Withanolide類化合物之熱休克蛋白90抑制作用與抗癌活性探討

Study on the heat shock protein 90-inhibitory effect and anticancer activities of withanolides

蔡宜伶(Yi-Ling Tsai)

指導教授 ： 吳志中

高雄醫學大學/藥學院/天然藥物研究所碩士班/碩士(2011年)

摘要

從植物中萃取出的天然化合物一直是研究發展抗癌藥物的重要來源。像是茄科植物中含有大量固醇酮類的withanolide類化合物，即具有抗腫瘤、抗血管增生能力，抗癌細胞侵犯性並具有化學預防作用 (chemoprevention)。在先前的研究中，我們利用MDA-MB-231人類乳癌細胞，證實了一種withanolide類化合物tubocapsenolide A可以誘導cell cycle中止與細胞凋亡，而這個現象與抑制熱休克蛋白90 (heat shock protein 90)有關。
為了要證實hsp90的抑制是否為withanolide類化合物的普遍現象，並且探討各個衍生物之間的結構與活性關係 (structure-activity of relationship, SAR)，我們在MDA-MB-231細胞，針對九個withanolide類化合物的對hsp90的抑制能力以及細胞毒殺作用進行研究。實驗結果顯示出大部分的withanolide類化合物會抑制hsp90的功能，因為MDA-MB-231細胞以withanolide類化合物處理後，hsp90的客戶蛋白 (client proteins)，如Raf-1, total Akt和CDK4，會明顯下降；反之hsp70則明顯上升。此外，將表現luciferase的MDA-MB-231細胞以熱休克處理，再測定withanolide類化合物對變性luciferase再摺疊 (refolding)的影響，更進一步證實withanolide類化合物可抑制hsp90的chaperone活性。重要的是，withanolide類化合物對hsp90的抑制能力與其毒殺MDA-MB-231細胞的能力具有高度正相關性。
因此，withanolide類化合物可視為新一代的hsp90抑制劑，具有發展成為新型抗癌藥物的潛力。

關鍵字

乳癌 ； 龍珠 ； 祕魯酸漿 ； 熱休克蛋白九十

並列摘要

Natural compounds from plants have been an important source for the discovery of anticancer drugs. It is known that withanolides, a group of steroidal lactones found in Solanaceae plants, exhibit anti-tumor, anti-angiogenic, anti-invasive, and chemo-preventive activities. In a previous study, we have demonstrated that a withanolide, tubocapsenolide A (TA), induced cycle arrest and apoptosis in human breast cancer MDA-MB-231 cells which was associated with the inhibition of heat shock protein 90 (hsp90). In order to confirm whether hsp90 inhibition is a general property of withanolides and to analyze the structure-activity of relationship, nine withanolide compounds were tested for their inhibitory effects on heat shock proteins and cell viability. Our results showed that most of the withanolides inhibited hsp90 function, as evident by degradation of hsp90 client proteins and induction of hsp70. The inhibitory effects of withanolides on hsp90 chaperone activity were further confirmed using in vivo heat shock luciferase activity recovery assays. Importantly, hsp 90 inhibition by withanolides correlated with their ability to induce cell death. Therefore, withanolides can be considered as a new type of inhibitor of hsp90, which has the potential to be developed as a novel strategy for cancer treatment.

並列關鍵字

withanolide ； MDA-MB-231 breast cancer ； heat shock protein 90

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