GLI1 inhibition promotes epithelial-to-mesenchymal transition in pancreatic cancer cells

Hedgehog pathway and cancer: A new area (Review)

In years of research on classical pathways, the composition, information transmission mechanism, crosstalk with other pathways, and physiological and pathological effects of hedgehog (HH) pathway have been gradually clarified. HH also plays a critical role in tumor formation and development. According to the update of interpretation of tumor phenotypes, the latest relevant studies have been sorted out, to explore the specific mechanism of HH pathway in regulating different tumor phenotypes through gene mutation and signal regulation. The drugs and natural ingredients involved in regulating HH pathway were also reviewed; five approved drugs and drugs under research exert efficacy by blocking HH pathway, and at least 22 natural components have potential to treat tumors by HH pathway. Nevertheless, there is a deficiency of existing studies. The present review confirmed the great potential of HH pathway in future cancer treatment with factual basis.

Targeting GLI1 and BAX by nanonoscapine could impede prostate adenocarcinoma progression

Prostate cancer as a critical global health issue, requires the exploration of a novel therapeutic approach. Noscapine, an opium-derived phthalide isoquinoline alkaloid, has shown promise in cancer treatment thanks to its anti-tumorigenic properties. However, limitations such as low bioavailability and potential side effects have hindered its clinical application. This study introduces nanonoscapine as a novel medication to overcome these challenges, leveraging the advantages of improved drug delivery and efficacy achieved in nanotechnology. We monitored the effects of nanonoscapine on the androgen-sensitive human prostate adenocarcinoma cell line, LNCaP, investigating its impact on GLI1 and BAX genes' expressions, crucial regulators of cell cycle and apoptosis. Our findings, from MTT assays, flow cytometry, and gene expression analyses, have demonstrated that nanonoscapine effectively inhibits prostate cancer cell proliferation by inducing G2/M phase arrest and apoptosis. Furthermore, through bioinformatics and computational analyses, we have revealed the underlying molecular mechanisms, underscoring the therapeutic potential of nanonoscapine in enhancing patient outcomes. This study highlights the significance of nanonoscapine as an alternative or adjunct treatment to conventional chemotherapy, warranting further investigation in clinical settings.

Chemotherapy Assessment in Advanced Multicellular 3D Models of Pancreatic Cancer: Unravelling the Importance of Spatiotemporal Mimicry of the Tumor Microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is a challenge for global health with very low survival rate and high therapeutic resistance. Hence, advanced preclinical models for treatment screening are of paramount importance. Herein, chemotherapeutic (gemcitabine) assessment on novel (polyurethane) scaffold-based spatially advanced 3D multicellular PDAC models is carried out. Through comprehensive image-based analysis at the protein level, and expression analysis at the mRNA level, the importance of stromal cells is confirmed, primarily activated stellate cells in the chemoresistance of PDAC cells within the models. Furthermore, it is demonstrated that, in addition to the presence of activated stellate cells, the spatial architecture of the scaffolds, i.e., segregation/compartmentalization of the cancer and stromal zones, affect the cellular evolution and is necessary for the development of chemoresistance. These results highlight that, further to multicellularity, mapping the tumor structure/architecture and zonal complexity in 3D cancer models is important for better mimicry of the in vivo therapeutic response.

The Double-Edged Effects of MLN4924: Rethinking Anti-Cancer Drugs Targeting the Neddylation Pathway

(1) Background: The neddylation pathway assumes a pivotal role in the initiation and progression of cancer. MLN4924, a potent small-molecule inhibitor of the NEDD8-activating enzyme (NAE), effectively intervenes in the early stages of the neddylation pathway. By instigating diverse cellular responses, such as senescence and apoptosis in cancer cells, MLN4924 also exerts regulatory effects on non-malignant cells within the tumor microenvironment (TME) and tumor virus-infected cells, thereby impeding the onset of tumors. Consequently, MLN4924 has been widely acknowledged as a potent anti-cancer drug. (2) Recent findings: Nevertheless, recent findings have illuminated additional facets of the neddylation pathway, revealing its active involvement in various biological processes detrimental to the survival of cancer cells. This newfound understanding underscores the dual role of MLN4924 in tumor therapy, characterized by both anti-cancer and pro-cancer effects. This dichotomy is herein referred to as the "double-edged effects" of MLN4924. This paper delves into the intricate relationship between the neddylation pathway and cancer, offering a mechanistic exploration and analysis of the causes underlying the double-edged effects of MLN4924-specifically, the accumulation of pro-cancer neddylation substrates. (3) Perspectives: Here, the objective is to furnish theoretical support and novel insights that can guide the development of next-generation anti-cancer drugs targeting the neddylation pathway.

A Vaccine against Cancer: Can There Be a Possible Strategy to Face the Challenge? Possible Targets and Paradoxical Effects

Is it possible to have an available vaccine that eradicates cancer? Starting from this question, this article tries to verify the state of the art, proposing a different approach to the issue. The variety of cancers and different and often unknown causes of cancer impede, except in some cited cases, the creation of a classical vaccine directed at the causative agent. The efforts of the scientific community are oriented toward stimulating the immune systems of patients, thereby preventing immune evasion, and heightening chemotherapeutic agents effects against cancer. However, the results are not decisive, because without any warning signs, metastasis often occurs. The purpose of this paper is to elaborate on a vaccine that must be administered to a patient in order to prevent metastasis; metastasis is an event that leads to death, and thus, preventing it could transform cancer into a chronic disease. We underline the fact that the field has not been studied in depth, and that the complexity of metastatic processes should not be underestimated. Then, with the aim of identifying the target of a cancer vaccine, we draw attention to the presence of the paradoxical actions of different mechanisms, pathways, molecules, and immune and non-immune cells characteristic of the tumor microenvironment at the primary site and pre-metastatic niche in order to exclude possible vaccine candidates that have opposite effects/behaviors; after a meticulous evaluation, we propose possible targets to develop a metastasis-targeting vaccine. We conclude that a change in the current concept of a cancer vaccine is needed, and the efforts of the scientific community should be redirected toward a metastasis-targeting vaccine, with the increasing hope of eradicating cancer.

NEDD8-Activating Enzyme Inhibitor MLN4924 Inhibits Both the Tumor Stroma and Angiogenesis in Pancreatic Cancer via Gli1 and REDD1

PURPOSE

Pancreatic cancer is characterized by a dense desmoplasia stroma, which hinders efficient drug delivery and plays a critical role in tumor progression and metastasis. MLN4924 is a first-in-class NEDD8-activating enzyme inhibitor that exhibits anti-tumor activities toward pancreatic cancer, and given the comprehensive effects that MLN4924 could have, we ask what impact MLN4924 would have on the stroma of pancreatic cancer and its underlying mechanisms.

METHODS

Primary pancreatic stellate cells (PSCs) and human HMEC-1 cells were treated with MLN4924 in vitro. The proliferation and extracellular matrix protein levels of PSCs were tested, and their relationship with transcription factor Gli1 in PSCs was investigated. The angiogenic phenotypes of HMEC-1 cells were evaluated using capillary-like tube formation assay, and their relationship with REDD1 in HMEC-1 cells was investigated.

RESULTS

In this study, we found that MLN4924 inhibited the proliferation of pancreatic stellate cells and their secretion of collagen and CXCL-1, and the collagen secretion inhibiting effect of MLN4924 was related with transcription factor Gli1. MLN4924 inhibited multiple angiogenic phenotypes of HMEC-1 cells, and mTOR agonist partially relieved the inhibition of MLN4924 on HEMCs. MLN4924 increased the expression of REDD1 and REDD1 knockdown promoted the angiogenic phenotypes of HMEC-1 cells.

CONCLUSIONS

Our study suggests that MLN4924 inhibits both the tumor stroma and angiogenesis in pancreatic cancer, and the inhibition effect is related with Gli1 in pancreatic stellate cells and REDD1 in vascular endothelial cells, respectively.

Natural compounds as a potential modifier of stem cells renewal: Comparative analysis

Cancer stem cells (CSCs) are indispensable for development, progression, drug resistance, and tumor metastasis. Current cancer-directed interventions target targeting rapidly dividing cancer cells and slow dividing CSCs, which are the root cause of cancer origin and recurrence. The most promising targets include several self-renewal pathways involved in the maintenance and renewal of CSCs, such as the Wnt/β-Catenin, Sonic Hedgehog, Notch, Hippo, Autophagy, and Ferroptosis. In view of safety, natural compounds are coming to the front line of treatment modalities for modifying various signaling pathways simultaneously involved in maintaining CSCs. Therefore, targeting CSCs with natural compounds is a promising approach to treating various types of cancers. In view of this, here we provide a comprehensive update on the current status of natural compounds that effectively tune key self-renewal pathways of CSCs. In addition, we highlighted surface expression markers in several types of cancer. We also emphasize how natural compounds target these self-renewal pathways to reduce therapy resistance and cancer recurrence properties of CSCs, hence providing valuable cancer therapeutic strategies. The inclusion of nutraceuticals is believed to enhance the therapeutic efficacy of current cancer-directed interventions significantly.

Aberrant transcription factors in the cancers of the pancreas

Transcription factors (TFs) are essential for proper activation of gene set during the process of organogenesis, differentiation, lineage specificity. Reactivation or dysregulation of TFs regulatory networks could lead to deformation of organs, diseases including various malignancies. Currently, understanding the mechanism of oncogenesis became necessity for the development of targeted therapeutic strategy for different cancer types. It is evident that many TFs go awry in cancers of the pancreas such as pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine neoplasms (PanNENs). These mutated or dysregulated TFs abnormally controls various signaling pathways in PDAC and PanNENs including RTK, PI3K-PTEN-AKT-mTOR, JNK, TGF-β/SMAD, WNT/β-catenin, SHH, NOTCH and VEGF which in turn regulate different hallmarks of cancer. Aberrant regulation of such pathways have been linked to the initiation, progression, metastasis, and resistance in pancreatic cancer. As of today, a number of TFs has been identified as crucial regulators of pancreatic cancer and a handful of them shown to have potential as therapeutic targets in pre-clinical and clinical settings. In this review, we have summarized the current knowledge on the role and therapeutic usefulness of TFs in PDAC and PanNENs.

Epithelial–mesenchymal transition: The history, regulatory mechanism, and cancer therapeutic opportunities

Epithelial–mesenchymal transition (EMT) is a program wherein epithelial cells lose their junctions and polarity while acquiring mesenchymal properties and invasive ability. Originally defined as an embryogenesis event, EMT has been recognized as a crucial process in tumor progression. During EMT, cell–cell junctions and cell–matrix attachments are disrupted, and the cytoskeleton is remodeled to enhance mobility of cells. This transition of phenotype is largely driven by a group of key transcription factors, typically Snail, Twist, and ZEB, through epigenetic repression of epithelial markers, transcriptional activation of matrix metalloproteinases, and reorganization of cytoskeleton. Mechanistically, EMT is orchestrated by multiple pathways, especially those involved in embryogenesis such as TGFβ, Wnt, Hedgehog, and Hippo, suggesting EMT as an intrinsic link between embryonic development and cancer progression. In addition, redox signaling has also emerged as critical EMT modulator. EMT confers cancer cells with increased metastatic potential and drug resistant capacity, which accounts for tumor recurrence in most clinic cases. Thus, targeting EMT can be a therapeutic option providing a chance of cure for cancer patients. Here, we introduce a brief history of EMT and summarize recent advances in understanding EMT mechanisms, as well as highlighting the therapeutic opportunities by targeting EMT in cancer treatment.

Gli1 promotes epithelial–mesenchymal transition and metastasis of non-small cell lung carcinoma by regulating Snail transcriptional activity and stability

Metastasis is crucial for the mortality of non-small cell lung carcinoma (NSCLC) patients. The epithelial–mesenchymal transition (EMT) plays a critical role in regulating tumor metastasis. Glioma-associated oncogene 1 (Gli1) is aberrantly active in a series of tumor tissues. However, the molecular regulatory relationships between Gli1 and NSCLC metastasis have not yet been identified. Herein, we reported Gli1 promoted NSCLC metastasis. High Gli1 expression was associated with poor survival of NSCLC patients. Ectopic expression of Gli1 in low metastatic A549 and NCI-H460 cells enhanced their migration, invasion abilities and facilitated EMT process, whereas knock-down of Gli1 in high metastatic NCI-H1299 and NCI-H1703 cells showed an opposite effect. Notably, Gli1 overexpression accelerated the lung and liver metastasis of NSCLC in the intravenously injected metastasis model. Further research showed that Gli1 positively regulated Snail expression by binding to its promoter and enhancing its protein stability, thereby facilitating the migration, invasion and EMT of NSCLC. In addition, administration of GANT-61, a Gli1 inhibitor, obviously suppressed the metastasis of NSCLC. Collectively, our study reveals that Gli1 is a critical regulator for NSCLC metastasis and suggests that targeting Gli1 is a prospective therapy strategy for metastatic NSCLC.

Targeting cancer stem cell pathways for cancer therapy

Since cancer stem cells (CSCs) were first identified in leukemia in 1994, they have been considered promising therapeutic targets for cancer therapy. These cells have self-renewal capacity and differentiation potential and contribute to multiple tumor malignancies, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. The biological activities of CSCs are regulated by several pluripotent transcription factors, such as OCT4, Sox2, Nanog, KLF4, and MYC. In addition, many intracellular signaling pathways, such as Wnt, NF-κB (nuclear factor-κB), Notch, Hedgehog, JAK-STAT (Janus kinase/signal transducers and activators of transcription), PI3K/AKT/mTOR (phosphoinositide 3-kinase/AKT/mammalian target of rapamycin), TGF (transforming growth factor)/SMAD, and PPAR (peroxisome proliferator-activated receptor), as well as extracellular factors, such as vascular niches, hypoxia, tumor-associated macrophages, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, extracellular matrix, and exosomes, have been shown to be very important regulators of CSCs. Molecules, vaccines, antibodies, and CAR-T (chimeric antigen receptor T cell) cells have been developed to specifically target CSCs, and some of these factors are already undergoing clinical trials. This review summarizes the characterization and identification of CSCs, depicts major factors and pathways that regulate CSC development, and discusses potential targeted therapy for CSCs.

PM2.5 promotes human bronchial smooth muscle cell migration via the sonic hedgehog signaling pathway

BACKGROUND

The contribution of airway remodeling in chronic obstructive pulmonary disease (COPD) has been well documented, with airway smooth muscle cell proliferation and migration playing a role in the remodeling process. Here, we aimed to verify the effects of fine particulate matter (PM2.5) on human bronchial smooth muscle cell (HBSMC) migration and to explore the underlying signaling pathways.

METHODS

HBSMC apoptosis, proliferation and migration were measured using flow cytometry, cell counting and transwell migration assays, respectively. The role of the hedgehog pathway in cell migration was assessed by western blotting to measure the expression of Sonic hedgehog (Shh), Gli1 and Snail. Furthermore, siRNA was used to knock down Gli1 or Snail expression.

RESULTS

PM2.5 induced HBSMC apoptosis in a dose-dependent manner, although certain concentrations of PM2.5 did not induce HBSMC proliferation or apoptosis. Interestingly, cell migration was stimulated by PM2.5 doses far below those that induced apoptosis. Additional experiments revealed that these PM2.5 doses enhanced the expression of Shh, Gli1 and Snail in HBSMCs. Furthermore, PM2.5-induced cell migration and protein expression were enhanced by recombinant Shh and attenuated by cyclopamine. Similar results were obtained by knocking down Gli1 or Snail.

CONCLUSIONS

These findings suggest that PM2.5, which may exert its effects through the Shh signaling pathway, is necessary for the migration of HBSMCs. These data define a novel role for PM2.5 in airway remodeling in COPD.

Gli promotes epithelial-mesenchymal transition in human lung adenocarcinomas

Adenocarcinoma is the most common type of lung cancer. Epithelial-mesenchymal transition (EMT) is required for tumor invasion/metastasis and the components that control this process are potential therapeutic targets. This study we examined the role of Gli in lung adenocarcinoma and whether its activation regulates metastasis through EMT in lung adenocarcinoma. We found that tumors with high Gli expression had significantly lower E-Cadherin expression in two independent cohorts of patients with lung adenocarcinoma that we studied. In vitro up-regulation of SHh resulted in increased cell migration while small molecule inhibitors of Smo or Gli significantly reduced cell mobility both in a wound healing assay and in a 3D cell invasion assay. Inhibition of Gli in vivo decreased tumor growth and induced an increase in E-Cadherin expression. Our results indicate that Gli may be critical for lung adenocarcinoma metastasis and that a novel Gli inhibitor shows promise as a therapeutic agent by preventing cell migration and invasion in vitro and significantly reducing tumor growth and increasing E-Cadherin expression in vivo.

Gli is activated and promotes epithelial-mesenchymal transition in human esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) accounts for the most esophageal cancer cases in the US, and is notoriously aggressive. This study examines the role of Sonic Hedgehog (SHh)/Gli signaling in the regulation of epithelial-mesenchymal transition (EMT), a process tied to invasion and metastasis, in EAC. Gli/EMT protein expression levels were examined by western blot in paired EAC patient tissues (n = 24) and cell lines (OE19, OE33). Functional analyses were performed (siRNA, treatment with Gli-inhibitor, AKT-inhibitor, and N-Shh recombinant proteins) to investigate SHh/Gli signaling and EMT, cell cycle, and prognostic markers in EAC cell lines. MTS, luciferase reporter, qRT-PCR, western blot, wound healing, and transwell assays were executed to analyze pathway activity, cell migration, and invasion. Aberrant Gli1/2 expression was found in EAC patient tissues, and was significantly associated with increased EMT and AKT pathway activity. Stimulation of SHh/Gli resulted in EMT signaling, including expression of E-cadherin, N-cadherin, Vimentin, β-catenin, Snail, and Slug, as well as cell cycle progression at mRNA and protein levels in EAC cell lines. Gli inhibition via small molecule administration and siRNA significantly reduced EMT, decreasing cell mobility and invasion. Both Gli and AKT inhibition rescued E-cadherin expression and suppressed AKT phosphorylation. This study provides evidence for a strong association between aberrant Gli1/2 expression and AKT/EMT markers in EAC; activated SHh/Gli signaling may be a critical component in promoting cell survival, metastases, and resistance to chemotherapy, and represents a promising avenue to target tumor proliferation and mobility.

Epiregulin Promotes Lung Metastasis of Salivary Adenoid Cystic Carcinoma

Salivary adenoid cystic carcinoma (SACC) is a peculiar malignant tumor, characterized by its slow but inexorable growth, with a high incidence of lung metastasis and poor prognosis. Here, we show the upregulated expression of EGFR ligand epiregulin in a subset of SACC cells correlates with lung metastasis and unfavorable outcome in patients with SACC. We found that upregulation of epiregulin in SACC cells induced epithelial-mesenchymal transition by regulating GLI1/E-cadherin. Elevated epiregulin increased the expression of pro-angiogenic factors, such as VEGFA, bFGF, and IL-8. We also show that epiregulin can be delivered via exosomes and was enriched in exosomes derived from epiregulin-overexpressing SACC cells. Furthermore, treating immunodeficient mice with these epiregulin-enriched exosomes greatly enhanced SACC metastasis to lung. These epiregulin-enriched exosomes significantly enhanced angiogenesis in the neighboring tumor microenvironment and increased vascular permeability in the pre-metastatic lung microenvironment in vivo. Therefore, epiregulin, as well as epiregulin-containing exosomes, may be a novel target for controlling SACC lung metastasis.

Gli1 expression in cancer stem-like cells predicts poor prognosis in patients with lung squamous cell carcinoma

PURPOSE

Glioma-associated oncogene homolog 1 (Gli1) is involved in cancer stem cell (CSC) maintenance in various tumors; however, its expression and clinical significance in lung squamous cell carcinoma (LSCC) has not been reported. In this study, we aimed to reveal the clinical significance of Gli1 in LSCC and investigate the potential of Gli1 as a CSC marker by comparing its expression with that of other stemness-related genes in LSCC.

METHODS

We assessed the expressions of Gli1, LSD1, CD44, Sox9 and Sox2 by immunohistochemistry in the tissue specimens obtained from 101 patients with LSCC. The relationship of Gli1 expression with clinicopathological parameters and cell-cycle regulating genes was investigated.

RESULTS

Gli1 expression was significantly correlated with T stage (P<0.001), lymph node metastasis (P=0.002), and clinical stage (P=0.005) of LSCC. The Kaplan-Meier survival analysis revealed that the expression of Gli1 in LSCC was all significantly associated with poor overall survival (OS: P=0.005). Cox regression analysis further confirmed that Gli1 is a prognostic marker of unfavorable clinical outcome of LSCC. Gli1 expression was significantly correlated with the expression of stemness-related genes such as LSD1 (P=0.009) and CD44 (P<0.001), but not with those of Sox2 and Sox9. However, Gli1 expression was associated with the expression of hypoxia-inducible factors1α (HIF1α; P<0.001) and Cyclin D1 (P=0.002), respectively. In additionally, microvessel density (MVD) was significantly higher in Gli1-positive LSCC than in the negative LSCC (P=0.026).

CONCLUSIONS

Our results suggest that Gli1 may be a potential LSCC stem cell marker and an independent indicator of poor prognosis for patients with LSCC.

Sclareolide enhances gemcitabine‑induced cell death through mediating the NICD and Gli1 pathways in gemcitabine‑resistant human pancreatic cancer

Pancreatic cancer is a type of cancer, which rapidly develops resistance to chemotherapy. Gemcitabine is the treatment used clinically, however, gemcitabine resistance leads to limited efficacy and patient survival rates of only a few months following diagnosis. The aim of the present study was to investigate the mechanisms underlying gemcitabine resistance in pancreatic cancer and to select targeted agents combined with gemcitabine to promote the treatment of pancreatic cancer. Panc-1 and ASPC-1 human pancreatic cancer cells (HPCCs) were used to establish the experimental model, and HPCCs were exposed to gemcitabine of serially increased concentrations to generate gemcitabine-resistant cells (GR-HPCCs). The anticancer effect of gemcitabine combined with sclareolide was then assessed. Epithelial to mesenchymal transition (EMT), human equilibrative nucleoside transporter 1 (hENT1) and ribonucleoside diphosphate reductase 1 (RRM1) were detected in the HPCCs and GR-HPCCs, and the mechanisms were investigated. Sclareolide resensitized the GR-HPCCs to gemcitabine. The expression levels of hENT1 and RRM1 were lower and higher, respectively, in GR-HPCCs, compared with HPCCs. Sclareolide upregulated hENT1, downregulated RRM1 and inhibited gemcitabine-induced EMT through the TWIST1/Slug pathway in the GR-HPCCs. In addition, sclareolide mediated the NOTCH 1 intracellular cytoplasmic domain (NICD)/glioma-associated oncogene 1 (Gli1) pathway, which triggered TWIST1/Slug-hENT1/RRM1 signaling and resensitized GR-HPCCs to gemcitabine. Finally, sclareolide resensitized GR-HPCCs to gemcitabine through inducing apoptosis; in vivo, the co-administraion of sclareolide and gemcitabine effectively suppressed tumor growth. Sclareolide may be a novel agent in combination with gemcitabine for the treatment of gemcitabine-resistant pancreatic cancer, which resensitizes GR-HPCCs to gemcitabine through mediating NICD and Gli1.

The sonic hedgehog signaling pathway stimulates anaplastic thyroid cancer cell motility and invasiveness by activating Akt and c-Met

The sonic hedgehog (Shh) pathway is highly activated in thyroid neoplasms and promotes thyroid cancer stem-like cell phenotype, but whether the Shh pathway regulates thyroid tumor cell motility and invasiveness remains unknown. Here, we report that the motility and invasiveness of two anaplastic thyroid tumor cell lines, KAT-18 and SW1736, were inhibited by two inhibitors of the Shh pathway (cyclopamine and GANT61). Consistently, the cell motility and invasiveness was decreased by Shh and Gli1 knockdown, and was increased by Gli1 overexpression in KAT-18 cells. Mechanistic studies revealed that Akt and c-Met phosphorylation was decreased by a Gli1 inhibitor and by Shh and Gli1 knockdown, but was increased by Gli1 overexpression. LY294002, a PI-3 kinase inhibitor, and a c-Met inhibitor inhibited the motility and invasiveness of Gli1-transfected KAT-18 cells more effectively than the vector-transfected cells. Knockdown of Snail, a transcription factor regulated by the Shh pathway, led to decreased cell motility and invasiveness in KAT-18 and SW1736 cells. However, key epithelial-to-mesenchymal transition (EMT) markers including E-cadherin and vimentin as well as Slug were not affected by cyclopamine and GANT61 in either SW1736 or WRO82, a well differentiated follicular thyroid carcinoma cell line. Our data suggest that the Shh pathway-stimulated thyroid tumor cell motility and invasiveness is largely mediated by AKT and c-Met activation with little involvement of EMT.

The hedgehog/Gli-1 signaling pathways is involved in the inhibitory effect of resveratrol on human colorectal cancer HCT116 cells

OBJECTIVES

The study aimed to investigate the effects of resveratrol on colorectal cancer HCT116 cells, including cell viability, apoptosis, and migration, and the partial mechanisms focused on hedgehog/gli-1 signaling pathways.

MATERIALS AND METHODS

We chose the appropriate time and concentration of recombinant human Sonic hedgehog (Shh) stimulation by cell viability. The proportion of cell apoptosis was detected by flow cytometry; HCT116 cell migration was measured by scratch test; the expression of Ptch, Smo, and Gli-1 was measured by Western blot analysis.

RESULTS

Shh signaling increased HCT116 cell viability and migration, inhibited cell apoptosis, and upregulated the expression of Ptch, Smo, and Gli-1. Resveratrol obviously inhibited HCT116 cell viability and migration, promoted cell apoptosis, and suppressed the protein of Ptch, Smo, and Gli-1. Furthermore, the effects of resveratrol and Shh on human colorectal cancer HCT116 cells were in a dose- and time-dependent manner.

CONCLUSION

The inhibitory effect of resveratrol on HCT116 cells may be mediated by hedgehog/gli-1 signaling pathways.

Roles of Signaling Pathways in the Epithelial-Mesenchymal Transition in Cancer

The epithelial-mesenchymal transition (EMT) is a cellular process though which an epithelial phenotype can be converted into a phenotype of mesenchymal cells. Under physiological conditions EMT is important for embryogenesis, organ development, wound repair and tissue remodeling. However, EMT may also be activated under pathologic conditions, especially in carcinogenesis and metastatic progression. Major signaling pathways involved in EMT include transforming growth factor β(TGF-β), Wnt, Notch, Hedgehog and other signaling pathways. These pathways are related to several transcription factors, including Twist, Smads and zinc finger proteins snail and slug. These interact with each other to provide crosstalk between the relevant signaling pathways. This review lays emphasis on studying the relationship between EMT and signaling pathways in carcinogenesis and metastatic progression.

Targeting the Hedgehog signaling pathway in cancer: beyond Smoothened

An essential role for Hedgehog (Hh) signaling in human cancer has been established beyond doubt. At present, targeting Hh signaling has mainly been investigated with SMO inhibitors. Unfortunately, resistance against currently used SMO inhibitors has already been observed in basal cell carcinoma (BCC) patients. Therefore, the use of Hh inhibitors targeting the signaling cascade more downstream of SMO could represent a more promising strategy. Furthermore, besides the classical canonical way of Hh signaling activation, non-canonical activation of the GLI transcription factors by multiple important signaling pathways (e.g. MAPK, PI3K, TGFβ) has also been described, pinpointing the importance of targeting the transcription factors GLI1/2. The most promising agent in this context is probably the GLI1/2 inhibitor GANT61 which has been investigated preclinically in numerous tumor types in the last few years. In this review, the emerging role of Hh signaling in cancer is critically evaluated focusing on the potential of targeting Hh signaling more downstream of SMO, i.e. at the level of the GLI transcription factors. Furthermore, the working mechanism and therapeutic potential of the most extensively studied GLI inhibitor in human cancer, i.e. GANT61, is discussed in detail. In conclusion, GANT61 appears to be highly effective against human cancer cells and in xenograft mouse models, targeting almost all of the classical hallmarks of cancer and could hence represent a promising treatment option for human cancer.

Hedgehog Signaling in Pancreatic Fibrosis and Cancer

The hedgehog signaling pathway was first discovered in the 1980s. It is a stem cell-related pathway that plays a crucial role in embryonic development, tissue regeneration, and organogenesis. Aberrant activation of hedgehog signaling leads to pathological consequences, including a variety of human tumors such as pancreatic cancer. Multiple lines of evidence indicate that blockade of this pathway with several small-molecule inhibitors can inhibit the development of pancreatic neoplasm. In addition, activated hedgehog signaling has been reported to be involved in fibrogenesis in many tissues, including the pancreas. Therefore, new therapeutic targets based on hedgehog signaling have attracted a great deal of attention to alleviate pancreatic diseases. In this review, we briefly discuss the recent advances in hedgehog signaling in pancreatic fibrogenesis and carcinogenesis and highlight new insights on their potential relationship with respect to the development of novel targeted therapies.

WNT signaling in glioblastoma and therapeutic opportunities

WNTs and their downstream effectors regulate proliferation, death, and migration and cell fate decision. Deregulation of WNT signaling is associated with various cancers including GBM, which is the most malignant primary brain cancer. In this review, we will summarize the experimental evidence supporting oncogenic roles of WNT signaling in GBM and discuss current progress in the targeting of WNT signaling as an anti-cancer approach. In particular, we will focus on (1) genetic and epigenetic alterations that lead to aberrant WNT pathway activation in GBM, (2) WNT-mediated control of GBM stem cell maintenance and invasion, and (3) cross-talk between WNT and other signaling pathways in GBM. We will then review the discovery of agents that can inhibit WNT signaling in preclinical models and the current status of human clinical trials.

Protein arginine methyltransferase 1 interacts with Gli1 and regulates its transcriptional activity

Protein arginine methylation, which is mediated by the protein arginine methyltransferases (PRMTs), is associated with numerous fundamental cellular processes. Our previous studies have shown that PRMT1 activated Hedgehog signaling in the esophageal squamous cell carcinoma (ESCC) cells and promoted the growth and migration of cancer cells. However, the detailed mechanisms are unknown. In this study, it was found that PRMT1 interacted with the transcriptional factor Gli1 (glioma-associated oncogene homolog 1) in ESCC cells. The DNA-binding domain (DBD) of Gli1 is responsible for its interaction with PRMT1. Moreover, PRMT1 promoted the methylation of Gli1, and knocking down the expression of PRMT1 impaired the transcriptional activity as well as the biological functions of Gli1. Taken together, our study demonstrated that PRMT1 is a positive regulator of Hedgehog signaling, and PRMT1 might be a therapeutic target for ESCC.

Crosstalk with cancer-associated fibroblasts induces resistance of non-small cell lung cancer cells to epidermal growth factor receptor tyrosine kinase inhibition

Although lung cancers with activating mutations in the epidermal growth factor receptor (EGFR) are highly sensitive to selective EGFR tyrosine kinase inhibitors (TKIs), these tumors invariably develop acquired drug resistance. Host stromal cells have been found to have a considerable effect on the sensitivity of cancer cells to EGFR TKIs. Little is known, however, about the signaling mechanisms through which stromal cells contribute to the response to EGFR TKI in non-small cell lung cancer. This work examined the role of hedgehog signaling in cancer-associated fibroblast (CAF)-mediated resistance of lung cancer cells to the EGFR TKI erlotinib. PC9 cells, non-small cell lung cancer cells with EGFR-activating mutations, became resistant to the EGFR TKI erlotinib when cocultured in vitro with CAFs. Polymerase chain reaction and immunocytochemical assays showed that CAFs induced epithelial to mesenchymal transition phenotype in PC9 cells, with an associated change in the expression of epithelial to mesenchymal transition marker proteins including vimentin. Importantly, CAFs induce upregulation of the 7-transmembrane protein smoothened, the central signal transducer of hedgehog, suggesting that the hedgehog signaling pathway is active in CAF-mediated drug resistance. Indeed, downregulation of smoothened activity with the smoothened antagonist cyclopamine induces remodeling of the actin cytoskeleton independently of Gli-mediated transcriptional activity in PC9 cells. These findings indicate that crosstalk with CAFs plays a critical role in resistance of lung cancer to EGFR TKIs through induction of the epithelial to mesenchymal transition and may be an ideal therapeutic target in lung cancer.

GLI inhibitor GANT-61 diminishes embryonal and alveolar rhabdomyosarcoma growth by inhibiting Shh/AKT-mTOR axis

Rhabdomyosarcoma (RMS) typically arises from skeletal muscle. Currently, RMS in patients with recurrent and metastatic disease have no successful treatment. The molecular pathogenesis of RMS varies based on cancer sub-types. Some embryonal RMS but not other sub-types are driven by sonic hedgehog (Shh) signaling pathway. However, Shh pathway inhibitors particularly smoothened inhibitors are not highly effective in animals. Here, we show that Shh pathway effectors GLI1 and/or GLI2 are over-expressed in the majority of RMS cells and that GANT-61, a specific GLI1/2 inhibitor dampens the proliferation of both embryonal and alveolar RMS cells-derived xenograft tumors thereby blocking their growth. As compared to vehicle-treated control, about 50% tumor growth inhibition occurs in mice receiving GANT-61 treatment. The proliferation inhibition was associated with slowing of cell cycle progression which was mediated by the reduced expression of cyclins D1/2/3 & E and the concomitant induction of p21. GANT-61 not only reduced expression of GLI1/2 in these RMS but also significantly diminished AKT/mTOR signaling. The therapeutic action of GANT-61 was significantly augmented when combined with chemotherapeutic agents employed for RMS therapy such as temsirolimus or vincristine. Finally, reduced expression of proteins driving epithelial mesenchymal transition (EMT) characterized the residual tumors.

Gli1 promotes transforming growth factor-beta1- and epidermal growth factor-induced epithelial to mesenchymal transition in pancreatic cancer cells

BACKGROUND

The Hedgehog signaling pathway and its key target effector Gli1 are linked closely to the development of the epithelial to mesenchymal transition (EMT) in many cancers. The definite function of Gli1 in regulating the EMT of pancreatic cancer (PC), however, is still unclear.

METHODS

At the cell and tissue levels, we investigated the role of Gli1 in the initiation of EMT in PC with and without external stimulus treatments.

RESULTS

The immunohistochemistry results showed that Gli1 was associated positively with MMP9 but not with E-cad or Vimentin. Gli1 expression was associated positively with tumor T (P = .025) and Union for International Cancer Control stage (P = .032), whereas MMP9 expression was associated positively with lymph node metastasis (P = .017) and Union for International Cancer Control stage (P = .006). Furthermore, patients with Gli1 and MMP9 coexpression had poor overall survival (P = .015). Silencing of Gli1 alone without external stimulus had no effect on EMT but inhibited transforming growth factor-beta1 (TGFβ1)- and epidermal growth factor (EGF)-induced EMT in PANC-1, AsPC-1, and BxPC-3 PC cell lines, along with the inhibition of TGFβ1- and EGF-induced EMT-like cell morphology and invasion, down-regulation of E-cad, and up-regulation of MMP9 and Vimentin in those 3 cell lines, respectively.

CONCLUSION

Gli1 silencing alone has no effect on EMT initiation; however, it exerts a protumor role in the aggressive invasion of PC cells by promoting TGFβ1- and EGF-induced EMT.

Hedgehog signaling through GLI1 and GLI2 is required for epithelial-mesenchymal transition in human trophoblasts

BACKGROUND

Epithelial to mesenchymal transition (EMT) is critical for human placental development, trophoblastic differentiation, and pregnancy-associated diseases. Here, we investigated the effects of hedgehog (HH) signaling on EMT in human trophoblasts, and further explored the underlying mechanism.

METHODS

Human primary cytotrophoblasts and trophoblast-like JEG-3 cells were used as in vitro models. Quantitative real-time RT-PCR and Western blot analysis were performed to examine mRNA and protein levels, respectively. Lentiviruses expressing short hairpin RNA were used to knock down the target genes. Reporter assays and chromatin immunoprecipitation were performed to determine the transactivity. Cell migration, invasion and colony formation were accessed by wound healing, Matrigel-coated transwell, and colony formation assays, respectively.

RESULTS

Activation of HH signaling induced the transdifferentiation of cytotrophoblasts and trophoblast-like JEG-3 cells from epithelial to mesenchymal phenotypes, exhibiting the decreases in E-Cadherin expression as well as the increases in vimentin expression, invasion, migration and colony formation. Knockdown of GLI1 and GLI2 but not GLI3 attenuated HH-induced transdifferentiation, whereas GLI1 was responsible for the expression of HH-induced key EMT regulators including Snail1, Slug, and Twist, and both GLI1 and GLI2 acted directly as transcriptional repressor of CDH1 gene encoding E-Cadherin.

CONCLUSION

HH through GLI1 and GLI2 acts as critical signals in supporting the physiological function of mature placenta.

GENERAL SIGNIFICANCE

HH signaling through GLI1 and GLI2 could be required for the maintenance of human pregnancy.

DACH1 inhibits SNAI1-mediated epithelial-mesenchymal transition and represses breast carcinoma metastasis

Epithelial-mesenchymal transition (EMT) has a major role in cancer progression and metastasis. However, the specific mechanism of transcriptional repression involved in this process remains largely unknown. Dachshund homologue 1 (DACH1) expression is lost in invasive breast cancer with poor prognosis, and the role of DACH1 in regulating breast cancer metastasis is poorly understood. In this study, significant correlation between the expression of DACH1 and the morphology of breast cancer cells was observed. Subsequent investigation into the relationship between DACH1 and EMT showed that overexpression of DACH1 in ZR-75-30 cells induced a shift towards epithelial morphology and cell-cell adhesion, as well as increased the expression of the epithelial marker E-cadherin and suppressed cell migration and invasion. In contrast, silencing DACH1 in MCF-7 and T47D cells disrupted the epithelial morphology and cell-cell contact, reduced the expression of E-cadherin, and induced cell migration and invasion. DACH1 also specifically interacted with SNAI1, but not SNAI2, to form a complex, which could bind to the E-box on the E-cadherin promoter in an SNAI1-dependent manner. DACH1 inhibited the transcriptional activity of SNAI1, leading to the activation of E-cadherin in breast cancer cells. Furthermore, the level of DACH1 also correlated with the extent of metastasis in a mouse model. DACH1 overexpression significantly decreased the metastasis and growth of 4T1/Luc cells in BALB/c mice. Analysis of tissue samples taken from human breast cancers showed a significant correlation between the expression of DACH1 and E-cadherin in SNAI1-positive breast cancer. Collectively, our data identified a new mechanistic pathway for the regulation of EMT and metastasis of breast cancer cells, one that is based on the regulation of E-cadherin expression by direct DACH1-SNAI1 interaction.

The Hedgehog pathway: role in cell differentiation, polarity and proliferation

Hedgehog (Hh) is first described as a genetic mutation that has "spiked" phenotype in the cuticles of Drosophila in later 1970s. Since then, Hh signaling has been implicated in regulation of differentiation, proliferation, tissue polarity, stem cell population and carcinogenesis. The first link of Hh signaling to cancer was established through discovery of genetic mutations of Hh receptor gene PTCH1 being responsible for Gorlin syndrome in 1996. It was later shown that Hh signaling is associated with many types of cancer, including skin, leukemia, lung, brain and gastrointestinal cancers. Another important milestone for the Hh research field is the FDA approval for the clinical use of Hh inhibitor Erivedge/Vismodegib for treatment of locally advanced and metastatic basal cell carcinomas. However, recent clinical trials of Hh signaling inhibitors in pancreatic, colon and ovarian cancer all failed, indicating a real need for further understanding of Hh signaling in cancer. In this review, we will summarize recent progress in the Hh signaling mechanism and its role in human cancer.

Back to the drawing board: Re-thinking the role of GLI1 in pancreatic carcinogenesis

Aberrant activation of the transcription factor GLI1, a central effector of the Hedgehog (HH) pathway, is associated with several malignancies, including pancreatic ductal adenocarcinoma (PDAC), one of most deadly human cancers. GLI1 has been described as an oncogene in PDAC, making it a promising target for drug therapy. Surprisingly, clinical trials targeting HH/GLI1 axis in advanced PDAC were unsuccessful, leaving investigators questioning the mechanism behind these failures. Recent evidence suggests the loss of GLI1 in the later stages of PDAC may actually accelerate disease. This indicates GLI1 may play a dual role in PDAC, acting as an oncogene in the early stages of disease and a tumor-suppressor in the late stages.

Back to the drawing board: Re-thinking the role of GLI1 in pancreatic carcinogenesis

Aberrant activation of the transcription factor GLI1, a central effector of the Hedgehog (HH) pathway, is associated with several malignancies, including pancreatic ductal adenocarcinoma (PDAC), one of most deadly human cancers. GLI1 has been described as an oncogene in PDAC, making it a promising target for drug therapy. Surprisingly, clinical trials targeting HH/GLI1 axis in advanced PDAC were unsuccessful, leaving investigators questioning the mechanism behind these failures. Recent evidence suggests the loss of GLI1 in the later stages of PDAC may actually accelerate disease. This indicates GLI1 may play a dual role in PDAC, acting as an oncogene in the early stages of disease and a tumor-suppressor in the late stages.

Gli1 protein regulates the S-phase checkpoint in tumor cells via Bid protein, and its inhibition sensitizes to DNA topoisomerase 1 inhibitors

Aberrant expression of hedgehog molecules, particularly Gli1, is common in cancers of many tissues and is responsible for their aggressive behavior and chemoresistance. Here we demonstrate a novel and tumor-specific role for aberrant Gli1 in the regulation of the S-phase checkpoint that suppresses replication stress and resistance to chemotherapy. Inhibition of Gli1 in tumor cells induced replication stress-mediated DNA damage response, attenuated their clonogenic potential, abrogated camptothecin (CPT)-induced Chk1 phosphorylation, and potentiated its cytotoxicity. However, in normal fibroblasts, Gli1 siRNAs showed no significant changes in CPT-induced Chk1 phosphorylation. Further analysis of ataxia telangiectasia and Rad3-related protein (ATR)/Chk1 signaling cascade genes in tumor cells revealed an unexpected mechanism whereby Gli1 regulates ATR-mediated Chk1 phosphorylation by transcriptional regulation of the BH3-only protein Bid. Consistent with its role in DNA damage response, Bid down-regulation in tumor cells abolished CPT-induced Chk1 phosphorylation and sensitized them to CPT. Correspondingly, Gli1 inhibition affected the expression of Bid and the association of replication protein A (RPA) with the ATR- interacting protein (ATRIP)-ATR complex, and this compromised the S-phase checkpoint. Conversely, complementation of Bid in Gli1-deficient cells restored CPT-induced Chk1 phosphorylation. An in silico analysis of the Bid promoter identified a putative Gli1 binding site, and further studies using luciferase reporter assays confirmed Gli1-dependent promoter activity. Collectively, our studies established a novel connection between aberrant Gli1 and Bid in the survival of tumor cells and their response to chemotherapy, at least in part, by regulating the S-phase checkpoint. Importantly, our data suggest a novel drug combination of Gli1 and Top1 inhibitors as an effective therapeutic strategy in treating tumors that expresses Gli1.

Signaling pathway cooperation in TGF-β-induced epithelial-mesenchymal transition

Transdifferentiation of epithelial cells into cells with mesenchymal properties and appearance, that is, epithelial-mesenchymal transition (EMT), is essential during development, and occurs in pathological contexts, such as in fibrosis and cancer progression. Although EMT can be induced by many extracellular ligands, TGF-β and TGF-β-related proteins have emerged as major inducers of this transdifferentiation process in development and cancer. Additionally, it is increasingly apparent that signaling pathways cooperate in the execution of EMT. This update summarizes the current knowledge of the coordination of TGF-β-induced Smad and non-Smad signaling pathways in EMT, and the remarkable ability of Smads to cooperate with other transcription-directed signaling pathways in the control of gene reprogramming during EMT.

Emerging role of mucins in epithelial to mesenchymal transition

Epithelial to mesenchymal transition (EMT) is an important and complex phenomenon that determines the aggressiveness of cancer cells. The morphological transformation of cancerous cells is accompanied by various cellular processes such as alterations in cell-cell adhesion, cell matrix degradation, down regulation of epithelial marker Ecadherin and upregulation of mesenchymal markers N-cadherin and Vimentin. Besides these markers several other important tumor antigens/mucins are also involved in the EMT process. Mainly high molecular weight glycoproteins such as mucin molecules (MUC1, MUC4 and MUC16) play a major role in the cellular transformation and signaling alteration in EMT process. In addition to these factors, EMT may be an essential process triggering the emergence or expansion of the CSC population, which slowly results in the initiation of tumor at metastatic sites. Furthermore, mucins have been demonstrated to be involved in the EMT process and also in the enrichment of cancer stem cell population. Mucin mediated EMT is very complex since the key components of tumor microenvironment are also regulating mucin molecules. In this review, we have discussed all the aforementioned factors and their mechanistic involvement for EMT process.

The Yes-associated protein controls the cell density regulation of Hedgehog signaling

The evolutionarily conserved Hedgehog (Hh) signaling pathway is essential for correct embryogenesis and is misregulated in several malignancies. In cell culture, Hh-sensitive cells display a striking dependence on cell density with active Hh signaling requiring cell-to-cell contact. As the Hippo/YAP system is tightly linked to cell density control and contact inhibition, we investigated the cross-talk between the two pathways. Our data reveal that the suppression of Hh signaling in the absence of cellular contacts is independent of primary cilia and is mediated by the YAP oncogene. Overexpression of YAP blocks Hh signaling whereas RNA interference-mediated knockdown of YAP enhances Hh/GLI activity. Despite this negative regulation, Hh signaling promotes YAP activity through post-transcriptional mechanisms, resulting in a negative feedback loop. In vivo, we found strong nuclear YAP immunoreactivity restricted to compartments with low Hh pathway activity in human and mouse pancreatic cancer. Finally, we identified protease-activated receptors (PARs) as molecules being able to override the inverse Hippo/Hh regulation, potentially giving tumors a mechanism to utilize both oncogenic pathways in parallel.

Hedgehog/Gli promotes epithelial-mesenchymal transition in lung squamous cell carcinomas

Background

Squamous cell carcinomas (SCC) account for approximately 30% of non-small cell lung cancer. Investigation of the mechanism of invasion and metastasis of lung SCC will be of great help for the development of meaningful targeted therapeutics. This study is intended to understand whether the activation of Hedgehog (Hh) pathway is involved in lung SCC, and whether activated Hh signaling regulates metastasis through epithelial-mesenchymal transition (EMT) in lung SCC.

Methods

Two cohorts of patients with lung SCC were studied. Protein expression was examined by immunohistochemistry, Western blot, or immunofluorescence. Protein expression levels in tissue specimens were scored and correlations were analyzed. Vismodegib and a Gli inhibitor were used to inhibit Shh/Gli activity, and recombinant Shh proteins were used to stimulate the Hh pathway in lung SCC cell lines. Cell migration assay was performed in vitro.

Results

Shh/Gli pathway components were aberrantly expressed in lung SCC tissue samples. Gli1 expression was reversely associated with the expression of EMT markers E-Cadherin and β-Catenin in lung SCC specimens. Inhibition of the Shh/Gli pathway suppressed migration and up-regulated E-Cadherin expression in lung SCC cells. Stimulation of the pathway increased migration and down-regulated E-Cadherin expression in lung SCC cells.

Conclusions

Our results suggested that the Shh/Gli pathway may be critical for lung SCC recurrence, metastasis and resistance to chemotherapy. Inhibition of the Shh/Gli pathway activity/function is a potential therapeutic strategy for the treatment of lung SCC patients.

The transcription factor GLI1 interacts with SMAD proteins to modulate transforming growth factor β-induced gene expression in a p300/CREB-binding protein-associated factor (PCAF)-dependent manner

The biological role of the transcription factor GLI1 in the regulation of tumor growth is well established; however, the molecular events modulating this phenomenon remain elusive. Here, we demonstrate a novel mechanism underlying the role of GLI1 as an effector of TGFβ signaling in the regulation of gene expression in cancer cells. TGFβ stimulates GLI1 activity in cancer cells and requires its transcriptional activity to induce BCL2 expression. Analysis of the mechanism regulating this interplay identified a new transcriptional complex including GLI1 and the TGFβ-regulated transcription factor, SMAD4. We demonstrate that SMAD4 physically interacts with GLI1 for concerted regulation of gene expression and cellular survival. Activation of the TGFβ pathway induces GLI1-SMAD4 complex binding to the BCL2 promoter whereas disruption of the complex through SMAD4 RNAi depletion impairs GLI1-mediated transcription of BCL2 and cellular survival. Further characterization demonstrated that SMAD2 and the histone acetyltransferase, PCAF, participate in this regulatory mechanism. Both proteins bind to the BCL2 promoter and are required for TGFβ- and GLI1-stimulated gene expression. Moreover, SMAD2/4 RNAi experiments showed that these factors are required for the recruitment of GLI1 to the BCL2 promoter. Finally, we determined whether this novel GLI1 transcriptional pathway could regulate other TGFβ targets. We found that two additional TGFβ-stimulated genes, INTERLEUKIN-7 and CYCLIN D1, are dependent upon the intact GLI1-SMAD-PCAF complex for transcriptional activation. Collectively, these results define a novel epigenetic mechanism that uses the transcription factor GLI1 and its associated complex as a central effector to regulate gene expression in cancer cells.

Inactivation of the transcription factor GLI1 accelerates pancreatic cancer progression

The role of GLI1 in pancreatic tumor initiation promoting the progression of preneoplastic lesions into tumors is well established. However, its function at later stages of pancreatic carcinogenesis remains poorly understood. To address this issue, we crossed the gli1 knock-out (GKO) animal with cre-dependent pancreatic activation of oncogenic kras concomitant with loss of the tumor suppressor tp53 (KPC). Interestingly, in this model, GLI1 played a tumor-protective function, where survival of GKO/KPC mice was reduced compared with KPC littermates. Both cohorts developed pancreatic cancer without significant histopathological differences in survival studies. However, analysis of mice using ultrasound-based imaging at earlier time points showed increased tumor burden in GKO/KPC mice. These animals have larger tumors, decreased body weight, increased lactate dehydrogenase production, and severe leukopenia. In vivo and in vitro expression studies identified FAS and FAS ligand (FASL) as potential mediators of this phenomenon. The FAS/FASL axis, an apoptotic inducer, plays a role in the progression of pancreatic cancer, where its expression is usually lost or significantly reduced in advanced stages of the disease. Chromatin immunoprecipitation and reporter assays identified FAS and FASL as direct targets of GLI1, whereas GKO/KPC mice showed lower levels of this ligand compared with KPC animals. Finally, decreased levels of apoptosis were detected in tumor tissue in the absence of GLI1 by TUNEL staining. Together, these findings define a novel pathway regulated by GLI1 controlling pancreatic tumor progression and provide a new theoretical framework to help with the design and analysis of trials targeting GLI1-related pathways.

Molecular mechanism underlying lymphatic metastasis in pancreatic cancer

As the most challenging human malignancies, pancreatic cancer is characterized by its insidious symptoms, low rate of surgical resection, high risk of local invasion, metastasis and recurrence, and overall dismal prognosis. Lymphatic metastasis, above all, is recognized as an early adverse event in progression of pancreatic cancer and has been described to be an independent poor prognostic factor. It should be noted that the occurrence of lymphatic metastasis is not a casual or stochastic but an ineluctable and designed event. Increasing evidences suggest that metastasis-initiating cells (MICs) and the microenvironments may act as a double-reed style in this crime. However, the exact mechanisms on how they function synergistically for this dismal clinical course remain largely elusive. Therefore, a better understanding of its molecular and cellular mechanisms involved in pancreatic lymphatic metastasis is urgently required. In this review, we will summarize the latest advances on lymphatic metastasis in pancreatic cancer.

Targeting hedgehog signaling in cancer: research and clinical developments

Since its first description in Drosophila by Drs Nusslein-Volhard and Wieschaus in 1980, hedgehog (Hh) signaling has been implicated in regulation of cell differentiation, proliferation, tissue polarity, stem cell maintenance, and carcinogenesis. The first link of Hh signaling to cancer was established through studies of Gorlin syndrome in 1996 by two independent teams. Later, it was shown that Hh signaling may be involved in many types of cancer, including skin, leukemia, lung, brain, and gastrointestinal cancers. In early 2012, the US Food and Drug Administration approved the clinical use of Hh inhibitor Erivedge/vismodegib for treatment of locally advanced and metastatic basal cell carcinomas. With further investigation, it is possible to see more clinical applications of Hh signaling inhibitors. In this review, we will summarize major advances in the last 3 years in our understanding of Hh signaling activation in human cancer, and recent developments in preclinical and clinical studies using Hh signaling inhibitors.

Possible role of sonic hedgehog and epithelial-mesenchymal transition in renal cell cancer progression

Purpose

Sonic hedgehog (Shh) signaling and epithelial-mesenchymal transition (EMT) are both known to relate to cancer progression. The purpose of this study was to investigate the role of Shh signaling and EMT in renal cell carcinoma (RCC).

Materials and Methods

Cell proliferation was assayed in RCC cell lines in the presence or absence of a Shh signaling stimulator, recombinant Shh (r-Shh) protein, or a Shh signaling inhibitor, cyclopamine. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed to study the expression of EMT markers (E-cadherin, N-cadherin, and vimentin) and osteonectin. The expression of Ki-67, Gli-1, osteonectin, and EMT markers in nephrectomy specimens from RCC patients was also measured by immunohistochemical (IHC) staining.

Results

RCC cells showed enhanced cell proliferation by r-Shh protein, whereas cell proliferation was suppressed by the addition of cyclopamine in RenCa cells. Real-time RT-PCR showed that r-Shh suppressed the expression of E-cadherin and that this suppression was partly blocked by cyclopamine alone in RenCa cells. In the IHC results, osteonectin significantly correlated with vein sinus invasion (p=0.0218), and the expression of vimentin significantly correlated with lymphatic invasion (p=0.0392).

Conclusions

Shh signaling and EMT play roles in RCC progression, and the Shh signaling inhibitor cyclopamine might be a possible molecular targeted therapeutic strategy for RCC.

Hedgehog signaling regulates hypoxia induced epithelial to mesenchymal transition and invasion in pancreatic cancer cells via a ligand-independent manner

Background

Hypoxia plays a vital role in cancer epithelial to mesenchymal transition (EMT) and invasion. However, it is not quite clear how hypoxia may contribute to these events. Here we investigate the role of Hedgehog (Hh) signaling in hypoxia induced pancreatic cancer EMT and invasion.

Methods

Pancreatic cancer cells were cultured under controlled hypoxia conditions (3% O2) or normoxic conditions. HIF-1α siRNA, cyclopamine (a SMO antagonist) and GLI1 siRNA were used to inhibit HIF-1α transcription or Hh signaling activation. The effect of hypoxia and Hh signaling on cancer cell EMT and invasion were evaluated by Quantitative real-time PCR analysis, Western blot analysis and invasion assay.

Results

Here, we show that non-canonical Hh signaling is required as an important role to switch on hypoxia-induced EMT and invasion in pancreatic cancer cells. Moreover, our data demonstrate hypoxia induces EMT process as well as invasion, and activates the non-canonical Hh pathway without affecting sonic hedgehog homolog (SHH) expression. Moreover, these effects are reversible upon HIF-1α siRNA interference with unchanged SHH and patched1 (PTCH1) level. Furthermore, our data demonstrate that hypoxia induced invasion and EMT process are effectively inhibited by Smoothened (SMO) antagonist cyclopamine and GLI1 siRNA. In addition, GLI1 interference inhibited EMT progress with significantly suppressed vimentin expression, whereas inhibition of SMO through cyclopamine could not reduce vimentin level. This data indicate that hypoxia could trigger other factors (such as TGF-β, KRAS or RTK) bypassing SMO to activate GLI1 directly.

Conclusions

Our findings suggest that Hh signaling modulates hypoxia induced pancreatic cancer EMT and invasion in a ligand-independent manner. Thus, Hh signaling may represent a promising therapeutic target for preventing pancreatic cancer progression.

Inhibition of cell migration by ouabain in the A549 human lung cancer cell line

The Na⁺/K⁺-ATPase α subunit is highly expressed in malignant cells. Ouabain, a cardioactive glycoside, binds to the Na⁺/K⁺-ATPase α subunit and inhibits the activity of Na⁺/K⁺-ATPase. In the present study, the effect of ouabain on the migration of A549 cells was analyzed using the wound healing and transwell chamber migration assays. The impact of ouabain on the expression of E-cadherin, N-cadherin, vimentin, matrix metalloprotease (MMP)-2 and MMP-9 was also evaluated. Ouabain treatment not only inhibited the epidermal growth factor (EGF)-enhanced migration of A549 cells, but also inhibited the basal migration of A549 cells in the absence of EGF. Ouabain decreased the overexpression of N-cadherin and vimentin induced by EGF, and decreased the expression of MMP-2 and -9 in the presence or absence of EGF. Na⁺/K⁺-ATPase is a potent therapeutic target in lung cancer and these observations indicated that the Na⁺/K⁺-ATPase inhibitor, ouabain, retards the invasion of lung cancer cells.

Persistent activation of pancreatic stellate cells creates a microenvironment favorable for the malignant behavior of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common malignant tumors with poor prognosis due to extremely high malignancy, low rate of eligibility for surgical resection and chemoradiation resistance. Increasing evidence indicate that the interaction between activated pancreatic stellate cells (PSCs) and PDAC cells plays an important role in the development of PDAC. By producing high levels of cytokines, chemotactic factors, growth factors and excessive extracellular matrix (ECM), PSCs create desmoplasia and a hypoxic microenvironment that promote the initiation, development, evasion of immune surveillance, invasion, metastasis and resistance to chemoradiation of PDAC. Therefore, targeting the interaction between PSCs and PDAC cells may represent a novel therapeutic approach to advanced PDAC, especially therapies that target PSCs of the pancreatic tumor microenvironment.

RNA editing of the GLI1 transcription factor modulates the output of Hedgehog signaling

The Hedgehog (HH) signaling pathway has important roles in tumorigenesis and in embryonal patterning. The Glioma-associated oncogene 1 (GLI1) is a key molecule in HH signaling, acting as a transcriptional effector and, moreover, is considered to be a potential therapeutic target for several types of cancer. To extend our previous focus on the implications of alternative splicing for HH signal transduction, we now report on an additional post-transcriptional mechanism with an impact on GLI1 activity, namely RNA editing. The GLI1 mRNA is highly edited at nucleotide 2179 by adenosine deamination in normal cerebellum, but the extent of this modification is reduced in cell lines from the cerebellar tumor medulloblastoma. Additionally, basal cell carcinoma tumor samples exhibit decreased GLI1 editing compared with normal skin. Interestingly, knocking down of either ADAR1 or ADAR2 reduces RNA editing of GLI1. This adenosine to inosine substitution leads to a change from Arginine to Glycine at position 701 that influences not only GLI1 transcriptional activity, but also GLI1-dependent cellular proliferation. Specifically, the edited GLI1, GLI1-701G, has a higher capacity to activate most of the transcriptional targets tested and is less susceptible to inhibition by the negative regulator of HH signaling suppressor of fused. However, the Dyrk1a kinase, implicated in cellular proliferation, is more effective in increasing the transcriptional activity of the non-edited GLI1. Finally, introduction of GLI1-701G into medulloblastoma cells confers a smaller increase in cellular growth relative to GLI1. In conclusion, our findings indicate that RNA editing of GLI1 is a regulatory mechanism that modulates the output of the HH signaling pathway.

A feedback regulation between Kindlin-2 and GLI1 in prostate cancer cells

Kindlin-2 is engaged in tumor progression. However, the mechanism accounting for Kindlin-2 regulation in tumor cells remained largely unknown. Here, we report a regulatory loop between Kindlin-2 and GLI1, an effector of Hedgehog signaling pathway. We show that Kindlin-2 is transcriptionally downregulated via GLI1 occupancy on the Kindlin-2 promoter. Adversely, we found that Kindlin-2 promotes GLI1 expression through a mechanism involving GSK3β inactivation and is independent of Smoothened. Functionally, knockdown of Kindlin-2 cooperates with cyclopamine, a Smoothened antagonist, to decrease the viability of prostate cancer cells. Taken together, targeting the Kindlin-2-GLI1 feedback loop may facilitate the killing of prostate cancer cells.