Hedgehog signal transduction: from flies to vertebrates

GIMAP7 inhibits epithelial-mesenchymal transition and glycolysis in lung adenocarcinoma cells via regulating the Smo/AMPK signaling pathway

BACKGROUND

GTPase immunity-associated protein 7 (GIMAP7) has been previously recognized as a prognostic marker in pan-cancer. Our objective was to explore the function of GIMAP7 in the progression of lung adenocarcinoma (LUAD).

METHODS

GIMAP7 was overexpressed by transfection with GIMAP7 plasmid, and knocked down using siRNAs. The biological functions of GIMAP7 were examined by employing CCK-8, EdU, colony formation, flow cytometry, wound healing, and transwell assays. The effects of GIMAP7 on the extracellular acidification rate (ECAR), oxygen consumption rate (OCR), lactate production, and glucose uptake were evaluated. In addition, the related mRNA and protein expression was detected employing immunohistochemical, western blot, and qRT-PCR. A xenograft tumor model was established in nude mice to evaluate the effects of GIMAP7 on tumor growth.

RESULTS

GIMAP7 was lowly expressed in LUAD tissues and cells. GIMAP7 inhibited the proliferation, mobility, EMT, glycolysis, but promoted apoptosis in LUAD cells. Moreover, we also confirmed that GIMAP7 suppressed Smo/AMPK signaling in LUAD cells. By adding the Smo agonist SAG and AMPK agonist GSK621, the results of rescue experiments further verified that GIMAP7 played a role in LUAD inhibition through inhibition of the Smo/AMPK signaling pathway. Furthermore, the role of GIMAP7 in inhibiting tumor growth was verified in vivo.

CONCLUSIONS

These results demonstrate that GIMAP7 could inhibit cell proliferation, mobility and glycolysis, but accelerate apoptosis via repressing the Smo/AMPK signaling pathway in LUAD.

PTCH1 mutant small cell glioblastoma in a patient with Gorlin syndrome: A case report

Gorlin syndrome or nevoid basal cell carcinoma syndrome is a rare genetic disease characterized by predisposition to congenital defects, basal cell carcinomas and medulloblastoma. The syndrome results from a heritable mutation in PATCHED1 (PTCH1), causing constitutive activation of the Hedgehog pathway. The present study described a patient with Gorlin syndrome who presented early in life with characteristic basal cell carcinomas and later developed a small cell glioblastoma (GBM), World Health Organization grade IV, associated with a Patched 1 (PTCH1) N97fs*43 mutation. Comprehensive genomic profiling of GBM tissues also revealed multiple co-occurring alterations including cyclin-dependent kinase 4 (CDK4) amplification, receptor tyrosine-protein kinase 3 (ERBB3) amplification, a fibroblast growth factor receptor 1 and transforming acidic coiled-coil containing protein 1 (FGFR1-TACC1) fusion, zinc finger protein (GLI1) amplification, E3 ubiquitin-protein ligase (MDM2) amplification and spectrin α chain, erythrocytic 1 (SPTA1) T1151fs*24. After the biopsy, imaging revealed extensive leptomeningeal enhancement intracranially and around the cervical spinal cord due to leptomeningeal disease. The patient underwent craniospinal radiation followed by 6 months of adjuvant temozolomide (150 mg/m²) with good response. She was then treated with vismodegib for 11 months, first combined with temozolomide and then with bevacizumab, until disease progression was noted on MRI, with no significant toxicities associated with the combination therapy. She received additional therapies but ultimately succumbed to the disease four months later. The current study presents the first documentation in the literature of a primary (non-radiation induced) glioblastoma secondary to Gorlin syndrome. Based on this clinical experience, vismodegib should be considered in combination with standard-of-care therapies for patients with known Gorlin syndrome-associated glioblastomas and sonic hedgehog pathway mutations.

A Four-Gene Signature Model Improves the Prediction of Distant Metastasis in Patients with Nasopharyngeal Carcinoma: A Retrospective, Three-Center Observational Study

Background: Similar to that in other malignant tumors, distant metastasis is one of the most important causes of poor prognosis in nasopharyngeal carcinoma (NPC). However, the genetic hallmarks and networks that regulate the distant metastasis of NPC are not fully understood. Methods: In this study, we performed high-throughput screening of mRNA expression profiles in 92 NPC samples collected from 3hospitals and detected the mRNA expression levels of 31,503 genes in these samples. Gene functional enrichment analyses were performed using gene set enrichment analysis (GSEA). Least absolute shrinkage and selection operator (LASSO) was applied to select prognostic genes and a Cox proportional hazards regression model including these genes was constructed to predict prognosis. The Kaplan-Meier curve and time-dependent receiver operating characteristic (ROC) curve were plotted to assess the performance of this model. Univariate and multivariate analyses were performed using the Cox proportion hazard model to test the independence of prognostic effect of gene model and other clinical features. Results: A total of 1837 differentially expressed genes between patients with and without distant metastasis were identified in the training cohort, including 869 upregulated genes and 968 downregulated genes. Six gene sets, including the Wnt/β catenin signaling pathway, hedgehog (Hh) signaling pathway, Notch signaling pathway, mitotic spindle, apical surface, and estrogen response late, were enriched in patients with distant metastasis. A four-gene signature model was constructed in the training cohort, and according to the time-dependent ROC curve, this model had certain accuracy in predicting distant metastasis-free survival (DMFS) in both the training and validation cohorts. Conclusion: We developed a four-gene signature model that can evaluate the distant metastasis risk of NPC patients and may also provide novel therapeutic targets for NPC treatment in the near future.

The Pleiotropic Intricacies of Hedgehog Signaling: From Craniofacial Patterning to Carcinogenesis

Hedgehog signaling was discovered more than 40 years ago in experiments demonstrating that it is a fundamental mediator of limb development. Since that time, it has been shown to be important in development, homeostasis, and disease. The hedgehog pathway proceeds through a pathway highly conserved throughout animals beginning with the extracellular diffusion of hedgehog ligands, proceeding through an intracellular signaling cascade, and ending with the activation of specific target genes. A vast amount of research has been done elucidating hedgehog signaling mechanisms and regulation. This research has found a complex system of genetics and signaling that helps determine how organisms develop and function. This review provides an overview of what is known about hedgehog genetics and signaling, followed by an in-depth discussion of the role of hedgehog signaling in craniofacial development and carcinogenesis.

Physalin A, 13,14-Seco-16, 24-Cyclo-Steroid, Inhibits Stemness of Breast Cancer Cells by Regulation of Hedgehog Signaling Pathway and Yes-Associated Protein 1 (YAP1)

The Hedgehog (HH) signaling pathway plays an important role in embryonic development and adult organ homeostasis. Aberrant activity of the Hedgehog signaling pathway induces many developmental disorders and cancers. Recent studies have investigated the relationship of this pathway with various cancers. GPCR-like protein Smoothened (SMO) and the glioma-associated oncogene (GLI1) are the main effectors of Hedgehog signaling. Physalin A, a bioactive substance derived from Physalis alkekengi, inhibits proliferation and migration of breast cancer cells and mammospheres formation. Physalin A-induced apoptosis and growth inhibition of mammospheres, and reduced transcripts of cancer stem cell (CSC) marker genes. Physalin A reduced protein expressions of SMO and GLI1/2. Down-regulation of SMO and GLI1 using siRNA inhibited mammosphere formation. Physalin A reduced mammosphere formation by reducing GLI1 gene expression. Down-regulation of GLI1 reduced CSC marker genes. Physalin A reduced protein level of YAP1. Down-regulation of YAP1 using siRNA inhibited mammosphere formation. Physalin A reduced mammosphere formation through reduction of YAP1 gene expression. Down-regulation of YAP1 reduced CSC marker genes. We showed that treatment of MDA-MB-231 breast cancer cells with GLI1 siRNA induced inhibition of mammosphere formation and down-regulation of YAP1, a Hippo pathway effector. These results show that Hippo signaling is regulated by the Hedgehog signaling pathway. Physalin A also inhibits the canonical Hedgehog and Hippo signaling pathways, CSC-specific genes, and the formation of mammospheres. These findings suggest that physalin A is a potential therapeutic agent for targeting CSCs.

Insight into the role of multiple signaling pathways in regulating cancer stem cells of gynecologic cancers

Mounting evidence has demonstrated that a myriad of developmental signaling pathways, such as the Wnt, Notch, Hedgehog and Hippo, are frequently deregulated and play a critical role in regulating cancer stem cell (CSC) activity in human cancers, including gynecologic malignancies. In this review article, we describe an overview of various signaling pathways in human cancers. We further discuss the developmental roles how these pathways regulate CSCs from experimental evidences in gynecologic cancers. Moreover, we mention several compounds targeting CSCs in gynecologic cancers to enhance the treatment outcomes. Therefore, these signaling pathways might be the potential targets for developing targeted therapy in gynecologic cancers.

Functions and Targets of miR-335 in Cancer

MicroRNAs (miRNAs) are small non-coding RNAs (18~25 nt in length) that act as master regulators of eukaryotic gene expression. They might play an oncogenic or tumor-suppressive role in multiple cancers. In recent decades, several studies have focused on the functions and mechanisms of miR-335 in cancer. The expression level of miR-335 in tissues and cells varies with cancer types, and miR-335 has been proposed as a potential biomarker for the prognosis of cancer. Besides, miR-335 may serve as an oncogene or tumor suppressor via regulating different targets or pathways in tumor initiation, development, and metastasis. Furthermore, miR-335 also influences tumor microenvironment and drug sensitivity. MiR-335 is regulated by various factors such as lncRNAs and microRNAs. In this review, we reveal the functions and targets of miR-335 in various cancers and its potential application as a possible biomarker in prognostic judgment and treatment of malignant tumors.

Exploring Sonic Hedgehog Cell Signaling in Neurogenesis: Its Potential Role in Depressive Behavior

Depression is the most prevalent form of neuropsychiatric disorder affecting all age groups globally. As per the estimation of the World Health Organization (WHO), depression will develop into the foremost reason for disability globally by the year 2030. The primary neurobiological mechanism implicated in depression remains ambiguous; however, dysregulation of molecular and signaling transductions results in depressive disorders. Several theories have been developed to explain the pathogenesis of depression, however, none of them completely explained all aspects of depressive-pathogenesis. In the current review, we aimed to explore the role of the sonic hedgehog (Shh) signaling pathway in the development of the depressive disorder and its potential as the therapeutic target. Shh signaling has a crucial function in neurogenesis and neural tube patterning during the development of the central nervous system (CNS). Shh signaling performs a basic function in embryogenesis and hippocampal neurogenesis. Moreover, antidepressants are also known to enhance neurogenesis in the hippocampus, which further suggests the potential of Shh signaling. Furthermore, there is decreased expression of a glioma-associated oncogene (Gli1) and Smoothened (Smo) in depression. Moreover, antidepressants also regulate brain-derived neurotrophic factor (BDNF) and wingless protein (Wnt) signaling, therefore, Shh may be implicated in the pathogenesis of the depressive disorder. Deregulation of Shh signaling in CNS results in neurological disorders such as depression.

Downregulation of miR-506-3p Facilitates EGFR-TKI Resistance through Induction of Sonic Hedgehog Signaling in Non-Small-Cell Lung Cancer Cell Lines

Non-small-cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation eventually develop resistance to EGFR-targeted tyrosine kinase inhibitors (TKIs). Treatment resistance remains the primary obstacle to the successful treatment of NSCLC. Although drug resistance mechanisms have been studied extensively in NSCLC, the regulation of these mechanisms has not been completely understood. Recently, increasing numbers of microRNAs (miRNAs) are implicated in EGFR-TKI resistance, indicating that miRNAs may serve as novel targets and may hold promise as predictive biomarkers for anti-EGFR therapy. MicroRNA-506 (miR-506) has been identified as a tumor suppressor in many cancers, including lung cancer; however, the role of miR-506 in lung cancer chemoresistance has not yet been addressed. Here we report that miR-506-3p expression was markedly reduced in erlotinib-resistant (ER) cells. We identified Sonic Hedgehog (SHH) as a novel target of miR-506-3p, aberrantly activated in ER cells. The ectopic overexpression of miR-506-3p in ER cells downregulates SHH signaling, increases E-cadherin expression, and inhibits the expression of vimentin, thus counteracting the epithelial-mesenchymal transition (EMT)-mediated chemoresistance. Our results advanced our understanding of the molecular mechanisms underlying EGFR-TKI resistance and indicated that the miR-506/SHH axis might represent a novel therapeutic target for future EGFR mutated lung cancer treatment.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

Acute Alcohol Intoxication Impairs Sonic Hedgehog-Gli1 Signaling and Activation of Primitive Hematopoietic Precursor Cells in the Early Stage of Host Response to Bacteremia

BACKGROUND

Activation of hematopoietic stem cells [HSCs, lineage(lin)- stem cell growth factor receptor (c-kit)+ stem cell antigen-1(Sca-1)+ , or LKS cells in mice] is critical for initiating the granulopoietic response. This study determined the effect of alcohol exposure on sonic hedgehog (SHH) signaling in the regulation of HSC activation during bacteremia.

METHODS

Acute alcohol intoxication was induced in mice by intraperitoneal (i.p.) injection of 20% alcohol (5 g alcohol/kg body weight). Control mice received i.p. saline. Thirty minutes later, mice were intravenously (i.v.) injected with Escherichia coli (E. coli, 1 to 5 × 107 CFUs/mouse) or saline.

RESULTS

SHH expression by lineage-negative bone marrow cells (BMCs) was significantly increased 24 hours after E. coli infection. Extracellular signal-regulated kinase 1/2 (ERK1/2)-specificity protein 1 (Sp1) signaling promotes SHH expression. ERK1/2 was markedly activated in BMCs 8 hours following E. coli infection. Alcohol suppressed both the activation of ERK1/2 and up-regulation of SHH expression following E. coli infection. E. coli infection up-regulated GLI family zinc finger 1 (Gli1) gene expression by BMCs and increased Gli1 protein content in LKS cells. The extent of Gli1 expression was correlated with the activity of proliferation in LKS cells. Alcohol inhibited up-regulation of Gli1 expression and activation of LKS cells in response to E. coli infection. Alcohol also interrupted the granulopoietic response to bacteremia.

CONCLUSION

These data show that alcohol disrupts SHH-Gli1 signaling and HSC activation in the early stage of the granulopoietic response, which may serve as an important mechanism underlying the impairment of immune defense against bacterial infection in host excessively consuming alcohol.

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.

Participation of HHIP Gene Variants in COPD Susceptibility, Lung Function, and Serum and Sputum Protein Levels in Women Exposed to Biomass-Burning Smoke

BACKGROUND

A variety of organic materials (biomass) are burned for cooking and heating purposes in poorly ventilated houses; smoke from biomass combustion is considered an environmental risk factor for chronic obstructive pulmonary disease COPD. In this study, we attempted to determine the participation of single-nucleotide variants in the HHIP (hedgehog-interacting protein) gene in lung function, HHIP serum levels, and HHIP sputum supernatant levels in Mexican women with and without COPD who were exposed to biomass-burning smoke.

METHODS

In a case-control study (COPD-BS, n = 186, BBES, n = 557) in Mexican women, three SNPs (rs13147758, rs1828591, and rs13118928) in the HHIP gene were analyzed by qPCR; serum and supernatant sputum protein levels were determined through ELISA.

RESULTS

The rs13118928 GG genotype is associated with decreased risk (p = 0.021, OR = 0.51, CI95% = 0.27-0.97) and the recessive genetic model (p = 0.0023); the rs1828591-rs13118928 GG haplotype is also associated with decreased risk (p = 0.04, OR = 0.65, CI95% 0.43-0.98). By the dominant model (rs13118928), the subjects with one or two copies of the minor allele (G) exhibited higher protein levels. Additionally, two correlations with the AG genotype were identified: BBES with FEV1 (p = 0.03, r2 = 0.53) and COPD-BS with FEV1/FVC (p = 0.012, r2 = 0.54).

CONCLUSIONS

Single-nucleotide variants in the HHIP gene are associated with decreased COPD risk, higher HHIP serum levels, and better lung function in Mexican women exposed to biomass burning.

Ixazomib Improves Bone Remodeling and Counteracts sonic Hedgehog signaling Inhibition Mediated by Myeloma Cells

Multiple myeloma (MM) is a clonal B-cell malignancy characterized by an accumulation of plasma cells (PC) in the bone marrow (BM), leading to bone loss and BM failure. Osteolytic bone disease is a common manifestation observed in MM patients and represents the most severe cause of morbidity, leading to progressive skeletal damage and disabilities. Pathogenetic mechanisms of MM bone disease are closely linked to PCs and osteoclast (OCs) hyperactivity, coupled with defective osteoblasts (OBs) function that is unable to counteract bone resorption. The aim of the present study was to investigate the effects of Ixazomib, a third-generation proteasome inhibitor, on osteoclastogenesis and osteogenic differentiation. We found that Ixazomib was able to reduce differentiation of human monocytes into OCs and to inhibit the expression of OC markers when added to the OC medium. Concurrently, Ixazomib was able to stimulate osteogenic differentiation of human mesenchymal stromal cells (MSCs), increasing osteogenic markers, either alone or in combination with the osteogenic medium. Given the key role of Sonic Hedgehog (SHH) signaling in bone homeostasis, we further investigated Ixazomib-induced SHH pathway activation. This set of experiments showed that Ixazomib, but not Bortezomib, was able to bind the Smoothened (SMO) receptor leading to nuclear translocation of GLI1 in human MSCs. Moreover, we demonstrated that PCs act as GLI1 suppressors on MSCs, thus reducing the potential of MSCs to differentiate in OBs. In conclusion, our data demonstrated that Ixazomib regulates bone remodeling by decreasing osteoclastogenesis and prompting osteoblast differentiation via the canonical SHH signaling pathway activation, thus, representing a promising therapeutic option to improve the complex pathological condition of MM patients.

Targeting signalling pathways and the immune microenvironment of cancer stem cells - a clinical update

Cancer stem cells (CSCs) have important roles in tumour development, relapse and metastasis; the intrinsic self-renewal characteristics and tumorigenic properties of these cells provide them with unique capabilities to resist diverse forms of anticancer therapy, seed recurrent tumours, and disseminate to and colonize distant tissues. The findings of several studies indicate that CSCs originate from non-malignant stem or progenitor cells. Accordingly, inhibition of developmental signalling pathways that are crucial for stem and progenitor cell homeostasis and function, such as the Notch, WNT, Hedgehog and Hippo signalling cascades, continues to be pursued across multiple cancer types as a strategy for targeting the CSCs hypothesized to drive cancer progression - with some success in certain malignancies. In addition, with the renaissance of anticancer immunotherapy, a better understanding of the interplay between CSCs and the tumour immune microenvironment might be the key to unlocking a new era of oncological treatments associated with a reduced propensity for the development of resistance and with enhanced antimetastatic activity, thus ultimately resulting in improved patient outcomes. Herein, we provide an update on the progress to date in the clinical development of therapeutics targeting the Notch, WNT, Hedgehog and Hippo pathways. We also discuss the interactions between CSCs and the immune system, including the potential immunological effects of agents targeting CSC-associated developmental signalling pathways, and provide an overview of the emerging approaches to CSC-targeted immunotherapy.

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.

Smoothened stabilizes and protects TRAF6 from degradation: A novel non-canonical role of smoothened with implications in lymphoma biology

Tumor necrosis factor receptor-associated factor 6 (TRAF6), an (K63) E3-ligase, plays a role in many biological processes and its activity is relevant in diffuse large B cell lymphoma (DLBCL) biology. Although molecules that trigger TRAF6 activation have been defined, those that stabilize TRAF6 and/or enhance TRAF6 function remain largely unclear. We found that TRAF6 amplifies pAKT signaling in DLBCL. Moreover, TRAF6 activation and stabilization of its ubiquitination profile are facilitated by smoothened (SMO), signal transducer of canonical Hedgehog signaling. Here, we report that SMO is needed to facilitate and maintain TRAF6-dependent elevated pAKT levels, and that the SMO/TRAF6 axis contributes to doxorubicin resistance in DLBCL. Mechanistically, we found that SMO, through its C-terminal tail, stabilizes and protects TRAF6 from degradation, an effect mediated by ubiquitin-specific protease-8. Moreover, this functional link between SMO and TRAF6 is reflected in DLBCL patients where high expression of both molecules correlates with poor prognosis. In summary, our study reveals a novel cell survival mechanism in which SMO stabilizes and protects TRAF6 from degradation. The axis SMO/TRAF6/AKT is highly relevant in the biology of DLBCL and is involved in doxorubicin resistance.

GLI1 inhibitor GANT61 exhibits antitumor efficacy in T-cell lymphoma cells through down-regulation of p-STAT3 and SOCS3

T-cell lymphomas are lymphoid malignancies with aggressive clinical course and poor prognosis. Increasing evidences suggest that deregulation of signal transducer and activator of transcription-3 (STAT3) and suppressor of cytokine signaling 3 (SOCS3) is associated with the pathogenesis of T-cell lymphomas. The hedgehog (Hh)/glioma-associated oncogene-1 (GLI1) pathway, aberrantly activated in a number of tumors, has also been extensively studied. We found that protein expressions of GL11, p-STAT3, STAT3, and SOCS3 were up-regulated in T-cell lymphoma tissues and cell lines. Moreover, the protein expressions of p-STAT3 and SOCS3 were positively correlated with GLI1 in T-cell lymphomas. GLI1 inhibitor GANT61 and lentivirus-mediated siGLI1 exhibited inhibitory effects in the three T-cell lines (Jurkat, Karpass299 and Myla3676 cells). The protein expressions of p-STAT3 and SOCS3 were decreased accompanied with the inhibition of GLI1. These findings indicated that GANT61 is a promising agent against T-cell lymphoma and the antitumor activity might be partly mediated by down-regulating p-STAT3 and SOCS3.

Sonic Hedgehog Signaling Regulates Hematopoietic Stem/Progenitor Cell Activation during the Granulopoietic Response to Systemic Bacterial Infection

Activation and reprogramming of hematopoietic stem/progenitor cells play a critical role in the granulopoietic response to bacterial infection. Our current study determined the significance of Sonic hedgehog (SHH) signaling in the regulation of hematopoietic precursor cell activity during the host defense response to systemic bacterial infection. Bacteremia was induced in male Balb/c mice via intravenous injection (i.v.) of Escherichia coli (5 × 10⁷ CFUs/mouse). Control mice received i.v. saline. SHH protein level in bone marrow cell (BMC) lysates was markedly increased at both 24 and 48 h of bacteremia. By contrast, the amount of soluble SHH ligand in marrow elutes was significantly reduced. These contrasting alterations suggested that SHH ligand release from BMCs was reduced and/or binding of soluble SHH ligand to BMCs was enhanced. At both 12 and 24 h of bacteremia, SHH mRNA expression by BMCs was significantly upregulated. This upregulation of SHH mRNA expression was followed by a marked increase in SHH protein expression in BMCs. Activation of the ERK1/2–SP1 pathway was involved in mediating the upregulation of SHH gene expression. The major cell type showing the enhancement of SHH expression in the bone marrow was lineage positive cells. Gli1 positioned downstream of the SHH receptor activation serves as a key component of the hedgehog (HH) pathway. Primitive hematopoietic precursor cells exhibited the highest level of baseline Gli1 expression, suggesting that they were active cells responding to SHH ligand stimulation. Along with the increased expression of SHH in the bone marrow, expression of Gli1 by marrow cells was significantly upregulated at both mRNA and protein levels following bacteremia. This enhancement of Gli1 expression was correlated with activation of hematopoietic stem/progenitor cell proliferation. Mice with Gli1 gene deletion showed attenuation in activation of marrow hematopoietic stem/progenitor cell proliferation and inhibition of increase in blood granulocytes following bacteremia. Our results indicate that SHH signaling is critically important in the regulation of hematopoietic stem/progenitor cell activation and reprogramming during the granulopoietic response to serious bacterial infection.

The role of the Hedgehog signaling pathway in cancer: A comprehensive review

The Hedgehog (Hh) signaling pathway was first identified in the common fruit fly. It is a highly conserved evolutionary pathway of signal transmission from the cell membrane to the nucleus. The Hh signaling pathway plays an important role in the embryonic development. It exerts its biological effects through a signaling cascade that culminates in a change of balance between activator and repressor forms of glioma-associated oncogene (Gli) transcription factors. The components of the Hh signaling pathway involved in the signaling transfer to the Gli transcription factors include Hedgehog ligands (Sonic Hh [SHh], Indian Hh [IHh], and Desert Hh [DHh]), Patched receptor (Ptch1, Ptch2), Smoothened receptor (Smo), Suppressor of fused homolog (Sufu), kinesin protein Kif7, protein kinase A (PKA), and cyclic adenosine monophosphate (cAMP). The activator form of Gli travels to the nucleus and stimulates the transcription of the target genes by binding to their promoters. The main target genes of the Hh signaling pathway are PTCH1, PTCH2, and GLI1. Deregulation of the Hh signaling pathway is associated with developmental anomalies and cancer, including Gorlin syndrome, and sporadic cancers, such as basal cell carcinoma, medulloblastoma, pancreatic, breast, colon, ovarian, and small-cell lung carcinomas. The aberrant activation of the Hh signaling pathway is caused by mutations in the related genes (ligand-independent signaling) or by the excessive expression of the Hh signaling molecules (ligand-dependent signaling - autocrine or paracrine). Several Hh signaling pathway inhibitors, such as vismodegib and sonidegib, have been developed for cancer treatment. These drugs are regarded as promising cancer therapies, especially for patients with refractory/advanced cancers.

Pharmacological evaluation of a series of smoothened antagonists in signaling pathways and after topical application in a depilated mouse model

The Hedgehog (HH) pathway has been linked to the formation of basal cell carcinoma (BCC), medulloblastoma, and other cancers. The recently approved orally active drugs vismodegib (GDC-0449) and sonidegib (LDE-225) were not only efficacious for the treatment of advanced or metastatic BCC by antagonizing the smoothened (SMO) receptor, but also produced important side effects, limiting their use for less invasive BCC. Herein, we compared a large series of SMO antagonists, including GDC-0449 and LDE-225, the clinically tested BMS-833923, CUR-61414, cyclopamine, IPI-926 (saridegib), itraconazole, LEQ-506, LY-2940680 (taladegib), PF-04449913 (glasdegib), and TAK-441 as well as preclinical candidates (PF-5274857, MRT-83) in two SMO-dependent cellular assays and for G-protein activation. We report marked differences in inhibitor potencies between compounds as well as a notable disparity between the G-protein assay and the cellular tests, suggesting that classification of drugs is assay dependent. Furthermore, we explored topical efficacies of SMO antagonists on depilated mice using Gli1 and Ptch1 mRNA quantification in skin as biomarkers of the HH signaling inhibition. This topical model rapidly discriminated drugs in terms of efficacies and potencies for inhibition of both biomarkers. SMO antagonists showed also a large variation in their blood and skin partition, suggesting that some drugs are more favorable for topical application. Overall, our data suggested that in vitro and in vivo efficacious drugs such as LEQ-506 and TAK-441 may be of interest for topical treatment of less invasive BCC with minimal side effects.

Metformin exerts anticancer effects through the inhibition of the Sonic hedgehog signaling pathway in breast cancer

Metformin, a widely prescribed antidiabetic drug, has previously been shown to lower the risk of certain types of cancer, including that of breast cancer, and to improve prognosis. Its anticancer effects, which are mediated by the activation of AMP-activated protein kinase (AMPK), have become notable. The Sonic hedgehog (Shh) signaling pathway is involved in changes in mammary ducts and malignant transformation. The aim of the present study was to elucidate the role of the Shh pathway in mediating the anticancer effects of metformin and the correlation between AMPK and the Shh pathway. We investigated the effectiveness of metformin in inhibiting the proliferation, migration, invasion and stemness of breast cancer cells in vitro using RNA extraction and reverse transcription‑polymerase chain reaction (RT-PCR), western blot analysis, cell proliferation assay, scratch-wound assay (cell migration assay), cell invasion assay, mammosphere culture and flow cytometry. In in vivo experiments, a tumor xenograft model was used to detect the effects of metformin on cancer cell proliferation. The results revealed that the treatment of breast cancer cells with metformin led to the inhibition of the Shh signaling pathway. Importantly, metformin inhibited recombinant human Shh (rhShh)‑induced cell migration, invasion, and stemness, and impaired cell proliferation both in vitro and in vivo. Furthermore, the small interfering RNA (siRNA)‑mediated downregulation of AMPK reversed the inhibitory effects of metformin on rhShh‑induced Gli-1 expression and stemness. Our findings identified a role of the Shh signaling pathway in the anticancer effects of metformin in breast cancer. Furthermore, we revealed that the metformin-mediated inhibition of the Shh signaling pathway may be dependent on AMPK.

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

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

Evolutionary genomics and adaptive evolution of the Hedgehog gene family (Shh, Ihh and Dhh) in vertebrates

The Hedgehog (Hh) gene family codes for a class of secreted proteins composed of two active domains that act as signalling molecules during embryo development, namely for the development of the nervous and skeletal systems and the formation of the testis cord. While only one Hh gene is found typically in invertebrate genomes, most vertebrates species have three (Sonic hedgehog – Shh; Indian hedgehog – Ihh; and Desert hedgehog – Dhh), each with different expression patterns and functions, which likely helped promote the increasing complexity of vertebrates and their successful diversification. In this study, we used comparative genomic and adaptive evolutionary analyses to characterize the evolution of the Hh genes in vertebrates following the two major whole genome duplication (WGD) events. To overcome the lack of Hh-coding sequences on avian publicly available databases, we used an extensive dataset of 45 avian and three non-avian reptilian genomes to show that birds have all three Hh paralogs. We find suggestions that following the WGD events, vertebrate Hh paralogous genes evolved independently within similar linkage groups and under different evolutionary rates, especially within the catalytic domain. The structural regions around the ion-binding site were identified to be under positive selection in the signaling domain. These findings contrast with those observed in invertebrates, where different lineages that experienced gene duplication retained similar selective constraints in the Hh orthologs. Our results provide new insights on the evolutionary history of the Hh gene family, the functional roles of these paralogs in vertebrate species, and on the location of mutational hotspots.

The E3 ubiquitin ligase MID1 catalyzes ubiquitination and cleavage of Fu

SHH (Sonic Hedgehog)-GLI signaling plays an important role during embryogenesis and in tumorigenesis. The survival and growth of several types of cancer depend on autonomously activated SHH-GLI signaling. A protein complex containing the ubiquitin ligase MID1 and protein phosphatase 2A regulates the nuclear localization and transcriptional activity of GLI3, a transcriptional effector molecule of SHH, in cancer cell lines with autonomously activated SHH signaling. However, the exact molecular mechanisms that mediate the interaction between MID1 and GLI3 remained unknown. Here, we show that MID1 catalyzes the ubiquitination and proteasomal cleavage of the GLI3 regulator Fu. Our data suggest that Fu ubiquitination and cleavage is one of the key elements connecting the MID1-PP2A protein complex with GLI3 activity control.

New insight into hedgehog signaling in hematological malignancies

The hedgehog (Hh) signaling pathway is well established as being evolutionarily conserved across vertebrates, and is involved in organogenesis, hematopoiesis, embryogenesis and homeostasis of adult tissues. At a microscopic level, the Hh signaling pathway controls the proliferation, apoptosis, cell-cycle and differentiation programs of stem and progenitor cells. Increasing evidence suggests that aberrant activation of the Hh signaling pathway is related to neoplasm, including solid tumors and hematologic malignancies. Currently the Hh signaling pathway has become one of the most studied potential therapeutic targets in hematological malignancies. In this review, we focus on findings related to Hh signaling in the initiation, maintenance, progression and chemoresistance of hematological malignancies, looking forward to better targeted treatment strategies.

A forkhead transcription factor is wound-induced at the planarian midline and required for anterior pole regeneration

Planarian regeneration requires positional information to specify the identity of tissues to be replaced as well as pluripotent neoblasts capable of differentiating into new cell types. We found that wounding elicits rapid expression of a gene encoding a Forkhead-family transcription factor, FoxD. Wound-induced FoxD expression is specific to the ventral midline, is regulated by Hedgehog signaling, and is neoblast-independent. FoxD is subsequently expressed within a medial subpopulation of neoblasts at wounds involving head regeneration. Ultimately, FoxD is co-expressed with multiple anterior markers at the anterior pole. Inhibition of FoxD with RNA interference (RNAi) results in the failure to specify neoblasts expressing anterior markers (notum and prep) and in anterior pole formation defects. FoxD(RNAi) animals fail to regenerate a new midline and to properly pattern the anterior blastema, consistent with a role for the anterior pole in organizing pattern of the regenerating head. Our results suggest that wound signaling activates a forkhead transcription factor at the midline and, if the head is absent, FoxD promotes specification of neoblasts at the prior midline for anterior pole regeneration.

Regeneration is widespread in the animal kingdom. Planarians are able to regenerate entire bodies from almost any fragment type. This ability requires a cell population called neoblasts, which include pluripotent stem cells, for the production of all missing tissues, as well as the information to form and pattern correct new tissue types. Two discrete regions of the body, called poles, are found at the anterior and posterior ends of the animal. Here we investigate the role of a gene encoding a Forkhead-family transcription factor, FoxD, in formation of the anterior pole. FoxD is expressed at the anterior pole and following injury, FoxD expression is induced in a restricted midline region of the animal. Next, FoxD is expressed in a subset of neoblasts at the midline. Inhibition of FoxD with RNA interference results in defective anterior pole regeneration, and subsequent failure to regenerate an organized head pattern around a new midline. FoxD is specifically required for anterior regeneration. These results suggest that there is a regenerative connection between the midline and the anterior pole.

Hedgehog signaling regulates drug sensitivity by targeting ABC transporters ABCB1 and ABCG2 in epithelial ovarian cancer

A major challenge of successful chemotherapy in ovarian cancer is overcoming intrinsic or acquired multi-drug resistance caused by active drug efflux mediated by ATP-binding cassette (ABC) transporters. Regulation of these transporters in ovarian cancer is poorly understood. We have found that abnormal expression of the hedgehog (Hh) signaling pathway transcription factor Gli1 is involved in the regulation of ABC transporters ABCB1 and ABCG2 in ovarian cancer. Hh is a known regulator of cancer cell proliferation and differentiation in several other types of invasive and metastatic malignancies. Our work has demonstrated that Gli1 is abnormally activated in a portion of ovarian cancers. Inhibition of Gli1 expression decreases ABCB1 and ABCG2 gene expression levels and enhances the response of ovarian cancer cells to certain chemotherapeutic drugs. The underlying mechanism is a direct association of Gli1 with a specific consensus sequence located in the promoter region of ABCB1 and ABCG2 genes. This study provides new understanding of ABC gene regulation by Hh signaling pathway, which may lead to the identification of new markers to detect and to anticipate ovarian cancer chemotherapy drug sensitivity.

Defining causative factors contributing in the activation of hedgehog signaling in diffuse large B-cell lymphoma

Hedgehog (Hh) signaling pathway is activated in diffuse large B-cell lymphoma (DLBCL). Genetic abnormalities that explain activation of Hh signaling in DLBCL are unknown. We investigate the presence of amplifications of Hh genes that might result in activation of this pathway in DLBCL. Our data showed few extra copies of GLI1 and SMO due to chromosomal aneuploidies in a subset of DLBCL cell lines. We also showed that pharmacologic inhibition of PI3K/AKT and NF-κB pathways resulted in decreased expression of GLI1 and Hh ligands. In conclusion, our data support the hypothesis that aberrant activation of Hh signaling in DLBCL mainly results from integration of deregulated oncogenic signaling inputs converging into Hh signaling.

Hedgehog signaling and osteoblast gene expression are regulated by purmorphamine in human mesenchymal stem cells

Several biological events are controlled by Hedgehog (Hh) signaling, including osteoblast phenotype development. This study aimed at evaluating the gene expression profile of human mesenchymal stem cells (hMSCs) treated with the Hh agonist, purmorphamine, focusing on Hh signaling and osteoblast differentiation. hMSCs from bone marrow were cultured in non-osteogenic medium with or without purmorphamine (2 µM) for periods of up to 14 days. Purmorphamine up-regulated gene expression of the mediators of Hh pathway, SMO, PTCH1, GLI1, and GLI2. The activation of Hh pathway by purmorphamine increased the expression of several genes (e.g., RUNX2 and BMPs) related to osteogenesis. Our results indicated that purmorphamine triggers Hh signaling pathway in hMSCs, inducing an increase in the expression of a set of genes involved in the osteoblast differentiation program. Thus, we conclude that Hh is a crucial pathway in the commitment of undifferentiated cells to the osteoblast lineage.

ABCG2 is a direct transcriptional target of hedgehog signaling and involved in stroma-induced drug tolerance in diffuse large B-cell lymphoma

Successful treatment of diffuse large B-cell lymphoma (DLBCL) is frequently hindered by development of resistance to conventional chemotherapy resulting in disease relapse and high mortality. High expression of anti-apoptotic and/or drug transporter proteins induced by oncogenic signaling pathways has been implicated in the development of chemoresistance in cancer. Previously, our studies showed high expression of ATP-binding cassette drug transporter ABCG2 in DLBCL correlated inversely with disease-free and failure-free survival. In this study, we have implicated activated hedgehog (Hh) signaling pathway as a key factor behind high ABCG2 expression in DLBCL through direct upregulation of ABCG2 gene transcription. We have identified a single binding site for GLI transcription factors in the ABCG2 promoter and established its functionality using luciferase reporter, site-directed mutagenesis and chromatin-immunoprecipitation assays. Furthermore, in DLBCL tumor samples, significantly high ABCG2 and GLI1 levels were found in DLBCL tumors with lymph node involvement in comparison to DLBCL tumor cells collected from pleural and/or peritoneal effusions. This suggests a role for the stromal microenvironment in maintaining high levels of ABCG2 and GLI1. Accordingly, in vitro co-culture of DLBCL cells with HS-5 stromal cells increased ABCG2 mRNA and protein levels by paracrine activation of Hh signaling. In addition to ABCG2, co-culture of DLBCL cells with HS-5 cells also resulted in increase expression of the antiapoptotic proteins BCL2, BCL-xL and BCL2A1 and in induced chemotolerance to doxorubicin and methotrexate, drugs routinely used for the treatment of DLBCL. Similarly, activation of Hh signaling in DLBCL cell lines with recombinant Shh N-terminal peptide resulted in increased expression of BCL2 and ABCG2 associated with increased chemotolerance. Finally, functional inhibition of ABCG2 drug efflux activity with fumitremorgin (FTC) or inhibition of Hh signaling with cyclopamine-KAAD abrogated the stroma-induced chemotolerance suggesting that targeting ABCG2 and Hh signaling may have therapeutic value in overcoming chemoresistance in DLBCL.

An 8.9 year old girl with autism and Gorlin syndrome

We present an 8.9 year old girl diagnosed with autism and macrocrania. Because of macrocrania, hypertelorism and epidermal punctiform lesions in the palm of the hand, Gorlin syndrome was clinically suspected and molecularly confirmed by finding a deletion of 22 base pairs in the PTCH1 gene. The possibility of an association between autism and Gorlin syndrome is discussed.

Glioma-associated oncogene homologue 3, a hedgehog transcription factor, is highly expressed in Hodgkin and Reed-Sternberg cells of classical Hodgkin lymphoma

The hedgehog signaling pathway has been shown to play a pathogenic role in diffuse large B-cell lymphoma and anaplastic large cell lymphoma, but has not been assessed in classical Hodgkin lymphoma. Glioma-associated oncogene homologues 1, 2, and 3 are transcriptional effectors of the hedgehog pathway. In this study, we first used real-time quantitative polymerase chain reaction to investigate the expressions of GLI1, GLI2, and GLI3 in 3 classical Hodgkin lymphoma cell lines. GLI1 and GLI2 were variably expressed, but GLI3 was highly expressed in all cell lines. We then used immunohistochemistry to assess glioma-associated oncogene homologues 1, 2, and 3 in 39 classical Hodgkin lymphoma patient samples. Glioma-associated oncogene homologues 1 and 2 were weakly to variably expressed in a subset of classical Hodgkin lymphoma patient samples. In contrast, glioma-associated oncogene homologue 3 showed strong, uniform nuclear expression in virtually all Hodgkin/Reed-Stenberg cells. We then performed an immunohistochemical survey of glioma-associated oncogene homologue 3 expression in 13 cases of nodular lymphocyte predominant Hodgkin lymphoma and 218 non-Hodgkin lymphomas. Most other lymphoma types showed variable or no expression of glioma-associated oncogene homologue 3, with a minor subset of cases of nodular lymphocyte predominant Hodgkin lymphoma, ALK-positive and ALK-negative anaplastic large cell lymphoma, and B-cell lymphoma, unclassifiable with features intermediate between diffuse large B-cell lymphoma and classical Hodgkin lymphoma showing a glioma-associated oncogene homologue 3 staining pattern indistinguishable from classical Hodgkin lymphoma. Our data provide a rationale to further investigate the biologic significance of glioma-associated oncogene homologue 3 in classical Hodgkin lymphoma biology.

Expression of hedgehog signaling molecules in Merkel cell carcinoma

BACKGROUND

The Hedgehog signaling pathway is important for human development and carcinogenesis in various malignancies.

METHODS

One tissue microarray with triplets of 28 samples from 25 patients with Merkel cell carcinoma (MCC) was constructed. Six samples of normal skin and 5 samples of normal oral mucosa served as controls. All samples were analyzed immunohistochemically with antibodies directed against Sonic hedgehog, Indian hedgehog, Patched, Smoothened, Gli-1, Gli-2, and Gli-3.

RESULTS

All investigated proteins were frequently and intensely overexpressed in MCCs (Sonic hedgehog, 93%; Indian hedgehog, 84%; Patched, 86%; Smoothened, 79%; Gli-1, 79%; Gli-2, 79%; Gli-3, 86%) compared with control samples. High levels of Patched and Indian hedgehog were significantly associated with an increase in patients overall (p = .015) and recurrence-free survival (p = .011), respectively.

CONCLUSIONS

Our results indicate that the Hedgehog signaling pathway is strongly activated in MCC and thus may play a role in carcinogenesis.

The Hedgehog morphogen in myocardial ischemia-reperfusion injury

The developmental Hedgehog (Hh) protein family is known to be pivotal in many embryonic patterning events and the number of processes in which Hh plays an essential role is expanding persistently. Recently, it has become clear that the Hh pathway is not only active in the developing embryo but also in the adult organism. For example, Hh has been suggested to salvage ischemia-induced tissue damage although endogenous Hh might be deleterious during the early phase of myocardial ischemia-reperfusion. The current review provides an overview of the history of Hh biology and discusses some novel insights on Hh cell biology. Hh function in pathophysiology as well as recent findings concerning Hh signaling in ischemia models, especially in light of cardiovascular disease, is discussed in more detail and future perspectives are proposed.

Hedgehog signaling and gastrointestinal cancer

Hedgehog (Hh) signaling is critical for embryonic development and in differentiation, proliferation, and maintenance of multiple adult tissues. De-regulation of the Hh pathway is associated with birth defects and cancer. In the gastrointestinal tract, Hh ligands Sonic (Shh) and Indian (Ihh), as well as the receptor Patched (Ptch1), and transcription factors of Glioblastoma family (Gli) are all expressed during development. In the adult, Shh expression is restricted to the stomach and colon, while Ihh expression occurs throughout the luminal gastrointestinal tract, its expression being highest in the proximal duodenum. Several studies have demonstrated a requirement for Hh signaling during gastrointestinal tract development. However to date, the specific role of the Hh pathway in the adult stomach and intestine is not completely understood. The current review will place into context the implications of recent published data related to the biochemistry and cell biology of Hh signaling on the luminal gastrointestinal tract during development, normal physiology and subsequently carcinogenesis.

Hedgehog signaling pathway is activated in diffuse large B-cell lymphoma and contributes to tumor cell survival and proliferation

Hedgehog (HH) signaling is important in the pathogenesis of several malignancies. Recently, we described that HH signaling proteins are commonly expressed in diffuse large B-cell lymphoma (DLBCL); however, the functional role of HH pathway in DLBCL has not been explored. Here, we assessed the possibility that HH pathway activation contributes to the survival of DLBCL. We found that HH signaling inhibition induces predominantly cell-cycle arrest in DLBCL cells of germinal center (GC) B-cell type, and apoptosis in DLBCL cells of activated B-cell (ABC) type. Apoptosis after HH signaling inhibition in DLBCL cells of ABC type was associated with downregulation of BCL2; however HH inhibition was not associated with BCL2 downregulation in DLBCL of GC type. Functional inhibition of BCL2 significantly increased apoptosis induced by HH inhibition in DLBCL cells of both types. We also showed that DLBCL cells synthesize, secrete and respond to endogenous HH ligands, providing support for the existence of an autocrine HH signaling loop. Our findings provide novel evidence that dysregulation of HH pathway is involved in the biology of DLBCL and have significant therapeutic implications as they identify HH signaling as a potential therapeutic target in DLBCL, in particular for those lymphomas expressing the HH receptor smoothened.

Arrestin development: emerging roles for beta-arrestins in developmental signaling pathways

Arrestins were identified as mediators of G protein-coupled receptor (GPCR) desensitization and endocytosis. However, it is now clear that they scaffold many intracellular signaling networks to modulate the strength and duration of signaling by diverse types of receptors--including those relevant to the Hedgehog, Wnt, Notch, and TGFbeta pathways--and downstream kinases such as the MAPK and Akt/PI3K cascades. The involvement of arrestins in many discrete developmental signaling events suggests an indispensable role for these multifaceted molecular scaffolds.

Point mutations in GLI3 lead to misregulation of its subcellular localization

Background

Mutations in the transcription factor GLI3, a downstream target of Sonic Hedgehog (SHH) signaling, are responsible for the development of malformation syndromes such as Greig-cephalopolysyndactyly-syndrome (GCPS), or Pallister-Hall-syndrome (PHS). Mutations that lead to loss of function of the protein and to haploinsufficiency cause GCPS, while truncating mutations that result in constitutive repressor function of GLI3 lead to PHS. As an exception, some point mutations in the C-terminal part of GLI3 observed in GCPS patients have so far not been linked to loss of function. We have shown recently that protein phosphatase 2A (PP2A) regulates the nuclear localization and transcriptional activity a of GLI3 function.

Principal Findings

We have shown recently that protein phosphatase 2A (PP2A) and the ubiquitin ligase MID1 regulate the nuclear localization and transcriptional activity of GLI3. Here we show mapping of the functional interaction between the MID1-α4-PP2A complex and GLI3 to a region between amino acid 568-1100 of GLI3. Furthermore we demonstrate that GCPS-associated point mutations, that are located in that region, lead to misregulation of the nuclear GLI3-localization and transcriptional activity. GLI3 phosphorylation itself however appears independent of its localization and remains untouched by either of the point mutations and by PP2A-activity, which suggests involvement of an as yet unknown GLI3 interaction partner, the phosphorylation status of which is regulated by PP2A activity, in the control of GLI3 subcellular localization and activity.

Conclusions

The present findings provide an explanation for the pathogenesis of GCPS in patients carrying C-terminal point mutations, and close the gap in our understanding of how GLI3-genotypes give rise to particular phenotypes. Furthermore, they provide a molecular explanation for the phenotypic overlap between Opitz syndrome patients with dysregulated PP2A-activity and syndromes caused by GLI3-mutations.

Sonic hedgehog signaling proteins and ATP-binding cassette G2 are aberrantly expressed in diffuse large B-cell lymphoma

Dysregulation of the sonic hedgehog (SHH) signaling pathway has been shown in several cancer types, but has not been explored in diffuse large B-cell lymphoma. We assessed 67 cases of diffuse large B-cell lymphoma for expression of SHH (ligand), GLI1, GLI2 and GLI3 (transcriptional effectors of SHH signaling), and the ATP-binding cassette (ABC)G2 (a downstream target of SHH signaling), using immunohistochemistry. For comparison, we assessed the expression levels of these proteins in 28 cases of follicular lymphoma, 5 chronic lymphocytic leukemia/small lymphocytic lymphoma, and 5 reactive lymph nodes. In diffuse large B-cell lymphoma, SHH was expressed in 61 of 67 (91%) cases, GLI1 in 62 of 67 (93%), GLI2 in 41 of 56 (73%), and GLI3 in 22 of 56 (39%). Expression of ABCG2 was detected in 52 of 55 (95%) cases and was high in 15 (27%) cases. SHH expression positively correlated with expression levels of ABCG2 (P=0.05). Patients with diffuse large B-cell lymphoma with high ABCG2 expression showed significantly shorter overall survival (P=0.031) and failure-free survival (P=0.029) compared with patients with tumors with low or no expression of ABCG2. Diffuse large B-cell lymphomas expressed SHH, and GLI1, GLI2, and GLI3 more frequently and more intensely than cases of follicular lymphoma or chronic lymphocytic leukemia/small lymphocytic lymphoma. In conclusion, our data show that SHH signaling proteins and ABCG2 are aberrantly expressed in diffuse large B-cell lymphoma and that ABCG2 expression has prognostic implications. These findings also provide evidence that dysregulation of the SHH pathway may be involved in the pathogenesis of diffuse large B-cell lymphoma.

Genetic basis of Hirschsprung's disease

Hirschsprung's disease (HSCR) is a developmental disorder characterized by the absence of ganglion cells in the lower digestive tract. Aganglionosis is attributed to a disorder of the enteric nervous system (ENS) whereby ganglion cells fail to innervate the lower gastrointestinal tract during embryonic development. HSCR is a complex disease that results from the interaction of several genes and manifests with low, sex-dependent penetrance and variability in the length of the aganglionic segment. The genetic complexity observed in HSCR can be conceptually understood in light of the molecular and cellular events that take place during the ENS development. DNA alterations in any of the genes involved in the ENS development may interfere with the colonization process, and represent a primary etiology for HSCR. This review will focus on the genes known to be involved in HSCR pathology, how they interact, and on how technology advances are being employed to uncover the pathological processes underlying this disease.

Quantitative analysis of mRNA transcripts of Hox, SHH, PTCH, Wnt, and Fzd genes in canine hematopoietic progenitor cells and various in vitro colonies differentiated from the cells

Homeobox (Hox), Sonic hedgehog (SHH), and Wingless-type MMTV integration site family (Wnt) are known to modulate the self-renewal and expansion of hematopoietic progenitor/stem cells in humans and mice. Frizzled (Fzd) and Patched1 (PTCH1) represent the receptors of Wnt and SHH, respectively. In this study, the amounts of mRNA transcripts of the genes associated with the self-renewal of hematopoietic stem cells, HoxB3, HoxB4, HoxA10, Wnt5a, Wnt2b, Fzd1, Fzd6, SHH, and PTCH1, were measured in canine unfractionated bone marrow cells, CD34-enriched cells, and various colony-forming units in culture (CFU-C). Partial cDNA sequences of these 9 canine genes were determined in this study. Quantitative real-time polymerase chain reaction was employed to indicate their relative amounts of mRNA transcripts. Amounts of mRNA transcripts of HoxB3, HoxA10, PTCH1, and Wnt5a genes in canine CD34-enriched cell fraction were significantly larger than those in the CD34-depleted cell fraction. Amounts of mRNA transcripts of HoxB3, HoxA10, PTCH1, Wnt5a, and Wnt2b genes in various CFU-C cells were significantly smaller than those in the seeded CD34-enriched cell fraction. These results suggested important roles of the products of these genes in self-renewal, expansion, and survival of hematopoietic progenitor cells in dogs as shown in humans and rodents.

Sonic hedgehog signaling pathway is activated in ALK-positive anaplastic large cell lymphoma

Deregulation of the sonic hedgehog (SHH) signaling pathway has been implicated in several cancers but has not been explored in T-cell lymphomas. Here, we report that the SHH/GLI1 signaling pathway is activated in anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL). We show that SHH, but not its transcriptional effector GLI1, is amplified in ALK+ ALCL tumors and cell lines, and that SHH and GLI1 proteins are highly expressed in ALK+ ALCL tumors and cell lines. We also show that inhibition of SHH/GLI1 signaling with cyclopamine-KAAD, as well as silencing GLI1 gene expression by small interfering (si)RNA, decreased cell viability and clonogenicity of ALK+ ALCL cells. Transfection of wild-type or mutant NPM-ALK into 293T cells showed that only wild-type NPM-ALK increased GLI1 protein levels and activated SHH/GLI1 signaling as shown by increase of CCND2 mRNA levels. Inhibition of ALK tyrosine kinase and phosphatidylinositol 3-kinase (PI3K)/AKT or forced expression of pAKT down-regulated or up-regulated SHH/GLI1 signaling, respectively. Inhibition of GSK3beta in 293T cells also increased protein levels of GLI1. In conclusion, the SHH/GLI1 signaling pathway is activated in ALK+ ALCL. SHH/GLI1 activation is the result of SHH gene amplification and is further mediated by NPM-ALK through activation of PI3K/AKT and stabilization of GLI1 protein. There is a positive synergistic effect between the SHH/GLI1 and PI3K/AKT pathways that contributes to the lymphomagenic effect of NPM-ALK.

Expression of Gli1 correlates with the transition of breast cancer cells to estrogen-independent growth

The failure of breast cancer treatment is largely due to the development of estrogen independence. Current data illustrate that Hedgehog (Hh) signaling may play an important role in breast cancer development. Here, we show that the expression of the Hh effector protein, Gli1 was significantly higher in estrogen-independent breast cancer cells than in estrogen-dependent cells. Our data showed for the first time that stable expression of Gli1 in ER positive breast cancer cell lines MCF-7 and T47D can induce estrogen-independent proliferation and promote G1/S phase transition, which associated with cyclin-Rb axi. Gli1 can also attenuate the response of proliferation to estrogenic stimulation, which was correlated with down-regulation of expression of ERalpha and PR, as well as down-regulation of transactivation of ERalpha. Our results suggest that up-regulation of Gli1 in breast cancer cells may be one of the mechanisms responsible for developing estrogen independence and this process may be regulated through down-regulation of expression and transactivation of ERalpha.

Ggamma1, a downstream target for the hmgcr-isoprenoid biosynthetic pathway, is required for releasing the Hedgehog ligand and directing germ cell migration

The isoprenoid biosynthetic pathway leading from the production of mevalonate by HMGCoA reductase (Hmgcr) to the geranylation of the G protein subunit, Ggamma1, plays an important role in cardiac development in the fly. Hmgcr has also been implicated in the release of the signaling molecule Hedgehog (Hh) from hh expressing cells and in the production of an attractant that directs primordial germ cells to migrate to the somatic gonadal precursor cells (SGPs). The studies reported here indicate that this same hmgcr-->Ggamma1 pathway provides a novel post-translational mechanism for modulating the range and activity of the Hh signal produced by hh expressing cells. We show that, like hmgcr, ggamma1 and quemao (which encodes the enzyme, geranylgeranyl diphosphate synthetase, that produces the substrate for geranylation of Ggamma1) are components of the hh signaling pathway and are required for the efficient release of the Hh ligand from hh expressing cells. We also show that the hmgcr-->Ggamma1 pathway is linked to production of the germ cell attractant by the SGPs through its ability to enhance the potency of the Hh signal. We show that germ cell migration is disrupted by the loss or gain of ggamma1 activity, by trans-heterozygous combinations between ggamma1 and either hmgcr or hh mutations, and by ectopic expression of dominant negative Ggamma1 proteins that cannot be geranylated.

Brothers and sisters: molecular insights into arterial-venous heterogeneity

The molecular differences between arteries and veins are genetically predetermined and are evident even before the first embryonic heart beat. Although ephrinB2 and EphB4 are expressed in cells that will ultimately differentiate into arteries and veins, respectively, many other genes have been shown to play a significant role in cell fate determination. The expression patterns of ephrinB2 and EphB4 are restricted to arterial-venous boundaries, and Eph/ephrin signaling provides repulsive cues at arterial-venous boundaries that are thought to prevent intermixing of arterial- and venous-fated cells. However, the maintenance of arterial-venous fate is susceptible to some degree of plasticity. Thus, in response to signals from the ambient microenvironment and shear stress, there is flow-mediated intercalation of the arteries and veins that ultimately leads to the formation of a functional, closed-loop circulation. In addition, cells in the blood vessels of each organ undergo epigenetic, morphological, and functional adaptive changes that are specific to the proximate function of their cognate organ(s). These adaptive changes result in an interorgan and intraorgan vessel heterogeneity that manifest clinically in a disparate response of different organs to identical risk factors and injury in the same animal. In this review, we focus on the molecular and physiological factors influencing arterial-venous heterogeneity between and within different organ(s). We explore arterial-venous differences in selected organs, as well as their respective endothelial cell architectural organization that results in their inter- and intraorgan heterogeneity.

Correlations between the Sonic Hedgehog pathway and basal cell carcinoma

The Hedgehog (HH) family of intercellular signaling proteins has some essential functions in patterning both invertebrate and vertebrate embryos. Identified as an important regulator of segment polarity and tissue organization in flies, the HH pathway can also play a significant role in human development and in cutaneous carcinogenesis. The family received their name because when the D. melanogaster HH protein malfunctions the mutant fly ends up looking like a small prickly ball, similar to a curled up hedgehog. The Sonic hedgehog (SHH) pathway is implicated in the etiology of the most common human cancer, the basal cell carcinoma (BCC). Mutations in the receptor of SHH, the patched gene (PTCH), have been characterized in sporadic BCCs as well as those from patients with the rare genetic syndrome nevoid BCC. Human PTCH is mutated in sporadic as well as hereditary BCCs, and inactivation of this gene is probably a necessary if not sufficient step for tumorigenesis. Delineation of the biochemical pathway in which PTCH functions may lead to rational medical therapy for skin cancer and possibly other tumors.