Marizomib activity as a single agent in malignant gliomas: ability to cross the blood-brain barrier

Antiproliferative metabolites against glioma cells from the marine-associated actinomycete Streptomyces sp. ZZ735

Metabolites produced by the genus Streptomyces are the most important resource for discovering bioactive compounds. In this study, chemical investigation on the metabolites produced by the marine-derived Streptomyces sp. ZZ735 in rice solid medium led to the isolation of eighteen compounds (1-18). Chemical structures of the isolated compounds were determined based on their HRESIMS data and the extensive NMR spectral analyses. Streptonaphthothiazines A (1), B (2), 2-(2-hydroxy-2-methylpropanoylamino)-benzoic acid (7), and streptomycinoic acids A (17), B (18) are characterized as five previously undescribed compounds. The structural backbones of streptonaphthothiazines A (1), B (2) and streptomycinoic acids A (17), B (18) are found from a natural resource for the first time. It is also the first report of 2-(2-methylpropanoylamino)-benzoic acid (3), 2-(2-methylpropanoylamino)-benzamide (4), methyl 2-(3-hydroxypropanoylamino)-benzoate (5), 2-propionylaminobenzamide (6), and (2E)-3-(3-hydroxy-4,5-dimethoxyphenyl)-2-propenoic acid (15) as natural products. Streptonaphthothiazines A (1), B (2) and streptomycinoic acids A (17), B (18) have antiproliferative activity against human glioma U87MG or U251 cells with IC50 values ranging from 31.8 to 37.9 μM.

Marizomib for patients with newly diagnosed glioblastoma: A randomized phase 3 trial

BACKGROUND

Standard treatment for patients with newly diagnosed glioblastoma includes surgery, radiotherapy (RT), and temozolomide (TMZ) chemotherapy (TMZ/RT→TMZ). The proteasome has long been considered a promising therapeutic target because of its role as a central biological hub in tumor cells. Marizomib is a novel pan-proteasome inhibitor that crosses the blood-brain barrier.

METHODS

European Organisation for Research and Treatment of Cancer 1709/Canadian Cancer Trials Group CE.8 was a multicenter, randomized, controlled, open-label phase 3 superiority trial. Key eligibility criteria included newly diagnosed glioblastoma, age > 18 years and Karnofsky performance status > 70. Patients were randomized in a 1:1 ratio. The primary objective was to compare overall survival (OS) in patients receiving marizomib in addition to TMZ/RT→TMZ with patients receiving the only standard treatment in the whole population and in the subgroup of patients with MGMT promoter-unmethylated tumors.

RESULTS

The trial was opened at 82 institutions in Europe, Canada, and the U.S. A total of 749 patients (99.9% of the planned 750) were randomized. OS was not different between the standard and the marizomib arm (median 17 vs. 16.5 months; HR = 1.04; P = .64). PFS was not statistically different either (median 6.0 vs. 6.3 months; HR = 0.97; P = .67). In patients with MGMT promoter-unmethylated tumors, OS was also not different between standard therapy and marizomib (median 14.5 vs. 15.1 months, HR = 1.13; P = .27). More CTCAE grade 3/4 treatment-emergent adverse events were observed in the marizomib arm than in the standard arm.

CONCLUSIONS

Adding marizomib to standard temozolomide-based radiochemotherapy resulted in more toxicity, but did not improve OS or PFS in patients with newly diagnosed glioblastoma.

The Proteasome Inhibitor Marizomib Evokes Endoplasmic Reticulum Stress and Promotes Apoptosis in Human Glioblastoma Cells

Proteasomes play an important role in the physiology of cancer cells, and inhibition of their activity may be used as a promising therapeutic strategy against glioblastoma (GBM). Although certain proteasome inhibitors (PIs) have been approved for the treatment of other malignancies, they have limited effectiveness against GBM due to low brain bioavailability. Marizomib (MZB) is an irreversible, second-generation proteasome inhibitor, which unlike other PIs can penetrate through the blood-brain barrier, making it a promising therapeutic tool in brain malignancies. The antitumor activity of MZB was investigated in LN229 and U118 cells. The MTT test and the ATP-based assay were performed to evaluate cytotoxicity. Flow cytometry analysis was used to determine the apoptotic death of GBM cells. Luminescent assays were used to assess levels of reactive oxygen species (ROS) and the activity of caspase 3/7. RT-qPCR and Western blot analyses were used to determine gene and protein expressions. Marizomib decreased the viability and caused apoptotic death of GBM cells. The proapoptotic effect was accompanied by activation of caspase 3 and overexpression of cl-PARP, Noxa, Cyt C, and DR5. Moreover, treatment with MZB triggered endoplasmic reticulum (ER) stress, as shown by increased expressions of GRP78, IRE1α, p-EIF2α, p-SAPK/JNK, CHOP, ATF6α, and ATF4. On the contrary, overproduction of ROS or increased expressions of ERO1α, LC3 II, Beclin 1, and ATG5 were not detected, suggesting that neither oxidative stress nor autophagy were involved in the process of MZB-induced cell death. Thus, marizomib represents a potentially promising compound for facilitating further progress in brain cancer therapy.

Marizomib (Salinosporamide A) Promotes Apoptosis in A375 and G361 Melanoma Cancer Cells

Malignant melanoma-a tumor originating from melanocytes-is characterized by dynamic growth and frequent metastases in the early stage of development. Current therapy methods are still insufficient, and there is a need to search for new ways of treating this malady. The induction of apoptosis-physiological cell death-by proteasome inhibitors is recognized as an effective method of non-invasive elimination of cancer cells. In our research, we wanted to check the potential of marizomib (MZB, salinosporamide A, NPI-0052)-an irreversible proteasome inhibitor derived from the marine actinomycete Salinispora tropica-to induce apoptosis in A375 and G361 malignant melanoma cells. We determined the cytotoxic activity of marizomib by performing an MTT test. Ethidium bromide and acridine orange staining demonstrated the disruption of membrane integrity in the examined cell lines. We confirmed the proapoptotic activity of marizomib by flow cytometry with the use of an FITC-Annexin V assay. A Western blot analysis presented an increase in the expression of proteins related to endoplasmic reticulum (ER) stress as well as markers of the apoptosis. The gathered findings suggest that marizomib induced the ER stress in the examined melanoma cancer cells and directed them towards the apoptosis pathway.

The role of proteasomes in tumorigenesis

Protein homeostasis is the basis of normal life activities, and the proteasome family plays an extremely important function in this process. The proteasome 20S is a concentric circle structure with two α rings and two β rings overlapped. The proteasome 20S can perform both ATP-dependent and non-ATP-dependent ubiquitination proteasome degradation by binding to various subunits (such as 19S, 11S, and 200 PA), which is performed by its active subunit β1, β2, and β5. The proteasome can degrade misfolded, excess proteins to maintain homeostasis. At the same time, it can be utilized by tumors to degrade over-proliferate and unwanted proteins to support their growth. Proteasomes can affect the development of tumors from several aspects including tumor signaling pathways such as NF-κB and p53, cell cycle, immune regulation, and drug resistance. Proteasome-encoding genes have been found to be overexpressed in a variety of tumors, providing a potential novel target for cancer therapy. In addition, proteasome inhibitors such as bortezomib, carfilzomib, and ixazomib have been put into clinical application as the first-line treatment of multiple myeloma. More and more studies have shown that it also has different therapeutic effects in other tumors such as hepatocellular carcinoma, non-small cell lung cancer, glioblastoma, and neuroblastoma. However, proteasome inhibitors are not much effective due to their tolerance and singleness in other tumors. Therefore, further studies on their mechanisms of action and drug interactions are needed to investigate their therapeutic potential.

WITHDRAWN: LonP1 Drives Proneural Mesenchymal Transition in IDH1-R132H Diffuse Glioma

The authors have withdrawn their manuscript owing to massive revision and data validation. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

WITHDRAWN: Dual targeting of mitochondrial Lon peptidase 1 and chymotrypsin-like protease by small molecule BT317, as potential therapeutics in malignant astrocytomas

The authors have withdrawn their manuscript owing to massive revision and data validation. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

Integrated proteomics spotlight the proteasome as a therapeutic vulnerability in embryonal tumors with multilayered rosettes

BACKGROUND

Embryonal tumors with multilayered rosettes (ETMR) are rare malignant embryonal brain tumors. The prognosis of ETMR is poor and novel therapeutic approaches are desperately needed. Comprehension of ETMR tumor biology is currently based on only few previous molecular studies, which mainly focused on the analyses of nucleic acids. In this study, we explored integrated ETMR proteomics.

METHODS

Using mass spectrometry, proteome data were acquired from 16 ETMR and the ETMR cell line BT183. Proteome data were integrated with case-matched global DNA methylation data, publicly available transcriptome data, and proteome data of further embryonal and pediatric brain tumors.

RESULTS

Proteome-based cluster analyses grouped ETMR samples according to histomorphology, separating neuropil-rich tumors with neuronal signatures from primitive tumors with signatures relating to stemness and chromosome organization. Integrated proteomics showcased that ETMR and BT183 cells harbor proteasome regulatory proteins in abundance, implicating their strong dependency on the proteasome machinery to safeguard proteostasis. Indeed, in vitro assays using BT183 highlighted that ETMR tumor cells are highly vulnerable toward treatment with the CNS penetrant proteasome inhibitor Marizomib.

CONCLUSIONS

In summary, histomorphology stipulates the proteome signatures of ETMR, and proteasome regulatory proteins are pervasively abundant in these tumors. As validated in vitro, proteasome inhibition poses a promising therapeutic option in ETMR.

Mechanistic insights and the clinical prospects of targeted therapies for glioblastoma: a comprehensive review

Glioblastoma (GBM) is a fatal brain tumour that is traditionally diagnosed based on histological features. Recent molecular profiling studies have reshaped the World Health Organization approach in the classification of central nervous system tumours to include more pathogenetic hallmarks. These studies have revealed that multiple oncogenic pathways are dysregulated, which contributes to the aggressiveness and resistance of GBM. Such findings have shed light on the molecular vulnerability of GBM and have shifted the disease management paradigm from chemotherapy to targeted therapies. Targeted drugs have been developed to inhibit oncogenic targets in GBM, including receptors involved in the angiogenic axis, the signal transducer and activator of transcription 3 (STAT3), the PI3K/AKT/mTOR signalling pathway, the ubiquitination-proteasome pathway, as well as IDH1/2 pathway. While certain targeted drugs showed promising results in vivo, the translatability of such preclinical achievements in GBM remains a barrier. We also discuss the recent developments and clinical assessments of targeted drugs, as well as the prospects of cell-based therapies and combinatorial therapy as novel ways to target GBM. Targeted treatments have demonstrated preclinical efficacy over chemotherapy as an alternative or adjuvant to the current standard of care for GBM, but their clinical efficacy remains hindered by challenges such as blood-brain barrier penetrance of the drugs. The development of combinatorial targeted therapies is expected to improve therapeutic efficacy and overcome drug resistance.

NF-κB in biology and targeted therapy: new insights and translational implications

NF-κB signaling has been discovered for nearly 40 years. Initially, NF-κB signaling was identified as a pivotal pathway in mediating inflammatory responses. However, with extensive and in-depth investigations, researchers have discovered that its role can be expanded to a variety of signaling mechanisms, biological processes, human diseases, and treatment options. In this review, we first scrutinize the research process of NF-κB signaling, and summarize the composition, activation, and regulatory mechanism of NF-κB signaling. We investigate the interaction of NF-κB signaling with other important pathways, including PI3K/AKT, MAPK, JAK-STAT, TGF-β, Wnt, Notch, Hedgehog, and TLR signaling. The physiological and pathological states of NF-κB signaling, as well as its intricate involvement in inflammation, immune regulation, and tumor microenvironment, are also explicated. Additionally, we illustrate how NF-κB signaling is involved in a variety of human diseases, including cancers, inflammatory and autoimmune diseases, cardiovascular diseases, metabolic diseases, neurological diseases, and COVID-19. Further, we discuss the therapeutic approaches targeting NF-κB signaling, including IKK inhibitors, monoclonal antibodies, proteasome inhibitors, nuclear translocation inhibitors, DNA binding inhibitors, TKIs, non-coding RNAs, immunotherapy, and CAR-T. Finally, we provide an outlook for research in the field of NF-κB signaling. We hope to present a stereoscopic, comprehensive NF-κB signaling that will inform future research and clinical practice.

Marine-Derived Anticancer Agents Targeting Apoptotic Pathways: Exploring the Depths for Novel Cancer Therapies

Extensive research has been conducted on the isolation and study of bioactive compounds derived from marine sources. Several natural products have demonstrated potential as inducers of apoptosis and are currently under investigation in clinical trials. These marine-derived compounds selectively interact with extrinsic and intrinsic apoptotic pathways using a variety of molecular mechanisms, resulting in cell shrinkage, chromatin condensation, cytoplasmic blebs, apoptotic bodies, and phagocytosis by adjacent parenchymal cells, neoplastic cells, or macrophages. Numerous marine-derived compounds are currently undergoing rigorous examination for their potential application in cancer therapy. This review examines a total of 21 marine-derived compounds, along with their synthetic derivatives, sourced from marine organisms such as sponges, corals, tunicates, mollusks, ascidians, algae, cyanobacteria, fungi, and actinobacteria. These compounds are currently undergoing preclinical and clinical trials to evaluate their potential as apoptosis inducers for the treatment of different types of cancer. This review further examined the compound's properties and mode of action, preclinical investigations, clinical trial studies on single or combination therapy, and the prospective development of marine-derived anticancer therapies.

Shikimate-Derived Meroterpenoids from the Ascidian-Derived Fungus Amphichorda felina SYSU-MS7908 and Their Anti-Glioma Activity

Glioma is a clinically heterogeneous type of brain tumor with a poor prognosis. Current treatment approaches have limited effectiveness in treating glioma, highlighting the need for novel drugs. One approach is to explore marine natural products for their therapeutic potential. In this study, we isolated nine shikimate-derived diisoprenyl-cyclohexene/ane-type meroterpenoids (1-9), including four new ones, amphicordins A-D (1-4) from the ascidian-derived fungus Amphichorda felina SYSU-MS7908, and further semisynthesized four derivatives (10-13). Their structures were extensively characterized using 1D and 2D NMR, modified Mosher's method, HR-ESIMS, NMR and ECD calculations, and X-ray crystallography. Notably, amphicordin C (3) possesses a unique benzo[g]chromene (6/6/6) skeleton in this meroterpenoid family. In an anti-glioma assay, oxirapentyn A (7) effectively inhibited the proliferation, migration, and invasion of glioma cells and induced their apoptosis. Furthermore, an in silico analysis suggested that oxirapentyn A has the potential to penetrate the blood-brain barrier. These findings highlight the potential of oxirapentyn A as a candidate for the development of novel anti-glioma drugs.

Advances in research on potential inhibitors of multiple myeloma

Multiple myeloma (MM) is a common hematological malignancy. Although recent clinical applications of immunomodulatory drugs, proteasome inhibitors and CD38-targeting antibodies have significantly improved the outcome of MM patient with increased survival, the incidence of drug resistance and severe treatment-related complications is gradually on the rise. This review article summarizes the characteristics and clinical investigations of several MM drugs in clinical trials, including their structures, mechanisms of action, structure-activity relationships, and clinical study progress. Furthermore, the application potentials of the drugs that have not yet entered clinical trials are also reviewed. The review also outlines the future directions of MM drug development.

Multiple Myeloma in 2023 Ways: From Trials to Real Life

Multiple myeloma is a chronic hematologic malignancy that obstinately tends to relapse. Basic research has made giant strides in better characterizing the molecular mechanisms of the disease. The results have led to the manufacturing of new, revolutionary drugs which have been widely tested in clinical trials. These drugs have been approved and are now part of the therapeutic armamentarium. As a consequence, it is essential to combine what we know from clinical trials with real-world data in order to improve therapeutic strategies. Starting with this premise, our review aims to describe the currently employed regimens in multiple myeloma and compare clinical trials with real-life experiences. We also intend to put a spotlight on promising therapies such as T-cell engagers and chimeric antigen receptor T-cells (CAR-T) which are proving to be effective in changing the course of advanced-stage disease.

Proteasome Inhibitors against Glioblastoma-Overview of Molecular Mechanisms of Cytotoxicity, Progress in Clinical Trials, and Perspective for Use in Personalized Medicine

Proteasome inhibitors are moieties targeting the proteolytic activity of a proteasome, with demonstrated efficacy in certain hematological malignancies and candidate drugs in other types of cancer, including glioblastoma (GBM). They disturb the levels of proteasome-regulated proteins and lead to the cell cycle inhibition and apoptosis of GBM cells. The accumulation of cell cycle inhibitors p21 and p27, and decreased levels of prosurvival molecules NFKB, survivin, and MGMT, underlie proteasome inhibitors' cytotoxicity when used alone or in combination with the anti-GBM cytostatic drug temozolomide (TMZ). The evidence gathered in preclinical studies substantiated the design of clinical trials that employed the two most promising proteasome inhibitors, bortezomib and marizomib. The drug safety profile, maximum tolerated dose, and interaction with other drugs were initially evaluated, mainly in recurrent GBM patients. A phase III study on newly diagnosed GBM patients who received marizomib as an adjuvant to the Stupp protocol was designed and completed in 2021, with the Stupp protocol receiving patients as a parallel control arm. The data from this phase III study indicate that marizomib does not improve the PFS and OS of GBM patients; however, further analysis of the genetic and epigenetic background of each patient tumor may shed some light on the sensitivity of individual patients to proteasome inhibition. The mutational and epigenetic makeup of GBM cells, like genetic alterations to TP53 and PTEN, or MGMT promoter methylation levels may actually determine the response to proteasome inhibition.

Proteasome inhibition protects blood-brain barrier P-glycoprotein and lowers Aβ brain levels in an Alzheimer's disease model

BACKGROUND

Loss of P-glycoprotein (P-gp) at the blood-brain barrier contributes to amyloid-β (Aβ) brain accumulation in Alzheimer's disease (AD). Using transgenic human amyloid precursor protein (hAPP)-overexpressing mice (Tg2576), we previously showed that Aβ triggers P-gp loss by activating the ubiquitin-proteasome pathway, which leads to P-gp degradation. Furthermore, we showed that inhibiting the ubiquitin-activating enzyme (E1) prevents P-gp loss and lowers Aβ accumulation in the brain of hAPP mice. Based on these data, we hypothesized that repurposing the FDA-approved proteasome inhibitor, bortezomib (Velcade®; BTZ), protects blood-brain barrier P-gp from degradation in hAPP mice in vivo.

METHODS

We treated hAPP mice with the proteasome inhibitor BTZ or a combination of BTZ with the P-gp inhibitor cyclosporin A (CSA) for 2 weeks. Vehicle-treated wild-type (WT) mice were used as a reference for normal P-gp protein expression and transport activity. In addition, we used the opioid receptor agonist loperamide as a P-gp substrate in tail flick assays to indirectly assess P-gp transport activity at the blood-brain barrier in vivo. We also determined P-gp protein expression by Western blotting, measured P-gp transport activity levels in isolated brain capillaries with live cell confocal imaging and assessed Aβ plasma and brain levels with ELISA.

RESULTS

We found that 2-week BTZ treatment of hAPP mice restored P-gp protein expression and transport activity in brain capillaries to levels found in WT mice. We also observed that hAPP mice displayed significant loperamide-induced central antinociception compared to WT mice indicating impaired P-gp transport activity at the blood-brain barrier of hAPP mice in vivo. Furthermore, BTZ treatment prevented loperamide-induced antinociception suggesting BTZ protected P-gp loss in hAPP mice. Further, BTZ-treated hAPP mice had lower Aβ40 and Aβ42 brain levels compared to vehicle-treated hAPP mice.

CONCLUSIONS

Our data indicate that BTZ protects P-gp from proteasomal degradation in hAPP mice, which helps to reduce Aβ brain levels. Our data suggest that the proteasome system could be exploited for a novel therapeutic strategy in AD, particularly since increasing Aβ transport across the blood-brain barrier may prove an effective treatment for patients.

Targeting mitochondrial energetics reverses panobinostat- and marizomib-induced resistance in pediatric and adult high-grade gliomas

In previous studies, we demonstrated that panobinostat, a histone deacetylase inhibitor, and bortezomib, a proteasomal inhibitor, displayed synergistic therapeutic activity against pediatric and adult high-grade gliomas. Despite the remarkable initial response to this combination, resistance emerged. Here, in this study, we aimed to investigate the molecular mechanisms underlying the anticancer effects of panobinostat and marizomib, a brain-penetrant proteasomal inhibitor, and the potential for exploitable vulnerabilities associated with acquired resistance. RNA sequencing followed by gene set enrichment analysis (GSEA) was employed to compare the molecular signatures enriched in resistant compared with drug-naïve cells. The levels of adenosine 5'-triphosphate (ATP), nicotinamide adenine dinucleotide (NAD)+ content, hexokinase activity, and tricarboxylic acid (TCA) cycle metabolites required for oxidative phosphorylation to meet their bioenergetic needs were analyzed. Here, we report that panobinostat and marizomib significantly depleted ATP and NAD+ content, increased mitochondrial permeability and reactive oxygen species generation, and promoted apoptosis in pediatric and adult glioma cell lines at initial treatment. However, resistant cells exhibited increased levels of TCA cycle metabolites, which required for oxidative phosphorylation to meet their bioenergetic needs. Therefore, we targeted glycolysis and the electron transport chain (ETC) with small molecule inhibitors, which displayed substantial efficacy, suggesting that resistant cell survival is dependent on glycolytic and ETC complexes. To verify these observations in vivo, lonidamine, an inhibitor of glycolysis and mitochondrial function, was chosen. We produced two diffuse intrinsic pontine glioma (DIPG) models, and lonidamine treatment significantly increased median survival in both models, with particularly dramatic effects in panobinostat- and marizomib-resistant cells. These data provide new insights into mechanisms of treatment resistance in gliomas.

Structural elucidation of recombinant Trichomonas vaginalis 20S proteasome bound to covalent inhibitors

Proteasomes are essential for protein homeostasis in mammalian cells1-4 and in protozoan parasites such as Trichomonas vaginalis (Tv).5 Tv and other protozoan 20S proteasomes have been validated as druggable targets.6-8 However, in the case of Tv 20S proteasome (Tv20S), biochemical and structural studies were impeded by low yields and purity of the native proteasome. We successfully made recombinant Tv20S by expressing all seven α and seven β subunits together with the Ump-1 chaperone in insect cells. We isolated recombinant proteasome and showed that it was biochemically indistinguishable from the native enzyme. We confirmed that the recombinant Tv20S is inhibited by the natural product marizomib (MZB)9 and the recently developed peptide inhibitor carmaphycin-17 (CP-17)8,10. Specifically, MZB binds to the β1, β2 and β5 subunits, while CP-17 binds the β2 and β5 subunits. Next, we obtained cryo-EM structures of Tv20S in complex with these covalent inhibitors at 2.8Å resolution. The structures revealed the overall fold of the Tv20S and the binding mode of MZB and CP-17. Our work explains the low specificity of MZB and higher specificity of CP-17 towards Tv20S as compared to human proteasome and provides the platform for the development of Tv20S inhibitors for treatment of trichomoniasis.

Evolution of Natural Product Scaffolds as Potential Proteasome Inhibitors in Developing Cancer Therapeutics

Homeostasis between protein synthesis and degradation is a critical biological function involving a lot of precise and intricate regulatory systems. The ubiquitin-proteasome pathway (UPP) is a large, multi-protease complex that degrades most intracellular proteins and accounts for about 80% of cellular protein degradation. The proteasome, a massive multi-catalytic proteinase complex that plays a substantial role in protein processing, has been shown to have a wide range of catalytic activity and is at the center of this eukaryotic protein breakdown mechanism. As cancer cells overexpress proteins that induce cell proliferation, while blocking cell death pathways, UPP inhibition has been used as an anticancer therapy to change the balance between protein production and degradation towards cell death. Natural products have a long history of being used to prevent and treat various illnesses. Modern research has shown that the pharmacological actions of several natural products are involved in the engagement of UPP. Over the past few years, numerous natural compounds have been found that target the UPP pathway. These molecules could lead to the clinical development of novel and potent anticancer medications to combat the onslaught of adverse effects and resistance mechanisms caused by already approved proteasome inhibitors. In this review, we report the importance of UPP in anticancer therapy and the regulatory effects of diverse natural metabolites, their semi-synthetic analogs, and SAR studies on proteasome components, which may aid in discovering a new proteasome regulator for drug development and clinical applications.

Streptonaphthyridine A, a new naphthyridine analogue with antiproliferative activity against human glioma cells from mariana trench-associated actinomycete Streptomyces sp. SY2111

A new naphthyridine analogue, named streptonaphthyridine A (1), together with eight previously reported compounds (2-9), were isolated from a Mariana Trench sediment-associated actinomycete Streptomyces sp. SY2111. Planar structure of streptonaphthyridine A was established by analyses of its HRESIMS data and extensive NMR spectra and its absolute configuration was determined by a combination of single crystal X-ray diffraction analysis and optical rotation calculations. Streptonaphthyridine A (1) had antiproliferative activity against human glioma U87MG and U251 cells with IC₅₀ values of 7.9 ± 1.3 and 13.4 ± 2.7 µM, respectively, and the known compound monomethylsulochrin (7) showed more potent activity with IC₅₀ values of 0.6 ± 0.1 µM for U87MG cells and 0.1 ± 0.0 µM for U251 cells.

Exploring the Past, Present, and Future of Anti-Angiogenic Therapy in Glioblastoma

Glioblastoma, a WHO grade IV astrocytoma, constitutes approximately half of malignant tumors of the central nervous system. Despite technological advancements and aggressive multimodal treatment, prognosis remains dismal. The highly vascularized nature of glioblastoma enables the tumor cells to grow and invade the surrounding tissue, and vascular endothelial growth factor-A (VEGF-A) is a critical mediator of this process. Therefore, over the past decade, angiogenesis, and more specifically, the VEGF signaling pathway, has emerged as a therapeutic target for glioblastoma therapy. This led to the FDA approval of bevacizumab, a monoclonal antibody designed against VEGF-A, for treatment of recurrent glioblastoma. Despite the promising preclinical data and its theoretical effectiveness, bevacizumab has failed to improve patients' overall survival. Furthermore, several other anti-angiogenic agents that target the VEGF signaling pathway have also not demonstrated survival improvement. This suggests the presence of other compensatory angiogenic signaling pathways that surpass the anti-angiogenic effects of these agents and facilitate vascularization despite ongoing VEGF signaling inhibition. Herein, we review the current state of anti-angiogenic agents, discuss potential mechanisms of anti-angiogenic resistance, and suggest potential avenues to increase the efficacy of this therapeutic approach.

Molecular targeted therapy: A new avenue in glioblastoma treatment

Glioblastoma, also referred to as glioblastoma multiforme (GBM), is grade IV astrocytoma characterized by being fast-growing and the most aggressive brain tumor. In adults, it is the most prevalent type of malignant brain tumor. Despite the advancements in both diagnosis tools and therapeutic treatments, GBM is still associated with poor survival rate without any statistically significant improvement in the past three decades. Patient's genome signature is one of the key factors causing the development of this tumor, in addition to previous radiation exposure and other environmental factors. Researchers have identified genomic and subsequent molecular alterations affecting core pathways that trigger the malignant phenotype of this tumor. Targeting intrinsically altered molecules and pathways is seen as a novel avenue in GBM treatment. The present review shed light on signaling pathways and intrinsically altered molecules implicated in GBM development. It discussed the main challenges impeding successful GBM treatment, such as the blood brain barrier and tumor microenvironment (TME), the plasticity and heterogeneity of both GBM and TME and the glioblastoma stem cells. The present review also presented current advancements in GBM molecular targeted therapy in clinical trials. Profound and comprehensive understanding of molecular participants opens doors for innovative, more targeted and personalized GBM therapeutic modalities.

Multiple myeloma with isolated central nervous system relapse after autologous stem cell transplantation: A case report and review of the literature

Patients with multiple myeloma (MM) rarely present with central nervous system (CNS) involvement as a manifestation of extramedullary disease (EMD), a condition that is associated with poor prognosis. CNS relapse without evidence of systemic involvement is even rarer, and there is no standardized treatment because there are only few case reports. We present a 47-year-old female who was diagnosed with nonsecretory multiple myeloma (NSMM) 9 years previously. She had a complete remission after receiving aggressive therapies, including high-dose chemotherapy and autologous stem cell transplantation (ASCT). However, after 7 years of progression-free survival, she had CNS relapse without evidence of systemic involvement. We switched to a salvage regimen consisting of high-dose methotrexate with lenalidomide. She achieved rapid clinical improvement, with a reduction in cerebrospinal fluid plasmacytosis of more than 80%, and no notable side effects. Our description of this unique case of a patient with MM and isolated CNS relapse after ASCT provides a reference for physicians to provide more appropriate management of these patients. We also reviewed previously reported cases and summarized the outcomes of isolated CNS relapse after ASCT, and discuss the pathogenesis and possible treatment strategies for MM with isolated CNS relapse.

Dissecting super-enhancer driven transcriptional dependencies reveals novel therapeutic strategies and targets for group 3 subtype medulloblastoma

BACKGROUND

Medulloblastoma is the most common malignant pediatric brain tumor and group 3 subtype medulloblastoma (G3-MB) exhibits the worst prognosis. Super enhancers (SEs) are large clusters of enhancers that play important roles in cancer through transcriptional control of cell identity genes, oncogenes and tumor-dependent genes. Dissecting SE-driven transcriptional dependencies of cancer leads to identification of novel oncogenic mechanisms, therapeutic strategies and targets.

METHODS

Integrative SE analyses of primary tissues and patient-derived tumor cell lines of G3-MB were performed to extract the conserved SE-associated gene signatures and their oncogenic potentials were evaluated by gene expression, tumor-dependency and patient prognosis analyses. SE-associated subtype-specific upregulated tumor-dependent genes, which were revealed as members of SE-driven core transcriptional regulatory network of G3-MB, were then subjected to functional validation and mechanistic investigation. SE-associated therapeutic potential was further explored by genetic or pharmaceutical targeting of SE complex components or SE-associated subtype-specific upregulated tumor-dependent genes individually or in combination, and the underlying therapeutic mechanisms were also examined.

RESULTS

The identified conserved SE-associated transcripts of G3-MB tissues and cell lines were enriched of subtype-specifically upregulated tumor-dependent genes and MB patients harboring enrichment of those transcripts exhibited worse prognosis. Fourteen such conserved SE-associated G3-MB-specific upregulated tumor-dependent genes were identified to be members of SE-driven core transcriptional regulatory network of G3-MB, including three well-recognized TFs (MYC, OTX2 and CRX) and eleven newly identified downstream effector genes (ARL4D, AUTS2, BMF, IGF2BP3, KIF21B, KLHL29, LRP8, MARS1, PSMB5, SDK2 and SSBP3). An OTX2-SE-ARL4D regulatory axis was further revealed to represent a subtype-specific tumor dependency and therapeutic target of G3-MB via contributing to maintaining cell cycle progression and inhibiting neural differentiation of tumor cells. Moreover, BET inhibition with CDK7 inhibition or proteasome inhibition, two combinatory strategies of targeting SE complex components (BRD4, CDK7) or SE-associated effector gene (PSMB5), were shown to exhibit synergistic therapeutic effects against G3-MB via stronger suppression of SE-associated transcription or higher induction of ER stress, respectively.

CONCLUSIONS

Our study verifies the oncogenic role and therapeutic potential of SE-driven transcriptional dependencies of G3-MB, resulting in better understanding of its tumor biology and identification of novel SE-associated therapeutic strategies and targets.

The E3 ubiquitin ligase HUWE1 acts through the N-Myc-DLL1-NOTCH1 signaling axis to suppress glioblastoma progression

BACKGROUND

Elucidation of the post-transcriptional modification has led to novel strategies to treat intractable tumors, especially glioblastoma (GBM). The ubiquitin-proteasome system (UPS) mediates a reversible, stringent and stepwise post-translational modification which is closely associated with malignant processes of GBM. To this end, developing novel therapeutic approaches to target the UPS may contribute to the treatment of this disease. This study aimed to screen the vital and aberrantly regulated component of the UPS in GBM. Based on the molecular identification, functional characterization, and mechanism investigation, we sought to elaborate a novel therapeutic strategy to target this vital factor to combat GBM.

METHODS

We combined glioma datasets and human patient samples to screen and identify aberrantly regulated E3 ubiquitin ligase. Multidimensional database analysis and molecular and functional experiments in vivo and in vitro were used to evaluate the roles of HECT, UBA and WWE domain-containing E3 ubiquitin ligase 1 (HUWE1) in GBM. dCas9 synergistic activation mediator system and recombinant adeno-associated virus (rAAV) were used to endogenously overexpress full-length HUWE1 in vitro and in glioma orthotopic xenografts.

RESULTS

Low expression of HUWE1 was closely associated with worse prognosis of GBM patients. The ubiquitination and subsequent degradation of N-Myc mediated by HUWE1, leading to the inactivation of downstream Delta-like 1 (DLL1)-NOTCH1 signaling pathways, inhibited the proliferation, invasion, and migration of GBM cells in vitro and in vivo. A rAAV dual-vector system for packaging and delivery of dCas9-VP64 was used to augment endogenous HUWE1 expression in vivo and showed an antitumor activity in glioma orthotopic xenografts.

CONCLUSIONS

The E3 ubiquitin ligase HUWE1 acts through the N-Myc-DLL1-NOTCH1 signaling axis to suppress GBM progression. Antitumor activity of rAAV dual-vector delivering dCas9-HUWE1 system uncovers a promising therapeutic strategy for GBM.

Combined treatment of marizomib and cisplatin modulates cervical cancer growth and invasion and enhances antitumor potential in vitro and in vivo

Proteasome inhibition is an attractive approach for anticancer therapy. Cisplatin (cis-diamminedichloroplatinum, CDDP) is widely used as a standard chemotherapy drug in the treatment of solid malignant tumors, such as cervical cancer, ovarian cancer, colorectal cancer, and lung cancer. However, the development of CDDP resistance largely limits its clinical application. Proteasome inhibitors may enhance traditional chemotherapy agent-induced cytotoxicity and apoptosis. Marizomib (NPI-0052, salinosporamide A, Mzb), a second-generation proteasome inhibitor, shows synergistic anticancer activity with some drugs. Currently, the effect of Mzb on cervical cancer cell proliferation remains unclear. In this study, we explored the role of Mzb in three cervical cancer cell lines, HeLa, CaSki, and C33A, representing major molecular subtypes of cervical cancer and xenografts. We found that Mzb alone showed noteworthy cytotoxic effects, and its combination with CDDP resulted in more obvious cytotoxicity and apoptosis in cervical cancer cell lines and xenografts. In order to investigate the mechanism of this effect, we probed whether Mzb alone or in combination with CDDP had a better antitumor response by enhancing CDDP-induced angiopoietin 1 (Ang-1) expression and inhibiting the expression of TEK receptor tyrosine kinase (Tie-2) in the Ang-1/Tie-2 pathway, FMS-like tyrosine kinase 3 ligand (Flt-3L) and stem cell factor (SCF) as identified by a cytokine antibody chip test. The results suggest that Mzb has better antitumor effects on cervical cancer cells and can sensitize cervical cancer cells to CDDP treatment both in vitro and in vivo. Accordingly, we conclude that the combination of CDDP with Mzb produces synergistic anticancer activity and that Mzb may be a potential effective drug in combination therapy for cervical cancer patients.

Advances in the treatment of extramedullary disease in multiple myeloma

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Extramedullary multiple myeloma results in an adverse prognosis.

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Novel agents such as bortezomib, lenalidomide, pomalidomide, isatuximab and selinexor showed efficacy and were recommended to treat EMD.

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For EMD at special sites, marizomib has advantages in the treatment of CNS-MM; Daratumumab combining with intrapleural bortezomib administration is active in treating myelomatous pleural effusion.

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Based on treatment experience of EMD in our department, we summarized treatment approach for EMD.

Extramedullary disease (EMD) is characterized by plasma cells outside of bone marrow in multiple myeloma (MM) patients, which results in an adverse prognosis. The cornerstone of treatment consists of combination therapy including proteasome inhibitors, immunomodulatory agents, steroids, followed by consolidative autologous hematopoietic stem cell transplantation in eligible patients. This review summarized the recent advances in the treatment of EMD. Bortezomib based therapy showed efficacy and was recommended to treat EMD. Marizomib had advantages in the treatment of central nervous system-multiple myeloma (CNS-MM) because of its good central nervous system penetrability. Immunomodulatory drugs such as lenalidomide and pomalidomide have been reported to be effective. Isatuximab and selinexor were also active. Based on the treatment experience of EMD in our department, we summarized treatment approach for EMD. However, the benefits of patients with EMD from the new era of novel drugs were limited. Novel drugs combination, monoclonal antibody, molecular targeted therapy, cellular immunotherapy and autologous stem cell transplantation (ASCT) are under investigation. Therapeutic studies and clinical trials specifically target EMD should be conducted. Hopefully, these treatment options for EMD will be demonstrated efficacy in the future.

Glioblastoma: Current Status, Emerging Targets, and Recent Advances

Glioblastoma (GBM) is a highly malignant brain tumor characterized by a heterogeneous population of genetically unstable and highly infiltrative cells that are resistant to chemotherapy. Although substantial efforts have been invested in the field of anti-GBM drug discovery in the past decade, success has primarily been confined to the preclinical level, and clinical studies have often been hampered due to efficacy-, selectivity-, or physicochemical property-related issues. Thus, expansion of the list of molecular targets coupled with a pragmatic design of new small-molecule inhibitors with central nervous system (CNS)-penetrating ability is required to steer the wheels of anti-GBM drug discovery endeavors. This Perspective presents various aspects of drug discovery (challenges in GBM drug discovery and delivery, therapeutic targets, and agents under clinical investigation). The comprehensively covered sections include the recent medicinal chemistry campaigns embarked upon to validate the potential of numerous enzymes/proteins/receptors as therapeutic targets in GBM.

Therapeutic Options in Neuro-Oncology

One of the biggest challenges in neuro-oncology is understanding the complexity of central nervous system tumors, such as gliomas, in order to develop suitable therapeutics. Conventional therapies in malignant gliomas reconcile surgery and radiotherapy with the use of chemotherapeutic options such as temozolomide, chloroethyl nitrosoureas and the combination therapy of procarbazine, lomustine and vincristine. With the unraveling of deregulated cancer cell signaling pathways, targeted therapies have been developed. The most affected signaling pathways in glioma cells involve tyrosine kinase receptors and their downstream pathways, such as the phosphatidylinositol 3-kinases (PI3K/AKT/mTOR) and mitogen-activated protein kinase pathways (MAPK). MAPK pathway inhibitors include farnesyl transferase inhibitors, Ras kinase inhibitors and mitogen-activated protein extracellular regulated kinase (MEK) inhibitors, while PI3K/AKT/mTOR pathway inhibitors are divided into pan-inhibitors, PI3K/mTOR dual inhibitors and AKT inhibitors. The relevance of the immune system in carcinogenesis has led to the development of immunotherapy, through vaccination, blocking of immune checkpoints, oncolytic viruses, and adoptive immunotherapy using chimeric antigen receptor T cells. In this article we provide a comprehensive review of the signaling pathways underlying malignant transformation, the therapies currently used in the treatment of malignant gliomas and further explore therapies under development, including several ongoing clinical trials.

Real-time evaluation of glioblastoma growth in patient-specific zebrafish xenografts

BACKGROUND

Patient-derived xenograft (PDX) models of glioblastoma (GBM) are a central tool for neuro-oncology research and drug development, enabling the detection of patient-specific differences in growth, and in vivo drug response. However, existing PDX models are not well suited for large-scale or automated studies. Thus, here, we investigate if a fast zebrafish-based PDX model, supported by longitudinal, AI-driven image analysis, can recapitulate key aspects of glioblastoma growth and enable case-comparative drug testing.

METHODS

We engrafted 11 GFP-tagged patient-derived GBM IDH wild-type cell cultures (PDCs) into 1-day-old zebrafish embryos, and monitored fish with 96-well live microscopy and convolutional neural network analysis. Using light-sheet imaging of whole embryos, we analyzed further the invasive growth of tumor cells.

RESULTS

Our pipeline enables automatic and robust longitudinal observation of tumor growth and survival of individual fish. The 11 PDCs expressed growth, invasion and survival heterogeneity, and tumor initiation correlated strongly with matched mouse PDX counterparts (Spearman R = 0.89, p < 0.001). Three PDCs showed a high degree of association between grafted tumor cells and host blood vessels, suggesting a perivascular invasion phenotype. In vivo evaluation of the drug marizomib, currently in clinical trials for GBM, showed an effect on fish survival corresponding to PDC in vitro and in vivo marizomib sensitivity.

CONCLUSIONS

Zebrafish xenografts of GBM, monitored by AI methods in an automated process, present a scalable alternative to mouse xenograft models for the study of glioblastoma tumor initiation, growth, and invasion, applicable to patient-specific drug evaluation.

Mono- and Dimeric Xanthones with Anti-Glioma and Anti-Inflammatory Activities from the Ascidian-Derived Fungus Diaporthe sp. SYSU-MS4722

Seven new xanthones, diaporthones A-G (1-7), together with 13 known analogues, including five mono- (8-14) and six dimeric xanthones (15-20), were obtained from the ascidian-derived fungus Diaporthe sp. SYSU-MS4722. Their planar structures were established by extensive spectroscopic analyses, including 1D and 2D NMR and high-resolution mass spectrometry (HR-ESIMS). The absolute configurations of 1-7 were clearly identified by X-ray crystallographic analysis and calculation of the ECD Spectra. Compounds 15-20 showed significant anti-inflammatory activity with IC50 values between 6.3 and 8.0 μM. In addition, dimeric xanthones (15-20) showed selective cytotoxicity against T98G cell lines with IC50 values ranging from 19.5 to 78.0 μM.

Secondary CNS myeloma with remission after systemic CNS-penetrating agents

Background

CNS myeloma is a rare manifestation of multiple myeloma and is often associated with a dismal prognosis; however, cases are increasing in frequency as overall survival improves for MM. There is currently no standardized treatment for CNS myeloma; however, different chemotherapy and radiotherapy regimens have been described.

Methods

We had previously reported on the efficacy of proton-based craniospinal irradiation in a patient with CNS myeloma; here we present a patient with a history of extramedullary plasmacytoma, 10 years in remission status post standard systemic chemotherapy, with biopsy-proven CNS myeloma successfully treated with systemic chemotherapy as a first-line treatment.

Results

The patient achieved clinical and radiographic remission on 2 separate occasions with systemic chemotherapy alone.

Conclusions

This case demonstrates that systemically administered agents may have activity in CNS myeloma. Further investigations are necessary to establish the optimal combination of agents and treatment schedules.

Therapeutic Targets in Diffuse Midline Gliomas-An Emerging Landscape

Simple Summary

Diffuse midline gliomas (DMGs) remain one of the most devastating childhood brain tumour types, for which there is currently no known cure. In this review we provide a summary of the existing knowledge of the molecular mechanisms underlying the pathogenesis of this disease, highlighting current analyses and novel treatment propositions. Together, the accumulation of these data will aid in the understanding and development of more effective therapeutic options for the treatment of DMGs.

Abstract

Diffuse midline gliomas (DMGs) are invariably fatal pediatric brain tumours that are inherently resistant to conventional therapy. In recent years our understanding of the underlying molecular mechanisms of DMG tumorigenicity has resulted in the identification of novel targets and the development of a range of potential therapies, with multiple agents now being progressed to clinical translation to test their therapeutic efficacy. Here, we provide an overview of the current therapies aimed at epigenetic and mutational drivers, cellular pathway aberrations and tumor microenvironment mechanisms in DMGs in order to aid therapy development and facilitate a holistic approach to patient treatment.

Cell-of-Origin and Genetic, Epigenetic, and Microenvironmental Factors Contribute to the Intra-Tumoral Heterogeneity of Pediatric Intracranial Ependymoma

Intra-tumoral heterogeneity (ITH) is a complex multifaceted phenomenon that posits major challenges for the clinical management of cancer patients. Genetic, epigenetic, and microenvironmental factors are concurrent drivers of diversity among the distinct populations of cancer cells. ITH may also be installed by cancer stem cells (CSCs), that foster unidirectional hierarchy of cellular phenotypes or, alternatively, shift dynamically between distinct cellular states. Ependymoma (EPN), a molecularly heterogeneous group of tumors, shows a specific spatiotemporal distribution that suggests a link between ependymomagenesis and alterations of the biological processes involved in embryonic brain development. In children, EPN most often arises intra-cranially and is associated with an adverse outcome. Emerging evidence shows that EPN displays large intra-patient heterogeneity. In this review, after touching on EPN inter-tumoral heterogeneity, we focus on the sources of ITH in pediatric intra-cranial EPN in the framework of the CSC paradigm. We also examine how single-cell technology has shed new light on the complexity and developmental origins of EPN and the potential impact that this understanding may have on the therapeutic strategies against this deadly pediatric malignancy.

Marizomib alone or in combination with bevacizumab in patients with recurrent glioblastoma: Phase I/II clinical trial data

Background

This phase I/II trial in patients with recurrent glioblastoma (GBM) evaluates the safety and preliminary efficacy of marizomib, an irreversible pan-proteasome inhibitor that crosses the blood–brain barrier.

Methods

Part A assessed the safety and efficacy of marizomib monotherapy. In Part B, escalating doses of marizomib (0.5–0.8 mg/m²) in combination with bevacizumab were evaluated. Part C explored intra-patient dose escalation of marizomib (0.8–1.0 mg/m²) for the combination.

Results

In Part A, 30 patients received marizomib monotherapy. The most common AEs were fatigue (66.7%), headache (46.7%), hallucination (43.3%), and insomnia (43.3%). One patient (3.3%) achieved a partial response. In Part B, the recommended phase II dose of marizomib was 0.8 mg/m² when combined with bevacizumab 10 mg/kg. In Part C, dose escalation to 1.0 mg/m² was not tolerated. Pooled analysis of 67 patients treated with marizomib ≤0.8 mg/m² and bevacizumab showed a nonoverlapping safety profile consistent with the known safety profile of each agent: the most common grade ≥3 AEs were hypertension (16.4%), confusion (13.4%), headache (10.4%), and fatigue (10.4%). The overall response rate was 34.3%, including 2 patients with complete response. Six-month progression-free survival was 29.8%; median overall survival was 9.1 months.

Conclusions

The safety profile of marizomib as monotherapy and in combination with bevacizumab was consistent with previous observations that marizomib crosses the blood–brain barrier. Preliminary efficacy did not demonstrate a meaningful benefit of the addition of marizomib to bevacizumab for the treatment of recurrent GBM.

Utilizing preclinical models to develop targeted therapies for rare central nervous system cancers

Patients with rare central nervous system (CNS) tumors typically have a poor prognosis and limited therapeutic options. Historically, these cancers have been difficult to study due to small number of patients. Recent technological advances have identified molecular drivers of some of these rare cancers which we can now use to generate representative preclinical models of these diseases. In this review, we outline the advantages and disadvantages of different models, emphasizing the utility of various in vitro and ex vivo models for target discovery and mechanistic inquiry and multiple in vivo models for therapeutic validation. We also highlight recent literature on preclinical model generation and screening approaches for ependymomas, histone mutated high-grade gliomas, and atypical teratoid rhabdoid tumors, all of which are rare CNS cancers that have recently established genetic or epigenetic drivers. These preclinical models are critical to advancing targeted therapeutics for these rare CNS cancers that currently rely on conventional treatments.

Clinical trial challenges, design considerations, and outcome measures in rare CNS tumors

Clinical research for patients with rare cancers has been very challenging. First and foremost, patient accrual to clinical trials typically requires a network, cooperative group, or even international collaboration in order to achieve the necessary numbers of patients to adequately evaluate a new treatment or intervention. Similar limitations in preclinical models and in the understanding the natural history of the disease or pertinent prognostic factors further impede the development of hypothesis-based, appropriately powered clinical trials. However, despite these challenges, several studies in rare cancers, including ependymoma and subependymal giant cell astrocytoma, have helped to establish new treatment regimens. Importantly, in these seminal trials, patient outcomes measures were critical in describing the clinical benefit derived from the therapy, underscoring the need to incorporate these measures in future trials. While obstacles still remain, novel and creative approaches to clinical trial designs have been developed that can be used to study new treatments for patients with rare cancers, thereby addressing a significant unmet need.

Generation, characterization, and drug sensitivities of 12 patient-derived IDH1-mutant glioma cell cultures

Background

Mutations of the isocitrate dehydrogenase (IDH) gene occur in over 80% of low-grade gliomas and secondary glioblastomas. Despite considerable efforts, endogenous in vitro IDH-mutated glioma models remain scarce. Availability of these models is key for the development of new therapeutic interventions.

Methods

Cell cultures were established from fresh tumor material and expanded in serum-free culture media. D-2-Hydroxyglutarate levels were determined by mass spectrometry. Genomic and transcriptomic profiling were carried out on the Illumina Novaseq platform, methylation profiling was performed with the Infinium MethylationEpic BeadChip array. Mitochondrial respiration was measured with the Seahorse XF24 Analyzer. Drug screens were performed with an NIH FDA-approved anti-cancer drug set and two IDH-mutant specific inhibitors.

Results

A set of twelve patient-derived IDHmt cell cultures was established. We confirmed high concordance in driver mutations, copy numbers and methylation profiles between the tumors and derived cultures. Homozygous deletion of CDKN2A/B was observed in all cultures. IDH-mutant cultures had lower mitochondrial reserve capacity. IDH-mutant specific inhibitors did not affect cell viability or global gene expression. Screening of 107 FDA-approved anti-cancer drugs identified nine compounds with potent activity against IDHmt gliomas, including three compounds with favorable pharmacokinetic characteristics for CNS penetration: teniposide, omacetaxine mepesuccinate, and marizomib.

Conclusions

Our twelve IDH-mutant cell cultures show high similarity to the parental tissues and offer a unique tool to study the biology and drug sensitivities of high-grade IDHmt gliomas in vitro. Our drug screening studies reveal lack of sensitivity to IDHmt inhibitors, but sensitivity to a set of nine available anti-cancer agents.

Exploring the role and clinical implications of proteasome inhibition in medulloblastoma

Ubiquitin proteasome-mediated protein degradation has been implicated in posttranslational oncogenesis in medulloblastoma. Current research is evaluating the clinical implications of proteasome inhibition as a therapeutic target. In medulloblastoma cell lines, proteasome inhibitors induce apoptosis and inhibit cell proliferation via multiple pathways involving activation of caspase pathways, NFκB (nuclear factor kappa-light-chain-enhancer of activated B cells) pathway inhibition, reduced AKT/mTOR pathway activity, and pro-apoptotic protein expression. Second-generation proteasome inhibitors demonstrate blood-brain barrier penetration while maintaining antitumor effect. This review summarizes the ubiquitin-proteasome system in the pathogenesis of medulloblastoma and the potential clinical implications.

Imposing Phase II and Phase III Clinical Trials of Targeted Drugs for Glioblastoma: Current Status and Progress

The most common primary intracranial tumor is glioma, among which glioblastoma (GBM) has the worst prognosis. Because of the high degree of malignancy of GBM and frequent recurrence after surgery, postoperative therapy, including chemotherapy, radiotherapy, targeted therapy, and immunotherapy, is particularly important. A wide variety of targeted drugs have undergone phase III clinical trials for patients with GBM, but these drugs do not work for all patients, and few patients in these trials have prolonged overall survival. In this review, some imposing phase III clinical trials of targeted drugs for glioma are introduced, and some prospective phase II clinical trials that have been completed or are in progress are summarized. In addition, the mechanisms of these drugs are briefly introduced, and deficiencies of these clinical trials are analyzed. This review aims to provide a comprehensive overview of current research on targeted drugs for glioma to clarify future research directions.

The Ubiquitin-Proteasome Pathway and Resistance Mechanisms Developed Against the Proteasomal Inhibitors in Cancer Cells

BACKGROUND

The ubiquitin-proteasome pathway is crucial for all cellular processes and is, therefore, a critical target for the investigation and development of novel strategies for cancer treatment. In addition, approximately 30% of newly synthesized proteins never attain their final conformations due to translational errors or defects in post-translational modifications; therefore, they are also rapidly eliminated by the ubiquitin-proteasome pathway.

OBJECTIVE

Here, an effort was made to outline the recent findings deciphering the new molecular mechanisms involved in the regulation of ubiquitin-proteasome pathway as well as the resistance mechanisms developed against proteasome inhibitors in cell culture experiments and in the clinical trials.

RESULTS

Since cancer cells have higher proliferation rates and are more prone to translational errors, they require the ubiquitin-proteasome pathway for selective advantage and sustained proliferation. Therefore, drugs targeting the ubiquitin-proteasome pathway are promising agents for the treatment of both hematological and solid cancers.

CONCLUSION

A number of proteasome inhibitors are approved and used for the treatment of advanced and relapsed multiple myeloma. Unfortunately, drug resistance mechanisms may develop very fast within days of the start of the proteasome inhibitor-treatment either due to the inherent or acquired resistance mechanisms under selective drug pressure. However, a comprehensive understanding of the mechanisms leading to the proteasome inhibitor-resistance will eventually help the design and development of novel strategies involving new drugs and/or drug combinations for the treatment of a number of cancers.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Research progress in proteasome inhibitor resistance to multiple myeloma

Multiple myeloma (MM) is a highly heterogeneous malignant plasma cell disease. Proteasome inhibitors (PIs) are the first line of medicine for MM. Bortezomib, ixazomib, and carfilzomib are also widely used for MM. Marizomib, oprozomib, and KZR-616 are in clinical trials. However, the drug resistance of PIs in MM is still a problem. The mechanisms for PIs resistance to MM include ubiquitin-proteasome pathway, autophagy lysosome pathway, endoplasmic reticulum stress pathway, cell survival signal pathway, exosome-mediated resistance, and bone marrow microenvironment-mediated resistance.

PTEN deficiency leads to proteasome addiction: a novel vulnerability in glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most common primary brain tumor in adults with a median survival of approximately 15 months; therefore, more effective treatment options for GBM are required. To identify new drugs targeting GBMs, we performed a high-throughput drug screen using patient-derived neurospheres cultured to preferentially retain their glioblastoma stem cell (GSC) phenotype.

METHODS

High-throughput drug screening was performed on GSCs followed by a dose-response assay of the 5 identified original "hits." A PI3K/mTOR dependency to a proteasome inhibitor (carfilzomib), was confirmed by genetic and pharmacologic experiments. Proteasome Inhibition Response Signatures were derived from proteomic and bioinformatic analysis. Molecular mechanism of action was determined using three-dimensional (3D) GBM-organoids and preclinical orthotopic models.

RESULTS

We found that GSCs were highly sensitive to proteasome inhibition due to an underlying dependency on an increased protein synthesis rate, and loss of autophagy, associated with PTEN loss and activation of the PI3K/mTOR pathway. In contrast, combinatory inhibition of autophagy and the proteasome resulted in enhanced cytotoxicity specifically in GSCs that did express PTEN. Finally, proteasome inhibition specifically increased cell death markers in 3D GBM-organoids, suppressed tumor growth, and increased survival of mice orthotopically engrafted with GSCs. As perturbations of the PI3K/mTOR pathway occur in nearly 50% of GBMs, these findings suggest that a significant fraction of these tumors could be vulnerable to proteasome inhibition.

CONCLUSIONS

Proteasome inhibition is a potential synthetic lethal therapeutic strategy for GBM with proteasome addiction due to a high protein synthesis rate and autophagy deficiency.

The Role of the Ubiquitin Proteasome System in Glioma: Analysis Emphasizing the Main Molecular Players and Therapeutic Strategies Identified in Glioblastoma Multiforme

Gliomas constitute the most frequent tumors of the brain. High-grade gliomas are characterized by a poor prognosis caused by a set of attributes making treatment difficult, such as heterogeneity and cell infiltration. Additionally, there is a subgroup of glioma cells with properties similar to those of stem cells responsible for tumor recurrence after treatment. Since proteasomal degradation regulates multiple cellular processes, any mutation causing disturbances in the function or expression of its elements can lead to various disorders such as cancer. Several studies have focused on protein degradation modulation as a mechanism of glioma control. The ubiquitin proteasome system is the main mechanism of cellular proteolysis that regulates different events, intervening in pathological processes with exacerbating or suppressive effects on diseases. This review analyzes the role of proteasomal degradation in gliomas, emphasizing the elements of this system that modulate different cellular mechanisms in tumors and discussing the potential of distinct compounds controlling brain tumorigenesis through the proteasomal pathway.

Marizomib sensitizes primary glioma cells to apoptosis induced by a latest-generation TRAIL receptor agonist

Due to the absence of curative treatments for glioblastoma (GBM), we assessed the efficacy of single and combination treatments with a translationally relevant 2nd generation TRAIL-receptor agonist (IZI1551) and the blood–brain barrier (BBB) permeant proteasome inhibitor marizomib in a panel of patient-derived glioblastoma cell lines. These cells were cultured using protocols that maintain the characteristics of primary tumor cells. IZI1551+marizomib combination treatments synergistically induced apoptotic cell death in the majority of cases, both in 2D, as well as in 3D spheroid cultures. In contrast, single-drug treatments largely failed to induce noticeable amounts of cell death. Kinetic analyses suggested that time-shifted drug exposure might further increase responsiveness, with marizomib pre-treatments indeed strongly enhancing cell death. Cell death responses upon the addition of IZI1551 could also be observed in GBM cells that were kept in a medium collected from the basolateral side of a human hCMEC/D3 BBB model that had been exposed to marizomib. Interestingly, the subset of GBM cell lines resistant to IZI1551+marizomib treatments expressed lower surface amounts of TRAIL death receptors, substantially lower amounts of procaspase-8, and increased amounts of cFLIP, suggesting that apoptosis initiation was likely too weak to initiate downstream apoptosis execution. Indeed, experiments in which the mitochondrial apoptosis threshold was lowered by antagonizing Mcl-1 re-established sensitivity to IZI1551+marizomib in otherwise resistant cells. Overall, our study demonstrates a high efficacy of combination treatments with a latest-generation TRAIL receptor agonist and the BBB permeant proteasome inhibitor marizomib in relevant GBM cell models, as well as strategies to further enhance responsiveness and to sensitize subgroups of otherwise resistant GBM cases.

A Systematic Review of Glioblastoma-Targeted Therapies in Phases II, III, IV Clinical Trials

Glioblastoma (GBM), the most frequent and aggressive glial tumor, is currently treated as first line by the Stupp protocol, which combines, after surgery, radiotherapy and chemotherapy. For recurrent GBM, in absence of standard treatment or available clinical trials, various protocols including cytotoxic drugs and/or bevacizumab are currently applied. Despite these heavy treatments, the mean overall survival of patients is under 18 months. Many clinical studies are underway. Based on clinicaltrials.org and conducted up to 1 April 2020, this review lists, not only main, but all targeted therapies in phases II-IV of 257 clinical trials on adults with newly diagnosed or recurrent GBMs for the last twenty years. It does not involve targeted immunotherapies and therapies targeting tumor cell metabolism, that are well documented in other reviews. Without surprise, the most frequently reported drugs are those targeting (i) EGFR (40 clinical trials), and more generally tyrosine kinase receptors (85 clinical trials) and (ii) VEGF/VEGFR (75 clinical trials of which 53 involving bevacizumab). But many other targets and drugs are of interest. They are all listed and thoroughly described, on an one-on-one basis, in four sections related to targeting (i) GBM stem cells and stem cell pathways, (ii) the growth autonomy and migration, (iii) the cell cycle and the escape to cell death, (iv) and angiogenesis.

Glioblastoma Cell Resistance to EGFR and MET Inhibition Can Be Overcome via Blockade of FGFR-SPRY2 Bypass Signaling

SPRY2 is a purported tumor suppressor in certain cancers that promotes tumor growth and resistance to receptor tyrosine kinase inhibitors in glioblastoma. Here, we identify a SPRY2-dependent bypass signaling mechanism in glioblastoma that drives resistance to EGFR and MET inhibition. In glioblastoma cells treated with EGFR and MET inhibitors, SPRY2 expression is initially suppressed but eventually rebounds due to NF-κB pathway activation, resultant autocrine FGFR activation, and reactivation of ERK, which controls SPRY2 transcription. In cells where FGFR autocrine signaling does not occur and ERK does not reactivate, or in which ERK reactivates but SPRY2 cannot be expressed, EGFR and MET inhibitors are more effective at promoting death. The same mechanism also drives acquired resistance to EGFR and MET inhibition. Furthermore, tumor xenografts expressing an ERK-dependent bioluminescent reporter engineered for these studies reveal that this bypass resistance mechanism plays out in vivo but can be overcome through simultaneous FGFR inhibition.