Inhibition of the hedgehog pathway in advanced basal-cell carcinoma

Challenges and perspective of drug repurposing strategies in early phase clinical trials

Despite significant investments in the development of new agents only 5% of cancer drugs entering Phase I clinical trials are ultimately approved for routine clinical cancer care. Drug repurposing strategies using novel combinations of previously tested anticancer agents could reduce the cost and improve treatment outcomes. At MD Anderson Cancer Center, early phase clinical trials with drug repurposing strategies demonstrated promising outcomes in patients with both rare and common treatment refractory advanced cancers. Despite clinical efficacy advancing drug repurposing strategies in the clinical trial trajectory beyond early phase studies has been challenging mainly due to lack of funding and interest from the pharmaceutical industry. In this review, we delineate our experience and challenges with drug repurposing strategies.

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.

Non-melanoma Skin Cancer in Canada Chapter 1: Introduction to the Guidelines

BACKGROUND

Non-melanoma skin cancer (NMSC), including basal and squamous cell carcinoma, represents the most common malignancy.

OBJECTIVE

The aim of this document is to provide guidance to Canadian health care practitioners on NMSC management.

METHODS

After conducting a literature review, the group developed recommendations for prevention, management, and treatment of basal cell carcinomas, squamous cell carcinomas, and actinic keratoses. These tumour types are considered separately in the accompanying articles. The Grading of Recommendations Assessment, Development and Evaluation system was used to assign strength to each recommendation.

RESULTS

This introduction describes the scope and structure of the guidelines and the methods used to develop them. The epidemiology of NMSC is reviewed, as are the pathophysiologic changes occurring with damage to the skin, which lead to the formation of actinic keratoses and invasive squamous or basal cell carcinomas.

CONCLUSIONS

This introduction describes the need for primary prevention and offers an overview of treatment options that are discussed in later chapters of the guidelines.

Non-melanoma Skin Cancer in Canada Chapter 4: Management of Basal Cell Carcinoma

Background

Basal cell carcinoma (BCC) is the most common malignancy. Growth of BCCs leads to local destruction of neighbouring healthy skin and underlying tissue and can result in significant functional and cosmetic morbidity.

Objective

To provide guidance to Canadian health care practitioners regarding management of BCCs.

Methods

Literature searches and development of graded recommendations were carried out as discussed in the accompanying Introduction.

Results

Although BCCs rarely metastasize“ they can be aggressive and disfiguring. This chapter describes the natural history and prognosis of BCCs. Risk stratification is based on clinical features” including the site and size of the tumour“ its histologic subtype (nodular vs sclerosing)” and its history of recurrence.

Conclusions

Various options should be considered for BCC treatment” including cryosurgery” curettage” and topical or photodynamic approaches, as well as fixed-margin surgery and Mohs micrographic surgery. Stratification of recurrence risk for individual BCCs determines the most appropriate therapeutic course.

The presence of primary cilia in cancer cells does not predict responsiveness to modulation of smoothened activity

Primary cilia are microtubule-based organelles that regulate smoothened-dependent activation of the GLI transcription factors in canonical hedgehog signaling. In many cancers, primary cilia are markedly decreased or absent. The lack of primary cilia may inhibit or alter canonical hedgehog signaling and, thereby, interfere in the cellular responsiveness to modulators of smoothened activity. Clinical trials of smoothened antagonists for cancer treatment have shown the best response in basal cell carcinomas, with limited response in other solid tumors. To determine whether the presence or absence of primary cilia in cancer cells will predict their responsiveness to modulation of smoothened activity, we compared the ability of an agonist and/or inhibitor of smoothened (SAG and SANT1, respectively) to modulate GLI-mediated transcription, as measured by GLI1 mRNA level or GLI-luciferase reporter activity, in non-cancer cells with primary cilia (ovarian surface epithelial cells and breast fibroblasts), in cancer cells that cannot assemble primary cilia (MCF7, MDA-MB-231 cell lines), and in cancer cells with primary cilia (SKOV3, PANC1 cell lines). As expected, SAG and SANT1 resulted in appropriate modulation of GLI transcriptional activity in ciliated non-cancer cells, and failed to modulate GLI transcriptional activity in cancer cells without primary cilia. However, there was also no modulation of GLI transcriptional activity in either ciliated cancer cell line. SAG treatment of SKOV3 induced localization of smoothened to primary cilia, as assessed by immunofluorescence, even though there was no increase in GLI transcriptional activity, suggesting a defect in activation of SMO in the primary cilia or in steps later in the hedgehog pathway. In contrast to SKOV3, SAG treatment of PANC1 did not cause the localization of smoothened to primary cilia. Our data demonstrate that the presence of primary cilia in the cancer epithelial cells lines tested does not indicate their responsiveness to smoothened activation or inhibition.

Cancer stem cells and therapeutic targets: an emerging field for cancer treatment

Recent paradigm in the field of cancer defines its origin from a small population of fast growing cells known as cancer stem cells (CSCs), and they are mainly responsible for disease aggressiveness, drug resistance and tumor relapse. The existence of CSCs has been proven in different types of cancer and possesses characteristic expression of a wide array of cell surface markers specific to the type of cancer. CSCs have been isolated and enriched using several surface markers in different cancer types. Self-renewal, drug resistance and the ability to transition from epithelial to mesenchymal phenotype are the major features attributed to this fraction of mutated stem cells. The CSC hypothesis proposes that these CSCs mimic stem cells by sharing similar pathways, such as Wnt, SHH, Notch and others. Further, the niche, which in this case is the tumor microenvironment, plays a very important role in the maintenance of CSCs. Altogether, this emerging field of research on CSCs is expected to unveil answers to the most difficult issues of one of the most dreadful diseases called cancer.

Mode and specificity of binding of the small molecule GANT61 to GLI determines inhibition of GLI-DNA binding

The GLI genes, GLI1 and GLI2, are transcription factors that regulate target genes at the distal end of the canonical Hedgehog (HH) signaling pathway (SHH->PTCH->SMO->GLI), tightly regulated in embryonic development, tissue patterning and differentiation. Both GLI1 and GLI2 are oncogenes, constitutively activated in many types of human cancers. In colon cancer cells oncogenic KRAS-GLI signaling circumvents the HH-SMO-GLI axis to channel through and activate GLI in the transcriptional regulation of target genes. We have observed extensive cell death in a panel of 7 human colon carcinoma cell lines using the small molecule GLI inhibitor GANT61. Using computational docking and experimental confirmation by Surface Plasmon Resonance, GANT61 binds to the 5-zinc finger GLI1 protein between zinc fingers 2 and 3 at sites E119 and E167, independent of the GLI-DNA binding region, and conserved between GLI1 and GLI2. GANT61 does not bind to other zinc finger transcription factors (KLF4, TFIIβ). Mutating the predicted GANT61 binding sites in GLI1 significantly inhibits GANT61-GLI binding and GLI-luciferase activity. Data establish the specificity of GANT61 for targeting GLI, and substantiate the critical role of GLI in cancer cell survival. Thus, targeting GLI in cancer therapeutics may be of high impact.

A massive neglected giant basal cell carcinoma in a schizophrenic patient treated successfully with vismodegib

The small molecule vismodegib is a great treatment alternative to patients challenged, e.g. psychiatric disorders, suffering from severe basal cell carcinoma of the skin in which surgery or other treatment modalities is not possible because of patient's wish or condition. We present a case of a 73-year-old schizophrenic patient with a 15-year history of a neglected tumour located at the forehead and scalp, admitted to hospital in a state of inanition because of tumour expansion to the meninges and severe anaemia caused by bleeding, treated successfully with vismodegib.

Targeting of the Hedgehog pathway in myeloid malignancies: still a worthy chase?

Deregulated Hedgehog (Hh) signalling activity may be associated with a broad range of cancer types and hence has become an attractive target for therapeutic intervention. Although initial haematological interest focused on the therapeutic targeting of this pathway in chronic myeloid leukaemia), small molecule inhibitors targeting the Hh pathway are now being tested in a range of other myeloid disorders, including myelofibrosis, myelodysplasia and acute myeloid leukaemia. In this review we will evaluate the rationale for targeting of the Hh pathway in myeloid diseases and discuss the novel agents that have entered the clinical arena. We will discuss pre-clinical models, emerging clinical trial data, and suggest how these targeted therapies may address current unmet medical needs. Finally, we will explore potential limitations of these therapies due to the emergence of secondary resistance mechanisms and speculate on future developments within this arena.

Synergistic inhibition of colon carcinoma cell growth by Hedgehog-Gli1 inhibitor arsenic trioxide and phosphoinositide 3-kinase inhibitor LY294002

The Hedgehog (Hh) signaling pathway not only plays important roles in embryogenesis and adult tissue homeostasis, but also in tumorigenesis. Aberrant Hh pathway activation has been reported in a variety of malignant tumors including colon carcinoma. Here, we sought to investigate the regulation of the Hh pathway transcription factor Gli1 by arsenic trioxide and phosphoinositide 3-kinase (PI3K) inhibitor LY294002 in colon carcinoma cells. We transfected cells with siGli1 and observed a significant reduction of Gli1 expression in HCT116 and HT29 cells, which was confirmed by quantitative real-time polymerase chain reaction and Western blots. Knocking down endogenous Gli1 reduced colon carcinoma cell viability through inducing cell apoptosis. Similarly, knocking down Gli2 using short interfering RNA impaired colon carcinoma cell growth in vitro. To elucidate the regulation of Gli1 expression, we found that both Gli inhibitor arsenic trioxide and PI3K inhibitor LY294002 significantly reduced Gli1 protein expression and colon carcinoma cell proliferation. Arsenic trioxide treatment also reduced Gli1 downstream target gene expression, such as Bcl2 and CCND1. More importantly, the inhibition of Hedgehog-Gli1 by arsenic trioxide showed synergistic anticancer effect with the PI3K inhibitor LY294002 in colon carcinoma cells. Our findings suggest that the Hh pathway transcription factor Gli1 is involved in the regulation of colon carcinoma cell viability. Inhibition of Hedgehog-Gli1 expression by arsenic trioxide and PI3K inhibitor synergistically reduces colon cancer cell proliferation, indicating that they could be used as an effective anti-colon cancer combination therapy.

Merkel Cell Carcinoma with a Suppressor of Fused (SUFU) Mutation: Case Report and Potential Therapeutic Implications

Introduction

Merkel cell carcinoma is a neuroendocrine malignancy. Suppressor of fused (SUFU) is a tumor suppressor oncogene that participates in the Hedgehog (Hh) signaling pathway. The aim of the study was to describe a patient whose Merkel cell carcinoma demonstrated a SUFU genomic alteration.

Case Study

The Hh signaling pathway is involved in the pathogenesis of several tumors, including nevoid basal cell carcinoma syndrome that is associated with an alteration of the patched-1 (PTCH1) gene. Targeted molecular therapy against smoothened (SMO) with vismodegib has been shown to be an effective therapeutic intervention for patients with PTCH-1 mutation. The reported patient was presented with metastatic Merkel cell carcinoma. Analysis of his tumor, using a next-generation sequencing-based assay, demonstrated a genomic aberration of SUFU protein, a component of the Hh signaling pathway that acts downstream to SMO and, therefore, is unlikely to be responsive to vismodegib. Of interest, arsenic trioxide or bromo and extra C-terminal inhibitors impact signals downstream to SUFU, making this aberration conceivably druggable. His tumor has initially been managed with chemotherapy (carboplatin and etoposide) and subsequent radiation therapy is planned.

Conclusion

The pathogenesis of Merkel cell carcinoma is multifactorial, and related to ultraviolet radiation exposure, immunosuppression, and Merkel cell polyomavirus. We report a patient with a mutation in SUFU, a potentially actionable component of the Hh signaling pathway.

Electronic supplementary material

The online version of this article (doi:10.1007/s13555-015-0074-5) contains supplementary material, which is available to authorized users.

Basal cell carcinoma-treatments for the commonest skin cancer

BACKGROUND

With an incidence of 70 to over 800 new cases per 100 000 persons per year, basal cell carcinoma (BCC) is a very common disease, accounting for about 80% of all cases of non-melanoma skin cancer. It very rarely metastasizes. A variety of treatments are available for the different subtypes and stages of BCC.

METHOD

This review is based on pertinent literature retrieved by a selective search in the Medline database, as well as the American Cancer Society guidelines on BCC and the German guidelines on BCC and skin cancer prevention.

RESULTS

The gold standard of treatment is surgical excision with histological control of excision margins, which has a 5-year recurrence rate of less than 3% on the face. For superficial BCC, approved medications such as imiquimod (total remission rate, 82-90%) and topical 5-fluorouracil (80%) are available, as is photodynamic therapy (71-87%). Other ablative methods (laser, cryosurgery) are applicable in some cases. Radiotherapy is an alternative treatment for invasive, inoperable BCC, with 5-year tumor control rates of 89-96%. Recently, drugs that inhibit an intracellular signaling pathway have become available for the treatment of locally advanced or metastatic BCC. Phase I and II clinical trials revealed that vismodegib was associated with objective response rates of 30-55% and tumor control rates of 80-90%. This drug was approved on the basis of a non-randomized trial with no control arm. It has side effects ranging from muscle cramps (71%) and hair loss (65%) to taste disturbances (55%) and birth defects.

CONCLUSION

The established, standard treatments are generally highly effective. Vismodegib is a newly approved treatment option for locally advanced BCC that is not amenable to either surgery or radiotherapy.

A comprehensive review of the role of the hedgehog pathway and vismodegib in the management of basal cell carcinoma

BACKGROUND

Basal cell carcinoma (BCC) is the most common cancer. Most cases of BCCs are treated with only optimal surgical resection. However, unresectable, locally advanced or metastatic tumors might have potential to progress. In this patient group, there is no standardized treatment approach. Vismodegib is a new selective inhibitor of the hedgehog (Hh) pathway. This manuscript is aimed to review the efficacy of the Hh pathway inhibitor vismodegib in BCC patients with locally advanced or metastatic disease.

SCOPE

Vismodegib showed positive results in clinical studies. A computerized search of the PubMed and American Society of Clinical Oncology Meeting abstracts was performed, by searching for the following keywords: 'vismodegib', 'pathway', 'inhibitor', and 'targeted therapies for BCC'. The last search was done on 1 September 2014. Most of the vismodegib data depend on phase I and II trials.

FINDINGS

Preclinical and clinical studies have shown that Hh pathway activation occurs in BCC. In BCC patients the role of chemotherapy is not completely known. Although conventional chemotherapies like cisplatins increase the response rate in BCC, improvement in overall survival and progression free survival were not demonstrated. Results of both phase I and phase II studies have shown that vismodegib is a potential new treatment strategy for patients with locally advanced and metastatic BCC. As in previously published phase I trials, in the ERIVANCE BCC study the primary endpoint, objective response rate, significantly increased by 43% and 30% in patients with locally advanced and metastatic BCC, respectively. Because of the promising results in phase I and II trials, vismodegib was approved by the Food and Drug Administration (FDA) in the treatment of patients with BCC who are not suitable for surgery or radiotherapy or with relapsed locally advanced disease following surgery or metastatic disease.

CONCLUSION

Recent trials have shown that vismodegib has produced promising activity in patients with locally advanced and metastatic BCC. The ongoing studies with vismodegib in other solid tumors and BCC will shed light on more certain treatment pathways.

Pancreatic cancer: from state-of-the-art treatments to promising novel therapies

Pancreatic cancer is expected to be the second deadliest malignancy in the USA by 2020. The survival rates for patients with other gastrointestinal malignancies have increased consistently during the past 30 years; unfortunately, however, the outcomes of patients with pancreatic cancer have not changed significantly. Although surgery remains the only curative treatment for pancreatic cancer, therapeutic strategies based on initial resection have not substantially improved the survival of patients with resectable disease over the past 25 years; presently, more than 80% of patients suffer disease relapse after resection. Preclinical evidence that pancreatic cancer is a systemic disease suggests a possible benefit for early administration of systemic therapy in these patients. In locally advanced disease, the role of chemoradiotherapy is increasingly being questioned, particularly considering the results of the LAP-07 trial. Novel biomarkers are clearly needed to identify subsets of patients likely to benefit from chemoradiotherapy. In the metastatic setting, FOLFIRINOX (folinic acid, 5-fluorouracil, irinotecan, and oxaliplatin), and nab-paclitaxel plus gemcitabine have yielded only modest improvements in survival. Thus, new treatments are urgently needed for patients with pancreatic cancer. Herein, we review the state-of-the-art of pancreatic cancer treatment, and the upcoming novel therapeutics that hold promise in this disease are also discussed.

An in vivo chemical genetic screen identifies phosphodiesterase 4 as a pharmacological target for hedgehog signaling inhibition

Hedgehog (Hh) signaling plays an integral role in vertebrate development, and its dysregulation has been accepted widely as a driver of numerous malignancies. While a variety of small molecules target Smoothened (Smo) as a strategy for Hh inhibition, Smo gain-of-function mutations have limited their clinical implementation. Modulation of targets downstream of Smo could define a paradigm for treatment of Hh-dependent cancers. Here, we describe eggmanone, a small molecule identified from a chemical genetic zebrafish screen, which induced an Hh-null phenotype. Eggmanone exerts its Hh-inhibitory effects through selective antagonism of phosphodiesterase 4 (PDE4), leading to protein kinase A activation and subsequent Hh blockade. Our study implicates PDE4 as a target for Hh inhibition, suggests an improved strategy for Hh-dependent cancer therapy, and identifies a unique probe of downstream-of-Smo Hh modulation.

Inhibition of Hedgehog signaling pathway impedes cancer cell proliferation by promotion of autophagy

Multiple lines of evidence implicate that aberrant activation of Hedgehog (Hh) signaling is involved in a variety of human cancers. However, the molecular mechanisms underlying how cancer cells respond to Hh inhibition remain to be elucidated. In this study, we found that blockade of Hh signaling suppresses cell proliferation in human cancer cells. Microarray analysis revealed that differentially expressed genes (DEGs) in human cancer cells are enriched in autophagy pathway in response to the inhibition of Hh signaling. Interestingly, inhibition of Hh signaling induced autophagy, whereas activation of Hh signaling by ligand treatments prevented the induction of autophagy. In addition, inhibition of autophagy by 3-methyladenine (3-MA) partially suppressed cytotoxicity induced by inhibition of Hh signaling. Finally, in autophagy deficient cells, cytotoxic effect triggered by inhibition of Hh signaling was partially reversed, indicating the modulation of autophagy by Hh signaling is autophagy-specific. These results suggest that inhibition of Hh signaling impedes cancer cell proliferation in part through induction of autophagy.

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.

Improving cancer therapy by targeting cancer stem cells: Directions, challenges, and clinical results

Cancer stem cells (CSC) are a rare cell population within a tumor characterized by the ability to form tumors following injection into an immunocompromised host. While the role of CSC has been clearly established in animal models, evidence of their clinical relevance has been harder to demonstrate. A number of markers, or combination thereof, have been used to detect and measure, although non-specifically, CSC in almost all human tumors. Several pathways have been identified as crucial for, but not necessarily unique to, CSC survival and proliferation, and novel agents have been designed to target such pathways. A number of such agents have entered early phase development. Further, drugs that have long been marketed for non-oncological indications have been redirected to oncology as they appear to affect one or more of such pathways. This article aims to review the available evidence on the clinical relevance of CSC from a drug development standpoint and the results of early phase clinical trials of agents interfering with the above pathways. It also discusses limitations of current clinical trial design and endpoints to demonstrate anti-CSC activity as well as possible strategies to overcome these limitations.

Expression of Hedgehog Pathway Mediator GLI Represents a Negative Prognostic Marker in Human Acute Myeloid Leukemia and Its Inhibition Exerts Antileukemic Effects

PURPOSE

The Hedgehog pathway plays an important role in stem-cell biology and malignant transformation. Therefore, we investigated the expression and prognostic impact of Hedgehog pathway members in acute myeloid leukemia (AML).

EXPERIMENTAL DESIGN

Pretreatment samples from 104 newly diagnosed AML patients (AMLSG 07-04 trial) were analyzed by qPCR, and expression of Hedgehog family members was correlated with clinical outcome. Inhibition of GLI by GANT61 or shRNA was investigated in AML cells in vitro and in vivo.

RESULTS

Expression of receptors Smoothened and Patched-1 and their downstream mediators, GLI1, GLI2, and GLI3, was found in AML patients in contrast to Hedgehog ligands. GLI2 expression had a significant negative influence on event-free survival (EFS), relapse-free survival (RFS), and overall survival (OS; P = 0.037, 0.026, and 0.013, respectively) and was correlated with FLT3 mutational status (P < 0.001). Analysis of a second, independent patient cohort confirmed the negative impact of GLI2 on EFS and OS (P = 0.007 and 0.003, respectively; n = 290). Within this cohort, GLI1 had a negative prognostic impact (P < 0.001 for both EFS and OS). Although AML cells did not express Hedgehog ligands by qPCR, AML patients had significantly increased Desert Hedgehog (DHH) plasma levels compared with healthy subjects (P = 0.002), in whom DHH was presumably provided by bone marrow niche cells. Moreover, the GLI inhibitor GANT61 or knockdown of GLI1/2 by shRNA caused antileukemic effects, including induction of apoptosis, reduced proliferation, and colony formation in AML cells, and a survival benefit in mice.

CONCLUSIONS

GLI expression is a negative prognostic factor and might represent a novel druggable target in AML.

Efficacy and safety of vismodegib : a new therapeutic agent in the treatment of basal cell carcinoma

INTRODUCTION

Basal cell carcinoma (BCC) is the most common human malignancy. Treatment options for the minority of patients presenting with locally advanced inoperable or metastatic BCC are very limited. The hedgehog (Hh) pathway plays a crucial role in the pathogenesis of BCC. Recent advances in targeting this pathway have led to the development of a first-in-class, small-molecule oral Hh inhibitor, vismodegib (Erivedge®, Genentech).

AREAS COVERED

In this article, we review vismodegib with regard to its mechanism of action, clinical efficacy, safety and tolerability, and we consider the causes of emerging resistance to the drug.

EXPERT OPINION

Vismodegib is a welcome addition to the treatment paradigm for BCC. Approval was based on Phase II evidence, the patient number was relatively small, there was no control group or a comparator group and survival data have not been presented so longer term follow-up and larger exposure to the drug is required to fully appreciate its clinical utility into the future. With ongoing use of the drug in the nontrial population and further studies investigating its use in both early- and later-stage disease, we will get a better understanding of the drug and determine its place in the armamentarium against BCC.

Histone deacetylase 6 represents a novel drug target in the oncogenic Hedgehog signaling pathway

Uncontrolled Hedgehog (Hh) signaling is the cause of several malignancies, including the pediatric cancer medulloblastoma, a neuroectodermal tumor affecting the cerebellum. Despite the development of potent Hh pathway antagonists, medulloblastoma drug resistance is still an unresolved issue that requires the identification of novel drug targets. Following up on our observation that histone deacetylase 6 (HDAC6) expression was increased in Hh-driven medulloblastoma, we found that this enzyme is essential for full Hh pathway activation. Intriguingly, these stimulatory effects of HDAC6 are partly integrated downstream of primary cilia, a known HDAC6-regulated structure. In addition, HDAC6 is also required for the complete repression of basal Hh target gene expression. These contrasting effects are mediated by HDAC6's impact on Gli2 mRNA and GLI3 protein expression. As a result of this complex interaction with Hh signaling, global transcriptome analysis revealed that HDAC6 regulates only a subset of Smoothened- and Gli-driven genes, including all well-established Hh targets such as Ptch1 or Gli1. Importantly, medulloblastoma cell survival was severely compromised by HDAC6 inhibition in vitro and pharmacologic HDAC6 blockade strongly reduced tumor growth in an in vivo allograft model. In summary, our data describe an important role for HDAC6 in regulating the mammalian Hh pathway and encourage further studies focusing on HDAC6 as a novel drug target in medulloblastoma.

Whole exome sequencing of a patient with metastatic hidradenocarcinoma and review of the literature

Hidradenocarcinoma is a rare malignancy of the sweat glands with only a few cases reported in literature. The management of these tumors is based on the extent of disease with local disease managed with surgical resection. These can tumors carry a high potential of lymphatic and vascular spread and local and distant metastases are not uncommon. Given the rarity of the tumor and lack of genetic and clinical data about these tumors, there is no consensus on the proper management of metastatic disease. Here in we report the first case of metastatic hidradenocarcinoma with detailed molecular profiling including whole exome sequencing. We identified mutations in multiple genes including two that are potentially targetable: PTCH1 and TCF7L1. Further work is necessary to not only confirm the presence of these mutations but also to confirm the clinical significance.

Anti-TNFα treatment decreases the previously increased serum Indian Hedgehog levels in patients with ankylosing spondylitis and affects the expression of functional Hedgehog pathway target genes

OBJECTIVE

Indian Hedgehog (Ihh) is the ligand that activates the Hedgehog pathway (HH) in the skeleton-the main controller of endochondral ossification. We aimed at assessing serum levels of Ihh in patients with ankylosing spondylitis (AS) and the effect of serum from patients with AS on HH pathway activation.

METHODS

Serum Ihh levels were measured in 59 patients with AS, 70 patients with rheumatoid arthritis (RA), and 53 healthy subjects. The effect of serum from patients with AS on HH pathway activation was evaluated using an osteoblast-like cell line model.

RESULTS

Patients with AS not on anti-TNFα treatment had significantly higher Ihh levels compared to patients with RA not on anti-TNFα treatment (mean ± SEM of OD: 0.370 ± 0.025 vs. 0.279 ± 0.026 for patients with AS and RA, respectively, p = 0.027) and healthy subjects (p = 0.031). Patients with AS on anti-TNFα treatment had significantly lower Ihh levels compared to patients with AS not on such treatment (p = 0.028). Patients with RA on anti-TNF treatment had higher levels of Ihh compared to patients not on such treatment (p = 0.013). PTHrP levels were similar in patients with RA, AS, and healthy subjects and were not affected by anti-TNFα treatment. We next assessed HH pathway activation in Saos2 cells following incubation with serum from AS patients prior to and following anti-TNF treatment. The HH pathway was downregulated following treatment.

CONCLUSIONS

Ihh levels are increased in patients with AS and decrease following anti-TNFα treatment; this finding may have pathogenic and clinical implications.

Hedgehog signaling: From basic research to clinical applications

Studies of the major signaling pathways have revealed a connection between development, regeneration, and cancer, highlighting common signaling networks in these processes. The Hedgehog (Hh) pathway plays a central role in the development of most tissues and organs in mammals. Hh signaling is also required for tissue homeostasis and regeneration in adults, while perturbed Hh signaling is associated with human cancers. A fundamental understanding of Hh signaling will not only enhance our knowledge of how the embryos are patterned but also provide tools to treat diseases related to aberrant Hh signaling. Studies have yielded a basic framework of Hh signaling, which establishes the foundation for addressing unresolved issues of Hh signaling. A detailed characterization of the biochemical interactions between Hh components will help explain the production of graded Hh responses required for tissue patterning. Additional cell biological and genetic studies will offer new insight into the role of Hh signaling in homeostasis and regeneration. Finally, drugs that are capable of manipulating the Hh pathway can be used to treat human diseases caused by disrupted Hh signaling. These investigations will serve as a paradigm for studying signal transduction/integration in homeostasis and disease, and for translating discovery from bench to bedside.

Cancer stem cell-specific scavenger receptor CD36 drives glioblastoma progression

Glioblastoma (GBM) contains a self-renewing, tumorigenic cancer stem cell (CSC) population which contributes to tumor propagation and therapeutic resistance. While the tumor microenvironment is essential to CSC self-renewal, the mechanisms by which CSCs sense and respond to microenvironmental conditions are poorly understood. Scavenger receptors are a broad class of membrane receptors well characterized on immune cells and instrumental in sensing apoptotic cellular debris and modified lipids. Here, we provide evidence that CSCs selectively use the scavenger receptor CD36 to promote their maintenance using patient-derived CSCs and in vivo xenograft models. CD36 expression was observed in GBM cells in addition to previously described cell types including endothelial cells, macrophages, and microglia. CD36 was enriched in CSCs and was able to functionally distinguish self-renewing cells. CD36 was coexpressed with integrin alpha 6 and CD133, previously described CSC markers, and CD36 reduction resulted in concomitant loss of integrin alpha 6 expression, self-renewal, and tumor initiation capacity. We confirmed oxidized phospholipids, ligands of CD36, were present in GBM and found that the proliferation of CSCs, but not non-CSCs, increased with exposure to oxidized low-density lipoprotein. CD36 was an informative biomarker of malignancy and negatively correlated to patient prognosis. These results provide a paradigm for CSCs to thrive by the selective enhanced expression of scavenger receptors, providing survival, and metabolic advantages.

Cooperative integration between HEDGEHOG-GLI signalling and other oncogenic pathways: implications for cancer therapy

The HEDGEHOG-GLI (HH-GLI) signalling is a key pathway critical in embryonic development, stem cell biology and tissue homeostasis. In recent years, aberrant activation of HH-GLI signalling has been linked to several types of cancer, including those of the skin, brain, lungs, prostate, gastrointestinal tract and blood. HH-GLI signalling is initiated by binding of HH ligands to the transmembrane receptor PATCHED and is mediated by transcriptional effectors that belong to the GLI family, whose activity is finely tuned by a number of molecular interactions and post-translation modifications. Several reports suggest that the activity of the GLI proteins is regulated by several proliferative and oncogenic inputs, in addition or independent of upstream HH signalling. The identification of this complex crosstalk and the understanding of how the major oncogenic signalling pathways interact in cancer is a crucial step towards the establishment of efficient targeted combinatorial treatments. Here we review recent findings on the cooperative integration of HH-GLI signalling with the major oncogenic inputs and we discuss how these cues modulate the activity of the GLI proteins in cancer. We then summarise the latest advances on SMO and GLI inhibitors and alternative approaches to attenuate HH signalling through rational combinatorial therapies.

Management of high-risk and advanced basal cell carcinoma

Despite that basal cell carcinoma (BCC) is curative in the vast majority of cases, some patients are at high risk of recurrence and, in a few patients, lesions can progress to a point unsuitable for local therapy and prognosis is quite poor. The aim of the present work is to review clinical and pathologic characteristics as well as classical and new treatment options for high-risk, metastatic and locally advanced BCC. Surgery and radiotherapy remain the selected treatments for the majority of high-risk lesions. However, some patients are located on a blurry clinical boundary between high-risk and locally advanced BCC. Treatment of these patients is challenging and need an individualized and highly specialized approach. The treatment of locally advanced BCC, in which surgery or radiotherapy is unfeasible, inappropriate or contraindicated, and metastatic BCC has changed with new Hedgehog pathway inhibitors of which vismodegib is the first drug approved by FDA and EMA.

Hedgehog/GLI and PI3K signaling in the initiation and maintenance of chronic lymphocytic leukemia

The initiation and maintenance of a malignant phenotype requires complex and synergistic interactions of multiple oncogenic signals. The Hedgehog (HH)/GLI pathway has been implicated in a variety of cancer entities and targeted pathway inhibition is of therapeutic relevance. Signal cross-talk with other cancer pathways including PI3K/AKT modulates HH/GLI signal strength and its oncogenicity. In this study, we addressed the role of HH/GLI and its putative interaction with the PI3K/AKT cascade in the initiation and maintenance of chronic lymphocytic leukemia (CLL). Using transgenic mouse models, we show that B-cell-specific constitutive activation of HH/GLI signaling either at the level of the HH effector and drug target Smoothened or at the level of the GLI transcription factors does not suffice to initiate a CLL-like phenotype characterized by the accumulation of CD5⁺ B cells in the lymphatic system and peripheral blood. Furthermore, Hh/Gli activation in Pten-deficient B cells with activated Pi3K/Akt signaling failed to enhance the expansion of leukemic CD5⁺ B cells, suggesting that genetic or epigenetic alterations leading to aberrant HH/GLI signaling in B cells do not suffice to elicit a CLL-like phenotype in mice. By contrast, we identify a critical role of GLI and PI3K signaling for the survival of human primary CLL cells. We show that combined targeting of GLI and PI3K/AKT/mTOR signaling can have a synergistic therapeutic effect in cells from a subgroup of CLL patients, thereby providing a basis for the evaluation of future combination therapies targeting HH/GLI and PI3K signaling in this common hematopoietic malignancy.

Identifying locally advanced basal cell carcinoma eligible for treatment with vismodegib: an expert panel consensus

ABSTRACT 

Basal cell carcinoma (BCC) is the most common skin cancer worldwide. Most occur on the head and neck, where cosmetic and functional outcomes are critical. BCC can be locally destructive if not diagnosed early and treated appropriately. Surgery is the treatment of choice for the majority of high-risk lesions. Aggressive, recurrent or unresectable tumors can be difficult to manage. Until recently, no approved systemic therapy was available for locally advanced or metastatic BCC inappropriate for surgery or radiotherapy. Vismodegib provides a systemic treatment option. However, a consensus definition of advanced BCC is lacking. A multidisciplinary panel with expertise in oncology, dermatology, dermatologic surgery and radiation oncology proposes a consensus definition based on published evidence and clinical experience.

MRT-92 inhibits Hedgehog signaling by blocking overlapping binding sites in the transmembrane domain of the Smoothened receptor

The Smoothened (Smo) receptor, a member of class F G protein-coupled receptors, is the main transducer of the Hedgehog (Hh) signaling pathway implicated in a wide range of developmental and adult processes. Smo is the target of anticancer drugs that bind to a long and narrow cavity in the 7-transmembrane (7TM) domain. X-ray structures of human Smo (hSmo) bound to several ligands have revealed 2 types of 7TM-directed antagonists: those binding mostly to extracellular loops (site 1, e.g., LY2940680) and those penetrating deeply in the 7TM cavity (site 2, e.g., SANT-1). Here we report the development of the acylguanidine MRT-92, which displays subnanomolar antagonist activity against Smo in various Hh cell-based assays. MRT-92 inhibits rodent cerebellar granule cell proliferation induced by Hh pathway activation through pharmacologic (half maximal inhibitory concentration [IC50] = 0.4 nM) or genetic manipulation. Using [(3)H]MRT-92 (Kd = 0.3 nM for hSmo), we created a comprehensive framework for the interaction of small molecule modulators with hSmo and for understanding chemoresistance linked to hSmo mutations. Guided by molecular docking and site-directed mutagenesis data, our work convincingly confirms that MRT-92 simultaneously recognized and occupied both sites 1 and 2. Our data demonstrate the existence of a third type of Smo antagonists, those entirely filling the Smo binding cavity from the upper extracellular part to the lower cytoplasmic-proximal subpocket. Our studies should help design novel potent Smo antagonists and more effective therapeutic strategies for treating Hh-linked cancers and associated chemoresistance.

Is reduction of tumor burden sufficient for the 21st century?

Currently, animal models are used to test the efficacy of tumor treatment. A significant reduction of tumor mass is lauded as great improvement. As we begin the 21st century, one wonders if this is sufficient and acceptable for cancer treatment. Although the presence of cancer stem cell (CSCs) is not a new phenomenon, their role in the initiation of the tumor for clinical resurgence is mostly ignored when testing drugs. The current treatment then poses a major limitation to aggressively target the cells most responsible for tumor initiation and resurgence. The review does not trivialize the problem since it is acknowledged that the tumors and cells within the tissue microenvironment would interact through complex mechanisms. It is quite possible that the interaction by CSCs and the microenvironment will vary, depending on the tissue, e.g., bone marrow versus brain. Research studies are needed to investigate if CSCs from the same organ differ after migrating to other tissues. If so, this will pose an economic dilemma for targeted drug development. It will not be feasible to develop drugs for each organ. Besides, the cost, there could be problems to effectively deliver the drugs to all organs, problems to assess drug distribution to particular tissues and toxicity for specific drugs. If multiple drugs are required to eradicate CSCs in different tissues, there is a problem of possible untoward effect for the simultaneous delivery of multiple drugs to a single cancer patient. As new drugs are developed, the investigators will need to pay attention for dedifferentiation of non-CSCs to CSCs. The metabolic pathways will have to be given equal attention as the stem cells genes since their pathways might show major differences rather than the stem cells genes, which are shared by the normal stem cells.

Unraveling the therapeutic potential of the LncRNA-dependent noncanonical Hedgehog pathway in cancer

Acquired resistance to Hedgehog pathway inhibitors has been reported in the clinical setting and upregulation of noncanonical Hedgehog signaling is one of the major underlying mechanisms behind this resistance. As demonstrated in our recent study, greater clinical efficacy might be achieved by focusing on downstream targets of the chemokine-activated noncanonical Hedgehog signaling pathway such as BCAR4 and phospho-GLI2 (Ser149).

Hedgehog pathway inhibitors promote adaptive immune responses in basal cell carcinoma

PURPOSE

Basal cell carcinomas (BCCs) are tumors ignored by immune surveillance. Activated Hedgehog (Hh) signaling within primary cilia is a key driver in the pathogenesis of BCCs. We examined immune alterations during treatment with systemic Hh inhibitors.

EXPERIMENTAL DESIGN

We investigated biopsies from patients with BCC before (23 patients) and after 4 weeks of treatment (5 patients) with Hh signaling inhibitor. Ber-Ep4, BCL-2, Ki-67, CD4, CD8, MHC class I, HLA-DR-class II, and SOX9 were analyzed by immunohistochemistry. Primary cilia were analyzed by double immunofluorescence of acetylated tubulin and SOX9. Differential gene expression for 84 cytokines and chemokines was analyzed in 3 patients.

RESULTS

After 4 weeks of treatment, we found reduction of Ki-67, SOX9, Ber-EP4, and BCL-2 expression in tumors associated with morphologic signs of squamous differentiation. In addition, the number of cilia-positive BCC cells was significantly decreased. An upregulation of MHC I expression on the cell membranes of residual tumor cells and an influx of CD4(+), HLA-DR-class II(+), and CD8(+) cells with invasion into the tumor cell nests were found. Finally, qPCR arrays showed the differential expression of genes involved in modulating immune responses.

CONCLUSIONS

We show that Hh pathway inhibitor-induced tumor regression is accompanied by a dynamic change of the microenvironment with a disruption of immune privilege involving an influx of cytotoxic T cells, activation of the adaptive immune functions, and a profound alteration of the local chemokine/cytokine network.

Evolution of targeted therapies in cancer: opportunities and challenges in the clinic

ABSTRACT 

Targeted therapies have changed the course of cancer treatment in recent years. By reducing toxicity and improving outcome, these new generations of precision medicines have extended patient lives beyond what could be achieved by the use of nontargeted therapies. In the last 2 years, several new molecular entities targeting signaling proteins and immune pathways have gone through successful clinical development resulting in their approval. These new targeted therapies require patient selection and the discovery of biomarkers of response. This review discusses the evolution of targeted therapies in cancer and challenges in translating the concepts into clinical practice.

A Spanish version of the Skin Cancer Index: a questionnaire for measuring quality of life in patients with cervicofacial nonmelanoma skin cancer

INTRODUCTION

The Skin Cancer Index (SCI) is the first specific patient-reported outcome measure for patients with cervicofacial nonmelanoma skin cancer. To date, only the original English version has been published.

OBJECTIVES

To develop a Spanish version of the SCI that is semantically and linguistically equivalent to the original, and to evaluate its measurement properties in this different cultural environment.

MATERIAL AND METHODS

A cross-sectional study was conducted of the cultural adaptation and empirical validation of the questionnaire, analysing the psychometric properties of the new index at different stages.

RESULTS

Of 440 patients recruited to the study, 431 (95%) completed the Spanish version of the SCI questionnaire, in a mean time of 6·3 min (SD 2·9). Factor analysis of the scale revealed commonality and loading values of < 0·5 for three of the 15 items. The remaining 12 items converged into two components: appearance/social aspects (seven items) and emotional aspects (five items). Both domains presented a high level of internal consistency, with Cronbach's alpha values above 0·8. The convergent-discriminant validity analysis produced correlations higher than 0·3 for the mental component of the Short Form Health Survey-12v2 Health Questionnaire (correlation coefficient 0·39) and the Dermatology Quality of Life Index (correlation coefficient -0·30). In the test-retest, nine of the 12 items produced a weighted kappa value exceeding 0·4, and for the remaining three items, the absolute agreement percentage exceeded 60%.

CONCLUSIONS

The Spanish version of the SCI quality of life scale has been satisfactorily adapted and validated for use in Spanish-speaking countries and populations.

Evolving toward a human-cell based and multiscale approach to drug discovery for CNS disorders

A disruptive approach to therapeutic discovery and development is required in order to significantly improve the success rate of drug discovery for central nervous system (CNS) disorders. In this review, we first assess the key factors contributing to the frequent clinical failures for novel drugs. Second, we discuss cancer translational research paradigms that addressed key issues in drug discovery and development and have resulted in delivering drugs with significantly improved outcomes for patients. Finally, we discuss two emerging technologies that could improve the success rate of CNS therapies: human induced pluripotent stem cell (hiPSC)-based studies and multiscale biology models. Coincident with advances in cellular technologies that enable the generation of hiPSCs directly from patient blood or skin cells, together with methods to differentiate these hiPSC lines into specific neural cell types relevant to neurological disease, it is also now possible to combine data from large-scale forward genetics and post-mortem global epigenetic and expression studies in order to generate novel predictive models. The application of systems biology approaches to account for the multiscale nature of different data types, from genetic to molecular and cellular to clinical, can lead to new insights into human diseases that are emergent properties of biological networks, not the result of changes to single genes. Such studies have demonstrated the heterogeneity in etiological pathways and the need for studies on model systems that are patient-derived and thereby recapitulate neurological disease pathways with higher fidelity. In the context of two common and presumably representative neurological diseases, the neurodegenerative disease Alzheimer's Disease, and the psychiatric disorder schizophrenia, we propose the need for, and exemplify the impact of, a multiscale biology approach that can integrate panomic, clinical, imaging, and literature data in order to construct predictive disease network models that can (i) elucidate subtypes of syndromic diseases, (ii) provide insights into disease networks and targets and (iii) facilitate a novel drug screening strategy using patient-derived hiPSCs to discover novel therapeutics for CNS disorders.

Biological and clinical significance of cancer stem cell plasticity

In the past decade, the traditional view of cancers as a homogeneous collection of malignant cells is being replaced by a model of ever increasing complexity suggesting that cancers are complex tissues composed of multiple cell types. This complex model of tumorigenesis has been well supported by a growing body of evidence indicating that most cancers including those derived from blood and solid tissues display a hierarchical organization of tumor cells with phenotypic and functional heterogeneity and at the apex of this hierarchy are cells capable of self-renewal. These "tumor imitating cells" or "cancer stem cells" drive tumorigenesis and contribute to metastasis, treatment resistance and tumor relapse. Although tumor stem cells themselves may display both genetic and phenotypic heterogeneity, recent studies have demonstrated that cancer stem cells maintain plasticity to transition between mesenchymal-like (EMT) and epithelial-like (MET) states, which may be regulated by the tumor microenvironment. These stem cell state transitions may play a fundamental role in tumor progression and treatment resistance. In this review, we discuss the emerging knowledge regarding the plasticity of cancer stem cells with an emphasis on the signaling pathways and noncoding RNAs including microRNAs (miRNA) and long non-coding RNAs (lncRNAs) in regulation of this plasticity during tumor growth and metastasis. Lastly, we point out the importance of targeting both the EMT and MET states of CSCs in order to eliminate these lethal seeds of cancers.

Autophagy is related to the hedgehog signaling pathway in human gastric adenocarcinoma: prognostic significance of Beclin-1 and Gli2 expression in human gastric adenocarcinoma

Beclin-1 induces autophagy, which is known to be involved in many physiopathological processes such as cell development, aging, stress response, immune response and cancer. Several studies showed that Beclin-1 expression is associated with several prognostic factors of gastric carcinomas. Recently, the connection between autophagy and the hedgehog (HH) signaling pathway has been studied. Here, we investigated the relationship between the autophagy and hedgehog (HH) signaling pathways in gastric adenocarcinoma. We evaluated Beclin-1 and Gli2 expression in 108 gastric adenocarcinoma tissues via immunohistochemical analysis, using a tissue microarray, in relation to survival and other prognostic factors. Our results show that increased Beclin-1 expression is correlated with favorable clinicopathological variables including histologic grade, tumor size, primary tumor (T) stage, lymph node metastasis, lymphatic invasion, neural invasion, and tumor recurrence. Furthermore, increased Gli-2 expression was correlated with several favorable clinicopathological variables including primary tumor (T) stage, lymphatic invasion, and tumor recurrence. Increased Beclin-1 expression was significantly correlated with increased Gli2. Univariate analyses for disease-free survival and overall survival revealed that the higher Beclin-1 and Gli2 expression group had a more favorable prognosis compared with the lower Beclin-1 and Gli2 expression group. Our results suggest that progressively increased Beclin-1 and Gli2 expression contributes to the inhibition of tumor growth and metastasis in gastric adenocarcinoma and Beclin-1 acts as a tumor suppressor by regulating the HH signaling pathway through Gli2 expression in gastric adenocarcinoma.

Identification of anaplastic lymphoma kinase as a potential therapeutic target in Basal Cell Carcinoma

The pathogenesis of BCC is associated with sonic hedgehog (SHH) signaling. Vismodegib, a smoothened inhibitor that targets this pathway, is now in clinical use for advanced BCC patients, but its efficacy is limited. Therefore, new therapeutic options for this cancer are required. We studied gene expression profiling of BCC tumour tissues coupled with laser capture microdissection to identify tumour specific receptor tyrosine kinase expression that can be targeted by small molecule inhibitors. We found a >250 fold increase (FDR<10⁻⁴) of the oncogene, anaplastic lymphoma kinase (ALK) as well as its ligands, pleiotrophin and midkine in BCC compared to microdissected normal epidermis. qRT-PCR confirmed increased expression of ALK (p<0.05). Stronger expression of phosphorylated ALK in BCC tumour nests than normal skin was observed by immunohistochemistry. Crizotinib, an FDA-approved ALK inhibitor, reduced keratinocyte proliferation in culture, whereas a c-Met inhibitor did not. Crizotinib significantly reduced the expression of GLI1 and CCND2 (members of SHH-pathway) mRNA by approximately 60% and 20%, respectively (p<0.01). Our data suggest that ALK may increase GLI1 expression in parallel with the conventional SHH-pathway and promote keratinocyte proliferation. Hence, an ALK inhibitor alone or in combination with targeting SHH-pathway molecules may be a potential treatment for BCC patients.

Repurposing the antihelmintic mebendazole as a hedgehog inhibitor

The hedgehog (Hh) signaling pathway is activated in many types of cancer and therefore presents an attractive target for new anticancer agents. Here, we show that mebendazole, a benzamidazole with a long history of safe use against nematode infestations and hydatid disease, potently inhibited Hh signaling and slowed the growth of Hh-driven human medulloblastoma cells at clinically attainable concentrations. As an antiparasitic, mebendazole avidly binds nematode tubulin and causes inhibition of intestinal microtubule synthesis. In human cells, mebendazole suppressed the formation of the primary cilium, a microtubule-based organelle that functions as a signaling hub for Hh pathway activation. The inhibition of Hh signaling by mebendazole was unaffected by mutants in the gene that encodes human Smoothened (SMO), which are selectively propagated in cell clones that survive treatment with the Hh inhibitor vismodegib. Combination of vismodegib and mebendazole resulted in additive Hh signaling inhibition. Because mebendazole can be safely administered to adults and children at high doses over extended time periods, we propose that mebendazole could be rapidly repurposed and clinically tested as a prospective therapeutic agent for many tumors that are dependent on Hh signaling.

Metastatic basal cell carcinoma to the lungs: Case report and review of literature

Basal cell carcinoma is the most common form of skin cancer and it rarely metastasizes. The prevalence of metastatic basal cell carcinoma (MBCC) varies between 0.0028% and 0.55% of all cases. Over 250 MBCC have been reported in the literature. We present a case with large recurrent basal cell carcinoma of the face with radiological and histopathological findings indicating the presence of metastasis to the lungs.

Activated hedgehog pathway is a potential target for pharmacological intervention in biliary tract cancer

Hedgehog (Hh) signalling contributes to carcinogenesis and represents a valid druggable target in human cancers, possibly also in biliary tract cancer (BTC). We analysed the expression of Hh components in BTC using eight heterogeneously differentiated cell lines, xenograft tumours and a human tissue microarray. The dose-, time- and cell line-dependent effects of two Hh inhibitors (cyclopamine and Gant-61) were analysed in vitro for survival, apoptosis, cell cycle distribution and possible synergism with conventional chemotherapeutic agents. In human BTC samples, the sonic Hh ligand and the Gli1 transcription factor showed increased expression in tumours compared to normal adjacent tissue and were significantly associated with high tumour grade and positive lymph node status. In BTC cell lines, we could confirm the Hh component expression at varying extent within the employed cell lines in vitro and in vivo indicating non-canonical signalling. Both Hh inhibitors showed dose-dependent cytotoxicity above 5 µM with a stronger effect for Gant-61 inducing apoptosis whereas cyclopamine rather inhibited proliferation. Cytotoxicity was associated with low cytokeratin expression and higher mesenchymal marker expression such as vimentin. Additionally, drug combinations of Gant-61 with conventional chemotherapy (cisplatin) exerted synergistic effects. In conclusion, Hh pathway is significantly activated in human BTC tissue compared to normal adjacent tissue. The current data demonstrate for the first time an effective anticancer activity of especially Gant-61 in BTC and suggest second generation Hh pathway inhibitors as a potential novel treatment strategy in BTC.

Vismodegib, an antagonist of hedgehog signaling, directly alters taste molecular signaling in taste buds

Vismodegib, a highly selective inhibitor of hedgehog (Hh) pathway, is an approved treatment for basal-cell carcinoma. Patients on treatment with vismodegib often report profound alterations in taste sensation. The cellular mechanisms underlying the alterations have not been studied. Sonic Hh (Shh) signaling is required for cell growth and differentiation. In taste buds, Shh is exclusively expressed in type IV taste cells, which are undifferentiated basal cells and the precursors of the three types of taste sensing cells. Thus, we investigated if vismodegib has an inhibitory effect on taste cell turnover because of its known effects on Hh signaling. We gavaged C57BL/6J male mice daily with either vehicle or 30 mg/kg vismodegib for 15 weeks. The gustatory behavior and immunohistochemical profile of taste cells were examined. Vismodegib-treated mice showed decreased growth rate and behavioral responsivity to sweet and bitter stimuli, compared to vehicle-treated mice. We found that vismodegib-treated mice had significant reductions in taste bud size and numbers of taste cells per taste bud. Additionally, vismodegib treatment resulted in decreased numbers of Ki67- and Shh-expressing cells in taste buds. The numbers of phospholipase Cβ2- and α-gustducin-expressing cells, which contain biochemical machinery for sweet and bitter sensing, were reduced in vismodegib-treated mice. Furthermore, vismodegib treatment resulted in reduction in numbers of T1R3, glucagon-like peptide-1, and glucagon-expressing cells, which are known to modulate sweet taste sensitivity. These results suggest that inhibition of Shh signaling by vismodegib treatment directly results in alteration of taste due to local effects in taste buds.