Activation of the transcription factor Gli1 and the Sonic hedgehog signalling pathway in skin tumours

The role of sonic hedgehog signaling in the oropharyngeal epithelium during jaw development

Sonic hedgehog (Shh) is expressed in the oropharyngeal epithelium, including the frontonasal ectodermal zone (FEZ), which is defined as the boundary between Shh and Fgf8 expression domains in the frontonasal epithelium. To investigate the role of SHH signaling from the oropharyngeal epithelium, we generated mice in which Shh expression is specifically deleted in the oropharyngeal epithelium (Isl1-Cre; Shhf/f). In the mutant mouse, Shh expression was excised in the oropharyngeal epithelium as well as FEZ and ventral forebrain, consistent with the expression pattern of Isl1. Isl1-Cre; Shhf/f mice exhibited a complete loss of lower jaw components and a malformed upper jaw with defects in the cranial base and secondary palate. Massive cell death was observed in the mandibular process at embryonic day (E) 9.5 and E10.5, while mild cell death was observed in the lambdoidal region (the fusion area in the maxillary, lateral nasal, and medial nasal processes) at E10.5. An RNA-seq analysis revealed that Satb2, a gene involved in cell survival during jaw formation, was downregulated in the lambdoidal region in Isl1-Cre; Shhf/f mice. These results suggest that Shh expression in the FEZ is required for cell survival and skeletogenesis in the lambdoidal region during the development of the upper jaw and that the developmental control governed by SHH signaling is different between upper and lower jaws.

Retinoic Acid Regulates Spermiogenesis Via Hoxb1 and Shh Signaling in Testicular Germ Cells

Retinoic acid (RA) regulates all four major events in spermatogenesis; spermatogonial differentiation, meiotic entry, spermiogenesis, and spermiation. For the pre-meiotic phase, Sertoli cells are the source of RA and for the post-meiotic phase, pachytene spermatocytes are the source of RA. While the entire spermatogenic process is regulated by RA, how each of these phases is regulated by RA remains completely unknown. Homeobox B1 (Hoxb1) has two retinoic acid response elements (RARE) upstream and downstream of the gene. In this study, we investigated if RA facilitates spermatogenesis by its action on Hoxb1. The expressions of the Hoxb1 and Sonic hedgehog (Shh) genes were analyzed in the post-natal mouse testes and the testicular localizations of Hoxb1, Shh and Gli1 were analyzed by immunohistochemistry in the adult rat testis. To delineate the signaling mechanisms, Hoxb1 expression was altered in vitro and in vivo using retinoic acid and miR-361-3p. Finally, the levels of miR-361-3p and HOXB1 were analyzed in infertile human sperm samples. Hoxb1 and Shh gene expressions were found to be low in the testis of post-natal Swiss mice of 7, 14, 28, 35, and 60 days, after which the expressions of both spiked. Immunohistochemistry in the adult mouse testis showed the expressions of Hoxb1, Shh, and Gli1 in the elongating spermatids. Exposure of GC2 cells to RA and in vivo IP RA injection upregulated Hoxb1 and Shh signaling in the testis with increased expressions of Shh, Gli1, and Hdac1. Retinoic acid administration in Swiss mice compromised sperm production and reduced epididymal sperm count. The analysis of infertile human semen samples revealed an increased level of HOXB1 and a decreased level of miR-361-3p as compared to fertile controls. We conclude that retinoic acid regulates late stage of spermatogenesis (spermiogenesis) by affecting Hoxb1 and Shh signaling.

Skin Cancer Precursors: From Cancer Genomics to Early Diagnosis

Skin cancers, including melanoma and keratinocyte carcinomas, are responsible for increasing health care burden internationally. Risk stratification and early detection are paramount for prevention and less risky treatment to overall improve patient outcomes and disease morbidity. Here, the authors discuss the key concepts leading to skin cancer initiation and progression. The authors also outline precursor and progression models for melanoma and keratinocyte carcinomas, including discussion of genetic alterations associated with the various stages of progression. Finally, the authors discuss the significance of immunoediting and the drivers behind increased risk of cutaneous malignancy in the state of immune dysregulation.

GLI Transcriptional Targets S100A7 and KRT16 Show Upregulated Expression Patterns in Epidermis Overlying the Tumor Mass in Melanoma Samples

Although not completely understood, the role of the Hedgehog-GLI (HH-GLI) signaling pathway in melanoma and epithelial skin tumors has been reported before. In this study, we confirmed in various melanoma cell line models that keratin 16 (KRT16) and S100 Calcium-Binding Protein A7 (S100A7) are transcriptional targets of GLI Family Zinc Finger (GLI) proteins. Besides their important role in protecting and maintaining the epidermal barrier, keratins are somehow tightly connected with the S100 family of proteins. We found that stronger expression of KRT16 indeed corresponds to stronger expression of S100A7 in our clinical melanoma samples. We also report a trend regarding staining of GLI1, which corresponds to stronger staining of GLI3, KRT16, and S100A7 proteins. The most interesting of our findings is that all the proteins are detected specifically in the epidermis overlying the tumor, but rarely in the tumor itself. The examined proteins were also not detected in the healthy epidermis at the edges of the sample, suggesting that the staining is specific to the epidermis overlaying the tumor mass. Of all proteins, only S100A7 demonstrated a statistically significant trend regarding tumor staging and staining intensity. Results from our clinical samples prove that immune infiltration is an important feature of melanoma. Pigmentophages and tumor-infiltrating lymphocytes (TIL) demonstrate a significant association with tumor stage, while mononuclear cells are equally present in all stages. For S100A7, we found an association between the number of TILs and staining intensity. Considering these new findings presented in our study, we suggest a more detailed examination of the possible role of the S100A7 protein as a biomarker in melanoma.

An Insight into the Role of GLIS1 in Embryonic Development, iPSC Generation, and Cancer

The curiosity to discover transcription factors to reprogram somatic cells to induced pluripotent stem cells (iPSCs) resulted in the identification of a reprogramming factor, Gli-similar transcription factor GLIS1. This proline-rich Kruppel-like zinc finger transcription factor has a role in embryonic development, iPSC generation, and cancer. The spatial and temporal expression of GLIS1 during embryonic development implicates that it can control gene expression at specific developmental stages. Moreover, GLIS1 in combination with OCT4, SOX2, and KLF4 reprogramming factors resulted in an increase in reprogramming efficiency, giving rise to primarily bona fide iPSCs. Mutations in the GLIS1 gene are associated with several types of tumors and cancers, and it shows a tissue-specific function where it acts either as an oncogene or as a tumor suppressor gene. This review gives a comprehensive overview of GLIS1 and its important role in embryonic development, cancer, and the generation of iPSCs.

A clinicopathological exploration of Hedgehog signaling: implications in oral carcinogenesis

INTRODUCTION

Hedgehog Signaling, a basic cancer stem cell pathway, plays a major role during the embryonic development, is known to play a quiescent role in adults. However, aberrant activation of Hedgehog signaling in adults is known to play a role in cancer development. Hence, the aim of the study was to identify the role of Hedgehog signaling pathway in the Oral cancers.

MATERIALS AND METHODS

The expression of Hedgehog signaling pathway was evaluated in 124 patients through the quantitative real-time PCR. The association between the gene expression and clinico-pathological parameters were analyzed using the Pearson chi-square test and survival analysis was carried out using Kaplan-Meier analysis.

RESULTS

SHH and GLI1 was found to be significantly associated with the Lymph Node Status and SUFU was significantly associated with the Age. SMO and SUFU were found to have a worse prognosis in oral cancer patients. According to our findings, IHH plays a critical role in the activation of the HH signaling pathway in oral cancer.

CONCLUSION

These findings back up the use of the Hedgehog signaling pathway as a biomarker for early disease prediction in oral cancer, as well as its role in tumor aggressiveness and invasiveness.

Targeting the Hedgehog pathway with novel Gli1 hydrophobic tagging degraders

The Hedgehog/Glioma-associated oncogene (Hh/Gli) signaling pathway plays an essential role in embryonic development and tissue homeostasis. Aberrant regulation of this pathway has been linked to various human malignancies. Gli1, the downstream transcription factor of the Hh pathway, is the ultimate effector of the canonical Hh pathway and has been identified as a common regulator of several tumorigenic pathways prevalent in Hh-independent cancers. Thus Gli1 represents a unique and promising drug target for a wide range of cancers. However, the identification and development of small molecules that directly target Gli1 protein have progressed slowly, due to an insufficient efficacy and selectivity. Herein, we developed novel small-molecule Gli1 degraders based on the hydrophobic tagging (HyT) strategy. The Gli1 HyT degrader 8e potently inhibited the proliferation of Gli1-overexpressed HT29 colorectal cancer cells, induced Gli1 degradation with a DC50 value of 5.4 μM in HT29 and achieved 70% degradation at 7.5 μM in MEFPTCH1-/- and MEFSUFU-/-cell lines, via proteasome pathway. Compared to the canonical Hh antagonist Vismodegib, 8e exhibited much stronger potency in suppressing the mRNA expression of Hh target genes in Hh-overactivated MEFPTCH1-/- and Vismodegib resistant MEFSUFU-/- cells. Our study provides small molecule Gli1 degraders effectively interfering with both canonical and noncanonical Hh signaling and overcoming current Smoothened (SMO) antagonists resistance, which might pave a new avenue for developing therapeutic modalities targeting Hh/Gli1 signaling pathway.

Hedgehog-Related Mutation Causes Bone Malformations with or without Hereditary Gene Mutations

The hedgehog (Hh) family consists of numerous signaling mediators that play important roles at various stages of development. Thus, the Hh pathway is essential for bone tissue development and tumorigenesis. Gorlin syndrome is a skeletal and tumorigenic disorder caused by gain-of-function mutations in Hh signaling. In this review, we first present the phenotype of Gorlin syndrome and the relationship between genotype and phenotype in bone and craniofacial tissues, including the causative gene as well as other Hh-related genes. Next, the importance of new diagnostic methods using next-generation sequencing and multiple gene panels will be discussed. We summarize Hh-related genetic disorders, including cilia disease, and the genetics of Hh-related bone diseases.

The Immune Microenvironment in Basal Cell Carcinoma

The immune system plays a key role in the suppression and progression of basal cell carcinoma (BCC). The primary aetiological factor for BCC development is exposure to ultraviolet radiation (UVR) which, particularly in lighter Fitzpatrick skin types, leads to the accumulation of DNA damage. UVR has roles in the generation of an immunosuppressive environment, facilitating cancer progression. Rates of BCC are elevated in immunosuppressed patients, and BCC may undergo spontaneous immune-mediated regression. Histologic and immunohistochemical profiling of BCCs consistently demonstrates the presence of an immune infiltrate and associated immune proteins. Early studies of immune checkpoint inhibitors reveal promising results in BCC. Therefore, the host immune system and tumor responses to it are important in BCC pathogenesis. Understanding these interactions will be beneficial for disease prognostication and therapeutic decisions.

Pharmacokinetics and pharmacodynamics of Hedgehog pathway inhibitors used in the treatment of advanced or treatment-refractory basal cell carcinoma

INTRODUCTION

Sonidegib and vismodegib are currently the only US Food and Drug Administration and European Medicines Agency-approved small-molecule Hedgehog pathway inhibitors (HHIs)for treating adults with advanced or refractory basal cell carcinoma (BCC) that is not amenable to conventional surgery or radiotherapy. At this time, there are no head-to-head clinical trials comparing these two HHIs for efficacy and safety to assist clinicians with determining which HHI may be best suited for their patients.

AREAS COVERED

This review briefly describes the pathogenesis of BCC, provides a detailed overview of the key pharmacokinetic profile differences between sonidegib and vismodegib, explains their pharmacodynamics, and highlights the therapeutic considerations when either HHI is used to treat special patient populations.

EXPERT OPINION

Although both HHIs act at the same molecular target in the Hedgehog pathway, there are significant differences in their pharmacokinetic profiles that may play a potential role in their efficacy and safety. Evidence-based recommendations serve to inform clinicians until direct comparative clinical trials of sonidegib versus vismodegib are conducted to determine the clinical relevance of the reported differences in their pharmacokinetic properties.

Yap controls notochord formation and neural tube patterning by integrating mechanotransduction with FoxA2 and Shh expression

Correct notochord and neural tube (NT) formation is crucial to the development of the central nervous system and midline structures. Integrated biochemical and biophysical signaling controls embryonic growth and patterning; however, the underlying mechanisms remain poorly understood. Here, we took the opportunities of marked morphological changes during notochord and NT formation and identified both necessary and sufficient roles of Yap, a key mechanosensor and mechanotransducer, in biochemical signaling activation during formation of notochord and floor plate, the ventral signaling centers that pattern the dorsal-ventral axis of NT and the surrounding tissues. We showed that Yap activation by a gradient of mechanical stress and tissue stiffness in the notochord and ventral NT induces FoxA2 and Shh expression. Hedgehog signaling activation rescued NT patterning defects caused by Yap deficiency, but not notochord formation. Therefore, mechanotransduction via Yap activation acts in feedforward mechanisms to induce FoxA2 expression for notochord formation and activate Shh expression for floor plate induction by synergistically interacting with FoxA2.

Keratinocytic skin cancers-Update on the molecular biology

Although much attention has been devoted to a detailed genomic exposition of cutaneous melanoma, other nonmelanoma skin cancers have also recently been subjected to similar analytical scrutiny. Chief among these are the most common malignancies worldwide: basal cell carcinomas and cutaneous squamous cell carcinomas. In this review, the authors summarize their latest knowledge about the molecular pathways and therapeutic opportunities attendant to these keratinocytic skin cancers. PLAIN LANGUAGE SUMMARY: The most common cancers in the United States arise from skin cells called keratinocytes. Although these tumors are not formally tracked by the National Cancer Institute, it is estimated that there are millions of skin cancers called basal cell carcinomas and squamous cell carcinomas. This article reviews the current recent genetic insights into these tumors and therapeutic opportunities.

Leveraging Tissue Engineering for Skin Cancer Models

Bioengineered in vitro three-dimensional (3D) skin model has emerged as a promising tool for recapitulating different types of skin cancer and performing pre-clinical tests. However, a full-thickness 3D model including the epidermis, dermis, and hypodermis layers is scarce despite its significance in human physiology and diverse biological processes. In this book chapter, an attempt has been made to summarize various skin cancer models, including utilized skin layers, materials, cell lines, specific treatments, and fabrication techniques for three types of skin cancer: melanoma, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC). Subsequently, current limitations and future directions of skin cancer models are discussed. The knowledge of the current status of skin cancer models can provide various potential applications in cancer research and thus a more effective way for cancer treatment.

ULK3-dependent activation of GLI1 promotes DNMT3A expression upon autophagy induction

Macroautophagy/autophagy is a tightly regulated catabolic process, which contributes at baseline level to cellular homeostasis, and upon its stimulation to the adaptive cellular response to intra- and extracellular stress stimuli. Decrease of autophagy activity is occurring upon aging and thought to contribute to age-related-diseases. Recently, we uncovered, upon autophagy induction, the role of de novo DNMT3A (DNA methyltransferase 3 alpha)-mediated DNA methylation on expression of the MAP1LC3 (microtubule associated protein 1 light chain 3) proteins, core components of the autophagy pathway, which resulted in reduced baseline autophagy activity. Here, we report that serine/threonine kinase ULK3 (unc-51 like kinase 3)-dependent activation of GLI1 (GLI family zinc finger 1) contributes to the transcriptional upregulation of DNMT3A gene expression upon autophagy induction, thereby bringing additional understanding of the long-term effect of autophagy induction and a possible mechanism for its decline upon aging, pathological conditions, or in response to treatment interventions.Abbreviations: CBZ: carbamazepine; ChIP: chromatin immunoprecipitation; Clon: clonidine; DNMT3A: DNA methyltransferase 3 alpha; GLI1: GLI family zinc finger 1; GLI2: GLI family zinc finger 2; MAP1LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PLA: proximity ligation assay; RT-qPCR: quantitative reverse transcription PCR; shRNA: small hairpin RNA; siRNA: small interfering RNA; Treh: trehalose; ULK3: unc-51 like kinase 3.

Cancer Metastasis and Treatment Resistance: Mechanistic Insights and Therapeutic Targeting of Cancer Stem Cells and the Tumor Microenvironment

Cancer metastasis and treatment resistance are the main causes of treatment failure and cancer-related deaths. Their underlying mechanisms remain to be fully elucidated and have been attributed to the presence of cancer stem cells (CSCs)-a small population of highly tumorigenic cancer cells with pluripotency and self-renewal properties, at the apex of a cellular hierarchy. CSCs drive metastasis and treatment resistance and are sustained by a dynamic tumor microenvironment (TME). Numerous pathways mediate communication between CSCs and/or the surrounding TME. These include a paracrine renin-angiotensin system and its convergent signaling pathways, the immune system, and other signaling pathways including the Notch, Wnt/β-catenin, and Sonic Hedgehog pathways. Appreciation of the mechanisms underlying metastasis and treatment resistance, and the pathways that regulate CSCs and the TME, is essential for developing a durable treatment for cancer. Pre-clinical and clinical studies exploring single-point modulation of the pathways regulating CSCs and the surrounding TME, have yielded partial and sometimes negative results. This may be explained by the presence of uninhibited alternative signaling pathways. An effective treatment of cancer may require a multi-target strategy with multi-step inhibition of signaling pathways that regulate CSCs and the TME, in lieu of the long-standing pursuit of a 'silver-bullet' single-target approach.

Influence of Long Non-Coding RNA in the Regulation of Cancer Stem Cell Signaling Pathways

Over the past two decades, cancer stem cells (CSCs) have emerged as an immensely studied and experimental topic, however a wide range of questions concerning the topic still remain unanswered; in particular, the mechanisms underlying the regulation of tumor stem cells and their characteristics. Understanding the cancer stem-cell signaling pathways may pave the way towards a better comprehension of these mechanisms. Signaling pathways such as WNT, STAT, Hedgehog, NOTCH, PI3K/AKT/mTOR, TGF-β, and NF-κB are responsible not only for modulating various features of CSCs but also their microenvironments. Recently, the prominent roles of various non-coding RNAs such as small non-coding RNAs (sncRNAs) and long non-coding RNAs (lncRNAs) in developing and enhancing the tumor phenotypes have been unfolded. This review attempts to shed light on understanding the influence of long non- coding RNAs in the modulation of various CSC-signaling pathways and its impact on the CSCs and tumor properties; highlighting the protagonistic and antagonistic roles of lncRNAs.

Homeostases of epidermis and hair follicle, and development of basal cell carcinoma

Hedgehog signaling (Hh) plays a critical role in embryogenesis. On the other hand, its overactivity may cause basal cell carcinoma (BCC), the most common human cancer. Further, epidermal and hair follicle homeostases may have a key role in the development of BCC. This article describes the importance of different signaling pathways in the different stages of the two processes. The description of the homeostases brought up the importance of the Notch signaling along with the sonic hedgehog (Shh) and the Wnt pathways. Loss of the Notch signaling adversely affects the late stages of hair follicle formation and allows the bulge cells in the hair follicles to take the fate of the keratinocytes in the interfollicular epidermis. Further, the loss of Notch activity upregulates the Shh and Wnt activities, adversely affecting the homeostases. Notably, the Notch signaling is suppressed in BCC, and the peripheral BCC cells, which have low Notch activity, show drug resistance in comparison to the interior suprabasal BCC cells, which have high Notch activity.

Hedgehog pathway modulation by glypican 3-conjugated heparan sulfate

Glypicans are a family of cell surface heparan sulfate proteoglycans that play critical roles in multiple cell signaling pathways. Glypicans consist of a globular core, an unstructured stalk modified with sulfated glycosaminoglycan chains, and a glycosylphosphatidylinositol anchor. Though these structural features are conserved, their individual contribution to glypican function remains obscure. Here, we investigate how glypican 3 (GPC3), which is mutated in Simpson-Golabi-Behmel tissue overgrowth syndrome, regulates Hedgehog signaling. We find that GPC3 is necessary for the Hedgehog response, surprisingly controlling a downstream signal transduction step. Purified GPC3 ectodomain rescues signaling when artificially recruited to the surface of GPC3-deficient cells but has dominant-negative activity when unattached. Strikingly, the purified stalk, modified with heparan sulfate but not chondroitin sulfate, is necessary and sufficient for activity. Our results demonstrate a novel function for GPC3-associated heparan sulfate and provide a framework for the functional dissection of glycosaminoglycans by in vivo biochemical complementation. This article has an associated First Person interview with the first author of the paper.

MicroRNAs as the critical regulators of tyrosine kinase inhibitors resistance in lung tumor cells

Lung cancer is the second most common and the leading cause of cancer related deaths globally. Tyrosine Kinase Inhibitors (TKIs) are among the common therapeutic strategies in lung cancer patients, however the treatment process fails in a wide range of patients due to TKIs resistance. Given that the use of anti-cancer drugs can always have side effects on normal tissues, predicting the TKI responses can provide an efficient therapeutic strategy. Therefore, it is required to clarify the molecular mechanisms of TKIs resistance in lung cancer patients. MicroRNAs (miRNAs) are involved in regulation of various pathophysiological cellular processes. In the present review, we discussed the miRNAs that have been associated with TKIs responses in lung cancer. MiRNAs mainly exert their role on TKIs response through regulation of Tyrosine Kinase Receptors (TKRs) and down-stream signaling pathways. This review paves the way for introducing a panel of miRNAs for the prediction of TKIs responses in lung cancer patients.

Three Novel Variants of CEP290 and CC2D2DA and a Link Between ZNF77 and SHH Signaling Pathway Are Found in Two Meckel-Gruber Syndrome Fetuses

Meckel-Gruber syndrome (MKS) is a rare lethal autosomal recessive inherited disorder. Missed diagnosis might happen in clinical works due to an unclear genotype–phenotype correlation. We analyzed two families visiting our center; the parents are normal; each of the family aborted a fetus at 12WG. Following ultrasonography and pathological examination, both were diagnosed as MKS. Whole exome sequencing identified a compound heterozygous of two novel variants of CEP290 and a heterozygous of a novel variant of CC2D2A. Frameshift mutations in ZNF77 were also detected. Western blot analyzing whole-brain tissue showed that the expression of ZNF77, CC2D2A, and CEP290 was enhanced. HEK293T transfected with over-expression wildtype/mutated ZNF77 plasmid showed that SHH was increased in wildtype ZNF77 cells, while SHH and CC2D2A were increased in mutated ZNF77 cells. Our research provided two novel pathogenic variants of CEP290 and CC2D2A and suggested that ZNF77 might promote the expression of CC2D2A and regulate the amount of SHH.

Hedgehog Pathway Inhibitors against Tumor Microenvironment

Targeting the hedgehog (HH) pathway to treat aggressive cancers of the brain, breast, pancreas, and prostate has been ongoing for decades. Gli gene amplifications have been long discovered within malignant glioma patients, and since then, inhibitors against HH pathway-associated molecules have successfully reached the clinical stage where several of them have been approved by the FDA. Albeit this success rate implies suitable progress, clinically used HH pathway inhibitors fail to treat patients with metastatic or recurrent disease. This is mainly due to heterogeneous tumor cells that have acquired resistance to the inhibitors along with the obstacle of effectively targeting the tumor microenvironment (TME). Severe side effects such as hyponatremia, diarrhea, fatigue, amenorrhea, nausea, hair loss, abnormal taste, and weight loss have also been reported. Furthermore, HH signaling is known to be involved in the regulation of immune cell maturation, angiogenesis, inflammation, and polarization of macrophages and myeloid-derived suppressor cells. It is critical to determine key mechanisms that can be targeted at different levels of tumor development and progression to address various clinical issues. Hence current research focus encompasses understanding how HH controls TME to develop TME altering and combinatorial targeting strategies. In this review, we aim to discuss the pros and cons of targeting HH signaling molecules, understand the mechanism involved in treatment resistance, reveal the role of the HH pathway in anti-tumor immune response, and explore the development of potential combination treatment of immune checkpoint inhibitors with HH pathway inhibitors to target HH-driven cancers.

The Roles of Non-coding RNA in the Development and Regeneration of Hair Follicles: Current Status and Further Perspectives

Alopecia is a common problem that affects almost every age group and is considered to be an issue for cosmetic or psychiatric reasons. The loss of hair follicles (HFs) and hair caused by alopecia impairs self-esteem, thermoregulation, tactile sensation and protection from ultraviolet light. One strategy to solve this problem is HF regeneration. Many signalling pathways and molecules participate in the morphology and regeneration of HF, such as Wnt/β-catenin, Sonic hedgehog, bone morphogenetic protein and Notch. Non-coding RNAs (ncRNAs), especially microRNAs and long ncRNAs, have significant modulatory roles in HF development and regeneration via regulation of these signalling pathways. This review provides a comprehensive overview of the status and future prospects of ncRNAs in HF regeneration and could prompt novel ncRNA-based therapeutic strategies.

The Role of the Hedgehog Pathway in Cholangiocarcinoma

Simple Summary

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

Abstract

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

PTCH1-GLI1 Fusion-Positive Ovarian Tumor: Report of a Unique Case With Response to Tyrosine Kinase Inhibitor Pazopanib

Recurrent GLI1 gene fusions have been recently described in a subset of soft tissue tumors showing a distinct monotonous epithelioid morphology with a rich capillary network and frequent S100 protein expression. Three different fusion partners-ACTB, MALAT1, and PTCH1-have been reported with the PTCH1-GLI1 fusion from 2 patients only, both with head and neck tumors. Herein, we report for the first time a PTCH1-GLI1 fusion in a primary ovarian tumor from a female patient aged 54 years who presented with a 21-cm right ovarian mass and mesenteric metastasis. The tumor was diagnosed as "favor malignant melanoma" based on histologic examination and extensive immunohistochemistry studies. The patient received 4 cycles of pembrolizumab and 2 cycles of trabectedin but developed multiple metastases. A next-generation sequencing-based assay detected a PTCH1-GLI1 fusion, which led to a revised pathologic diagnosis and a change of the patient's management. The patient was switched to the tyrosine kinase inhibitor (TKI) pazopanib to target the sonic hedgehog pathway. Her disease was stable 49 months post TKI therapy. Our case report is the first to show that a tumor with GLI1 oncogenic activation was sensitive to a TKI. The morphologic and immunohistochemistry similarities of our patient's tumor to other recently described tumors harboring GLI1 fusions suggest that these tumors may all belong to the same entity of GLI1 fusion-positive neoplasms and may be treated similarly.

GANT-61 Induces Autophagy and Apoptosis in Glioblastoma Cells despite their heterogeneity

Glioblastoma (GBM) is the most common adult primary tumor of the CNS characterized by rapid growth and diffuse invasiveness into the brain parenchyma. The GBM resistance to chemotherapeutic drugs may be due to the presence of cancer stem cells (CSCs). The CSCs activate the same molecular pathways as healthy stem cells such as WNT, Sonic hedgehog (SHH), and Notch. Mutations or deregulations of those pathways play a key role in the proliferation and differentiation of their surrounding environment, leading to tumorigenesis. Here we investigated the effect of SHH signaling pathway inhibition in human GBM cells by using GANT-61, considering stem cell phenotype, cell proliferation, and cell death. Our results demonstrated that GANT-61 induces apoptosis and autophagy in GBM cells, by increasing the expression of LC3 II and cleaved caspase 3 and 9. Moreover, we observed that SHH signaling plays a crucial role in CSC phenotype maintenance, being also involved in the epithelial-mesenchymal transition (EMT) phenotype. We also noted that SHH pathway modulation can regulate cell proliferation as revealed through the analysis of Ki-67 and c-MYC expressions. We concluded that SHH signaling pathway inhibition may be a promising therapeutic approach to treat patients suffering from GBM refractory to traditional treatments.

Review of the Molecular Genetics of Basal Cell Carcinoma; Inherited Susceptibility, Somatic Mutations, and Targeted Therapeutics

Simple Summary

Basal cell carcinoma is the most common human cancer worldwide. The molecular basis of BCC involves an interplay of inherited genetic susceptibility and somatic mutations, commonly induced by exposure to UV radiation. In this review, we outline the currently known germline and somatic mutations implicated in the pathogenesis of BCC with particular attention paid toward affected molecular pathways. We also discuss polymorphisms and associated phenotypic traits in addition to active areas of BCC research. We finally provide a brief overview of existing non-surgical treatments and emerging targeted therapeutics for BCC such as Hedgehog pathway inhibitors, immune modulators, and histone deacetylase inhibitors.

Abstract

Basal cell carcinoma (BCC) is a significant public health concern, with more than 3 million cases occurring each year in the United States, and with an increasing incidence. The molecular basis of BCC is complex, involving an interplay of inherited genetic susceptibility, including single nucleotide polymorphisms and genetic syndromes, and sporadic somatic mutations, often induced by carcinogenic exposure to UV radiation. This review outlines the currently known germline and somatic mutations implicated in the pathogenesis of BCC, including the key molecular pathways affected by these mutations, which drive oncogenesis. With advances in next generation sequencing and our understanding of the molecular genetics of BCC, established and emerging targeted therapeutics are offering new avenues for the non-surgical treatment of BCC. These agents, including Hedgehog pathway inhibitors, immune modulators, and histone deacetylase inhibitors, will also be discussed.

miR‑367‑3p downregulates Rab23 expression and inhibits Hedgehog signaling resulting in the inhibition of the proliferation, migration, and invasion of prostate cancer cells

MicroRNAs play an important role in tumor cell proliferation, invasion, and Rab23 is a member of the Ras-related small GTPase family and plays a critical role in the progression of may types of tumors. The present study was designed to investigate the inhibitory effect of microRNA (miR)-367-3p on the proliferation, invasion, and metastasis of prostate cancer cells. qRT-PCR was used to detect the expression of miR-367-3p in prostate cancer and adjacent tissues. Cell proliferation, scratch, and Transwell assays were performed to verify the inhibitory effect of miR-367-3p overexpression or Ras-related protein Rab 23 (Rab23) knockdown on prostate cancer. Double luciferase reporter assay was utilized to verify whether miR-367-3p could target the Rab23 3′-untranslated region (UTR). The expression levels of Rab23, Gli1, and Gli2 in prostate cancer cells transfected with the miR-367-3p mimic were detected via qRT-PCR analysis. miR-367-3p expression in the prostate cancer tissues was downregulated compared with that in the para-cancer control tissues. miR-367-3p expression in DU145 and PC3 cells was also downregulated compared with that in the human prostate epithelial cell line RWPE-1. The overexpression of miR-367-3p or the knockdown of Rab23 inhibited the proliferation, invasion, and metastasis of prostate cancer cells. The results of the luciferase reporter assay confirmed that Rab23 was a target gene that was regulated by miR-367-3p. miR-367-3p specifically bound to the 3′-UTR of Rab23 mRNA. The overexpression of miR-367-3p inhibited Rab23 expression and the Hedgehog pathway. Cell function experiments confirmed that the overexpression of Rab23 reversed the anticancer effect of miR-367-3p. miR-367-3p was able to inhibit the Hedgehog pathway by targeting the expression of the Rab23 gene, thus inhibiting the proliferation, invasion, and metastasis of prostate cancer cells.

Germ Line Mutations in the Thyroid Hormone Receptor Alpha Gene Predispose to Cutaneous Tags and Melanocytic Nevi

Background: Many physiological effects of thyroid hormone (TH) are mediated by its canonical action via nuclear receptors (TH receptor α and β [TRα and TRβ]) to regulate transcription of target genes. Heterozygous dominant negative mutations in human TRα mediate resistance to thyroid hormone alpha (RTHα), characterized by features of hypothyroidism (e.g., skeletal dysplasia, neurodevelopmental retardation, constipation) in specific tissues, but near-normal circulating TH concentrations. Hitherto, 41 RTHα cases have been recorded worldwide. Methods: RTHα cases (n = 10) attending a single center underwent cutaneous assessment, recording skin lesions. Lesions excised from different RTHα patients were analyzed histologically and profiled for cellular markers of proliferation and oncogenic potential. Proliferative characteristics of dermal fibroblasts and inducible pluripotent stem cell (iPSC)-derived keratinocytes from patients and control subjects were analyzed. Results: Multiple skin tags and nevi were recorded in all cases, mainly in the head and neck area with a predilection for flexures. The affected patients had highly deleterious mutations (p.E403X, p.E403K, p.F397fs406X, p.A382PfsX7) involving TRα1 alone or mild/moderate loss-of-function mutations (p.A263V, p.L274P) common to TRα1 and TRα2 isoforms. In four patients, although lesions excised for cosmetic reasons were benign intradermal melanocytic nevi histologically, they significantly overexpressed markers of cell proliferation (K17, cyclin D1) and type 3 deiodinase. In addition, oncogenic markers typical of basal cell carcinoma (Gli-1, Gli-2, Ptch-1, n = 2 cases) and melanoma (c-kit, MAGE, CDK4, n = 1) were markedly upregulated in skin lesions. Cell cycle progression and proliferation of TRα mutation-containing dermal fibroblasts and iPSC-derived keratinocytes from patients were markedly increased. Conclusions: Our observations highlight frequent occurrence of skin tags and benign melanocytic nevi in RTHα, with cutaneous cells from patients being in a hyperproliferative state. Such excess of skin lesions, including nevi expressing oncogenic markers, indicates that dermatologic surveillance of RTHα patients, monitoring lesions for features that are suspicious for neoplastic change, is warranted.

A review of emerging and non-US FDA-approved topical agents for the treatment of basal cell carcinoma

Although surgical therapy continues to be the gold standard for the treatment of basal cell carcinoma given high cure rates and the ability to histologically confirm tumor clearance, there are a number of nonsurgical treatment options that may be considered based on individual tumor characteristics, functional and cosmetic considerations, patient comorbidities and patient preference. Topical 5-fluorouracil 5% cream and imiquimod 5% cream have been US FDA-approved for the treatment of superficial basal cell carcinoma. Additionally, a number of new and emerging topical agents and techniques have been described for the treatment of basal cell carcinoma and will be reviewed herein.

The Impact of Notch Signaling for Carcinogenesis and Progression of Nonmelanoma Skin Cancer: Lessons Learned from Cancer Stem Cells, Tumor Angiogenesis, and Beyond

Since many decades, nonmelanoma skin cancer (NMSCs) is the most common malignancy worldwide. Basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) are the major types of NMSCs, representing approximately 70% and 25% of these neoplasias, respectively. Because of their continuously rising incidence rates, NMSCs represent a constantly increasing global challenge for healthcare, although they are in most cases nonlethal and curable (e.g., by surgery). While at present, carcinogenesis of NMSC is still not fully understood, the relevance of genetic and molecular alterations in several pathways, including evolutionary highly conserved Notch signaling, has now been shown convincingly. The Notch pathway, which was first developed during evolution in metazoans and that was first discovered in fruit flies (Drosophila melanogaster), governs cell fate decisions and many other fundamental processes that are of high relevance not only for embryonic development, but also for initiation, promotion, and progression of cancer. Choosing NMSC as a model, we give in this review a brief overview on the interaction of Notch signaling with important oncogenic and tumor suppressor pathways and on its role for several hallmarks of carcinogenesis and cancer progression, including the regulation of cancer stem cells, tumor angiogenesis, and senescence.

Glioma-Associated Oncogene-1 Expression in Basal Cell Carcinoma and Its Histologic Mimics

ABSTRACT

Basal cell carcinoma (BCC) is the most common skin cancer, and it has numerous histologic mimics with variable prognoses and treatments. Although some immunohistochemical stains can be used for the differential diagnosis of BCC, variability and overlap in results can complicate their interpretation. Immunohistochemical staining for glioma-associated oncogene-1 (Gli-1) was performed on 26 nodular BCCs, 22 infiltrative BCCs, 9 basaloid squamous cell carcinomas, 12 desmoplastic trichoepitheliomas, 19 Merkel cell carcinomas, 11 sebaceous carcinomas, 10 cylindromas, 14 spiradenomas, 12 adenoid cystic carcinomas (AdCC), and 1 solitary trichoepithelioma. Strength of staining was scored as 0, 1+, 2+, or 3+, and distribution of staining was categorized as diffuse, multifocal, or focal. Strong, diffuse Gli-1 expression was seen in all tumors with basal epidermal-type differentiation, including BCC, trichoepithelioma, and basaloid squamous cell carcinoma. All examples of Merkel cell carcinoma were negative for cytoplasmic expression. Seven out of 11 sebaceous carcinomas were negative for Gli-1, and the remaining 4 showed 1+ expression. Cylindroma, spiradenoma, and AdCC, each an adnexal skin tumor, showed the most variable staining, but with cylindroma and spiradenoma demonstrating comparable labeling patterns. Overall, although Gli-1 may not distinguish between basal epidermal-type tumors, it may have a role in separating that group from lesions with adnexal differentiation, particularly sebaceous carcinoma, but also cylindroma, spiradenoma, and AdCC. Any cytoplasmic staining seems to exclude the diagnosis of Merkel cell carcinoma.

Epigenetic regulation in the pathogenesis of non-melanoma skin cancer

Understanding of cancer with the help of ever-expanding cutting edge technological tools and bioinformatics is revolutionizing modern cancer research by broadening the space of discovery window of various genomic and epigenomic processes. Genomics data integrated with multi-omics layering have advanced cancer research. Uncovering such layers of genetic mutations/modifications, epigenetic regulation and their role in the complex pathophysiology of cancer progression could lead to novel therapeutic interventions. Although a plethora of literature is available in public domain defining the role of various tumor driver gene mutations, understanding of epigenetic regulation of cancer is still emerging. This review focuses on epigenetic regulation association with the pathogenesis of non-melanoma skin cancer (NMSC). NMSC has higher prevalence in Caucasian populations compared to other races. Due to lack of proper reporting to cancer registries, the incidence rates for NMSC worldwide cannot be accurately estimated. However, this is the most common neoplasm in humans, and millions of new cases per year are reported in the United States alone. In organ transplant recipients, the incidence of NMSC particularly of squamous cell carcinoma (SCC) is very high and these SCCs frequently become metastatic and lethal. Understanding of solar ultraviolet (UV) light-induced damage and impaired DNA repair process leading to DNA mutations and nuclear instability provide an insight into the pathogenesis of metastatic neoplasm. This review discusses the recent advances in the field of epigenetics of NMSCs. Particularly, the role of DNA methylation, histone hyperacetylation and non-coding RNA such as long-chain noncoding (lnc) RNAs, circular RNAs and miRNA in the disease progression are summarized.

Targeting the GLI family of transcription factors for the development of anti-cancer drugs

INTRODUCTION

GLI1 is a transcription factor that has been identified as a downstream effector for multiple tumorigenic signaling pathways. These include the Hedgehog, RAS-RAF-MEK-ERK, and PI3K-AKT-mTOR pathways, which have all been separately validated as individual anti-cancer drug targets. The identification of GLI1 as a key transcriptional regulator for each of these pathways highlights its promise as a therapeutic target. Small molecule GLI1 inhibitors are potentially efficacious against human malignancies arising from multiple oncogenic mechanisms.

AREAS COVERED

This review provides an overview of the key oncogenic cellular pathways that regulate GLI1 transcriptional activity. It also provides a detailed account of small molecule GLI1 inhibitors that are currently under development as potential anti-cancer chemotherapeutics.

EXPERT OPINION

Interest in developing inhibitors of GLI1-mediated transcription has significantly increased as its role in multiple oncogenic signaling pathways has been elucidated. To date, it has proven difficult to directly target GLI1 with small molecules, and the majority of compounds that inhibit GLI1 activity function through indirect mechanisms. To date, no direct-acting GLI1 inhibitor has entered clinical trials. The identification and development of new scaffolds that can bind and directly inhibit GLI1 are essential to further advance this class of chemotherapeutics.

Hedgehog Signaling and Truncated GLI1 in Cancer

The hedgehog (HH) signaling pathway regulates normal cell growth and differentiation. As a consequence of improper control, aberrant HH signaling results in tumorigenesis and supports aggressive phenotypes of human cancers, such as neoplastic transformation, tumor progression, metastasis, and drug resistance. Canonical activation of HH signaling occurs through binding of HH ligands to the transmembrane receptor Patched 1 (PTCH1), which derepresses the transmembrane G protein-coupled receptor Smoothened (SMO). Consequently, the glioma-associated oncogene homolog 1 (GLI1) zinc-finger transcription factors, the terminal effectors of the HH pathway, are released from suppressor of fused (SUFU)-mediated cytoplasmic sequestration, permitting nuclear translocation and activation of target genes. Aberrant activation of this pathway has been implicated in several cancer types, including medulloblastoma, rhabdomyosarcoma, basal cell carcinoma, glioblastoma, and cancers of lung, colon, stomach, pancreas, ovarian, and breast. Therefore, several components of the HH pathway are under investigation for targeted cancer therapy, particularly GLI1 and SMO. GLI1 transcripts are reported to undergo alternative splicing to produce truncated variants: loss-of-function GLI1ΔN and gain-of-function truncated GLI1 (tGLI1). This review covers the biochemical steps necessary for propagation of the HH activating signal and the involvement of aberrant HH signaling in human cancers, with a highlight on the tumor-specific gain-of-function tGLI1 isoform.

Selective Targeting of the Hedgehog Signaling Pathway by PBM Nanoparticles in Docetaxel-Resistant Prostate Cancer

An abnormality in hedgehog (Hh) signaling has been implicated in the progression of prostate cancer (PCa) to a more aggressive and therapy-resistant disease. Our assessments of human PCa tissues have shown an overexpression of the Hh pathway molecules, glioma-associated oncogene homolog 1 (GLI-1), and sonic hedgehog (SHH). The effect of the natural compound thymoquinone (TQ) in controlling the expression of Hh signaling molecules in PCa was investigated in this study. We generated planetary ball-milled nanoparticles (PBM-NPs) made with a natural polysaccharide, containing TQ, and coated with an RNA aptamer, A10, which binds to prostate-specific membrane antigen (PSMA). We prepared docetaxel-resistant C4-2B-R and LNCaP-R cells with a high expression of Hh, showing the integration of drug resistance and Hh signaling. Compared to free TQ, A10-TQ-PBM-NPs were more effective in controlling the Hh pathway. Our findings reveal an effective treatment strategy to inhibit the Hh signaling pathway, thereby suppressing PCa progression.

Sonidegib: Safety and Efficacy in Treatment of Advanced Basal Cell Carcinoma

Hedgehog inhibitors are promising alternative treatments for patients with advanced basal cell carcinomas. Sonidegib (Odomzo®), an oral smoothened (SMO) antagonist, is indicated for the treatment of adult patients with locally advanced basal cell carcinoma (laBCC) who present recurrence following surgery or radiation therapy, or those who are not candidates for surgery or radiotherapy. Several studies and randomized controlled trials have been conducted to evaluate the efficacy, safety, and tolerability of this new molecule that has demonstrated a good response rate (44%). Grade 1-2 adverse events have also been reported. Further studies of real-world experiences are needed to better understand the correct management of the drug, alternative dosing regimens, and differences with other hedgehog inhibitors. This article provides a complete overview of the pharmacology and pharmacokinetics of sonidegib and a report of the trials and studies conducted. The most frequent adverse events and their correct management are also discussed.

Cooperation of Indian Hedgehog and Vascular Endothelial Growth Factor in Tumor Angiogenesis and Growth in Human Hepatocellular Carcinomas, an Immunohistochemical Study

The Hedgehog pathway was recently shown to be involved in vascular development and neovascularization in human embryogenesis and disease. However, the role of Hedgehog pathway in modulating tumor angiogenesis is still unexplored. In the current study, we investigated the expression of Indian Hedgehog (Ihh) and vascular endothelial cell growth factor (VEGF) in human hepatocellular carcinomas (HCCs) with immunohistochemical staining and compared the immunoreaction data with various clinicopathologic characteristics. Immunoreactivity of Ihh and VEGF proteins was observed in 61.5% (56/91) and 64.5% (59/91) cases of HCC tumor tissues, respectively, which was considerably higher than the adjacent nonmalignant tissues. Ihh protein was observed predominantly in the cytoplasm of the tumor cells with a staining pattern of which was sparse and dot-like, or circular around the cell membrane. VEGF protein was expressed heterogenously in the cytoplasm in tumor cells and was negative in peritumoral areas in all cases. CD34 showed diffuse staining in the tumor parenchyma in most HCC specimens. The association of expression of Ihh and VEGF with tumor size was statistically significant (P<0.05), but there was no significant association with other clinicopathologic parameters. Moreover, there was a significant association of the expressions of Ihh and VEGF proteins in HCC (r=0.6, P<0.0001), and of Ihh and CD34 staining (r=0.261, P=0.012). Our findings suggest that Ihh is involved in the development of HCC. These findings are also consistent with the concept that cooperation of Ihh and VEGF modulate HCC tumor angiogenesis and growth.

Sonidegib: Safety and Efficacy in Treatment of Advanced Basal Cell Carcinoma

Hedgehog inhibitors are promising alternative treatments for patients with advanced basal cell carcinomas. Sonidegib (Odomzo^®), an oral smoothened (SMO) antagonist, is indicated for the treatment of adult patients with locally advanced basal cell carcinoma (laBCC) who present recurrence following surgery or radiation therapy, or those who are not candidates for surgery or radiotherapy. Several studies and randomized controlled trials have been conducted to evaluate the efficacy, safety, and tolerability of this new molecule that has demonstrated a good response rate (44%). Grade 1-2 adverse events have also been reported. Further studies of real-world experiences are needed to better understand the correct management of the drug, alternative dosing regimens, and differences with other hedgehog inhibitors. This article provides a complete overview of the pharmacology and pharmacokinetics of sonidegib and a report of the trials and studies conducted. The most frequent adverse events and their correct management are also discussed.

Establishment of a Gorlin syndrome model from induced neural progenitor cells exhibiting constitutive GLI1 expression and high sensitivity to inhibition by smoothened (SMO)

The hedgehog signaling pathway is a vital factor for embryonic development and stem cell maintenance. Dysregulation of its function results in tumor initiation and progression. The aim of this research was to establish a disease model of hedgehog-related tumorigenesis with Gorlin syndrome-derived induced pluripotent stem cells (GS-iPSCs). Induced neural progenitor cells from GS-iPSCs (GS-NPCs) show constitutive high GLI1 expression and higher sensitivity to smoothened (SMO) inhibition compared with wild-type induced neural progenitor cells (WT-NPCs). The differentiation process from iPSCs to NPCs may have similarity in gene expression to Hedgehog signal-related carcinogenesis. Therefore, GS-NPCs may be useful for screening compounds to find effective drugs to control Hedgehog signaling activity.

Blocking SHH/Patched Interaction Triggers Tumor Growth Inhibition through Patched-Induced Apoptosis

The Sonic Hedgehog (SHH) pathway plays a key role in cancer. Alterations of SHH canonical signaling, causally linked to tumor progression, have become rational targets for cancer therapy. However, Smoothened (SMO) inhibitors have failed to show clinical benefit in patients with cancers displaying SHH autocrine/paracrine expression. We reported earlier that the SHH receptor Patched (PTCH) is a dependence receptor that triggers apoptosis in the absence of SHH through a pathway that differs from the canonical one, thus generating a state of dependence on SHH for survival. Here, we propose a dual function for SHH: its binding to PTCH not only activates the SHH canonical pathway but also blocks PTCH-induced apoptosis. Eighty percent, 64%, and 8% of human colon, pancreatic, and lung cancer cells, respectively, overexpressed SHH at transcriptional and protein levels. In addition, SHH-overexpressing cells expressed all the effectors of the PTCH-induced apoptotic pathway. Although the canonical pathway remained unchanged, autocrine SHH interference in colon, pancreatic, and lung cell lines triggered cell death through PTCH proapoptotic signaling. In vivo, SHH interference in colon cancer cell lines decreased primary tumor growth and metastasis. Therefore, the antitumor effect associated to SHH deprivation, usually thought to be a consequence of the inactivation of the canonical SHH pathway, is, at least in part, because of the engagement of PTCH proapoptotic activity. Together, these data strongly suggest that therapeutic strategies based on the disruption of SHH/PTCH interaction in SHH-overexpressing cancers should be explored. SIGNIFICANCE: Sonic Hedgehog-overexpressing tumors express PTCH-induced cell death effectors, suggesting that this death signaling could be activated as an antitumor strategy.

GLI2-Mediated Inflammation in the Tumor Microenvironment

The tumor microenvironment (TME) plays an important role in the development and progression of cancer and has been shown to contribute to resistance to therapy. Inflammation is one of the hallmarks of cancer implicated in disease phenotype. Therefore, understanding the mechanisms that regulate inflammation in cancer and consequently how inflammatory mediators promote cancer progression is important for our understanding of cancer cell biology. The transcription factor GLI2 was initially identified as a member of the Hedgehog (HH) signaling pathway. During the last decade, studies have shown a novel mechanism of GLI2 regulation independent of HH signaling, where GLI2 consequently modulated several cytokine genes in the TME. These studies highlight a novel role for GLI2 as an inflammatory mediatory independent of HH stimulation. This chapter will discuss canonical and noncanonical pathways of GLI2 regulation and some of the downstream cytokine target genes regulated by GLI2.

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.

Mutations in the sonic hedgehog pathway cause macrocephaly-associated conditions due to crosstalk to the PI3K/AKT/mTOR pathway

The hedgehog (Hh) pathway is highly conserved and required for embryonic patterning and determination. Mutations in the Hh pathway are observed in sporadic tumors as well as under syndromic conditions. Common to these syndromes are the findings of polydactyly/syndactyly and brain overgrowth. The latter is also a finding most commonly observed in the cases of mutations in the PI3K/AKT/mTOR pathway. We have identified novel Hh pathway mutations and structural copy number variations in individuals with somatic overgrowth, macrocephaly, dysmorphic facial features, and developmental delay, which phenotypically closely resemble patients with phosphatase and tensin homolog (PTEN) mutations. We hypothesized that brain overgrowth and phenotypic overlap with syndromic overgrowth syndromes in these cases may be due to crosstalk between the Hh and PI3K/AKT/mTOR pathways. To test this, we modeled disease-associated variants by generating PTCH1 and Suppressor of Fused (SUFU) heterozygote cell lines using the CRISPR/Cas9 system. These cells demonstrate activation of PI3K signaling and increased phosphorylation of its downstream target p4EBP1 as well as a distinct cellular phenotype. To further investigate the mechanism underlying this crosstalk, we treated human neural stem cells with sonic hedgehog (SHH) ligand and performed transcriptional analysis of components of the mTOR pathway. These studies identified decreased expression of a set of mTOR negative regulators, leading to its activation. We conclude that there is a significant crosstalk between the SHH and PI3K/AKT/mTOR. We propose that this crosstalk is responsible for why mutations in PTCH1 and SUFU lead to macrocephaly phenotypes similar to those observed in PTEN hamartoma and other overgrowth syndromes associated with mutations in PI3K/AKT/mTOR pathway genes.

Transcriptome profiling reveals transcriptional and alternative splicing regulation in the early embryonic development of hair follicles in the cashmere goat

The undercoat fiber of the cashmere goat, from the secondary hair follicle (HF), possesses commercial value. However, very few studies have focused on the molecular details of primary and secondary HF initiation and development in goat embryos. In this study, skin samples at embryonic day 45, 55, and 65 (E45, E55, and E65) were collected and prepared for RNA sequencing (RNA-seq). We found that the HF probably initiated from E55 to E65 by analyzing the functional pathways of differentially expressed genes (DEGs). Most key genes in canonical signaling pathways, including WNT, TGF-β, FGF, Hedgehog, NOTCH, and other factors showed clear expression changes from E55 to E65. We, for the first time, explored alternative splicing (AS) alterations, which showed distinct patterns among these three stages. Functional pathways of AS-regulated genes showed connections to HF development. By comparing the published RNA-seq samples from the E60, E120, and newborn (NB) stages, we found the majority of WNT/β-catenin signaling genes were important in the initiation of HF development, while other factors including FOXN1, GATA3, and DLX3 may have a consistent influence on HF development. Our investigation supported the time points of embryonic HF initiation and identified genes that have potential functions of embryonic HF initiation and development. We further explored the potential regulatory roles of AS in HF initiation, which extended our knowledge about the molecular mechanisms of HF development.

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.

Wnt Signaling Pathways in Keratinocyte Carcinomas

The skin functions as a barrier between the organism and the surrounding environment. Direct exposure to external stimuli and the accumulation of genetic mutations may lead to abnormal cell growth, irreversible tissue damage and potentially favor skin malignancy. Skin homeostasis is coordinated by an intricate signaling network, and its dysregulation has been implicated in the development of skin cancers. Wnt signaling is one such regulatory pathway orchestrating skin development, homeostasis, and stem cell activation. Aberrant regulation of Wnt signaling cascades not only gives rise to tumor initiation, progression and invasion, but also maintains cancer stem cells which contribute to tumor recurrence. In this review, we summarize recent studies highlighting functional evidence of Wnt-related oncology in keratinocyte carcinomas, as well as discussing preclinical and clinical approaches that target oncogenic Wnt signaling to treat cancers. Our review provides valuable insight into the significance of Wnt signaling for future interventions against keratinocyte carcinomas.

ZNF692 promotes colon adenocarcinoma cell growth and metastasis by activating the PI3K/AKT pathway

Despite considerable recent advancements in colorectal cancer (CRC) therapy, the prognosis of patients with advanced disease remains poor. Further understanding of the molecular mechanisms and treatment strategies of this disease is required. Zinc finger protein 692 (ZNF692), also known as AREBP and Zfp692, was first reported to have an important role in gluconeogenesis. A recent study demonstrated that ZNF692 is overexpressed in lung adenocarcinoma (LUAD) tissues and that ZNF692 knockdown inhibited LUAD cell proliferation, migration, and invasion both in vitro and in vivo. However, the role of ZNF692 in colon adenocarcinoma (COAD) remains unclear. The present study revealed that ZNF692 was upregulated in COAD tissues and cells and that high ZNF692 expression was significantly correlated with lymph node metastasis, distant metastasis and tumor stage in COAD patients. Gain‑ and loss‑of‑function experiments were employed to identify the function of ZNF692 in COAD progression. In vitro and in vivo assays revealed that ZNF692 promoted COAD cell proliferation, migration and invasion. Furthermore, western blot analysis demonstrated that the effects of ZNF692 were mediated by upregulating cyclin D1, cyclin‑dependent kinase 2 (CDK2) and matrix metalloproteinase‑9 (MMP‑9) and by downregulating p27Kip1 through the phosphoinositide 3‑kinase/AKT signaling pathway. Collectively, these data indicated that ZNF692 may serve as a novel oncogene and a potential treatment target in COAD patients.

Influence of SHH/GLI1 axis on EMT mediated migration and invasion of breast cancer cells

Sonic Hedgehog signaling is critical for breast morphogenesis and cancer. The present study was conducted to explore the influence of SHH/GLI1 axis on epithelial mesenchymal transition and invasion in breast cancer cells. SHH/GLI1 positive samples demonstrated high expression of Snail and Vimentin with relatively low expression of E-cadherin. Overexpression of Vimentin and Snail in SHH/GLI1 positive patients was also associated with poor overall survival. Interestingly, GANT61 (GLI1 inhibitor) exposure significantly reduced cell viability and induced apoptosis at 10 µM. Suppression of Hedgehog pathway either by CRISPR mediated SHH knock out or GANT61 altered regulation of EMT markers in breast cancer cells. Moreover, in-activation of SHH/GLI1 axis also significantly restricted cell migration and invasiveness. These findings suggest that targeting SHH/GLI1 axis alters expression of EMT markers and abrogates neoplastic invasion in breast cancer cells.