Activating Smoothened mutations in sporadic basal-cell carcinoma

Metastatic Basal Cell Carcinoma of the Skin: A Comprehensive Literature Review, Including Advances in Molecular Therapeutics

Basal cell carcinoma (BCC) of the skin is the most common type of malignant human tumor. In Europe, the incidence of BCC ranges from 44.6 to 128 cases per 100,000 inhabitants annually, whereas in the United States, the yearly incidence rate ranges between 500 and 1500. The global incidence has been calculated to be as high as 10 million cases of BCC per year. There are 2 main clinical patterns of BCC-the familial BCC in basal cell nevus syndrome and sporadic BCC. The etiology of cutaneous BCC is usually the result of the interaction between solar ultraviolet radiation and genetic factors. Somatic or germline mutations in the effector components of the hedgehog signaling pathway (ie, PTCH1, PTCH2, SMO or SUFU genes) are responsible for ∼90% of the cases of both sporadic and familial BCC, all causing a constitutive activation of the hedgehog pathway. Cutaneous BCC very rarely metastasizes, and diagnosis in metastatic sites can be very difficult. Metastatic BCC has weakly effective therapeutic options with a poor prognosis until few years ago. In 2012, small-molecule therapies, involving inactivation of the hedgehog signaling pathway, and capable of reducing tumor growth and progression have been introduced into clinical practice for advanced (locally advanced or metastatic) BCC. We performed a comprehensive literature review on metastatic BCC and found at least 915 cases reported to date. In addition, we extensively discussed the differential diagnosis of metastatic BCC, and outlined the advances in clinical therapeutics involving these small molecules.

24-Dehydrocholesterol reductase promotes the growth of breast cancer stem-like cells through the Hedgehog pathway

Cholesterol is a risk factor for breast cancer. However, it is still unclear whether the cholesterol biosynthesis pathway plays any significant role in breast carcinogenesis. 24-Dehydrocholesterol reductase (DHCR24) is a key enzyme in the cholesterol synthesis pathway. Although DHCR24 is reported to have different functions in different cancers, it is not clear whether DHCR24 is involved in breast cancer. In this study, we found that DHCR24 expression was higher in breast cancer especially in luminal and HER2 positive breast cancer tissues compared with normal breast. Changes in DHCR24 expression altered cellular cholesterol content without affecting the adherent growth of breast cancer cells. However, DHCR24 knockdown reduced whereas DHCR24 overexpression enhanced breast cancer stem-like cell populations such as mammosphere and aldehyde dehydrogenase positive cell numbers. In addition, DHCR24 overexpression increased the expression of the Hedgehog pathway-regulated genes. Treating DHCR24 overexpressing breast cancer cell lines with the Hedgehog pathway inhibitor GANT61 blocked DHCR24-induced mammosphere growth and increased mRNA levels of the Hedgehog regulated genes. Furthermore, expression of a constitutively activated mutant of Smoothened, a key hedgehog signal transducer, rescued the decreases in mammosphere growth and Hedgehog regulated gene expression induced by knockdown of DHCR24. These results indicate that DHCR24 promotes the growth of breast cancer stem-like cells in part through enhancing the Hedgehog signaling pathway. Our data suggest that cholesterol contribute to breast carcinogenesis by enhancing Hedgehog signaling and cancer stem-like cell populations. Enzymes including DHCR24 involved in cholesterol biosynthesis should be considered as potential treatment targets for breast cancer.

Hedgehog promotes cell proliferation in the midgut of silkworm, Bombyx mori

The Hedgehog (Hh) signaling pathway is one of the major regulators of embryonic development and tissue homeostasis in multicellular organisms. However, the role of this pathway in the silkworm, especially in the silkworm midgut, remains poorly understood. Here, we report that Bombyx mori Hedgehog (BmHh) is expressed in most tissues of silkworm larvae and that its functions are well-conserved throughout evolution. We further demonstrate that the messenger RNA of four Hh signaling components, BmHh ligand, BmPtch receptor, signal transducer BmSmo and transcription factor BmCi, are all upregulated following Escherichia coli or Bacillus thuringiensis infection, indicating the activation of the Hh pathway. Simultaneously, midgut cell proliferation is strongly promoted. Conversely, the repression of Hh signal transduction with double-stranded RNA or cyclopamine inhibits the expression of BmHh and BmCi and reduces cell proliferation. Overall, these findings provide new insights into the Hh signaling pathway in the silkworm, B. mori.

Biallelic PTCH1 Inactivation Is a Dominant Genomic Change in Sporadic Keratocystic Odontogenic Tumors

Keratocystic odontogenic tumors (KCOTs) are locally aggressive odontogenic neoplasms with recurrence rates of up to 60%. Approximately 5% of KCOTs are associated with nevoid basal cell carcinoma (Gorlin) syndrome and 90% of these show genomic inactivation of the PTCH1 gene encoding Patched 1. Sporadic KCOTs reportedly have PTCH1 mutations in 30% of cases, but previous genomic analyses have been limited by low tumor DNA yield. The aim of this study was to identify recurrent genomic aberrations in sporadic KCOTs using a next-generation sequencing panel with complete exonic coverage of sonic hedgehog (SHH) pathway members PTCH1, SMO, SUFU, GLI1, and GLI2. Included were 44 sporadic KCOTs from 23 female and 21 male patients with a median age of 50 years (range, 10 to 82 y) and located in the mandible (N=33) or maxilla (N=11). Sequencing identified PTCH1 inactivating mutations in 41/44 (93%) cases, with biallelic inactivation in 35 (80%) cases; 9q copy neutral loss of heterozygosity targeting the PTCH1 locus was identified in 15 (34%) cases. No genomic aberrations were identified in other sequenced SHH pathway members. In summary, we demonstrate PTCH1 inactivating mutations in 93% of sporadic KCOTs, indicating that SHH pathway alterations are a near-universal event in these benign but locally aggressive neoplasms. The high frequency of complete PTCH1 loss of function may provide a rational target for SHH pathway inhibitors to be explored in future studies.

Epidermal activation of Hedgehog signaling establishes an immunosuppressive microenvironment in basal cell carcinoma by modulating skin immunity

Genetic activation of hedgehog/glioma‐associated oncogene homolog (HH/GLI) signaling causes basal cell carcinoma (BCC), a very frequent nonmelanoma skin cancer. Small molecule targeting of the essential HH effector Smoothened (SMO) has proven an effective therapy of BCC, though the frequent development of drug resistance poses major challenges to anti‐HH treatments. In light of recent breakthroughs in cancer immunotherapy, we analyzed the possible immunosuppressive mechanisms in HH/GLI‐induced BCC in detail. Using a genetic mouse model of BCC, we identified profound differences in the infiltration of BCC lesions with cells of the adaptive and innate immune system. Epidermal activation of Hh/Gli signaling led to an accumulation of immunosuppressive regulatory T cells, and to an increased expression of immune checkpoint molecules including programmed death (PD)‐1/PD‐ligand 1. Anti‐PD‐1 monotherapy, however, did not reduce tumor growth, presumably due to the lack of immunogenic mutations in common BCC mouse models, as shown by whole‐exome sequencing. BCC lesions also displayed a marked infiltration with neutrophils, the depletion of which unexpectedly promoted BCC growth. The study provides a comprehensive survey of and novel insights into the immune status of murine BCC and serves as a basis for the design of efficacious rational combination treatments. This study also underlines the need for predictive immunogenic mouse models of BCC to evaluate the efficacy of immunotherapeutic strategies in vivo.

Discovery of Small Molecule Inhibitors Targeting the Sonic Hedgehog

The aberrant activation of hedgehog (Hh) signaling pathway is closely related to human diseases. The upstream protein, N-terminal product of sonic hedgehog (ShhN) is overexpressed in many cancers and considered as a promising antitumor target. Inhibitors that bind to ShhN and break its interaction with the 12-transmembrane glycoprotein patched (Ptch) protein are highly wanted to tune down the abnormal Hh pathway activation. However, research of ShhN inhibitors remains lacking. In this paper, we computationally screened potential inhibitors against the ShhN-Ptch interaction interface, and tested their activities by experimental studies. Seven compounds (1-7) with diverse scaffolds, showed inhibition in cellular assays and directly bound to ShhN in vitro. The compounds were verified to modulate the Hh pathway activity. Furthermore, we studied the structure-activity relationship of the pyrimidine (7) derivatives and identified a potent compound (7_3d3) with IC₅₀ of 0.4 ± 0.1 μM in cellular assays. These small molecule inhibitors of ShhN provide novel chemical probes for future investigations of Hh signaling.

Bi-allelic Variations of SMO in Humans Cause a Broad Spectrum of Developmental Anomalies Due to Abnormal Hedgehog Signaling

The evolutionarily conserved hedgehog (Hh) pathway is essential for organogenesis and plays critical roles in postnatal tissue maintenance and renewal. A unique feature of the vertebrate Hh pathway is that signal transduction requires the primary cilium (PC) where major pathway components are dynamically enriched. These factors include smoothened (SMO) and patched, which constitute the core reception system for sonic hedgehog (SHH) as well as GLI transcription factors, the key mediators of the pathway. Here, we report bi-allelic loss-of-function variations in SMO in seven individuals from five independent families; these variations cause a wide phenotypic spectrum of developmental anomalies affecting the brain (hypothalamic hamartoma and microcephaly), heart (atrioventricular septal defect), skeleton (postaxial polydactyly, narrow chest, and shortening of long bones), and enteric nervous system (aganglionosis). Cells derived from affected individuals showed normal ciliogenesis but severely altered Hh-signal transduction as a result of either altered PC trafficking or abnormal activation of the pathway downstream of SMO. In addition, Hh-independent GLI2 accumulation at the PC tip in cells from the affected individuals suggests a potential function of SMO in regulating basal ciliary trafficking of GLI2 when the pathway is off. Thus, loss of SMO function results in abnormal PC dynamics of key components of the Hh signaling pathway and leads to a large continuum of malformations in humans.

Cilia and polycystic kidney disease

Polycystic kidney disease (PKD), comprising autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD), is characterized by incessant cyst formation in the kidney and liver. ADPKD and ARPKD represent the leading genetic causes of renal disease in adults and children, respectively. ADPKD is caused by mutations in PKD1 encoding polycystin1 (PC1) and PKD2 encoding polycystin 2 (PC2). PC1/2 are multi-pass transmembrane proteins that form a complex localized in the primary cilium. Predominant ARPKD cases are caused by mutations in polycystic kidney and hepatic disease 1 (PKHD1) gene that encodes the Fibrocystin/Polyductin (FPC) protein, whereas a small subset of cases are caused by mutations in DAZ interacting zinc finger protein 1 like (DZIP1L) gene. FPC is a type I transmembrane protein, localizing to the cilium and basal body, in addition to other compartments, and DZIP1L encodes a transition zone/basal body protein. Apparently, PC1/2 and FPC are signaling molecules, while the mechanism that cilia employ to govern renal tubule morphology and prevent cyst formation is unclear. Nonetheless, recent genetic and biochemical studies offer a glimpse of putative physiological malfunctions and the pathomechanisms underlying both disease entities. In this review, I summarize the results of genetic studies that deduced the function of PC1/2 on cilia and of cilia themselves in cyst formation in ADPKD, and I discuss studies regarding regulation of polycystin biogenesis and cilia trafficking. I also summarize the synergistic genetic interactions between Pkd1 and Pkhd1, and the unique tissue patterning event controlled by FPC, but not PC1. Interestingly, while DZIP1L mutations generate compromised PC1/2 cilia expression, FPC deficiency does not affect PC1/2 biogenesis and ciliary localization, indicating that divergent mechanisms could lead to cyst formation in ARPKD. I conclude by outlining promising areas for future PKD research and highlight rationales for potential therapeutic interventions for PKD treatment.

Sex-specific differences in patients with nonmelanoma skin cancer of the pinna

Background

Generally, it is known that men are affected more frequently by nonmelanoma skin cancer (NMSC) than women. The aim of our study was to investigate the effect of sex on the characteristics of NMSCs of the pinna at the population that our center serves and to compare it with the international data.

Methods

We analyzed retrospectively the data of 225 patients with NMSC of the pinna. Sex‐specific differences were investigated for basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC) subgroups.

Results

The ratio of BCC to cSCC was determined in male patients at 1:1.3, in contrast in females it was identified at 4:1 (P = .001).

Conclusion

In our study, a new aspect of the sex‐dependent distribution of cSCC and BCC of the pinna was demonstrated. Women are affected four times more frequently by BCC than by cSCC, whereas in men this ratio is approximately equal.

Prostaglandin E1 Inhibits GLI2 Amplification-Associated Activation of the Hedgehog Pathway and Drug Refractory Tumor Growth

Aberrant activation of the Hedgehog (HH) signaling pathway underlines the initiation and progression of a multitude of cancers. The effectiveness of the leading drugs vismodegib (GDC-0449) and sonidegib (LDE225), both Smoothened (SMO) antagonists, is compromised by acquisition of mutations that alter pathway components, notably secondary mutations in SMO and amplification of GLI2, a transcriptional mediator at the end of the pathway. Pharmacologic blockade of GLI2 activity could ultimately overcome these diversified refractory mechanisms, which would also be effective in a broader spectrum of primary tumors than current SMO antagonists. To this end, we conducted a high-content screening directly analyzing the ciliary translocation of GLI2, a key event for GLI2 activation in HH signal transduction. Several prostaglandin compounds were shown to inhibit accumulation of GLI2 within the primary cilium (PC). In particular, prostaglandin E1 (PGE1), an FDA-approved drug, is a potent GLI2 antagonist that overcame resistance mechanisms of both SMO mutagenesis and GLI2 amplification. Consistent with a role in HH pathway regulation, EP4 receptor localized to the PC. Mechanistically, PGE1 inhibited HH signaling through the EP4 receptor, enhancing cAMP-PKA activity, which promoted phosphorylation and degradation of GLI2 via the ubiquitination pathway. PGE1 also effectively inhibited the growth of drug refractory human medulloblastoma xenografts. Together, these results identify PGE1 and other prostaglandins as potential templates for complementary therapeutic development to circumvent resistance to current generation SMO antagonists in use in the clinic. SIGNIFICANCE: These findings show that PGE1 exhibits pan-inhibition against multiple drug refractory activities for Hedgehog-targeted therapies and elicits significant antitumor effects in xenograft models of drug refractory human medulloblastoma mimicking GLI2 amplification.

Human Organ-Specific 3D Cancer Models Produced by the Stromal Self-Assembly Method of Tissue Engineering for the Study of Solid Tumors

Cancer research has considerably progressed with the improvement of in vitro study models, helping to understand the key role of the tumor microenvironment in cancer development and progression. Over the last few years, complex 3D human cell culture systems have gained much popularity over in vivo models, as they accurately mimic the tumor microenvironment and allow high-throughput drug screening. Of particular interest, in vitrohuman 3D tissue constructs, produced by the self-assembly method of tissue engineering, have been successfully used to model the tumor microenvironment and now represent a very promising approach to further develop diverse cancer models. In this review, we describe the importance of the tumor microenvironment and present the existing in vitro cancer models generated through the self-assembly method of tissue engineering. Lastly, we highlight the relevance of this approach to mimic various and complex tumors, including basal cell carcinoma, cutaneous neurofibroma, skin melanoma, bladder cancer, and uveal melanoma.

SHARPIN regulates cell proliferation of cutaneous basal cell carcinoma via inactivation of the transcriptional factors GLI2 and c‑JUN

SHANK‑associated RH domain‑interacting protein (SHARPIN) is a component of the linear ubiquitin chain assembly complex that can enhance the NF‑κB and JNK signaling pathways, acting as a tumor‑associated protein in a variety of cancer types. The present study investigated the role of SHARPIN in cutaneous basal cell carcinoma (BCC). Human BCC (n=26) and normal skin (n=5) tissues, and BCC (TE354.T) and normal skin (HaCaT) cell lines were used to evaluate SHARPIN expression level using immunohistochemistry and western blotting, respectively. A lentivirus carrying SHARPIN‑targeting or negative control short hairpin RNA was infected into TE354.T cells, and the infected stable cells were assayed to analyze tumor cell proliferation, cell cycle, apoptosis, migration and invasion by Cell Counting Kit‑8 and 5‑ethynyl‑2'‑deoxyuridine incorporation assays, flow cytometry and Transwell assays. Western blotting was performed to assess the protein expression levels of gene signaling in SHARPIN‑silenced BCC cells. SHARPIN protein expression levels were downregulated or absent in BCC cancer nests and precancerous lesions compared with normal skin samples. In addition, SHARPIN expression levels were lower in TE354.T cells compared with HaCaT cells. SHARPIN shRNA enhanced tumor cell proliferation and the S phase of the cell cycle, whereas BCC cell apoptotic rates, and migratory and invasive abilities were not significantly altered. The expression levels of cyclin D1, cyclin‑dependent kinase 4, phosphorylated‑c‑JUN and GLI family zinc finger 2 proteins were increased, whereas Patched 1 (PTCH1) and PTCH2 were decreased in the SHARPIN‑shRNA‑infected BCC cells. Therefore, the present results suggested that SHARPIN may act as a tumor suppressor during BCC development.

Clinical Implications of Primary Cilia in Skin Cancer

The primary cilium is a cell surface organelle that is an important component of cellular biology. While it was once believed to be a vestigial structure without biologic function, it is now known to have essential roles in critical cellular signaling pathways such as Hedgehog (HH) and Wnt. The HH and Wnt pathways are involved in pathogenesis of basal cell carcinoma and melanoma, respectively, and this knowledge is now beginning to inform therapeutic and diagnostic options for patients. The purpose of this review is to familiarize clinicians with primary cilia biology and how this complex cellular organelle has started to translate into clinical care.

Therapeutically actionable PAK4 is amplified, overexpressed, and involved in bladder cancer progression

Muscle-invasive bladder carcinomas (MIBCs) are aggressive genitourinary malignancies. Metastatic urothelial carcinoma of the bladder is generally incurable by current chemotherapy and leads to early mortality. Recent studies have identified molecular subtypes of MIBCs with different sensitivities to frontline therapy, suggesting tumor heterogeneity. We have performed multi-omic profiling of the kinome in bladder cancer patients with the goal of identify therapeutic targets. Our analyses revealed amplification, overexpression, and elevated kinase activity of P21 (RAC1) activated kinase 4 (PAK4) in a subset of Bladder cancer (BLCA). Using bladder cancer cells, we confirmed the role of PAK4 in BLCA cell proliferation and invasion. Furthermore, we observed that a PAK4 inhibitor was effective in curtailing growth of BLCA cells. Transcriptomic analyses identified elevated expression of another kinase, protein tyrosine kinase 6 (PTK6), upon treatment with a PAK4 inhibitor and RNA interference of PAK4. Treatment with a combination of kinase inhibitors (vandetanib and dasatinib) showed enhanced sensitivity compared with either drug alone. Thus, PAK4 may be therapeutically actionable for a subset of MIBC patients with amplified and/or overexpressed PAK4 in their tumors. Our results also indicate that combined inhibition of PAK4 and PTK6 may overcome resistance to PAK4. These observations warrant clinical investigations with selected BLCA patients.

Benzene and its effects on cell signaling pathways related to hematopoiesis and leukemia

Benzene is an environmental toxicant found in many consumer products. It is an established human carcinogen and is known to cause acute myeloid leukemia in adults. Epidemiological evidence has since shown that benzene can cross the placenta and affect the fetal liver. Animal studies have shown that in utero exposure to benzene can increase tumor incidence in offspring. Although there have been risk factors established for acute myeloid leukemia, they still do not account for many of the cases. Clearly then, current efforts to elucidate the mechanism by which benzene exerts its carcinogenic properties have been superficial. Owing to the critical role of cell signaling pathways in the development of an organism and its various organ systems, it seems plausible to suspect that these pathways may have a role in leukemogenesis. This review article assesses current evidence of the effects of benzene on critical hematopoietic signaling pathways. Pathways discussed included Hedgehog, Notch/Delta, Wingless/Integrated, nuclear factor-kappaB and others. Following a review of the literature, it seems that current evidence about the effects of benzene on these critical signaling pathways remains limited. Given the important role of these pathways in hematopoiesis, more attention should be given to them.

Signaling in the primary cilium through the lens of the Hedgehog pathway

Cilia are microtubule-based, cell-surface projections whose machinery is evolutionarily conserved. In vertebrates, cilia are observed on almost every cell type and are either motile or immotile. Immotile sensory, or primary cilia, are responsive to extracellular ligands and signals. Cilia can be thought of as compartments, functionally distinct from the cell that provides an environment for signaling cascades. Hedgehog is a critical developmental signaling pathway which is functionally linked to primary cilia in vertebrates. The major components of the vertebrate Hedgehog signaling pathway dynamically localize to the ciliary compartment and ciliary membrane. Critically, G-protein coupled receptor (GPCR) Smoothened, the obligate transducer of the pathway, is enriched and activated in the cilium. While Smoothened is the most intensely studied ciliary receptor, many GPCRs localize within cilia. Understanding the link between Smoothened and cilia defines common features, and distinctions, of GPCR signaling within the primary cilium. This article is categorized under: Signaling Pathways > Global Signaling Mechanisms Signaling Pathways > Cell Fate Signaling.

Gene-Related Response of Basal Cell Carcinoma to Biologic Treatment with Vismodegib

We aimed to characterise the response of locally advanced basal cell carcinoma (BCC) to systemic treatment with Vismodegib, a Hedgehog pathway inhibitor, by changes in the expression levels of Hedgehog pathway genes. Data were collected prospectively on 12 patients treated systemically for locally advanced BCC. Biopsy samples taken on admission and after treatment cessation were analysed pathologically and with the NanoString nCounter system to quantify the expression of 40 Hedgehog signaling pathway genes. Findings were compared before and after treatment, between complete and partial responders, and with localised BCC samples from 22 patients. Sixteen Hedgehog pathway genes changed significantly from before to after treatment. GAS1 was the only gene with a significantly different expression at baseline between complete responders (6 patients) and partial responders (4 patients) to Vismodegib (P = 0.014). GAS, GLIS2 and PRKACG1 showed different expression before treatment between the locally advanced and localised BCCs. The baseline expression level of GAS1 appears to be predictive of the response of locally advanced BCC to systemic Vismodegib treatment. A change in expression of many Hedgehog pathway genes, albeit expected by the known activity of Vismodegib, may nevertheless serve as an indicator of the response potential of the tumour.

The Role of Dermal Fibroblasts in Nevoid Basal Cell Carcinoma Syndrome Patients: An Overview

Nevoid basal cell carcinoma syndrome (NBCCS), also named Gorlin syndrome, is a rare multisystem genetic disorder characterized by marked predisposition to basal cell carcinomas (BCCs), childhood medulloblastomas, maxillary keratocysts, celebral calcifications, in addition to various skeletal and soft tissue developmental abnormalities. Mutations in the tumor suppressor gene PATCHED1 (PTCH1) have been found to be associated in the majority of NBCCS cases. PATCH1 somatic mutations and loss of heterozygosity are also very frequent in sporadic BCCs. Unlike non-syndromic patients, NBCCS patients develop multiple BCCs in sun-protected skin area starting from early adulthood. Recent studies suggest that dermo/epidermal interaction could be implicated in BCC predisposition. According to this idea, NBCCS fibroblasts, sharing with keratinocytes the same PTCH1 germline mutation and consequent constitutive activation of the Hh pathway, display features of carcinoma-associated fibroblasts (CAF). This phenotypic traits include the overexpression of growth factors, specific microRNAs profile, modification of extracellular matrix and basement membrane composition, increased cytokines and pro-angiogenic factors secretion, and a complex alteration of the Wnt/-catenin pathway. Here, we review studies about the involvement of dermal fibroblasts in BCC predisposition of Gorlin syndrome patients. Further, we matched the emerged NBCCS fibroblast profile to those of CAF to compare the impact of cell autonomous "pre-activated state" due to PTCH1 mutations to those of skin tumor stroma.

An ABC Transporter Drives Medulloblastoma Pathogenesis by Regulating Sonic Hedgehog Signaling

Mutations in Sonic hedgehog (SHH) signaling promote aberrant proliferation and tumor growth. SHH-medulloblastoma (MB) is among the most frequent brain tumors in children less than 3 years of age. Although key components of the SHH pathway are well-known, we hypothesized that new disease-modifying targets of SHH-MB might be identified from large-scale bioinformatics and systems biology analyses. Using a data-driven systems biology approach, we built a MB-specific interactome. The ATP-binding cassette transporter ABCC4 was identified as a modulator of SHH-MB. Accordingly, increased ABCC4 expression correlated with poor overall survival in patients with SHH-MB. Knockdown of ABCC4 expression markedly blunted the constitutive activation of the SHH pathway secondary to Ptch1 or Sufu insufficiency. In human tumor cell lines, ABCC4 knockdown and inhibition reduced full-length GLI3 levels. In a clinically relevant murine SHH-MB model, targeted ablation of Abcc4 in primary tumors significantly reduced tumor burden and extended the lifespan of tumor-bearing mice. These studies reveal ABCC4 as a potent SHH pathway regulator and a new candidate to target with the potential to improve SHH-MB therapy. SIGNIFICANCE: These findings identify ABCC4 transporter as a new target in SHH-MB, prompting the development of inhibitors or the repurporsing of existing drugs to target ABCC4.

Cilia-driven asymmetric Hedgehog signalling determines the amphioxus left-right axis by controlling Dand5 expression

Cilia rotation-driven nodal flow is crucial for the left-right (L-R) break in symmetry in most vertebrates. However, the mechanism by which the flow signal is translated to asymmetric gene expression has been insufficiently addressed. Here, we show that Hedgehog (Hh) signalling is asymmetrically activated (L<R) in the region in which initial asymmetric Dand5 expression is detected. Upregulation of Hh signalling on the left side of wild-type embryos induces ectopic Dand5 expression on the left side, and the unilateral recovery of Hh signalling in Hh homozygous mutants induces Dand5 expression in the Hh signal recovery side. Immunofluorescence analysis results revealed that Hh fusion protein is asymmetrically enriched in the anterior-right paraxial mesoderm at the early neurula stage. Inhibiting embryonic cilia motility using methylcellulose (MC) blocks Hh protein enrichment on the right hand side and randomizes Dand5 expression and organ positioning along the L-R axis. These findings present a model showing that cilia movement is crucial for the symmetry breaks in amphioxus through asymmetric Hh protein transport. The resultant asymmetric Hh signalling provides a clue into the induction of asymmetric Dand5 expression.This article has an associated 'The people behind the papers' interview.

Identification of recurrent FHL2-GLI2 oncogenic fusion in sclerosing stromal tumors of the ovary

Sclerosing stromal tumor (SST) of the ovary is a rare type of sex cord-stromal tumor (SCST), whose genetic underpinning is currently unknown. Here, using whole-exome, targeted capture and RNA-sequencing, we report recurrent FHL2-GLI2 fusion genes in 65% (17/26) of SSTs and other GLI2 rearrangements in additional 15% (4/26) SSTs, none of which are detected in other types of SCSTs (n = 48) or common cancer types (n = 9,950). The FHL2-GLI2 fusions result in transcriptomic activation of the Sonic Hedgehog (SHH) pathway in SSTs. Expression of the FHL2-GLI2 fusion in vitro leads to the acquisition of phenotypic characteristics of SSTs, increased proliferation, migration and colony formation, and SHH pathway activation. Targeted inhibition of the SHH pathway results in reversal of these oncogenic properties, indicating its role in the pathogenesis of SSTs. Our results demonstrate that the FHL2-GLI2 fusion is likely the oncogenic driver of SSTs, defining a genotypic–phenotypic correlation in ovarian neoplasms.

Little is known about the genetics of sclerosing stromal tumor of the ovary, a rare type of sex cord-stromal tumor. Here, the authors use sequencing strategies to show that in a cohort of 26 tumor samples 65% carry a FHL2-GLI2 fusion gene and demonstrate in vitro that the fusion gene has oncogenic properties.

The Loss of 1p as a Reliable Marker of Progression in a Child with Aggressive Meningioma: A 16-Year Follow-Up Case Report

BACKGROUND

Here, we present the case of a 32-year-old female with a progressing history of meningioma for 16 years starting with an ethmoidal lesion in 2002. The initial tumor specimen of this patient showed a deletion of the short arm of chromosome 1 through a translocation between chromosomes 1 and 11 (t[1; 11]) as well as additional chromosomal aberrations, including partial or complete monosomy of chromosomes 2, 6, 7, 11, 13, and 22. These molecular characteristics were already known to be associated with an aggressive course of the disease, and the patient was, therefore, included in a strict follow-up regime. From 2003 to 2019, the patient suffered multiple relapses and consecutive tumor resections.

METHODS

Tumor specimen from 2017 was examined using a genome-wide methylation analysis as well as a whole-genome sequencing.

RESULTS

These analyses confirmed the findings of 2002 and proved genetic alteration in the meningioma to be very stable over the time. Yet SMO and AKT1 mutations, which have been described to be paradigmatic in frontobasal meningioma, could not be found.

CONCLUSIONS

Genetic characteristics seem to be very stable during progression of the disease. The loss of 1p represents to be a potential marker for the poor clinical course of our child meningioma. In 2019, our patient passed away due to the progress of her meningioma disease.

Molecular Biology of Basal and Squamous Cell Carcinomas

The prevalent keratinocyte-derived neoplasms of the skin are basal cell carcinoma and squamous cell carcinoma. Both so-called non-melanoma skin cancers comprise the most common cancers in humans by far. Common risk factors for both tumor entities include sun exposure, DNA repair deficiencies leading to chromosomal instability, or immunosuppression. Yet, fundamental differences in the development of the two different entities have been and are currently unveiled. The constitutive activation of the sonic hedgehog signaling pathway by acquired mutations in the PTCH and SMO genes appears to represent the early basal cell carcinoma developmental determinant. Although other signaling pathways are also affected, small hedgehog inhibitory molecules evolve as the most promising basal cell carcinoma treatment options systemically as well as topically in current clinical trials. For squamous cell carcinoma development, mutations in the p53 gene, especially UV-induced mutations, have been identified as early events. Yet, other signaling pathways including epidermal growth factor receptor, RAS, Fyn, or p16INK4a signaling may play significant roles in squamous cell carcinoma development. The improved understanding of the molecular events leading to different tumor entities by de-differentiation of the same cell type has begun to pave the way for modulating new molecular targets therapeutically with small molecules.

SMO-M2 mutation does not support cell-autonomous Hedgehog activity in cerebellar granule cell precursors

Growth and patterning of the cerebellum is compromised if granule cell precursors do not properly expand and migrate. During embryonic and postnatal cerebellar development, the Hedgehog pathway tightly regulates granule cell progenitors to coordinate appropriate foliation and lobule formation. Indeed, granule cells impairment or defects in the Hedgehog signaling are associated with developmental, neurodegenerative and neoplastic disorders. So far, scant and inefficient cellular models have been available to study granule cell progenitors, in vitro. Here, we validated a new culture method to grow postnatal granule cell progenitors as hedgehog-dependent neurospheres with prolonged self-renewal and ability to differentiate into granule cells, under appropriate conditions. Taking advantage of this cellular model, we provide evidence that Ptch1-KO, but not the SMO-M2 mutation, supports constitutive and cell-autonomous activity of the hedgehog pathway.

Repurposing Drugs for Skin Cancer

Drug repurposing is the process of developing existing or abandoned drugs for a different disease. Repurposing can circumvent higher costs and times associated with conventional drug discovery strategies because toxicity and pharmacokinetics profiles are typically already established. This brief review focuses on efforts to repurpose drugs for skin cancer and includes reuse of antihypertensives, anthelmintics and antifungals among a range of other medicines. Repurposing not only ushers promising known drugs for new indications, the process of repurposing can uncover new mechanistic insights in the pathogenesis of disease and uncover new opportunities for pharmaceutical intervention.

The role of hedgehog signaling in gastric cancer: molecular mechanisms, clinical potential, and perspective

Patients with advanced gastric cancer usually have a poor prognosis and limited therapeutic options. Overcoming this challenge requires novel targets and effective drugs. The Hedgehog (Hh) signaling pathway plays a crucial role in the development of the gastrointestinal tract and maintenance of the physiologic function of the stomach. Aberrantly activated Hh signaling is implicated in carcinogenesis as well as maintenance of cancer stem cells. Somatic mutations in the components of Hh signaling (PTCH1 and SMO) have been shown to be a major cause of basal cell carcinoma, and dozens of Hh inhibitors have been developed. To date, two inhibitors (GDC-0449 and LDE225) have been approved by the U.S. Food and Drug Administration to treat basal cell carcinoma and medulloblastoma. Here, we review the role of the Hh signaling in the carcinogenesis and progression of gastric cancer and summarize recent findings on Hh inhibitors in gastric cancer. Hedgehog signaling is often aberrantly activated and plays an important role during inflammation and carcinogenesis of gastric epithelial cells. Further study of the precise mechanisms of Hh signaling in this disease is needed for the validation of therapeutic targets and evaluation of the clinical utility of Hh inhibitors for gastric cancer.

Expression profile of sonic hedgehog signaling-related molecules in basal cell carcinoma

Basal cell carcinoma (BCC) is the most common human cancer, characterized by aberrant activation of the hedgehog (HH) signaling pathway resulting from mutations in the patched 1 (PTCH1) or smoothened (SMO) genes. In the present study, to uncover the expression profile of HH signaling-related molecules, we thoroughly examined the mRNA and protein expression levels of six molecules including GLI1, GLI2, PTCH1, PTCH2, SHH, and SMO in BCC and various other cutaneous tumors. Real-time PCR analysis demonstrated that BCC showed remarkably enhanced mRNA expression of all HH molecules, except SMO compared to other skin tumors. However, immunohistochemical analysis revealed that only GLI1 protein was specifically upregulated in BCC, while the other HH-related proteins did not show any significant differences between the tumors. Notably, other skin malignancies such as squamous cell carcinoma, sebaceous carcinoma, and malignant melanoma showed no GLI1 expression and there was no difference in GLI1 expression between the BCC subtypes. In addition, GLI1 and GLI2 expression were strongly associated with the hair follicle stem cell markers, LGR4 and LGR5, which are known target genes of the Wnt pathway. Our results suggest that GLI1 has the potential to be a diagnostically useful marker for differentiating BCC from other skin malignancies and an interaction between the HH and Wnt signaling pathways may be involved in the development of BCCs.

Discovery of the Hedgehog Pathway Inhibitor Pipinib that Targets PI4KIIIß

The Hedgehog (Hh) signaling pathway is crucial for vertebrate embryonic development, tissue homeostasis and regeneration. Hh signaling is upregulated in basal cell carcinoma and medulloblastoma and Hh pathway inhibitors targeting the Smoothened (SMO) protein are in clinical use. However, the signaling cascade is incompletely understood and novel druggable proteins in the pathway are in high demand. We describe the discovery of the Hh-pathway modulator Pipinib by means of cell-based screening. Target identification and validation revealed that Pipinib selectively inhibits phosphatidylinositol 4-kinase IIIβ (PI4KB) and suppresses GLI-mediated transcription and Hh target gene expression by impairing SMO translocation to the cilium. Therefore, inhibition of PI4KB and, consequently, reduction in phosphatidyl-4-phosphate levels may be considered an alternative approach to inhibit SMO function and thus, Hedgehog signaling.

Hedgehog Signal and Genetic Disorders

The hedgehog (Hh) family comprises sonic hedgehog (Shh), Indian hedgehog (Ihh), and desert hedgehog (Dhh), which are versatile signaling molecules involved in a wide spectrum of biological events including cell differentiation, proliferation, and survival; establishment of the vertebrate body plan; and aging. These molecules play critical roles from embryogenesis to adult stages; therefore, alterations such as abnormal expression or mutations of the genes involved and their downstream factors cause a variety of genetic disorders at different stages. The Hh family involves many signaling mediators and functions through complex mechanisms, and achieving a comprehensive understanding of the entire signaling system is challenging. This review discusses the signaling mediators of the Hh pathway and their functions at the cellular and organismal levels. We first focus on the roles of Hh signaling mediators in signal transduction at the cellular level and the networks formed by these factors. Then, we analyze the spatiotemporal pattern of expression of Hh pathway molecules in tissues and organs, and describe the phenotypes of mutant mice. Finally, we discuss the genetic disorders caused by malfunction of Hh signaling-related molecules in humans.

Oxysterols as lipid mediators: Their biosynthetic genes, enzymes and metabolites

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Pathways of oxysterol biosynthesis.

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Pathways of oxysterol metabolism.

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Oxysterols as bioactive molecules.

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Disorders of oxysterol metabolism.

There is growing evidence that oxysterols are more than simple metabolites in the pathway from cholesterol to bile acids. Recent data has shown oxysterols to be ligands to nuclear receptors and to G protein-coupled receptors, modulators of N-methyl-d-aspartate receptors and regulators of cholesterol biosynthesis. In this mini-review we will discuss the biosynthetic mechanisms for the formation of different oxysterols and the implication of disruption of these mechanisms in health and disease.

Follow-Up of Patients With Complete Remission of Locally Advanced Basal Cell Carcinoma After Vismodegib Discontinuation: A Multicenter French Study of 116 Patients

PURPOSE

Vismodegib is a hedgehog pathway inhibitor indicated for the treatment of locally advanced basal cell carcinoma (laBCC), with an objective response rate of 65%, including a 32% complete response (CR). However, adverse effects often lead to drug discontinuation. The objective of our study was to evaluate long-term responses, predictive factors, and management of relapse after vismodegib discontinuation.

METHODS

An observational retrospective study was conducted in nine French oncodermatology units. We included patients with laBCC with CR on vismodegib who discontinued treatment between March 2012 and January 2016; we reviewed charts up to June 2016. The primary objective was to evaluate median relapse-free survival (RFS). Secondary objectives were risk factors associated with RFS, relapse, and death and treatment modalities after relapse and their efficacy.

RESULTS

One hundred sixteen patients with laBCC were included. The median RFS was 18.4 months (95% CI, 13.5 to 24.8 months). The RFS rate at 36 months was 35.4% (95% CI, 22.5% to 47.9%) for the total population and 40.0% (95% CI, 25.7% to 53.7%) for patients without Gorlin syndrome. LaBCC to the limbs and trunk was the only variable independently associated with a higher risk of relapse (hazard ratio, 2.77; 95% CI, 1.23 to 6.22; P = .019). Twenty-seven patients (50%) who experienced relapse during follow-up were retreated with vismodegib, with an objective response in 23 (objective response rate, 85%; CR rate, 37%; partial response rate, 48%) and eligibility for surgery in 24 (42%).

CONCLUSION

Long-term response after vismodegib discontinuation is frequent. Most patients who experience a relapse still respond to vismodegib rechallenge.

Hedgehog Signaling: An Achilles' Heel in Cancer

Hedgehog signaling pathway originally identified in the fruit fly Drosophila is an evolutionarily conserved signaling mechanism with crucial roles in embryogenesis, growth and patterning. It exerts its biological effect through a signaling mechanism that terminates at glioma-associated oncogene (GLI) transcription factors which alternate between activator and repressor forms and mediate various responses. The important components of the pathway include the hedgehog ligands (SHH), the Patched (PTCH) receptor, Smoothened (SMO), Suppressor of Fused (SuFu) and GLI transcription factors. Activating or inactivating mutations in key genes cause uncontrolled activation of the pathway in a ligand independent manner. The ligand-dependent aberrant activation of the hedgehog pathway causing overexpression of hedgehog pathway components and its target genes occurs in autocrine as well as paracrine fashion. In adults, aberrant activation of hedgehog signaling has been linked to birth defects and multiple solid cancers. In this review, we assimilate data from recent studies to understand the mechanism of functioning of the hedgehog signaling pathway, role in cancer, its association in various solid malignancies and the current strategies being used to target this pathway for cancer treatment.

The Landmark Series: Non-melanoma Skin Cancers

Surgery with or without radiation has always been the mainstay of treatment for patients with non-melanoma skin cancers, including basal cell carcinoma, squamous cell carcinoma, and Merkel cell carcinoma. Until recently, there were no effective systemic therapies for patients with advanced disease. This review will focus on the landmark clinical trials that led to Food and Drug Administration (FDA) approval of Vismodegib for advanced basal cell carcinoma (ERIVANCE BCC) and pembrolizumab for advanced Merkel cell carcinoma (KEYNOTE-017). These trials have not only changed the landscape for patients with metastatic disease but also notably for patients with locally advanced disease that is either unresectable or resectable with high morbidity. Additional mention is made for the clinical trial that led to FDA approval of cemiplimab for advanced cutaneous squamous cell carcinoma (EMPOWER-CSCC-1), which is already changing practice patterns, but for which longer-term data are still needed.

Patched1 haploinsufficiency severely impacts intermediary metabolism in the skin of Ptch1+/-/ODC transgenic mice

The study of dominantly heritable cancers has provided insights about tumor development. Gorlin syndrome (GS) is an autosomal dominant disorder wherein affected individuals develop multiple basal cell carcinomas (BCCs) of the skin. We developed a murine model of Ptch1 haploinsufficiency on an ornithine decarboxylase (ODC) transgenic background (Ptch1^+/−/ODC^t/C57BL/6) that is more sensitive to BCCs growth as compared with Ptch1^+/+/ODC^t/C57BL/6 littermates. Ptch1^+/−/ODC^t/C57BL/6 mice show an altered metabolic landscape in the phenotypically normal skin, including restricted glucose availability, restricted ribose/deoxyribose flow and NADPH production, an accumulation of α-ketoglutarate, aconitate, and citrate that is associated with reversal of the tricarboxylic acid cycle, coupled with increased ketogenic/lipogenic activity via acetyl-CoA, 3-hydroybutyrate, and cholesterol metabolites. Also apparent was an increased content/acetylation of amino-acids, glutamine and glutamate, in particular. Accordingly, metabolic alterations due to a single copy loss of Ptch1 in Ptch1^+/−/ODC^t/C57BL/6 heterozygous mice may provide insights about the cancer prone phenotype of BCCs in GS patients, including biomarkers/targets for early intervention.

Evaluation of Patched-1 Protein Expression Level in Low Risk and High Risk Basal Cell Carcinoma Subtypes

Objective:

Basal cell carcinoma (BCC) is the most common malignancy in humans and represents a growing public health care problem. The major etiological factors contributing to BCC development are exposure to ultraviolet radiation and genetic alterations. BCC is primarily caused by dysregulation of sonic Hedgehog (HH) signaling pathway in basal cells of the skin. BCC can be classified into low risk non-aggressive and high risk aggressive subtypes. BCC subtypes differentiation is essential for prognosis and for better disease management and treatment strategies. The aim of this study was to assess the correlation between PTCH1 protein expression level and the aggressiveness of BCC histopathology.

Methods:

Archival paraffin embedded blocks containing BCC were retrieved from a cohort of 101 patients. Immunohistochemistry staining was performed to assess the expression level of PTCH1 which is a key component of Hedgehog pathway.

Results:

101 paraffin embedded samples were evaluated and classified as high risk and low risk BCC subtypes by histopathological finding. High risk BCC subtypes were found in 40 samples (39.6%) and low risk subtypes were identified in 61 samples (60.4%). Nodular was the most frequent subtype which was found in (56/ 101), followed by infiltrative (22/101) and micronodular (14/ 101) subtypes. Positive PTCH1 expression was found highest in nodular subtypes (46.5%).

Conclusion:

In this study, the correlation between low risk or high risk BCC subtypes and PTCH1 expression level was not statistically significant (p>0.05), but the frequency of positive PTCH1 expression was found to be higher in low risk subtypes than high risk BCC subtypes.

Cell-Autonomous Hedgehog Signaling Is Not Required for Cyst Formation in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

PKD1 or PKD2, the two main causal genes for autosomal dominant polycystic kidney disease (ADPKD), encode the multipass transmembrane proteins polycystin-1 (PC1) and polycystin-2 (PC2), respectively. Polycystins localize to the primary cilium, an organelle essential for cell signaling, including signal transduction of the Hedgehog pathway. Mutations in ciliary genes that build and maintain the cilium also cause renal cystic disease through unknown pathways. Although recent studies have found alterations in Hedgehog signaling in ADPKD-related models and tissues, the relationship between Hedgehog and polycystic kidney disease is not known.

METHODS

To examine the potential role of cell-autonomous Hedgehog signaling in regulating kidney cyst formation in vivo in both early- and adult-onset mouse models of ADPKD, we used conditional inactivation of Pkd1 combined with conditional modulation of Hedgehog signaling components in renal epithelial cells, where mutations in Pkd1 initiate cyst formation. After increasing or decreasing levels of Hedgehog signaling in cells that underwent inactivation of Pkd1, we evaluated the effects of these genetic manipulations on quantitative parameters of polycystic kidney disease severity.

RESULTS

We found that in Pkd1 conditional mutant mouse kidneys, neither downregulation nor activation of the Hedgehog pathway in epithelial cells along the nephron significantly influenced the severity of the polycystic kidney phenotype in mouse models of developmental or adult-onset of ADPKD.

CONCLUSIONS

These data suggest that loss of Pkd1 function results in kidney cysts through pathways that are not affected by the activity of the Hedgehog pathway.

Wnt, Notch, and TGF-β Pathways Impinge on Hedgehog Signaling Complexity: An Open Window on Cancer

Constitutive activation of the Hedgehog (Hh) signaling pathway is associated with increased risk of developing several malignancies. The biological and pathogenic importance of Hh signaling emphasizes the need to control its action tightly, both physiologically and therapeutically. Evidence of crosstalk between Hh and other signaling pathways is reported in many tumor types. Here, we provide an overview of the current knowledge about the communication between Hh and major signaling pathways, such as Notch, Wnt, and transforming growth factor β (TGF-β), which play critical roles in both embryonic and adult life. When these pathways are unbalanced, impaired crosstalk contributes to disease development. It is reported that more than one of these pathways are active in different type of tumors, at the same time. Therefore, starting from a plethora of stimuli that activate multiple signaling pathways, we describe the signals that preferentially converge on the Hh signaling cascade that influence its activity. Moreover, we highlight several connection points between Hh and Notch, Wnt, or TGF-β pathways, showing a reciprocal synergism that contributes to tumorigenesis, supporting a more malignant behavior by tumor cells, such as in leukemia and brain tumors. Understanding the importance of these molecular interlinking networks will provide a rational basis for combined anticancer drug development.

Updates on the Systemic Treatment of Advanced Non-melanoma Skin Cancer

Non-melanoma skin cancers (NMSCs), which represent a diverse group of cutaneous malignancies, are the most common forms of human neoplasia. The incidence of these diseases is increasing due to a number of factors, including that of increasing human lifespans. The majority of NMSCs are basal cell carcinomas (BCC) and cutaneous squamous cell carcinomas (cSCC), with the remainder being various rare skin cancers, including extramammary Paget's disease (EMPD), Merkel cell carcinoma (MCC), and several skin adnexal carcinomas. Of these, MCC usually shows aggressive behavior with a high mortality rate. On the other hand, BCC, cSCC, EMPD, and skin adnexal tumors usually show an indolent clinical course and metastasize only rarely. Nevertheless, the metastatic forms of these tumors commonly lead to poor patient outcome. A definitive management strategy for the treatment of advanced NMSC has not been established, mainly due to their rarity and lack of reliable information based on well-controlled randomized trials. Chemotherapeutic regimens for treatment of these diseases have been mainly based on the observations of isolated, small case series or clinical trials with a limited numbers of patients. However, accumulating evidence regarding their pathobiological backgrounds as well as recent advances in molecular biotechnology have facilitated the development of novel drugs for treatment of these diseases. Over the past decade, the U.S. Food and Drug Administration has approved several molecular targeting therapies, including Hedgehog inhibitors for BCC, monoclonal antibodies targeting anti-programmed death ligand-1 and anti- programmed cell death 1 (PD-1) for MCC, and anti-PD-1 for cSCC. Here, we review their clinical utility and discuss updated systemic treatment strategies for advanced NMSC.

Phosphorylation of Ci/Gli by Fused Family Kinases Promotes Hedgehog Signaling

Hedgehog (Hh) signaling culminates in the conversion of the latent transcription factor Cubitus interruptus (Ci)/Gli into its activator form (Ci^A/Gli^A), but the underlying mechanism remains poorly understood. Here, we demonstrate that Hh stimulates the phosphorylation of Ci by the Ser/Thr kinase Fused (Fu) and that Fu-mediated phosphorylation of Ci promotes its activation. We find that Fu directly phosphorylates Ci on Ser218 and Ser1230, which primes its further phosphorylation by CK1 on adjacent sties. These phosphorylation events alter Ci binding to the pathway inhibitor Suppressor of fused (Sufu) and facilitate the recruitment of Transportion and the transcriptional coactivator CBP. Furthermore, we provide evidence that Sonic hedgehog (Shh) activates Gli2 by stimulating its phosphorylation on conserved sites through the Fu-family kinases ULK3 and mFu/STK36 in a manner depending on Gli2 ciliary localization. Hence, Fu-family kinase-mediated phosphorylation of Ci/Gli serves as a conserved mechanism that activates the Hh pathway transcription factor.

PTCH1 Mutation in a Patient With Metastatic Undifferentiated Carcinoma With Clear Cell Change

Clear cell basal cell carcinoma (BCC) is an unusual variant of BCC. Its pathogenesis, prognosis, and optimal management remain poorly described due to its rarity. This report presents a 51-year-old man with a history of excised BCC and cutaneous squamous cell carcinomas of the face, with multiple recurrent poorly differentiated carcinomas with clear cell changes of the shoulder for which further classification using conventional histologic means was not possible. His tumor tissue was sent to Foundation Medicine for testing, which revealed a high number of pathogenic genomic alterations, including a mutation inPTCH1. He was diagnosed with dedifferentiated BCC and started on vismodegib. He developed lung metastases while receiving vismodegib, and his disease continued to progress while he was undergoing treatment in a phase I clinical trial. Given the high number of pathogenic alterations suggestive of high tumor mutational burden, immunotherapy was considered and off-label authorization was obtained for treatment with a PD-1 antibody (pembrolizumab). He had a dramatic disease response after 4 infusions of pembrolizumab. Molecular testing was instrumental in determining the correct diagnosis and formulating appropriate treatment options for this patient. Molecular profiling of metastatic BCCs and its subtypes is essential to the development of effective targeted therapies and combination approaches.

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.

Activation of hedgehog signaling associates with early disease progression in chronic lymphocytic leukemia

Targeted sequencing of 103 leukemia-associated genes in leukemia cells from 841 treatment-naive patients with chronic lymphocytic leukemia (CLL) identified 89 (11%) patients as having CLL cells with mutations in genes encoding proteins that putatively are involved in hedgehog (Hh) signaling. Consistent with this finding, there was a significant association between the presence of these mutations and the expression of GLI1 (χ2 test, P < .0001), reflecting activation of the Hh pathway. However, we discovered that 38% of cases without identified mutations also were GLI1+ Patients with GLI1+ CLL cells had a shorter median treatment-free survival than patients with CLL cells lacking expression of GLI1 independent of IGHV mutation status. We found that GANT61, a small molecule that can inhibit GLI1, was highly cytotoxic for GLI1+ CLL cells relative to that of CLL cells without GLI1. Collectively, this study shows that a large proportion of patients have CLL cells with activated Hh signaling, which is associated with early disease progression and enhanced sensitivity to inhibition of GLI1.

Deciphering the Allosteric Effect of Antagonist Vismodegib on Smoothened Receptor Deactivation Using Metadynamics Simulation

The smoothened receptor (Smo) plays a key role in Hedgehog (Hh) signaling pathway and it has been regarded as an efficacious therapeutic target for basal cell carcinoma (BCC) and medulloblastoma (MB). Nevertheless, the resistance mutation and active mutants of Smo have put forward the requirement of finding more effective inhibitors. Herein, we performed metadynamics simulations on Smo bound with vismodegib (Smo-Vismod) and with cholesterol (Smo-CLR), respectively, to explore the inhibition mechanism of vismodegib. The simulation results indicated that vismodegib-induced shifts of TM5, TM6, and TM7, which permitted the extracellular extension of TM6 and extracellular loop3 (ECL3) to enter the extracellular cysteine-rich domain (CRD) groove. Therefore, an open CRD groove that has not been noticed previously was observed in Smo-Vismod complex. As a consequence, the occupied CRD groove prevents the binding of cholesterol. In addition, the HD and ECLs play crucial roles in the interaction of CRD and TMD. These results reveal that TM5, TM6, and TM7 play important roles in allosteric inhibition the activation of Smo and disrupting cholesterol binding by vismodegib binding. Our results are expected to contribute to understanding the allosteric inhibition mechanism of Smo by vismodegib. Moreover, the detailed conformational changes contribute to the development of novel Smo inhibitors against resistance mutation and active mutants of Smo.

New molecular targets in meningiomas: the present and the future

PURPOSE OF REVIEW

Meningiomas, the most common primary brain tumor, have historically been managed with surgery and radiation. Traditional chemotherapy has not been effective. Fortunately, recent advances in genetic sequencing have led to an improved understanding of the molecular drivers in meningioma. This article aims to discuss the diagnostic and therapeutic implications of recently discovered genetic alterations in meningiomas.

RECENT FINDINGS

Many of the recently discovered genetic alterations correlate with distinct clinical phenotypes. SMO, AKT and PIK3CA mutations are enriched in the anterior skull base. KLF4 mutations are specific for secretory histology, and BAP1 alterations are common in progressive rhabdoid meningiomas. Alterations in TERT, DMD and BAP1 correlate with poor clinical outcomes. Importantly, the discovery of clinically actionable alterations in a number of genes, including SMO, AKT1 and PIK3CA, has opened up novel potential avenues for therapeutic management of meningiomas. Overexpression of PD-L1 in higher grade meningiomas also provides preclinical support for the investigation of checkpoint blockade.

SUMMARY

The discovery of genetic alterations has improved our understanding of the natural history and classification of meningiomas. Clinical trials with several novel agents targeting driver mutations are currently accruing patients and they can lead to better treatment strategies.