Targeting Hedgehog Signaling Research Articles

A Systems Pharmacology Approach Uncovers Wogonoside as an Angiogenesis Inhibitor of Triple-Negative Breast Cancer by Targeting Hedgehog Signaling

Triple-negative breast cancer (TNBC) is an aggressive and heterogeneous disease that lacks clinically actionable genetic alterations that limit targeted therapies. Here we explore a systems pharmacology approach that integrates drug-target networks andlarge-scale genomic profiles of TNBC and identify wogonoside, one of the major active flavonoids, as a potent angiogenesis inhibitor. Wevalidate that wogonoside attenuates cell migration, tube formation, and rat aorta microvessel outgrowth, and reduces formation of blood vessels in chicken chorioallantoic membrane and TNBC cell-induced Matrigel plugs. In addition, wogonoside inhibits growth and angiogenesis in TNBC cell xenograft models. This network-based approach predicts, and we empirically validate, wogonoside's antiangiogenic effects resulting from vascular endothelial growth factor secretion. Mechanistically, wogonoside inhibits Gli1 nuclear translocation and transcriptional activities associated with Hedgehog signaling, by promoting Smoothened degradation in a proteasome-dependent mechanism. This study offers a powerful, integrated, systems pharmacology-based strategy for oncological drug discovery and identifies wogonoside as a potential TNBC angiogenesis inhibitor.

Targeting Hedgehog Signalling through the Ubiquitylation Process: The Multiple Roles of the HECT-E3 Ligase Itch.

Hedgehog signalling (Hh) is a developmental conserved pathway strongly involved in cancers when deregulated. This important pathway is orchestrated by numerous regulators, transduces through distinct routes and is finely tuned at multiple levels. In this regard, ubiquitylation processes stand as essential for controlling Hh pathway output. Although this post-translational modification governs proteins turnover, it is also implicated in non-proteolytic events, thereby regulating the most important cellular functions. The HECT E3 ligase Itch, well known to control immune response, is emerging to have a pivotal role in tumorigenesis. By illustrating Itch specificities on Hh signalling key components, here we review the role of this HECT E3 ubiquitin ligase in suppressing Hh-dependent tumours and explore its potential as promising target for innovative therapeutic approaches.

MicroRNA-361-3p regulates retinoblastoma cell proliferation and stemness by targeting hedgehog signaling.

Retinoblastoma (RB) is the most common type of intraocular malignancy in children. During RB oncogenesis, sonic hedgehog (SHH) is commonly differentially expressed. Additionally, microRNAs (miRs) are known to serve crucial roles as oncogenes or tumor suppressors. Specifically, miR-361-3p has been revealed to serve a vital role in cutaneous squamous cell carcinoma, cervical cancer, prostate cancer, colorectal cancer, gastric cancer, hepatocellular carcinoma, breast cancer and lung cancer. However, the role of miR-361-3p in RB and the potential molecular mechanisms involved remain unknown. Therefore, the current study aimed to determine the involvement of miR-361-3p in the development of RB by targeting SHH signaling. In the present study, miR-361-3p expression levels in RB tissue and serum samples obtained from 10 patients with RB, normal retinal tissue and serum samples obtained from 10 healthy controls, and two human RB cell lines (Y79 and Weri-Rb-1) were determined using reverse transcription-quantitative polymerase chain reaction. In addition, a cell counting kit-8 assay, a cell transfection assay, a MTT assay, western blotting, a tumor sphere formation assay and a luciferase assay were used to assess the expression, function and molecular mechanism of miR-361-3p in human RB. It was demonstrated that miR-361-3p was significantly downregulated in RB tissues, RB serum and RB cell lines compared with normal retinal tissues and normal serum. The ectopic expression of miR-361-3p decreased RB cell proliferation and stemness. Furthermore, GLI1 and GLI3 were verified as potential direct targets of miR-361-3p. miR-361-3p was also revealed to exhibit a negative correlation with GLI1/3 expression in RB samples. Taken together, the results indicate that miR-361-3p functions as a tumor suppressor in the carcinogenesis and progression of RB by targeting SHH signaling. Thus, miR-361-3p should be further assessed as a potential therapeutic target for RB treatment.

Gastric cancer and Hedgehog signaling pathway: emerging new paradigms.

Ever since its initial discovery in Drosophila, hedgehog signaling has been linked to foregut development, The mammalian genome expresses three Hedgehog paralogues, sonic hedgehog (Shh), Indian Hedgehog, and desert hedgehog. In the mucosa of the embryonic and adult foregut, Shh expression is the highest. It has now become clear that hedgehog signaling is of pivotal importance in gastric homeostasis. Aberrant activation of hedgehog signaling is associated with a range of pathological consequences including various cancers. Also in gastric cancer, clinical and preclinical data support a role of Hedgehog signaling in neoplastic transformation, and gastrointestinal cancer development, also through cancer stroma interaction. Technological advance are facilitating monitoring Hedgehog signaling broadening options for the more efficient screening of individuals predisposed to eventually developing gastric cancer and targeting Hedgehog signaling may provide opportunities for prophylactic therapy once atrophic gastritis develops. Nevertheless, convincing evidence that Hedgehog antagonists are of clinically useful in the context of gastric cancer is still conspicuously lacking. Here we analyze review the role of Hedgehog in gastric physiology and the potential usefulness of targeting Hedgehog signaling in gastric cancer.

MicroRNA-324-5p regulates stemness, pathogenesis and sensitivity to bortezomib in multiple myeloma cells by targeting hedgehog signaling.

Chromosome 17p deletions are present in 10% of patients with newly diagnosed multiple myeloma (MM), and are associated with inferior prognosis. miR-324-5p is located on chromosome 17p, and shows diverse functions in different types of cancers. However, its role in MM is largely unknown. Here we found the expression of miR-324-5p was decreased in MM, especially in del(17p) MM. In contrast, the expression of hedgehog (Hh) signaling components was elevated, indicating a correlation between miR-324-5p and Hh signaling in MM. Hh signaling is important for the pathogenesis of MM and maintenance of MM stem cell compartment. Indeed, overexpression of miR-324-5p significantly decreased Hh signaling components Smo and Gli1, and functionally reduced cell growth, survival as well as stem cell compartment in MM. Moreover, miR-324-5p potentiated the anti-MM efficacy of bortezomib through regulating the activities of multidrug-resistance proteins and the expression of Bcl-2 family genes. Consistent results were obtained in vivo. Finally, miR-324-5p overcame the protective effect of bone marrow stromal cells on MM cells. Taken together, our data demonstrate that miR-324-5p is essential for MM pathogenesis and downregulation of miR-324-5p is a novel mechanism of Hh signaling activation in MM. Therefore, targeting miR-324-5p provides a potential therapeutic strategy for MM.

16 ヘッジホッグシグナル伝達経路を阻害する天然物の探索(口頭発表の部)

16 ヘッジホッグシグナル伝達経路を阻害する天然物の探索(口頭発表の部)

Abstract 3086: Cyclopamine tartrate, an anti-cancer agent targeting Hedgehog signaling, strongly interferes with mitochondrial function and suppresses aerobic respiration

Abstract The Hedgehog (Hh) pathway is a major regulator of many fundamental processes in mammalian embryonic development. These processes include stem cell maintenance, determination of cell fate, tissue polarity, cell survival, cell differentiation and proliferation. Although this pathway is usually silenced in adult tissues, constitutive activation of the Hh pathway can lead to tumorigenesis. This aberrant characteristic can be observed in different types of human cancer including basal cell carcinomas, medulloblastoma, lung cancer, ovarian cancer, gastrointestinal cancer, breast and prostate cancer. This pathway has been shown to regulate proliferation of cancer stem cells and increase tumor invasiveness. Targeted inhibition of Hh signaling pathway is shown to be effective in cancer treatment and prevention. Therefore, the discovery of Hh pathway inhibitors can pave the way of finding effective cancer treatments. The steroidal alkaloid cyclopamine was the first compound found to inhibit Hh signaling and has been invaluable for understanding the function of Hh signaling in development and cancer. Cyclopamine tartrate (CycT) is an improved analogue of cyclopamine with increased water solubility and bioavailabilty. We performed numerous experiments to examine the effect of CycT in inhibiting Hh signaling on an array of non-small-cell lung cancer (NSCLC) lines. We discovered that CycT has a novel activity in disrupting mitochondrial function and aerobic respiration. Our data show that CycT causes a substantial decrease in aerobic respiration of NSCLC cells, similar to the effect of glutamine deprivation. Mitotracker staining showed that CycT causes mitochondrial fragmentation by increasing mitochondrial fission, which is indicated by the localization of DRP1 at fission sites. Further experiments showed that CycT increases ROS generation, which is presumably a consequence of mitochondrial hyperpolarization. Concomitantly, CycT causes apoptosis and suppress proliferation of NSCLC cells. Citation Format: Md Maksudul Alam, Sagar Sohoni, Sarada Preeta Kalainayakan, Massoud Garrossian, Li Zhang. Cyclopamine tartrate, an anti-cancer agent targeting Hedgehog signaling, strongly interferes with mitochondrial function and suppresses aerobic respiration. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3086.

Targeting hedgehog signaling pathway in pediatric tumors: in vitro evaluation of SMO and GLI inhibitors.

The successful use of SMO inhibitors in tumors with activating mutations in hedgehog signaling raised interests in their exploitation against other malignancies. The role of hedgehog signaling in pediatric malignancies remains unclear. We investigated the hedgehog signaling and its inhibition in a panel of 18 tumor cell lines derived from six of the most common and highly aggressive pediatric tumor types. None of the cell lines was known to stem from tumors with activating hedgehog mutations. Tetrazolium-based assays (MTT and MTS) and BrdU assays were used to analyze cell viability and proliferation after exposure to SANT1 and GANT61. Expression analysis of hedgehog signaling members and cyclins was performed by quantitative real-time PCR and Western blot. Key members of hedgehog signaling (SHH, PTCH1, SMO, GLI1, GLI2 and SUFU) were expressed in all cell lines. In 50% of the cell lines viability was significantly increased by SHH exposure. Stimulation was not restricted to distinct tumor types, but related to cell lines with higher mRNA levels of PTCH1, SMO, GLI1 and GLI2. SMO inhibition by SANT1 moderately decreased cell viability with GI50s between 28 and 93 µmol/l. Sensitivity to SANT1 was not related to distinct tumor types. The GLI inhibitor GANT61 inhibited cell viability and proliferation more effectively than SANT1. Our preclinical data provide evidence that hedgehog signaling is active and can be stimulated by PTCH1 ligands in various pediatric tumors. We suggest further evaluation of GLI inhibitors as inhibitors of hedgehog signaling for the treatment of the investigated tumor types.

Targeting hedgehog signalling by arsenic trioxide reduces cell growth and induces apoptosis in rhabdomyosarcoma.

Rhabdomyosarcomas (RMS) are soft tissue tumours treated with a combination of surgery and chemotherapy. However, mortality rates remain high in case of recurrences and metastatic disease due to drug resistance and failure to undergo apoptosis. Therefore, innovative approaches targeting specific signalling pathways are urgently needed. We analysed the impact of different hedgehog (Hh) pathway inhibitors on growth and survival of six RMS cell lines using MTS assay, colony formation assay, 3D spheroid cultures, flow cytometry and western blotting. Especially the glioma-associated oncogene family (GLI) inhibitor arsenic trioxide (ATO) effectively reduced viability as well as clonal growth and induced cell death in RMS cell lines of embryonal, alveolar and sclerosing, spindle cell subtype, whereas normal skeletal muscle cells were hardly compromised by ATO. Combination of ATO with itraconazole potentiated the reduction of colony formation and spheroid size. These results show that ATO is a promising substance for treatment of relapsed and refractory RMS by directly targeting GLI transcription factors. The combination with itraconazole or other chemotherapeutic drugs has the opportunity to enforce the treatment efficiency of resistant and recurrent RMS.

Inhibition of hedgehog signaling reduces the side population in human malignant mesothelioma cell lines.

Deregulation of crucial embryonic pathways, including hedgehog signaling, has been frequently implicated in a variety of human cancers and is emerging as an important target for anticancer therapy. This study evaluated the potential anticancer effects of cyclopamine, a chemical inhibitor of hedgehog signaling, in human malignant mesothelioma (HMM) cell lines. Cyclopamine treatment significantly decreased the proliferation of HMM cells by promoting apoptosis and shifting the cell cycle toward dormant phase. The clonogenicity and mobility of HMM cells were significantly decreased by cyclopamine treatment. Treatment of HMM cells with cyclopamine significantly reduced the abundance of side population cells, which were measured using an assay composed of Hoechst 33342 dye staining and subsequent flow cytometry. Furthermore, the expression levels of stemness-related genes were significantly affected by cyclopamine treatment. Taken together, the present study showed that targeting hedgehog signaling could reduce a more aggressive subpopulation of the cancer cells, suggesting an alternative approach for HMM therapy.

Targeting hedgehog signaling reduces self-renewal in embryonal rhabdomyosarcoma.

Current treatment regimens for rhabdomyosarcoma (RMS), the most common pediatric soft tissue cancer, rely on conventional chemotherapy, and although they show clinical benefit, there is a significant risk of adverse side effects and secondary tumors later in life. Therefore, identifying and targeting sub-populations with higher tumorigenic potential and self-renewing capacity would offer improved patient management strategies. Hedgehog signaling has been linked to the development of embryonal RMS (ERMS) through mouse genetics and rare human syndromes. However, activating mutations in this pathway in sporadic RMS are rare and therefore the contribution of hedgehog signaling to oncogenesis remains unclear. Here, we show by genetic loss- and gain-of-function experiments and the use of clinically relevant small molecule modulators that hedgehog signaling is important for controlling self-renewal of a subpopulation of RMS cells in vitro and tumor initiation in vivo. In addition, hedgehog activity altered chemoresistance, motility and differentiation status. The core stem cell gene NANOG was determined to be important for ERMS self-renewal, possibly acting downstream of hedgehog signaling. Crucially, evaluating the presence of a subpopulation of tumor-propagating cells in patient biopsies identified by GLI1 and NANOG expression had prognostic significance. Hence, this work identifies novel functional aspects of hedgehog signaling in ERMS, redefines the rationale for its targeting as means to control ERMS self-renewal and underscores the importance of studying functional tumor heterogeneity in pediatric cancers.

Targeting Hedgehog signaling pathway and autophagy overcomes drug resistance of BCR-ABL-positive chronic myeloid leukemia

The frontline tyrosine kinase inhibitor (TKI) imatinib has revolutionized the treatment of patients with chronic myeloid leukemia (CML). However, drug resistance is the major clinical challenge in the treatment of CML. The Hedgehog (Hh) signaling pathway and autophagy are both related to tumorigenesis, cancer therapy, and drug resistance. This study was conducted to explore whether the Hh pathway could regulate autophagy in CML cells and whether simultaneously regulating the Hh pathway and autophagy could induce cell death of drug-sensitive or -resistant BCR-ABL+ CML cells. Our results indicated that pharmacological or genetic inhibition of Hh pathway could markedly induce autophagy in BCR-ABL+ CML cells. Autophagic inhibitors or ATG5 and ATG7 silencing could significantly enhance CML cell death induced by Hh pathway suppression. Based on the above findings, our study demonstrated that simultaneously inhibiting the Hh pathway and autophagy could markedly reduce cell viability and induce apoptosis of imatinib-sensitive or -resistant BCR-ABL+ cells. Moreover, this combination had little cytotoxicity in human peripheral blood mononuclear cells (PBMCs). Furthermore, this combined strategy was related to PARP cleavage, CASP3 and CASP9 cleavage, and inhibition of the BCR-ABL oncoprotein. In conclusion, this study indicated that simultaneously inhibiting the Hh pathway and autophagy could potently kill imatinib-sensitive or -resistant BCR-ABL+ cells, providing a novel concept that simultaneously inhibiting the Hh pathway and autophagy might be a potent new strategy to overcome CML drug resistance.

Targeting hedgehog signaling in myelofibrosis and other hematologic malignancies.

Treatment of myelofibrosis (MF), a BCR-ABL–negative myeloproliferative neoplasm, is challenging. The only current potentially curative option, allogeneic hematopoietic stem cell transplant, is recommended for few patients. The remaining patients are treated with palliative therapies to manage MF-related anemia and splenomegaly. Identification of a mutation in the Janus kinase 2 (JAK2) gene (JAK2 V617F) in more than half of all patients with MF has prompted the discovery and clinical development of inhibitors that target JAK2. Although treatment with JAK2 inhibitors has been shown to improve symptom response and quality of life in patients with MF, these drugs do not alter the underlying disease; therefore, novel therapies are needed. The hedgehog (Hh) signaling pathway has been shown to play a role in normal hematopoiesis and in the tumorigenesis of hematologic malignancies. Moreover, inhibitors of the Hh pathway have been shown to inhibit growth and self-renewal capacity in preclinical models of MF. In a mouse model of MF, combined inhibition of the Hh and JAK pathways reduced JAK2 mutant allele burden, reduced bone marrow fibrosis, and reduced white blood cell and platelet counts. Preliminary clinical data also suggest that inhibition of the Hh pathway, alone or in combination with JAK2 inhibition, may enable disease modification in patients with MF. Future studies, including one combining the Hh pathway inhibitor sonidegib and the JAK2 inhibitor ruxolitinib, are underway in patients with MF and will inform whether this combination approach can lead to true disease modification.

Targeting hedgehog signaling in cancer: research and clinical developments

Since its first description in Drosophila by Drs Nusslein-Volhard and Wieschaus in 1980, hedgehog (Hh) signaling has been implicated in regulation of cell differentiation, proliferation, tissue polarity, stem cell maintenance, and carcinogenesis. The first link of Hh signaling to cancer was established through studies of Gorlin syndrome in 1996 by two independent teams. Later, it was shown that Hh signaling may be involved in many types of cancer, including skin, leukemia, lung, brain, and gastrointestinal cancers. In early 2012, the US Food and Drug Administration approved the clinical use of Hh inhibitor Erivedge/vismodegib for treatment of locally advanced and metastatic basal cell carcinomas. With further investigation, it is possible to see more clinical applications of Hh signaling inhibitors. In this review, we will summarize major advances in the last 3 years in our understanding of Hh signaling activation in human cancer, and recent developments in preclinical and clinical studies using Hh signaling inhibitors.

Abstract 3664: Silibinin induces cell cycle arrest and apoptotic death via targeting hedgehog signaling in basal cell carcinoma cells.

Abstract Skin cancer is the most common malignancy in the United States with the number of incidences persistently rising due to the depletion of the ozone layer and lack of adequate solar protection. Non-melanoma skin cancer (NMSC), composed of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), encompasses the vast majority of skin cancers with over 2 million new cases each year. Silibinin, an active bioflavanone was previously shown to have major protective effect against ultraviolet B radiation (UVB)-induced SCC through promoting DNA damage repair as well as inhibiting inflammation and angiogenesis. To date, however, the efficacy of silibinin has not been tested against BCC, which alone accounts for about 80% of NMSC incidences. BCC mostly causes disfigurement, pain and morbidity, and warrants greater attention for its prevention and treatment. The hallmark of BCC has been the constitutive activation of hedgehog (Hh) signaling pathway, mostly through the loss of function mutations in the patched (PTCH) gene. In the present study, we utilized ASZ001 cell line, derived from a mouse BCC tumor induced by UV-radiation in a PTCH1 heterozygous mouse, to evaluate the anti-cancer efficacy of silibinin against BCC. ASZ001 cells lack both copies of the PTCH1 gene and closely resembles the PTCH1 status in human BCC. We treated ASZ001 cells with either DMSO (control) or various doses of silibinin (25-100 μM), and performed trypan blue exclusion, clonogenic, apoptosis and cell cycle distribution assays. Results showed that silibinin treatment (25-100 μM) decreases the total cell number by 38-51% (p<0.001), 67-84% (p<0.001) and 40-95% (p<0.05-p<0.001) after 24, 48 and 72 h of treatment. Clonogenic assay further confirmed the decrease in cell viability by silibinin, and we observed 18% (p<0.05), 92% (p<0.001) and 100% (p<0.001) decrease in colony formation with 25, 50 and 100 μM doses of silibinin, respectively, in ASZ001 cells. Trypan blue exclusion assay showed that silibinin treatment (25-100 μM) also increased the cell death by 2 folds (p<0.05), 3 folds (p<0.001), and 4 folds (p<0.001) after 24, 48 and 72 h of treatment while annexin/PI staining confirmed that silibinin-induced cell death in ASZ001 cells is mainly apoptotic in nature. FACS analyses revealed that silibinin treatment significantly modulated the cell cycle distribution in ASZ001 cells, and we observed an S-phase arrest at 50 μM silibinin dose and a G2M arrest at 100 μM silibinin dose after 24 and 48 h of treatment. Molecular studies showed that silibinin treatment strongly decreases the expression of hedgehog signaling transcriptional factor Gli1, which is typically overexpressed in BCC and is known to regulate the expression of several oncogenes. Together, these results provide the first evidence of silibinin's efficacy against BCC cells, and suggest that silibinin could be useful in the prevention and/or treatment of both types of NMSCs. Citation Format: Cynthia Tilley, Gagan Deep, Chapla Agarwal, Rajesh Agarwal. Silibinin induces cell cycle arrest and apoptotic death via targeting hedgehog signaling in basal cell carcinoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3664. doi:10.1158/1538-7445.AM2013-3664

Dual Targeting ErbB and Hedgehog (HH) Signaling Pathways in Pancreatic Ductal Adenocarcinoma (PDAC) Cells

Dual Targeting ErbB and Hedgehog (HH) Signaling Pathways in Pancreatic Ductal Adenocarcinoma (PDAC) Cells

Inhibition of hedgehog signaling for the treatment of murine sclerodermatous chronic graft-versus-host disease

AbstractChronic graft-versus-host disease (cGVHD) is a prognosis limiting complication of allogeneic stem cell transplantation. The molecular mechanisms underlying cGVHD are incompletely understood, and targeted therapies are not yet established for clinical use. Here we examined the role of the hedgehog pathway in sclerodermatous cGVHD. Hedgehog signaling was activated in human and murine cGVHD with increased expression of sonic hedgehog and accumulation of the transcription factors Gli-1 and Gli-2. Treatment with LDE223, a highly selective small-molecule antagonist of the hedgehog coreceptor Smoothened (Smo), abrogated the activation of hedgehog signaling and protected against experimental cGVHD. Preventive therapy with LDE223 almost completely impeded the development of clinical and histologic features of sclerodermatous cGVHD. Treatment with LDE223 was also effective, when initiated after the onset of clinical manifestations of cGVHD. Hedgehog signaling stimulated the release of collagen from cultured fibroblasts but did not affect leukocyte influx in murine cGVHD, suggesting direct, leukocyte-independent stimulatory effects on fibroblasts as the pathomechanism of hedgehog signaling in cGVHD. Considering the high morbidity of cGVHD, the current lack of efficient molecular therapies for clinical use, and the availability of well-tolerated inhibitors of Smo, targeting hedgehog signaling might be a novel strategy for clinical trials in cGVHD.

Targeting Hedgehog signaling and understanding refractory response to treatment with Hedgehog pathway inhibitors

Hedgehog (Hh) signaling is a principal component of the morphogenetic code best known to direct pattern formation during embryogenesis. The Hh pathway remains active in adulthood however where it guides tissue regeneration and remodeling and Hh production in the niche plays an important role in maintaining stem cell compartment size. Deregulated Hh signaling activity is associated, depending on the context, with both cancer initiation and progression. Interestingly, the Hh pathway is remarkably druggable, raising hopes that inhibition of the pathway could support anticancer therapy. Indeed, a large body of preclinical data supports such an action, but promising clinical data are still limited to basal cell carcinoma (BSC) and medulloblastoma. Nevertheless cancer resistance against Hh targeting has already emerged as a major problem. Here we shall review the current situation with respect to targeting the Hh pathway in cancer in general and in chemotolerance in particular with a focus on the problems associated with the emergence of tumors resistant to treatment with inhibitors targeting the Hh receptor Smoothened (SMO).

Vitamin D3 triggers antitumor activity through targeting hedgehog signaling in human renal cell carcinoma

Human clear cell renal cell carcinoma (CCC) remains resistant to treatments despite the progress in targeted therapies. Several signaling pathways acting during renal development are reactivated during kidney tumorigenesis; this is the case of the sonic hedgehog (SHH)-Gli. Interestingly, the precursor of active vitamin D3 (VD3), cholecalciferol, has been demonstrated to be a strong inhibitor of SHH-Gli signaling. Here, we show the preclinical efficacy of cholecalciferol in CCC both in vitro and in vivo. A panel of CCC cell lines, tumors and normal corresponding tissues from CCC patients were used to evaluate the expression of the VD3 receptor and metabolizing enzymes and the effects of cholecalciferol treatment. Subsequently, xenografted mice were treated with cholecalciferol in a prophylactic or therapeutic manner; their response and the adverse effects were evaluated on the basis of weekly monitoring, followed by blood collection procedures and X-ray micro-computed tomography. VD3 receptor and metabolizing enzymes are dramatically decreased in human cell lines and tumors. Cholecalciferol decreases cell proliferation and increases cell death by inhibition of the SHH-Gli pathway. Xenografted mice treated with cholecalciferol exhibit absence of tumor development or substantial growth inhibition. The treatment was shown to be safe; it did not induce calcification or calcium reabsorption. These findings establish that, although VD3 receptors and metabolizing enzymes are absent in CCC, cholecalciferol supplementation is a strong tool to block the reactivation of SHH-Gli pathway in this pathology, leading ultimately to tumor regression. Cholecalciferol may have highly therapeutic potential in CCC.

A better way forward: targeting hedgehog signaling in liver cancer

Accumulated experimental evidence indicates that Hedgehog (Hh) signaling regulates cell proliferation and specification in a variety of organs during embryonic development. However, abnormal activation of this pathway in postnatal tissues has been linked to a large number of human cancers. With respect to the liver, it is known that Hh signaling not only influences bipotential precursor cells capable of pancreas and liver development, but is also implicated in the pathogenesis of liver tumors such as hepatoblastoma, hepatocellular and cholangiocellular carcinoma, if aberrantly activated. Blockade of Hh signaling by several specific inhibitors has been proven to successfully inhibit tumor growth of various Hh-associated cancers in vitro and in preclinical mouse models, and recent clinical data suggest that the implementation of novel anticancer therapeutics based on Hh interference into commonly accepted regimens are within reach. Thus, it is highly probable that Hh targeted therapies could be used for the treatment of Hh-dependent liver cancers in the future.