gant58 and cyclopamine

Important steps in embryonic development are governed by the Hedgehog (Hh) signaling pathway, an evolutionary conserved signal transduction cascade. However, Hh activity not only is crucial during embryo formation but also is involved in adult tissue repair and in several malignancies. Particularly due to its link to cancer, small molecule Hh pathway inhibitors have been developed and the first compounds have been approved for use in Hh-driven basal cell carcinoma. Almost all advanced Hh inhibitors target the critical signaling component Smoothened (SMO), but preclinical research has identified additional compounds that can block the Hh pathway along its entire signaling cascade, which, in light of emerging drug resistance occurring with SMO inhibitors, is of high importance. Herein we give an overview on currently known Hh pathway inhibitors, delineating their respective strengths and weaknesses and describing potential drug targeting strategies to interfere with Hh signaling in different cancer settings.

Topics: Animals; Antineoplastic Agents; Carcinoma, Basal Cell; Drug Approval; Drug Design; Hedgehog Proteins; Humans; Ligands; Molecular Targeted Therapy; Neoplasms; Receptors, G-Protein-Coupled; Signal Transduction; Smoothened Receptor; Veratrum Alkaloids

Since its discovery by C. Nüsslein-Volhard and E. F. Wieschaus, hedgehog (hh) signaling has come a long way. Today it is regarded as a key regulator in embryogenesis where it governs processes like cell proliferation, differentiation, and tissue patterning. Furthermore, in adults it is involved in the maintenance of stem cells, and in tissue repair and regeneration. But hh signaling has a second-much darker-face: it plays an important role in several types of human cancers where it promotes growth and enables proliferation of tumor stem cells. The etiology of medulloblastoma and basal cell carcinoma is tightly linked to aberrant hh activity, but also cancers of the prostate, the pancreas, the colon, the breasts, rhabdomyosarcoma, and leukemia, are dependent on irregular hh activity. Recent clinical studies have shown that hh signaling can be the basis of an important new class of therapeutic agents with far-reaching implications in oncology. Thus, modulation of hh signaling by means of small molecules has emerged as a valuable tool in combating these hh-dependent cancers. Cyclopamine, a unique natural product with a fascinating history, was the first identified inhibitor of hh signaling and its story is closely linked to the progress in the whole field. In this review we will trace the story of cyclopamine, give an overview on the biological modes of hh signaling both in untransformed and malignant cells, and finally present potent modulators of the hh pathway-many of them already in clinical studies. For more than 30 years now the knowledge on hh signaling has grown steadily-an end to this development is far from being conceivable.

Topics: Antineoplastic Agents; Hedgehog Proteins; Humans; Neoplasms; Signal Transduction; Veratrum Alkaloids

Sonic hedgehog (Shh) is the most widely characterized of the three vertebrate Hedgehog homologs, and is essential for proper embryonic development. Shh binds to its receptor, Patched (Ptch1), resulting in the de-repression of Smoothened (Smo). This leads to the activation of Gli2, which regulates the transcription of target genes that include Gli1 and Ptch1. Several synthetic and naturally occurring small-molecule modulators of Smo have been discovered. Shh-signaling antagonists that bind to Smo include cyclopamine, SANT1, and Cur-61414. Shh signaling agonists that bind to Smo include the synthetic small molecules purmorphamine and SAG. Small molecules that inhibit Shh signaling downstream of Smo, GANT58 and GANT61 have also been reported. Robotnikinin inhibits the Shh pathway by directly targeting Shh. Although progress has been made in understanding and modulating Shh signaling, fundamental aspects of Shh signal transduction remain obscure, including the mechanism(s) whereby Ptch1 regulates Smo activity. Small-molecule modulators of Shh signaling provide a means to regulate the activity of a pathway implicated in medulloblastoma, basal cell carcinoma (BCC), pancreatic cancer, prostate cancer and developmental disorders. Several Shh inhibitors have not succeeded in the clinic for unknown reasons, but clinical trials in BCC and pancreatic cancer with the promising Smo antagonists GDC-0449 and IPI-926 are currently underway.

Topics: Anilides; Animals; Dioxoles; Hedgehog Proteins; Humans; Models, Biological; Molecular Structure; Piperazines; Pyrazoles; Pyridines; Receptors, G-Protein-Coupled; Signal Transduction; Smoothened Receptor; Thiophenes; Veratrum Alkaloids

Cervical cancer is one of the leading causes of mortality amongst women in developing countries, and resistance to therapy is the main reason for treatment failure. Recent advances suggest that cancer stem cells (CSCs) are critically involved in regulating the chemo-resistant behavior of cervical cancer cells. In our study, cells with the CSC phenotype were isolated, and we examined the expression levels of stem cell markers and genes associated with epithelial-mesenchymal transition (EMT) using different assays. However, the cells with the CSC phenotype could not be cultured for further cytotoxicity studies, so we established a model of CSC in cervical cancer cells. We performed siRNA-mediated knockdown of E-cadherin in these cells, and studied them for EMT-associated stem-cell-like properties. We also performed dose-dependent cell viability assays using clinically relevant drugs such as cisplatin, cyclopamine, and GANT58 to analyze the drug resistant behavior of these cancer cells. We found that knockdown of E-cadherin induces EMT in cervical cancer cells, imparting stem-cell like characteristics along with enhanced tumorsphere formation, cell migration, invasiveness, and drug resistance. This is the first study to establish a CSC model in cervical cancer cells by knockdown of E-cadherin, which can be used to develop anti-cancer therapies.

Topics: Antineoplastic Agents; Cadherins; Cell Line, Tumor; Cell Survival; Cisplatin; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Epithelial-Mesenchymal Transition; Female; Humans; Neoplastic Stem Cells; Phenotype; Pyridines; RNA, Small Interfering; Thiophenes; Uterine Cervical Neoplasms; Veratrum Alkaloids

Topics: Aging; Animals; Cell Survival; Cells, Cultured; Gene Expression Regulation, Developmental; Hedgehog Proteins; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Osteoclasts; Osteogenesis; Osteoporosis; Pyridines; Pyrimidines; Receptor, Macrophage Colony-Stimulating Factor; Signal Transduction; Smoothened Receptor; Thiophenes; Up-Regulation; Veratrum Alkaloids; X-Ray Microtomography; Zinc Finger Protein GLI1; Zinc Finger Protein Gli2

The hedgehog (Hh) signaling pathways have a crucial role in cell proliferation and survival, and the de-regulation of these pathways can lead to tumorigenesis. Here we investigated the expression and function of these pathways in acute T lymphocytic leukemia cells (T-ALL). Profiling of Hh pathway members revealed common expression of key Hh signaling effectors in all T-ALL cells. We found that T-ALL cells were insensitive to specific Smoothened (SMO) inhibition following the use of low concentrations of the SMO antagonist cyclopamine. In contrast, treatment with the novel GLI antagonist GANT58 reduced expression of the target gene Patched 1 as well as GLI family zinc finger 1 (GLI1) and preferentially decreased the viability of T-ALL cells. We also found perifosine, a novel AKT inhibitor, down-regulated GLI1 protein by dephosphorylation of AKT and GSK3β dose-dependently and that pre-treatment with PD98059, a MEK/ERK pathway inhibitor, enhanced this down-regulation by 20%-30%. Then we questioned whether use of both GANT58 and AKT inhibitor together could confer a synergistic effect to decrease T-ALL cell viability. By applying the Chou-Talalay method, low concentration of GANT58 induced T-ALL cell death in a synergism fashion with perifosine or GSK690693 when used simultaneously. These findings indicate that the combined use of GANT58 and AKT inhibitor could help treat a broad range of malignant tumors in conjunction with existing cancer treatments.

Topics: Antineoplastic Agents; Apoptosis; Drug Screening Assays, Antitumor; Drug Synergism; Hedgehog Proteins; Humans; Jurkat Cells; MAP Kinase Signaling System; Oxadiazoles; Phosphorylcholine; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma; Proto-Oncogene Proteins c-akt; Pyridines; Thiophenes; Transcription Factors; Veratrum Alkaloids; Zinc Finger Protein GLI1