Non-Tumor Cells within the Tumor Microenvironment-The "Eminence Grise" of the Glioblastoma Pathogenesis and Potential Targets for Therapy.

Glioblastoma (GBM) is the most common malignancy of the central nervous system in adults. GBM has high levels of therapy failure and its prognosis is usually dismal. The phenotypic heterogeneity of the tumor cells, dynamic complexity of non-tumor cell populations within the GBM tumor microenvironment (TME), and their bi-directional cross-talk contribute to the challenges of current therapeutic approaches. Herein, we discuss the etiology of GBM, and describe several major types of non-tumor cells within its TME, their impact on GBM pathogenesis, and molecular mechanisms of such an impact. We also discuss their value as potential therapeutic targets or prognostic biomarkers, with reference to the most recent works on this subject. We conclude that unless all "key player" populations of non-tumor cells within the TME are considered, no breakthrough in developing treatment for GBM can be achieved.

Recombinant Strains of Oncolytic Vaccinia Virus for Cancer Immunotherapy.

Cancer virotherapy is an alternative therapeutic approach based on the viruses that selectively infect and kill tumor cells. Vaccinia virus (VV) is a member of the Poxviridae, a family of enveloped viruses with a large linear double-stranded DNA genome. The proven safety of the VV strains as well as considerable transgene capacity of the viral genome, make VV an excellent platform for creating recombinant oncolytic viruses for cancer therapy. Furthermore, various genetic modifications can increase tumor selectivity and therapeutic efficacy of VV by arming it with the immune-modulatory genes or proapoptotic molecules, boosting the host immune system, and increasing cross-priming recognition of the tumor cells by T-cells or NK cells. In this review, we summarized the data on bioengineering approaches to develop recombinant VV strains for enhanced cancer immunotherapy.

Novel B-Cell Epitopes of Non-Neutralizing Antibodies in the Receptor-Binding Domain of the SARS-CoV-2 S-Protein with Different Effects on the Severity of COVID-19.

Antibodies against the receptor-binding domain of the SARS-CoV-2 spike protein (RBD S-protein) contribute significantly to the humoral immune response during coronavirus infection (COVID-19) and after vaccination. The main focus of the studies of the RBD epitope composition is usually concentrated on the epitopes recognized by the virus-neutralizing antibodies. The role of antibodies that bind to RBD but do not neutralize SARS-CoV-2 remains unclear. In this study, immunochemical properties of the two mouse monoclonal antibodies (mAbs), RS17 and S11, against the RBD were examined. Both mAbs exhibited high affinity to RBD, but they did not neutralize the virus. The epitopes of these mAbs were mapped using phage display: the epitope recognized by the mAb RS17 is located at the N-terminal site of RBD (348-SVYAVNRKRIS-358); the mAb S11 epitope is inside the receptor-binding motif of RBD (452-YRLFRKSN-459). Three groups of sera were tested for presence of antibodies competing with the non-neutralizing mAbs S11 and RS17: (i) sera from the vaccinated healthy volunteers without history of COVID-19; (ii) sera from the persons who had a mild form of COVID-19; (iii) sera from the persons who had severe COVID-19. Antibodies competing with the mAb S11 were found in each group of sera with equal frequency, whereas presence of the antibodies competing with the mAb RS17 in the sera was significantly more frequent in the group of sera obtained from the patients recovered from severe COVID-19 indicating that such antibodies are associated with the severity of COVID-19. In conclusion, despite the clear significance of anti-RBD antibodies in the effective immune response against SARS-CoV-2, it is important to analyze their virus-neutralizing activity and to confirm absence of the antibody-mediated enhancement of infection by the anti-RBD antibodies.

Oncolytic therapy with recombinant vaccinia viruses targeting the interleukin-15 pathway elicits a synergistic response.

We developed recombinant variants of oncolytic vaccinia virus LIVP strain expressing interleukin-15 (IL-15) or its receptor subunit alpha (IL-15Rα) to stimulate IL-15-dependent immune cells. We evaluated their oncolytic activity either alone or in combination with each other in vitro and in vivo using the murine CT26 colon carcinoma and 4T1 breast carcinoma models. We demonstrated that the admixture of these recombinant variants could promote the generation of the IL-15/IL-15Rα complex. In vitro studies indicated that 4T1 breast cancer cells were more susceptible to the developed recombinant viruses. In vivo studies showed significant survival benefits and tumor regression in 4T1 breast cancer syngeneic mice that received a combination of LIVP-IL15-RFP with LIVP-IL15Ra-RFP. Histological analysis showed recruited lymphocytes at the tumor region, while no harmful effects to the liver or spleen of the animals were detected. Evaluating tumor-infiltrated lymphocytes represented profound activation of cytotoxic T cells and macrophages in mice receiving combination therapy. Thus, our experiments showed superior oncolytic effectiveness of simultaneous injection of LIVP-IL15-RFP and LIVP-IL15Ra-RFP in breast cancer-bearing mice. The combined therapy by these recombinant variants represents a potent and versatile approach for developing new immunotherapies for breast cancer.

Alterations in the CD56- and CD56+ T Cell Subsets during COVID-19.

The effectiveness of the antiviral immune response largely depends on the activation of cytotoxic T cells. The heterogeneous group of functionally active T cells expressing the CD56 molecule (NKT-like cells), that combines the properties of T lymphocytes and NK cells, is poorly studied in COVID-19. This work aimed to analyze the activation and differentiation of both circulating NKT-like cells and CD56- T cells during COVID-19 among intensive care unit (ICU) patients, moderate severity (MS) patients, and convalescents. A decreased proportion of CD56+ T cells was found in ICU patients with fatal outcome. Severe COVID-19 was accompanied by a decrease in the proportion of CD8+ T cells, mainly due to the CD56- cell death, and a redistribution of the NKT-like cell subset composition with a predominance of more differentiated cytotoxic CD8+ T cells. The differentiation process was accompanied by an increase in the proportions of KIR2DL2/3+ and NKp30+ cells in the CD56+ T cell subset of COVID-19 patients and convalescents. Decreased percentages of NKG2D+ and NKG2A+ cells and increased PD-1 and HLA-DR expression levels were found in both CD56- and CD56+ T cells, and can be considered as indicators of COVID-19 progression. In the CD56- T cell fraction, increased CD16 levels were observed in MS patients and in ICU patients with lethal outcome, suggesting a negative role for CD56-CD16+ T cells in COVID-19. Overall, our findings suggest an antiviral role of CD56+ T cells in COVID-19.

Oncolytic Efficacy of a Recombinant Vaccinia Virus Strain Expressing Bacterial Flagellin in Solid Tumor Models.

Oncolytic viral therapy is a promising novel approach to cancer treatment. Oncolytic viruses cause tumor regression through direct cytolysis on the one hand and recruiting and activating immune cells on the other. In this study, to enhance the antitumor efficacy of the thymidine kinase-deficient vaccinia virus (VV, Lister strain), recombinant variants encoding bacterial flagellin (subunit B) of Vibrio vulnificus (LIVP-FlaB-RFP), firefly luciferase (LIVP-Fluc-RFP) or red fluorescent protein (LIVP-RFP) were developed. The LIVP-FLuc-RFP strain demonstrated exceptional onco-specificity in tumor-bearing mice, detected by the in vivo imaging system (IVIS). The antitumor efficacy of these variants was explored in syngeneic murine tumor models (B16 melanoma, CT26 colon cancer and 4T1 breast cancer). After intravenous treatment with LIVP-FlaB-RFP or LIVP-RFP, all mice tumor models exhibited tumor regression, with a prolonged survival rate in comparison with the control mice. However, superior oncolytic activity was observed in the B16 melanoma models treated with LIVP-FlaB-RFP. Tumor-infiltrated lymphocytes and the cytokine analysis of the serum and tumor samples from the melanoma-xenografted mice treated with these virus variants demonstrated activation of the host's immune response. Thus, the expression of bacterial flagellin by VV can enhance its oncolytic efficacy against immunosuppressive solid tumors.

Recent Developments in Glioblastoma Therapy: Oncolytic Viruses and Emerging Future Strategies.

Glioblastoma is the most aggressive form of malignant brain tumor. Standard treatment protocols and traditional immunotherapy are poorly effective as they do not significantly increase the long-term survival of glioblastoma patients. Oncolytic viruses (OVs) may be an effective alternative approach. Combining OVs with some modern treatment options may also provide significant benefits for glioblastoma patients. Here we review virotherapy for glioblastomas and describe several OVs and their combination with other therapies. The personalized use of OVs and their combination with other treatment options would become a significant area of research aiming to develop the most effective treatment regimens for glioblastomas.

SARS-CoV-2 Establishes a Productive Infection in Hepatoma and Glioblastoma Multiforme Cell Lines.

Severe acute respiratory syndrome associated coronavirus 2 (SARS-CoV-2) emerged at the end of 2019 and rapidly caused a pandemic that led to the death of >6 million people due to hypercoagulation and cytokine storm. In addition, SARS-CoV-2 triggers a wide array of pathologies, including liver dysfunction and neurological disorders. It remains unclear if these events are due to direct infection of the respective tissues or result from systemic inflammation. Here, we explored the possible infection of hepatic and CNS cell lines by SARS-CoV-2. We show that even moderate expression levels of the angiotensin-converting enzyme 2 (ACE2) are sufficient for productive infection. SARS-CoV-2 infects hepatoma Huh7.5 and HepG2 cells but not non-transformed liver progenitor or hepatocyte/cholangiocyte-like HepaRG cells. However, exposure to the virus causes partial dedifferentiation of HepaRG cells. SARS-CoV-2 can also establish efficient replication in some low-passage, high-grade glioblastoma cell lines. In contrast, embryonal primary astrocytes or neuroblastoma cells did not support replication of the virus. Glioblastoma cell permissiveness is associated with defects in interferon production. Overall, these results suggest that liver dysfunction during COVID-19 is not due to infection of these tissues by SARS-CoV-2. Furthermore, tumors may potentially serve as reservoirs for the virus during infection.

Coordinated Loss and Acquisition of NK Cell Surface Markers Accompanied by Generalized Cytokine Dysregulation in COVID-19.

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, is accompanied by a dysregulated immune response. In particular, NK cells, involved in the antiviral response, are affected by the infection. This study aimed to investigate circulating NK cells with a focus on their activation, depletion, changes in the surface expression of key receptors, and functional activity during COVID-19, among intensive care unit (ICU) patients, moderately ill patients, and convalescents (CCP). Our data confirmed that NK cell activation in patients with COVID-19 is accompanied by changes in circulating cytokines. The progression of COVID-19 was associated with a coordinated decrease in the proportion of NKG2D+ and CD16+ NK cells, and an increase in PD-1, which indicated their exhaustion. A higher content of NKG2D+ NK cells distinguished surviving patients from non-survivors in the ICU group. NK cell exhaustion in ICU patients was additionally confirmed by a strong negative correlation of PD-1 and natural cytotoxicity levels. In moderately ill patients and convalescents, correlations were found between the levels of CD57, NKG2C, and NKp30, which may indicate the formation of adaptive NK cells. A reduced NKp30 level was observed in patients with a lethal outcome. Altogether, the phenotypic changes in circulating NK cells of COVID-19 patients suggest that the intense activation of NK cells during SARS-CoV-2 infection, most likely induced by cytokines, is accompanied by NK cell exhaustion, the extent of which may be critical for the disease outcome.

Effect of vitamin D3 supplementation on cellular immunity and inflammatory markers in COVID-19 patients admitted to the ICU.

Vitamin D as an immunomodulator has not been studied in patients with severe COVID-19. This study aimed to estimate the efficacy of vitamin D3 supplementation on cellular immunity and inflammatory markers in patients with COVID-19 admitted to the intensive care unit (ICU). A single-center, double-blind, randomized, placebo-controlled pilot trial was conducted (N = 110). Patients were randomly assigned to receive a weekly oral dose of 60,000 IU of vitamin D3 followed by daily maintenance doses of 5000 IU (n = 55) or placebo (n = 55). Primary outcomes were lymphocyte counts, natural killer (NK) and natural killer T (NKT) cell counts, neutrophil-to-lymphocyte ratio (NLR), and serum levels of inflammatory markers on 7th day of treatment. On day 7, patients in the vitamin D3 group displayed significantly higher NK and NKT cell counts and NLR than those in the placebo group did. The mortality rate (37% vs 50%, P = 0.16), need for mechanical ventilation (63% vs 69%, P = 0.58), incidence of nosocomial infection (60% vs 41%, P = 0.05) did not significantly differ between groups. Vitamin D3 supplementation, compared with placebo, significantly increased lymphocyte counts, but did not translate into reduced mortality in ICU.Trial Registration: ClinicalTrials.gov Identifier: NCT05092698.

Functional Profiling of In Vitro Reactivated Memory B Cells Following Natural SARS-CoV-2 Infection and Gam-COVID-Vac Vaccination.

Both SARS-CoV-2 infection and vaccination have previously been demonstrated to elicit robust, yet somewhat limited immunity against the evolving variants of SARS-CoV-2. Nevertheless, reports performing side-by-side comparison of immune responses following infection vs. vaccination have been relatively scarce. The aim of this study was to compare B-cell response to adenovirus-vectored vaccination in SARS-CoV-2-naive individuals with that observed in the COVID-19 convalescent patients six months after the first encounter with the viral antigens. We set out to use a single analytical platform and performed comprehensive analysis of serum levels of receptor binding domain (RBD)-specific and virus-neutralizing antibodies, frequencies of RBD-binding circulating memory B cells (MBCs), MBC-derived antibody-secreting cells, as well as RBD-specific and virus-neutralizing activity of MBC-derived antibodies after Gam-COVID-Vac (Sputnik V) vaccination and/or natural SARS-CoV-2 infection. Overall, natural immunity was superior to Gam-COVID-Vac vaccination. The levels of neutralizing MBC-derived antibodies in the convalescent patients turned out to be significantly higher than those found following vaccination. Our results suggest that after six months, SARS-CoV-2-specific MBC immunity is more robust in COVID-19 convalescent patients than in Gam-COVID-Vac recipients. Collectively, our data unambiguously indicate that natural immunity outperforms Gam-COVID-Vac-induced immunity six months following recovery/vaccination, which should inform healthcare and vaccination decisions.

Superior infectivity of the fiber chimeric oncolytic adenoviruses Ad5/35 and Ad5/3 over Ad5-delta-24-RGD in primary glioma cultures.

Ad5-delta-24-RGD is currently the most clinically advanced recombinant adenovirus (rAd) for glioma therapy. We constructed a panel of fiber-modified rAds (Ad5RGD, Ad5/3, Ad5/35, Ad5/3RGD, and Ad5/35RGD, all harboring the delta-24 modification) and compared their infectivity, replication, reproduction, and cytolytic efficacy in human and rodent glioma cell lines and short-term cultures from primary gliomas. In human cells, both Ad5/35-delta-24 and Ad5/3-delta-24 displayed superior infectivity and cytolytic efficacy over Ad5-delta-24-RGD, while Ad5/3-delta-24-RGD and Ad5/35-delta-24-RGD did not show further improvements in efficacy. The expression of the adenoviral receptors/coreceptors CAR, DSG2, and CD46 and the integrins αVß3/αVß5 did not predict the relative cytolytic efficacy of the fiber-modified rAds. The cytotoxicity of the fiber-modified rAds in human primary normal cultures of different origins and in primary glioma cultures was comparable, indicating that the delta-24 modification did not confer tumor cell selectivity. We also revealed that CT-2A and GL261 glioma cells might be used as murine cell models for the fiber chimeric rAds in vitro and in vivo. In GL261 tumor-bearing mice, Ad5/35-delta-24, armed with the immune costimulator OX40L as the E2A/DBP-p2A-mOX40L fusion, produced long-term survivors, which were able to reject tumor cells upon rechallenge. Our data underscore the potential of local Ad5/35-delta-24-based immunovirotherapy for glioblastoma treatment.

Isolation of a panel of ultra-potent human antibodies neutralizing SARS-CoV-2 and viral variants of concern.

In the absence of virus-targeting small-molecule drugs approved for the treatment and prevention of COVID-19, broadening the repertoire of potent SARS-CoV-2-neutralizing antibodies represents an important area of research in response to the ongoing pandemic. Systematic analysis of such antibodies and their combinations can be particularly instrumental for identification of candidates that may prove resistant to the emerging viral escape variants. Here, we isolated a panel of 23 RBD-specific human monoclonal antibodies from the B cells of convalescent patients. A surprisingly large proportion of such antibodies displayed potent virus-neutralizing activity both in vitro and in vivo. Four of the isolated nAbs can be categorized as ultrapotent with an apparent IC100 below 16 ng/mL. We show that individual nAbs as well as dual combinations thereof retain activity against currently circulating SARS-CoV-2 variants of concern (such as B.1.1.7, B.1.351, B.1.617, and C.37), as well as against other viral variants. When used as a prophylactics or therapeutics, these nAbs could potently suppress viral replication and prevent lung pathology in SARS-CoV-2-infected hamsters. Our data contribute to the rational development of oligoclonal therapeutic nAb cocktails mitigating the risk of SARS-CoV-2 escape.

Low Circulating Vitamin D in Intensive Care Unit-Admitted COVID-19 Patients as a Predictor of Negative Outcomes.

BACKGROUND: Vitamin D deficiency has been associated with an increased risk of respiratory infections. OBJECTIVES: The study aimed to evaluate the serum 25-hydroxyvitamin D [25(OH)D] concentration in patients admitted to the intensive care unit (ICU) as a predictor of coronavirus disease 2019 (COVID-19) mortality. METHODS: A single-center retrospective observational study was conducted. Forty adult patients (50% men) with confirmed COVID-19 who were admitted to the ICU were enrolled. The primary endpoint was mortality at day 60. Serum 25(OH)D concentration was measured on the day of admission to the ICU. We used the Mann-Whitney test, Fisher's exact test, Kaplan-Meier analysis, and receiver operator characteristic (ROC) analysis to assess serum 25(OH)D concentration as a predictor of COVID-19 mortality. RESULTS: All 40 patients had a low median (IQR) serum 25(OH)D concentration at admission [12 (9-15) ng/mL]. The median (IQR) serum 25(OH)D concentration was greater in survivors [13.3 (10.0-17.1) ng/mL, n = 22] than in nonsurvivors [9.6 (7.9-14.2) ng/mL; n = 18], P = 0.044. The area under the ROC curve was 0.69 (95% CI: 0.52, 0.86; P = 0.044). The 60-d mortality rate of those with serum 25(OH)D concentrations ≤9.9 ng/mL (n = 14, 71%) tended to be greater than that of those with concentrations >9.9 ng/mL (n = 26, 31%) (P = 0.065), and they had a 5.6-fold higher risk of death (OR: 5.63; 95% CI: 1.35, 23.45; P = 0.018). CONCLUSIONS: The ICU patients had a low serum 25(OH)D concentration. Serum 25(OH)D concentrations ≤9.9 ng/mL on admission can be used to predict in-hospital mortality in patients with COVID-19.This trial was registered at clinicaltrials.gov as NCT04450017.

VAV1-overexpressing YT cells display improved cytotoxicity against malignant cells.

Immunotherapy based on adoptive transfer of genetically engineered T- and NK-cells is an area of active ongoing research and has proven highly efficacious for patients with certain B-cell malignancies. Use of NK cells and NK cell lines as carriers of chimeric antigen receptors (CARs) appears particularly promising, as this opens an opportunity for moving the therapy from autologous to the allogeneic (universal) format. This "off-the-shelf" approach is thought to significantly reduce the price of the treatment and make it available to many more patients in need. Yet, the efficacy of CAR-NK cells in vivo presently remains low, and boosting the activity of CAR NK cells via stronger tumor homing, resistance to tumor microenvironment, as well as greater cytotoxicity may translate into improved patient outcomes. Here, we established a derivative of a human NK cell line YT overexpressing a positive regulator of cytotoxicity, VAV1. Activity of YT-VAV1 cells obtained was assayed in vitro against several cancer cell lines and primary patient-derived cancer cells. YT-VAV1 cells outperform parental YT cells in terms of cytotoxicity.

Treatment of glioma by cisplatin-loaded nanogels conjugated with monoclonal antibodies against Cx43 and BSAT1.

Targeted drug delivery for brain tumor treatment is one of the important objectives in nanomedicine. Human glioblastoma is the most frequent and aggressive type of brain tumors. The preferential expression of membrane protein connexin 43 (Cx43) and brain-specific anion transporter (BSAT1) in the tumor and peritumoral area is a key component for targeted drug delivery. The purpose of this study was to design cisplatin-loaded nanogels conjugated with monoclonal antibodies to Cx43 and BSAT1 for treatment of intracranial gliomas 101/8. MRI volumetric analysis of tumor-bearing rats indicated significantly reduced tumor volume with cisplatin-loaded targeted-nanogel treatment compared to other formulations. The median survival of rats treated with targeted nanogels conjugated with specific mAbs against extracellular loops of Cx43 and BSAT1 were 27 and 26.6 days higher than that in control group, respectively. For the first time we demonstrated the efficiency of mAb-targeted cisplatin-loaded nanogels in the experimental model of glioma 101/8. This approach could facilitate the development of new drug delivery systems for the treatment of gliomas.

Targeted delivery of liposomal nanocontainers to the peritumoral zone of glioma by means of monoclonal antibodies against GFAP and the extracellular loop of Cx43.

The selectivity of PEGylated immunoliposomes based on monoclonal antibodies against GFAP and the E2 extracellular loop of connexin 43 (MAbE2Cx43) with respect to the focus of a glioma was estimated in experiments on animals with intracranial C6 glioma. Stealth immunoliposomes were labeled with 2 alternative labels, a fluorescent (Dil C18) and a paramagnetic (Gd-DTPA) one. Fluorescent-labeled liposomal nanocontainers were detected at the periphery of the glioma, where the target antigens were overexpressed, 48 hours after injection. Dynamic T1 MRI of rats injected with paramagnetic immunoliposomes carrying MAbE2Cx43 showed distinct accumulation of the paramagnetic contrast agent at the periphery of the glioma, which began 6 hours after administration. These data suggest that immunoliposomal nanocontainers based on antibodies against GFAP and the E2 extracellular fragment of connexin 43 are suitable for targeted delivery of diagnostic and therapeutic drugs to the peritumoral invasion zone of high-grade gliomas. FROM THE CLINICAL EDITOR: PEGylated immunoliposomes based on monoclonal antibodies against GFAP and the E2 extracellular loop of connexin 43 were investigated in animals with intracranial C6 glioma. These immunoliposomal nanocontainers were found suitable for targeted delivery of diagnostic and therapeutic drugs to the peritumoral invasion zone of high-grade gliomas.

Visualization of Connexin 43-positive cells of glioma and the periglioma zone by means of intravenously injected monoclonal antibodies.

The selectivity of monoclonal antibodies against the E2 extracellular fragment of connexin 43 (Cx43) for a glioma focus was studied in in vivo experiments on animals with intracranial C6 glioma. Antibodies labeled with two alternative labels, the radioisotope (125)I and the fluorophore Alexa 660, were intravenously injected to rats with 18-day gliomas. Seventy-two hours after injection, (125)I-labeled antibodies accumulated in the hemisphere where the glioma was located to a concentration of 0.27 ± 0.01% of the injected dose per gram of wet weight, which exceeded their accumulation in the liver, spleen, and other organs. Fluorescent-labeled antibodies against the Cx43 fragment E2 specifically visualized cells in the peritumoral astroglial bank (a zone of active invasion of glioma cells). Double immunofluorescent visualization using antibodies against the Cx43 fragment E2 and glial fibrillar acidic protein (GFAP) showed that only a small proportion of the cells that bound the antibodies injected into the blood circulation were reactive astrocytes, whereas most of these cells were GFAP-negative and morphologically corresponded to astroblasts. These results suggest that antibodies against the extracellular Cx43 fragment E2 can be used for targeted transport of diagnostic and therapeutic drugs to the peritumoral invasion zone of high-grade gliomas.

Gene Encoding Chitinase 3-Like 1 Protein (CHI3L1) is a Putative Oncogene.

An important task in understanding oncogenesis is the identification of those genes whose copy number and expression increase during tumorigenesis. Previously, in an effort to identify genes which could be used as molecular markers for glial tumors, we compared gene expression in glioblastoma to the normal brain cells. Among the genes with the most pronounced increased expression in tumors there was CHI3L1, encoding the secreted chitinase 3-like 1 protein (also known as HC gp-39 or YKL-40). Expression of CHI3L1 was found increased significantly in various tumors in comparison with corresponding normal tissues. Here we show that CHI3L1 can decrease the doubling time of 293 cells. We have also demonstrated that CHI3L1 allows the anchorage-independent growth in soft agar and, in addition, stable CHI3L1 expression made 293 cells tumorigenic: these cells stimulate the initiation of tumors after their xenograft transplantation into the Wistar rat brains. Thus, the overexpression of CHI3L1 is likely to be critical in the development of some tumors and when we gain more information about mechanisms of CHI3L1 oncogenicity, it could be used as one of the potential targets for anticancer therapy.

Targeted transport of 125I-labeled antibody to GFAP and AMVB1 in an experimental rat model of C6 glioma.

Glioblastoma is the most common high-grade glioma characterized by strikingly poor therapeutic outcome with survival time of about a year. This makes a search for new therapeutic approaches to glioblastoma treatment an area of great clinical importance. The present study aims to explore the potential of targeted delivery of 125I-radiolabeled antibodies, specific to glial fibrillary acidic protein (GFAP) and AMVB1 (antigen of abluminal membrane of endotheliocytes predominantly expressed in glioblastoma microvessels) as a strategy for in vivo tumor targeting. Rat C6 glioma model was used to test this hypothesis. Tumor bearing animals, injected with radiolabeled monoclonal antibodies to GFAP or AMVB1, were compared to control group, which received nonspecific mouse IgG. Radioactivity of blood, brain hemispheres, and some other tissues was measured 6, 24, 48, 72, and 96 h posttreatment. Our results demonstrate accumulation of both types of antibodies in tumors. Concentrations of both antibodies were significantly increased in tumor-bearing hemisphere compared to intact hemisphere. Antibodies to GFAP specifically accumulated in brain and bound tumor tissue with the high affinity. In contrast, increased accumulation of anti-AMVB1 antibody was detected in antigen-expressing organs, such as spleen and kidney. Based on results presented, we propose that the monoclonal antibodies to GFAP can be used as vectors for the delivery of diagnostic and pharmacological agents to high-grade gliomas. Development of this strategy would open new clinical perspectives for glioblastoma diagnostics and therapy.