Targeting the hedgehog signal transduction pathway at the level of GLI inhibits neuroblastoma cell growth in vitro and in vivo

The mechanism of polyphyllin in the treatment of gastric cancer was verified based on network pharmacology and experimental validation

Background

Polyphyllin is a class of saponins extracted from Paris polyphylla rhizomes and has been used in clinical application in China for more than 2000 years. However, the mechanism for treating gastric cancer (GC) is still unclear. This study was designed to predict the targets and mechanisms of total Polyphyllin from Paris polyphylla rhizomes for the treatment of GC.

Method

Firstly, PubChem and Swiss Target Prediction databases were utilized to collect the 12 ingredients of total Polyphyllin from Paris polyphylla rhizomes and their targets. GC-related genes were obtained from the GEO database. Then the intersecting targets to all these molecules that identified using Venny. Secondly, the intersecting targets were imported into STRING platform for protein-protein interaction (PPI) network. Moreover, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted in DAVID website. In addition, the GEPIA was applied to perform the expression levels, transcript levels, staging, and overall survival of hub genes. In addition, we used AutoDock Vina to evaluate binding affinity of molecular docking between key ingredients and anti-GC targets. In vitro cell experiments, we detected the cell viability of gastric cancer cells at 24, 36, and 48 h using CCK-8 assay. The G0/G1 of cell cycle and apoptosis were detected by flow cytometry. Finally, quantitative real time polymerase chain reaction (qRT-PCR) was used to detect the level of hub genes, and Western blot was used to detect the changes of PI3K/Akt signal pathway.

Results

Firstly, we identified 12 ingredients and 286 targets of total Polyphyllin. A total of 2653 GC-related differentially expressed genes (DEGs) were collected, including 1366 up-regulated genes and 1287 down-regulated genes. Moreover, 45 targets were obtained after intersection. Secondly, results of the GO enrichment suggested that these genes were closely related to cell proliferation, migration and aging. KEGG analysis suggested that Polyphyllin in GC therapy were mostly regulated by multiple pathways, including the pathways in cancer, calcium signaling pathway, Rap1 signaling pathway, phospholipase D signaling pathway, etc. In addition, GEPIA results exhibited that PDGFRB, KIT, FGF1, GLI1, F2R, and HIF1A were associated with GC progression, stage, and survival. Besides, the molecular docking results further confirmed that the binding energy of Polyphyllin Ⅲ with HIF1A was minimal. In vitro cell experiments, Polyphyllin Ⅲ inhibited the cell viability of gastric cancer cells, blocked the cell cycle G0/G1 phase, and induced cell apoptosis. In addition, Polyphyllin Ⅲ down-regulated the mRNA levels of PDGFRB, KIT, FGF1, GLI1, F2R, and HIF1A, and regulated the PI3K/Akt signal pathway.

Conclusions

The results revealed that total Polyphyllin treated GC through multiple targets, multiple channels, and multiple pathways. In addition, Polyphyllin Ⅲ played an anti-gastric cancer role by inhibiting the proliferation of gastric cancer.

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.

Transcriptome analysis reveals molecular mechanisms of lymphocystis formation caused by lymphocystis disease virus infection in flounder (Paralichthys olivaceus)

Lymphocystis disease is frequently prevalent and transmissible in various teleost species worldwide due to lymphocystis disease virus (LCDV) infection, causing unsightly growths of benign lymphocystis nodules in fish and resulting in huge economic losses to aquaculture industry. However, the molecular mechanism of lymphocystis formation is unclear. In this study, LCDV was firstly detected in naturally infected flounder (Paralichthys olivaceus) by PCR, histopathological, and immunological techniques. To further understand lymphocystis formation, transcriptome sequencing of skin nodule tissue was performed by using healthy flounder skin as a control. In total, RNA-seq produced 99.36%-99.71% clean reads of raw reads, of which 91.11%-92.89% reads were successfully matched to the flounder genome. The transcriptome data showed good reproducibility between samples, with 3781 up-regulated and 2280 down-regulated differentially expressed genes. GSEA analysis revealed activation of Wnt signaling pathway, Hedgehog signaling pathway, Cell cycle, and Basal cell carcinoma associated with nodule formation. These pathways were analyzed to interact with multiple viral infection and tumor formation pathways. Heat map and protein interaction analysis revealed that these pathways regulated the expression of cell cycle-related genes such as ccnd1 and ccnd2 through key genes including ctnnb1, lef1, tcf3, gli2, and gli3 to promote cell proliferation. Additionally, cGMP-PKG signaling pathway, Calcium signaling pathway, ECM-receptor interaction, and Cytokine-cytokine receptor interaction associated with nodule formation were significantly down-regulated. Among these pathways, tnfsf12, tnfrsf1a, and tnfrsf19, associated with pro-apoptosis, and vdac2, which promotes viral replication by inhibiting apoptosis, were significantly up-regulated. Visual analysis revealed significant down-regulation of cytc, which expresses the pro-apoptotic protein cytochrome C, as well as phb and phb2, which have anti-tumor activity, however, casp3 was significantly up-regulated. Moreover, bcl9, bcl11a, and bcl-xl, which promote cell proliferation and inhibit apoptosis, were significantly upregulated, as were fgfr1, fgfr2, and fgfr3, which are related to tumor formation. Furthermore, RNA-seq data were validated by qRT-PCR, and LCDV copy numbers and expression patterns of focused genes in various tissues were also investigated. These results clarified the pathways and differentially expressed genes associated with lymphocystis nodule development caused by LCDV infection in flounder for the first time, providing a new breakthrough in molecular mechanisms of lymphocystis formation in fish.

Targeting the epigenome of cancer stem cells in pediatric nervous system tumors

Medulloblastoma, neuroblastoma, and pediatric glioma account for almost 30% of all cases of pediatric cancers. Recent evidence indicates that pediatric nervous system tumors originate from stem or progenitor cells and present a subpopulation of cells with highly tumorigenic and stem cell-like features. These cancer stem cells play a role in initiation, progression, and resistance to treatment of pediatric nervous system tumors. Histone modification, DNA methylation, chromatin remodeling, and microRNA regulation display a range of regulatory activities involved in cancer origin and progression, and cellular identity, especially those associated with stem cell features, such as self-renewal and pluripotent differentiation potential. Here, we review the contribution of different epigenetic mechanisms in pediatric nervous system tumor cancer stem cells. The choice between a differentiated and undifferentiated state can be modulated by alterations in the epigenome through the regulation of stemness genes such as CD133, SOX2, and BMI1 and the activation neuronal of differentiation markers, RBFOX3, GFAP, and S100B. Additionally, we highlighted the stage of development of epigenetic drugs and the clinical benefits and efficacy of epigenetic modulators in pediatric nervous system tumors.

Role of non-coding RNAs in neuroblastoma

Neuroblastoma is known as the most prevalent extracranial malignancy in childhood with a neural crest origin. It has been widely accepted that non-coding RNAs (ncRNAs) play important roles in many types of cancer, including glioma and gastrointestinal cancers. They may regulate the cancer gene network. According to recent sequencing and profiling studies, ncRNAs genes are deregulated in human cancers via deletion, amplification, abnormal epigenetic, or transcriptional regulation. Disturbances in the expression of ncRNAs may act either as oncogenes or as anti-tumor suppressor genes, and can lead to the induction of cancer hallmarks. ncRNAs can be secreted from tumor cells inside exosomes, where they can be transferred to other cells to affect their function. However, these topics still need more study to clarify their exact roles, so the present review addresses different roles and functions of ncRNAs in neuroblastoma.

GANT-61 induces cell cycle resting and autophagy by down-regulating RNAP III signal pathway and tRNA-Gly-CCC synthesis to combate chondrosarcoma

Chondrosarcoma is ineffective for conventional radiotherapy and chemotherapy with a poor prognosis. Hedgehog (Hh) signal pathway plays a crucial role in tumor growth and progression, which is constitutive activated in chondrosarcoma. GLI transcription factors as targets for new drugs or interference technology for the treatment of chondrosarcoma are of great significance. In this study, we indicated that the Hedgehog-GLI1 signal pathway is activated in chondrosarcoma, which further enhances the RNAP III signal pathway to mediate endogenous tRNA fragments synthesis. Downstream oncology functions of endogenous tRNA fragments, such as "cell cycle" and "death receptor binding", are involved in malignant chondrosarcoma. The GANT-61, as an inhibitor of GLI1, could inhibit chondrosarcoma tumor growth effectively by inhibiting the RNAP III signal pathway and tRNA-Gly-CCC synthesis in vivo. Induced G2/M cell cycle resting, apoptosis, and autophagy were the main mechanisms for the inhibitory effect of GANT-61 on chondrosarcoma, which correspond with the above-described downstream oncology functions of endogenous tRNA fragments. We also identified the molecular mechanism by which GANT-61-induced autophagy is involved in ULK1 expression and MAPK signaling pathway. Thus, GANT-61 will be an ideal and promising strategy for combating chondrosarcoma.

Role of sonic hedgehog ligand in gastric cancer therapeutics

Purpose

The abnormal activation of the sonic hedgehog (SHH) signaling pathway is responsible for the progression of several types of cancers including Gastric Cancer (GC). SHH has been associated with the activation of different signaling pathways. Therefore, in this study, we investigated messenger RNA (mRNA) and protein expression of SHH in gastric malignancies and possible correlation with various clinicopathological parameters.

Materials and Methods

A total of 53 surgically resected tumors and adjacent histologically normal tissues from GC patients were investigated in study subjects. A quantitative real-time polymerase chain reaction and immunohistochemistry methods were used for expression analysis of SHH.

Results

At mRNA level, SHH was overexpressed in 60% (27/45) of GC cases as compared to their adjacent normal tissues. SHH immunohistochemical analysis revealed abundant cytoplasmic localization and overexpression in 43.39% (23/53) of GC tissues. SHH overexpression was not associated with any of the clinicopathological parameters.

Conclusion

Our results showed that SHH is dysregulated in GC and might be considered as a biomarker for GC progression and can be used as a target in cancer therapeutics.

From mesenchymal niches to engineered in vitro model systems: Exploring and exploiting biomechanical regulation of vertebrate hedgehog signalling

Tissue patterning is the result of complex interactions between transcriptional programs and various mechanical cues that modulate cell behaviour and drive morphogenesis. Vertebrate Hedgehog signalling plays key roles in embryogenesis and adult tissue homeostasis, and is central to skeletal development and the osteogenic differentiation of mesenchymal stem cells. The expression of several components of the Hedgehog signalling pathway have been reported to be mechanically regulated in mesodermal tissue patterning and osteogenic differentiation in response to external stimulation. Since a number of bone developmental defects and skeletal diseases, such as osteoporosis, are directly linked to aberrant Hedgehog signalling, a better knowledge of the regulation of Hedgehog signalling in the mechanosensitive bone marrow-residing mesenchymal stromal cells will present novel avenues for modelling these diseases and uncover novel opportunities for extracellular matrix-targeted therapies. In this review, we present a brief overview of the key molecular players involved in Hedgehog signalling and the basic concepts of mechanobiology, with a focus on bone development and regeneration. We also highlight the correlation between the activation of the Hedgehog signalling pathway in response to mechanical cues and osteogenesis in bone marrow-derived mesenchymal stromal cells. Finally, we propose different tissue engineering strategies to apply the expanding knowledge of 3D material-cell interactions in the modulation of Hedgehog signalling in vitro for fundamental and translational research applications.

RNA-seq and ChIP-seq Identification of Unique and Overlapping Targets of GLI Transcription Factors in Melanoma Cell Lines

BACKGROUND

Despite significant progress in therapy, melanoma still has a rising incidence worldwide, and novel treatment strategies are needed. Recently, researchers have recognized the involvement of the Hedgehog-GLI (HH-GLI) signaling pathway in melanoma and its consistent crosstalk with the MAPK pathway. In order to further investigate the link between the two pathways and to find new target genes that could be considered for combination therapy, we set out to find transcriptional targets of all three GLI proteins in melanoma.

METHODS

We performed RNA sequencing on three melanoma cell lines (CHL-1, A375, and MEL224) with overexpressed GLI1, GLI2, and GLI3 and combined them with the results of ChIP-sequencing on endogenous GLI1, GLI2, and GLI3 proteins. After combining these results, 21 targets were selected for validation by qPCR.

RESULTS

RNA-seq revealed a total of 808 differentially expressed genes (DEGs) for GLI1, 941 DEGs for GLI2, and 58 DEGs for GLI3. ChIP-seq identified 527 genes that contained GLI1 binding sites in their promoters, 1103 for GLI2 and 553 for GLI3. A total of 15 of these targets were validated in the tested cell lines, 6 of which were detected by both RNA-seq and ChIP-seq.

CONCLUSIONS

Our study provides insight into the unique and overlapping transcriptional output of the GLI proteins in melanoma. We suggest that our findings could provide new potential targets to consider while designing melanoma-targeted therapy.

Advances in Management and Therapeutics of Cutaneous Basal Cell Carcinoma

Simple Summary

Basal cell carcinoma (BCC) is the most common malignancy in humans with a range of treatment options available. Tumor and patient characteristics aid in risk-stratification, which influences treatment considerations. Here, we review the advancements in surgical, topical, field, immunotherapeutic, molecular-targeted, and experimental treatment modalities that can be employed in the correct clinical setting for the treatment of BCC.

Abstract

Basal cell carcinoma (BCC), the most common cancer in humans, is a malignant neoplasm of cells derived from the basal layer of the epidermis. Tumor characteristics such as histologic subtype, primary versus recurrent tumor, anatomic location, size, and patient attributes determine the risk level and acceptable treatment options. Surgical options offer histologic confirmation of tumor clearance. Standard excision provides post-treatment histologic assessment, while Mohs micrographic surgery (MMS) provides complete margin assessment intraoperatively. Additional treatment options may be employed in the correct clinical context. Small and low-risk BCCs, broad field cancerization, locally-advanced disease, metastatic disease, cosmetic concerns, or morbidity with surgical approaches raise consideration of other treatment modalities. We review herein a range of treatment approaches and advances in treatments for BCC, including standard excision, MMS, electrodesiccation and curettage, ablative laser treatment, radiation therapy, targeted molecular therapies, topical therapies, field therapies, immunotherapy, and experimental therapies.

Cannabinol Inhibits Cellular Proliferation, Invasion, and Angiogenesis of Neuroblastoma via Novel miR-34a/tRiMetF31/PFKFB3 Axis

Simple Summary

The prognosis of high-risk neuroblastoma is poor due to its high relapse rate. To date, no effective treatment for this disease has been developed. In this study, we utilized two neuroblastoma cell lines (IMR-5 and SK-N-AS) as a model system to explore the effects of cannabinol (CBN) on neuroblastoma and elucidate the potential mechanisms of action. We reveal an inhibitory role of CBN on neuroblastoma cell proliferation, invasion, and angiogenesis through miR-34a-mediated targeting. We identified 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) as a direct target of a novel 31 nt tRNA_i^Met fragment tRiMetF31 generated from miR-34a-guided cleavage, highlighting the crucial role of the miR-34a/tRiMetF31/PFKFB3 axis in CBN-mediated suppression in neuroblastoma biology.

Abstract

High-risk neuroblastoma is an aggressive pediatric tumor. Despite great advances in neuroblastoma therapy and supportive care protocols, no curative treatment is available for most patients with this disease. Here, we uncover that CBN attenuated the cell proliferation, invasion, and angiogenesis of neuroblastoma cell lines in a dose-dependent manner via the inhibition of the AKT pathway and the upregulation of miR-34a that targets E2F1. Both miR-34a and a 31-nt tRNA_i^Met fragment (tRiMetF31) derived from miR-34a-guided cleavage were downregulated in 4 examined neuroblastoma cell lines inversely correlated with the levels of its direct target, the PFKFB3 protein. Moreover, ectopic tRiMetF31 suppressed proliferation, migration, and angiogenesis in the studied neuroblastoma cell lines. Conversely, tRiMetF31 knockdown promoted PFKFB3 expression, resulting in enhanced angiogenesis. Our findings reveal a suppressive role of CBN in neuroblastoma tumorigenesis, highlighting a novel and crucial miR-34a tumor suppressor network in CBN’s antineuroblastoma actions.

Targeting GLI1 Transcription Factor for Restoring Iodine Avidity with Redifferentiation in Radioactive-Iodine Refractory Thyroid Cancers

Simple Summary

Thyroid cancers have an excellent prognosis by standard therapy of surgery followed by radioactive-iodine therapy. However, metastatic thyroid cancers do not response to radioactive-iodine therapy by losing iodine avidity. Therefore, reversing iodine avidity to metastatic thyroid cancers gives a new chance of applying radioactive-iodine therapy to the cancers. In the current study, we found that GLI1 knockdown can revert iodine non-avid thyroid cancers to iodine avid cancers by increasing expression of thyroid-specific proteins. Restoration of iodine avidity in thyroid cancers makes the cancers sensitive to radioactive-iodine therapy again. Therefore, the GLI1 can be a potential therapeutic target of radioactive-iodine resistant thyroid cancers.

Abstract

Radioactive-iodine (RAI) therapy is the mainstay for patients with recurrent and metastatic thyroid cancer. However, many patients exhibit dedifferentiation characteristics along with lack of sodium iodide symporter (NIS) functionality, low expression of thyroid-specific proteins, and poor RAI uptake, leading to poor prognosis. Previous studies have demonstrated the effect of GLI family zinc finger 1 (GLI1) inhibition on tumor growth and apoptosis. In this study, we investigated the role of GLI1 in the context of redifferentiation and improvement in the efficacy of RAI therapy for thyroid cancer. We evaluated GLI1 expression in several thyroid cancer cell lines and selected TPC-1 and SW1736 cell lines showing the high expression of GLI. We performed GLI1 knockdown and evaluated the changes of thyroid-specific proteins expression, RAI uptake and I-131-mediated cytotoxicity. The effect of GANT61 (GLI1 inhibitor) on endogenous NIS expression was also assessed. Endogenous NIS expression upregulated by inhibiting GLI1, in addition, increased expression level in plasma membrane. Also, GLI1 knockdown increased expression of thyroid-specific proteins. Restoration of thyroid-specific proteins increased RAI uptake and I-131-mediated cytotoxic effect. Treatment with GANT61 also increased expression of endogenous NIS. Targeting GLI1 can be a potential strategy with redifferentiation for restoring RAI avidity in dedifferentiated thyroid cancers.

Evolving Roles of Notch Signaling in Cortical Development

Expansion of the neocortex is thought to pave the way toward acquisition of higher cognitive functions in mammals. The highly conserved Notch signaling pathway plays a crucial role in this process by regulating the size of the cortical progenitor pool, in part by controlling the balance between self-renewal and differentiation. In this review, we introduce the components of Notch signaling pathway as well as the different mode of molecular mechanisms, including trans- and cis-regulatory processes. We focused on the recent findings with regard to the expression pattern and levels in regulating neocortical formation in mammals and its interactions with other known signaling pathways, including Slit–Robo signaling and Shh signaling. Finally, we review the functions of Notch signaling pathway in different species as well as other developmental process, mainly somitogenesis, to discuss how modifications to the Notch signaling pathway can drive the evolution of the neocortex.

Advances in the drug management of basal cell carcinoma

INTRODUCTION

Basal cell carcinoma (BCC) is the most common skin cancer in humans. Recently, BCCs were suggested to be classified into 'easy to treat' and 'difficult to treat,' and different therapeutic options are suggested for their management.

AREAS COVERED

In this review, the authors discuss treatment options that are approved, recommended for, or are still in development for treatment of BCC. The review covers approved local therapies, such as imiquimod and 5-fluorouracil, and systemic therapies, such as hedgehog inhibitors. New medical agents, investigated in clinical trials, are reviewed. These include: targeted therapies, such as GLI antagonists or anti-VEGFR agents, immunotherapies, such as checkpoint inhibitors, recombinant cytokines or silencing RNA, as well as intralesional virotherapies with modified adeno- or herpes viruses.

EXPERT OPINION

The progress made in recent years has improved the management of patients with advanced BCC; however, neither tumor targeting nor immune system engaging agents provide a cure. New treatment approaches directed not only to known targets but also the tumor microenvironment are in development and are anticipated to improve the management of difficult to treat BCC.

Molecular Targeted Therapies: Time for a Paradigm Shift in Medulloblastoma Treatment?

Medulloblastoma is a rare malignancy of the posterior cranial fossa. Although until now considered a single disease, according to the current WHO classification, it is a heterogeneous tumor that comprises multiple molecularly defined subgroups, with distinct gene expression profiles, pathogenetic driver alterations, clinical behaviors and age at onset. Adult medulloblastoma, in particular, is considered a rarer "orphan" entity in neuro-oncology practice because while treatments have progressively evolved for the pediatric population, no practice-changing prospective, randomized clinical trials have been performed in adults. In this scenario, the toughest challenge is to transfer the advances in cancer genomics into new molecularly targeted therapeutics, to improve the prognosis of this neoplasm and the treatment-related toxicities. Herein, we focus on the recent advances in targeted therapy of medulloblastoma based on the new and deeper knowledge of disease biology.

Hedgehog signaling underlying tendon and enthesis development and pathology

Hedgehog (Hh) signaling has been widely acknowledged to play essential roles in many developmental processes, including endochondral ossification and growth plate maintenance. Furthermore, a rising number of studies have shown that Hh signaling is necessary for tendon enthesis development. Specifically, the well-tuned regulation of Hh signaling during development drives the formation of a mineral gradient across the tendon enthesis fibrocartilage. However, aberrant Hh signaling can also lead to pathologic heterotopic ossification in tendon or osteophyte formation at the enthesis. Therefore, the therapeutic potential of Hh signaling modulation for treating tendon and enthesis diseases remains uncertain. For example, increased Hh signaling may enhance tendon-to-bone healing by promoting the formation of mineralized fibrocartilage at the healing interface, but pathologic heterotopic ossification may also be triggered in the adjacent tendon. Further work is needed to elucidate the distinct functions of Hh signaling in the tendon and enthesis to support the development of therapies that target the pathway.

Challenges and Recent Advances of Novel Chemical Inhibitors in Medulloblastoma Therapy

Medulloblastoma is a common term used for the juvenile malignant brain tumor, and its treatment is exciting due to different genetic origins, improper transportation of drug across the blood-brain barrier, and chemo-resistance with various side effects. Currently, medulloblastoma divided into four significant subsections (Wnt, Shh, Group 3, and Group 4) is based on their hereditary modulation and histopathological advancement. In this chapter, we tried to combine several novel chemical therapeutic agents active toward medulloblastoma therapy. All these compounds have potent activity to inhibit the medulloblastoma.

MiR-144-3p inhibits gastric cancer progression and stemness via directly targeting GLI2 involved in hedgehog pathway

Background

Gastric cancer (GC) is the fifth most commonly diagnosed cancer worldwide. Due to the dismal prognosis, identifying novel therapeutic targets in GC is urgently needed. Evidences have shown that miRNAs played critical roles in the regulation of tumor initiation and progression. GLI family zinc finger 2 (GLI2) has been reported to be up-regulated and facilitate cancer progression in multiple malignancies. In this study, we focused on identifying GLI2-targeted miRNAs and clarifying the underlying mechanism in GC.

Methods

Paired fresh gastric cancer tissues were collected from gastrectomy patients. GLI2 and miRNAs expression were detected in gastric cancer tissues and cell lines. Bioinformatics analysis was used to predict GLI2-targeted miRNAs and dual-luciferase reporter assay was applied for target verification. CCK-8, clone formation, transwell and flow cytometry were carried out to determine the proliferation, migration, invasion and cell cycle of gastric cancer cells. Tumorsphere formation assay and flow cytometry were performed to detail the stemness of gastric cancer stem cells (GCSCs). Xenograft models in nude mice were established to investigate the role of the miR-144-3p in vivo.

Results

GLI2 was frequently upregulated in GC and indicated a poor survival. Meanwhile, miR-144-3p was downregulated and negatively correlated with GLI2 in GC. GLI2 was a direct target gene of miR-144-3p. MiR-144-3p overexpression inhibited proliferation, migration and invasion of gastric cancer cells. Enhanced miR-144-3p expression inhibited tumorsphere formation and CD44 expression of GCSCs. Restoration of GLI2 expression partly reversed the suppressive effect of miR-144-3p. Xenograft assay showed that miR-144-3p could inhibit the tumorigenesis of GC in vivo.

Conclusions

MiR-144-3p was downregulated and served as an essential tumor suppressor in GC. Mechanistically, miR-144-3p inhibited gastric cancer progression and stemness by, at least in part, regulating GLI2 expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03093-w.

Evaluation of Hedgehog Pathway Inhibitors as a Therapeutic Option for Uterine Leiomyosarcoma Using the Xenograft Model

Uterine leiomyosarcoma (LMS) contributes to a significant proportion of uterine cancer deaths. It is a rare and high-risk gynecological cancer. LMS is challenging to the treatment due to the resistance of several therapies. The activation of the Hedgehog (HH) pathway has been reported in several types of female cancers. Uterine LMS presents an upregulation of the crucial HH signaling pathway members such as SMO and GLI1. Although targeting the HH pathway exhibited a potent inhibitory effect on the phenotype of uterine LMS in vitro, the effect of the HH inhibitors on LMS growth in vivo has not been identified. The present study aimed to assess the effect of Hedgehog pathway inhibitors (SMO-LDE225 and GLI-Gant61) as a therapeutic option in the xenograft model of uterine LMS. The results demonstrated that LDE225 treatment did not show any inhibitory effect on LMS tumor growth; however, treatment with GLI inhibitor (Gant61) induced a remarkable tumor regression with a significant decrease in Ki67 expression, compared to control (p < 0.01). Moreover, administration of Gant61 decreased the expression of GLI1, GLI target genes BMP4 and c-MYC (p < 0.05), indicating that the HH pathway is implicated in the LMS experimental model. In conclusion, our studies demonstrate for the first time that GLI inhibitor (Gant61), but not SMO inhibitor (LDE225), shows a potent inhibitory effect on LMS tumor growth and concomitantly suppresses the expression of GLI1- and GLI-targeted genes using the xenograft model of uterine LMS.

Improved Outcomes with Induction Chemotherapy Combined with Arsenic Trioxide in Stage 4 Neuroblastoma: A Case Series

Objective: The apoptotic and cytotoxic effects of arsenic trioxide (ATO) makes it a potentially suitable agent for the treatment of patients with neuroblastoma with poor prognosis; therefore, we try to evaluate the effectiveness and safety of ATO combined with reinduction/induction chemotherapy in children with recurrent/refractory or newly diagnosed stage 4 neuroblastoma. Methods: Retrospective analysis was performed on seven pediatric patients with recurrent /refractory or newly diagnosed stage 4 neuroblastoma treated with traditional reinduction/induction chemotherapy combined with ATO. Results: A total of 7 patients were treated synchronously with ATO and chemotherapy for up to nine courses; all patients received conventional chemotherapy plus a 0.16 mg/kg/day dose of intravenous ATO during reinduction/induction chemotherapy. Treatment was effective in five patients and ineffective in the other two patients. The overall response rate was 71.43% (5 of 7). The side effects of the ATO combination were minor, whereby only treatment in one patient was terminated at the sixth course due to a prolonged QT interval (0.51 s), which returned to normal after symptomatic treatment. Conclusions: ATO can be safely and effectively combined with chemotherapy drugs as a potential alternative means of treatment for high-risk stage 4 neuroblastoma, and we have observed that ATO can restore the sensitivity of chemotherapy in some patients who were resistant to previous chemotherapy. Further investigations and clinical data are required to confirm these observations.

Excellent Early Outcomes of Combined Chemotherapy With Arsenic Trioxide for Stage 4/M Neuroblastoma in Children: A Multicenter Nonrandomized Controlled Trial

This nonrandomized, multicenter cohort, open-label clinical trial evaluated the efficacy and safety of combined chemotherapy with arsenic trioxide (ATO) in children with stage 4/M neuroblastoma (NB). We enrolled patients who were newly diagnosed with NB and assessed as stage 4/M and received either traditional chemotherapy or ATO combined with chemotherapy according to their own wishes. Twenty-two patients were enrolled in the trial group (ATO combined with chemotherapy), and 13 patients were enrolled in the control group (traditional chemotherapy). Objective response rate (ORR) at 4 weeks after completing induction chemotherapy was defined as the main outcome, and adverse events were monitored and graded in the meantime. Data cutoff date was December 31, 2019. Finally, we found that patients who received ATO combined with chemotherapy had a significantly higher response rate than those who were treated with traditional chemotherapy (ORR: 86.36% vs. 46.16%, p=0.020). Reversible cardiotoxicity was just observed in three patients who were treated with ATO, and no other differential adverse events were observed between the two groups. ATO combined with chemotherapy can significantly improve end-induction response in high-risk NB, and our novel regimen is well tolerated in pediatric patients. These results highlight the superiority of chemotherapy with ATO, which creates new opportunity for prolonging survival. In addition, this treatment protocol minimizes therapeutic costs compared with anti-GD2 therapy, MIBG, and proton therapy and can decrease the burden to families and society. However, we also need to evaluate more cases to consolidate our conclusion.

Activation of Cilia-Independent Hedgehog/GLI1 Signaling as a Novel Concept for Neuroblastoma Therapy

Simple Summary

Elevated GLI1 expression levels are associated with improved survival in NB patients and GLI1 overexpression exerts tumor-suppressive traits in cultured NB cells. However, NB cells are protected from increased GLI1 levels as they have lost the ability to form primary cilia and transduce Hedgehog signals. This study identifies an isoxazole (ISX) molecule with primary cilia-independent GLI1-activating properties, which blocks NB cell growth. Mechanistically, ISX combines the removal of GLI3 repressor and the inhibition of class I HDACs, providing proof-of-principle evidence that small molecule-mediated activation of GLI1 could be harnessed therapeutically in the future.

Abstract

Although being rare in absolute numbers, neuroblastoma (NB) represents the most frequent solid tumor in infants and young children. Therapy options and prognosis are comparably good for NB patients except for the high risk stage 4 class. Particularly in adolescent patients with certain genetic alterations, 5-year survival rates can drop below 30%, necessitating the development of novel therapy approaches. The developmentally important Hedgehog (Hh) pathway is involved in neural crest differentiation, the cell type being causal in the etiology of NB. However, and in contrast to its function in some other cancer types, Hedgehog signaling and its transcription factor GLI1 exert tumor-suppressive functions in NB, rendering GLI1 an interesting new candidate for anti-NB therapy. Unfortunately, the therapeutic concept of pharmacological Hh/GLI1 pathway activation is difficult to implement as NB cells have lost primary cilia, essential organelles for Hh perception and activation. In order to bypass this bottleneck, we have identified a GLI1-activating small molecule which stimulates endogenous GLI1 production without the need for upstream Hh pathway elements such as Smoothened or primary cilia. This isoxazole compound potently abrogates NB cell proliferation and might serve as a starting point for the development of a novel class of NB-suppressive molecules.

Sonic Hedgehog Signature in Pediatric Primary Bone Tumors: Effects of the GLI Antagonist GANT61 on Ewing's Sarcoma Tumor Growth

Simple Summary

The poor clinical outcomes for Osteosarcoma (OS) and Ewing’s sarcoma (ES) patients underscore the urgency of developing novel therapeutic strategies for these pathologies. In this context, the emerging role of Sonic hedgehog (SHH) signaling in cancer has been critically evaluated, focusing on the potential for targeting SHH signaling as an anticancer strategy. The aims of this work were (1) to highlight and to compare a possible SHH/Gli signature between OS and ES, (2) to strengthen our knowledge concerning the role of EWS-FLI1 in the SHH signature in ES and (3) to evaluate the effect of the specific Gli inhibitor GANT61 in vivo on the growth of ES tumors using an orthotopic mice model. Our work identifies Gli1 as a promising therapeutic target in ES and demonstrates that GANT61, through inhibition of Gli1 transcriptional activity, may be a promising therapeutic strategy hindering ES tumor progression, and specifically primary tumor growth.

Abstract

Osteosarcoma (OS) and Ewing’s sarcoma (ES) are the most common malignant bone tumors in children and adolescents. In many cases, the prognosis remains very poor. The Sonic hedgehog (SHH) signaling pathway, strongly involved in the development of many cancers, regulate transcription via the transcriptional factors Gli1-3. In this context, RNAseq analysis of OS and ES cell lines reveals an increase of some major compounds of the SHH signaling cascade in ES cells, such as the transcriptional factor Gli1. This increase leads to an augmentation of the transcriptional response of Gli1 in ES cell lines, demonstrating a dysregulation of Gli1 signaling in ES cells and thus the rationale for targeting Gli1 in ES. The use of a preclinical model of ES demonstrates that GANT61, an inhibitor of the transcriptional factor Gli1, reduces ES primary tumor growth. In vitro experiments show that GANT61 decreases the viability of ES cell, mainly through its ability to induce caspase-3/7-dependent cell apoptosis. Taken together, these results demonstrates that GANT61 may be a promising therapeutic strategy for inhibiting the progression of primary ES tumors.

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.

Emerging role of tumor cell plasticity in modifying therapeutic response

Resistance to cancer therapy is a major barrier to cancer management. Conventional views have proposed that acquisition of resistance may result from genetic mutations. However, accumulating evidence implicates a key role of non-mutational resistance mechanisms underlying drug tolerance, the latter of which is the focus that will be discussed here. Such non-mutational processes are largely driven by tumor cell plasticity, which renders tumor cells insusceptible to the drug-targeted pathway, thereby facilitating the tumor cell survival and growth. The concept of tumor cell plasticity highlights the significance of re-activation of developmental programs that are closely correlated with epithelial-mesenchymal transition, acquisition properties of cancer stem cells, and trans-differentiation potential during drug exposure. From observations in various cancers, this concept provides an opportunity for investigating the nature of anticancer drug resistance. Over the years, our understanding of the emerging role of phenotype switching in modifying therapeutic response has considerably increased. This expanded knowledge of tumor cell plasticity contributes to developing novel therapeutic strategies or combination therapy regimens using available anticancer drugs, which are likely to improve patient outcomes in clinical practice.

GANT61 Reduces Hedgehog Molecule (GLI1) Expression and Promotes Apoptosis in Metastatic Oral Squamous Cell Carcinoma Cells

Due to its importance in the pathogenesis of oral squamous cell carcinoma (OSCC), the Hedgehog (HH) pathway is considered a potential therapeutic target. We investigated the effects of GANT61, a GLI inhibitor, on HH gene expression, as well as on metastatic OSCC cell proliferation and death. Following culture in DMEM medium, cytotoxicity of GANT61 against different tumor and non-tumor cell types was assessed by alamarBlue assays. Cytotoxicity analysis revealed that the metastatic HSC3 cell line was the most sensitive (IC₅₀: 36 µM) to the tested compound. The compound’s effects on the expression of HH pathways components were analyzed by qPCR and Western blot; cell viability was analyzed by trypan blue assay and flow cytometry were used to investigate cell cycle phase, morphology, and death patterns in HSC3 cells. A significant reduction in mRNA levels of the GLI1 transcription factor was found after 12 h of treatment withGANT61. Protein expression levels of other HH pathway components (PTCH1, SHH, and Gli1) and HSC3 cell viability also decreased after 24 h of treatment. Cell cycle analysis and death pattern evaluations revealed significantly increased nuclear fragmentation in sub-G1 phase, as well as cell death due to apoptosis. In conclusion, the significantly reduced GLI1 gene expression seen in response to the GLI inhibitor indicates diminished downstream activation in HH pathway components. GANT61 significantly reduced cell viability in the metastatic cell line of OSCC and promoted a significant increase in nuclear fragmentation and cell death by apoptosis.

Circular RNA DGKB Promotes the Progression of Neuroblastoma by Targeting miR-873/GLI1 Axis

Accumulated evidences suggested that circular RNAs (circRNA) played critical roles in tumorigenesis and progression. To our knowledge, no study reported the function of circular RNA DGKB (circDGKB, circRNA ID: hsa_circ_0133622) on progression of neuroblastoma (NB). Here, we showed that circDGKB was upregulated in NB tissues compared to the normal dorsal root ganglia. Moreover, the expression level of circDGKB was negatively correlated with the survival rate of NB patients. Mechanically, overexpression of circDGKB promoted the proliferation, migration, invasion, and tumorigenesis of NB cells and reduced cell apoptosis, and vice versa. In addition, qRT-PCR and/or Western blot results showed that circDGKB overexpression inhibited the expression level of miR-873 and enhanced GLI1 expression. Moreover, miR-873 functioned an opposite role to circDGKB and significantly weakened circDGKB role in promoting NB progression. Furthermore, GLI1 upregulation also rescued the miR-873 role in inhibiting NB progression. In conclusion, our work proved that circDGKB promoted NB progression via targeting miR-873/GLI1 axis in vitro and in vivo. Our study provided a new target for NB treatment and indicated that circDGKB could act as a novel diagnostic marker for NB.

GLI3: a mediator of genetic diseases, development and cancer

The transcription factor GLI3 is a member of the Hedgehog (Hh/HH) signaling pathway that can exist as a full length (Gli3-FL/GLI3-FL) or repressor (Gli3-R/GLI3-R) form. In response to HH activation, GLI3-FL regulates HH genes by targeting the GLI1 promoter. In the absence of HH signaling, GLI3 is phosphorylated leading to its partial degradation and the generation of GLI3-R which represses HH functions. GLI3 is also involved in tissue development, immune cell development and cancer. The absence of Gli3 in mice impaired brain and lung development and GLI3 mutations in humans are the cause of Greig cephalopolysyndactyly (GCPS) and Pallister Hall syndromes (PHS). In the immune system GLI3 regulates B, T and NK-cells and may be involved in LPS-TLR4 signaling. In addition, GLI3 was found to be upregulated in multiple cancers and was found to positively regulate cancerous behavior such as anchorage-independent growth, angiogenesis, proliferation and migration with the exception in acute myeloid leukemia (AML) and medulloblastoma where GLI plays an anti-cancerous role. Finally, GLI3 is a target of microRNA. Here, we will review the biological significance of GLI3 and discuss gaps in our understanding of this molecule. Video Abstract.

Krüppel-like factor 9 promotes neuroblastoma differentiation via targeting the sonic hedgehog signaling pathway

BACKGROUND

Neuroblastoma (NB) is a deadly solid tumor of children. Krüppel-like factor 9 (KLF9) has prodifferentiation and tumor suppression functions in several types of cancers. Here, we aimed to investigate the effects of KLF9 on NB differentiation and growth and to elucidate the underlying mechanism.

PROCEDURE

Sixty-five NB paraffin samples were assessed for expression levels of KLF9 and sonic hedgehog (SHH) signaling pathway proteins by immunohistochemistry. The associations between expression of KLF9 and the SHH pathway components and patients' clinicopathologic characteristics were estimated. The impacts of KLF9 on cell differentiation, proliferation, and invasion were investigated in two NB cell lines (SH-SY5Y and IMR32). Additionally, chromatin immunoprecipitation (ChIP) and luciferase reporter assays were used to elucidate the mechanism by which KLF9 regulates SHH signaling.

RESULTS

Differentiating NB specimens showed significantly higher KLF9 expression levels than undifferentiated/poorly differentiated ones. Moreover, increased KLF9 expression was associated with favorable prognoses in patients with NB. A negative correlation was found between KLF9 and SHH signaling expression levels in NB specimens. In vitro assays revealed that KLF9 promoted the differentiation of NB cells and inhibited their proliferation and invasion via suppression of the SHH pathway. Furthermore, KLF9 binding sites in the SHH promoter were identified by ChIP and luciferase reporter assays.

CONCLUSIONS

KLF9 exerts prodifferentiation and growth-inhibition effects on NB via suppression of the SHH pathway, suggesting a potential role of KLF9 in NB therapy.

Self-Renewal Signalling Pathway Inhibitors: Perspectives on Therapeutic Approaches for Cancer Stem Cells

The poor survival and prognosis of individuals with cancer are often attributed to tumour relapse and metastasis, which may be due to the presence of cancer stem cells (CSCs). CSCs have the characteristics of self-renewal, differentiation potential, high carcinogenicity, and drug resistance. In addition, CSCs exhibit many characteristics similar to those of embryonic or tissue stem cells while displaying persistent abnormal activation of self-renewal pathways associated with development and tissue homeostasis, including the Wnt, Notch, Hedgehog (Hh), TGF-β, JAK/STAT3, and NF-κB pathways. Therefore, we can eliminate CSCs by targeting these self-renewal pathways to constrain stem cell replication, survival and differentiation. At the same time, we cannot neglect the ping-pong effect of the tumour microenvironment, which releases cytokines and promotes self-renewal pathways in CSCs. Recently, meaningful progress has been made in the study of inhibitors of self-renewal pathways in tumours. This review primarily summarizes several representative and novel agents targeting these self-renewal signalling pathways and the tumour microenvironment and that represent a promising strategy for treating refractory and recurrent cancer.

Hypoxia in the Initiation and Progression of Neuroblastoma Tumours

Neuroblastoma is the most frequent extracranial solid tumour in children, causing 10% of all paediatric oncology deaths. It arises in the embryonic neural crest due to an uncontrolled behaviour of sympathetic nervous system progenitors, giving rise to heterogeneous tumours. Low local or systemic tissue oxygen concentration has emerged as a cellular stimulus with important consequences for tumour initiation, evolution and progression. In neuroblastoma, several evidences point towards a role of hypoxia in tumour initiation during development, tumour cell differentiation, survival and metastatic spreading. However, the heterogeneous nature of the disease, its developmental origin and the lack of suitable experimental models have complicated a clear understanding of the effect of hypoxia in neuroblastoma tumour progression and the molecular mechanisms implicated. In this review, we have compiled available evidences to try to shed light onto this important field. In particular, we explore the effect of hypoxia in neuroblastoma cell transformation and differentiation. We also discuss the experimental models available and the emerging alternatives to study this problem, and we present hypoxia-related therapeutic avenues being explored in the field.

Gant61 ameliorates CCl4-induced liver fibrosis by inhibition of Hedgehog signaling activity

As an intercellular signaling molecule, Hedgehog (Hh) plays a critical role in liver fibrosis/regeneration. Transcription effectors Gli1 and Gli2 are key components of the Hh signaling pathway. However, whether inhibition of Gli1/2 activity can affect liver fibrogenesis is largely unknown. In the present study, we investigated the effect of Gant61 (a Gli1/2 transcription factor inhibitor) on liver fibrosis and its possible mechanism. Wild-type and Shh-EGFP-Cre male mice were exposed to CCl₄, and then treated with or without Gant61 for four weeks. The level of liver injury/fibrosis and expression levels of mRNA and protein related to the Hh ligand/pathway were assessed. In our study, CCl₄ treatment induced liver injury/fibrosis and promoted activation of hepatic stellate cells (HSCs). In addition, CCl₄ induced the expression of Shh ligands in and around the fibrotic lesion, accompanied by induction of mRNA and protein expression of Hh components (Smo, Gli1 and Gli2). However, administration of Gant61 decreased liver fibrosis by reduction in HSC number, down-regulation of mRNA and protein expression of Hh components (Smo, Gli1 and Gli2), and cell-cycle arrest of HSCs. Our data highlight the importance of the Shh pathway for the development of liver fibrosis, and also suggest Glis as potential therapeutic targets for the treatment of liver fibrosis.

Lichen Secondary Metabolite Physciosporin Decreases the Stemness Potential of Colorectal Cancer Cells

Secondary metabolites of lichens are promising bioresources for candidate anti-cancer drugs. Accordingly, several approaches have been proposed for screening these molecules for novel anti-cancer lead compounds. In this study, we found that a non-toxic concentration of physciosporin, a compound isolated from Pseudocyphellaria granulata, significantly decreased colony formation on soft agar and spheroid formation by CSC221 cancer stem-like cells. Physciosporin also decreased spheroid formation in other colorectal cancer cell lines, including DLD1, Caco2, and HT29. Aldehyde dehydrogenase-1 (ALDH1), the most important cancer stem marker, was sharply downregulated at both the protein and mRNA level following treatment with physciosporin. Physciosporin also decreased the transcriptional activity of the glioma-associated oncogene homolog zinc finger protein (Gli), as well as the Hes1 and CSL promoters, in reporter assays. Moreover, the drug significantly suppressed spheroid formation in CSC221 cells overexpressing Gli1/2 or EN1 (an S2-cleaved but membrane-tethered form of human Notch1) but did not suppress spheroid formation in cells overexpressing both Gli1/2 and ∆EN1, suggesting that physciosporin suppresses colon cancer cell stemness through the Sonic hedgehog and Notch signaling pathways. Together, these results demonstrate for the first time that physciosporin is a potent inhibitor of colorectal cancer cell stemness.

IL-24 Inhibits Lung Cancer Growth by Suppressing GLI1 and Inducing DNA Damage

Aberrant expression of GLI1 is responsible for aggressive tumor behavior and survival due to its effects on the DNA damage response (DDR). We investigated whether interleukin (IL)-24, a tumor suppressor, inhibits GLI1 and the associated DDR pathway in human NSCLCs. IL-24 treatment reduces mRNA and protein expression of GLI1 in lung tumor cells, but not in normal cells. GLI1 reporter assay and mRNA studies demonstrated that IL-24 regulates GLI1 at the post-transcriptional level by favoring mRNA degradation. Associated with GLI1 inhibition was marked suppression of the ATM-mediated DDR pathway resulting in increased DNA damage, as evidenced by γ-H2AX foci and Comet assay. Furthermore, attenuation of GLI1-associated DDR by IL-24 increased caspase-3 and PARP activity, resulting in cancer cell apoptosis. GLI1 inhibition and overexpression confirmed that IL-24-mediated anti-tumor effects involved the GLI-dependent pathway. Finally, we observed that IL-24-mediated alteration in GLI1 is independent of the canonical hedgehog-signaling pathway. Our study provides evidence that IL-24 treatment induces DNA damage, and reduces GLI1 expression and offers an opportunity for testing IL-24-based therapy for inhibiting GLI1 in lung cancer.

Targeting cancer stem cells in drug discovery: Current state and future perspectives

In recent decades, cancer stem cells (CSCs) have been increasingly identified in many malignancies. CSC-related signaling pathways and their functions provide new strategies for treating cancer. The aberrant activation of related signaling pathways (e.g., Wnt, Notch, and Hedgehog pathways) has been linked to multiple types of malignant tumors, which makes these pathways attractive targets for cancer therapy. CSCs display many characteristic features, such as self-renewal, differentiation, high tumorigenicity, and drug resistance. Therefore, there is an urgent need to develop new therapeutic strategies to target these pathways to control stem cell replication, survival, and differentiation. Notable crosstalk occurs among different signaling pathways and potentially leads to compensatory escape. Therefore, multitarget inhibitors will be one of the main methods to overcome the drug resistance of CSCs. Many small molecule inhibitors of components of signaling pathways in CSCs have entered clinical trials, and some inhibitors, such as vismodegib, sonidegib, and glasdegib, have been approved. Tumor cells are susceptible to sonidegib and vismodegib resistance due to mutations in the Smo protein. The signal transducers and activators of transcription 3 (STAT3) inhibitor BBI608 is being evaluated in a phase III trial for a variety of cancers. Structural derivatives of BBI608 are the main focus of STAT3 inhibitor development, which is another strategy for CSC therapy. In addition to the potential pharmacological inhibitors targeting CSC-related signaling pathways, other methods of targeting CSCs are available, such as nano-drug delivery systems, mitochondrion targeting, autophagy, hyperthermia, immunotherapy, and CSC microenvironment targeting. In addition, we summarize the latest advances in the clinical development of agents targeting CSC-related signaling pathways and other methods of targeting CSCs.

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.

GANT61 alleviates arthritic symptoms by targeting fibroblast-like synoviocytes in CIA rats

BACKGROUND

Studies have identified that the fibroblast-like synoviocytes (FLS) exhibited tumor-like characteristics and was the key factor in the pathogenesis of Rheumatoid arthritis (RA). GANT61, an antagonist of the sonic hedgehog pathway, has been verified with inhibitory effect on many cancers. Here we investigated the effect of GANT61 on FLS and the development of collagen-induced arthritis (CIA).

METHODS

40 Sprague Dawley (SD) rats were randomly divided into four groups: normal, CIA, CIA+10 mg/kg GANT61 and CIA+20 mg/kg GANT61. CIA was induced in rat with collagen injecting. The GANT61 was administered by intraperitoneal injection every 2 days for 3 weeks. The CIA model was identified with the paw swelling, arthritis score and the pathologic changes in joint. The FLS of different group were primary cultured. The proliferative capacity of FLS was detecteded via Cell Counting Kit-8 (CCK-8) method, and the apoptosis was detecteded by flow cytometry. The Bcl-2, Bax, Caspases3 and cleaved Caspases3 in synovium and FLS were detecteded by Western Blot.

RESULTS

The 20 mg/kg GANT61 treatment reduced the incidence of CIA and relieved the arthritis symptoms in CIA rats. The Bcl-2 was upregulated and the Bax was downregulated in the CIA rats synovium. The 10 mg/kg and 20 mg/kg GANT61 diminished the Bcl-2 expression, 20 mg/kg GANT61 increased the Bax and activated the Caspases3 in the CIA synovium. The proliferation of CIA-FLS was significantly higher and the apoptosis of the CIA-FLS was lower than that of the control group. The 10 mg/kg and 20 mg/kg GANT61 treatment can reduce cell proliferation and induce apoptosis by diminishing Bcl-2 and increasing the Bax in CIA-FLS.

CONCLUSIONS

The GANT61 inhibit the proliferation of FLS and alleviated the arthritic symptoms in CIA rats, this implied the GANT61 may be recommended as a possible candidate for the therapy of RA.

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.

Targeting the Hedgehog Pathway in Cancer: Current Evidence and Future Perspectives

The Hedgehog pathway (HhP) plays an important role in normal embryonic development and its abnormal function has been linked to a variety of neoplasms. Recently, the complex mechanisms involved in this pathway have been deciphered and the cross talks with other important pathways involved in carcinogenesis have been characterized. This knowledge has led to the development of targeted therapies against key components of HhP, which culminated in the approval of vismodegib for the treatment of advanced basal cell carcinoma in 2012. Since then, other compounds have been developed and evaluated in preclinical and clinical studies with interesting results. Today, several medications against components of the HhP have demonstrated clinical activity as monotherapies and in combination with cytotoxic treatment or other targeted therapies against mitogenic pathways that are linked to the HhP. This review aims to clarify the mechanism of the HhP and the complex crosstalk with others pathways involved in carcinogenesis and to discuss both the evidence associated with the growing number of medications and combined therapies addressing this pathway and future perspectives.

RITA downregulates Hedgehog-GLI in medulloblastoma and rhabdomyosarcoma via JNK-dependent but p53-independent mechanism

Overactivation of the Hedgehog (HH) signaling pathway is implicated in many cancers. In this study, we demonstrate that the small molecule RITA, a p53 activator, effectively downregulates HH signaling in human medulloblastoma and rhabdomyosarcoma cells irrespective of p53. This is mediated by a ROS-independent activation of the MAP kinase JNK. We also show that in vitro RITA sensitized cells to the GLI antagonist GANT61, as co-administration of the two drugs had more pronounced effects on cell proliferation and apoptosis. In vivo administration of RITA or GANT61 suppressed rhabdomyosarcoma xenograft growth in nude mice; however, co-administration did not further enhance tumor suppression, even though cell proliferation was decreased. RITA was more potent than GANT61 in downregulating HH target gene expression; surprisingly, this suppressive effect was almost completely eliminated when the two drugs were administered together. Notably, RNA-seq demonstrated a broader response of pathways involved in cancer cell growth in the combination treatment, providing a plausible interpretation for tumor reduction in the absence of HH signaling downregulation.

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.

A bottom-up synthesis of rare-earth-hydrotalcite monolayer nanosheets toward multimode imaging and synergetic therapy

Recently, ultrathin two-dimensional (2D) nanomaterials have attracted considerable research interest in biomedical applications, owing to their intriguing quantum size and surface effects. In this work, a one-step "bottom-up" method is developed to prepare rare-earth (Gd3+ and Yb3+) co-doped layered double hydroxide (LDH) monolayer nanosheets, with a precisely controlled composition and uniform morphology. Due to the successful introduction of Gd3+ and Yb3+ into the LDH host layer, the Gd&Yb-LDH monolayer nanosheets exhibit excellent magnetic resonance (MR)/X-ray computed tomography (CT) dual-mode imaging functionality. Moreover, the Gd&Yb-LDH monolayer nanosheets achieve an ultrahigh loading of a chemotherapeutic drug (SN38) with a loading content (LC) of 925%, which is a one order of magnitude enhancement compared with previously reported delivery systems of hydrophobic drugs. Interestingly, by further combination with indocyanine green (ICG), in vivo tri-mode imaging, including CT, MR and near infrared fluorescence (NIRF) imaging, is achieved, which enables a noninvasive visualization of cancer cell distribution with deep spatial resolution and high sensitivity. In addition, in vitro and in vivo therapeutic evaluations demonstrate an extremely high tri-mode synergetic anticancer activity and superior biocompatibility of SN38&ICG/Gd&Yb-LDH. Therefore, this work demonstrates a paradigm for the synthesis of novel multifunctional 2D monolayer materials via a facile "bottom-up" route, which shows promising applications in cancer synergetic theranostics.

Targeting GLI Transcription Factors in Cancer

Aberrant activation of hedgehog (Hh) signaling has been observed in a wide variety of tumors and accounts for more than 25% of human cancer deaths. Inhibitors targeting the Hh signal transducer Smoothened (SMO) are widely used and display a good initial efficacy in patients suffering from basal cell carcinoma (BCC); however, a large number of patients relapse. Though SMO mutations may explain acquired therapy resistance, a growing body of evidence suggests that the non-canonical, SMO-independent activation of the Hh pathway in BCC patients can also account for this adverse effect. In this review, we highlight the importance of glioma-associated oncogene (GLI) transcription factors (the main downstream effectors of the canonical and the non-canonical Hh cascade) and their putative role in the regulation of multiple oncogenic signaling pathways. Moreover, we discuss the contribution of the Hh signaling to malignant transformation and propose GLIs as central hubs in tumor signaling networks and thus attractive molecular targets in anti-cancer therapies.

Hedgehog signaling pathway: Epigenetic regulation and role in disease and cancer development

The evolutionarily conserved Hedgehog (Hh) signaling pathway have critical roles in development and homeostasis of tissues. Under physiological conditions, Hh is controlled at different levels via stem cell maintenance and tissue regeneration. Aberrant activation of this signaling pathway may occur in a wide range of human diseases including different types of cancer. In this review we present a concise overview on the key genes composing Hh signaling pathway and provide recent advances on the molecular mechanisms that regulate Hh signaling pathway from extracellular and receptors to the cytoplasmic and nuclear machinery with a highlight on the role of microRNAs. Furthermore, we focus on critical studies demonstrating dysregulation of the Hh pathway in human disease development, and potential therapeutic implications. Finally, we introduce recent therapeutic drugs acting as Shh signaling pathway inhibitors, including those in clinical trials and preclinical studies.

Molecular mechanisms and therapeutic targets in neuroblastoma

Neuroblastoma is the most common extracranical tumor of childhood and the most deadly tumor of infancy. It is characterized by early age onset and high frequencies of metastatic disease but also the capacity to spontaneously regress. Despite intensive therapy, the survival for patients with high-risk neuroblastoma and those with recurrent or relapsed disease is low. Hence, there is an urgent need to develop new therapies for these patient groups. The molecular pathogenesis based on high-throughput omics technologies of neuroblastoma is beginning to be resolved which have given the opportunity to develop personalized therapies for high-risk patients. Here we discuss the potential of developing targeted therapies against aberrantly expressed molecules detected in sub-populations of neuroblastoma patients and how these selected targets can be drugged in order to overcome treatment resistance, improve survival and quality of life for these patients and also the possibilities to transfer preclinical research into clinical testing.

The protective autophagy activated by GANT-61 in MYCN amplified neuroblastoma cells is mediated by PERK

The proto-oncogene MYC can trigger the unfolded protein response (UPR). The double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (PERK), one of three primary branches of the UPR, is a key regulator of autophagy, promoting tumorigenesis. Upon activation of PERK, there is an increase in phosphorylation of the eukaryotic initiation factor-2 alpha (eIF2α), which in turn, activates the transcription factor-4 (ATF4), responsible for an increased expression of LC3, a common autophagy marker. PERK is repressed upon GLI1 and GLI2 induction. GANT-61 is an inhibitor of GLI1 and GLI2, known to reduce autophagy in MYCN non-amplified, but not in MYCN amplified neuroblastoma (NB) cells. In our study, we tested the effect of the joint administration of a PERK inhibitor (GSK2606414) and the GLI inhibitor GANT-61 to MYCN amplified and MYCN non-amplified NB cells. Our results suggest that inhibition of PERK impairs GANT-61 induced autophagy in NB cells with MYCN amplification, but had no effect on the MYCN non-amplified NB cells. In summary, PERK seems to be a good therapeutic target for NB. Inhibition of PERK reduces autophagy in MYCN amplified NB cells, thus amplifying the efficacy of the GLI inhibitor GANT-61 in reducing proliferation of this type of cancer cells.

Improved therapy for neuroblastoma using a combination approach: superior efficacy with vismodegib and topotecan

Aberrant activation/expression of pathways/molecules including NF-kB, mTOR, hedgehog and polo-like-kinase-1 (PLK1) are correlated with poor-prognosis neuroblastoma. Therefore, to identify a most efficacious treatment for neuroblastoma, we investigated the efficacy of NF-kB/mTOR dual-inhibitor 13-197, hedgehog inhibitor vismodegib and PLK1 inhibitor BI2536 alone or combined with topotecan against high-risk neuroblastoma. The in vitro efficacy of the inhibitors alone or combined with topotecan on cell growth/apoptosis and molecular mechanism(s) were investigated. Results showed that as single agents 13-197, BI2536 and vismodegib significantly decreased neuroblastoma cell growth and induced apoptosis by targeting associated pathways/molecules. In combination with topotecan, 13-197 did not show significant additive/synergistic effects against neuroblastoma. However, BI2536 or vismodegib further significantly decreased neuroblastoma cell growth/survival. These results clearly showed that vismodegib combination with topotecan was synergistic and more efficacious compared with BI2536 in combination. Together, in vitro data demonstrated that vismodegib was most efficacious in potentiating topotecan-induced antineuroblastoma effects. Therefore, we tested the combined efficacy of vismodegib and topotecan against neuroblastoma in vivo using NSG mice. This resulted in significantly (p<0.001) reduced tumor growth and increased survival of mice. Together, the combination of vismodegib and topotecan showed a significant enhanced antineuroblastoma efficacy by targeting associated pathways/molecules which warrants further preclinical evaluation for translation to the clinic.

Pharmacological targeting of GLI1 inhibits proliferation, tumor emboli formation and in vivo tumor growth of inflammatory breast cancer cells

Activation of the Hedgehog (Hh) pathway effector GLI1 is linked to tumorigenesis and invasiveness in a number of cancers, with targeting of GLI1 by small molecule antagonists shown to be effective. We profiled a collection of GLI antagonists possessing distinct mechanisms of action for efficacy in phenotypic models of inflammatory and non-inflammatory breast cancer (IBC and non-IBC) that we showed expressed varying levels of Hh pathway mediators. Compounds GANT61, HPI-1, and JK184 decreased cell proliferation, inhibited GLI1 mRNA expression and decreased the number of colonies formed in TN-IBC (SUM149) and TNBC (MDA-MB-231 and SUM159) cell lines. In addition, GANT61 and JK184 significantly down-regulated GLI1 targets that regulate cell cycle (cyclin D and E) and apoptosis (Bcl2). GANT61 reduced SUM149 spheroid growth and emboli formation, and in orthotopic SUM149 tumor models significantly decreased tumor growth. We successfully utilized phenotypic profiling to identify a subset of GLI1 antagonists that were prioritized for testing in in vivo models. Our results indicated that GLI1 activation in TN-IBC as in TNBC, plays a vital role in promoting cell proliferation, motility, tumor growth, and formation of tumor emboli.