IL13RA2 targeted alpha particle therapy against glioblastomas

IL13RA2 promotes progression of infantile haemangioma by activating glycolysis and the Wnt/β-catenin signaling pathway

Background

Interleukin 13 receptor subunit alpha 2 (IL13RA2) plays an essential role in the progression of many cancers. However, the role of IL13RA2 in infantile haemangioma (IH) is still unknown.

Materials and Methods

IL13RA2 expression in IH tissues was analyzed using western blot, qRT-PCR, and immunofluorescence. The role of IL13RA2 in haemangioma-derived endothelial cells (HemECs) was determined following knockdown or overexpression of IL13RA2 using CCK-8, colony formation, apoptosis, wound healing, tubule formation, Transwell, and western blot.

Results

IL13RA2 expression was upregulated in IH tissues. IL13RA2 overexpression promoted proliferation, migration, and invasion of HemECs and induced glycolysis, which was confirmed with a glycolysis inhibitor. Specifically, IL13RA2 interacted with β-catenin and activated the Wnt/β-catenin pathway in HemECs, which were involved in the above-mentioned effects of IL13RA2.

Conclusions

These findings revealed that targeting IL13RA2 is a potential therapeutic approach for IH.

Anticancer and bioactivity effect of the AraA-IL13 fusion protein on the glioblastoma cell line

Background and purpose

Glioblastoma (GBM) is an aggressive and malignant brain cancer with the highest mortality and low survival rates. To discover a more specific and efficient treatment for GBM, we synthesized and examined the cytotoxic effect of arazyme-interleukin-13 (Ara-IL13) fusion protein on GBM cells.

Experimental approach

At first, the araA-IL13 chimeric gene in the pET28a (+) vector was designed and synthesized. After transformation into Escherichia coli BL21 (DE3), the chimeric gene was verified by colony polymerase chain reaction. Expression optimization and purification of the AraA-IL13 fusion protein was performed and subsequently evaluated by 10% SDS-PAGE. The protein was purified and concentrated using the Amicon® Ultra- 15 centrifugal filter unit. The presence of AraA-IL13 was investigated by the western blotting technique. The enzyme was evaluated for proteolytic activity after purification on skim milk agar. The cytotoxic effect of the AraA-IL13 fusion protein was evaluated by MTT assay on U251 and T98G cell lines in vitro.

Findings/Results

The chimeric protein had no proteolytic activity on skim milk agar despite high expression. Furthermore, no cytotoxic effect of this fusion protein (up to 400 μg/mL) was observed on the U251 and T98G cell lines.

Conclusion and implications

The lack of proteolytic activity and cytotoxic effect of AraA-IL13 may be due to the disruption of the three-dimensional structure of the protein or the large structure of the arazyme coupled with the ligand and the lack of proper folding of the arazyme to make the active site of the enzyme inaccessible.

Citric Acid: A Nexus Between Cellular Mechanisms and Biomaterial Innovations

Citrate-based biodegradable polymers have emerged as a distinctive biomaterial platform with tremendous potential for diverse medical applications. By harnessing their versatile chemistry, these polymers exhibit a wide range of material and bioactive properties, enabling them to regulate cell metabolism and stem cell differentiation through energy metabolism, metabonegenesis, angiogenesis, and immunomodulation. Moreover, the recent US Food and Drug Administration (FDA) clearance of the biodegradable poly(octamethylene citrate) (POC)/hydroxyapatite-based orthopedic fixation devices represents a translational research milestone for biomaterial science. POC joins a short list of biodegradable synthetic polymers that have ever been authorized by the FDA for use in humans. The clinical success of POC has sparked enthusiasm and accelerated the development of next-generation citrate-based biomaterials. This review presents a comprehensive, forward-thinking discussion on the pivotal role of citrate chemistry and metabolism in various tissue regeneration and on the development of functional citrate-based metabotissugenic biomaterials for regenerative engineering applications.

Peptide-Hitchhiking for the Development of Nanosystems in Glioblastoma

Glioblastoma (GBM) remains the epitome of aggressiveness and lethality in the spectrum of brain tumors, primarily due to the blood-brain barrier (BBB) that hinders effective treatment delivery, tumor heterogeneity, and the presence of treatment-resistant stem cells that contribute to tumor recurrence. Nanoparticles (NPs) have been used to overcome these obstacles by attaching targeting ligands to enhance therapeutic efficacy. Among these ligands, peptides stand out due to their ease of synthesis and high selectivity. This article aims to review single and multiligand strategies critically. In addition, it highlights other strategies that integrate the effects of external stimuli, biomimetic approaches, and chemical approaches as nanocatalytic medicine, revealing their significant potential in treating GBM with peptide-functionalized NPs. Alternative routes of parenteral administration, specifically nose-to-brain delivery and local treatment within the resected tumor cavity, are also discussed. Finally, an overview of the significant obstacles and potential strategies to overcome them are discussed to provide a perspective on this promising field of GBM therapy.

Targeted Alpha Therapy for Glioblastoma: Review on In Vitro, In Vivo and Clinical Trials

Glioblastoma (GB), a prevalent and highly malignant primary brain tumour with a very high mortality rate due to its resistance to conventional therapies and invasive nature, resulting in 5-year survival rates of only 4-17%. Despite recent advancements in cancer management, the survival rates for GB patients have not significantly improved over the last 10-20 years. Consequently, there exists a critical unmet need for innovative therapies. One promising approach for GB is Targeted Alpha Therapy (TAT), which aims to selectively deliver potentially therapeutic radiation doses to malignant cells and the tumour microenvironment while minimising radiation exposure to surrounding normal tissue with or without conventional external beam radiation. This approach has shown promise in both pre-clinical and clinical settings. A review was conducted following PRISMA 2020 guidelines across Medline, SCOPUS, and Embase, identifying 34 relevant studies out of 526 initially found. In pre-clinical studies, TAT demonstrated high binding specificity to targeted GB cells, with affinity rates between 60.0% and 84.2%, and minimal binding to non-targeted cells (4.0-5.6%). This specificity significantly enhanced cytotoxic effects and improved biodistribution when delivered intratumorally. Mice treated with TAT showed markedly higher median survival rates compared to control groups. In clinical trials, TAT applied to recurrent GB (rGB) displayed varying success rates in extending overall survival (OS) and progression-free survival. Particularly effective when integrated into treatment regimens for both newly diagnosed and recurrent cases, TAT increased the median OS by 16.1% in newly diagnosed GB and by 36.4% in rGB, compared to current standard therapies. Furthermore, it was generally well tolerated with minimal adverse effects. These findings underscore the potential of TAT as a viable therapeutic option in the management of GB.

Chimeric Antigen Receptor T Cell and Chimeric Antigen Receptor NK Cell Therapy in Pediatric and Adult High-Grade Glioma-Recent Advances

High-grade gliomas (HGG) account for approximately 10% of central nervous system (CNS) tumors in children and 25% of CNS tumors in adults. Despite their rare occurrence, HGG are a significant clinical problem. The standard therapeutic procedure in both pediatric and adult patients with HGG is the surgical resection of the tumor combined with chemotherapy and radiotherapy. Despite intensive treatment, the 5-year overall survival in pediatric patients is below 20-30%. This rate is even lower for the most common HGG in adults (glioblastoma), at less than 5%. It is, therefore, essential to search for new therapeutic methods that can extend the survival rate. One of the therapeutic options is the use of immune cells (T lymphocytes/natural killer (NK) cells) expressing a chimeric antigen receptor (CAR). The objective of the following review is to present the latest results of preclinical and clinical studies evaluating the efficacy of CAR-T and CAR-NK cells in HGG therapy.

A review of recent advancements in Actinium-225 labeled compounds and biomolecules for therapeutic purposes

In nuclear medicine, cancers that cannot be cured or can only be treated partially by traditional techniques like surgery or chemotherapy are killed by ionizing radiation as a form of therapeutic treatment. Actinium-225 is an alpha-emitting radionuclide that is highly encouraging as a therapeutic approach and more promising for targeted alpha therapy (TAT). Actinium-225 is the best candidate for tumor cells treatment and has physical characteristics such as high (LET) linear energy transfer (150 keV per μm), half-life (t1/2  = 9.92d), and short ranges (400-100 μm) which prevent the damage of normal healthy tissues. The introduction of various new radiopharmaceuticals and radioisotopes has significantly assisted the advancement of nuclear medicine. Ac-225 radiopharmaceuticals continuously demonstrate their potential as targeted alpha therapeutics. 225 Ac-labeled radiopharmaceuticals have confirmed their importance in medical and clinical areas by introducing [225 Ac]Ac-PSMA-617, [225 Ac]Ac-DOTATOC, [225 Ac]Ac-DOTA-substance-P, reported significantly improved response in patients with prostate cancer, neuroendocrine, and glioma, respectively. The development of these radiopharmaceuticals required a suitable buffer, incubation time, optimal pH, and reaction temperature. There is a growing need to standardize quality control (QC) testing techniques such as radiochemical purity (RCP). This review aims to summarize the development of the Ac-225 labeled compounds and biomolecules. The current state of their reported resulting clinical applications is also summarized as well.

A Radioluminescent Metal-Organic Framework for Monitoring 225Ac in Vivo

²²⁵Ac is considered as one of the most promising radioisotopes for alpha-therapy because its emitted high-energy α-particles can efficiently damage tumor cells. However, it also represents a significant threat to healthy tissues owing to extremely high radiotoxicity if targeted therapy fails. This calls for a pressing requirement of monitoring the biodistribution of ²²⁵Ac in vivo during the treatment of tumors. However, the lack of imageable photons or positrons from therapeutic doses of ²²⁵Ac makes this task currently quite challenging. We report here a nanoscale luminescent europium-organic framework (EuMOF) that allows for fast, simple, and efficient labeling of ²²⁵Ac in its crystal structure with sufficient ²²⁵Ac-retention stability based on similar coordination behaviors between Ac³⁺ and Eu³⁺. After labeling, the short distance between ²²⁵Ac and Eu³⁺ in the structure leads to exceedingly efficient energy transduction from²²⁵Ac-emitted α-particles to surrounding Eu³⁺ ions, which emits red luminescence through a scintillation process and produces sufficient photons for clearcut imaging. The in vivo intensity distribution of radioluminescence signal originating from the ²²⁵Ac-labeled EuMOF is consistent with the dose of ²²⁵Ac dispersed among the various organs determined by the radioanalytical measurement ex vivo, certifying the feasibility of in vivo directly monitoring ²²⁵Ac using optical imaging for the first time. In addition, ²²⁵Ac-labeled EuMOF displays notable efficiency in treating the tumor. These results provide a general design principle for fabricating ²²⁵Ac-labeled radiopharmaceuticals with imaging photons and propose a simple way to in vivo track radionuclides with no imaging photons, including but not limited to ²²⁵Ac.

Expression of IL-13Rα2 and FUS in glioma: clinicopathological and prognostic correlation

BACKGROUND

IL-13Rα2 is one of the most widely studied tumor-associated antigens in glioma research. Fused in sarcoma (FUS) is a DNA/RNA binding protein that is dysfunctional in various malignant tumors. However, the expression of IL-13Rα2 and FUS, their relationship with clinicopathological parameters and their prognostic value in glioma remain unclear.

METHODS

In the present study, the expression of IL-13Rα2 and FUS was measured in a glioma tissue array by immunohistochemistry. Pearson's X² test was used to determine the correlation between immunohistochemical expressions and clinicopathological parameters. Pearson's or Spearman's correlation test was used to determine the association between these two proteins expression. The Kaplan-Meier analysis was used to investigate the effect of these proteins on prognosis.

RESULTS

The expressions of IL-13Rα2 were significantly higher in high-grade gliomas (HGG) than that in low-grade gliomas (LGG) and was associated with IDH mutation status, whereas FUS location demonstrated no significant correlation with clinicopathological parameters. Moreover, a positive relationship was found between nuclear and cytoplasmic co-localization FUS and IL-13Rα2 expression. Kaplan-Meier analysis revealed that patients with IDH wide type or IL-13Rα2 had worst overall survival (OS) compared to other biomarkers. In HGG, IL-13Rα2 combined with nuclear and cytoplasmic co-localization of FUS was associated with worse OS. Multivariate analysis showed that tumor grade, Ki-67, P53 and IL-13Rα2 could be the independent prognostic factors for OS.

CONCLUSION

IL-13Rα2 expression was significantly associated with cytoplasmic distribution of FUS in human glioma samples and could be the independent prognostic factors for OS, while the prognostic value of its co-expression with cytoplasmic FUS in glioma need to be addressed in the future studies.

CAR T Cell Therapy in Glioblastoma: Overcoming Challenges Related to Antigen Expression

Glioblastoma (GBM) is the most common primary brain tumor, yet prognosis remains dismal with current treatment. Immunotherapeutic strategies have had limited effectiveness to date in GBM, but recent advances hold promise. One such immunotherapeutic advance is chimeric antigen receptor (CAR) T cell therapy, where autologous T cells are extracted and engineered to express a specific receptor against a GBM antigen and are then infused back into the patient. There have been numerous preclinical studies showing promising results, and several of these CAR T cell therapies are being tested in clinical trials for GBM and other brain cancers. While results in tumors such as lymphomas and diffuse intrinsic pontine gliomas have been encouraging, early results in GBM have not shown clinical benefit. Potential reasons for this are the limited number of specific antigens in GBM, their heterogenous expression, and their loss after initiating antigen-specific therapy due to immunoediting. Here, we review the current preclinical and clinical experiences with CAR T cell therapy in GBM and potential strategies to develop more effective CAR T cells for this indication.

Targeting of the Interleukin-13 Receptor (IL-13R)α2 Expressing Prostate Cancer by a Novel Hybrid Lytic Peptide

The IL-13Rα2 cell surface receptor is highly expressed in tumours such as prostate cancer. In this report, we evaluated the hypothesis that prostate cancer cells with enhanced IL-13Rα2 expression are a suitable target for the hybrid lytic peptide (Pep-1-Phor21) peptide, which is generated by fusing the IL-13Rα2 specific ligand (Pep-1) and a cell membrane disrupting lytic peptide (Phor21). The expression of IL-13Rα2 mRNA and protein in prostate cancer tissues and cell lines was assessed via real-time PCR (RT-PCR) and immunoblotting. The effect of Pep-1-Phor21 on the viability of prostate cancer cells grown in monolayers (2D) and microtissue spheroids (3D) was assessed via CellTox green cytotoxic assay. IL-13Rα2 expression and Pep-1-Phor21-mediated killing were also determined in the cells treated with epigenetic regulators (Trichostatin A (TSA) and 5-aza-2 deoxycytidine (5-Aza-dC)). The hybrid lytic peptide cytotoxic activity correlated with the expression of IL-13Rα2 in prostate cancer cell lines cultured as monolayers (2D) or 3D spheroids. In addition, TSA or 5-Aza-dC treatment of prostate cancer cells, particularly those with low expression of IL-13Rα2, enhanced the cells' sensitivity to the lytic peptide by increasing IL-13Rα2 expression. These results demonstrate that the Pep-1-Phor21 hybrid lytic peptide has potent and selective anticancer properties against IL-13Rα2-expressing prostate cancer cells.

Targeting interleukin-13 receptor α2 (IL-13Rα2) for glioblastoma therapy with surface functionalized nanocarriers

Despite surgical and therapeutic advances, glioblastoma multiforme (GBM) is among the most fatal primary brain tumor that is aggressive in nature. Patients with GBM have a median lifespan of just 15 months when treated with the current standard of therapy, which includes surgical resection and concomitant chemo-radiotherapy. In recent years, nanotechnology has shown considerable promise in treating a variety of illnesses, and certain nanomaterials have been proven to pass the blood-brain barrier (BBB) and stay in glioblastoma tissues. Recent preclinical research suggests that the diagnosis and treatment of brain tumor is significantly explored through the intervention of nanomaterials that has showed enhanced effect. In order to elicit an antitumor response, it is necessary to retain the therapeutic candidates within glioblastoma tissues and this job is effectively carried out by nanocarrier particularly functionalized nanocarriers. In the arena of neoplastic diseases including GBM have achieved great attention in recent decades. Furthermore, interleukin-13 receptor α chain variant 2 (IL13Rα2) is a highly expressed and studied target in GBM that is lacked by the surrounding environment. The absence of IL13Rα2 in surrounding normal tissues has made it a suitable target in glioblastoma therapy. In this review article, we highlighted the role of IL13Rα2 as a potential target in GBM along with design and fabrication of efficient targeting strategies for IL13Rα2 through surface functionalized nanocarriers.

[18F]KS1, a novel ascorbate-based ligand images ROS in tumor models of rodents and nonhuman primates

Over production of reactive oxygen species (ROS) caused by altered redox regulation of signaling pathways is common in many types of cancers. While PET imaging is recognized as the standard tool for cancer imaging, there are no clinically-approved PET radiotracers for ROS-imaging in cancer diagnosis and treatment. An ascorbate-based radio ligand promises to meet this urgent need. Our laboratory recently synthesized [18F] KS1, a fluoroethoxy furanose ring-containing ascorbate derivative, to track ROS in prostate tumor-bearing mice. Here we report cell uptake assays of [18F]KS1 with different ROS-regulating agents, PET imaging in head and neck squamous cell carcinoma (HNSCC) mice, and doxorubicin-induced rats; PET imaging in healthy and irradiated hepatic tumor-bearing rhesus to demonstrate its translational potential. Our preliminary evaluations demonstrated that KS1 do not generate ROS in tumor cells at tracer-level concentrations and tumor-killing properties at pharmacologic doses. [18F]KS1 uptake was low in HNSCC pretreated with ROS blockers, and high with ROS inducers. Tumors in high ROS-expressing SCC-61 took up significantly more [18F]KS1 than rSCC-61 (low-ROS expressing HNSCC); high uptake in doxorubicin-treated rats compared to saline-treated controls. Rodent biodistribution and PET imaging of [18F]KS1 in healthy rhesus monkeys demonstrated its favorable safety, pharmacokinetic properties with excellent washout profile, within 3.0 h of radiotracer administration. High uptake of [18F]KS1 in liver tumor tissues of the irradiated hepatic tumor-bearing monkey showed target selectivity. Our strong data in vitro, in vivo, and ex vivo here supports the high translational utility of [18F]KS1 to image ROS.

The immunosuppressive microenvironment and immunotherapy in human glioblastoma

Glioblastoma multiforme (GBM) is the most malignant intracranial tumor in adults, characterized by extensive infiltrative growth, high vascularization, and resistance to multiple therapeutic approaches. Among the many factors affecting the therapeutic effect, the immunosuppressive GBM microenvironment that is created by cells and associated molecules via complex mechanisms plays a particularly important role in facilitating evasion of the tumor from the immune response. Accumulating evidence is also revealing a close association of the gut microbiota with the challenges in the treatment of GBM. The gut microbiota establishes a connection with the central nervous system through bidirectional signals of the gut-brain axis, thus affecting the occurrence and development of GBM. In this review, we discuss the key immunosuppressive components in the tumor microenvironment, along with the regulatory mechanism of the gut microbiota involved in immunity and metabolism in the GBM microenvironment. Lastly, we concentrate on the immunotherapeutic strategies currently under investigation, which hold promise to overcome the hurdles of the immunosuppressive tumor microenvironment and improve the therapeutic outcome for patients with GBM.

Recent Advances in Glioma Cancer Treatment: Conventional and Epigenetic Realms

Glioblastoma (GBM) is the most typical and aggressive form of primary brain tumor in adults, with a poor prognosis. Successful glioma treatment is hampered by ineffective medication distribution across the blood-brain barrier (BBB) and the emergence of drug resistance. Although a few FDA-approved multimodal treatments are available for glioblastoma, most patients still have poor prognoses. Targeting epigenetic variables, immunotherapy, gene therapy, and different vaccine- and peptide-based treatments are some innovative approaches to improve anti-glioma treatment efficacy. Following the identification of lymphatics in the central nervous system, immunotherapy offers a potential method with the potency to permeate the blood-brain barrier. This review will discuss the rationale, tactics, benefits, and drawbacks of current glioma therapy options in clinical and preclinical investigations.

In vivo DNA-launched bispecific T cell engager targeting IL-13Rα2 controls tumor growth in an animal model of glioblastoma multiforme

Glioblastoma is an aggressive tumor with poor survival rates. Bispecific T cell engagers (BTEs) against different cancers are in various stages of clinical development. Toxicity resulting from cytokine release syndrome and the short half-life of BTEs, which necessitates continuous infusion, complicating delivery and increasing costs, are major challenges in the field. Here we describe the development of in vivo DNA-launched BTEs (dBTEs) with highly focused targeting of interleukin-13 receptor α2 (IL-13Rα2), a glioblastoma cell-surface target. We developed 4 BTEs targeting 2 epitopes of IL-13Rα2 and studied how heavy-light chain orientation affects BTE function. The dBTEs induced T cell activation, cytokine production, and tumor cytolysis in the presence of IL-13Rα2⁺ tumor cells, but we observed unique patterns of immune activation. We found a strong correlation between granzyme B secretion and dBTE-induced cytolysis of specific and nonspecific tumors. We down-selected dBTE PB01-forward based on lower cytokine induction profile and highest activation specificity. In vivo, dBTE PB01-forward demonstrated an improved half-life versus intravenous recombinant BTE delivery. In an orthotopic glioblastoma model, dBTE PB01-forward controlled tumor growth, improving animal survival, supporting the hypothesis that the blood-brain barrier does not affect the function of systemically delivered dBTE. Further study of PB01-forward for targeting glioblastoma and other IL-13Rα2⁺ cancers is warranted.

The DNA Double-Strand Break Repair in Glioma: Molecular Players and Therapeutic Strategies

Gliomas are the most frequent type of tumor in the central nervous system, which exhibit properties that make their treatment difficult, such as cellular infiltration, heterogeneity, and the presence of stem-like cells responsible for tumor recurrence. The response of this type of tumor to chemoradiotherapy is poor, possibly due to a higher repair activity of the genetic material, among other causes. The DNA double-strand breaks are an important type of lesion to the genetic material, which have the potential to trigger processes of cell death or cause gene aberrations that could promote tumorigenesis. This review describes how the different cellular elements regulate the formation of DNA double-strand breaks and their repair in gliomas, discussing the therapeutic potential of the induction of this type of lesion and the suppression of its repair as a control mechanism of brain tumorigenesis.

Recent Advances in IL-13Rα2-Directed Cancer Immunotherapy

Interleukin-13 receptor subunit alpha-2 (IL-13Rα2, CD213A), a high-affinity membrane receptor of the anti-inflammatory Th2 cytokine IL-13, is overexpressed in a variety of solid tumors and is correlated with poor prognosis in glioblastoma, colorectal cancer, adrenocortical carcinoma, pancreatic cancer, and breast cancer. While initially hypothesized as a decoy receptor for IL-13-mediated signaling, recent evidence demonstrates IL-13 can signal through IL-13Rα2 in human cells. In addition, expression of IL-13Rα2 and IL-13Rα2-mediated signaling has been shown to promote tumor proliferation, cell survival, tumor progression, invasion, and metastasis. Given its differential expression in tumor versus normal tissue, IL-13Rα2 is an attractive immunotherapy target, as both a targetable receptor and an immunogenic antigen. Multiple promising strategies, including immunotoxins, cancer vaccines, and chimeric antigen receptor (CAR) T cells, have been developed to target IL-13Rα2. In this mini-review, we discuss recent developments surrounding IL-13Rα2-targeted therapies in pre-clinical and clinical study, including potential strategies to improve IL-13Rα2-directed cancer treatment efficacy.

99mTc-labeled peptide targeting interleukin 13 receptor α 2 for tumor imaging in a cervical cancer mouse model

OBJECTIVE

Pep-1 (CGEMGWVRC) can potently bind to interleukin 13 receptor α 2 (IL-13Rα2), a tumor-restricted receptor found to be expressed in various malignancies. In this study, we intended to prepare a ^99mTc-labeled probe and evaluate its in vivo tumor accumulation properties in a cervical cancer xenograft model.

METHODS

The Pep-1 was designed and radiolabeled with ^99mTc by conjugation with mercaptoacetyl-triglycine (MAG₃). The labeling yield, radiochemical purity and stability were characterized in vitro. Cell uptake assays and fluorescence imaging were conducted for qualitative and quantitative evaluation of the specificity and affinity of Pep-1. Flow cytometry and tissue immunofluorescence were used to confirm the IL-13Rα2 expression in cervical cancer. Biodistribution and in vivo imaging were performed periodically to evaluate the imaging value of ^99mTc-MAG₃-Pep-1 in cervical cancer xenograft model.

RESULTS

^99mTc-MAG₃-Pep-1 was successfully prepared with a high labeling yield and radiochemical purity (> 95%). Specific cell uptake was demonstrated by scramble control and unlabeled MAG₃-Pep-1 blockade. Flow cytometry and tissue immunofluorescence also confirmed the mild IL-13Rα2 expression of HeLa. In the gamma imaging study and biodistribution, the tumors were imaged clearly at 2-6 h after injection of ^99mTc-MAG₃-Pep-1 and the accumulation of ^99mTc-MAG₃-Pep-1 in tumor was significantly higher than that in the blocking and scramble controls, demonstrating ligand-receptor binding specificity.

CONCLUSIONS

This work demonstrated that ^99mTc-MAG₃-Pep-1 can bind to cervical cancer with high affinity and specificity. MAG₃-Pep-1 may be a prospective precursor for IL-13Rα2-expressing cancer therapy.

Advances in Immunotherapies for Gliomas

PURPOSE OF REVIEW

Immunotherapy-based treatment of glioblastoma has been challenging because of the tumor's limited neoantigen profile and weakly immunogenic composition. This article summarizes the current clinical trials underway by evaluating the leading immunotherapy paradigms, the encountered barriers, and the future directions needed to overcome such tumor evasion.

RECENT FINDINGS

A limited number of phase III trials have been completed for checkpoint inhibitor, vaccine, as well as gene therapies, and have been unable to show improvement in survival outcomes. Nevertheless, these trials have also shown these strategies to be safe and promising with further adaptations. Further large-scale studies for chimeric antigen receptors T cell therapies and viral therapies are anticipated. Many current trials are broadening the number of antigens targeted and modulating the microtumor environment to abrogate early mechanisms of resistance. Future GBM treatment will also likely require synergistic effects by combination regimens.

Diacerein, an inhibitor of IL-1β downstream mediated apoptosis, improves radioimmunotherapy in a mouse model of Burkitt's lymphoma

Lymphoma has the characteristics of a solid tumor. Penetration of monoclonal antibodies is limited in solid tumors during radioimmunotherapy (RIT). Here, we first investigated the use of diacerein (DIA) as a combination drug to improve the penetration and therapeutic efficacy of ¹³¹I-rituximab (RTX) using the Burkitt's lymphoma mouse model. We selected DIA through computational drug repurposing and focused on rheumatoid arthritis (RA) drug interaction genes to minimize side effects. Then, the cytotoxicity of DIA was assessed in vitro using three different lymphoma cell lines. DIA-induced apoptosis was confirmed by Western blotting. After confirming apoptosis, we confirmed the enhanced uptake of ¹³¹I-RTX in Burkitt's lymphoma mouse model using SPECT/CT. Autoradiography of ¹³¹I-RTX confirmed the therapeutic effect of DIA. Finally, the tumor size and survival rate were assessed to measure the enhanced therapeutic efficacy when DIA was used. In addition, we assessed the dose-dependency of DIA in terms of the accumulation of ¹³¹I-RTX in tumor tissue, the tumor size, and the survival rate. The in vitro cytotoxicity was 10.9%. We showed that DIA induced apoptosis which was related to downstream IL-1β signaling by Western blotting. We found increased Annexin V positive apoptosis after DIA administration. Immuno SPECT/CT images demonstrated a higher uptake of ¹³¹I-RTX in tumors in the DIA-administered group than that in the PBS-alone group. However, there were no statistical differences of dose-dependency between 20 mg/kg and 40 mg/kg of DIA. Tumor growth was significantly inhibited in the group treated with the combination of DIA plus ¹³¹I-RTX at 7 days after injection. Our suggested combination of DIA and ¹³¹I-RTX strategies could enhance the efficacy of ¹³¹I-RTX treatment.

Targeted α-therapy in non-prostate malignancies

Progress in unraveling the complex biology of cancer, novel developments in radiochemistry, and availability of relevant α-emitters for targeted therapy have provided innovative approaches to precision cancer management. The approval of 223Ra dichloride for treatment of men with osseous metastatic castrate-resistant prostate cancer unleashed targeted α-therapy as a safe and effective cancer management strategy. While there is currently active research on new α-therapy regimens for prostate cancer based on the prostate-specific membrane antigen, there is emerging development of radiopharmaceutical therapy with a range of biological targets and α-emitting radioisotopes for malignancies other than the prostate cancer. This article provides a brief review of preclinical and first-in-human studies of targeted α-therapy in the cancers of brain, breast, lung, gastrointestinal, pancreas, ovary, and the urinary bladder. The data on leukemia, melanoma, myeloma, and neuroendocrine tumors will also be presented. It is anticipated that with further research the emerging role of targeted α-therapy in cancer management will be defined and validated.

A small molecule targeting CHI3L1 inhibits lung metastasis by blocking IL-13Rα2-mediated JNK-AP-1 signals

Our previous big data analyses showed a high level of association between chitinase 3 like1 (CHI3L1) expression and lung tumor development. In the present study, we investigated whether a CHI3L1‐inhibiting chemical, 2‐({3‐[2‐(1‐cyclohexen‐1‐yl)ethyl]‐6,7‐dimethoxy‐4‐oxo‐3,4‐dihydro‐2‐quinazolinyl}sulfanyl)‐N‐(4‐ethylphenyl)butanamide (K284), could inhibit lung metastasis and studied its mechanism of action. We investigated the antitumor effect of K284 both in vitro and in vivo. K284 (0.5 mg·kg⁻¹ body weight) significantly inhibited lung metastasis in in vivo models after injection of murine melanoma cells (B16F10) or adenocarcinomic human alveolar basal epithelial cells (A549). K284 significantly and concentration‐dependently also inhibited cancer cell proliferation and migration in the A549 and H460 lung cancer cell lines. We found that the binding of K284 to the chitin‐binding domain (CBD) of CHI3L1 prevented the binding of CHI3L1 to its receptor, interleukin‐13 receptor subunit alpha‐2 (IL‐13Rα2), thereby suppressing the CHI3L1 signal. This blocking of the CHI3L1‐IL‐13Rα2 signal caused the inhibition of c‐Jun N‐terminal kinase (JNK)‐activator protein 1 (AP‐1) signals, resulting in the prevention of lung metastasis and cancer cell growth. Our data demonstrate that K284 may serve as a potential candidate anticancer compound targeting CHI3L1.

The IL13α 2R paves the way for anti-glioma nanotherapy

Glioblastoma (GBM) is one of the most aggressive (grade IV) gliomas characterized by a high rate of recurrence, resistance to therapy and a grim survival prognosis. The long-awaited improvement in GBM patients' survival rates essentially depends on advances in the development of new therapeutic approaches. Recent preclinical studies show that nanoscale materials could greatly contribute to the improvement of diagnosis and management of brain cancers. In the current review, we will discuss how specific features of glioma pathobiology can be employed for designing efficient targeting approaches. Moreover, we will summarize the main evidence for the potential of the IL-13R alpha 2 receptor (IL13α2R) targeting in GBM early diagnosis and experimental therapy.

Targeting and pharmacology of an anti-IL13Rα2 antibody and antibody-drug conjugate in a melanoma xenograft model

IL13Rα2 is a cell surface tumor antigen that is overexpressed in multiple tumor types. Here, we studied biodistribution and targeting potential of an anti-IL13Rα2 antibody (Ab) and anti-tumor activity of anti-IL13Rα2-antibody-drug conjugate (ADC). The anti-IL13Rα2 Ab was labeled with fluorophore AF680 or radioisotope ⁸⁹Zr for in vivo tracking using fluorescence molecular tomography (FMT) or positron emission tomography (PET) imaging, respectively. Both imaging modalities showed that the tumor was the major uptake site for anti-IL13Rα2-Ab, with peak uptake of 5–8% ID and 10% ID/g as quantified from FMT and PET, respectively. Pharmacological in vivo competition with excess of unlabeled anti-IL13Rα2-Ab significantly reduced the tumor uptake, indicative of antigen-specific tumor accumulation. Further, FMT imaging demonstrated similar biodistribution and pharmacokinetic profiles of an auristatin-conjugated anti-IL13Rα2-ADC as compared to the parental Ab. Finally, the anti-IL13Rα2-ADC exhibited a dose-dependent anti-tumor effect on A375 xenografts, with 90% complete responders at a dose of 3 mg/kg. Taken together, both FMT and PET showed a favorable biodistribution profile for anti-IL13Rα2-Ab/ADC, along with antigen-specific tumor targeting and excellent therapeutic efficacy in the A375 xenograft model. This work shows the great potential of this anti-IL13Rα2-ADC as a targeted anti-cancer agent.

A perspective on the radiopharmaceutical requirements for imaging and therapy of glioblastoma

Despite numerous clinical trials and pre-clinical developments, the treatment of glioblastoma (GB) remains a challenge. The current survival rate of GB averages one year, even with an optimal standard of care. However, the future promises efficient patient-tailored treatments, including targeted radionuclide therapy (TRT). Advances in radiopharmaceutical development have unlocked the possibility to assess disease at the molecular level allowing individual diagnosis. This leads to the possibility of choosing a tailored, targeted approach for therapeutic modalities. Therapeutic modalities based on radiopharmaceuticals are an exciting development with great potential to promote a personalised approach to medicine. However, an effective targeted radionuclide therapy (TRT) for the treatment of GB entails caveats and requisites. This review provides an overview of existing nuclear imaging and TRT strategies for GB. A critical discussion of the optimal characteristics for new GB targeting therapeutic radiopharmaceuticals and clinical indications are provided. Considerations for target selection are discussed, i.e. specific presence of the target, expression level and pharmacological access to the target, with particular attention to blood-brain barrier crossing. An overview of the most promising radionuclides is given along with a validation of the relevant radiopharmaceuticals and theranostic agents (based on small molecules, peptides and monoclonal antibodies). Moreover, toxicity issues and safety pharmacology aspects will be presented, both in general and for the brain in particular.

Overview of the Most Promising Radionuclides for Targeted Alpha Therapy: The "Hopeful Eight"

Among all existing radionuclides, only a few are of interest for therapeutic applications and more specifically for targeted alpha therapy (TAT). From this selection, actinium-225, astatine-211, bismuth-212, bismuth-213, lead-212, radium-223, terbium-149 and thorium-227 are considered as the most suitable. Despite common general features, they all have their own physical characteristics that make them singular and so promising for TAT. These radionuclides were largely studied over the last two decades, leading to a better knowledge of their production process and chemical behavior, allowing for an increasing number of biological evaluations. The aim of this review is to summarize the main properties of these eight chosen radionuclides. An overview from their availability to the resulting clinical studies, by way of chemical design and preclinical studies is discussed.

Radioimmunotherapy of glioblastoma multiforme - Current status and future prospects

Glioblastoma multiforme (GBM) or grade IV astrocytoma is the most diagnosed form of primary brain tumours in adults. Radioimmunotherapy (RIT), mostly in combination with conventional therapies, is presented in the current review as a therapeutic strategy of high potential in the management of GBM. A systematic literature search was performed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) to identify clinical studies that employed a form of radioimmunotherapy using alpha- or beta-emitting radioisotopes. The available literature on RIT in GBM and high-grade gliomas is presented and discussed. The results suggest that this promising treatment approach merits further investigation in future clinical studies.

Innovative and Promising Strategies to Enhance Effectiveness of Immunotherapy for CNS Tumors: Where Are We?

Although there are several immunotherapy approaches for the treatment of Central Nervous System (CNS) tumors under evaluation, currently none of these approaches have received approval from the regulatory agencies. CNS tumors, especially glioblastomas, are tumors characterized by highly immunosuppressive tumor microenvironment, limiting the possibility of effectively eliciting an immune response. Moreover, the peculiar anatomic location of these tumors poses relevant challenges in terms of safety, since uncontrolled hyper inflammation could lead to cerebral edema and cranial hypertension. The most promising strategies of immunotherapy in neuro-oncology consist of the use of autologous T cells redirected against tumor cells through chimeric antigen receptor (CAR) constructs or genetically modified T-cell receptors. Trials based on native or genetically engineered oncolytic viruses and on vaccination with tumor-associated antigen peptides are also under evaluation. Despite some sporadic complete remissions achieved in clinical trials, the outcome of patients with CNS tumors treated with different immunotherapeutic approaches remains poor. Based on the lessons learned from these unsatisfactory experiences, novel immune-therapy approaches aimed at overcoming the profound immunosuppressive microenvironment of these diseases are bringing new hope to reach the cure for CNS tumors.

Current State of Targeted Radiometal-Based Constructs for the Detection and Treatment of Disease in the Brain

The continual development of radiopharmaceutical agents for the field of nuclear medicine is integral to promoting the necessity of personalized medicine. One way to greatly expand the selection of radiopharmaceuticals available is to broaden the range of radionuclides employed in such agents. Widening the scope of development to include radiometals with their variety of physical decay characteristics and chemical properties opens up a myriad of possibilities for new actively targeted molecules and bioconjugates. This is especially true to further advance the imaging and treatment of disease in the brain. Over the past few decades, imaging of disease in the brain has heavily relied on agents which exploit metabolic uptake. However, through utilizing the broad range of physical characteristics that radiometals offer, the ability to target other processes has become more available. The varied chemistries of radiometals also allows for them to incorporated into specifically designed diverse constructs. A major limitation to efficient treatment of disease in the brain is the ability for relevant agents to penetrate the blood-brain barrier. Thus, along with efficient disease targeting, there must be intentional thought put into overcoming this challenge. Here, we review the current field of radiometal-based agents aimed at either imaging or therapy of brain disease that have been evaluated through at least in vivo studies.

Effect of ethanol and cocaine on [11C]MPC-6827 uptake in SH-SY5Y cells

Microtubules (MTs) are structural units in the cytoskeleton. In brain cells they are responsible for axonal transport, information processing, and signaling mechanisms. Proper function of these processes is critical for healthy brain functions. Alcohol and substance use disorders (AUD/SUDs) affects the function and organization of MTs in the brain, making them a potential neuroimaging marker to study the resulting impairment of overall neurobehavioral and cognitive processes. Our lab reported the first brain-penetrant MT-tracking Positron Emission Tomography (PET) ligand [¹¹C]MPC-6827 and demonstrated its in vivo utility in rodents and non-human primates. To further explore the in vivo imaging potential of [¹¹C]MPC-6827, we need to investigate its mechanism of action. Here, we report preliminary in vitro binding results in SH-SY5Y neuroblastoma cells exposed to ethanol (EtOH) or cocaine in combination with multiple agents that alter MT stability. EtOH and cocaine treatments increased MT stability and decreased free tubulin monomers. Our initial cell-binding assay demonstrated that [¹¹C]MPC-6827 may have high affinity to free/unbound tubulin units. Consistent with this mechanism of action, we observed lower [¹¹C]MPC-6827 uptake in SH-SY5Y cells after EtOH and cocaine treatments (e.g., fewer free tubulin units). We are currently performing in vivo PET imaging and ex vivo biodistribution studies in rodent and nonhuman primate models of AUD and SUDs and Alzheimer's disease.

An Immune-Related Gene Pairs Signature for Predicting Survival in Glioblastoma

Background: Glioblastoma (GBM) is the frequently occurring and most aggressive form of brain tumors. In the study, we constructed an immune-related gene pairs (IRGPs) signature to predict overall survival (OS) in patients with GBM.

Methods: We established IRGPs with immune-related gene (IRG) matrix from The Cancer Genome Atlas (TCGA) database (Training cohort). After screened by the univariate regression analysis and least absolute shrinkage and selection operator (LASSO) regression analysis, IRGPs were subjected to the multivariable Cox regression to develop an IRGP signature. Then, the predicting accuracy of the signature was assessed with the area under the receiver operating characteristic curve (AUC) and validated the result using the Chinese Glioma Genome Atlas (CGGA) database (Validation cohorts 1 and 2).

Results: A 10-IRGP signature was established for predicting the OS of patients with GBM. The AUC for predicting 1-, 3-, and 5-year OS in Training cohort was 0.801, 0.901, and 0.964, respectively, in line with the AUC of Validation cohorts 1 and 2 [Validation cohort 1 (1 year: 0.763; 3 years: 0.786; and 5 years: 0.884); Validation cohort 2 (1 year: 0.745; 3 years: 0.989; and 5 years: 0.987)]. Moreover, survival analysis in three cohorts suggested that patients with low-risk GBM had better clinical outcomes than patients with high-risk GBM. The univariate and multivariable Cox regression demonstrated that the IRGPs signature was an independent prognostic factor.

Conclusions: We developed a novel IRGPs signature for predicting OS in patients with GBM.

Real-Time Positron Emission Tomography Evaluation of Topotecan Brain Kinetics after Ultrasound-Mediated Blood-Brain Barrier Permeability

Glioblastoma (GBM) is the most common primary adult brain malignancy with an extremely poor prognosis and a median survival of fewer than two years. A key reason for this high mortality is that the blood-brain barrier (BBB) significantly restricts systemically delivered therapeutics to brain tumors. High-intensity focused ultrasound (HIFU) with microbubbles is a methodology being used in clinical trials to noninvasively permeabilize the BBB for systemic therapeutic delivery to GBM. Topotecan is a topoisomerase inhibitor used as a chemotherapeutic agent to treat ovarian and small cell lung cancer. Studies have suggested that topotecan can cross the BBB and can be used to treat brain metastases. However, pharmacokinetic data demonstrated that topotecan peak concentration in the brain extracellular fluid after systemic injection was ten times lower than in the blood, suggesting less than optimal BBB penetration by topotecan. We hypothesize that HIFU with microbubbles treatment can open the BBB and significantly increase topotecan concentration in the brain. We radiolabeled topotecan with 11C and acquired static and dynamic positron emission tomography (PET) scans to quantify [11C] topotecan uptake in the brains of normal mice and mice after HIFU treatment. We found that HIFU treatments significantly increased [11C] topotecan brain uptake. Moreover, kinetic analysis of the [11C] topotecan dynamic PET data demonstrated a substantial increase in [11C] topotecan volume of distribution in the brain. Furthermore, we found a decrease in [11C] topotecan brain clearance, confirming the potential of HIFU to aid in the delivery of topotecan through the BBB. This opens the potential clinical application of [11C] topotecan as a tool to predict topotecan loco-regional brain concentration in patients with GBMs undergoing experimental HIFU treatments.

3D optical/CT as a preclinical companion imaging platform for glioblastoma drug development

Multimodality 3D Optical Imaging (OI)/CT has the potential to play a major role in drug development for glioblastomas (GBM), as it is an accessible preclinical method. To demonstrate the potential of 3D OI/CT to visualize orthotopic GBM implantation, we labeled GBM cells with Cy7 and imaged their location using 3D OI/CT. To confirm the accuracy of the spatial localization and demonstrate the ability to image locoregionally delivered therapies, we labeled mouse albumin with Cy7 (Cy7ALB) and delivered it via locoregional infusion 1 mm or 3 mm into the brain and demonstrated correlation of signal between the 3D OI/CT and post necropsy brain slices. In addition, we demonstrated the potential of systemically delivered Cy7ALB contrast to detect blood-brain barrier (BBB) permeability caused by orthotopic GBMs using 3D OI/CT. We also tested the potential of 3D OI/CT to assess focal BBB permeability induced by high intensity focused ultrasound (HIFU), a methodology being used in clinical trials to noninvasively permeabilize the BBB for systemic therapeutic delivery to GBM. We demonstrated the ability of systemic Cy7ALB contrast together with 3D OI/CT to accurately assess real-time HIFU-induced BBB permeability, which correlated to post necropsy imaging of brains. Furthermore, we demonstrated that 3D OI/CT can also image the therapeutic distribution of a Cy7-labeled anti-PD-1 antibody, a prototype translational antibody therapy. We successfully imaged real-time antibody distribution after HIFU-induced BBB permeability, which correlated with post necropsy Cy7 signal and translational PET imaging after injection of [89Zr] anti-PD-1 antibody. Thus, we demonstrated the broad potential of using 3D OI/CT as an accessible preclinical tool to develop anti-GBM therapies.

Chimeric antigen receptor T-cell therapy in glioblastoma: charging the T cells to fight

Glioblastoma multiforme (GBM) is the most common malignant brain cancer that invades normal brain tissue and impedes surgical eradication, resulting in early local recurrence and high mortality. In addition, most therapeutic agents lack permeability across the blood brain barrier (BBB), further reducing the efficacy of chemotherapy. Thus, effective treatment against GBM requires tumor specific targets and efficient intracranial drug delivery. With the most recent advances in immunotherapy, genetically engineered T cells with chimeric antigen receptors (CARs) are becoming a promising approach for treating cancer. By transducing T lymphocytes with CAR constructs containing a tumor-associated antigen (TAA) recognition domain linked to the constant regions of a signaling T cell receptor, CAR T cells may recognize a predefined TAA with high specificity in a non-MHC restricted manner, and is independent of antigen processing. Active T cells can travel across the BBB, providing additional advantage for drug delivery and tumor targeting. Here we review the CAR design and technical innovations, the major targets that are in pre-clinical and clinical development with a focus on GBM, and multiple strategies developed to improve CAR T cell efficacy.

Copper-64 based radiopharmaceuticals for brain tumors and hypoxia imaging

INTRODUCTION

The most common and aggressive primary malignancy of the central nervous system is Glioblastoma that, as a wide range of malignant solid tumor, is characterized by extensive hypoxic regions. A great number of PET radiopharmaceuticals have been developed for the identification of hypoxia in solid tumors, among these, we find copper-based tracers. The aim of the current review paper was to provide an overview of radiocopper compounds applied for preclinical and clinical research in brain tumors and hypoxia imaging or therapy.

EVIDENCE ACQUISITION

Copper offers a wide variety of isotopes, useful for nuclear medicine applications, but only ⁶⁴Cu and ⁶⁷Cu are under the spotlight of the scientific community since being good candidates for theranostic applications. Between the two, ⁶⁴Cu availability and production cost have attracted more interest of the scientific community.

EVIDENCE SYNTHESIS

In order to better understand the application of copper-bis thiosemicarbazones in hypoxia imaging, an overview of the role of hypoxia in cancer, existing non-imaging and imaging techniques for hypoxia identification and promising future avenues regarding hypoxia is necessary. Different proposed uptake mechanisms of [⁶⁴Cu][Cu(ATSM)] inside the cell will be discussed and other ⁶⁴Cu-based tracers for brain tumors described.

CONCLUSIONS

Among radio copper compounds [⁶⁴Cu][Cu(ATSM)] is the most studied radiopharmaceutical for imaging and treatment of brain tumors. Experimental evidence suggested that [⁶⁴Cu][Cu(ATSM)] could be more appropriately considered as a marker of over-reduced intracellular state rather than a pure hypoxia agent. Moreover, preliminary clinical data suggested that [⁶⁴Cu]CuCl<inf>2</inf> can be a potentially useful diagnostic agent for malignancies of the central nervous system (CNS).

Imaging of Fibroblast Activation Protein Alpha Expression in a Preclinical Mouse Model of Glioma Using Positron Emission Tomography

Glioblastoma multiforme (GBM) is the most aggressive glioma of the primary central nervous system. Due to the lack of effective treatment options, the prognosis for patients remains bleak. Fibroblast activation protein alpha (FAP), a 170 kDa type II transmembrane serine protease was observed to be expressed on glioma cells and within the glioma tumor microenvironment. To understand the utility of targeting FAP in this tumor type, the immuno-PET radiopharmaceutical [⁸⁹Zr]Zr-Df-Bz-F19 mAb was prepared and Lindmo analysis was used for its in vitro evaluation using the U87MG cell line, which expresses FAP endogenously. Lindmo analysis revealed an association constant (K_a) of 10^-8 M^-1 and an immunoreactivity of 52%. Biodistribution studies in U87MG tumor-bearing mice revealed increasing radiotracer retention in tumors over time, leading to average tumor-to-muscle ratios of 3.1, 7.3, 7.2, and 8.3 at 2, 24, 48 and 72 h, respectively. Small animal PET corroborated the biodistribution studies; tumor-to-muscle ratios at 2, 24, 48, and 72 h were 2.0, 5.0, 6.1 and 7.8, respectively. Autoradiography demonstrated accumulated activity throughout the interior of FAP⁺ tumors, while sequential tumor sections stained positively for FAP expression. Conversely, FAP^- tissues retained minimal radioactivity and were negative for FAP expression by immunohistochemistry. These results demonstrate FAP as a promising biomarker that may be exploited to diagnose and potentially treat GBM and other neuroepithelial cancers.

Targeted alpha therapy: a critical review of translational dosimetry research with emphasis on actinium-225

This review provides a general overview of the current achievements and challenges in translational dosimetry for targeted alpha therapy (TAT). The concept of targeted radionuclide therapy (TRNT) is described with an overview of its clinical applicability and the added value of TAT is discussed. For TAT, we focused on actinium-225 (225Ac) as an example for alpha particle emitting radionuclides and their features, such as limited range within tissue and high linear energy transfer, which make alpha particle emissions more effective in targeted killing of tumour cells compared to beta radiation. Starting with the state-of-the-art dosimetry for TRNT and TAT, we then describe the challenges that still need to be met in order to move to a personalized dosimetry approach for TAT. Specifically for 225Ac, we discuss the recoiled daughter effect which may provoke significant damage to healthy tissue or organs and should be considered. Next, a broad overview is given of the pre-clinical research on 225Ac-TAT with an extensive description of tools which are only available in a pre-clinical setting and their added value. In addition, we review the preclinical biodistribution and dosimetry studies that have been performed on TAT-agents and more specifically of 225Ac and its multiple progeny, and describe their potential role to better characterize the pharmacokinetic (PK) profile of TAT-agents and to optimize the use of theranostic approaches for dosimetry. Finally, we discuss the support pre-clinical studies may provide in understanding dose-effect relationships, linking radiation dose quantities to biological endpoints and even moving away from macro- to microdosimetry. As such, the translation of pre-clinical findings may provide valuable information and new approaches for improved clinical dosimetry, thus paving the way to personalized TAT.

HMGA1-pseudogene7 transgenic mice develop B cell lymphomas

We have recently identified and characterized two pseudogenes (HMGA1P6 and HMGA1P7) of the HMGA1 gene, which has a critical role in malignant cell transformation and cancer progression. HMGA1P6 and HMGAP17 act as microRNA decoy for HMGA1 and other cancer-related genes upregulating their protein levels. We have previously shown that they are upregulated in several human carcinomas, and their expression positively correlates with a poor prognosis and an advanced cancer stage. To evaluate in vivo oncogenic activity of HMGA1 pseudogenes, we have generated a HMGA1P7 transgenic mouse line overexpressing this pseudogene. By a mean age of 12 months, about 50% of the transgenic mice developed splenomegaly and accumulation of lymphoid cells in several body compartments. For these mice FACS and immunohistochemical analyses suggested the diagnosis of B-cell lymphoma that was further supported by clonality analyses and RNA expression profile of the pathological tissues of the HMGA1P7 transgenic tissues. Therefore, these results clearly demonstrate the oncogenic activity of HMGA1 pseudogenes in vivo.

Drug Conjugates for Targeting Eph Receptors in Glioblastoma

Glioblastoma (GBM) is a complex and heterogeneous tumor that warrants a comprehensive therapeutic approach for treatment. Tumor-associated antigens offer an opportunity to selectively target various components of the GBM microenvironment while sparing the normal cells within the central nervous system. In this study, we conjugated a multivalent vector protein, QUAD 3.0, that can target four receptors: EphA3, EphA2, EphB2, and also IL-13RA2, spanning virtually 100% of the GBM microenvironment, to doxorubicin derivatives. The conjugates effectively bound to all four receptors, although to varying degrees, and delivered cytotoxic loads to both established and patient-derived GBM cell lines, with IC50 values in the low nM range. The conjugates were also non-toxic to animals. We anticipate that the QUAD 3.0 Dox conjugates will be further used in preclinical models and possibly clinics in the foreseeable future.

Challenges to Successful Implementation of the Immune Checkpoint Inhibitors for Treatment of Glioblastoma

Glioblastoma (GBM) is the most common and aggressive malignant glioma, treatment of which has not improved significantly in many years. This is due to the unique challenges that GBM tumors present when designing and implementing therapies. Recently, immunotherapy in the form of immune checkpoint inhibition (ICI) has revolutionized the treatment of various malignancies. The application of immune checkpoint inhibition in GBM treatment has shown promising preclinical results. Unfortunately, this has met with little to no success in the clinic thus far. In this review, we will discuss the challenges presented by GBM tumors that likely limit the effect of ICI and discuss the approaches being tested to overcome these challenges.

Proposing a tandem AND-gate CAR T cell targeting glioblastoma multiforme

CAR T cell therapy is suggested as an effective method to treat hematological malignancies. However, high recurrence rates and in vivo toxicities have limited their widespread use. In order to reduce toxicity and improve tumor specificity, we propose a CAR T cell targeting glioblastoma multiforme utilizing the synNotch receptor pathway linked to a tandem CAR T cell. The extracellular domain of the synNotch receptor is replaced by a single chain fragment variable specific for the EGF receptor variant III (scfv-EGFRvIII), and covalently bonded to a IL-13Rα2-CD133-tandem CAR. This would produce an AND-gate CAR-T cell, which requires activation of both signals from synNotch receptor binding to EGFRvIII and then binding of the tandem CAR to either of the two IL-13Rα2 or CD133 ligands-specific antigens for glioblastoma stem cells. SynNotch receptor activation along with the 4-1BB costimulatory domain results in CAR T cell expression under the TRE promoter, culminating in a tri-specific and effective tumor stem cell recognition and elimination of glioblastoma multiforme.

Development of Targeted Alpha Particle Therapy for Solid Tumors

Targeted alpha-particle therapy (TAT) aims to selectively deliver radionuclides emitting α-particles (cytotoxic payload) to tumors by chelation to monoclonal antibodies, peptides or small molecules that recognize tumor-associated antigens or cell-surface receptors. Because of the high linear energy transfer (LET) and short range of alpha (α) particles in tissue, cancer cells can be significantly damaged while causing minimal toxicity to surrounding healthy cells. Recent clinical studies have demonstrated the remarkable efficacy of TAT in the treatment of metastatic, castration-resistant prostate cancer. In this comprehensive review, we discuss the current consensus regarding the properties of the α-particle-emitting radionuclides that are potentially relevant for use in the clinic; the TAT-mediated mechanisms responsible for cell death; the different classes of targeting moieties and radiometal chelators available for TAT development; current approaches to calculating radiation dosimetry for TATs; and lead optimization via medicinal chemistry to improve the TAT radiopharmaceutical properties. We have also summarized the use of TATs in pre-clinical and clinical studies to date.

Delivery of GalNAc-Conjugated Splice-Switching ASOs to Non-hepatic Cells through Ectopic Expression of Asialoglycoprotein Receptor

Splice-switching antisense oligonucleotides (ASOs) are promising therapeutic tools to target various genetic diseases, including cancer. However, in vivo delivery of ASOs to orthotopic tumors in cancer mouse models or to certain target tissues remains challenging. A viable solution already in use is receptor-mediated uptake of ASOs via tissue-specific receptors. For example, the asialoglycoprotein receptor (ASGP-R) is exclusively expressed in hepatocytes. Triantennary N-acetylgalactosamine (GalNAc) (GN3)-conjugated ASOs bind to the receptor and are efficiently internalized by endocytosis, enhancing ASO potency in the liver. Here we explore the use of GalNAc-mediated targeting to deliver therapeutic splice-switching ASOs to cancer cells that ectopically express ASGP-R, both in vitro and in tumor mouse models. We found that ectopic expression of the major isoform ASGP-R1 H1a is sufficient to promote uptake and increase GN3-ASO potency to various degrees in four of five tested cancer cells. We show that cell-type-specific glycosylation of the receptor does not affect its activity. In vivo, GN3-conjugated ASOs specifically target subcutaneous xenograft tumors that ectopically express ASGP-R1, and modulate splicing significantly more strongly than unconjugated ASOs. Our work shows that GN3-targeting is a useful tool for proof-of-principle studies in orthotopic cancer models, until endogenous receptors are identified and exploited for efficiently targeting cancer cells.

Tumor targeting peptides: novel therapeutic strategies in glioblastoma

Peptides are a promising new therapeutic approach for glioblastoma with potential for more effective targeting and fewer devastating side effects compared to conventional cancer therapies. With the specificity to target receptors which are uniquely or overexpressed on cancer cells as well as accurately targeting dysregulated signaling pathways, peptides demonstrate a high potential for the treatment of even the most aggressive cancers. By binding to these targets, peptides can be used to deliver drugs, serve as antagonists to various ligands, or, given some inherent anticancer activity, provide additional treatment options alone or in combination therapy. The highly specific targeting capacity of peptides is critical to achieve effective cancer treatment with limited side effects, and in preclinical studies peptides have shown to have both cell and blood brain barrier penetrating capacity. As tumor targeting peptides move beyond the preclinical setting, identification of additional glioblastoma-specific peptide ligands becomes imperative to expand the potential of this encouraging treatment strategy.