many groups to design innovative Nanobody-based multi-domain constructs to explore novel applications. As such, Nanobodies have been employed as an exquisite research tool in structural, cell, and developmental biology. Furthermore, Nanobodies have demonstrated their benefit for more sensitive diagnostic tests. Finally, several Nanobody-based constructs have been designed to develop new therapeutic products.

TUFM-knockdown inhibits the migration and proliferation of gastrointestinal stromal tumor cells

Gastrointestinal stromal tumors (GISTs) are the most common pathologic type of mesenchymal tumor in the digestive tract. Patients with GIST face the risk of metastasis, postoperative recurrence and imatinib mesylate (IM) resistance. Mitochondrial Tu translation elongation factor (TUFM) is highly expressed in GISTs, and is associated with oncogenesis, progression and prognosis. There is evidence that TUFM is involved in tumor invasion and metastasis. However, the effect of TUFM on GIST-T1 cells and the IM-resistant GIST-IR cell line remains unclear. The present study aimed to evaluate the effects of TUFM on the proliferation, migration and apoptosis of GIST cells in vitro. TUFM short hairpin (sh)RNA expression plasmids were transfected into GIST-T1 and GIST-IR cells by electroporation. The expression levels of enhanced green fluorescent protein were observed by fluorescence microscopy to evaluate the electroporation efficiency. The expression levels of TUFM were detected by western blot analysis and reverse transcription-quantitative PCR. Cell proliferation was assessed by counting cells and using a Cell Counting Kit-8 assay. Cell migration was analyzed using wound healing and Transwell migration assays. Cell cycle distribution and late apoptosis were assessed by flow cytometry. TUFM shRNA expression plasmids were successfully transfected into the GIST cell line by electroporation. The transfection efficiency was >75%, and the TUFM gene silencing efficiency was 73.2±1.4%. TUFM-knockdown decreased the proliferation and migration capacity of GIST-T1 and GIST-IR cells. The proportion of cells in the pre-G1 stage was increased without change in the proportions of cells in the G₁, S and G₂/M stages after TUFM silencing in GIST-T1 and GIST-IR cells. TUFM may be related to GIST infiltration and metastatic recurrence, suggesting that TUFM may be an effective target for preventing the progression and metastasis of GISTs.

Nanobodies: Next Generation of Cancer Diagnostics and Therapeutics

The development of targeted medicine has greatly expanded treatment options and spurred new research avenues in cancer therapeutics, with monoclonal antibodies (mAbs) emerging as a prevalent treatment in recent years. With mixed clinical success, mAbs still hold significant shortcomings, as they possess limited tumor penetration, high manufacturing costs, and the potential to develop therapeutic resistance. However, the recent discovery of “nanobodies,” the smallest-known functional antibody fragment, has demonstrated significant translational potential in preclinical and clinical studies. This review highlights their various applications in cancer and analyzes their trajectory toward their translation into the clinic.

Anti-vimentin, anti-TUFM, anti-NAP1L1 and anti-DPYSL2 nanobodies display cytotoxic effect and reduce glioblastoma cell migration

Background:

Glioblastoma is a particularly common and very aggressive primary brain tumour. One of the main causes of therapy failure is the presence of glioblastoma stem cells that are resistant to chemotherapy and radiotherapy, and that have the potential to form new tumours. This study focuses on validation of eight novel antigens, TRIM28, nucleolin, vimentin, nucleosome assembly protein 1-like 1 (NAP1L1), mitochondrial translation elongation factor (EF-TU) (TUFM), dihydropyrimidinase-related protein 2 (DPYSL2), collapsin response mediator protein 1 (CRMP1) and Aly/REF export factor (ALYREF), as putative glioblastoma targets, using nanobodies.

Methods:

Expression of these eight antigens was analysed at the cellular level by qPCR, ELISA and immunocytochemistry, and in tissues by immunohistochemistry. The cytotoxic effects of the nanobodies were determined using AlamarBlue and water-soluble tetrazolium tests. Annexin V/propidium iodide tests were used to determine apoptotsis/necrosis of the cells in the presence of the nanobodies. Cell migration assays were performed to determine the effects of the nanobodies on cell migration.

Results:

NAP1L1 and CRMP1 were significantly overexpressed in glioblastoma stem cells in comparison with astrocytes and glioblastoma cell lines at the mRNA and protein levels. Vimentin, DPYSL2 and ALYREF were overexpressed in glioblastoma cell lines only at the protein level. The functional part of the study examined the cytotoxic effects of the nanobodies on glioblastoma cell lines. Four of the nanobodies were selected in terms of their specificity towards glioblastoma cells and protein overexpression: anti-vimentin (Nb79), anti-NAP1L1 (Nb179), anti-TUFM (Nb225) and anti-DPYSL2 (Nb314). In further experiments to optimise the nanobody treatment schemes, to increase their effects, and to determine their impact on migration of glioblastoma cells, the anti-TUFM nanobody showed large cytotoxic effects on glioblastoma stem cells, while the anti-vimentin, anti-NAP1L1 and anti-DPYSL2 nanobodies were indicated as agents to target mature glioblastoma cells. The anti-vimentin nanobody also had significant effects on migration of mature glioblastoma cells.

Conclusion:

Nb79 (anti-vimentin), Nb179 (anti-NAP1L1), Nb225 (anti-TUFM) and Nb314 (anti-DPYSL2) nanobodies are indicated for further examination for cell targeting. The anti-TUFM nanobody, Nb225, is particularly potent for inhibition of cell growth after long-term exposure of glioblastoma stem cells, with minor effects seen for astrocytes. The anti-vimentin nanobody represents an agent for inhibition of cell migration.

Influenza A virus protein PB1-F2 impairs innate immunity by inducing mitophagy

Influenza A virus (IAV) infection induces mitophagy, which is essential for the clearance of damaged mitochondria. Dysfunctional mitochondria can be selectively targeted by PINK1, which recruits PRKN/PARK2 and leads to subsequent mitochondrial sequestration within autophagosomes. The IAV PB1-F2 protein translocates to mitochondria, accelerates the mitochondrial fragmentation and impairs the innate immunity. However, whether PB1-F2 mediates IAV-induced mitophagy and the relation between mitophagy and PB1-F2-attenuated innate immunity remain obscure. Here, we showed that PB1-F2 translocated to mitochondria by interacting and colocalizing with TUFM (Tu translation elongation factor, mitochondrial). Further studies revealed that PB1-F2 induced complete mitophagy, which required the interactions of PB1-F2 with both TUFM and MAP1LC3B/LC3B that mediated the autophagosome formation. PB1-F2-induced mitophagy was critical for the MAVS (mitochondrial antiviral signaling protein) degradation and led to its suppression of the type I IFN production. Importantly, the C-terminal LIR motif of PB1-F2 protein was demonstrated to be essential for its mitophagy induction and attenuated innate immunity. In conclusion, PB1-F2-induced mitophagy strongly correlates with impaired cellular innate immunity, revealing it is a potential therapeutic target.Abbreviations: BCL2L13: BCL2 like 13; BECN1: beclin 1; BNIP3L/Nix: BCL2 interacting protein 3 like; CQ: chloroquine; DDX58: DExD/H-box helicase 58; eGFP: enhanced green fluorescent protein; hpi: hours post infection; IAV: influenza A virus; IFN: interferon; IP: immunoprecipitation; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAVS: mitochondrial antiviral signaling protein; MMP: mitochondrial membrane potential; MOI, multiplicity of infection; mRFP: monomeric red fluorescent protein; NBR1: NBR1 autophagy cargo receptor; NC: negative control; NLRP3: NLR family pyrin domain containing 3; PINK1: PTEN induced kinase 1; PRKN/PARK2: parkin RBR E3 ubiquitin protein ligase; RLR: RIG-I-like-receptor; ROS: reactive oxygen species; SEV: sendai virus; SQSTM1/p62: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TM: transmembrane; TOMM20/40: translocase of outer mitochondrial membrane 20/40; TUFM: Tu translation elongation factor, mitochondrial.

Antibodies for the Treatment of Brain Metastases, a Dream or a Reality?

The incidence of brain metastases (BM) in cancer patients is increasing. After diagnosis, overall survival (OS) is poor, elicited by the lack of an effective treatment. Monoclonal antibody (mAb)-based therapy has achieved remarkable success in treating both hematologic and non-central-nervous system (CNS) tumors due to their inherent targeting specificity. However, the use of mAbs in the treatment of CNS tumors is restricted by the blood-brain barrier (BBB) that hinders the delivery of either small-molecules drugs (sMDs) or therapeutic proteins (TPs). To overcome this limitation, active research is focused on the development of strategies to deliver TPs and increase their concentration in the brain. Yet, their molecular weight and hydrophilic nature turn this task into a challenge. The use of BBB peptide shuttles is an elegant strategy. They explore either receptor-mediated transcytosis (RMT) or adsorptive-mediated transcytosis (AMT) to cross the BBB. The latter is preferable since it avoids enzymatic degradation, receptor saturation, and competition with natural receptor substrates, which reduces adverse events. Therefore, the combination of mAbs properties (e.g., selectivity and long half-life) with BBB peptide shuttles (e.g., BBB translocation and delivery into the brain) turns the therapeutic conjugate in a valid approach to safely overcome the BBB and efficiently eliminate metastatic brain cells.

PET imaging of distinct brain uptake of a nanobody and similarly-sized PAMAM dendrimers after intra-arterial administration

INTRODUCTION

We have recently shown that intracerebral delivery of an anti-VEGF monoclonal antibody bevacizumab using an intra-arterial (IA) infusion is more effective than intravenous administration. While antibodies are quickly emerging as therapeutics, their disadvantages such as large size, production logistics and immunogenicity motivate search for alternatives. Thus we have studied brain uptake of nanobodies and polyamidoamine (PAMAM) dendrimers.

METHODS

Nanobodies were conjugated with deferoxamine (DFO) to generate NB(DFO)₂. Generation-4 PAMAM dendrimers were conjugated with DFO, and subsequently primary amines were capped with butane-1,2-diol functionalities to generate G4(DFO)₃(Bdiol)₁₁₀. Resulting conjugates were radiolabeled with zirconium-89. Brain uptake of ⁸⁹ZrNB(DFO)₂ and ⁸⁹ZrG4(DFO)₃(Bdiol)₁₁₀ upon carotid artery vs tail vein infusions with intact BBB or osmotic blood-brain barrier opening (OBBBO) with mannitol in mice was monitored by dynamic positron emission tomography (PET) over 30 min to assess brain uptake and clearance, followed by whole-body PET-CT (computed tomography) imaging at 1 h and 24 h post-infusion (pi). Imaging results were subsequently validated by ex-vivo biodistribution.

RESULTS

Intravenous administration of ⁸⁹ZrNB(DFO)₂ and ⁸⁹ZrG4(DFO)₃(Bdiol)₁₁₀ resulted in their negligible brain accumulation regardless of BBB status and timing of OBBBO. Intra-arterial (IA) administration of ⁸⁹ZrNB(DFO)₂ dramatically increased its brain uptake, which was further potentiated with prior OBBBO. Half of the initial brain uptake was retained after 24 h. In contrast, IA infusion of ⁸⁹ZrG4(DFO)₃(Bdiol)₁₁₀ resulted in poor initial accumulation in the brain, with complete clearance within 1 h of administration. Ex-vivo biodistribution results reflected those on PET-CT.

CONCLUSIONS

IA delivery of nanobodies might be an attractive therapeutic platform for CNS disorders where prolonged intracranial retention is necessary.

Nanotechnology Meets Oncology: Nanomaterials in Brain Cancer Research, Diagnosis and Therapy

Advances in technology of the past decades led to development of new nanometer scale diagnosis and treatment approaches in cancer medicine leading to establishment of nanooncology. Inorganic and organic nanomaterials have been shown to improve bioimaging techniques and targeted drug delivery systems. Their favorable physico-chemical characteristics, like small sizes, large surface area compared to volume, specific structural characteristics, and possibility to attach different molecules on their surface transform them into excellent transport vehicles able to cross cell and/or tissue barriers, including the blood–brain barrier. The latter is one of the greatest challenges in diagnosis and treatment of brain cancers. Application of nanomaterials can prolong the circulation time of the drugs and contrasting agents in the brain, posing an excellent opportunity for advancing the treatment of the most aggressive form of the brain cancer—glioblastomas. However, possible unwanted side-effects and toxicity issues must be considered before final clinical translation of nanoparticles.

Single-Domain Antibodies as Therapeutic and Imaging Agents for the Treatment of CNS Diseases

Antibodies have become one of the most successful therapeutics for a number of oncology and inflammatory diseases. So far, central nervous system (CNS) indications have missed out on the antibody revolution, while they remain 'hidden' behind several hard to breach barriers. Among the various antibody modalities, single-domain antibodies (sdAbs) may hold the 'key' to unlocking the access of antibody therapies to CNS diseases. The unique structural features of sdAbs make them the smallest monomeric antibody fragments suitable for molecular targeting. These features are of particular importance when developing antibodies as modular building blocks for engineering CNS-targeting therapeutics and imaging agents. In this review, we first introduce the characteristic properties of sdAbs compared to traditional antibodies. We then present recent advances in the development of sdAbs as potential therapeutics across brain barriers, including their use for the delivery of biologics across the blood-brain and blood-cerebrospinal fluid (CSF) barriers, treatment of neurodegenerative diseases and molecular imaging of brain targets.