Hedgehog pathway as a potential treatment target in human cholangiocarcinoma

Epithelial-Mesenchymal Transition in Cancer: A Focus on Itraconazole, a Hedgehog Inhibitor

Cancer, and the resulting mortality from it, is an ever-increasing concern in global health. Cancer mortality stems from the metastatic progression of the disease, by dissemination of the tumor cells. Epithelial-Mesenchymal Transition, the major hypothesis purported to be the origin of metastasis, confers mesenchymal phenotype to epithelial cells in a variety of contexts, physiological and pathological. EMT in cancer leads to rise of cancer-stem-like cells, drug resistance, relapse, and progression of malignancy. Inhibition of EMT could potentially attenuate the mortality. While novel molecules for inhibiting EMT are underway, repurposing drugs is also being considered as a viable strategy. In this review, Itraconazole is focused upon, as a repurposed molecule to mitigate EMT. Itraconazole is known to inhibit Hedgehog signaling, and light is shed upon the existing evidence, as well as the questions remaining to be answered.

Beyond cyclopamine: Targeting Hedgehog signaling for cancer intervention

Hedgehog (Hh) signaling plays a significant role in embryogenesis and several physiological processes, such as wound healing and organ homeostasis. In a pathological setting, it is associated with oncogenesis and is responsible for disease progression and poor clinical outcomes. Hedgehog signaling mediates downstream actions via Glioma Associated Oncogene Homolog (GLI) transcription factors. Inhibiting Hh signaling is an important oncological strategy in which inhibitors of the ligands SMO or GLI have been looked at. This review briefly narrates the Hh ligands, signal transduction, the target genes involved and comprehensively describes the numerous inhibitors that have been evaluated for use in various neoplastic settings.

Repurposing the Hedgehog pathway inhibitor, BMS-833923, as a phosphatidylglycerol-selective membrane-disruptive colistin adjuvant against ESKAPE pathogens

The rapid emergence and spread of multi-drug- or pan-drug-resistant bacterial pathogens, such as ESKAPE, pose a serious threat to global health. However, the development of novel antibiotics is hindered by difficulties in identifying new antibiotic targets and the rapid development of drug resistance. Drug repurposing is an effective alternative strategy for combating antibiotic resistance that both saves resources and extends the life of existing antibiotics in combination treatment regimens. Screening of a chemical compound library identified BMS-833923 (BMS), a smoothened antagonist that kills Gram-positive bacteria directly, and potentiates colistin to destroy various Gram-negative bacteria. BMS did not induce detectable antibiotic resistance in vitro, and showed effective activity against drug-resistant bacteria in vivo. Mechanistic studies revealed that BMS caused membrane disruption by targeting the membrane phospholipids phosphatidylglycerol and cardiolipin, promoting membrane dysfunction, metabolic disturbance, leakage of cellular components, and, ultimately, cell death. This study describes a potential strategy to enhance the efficacy of colistin and combat multi-drug-resistant ESKAPE pathogens.

Hedgehog signaling in tissue homeostasis, cancers, and targeted therapies

The past decade has seen significant advances in our understanding of Hedgehog (HH) signaling pathway in various biological events. HH signaling pathway exerts its biological effects through a complex signaling cascade involved with primary cilium. HH signaling pathway has important functions in embryonic development and tissue homeostasis. It plays a central role in the regulation of the proliferation and differentiation of adult stem cells. Importantly, it has become increasingly clear that HH signaling pathway is associated with increased cancer prevalence, malignant progression, poor prognosis and even increased mortality. Understanding the integrative nature of HH signaling pathway has opened up the potential for new therapeutic targets for cancer. A variety of drugs have been developed, including small molecule inhibitors, natural compounds, and long non-coding RNA (LncRNA), some of which are approved for clinical use. This review outlines recent discoveries of HH signaling in tissue homeostasis and cancer and discusses how these advances are paving the way for the development of new biologically based therapies for cancer. Furthermore, we address status quo and limitations of targeted therapies of HH signaling pathway. Insights from this review will help readers understand the function of HH signaling in homeostasis and cancer, as well as opportunities and challenges of therapeutic targets for cancer.

Cholangiocarcinoma tumor microenvironment highlighting fibrosis and matrix components

Cholangiocarcinoma (CCA) is an extremely aggressive malignancy characterized by a very limited prognosis and scarce treatment options. The majority of patients are diagnosed at an advanced stage and do not qualify for potentially curative surgical treatments, making CCA an increasingly prevalent global challenge. CCA is characterized by a highly reactive desmoplastic stroma, with complex mechanisms underlying the mutual interactions between tumor cells and stromal compartment. This review focuses on the recent studies examining CCA’s biological features, with particular reference to the tumor reactive stroma (TRS) and its role in CCA progression, including matrix remodeling, angiogenesis and lymphangiogenesis, metastasis, and immune evasion. After giving a panoramic view of the relationship between the tumoral and stromal compartment (cancer-associated fibroblast, CAFs and tumor-associated macrophages, TAMs), this review also discusses the current therapeutic approaches to counteract CAFs and TAMs effects on CCA progression.

Understanding Abnormal SMO-SHH Signaling in Autism Spectrum Disorder: Potential Drug Target and Therapeutic Goals

Autism is a multifactorial neurodevelopmental condition; it demonstrates some main characteristics, such as impaired social relationships and increased repetitive behavior. The initiation of autism spectrum disorder is mostly triggered during brain development by the deregulation of signaling pathways. Sonic hedgehog (SHH) signaling is one such mechanism that influences neurogenesis and neural processes during the development of the central nervous system. SMO-SHH signaling is also an important part of a broad variety of neurological processes, including neuronal cell differentiation, proliferation, and survival. Dysregulation of SMO-SHH signaling leads to many physiological changes that lead to neurological disorders such as ASD and contribute to cognitive decline. The aberrant downregulation of SMO-SHH signals contributes to the proteolytic cleavage of GLI (glioma-associated homolog) into GLI3 (repressor), which increases oxidative stress, neuronal excitotoxicity, neuroinflammation, and apoptosis by suppressing target gene expression. We outlined in this review that SMO-SHH deregulation plays a crucial role in the pathogenesis of autism and addresses the current status of SMO-SHH pathway modulators. Additionally, a greater understanding of the SHH signaling pathway is an effort to improve successful treatment for autism and other neurological disorders.

Pharmacological Inhibition of Sonic Hedgehog Signaling Suppresses Tumor Development in a Murine Model of Intrahepatic Cholangiocarcinoma

Cholangiocarcinoma (CCC) is the second most primary liver cancer with an aggressive biological behavior, and its incidence increases steadily. An aberrant up-regulation of the sonic hedgehog signaling pathway has been reported in a variety of hepatic diseases including hepatic inflammation, fibrosis, as well as cancer. In this study, we determined the effect of a sonic hedgehog inhibitor, vismodegib, on the development of CCC. Through database analyses, we found sonic hedgehog signaling was up-regulated in human CCC, based on overexpression of its target genes, GLI1 and GLI2. Further, human CCC cells were highly sensitive to the treatment with vismodegib in vitro. Based on the data, we investigated the in vivo anti-cancer efficacy of vismodegib in CCC employing a murine model of CCC developed by hydrodynamic tail vein injection method. In the murine model, CCC induced by constitutively active forms of TAZ and PI3K exhibited up-regulated sonic hedgehog signaling. Treatment of vismodegib significantly suppressed tumor development in the murine CCC model, based on comparison of gross morphologies and liver weight/body weight. It is expected that pharmacological inhibition of sonic hedgehog signaling would be an effective molecular target therapy for CCC.

Cancer Stem Cell for Tumor Therapy

Simple Summary

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

Abstract

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

The Role of the Hedgehog Pathway in Cholangiocarcinoma

Simple Summary

Cholangiocarcinoma (CCA) is one of the most refractory malignancies with a high mortality rate. Among all the pathways involved in CCA development, emerging evidence highlights Hedgehog (HH) signaling as a substantial player in CCA-genesis and development. The pro-tumoral function of HH provides potential therapeutic implications, and recently the use of HH inhibitors has paved the way for clinical application in various solid tumors. Targeting HH members, namely Hedgehog ligands, SMO transmembrane protein and GLI transcription factors may thus confer therapeutic options for the improvement of CCA treatment outcome.

Abstract

Cholangiocarcinoma (CCA) is a poorly treatable type of cancer and, along with hepatocellular carcinoma (HCC), is the predominant type of primitive liver cancer in adults. The lack of understanding of CCA biology has slowed down the identification of novel targets and the development of effective treatments. While tumors share some general characteristics, detailed knowledge of specific features is essential for the development of effectively tailored therapeutic approaches. The Hedgehog (HH) signaling cascade regulates stemness biology, embryonal development, tissue homeostasis, and cell proliferation and differentiation. Its aberrant activation has been associated with a variety of solid and hematological human malignancies. Several HH-inhibiting compounds have been indeed developed as potential anticancer agents in different types of tumors, with Smoothened and GLI inhibitors showing the most promising results. Beside its well-established function in other tumors, findings regarding the HH signaling in CCA are still controversial. Here we will give an overview of the most important clinical and molecular features of cholangiocarcinoma, and we will discuss the available evidence of the crosstalk between the HH signaling pathway and the cholangiocarcinoma cell biology.

Cholangiocarcinoma: shedding light on the most promising drugs in clinical development

Introduction: Cholangiocarcinoma (CCA) is a diverse group of fatal malignancies arising from the biliary tract. Surgical resection with negative margin offers the only potentially curative option. The majority of patients present at locally advanced or metastatic stages, when surgical resection is not feasible, highlighting the significance of systemic therapy. Given the limited effectiveness of traditional chemotherapy regimens in CCA, many investigators have focused on developing novel molecular therapies targeting key aberrant signaling pathways.Areas covered: We present the main genomic aberrations known to play a key role in cholangiocarcinogenesis and discuss promising targeted therapies in clinical development.In October of 2020, a review of the English literature was performed utilizing PubMed and Web of Science databases for the keywords of 'cholangiocarcinoma', 'biliary tract cancer', and 'targeted therapy'.Expert opinion: Unfortunately, despite encouraging results in preclinical studies, the outcome of clinical trials with established targeted therapies like anti-EGFR medications have been discouraging. Currently, agents targeting FGFR2 fusion and IDH1/2 mutations hold great promise for improving the management of CCA. Future studies focused on enhancing our understanding of key aberrant signaling pathways of cholangiocarcinogenesis and the design of homogeneous and biomarker-driven cohorts are key elements of establishing precision medicine in CCA.

Targeted therapies for extrahepatic cholangiocarcinoma: preclinical and clinical development and prospects for the clinic

Introduction: Until recently, cholangiocarcinoma (CCA) was a largely overlooked disease, and among CCAs, extrahepatic CCA (eCCA) was even more neglected. Despite the growing impact of molecularly targeted therapies and immunotherapy, prognosis of eCCA is dismal. Therefore, unraveling the complex molecular landscape of eCCA has become an urgent need. Deep phenotyping studies have revealed that eCCA is a heterogeneous tumor, harboring specific alterations categorizable into four classes, 'Mesenchymal', 'Proliferation', 'Immune', 'Metabolic'. Molecular alterations convey the activation of several pro-oncogenic pathways, where either actionable drivers or outcome predictors can be identified.Areas covered: We offer insights on perturbed pathways, molecular profiling, and actionable targets in eCCA and present a perspective on the potential stepping-stones to future progress. A systematic literature search in PubMed/ClinicalTrials.gov websites was performed by authors from different disciplines according to their specific topic knowledge to identify the newest and most relevant advances in precision medicine of eCCA.Expert opinion: eCCA is a distinct entity with unique features in terms of molecular classes, oncogenic drivers, and tumor microenvironment. Since more prevalent mutations are currently undruggable, and immunotherapy can be offered only to a minority of patients, international collaborations are instrumental to improve the understanding of the molecular underpins of this disease.

The Role of Smoothened in Cancer

Smoothened (SMO) belongs to the Hedgehog (HH) signaling pathway, which regulates cell growth, migration, invasion and stem cells in cancer. The HH signaling pathway includes both canonical and noncanonical pathways. The canonical HH pathway functions through major HH molecules such as HH ligands, PTCH, SMO and GLI, whereas the noncanonical HH pathway involves the activation of SMO or GLI through other pathways. The role of SMO has been discussed in different types of cancer, including breast, liver, pancreatic and colon cancers. SMO expression correlates with tumor size, invasiveness, metastasis and recurrence. In addition, SMO inhibitors can suppress cancer formation, reduce the proliferation of cancer cells, trigger apoptosis and suppress cancer stem cell activity. A better understanding of the role of SMO in cancer could contribute to the development of novel therapeutic approaches.

Emerging pathways for precision medicine in management of cholangiocarcinoma

Cholangiocarcinoma (CCA) is the second most common biliary tract malignancy with a dismal prognosis. Surgical resection with a negative microscopic margin offers the only hope for long-term survival. However, the majority of patients present with advanced disease not amenable to curative resection, mainly due to late presentation and aggressive nature of the disease. Unfortunately, due to the heterogeneous nature of CCA as well as limitations of available chemotherapy medications, traditional chemotherapy regimens offer limited survival benefit. Recent advances in genomic studies and next-generation sequencing techniques have assisted in better understanding of cholangiocarcinogenesis and identification of potential aberrant signaling pathways. Targeting the specific genomic abnormalities via novel molecular therapies has opened a new avenue in management of CCA with encouraging results in preclinical studies and early clinical trials. In this review, we present emerging therapies for precision medicine in CCA.

Common features between neoplastic and preneoplastic lesions of the biliary tract and the pancreas

the bile duct system and pancreas show many similarities due to their anatomical proximity and common embryological origin. Consequently, preneoplastic and neoplastic lesions of the bile duct and pancreas share analogies in terms of molecular, histological and pathophysiological features. Intraepithelial neoplasms are reported in biliary tract, as biliary intraepithelial neoplasm (BilIN), and in pancreas, as pancreatic intraepithelial neoplasm (PanIN). Both can evolve to invasive carcinomas, respectively cholangiocarcinoma (CCA) and pancreatic ductal adenocarcinoma (PDAC). Intraductal papillary neoplasms arise in biliary tract and pancreas. Intraductal papillary neoplasm of the biliary tract (IPNB) share common histologic and phenotypic features such as pancreatobiliary, gastric, intestinal and oncocytic types, and biological behavior with the pancreatic counterpart, the intraductal papillary mucinous neoplasm of the pancreas (IPMN). All these neoplastic lesions exhibit similar immunohistochemical phenotypes, suggesting a common carcinogenic process. Indeed, CCA and PDAC display similar clinic-pathological features as growth pattern, poor response to conventional chemotherapy and radiotherapy and, as a consequence, an unfavorable prognosis. The objective of this review is to discuss similarities and differences between the neoplastic lesions of the pancreas and biliary tract with potential implications on a common origin from similar stem/progenitor cells.

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.

Genomic testing, tumor microenvironment and targeted therapy of Hedgehog-related human cancers

Hedgehog signals are transduced through Patched receptors to the Smoothened (SMO)-SUFU-GLI and SMO-Gi-RhoA signaling cascades. MTOR-S6K1 and MEK-ERK signals are also transduced to GLI activators through post-translational modifications. The GLI transcription network up-regulates target genes, such as BCL2, FOXA2, FOXE1, FOXF1, FOXL1, FOXM1, GLI1, HHIP, PTCH1 and WNT2B, in a cellular context-dependent manner. Aberrant Hedgehog signaling in tumor cells leads to self-renewal, survival, proliferation and invasion. Paracrine Hedgehog signaling in the tumor microenvironment (TME), which harbors cancer-associated fibroblasts, leads to angiogenesis, fibrosis, immune evasion and neuropathic pain. Hedgehog-related genetic alterations occur frequently in basal cell carcinoma (BCC) (85%) and Sonic Hedgehog (SHH)-subgroup medulloblastoma (87%) and less frequently in breast cancer, colorectal cancer, gastric cancer, pancreatic cancer, non-small-cell lung cancer (NSCLC) and ovarian cancer. Among investigational SMO inhibitors, vismodegib and sonidegib are approved for the treatment of patients with BCC, and glasdegib is approved for the treatment of patients with acute myeloid leukemia (AML). Resistance to SMO inhibitors is caused by acquired SMO mutations, SUFU deletions, GLI2 amplification, other by-passing mechanisms of GLI activation and WNT/β-catenin signaling activation. GLI-DNA-interaction inhibitors (glabrescione B and GANT61), GLI2 destabilizers (arsenic trioxide and pirfenidone) and a GLI-deacetylation inhibitor (4SC-202) were shown to block GLI-dependent transcription and tumorigenesis in preclinical studies. By contrast, SMO inhibitors can remodel the immunosuppressive TME that is dominated by M2-like tumor-associated macrophages (M2-TAMs), myeloid-derived suppressor cells and regulatory T cells, and thus, a Phase I/II clinical trial of the immune checkpoint inhibitor pembrolizumab with or without vismodegib in BCC patients is ongoing.

Targeted Therapies in Cholangiocarcinoma: Emerging Evidence from Clinical Trials

Cholangiocarcinoma (CCA) is a highly-aggressive malignancy arising from the biliary tree, characterized by a steady increase in incidence globally and a high mortality rate. Most CCAs are diagnosed in the advanced and metastatic phases of the disease, due to the paucity of signs and symptoms in the early stages. This fact, along with the poor results of the local and systemic therapies currently employed, is responsible for the poor outcome of CCA patients and strongly supports the need for novel therapeutic agents and strategies. In recent years, the introduction of next-generation sequencing technologies has opened new horizons for a better understanding of the genetic pathophysiology of CCA and, consequently, for the identification and evaluation of new treatments tailored to the molecular features or alterations progressively elucidated. In this review article, we describe the potential targets under investigation and the current molecular therapies employed in biliary tract cancers. In addition, we summarize the main drugs against CCA under evaluation in ongoing trials and describe the preliminary data coming from these pioneering studies.

Targeting the Oncoprotein Smoothened by Small Molecules: Focus on Novel Acylguanidine Derivatives as Potent Smoothened Inhibitors

Hedgehog-GLI (HH) signaling was originally identified as a critical morphogenetic pathway in embryonic development. Since its discovery, a multitude of studies have reported that HH signaling also plays key roles in a variety of cancer types and in maintaining tumor-initiating cells. Smoothened (SMO) is the main transducer of HH signaling, and in the last few years, it has emerged as a promising therapeutic target for anticancer therapy. Although vismodegib and sonidegib have demonstrated effectiveness for the treatment of basal cell carcinoma (BCC), their clinical use has been hampered by severe side effects, low selectivity against cancer stem cells, and the onset of mutation-driven drug resistance. Moreover, SMO antagonists are not effective in cancers where HH activation is due to mutations of pathway components downstream of SMO, or in the case of noncanonical, SMO-independent activation of the GLI transcription factors, the final mediators of HH signaling. Here, we review the current and rapidly expanding field of SMO small-molecule inhibitors in experimental and clinical settings, focusing on a class of acylguanidine derivatives. We also discuss various aspects of SMO, including mechanisms of resistance to SMO antagonists.

Progress in molecular targeted therapy of intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma is an uncommon malignant tumor with a poor prognosis due to an incomplete understanding of its molecular pathogenesis and a lack of effective treatment. Precision medical planning and cancer genomics can help to understand the molecular pathogenesis of cancer and identify potential therapeutic targets. With the deepening of basic and clinical research, accurate targeted therapy will be able to improve the prognosis and overall survival of patients with intrahepatic cholangiocarcinoma.

LncRNA ASAP1-IT1 positively modulates the development of cholangiocarcinoma via hedgehog signaling pathway

Over the past decades, lncRNAs have attracted more and more attentions of researchers. It has been verified that lncRNAs can modulate multiple biological behaviors in various human cancers. LncRNA ASAP1-IT1 has been certified to be a tumor facilitator in several malignant tumors. This study aims to investigate the effects of dysregulated ASAP1-IT1 on biological processes of Cholangiocarcinoma. The high expression level of ASAP1-IT1 was tested in Cholangiocarcinoma tissues and cells with qRT-PCR. Upregulation of ASAP1-IT predicted the unfavorable prognosis for Cholangiocarcinoma patients. Next, ASAP1-IT1 was knocked down in cancerous cells for loss-of function assay. MTT, colony formation and transwell and western bot assays were performed to demonstrate the specific impacts of ASAP1-IT1 on proliferation, migration and EMT progression of Cholangiocarcinoma. Cells. As a results, the Cholangiocarcinoma progression was inhibited. Hedgehog signaling pathway has been discovered to be a treatment target in Cholangiocarcinoma. In this study, the interaction between ASAP1-IT1 and hedgehog pathway was specifically investigated. Smo and Gli1, two hedgehog-related proteins were examined in Cholangiocarcinoma cells. The results of qRT-PCR and western blot assay suggested that ASAP1-IT1 could positively modulate Smo and Gli1 in Cholangiocarcinoma. Finally, rescue assays were carried out to prove that ASAP1-IT1 could improve Cholangiocarcinoma progression and development via hedgehog signaling pathway.

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.

Desmoplastic Tumor Microenvironment and Immunotherapy in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a dismal disease which often is diagnosed at a late stage where the tumor is locally advanced, metastatic, and, as a result, is associated with low resectability. The heterogeneity of this cancer type is a major reason why the majority of patients fail to respond to therapy, and surgery remains their only curative option. Among patients who undergo surgical intervention, such tumors typically recur in 50% of cases within 1year. Thus, CCA is among the most aggressive and chemoresistant malignancies. CCA is characterized by marked tumor reactive stroma, a fibrogenic connective tissue which surrounds and infiltrates the tumor epithelium. This desmoplastic environment presents a clinical challenge, limiting drug delivery and supporting the growth of the tumor mass. In this review we attempt to highlight key pathways involved in cell to cell communication between the tumor epithelium and stroma, the immune components, and opportunities for novel strategies to improve patient outcome.

Role of canonical Hedgehog signaling pathway in liver

Hedgehog (Hh) signaling pathway plays an important role in embryonic development. It becomes reactivated in many types of acute and chronic liver injuries. Hh signaling is required for liver regeneration, regulates capillarisation, controls the fates of hepatic stellate cells, promotes liver fibrosis and liver cancers. In this review, we summarize the current knowledge of the role of canonical Hh signaling pathway in adult liver. This help to understand the pathogenesis of liver diseases and find out the new effective targeted therapeutic strategies for liver diseases treatments.

Emerging molecular therapeutic targets for cholangiocarcinoma

Cholangiocarcinomas (CCAs) are diverse epithelial tumors arising from the liver or large bile ducts with features of cholangiocyte differentiation. CCAs are classified anatomically into intrahepatic (iCCA), perihilar (pCCA), and distal CCA (dCCA). Each subtype has distinct risk factors, molecular pathogenesis, therapeutic options, and prognosis. CCA is an aggressive malignancy with a poor overall prognosis and median survival of less than 2years in patients with advanced disease. Potentially curative surgical treatment options are limited to the subset of patients with early-stage disease. Presently, the available systemic medical therapies for advanced or metastatic CCA have limited therapeutic efficacy. Molecular alterations define the differences in biological behavior of each CCA subtype. Recent comprehensive genetic analysis has better characterized the genomic and transcriptomic landscape of each CCA subtype. Promising candidates for targeted, personalized therapy have emerged, including potential driver fibroblast growth factor receptor (FGFR) gene fusions and somatic mutations in isocitrate dehydrogenase (IDH)1/2 in iCCA, protein kinase cAMP-activated catalytic subunit alpha (PRKACA) or beta (PRKACB) gene fusions in pCCA, and ELF3 mutations in dCCA/ampullary carcinoma. A precision genomic medicine approach is dependent on an enhanced understanding of driver mutations in each subtype and stratification of patients according to their genetic drivers. We review the current genomic landscape of CCA, the potentially actionable molecular aberrations in each CCA subtype, and the role of immunotherapy in CCA.

New Horizons for Precision Medicine in Biliary Tract Cancers

Biliary tract cancers (BTC), including cholangiocarcinoma and gallbladder cancer, are poor-prognosis and low-incidence cancers, although the incidence of intrahepatic cholangiocarcinoma is rising. A minority of patients present with resectable disease but relapse rates are high; benefit from adjuvant capecitabine chemotherapy has been demonstrated. Cisplatin/gemcitabine combination chemotherapy has emerged as the reference first-line treatment regimen; there is no standard second-line therapy. Selected patients may be suitable for liver-directed therapy (e.g., radioembolization or external beam radiation), pending confirmation of benefit in randomized studies. Initial trials targeting the epithelial growth factor receptor and angiogenesis pathways have failed to deliver new treatments. Emerging data from next-generation sequencing analyses have identified actionable mutations (e.g., FGFR fusion rearrangements and IDH1 and IDH2 mutations), with several targeted drugs entering clinical development with encouraging results. The role of systemic therapies, including targeted therapies and immunotherapy for BTC, is rapidly evolving and is the subject of this review.Significance: The authors address genetic drivers and molecular biology from a translational perspective, in an intent to offer a clear view of the recent past, present, and future of BTC. The review describes a state-of-the-art update of the current status and future directions of research and therapy in advanced BTC. Cancer Discov; 7(9); 943-62. ©2017 AACR.

New Horizons for Precision Medicine in Biliary Tract Cancers

Biliary tract cancers (BTC), including cholangiocarcinoma and gallbladder cancer, are poor-prognosis and low-incidence cancers, although the incidence of intrahepatic cholangiocarcinoma is rising. A minority of patients present with resectable disease but relapse rates are high; benefit from adjuvant capecitabine chemotherapy has been demonstrated. Cisplatin/gemcitabine combination chemotherapy has emerged as the reference first-line treatment regimen; there is no standard second-line therapy. Selected patients may be suitable for liver-directed therapy (e.g., radioembolization or external beam radiation), pending confirmation of benefit in randomized studies. Initial trials targeting the epithelial growth factor receptor and angiogenesis pathways have failed to deliver new treatments. Emerging data from next-generation sequencing analyses have identified actionable mutations (e.g., FGFR fusion rearrangements and IDH1 and IDH2 mutations), with several targeted drugs entering clinical development with encouraging results. The role of systemic therapies, including targeted therapies and immunotherapy for BTC, is rapidly evolving and is the subject of this review.Significance: The authors address genetic drivers and molecular biology from a translational perspective, in an intent to offer a clear view of the recent past, present, and future of BTC. The review describes a state-of-the-art update of the current status and future directions of research and therapy in advanced BTC. Cancer Discov; 7(9); 943-62. ©2017 AACR.

Emerging concepts in biliary repair and fibrosis

Chronic diseases of the biliary tree (cholangiopathies) represent one of the major unmet needs in clinical hepatology and a significant knowledge gap in liver pathophysiology. The common theme in cholangiopathies is that the target of the disease is the biliary tree. After damage to the biliary epithelium, inflammatory changes stimulate a reparative response with proliferation of cholangiocytes and restoration of the biliary architecture, owing to the reactivation of a variety of morphogenetic signals. Chronic damage and inflammation will ultimately result in pathological repair with generation of biliary fibrosis and clinical progression of the disease. The hallmark of pathological biliary repair is the appearance of reactive ductular cells, a population of cholangiocyte-like epithelial cells of unclear and likely mixed origin that are able to orchestrate a complex process that involves a number of different cell types, under joint control of inflammatory and morphogenetic signals. Several questions remain open concerning the histogenesis of reactive ductular cells, their role in liver repair, their mechanism of activation, and the signals exchanged with the other cellular elements cooperating in the reparative process. This review contributes to the current debate by highlighting a number of new concepts derived from the study of the pathophysiology of chronic cholangiopathies, such as congenital hepatic fibrosis, biliary atresia, and Alagille syndrome.

Autocrine and Paracrine Mechanisms Promoting Chemoresistance in Cholangiocarcinoma

Resistance to conventional chemotherapeutic agents, a typical feature of cholangiocarcinoma, prevents the efficacy of the therapeutic arsenal usually used to combat malignancy in humans. Mechanisms of chemoresistance by neoplastic cholangiocytes include evasion of drug-induced apoptosis mediated by autocrine and paracrine cues released in the tumor microenvironment. Here, recent evidence regarding molecular mechanisms of chemoresistance is reviewed, as well as associations between well-developed chemoresistance and activation of the cancer stem cell compartment. It is concluded that improved understanding of the complex interplay between apoptosis signaling and the promotion of cell survival represent potentially productive areas for active investigation, with the ultimate aim of encouraging future studies to unveil new, effective strategies able to overcome current limitations on treatment.

Targeting the Sonic Hedgehog Signaling Pathway: Review of Smoothened and GLI Inhibitors

The sonic hedgehog (Shh) signaling pathway is a major regulator of cell differentiation, cell proliferation, and tissue polarity. Aberrant activation of the Shh pathway has been shown in a variety of human cancers, including, basal cell carcinoma, malignant gliomas, medulloblastoma, leukemias, and cancers of the breast, lung, pancreas, and prostate. Tumorigenesis, tumor progression and therapeutic response have all been shown to be impacted by the Shh signaling pathway. Downstream effectors of the Shh pathway include smoothened (SMO) and glioma-associated oncogene homolog (GLI) family of zinc finger transcription factors. Both are regarded as important targets for cancer therapeutics. While most efforts have been devoted towards pharmacologically targeting SMO, developing GLI-targeted approach has its merit because of the fact that GLI proteins can be activated by both Shh ligand-dependent and -independent mechanisms. To date, two SMO inhibitors (LDE225/Sonidegib and GDC-0449/Vismodegib) have received FDA approval for treating basal cell carcinoma while many clinical trials are being conducted to evaluate the efficacy of this exciting class of targeted therapy in a variety of cancers. In this review, we provide an overview of the biology of the Shh pathway and then detail the current landscape of the Shh-SMO-GLI pathway inhibitors including those in preclinical studies and clinical trials.

Induction of MITF expression in human cholangiocarcinoma cells and hepatocellular carcinoma cells by cyclopamine, an inhibitor of the Hedgehog signaling

Microphthalmia-associated transcription factor (MITF) is a key regulator of differentiation of melanocytes and retinal pigment epithelial cells, but it also has functions in non-pigment cells. MITF consists of multiple isoforms, including widely expressed MITF-A and MITF-H. In the present study, we explored the potential role played by the Hedgehog signaling on MITF expression in two common types of primary liver cancer, using human cholangiocarcinoma cell lines, the KKU-100 and HuCCT1, along with the HepG2 human hepatocellular carcinoma cell line. Importantly, cholangiocarcinoma is characterized by the activated Hedgehog signaling. Here we show that MITF-A mRNA is predominantly expressed in all three human liver cancer cell lines examined. Moreover, cyclopamine, an inhibitor of the Hedgehog signalling, increased the expression levels of MITF proteins in HuCCT1 and HepG2 cells, but not in KKU-100 cells, suggesting that MITF expression may be down-regulated in some liver cancer cases.

Mitogen-activated protein kinases and Hedgehog-GLI signaling in cancer: A crosstalk providing therapeutic opportunities?

The Hedgehog-GLI (HH-GLI) signaling is of critical importance during embryonic development, where it regulates a number of cellular processes, including patterning, proliferation and differentiation. Its aberrant activation has been linked to several types of cancer. HH-GLI signaling is triggered by binding of ligands to the transmembrane receptor patched and is subsequently mediated by transcriptional effectors belonging to the GLI family, whose function is fine tuned by a series of molecular interactions and modifications. Several HH-GLI inhibitors have been developed and are in clinical trials. Similarly, the mitogen-activated protein kinases (MAPK) are involved in a number of biological processes and play an important role in many diseases including cancer. Inhibiting molecules targeting MAPK signaling, especially those elicited by the MEK1/2-ERK1/2 pathway, have been developed and are moving into clinical trials. ERK1/2 may be activated as a consequence of aberrant activation of upstream signaling molecules or during development of drug resistance following treatment with kinase inhibitors such as those for PI3K or BRAF. Evidence of a crosstalk between HH-GLI and other oncogenic signaling pathways has been reported in many tumor types, as shown by recent reviews. Here we will focus on the interaction between HH-GLI and the final MAPK effectors ERK1/2, p38 and JNK in cancer in view of its possible implications for cancer therapy. Several reports highlight the existence of a consistent crosstalk between HH signaling and MAPK, especially with the MEK1/2-ERK1/2 pathway, and this fact should be taken into consideration for designing optimal treatment and prevent tumor relapse.

Digging a hole under Hedgehog: downstream inhibition as an emerging anticancer strategy

Hedgehog signaling is a key regulator of development and stem cell fate and its aberrant activation is a leading cause of a number of tumors. Activating germline or somatic mutations of genes encoding Hh pathway components are found in Basal Cell Carcinoma (BCC) and Medulloblastoma (MB). Ligand-dependent Hedgehog hyperactivation, due to autocrine or paracrine mechanisms, is also observed in a large number of malignancies of the breast, colon, skin, bladder, pancreas and other tissues. The key tumorigenic role of Hedgehog has prompted effort aimed at identifying inhibitors of this signaling. To date, only the antagonists of the membrane transducer Smo have been approved for therapy or are under clinical trials in patients with BCC and MB linked to Ptch or Smo mutations. Despite the good initial response, patients treated with Smo antagonists have eventually developed resistance due to the occurrence of compensating mechanisms. Furthermore, Smo antagonists are not effective in tumors where the Hedgehog hyperactivation is due to mutations of pathway components downstream of Smo, or in case of non-canonical, Smo-independent activation of the Gli transcription factors. For all these reasons, the research of Hh inhibitors acting downstream of Smo is becoming an area of intensive investigation. In this review we illustrate the progresses made in the identification of effective Hedgehog inhibitors and their application in cancer, with a special emphasis on the newly identified downstream inhibitors. We describe in detail the Gli inhibitors and illustrate their mode of action and applications in experimental and/or clinical settings.

Novel therapeutic strategy targeting the Hedgehog signalling and mTOR pathways in biliary tract cancer

Background:

Activation of the PI3K/mTOR and Hedgehog (Hh) signalling pathways occurs frequently in biliary tract cancer (BTC). Crosstalk between these pathways occurs in other gastrointestinal cancers. The respective signalling inhibitors rapamycin and vismodegib may inhibit BTC synergistically and suppress cancer stem cells (CSCs).

Methods:

Gene expression profiling for p70S6k and Gli1 was performed with BTC cell lines. Tumour and pathway inhibitory effects of rapamycin and vismodegib were investigated in BTC preclinical models and CSCs.

Results:

Rapamycin and vismodegib synergistically reduced BTC cell viability and proliferation. This drug combination arrested BTC Mz-ChA-1 cells in the G1 phase but had no significant effect on the cell cycle of BTC Sk-ChA-1 cells. Combined treatment inhibited the proliferation of CSCs and ALDH-positive cells. Nanog and Oct-4 expression in CSCs was decreased by the combination treatment. Western blotting results showed the p-p70S6K, p-Gli1, p-mTOR, and p-AKT protein expression were inhibited by the combination treatment in BTC cells. In an Mz-ChA-1 xenograft model, combination treatment resulted in 80% inhibition of tumour growth and prolonged tumour doubling time. In 4 of 10 human BTC specimens, tumour p-p70S6K and Gli1 protein expression levels were decreased with the combination treatment.

Conclusions:

Targeted inhibition of the PI3K/mTOR and Hhpathways indicates a new avenue for BTC treatment with combination therapy.

Anti-cancer effect and gene modulation of ET-743 in human biliary tract carcinoma preclinical models

Background

Standard chemotherapy in unresectable biliary tract carcinoma (BTC) patients is based on gemcitabine combined with platinum derivatives. However, primary or acquired resistance is inevitable and no second-line chemotherapy is demonstrated to be effective. Thus, there is an urgent need to identify new alternative (chemo)therapy approaches.

Methods

We evaluated the mechanism of action of ET-743 in preclinical models of BTC. Six BTC cell lines (TFK-1, EGI-1, TGBC1, WITT, KMCH, HuH28), two primary cell cultures derived from BTC patients, the EGI-1 and a new established BTC patient-derived xenografts, were used as preclinical models to investigate the anti-tumor activity of ET-743 in vitro and in vivo. Gene expression profiling was also analyzed upon ET-743 treatment in in vivo models.

Results

We found that ET-743 inhibited cell growth of BTC cell lines and primary cultures (IC50 ranging from 0.37 to 3.08 nM) preferentially inducing apoptosis and activation of the complex DNA damage-repair proteins (p-ATM, p-p53 and p-Histone H2A.x) in vitro. In EGI-1 and patient-derived xenografts, ET-743 induced tumor growth delay and reduction of vasculogenesis. In vivo ET-743 induced a deregulation of genes involved in cell adhesion, stress-related response, and in pathways involved in cholangiocarcinogenesis, such as the IL-6, Sonic Hedgehog and Wnt signaling pathways.

Conclusions

These results suggest that ET-743 could represent an alternative chemotherapy for BTC treatment and encourage the development of clinical trials in BTC patients resistant to standard chemotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-918) contains supplementary material, which is available to authorized users.