Cyclopamine is a naturally occuring steroidal alkaloid that causes cyclopia by blocking sonic hedgehog signaling. It specifically inhibits the hedgehog (Hh) pathway by interaction with the Hh signaling protein smoothened. Cyclopamine blocks the oncogenic effects of mutations of Ptch in fibroblasts and inhibits the growth of cells lacking Ptch function. It arrested cell cycle at G0/G1 and induced apoptosis in several small-cell lung cancer cell lines at 5 µM. Cyclopamine also induces expression of the transcription factor pdx-1, which stimulates insulin secretion in differentiation protocols for mouse embryonic stem cells.

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