Wnt/β-catenin Antagonists: Exploring New Avenues to Trigger Old Drugs in Alleviating Glioblastoma Multiforme

Navigating Glioma Complexity: The Role of Abnormal Signaling Pathways in Shaping Future Therapies

Gliomas are a type of highly heterogeneous and invasive central nervous system tumor. Traditional treatment methods have limited efficacy, and the prognosis for patients remains poor. Recent studies have revealed the crucial roles of several abnormal signaling pathways in the pathogenesis of gliomas, including the Receptor Tyrosine Kinase/Rat Sarcoma Virus Oncogene/Phosphatidylinositol-3-Kinase (RTK/RAS/PI3K) pathway, the Wingless-Related Integration Site/β-Catenin (Wnt/β-Catenin) pathway, the Hippo/YAP (Hippo/Yes-associated protein) pathway, and the Slit/Robo (Slit Guidance Ligands/Roundabout) signaling pathway. These pathways play extremely vital roles in tumor proliferation, invasion, and treatment resistance. This article comprehensively and systematically reviews the molecular mechanisms of these signaling pathways, deeply summarizing the research progress of various treatment strategies, including targeted inhibitors, gene therapy, and nanomedicine against them. Moreover, the combination of targeted therapy and personalized treatment regimens is expected to overcome the current treatment bottleneck and provide a more favorable survival prognosis for glioblastoma patients.

Microtubule actin crosslinking factor 1, a brain tumor oncoprotein (Review)

Microtubule actin crosslinking factor 1 (MACF1), is a cytoskeletal protein that functions as a crosslinker between microtubules and actin filaments, with early studies expanding the role of this spectraplakin protein to the central nervous system and Wnt signaling. In the early 2000's, genetic alterations of MACF1 were identified in several cancers suggesting that this cytoskeletal crosslinker was involved in tumor development and progression, while preclinical studies provided evidence that MACF1 is a potential diagnostic and prognostic biomarker and therapeutic target in glioblastomas, a central nervous system cancer derived from astrocytes and neural progenitor stem cells. Furthermore, investigations in glioblastomas demonstrated that genetic inhibitory targeting of this spectraplakin protein alone and in combination with DNA damaging agents had synergistic antitumorigenic effects. The established role of MACF1 in Wnt signaling, a known mechanistic driver of central nervous system development and pro-tumorigenic cell behavior in glioblastomas, provide a premise for addressing the potential of this spectraplakin protein as a novel oncoprotein in cancers with origins in the nervous system. The present review provides a summary of the role and function of MACF1 in the central nervous system, Wnt signaling and cancer development, specifically as an oncoprotein that underlie the transformation and oncogenic properties of glioblastomas.

Fructose 1,6-bisphosphatase 1 is a potential biomarker affecting the malignant phenotype and aerobic glycolysis in glioblastoma

Background

Fructose 1,6-bisphosphatase 1 (FBP1) has been considered as a potential prognostic biomarker in glioblastoma (GBM), and this study explored the underlying mechanism.

Methods

The expression and effect of FBP1 expression on the prognosis of GBM patients were examined applying bioinformatics analyses. After measuring the expression of FBP1 in normal glial cell line HEB and GBM cells, cell counting kit-8 (CCK-8), 5-ethynyl-2-deoxyuridine (EdU), colony formation, transwell, and wound healing assay were carried out to examine the effects of silencing FBP1 on the proliferation and invasion of GBM cells. Aerobic glycolysis was measured by calculating the extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) of FBP1-silenced GBM cells. Furthermore, the protein levels of the mediators related to PI3K/AKT pathway and BCL2 protein family were detected via immunoblotting. Additionally, the effects of FBP1 silencing on the macrophage M2 polarization were assessed based on the fluorescence intensity of CD206 and the phosphorylation of STAT6 quantified by immunofluorescence and immunoblotting, respectively.

Results

High-expressed FBP1 was indicative of a worse prognosis of GBM. FBP1 knockdown in GBM cells suppressed the proliferation, invasion, migration, and aerobic glycolysis of GBM cells, lowered the phosphorylation levels of AKT and PI3K and the protein expression of BCL2 but promoted BAX protein expression. Moreover, FBP1 knockdown reduced CD206 fluorescence intensity and the phosphorylation of STAT6.

Conclusion

To conclude, FBP1 could be considered as a biomarker that affected the malignant phenotypes and aerobic glycolysis in GBM, contributing to the diagnosis and treatment of GBM.

Clofazimine enhances anti-glioma effect of immunotherapy

RATIONALE

Glioblastoma is one of the most aggressive human brain tumors. The prognosis is unfavorable and treatment effects are relatively low. However, temozolomide (TMZ) chemotherapy may prolong patients' survival.

OBJECTIVE OF THE PAPER

The anti-glioma effect of clofazimine used in immunotherapy is examined in vivo.

MATERIALS AND METHODS

Method of obtaining TMZ-resistant GB cells included treatment of T98G glioblastoma cells with 150 μmol/l TMZ. To confirm resistance to TMZ, MTT assay was performed according to the manufacturer's protocol. Untreated cells were used as a control group. C6 glioma cells were stereotactically implanted into the brain of Wistar rats and irradiated (24 Gy) in combination with oral administration of TMZ (20 mg/ kg) and clofazimine (CFZ) (30 mg/kg). This was followed by subsequent immunotherapy including tumor cell and dendritic cell vaccines. Neurovisualisation, immunocytochemical and immunohistochemical assays were used and animals' survival was analyzed with Kaplan-Meier estimator.

RESULTS

T98G resistant glioblastoma cell line is characterized by immunoreactive β-catenin, CD133, CD44, and N-cadherin as compared to the control cell line. The IC 50 of clofazimine for T98G glioblastoma cell line is 38.3 ± 4,1 μmol/l, for C6 rat glioma cell line is 37,6 ± 3,2 μmol/l. Clofazimine enhanced the cytotoxic activity of temozolomide, paclitaxel, and carboplatin in cancer cells of T98G line as compared to the control group. The cytotoxic effect of lomustine and carboplatin against T98G resistant glioblastoma cells was also enhanced by Clofazimine. Tumor cell vaccine (TCV) and dendritic cell vaccine (DCV) in combination with clofazimine produces a stronger anti-tumor immune response in C6 glioma. This is evident with development of local inflammatory reaction with higher content of interleukin 1β and 18 in serum, as well as greater level of IBA1+, CD68 + in pro-inflammatory microglia of neoplastic tissues. Combined use of DCV and clofazimine results in higher survival rates in experimental animals (- 90 ± 7 days against 45 ± 5 days) in the treated group with chemoradiation therapy (CRT).

CONCLUSIONS

Combination of clofazimine and immunotherapy enhances anti-glioma effect of TMZ in an in vivo model experiment.

Regulation of cancer stem cells and immunotherapy of glioblastoma (Review)

Glioblastoma (GB) is one of the most adverse diagnoses in oncology. Complex current treatment results in a median survival of 15 months. Resistance to treatment is associated with the presence of cancer stem cells (CSCs). The present review aimed to analyze the mechanisms of CSC plasticity, showing the particular role of β-catenin in regulating vital functions of CSCs, and to describe the molecular mechanisms of Wnt-independent increase of β-catenin levels, which is influenced by the local microenvironment of CSCs. The present review also analyzed the reasons for the low effectiveness of using medication in the regulation of CSCs, and proposed the development of immunotherapy scenarios with tumor cell vaccines, containing heterogenous cancer cells able of producing a multidirectional antineoplastic immune response. Additionally, the possibility of managing lymphopenia by transplanting hematopoietic stem cells from a healthy sibling and using clofazimine or other repurposed drugs that reduce β-catenin concentration in CSCs was discussed in the present study.

Repurposing synthetic and natural derivatives induces apoptosis in an orthotopic glioma-induced xenograft model by modulating WNT/β-catenin signaling

BACKGROUND

Glioblastomas arise from multistep tumorigenesis of the glial cells. Despite the current state-of-art treatment, tumor recurrence is inevitable. Among the innovations blooming up against glioblastoma, drug repurposing could provide profound premises for treatment enhancement. While considering this strategy, the efficacy of the repurposed drugs as monotherapies were not up to par; hence, the focus has now shifted to investigate the multidrug combinations.

AIM

To investigate the efficacy of a quadruple-combinatorial treatment comprising temozolomide along with chloroquine, naringenin, and phloroglucinol in an orthotopic glioma-induced xenograft model.

METHODS

Antiproliferative effect of the drugs was assessed by immunostaining. The expression profiles of WNT/β-catenin and apoptotic markers were evaluated by qRT-PCR, immunoblotting, and ELISA. Patterns of mitochondrial depolarization was determined by flow cytometry. TUNEL assay was performed to affirm apoptosis induction. In vivo drug detection study was carried out by ESI-Q-TOF MS analysis.

RESULTS

The quadruple-drug treatment had significantly hampered glioma proliferation and had induced apoptosis by modulating the WNT/β-catenin signaling. Interestingly, the induction of apoptosis was associated with mitochondrial depolarization. The quadruple-drug cocktail had breached the blood-brain barrier and was detected in the brain tissue and plasma samples.

CONCLUSION

The quadruple-drug combination served as a promising adjuvant therapy to combat glioblastoma lethality in vivo and can be probed for translation from bench to bedside.

Wnt Signaling in Brain Tumors: A Challenging Therapeutic Target

The involvement of Wnt signaling in normal tissue homeostasis and disease has been widely demonstrated over the last 20 years. In particular, dysregulation of Wnt pathway components has been suggested as a relevant hallmark of several neoplastic malignancies, playing a role in cancer onset, progression, and response to treatments. In this review, we summarize the current knowledge on the instructions provided by Wnt signaling during organogenesis and, particularly, brain development. Moreover, we recapitulate the most relevant mechanisms through which aberrant Wnt pathway activation may impact on brain tumorigenesis and brain tumor aggressiveness, with a particular focus on the mutual interdependency existing between Wnt signaling components and the brain tumor microenvironment. Finally, the latest anti-cancer therapeutic approaches employing the specific targeting of Wnt signaling are extensively reviewed and discussed. In conclusion, here we provide evidence that Wnt signaling, due to its pleiotropic involvement in several brain tumor features, may represent a relevant target in this context, although additional efforts will be needed to: (i) demonstrate the real clinical impact of Wnt inhibition in these tumors; (ii) overcome some still unsolved concerns about the potential systemic effects of such approaches; (iii) achieve efficient brain penetration.

A combination of metformin and epigallocatechin gallate potentiates glioma chemotherapy in vivo

Glioma is the most devastating high-grade tumor of the central nervous system, with dismal prognosis. Existing treatment modality does not provide substantial benefit to patients and demands novel strategies. One of the first-line treatments for glioma, temozolomide, provides marginal benefit to glioma patients. Repurposing of existing non-cancer drugs to treat oncology patients is gaining momentum in recent years. In this study, we investigated the therapeutic benefits of combining three repurposed drugs, namely, metformin (anti-diabetic) and epigallocatechin gallate (green tea-derived antioxidant) together with temozolomide in a glioma-induced xenograft rat model. Our triple-drug combination therapy significantly inhibited tumor growth in vivo and increased the survival rate (50%) of rats when compared with individual or dual treatments. Molecular and cellular analyses revealed that our triple-drug cocktail treatment inhibited glioma tumor growth in rat model through ROS-mediated inactivation of PI3K/AKT/mTOR pathway, arrest of the cell cycle at G1 phase and induction of molecular mechanisms of caspases-dependent apoptosis.In addition, the docking analysis and quantum mechanics studies performed here hypothesize that the effect of triple-drug combination could have been attributed by their difference in molecular interactions, that maybe due to varying electrostatic potential. Thus, repurposing metformin and epigallocatechin gallate and concurrent administration with temozolomide would serve as a prospective therapy in glioma patients.

Crosstalk between PI3K/AKT/mTOR and WNT/β-Catenin signaling in GBM - Could combination therapy checkmate the collusion?

Glioblastoma multiforme is one of the calamitous primary glial brain tumors with extensive heterogeneity at cellular and molecular levels. While maximal surgical resection trailed by radio and chemotherapy employing temozolomide remains the gold-standard treatment for malignant glioma patients, the overall prognosis remains dismal and there exists an unmet need for effective therapeutic strategies. In this context, we hypothesize that proper understanding of signaling pathways responsible for glioblastoma multiforme proliferation would be the first trump card while searching for novel targeted therapies. Among the pathways aberrantly activated, PI3K/AKT/mTOR is the most significant pathway, that is clinically implicated in malignancies such as high-grade glioma. Further, the WNT/β-Catenin cascade is well-implicated in several malignancies, while its role in regulating glioma pathogenesis has only emerged recently. Nevertheless, oncogenic activation of both these pathways is a frequent event in malignant glioma that facilitates tumor proliferation, stemness and chemo-resistance. Recently, it has been reported that the cross-talk of PI3K/AKT/mTOR pathway with multiple signaling pathways could promote glioma progression and reduce the sensitivity of glioma cells to the standard therapy. However, very few studies had focused on the relationship between PI3K/AKT/mTOR and WNT/β-Catenin pathways in glioblastoma multiforme. Interestingly, in homeostatic and pathologic circumstances, both these pathways depict fine modulation and are connected at multiple levels by upstream and downstream effectors. Thus, gaining deep insights on the collusion between these pathways would help in discovering unique therapeutic targets for glioblastoma multiforme management. Hence, the current review aims to address, "the importance of inter-play between PI3K/AKT/mTOR and WNT/β-Catenin pathways", and put forward, "the possibility of combinatorially targeting them", for glioblastoma multiforme treatment enhancement.