A paracrine requirement for hedgehog signalling in cancer (original) (raw)
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Non-Canonical Hh Signaling in Cancer—Current Understanding and Future Directions
Cancers, 2015
As a major regulatory pathway for embryonic development and tissue patterning, hedgehog signaling is not active in most adult tissues, but is reactivated in a number of human cancer types. A major milestone in hedgehog signaling in cancer is the Food and Drug Administration (FDA) approval of a smoothened inhibitor Vismodegib for treatment of basal cell carcinomas. Vismodegib can block ligand-mediated hedgehog signaling, but numerous additional clinical trials have failed to show significant improvements in cancer patients. Amounting evidence indicate that ligand-independent hedgehog signaling plays an essential role in cancer. Ligand-independent hedgehog signaling, also named non-canonical hedgehog signaling, generally is not sensitive to smoothened inhibitors. What we know about non-canonical hedgehog signaling in cancer, and how should we prevent its activation? In this review, we will summarize recent development of non-canonical hedgehog signaling in cancer, and will discuss potential ways to prevent this type of hedgehog signaling.
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.
Cancer Research, 2006
Gene expression profiling indicates that the Sonic Hedgehog (Shh) pathway is active in f30% of human medulloblastomas, suggesting that it could provide a useful therapeutic target. Previously, we showed that spontaneous medulloblastomas in Ptc1 +/À p53 À/À mice could be eradicated by treatment with a small-molecule inhibitor (HhAntag) of Smoothened (Smo). Here, we compared the responses of mouse medulloblastoma cells propagated in flank allografts, either directly or after culture in vitro, to HhAntag. We found that Shh pathway activity was suppressed in medulloblastoma cells cultured in vitro and it was not restored when these cells were transplanted into the flank of nude mice. The growth of these transplanted tumor cells was not inhibited by treatment of mice with doses of HhAntag that completely suppressed Smo activity. Interestingly, tumor cells transplanted directly into the flank maintained Smo activity and were sensitive to treatment with HhAntag. These findings indicate that propagation of tumor cells in culture inhibits Smo activity in a way that cannot be reversed by transplantation in vivo, and they raise concerns about the use of cultured tumor cells to test the efficacy of Shh pathway inhibitors as anticancer therapies.
Hedgehog signalling pathway: Carcinogenesis and targeted therapy
Iranian Journal of Cancer Prevention, 2013
Hedgehog signalling pathway has not only a critical role in cell proliferation, differentiation and tissue polarity at embryonic period but also has a vital role in stem cell proliferation, tissue healing and carcinogenesis. Recent research has increased our understanding of this pathway and its relation to other signalling pathways. In addition, a large number of studies confirmed the alteration of Hh signalling pathway in various types of human malignancies including basal cell carcinomas, medulloblastomas, lung, gastrointestinal, ovarian, breast, prostate cancers and leukemia. More than 50 small biomolecules have been introduced which have inhibitory effects on Hh signalling pathway. Although, in many tumors some acceptable results have been showed in phase I clinical trial, closer studies are required to improve drug bioavailability, to decrease the side effects and to find the right small molecules for specific types of cancers, considering patients overall benefits as well.
Blocking SHH/Patched Interaction Triggers Tumor Growth Inhibition through Patched-Induced Apoptosis
Cancer Research, 2020
The Sonic Hedgehog (SHH) pathway plays a key role in cancer. Alterations of SHH canonical signaling, causally linked to tumor progression, have become rational targets for cancer therapy. However, Smoothened (SMO) inhibitors have failed to show clinical benefit in patients with cancers displaying SHH autocrine/paracrine expression. We reported earlier that the SHH receptor Patched (PTCH) is a dependence receptor that triggers apoptosis in the absence of SHH through a pathway that differs from the canonical one, thus generating a state of dependence on SHH for survival. Here, we propose a dual function for SHH: its binding to PTCH not only activates the SHH canonical pathway but also blocks PTCH-induced apoptosis. Eighty percent, 64%, and 8% of human colon, pancreatic, and lung cancer cells, respectively, overexpressed SHH at transcriptional and protein levels. In addition, SHH-overexpressing cells expressed all the effectors of the PTCH-induced apoptotic pathway. Although the canonical pathway remained unchanged, autocrine SHH interference in colon, pancreatic, and lung cell lines triggered cell death through PTCH proapoptotic signaling. In vivo, SHH interference in colon cancer cell lines decreased primary tumor growth and metastasis. Therefore, the antitumor effect associated to SHH deprivation, usually thought to be a consequence of the inactivation of the canonical SHH pathway, is, at least in part, because of the engagement of PTCH proapoptotic activity. Together, these data strongly suggest that therapeutic strategies based on the disruption of SHH/PTCH interaction in SHH-overexpressing cancers should be explored. Significance: Sonic Hedgehog-overexpressing tumors express PTCH-induced cell death effectors, suggesting that this death signaling could be activated as an antitumor strategy.
Tumor shrinkage by cyclopamine tartrate through inhibiting hedgehog signaling
Chinese Journal of Cancer, 2011
The link of hedgehog (Hh) signaling activation to human cancer and synthesis of a variety of Hh signaling inhibitors raise great expectation that inhibiting Hh signaling may be effective in human cancer treatment. Cyclopamine (Cyc), an alkaloid from the plant, is a specific natural product inhibitor of the Hh pathway that acts by targeting smoothened (SMO) protein. However, its poor solubility, acid sensitivity, and weak potency relative to other Hh antagonists prevent the clinical development of Cyc as a therapeutic agent. Here, we report properties of cyclopamine tartrate salt (CycT) and its activities in Hh signaling鄄 mediated cancer and. Unlike Cyc, CycT is water soluble (5-10 mg/mL). The median lethal dose (LD 50) of CycT was 62.5 mg/kg body weight compared to 43.5 mg/kg for Cyc, and the plasma half鄄 life (T 1/2) of CycT was not significantly different from that of Cyc. We showed that CycT had a higher inhibitory activity for Hh signaling鄄 dependent motor neuron differentiation than did Cyc (IC 50 = 50 nmol/L for CycT vs. 300 nmol/L for Cyc). We also tested the antitumor effectiveness of these Hh inhibitors using two mouse models of basal cell carcinomas (K14cre: and K14cre:). After topical application of CycT or Cyc daily for 21 days, we found that all CycT鄄 treated mice had tumor shrinkage and decreased expression of Hh target genes. Taken together, we found that CycT is an effective inhibitor of Hh signaling鄄 mediated carcinogenesis.
Molecular Cancer, 2009
Background: Human clear cell renal cell carcinoma (CRCC) remains resistant to therapies. Recent advances in Hypoxia Inducible Factors (HIF) molecular network led to targeted therapies, but unfortunately with only limited clinical significance. Elucidating the molecular processes involved in kidney tumorigenesis and resistance is central to the development of improved therapies, not only for kidney cancer but for many, if not all, cancer types. The oncogenic PI3K/Akt, NF-kB and MAPK pathways are critical for tumorigenesis. The sonic hedgehog (SHH) signaling pathway is crucial to normal development.
Review: Targeting the Hedgehog pathway in cancer
Therapeutic Advances in Medical Oncology, 2010
The Hedgehog (Hh) pathway is a major regulator of many fundamental processes in vertebrate embryonic development including stem cell maintenance, cell differentiation, tissue polarity and cell proliferation. Constitutive activation of the Hh pathway leading to tumorigenesis is seen in basal cell carcinomas and medulloblastoma. A variety of other human cancers, including brain, gastrointestinal, lung, breast and prostate cancers, also demonstrate inappropriate activation of this pathway. Paracrine Hh signaling from the tumor to the surrounding stroma was recently shown to promote tumorigenesis. This pathway has also been shown to regulate proliferation of cancer stem cells and to increase tumor invasiveness. Targeted inhibition of Hh signaling may be effective in the treatment and prevention of many types of human cancers. The discovery and synthesis of specific Hh pathway inhibitors have significant clinical implications in novel cancer therapeutics. Several synthetic Hh antagonists are now available, several of which are undergoing clinical evaluation. The orally available compound, GDC-0449, is the farthest along in clinical development. Initial clinical trials in basal cell carcinoma and treatment of select patients with medulloblastoma have shown good efficacy and safety. We review the molecular basis of Hh signaling, the current understanding of pathway activation in different types of human cancers and we discuss the clinical development of Hh pathway inhibitors in human cancer therapy.