Cyclopamine

Cyclopamine is a naturally occurring Hedgehog (Hh)?specific small?molecule signaling steroidal alkaloid inhibitor, causes a profound inhibition of tumor growth, has significant anti?invasive, anti?proliferative and anti?estrogenic potency in human breast cancer cells [2] [1]. The EC50 of cyclopamine is 10.57 μM, it was identified by an FXR-bla (farnesoid X receptor- b-lactamase) assay [3].

Hh signaling pathway plays a critical role in embryonic development and tumorigenesis [4]. Hh signaling pathway shows saliency in regulating cellular proliferation and differentiation in a wide array of human tissues. It is related to aberrant cell survival in numerous human malignancies, ranging from BCCs and medulloblastomas to small cell lung, gastrointestinal, breast and prostate tumors [1].

Treated with cyclopamine (10 or 20 μM) only and incubated for time periods ranging from 0 to10 days, MCF-7 cells and MDA?MB?231 cells displayed a significant reduction in proliferation rate compared with the control cells on days 3 and 6 (P<0.01). In the MCF?7 cells, cyclopamine significantly induced cell accumulation in the G1 phase (P<0.01) and a modest decrease in the S population percentage, from 22 to 16% (P<0.01). In the MDA?MB?231 cells, cyclopamine caused a significant increase in G1 cells. The invasion rate of cyclopamine?treated MCF?7 and MDA?MB?231cells significantly decreased compared with the CK [2].

Embryoes exposed to cyclopamine resulted in visible external defects, including cyclopia, proboscis formation, microphthalmia, thoracic lordosis, amelia and decreased body size. Examination of gastrointestinal organs revealed severe deficits, including less length of the gut tube and mesenchymal cell numbers in foregut-derived organs. Ectopic structures in duodenum, stomach, and dorsal pancreas were also found [5].

References:
[1].  Marc J. Meth and Jeffrey M. Weinberg. Cyclopamine: Inhibiting Hedgehog in the Treatment of Psoriasis. Continuing Medical Education, 2006, 78: 185-188.
[2].  Jun Che, Fu-Zheng Zhang, Chao-Qian Zhao, et al. Cyclopamine is a novel Hedgehog signaling inhibitor with significant anti?proliferative, anti?invasive and anti?estrogenic potency in human breast cancer cells. Oncology Letters, 2013, 5: 1417-1421.
[3].  Chia-Wen Hsu, Jinghua Zhao, Ruili Huang, et al. Quantitative High-Throughput Profiling of Environmental Chemicals and Drugs that Modulate Farnesoid X Receptor. Scientific Reports, 2014, 4: 6437.
[4].  Robert J. Lipinski, Paul R. Hutson, Paul W. Hannam, et al. Dose- and Route-Dependent Teratogenicity, Toxicity, and Pharmacokinetic Profiles of the Hedgehog Signaling Antagonist Cyclopamine in the Mouse. Toxicological Sciences, 2008, 104(1):189-197.
[5].  Seung K. Kim and Douglas A. Melton. Pancreas development is promoted by cyclopamine, a Hedgehog signaling inhibitor. Proc. Natl. Acad. Sci. USA, 1998, 95: 13036-13041.

Cyclopamine increases the cytotoxic effects of paclitaxel and radiation but not cisplatin and gemcitabine in Hedgehog expressing pancreatic cancer cells.[Pubmed:16552573]

Cancer Chemother Pharmacol. 2006 Dec;58(6):765-70.

INTRODUCTION: The hedgehog signaling pathway (Hh) is frequently over expressed in pancreatic adenocarcinomas. We studied the potential cytotoxic interactions between Cyclopamine, a Hh pathway inhibitor and paclitaxel, cisplatin, gemcitabine and ionizing radiation (IR). METHODS: In vitro clonogenic survival analysis was performed with Cyclopamine alone or Cyclopamine in combination with paclitaxel, gemcitabine, cisplatin and IR in Hh expressing human pancreatic tumor cells and Hh non-expressing colon cancer cells. Relative cytotoxicity was assessed in combination treatment compared with exposure to single agents. Assays of apoptosis (annexin V) were performed in the presence of Cyclopamine, chemotherapeutic agents, and IR. RESULTS: We report that Cyclopamine increased the cytotoxic effects of paclitaxel and IR in Hh expressing pancreatic carcinoma cells. These effects were not observed in Hh non-expressing cells. Cyclopamine did not significantly increase killing by cisplatin or gemcitabine in Hh expressing pancreatic cancer cells. CONCLUSIONS: These data suggest strategies to combine Hh inhibitors with radiotherapy and chemotherapeutic agents, specifically paclitaxel and related compounds in the treatment of pancreatic cancer.

Cyclopamine and quercetin suppress the growth of leukemia and lymphoma cells.[Pubmed:20032413]

Anticancer Res. 2009 Nov;29(11):4629-32.

BACKGROUND: Hedgehog (Hh) and Wnt signaling pathways are involved in the stimulation of growth of leukemia and lymphoma cells. In the present study, whether or not the Hh inhibitor, Cyclopamine, and the Wnt inhibitor, quercetin, suppress cell growth was investigated. MATERIALS AND METHODS: The effects of Cyclopamine and quercetin on the in vitro growth and protein expression of ten acute leukemia and B-cell lymphoma cell lines were examined. RESULTS: Cyclopamine and quercetin suppressed cell growth and induced apoptosis in seven and eight cell lines respectively. Cyclopamine decreased the level of Gli1 protein, a target gene product of Hh signaling. Quercetin decreased the level of Notch1 protein and its active fragment in the DND-41 T-lymphoblastic leukemia cell line with constitutive Notch activation. CONCLUSION: Cyclopamine and quercetin suppress the growth of a number of leukemia and lymphoma cells. This finding suggests the potential use of these compounds in molecularly-targeted therapy for leukemia and lymphoma.

Cyclopamine is a novel Hedgehog signaling inhibitor with significant anti-proliferative, anti-invasive and anti-estrogenic potency in human breast cancer cells.[Pubmed:23599805]

Oncol Lett. 2013 Apr;5(4):1417-1421.

Stimulation of Hedgehog (Hh) signaling induces carcinogenesis or promotes cell survival in cancers of multiple organs. In epithelial cancer with aberrant Hedgehog activation, abrogation of Hedgehog signaling by Cyclopamine, a naturally occurring Hedgehog-specific small-molecule inhibitor, causes profound inhibition of tumor growth. In the present study, Cyclopamine displayed a significant potency in suppressing the proliferation of both estrogen-responsive (MCF-7) and estrogen-independent (MDA-MB-231) human breast cancer cells. Cyclopamine induced a robust G1 cell cycle arrest and elicited notable effects on the expression of cyclin D1 through modulation of the MAPK/ERK signaling pathway. Cyclopamine also inhibited the invasive ability of both breast cancer cell lines by suppressing the expression levels of NF-kappaB, MMP2 and MMP9 protein. Furthermore, in estrogen-responsive MCF-7 cells, Cyclopamine significantly downregulated the production of estrogen receptor-alpha protein. Our results implicate Cyclopamine as a novel, potent inhibitor of human breast cancer proliferation and estrogen responsiveness that could potentially be developed into a promising therapeutic agent for the treatment of breast cancer.

The hedgehog pathway inhibitor cyclopamine increases levels of p27, and decreases both expression of IGF-II and activation of Akt in PC-3 prostate cancer cells.[Pubmed:17602833]

Cancer Lett. 2007 Oct 8;255(2):300-6.

The hedgehog signalling inhibitor Cyclopamine has been shown to induce growth inhibition and cell cycle arrest in prostate cancer cell lines, but the mechanism of action has not been clearly defined, and observations between laboratories have not always been consistent. We first observed that albumin can protect PC-3 prostate cancer cells from Cyclopamine-induced growth inhibition, suggesting that Cyclopamine binds to albumin, and that only free Cyclopamine is active. We then conducted a phospho-site protein kinase screen to elucidate the mechanism of Cyclopamine-induced growth inhibition. Treatment of PC-3 cells with 5 or 10 microM Cyclopamine for 72h resulted in a decrease in cell viability of approximately 50% and approximately 75%, respectively. A phospho-site protein kinase screen showed that Cyclopamine decreased levels of phospho-Thr(187)-p27 by 71%. This phospho-site on p27 positively regulates its ubiquitin degradation; therefore a decrease in phospho-Thr(187)-p27 should correlate with increased levels of p27. Consistent with this hypothesis, treatment of PC-3 cells with Cyclopamine resulted in a approximately 3-fold increase in p27 protein levels. Cdk-2 phosphorylates Thr(187)-p27, and immunoblotting demonstrated that Cyclopamine treatment of PC-3 cells reduces the expression of cdk-2. Furthermore, Cyclopamine decreased the levels of phosphorylated (activated) Akt, which is known to increase p27 degradation via Skp-2-induced ubiquitination. The mechanism by which Cyclopamine decreases phosphorylated Akt is currently under investigation, but it may involve our observed Cyclopamine-induced reduction in IRS-1 and IGF-II expression. These results demonstrate novel molecular correlates of Cyclopamine-induced growth inhibition of prostate cancer cells.

Cyclopamine-mediated hedgehog pathway inhibition depletes stem-like cancer cells in glioblastoma.[Pubmed:17628016]

Stem Cells. 2007 Oct;25(10):2524-33.

Brain tumors can arise following deregulation of signaling pathways normally activated during brain development and may derive from neural stem cells. Given the requirement for Hedgehog in non-neoplastic stem cells, we investigated whether Hedgehog blockade could target the stem-like population in glioblastoma multiforme (GBM). We found that Gli1, a key Hedgehog pathway target, was highly expressed in 5 of 19 primary GBM and in 4 of 7 GBM cell lines. Shh ligand was expressed in some primary tumors, and in GBM-derived neurospheres, suggesting a potential mechanism for pathway activation. Hedgehog pathway blockade by Cyclopamine caused a 40%-60% reduction in growth of adherent glioma lines highly expressing Gli1 but not in those lacking evidence of pathway activity. When GBM-derived neurospheres were treated with Cyclopamine and then dissociated and seeded in media lacking the inhibitor, no new neurospheres formed, suggesting that the clonogenic cancer stem cells had been depleted. Consistent with this hypothesis, the stem-like fraction in gliomas marked by both aldehyde dehydrogenase activity and Hoechst dye excretion (side population) was significantly reduced or eliminated by Cyclopamine. In contrast, we found that radiation treatment of our GBM neurospheres increased the percentage of these stem-like cells, suggesting that this standard therapy preferentially targets better-differentiated neoplastic cells. Most importantly, viable GBM cells injected intracranially following Hedgehog blockade were no longer able to form tumors in athymic mice, indicating that a cancer stem cell population critical for ongoing growth had been removed. Disclosure of potential conflicts of interest is found at the end of this article.

Production of pancreatic hormone-expressing endocrine cells from human embryonic stem cells.[Pubmed:17053790]

Nat Biotechnol. 2006 Nov;24(11):1392-401.

Of paramount importance for the development of cell therapies to treat diabetes is the production of sufficient numbers of pancreatic endocrine cells that function similarly to primary islets. We have developed a differentiation process that converts human embryonic stem (hES) cells to endocrine cells capable of synthesizing the pancreatic hormones insulin, glucagon, somatostatin, pancreatic polypeptide and ghrelin. This process mimics in vivo pancreatic organogenesis by directing cells through stages resembling definitive endoderm, gut-tube endoderm, pancreatic endoderm and endocrine precursor--en route to cells that express endocrine hormones. The hES cell-derived insulin-expressing cells have an insulin content approaching that of adult islets. Similar to fetal beta-cells, they release C-peptide in response to multiple secretory stimuli, but only minimally to glucose. Production of these hES cell-derived endocrine cells may represent a critical step in the development of a renewable source of cells for diabetes cell therapy.

Inhibition of Hedgehog signaling by direct binding of cyclopamine to Smoothened.[Pubmed:12414725]

Genes Dev. 2002 Nov 1;16(21):2743-8.

The steroidal alkaloid Cyclopamine has both teratogenic and antitumor activities arising from its ability to specifically block cellular responses to vertebrate Hedgehog signaling. We show here, using photoaffinity and fluorescent derivatives, that this inhibitory effect is mediated by direct binding of Cyclopamine to the heptahelical bundle of Smoothened (Smo). Cyclopamine also can reverse the retention of partially misfolded Smo in the endoplasmic reticulum, presumably through binding-mediated effects on protein conformation. These observations reveal the mechanism of Cyclopamine's teratogenic and antitumor activities and further suggest a role for small molecules in the physiological regulation of Smo.