Therapeutic Drug-Induced Metabolic Reprogramming in Glioblastoma

Extracellular Vesicles Derived from Glioma Stem Cells Affect Glycometabolic Reprogramming of Glioma Cells Through the miR-10b-5p/PTEN/PI3K/Akt Pathway

OBJECTIVE

Glioma is one of the most prevalently diagnosed types of primary malignant brain tumors. Glioma stem cells (GSCs) are crucial in glioma recurrence. This study aims to elucidate the mechanism by which extracellular vehicles (EVs) derived from GSCs modulate glycometabolic reprogramming in glioma.

METHODS

Xenograft mouse models and cell models of glioma were established and treated with GSC-EVs. Additionally, levels and activities of PFK1, LDHA, and FASN were assessed to evaluate the effect of GSC-EVs on glycometabolic reprogramming in glioma. Glioma cell proliferation, invasion, and migration were evaluated using MTT, EdU, Colony formation, and Transwell assays. miR-10b-5p expression was determined, with its target gene PTEN and downstream pathway PI3K/Akt evaluated. The involvement of miR-10b-5p and the PI3K/Akt pathway in the effect of GSC-EVs on glycometabolic reprogramming was tested through joint experiments.

RESULTS

GSC-EVs facilitated glycometabolic reprogramming in glioma mice, along with enhancing glucose uptake, lactate level, and adenosine monophosphate-to-adenosine triphosphate ratio. Moreover, GSC-EV treatment potentiated glioma cell proliferation, invasion, and migration, reinforced cell resistance to temozolomide, and raised levels and activities of PFK1, LDHA, and FASN. miR-10b-5p was highly-expressed in GSC-EV-treated glioma cells while being carried into glioma cells by GSC-EVs. miR-10b-5p targeted PTEN and activated the PI3K/Akt pathway, hence stimulating glycometabolic reprogramming.

CONCLUSION

GSC-EVs target PTEN and activate the PI3K/Akt pathway through carrying miR-10b-5p, subsequently accelerating glycometabolic reprogramming in glioma, which might provide new insights into glioma treatment.

Progress in Glioma Stem Cell Research

Glioblastoma multiforme (GBM) represents a diverse spectrum of primary tumors notorious for their resistance to established therapeutic modalities. Despite aggressive interventions like surgery, radiation, and chemotherapy, these tumors, due to factors such as the blood-brain barrier, tumor heterogeneity, glioma stem cells (GSCs), drug efflux pumps, and DNA damage repair mechanisms, persist beyond complete isolation, resulting in dismal outcomes for glioma patients. Presently, the standard initial approach comprises surgical excision followed by concurrent chemotherapy, where temozolomide (TMZ) serves as the foremost option in managing GBM patients. Subsequent adjuvant chemotherapy follows this regimen. Emerging therapeutic approaches encompass immunotherapy, including checkpoint inhibitors, and targeted treatments, such as bevacizumab, aiming to exploit vulnerabilities within GBM cells. Nevertheless, there exists a pressing imperative to devise innovative strategies for both diagnosing and treating GBM. This review emphasizes the current knowledge of GSC biology, molecular mechanisms, and associations with various signals and/or pathways, such as the epidermal growth factor receptor, PI3K/AKT/mTOR, HGFR/c-MET, NF-κB, Wnt, Notch, and STAT3 pathways. Metabolic reprogramming in GSCs has also been reported with the prominent activation of the glycolytic pathway, comprising aldehyde dehydrogenase family genes. We also discuss potential therapeutic approaches to GSC targets and currently used inhibitors, as well as their mode of action on GSC targets.

The iron chelator and OXPHOS inhibitor VLX600 induces mitophagy and an autophagy-dependent type of cell death in glioblastoma cells

Induction of alternative, non-apoptotic cell death programs such as cell-lethal autophagy and mitophagy represent possible strategies to combat glioblastoma (GBM). Here we report that VLX600, a novel iron chelator and oxidative phosphorylation (OXPHOS) inhibitor, induces a caspase-independent type of cell death that is partially rescued in adherent U251 ATG5/7 (autophagy related 5/7) knockout (KO) GBM cells and NCH644 ATG5/7 knockdown (KD) glioma stem-like cells (GSCs), suggesting that VLX600 induces an autophagy-dependent cell death (ADCD) in GBM. This ADCD is accompanied by decreased oxygen consumption, increased expression/mitochondrial localization of BNIP3 (BCL2 interacting protein 3) and BNIP3L (BCL2 interacting protein 3 like), the induction of mitophagy as demonstrated by diminished levels of mitochondrial marker proteins [e.g., COX4I1 (cytochrome c oxidase subunit 4I1)] and the mitoKeima assay as well as increased histone H3 and H4 lysine tri-methylation. Furthermore, the extracellular addition of iron is able to significantly rescue VLX600-induced cell death and mitophagy, pointing out an important role of iron metabolism for GBM cell homeostasis. Interestingly, VLX600 is also able to completely eliminate NCH644 GSC tumors in an organotypic brain slice transplantation model. Our data support the therapeutic concept of ADCD induction in GBM and suggest that VLX600 may be an interesting novel drug candidate for the treatment of this tumor.NEW & NOTEWORTHY Induction of cell-lethal autophagy represents a possible strategy to combat glioblastoma (GBM). Here, we demonstrate that the novel iron chelator and OXPHOS inhibitor VLX600 exerts pronounced tumor cell-killing effects in adherently cultured GBM cells and glioblastoma stem-like cell (GSC) spheroid cultures that depend on the iron-chelating function of VLX600 and on autophagy activation, underscoring the context-dependent role of autophagy in therapy responses. VLX600 represents an interesting novel drug candidate for the treatment of this tumor.

Using the metabolite alterations monitoring the AEG-1 expression level and cell biological behaviour of U251 cell in vitro

Astrocyte elevated gene-1 (AEG-1) is an important oncogene that overexpresses in gliomas and plays a vital role in their occurrence and progression. However, few reports have shown which biomarkers could reflect the level of AEG-1 expression in vivo so far. In recent years, intracellular metabolites monitored by proton magnetic resonance spectroscopy (1H MRS) as non-invasive imaging biomarkers have been applied to the precise diagnosis and therapy feedback of gliomas. Therefore, understanding the correlation between 1H MRS metabolites and AEG-1 gene expression in U251 cells may help to identify relevant biomarkers. This study constructed three monoclonal AEG-1-knockout U251 cell lines using the clustered regularly interspaced short palindromic repeat (CRISPR) /Cas9 technique and evaluated the biological behaviors and metabolite ratios of these cell lines. With the decline in AEG-1 expression, the apoptosis rate of the AEG-1-knockout cell lines increased. At the same time, the metastatic capacities decreased, and the relative contents of total choline (tCho) and lactate (Lac) were also reduced. In conclusion, deviations in AEG-1 expression influence the apoptosis rate and metastasis capacity of U251 cells, which the 1H MRS metabolite ratio could monitor. The tCho/creatinine(Cr) and Lac/Cr ratios positively correlated with the AEG-1 expression and malignant cell behavior. This study may provide potential biomarkers for accurate preoperative diagnosis and future AEG-1-targeting treatment evaluation of gliomas in vivo.

Targeting cellular respiration as a therapeutic strategy in glioblastoma

While glycolysis is abundant in malignancies, mitochondrial metabolism is significant as well. Mitochondria harbor the enzymes relevant for cellular respiration, which is a critical pathway for both regeneration of reduction equivalents and energy production in the form of ATP. The oxidation of NADH₂ and FADH₂ are fundamental since NAD and FAD are the key components of the TCA-cycle that is critical to entertain biosynthesis in cancer cells. The TCA-cycle itself is predominantly fueled through carbons from glucose, glutamine, fatty acids and lactate. Targeting mitochondrial energy metabolism appears feasible through several drug compounds that activate the CLPP protein or interfere with NADH-dehydrogenase, pyruvate-dehydrogenase, enzymes of the TCA-cycle and mitochondrial matrix chaperones. While these compounds have demonstrated anti-cancer effects in vivo, recent research suggests which patients most likely benefit from such treatments. Here, we provide a brief overview of the status quo of targeting mitochondrial energy metabolism in glioblastoma and highlight a novel combination therapy.

Deregulated Metabolic Pathways in Ovarian Cancer: Cause and Consequence

Ovarian cancers are tumors that originate from the different cells of the ovary and account for almost 4% of all the cancers in women globally. More than 30 types of tumors have been identified based on the cellular origins. Epithelial ovarian cancer (EOC) is the most common and lethal type of ovarian cancer which can be further divided into high-grade serous, low-grade serous, endometrioid, clear cell, and mucinous carcinoma. Ovarian carcinogenesis has been long attributed to endometriosis which is a chronic inflammation of the reproductive tract leading to progressive accumulation of mutations. Due to the advent of multi-omics datasets, the consequences of somatic mutations and their role in altered tumor metabolism has been well elucidated. Several oncogenes and tumor suppressor genes have been implicated in the progression of ovarian cancer. In this review, we highlight the genetic alterations undergone by the key oncogenes and tumor suppressor genes responsible for the development of ovarian cancer. We also summarize the role of these oncogenes and tumor suppressor genes and their association with a deregulated network of fatty acid, glycolysis, tricarboxylic acid and amino acid metabolism in ovarian cancers. Identification of genomic and metabolic circuits will be useful in clinical stratification of patients with complex etiologies and in identifying drug targets for personalized therapies against cancer.

The addition of arginine deiminase potentiates Mithramycin A-induced cell death in patient-derived glioblastoma cells via ATF4 and cytochrome C

BACKGROUND

Arginine auxotrophy constitutes a shortcoming for ~ 30% of glioblastoma multiforme (GBM). Indeed, arginine-depleting therapy using arginine deiminase from Streptococcus pyogenes (SpyADI) has proven activity against GBM in preclinical studies. The good safety profile of SpyADI renders this agent an ideal combination partner for cytostatic therapy.

METHODS

In this study, we combined the antineoplastic antibiotic Mithramycin A (MitA) with SpyADI to boost single-agent activity and analyzed underlying response mechanisms in-depth.

RESULTS

MitA monotherapy induced a time- and dose-dependent cytotoxicity in eight patient-derived GBM cell lines and had a radiosensitizing effect in all but one cell line. Combination treatment boosted the effects of the monotherapy in 2D- and 3D models. The simultaneous approach was superior to the sequential application and significantly impaired colony formation after repetitive treatment. MitA monotherapy significantly inhibited GBM invasiveness. However, this effect was not enhanced in the combination. Functional analysis identified SpyADI-triggered senescence induction accompanied by increased mitochondrial membrane polarization upon mono- and combination therapy. In HROG63, induction of lysosomes was seen after both monotherapies, indicative of autophagy. These cells seemed swollen and had a more pronounced cortically formed cytoskeleton. Also, cytochrome C and endoplasmatic reticulum-stress-associated proteins ATF4 and Calnexin were enhanced in the combination, contributing to apoptosis. Notably, no significant increases in glioma-stemness marker were seen.

CONCLUSIONS

Therapeutic utilization of a metabolic defect in GBM along with cytostatic therapy provides a novel combination approach. Whether this SpyADI/MitA regimen will provide a safe alternative to combat GBM, will have to be addressed in subsequent (pre-)clinical trials.

Valtrate, an iridoid compound in Valeriana, elicits anti-glioblastoma activity through inhibition of the PDGFRA/MEK/ERK signaling pathway

BACKGROUND

Valtrate, a natural compound isolated from the root of Valeriana, exhibits antitumor activity in many cancers through different mechanisms. However, its efficacy for the treatment of glioblastoma (GBM), a tumor type with a poor prognosis, has not yet been rigorously investigated.

METHODS

GBM cell lines were treated with valtrate and CCK-8, colony formation and EdU assays, flow cytometry, and transwell, 3D tumor spheroid invasion and GBM-brain organoid co-culture invasion assays were performed to assess properties of proliferation, viability, apoptosis and invasion/migration. RNA sequencing analysis on valtrate-treated cells was performed to identify putative target genes underlying the antitumor activity of the drug in GBM cells. Western blot analysis, immunofluorescence and immunohistochemistry were performed to evaluate protein levels in valtrate-treated cell lines and in samples obtained from orthotopic xenografts. A specific activator of extracellular signal-regulated kinase (ERK) was used to identify the pathways mediating the effect.

RESULTS

Valtrate significantly inhibited the proliferation of GBM cells in vitro by inducing mitochondrial apoptosis and suppressed invasion and migration of GBM cells by inhibiting levels of proteins associated with epithelial mesenchymal transition (EMT). RNA sequencing analysis of valtrate-treated GBM cells revealed platelet-derived growth factor receptor A (PDGFRA) as a potential target downregulated by the drug. Analysis of PDGFRA protein and downstream mediators demonstrated that valtrate inhibited PDGFRA/MEK/ERK signaling. Finally, treatment of tumor-bearing nude mice with valtrate led to decreased tumor volume (fivefold difference at day 28) and enhanced survival (day 27 vs day 36, control vs valtrate-treated) relative to controls.

CONCLUSIONS

Taken together, our study demonstrated that the natural product valtrate elicits antitumor activity in GBM cells through targeting PDGFRA and thus provides a candidate therapeutic compound for the treatment of GBM.