Targeting the Hedgehog pathway in cancer

Functions of Wnt and Hedgehog-containing extracellular vesicles in development and disease

Secreted morphogens play a major role in the intercellular communication necessary for animal development. It was initially thought that, in order to organize tissue morphogenesis and control cell fate and proliferation, morphogens diffused freely in the extracellular space. This view has since changed following the discovery that morphogens of the Wnt and Hedgehog (Hh) families are modified by various lipid adducts during their biosynthesis, providing them with high affinity for the membrane bilayer. Recent work performed in model organisms suggests that Wnt and Hh proteins are carried on extracellular vesicles. In this Review, we provide our perspectives on the mechanisms of formation of Wnt- and Hh-containing extracellular vesicles, and discuss their functions during animal development, as well as in various human physiopathologies.

The SNP rs13147758 in the HHIP Gene Is Associated With COPD Susceptibility, Serum, and Sputum Protein Levels in Smokers

BACKGROUND

Genetic association studies have identified single nucleotide polymorphisms (SNPs) related to chronic obstructive pulmonary disease (COPD) susceptibility. The aim of this study was to identify HHIP genetic variants associated with COPD, pulmonary function, and serum and sputum HHIP protein levels in Mexican mestizo smokers.

MATERIALS AND METHODS

Association analysis was performed by carrying out a case-control study in Mexican mestizo smokers comprised of two groups: tobacco-smoking subjects with COPD (COPD-TS, n = 222) and smokers without COPD (SWOC, n = 333). We evaluated three SNPs (rs13147758, rs1828591, and rs13118928) in the HHIP gene. Allele discrimination was accomplished by qPCR using TaqMan probes, and determination of protein levels in the serum and sputum supernatants (SS) was performed using ELISA.

RESULTS

Statistically significant differences were observed in the rs13147758 GG genotype (adjusted p = 0.014, OR = 1.95) and the rs13147758-rs1828591 GA haplotype (p = 6.6E-06, OR = 2.65) in the case-control comparison. HHIP protein levels were elevated in SS samples from the COPD-TS group compared to those from the SWOC group (p = 0.03). Based on genotype analysis, HHIP protein levels were lower in the serum samples of rs13147758 GG genotype carriers in the COPD-TS group than in the serum samples of rs13147758 GG genotype carriers from the SWOC group (p < 0.05), but there were no differences in the sputum samples.

CONCLUSION

The rs13147758 GG genotype and the rs13147758-rs1828591 GA haplotype are associated with susceptibility to COPD. Furthermore, an association in protein levels was observed between the HHIP rs13147758 genotype and COPD in Mexican mestizo smokers.

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.

Crosstalk between Hedgehog pathway and the glucocorticoid receptor pathway as a basis for combination therapy in T-cell acute lymphoblastic leukemia

Notwithstanding intensified therapy, a considerable fraction of T-cell acute lymphoblastic leukemia (T-ALL) patients face a dismal prognosis due to primary resistance to treatment and relapse, raising the need for more efficient and targeted therapies. Hedgehog (HH) signaling is a major developmental pathway frequently deregulated in cancer, for which a role in T-ALL is emerging. Mounting evidence suggests that ligand-independent activation of HH pathway occurs in cancer including T-ALL, emphasizing the necessity of dissecting the complex interplay between HH and other signaling pathways regulating activation. In this work, we present a therapeutically relevant crosstalk between HH signaling and the glucocorticoid receptor (NR3C1) pathway acting at the level of GLI1 transcription factor. GLI inhibitor GANT61 and dexamethasone were shown to exert a synergistic anti-leukemic effect in vitro in T-ALL cell lines and patient-derived xenografts. Mechanistically, dexamethasone-activated NR3C1 impaired GLI1 function by dynamically modulating the recruitment of PCAF acetyltransferase and HDAC1 deacetylase. Increased GLI1 acetylation was associated with compromised transcriptional activity and reduced protein stability. In summary, our study identifies a novel crosstalk between GLI1 and NR3C1 signaling pathway which could be exploited in HH-dependent malignancies to increase therapeutic efficacy.

Distinct Cation Gradients Power Cholesterol Transport at Different Key Points in the Hedgehog Signaling Pathway

Cholesterol plays two critical roles in Hedgehog signaling, a fundamental pathway in animal development and cancer: it covalently modifies the Sonic hedgehog (SHH) ligand, restricting its release from producing cells, and directly activates Smoothened in responding cells. In both contexts, a membrane protein related to bacterial RND transporters regulates cholesterol: Dispatched1 controls release of cholesterylated SHH, and Patched1 antagonizes Smoothened activation by cholesterol. The mechanism and driving force for eukaryotic RND proteins, including Dispatched1 and Patched1, are unknown. Here, we show that Dispatched1 acts enzymatically to catalyze SHH release. Dispatched1 uses the energy of the plasma membrane Na⁺ gradient, thus functioning as an SHH/Na⁺ antiporter. In contrast, Patched1 repression of Smoothened requires the opposing K⁺ gradient. Our results clarify the transporter activity of essential eukaryotic RND proteins and demonstrate that the two main cation gradients of animal cells differentially power cholesterol transport at two crucial steps in the Hedgehog pathway.

Single cell transcriptomics identifies a signaling network coordinating endoderm and mesoderm diversification during foregut organogenesis

Visceral organs, such as the lungs, stomach and liver, are derived from the fetal foregut through a series of inductive interactions between the definitive endoderm (DE) and the surrounding splanchnic mesoderm (SM). While DE patterning is fairly well studied, the paracrine signaling controlling SM regionalization and how this is coordinated with epithelial identity is obscure. Here, we use single cell transcriptomics to generate a high-resolution cell state map of the embryonic mouse foregut. This identifies a diversity of SM cell types that develop in close register with the organ-specific epithelium. We infer a spatiotemporal signaling network of endoderm-mesoderm interactions that orchestrate foregut organogenesis. We validate key predictions with mouse genetics, showing the importance of endoderm-derived signals in mesoderm patterning. Finally, leveraging these signaling interactions, we generate different SM subtypes from human pluripotent stem cells (hPSCs), which previously have been elusive. The single cell data can be explored at: https://research.cchmc.org/ZornLab-singlecell.

The fetal murine foregut develops into visceral organs via interactions between the mesoderm and endoderm, but how is unclear. Here, the authors use single cell RNAseq to show a diversity in organ specific splanchnic mesoderm cell-types, infer a signalling network governing organogenesis and use this to differentiate human pluripotent stem cells.

Cellular signalling pathways mediating the pathogenesis of chronic inflammatory respiratory diseases: an update

Respiratory disorders, especially non-communicable, chronic inflammatory diseases, are amongst the leading causes of mortality and morbidity worldwide. Respiratory diseases involve multiple pulmonary components, including airways and lungs that lead to their abnormal physiological functioning. Several signaling pathways have been reported to play an important role in the pathophysiology of respiratory diseases. These pathways, in addition, become the compounding factors contributing to the clinical outcomes in respiratory diseases. A range of signaling components such as Notch, Hedgehog, Wingless/Wnt, bone morphogenetic proteins, epidermal growth factor and fibroblast growth factor is primarily employed by these pathways in the eventual cascade of events. The different aberrations in such cell-signaling processes trigger the onset of respiratory diseases making the conventional therapeutic modalities ineffective. These challenges have prompted us to explore novel and effective approaches for the prevention and/or treatment of respiratory diseases. In this review, we have attempted to deliberate on the current literature describing the role of major cell signaling pathways in the pathogenesis of pulmonary diseases and discuss promising advances in the field of therapeutics that could lead to novel clinical therapies capable of preventing or reversing pulmonary vascular pathology in such patients.

Nanoparticles for Manipulation of the Developmental Wnt, Hedgehog, and Notch Signaling Pathways in Cancer

The Wnt, Hedgehog, and Notch signaling pathways play a crucial role in early development and the maintenance of adult tissues. When dysregulated, these developmental signaling pathways can drive the formation and progression of cancer by facilitating cell survival, proliferation, and stem-like behavior. While this makes these pathways promising targets for therapeutic intervention, their pharmacological inhibition has been challenging due to the substantial complexity that exists within each pathway and the complicated crosstalk that occurs between the pathways. Recently, several small molecule inhibitors, ribonucleic acid (RNA) molecules, and antagonistic antibodies have been developed that can suppress these signaling pathways in vitro, but many of them face systemic delivery challenges. Nanoparticle-based delivery vehicles can overcome these challenges to enhance the performance and anti-cancer effects of these therapeutic molecules. This review summarizes the mechanisms by which the Wnt, Hedgehog, and Notch signaling pathways contribute to cancer growth, and discusses various nanoparticle formulations that have been developed to deliver small molecules, RNAs, and antibodies to cancer cells to inhibit these signaling pathways and halt tumor progression. This review also outlines some of the challenges that these nanocarriers must overcome to achieve therapeutic efficacy and clinical translation.

Small Molecule Intervention in a Protein Kinase C-Gli Transcription Factor Axis

Aberrations in the Hedgehog (Hh) signaling pathway are responsible for a broad range of human cancers, yet only a subset rely on the activity of the clinical target, Smoothened (Smo). Emerging cases of cancers that are insensitive to Smo-targeting drugs demand new therapeutic targets and agents for inhibition. As such, we sought to pursue a recently discovered connection between the Hedgehog pathway transcription factors, the glioma-associated oncogene homologues (Glis), and protein kinase C (PKC) isozymes. Here, we report our assessment of a structurally diverse library of PKC effectors for their influence on Gli function. Using cell lines that employ distinct mechanisms of Gli activation up- and downstream of Smo, we identify a PKC effector that acts as a nanomolar Gli antagonist downstream of Smo through a mitogen-activated protein kinase kinase (MEK)-independent mechanism. This agent provides a unique tool to illuminate crosstalk between PKC isozymes and Hh signaling and new opportunities for therapeutic intervention in Hh pathway-dependent cancers.

Expression of GLI1 Correlates with Expression of Lymphangiogenesis Proteins, Vascular Endothelial Growth Factor C and Vascular Endothelial Growth Factor Receptor 3, in Colorectal Cancer

Aberrant activation of the hedgehog (Hh) signaling pathway is associated with tumorigenesis in various tissues. In colorectal cancer (CRC), evidence for Hh activation is inconsistent, and the relationship between the Hh signaling pathway and lymphangiogenesis has not been studied. The aim of this study was to determine the relationship between Hh signaling and lymphangio-genesis and the association of this relationship with lymph node metastasis in CRC. We investigated 189 patients who underwent curative surgical resection for CRC between 2002 and 2004 at Korea University Guro Hospital. Paraffin-embedded specimens of colorectal adenocarcinoma and adjacent normal mucosa were evaluated. Immunohistochemical staining for Sonic hedgehog (Shh), Gli1, vascular endothelial growth factor C (VEGFC), and VEGF receptor 3 (VEGFR3) was performed for each specimen. Tumor specimen showed significantly strong staining of Shh, Gli1, VEGFC, and VEGFR3 compared with a normal specimen. Shh expression was not associated with Gli1 expression. Gli1 expression correlated positively with VEGFC and VEGFR3 expression ( P < 0.05 in both) but not with lymph node metastasis. Activation of the Hh signaling pathway associated with Gli1 promotes expression of lymphangiogenesis proteins, VEGFC and VEGFR3, in CRC. Further studies are necessary to determine the association of this relationship with lymph node metastasis in CRC.

Bicyclic Imidazolium Inhibitors of Gli Transcription Factor Activity

Gli transcription factors within the Hedgehog (Hh) signaling pathway direct key events in mammalian development and promote a number of human cancers. Current therapies for Gli-driven tumors target Smoothened (SMO), a G protein-coupled receptor-like protein that functions upstream in the Hh pathway. Although these drugs can have remarkable clinical efficacy, mutations in SMO and downstream Hh pathway components frequently lead to chemoresistance. In principle, therapies that act at the level of Gli proteins, through direct or indirect mechanisms, would be more efficacious. We therefore screened 325 120 compounds for their ability to block the constitutive Gli activity induced by loss of Suppressor of Fused (SUFU), a scaffolding protein that directly inhibits Gli function. Our studies reveal a family of bicyclic imidazolium derivatives that can inhibit Gli-dependent transcription without affecting the ciliary trafficking or proteolytic processing of these transcription factors. We anticipate that these chemical antagonists will be valuable tools for investigating the mechanisms of Gli regulation and developing new strategies for targeting Gli-driven cancers.

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.

DUBs Activating the Hedgehog Signaling Pathway: A Promising Therapeutic Target in Cancer

The Hedgehog (HH) pathway governs cell proliferation and patterning during embryonic development and is involved in regeneration, homeostasis and stem cell maintenance in adult tissues. The activity of this signaling is finely modulated at multiple levels and its dysregulation contributes to the onset of several human cancers. Ubiquitylation is a coordinated post-translational modification that controls a wide range of cellular functions and signaling transduction pathways. It is mediated by a sequential enzymatic network, in which ubiquitin ligases (E3) and deubiquitylase (DUBs) proteins are the main actors. The dynamic balance of the activity of these enzymes dictates the abundance and the fate of cellular proteins, thus affecting both physiological and pathological processes. Several E3 ligases regulating the stability and activity of the key components of the HH pathway have been identified. Further, DUBs have emerged as novel players in HH signaling transduction, resulting as attractive and promising drug targets. Here, we review the HH-associated DUBs, discussing the consequences of deubiquitylation on the maintenance of the HH pathway activity and its implication in tumorigenesis. We also report the recent progress in the development of selective inhibitors for the DUBs here reviewed, with potential applications for the treatment of HH-related tumors.

Projected t-SNE for batch correction

MOTIVATION

Low-dimensional representations of high-dimensional data are routinely employed in biomedical research to visualize, interpret and communicate results from different pipelines. In this article, we propose a novel procedure to directly estimate t-SNE embeddings that are not driven by batch effects. Without correction, interesting structure in the data can be obscured by batch effects. The proposed algorithm can therefore significantly aid visualization of high-dimensional data.

RESULTS

The proposed methods are based on linear algebra and constrained optimization, leading to efficient algorithms and fast computation in many high-dimensional settings. Results on artificial single-cell transcription profiling data show that the proposed procedure successfully removes multiple batch effects from t-SNE embeddings, while retaining fundamental information on cell types. When applied to single-cell gene expression data to investigate mouse medulloblastoma, the proposed method successfully removes batches related with mice identifiers and the date of the experiment, while preserving clusters of oligodendrocytes, astrocytes, and endothelial cells and microglia, which are expected to lie in the stroma within or adjacent to the tumours.

AVAILABILITY AND IMPLEMENTATION

Source code implementing the proposed approach is available as an R package at https://github.com/emanuelealiverti/BC_tSNE, including a tutorial to reproduce the simulation studies.

CONTACT

aliverti@stat.unipd.it.

Antifibrotic therapy to normalize the tumor microenvironment

Most tumors develop abnormal fibrotic regions consisting of fibroblasts, immune cells, and a dense extracellular matrix (ECM) immersed in a viscous interstitial fluid, and an abundant fibrotic tumor microenvironment (TME) is associated with poor outcome of treatment. It has been hypothesized that the treatment of cancer may be improved by interventions aiming to normalize this TME. The approaches used in attempts to normalize the fibrotic TME can be categorized into three strategies of targeted antifibrotic therapy: targeting of components of the ECM, targeting of the producers of the ECM components-the activated cancer-associated fibroblasts (CAFs), and targeting of the signaling pathways activating CAFs. To target the ECM, enzymes against components of the ECM have been used, including collagenase, relaxin, hyaluronidase, and lyxyl oxidase. Targeting of CAFs have been investigated by using agents aiming to eliminate or reprogram CAFs. CAFs are activated primarily by transforming growth factor-β (TGF-β), hedgehog, or focal adhesion kinase signaling, and several agents have been used to target these signaling pathways, including angiotensin II receptor I blockers (e.g., losartan) to inhibit the TGF-β pathway. Taken together, these studies have revealed that antifibrotic therapy is a two-edged sword: while some studies suggest enhanced response to treatment after antifibrotic therapy, others suggest that antifibrotic therapy may lead to increased tumor growth, metastasis, and impaired outcome of treatment. There are several possible explanations of these conflicting observations. Most importantly, tumors contain different subpopulations of CAFs, and while some subpopulations may promote tumor growth and metastasis, others may inhibit malignant progression. Furthermore, the outcome of antifibrotic therapy may depend on stage of disease, duration of treatment, treatment-induced activation of alternative profibrotic signaling pathways, and treatment-induced recruitment of tumor-supporting immune cells. Nevertheless, losartan-induced suppression of TGF-β signaling appears to be a particularly promising strategy. Losartan is a widely prescribed antihypertensive drug and highly advantageous therapeutic effects have been observed after losartan treatment of pancreatic cancer. However, improved understanding of the mechanisms governing the development of fibrosis in tumors is needed before safe antifibrotic treatments can be established.

Progress toward a Convergent, Asymmetric Synthesis of Jervine

Progress toward a convergent approach for the enantioselective synthesis of the Veratrum alkaloid jervine is presented. The two requisite fragments were stereoselectively and efficiently fashioned from economical and readily available reagents. Key reactions include (a) a highly diastereoselective Ireland-Claisen rearrangement to establish the necessary cis-relationship between the amine and methyl group on the tetrahydrofuran E-ring; (b) a diastereoselective selenoetherification reaction that enabled the assembly of the D/E oxaspiro[4.5]decene in the needed configuration; and (c) an enzymatic desymmetrization of an abundant achiral diol en route to a key four-carbon building block as a practical alternative to a protected Roche ester reduction.

LncRNA EGOT decreases breast cancer cell viability and migration via inactivation of the Hedgehog pathway

The long noncoding RNA (lncRNA) Eosinophil Granule Ontogeny Transcript (EGOT) has been reported to inhibit the proliferation and migration of glioma cells, and promote the development and progression of gastric cancer through the Hedgehog (Hh) signaling pathway. This study was conducted to assess the role of EGOT in the progression of breast cancer. We observed that EGOT is significantly down-regulated in breast cancer tissues and cell lines, and EGOT expression is negatively correlated with the Ki67 expression. Overexpression of EGOT in BT549 cells decreased cell viability and migration. In addition, overexpression of EGOT resulted in decreases in expression of key genes in the Hh pathway, including Gli1, smoothened protein, protein patched homolog 1 and Hedgehog-interacting protein (HHIP). Breast cancer tissues exhibited an increase in Gli1 expressions. Altered expression of Gli1, smoothened protein, protein patched homolog 1 and HHIP caused by EGOT overexpression were fully restored in cells transfected with plasmid complementory DNA (pcDNA) EGOT and treated with purmorphamine, an agonist of the Hh pathway. Cell viability and migration were also restored by purmorphamine. We conclude that lncRNA EGOT may inhibit breast cancer cell viability and migration via inactivation of the Hh pathway.

Secondary Resistant Mutations to Small Molecule Inhibitors in Cancer Cells

Secondary resistant mutations in cancer cells arise in response to certain small molecule inhibitors. These mutations inevitably cause recurrence and often progression to a more aggressive form. Resistant mutations may manifest in various forms. For example, some mutations decrease or abrogate the affinity of the drug for the protein. Others restore the function of the enzyme even in the presence of the inhibitor. In some cases, resistance is acquired through activation of a parallel pathway which bypasses the function of the drug targeted pathway. The Catalogue of Somatic Mutations in Cancer (COSMIC) produced a compendium of resistant mutations to small molecule inhibitors reported in the literature. Here, we build on these data and provide a comprehensive review of resistant mutations in cancers. We also discuss mechanistic parallels of resistance.

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.

[Cartilage tumors: morphology, genetics, and current aspects of target therapy]

Cartilage tumors are a heterogeneous group of mesenchymal tumors whose common characteristic is the formation of a chondroblastic differentiated groundsubstance by the tumor cells. The basic features of their histological classification were already developed in the 1940s and supplemented by further entities in the following decades. Only in the past 10-15 years have fundamental new insights been gained through molecular genetic analysis. So, osteochondromas are characterized by alterations in the EXT1 and EXT2 genes. The description of mutations of isocitrate dehydrogenase 1 and 2 (IDH 1 and 2) in chondromas and chondrosarcomas is particularly important. The mesenchymal chondrosarcoma is characterized by a fusion of the HEY1-NCOA2 genes. The molecular genetic alterations characteristic for the individual tumor entities are first of all an essential supplement for the differential diagnosis of radiologically and histologically difficult cases. They also provide the basis for the establishment of molecular target therapies for malignant chondrogenic tumors. This applies in particular to conventional chondrosarcoma, for which all approaches to chemo- and radiotherapy have proven to be ineffective. However, the use of target therapies is still in its beginnings.

Colorectal cancer (CRC) as a multifactorial disease and its causal correlations with multiple signaling pathways

Colorectal cancer (CRC) is the third most common malignancy and one of the leading causes of cancer-related death among men worldwide. CRC is a multifactor digestive pathology, which is a huge problem faced not only by clinicians but also by researchers. Importantly, a unique feature of CRC is the dysregulation of molecular signaling pathways. To date, a series of reviews have indicated that different signaling pathways are disordered and have potential as therapeutic targets in CRC. Nevertheless, an overview of the function and interaction of multiple signaling pathways in CRC is needed. Therefore, we summarized the pathways, biological functions and important interactions involved in CRC. First, we investigated the involvement of signaling pathways, including Wnt, PI3K/Akt, Hedgehog, ErbB, RHOA, Notch, BMP, Hippo, AMPK, NF-κB, MAPK and JNK. Subsequently, we discussed the biological function of these pathways in pathophysiological aspects of CRC, such as proliferation, apoptosis and metastasis. Finally, we summarized important interactions among these pathways in CRC. We believe that the interaction of these pathways could provide new strategies for the treatment of CRC.

MOrPH-PhD: An Integrated Phage Display Platform for the Discovery of Functional Genetically Encoded Peptide Macrocycles

Macrocyclic peptides represent attractive scaffolds for targeting protein-protein interactions, making methods for the diversification and functional selection of these molecules highly valuable for molecular discovery purposes. Here, we report the development of a novel strategy for the generation and high-throughput screening of combinatorial libraries of macrocyclic peptides constrained by a nonreducible thioether bridge. In this system, spontaneous, posttranslational peptide cyclization by means of a cysteine-reactive noncanonical amino acid was integrated with M13 bacteriophage display, enabling the creation of genetically encoded macrocyclic peptide libraries displayed on phage particles. This platform, named MOrPH-PhD, was successfully applied to produce and screen 10⁵- to 10⁸-member libraries of peptide macrocycles against three different protein targets, resulting in the discovery of a high-affinity binder for streptavidin (K _D: 20 nM) and potent inhibitors of the therapeutically relevant proteins Kelch-like ECH-associated protein 1 (K _D: 40 nM) and Sonic Hedgehog (K _D: 550 nM). This work introduces and validates an efficient and general platform for the discovery and evolution of functional, conformationally constrained macrocyclic peptides useful for targeting proteins and protein-mediated interactions.

Glypican-3: A New Target for Diagnosis and Treatment of Hepatocellular Carcinoma

Liver cancer is the second leading cause of cancer-related deaths worldwide, and hepatocellular carcinoma is the most common type. The pathogenesis of hepatocellular carcinoma is concealed, its progress is rapid, its prognosis is poor, and the mortality rate is high. Therefore, novel molecular targets for hepatocellular carcinoma early diagnosis and development of targeted therapy are critically needed. Glypican-3, a cell-surface glycoproteins in which heparan sulfate glycosaminoglycan chains are covalently linked to a protein core, is overexpressed in HCC tissues but not in the healthy adult liver. Thus, Glypican-3 is becoming a promising candidate for liver cancer diagnosis and immunotherapy. Up to now, Glypican-3 has been a reliable immunohistochemical marker for hepatocellular carcinoma diagnosis, and soluble Glypican-3 in serum has becoming a promising marker for liquid biopsy. Moreover, various immunotherapies targeting Glypican-3 have been developed, including Glypican-3 vaccines, anti- Glypican-3 immunotoxin and chimeric-antigen-receptor modified cells. In this review, we summarize and analyze the structure and physicochemical properties of Glypican-3 molecules, then review their biological functions and applications in clinical diagnosis, and explore the diagnosis and treatment strategies based on Glypican-3.

Assessment of Hedgehog Signaling Pathway Activation for Craniofacial Bone Regeneration in a Critical-Sized Rat Mandibular Defect

Importance

Osseous craniofacial defects are currently reconstructed with bone grafting, rigid fixation, free tissue transfer, and/or recombinant human bone morphogenetic protein 2. Although these treatment options often have good outcomes, they are associated with substantial morbidity, and many patients are not candidates for free tissue transfer.

Objective

To assess whether polysaccharide-based scaffold (PS) constructs that are cross-linked with smoothened agonist (SAG), vascular endothelial growth factor (VEGF), and bone morphogenetic protein 6 (BMP-6) would substantially increase bone regeneration.

Design, Setting, and Participants

This animal model study was conducted at the University of Virginia School of Medicine Cui Laboratory from March 1, 2017, to June 30, 2017. Thirty-three 10-week-old female Lewis rats were acquired for the study. Bilateral nonsegmental critical-sized defects were created in the angle of rat mandibles. The defects were either left untreated or filled with 1 of the 9 PSs. The rats were killed after 8 weeks, and bone regeneration was evaluated using microcomputed tomographic imaging and mechanical testing. Analysis of variance testing was used to compare the treatment groups.

Main Outcomes and Measures

Blinded analysis and computer analysis of the microcomputed tomographic images were used to assess bone regeneration.

Results

In the 33 female Lewis rats, minimal healing was observed in the untreated mandibles. Addition of SAG was associated with increases in bone regeneration and bone density in all treatment groups, and maximum bone healing was seen in the group with BMP-6, VEGF, and SAG cross-linked to PS. For each of the 5 no scaffold group vs BMP-6, VEGF, and SAG cross-linked to PS group comparisons, mean defect bone regeneration was 4.14% (95% CI, 0.94%-7.33%) vs 66.19% (95% CI, 54.47%-77.90%); mean bone volume, 14.52 mm3 (95% CI, 13.07-15.97 mm3) vs 20.87 mm3 (95% CI, 14.73- 27.01 mm3); mean bone surface, 68.97 mm2 (95% CI, 60.08-77.85 mm2) vs 96.77 mm2 (95% CI, 76.11-117.43 mm2); mean ratio of bone volume to total volume, 0.11 (95% CI, 0.10-0.11) vs 0.15 (95% CI, 0.10-0.19); and mean connectivity density 0.03 (95% CI, 0.02-0.05) vs 0.32 (95% CI, 0.25-0.38). On mechanical testing, mandibles with untreated defects broke with less force than control mandibles in which no defect was made, although this force did not reach statistical significance. No significant difference in force to fracture was observed among the treatment groups.

Conclusions and Relevance

In this rat model study, activation of the hedgehog signaling pathway using smoothened agonist was associated with increased craniofacial bone regeneration compared with growth factors alone, including US Food and Drug Administration-approved recombinant human bone morphogenetic protein 2. Pharmaceuticals that target this pathway may offer a new reconstructive option for bony craniofacial defects as well as nonunion and delayed healing fractures.

Level of Evidence

NA.

Guided by evolution: from biology oriented synthesis to pseudo natural products

This review provides an overview and historical context to two concepts for the design of natural product-inspired compound libraries and highlights the used synthetic methodologies.

scRNA-seq in medulloblastoma shows cellular heterogeneity and lineage expansion support resistance to SHH inhibitor therapy

Targeting oncogenic pathways holds promise for brain tumor treatment, but inhibition of Sonic Hedgehog (SHH) signaling has failed in SHH-driven medulloblastoma. Cellular diversity within tumors and reduced lineage commitment can undermine targeted therapy by increasing the probability of treatment-resistant populations. Using single-cell RNA-seq and lineage tracing, we analyzed cellular diversity in medulloblastomas in transgenic, medulloblastoma-prone mice, and responses to the SHH-pathway inhibitor vismodegib. In untreated tumors, we find expected stromal cells and tumor-derived cells showing either a spectrum of neural progenitor-differentiation states or glial and stem cell markers. Vismodegib reduces the proliferative population and increases differentiation. However, specific cell types in vismodegib-treated tumors remain proliferative, showing either persistent SHH-pathway activation or stem cell characteristics. Our data show that even in tumors with a single pathway-activating mutation, diverse mechanisms drive tumor growth. This diversity confers early resistance to targeted inhibitor therapy, demonstrating the need to target multiple pathways simultaneously.

Although the hedgehog (HH) pathway is known to be deregulated in medulloblastoma, inhibitors of the pathway have shown disappointing clinical benefit. Using single-cell sequencing in a mouse model of the disease, the authors show that the response to the HH pathway inhibitor vismodegib is cell-type specific.

Heteroarylamide smoothened inhibitors: Discovery of N-[2,4-dimethyl-5-(1-methylimidazol-4-yl)phenyl]-4-(2-pyridylmethoxy)benzamide (AZD8542) and N-[5-(1H-imidazol-2-yl)-2,4-dimethyl-phenyl]-4-(2- pyridylmethoxy)benzamide (AZD7254)

Aberrant hedgehog (Hh) pathway signaling is implicated in multiple cancer types and targeting the Smoothened (SMO) receptor, a key protein of the Hh pathway, has proven effective in treating metastasized basal cell carcinoma. Our lead optimization effort focused on a series of heteroarylamides. We observed that a methyl substitution ortho to the heteroaryl groups on an aniline core significantly improved the potency of this series of compounds. These findings predated the availability of SMO crystal structure in 2013. Here we retrospectively applied quantum mechanics calculations to demonstrate the o-Me substitution favors the bioactive conformation by inducing a dihedral twist between the heteroaryl rings and the core aniline. The o-Me also makes favorable hydrophobic interactions with key residue side chains in the binding pocket. From this effort, two compounds (AZD8542 and AZD7254) showed excellent pharmacokinetics across multiple preclinical species and demonstrated in vivo activity in abrogating the Hh paracrine pathway as well as anti- tumor effects.

The structure-based traceless specific fluorescence labeling of the smoothened receptor

The smoothened receptor (SMO) mediates the hedgehog (Hh) signaling pathway and plays a vital role in embryonic development and tumorigenesis. The visualization of SMO has the potential to provide new insights into its enigmatic mechanisms and associated disease pathogenesis. Based on recent progress in structural studies of SMO, we have designed and characterized a group of affinity probes to facilitate the turn-on fluorescence labeling of SMO at the ε-amine of K395. These chemical probes were derived from a potent SMO antagonist skeleton by the conjugation of a small non-fluorescent unit, O-nitrobenzoxadiazole (O-NBD). In this context, optimal probes were developed to be capable of efficiently and selectively lighting up SMO regardless of whether it is in micelles or in native membranes. More importantly, the resulting labeled SMO only bears a very small fluorophore and allows for the recovery of the unoccupied pocket by dissociation of the residual ligand module. These advantages should allow the probe to serve as a potential tool for monitoring SMO trafficking, understanding Hh activation mechanisms, and even the diagnosis of tumorigenesis in the future.

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.

Structure of Sonic Hedgehog protein in complex with zinc(II) and magnesium(II) reveals ion-coordination plasticity relevant to peptide drug design

The Hedgehog pathway is an essential cell-signaling paradigm implicated in cancer tumorigenesis and the developmental disorder holoprosencephaly, making it an attractive target for therapeutic design. The N-terminal domain of the Sonic Hedgehog protein (Shh-N) is the essential signaling molecule in the Hedgehog pathway. In this role Shh-N interacts with its cognate membrane receptor Patched, as well as the regulatory proteins HHIP and CDO, by utilizing interfaces harboring one or more divalent ions. Here, the crystal structure of human Shh-N is presented at 1.43 Å resolution, representing a landmark in the characterization of this protein. The structure reveals that the conserved Zn2+-binding site adopts an atypical octahedral coordination geometry, whereas an adjacent binding site, normally occupied by binuclear Ca2+, has been supplanted by a single octahedrally bound Mg2+. Both divalent sites are compared with those in previous Shh-N structures, which demonstrates a significant degree of plasticity of the Shh-N protein in terms of divalent ion binding. The presence of a high Mg2+ concentration in the crystallization medium appears to have influenced metal loading at both metal ion-binding sites. These observations have technical and design implications for efforts focused on the development of inhibitors that target Shh-N-mediated protein-protein interactions.

Colocalization Strategy Unveils an Underside Binding Site in the Transmembrane Domain of Smoothened Receptor

We unveiled an underside binding site on smoothened receptor (SMO) by a colocalization strategy using two structurally complementary photoaffinity probes derived from a known ligand Allo-1. Docking study and structural dissection identified key interactions within the site, including hydrogen bonding, π-π interactions, and hydrophobic interactions between Allo-1 and its contacting residues. Taken together, our results reveal the molecular base of Allo-1 binding and provide a basis for the design of new-generation ligands to overcome drug resistance.

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.

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.

Krüppel-like Factor 5 Promotes Sonic Hedgehog Signaling and Neoplasia in Barrett's Esophagus and Esophageal Adenocarcinoma

Krüppel-like Factor 5 (KLF5) is a zinc-finger transcription factor associated with cell cycle progression and cell survival. KLF5 plays a key role in mammalian intestinal epithelium development and maintenance, expressed at high levels in basal proliferating cells and low levels in terminally differentiated cells. Considering Barrett's esophagus (BE) and esophageal adenocarcinoma's (EAC) histopathological similarities to intestinal epithelium, we sought to determine KLF5's role in BE and EAC, as well as KLF5's possible connection to the sonic hedgehog (SHH) pathway which is highly active in BE and EAC development. Low levels of KLF5 mRNA were found in BE cell lines and tissue- similar to what has been reported in differentiated intestinal epithelium. In contrast, higher KLF5 levels were observed in EAC cells and tissues. KLF5 knockdown in EAC cells caused significant decreases in cell migration, proliferation, and EAC-associated gene expression. Moreover, KLF5 knockdown led to decreased SHH signaling. These results suggest that KLF5 is connected to the SHH pathway in BE and EAC and may represent a potential drug target in EAC; further studies are now indicated to verify these findings and elucidate underlying mechanisms involved.

Application of Nanotechnology in Targeting of Cancer Stem Cells: A Review

Cancer is increasingly apparent as a systems-level, network happening. The central tendency of malignant alteration can be described as a two-phase procedure, where an initial increase of network plasticity is followed by reducing plasticity at late stages of tumor improvement. Cancer stem cells (CSCs) are cancer cells that take characteristics associated with normal stem cells. Cancer therapy has been based on the concept that most of the cancer cells have a similar ability to separate metastasise and kill the host. In this review, we addressed the use of nanotechnology in the treatment of cancer stem cells.

Recent Treatment Advances and the Role of Nanotechnology, Combination Products, and Immunotherapy in Changing the Therapeutic Landscape of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common acute leukemia that is becoming more prevalent particularly in the older (65 years of age or older) population. For decades, "7 + 3" remission induction therapy with cytarabine and an anthracycline, followed by consolidation therapy, has been the standard of care treatment for AML. This stagnancy in AML treatment has resulted in less than ideal treatment outcomes for AML patients, especially for elderly patients and those with unfavourable profiles. Over the past two years, six new therapeutic agents have received regulatory approval, suggesting that a number of obstacles to treating AML have been addressed and the treatment landscape for AML is finally changing. This review outlines the challenges and obstacles in treating AML and highlights the advances in AML treatment made in recent years, including Vyxeos®, midostaurin, gemtuzumab ozogamicin, and venetoclax, with particular emphasis on combination treatment strategies. We also discuss the potential utility of new combination products such as one that we call "EnFlaM", which comprises an encapsulated nanoformulation of flavopiridol and mitoxantrone. Finally, we provide a review on the immunotherapeutic landscape of AML, discussing yet another angle through which novel treatments can be designed to further improve treatment outcomes for AML patients.

Inhibition of the Hedgehog pathway in lung cancer

Inhibitors of the hedgehog pathway are effective in patients with basal cell carcinoma and a subgroup of patients with medulloblastoma with active hedgehog signaling. Despite preclinical work suggesting otherwise, clinical trials in solid tumors of epithelial origin have not shown added benefit with these drugs. Here, we review the preclinical and clinical data of hedgehog pathway inhibition in the most common histologic types of lung cancer. We focus on highlighting areas of uncertainty, where further research might define a niche for hedgehog pathway inhibition in patients with lung cancer.

Recent Advances in the Clinical Targeting of Hedgehog/GLI Signaling in Cancer

The Hedgehog/GLI signaling pathway plays an important role in normal embryonic tissue development and has been implicated in the pathogenesis of various human cancers. In this review article, we summarize pre-clinical evidence supporting the suitability of targeting this signaling pathway in cancers. We review agents blocking both the ligand-dependent and ligand-independent cascades, and discuss the clinical evidence, which has led to the FDA approval of Hedgehog receptor Smoothened inhibitors, vismodegib, and sonidegib, in different malignancies. Finally, we provide an overview of published and ongoing clinical trial data on single agent or combination therapeutic strategies, targeting Hedgehog/GLI signaling pathway, in both advanced solid tumors and hematologic malignancies.

Leptin Promotes White Adipocyte Browning by Inhibiting the Hh Signaling Pathway

Leptin is an important secretory protein that regulates the body’s intake and energy consumption, and the functions of the Hh signaling pathway related to white adipocyte browning are controversial. It has been reported that leptin plays a critical role in adipogenesis by regulating the Hh signaling pathway, but whether there is a functional relationship between leptin, the Hh signaling pathway, and adipocyte browning is not clear. In this research, mouse white pre-adipocytes were isolated to explore the influence of the Hh signal pathway and leptin during the process described above. This showed that leptin decreased high fat diet-induced obese mice body weight and inhibited the Hh signaling pathway, which suggested that leptin and the Hh signaling pathway have an important role in obesity. After activation of the Hh signaling pathway, significantly decreased browning fat-relative gene expression levels were recorded, whereas inhibition of the Hh signaling pathway significantly up-regulated the expression of these genes. Similarly, leptin also up-regulated the expression of these genes, and increased mitochondrial DNA content, but decreased the expression of Gli, the key transcription factors of the Hh signaling pathway. In short, the results show that leptin promotes white adipocyte browning through inhibiting the Hh signaling pathway. Overall, these results demonstrate that leptin serves as a potential intervention to decrease obesity by inhibiting the Hh signaling pathway.

Targeting Hedgehog (Hh) Pathway for the Acute Myeloid Leukemia Treatment

The Hedgehog (Hh) pathway, containing the Patched (PTCH) and Smoothened (SMO) multitransmembrane proteins, is the main regulator of vertebrate embryonic development. A non-canonical Hh pathway was recently observed in numerous types of solid cancers and hematological malignancies. Although acute myeloid leukemia (AML) is a common and lethal myeloid malignancy, the chemotherapy for AML has not changed in the last three decades. The Hh pathway and other intracellular signaling pathways are important for the tumor cells’ cycle or therapeutic resistance of AML cells. In this article, we will review the current trends in Hh pathway inhibitors for treating AML.

Loss of Primary Cilia Drives Switching from Hedgehog to Ras/MAPK Pathway in Resistant Basal Cell Carcinoma

Basal cell carcinomas (BCCs) rely on Hedgehog (HH) pathway growth signal amplification by the microtubule-based organelle, the primary cilium. Despite naive tumor responsiveness to Smoothened inhibitors (Smoⁱ), resistance in advanced tumors remains common. Although the resistant BCCs usually maintain HH pathway activation, squamous cell carcinomas with Ras/MAPK pathway activation also arise, and the molecular basis of tumor type and pathway selection are still obscure. Here, we identify the primary cilium as a critical determinant controlling tumor pathway switching. Strikingly, Smoothened inhibitor-resistant BCCs have an increased mutational load in ciliome genes, resulting in reduced primary cilia and HH pathway activation compared with naive or Gorlin syndrome patient BCCs. Gene set enrichment analysis of resistant BCCs with a low HH pathway signature showed increased Ras/MAPK pathway activation. Tissue analysis confirmed an inverse relationship between primary cilia presence and Ras/MAPK activation, and primary cilia removal in BCCs potentiated Ras/MAPK pathway activation. Moreover, activating Ras in HH-responsive cell lines conferred resistance to both canonical (vismodegib) and noncanonical (atypical protein kinase C and MRTF inhibitors) HH pathway inhibitors and conferred sensitivity to MAPK inhibitors. Our results provide insights into BCC treatment and identify the primary cilium as an important lineage gatekeeper, preventing HH-to-Ras/MAPK pathway switching.

Design of Hedgehog pathway inhibitors for cancer treatment

Hedgehog (Hh) signaling is involved in the initiation and progression of various cancers and is essential for embryonic and postnatal development. This pathway remains in the quiescent state in adult tissues but gets activated upon inflammation and injuries. Inhibition of Hh signaling pathway using natural and synthetic compounds has provided an attractive approach for treating cancer and inflammatory diseases. While the majority of Hh pathway inhibitors target the transmembrane protein Smoothened (SMO), some small molecules that target the signaling cascade downstream of SMO are of particular interest. Substantial efforts are being made to develop new molecules targeting various components of the Hh signaling pathway. Here, we have discussed the discovery of small molecules as Hh inhibitors from the diverse chemical background. Also, some of the recently identified natural products have been included as a separate section. Extensive structure-activity relationship (SAR) of each chemical class is the focus of this review. Also, clinically advanced molecules are discussed from the last 5 to 7 years. Nanomedicine-based delivery approaches for Hh pathway inhibitors are also discussed concisely.

Targeted next-generation sequencing reveals recurrence-associated genomic alterations in early-stage non-small cell lung cancer

Purpose

The identification of genomic alterations related to recurrence in early-stage non-small cell lung cancer (NSCLC) patients may help better stratify high-risk individuals and guide treatment strategies. This study aimed to identify the molecular biomarkers of recurrence in early-stage NSCLC.

Results

Of the 42 tumors evaluable for genomic alterations, TP53 and EGFR were the most frequent alterations with population frequency 52.4% and 50.0%, respectively. Fusion genes were detected in four patients, which had lower mutational burden and relatively better genomic stability. EGFR mutation and fusion gene were mutually exclusive in this study. CDKN2A, FAS, SUFU and SMARCA4 genomic alterations were only observed in the relapsed patients. Increased copy number alteration index was observed in early relapsed patients. Among these genomic alterations, early-stage NSCLCs harboring CDKN2A, FAS, SUFU and SMARCA4 genomic alterations were found to be significantly associated with recurrence. Some of these new findings were validated using The Cancer Genome Atlas (TCGA) dataset.

Conclusions

The genomic alterations of CDKN2A, FAS, SUFU and SMARCA4 in early-stage NSCLC are found to be associated with recurrence, but confirmation in a larger independent cohort is required to define the clinical impact.

Materials and Methods

Paired primary tumor and normal lung tissue samples were collected for targeted next-generation sequencing analysis. A panel targets exons for 440 genes was used to assess the mutational and copy number status of selected genes in three clinically relevant groups of stage I/II NSCLC patients: 1) Early relapse; 2) Late relapse; and 3) No relapse.

Hedgehog Signaling in Cancer: A Prospective Therapeutic Target for Eradicating Cancer Stem Cells

The Hedgehog (Hh) pathway is a signaling cascade that plays a crucial role in many fundamental processes, including embryonic development and tissue homeostasis. Moreover, emerging evidence has suggested that aberrant activation of Hh is associated with neoplastic transformations, malignant tumors, and drug resistance of a multitude of cancers. At the molecular level, it has been shown that Hh signaling drives the progression of cancers by regulating cancer cell proliferation, malignancy, metastasis, and the expansion of cancer stem cells (CSCs). Thus, a comprehensive understanding of Hh signaling during tumorigenesis and development of chemoresistance is necessary in order to identify potential therapeutic strategies to target various human cancers and their relapse. In this review, we discuss the molecular basis of the Hh signaling pathway and its abnormal activation in several types of human cancers. We also highlight the clinical development of Hh signaling inhibitors for cancer therapy as well as CSC-targeted therapy.

Novel targeting approaches and signaling pathways of colorectal cancer: An insight

Colorectal cancer (CRC) is the third most common cancer of mortality in the world. Chemotherapy based treatment leads to innumerable side effects as it delivers the anticancer drug to both normal cells besides cancer cells. Sonic Hedgehog (SHH), Wnt wingless-type mouse mammary tumor virus/β-catenin, transforming growth factor-β/SMAD, epidermal growth factor receptor and Notch are the main signaling pathways involved in the progression of CRC. Targeted therapies necessitate information regarding the particular aberrant pathways. Advancements in gene therapies have resulted in the recognition of novel therapeutic targets related with these signal-transduction cascades. CRC is a step-wise process where mutations occur over the time and activation of oncogenes and deactivation of tissue suppressor genes takes place. Genetic changes which are responsible for the induction of carcinogenesis include loss of heterozygosity in tumor suppressor genes such as adenomatous polyposis coli, mutation or deletion of genes like p53 and K-ras. Therefore, many gene-therapy approaches like gene correction, virus-directed enzyme-prodrug therapy, immunogenetic manipulation and virotherapy are currently being explored. Development of novel strategies for the safe and effective delivery of drugs to the cancerous site is the need of the hour. This editorial accentuates different novel strategies with emphasis on gene therapy and immunotherapy for the management of CRC.