Study on the anti-cancer effects of Hsp90 inhibition induced by andrographolide and its derivatives

• Main Authors: Sheng-Hung Liu, 劉勝紘
• Other Authors: Shu-Ling Fu
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/95571198072126092771

博士 === 國立陽明大學 === 藥理學研究所 === 102 === Andrographolide is a diterpenoid compound isolated from Andrographis paniculata that exhibits anticancer activity. Our lab previously reported that andrographolide suppressed v-Src-mediated cellular transformation by promoting the degradation of Src. In addition, a cleaved fragment of Hsp90 was identified in andrographolide-treated cells by a proteomics approach. This study further demonstrated the involvement of Hsp90 in the andrographolide-mediated inhibition of Src oncogenic activity. The concentration- and time-dependent induction of Hsp90 cleavage that accompanied the reduction in Src was validated in andrographolide-treated RK3E cells transformed with either v-Src or a human truncated c-Src variant. In cancer cells, the induction of Hsp90 cleavage by andrographolide and its structural derivatives (NCTU-030 and NCTU-322) correlated well with the decreased Src levels, the suppression of transformation, and the induction of apoptosis. Moreover, the andrographolide-induced Hsp90 cleavage, Src degradation, inhibition of transformation, and induction of apoptosis were abolished by ROS inhibitors, N-acetyl-cysteine and Trolox. Notably, Hsp90 cleavage, decreased levels of Bcr-Abl (another known Hsp90 client protein), and the induction of apoptosis were also observed in human K562 leukemia cells treated with andrographolide or its active derivatives. Andrographolide selectively suppressed Hap90 client proteins but not non-Hsp90 client proteins in transformed ts-v-Src cells. The normal Bcr protein was also more resistant to andrographolide treatment than oncoprotein Bcr-Abl in human K562 cells. Pretreatment of a pan-caspase inhibitor, Z-VAD-FMK, blocked Hsp90 cleavage but did not restore v-Src degradation after andrographolide treatment. Moreover, andrographolide treatment reduced the interaction of Hsp90α and v-Src. Since the disruption of Hsp90-v-Src interaction appears to occur earlier than Hsp90 cleavage after andrographolide treatment, the major effect of andrographolide on Hsp90 function may attribute to the disruption of interaction between Hsp90 and its client proteins. This study recently also established a system to express and purify a biotinylated Hsp90, which will be an efficient tool to further study the interaction between andrographolide and Hsp90. A bioactive fluorescent derivative of andrographolide was also created to further study andrographolide-interacting proteins. The molecular mechanism(s) by which andrographolide attenuated the binding of Hsp90 and its client proteins merit further investigation. In summary, this thesis demonstrated a novel mechanism by which andrographolide suppressed cancer malignancy that involves inhibiting Hsp90 function and reducing the levels of Hsp90 client proteins. These results broaden the molecular basis of andrographolide-mediated anticancer activity.