Monoclonal antibodies in neuro-oncology: Getting past the blood-brain barrier

Monoclonal antibodies (mAbs) are used with increasing success against many tumors, but for brain tumors the blood-brain barrier (BBB) is a special concern. The BBB prevents antibody entry to the normal brain; however, its role in brain tumor therapy is more complex. The BBB is closest to normal at micro-tumor sites; its properties and importance change as the tumor grows. In this review, evolving insight into the role of the BBB is balanced against other factors that affect efficacy or interpretation when mAbs are used against brain tumor targets. As specific examples, glioblastoma multiforme (GBM), primary central nervous system lymphoma (PCNSL) and blood-borne metastases from breast cancer are discussed in the context of treatment, respectively, with the mAbs bevacizumab, rituximab and trastuzumab, each of which is already widely used against tumors outside the brain. It is suggested that success against brain tumors will require getting past the BBB in two senses: physically, to better attack brain tumor targets, and conceptually, to give equal attention to problems that are shared with other tumor sites.Key words: monoclonal antibody, brain tumor, immunotherapy, glioma, primary central nervous system lymphoma, brain metastases, bevacizumab, rituximab, trastuzumab     

Epidermal growth factor receptor (EGFR) involvement in epithelial‐derived cancers and its current antibody‐based immunotherapies

The epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein that is part of the family of tyrosine kinase receptors. The binding of EGFR to its cognate ligands leads to its autophosphorylation and subsequent activation of the signal transduction pathways involved in regulating cellular proliferation, differentiation, and survival. Accordingly, this receptor carries out both redundant and restricted functions in the germline development of mammals and in the maintenance of various adult tissues. Correspondingly, the loss of EGFR regulation results in many human diseases, with the most notable cancer. This receptor is overexpressed and/or mutated in multiple epithelial‐derived tumors, and associated with poor prognosis and survival in cancer patients. Here, we discuss in detail the role of EGFR in specific epithelial‐derived cancer pathologies; these include lung cancer, colorectal cancer, and squamous cell carcinomas. The development of multiple anticancer agents against EGFR diminished the progression and metastasis of tumors. Some of the most versatile therapeutic anti‐EGFR agents include the monoclonal antibodies (mAbs), demonstrating success in clinical settings when used in combination with cytotoxic treatments, such as chemotherapy and/or radiation. We thus discuss the development and application of two of the most notable therapeutic mAbs, cetuximab, and panitumumab, currently utilized in various EGFR‐related epithelial cancers.     

Induction of the blood–brain barrier marker neurothelin/HT7 in endothelial cells by a variety of tumors in chick embryos

Neurothelin/HT7, a transmembrane glycoprotein of the immunoglobulin superfamily, is a marker of blood–brain barrier (BBB)-forming endothelial cells. We have studied the expression of neurothelin in tumors grown on the chorioallantoic membrane (CAM) of chick embryos. We inoculated each 3–5×10⁶ rat C6 glioma, rat 10AS pancreatic carcinoma, human A375 melanoma, and human mammary duct adenoma cells on the CAM of 10-day-old chick embryos. The tumors were harvested on day 17. All four tumor cell lines formed solid tumors which were supplied by vessels of CAM origin. Foci of bleeding were regularly observed within the tumors. All four tumors induced the expression of neurothelin/HT7 (but not of glucose transporter-1) in tumor endothelial cells, whereas expression in adjacent endothelial cells of normal CAM did not occur. Confocal laser scanning microscopy revealed that the pattern of neurothelin expression in tumor endothelial cells was different from that in normal central nervous system (CNS) endothelium, but the relative molecular weight of neurothelin, studied by western blot analysis, was the same in brain and in tumors. It has been shown that, with increasing malignancy, vessels of CNS tumors lose their morphological characteristics, and BBB markers such as the glucose transporter-1 are downregulated. Our results show that, in contrast, the BBB marker, neurothelin, is expressed de novo in tumor endothelial cells. Potential common functions of neurothelin in endothelial cells of the CNS and tumors are discussed. Accepted: 6 December 1999     

Modulation of feeding-related peptide/protein signals by the blood-brain barrier

The peptide urocortin is a member of the corticotropin-releasing factor (CRF) family and a potent satiety signal to the brain. Urocortin in blood does not reach the brain significantly by itself, but its permeation across the blood-brain barrier (BBB) can be enhanced by leptin. How leptin facilitates the influx of urocortin has not been elucidated. In this study, we tested the hypothesis that leptin activates receptor-mediated endocytosis of urocortin. We measured the kinetics of permeation of radioactively labeled urocortin across the mouse BBB and determined the specific effects of leptin and receptor antibodies. The results show that the influx transfer constant of urocortin was enhanced in the presence of leptin and mediated by CRF-2beta, the specific receptor for urocortin. To determine the specificity of this modulation, the effect of leptin was compared with that of TNFalpha. Both TNFalpha and leptin independently facilitated receptor-mediated transport of urocortin across the BBB. Even though TNFalpha and leptin have similar effects on urocortin transport, leptin did not significantly affect the influx of TNFalpha across the BBB. The results indicate that permeation of ingestive peptides and cytokines across the BBB can be acutely modulated, consistent with a role of BBB in regulating feeding behavior. Thus, sites of action of leptin, urocortin, and TNFalpha exist not only in the brain but also at the BBB where they each control the flow of other ingestive signals to CNS targets.     

Glioma-associated antigen expression in oligodendroglial neoplasms. Tenascin and epidermal growth factor receptor.

Epidermal growth factor receptor (EGFR), its variant, EGFRvIII, and tenascin are glioma-associated antigens that are hyperexpressed by neoplastic glial cells relative to normal brain, making them attractive antigenic targets for immunotherapy. Preliminary surveys indicate that oligodendroglial tumors also produce these proteins, although the exact patterns and degrees of reactivity are not known. In this study we examined the immunoreactivity of tenascin among 50 oligodendroglial tumors, including 25 well-differentiated oligodendrogliomas (WDOs) and 12 glioblastomas (GBMs) exhibiting high proportions of oligodendroglia-like cells. We used well-characterized immunoreagents with defined specificities against the target antigens on formalin-fixed, paraffin-embedded archival tissue. The tumors were graded according to WHO guidelines. Immunoreactivity was reported on a 1-3 scale according to staining intensity multiplied by a 1-3 distribution scale distribution within tumor as focal (1), multifocal (2), and diffuse (3) for both the parenchymal and the perivascular components. Although there is considerable overlap in antigen production among the grades of tumor, this study establishes the production of tenascin and wild-type EGFR (but not EGFR vIII) in oligodendroglial neoplasms and supports the concept that antigen production increases with tumor grade.     

Biomaterial-based technologies for brain anti-cancer therapeutics and imaging

Treating malignant brain tumors represents one of the most formidable challenges in oncology. Contemporary treatment of brain tumors has been hampered by limited drug delivery across the blood–brain barrier (BBB) to the tumor bed. Biomaterials are playing an increasingly important role in developing more effective brain tumor treatments. In particular, polymer (nano)particles can provide prolonged drug delivery directly to the tumor following direct intracerebral injection, by making them physiochemically able to cross the BBB to the tumor, or by functionalizing the material surface with peptides and ligands allowing the drug-loaded material to be systemically administered but still specifically target the tumor endothelium or tumor cells themselves. Biomaterials can also serve as targeted delivery devices for novel therapies including gene therapy, photodynamic therapy, anti-angiogenic and thermotherapy. Nanoparticles also have the potential to play key roles in the diagnosis and imaging of brain tumors by revolutionizing both preoperative and intraoperative brain tumor detection, allowing early detection of pre-cancerous cells, and providing real-time, longitudinal, non-invasive monitoring/imaging of the effects of treatment. Additional efforts are focused on developing biomaterial systems that are uniquely capable of delivering tumor-associated antigens, immunotherapeutic agents or programming immune cells in situ to identify and facilitate immune-mediated tumor cell killing. The continued translation of current research into clinical practice will rely on solving challenges relating to the pharmacology of nanoparticles but it is envisioned that novel biomaterials will ultimately allow clinicians to target tumors and introduce multiple, pharmaceutically relevant entities for simultaneous targeting, imaging, and therapy in a unique and unprecedented manner.     

Influence of improved FcRn binding on the subcutaneous bioavailability of monoclonal antibodies in cynomolgus monkeys

Engineering monoclonal antibodies (mAbs) with improved binding to the neonatal Fc receptor (FcRn) is a strategy that can extend their in vivo half-life and slow their systemic clearance. Published reports have predominantly characterized the pharmacokinetics of mAbs after intravenous administration. Recently, studies in mice suggest FcRn may also play a role in affecting the subcutaneous bioavailability of mAbs. Herein, we examined whether five mAbs engineered with the T250Q/M428L Fc mutations that improved their FcRn interactions, and subsequently their in vivo pharmacokinetics after intravenous administration, had improved subcutaneous bioavailability compared with their wild-type counterparts in cynomolgus monkeys. Similar to the intravenous administration findings, the pharmacokinetic profiles of our variant mAbs after subcutaneous injection showed improved half-life or clearance. In contrast, a clear effect was not observed on the subcutaneous bioavailability. We expect that while FcRn may play a role in determining mAb subcutaneous bioavailability, multiple biopharmaceutical and physiological factors are likely to influence the success of engineering strategies aimed at targeting this pathway for improving bioavailability.     

Ephrin receptor A10 monoclonal antibodies and the derived chimeric antigen receptor T cells exert an antitumor response in mouse models of triple-negative breast cancer

Expression of the receptor tyrosine kinase ephrin receptor A10 (EphA10), which is undetectable in most normal tissues except for the male testis, has been shown to correlate with tumor progression and poor prognosis in several malignancies, including triple-negative breast cancer (TNBC). Therefore, EphA10 could be a potential therapeutic target, likely with minimal adverse effects. However, no effective clinical drugs against EphA10 are currently available. Here, we report high expression levels of EphA10 in tumor regions of breast, lung, and ovarian cancers as well as in immunosuppressive myeloid cells in the tumor microenvironment. Furthermore, we developed anti-EphA10 monoclonal antibodies (mAbs) that specifically recognize cell surface EphA10, but not other EphA family isoforms, and target tumor regions precisely in vivo with no apparent accumulation in other organs. In syngeneic TNBC mouse models, we found that anti-EphA10 mAb clone #4 enhanced tumor regression, therapeutic response rate, and T cell–mediated antitumor immunity. Notably, the chimeric antigen receptor T cells derived from clone #4 significantly inhibited TNBC cell viability in vitro and tumor growth in vivo. Together, our findings suggest that targeting EphA10 via EphA10 mAbs and EphA10-specific chimeric antigen receptor–T cell therapy may represent a promising strategy for patients with EphA10-positive tumors.     

Preclinical and early clinical development of GNbAC1, a humanized IgG4 monoclonal antibody targeting endogenous retroviral MSRV-Env protein

Monoclonal antibodies (mAbs) play an increasing important role in the therapeutic armamentarium against multiple sclerosis (MS), an inflammatory and degenerative disorder of the central nervous system. Most of the mAbs currently developed for MS are immunomodulators blocking the inflammatory immune process. In contrast with mAbs targeting immune function, GNbAC1, a humanized IgG4 mAb, targets the multiple sclerosis associated retrovirus envelope (MSRV-Env) protein, an upstream factor in the pathophysiology of MS. MSRV-Env protein is of endogenous retroviral origin, expressed in MS brain lesions, and it is pro-inflammatory and toxic to the remyelination process, by preventing the differentiation of oligodendrocyte precursor cells. We present the preclinical and early clinical development results of GNbAC1. The specificity of GNbAC1 for its endogenous retroviral target is described. Efficacy of different mAb versions of GNbAC1 were assessed in MSRV-Env induced experimental allergic encephalitis (EAE), an animal model of MS. Because the target MSRV-Env is not expressed in animals, no relevant animal model exists for a proper in vivo toxicological program. An off-target 2-week toxicity study in mice was thus performed, and it showed an absence of safety risk. Additional in vitro analyses showed an absence of complement or antibody-dependent cytotoxicity as well as a low level of cross-reactivity to human tissues. The first-in-man clinical study in 33 healthy subjects and a long-term clinical study in 10 MS patients showed that GNbAC1 is well tolerated in humans without induction of immunogenicity and that it induces a pharmacodynamic response on MSRV biomarkers. These initial results suggest that the mAb GNbAC1 could be a safe long-term treatment for patients with MS with a unique therapeutic mechanism of action.     

Analysis of rat natural killer cytotoxic factor (NKCF): mechanism of action and relationship to other cytotoxic/cytostatic factors

Natural killer cytotoxic factor (NKCF) has been proposed as one of the factors that mediates lysis induced by natural killer (NK) cells. Recently, an excellent source of NKCF has been found to be the rat large granular lymphocyte (LGL) tumor (RNK) cell line. In this study, the kinetics of lysis of the NK-sensitive, tumor target YAC-1 by the RNK-NKCF was analyzed and found to parallel that seen with NK cell-mediated killing. RNK-NKCF was also capable of killing the NK-resistant target cell, MBL-2, over a longer time period. This study utilized monoclonal antibodies (mAbs) prepared against granule protein, previously termed "anti-NKCF mAbs." These mAbs established the nature of RNK-NKCF as compared to other known cytotoxic factors in combination with studies that show that RNK-NKCF causes both 51Cr release and nuclear degradation. Antibody inhibition experiments have verified that RNK-NKCF is unique from tumor necrosis factor (TNF), leukoregulin, or complement. Anti-NKCF mAbs were capable, however, of neutralizing the RNK cell granule activity against YAC-1 tumor target cells. Based on these results, the ability of anti-NKCF mAbs to neutralize the cytolytic function of pore-forming protein (PFP), a component of these granules, was analyzed. In these experiments, the antibodies were found to inhibit the hemolytic activity of granules. Interestingly, the antibodies were effective in inhibiting the activity of unbound granule proteins as well as those bound to sheep red blood cell (SRBC) targets. Further studies to examine the target lysis requirements demonstrated that in contrast to PFP, the RNK-NKCF was able to lyse the tumor target in the absence of calcium. In addition, treatment of targets with RNA and protein synthesis inhibitors indicated that the mechanism of lysis of NKCF is quite unique from other defined cytotoxic moieties.     

Preclinical and early clinical development of GNbAC1, a humanized IgG4 monoclonal antibody targeting endogenous retroviral MSRV-Env protein

Monoclonal antibodies (mAbs) play an increasing important role in the therapeutic armamentarium against multiple sclerosis (MS), an inflammatory and degenerative disorder of the central nervous system. Most of the mAbs currently developed for MS are immunomodulators blocking the inflammatory immune process. In contrast with mAbs targeting immune function, GNbAC1, a humanized IgG4 mAb, targets the multiple sclerosis associated retrovirus envelope (MSRV-Env) protein, an upstream factor in the pathophysiology of MS. MSRV-Env protein is of endogenous retroviral origin, expressed in MS brain lesions, and it is pro-inflammatory and toxic to the remyelination process, by preventing the differentiation of oligodendrocyte precursor cells. We present the preclinical and early clinical development results of GNbAC1. The specificity of GNbAC1 for its endogenous retroviral target is described. Efficacy of different mAb versions of GNbAC1 were assessed in MSRV-Env induced experimental allergic encephalitis (EAE), an animal model of MS. Because the target MSRV-Env is not expressed in animals, no relevant animal model exists for a proper in vivo toxicological program. An off-target 2-week toxicity study in mice was thus performed, and it showed an absence of safety risk. Additional in vitro analyses showed an absence of complement or antibody-dependent cytotoxicity as well as a low level of cross-reactivity to human tissues. The first-in-man clinical study in 33 healthy subjects and a long-term clinical study in 10 MS patients showed that GNbAC1 is well tolerated in humans without induction of immunogenicity and that it induces a pharmacodynamic response on MSRV biomarkers. These initial results suggest that the mAb GNbAC1 could be a safe long-term treatment for patients with MS with a unique therapeutic mechanism of action.     

Heterotopic Mucosal Engrafting Procedure for Direct Drug Delivery to the Brain in Mice

Delivery of therapeutics into the brain is impeded by the presence of the blood-brain barrier (BBB) which restricts the passage of polar and high molecular weight compounds from the bloodstream and into brain tissue. Some direct delivery success in humans has been achieved via implantation of transcranial catheters; however this method is highly invasive and associated with numerous complications. A less invasive alternative would be to dose the brain through a surgically implanted, semipermeable membrane such as the nasal mucosa that is used to repair skull base defects following endoscopic transnasal tumor removal surgery in humans. Drug transfer though this membrane would effectively bypass the BBB and diffuse directly into the brain and cerebrospinal fluid. Inspired by this approach, a surgical approach in mice was developed that uses a donor septal mucosal membrane engrafted over an extracranial surgical BBB defect. This model has been shown to effectively allow the passage of high molecular weight compounds into the brain. Since numerous drug candidates are incapable of crossing the BBB, this model is valuable for performing preclinical testing of novel therapies for neurological and psychiatric diseases.     

Regulation of CD38 on Multiple Myeloma and NK Cells by Monoclonal Antibodies

CD38 is highly expressed on multiple myeloma (MM) cells and plays a role in regulating tumor generation and development. CD38 monoclonal antibodies (mAbs) have been used as an effective therapy for MM treatment by various mechanisms, including complement-dependent cytotoxic effects, antibody-dependent cell-mediated cytotoxicity, antibody-dependent cellular phagocytosis, programmed cell death, enzymatic modulation, and immunomodulation. Although CD38 mAbs inhibit the proliferation and survival of MM cells, there are substantial side effects on antitumoral NK cells. The NK-mediated immune response needs to be further evaluated to minimize the adverse effects of NK cell loss. The killing effect of CD38 mAbs on CD38^high NK cells should be minimized and the potential combination of CD38^low/- NK cells and CD38 mAbs should be maximized to better benefit from their therapeutic efficacy against MM. CD38 mAb effects against MM can be maximized by combination therapies with immunomodulatory imide drugs (IMiDs), proteasome inhibitors (PIs), anti-programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) antibodies, or cellular therapies for the treatment of MM, especially in patients with relapsed or refractory MM (R/R MM) and drug-resistant MM.     

The Sonic Hedgehog-Gli pathway regulates dorsal brain growth and tumorigenesis.

The mechanisms that regulate the growth of the brain remain unclear. We show that Sonic hedgehog (Shh) is expressed in a layer-specific manner in the perinatal mouse neocortex and tectum, whereas the Gli genes, which are targets and mediators of SHH signaling, are expressed in proliferative zones. In vitro and in vivo assays show that SHH is a mitogen for neocortical and tectal precursors and that it modulates cell proliferation in the dorsal brain. Together with its role in the cerebellum, our findings indicate that SHH signaling unexpectedly controls the development of the three major dorsal brain structures. We also show that a variety of primary human brain tumors and tumor lines consistently express the GLI genes and that cyclopamine, a SHH signaling inhibitor, inhibits the proliferation of tumor cells. Using the in vivo tadpole assay system, we further show that misexpression of GLI1 induces CNS hyperproliferation that depends on the activation of endogenous Gli1 function. SHH-GLI signaling thus modulates normal dorsal brain growth by controlling precursor proliferation, an evolutionarily important and plastic process that is deregulated in brain tumors.     

Allogeneic tumor-specific cytotoxic T lymphocytes

Summary We report the development of cytotoxic T lymphocytes specific for an allogeneic brain tumor in a rat model. DA strain cytotoxic T cell precursors stimulated by an allogeneic tumor (9L gliosarcoma) from the Fischer rat could generate a population of cytotoxic T lymphocytes that lysed the allogeneic 9L tumor but failed to lyse other targets, including Fischer concanavalin-A(ConA)-stimulated lymphoid blast targets. DA T cells depleted of reactivity to the Fischer haplotype (DA-f) retained reactivity to the 9L tumor, demonstrating that T cell precursors with specificity for normal Fischer alloantigens were not required for the generation of a response to the 9L Fischer tumor. The preferential lysis of the tumor target did not simply reflect a higher density of Fischer target antigens on the tumor than that found on normal Fischer ConA blast targets. First, the relative densities of class I antigen on the 9L tumor and normal Fischer ConA blasts were comparable. Second, cytotoxic T cells could not be generated from DA-f precursors when Fischer ConA blasts were used as stimulators. If DA-f T cells were simply responding to the higher density of Fischer antigen found on 9L tumor, it would have been expected that the ConA blasts expressing comparable levels of antigen to that found on the tumor would have generated cytotoxicity for both the 9L and ConA targets. We conclude that the cytotoxic T cells are specific for a determinant expressed only by the tumor. Such tumor-specific cytotoxic T cells could be useful in vivo for adoptive immunotherapy of brain tumors.     

Characterization and utility of monoclonal antibodies against spike protein of transmissible gastroenteritis virus

Aims: This work aims to characterize the utility of four newly generated monoclonal antibodies (mAbs) against transmissible gastroenteritis virus (TGEV). Methods and Results: Four monoclonal antibodies (mAbs) against the N‐terminal half of spike protein (S1 protein) of TGEV were identified. Affinity constant of these mAbs was analysed. These mAbs were capable of reacting with the TGEV S1 protein analysed by ELISA and Western blot. A competition assay between the different mAbs was performed to determine whether the different antibodies mapped in the same or a different antigenic region of the protein. Investigation on the neutralizing ability of these mAbs indicated that two of these mAbs completely neutralized TGEV at an appropriate concentration. These mAbs were able to detect the TGEV‐infected cells in immunofluorescence assays and Western blot. Moreover, they differentiated TGEV S protein from other control proteins. Conclusions: The generated four mAbs are very specific, and the established immunofluorescence assays, Western blot and discrimination ELISA are useful approaches for detecting of TGEV. Significance and Impact of the Study: It is a novel report regarding the use of the S1 protein of TGEV to generate specific mAbs. Their utility and the established immunoassays contribute to the surveillance of TGE coronavirus.     

Intratumoral injection of α-gal glycolipids induces a protective anti-tumor T cell response which overcomes Treg activity

α-Gal glycolipids capable of converting tumors into endogenous vaccines, have α-gal epitopes (Galα1-3Galβ1-4GlcNAc-R) and are extracted from rabbit RBC membranes. α-Gal epitopes bind anti-Gal, the most abundant natural antibody in humans constituting 1% of immunoglobulins. α-Gal glycolipids insert into tumor cell membranes, bind anti-Gal and activate complement. The complement cleavage peptides C5a and C3a recruit inflammatory cells and APC into the treated lesion. Anti-Gal further opsonizes the tumor cells and targets them for effective uptake by recruited APC, via Fcγ receptors. These APC transport internalized tumor cells to draining lymph nodes, and present immunogenic tumor antigen peptides for activation of tumor specific T cells. The present study demonstrates the ability of α-gal glycolipids treatment to prevent development of metastases at distant sites and to protect against tumor challenge in the treated mice. Adoptive transfer studies indicate that this protective immune response is mediated by CD8+ T cells, activated by tumor lesions turned vaccine. This T cell activation is potent enough to overcome the suppressive activity of Treg cells present in tumor bearing mice, however it does not elicit an autoimmune response against antigens on normal cells. Insertion of α-gal glycolipids and subsequent binding of anti-Gal are further demonstrated with human melanoma cells, suggesting that intratumoral injection of α-gal glycolipids is likely to elicit a protective immune response against micrometastases also in cancer patients.     

Inhibition of angiogenesis by a novel neutralizing antibody targeting human VEGFR-3

Vascular endothelial growth factor receptor 3 (VEGFR-3) is a receptor for the vascular endothelial growth factor C and D (VEGF-C and D) and plays a critical role in the development of embryonic vascular system and regulation of tumor lymphangiogenesis. In this report, we generated a novel panel of 17 monoclonal antibodies (mAbs) against human VEGFR-3 and determined their ability to inhibit the proliferation of human erythroleukemia (HEL) cells and angiogenesis of chick embryo chorioallantoic membrane (CAM). Among these mAbs, BDD073 was demonstrated to inhibit the interaction of soluble VEGFR-3 with VEGF-D and the proliferation of HEL cells. Furthermore, in chick embryo CAM angiogenesis experiments, the angiogenesis induced by recombinant glutathione-S-transferase-VEGF-D was decreased in the presence of antibody BDD073. These data suggest that this novel neutralizing antibody against human VEGFR-3 could be a tool for the investigations into the biology of VEGFR-3, and potentially a reagent for blocking VEGF-D-induced angiogenesis and lymphogenesis.     

Structure Based Prediction of Asparagine Deamidation Propensity in Monoclonal Antibodies

Identification of asparagine (Asn) sites that are prone to deamidation is critical for the development of therapeutic monoclonal antibodies (mAbs). Despite a common chemical degradation pathway, the rates of Asn deamidation can vary dramatically among different sites, and prediction of the sensitive deamidation sites is still challenging. In this study, characterization of Asn deamidation for five IgG1 and five IgG4 mAbs under both normal and stressed conditions revealed dramatic differences in the Asn deamidation rates. A comprehensive analysis of the deamidation sites indicated that the deamidation rate differences could be explained by differences in the local structure conformation, structure flexibility and solvent accessibility. A decision tree was developed to predict the deamidation propensity for all Asn sites in IgG mAbs based on the analysis of these three structural parameters. This decision tree will allow potential Asn deamidation hot spots to be identified early in development.     

Progress on Potential Strategies to Target Brain Tumor Stem Cells

The identification of brain tumor stem cells (BTSCs) leads to promising progress on brain tumor treatment. For some brain tumors, BTSCs are the driving force of tumor growth and the culprits that make tumor revive and resistant to radiotherapy and chemotherapy. Therefore, it is specifically significant to eliminate BTSCs for treatment of brain tumors. There are considerable similarities between BTSCs and normal neural stem cells (NSCs), and diverse aspects of BTSCs have been studied to find potential targets that can be manipulated to specifically eradicate BTSCs without damaging normal NSCs, including their surface makers, surrounding niche, and aberrant signaling pathways. Many strategies have been designed to kill BTSCs, and some of them have reached, or are approaching, effective therapeutic results. Here, we will focus on advantages in the issue of BTSCs and emphasize on potential therapeutic strategies targeting BTSCs.