Long-lasting WNT-TCF response blocking and epigenetic modifying activities of withanolide F in human cancer cells

The WNT-TCF signaling pathway participates in adult tissue homeostasis and repair, and is hyperactive in a number of human diseases including cancers of the colon. Whereas to date there are no antagonists approved for patient use, a potential problem for their sustained use is the blockade of WNT signaling in healthy tissues, thus provoking potentially serious co-lateral damage. Here we have screened a library of plant and microorganism small molecules for novel WNT signaling antagonists and describe withanolide F as a potent WNT-TCF response blocker. This steroidal lactone inhibits TCF-dependent colon cancer xenograft growth and mimics the effects of genetic blockade of TCF and of ivermectin, a previously reported WNT-TCF blocker. However, withanolide F is unique in that it imposes a long-lasting repression of tumor growth, WNT-TCF targets and cancer stem cell clonogenicity long after drug treatment LS174T cells were treated with DMSO or 5uM CAP2 or ivermectin for 16h. Cells were then collected, RNA extracted and used for expression analysis.

WNT-TCF信号通路（WNT-TCF signaling pathway）参与成体组织稳态维持与损伤修复，在包括结肠癌在内的多种人类疾病中呈现过度激活状态。目前尚无获批用于临床的WNT-TCF通路拮抗剂，而长期使用这类拮抗剂的潜在风险在于会阻断健康组织内的WNT信号通路，进而引发潜在的严重附带损伤。本研究针对植物与微生物来源的小分子化合物文库展开筛选，以发掘新型WNT信号通路拮抗剂，并报道醉茄内酯F（withanolide F）是一种强效WNT-TCF应答阻断剂。该甾体内酯可抑制依赖TCF的结肠癌异种移植瘤生长，且能够模拟TCF基因阻断以及此前报道的WNT-TCF阻断剂伊维菌素（ivermectin）的生物学效应。但醉茄内酯F的独特之处在于：即便在药物处理结束后较长时间，其仍可对肿瘤生长、WNT-TCF靶基因表达以及癌症干细胞的克隆形成能力产生持久抑制效果。本研究中，研究人员将LS174T细胞经二甲基亚砜（DMSO）、5μM CAP2或伊维菌素处理16小时后，收集细胞并提取RNA，用于后续的基因表达分析。