Dosage-dependent regulation of pancreatic cancer growth and angiogenesis by hedgehog signaling

Targeting GLI Transcription Factors in Cancer

Aberrant activation of hedgehog (Hh) signaling has been observed in a wide variety of tumors and accounts for more than 25% of human cancer deaths. Inhibitors targeting the Hh signal transducer Smoothened (SMO) are widely used and display a good initial efficacy in patients suffering from basal cell carcinoma (BCC); however, a large number of patients relapse. Though SMO mutations may explain acquired therapy resistance, a growing body of evidence suggests that the non-canonical, SMO-independent activation of the Hh pathway in BCC patients can also account for this adverse effect. In this review, we highlight the importance of glioma-associated oncogene (GLI) transcription factors (the main downstream effectors of the canonical and the non-canonical Hh cascade) and their putative role in the regulation of multiple oncogenic signaling pathways. Moreover, we discuss the contribution of the Hh signaling to malignant transformation and propose GLIs as central hubs in tumor signaling networks and thus attractive molecular targets in anti-cancer therapies.

Donor-dependent variation of human umbilical cord blood mesenchymal stem cells in response to hypoxic preconditioning and amelioration of limb ischemia

With the rapidly growing demand for mesenchymal stem cell (MSC) therapy, numerous strategies using MSCs for different diseases have been studied and reported. Because of their immunosuppressive properties, MSCs are commonly used as an allogeneic treatment. However, for the many donors who could potentially be used, it is important to understand the capacity for therapeutic usage with donor-to-donor heterogeneity. In this study, we aimed to investigate MSCs as a promising therapeutic strategy for critical limb ischemia. We evaluated MSCs from two donors (#55 and #64) and analyzed the capacity for angiogenesis through in vivo and in vitro assays to compare the therapeutic effect between different donors. We emphasized the importance of intra-population heterogeneity of MSCs on therapeutic usage by evaluating the effects of hypoxia on activating cellular angiogenesis in MSCs. The precondition of hypoxia in MSCs is known to enhance therapeutic efficacy. Our study suggests that sensitivity to hypoxic conditions is different between cells originating from different donors, and this difference affects the contribution to angiogenesis. The bioinformatics analysis of different donors under hypoxic culture conditions identified intrinsic variability in gene expression patterns and suggests alternative potential genetic factors ANGPTL4, ADM, SLC2A3, and CDON as guaranteed general indicators for further stem cell therapy.

The critical roles of activated stellate cells-mediated paracrine signaling, metabolism and onco-immunology in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant diseases worldwide. It is refractory to conventional treatments, and consequently has a documented 5-year survival rate as low as 7%. Increasing evidence indicates that activated pancreatic stellate cells (PSCs), one of the stromal components in tumor microenvironment (TME), play a crucial part in the desmoplasia, carcinogenesis, aggressiveness, metastasis associated with PDAC. Despite the current understanding of PSCs as a "partner in crime" to PDAC, detailed regulatory roles of PSCs and related microenvironment remain obscure. In addition to multiple paracrine signaling pathways, recent research has confirmed that PSCs-mediated tumor microenvironment may influence behaviors of PDAC via diverse mechanisms, such as rewiring metabolic networks, suppressing immune responses. These new activities are closely linked with treatment and prognosis of PDAC. In this review, we discuss the recent advances regarding new functions of activated PSCs, including PSCs-cancer cells interaction, mechanisms involved in immunosuppressive regulation, and metabolic reprogramming. It's clear that these updated experimental or clinical studies of PSCs may provide a promising approach for PDAC treatment in the near future.

Genetic interactions between the hedgehog co-receptors Gas1 and Boc regulate cell proliferation during murine palatogenesis

Abnormal regulation of Sonic hedgehog (Shh) signaling has been described in a variety of human cancers and developmental anomalies, which highlights the essential role of this signaling molecule in cell cycle regulation and embryonic development. Gas1 and Boc are membrane co-receptors for Shh, which demonstrate overlapping domains of expression in the early face. This study aims to investigate potential interactions between these co-receptors during formation of the secondary palate. Mice with targeted mutation in Gas1 and Boc were used to generate Gas1; Boc compound mutants. The expression of key Hedgehog signaling family members was examined in detail during palatogenesis via radioactive in situ hybridization. Morphometric analysis involved computational quantification of BrdU-labeling and cell packing; whilst TUNEL staining was used to assay cell death. Ablation of Boc in a Gas1 mutant background leads to reduced Shh activity in the palatal shelves and an increase in the penetrance and severity of cleft palate, associated with failed elevation, increased proliferation and reduced cell death. Our findings suggest a dual requirement for Boc and Gas1 during early development of the palate, mediating cell cycle regulation during growth and subsequent fusion of the palatal shelves.

Novel agents for pancreatic ductal adenocarcinoma: emerging therapeutics and future directions

A poor prognosis of pancreatic ductal adenocarcinoma (PDAC) associated with chemoresistance has not changed for the past three decades. A multidisciplinary diagnosis followed by surgery and chemo(radiation)therapy is the main treatment approach. However, gemcitabine- and 5-fluorouracil-based therapies did not present satisfying outcomes. Novel regimens targeting pancreatic cancer cells, the tumor microenvironment, and immunosuppression are emerging. Biomarkers concerning the treatment outcome and patient selection are being discovered in preclinical or clinical studies. Combination therapies of classic chemotherapeutic drugs and novel agents or novel therapeutic combinations might bring hope to the dismal prognosis for PDAC patients.

Seed-in-Soil: Pancreatic Cancer Influenced by Tumor Microenvironment

Pancreatic ductal adenocarcinoma is a fatal malignancy with a five-year survival rate lower than 7%, and most patients dying within six months of diagnosis. The factors that contribute to the aggressiveness of the disease include, but are not limited to: late diagnosis, prompt metastasis to adjacent vital organs, poor response, and resistance to anticancer treatments. This malignancy is uniquely associated with desmoplastic stroma that accounts for 80% of tumor mass. Understanding the biology of stroma can aid the discovery of innovative strategies for eradicating this lethal cancer in the future. This review highlights the critical components in the stroma and how they interact with the cancer cells to convey the devastating tumor progression.

BOC is a modifier gene in holoprosencephaly

Holoprosencephaly (HPE), a common developmental defect of the forebrain and midface, has a complex etiology. Heterozygous, loss-of-function mutations in the sonic hedgehog (SHH) pathway are associated with HPE. However, mutation carriers display highly variable clinical presentation, leading to an "autosomal dominant with modifier" model, in which the penetrance and expressivity of a predisposing mutation is graded by genetic or environmental modifiers. Such modifiers have not been identified. Boc encodes a SHH coreceptor and is a silent HPE modifier gene in mice. Here, we report the identification of missense BOC variants in HPE patients. Consistent with these alleles functioning as HPE modifiers, individual variant BOC proteins had either loss- or gain-of-function properties in cell-based SHH signaling assays. Therefore, in addition to heterozygous loss-of-function mutations in specific SHH pathway genes and an ill-defined environmental component, our findings identify a third variable in HPE: low-frequency modifier genes, BOC being the first identified.

Neuropilin-1 promotes Hedgehog signaling through a novel cytoplasmic motif

Hedgehog (HH) signaling critically regulates embryonic and postnatal development as well as adult tissue homeostasis, and its perturbation can lead to developmental disorders, birth defects, and cancers. Neuropilins (NRPs), which have well-defined roles in Semaphorin and VEGF signaling, positively regulate HH pathway function, although their mechanism of action in HH signaling remains unclear. Here, using luciferase-based reporter assays, we provide evidence that NRP1 regulates HH signaling specifically at the level of GLI transcriptional activator function. Moreover, we show that NRP1 localization to the primary cilium, a key platform for HH signal transduction, does not correlate with HH signal promotion. Rather, a structure-function analysis suggests that the NRP1 cytoplasmic and transmembrane domains are necessary and sufficient to regulate HH pathway activity. Furthermore, we identify a previously uncharacterized, 12-amino acid region within the NRP1 cytoplasmic domain that mediates HH signal promotion. Overall, our results provide mechanistic insight into NRP1 function within and potentially beyond the HH signaling pathway. These insights have implications for the development of novel modulators of HH-driven developmental disorders and diseases.

Hedgehog Signal Transduction: Key Players, Oncogenic Drivers, and Cancer Therapy

The Hedgehog (Hh) signaling pathway governs complex developmental processes, including proliferation and patterning within diverse tissues. These activities rely on a tightly regulated transduction system that converts graded Hh input signals into specific levels of pathway activity. Uncontrolled activation of Hh signaling drives tumor initiation and maintenance. However, recent entry of pathway-specific inhibitors into the clinic reveals mixed patient responses and thus prompts further exploration of pathway activation and inhibition. In this review, we share emerging insights into regulated and oncogenic Hh signaling, supplemented with updates on the development and use of Hh pathway-targeted therapies.

Palmitoylation of proteins in cancer

Post-translational modification of proteins by attachment of palmitate serves as a mechanism to regulate protein localization and function in both normal and malignant cells. Given the essential role that palmitoylation plays in cancer cell signaling, approaches that target palmitoylated proteins and palmitoyl acyltransferases (PATs) have the potential for therapeutic intervention in cancer. Highlighted here are recent advances in understanding the importance of protein palmitoylation in tumorigenic pathways. A new study has uncovered palmitoylation sites within the epidermal growth factor receptor that regulate receptor trafficking, signaling and sensitivity to tyrosine kinase inhibitors. Global data analysis from nearly 150 cancer studies reveals genomic alterations in several PATs that may account for their ability to function as tumor suppressors or oncogenes. Selective inhibitors have recently been developed that target hedgehog acyltransferase (Hhat) and Porcupine (Porcn), the acyltransferases that modify hedgehog and Wnt proteins, respectively. These inhibitors, coupled with targeted knockdown of Hhat and Porcn, reveal the essential functions of fatty acylation of secreted morphogens in a wide variety of human tumors.

Tongue and Taste Organ Biology and Function: Homeostasis Maintained by Hedgehog Signaling

The tongue is an elaborate complex of heterogeneous tissues with taste organs of diverse embryonic origins. The lingual taste organs are papillae, composed of an epithelium that includes specialized taste buds, the basal lamina, and a lamina propria core with matrix molecules, fibroblasts, nerves, and vessels. Because taste organs are dynamic in cell biology and sensory function, homeostasis requires tight regulation in specific compartments or niches. Recently, the Hedgehog (Hh) pathway has emerged as an essential regulator that maintains lingual taste papillae, taste bud and progenitor cell proliferation and differentiation, and neurophysiological function. Activating or suppressing Hh signaling, with genetic models or pharmacological agents used in cancer treatments, disrupts taste papilla and taste bud integrity and can eliminate responses from taste nerves to chemical stimuli but not to touch or temperature. Understanding Hh regulation of taste organ homeostasis contributes knowledge about the basic biology underlying taste disruptions in patients treated with Hh pathway inhibitors.

Tetramethylpyrazine attenuates sinusoidal angiogenesis via inhibition of hedgehog signaling in liver fibrosis

Accumulating evidence indicates that hedgehog signaling plays a pivotal role in pathological angiogenesis and is involved in wound-healing responses in a number of adult tissues, including the liver. We previously demonstrated that hedgehog signaling promoted proliferation and inhibited apoptosis in hepatic stellate cells. This study was aimed to evaluate the effect of tetramethylpyrazine (TMP) on hedgehog signaling and to further examine the molecular mechanisms of TMP-induced antiangiogenesic effects in liver fibrosis. We found that TMP ameliorated the expression of proangiogenic markers vascular endothelial growth factor A (VEGF-A), vascular endothelial growth factor receptor 2 (VEGF-R2), platelet-derived growth factor BB (PDGF-BB), platelet-derived growth factor-β receptor (PDGF-βR) and hypoxia inducible factor 1α (HIF-1α), concomitant with reduced abundance of endothelial markers platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31), CD34 and von willebrand factor in vivo and in vitro. Interestingly, TMP attenuated the abundance of sonic hedgehog, smoothened (Smo) and glioblastoma but increased the expression of hedgehog-interacting protein in liver sinusoidal endothelial cells, which was underlying mechanism for the antiangiogenesic activity of TMP. Downregulation of Smo activity, using selective Smo inhibitor cyclopamine, lead to a synergistic effect with TMP, whereas Smo overexpression plasmid impaired the induction of antiangiogenesic effects of TMP. Overall, these results provide novel implications to reveal the molecular mechanism of TMP-inhibited liver sinusoidal angiogenesis, by which points to the possibility of using TMP-based antiangiogenic drugs for the treatment of liver fibrosis. © 2017 IUBMB Life, 69(2):115-127, 2017.

Employing Metabolism to Improve the Diagnosis and Treatment of Pancreatic Cancer

Pancreatic ductal adenocarcinoma is on pace to become the second leading cause of cancer-related death. The high mortality rate results from a lack of methods for early detection and the inability to successfully treat patients once diagnosed. Pancreatic cancer cells have extensively reprogrammed metabolism, which is driven by oncogene-mediated cell-autonomous pathways, the unique physiology of the tumor microenvironment, and interactions with non-cancer cells. In this review, we discuss how recent efforts delineating rewired metabolic networks in pancreatic cancer have revealed new in-roads to develop detection and treatment strategies for this dreadful disease.

Stromal hedgehog signaling maintains smooth muscle and hampers micro-invasive prostate cancer

It is widely appreciated that reactive stroma or carcinoma-associated fibroblasts can influence epithelial tumor progression. In prostate cancer (PCa), the second most common male malignancy worldwide, the amount of reactive stroma is variable and has predictive value for tumor recurrence. By analyzing human PCa protein and RNA expression databases, we found smooth muscle cells (SMCs) are decreased in advanced tumors, whereas fibroblasts are maintained. In three mouse models of PCa, PB-MYC, ERG/PTEN and TRAMP, we found the composition of the stroma is distinct. SMCs are greatly depleted in advanced PB-MYC tumors and locally reduced in ERG/PTEN prostates, whereas in TRAMP tumors the SMC layers are increased. In addition, interductal fibroblast-like cells expand in PB-MYC and ERG/PTEN tumors, whereas in TRAMP PCa they expand little and stromal cells invade into intraductal adenomas. Fate mapping of SMCs showed that in PB-MYC tumors the cells are depleted, whereas they expand in TRAMP tumors and interestingly contribute to the stromal cells in intraductal adenomas. Hedgehog (HH) ligands secreted by epithelial cells are known to regulate prostate mesenchyme expansion differentially during development and regeneration. Any possible role of HH signaling in stromal cells during PCa progression is poorly understood. We found that HH signaling is high in SMCs and fibroblasts near tumor cells in all models, and epithelial Shh expression is decreased whereas Ihh and Dhh are increased. In human primary PCa, expression of IHH is the highest of the three HH genes, and elevated HH signaling correlates with high stromal gene expression. Moreover, increasing HH signaling in the stroma of PB-MYC PCa resulted in more intact SMC layers and decreased tumor progression (micro-invasive carcinoma). Thus, we propose HH signaling restrains tumor progression by maintaining the smooth muscle and preventing invasion by tumor cells. Our studies highlight the importance of understanding how HH signaling and stromal composition impact on PCa to optimize drug treatments.

Characterization of Hedgehog Acyltransferase Inhibitors Identifies a Small Molecule Probe for Hedgehog Signaling by Cancer Cells

The Sonic Hedgehog (Shh) signaling pathway plays a critical role during embryonic development and cancer progression. N-terminal palmitoylation of Shh by Hedgehog acyltransferase (Hhat) is essential for efficient signaling, raising interest in Hhat as a novel drug target. A recently identified series of dihydrothienopyridines has been proposed to function via this mode of action; however, the lead compound in this series (RUSKI-43) was subsequently shown to possess cytotoxic activity unrelated to canonical Shh signaling. To identify a selective chemical probe for cellular studies, we profiled three RUSKI compounds in orthogonal cell-based assays. We found that RUSKI-43 exhibits off-target cytotoxicity, masking its effect on Hhat-dependent signaling, hence results obtained with this compound in cells should be treated with caution. In contrast, RUSKI-201 showed no off-target cytotoxicity, and quantitative whole-proteome palmitoylation profiling with a bioorthogonal alkyne-palmitate reporter demonstrated specific inhibition of Hhat in cells. RUSKI-201 is the first selective Hhat chemical probe in cells and should be used in future studies of Hhat catalytic function.

Maintenance of Taste Organs Is Strictly Dependent on Epithelial Hedgehog/GLI Signaling

For homeostasis, lingual taste papilla organs require regulation of epithelial cell survival and renewal, with sustained innervation and stromal interactions. To investigate a role for Hedgehog/GLI signaling in adult taste organs we used a panel of conditional mouse models to manipulate GLI activity within epithelial cells of the fungiform and circumvallate papillae. Hedgehog signaling suppression rapidly led to taste bud loss, papilla disruption, and decreased proliferation in domains of papilla epithelium that contribute to taste cells. Hedgehog responding cells were eliminated from the epithelium but retained in the papilla stromal core. Despite papilla disruption and loss of taste buds that are a major source of Hedgehog ligand, innervation to taste papillae was maintained, and not misdirected, even after prolonged GLI blockade. Further, vimentin-positive fibroblasts remained in the papilla core. However, retained innervation and stromal cells were not sufficient to maintain taste bud cells in the context of compromised epithelial Hedgehog signaling. Importantly taste organ disruption after GLI blockade was reversible in papillae that retained some taste bud cell remnants where reactivation of Hedgehog signaling led to regeneration of papilla epithelium and taste buds. Therefore, taste bud progenitors were either retained during epithelial GLI blockade or readily repopulated during recovery, and were poised to regenerate taste buds once Hedgehog signaling was restored, with innervation and papilla connective tissue elements in place. Our data argue that Hedgehog signaling is essential for adult tongue tissue maintenance and that taste papilla epithelial cells represent the key targets for physiologic Hedgehog-dependent regulation of taste organ homeostasis. Because disruption of GLI transcriptional activity in taste papilla epithelium is sufficient to drive taste organ loss, similar to pharmacologic Hedgehog pathway inhibition, the findings suggest that taste alterations in cancer patients using systemic Hedgehog pathway inhibitors result principally from interruption of signaling activity in taste papillae.

Sonoporation with Acoustic Cluster Therapy (ACT®) induces transient tumour volume reduction in a subcutaneous xenograft model of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers with survival averaging only 3months if untreated following diagnosis. A major limitation in effectively treating PDAC using conventional and targeted chemotherapeutic agents, is inadequate drug delivery to the target location, predominantly due to a poorly vascularised, desmoplastic tumour microenvironment. Ultrasound in combination with ultrasound contrast agents, i.e., microbubbles, that flow through the vasculature and capillaries can be used to disrupt such mechanical barriers, potentially allowing for a greater therapeutic efficacy. This phenomenon is commonly referred to as sonoporation. In an attempt to improve the efficacy of sonoporation, novel microbubble formulations are being developed to address the limitation of commercially produced clinical diagnostic ultrasound contrast agents. In our work here we evaluate the ability of a novel formulation; namely Acoustic Cluster Therapy (ACT®) to improve the therapeutic efficacy of the chemotherapeutic agent paclitaxel, longitudinally in a xenograft model of PDAC. Results indicated that ACT® bubbles alone demonstrated no observable toxic effects, whilst ACT® in combination with paclitaxel can transiently reduce tumour volumes significantly, three days posttreatment (p=0.0347-0.0458). Quantitative 3D ultrasound validated the calliper measurements. Power Doppler ultrasound imaging indicated that ACT® in combination with paclitaxel was able to transiently sustain peak vasculature percentages as observed in the initial stages of tumour development. Nevertheless, there was no significant difference in tumour vasculature percentage at the end of treatment. The high vascular percentage correlated to the transient decrease and overall inhibition of the tumour volumes. In conclusion, ACT® improves the therapeutic efficacy of paclitaxel in a PDAC xenograft model allowing for transient tumour volume reduction and sustained tumour vasculature percentage.

GLI1, a master regulator of the hallmark of pancreatic cancer

Hedgehog signaling is highly conserved across species and governs proper embryonic development. Germline gene mutations that reduce this signaling activity cause a variety of developmental abnormalities such as holoprosencephaly, while those that enhance Hedgehog signaling activity induce a tumor-predisposition condition Nevoid basal cell carcinoma syndrome. Furthermore, dysregulated activation of Hedgehog signaling has been recognized in various sporadic malignancies, including pancreatic adenocarcinoma. Pancreatic adenocarcinoma develops through a multistep carcinogenesis starting with oncogenic mutation of the KRAS gene. During this process, precancerous or cancer cells secrete Hedgehog ligand proteins to promote characteristic desmoplastic stroma around the cells, which in turn activates the expression of the downstream transcription factor GLI1 inside the cells. The quantitative and spatiotemporal dysregulation of GLI1 subsequently leads to the expression of transcriptional target genes of GLI1 that govern the hallmark of malignant properties. Here, after a brief introductory outline, a perspective is offered of Hedgehog signaling with a special focus on the role of GLI1 in pancreatic carcinogenesis.

Association between FOXM1 and hedgehog signaling pathway in human cervical carcinoma by tissue microarray analysis

Forkhead box M1 (FOXM1) and hedgehog (Hh) signaling pathway are implicated in the formation and development of human tumors, including cervical cancer. Previous studies have indicated that FOXM1 may be a downstream target gene of the Hh signaling pathway, but their association in cervical cancer is largely unknown. In the present study, the expression of FOXM1 and Hh signaling molecules was evaluated by immunohistochemical analysis in a tissue microarray that contained 70 cervical cancer tissues and 10 normal cervical tissues. In addition, the association of these molecules with clinicopathological parameters, and the association between FOXM1 and various molecules involved in the Hh signaling pathway was investigated. The results indicated that FOXM1 and Hh signaling molecules were overexpressed in cervical cancer tissues. The protein expression levels of FOXM1, glioma-associated oncogene 1 (GLI1) and smoothened (SMO) correlated with the clinical stage of the tumors, while the protein expression levels of Sonic Hh (SHh), patched 1 (PTCH1) and GLI1 correlated with the pathological grade of the tumors. The expression levels of GLI1 were lower in tissues without lymph node metastasis than in tissues with lymph node metastasis. In addition, FOXM1 expression correlated with GLI1, SHh and PTCH1 expression in cancer tissues. These findings confirmed the participation of FOXM1 and the Hh signaling pathway in cervical cancer. Furthermore, the finding that FOXM1 may be a downstream target gene of the Hh signaling pathway in cervical cancer provides a potential novel diagnostic and therapeutic target for cervical cancer.

GAS1 is present in the cerebrospinal fluid and is expressed in the choroid plexus of the adult rat

Growth arrest specific 1 (GAS1) is a GPI-anchored protein that inhibits proliferation when overexpressed in tumors but during development it promotes proliferation and survival of different organs and tissues. This dual ability is caused by its capacity to interact both by inhibiting the signaling induced by the glial cell line-derived neurotrophic factor and by facilitating the activity of the sonic hedgehog pathway. GAS1 is expressed as membrane bound in different organs and as a secreted form by glomerular mesangial cells. In the developing central nervous system, GAS1 is found in neural progenitors; however, it continues to be expressed in the adult brain. Here, we demonstrate that soluble GAS1 is present in the cerebrospinal fluid (CSF) and it is expressed in the choroid plexus (CP) of the adult rat, the main producer of CSF. Additionally, we confirm the presence of GAS1 in blood plasma and liver of the adult rat, the principal source of blood plasma proteins. The pattern of expression of GAS1 is perivascular in both the CP and the liver. In vitro studies show that the fibroblast cell line NIH/3T3 expresses one form of GAS1 and releases two soluble forms into the supernatant. Briefly, in the present work, we show the presence of GAS1 in adult rat body fluids focusing in the CSF and the CP, and suggest that secreted GAS1 exists as two different isoforms.

Micelle Mixtures for Coadministration of Gemcitabine and GDC-0449 To Treat Pancreatic Cancer

Hedgehog (Hh) signaling plays an important role in the development and metastasis of pancreatic ductal adenocarcinoma (PDAC). Although gemcitabine (GEM) has been used as a first-line therapy for PDAC, its rapid metabolism and short plasma half-life restrict its use as a single chemotherapy. Combination therapy with more than one drug is a promising approach for treating cancer. Herein, we report the use of methoxy poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate)-graft-dodecanol (mPEG-b-PCC-g-DC) copolymer for conjugating GEM and encapsulating a Hh inhibitor, vismodegib (GDC-0449), into its hydrophobic core for treating PDAC. Our objective was to determine whether the micelle mixtures of these two drugs could show better response in inhibiting Hh signaling pathway and restraining the proliferation and metastasis of pancreatic cancer. The in vivo stability of GEM significantly increased after conjugation, which resulted in its increased antitumor efficacy. Almost 80% of encapsulated GDC-0449 and 19% conjugated GEM were released in vitro at pH 5.5 in 48 h in a sustained manner. The invasion, migration, and colony forming features of MIA PaCa-2 cells were significantly inhibited by micelle mixture carrying GEM and GDC-0449. Remarkable increase in PARP cleavage and Bax proved increased apoptosis by this combination formulation compared to individual micelles. This combination therapy efficiently inhibited tumor growth, increased apoptosis, reduced Hh ligands PTCH-1 and Gli-1, and lowered EMT-activator ZEB-1 when injected to athymic nude mice bearing subcutaneous tumor generated using MIA PaCa-2 cells compared to monotherapy as observed from immunohistochemical analysis. In conclusion, micelle mixtures carrying GEM and GDC-0449 have the potential to treat pancreatic cancer.

Deciphering the role of hedgehog signaling in pancreatic cancer

Pancreatic cancer, mostly pancreatic ductal adenocarcinoma (PDAC), is a leading cause of cancer-related death in the US, with a dismal median survival of 6 months. Thus, there is an urgent unmet need to identify ways to diagnose and to treat this deadly cancer. Although a number of genetic changes have been identified in pancreatic cancer, their mechanisms of action in tumor development, progression and metastasis are not completely understood. Hedgehog signaling, which plays a major role in embryonic development and stem cell regulation, is known to be activated in pancreatic cancer; however, specific inhibitors targeting the smoothened molecule failed to improve the condition of pancreatic cancer patients in clinical trials. Furthermore, results regarding the role of Hh signaling in pancreatic cancer are controversial with some reporting tumor promoting activities whereas others tumor suppressive actions. In this review, we will summarize what we know about hedgehog signaling in pancreatic cancer, and try to explain the contradicting roles of hedgehog signaling as well as the reason(s) behind the failed clinical trials. In addition to the canonical hedgehog signaling, we will also discuss several non-canonical hedgehog signaling mechanisms.

Hedgehog signaling: modulation of cancer properies and tumor mircroenvironment

Cancer poses a serious health problem in society and is increasingly surpassing cardiovascular disease as the leading cause of mortality in the United States. Current therapeutic strategies for cancer are extreme and harsh to patients and often have limited success; the danger of cancer is intensified as it metastasizes to secondary locations such as lung, bone, and liver, posing a dire threat to patient treatment and survival. Hedgehog signaling is an important pathway for normal development. Initially identified in Drosophila, the vertebrate and mammalian equivalent of the pathway has been studied extensively for its role in cancer development and progression. As this pathway regulates key target genes involved in development, its action also allows for the modulation of the microenvironment to prepare a tumor-suitable niche by manipulating tumor cell growth, differentiation, and immune regulation, thus creating an enabling environment for progression and metastasis. In this review, we will summarize recent scientific discoveries reporting the impact of the Hedgehog signaling pathway on the tumor initiation process and metastatic cascade, shedding light on the ability of the tumor to take over a mechanism crucially intended for development and normal function.

Hedgehog signaling: modulation of cancer properies and tumor mircroenvironment

Cancer poses a serious health problem in society and is increasingly surpassing cardiovascular disease as the leading cause of mortality in the United States. Current therapeutic strategies for cancer are extreme and harsh to patients and often have limited success; the danger of cancer is intensified as it metastasizes to secondary locations such as lung, bone, and liver, posing a dire threat to patient treatment and survival. Hedgehog signaling is an important pathway for normal development. Initially identified in Drosophila, the vertebrate and mammalian equivalent of the pathway has been studied extensively for its role in cancer development and progression. As this pathway regulates key target genes involved in development, its action also allows for the modulation of the microenvironment to prepare a tumor-suitable niche by manipulating tumor cell growth, differentiation, and immune regulation, thus creating an enabling environment for progression and metastasis. In this review, we will summarize recent scientific discoveries reporting the impact of the Hedgehog signaling pathway on the tumor initiation process and metastatic cascade, shedding light on the ability of the tumor to take over a mechanism crucially intended for development and normal function.

LRP2, an auxiliary receptor that controls sonic hedgehog signaling in development and disease

To fulfill their multiple roles in organ development and adult tissue homeostasis, hedgehog (HH) morphogens act through their receptor Patched (PTCH) on target cells. However, HH actions also require HH binding proteins, auxiliary cell surface receptors that agonize or antagonize morphogen signaling in a context-dependent manner. Here, we discuss recent findings on the LDL receptor-related protein 2 (LRP2), an exemplary HH binding protein that modulates sonic hedgehog activities in stem and progenitor cell niches in embryonic and adult tissues. LRP2 functions are crucial for developmental processes in a number of tissues, including the brain, the eye, and the heart, and defects in this receptor pathway are the cause of devastating congenital diseases in humans. Developmental Dynamics 245:569-579, 2016. © 2016 Wiley Periodicals, Inc.

Hedgehog Signaling in Pancreatic Fibrosis and Cancer

The hedgehog signaling pathway was first discovered in the 1980s. It is a stem cell-related pathway that plays a crucial role in embryonic development, tissue regeneration, and organogenesis. Aberrant activation of hedgehog signaling leads to pathological consequences, including a variety of human tumors such as pancreatic cancer. Multiple lines of evidence indicate that blockade of this pathway with several small-molecule inhibitors can inhibit the development of pancreatic neoplasm. In addition, activated hedgehog signaling has been reported to be involved in fibrogenesis in many tissues, including the pancreas. Therefore, new therapeutic targets based on hedgehog signaling have attracted a great deal of attention to alleviate pancreatic diseases. In this review, we briefly discuss the recent advances in hedgehog signaling in pancreatic fibrogenesis and carcinogenesis and highlight new insights on their potential relationship with respect to the development of novel targeted therapies.

Pharmacological targeting of the protein synthesis mTOR/4E-BP1 pathway in cancer-associated fibroblasts abrogates pancreatic tumour chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) is extremely stroma-rich. Cancer-associated fibroblasts (CAFs) secrete proteins that activate survival and promote chemoresistance of cancer cells. Our results demonstrate that CAF secretome-triggered chemoresistance is abolished upon inhibition of the protein synthesis mTOR/4E-BP1 regulatory pathway which we found highly activated in primary cultures of α-SMA-positive CAFs, isolated from human PDAC resections. CAFs selectively express the sst1 somatostatin receptor. The SOM230 analogue (Pasireotide) activates the sst1 receptor and inhibits the mTOR/4E-BP1 pathway and the resultant synthesis of secreted proteins including IL-6. Consequently, tumour growth and chemoresistance in nude mice xenografted with pancreatic cancer cells and CAFs, or with pieces of resected human PDACs, are reduced when chemotherapy (gemcitabine) is combined with SOM230 treatment. While gemcitabine alone has marginal effects, SOM230 is permissive to gemcitabine-induced cancer cell apoptosis and acts as an antifibrotic agent. We propose that selective inhibition of CAF protein synthesis with sst1-directed pharmacological compounds represents an anti-stromal-targeted therapy with promising chemosensitization potential.

SHh-Gli1 signaling pathway promotes cell survival by mediating baculoviral IAP repeat-containing 3 (BIRC3) gene in pancreatic cancer cells

The abnormally activated hedgehog (Hh) signaling pathway is involved in the regulation of proliferation and apoptosis in pancreatic cancer cells, while its exact molecular mechanism is not clear. The purpose of this study was to investigate the regulatory effect of Hh signaling pathway on the transcription of BIRC3 gene and its underlying mechanism in pancreatic cancer cells, as well as the relationship between the Gli1-dependent BIRC3 transcription and cell survival. Firstly, we examined the effect of knockdown or overexpression of Hh on BIRC3 messenger RNA (mRNA) expression by real-time RT-PCR. Then, the regulatory mechanism of Gli1 to BIRC3 gene transcription was investigated by XChIP-PCR and luciferase assays. Finally, the cell survival mediated by the Gli1-dependent BIRC3 transcription was studied by MTT and annexin V-FITC/propidiumiodide (PI) assays. We found that the expression level of BIRC3 mRNA was positively correlated to SHh/Gli1 signaling activation in three pancreatic cancer cell lines. The XChIP-PCR and luciferase assays data showed that the transcription factor Gli1 bound to some enhancers within the promoter regions of BIRC3 gene and promoted gene transcription. The cell proliferation was increased significantly by SHh/Gli1 expression while the apoptotic rate was reduced under the same condition. Moreover, BIRC3 knockdown inhibited cell proliferation and survival induced by SHh overexpression. Our study reveals that Gli1 promoted transcription of BIRC3 gene via cis-acting elements and the SHh-Gli1 signaling pathway maintained cell survival partially through this Gli1-dependent BIRC3 model in pancreatic cancer cells.

Selective inhibition of the p38 alternative activation pathway in infiltrating T cells inhibits pancreatic cancer progression

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive neoplasm characterized by a marked fibro-inflammatory microenvironment¹, the presence of which can promote both cancer induction and growth^2–4. Therefore, selective manipulation of local cytokines is an attractive if unrealized therapeutic approach. T cells possess a unique mechanism of activation of p38 MAPK downstream of T cell receptor (TCR) engagement by phosphorylation of Tyr-323 (pY323). This alternative p38 activation pathway is required for pro-inflammatory cytokine production^5,6. Here we show in human PDAC that a high percentage of infiltrating pY323⁺ T cells was associated with large numbers of TNFα and IL-17-producing CD4⁺ tumor-infiltrating lymphocytes (TIL) and aggressive disease. The growth of murine pancreatic tumors was inhibited by genetic ablation of the alternative p38 pathway, and transfer of wild type CD4⁺ T cells but not those lacking the alternative pathway enhanced tumor growth in T cell-deficient mice. Strikingly, a plasma membrane-permeable peptide derived from Gadd45α, the naturally-occurring inhibitor of p38 pY323⁺ (ref. 7), reduced CD4⁺ TIL production of TNFα, IL-17A, IL-10, and secondary cytokines, halted growth of implanted tumors, and inhibited progression of spontaneous K-ras-driven adenocarcinoma in mice. Thus, TCR-mediated activation of CD4⁺ TIL results in alternative p38 activation and production of pro-tumorigenic factors, and can be targeted for therapeutic benefit.

Identification of a novel actin-dependent signal transducing module allows for the targeted degradation of GLI1

The Down syndrome-associated DYRK1A kinase has been reported as a stimulator of the developmentally important Hedgehog (Hh) pathway, but cells from Down syndrome patients paradoxically display reduced Hh signalling activity. Here we find that DYRK1A stimulates GLI transcription factor activity through phosphorylation of general nuclear localization clusters. In contrast, in vivo and in vitro experiments reveal that DYRK1A kinase can also function as an inhibitor of endogenous Hh signalling by negatively regulating ABLIM proteins, the actin cytoskeleton and the transcriptional co-activator MKL1 (MAL). As a final effector of the DYRK1A-ABLIM-actin-MKL1 sequence, we identify the MKL1 interactor Jumonji domain demethylase 1A (JMJD1A) as a novel Hh pathway component stabilizing the GLI1 protein in a demethylase-independent manner. Furthermore, a Jumonji-specific small-molecule antagonist represents a novel and powerful inhibitor of Hh signal transduction by inducing GLI1 protein degradation in vitro and in vivo.

Codelivery of small molecule hedgehog inhibitor and miRNA for treating pancreatic cancer

Successful treatment of pancreatic ductal adenocarcinoma (PDAC) remains a challenge due to the desmoplastic microenvironment that promotes both tumor growth and metastasis and forms a barrier to chemotherapy. Hedgehog (Hh) signaling is implicated in initiation and progression of PDAC and also contributes to desmoplasia. While Hh levels are increased in pancreatic cancer cells, levels of tumor suppressor miR-let7b, which targets several genes involved in PDAC pathogenesis, is downregulated. Therefore, our overall objective was to inhibit Hh pathway and restore miR-let7b simultaneously for synergistically treating PDAC. miR-let7b and Hh inhibitor GDC-0449 could inhibit the proliferation of human pancreatic cancer cells (Capan-1, HPAF-II, T3M4, and MIA PaCa-2), and there was synergistic effect when miR-let7b and GDC-0449 were coformulated into micelles using methoxy poly(ethylene glycol)-block-poly(2-methyl- 2-carboxyl-propylenecarbonate-graft-dodecanol-graft-tetraethylene-pentamine) (mPEG-b-PCC-g-DC-g-TEPA). This copolymer self-assembled into micelles of <100 nm and encapsulated hydrophobic GDC-0449 into its core with 5% w/w drug loading and allowed complex formation between miR-let7b and its cationic pendant chains. Complete polyplex formation with miRNA was observed at the N/P ratio of 16/1. Almost 80% of GDC-0449 was released from the polyplex in a sustained manner in 2 days. miRNA in the micelle formulation was stable for up to 24 h in the presence of serum and high uptake efficiency was achieved with low cytotoxicity. This combination therapy effectively inhibited tumor growth when injected to athymic nude mice bearing ectopic tumor generated using MIA PaCa-2 cells compared to micelles carrying GDC-0449 or miR-let7b alone. Immunohistochemical analysis revealed decreased tumor cell proliferation with increased apoptosis in the animals treated with miR-let7b and GDC-0449 combination.