GANT61, a GLI inhibitor, sensitizes glioma cells to the temozolomide treatment

Conditioned Medium From Reactive Astrocytes Inhibits Proliferation, Resistance, and Migration of p53-Mutant Glioblastoma Spheroid Through GLI-1 Downregulation

Glioblastoma (GBM) aggressiveness is partly driven by the reactivation of signaling pathways such as Sonic hedgehog (SHH) and the interaction with its microenvironment. SHH pathway activation is one of the phenomena behind the glial transformation in response to tumor growth. The reactivation of the SHH signaling cascade during GBM-astrocyte interaction is highly relevant to understanding the mechanisms used by the tumor to modulate the adjacent stroma. The role of reactive astrocytes considering SHH signaling during GBM progression is investigated using a 3D in vitro model. T98G GBM spheroids displayed significant downregulation of SHH (61.4 ± 9.3%), GLI-1 (6.5 ± 3.7%), Ki-67 (33.7 ± 8.1%), and mutant MTp53 (21.3 ± 10.6%) compared to the CONTROL group when incubated with conditioned medium of reactive astrocytes (CM-AST). The SHH pathway inhibitor, GANT-61, significantly reduced previous markers (SHH = 43.0 ± 12.1%; GLI-1 = 9.5 ± 3.4%; Ki-67 = 31.9 ± 4.6%; MTp53 = 6.5 ± 7.5%) compared to the CONTROL, and a synergistic effect could be observed between GANT-61 and CM-AST. The volume (2.0 ± 0.2 × 107 µm³), cell viability (80.4 ± 3.2%), and migration (41 ± 10%) of GBM spheroids were significantly reduced in the presence of GANT-61 and CM-AST when compared to CM-AST after 72 h (volume = 2.3 ± 0.4 × 107 µm³; viability = 92.2 ± 6.5%; migration = 102.5 ± 14.6%). Results demonstrated that factors released by reactive astrocytes promoted a neuroprotective effect preventing GBM progression using a 3D in vitro model potentiated by SHH pathway inhibition.

Identification of Novel GANT61 Analogs with Activity in Hedgehog Functional Assays and GLI1-Dependent Cancer Cells

Aberrant activation of hedgehog (Hh) signaling has been implicated in various cancers. Current FDA-approved inhibitors target the seven-transmembrane receptor Smoothened, but resistance to these drugs has been observed. It has been proposed that a more promising strategy to target this pathway is at the GLI1 transcription factor level. GANT61 was the first small molecule identified to directly suppress GLI-mediated activity; however, its development as a potential anti-cancer agent has been hindered by its modest activity and aqueous chemical instability. Our study aimed to identify novel GLI1 inhibitors. JChem searches identified fifty-two compounds similar to GANT61 and its active metabolite, GANT61-D. We combined high-throughput cell-based assays and molecular docking to evaluate these analogs. Five of the fifty-two GANT61 analogs inhibited activity in Hh-responsive C3H10T1/2 and Gli-reporter NIH3T3 cellular assays without cytotoxicity. Two of the GANT61 analogs, BAS 07019774 and Z27610715, reduced Gli1 mRNA expression in C3H10T1/2 cells. Treatment with BAS 07019774 significantly reduced cell viability in Hh-dependent glioblastoma and lung cancer cell lines. Molecular docking indicated that BAS 07019774 is predicted to bind to the ZF4 region of GLI1, potentially interfering with its ability to bind DNA. Our findings show promise in developing more effective and potent GLI inhibitors.

GANT61, an inhibitor of Gli1, inhibits the proliferation and migration of hepatocellular carcinoma cells

Constitutive activation of Hedgehog (Hh) signaling has been implicated in many cancers including hepatocellular carcinoma (HCC). Among them, the terminal glioma-associated oncogene homolog 1 (Gli1) regulates the expression of critical genes in the Hh pathway. The current study aims to evaluate the anti-HCC effect of the Gli1 inhibitor, GANT61. In vitro analysis including cell counting kit-8 (CCK-8) assay, flow cytometry, and migration and invasion assay were adopted to evaluate the effect of GANT61 on HCC cell lines. In vivo, xenograft studies were also performed to verify the effect of GANT61 on HCC. By CCK-8 assay, we found that GANT61 could significantly reduce the growth of HCC cell lines Huh7 and hemophagocytic lymphohistiocytosis (HLE), and their IC50 concentrations were 4.481 and 6.734 μM, respectively. Flow cytometry shows that GANT61 induced cell cycle arrest in the G2/M phase and accelerated apoptosis of both HLE and Huh7 cells. While migration and invasion assay shows that GANT61 weakens cells' migration and invasion ability. Besides that, GANT61 inhibits the expression of Gli1, FoxM1, CyclinD1, and Bcl-2, upregulates the level of Bax protein, and also reverses the epithelial-mesenchymal transition program by downregulating the expression of Vimentin and N-Cadherin and upregulating the expression of epithelial E-Cadherin expression. Furthermore, GANT61 inhibits the growth of subcutaneous xenografts of Huh7 cells in nude mice. Overall, this study suggests that Gli1 is a potential target for therapy and GANT61 shows promising therapeutic potential for future treatment in HCC.

Oncofetal reprogramming in tumor development and progression: novel insights into cancer therapy

Emerging evidence indicates that cancer cells can mimic characteristics of embryonic development, promoting their development and progression. Cancer cells share features with embryonic development, characterized by robust proliferation and differentiation regulated by signaling pathways such as Wnt, Notch, hedgehog, and Hippo signaling. In certain phase, these cells also mimic embryonic diapause and fertilized egg implantation to evade treatments or immune elimination and promote metastasis. Additionally, the upregulation of ATP-binding cassette (ABC) transporters, including multidrug resistance protein 1 (MDR1), multidrug resistance-associated protein 1 (MRP1), and breast cancer-resistant protein (BCRP), in drug-resistant cancer cells, analogous to their role in placental development, may facilitate chemotherapy efflux, further resulting in treatment resistance. In this review, we concentrate on the underlying mechanisms that contribute to tumor development and progression from the perspective of embryonic development, encompassing the dysregulation of developmental signaling pathways, the emergence of dormant cancer cells, immune microenvironment remodeling, and the hyperactivation of ABC transporters. Furthermore, we synthesize and emphasize the connections between cancer hallmarks and embryonic development, offering novel insights for the development of innovative cancer treatment strategies.

Targeting hedgehog-driven mechanisms of drug-resistant cancers

Due to the cellular plasticity that is inherent to cancer, the acquisition of resistance to therapy remains one of the biggest obstacles to patient care. In many patients, the surviving cancer cell subpopulation goes on to proliferate or metastasize, often as the result of dramatically altered cell signaling and transcriptional pathways. A notable example is the Hedgehog (Hh) signaling pathway, which is a driver of several cancer subtypes and aberrantly activated in a wide range of malignancies in response to therapy. This review will summarize the field's current understanding of the many roles played by Hh signaling in drug resistance and will include topics such as non-canonical activation of Gli proteins, amplification of genes which promote tolerance to chemotherapy, the use of hedgehog-targeted drugs and tool compounds, and remaining gaps in our knowledge of the transcriptional mechanisms at play.

Modulating MGMT expression through interfering with cell signaling pathways

Guanine O6-alkylating agents are widely used as first-line chemotherapeutic drugs due to their ability to induce cytotoxic DNA damage. However, a major hurdle in their effectiveness is the emergence of chemoresistance, largely attributed to the DNA repair pathway mediated by O6-methylguanine-DNA methyltransferase (MGMT). MGMT plays an important role in removing the alkyl groups from lethal O6-alkylguanine (O6-AlkylG) adducts formed by chemotherapeutic alkylating agents. By doing so, MGMT enables tumor cells to evade apoptosis and develop drug resistance toward DNA alkylating agents. Although covalent inhibitors of MGMT, such as O6-benzylguanine (O6-BG) and O6-(4-bromothenyl)guanine (O6-4-BTG or lomeguatrib), have been explored in clinical settings, their utility is limited due to severe delayed hematological toxicity observed in most patients when combined with alkylating agents. Therefore, there is an urgent need to identify new targets and unravel the underlying molecular mechanisms and to develop alternative therapeutic strategies that can overcome MGMT-mediated tumor resistance. In this context, the regulation of MGMT expression via interfering the specific cell signaling pathways (e.g., Wnt/β-catenin, NF-κB, Hedgehog, PI3K/AKT/mTOR, JAK/STAT) emerges as a promising strategy for overcoming tumor resistance, and ultimately enhancing the efficacy of DNA alkylating agents in chemotherapy.

Zinc finger and SCAN domain-containing 18 suppresses the proliferation, self-renewal, and drug resistance of glioblastoma cells

Elucidation of cellular and molecular mechanisms key to glioblastoma growth, self-renewal, survival, and metastasis is important for developing novel therapeutic strategies. In this study, the expression and function of zinc finger and SCAN domain-containing 18 (ZSCAN18) in human glioblastoma cell lines were characterized. Compared with normal astrocytes, ZSCAN18 was significantly down-regulated in all tested glioblastoma cell lines, with the LN-229 cell line having the lowest ZSCAN18 expression. Lentivirus-mediated ZSCAN18 overexpression suppressed glioblastoma cell proliferation, sphere formation, and SOX2 and OCT4 expression, implying the negative role of ZSCAN18 in glioblastoma development. ZSCAN18 overexpression enhanced the sensitivity of glioblastoma cells to Temozolomide. The glioblastoma implantation model showed a consistent inhibitory effect of ZSCAN18 on the proliferation and self-renewal of glioblastoma cells in vivo. Notably, ZSCAN18 overexpression resulted in the down-regulation of glioma-associated oncogene homolog 1 (GLI1) which is the terminal component of the Hedgehog signaling. Lentivirus-mediated GLI1 overexpression restored the proliferation and promoted the resistance of glioblastoma cells to Temozolomide. However, GLI1 overexpression did not affect the self-renewal of ZSCAN18-overexpressing glioblastoma cells. Taken together, this research uncovers the role of ZSCAN18 in regulating glioblastoma cell growth and maintenance. ZSCAN18 could be a potential glioblastoma biomarker.

Fluoride in the Central Nervous System and Its Potential Influence on the Development and Invasiveness of Brain Tumours-A Research Hypothesis

The purpose of this review is to attempt to outline the potential role of fluoride in the pathogenesis of brain tumours, including glioblastoma (GBM). In this paper, we show for the first time that fluoride can potentially affect the generally accepted signalling pathways implicated in the formation and clinical course of GBM. Fluorine compounds easily cross the blood-brain barrier. Enhanced oxidative stress, disruption of multiple cellular pathways, and microglial activation are just a few examples of recent reports on the role of fluoride in the central nervous system (CNS). We sought to present the key mechanisms underlying the development and invasiveness of GBM, as well as evidence on the current state of knowledge about the pleiotropic, direct, or indirect involvement of fluoride in the regulation of these mechanisms in various tissues, including neural and tumour tissue. The effects of fluoride on the human body are still a matter of controversy. However, given the growing incidence of brain tumours, especially in children, and numerous reports on the effects of fluoride on the CNS, it is worth taking a closer look at these mechanisms in the context of brain tumours, including gliomas.

The role of Hedgehog and Notch signaling pathway in cancer

Notch and Hedgehog signaling are involved in cancer biology and pathology, including the maintenance of tumor cell proliferation, cancer stem-like cells, and the tumor microenvironment. Given the complexity of Notch signaling in tumors, its role as both a tumor promoter and suppressor, and the crosstalk between pathways, the goal of developing clinically safe, effective, tumor-specific Notch-targeted drugs has remained intractable. Drugs developed against the Hedgehog signaling pathway have affirmed definitive therapeutic effects in basal cell carcinoma; however, in some contexts, the challenges of tumor resistance and recurrence leap to the forefront. The efficacy is very limited for other tumor types. In recent years, we have witnessed an exponential increase in the investigation and recognition of the critical roles of the Notch and Hedgehog signaling pathways in cancers, and the crosstalk between these pathways has vast space and value to explore. A series of clinical trials targeting signaling have been launched continually. In this review, we introduce current advances in the understanding of Notch and Hedgehog signaling and the crosstalk between pathways in specific tumor cell populations and microenvironments. Moreover, we also discuss the potential of targeting Notch and Hedgehog for cancer therapy, intending to promote the leap from bench to bedside.

Current Opportunities for Targeting Dysregulated Neurodevelopmental Signaling Pathways in Glioblastoma

Glioblastoma (GBM) is the most common and highly lethal type of brain tumor, with poor survival despite advances in understanding its complexity. After current standard therapeutic treatment, including tumor resection, radiotherapy and concomitant chemotherapy with temozolomide, the median overall survival of patients with this type of tumor is less than 15 months. Thus, there is an urgent need for new insights into GBM molecular characteristics and progress in targeted therapy in order to improve clinical outcomes. The literature data revealed that a number of different signaling pathways are dysregulated in GBM. In this review, we intended to summarize and discuss current literature data and therapeutic modalities focused on targeting dysregulated signaling pathways in GBM. A better understanding of opportunities for targeting signaling pathways that influences malignant behavior of GBM cells might open the way for the development of novel GBM-targeted therapies.

GANT61 elevates chemosensitivity to cisplatin through regulating the Hedgehog, AMPK and cAMP pathways in ovarian cancer

Background: This study aimed to explore the effect of GANT61 on ovarian cancer (OC) chemosensitivity. Materials & methods: OC cells (Caov-3 and SKOV-3) were treated by GANT61 alone or combined with cisplatin/taxol. The mRNA sequencing was conducted, followed by rescue experiments. Results: GANT61 reduced OC cell viability in a dose-dependent manner and enhanced chemosensitivity to cisplatin but not to taxol. In total, 545 dysregulated genes were identified after the addition of GANT61 to cisplatin-treated OC cells, which were enriched in the AMPK, Hedgehog and cAMP pathways, then further validated by western blot. Furthermore, rescue experiments observed that AMPK pathway inhibitor and cAMP pathway inhibitor attenuated GANT61's chemosensitivity to cisplatin. Conclusion: GANT61 enforces OC chemosensitivity to cisplatin by regulating the Hedgehog, AMPK and cAMP pathways.

Inhibition of Gli2 suppresses tumorigenicity in glioblastoma stem cells derived from a de novo murine brain cancer model

The prognosis of glioblastoma remains poor despite intensive research efforts. Glioblastoma stem cells (GSCs) contribute to tumorigenesis, invasive capacity, and therapy resistance. Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5), a stem cell marker, is involved in the maintenance of GSCs, although the properties of Lgr5-positive GSCs remain unclear. Here, the Sleeping-Beauty transposon-induced glioblastoma model was used in Lgr5-GFP knock-in mice identify GFP-positive cells in neurosphere cultures from mouse glioblastoma tissues. Global gene expression analysis showed that Gli2 was highly expressed in GFP-positive GSCs. Gli2 knockdown using lentiviral-mediated shRNA downregulated Hedgehog-related and Wnt signaling pathway-related genes, including Lgr5; suppressed tumor cell proliferation and invasion capacity; and induced apoptosis. Pharmacological Gli inhibition with GANT61 suppressed tumor cell proliferation. Silencing Gli2 suppressed the tumorigenicity of GSCs in an orthotopic transplantation model in vivo. These findings suggest that Gli2 affects the Hedgehog and Wnt pathways and plays an important role in GSC maintenance, suggesting Gli2 as a therapeutic target for glioblastoma treatment.

Advances in glioma-associated oncogene (GLI) inhibitors for cancer therapy

The Hedgehog/Glioma-associated oncogene homolog (HH/GLI) signaling pathway regulates self-renewal of rare and highly malignant cancer stem cells, which have been shown to account for the initiation and maintenance of tumor growth as well as for drug resistance, metastatic spread and relapse. As an important component of the Hh signaling pathway, glioma-associated oncogene (GLI) acts as a key signal transmission hub for various signaling pathways in many tumors. Here, we review direct and indirect inhibitors of GLI; summarize the abundant active structurally diverse natural GLI inhibitors; and discuss how to better develop and utilize GLI inhibitors to solve the problem of drug resistance in tumors of interest. In summary, GLI inhibitors will be promising candidates for various cancer treatments.

The PI3K Inhibitor XH30 Enhances Response to Temozolomide in Drug-Resistant Glioblastoma via the Noncanonical Hedgehog Signaling Pathway

Glioblastoma multiforme (GBM) is the most common malignant tumor of the central nervous system. Temozolomide (TMZ)-based adjuvant treatment has improved overall survival, but clinical outcomes remain poor; TMZ resistance is one of the main reasons for this. Here, we report a new phosphatidylinositide 3-kinase inhibitor, XH30; this study aimed to assess the antitumor activity of this compound against TMZ-resistant GBM. XH30 inhibited cell proliferation in TMZ-resistant GBM cells (U251/TMZ and T98G) and induced cell cycle arrest in the G1 phase. In an orthotopic mouse model, XH30 suppressed TMZ-resistant tumor growth. XH30 was also shown to enhance TMZ cytotoxicity both in vitro and in vivo. Mechanistically, the synergistic effect of XH30 may be attributed to its repression of the key transcription factor GLI1 via the noncanonical hedgehog signaling pathway. XH30 reversed sonic hedgehog-triggered GLI1 activation and decreased GLI1 activation by insulin-like growth factor 1 via the noncanonical hedgehog signaling pathway. These results indicate that XH30 may represent a novel therapeutic option for TMZ-resistant GBM.

Cancer Stem Cell for Tumor Therapy

Simple Summary

Although many methods have been applied in clinical treatment for tumors, they still always show a poor prognosis. Molecule targeted therapy has revolutionized tumor therapy, and a proper target must be found urgently. With a crucial role in tumor development, metastasis and recurrence, cancer stem cells have been found to be a feasible and potential target for tumor therapy. We list the unique biological characteristics of cancer stem cells and summarize the recent strategies to target cancer stem cells for tumor therapy, through which we hope to provide a comprehensive understanding of cancer stem cells and find a better combinational strategy to target cancer stem cells for tumor therapy.

Abstract

Tumors pose a significant threat to human health. Although many methods, such as operations, chemotherapy and radiotherapy, have been proposed to eliminate tumor cells, the results are unsatisfactory. Targeting therapy has shown potential due to its specificity and efficiency. Meanwhile, it has been revealed that cancer stem cells (CSCs) play a crucial role in the genesis, development, metastasis and recurrence of tumors. Thus, it is feasible to inhibit tumors and improve prognosis via targeting CSCs. In this review, we provide a comprehensive understanding of the biological characteristics of CSCs, including mitotic pattern, metabolic phenotype, therapeutic resistance and related mechanisms. Finally, we summarize CSCs targeted strategies, including targeting CSCs surface markers, targeting CSCs related signal pathways, targeting CSC niches, targeting CSC metabolic pathways, inducing differentiation therapy and immunotherapy (tumor vaccine, CAR-T, oncolytic virus, targeting CSCs–immune cell crosstalk and immunity checkpoint inhibitor). We highlight the potential of immunity therapy and its combinational anti-CSC therapies, which are composed of different drugs working in different mechanisms.

Quercetin-loaded platelets as a potential targeted therapy for glioblastoma multiforme cell line U373-MG

Over the globe, the incidence of glioblastoma multiforme (GM) is very low, that is, 1-4 cases per 100,000, but it is fatal and cancer grows very fast inside the brain tissues, namely astrocytes and oligodendrocytes. Because of the rapid growth, it is difficult to halt the dissemination of tumor in adjacent tissues. Although temozolomide (TMZ) is a currently approved standard of care, it develops resistance over the period. Therefore, there is a need to develop a novel drug delivery system. In this work, authors have developed platelets as drug delivery carriers-loaded with quercetin (QCT) for targeting GM. The effect of QCT and QCT-platelet was assessed on the U373-MG cell line. Natural human platelets were used as carriers for drug loading and drug delivery. Platelets possess an open canalicular system that allows the uptake of drug molecules in the platelet cytoplasm. The study showed that the maximum encapsulation efficiency of QCT-platelet was 93.96 ± 0.12% and the maximum drug release in 24 h was 76.26 ± 0.13% in-vitro at pH 5.5 that mimics the tumor microenvironment. In this work, there is a three-fold enhancement of solubility of QCT. The cytotoxic activity of QCT-platelets was studied in the U373-MG human astrocytoma glioblastoma cell line and the cell viability was 14.52 ± 1.53% after 48 h. Thus, platelets were proved as good carriers for therapeutic moieties and can be effectively used to target the glioblastoma tumor in the near future.

Defining the Role of GLI/Hedgehog Signaling in Chemoresistance: Implications in Therapeutic Approaches

Insight into cancer signaling pathways is vital in the development of new cancer treatments to improve treatment efficacy. A relatively new but essential developmental signaling pathway, namely Hedgehog (Hh), has recently emerged as a major mediator of cancer progression and chemoresistance. The evolutionary conserved Hh signaling pathway requires an in-depth understanding of the paradigm of Hh signaling transduction, which is fundamental to provide the necessary means for the design of novel tools for treating cancer related to aberrant Hh signaling. This review will focus substantially on the canonical Hh signaling and the treatment strategies employed in different studies, with special emphasis on the molecular mechanisms and combination treatment in regard to Hh inhibitors and chemotherapeutics. We discuss our views based on Hh signaling's role in regulating DNA repair machinery, autophagy, tumor microenvironment, drug inactivation, transporters, epithelial-to-mesenchymal transition, and cancer stem cells to promote chemoresistance. The understanding of this Achilles' Heel in cancer may improve the therapeutic outcome for cancer therapy.

Mediators of human ureteral smooth muscle contraction-a role for erythropoietin, tamsulosin and Gli effectors

Background

Ureteral contractility is a poorly understood process. Contractions have been demonstrated to occur in the smooth muscle layers of the ureter. Previous work suggests the involvement of Gli family proteins and erythropoietin (EPO) in regulating mammalian ureteral smooth muscle contraction. We sought to devise a method by which the effects of these proteins and tamsulosin on distal human ureteral tissue contractility could be investigated to better understand mechanisms regulating human ureteral function.

Methods

IRB approval was obtained to procure portions of extraneous distal ureteral tissue from living donor renal transplants. Contractility was measured by placing the tissue in Krebs buffer and stimulating via a uniform electric current. Contractile force was recorded with each stimulation with and without the presence of a Gli inhibitor (GANT61) or EPO. Each ureteral specimen was subsequently fixed and tested by immunohistochemistry to determine Gli, EPO and alpha-adrenergic receptor activity.

Results

Electrical field stimulation successfully elicited contractions in the ureteral tissue. Administering tamsulosin decreased force and duration of ureteral contractions. Inhibiting Gli signaling decreased contractility and EPO decreased ureteral contractile forces within 5 minutes of administration versus untreated controls. Staining confirmed Gli1 protein and α-adrenergic receptor expression in ureteral smooth muscle and epithelial tissue with EPO receptor expression confined to the epithelial layer.

Conclusions

Distal ureteral contractile forces are decreased by inhibition of Gli family proteins and the α-adrenergic receptor. EPO acts within five minutes, suggesting ion channel involvement instead of changes in gene expression. Continuing work will elucidate the role of these proteins in coordinating ureteral contractions. This has implications for the use of pharmacologic methods to address ureteral contractility and dysfunctional peristalsis during stone passage, ureteroscopy, in transplant patients and potentially to reduce symptoms from ureteral stents.

MiRNA-Wnt signaling regulatory network in colorectal cancer

Colorectal cancer (CRC) is one of the common malignancies worldwide and the Wnt signaling pathway is recognized as the main disrupted pathway in this malignancy. MicroRNAs (miRNAs) are recognized to contribute to the pathogenesis of CRC by triggering or impeding the Wnt signaling pathway. In addition, transcriptional regulation of miRNAs by canonical Wnt signaling also participates in CRC cell progression. In this review, we present comprehensive literature of the existing data on the interaction of miRNAs and Wnt signaling that could be useful in future studies in the field of CRC management.

GLI1: A Therapeutic Target for Cancer

GLI1 is a transcriptional effector at the terminal end of the Hedgehog signaling (Hh) pathway and is tightly regulated during embryonic development and tissue patterning/differentiation. GLI1 has low-level expression in differentiated tissues, however, in certain cancers, aberrant activation of GLI1 has been linked to the promotion of numerous hallmarks of cancer, such as proliferation, survival, angiogenesis, metastasis, metabolic rewiring, and chemotherapeutic resistance. All of these are driven, in part, by GLI1’s role in regulating cell cycle, DNA replication and DNA damage repair processes. The consequences of GLI1 oncogenic activity, specifically the activity surrounding DNA damage repair proteins, such as NBS1, and cell cycle proteins, such as CDK1, can be linked to tumorigenesis and chemoresistance. Therefore, understanding the underlying mechanisms driving GLI1 dysregulation can provide prognostic and diagnostic biomarkers to identify a patient population that would derive therapeutic benefit from either direct inhibition of GLI1 or targeted therapy towards proteins downstream of GLI1 regulation.

Targeting the GLI family of transcription factors for the development of anti-cancer drugs

INTRODUCTION

GLI1 is a transcription factor that has been identified as a downstream effector for multiple tumorigenic signaling pathways. These include the Hedgehog, RAS-RAF-MEK-ERK, and PI3K-AKT-mTOR pathways, which have all been separately validated as individual anti-cancer drug targets. The identification of GLI1 as a key transcriptional regulator for each of these pathways highlights its promise as a therapeutic target. Small molecule GLI1 inhibitors are potentially efficacious against human malignancies arising from multiple oncogenic mechanisms.

AREAS COVERED

This review provides an overview of the key oncogenic cellular pathways that regulate GLI1 transcriptional activity. It also provides a detailed account of small molecule GLI1 inhibitors that are currently under development as potential anti-cancer chemotherapeutics.

EXPERT OPINION

Interest in developing inhibitors of GLI1-mediated transcription has significantly increased as its role in multiple oncogenic signaling pathways has been elucidated. To date, it has proven difficult to directly target GLI1 with small molecules, and the majority of compounds that inhibit GLI1 activity function through indirect mechanisms. To date, no direct-acting GLI1 inhibitor has entered clinical trials. The identification and development of new scaffolds that can bind and directly inhibit GLI1 are essential to further advance this class of chemotherapeutics.

The Role of Hedgehog Pathway in Female Cancers

Background:

The hedgehog pathway (HH) is one of the key regulators involved in many biological events. Malfunction of this pathway is associated with a variety of diseases including several types of cancers.

Methods:

We collected data from public databases and conducted a comprehensive search linking the HH pathway with female cancers. In addition, we overviewed clinical trials of targeting HH pathway in female cancers.

Results:

The activation of HH pathway and its role in female cancers, including breast cancer, ovarian cancer, cervical cancer, endometrial cancer, and uterine leiomyosarcoma were summarized. Treatment options targeting SMO and GLI in HH pathway were reviewed and discussed.

Conclusions:

The hedgehog pathway was shown to be activated in several types of female cancers. Therefore, targeting HH pathway may be considered as a therapeutic option to be acknowledged in the treatment of female cancers.

The Hedgehog signaling pathway promotes chemotherapy resistance via multidrug resistance protein 1 in ovarian cancer

Various studies have revealed that the Hedgehog (Hh) signaling pathway promotes ovarian cancer invasion, migration and drug resistance. Previous studies by our group have identified a set of genes, including multidrug resistance gene 1 (MDR1), that are regulated by Hh signaling in ovarian cancer. However, the association between Hh signaling activation and MDR1 expression requires further validation. In the present study, reverse transcription-quantitative PCR or western blot assays were used to evaluate the mRNA and protein expression levels of MDR1, Sonic Hh (Shh), glioma-associated oncogene 2 (Gli2), Gli1 and γ-phosphorylated H2A.X variant histone (γ-H2AX). MTT and colony-formation assays were performed to determine the effect of cisplatin (DDP) after inhibiting the Hh pathway in ovarian cancer cells. The results indicated that MDR1, Gli2 and Shh levels were much higher in SK-OV-3 cells with acquired DDP resistance than in native SK-OV-3 cells. ES-2 cells with overexpression of Gli2 were capable of efficiently forming colonies in the presence of low DDP concentrations. By contrast, Gli2 knockdown in SK-OV-3 cells decreased the colony-forming ability under the same concentration of DDP. As determined by MTT assays, knockdown of Gli2 or targeting of the Hh signaling pathway with either Gli-antagonist 61 (GANT61) or cyclopamine, in combination with DDP treatment, diminished the viability of ES-2 and SK-OV-3 cells, whereas Gli2 overexpression increased the viability of ES-2 cells in the presence of DDP. Knockdown of Gli2 or targeting the Hh signaling pathway with GANT61 also increased γ-H2AX levels but decreased the expression of MDR1 in the presence of DDP. MDR1 expression is regulated by the Hh signaling pathway and is likely a downstream transcription factor of Gli2. In conclusion, targeting the Hh signaling pathway increases the sensitivity of ovarian cancer to DDP. MDR1 is a target gene of the Hh signaling pathway and this pathway may affect chemoresistance of ovarian cancer to DDP via MDR1.

Cyclopamine sensitizes glioblastoma cells to temozolomide treatment through Sonic hedgehog pathway

AIM

Glioblastoma is an extremely aggressive glioma, resistant to radio and chemotherapy usually performed with temozolomide. One of the main reasons for glioblastoma resistance to conventional therapies is due to the presence of cancer stem-like cells. These cells could recapitulate some signaling pathways important for embryonic development, such as Sonic hedgehog. Here, we investigated if the inhibitor of the Sonic hedgehog pathway, cyclopamine, could potentiate the temozolomide effect in cancer stem-like cells and glioblastoma cell lines in vitro.

MAIN METHODS

The viability of glioblastoma cells exposed to cyclopamine and temozolomide treatment was evaluated by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay while the induction of apoptosis was assessed by western blot. The stemness properties of glioma cells were verified by clonogenic and differentiation assay and the expression of stem cell markers were measured by fluorescence microscopy and western blot.

KEY FINDINGS

The glioblastoma viability was reduced by cyclopamine treatment. Cyclopamine potentiated temozolomide treatment in glioblastoma cell lines by inducing apoptosis through activation of caspase-3 cleaved. Conversely, the combined treatment of cyclopamine and temozolomide potentiated the stemness properties of glioblastoma cells by inducing the expression of SOX-2 and OCT-4.

SIGNIFICANCE

Cyclopamine plays an effect on glioblastoma cell lines but also sensibilize them to temozolomide treatment. Thus, first-line treatment with Sonic hedgehog inhibitor followed by temozolomide could be used as a new therapeutic strategy for glioblastoma patients.

The hedgehog pathway regulates cancer stem cells in serous adenocarcinoma of the ovary

PURPOSE

Signaling by cancer stem cells (CSCs) is known to occur at least in part through conserved developmental pathways. Here, the role of one of these pathways, i.e., the hedgehog pathway, was evaluated in high-grade serous ovarian carcinoma (HGSOC).

METHODS AND RESULTS

We found that in HGSOC, hedgehog inhibitors (HHIs) GANT61, LDE225 and GDC0449 reduced or inhibited the formation of spheroids enriched in CSCs. Primary malignant cells (PMCs) in ascites from HGSOC patients cultured in the presence of HHIs showed significant reduction in CSCs. Sonic hedgehog (SHH) significantly increased the expression of ALDH1A1, which was inhibited by GANT61. In the presence of a SHH neutralizing antibody (5E1), a significant reduction in the number of spheroids was observed in HGSOC-derived cell lines. Further, the motility, migration and clonogenic growth of the cells were significantly reduced by HHIs. In the presence of GANT61, a reduction of cells from PMCs in the G0 phase of the cell cycle was observed. The magnitude of difference in expression of Gli1 in tumors from the same HGSOC patients at presentation and at interval debulking surgery was greater in patients who had a recurrence on follow up. GANT61 also significantly inhibited the growth of CSCs in nude mice. Finally, RNA sequencing of HGSOC cells treated with GANT61 showed a significantly reduced expression of CSC markers.

CONCLUSIONS

Our results indicate that the hedgehog pathway plays an important role in maintaining the integrity of CSCs in HGSOC and could be a potential therapeutic target.

CDK4/6 inhibition suppresses tumour growth and enhances the effect of temozolomide in glioma cells

In adults, glioma is the most commonly occurring and invasive brain tumour. For malignant gliomas, the current advanced chemotherapy includes TMZ (temozolomide). However, a sizeable number of gliomas are unyielding to TMZ, hence, giving rise to an urgent need for more efficient treatment choices. Here, we report that cyclin-dependent kinases 4 (CDK4) is expressed at significantly high levels in glioma cell lines and tissues. CDK4 overexpression enhances colony formation and proliferation of glioma cells and extends resistance to inhibition of TMZ-mediated cell proliferation and induction of apoptosis. However, CDK4 knockdown impedes colony formation and cell proliferation, and enhances sensitivity of glioma cells to TMZ. The selective inhibition of CDK4/6 impedes glioma cell proliferation and induces apoptotic induction. The selective inhibitors of CDK4/6 may enhance glioma cell sensitivity to TMZ. We further showed the possible role of RB phosphorylation mediated by CDK4 for its oncogenic function in glioma. The growth of glioma xenografts was inhibited in vivo, through combination treatment, and corresponded to enhanced p-RB levels, reduced staining of Ki-67 and enhanced activation of caspase 3. Therefore, CDK4 inhibition may be a favourable strategy for glioma treatment and overcomes TMZ resistance.

Hedgehog Signal Inhibitor GANT61 Inhibits the Malignant Behavior of Undifferentiated Hepatocellular Carcinoma Cells by Targeting Non-Canonical GLI Signaling

The Hedgehog (HH)–GLI pathway plays an important role in cell dedifferentiation and is therefore pivotally involved in the malignant transformation of cancer cells. GANT61, a selective inhibitor of GLI1 and GLI2, was reported as a promising treatment for cancer in various tissues; however, the biological impact of GANT61 in hepatocellular carcinoma (HCC), especially in undifferentiated HCC cells, remains unclear. In this study, we investigated the antitumor effect of GANT61 using two undifferentiated hepatoma cell lines: HLE and HLF. Quantitative PCR and RT-PCR analyses revealed that these cells express GLI transcripts, showing mesenchymal phenotypes characterized by the loss of epithelial and hepatic markers and specific expression of epithelial–mesenchymal transition (EMT)-related genes. GANT61 significantly reduced the proliferation and cell viability after drug treatment using 5-FU and Mitomycin C. We showed that GLI transcript levels were down-regulated by the MEK inhibitor U0126 and the Raf inhibitor sorafenib, suggesting that non-canonical signaling including the Ras–Raf–MEK–ERK pathway is involved. Sphere formation and migration were significantly decreased by GANT61 treatment, and it is suggested that the underlying molecular mechanisms are the down-regulation of stemness-related genes (Oct4, Bmi1, CD44, and ALDH) and the EMT-related gene Snail1. The data presented here showed that direct inhibition of GLI might be beneficial for the treatment of dedifferentiated HCC.

GLI1 is increased in ovarian endometriosis and regulates migration, invasion and proliferation of human endometrial stromal cells in endometriosis

BACKGROUND

Endometriosis is a benign gynecological disorder which shares certain characteristics with malignant tumor like migration, invasion and proliferation. Glioma-associated oncogene homolog 1 (GLI1) has been implicated in some cancers including endometrial cancer, however, its role in endometriosis remains unknown.

METHODS

The aim of this study was to explore the expression pattern of GLI1 in endometriosis, and further investigate the effect of GLI1 regulation on human endometrial stromal cells. The expression of GLI1 in normal endometrium and ectopic tissues was analyzed by immunohistochemistry, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. The Short hairpin RNA (ShRNA) intervention technique and GLI1 inhibitor GANT-61 were used to silence GLI1. The expression levels of GLI1, MMP2 and MMP9 was detected by qRT-PCR and western blot. The migration and invasion ability of human endometrial stromal cells was determined by wound healing assay and transwell migration/invasion assay. The viability and proliferation potentiality of cells was detected by MTT assays and colony formation assay, respectively.

RESULTS

We found that the expression of GLI1 mRNA and protein were significantly higher in ectopic endometrium from patients with endometriosis. Our analyses also show that GLI1 downregulation attenuated cells migration, invasion and proliferation abilities. What's more, reduced expression of GLI1 inhibited the expression of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9).

CONCLUSIONS

Our findings suggest that high levels of GLI1 may contribute to the development of endometriosis by promoting cell migration, invasion and proliferation involving regulation of MMP2 and MMP9 expression. Therefore, inhibition of GLI1 might be a novel potential therapeutic approach to the treatment of endometriosis, which sheds new light on our understanding of the pathogenesis of endometriosis.

GLI1-amplifications expand the spectrum of soft tissue neoplasms defined by GLI1 gene fusions

GLI1 fusions involving ACTB, MALAT1, and PTCH1 genes have been recently reported in a subset of malignant soft tissue tumors with characteristic monomorphic nested epithelioid morphology and frequent S100 positivity. However, we encountered a group of morphologically similar soft tissue tumors lacking the canonical GLI1 gene fusions and sought to investigate their genetic abnormalities. A combined approach including RNA sequencing, targeted exome sequencing and FISH methodologies were used to identify potential novel genetic abnormalities. Ten patients (five females, five males) with an age range of 4-65 years (median 32.5) were identified. Tumors were located in the soft tissues of the limbs, trunk and head and neck, with one each in the tongue and lung. Histologically, tumors revealed ovoid to epithelioid cells arranged in a distinctive nested-trabecular pattern, separated by thin septa and a delicate vascular network. Two cases showed areas of increased nuclear pleomorphism and focal fascicular spindle cell growth. Four tumors showed a high mitotic count (≥15/10 HPFs), with necrosis seen in three of them. Lymphovascular invasion was noted in two cases. No consistent immunoprofile was detected, with positivity for CD56 (six cases), S100 (four cases), SMA (two cases), and pan-CK (one case). FISH showed GLI1 (12q13.3) gene amplification in all 10 cases, with co-amplification of CDK4 (12q14.1) in nine (90%) and MDM2 (12q15) in eight (80%) cases. Targeted exome sequencing performed in three cases confirmed the GLI1, CDK4, and MDM2 co-amplification. Only one case showed the presence of both GLI1 break-apart and amplification, although no gene partner was detected. Our findings suggest that GLI1 amplification, often associated with co-amplifications of CDK4 and MDM2 genes, may represent an alternative genetic mechanism of GLI1 oncogenic activation akin to GLI1 fusions, defining the pathogenesis of an emerging group of malignant soft tissue tumors with a distinctive nested growth pattern and variable immunoprofile.

Repurposing Penfluridol in Combination with Temozolomide for the Treatment of Glioblastoma

Despite the presence of aggressive treatment strategies, glioblastoma remains intractable, warranting a novel therapeutic modality. An oral antipsychotic agent, penflurido (PFD), used for schizophrenia treatment, has shown an antitumor effect on various types of cancer cells. As glioma sphere-forming cells (GSCs) are known to mediate drug resistance in glioblastoma, and considering that antipsychotics can easily penetrate the blood-brain barrier, we investigated the antitumor effect of PFD on patient-derived GSCs. Using five GSCs, we found that PFD exerts an antiproliferative effect in a time- and dose-dependent manner. At IC50, spheroid size and second-generation spheroid formation were significantly suppressed. Stemness factors, SOX2 and OCT4, were decreased. PFD treatment reduced cancer cell migration and invasion by reducing the Integrin α6 and uPAR levels and suppression of the expression of epithelial-to-mesenchymal transition (EMT) factors, vimentin and Zeb1. GLI1 was found to be involved in PFD-induced EMT inhibition. Furthermore, combinatorial treatment of PFD with temozolomide (TMZ) significantly suppressed tumor growth and prolonged survival in vivo. Immunostaining revealed decreased expression of GLI1, SOX2, and vimentin in the PFD treatment group but not in the TMZ-only treatment group. Therefore, PFD can be effectively repurposed for the treatment of glioblastoma by combining it with TMZ.

QKI deficiency maintains glioma stem cell stemness by activating the SHH/GLI1 signaling pathway

PURPOSE

Glioblastoma (GBM) stem cells (GSCs) have been found to be the main cause of malignant GBM progression. It has also been found that Quaking homolog (QKI) plays a predominant role in driving GBM development. Here, we aimed to asses the role of QKI in maintaining GSC stemness and inducing the invasiveness of GBM cells.

METHODS

Public databases were used to assess the expression of QKI and its correlation with stemness markers in primary GBMs. The CRISPR-Cas9 technology was used to generate QKI knockout GBM cells, and RNA immunoprecipitation was used to assess QKI-GLI1 protein-mRNA interactions. In addition, in vitro and in vivo GBM cell proliferation, migration, xenografting and neurosphere formation assays were performed.

RESULTS

Using public GBM databases, QKI was identified as a potential GSC regulator. We found that QKI could inhibit stem-like cell (SLC) stemness and prolong the survival of xenografted mice. Mechanistically, we found that QKI knockout increased the GLI Family Zinc Finger 1 (GLI1) mRNA level, which is essential for maintaining the self-renewal ability of GSCs. In addition, we found that QKI knockout activated the Hedgehog signaling pathway via Tra-2 and GLI response element (TGE)-specific GLI1 mRNA disruption.

CONCLUSION

Our data indicate that upregulation of GLI1 induced by QKI deficiency maintains GSC stemness and enhances the invasiveness of GBM cells, thereby hinting at new options for the treatment of GBM.

Safety and Tolerability of Sonic Hedgehog Pathway Inhibitors in Cancer

The hedgehog pathway, for which sonic hedgehog (Shh) is the most prominent ligand, is highly conserved and is tightly associated with embryonic development in a number of species. This pathway is also tightly associated with the development of several types of cancer, including basal cell carcinoma (BCC) and acute promyelocytic leukemia, among many others. Inactivating mutations in Patched-1 (PTCH1), leading to ligand-independent pathway activation, are frequent in several cancer types, but most prominent in BCC. This has led to the development of several compounds targeting this pathway as a cancer therapeutic. These compounds target the inducers of this pathway in Smoothened (SMO) and the GLI transcription factors, although targeting SMO has had the most success. Despite the many attempts at targeting this pathway, only three US FDA-approved drugs for cancers affect the Shh pathway. Two of these compounds, vismodegib and sonidegib, target SMO to suppress signaling from either PTCH1 or SMO mutations that lead to upregulation of the pathway. The other approved compound is arsenic trioxide, which can suppress this pathway at the level of the GLI proteins, although current evidence suggests it also has other targets. This review focuses on the safety and tolerability of these clinically approved drugs targeting the Shh pathway, along with a discussion on other Shh pathway inhibitors being developed.

Recent Advances in the Clinical Targeting of Hedgehog/GLI Signaling in Cancer

The Hedgehog/GLI signaling pathway plays an important role in normal embryonic tissue development and has been implicated in the pathogenesis of various human cancers. In this review article, we summarize pre-clinical evidence supporting the suitability of targeting this signaling pathway in cancers. We review agents blocking both the ligand-dependent and ligand-independent cascades, and discuss the clinical evidence, which has led to the FDA approval of Hedgehog receptor Smoothened inhibitors, vismodegib, and sonidegib, in different malignancies. Finally, we provide an overview of published and ongoing clinical trial data on single agent or combination therapeutic strategies, targeting Hedgehog/GLI signaling pathway, in both advanced solid tumors and hematologic malignancies.

Arsenic Trioxide and (-)-Gossypol Synergistically Target Glioma Stem-Like Cells via Inhibition of Hedgehog and Notch Signaling

Glioblastoma is one of the deadliest malignancies and is virtually incurable. Accumulating evidence indicates that a small population of cells with a stem-like phenotype is the major culprit of tumor recurrence. Enhanced DNA repair capacity and expression of stemness marker genes are the main characteristics of these cells. Elimination of this population might delay or prevent tumor recurrence following radiochemotherapy. The aim of this study was to analyze whether interference with the Hedgehog signaling (Hh) pathway or combined Hh/Notch blockade using small-molecule inhibitors can efficiently target these cancer stem cells and sensitize them to therapy. Using tumor sphere lines and primary patient-derived glioma cultures we demonstrate that the Hh pathway inhibitor GANT61 (GANT) and the arsenic trioxide (ATO)-mediated Hh/Notch inhibition are capable to synergistically induce cell death in combination with the natural anticancer agent (−)-Gossypol (Gos). Only ATO in combination with Gos also strongly decreased stemness marker expression and prevented sphere formation and recovery. These synergistic effects were associated with distinct proteomic changes indicating diminished DNA repair and markedly reduced stemness. Finally, using an organotypic brain slice transplantation model, we show that combined ATO/Gos treatment elicits strong growth inhibition or even complete elimination of tumors. Collectively, our data show for the first time that ATO and Gos, two drugs that can be used in the clinic, represent a promising targeted therapy approach for the synergistic elimination of glioma stem-like cells.

Oroxylin A increases the sensitivity of temozolomide on glioma cells by hypoxia-inducible factor 1α/hedgehog pathway under hypoxia

Microenvironmental hypoxia-mediated drug resistance is responsible for the failure of cancer therapy. To date, the role of the hedgehog pathway in resistance to temozolomide (TMZ) under hypoxia has not been investigated. In this study, we discovered that the increasing hypoxia-inducible factor 1α (HIF-1α) activated the hedgehog pathway in hypoxic microenvironment by promoting autocrine secretion of sonic hedgehog protein (Shh), and then upregulating transfer of Gli1 to the nucleus, finally contributed to TMZ resistance in glioma cells. Oroxylin A (C16H12O5), a bioactive flavonoid, could induce HIF-1α degradation via prolyl-hydroxylases-VHL signaling pathway, resulting in the inactivation of the hedgehog. Besides, oroxylin A increased the expression of Sufu, which is a negative regulator of Gli1. By this mechanism, oroxylin A sensitized TMZ on glioma cells. U251 intracranial transplantation model and GL261 xenograft model were used to confirm the reversal effects of oroxylin A in vivo. In conclusion, our results demonstrated that HIF-1α/hedgehog pathway conferred TMZ resistance under hypoxia, and oroxylin A was capable of increasing the sensitivity of TMZ on glioma cells in vitro and in vivo by inhibiting HIF-1α/hedgehog pathway and depressing the activation of Gli1 directly.

Abnormal activity of transcription factors gli in high-grade gliomas

Malignant transformation is associated with loss of cell differentiation, anaplasia. Transcription factors gli, required for embryonic development, may be involved in this process. We studied the activity of transcription factors gli in high-grade gliomas and their role in maintenance of stem cell state and glioma cell survival. 20 glioma cell lines and a sample of a normal adult brain tissue were used in the present study. We found the expression of gli target genes, including GLI1 and FOXM1, in all tested glioma cell lines, but not in the normal tissue. Interestingly, the expression of gli target genes in some glioma cell lines was observed together with a high level of their transcriptional repressor, Gli3R. Knockdown of GLI3 in one of these lines resulted in decrease of gli target gene expression. These data suggest that Gli3R does not prevent the gli target genes transcription, and gli3 acts in glioma cells more as an activator, than a repressor of transcription. We observed that gli regulated the expression of such genes, as SOX2 or OCT4 that maintain stem cell state, and TET1, involving in DNA demethylation. Treatment with GANT61 or siRNA against GLI1, GLI2, or GLI3 could result in complete glioma cell death, while cyclopamine had a weaker and line-specific effect on glioma cell survival. Thus, the gli transcription factors are abnormally active in high-grade gliomas, regulate expression of genes, maintaining the stem cell state, and contribute to glioma cell survival.

Suppression of minichromosome maintenance 7 expression sensitizes chronic lymphocytic leukemia cells to fludarabine

Chronic lymphocytic leukemia (CLL) constitutes the largest percentage of adult leukemia cases in Western countries. Classically, fludarabine (Flu) is an effective drug used as a first-line therapy for CLL; however, Flu resistance limits its clinical effect. Minichromosome maintenance (MCM) complex components 2-7 exert important functions in maintaining genomic stability. Replication stress occurs upon dysregulation of MCM7, which potentiates malignant phenotypes. In this study, primary CLL cells and CLL-derived cell lines displayed elevated MCM7 expression. In CD40-stimulated primary CLL cells, MCM7 inhibition resulted in increased Flu-induced apoptosis and delayed repair of DNA damage. In the MEC-1 and EHEB cell lines, knockdown of MCM7 with lentivirus significantly inhibited cell proliferation and promoted cell cycle arrest at S phase. Moreover, MCM7 silencing sensitized both cell lines to Flu by increasing replication stress. The combination of Flu administration with MCM7 inhibition represents a novel approach to reverse Flu resistance in CLL.

MCCK1 enhances the anticancer effect of temozolomide in attenuating the invasion, migration and epithelial-mesenchymal transition of glioblastoma cells in vitro and in vivo

Chemotherapy with temozolomide (TMZ) is the traditional treatment for glioblastoma (GBM). Nevertheless, majority of GBM patients have recurrence from resistance to the chemotherapy. Herein, we examined combinational effects of MCCK1 (a specific and effective IKKε inhibitor) with TMZ in GBM U251MG and U‐87MG cell lines as well as U251MG xenograft models to overcome the therapeutic limitation of chemotherapy for GBM. Although MCCK1 alone showed inhibitory effects on in vitro proliferation, migration, invasion, and EMT of U251MG and U‐87MG cells, combination of MCCK1 and TMZ showed enhanced inhibitory effects. In the U251MG GBM xenograft models, MCCK1 showed synergistic therapeutic effects in combination with TMZ to reduce tumor volumes significantly. These data indicated that MCCK1 could be a candidate sensitizer to potentiate therapeutic effects of conventional cytotoxic treatment for GBM.

TRA2A promotes proliferation, migration, invasion and epithelial mesenchymal transition of glioma cells

TRA2A, Transformer2A proteins, plays important roles in paclitaxel resistance and progression of breast cancer. However, whether TRA2A was involved in the progression of glioma remains to be elucidated. In this study, our results demonstrated that the expression of TRA2A was higher in the glioma tissue than that of normal tissue. Overexpression of TRA2A in glioma SHG44 cell lines promoted the tumor cells proliferation, migration, invasion and epithelial mesenchymal transition (EMT), while, knockdown of TRA2A showed the opposite effect. Thus, our findings provide new insights into the role of TRA2A in the progression of glioma, and implicate the potential application of TRA2A in glioma therapy.

GLI2 promotes cell proliferation and migration through transcriptional activation of ARHGEF16 in human glioma cells

BACKGROUND

The Hedgehog (Hh) signaling pathway plays critical roles in modulating embryogenesis and maintaining tissue homeostasis, with glioma-associated oncogene (GLI) transcription factors being the main mediators. Aberrant activation of this pathway is associated with various human malignancies including glioblastoma, although the mechanistic details are not well understood.

METHODS

We performed a microarray analysis of genes that are differentially expressed in glioblastoma U87 cells overexpressing GLI2A, the active form of GLI2, relative to the control cells. Chromatin immunoprecipitation and dual-luciferase assays were used to determine whether Rho guanine nucleotide exchange factor 16 (ARHGEF16) is a downstream target of GLI2. Then, transwell migration, EdU and soft-agar colony formation assays were employed to test effects of ARHGEF16 on glioma cancer cell migration and proliferation, and the effects of GLI2/ARHGEF16 signaling on tumor growth were examined in vivo. Finally, we performed yeast two-hybrid assay, Co-IP and GST-pull down to identify factors that mediate effects of ARHGEF16.

RESULTS

We found that ARHGEF16 mRNA level was upregulated in U87 cells overexpressing GLI2A relative to control cells. GLI2 binds to the ARHGEF16 promoter and activates gene transcription. Glioma cells U87 and U118 overexpressing ARHGEF16 showed enhanced migration and proliferation relative to the control cells, while knockdown of ARHGEF16 in H4 cells led to decreased cell proliferation compared to the control H4 cells. In contrast to the promoting effect of GLI2A overexpression on glioma xenograft growth, both GLI2 inhibition and ARHGEF16 knockdown retarded tumor growth. Cytoskeleton-associated protein 5 (CKAP5) was identified as an interaction protein of ARHGEF16, which is important for the stimulatory effects of ARHGEF16 on glioma cell migration and proliferation.

CONCLUSIONS

These results suggest that therapeutic strategies targeting the GLI2/ARHGEF16/CKAP5 signaling axis could inhibit glioma progression and recurrence.

Potential use of CXCL12/CXCR4 and sonic hedgehog pathways as therapeutic targets in medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor occurring in children, and although high long-term survival rates have been reached with current therapeutic protocols, several neurological injuries are still observed among survivors. It has been shown that the development of MB is highly dependent on the microenvironment surrounding it and that the CXCL12 chemokine and its receptor, CXCR4 and the Sonic Hedgehog (SHH) pathway are crucial for cerebellar development, coordinating proliferation and migration of embryonic cells and malfunctions in these axes can lead to MB development. Indeed, the concomitant overactivation of these axes was suggested to define a new MB molecular subgroup. New molecules are being studied, aiming to inhibit either CXCR4 or the SHH pathways and have been tested in preclinical settings for the treatment of cancers. The use of these molecules could improve MB treatment and save patients from aggressive surgery, chemotherapy and radiotherapy regimens, which are responsible for severe neurological consequences. This review aims to summarize current data about the experimental inhibition of CXCR4 and SHH pathways in MB and its potential implications in treatment of this cancer.

Targeting the Notch1 oncogene by miR-139-5p inhibits glioma metastasis and epithelial-mesenchymal transition (EMT)

BACKGROUND

Glioma metastasis, invasion, epithelial-mesenchymal transition (EMT) and chemoresistance indicate poor prognosis. Accumulating evidence reveals that Notch1 is an important factor in tumour progression. However, the role of Notch1 in glioma EMT and associated microRNAs (miRNAs) with the Notch pathway remain controversial.

METHODS

Utilizing cBioPortal database to examine the gene signature of NOTCH1 (encoding Notch1), CDH2 (encoding N-cadherin) and SNAI1 (encoding Snail-1) in disease-free survival (DFS) and overall survival (OS). We analyzed the Notch1 expression from Oncomine. We used Western blot (WB), immunohistochemistry (IHC) and immunofluorescence to determine protein levels. Transcription was evaluated by quantitative real-time (qRT)-PCR. siRNA and lentivirus were used to knock down Notch1 and overexpress miR-139-5p, respectively. The migration and invasion of glioma cells were assessed by wound healing and transwell assays. Luciferase reporter assays were utilized to verify the relationship between Notch1 and miR-139-5p. A U87-implanted intracranial model was used to study the effect of miR-139-5p on tumour growth and Notch1 suppression efficacy or EMT reversion.

RESULTS

It revealed the association of NOTCH1, CDH2, SNAI1 genomic alterations with decreases in DFS and OS. Notch1 was upregulated in classical and proneural subtypes of GBM, and associated with tumour grade. Notch1 inhibition suppressed the biological behaviours of metastasis, invasion and EMT. Notch1 was identified as a novel direct target of miR-139-5p. MiR-139-5p overexpression partially phenocopied Notch1 siRNA, whereas the forced expression of Notch1 reversed the effects of miR-139-5p on the invasion of glioma. Moreover, intracranial tumourigenicity and EMT behaviours were reduced by the introduction of miR-139-5p and partially mediated by the decreased Notch1 expression.

CONCLUSIONS

miR-139-5p was identified as a tumour suppressor by negatively targeting Notch1, and this work suggests a possible molecular mechanism of the miR-139/Notch1/EMT axis for glioma treatment.

Role of GLI Transcription Factors in Pathogenesis and Their Potential as New Therapeutic Targets

GLI transcription factors have important roles in intracellular signaling cascade, acting as the main mediators of the HH-GLI signaling pathway. This is one of the major developmental pathways, regulated both canonically and non-canonically. Deregulation of the pathway during development leads to a number of developmental malformations, depending on the deregulated pathway component. The HH-GLI pathway is mostly inactive in the adult organism but retains its function in stem cells. Aberrant activation in adult cells leads to carcinogenesis through overactivation of several tightly regulated cellular processes such as proliferation, angiogenesis, EMT. Targeting GLI transcription factors has recently become a major focus of potential therapeutic protocols.

CAT3, a prodrug of 13a(S)-3-hydroxyl-6,7-dimethoxyphenanthro[9,10-b]-indolizidine, circumvents temozolomide-resistant glioblastoma via the Hedgehog signaling pathway, independently of O6-methylguanine DNA methyltransferase expression

PURPOSE

Glioblastoma multiforme (GBM) is a malignant high-grade glioma with a poor clinical outcome. Temozolomide (TMZ) is the first-line GBM chemotherapy; however, patients commonly develop resistance to its effects.

MATERIALS AND METHODS

We investigated the antitumor activity of CAT3 in TMZ-resistant glioblastoma cell lines U251/TMZ and T98G. Orthotopic and subcutaneous mice tumor models were used to investigate the effects of various treatment regimes.

RESULTS

We found that PF403, the active metabolite of CAT3, inhibited proliferation of both cell lines. PF403 repressed the Hedgehog signaling pathway in the U251/TMZ cell line, reduced O6-methylguanine DNA methyltransferase (MGMT) expression, and abolished the effects of the Shh pathway. Moreover, PF403 blocked the Hedgehog signaling pathway in T98G MGMT-expressing cells and downregulated the expression of MGMT. CAT3 suppressed growth in the U251/TMZ orthotopic and T98G subcutaneous xenograft tumor models in vivo. We also demonstrated that inhibition of the Hedgehog pathway by PF403 counteracted TMZ resistance and enhanced the antitumor activity of TMZ in vitro and in vivo.

CONCLUSION

These results indicate that CAT3 is a potential therapeutic agent for TMZ-resistant GBM.

Targeting Transcription Factors for Cancer Treatment

Transcription factors are involved in a large number of human diseases such as cancers for which they account for about 20% of all oncogenes identified so far. For long time, with the exception of ligand-inducible nuclear receptors, transcription factors were considered as “undruggable” targets. Advances knowledge of these transcription factors, in terms of structure, function (expression, degradation, interaction with co-factors and other proteins) and the dynamics of their mode of binding to DNA has changed this postulate and paved the way for new therapies targeted against transcription factors. Here, we discuss various ways to target transcription factors in cancer models: by modulating their expression or degradation, by blocking protein/protein interactions, by targeting the transcription factor itself to prevent its DNA binding either through a binding pocket or at the DNA-interacting site, some of these inhibitors being currently used or evaluated for cancer treatment. Such different targeting of transcription factors by small molecules is facilitated by modern chemistry developing a wide variety of original molecules designed to specifically abort transcription factor and by an increased knowledge of their pathological implication through the use of new technologies in order to make it possible to improve therapeutic control of transcription factor oncogenic functions.

Investigating the role of Hedgehog/GLI1 signaling in glioblastoma cell response to temozolomide

Resistance to chemotherapy substantially hinders successful glioblastoma (GBM) treatment, contributing to an almost 100% mortality rate. Resistance to the frontline chemotherapy, temozolomide (TMZ), arises from numerous signaling pathways that are deregulated in GBM, including Hedgehog (Hh) signaling. Here, we investigate suppression of Hh signaling as an adjuvant to TMZ using U87-MG and T98G cell lines as in vitro models of GBM. We found that silencing GLI1 with siRNA reduces cell metabolic activity by up to 30% in combination with TMZ and reduces multidrug efflux activity by 2.5-fold. Additionally, pharmacological GLI inhibition modulates nuclear p53 levels and decreases MGMT expression in combination with TMZ. While we surprisingly found that silencing GLI1 does not induce apoptosis in the absence of TMZ co-treatment, we discovered silencing GLI1 without TMZ co-treatment induces senescence as evidenced by a significant 2.3-fold increase in senescence associated β-galactosidase staining, and this occurs in a loss of PTEN-dependent manner. Finally, we show that GLI inhibition increases apoptosis in glioma stem-like cells by up to 6.8-fold in combination with TMZ, and this reduces the size and number of neurospheres grown from glioma stem-like cells. In aggregate, our data warrant the continued investigation of Hh pathway inhibitors as adjuvants to TMZ chemotherapy and highlight the importance of identifying signaling pathways that determine whether co-treatment will be successful.

Combination epidermal growth factor receptor variant III peptide-pulsed dendritic cell vaccine with miR-326 results in enhanced killing on EGFRvIII-positive cells

The mutant Type III variant of epidermal growth factor receptor (EGFRvIII) is present in approximately one-third of glioblastoma (GBM) patients. It is never found in normal tissues; therefore, it represents a candidate target for GBM immunotherapy. PEPvIII, a peptide sequence from EGFRvIII, was designed to represent a target of glioma and is presented by MHC I/II complexes. Dendritic cells (DCs) have great potential to sensitize CD4+ T and CD8+ T cells to precisely target and eradicate GBM. Here, we show that PEPvIII could be loaded by DCs and presented to T lymphocytes, especially PEPvIII-specific CTLs, to precisely kill U87-EGFRvIII cells. In addition to inhibiting proliferation and inducing the apoptosis of U87-EGFRvIII cells, miR-326 also reduced the expression of TGF-β1 in the tumour environment, resulting in improved efficacy of T cell activation and killing via suppressing the SMO/Gli2 axis, which at least partially reversed the immunosuppressive environment. Furthermore, combining the EGFRvIII-DC vaccine with miR-326 was more effective in killing U87-EGFRvIII cells compared with the administration of either one alone. This finding suggested that a DC-based vaccine combined with miR-326 may induce more powerful anti-tumour immunity against GBM cells that express a relevant antigen, which provides a promising approach for GBM immunotherapy.

Aspirin inhibits the SHH/GLI1 signaling pathway and sensitizes malignant glioma cells to temozolomide therapy

Aberrant activation of sonic hedgehog (SHH)/glioma-associated oncogene homolog 1 (GLI1) pathway plays an important role in the tumorigenicity of malignant glioma cells and resistance to temozolomide (TMZ). Here we investigated the aspirin's antineoplastic molecular route by targeting SHH/GLI1 pathway and examined the feasibility of aspirin combined with TMZ therapy. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) revealed that the activity of the SHH/GLI1 pathway was strongly inhibited by aspirin. Aspirin acted as the glioma growth-inhibitory and pro-apoptosis roles by inhibiting the SHH/GLI1 pathway and reprogramming the epithelial to mesenchymal transition (EMT). The immunofluorescence assay showed aspirin could prevent the nuclear translocation of GLI1 to inhibit its transcriptional regulation. The stable lentiviral overexpression of GLI1 reversed the DNA double strand breaks (DSBs) caused by the GANT61 and TMZ. Furthermore, aspirin combined with TMZ enhanced chemosensitivity and GLI1-induced chemoprotection was partly blocked by aspirin in vitro and in vivo. Collectively, aspirin has a therapeutic potential for SHH/GLI1 targeted therapy against glioma cells. Acquired activation of GLI1 protects glioma cells against TMZ therapy. Impairment of DNA DSBs repair activity might be involved in the route of aspirin-induced chemosensitivity. Combined aspirin with TMZ may be a promising strategy against malignant glioma.