Activity In Glioblastoma Research Articles

Abstract A011: Enhancing chaperone-mediated autophagy to impede glioblastoma growth

Abstract Chaperone-mediated autophagy (CMA) is a selective form of autophagy that targets proteins with the KFERQ-like motif for lysosomal degradation. This process involves the binding of substrate proteins to the chaperone HSC70 and their subsequent transport to the receptor LAMP2A on the lysosome membrane for degradation. Previous studies have shown a significant increase in the expression level of LAMP2A and the CMA activity in glioblastoma (GBM). However, the comprehensive role of CMA in GBM pathogenesis remains unclear. In this study, we observed a progressive elevation in LAMP2A expression with increasing GBM cell confluence. Notably, inhibition of CMA through LAMP2A knockdown markedly promoted GBM growth in orthotopic mouse models, accompanied by upregulation of positive cell cycle regulators. Conversely, overexpression of LAMP2A delayed GBM cell growth and increased sub-G1 cell percentages. Treatment with CMA activators induced cell death in GBM cells while preserving normal astrocyte viability at equivalent concentrations. Our results suggest that the upregulated expression of LAMP2A in GBM cells may be influenced by the tumor microenvironment rather than being a primary driver of GBM aggressiveness. Furthermore, activating CMA could serve as a potential therapeutic strategy to inhibit GBM growth while safeguarding normal cell viability. Citation Format: Wanjun Tang, Karrie Mei Yee Kiang, Gilberto Ka Kit Leung. Enhancing chaperone-mediated autophagy to impede glioblastoma growth [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr A011.

Incorporating IL7 receptor alpha signaling in the endodomain of B7H3-targeting chimeric antigen receptor T cells mediates antitumor activity in glioblastoma.

CAR-T-cell therapy has shown promise in treating hematological malignancies but faces challenges in treating solid tumors due to impaired T-cell function in the tumor microenvironment. To provide optimal T-cell activation, we developed a B7 homolog 3 protein (B7H3)-targeting CAR construct consisting of three activation signals: CD3ζ (signal 1), 41BB (signal 2), and the interleukin 7 receptor alpha (IL7Rα) cytoplasmic domain (signal 3). We generated B7H3 CAR-T cells with different lengths of the IL7Rα cytoplasmic domain, including the full length (IL7R-L), intermediate length (IL7R-M), and short length (IL7R-S) domains, and evaluated their functionality in vitro and in vivo. All the B7H3-IL7Rα CAR-T cells exhibited a less differentiated phenotype and effectively eliminated B7H3-positive glioblastoma in vitro. Superiority was found in B7H3 CAR-T cells contained the short length of the IL7Rα cytoplasmic domain. Integration of the IL7R-S cytoplasmic domain maintained pSTAT5 activation and increased T-cell proliferation while reducing activation-induced cell death. Moreover, RNA-sequencing analysis of B7H3-IL7R-S CAR-T cells after coculture with a glioblastoma cell line revealed downregulation of proapoptotic genes and upregulation of genes associated with T-cell proliferation compared with those in 2nd generation B7H3 CAR-T cells. In animal models, compared with conventional CAR-T cells, B7H3-IL7R-S CAR-T cells suppressed tumor growth and prolonged overall survival. Our study demonstrated the therapeutic potential of IL7Rα-incorporating CAR-T cells for glioblastoma treatment, suggesting a promising strategy for augmenting the effectiveness of CAR-T cell therapy.

Abstract 1432: Development of transparent transgenic zebrafish model to study CNS microglia and NF-kB activity in glioblastoma

Abstract Microglia are resident macrophages of the central nervous system (CNS) and have crucial roles in normal brain homeostasis, function, and immune response. Microglia play key roles in the healthy brain, ranging from phagocytosis of dying neurons and CNS debris to modulating adaptability. The role of microglia has been well documented but their specific contributions to the development and progression of cancers, such as glioblastoma, have recently garnered wide attention. The zebrafish have proven novel tool for modeling innate immune responses. A macrophage-specific marker mpeg1 and its promoter are used in mpeg1-driven transgenes. mpeg1-driven transgenes mpeg1:mCherryFP are expressed in macrophage-lineage cells that do not express neutrophil-marking transgenes. These zebrafish transgenes contribute to the fields of inflammation, infection, and leukocyte biology. We have recently developed a novel transparent transgenic homozygous strain Tg(6xNF-kB:EGFP); Casper(roy−/−, nacre−/−) of zebrafish to the in-vivo study of NF-kB activity under normal and inflammation stage at the cellular, organ-specific and whole organism level. To perform an in-vivo study of microglial function, we are developing Casper;mpeg1:mCherryFP microglia specific strain and integrating with newly developed Tg(6xNF-kB:EGFP); Casper(roy−/−, nacre−/−) strain through crossbreeding of Casper and transgenic zebrafish. We have generated F1 generation of newly developed strains of Casper;mpeg1:mCherryFP and Tg(6xNF-kB:EGFP);Casper. The presence of fluorescence mCherry and GFP, in crossbred progeny was identified through the screening of larvae at 72 HPF stage. The expression of these fluorescent proteins determines the presence of the reporter genes. F1 generation confirmed heterozygous and allowed them to grow into adults to breed transparent transgenic strain to get F2 generation. This process will be continued to F2, F3, F4, and F5 generation until achieving homozygous progeny. This model allows for in-vivo examination of microglia functional morphology by using fluorescent and confocal microscopy. This novel transgenic model will be applied to identify novel anti-inflammatory drug inhibitors in NF-kB pathophysiology for glioblastoma and cardio-oncology experimental therapeutics. Citation Format: Surendra K. Rajpurohit, Sai Nasanally, Simran Hotwani, Taitum Gossman, Keshu Bhatt, Aiden Van Derhei, Rohan Pasi, Devan-Anmol Manhiani, Kirk Kimmerling, Balakrishna L. Lokeshwar. Development of transparent transgenic zebrafish model to study CNS microglia and NF-kB activity in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1432.

Targeting SIRT3 sensitizes glioblastoma to ferroptosis by promoting mitophagy and inhibiting SLC7A11

Glioblastoma (GBM) cells require large amounts of iron for tumor growth and progression, which makes these cells vulnerable to destruction via ferroptosis induction. Mitochondria are critical for iron metabolism and ferroptosis. Sirtuin-3 (SIRT3) is a deacetylase found in mitochondria that regulates mitochondrial quality and function. This study aimed to characterize SIRT3 expression and activity in GBM and investigate the potential therapeutic effects of targeting SIRT3 while also inducing ferroptosis in these cells. We first found that SIRT3 expression was higher in GBM tissues than in normal brain tissues and that SIRT3 protein expression was upregulated during RAS-selective lethal 3 (RSL3)-induced GBM cell ferroptosis. We then observed that inhibition of SIRT3 expression and activity in GBM cells sensitized GBM cells to RSL3-induced ferroptosis both in vitro and in vivo. Mechanistically, SIRT3 inhibition led to ferrous iron and ROS accumulation in the mitochondria, which triggered mitophagy. RNA-Sequencing analysis revealed that upon SIRT3 knockdown in GBM cells, the mitophagy pathway was upregulated and SLC7A11, a critical antagonist of ferroptosis via cellular import of cystine for glutathione (GSH) synthesis, was downregulated. Forced expression of SLC7A11 in GBM cells with SIRT3 knockdown restored cellular cystine uptake and consequently the cellular GSH level, thereby partially rescuing cell viability upon RSL3 treatment. Furthermore, in GBM cells, SIRT3 regulated SLC7A11 transcription through ATF4. Overall, our study results elucidated novel mechanisms underlying the ability of SIRT3 to protect GBM from ferroptosis and provided insight into a potential combinatorial approach of targeting SIRT3 and inducing ferroptosis for GBM treatment.

The Synthesis and Characterization of a Delivery System Based on Polymersomes and a Xanthone with Inhibitory Activity in Glioblastoma.

Glioblastoma (GBM) is the most common and deadly primary malignant brain tumor. Current therapies are insufficient, and survival for individuals diagnosed with GBM is limited to a few months. New GBM treatments are urgent. Polymeric nanoparticles (PNs) can increase the circulation time of a drug in the brain capillaries. Polymersomes (PMs) are PNs that have been described as having attractive characteristics, mainly due to their stability, prolonged circulation period, biodegradability, their ability to sustain the release of drugs, and the possibility of surface functionalization. In this work, a poly(ethylene glycol)-ε-caprolactone (PEG-PCL) copolymer was synthesized and PMs were prepared and loaded with an hydrolytic instable compound, previously synthesized by our research team, the 3,6-bis(2,3,4,6-tetra-O-acetyl-β-glucopyranosyl)xanthone (XGAc), with promising cytotoxicity on glioblastoma cells (U-373 MG) but also on healthy cerebral endothelial cells (hCMEC/D3). The prepared PMs were spherical particles with uniform morphology and similar sizes (mean diameter of 200 nm) and were stable in aqueous suspension. The encapsulation of XGAc in PMs (80% encapsulation efficacy) protected the healthy endothelial cells from the cytotoxic effects of this compound, while maintaining cytotoxicity for the glioblastoma cell line U-373 MG. Our studies also showed that the prepared PMs can efficiently release XGAc at intratumoral pHs.

Cyclohexene oxide CA, a derivative of zeylenone, exhibits anti-cancer activity in glioblastoma by inducing G0/G1 phase arrest through interference with EZH2.

Introduction: Due to its highly aggressiveness and malignancy, glioblastoma (GBM) urgently requires a safe and effective treatment strategy. Zeylenone, a natural polyoxygenated cyclohexenes compound isolated from Uvaria grandiflora, has exhibited potential biological activities in various human diseases, including tumors. Methods: We designed and synthesized a series of (+)-Zeylenone analogues and evaluated their anti-GBM roles through structural-activity analysis. Cell Counting Kit-8, TUNEL, transwell and flow cytometry were employed for investigating the anticancer effects of CA on GBM cells. Western blotting, molecular docking, qRT-PCR and ChIP assays were performed to reveal the underlying mechanisms by which CA regulates the GBM cell cycle. The nude mouse xenograft model, HE staining, immunohistochemistry and was used to evaluate the anticancer effect of CA in vivo. Results: We identified CA ((1R, 2R, 3S)-3-p-fluorobenzoyl-zeylenone) as having the lowest IC50 value in GBM cells. CA treatment significantly inhibited the malignant behaviors of GBM cells and induced G0/G1 phase arrest in vitro. Furthermore, we validated the molecular mechanism by which CA interferes with EZH2, attenuating the down-regulation of cyclin-dependent kinase inhibitors p27 and p16 by the PRC2 complex. By establishing orthotopic nude mice models, we further validated the inhibitory role of CA on tumorigenesis of GBM cells in vivo and its potential values to synergistically potentiate the anti-tumor effects of EZH2 inhibitors. Conclusion: Overall, this paper elucidated the anti-GBM effects and potential mechanisms of CA, and may provide a therapeutic drug candidate for GBM treatment.

Eliciting calcium transients with UV nanosecond laser stimulation in adult patient-derived glioblastoma brain cancer cells in vitro

Objective. Glioblastoma (GBM) is the most common and lethal type of high-grade adult brain cancer. The World Health Organization have classed GBM as an incurable disease because standard treatments have yielded little improvement with life-expectancy being 6–15 months after diagnosis. Different approaches are now crucial to discover new knowledge about GBM communication/function in order to establish alternative therapies for such an aggressive adult brain cancer. Calcium (Ca2+) is a fundamental cell molecular messenger employed in GBM being involved in a wide dynamic range of cellular processes. Understanding how the movement of Ca2+ behaves and modulates activity in GBM at the single-cell level is relatively unexplored but holds the potential to yield opportunities for new therapeutic strategies and approaches for cancer treatment. Approach. In this article we establish a spatially and temporally precise method for stimulating Ca2+ transients in three patient-derived GBM cell-lines (FPW1, RN1, and RKI1) such that Ca2+ communication can be studied from single-cell to larger network scales. We demonstrate that this is possible by administering a single optimized ultra-violet (UV) nanosecond laser pulse to trigger GBM Ca2+ transients. Main results. We determine that 1.58 µJ µm−2 is the optimal UV nanosecond laser pulse energy density necessary to elicit a single Ca2+ transient in the GBM cell-lines whilst maintaining viability, functionality, the ability to be stimulated many times in an experiment, and to trigger further Ca2+ communication in a larger network of GBM cells. Significance. Using adult patient-derived mesenchymal GBM brain cancer cell-lines, the most aggressive form of GBM cancer, this work is the first of its kind as it provides a new effective modality of which to stimulate GBM cells at the single-cell level in an accurate, repeatable, and reliable manner; and is a first step toward Ca2+ communication in GBM brain cancer cells and their networks being more effectively studied.

In vivo antiangiogenic effect of nimbolide, trans-chalcone and piperine for use against glioblastoma

BackgroundAngiogenesis is an important hallmark of Glioblastoma (GBM) marked by elevated vascular endothelial growth factor-A (VEGF-A) and its receptor 2 (VEGFR-2). As previously reported nimbolide (NBL), trans-chalcone (TC) and piperine (PPR) possess promising antiangiogenic activity in several cancers however, their comparative efficacy and mechanism of antiangiogenic activity in GBM against VEGFR-2 has not been elucidated.Methods2D and 3D spheroids cultures of U87 (Uppsala 87 Malignant Glioma) were used for evaluation of non-cytotxoic dose for anti-angiogenic activity. The antiangiogenic effect was investigated by the GBM U87 cell line bearing chick CAM model. Excised U87 xenografts were histologically examined for blood vascular density by histochemistry. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect the presence of avian and human VEGF-A and VEGFR-2 mRNA transcripts.ResultsUsing 2D and 3D spheroid models, the non-cytotoxic dose of NBL, TC and PPR was ≤ 11 µM. We found NBL, TC and PPR inhibit U87-induced neoangiogenesis in a dose-dependent manner in the CAM stand-alone model as well as in CAM U87 xenograft model. The results also indicate that these natural compounds inhibit the expression of notable angiogenic factors, VEGF-A and VEGFR-2. A positive correlation was found between blood vascular density and VEGF-A as well as VEGFR-2 transcripts.ConclusionTaken together, NBL, TC and PPR can suppress U87-induced neoangiogenesis via a reduction in VEGF-A and its receptor VEGFR-2 transcript expression at noncytotoxic concentrations. These phytochemicals showed their utility as adjuvants to GBM therapy, with Piperine demonstrating superior effectiveness among them all.

2-Aminothiazole-Flavonoid Hybrid Derivatives Binding to Tau Protein and Responsible for Antitumor Activity in Glioblastoma.

Tau protein has been described for several decades as a promoter of tubulin assembly into microtubules. Dysregulation or alterations in Tau expression have been related to various brain cancers, including the highly aggressive and lethal brain tumor glioblastoma multiform (GBM). In this respect, Tau holds significant promise as a target for the development of novel therapies. Here, we examined the structure-activity relationship of a new series of seventeen 2-aminothiazole-fused to flavonoid hybrid compounds (TZF) on Tau binding, Tau fibrillation, and cellular effects on Tau-expressing cancer cells. By spectrofluorometric approach, we found that two compounds, 2 and 9, demonstrated high affinity for Tau and exhibited a strong propensity to inhibit Tau fibrillation. Then, the biological activity of these compounds was evaluated on several Tau-expressing cells derived from glioblastoma. The two lead compounds displayed a high anti-metabolic activity on cells related to an increased fission of the mitochondria network. Moreover, we showed that both compounds induced microtubule bundling within newly formed neurite-like protrusions, as well as with defection of cell migration. Taken together, our results provide a strong experimental basis to develop new potent molecules targeting Tau-expressing cancer cells, such as GBM.

Novel TCF4:TCF12 heterodimer inhibits glioblastoma growth.

TWIST1 (TW) is a pro-oncogenic basic helix-loop-helix (bHLH) transcription factor and promotes the hallmark features of malignancy (e.g., cell invasion, cancer cell stemness, and treatment resistance), which contribute to poor prognoses of glioblastoma (GBM). We previously reported that specific TW dimerization motifs regulate unique cellular phenotypes in GBM. For example, the TW:E12 heterodimer increases periostin (POSTN) expression and promotes cell invasion. TW dimer-specific transcriptional regulation requires binding to the regulatory E-box consensus sequences, but alternative bHLH dimers that balance TW dimer activity in regulating pro-oncogenic TW target genes are unknown. We leveraged the ENCODE DNase I hypersensitivity data to identify E-box sites and tethered TW:E12 and TW:TW proteins to validate dimer binding to E-boxes in vitro. Subsequently, TW knockdown revealed a novel TCF4:TCF12 bHLH dimer occupying the same TW E-box site that, when expressed as a tethered TCF4:TCF12 dimer, markedly repressed POSTN expression and extended animal survival. These observations support TCF4:TCF12 as a novel dimer with tumor-suppressor activity in GBM that functions in part through displacement of and/or competitive inhibition of pro-oncogenic TW dimers at E-box sites.

Marine Antimicrobial Peptide Epinecidin-1 Inhibits Proliferation Induced by Lipoteichoic acid and Causes cell Death in non-small cell lung cancer Cells via Mitochondria Damage.

Non-small cell lung cancer (NSCLC) is among the deadliest cancers worldwide. Despite the recent introduction of several new therapeutic approaches for the disease, improvements in overall survival and progression-free survival have been minimal. Conventional treatments for NSCLC include surgery, chemotherapy and radiotherapy. Except for surgery, these treatments can impair a patient's immune system, leaving them susceptible to bacterial infections. As such, Staphylococcus aureus infections are commonly seen in NSCLC patients receiving chemotherapy, and a major constituent of the S. aureus cell surface, lipoteichoic acid (LTA), is thought to stimulate NSCLC cancer cell proliferation. Thus, inhibition of LTA-mediated cell proliferation might be a useful strategy for treating NSCLC. Epinecidin-1 (EPI), a marine antimicrobial peptide, exhibits broad-spectrum antibacterial activity, and it also displays anti-cancer activity in glioblastoma and synovial sarcoma cells. Furthermore, EPI has been shown to inhibit LTA-induced inflammatory responses in murine macrophages. Nevertheless, the anti-cancer and anti-LTA activities of EPI and the underlying mechanisms of these effects have not been fully tested in the context of NSCLC. In the present study, we demonstrate that EPI suppresses LTA-enhanced proliferation of NSCLC cells by neutralizing LTA and blocking its effects on toll-like receptor 2 and interleukin-8. Moreover, we show that EPI induces necrotic cell death via mitochondrial damage, elevated reactive oxygen species levels, and disrupted redox balance. Collectively, our results reveal dual anti-cancer activities of EPI in NSCLC, as the peptide not only directly kills cancer cells but it also blocks LTA-mediated enhancement of cell proliferation.

M6A-modification of cyclin D1 and c-myc IRESs in glioblastoma controls ITAF activity and resistance to mTOR inhibition

A major mechanism conferring resistance to mTOR inhibitors is activation of a salvage pathway stimulating internal ribosome entry site (IRES)-mediated mRNA translation, driving the synthesis of proteins promoting resistance of glioblastoma (GBM). Previously, we found this pathway is stimulated by the requisite IRES-trans-acting factor (ITAF) hnRNP A1, which itself is subject to phosphorylation and methylation events regulating cyclin D1 and c-myc IRES activity. Here we describe the requirement for m6A-modification of IRES RNAs for efficient translation and resistance to mTOR inhibition. DRACH-motifs within these IRES RNAs upon m6A modification resulted in enhanced IRES activity via increased hnRNP A1-binding following mTOR inhibitor exposure. Inhibitor exposure stimulated the expression of m6A-methylosome components resulting in increased activity in GBM. Silencing of METTL3-14 complexes reduced IRES activity upon inhibitor exposure and sensitized resistant GBM lines. YTHDF3 associates with m6A-modified cyclin D1 or c-myc IRESs, regulating IRES activity, and mTOR inhibitor sensitivity in vitro and in xenograft experiments. YTHDF3 interacted directly with hnRNP A1 and together stimulated hnRNP A1-dependent nucleic acid strand annealing activity. These data demonstrate that m6A-methylation of IRES RNAs regulate GBM responses to this class of inhibitors.

Lead Optimization of Androgen Receptor-HSP27 Disrupting Agents in Glioblastoma.

Glioblastoma (GBM) is the most common malignant brain tumor with poor prognosis under the current standard treatment. It is critical to develop new approaches to selectively battle the disease. GBM sex differences suggest that an androgen receptor (AR) is a potential therapeutic target to treat AR-overexpressed GBM. Heat shock 27 kDa protein (HSP27) is a well-documented chaperone protein that stabilizes AR. Inhibition of HSP27 leads to AR degradation, indicating that HSP27 inhibitors could suppress AR activity in GBM. We have identified a lead HSP27 inhibitor that could induce AR degradation. Lead optimization resulted with two new derivatives (compounds 4 and 26) showing potent anti-GBM activity and improved drug distribution in comparison to the lead compound. Compounds 4 and 6 exhibit IC50s of 35 and 23 nM, respectively, to inhibit cell proliferation and also show significant activity to decrease the tumor growth in vivo.

Abstract 3191: Genetically modified TGF-β dominant negative receptor and IL15 enhance Natural Killer (NK) cell mediated cytolytic activity in glioblastoma

Abstract Introduction: Glioblastoma (GBM) presents with a poor prognosis and dismal survival rates. While cell-based immune therapies have shown success in other malignancies, there is currently little evidence that GBM is as responsive to current approaches. Novel therapies for these patients are therefore urgently needed. The antitumor effect may be limited by GBM’s rapid progression, its extensive intertumoral heterogeneity, and its immune suppressive microenvironment. For cell-based therapies to be effective, they need to be manufactured rapidly or in advance, recognize multiple targets on GBM, and resist immune suppression. We therefore sought to develop “off-the-shelf” cord blood-derived NK cell therapies capable of recognizing multiple stress ligands on tumor cells but are protected from the microenvironment by expression of a dominant negative receptor to TGFβ (abrogating the negative effects of the cytokine) and secretion of IL15 (overcoming negative signals from the microenvironment). We investigate the therapeutic efficacy of NK cells engineered to express IL15-and/or TGFβ-DNR in glioblastoma model in-vitro and in-vivo. Methods: NK cells were isolated from umbilical cord blood by magnetic selection, and subsequently modified to express IL-15, and/or TGFβ-DNR. Engineered NK cells were expanded with feeder cells. Retroviral transduction efficiency was confirmed by flow cytometry. IL15 expression was quantified by ELISA. To determine the cytotoxicity activity of our engineered NK cells against glioblastoma, we measured lysis of the U87MG cell line. To determine in vivo efficacy of our engineered NK cells, we used xenograft NSG mouse models that were orthotopically engrafted with U87MG in the brain. Tumor growth was measured by bioluminescence. Results: CAR-NK cells were successfully transduced (with a transduction efficiency ranging from 66-83% (mean 74.55% + 10.6, n>3) from umbilical cord blood. NK cells engineered to secrete IL15 secreted a mean of 288.3 pg/mL. After exposure to TGFβ in vitro, NK cells transduced with TGFβ-DNR had a increase of killing [mean 58.25 % + 4.51 at 20:1 (E:T) 48.57% + 11.55 without TGFβ, n=3] compared to un-transduced NK cells [mean 11.98 % + 4.51 at 20:1 (E:T) 49.04% + 5.34 without TGFβ, n=3]. Mice injected with IL15 and TGFβ DNR showed better control of tumor (3.99 x 105 + 0.0007 bioluminescence Vs 1.673 x 107 + 0.160 in mice given mock-transduced NK cells and 8.44 x 109 + 28.62 in control mice). Conclusion: Our preliminary results show that cord blood NK cells modified to secrete IL15 and express TGFβ-DNR can recognize and lyse GBM cells in vitro and orthotopically implanted GBM tumors in vivo. Citation Format: Nethaji Muniraj, Kajal Chaudhry, Joshua Luke Terao, Vipin Suri, Luke Barron, Catherine Bollard, Conrad Russell Cruz. Genetically modified TGF-β dominant negative receptor and IL15 enhance Natural Killer (NK) cell mediated cytolytic activity in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3191.

Targeting XBP1 mRNA splicing sensitizes glioblastoma to chemotherapy.

Glioblastoma (GBM) is the most frequent and deadly primary brain tumor in adults. Temozolomide (TMZ) is the standard systemic therapy in GBM but has limited and restricted efficacy. Better treatments are urgently needed. The role of endoplasmic reticulum stress (ER stress) is increasingly described in GBM pathophysiology. A key molecular mediator of ER stress, the spliced form of the transcription factor x-box binding protein 1 (XBP1s) may constitute a novel therapeutic target; here we report XBP1s expression and biological activity in GBM. Tumor samples from patients with GBM (n= 85) and low-grade glioma (n= 20) were analyzed by immunohistochemistry for XBP1s with digital quantification. XBP1s expression was significantly increased in GBM compared to low-grade gliomas. XBP1s mRNA showed upregulation by qPCR analysis in a panel of patient-derived GBM cell lines. Inhibition of XBP1 splicing using the small molecular inhibitor MKC-3946 significantly reduced GBM cell viability and potentiated the effect of TMZ in GBM cells, particularly in those with methylated O6-methylguanine-DNA methyl transferase gene promoter. GBM cells resistant to TMZ were also responsive to MKC-3946 and the long-term inhibitory effect of MKC-3946 was confirmed by colony formation assay. In conclusion, this data reveals that XBP1s is overexpressed in GBM and contributes to cancer cell growth. XBP1s warrants further investigation as a clinical biomarker and therapeutic target in GBM.

Features of epileptiform activity in patients with diagnosed glioblastoma: from genetic and biochemical mechanisms to clinical aspects

Introduction. glioblastomas multiforme (grade Iv gliomas) are common and the most aggressive primary tumors of the brain with very unfavorable prognosis. In all previously published papers on epileptiform activity in glioblastomas, not enough information on encephalogram results is presented.Aim. To study the features of epileptiform activity in patients with glioblastomas and development of a plan for further study of these patients.Materials and methods. An analysis of articles from Elsevier, Embase, Scopus, The Cochrane Library, global Health, Russian Science Citation Index (RSCI) databases, Scholar, google, web of Science, pubmed search engines and scientific electronic library CyberLeninka was performed. materials were selected considering journal indexing system and citations, scientific novelty of the studies, statistical significance of the results. publications repeating data from previous articles or describing animal experiments were excluded from analysis.Results. During the study, data on mechanisms of epileptiform activity pathogenesis, predisposing factors (tumor location in the temporal, frontal or parietal lobes, IDH-1 and / or IDH-2 gene mutations), treatment options in patients with glioblastomas were systemized. Additionally, and original plan of data accumulation for clinical studied taking into account limitations of the previous studies was developed to increase quality of results interpretation.Conclusion. Epileptiform symptoms in glioblastomas negatively affect patients’ quality of life and lifespan. Currently, researchers actively search for an effective method of treatment of epileptic seizures in patients with glioblastomas. The most effective is combination of temozolomide with valproate and levetiracetam due to good control of seizure frequency, low toxicity, and pharmacological synergy between the drugs.

ZBTB18 inhibits SREBP-dependent lipid synthesis by halting CTBPs and LSD1 activity in glioblastoma.

Enhanced fatty acid synthesis is a hallmark of tumors, including glioblastoma. SREBF1/2 regulate the expression of enzymes involved in fatty acid and cholesterol synthesis. Yet, little is known about the precise mechanism regulating SREBP gene expression in glioblastoma. Here, we show that a novel interaction between the co-activator/co-repressor CTBP and the tumor suppressor ZBTB18 regulates the expression of SREBP genes. In line with our findings, metabolic assays and glucose tracing analysis confirm the reduction in several phospholipid species upon ZBTB18 expression. Our study identifies CTBP1/2 and LSD1 as co-activators of SREBP genes and indicates that the functional activity of the CTBP-LSD1 complex is altered by ZBTB18. ZBTB18 binding to the SREBP gene promoters is associated with reduced LSD1 demethylase activity of H3K4me2 and H3K9me2 marks. Concomitantly, the interaction between LSD1, CTBP, and ZNF217 is increased, suggesting that ZBTB18 promotes LSD1 scaffolding function. Our results outline a new epigenetic mechanism enrolled by ZBTB18 and its co-factors to regulate fatty acid synthesis that could be targeted to treat glioblastoma patients.

EXTH-101. MECHANISTIC INSIGHTS INTO CYTOTOXIC EFFECTS OF LETROZOLE AGAINST GLIOBLASTOMA CELLS

Abstract PURPOSE Despite significant advances in multimodal approaches for the treatment of glioblastoma (GBM), the outcome for the patients remains dismal. Previous research from our lab has shown that aromatase (CYP19A1), an enzyme that catalyzes in situ production of estrogens, is markedly elevated in GBM tissues. Additionally, letrozole (LTZ), an aromatase inhibitor with extensive record of efficacious use in breast cancer, exhibited significant activity against GBM in preclinical studies. The purpose of this study was to investigate the mechanism(s) of LTZ activity in GBM. METHODS Patient-derived GBM cells with varying aromatase expression and other genotypic/phenotypic characteristics were employed including aromatase expressing G43, G75, G76, BT-142-gfp-luc and aromatase-null G80 cells. The effects of LTZ on cell viability, neurosphere growth, DNA damage (assessed by measuring phosphorylated histone product ỴH2A.X using flow cytometry) and induction of apoptosis (caspase3/7 activity) were assessed. The effects of exogenous addition of estradiol (E2) was also examined. RESULTS LTZ treatment (72 hours) caused a marked reduction in viability and growth of all GBM cells (IC50 ranging from 0.08 to 0.7 µM) except in G80 cells where LTZ had no effects. LTZ treatment also resulted in inhibition of E2 synthesis in a time and dose-dependent fashion. Furthermore, in aromatase expressing cells LTZ treatment induced apoptosis as measured by increase in Caspase-3/7 activity and triggered significant DNA double strand break as determined by ỴH2A.X formation. The addition of exogenous E2 (250 pg/ml) abrogated the effects of LTZ on cell viability, DNA damage and induction of apoptosis. CONCLUSIONS Our study suggests that the cytotoxic effects of LTZ against GBM are mediated, at least partially, by the inhibition of aromatase activity which results in estrogen deprivation. These mechanistic insights are important to facilitate repurposing LTZ as a novel anti-GBM drug.

The Influence of the Ketogenic Diet on the Immune Tolerant Microenvironment in Glioblastoma.

Glioblastoma (GBM) represents an aggressive and immune-resistant cancer. Preclinical investigations have identified anti-tumor activity of a ketogenic diet (KD) potentially being used to target GBM's glycolytic phenotype. Since immune cells in the microenvironment have a similar reliance upon nutrients to perform their individual functions, we sought to determine if KD influenced the immune landscape of GBM. Consistent with previous publications, KD improved survival in GBM in an immune-competent murine model. Immunophenotyping of tumors identified KD-influenced macrophage polarization, with a paradoxical 50% increase in immune-suppressive M2-like-macrophages and a decrease in pro-inflammatory M1-like-macrophages. We recapitulated KD in vitro using a modified cell culture based on metabolomic profiling of serum in KD-fed mice, mechanistically linking the observed changes in macrophage polarization to PPARγ-activation. We hypothesized that parallel increases in M2-macrophage polarization tempered the therapeutic benefit of KD in GBM. To test this, we performed investigations combining KD with the CSF-1R inhibitor (BLZ945), which influences macrophage polarization. The combination demonstrated a striking improvement in survival and correlative studies confirmed BLZ945 normalized KD-induced changes in macrophage polarization. Overall, KD demonstrates antitumor activity in GBM; however, its efficacy is attenuated by promoting an immunosuppressive phenotype in macrophages. Combinatorial strategies designed to modulate macrophage polarization represent a rational approach to improve the anti-tumor activity of KD in GBM.

CHI3L1 predicted in malignant entities is associated with glioblastoma immune microenvironment

Effective immunotherapies for patients with glioblastoma (GBM) are urgently needed. Chitinase-3 like-protein-1 (CHI3L1) play important roles in the development of gliomas. However, its role in glioma-related immune responses remains unclear. We aimed to comprehensively investigate its biological features and clinical value in glioma, especially in GBM. Transcriptome, proteome and single-cell RNA-sequencing databases were enrolled in the study. Immunostaining and immunoblotting were performed for validation. CHI3L1 was highly correlated with clinical and molecular features, suggesting that high CHI3L1 expression is more likely to be predicted as malignant entities. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed CHI3L1 closely associated with immune responses and inflammatory activities in GBM. In addition, CHI3L1 also correlated with immune cell infiltration and immune checkpoints. Our study suggests that inhibition of CHI3L1 may help to reduce immunosuppression and overcome immunotherapy resistance, which would be an therapeutic area for the treatment of GBM.