Heteronemin, a Marine Sesterterpenoid-Type Metabolite, Induces Apoptosis in Prostate LNcap Cells via Oxidative and ER Stress Combined with the Inhibition of Topoisomerase Ⅱ and Hsp90

• Main Authors: Man-Gang Lee, 李蠻剛
• Other Authors: Wen Zhi-Hong
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/f396g4

博士 === 國立中山大學 === 海洋生物科技暨資源學系研究所 === 107 === Heteronemin, a marine sesterterpenoid-type natural product, possesses diverse bioactivities, especially antitumor effect. Accumulating evidence showed that heteronemin may act as a potent anticancer agent in clinical therapy. To fully understand the antitumor mechanism of heteronemin, we further explored the precise molecular targets in prostate cancer cells. Initially, heteronemin exhibited potent cytotoxic effect against LNcap and PC3 prostate cancer cells with IC50 1.4 and 2.7 μM after 24 h, respectively. In the xenograft animal model, the tumor size was significantly suppressed to about 51.9% in the heteronemin-treated group in comparison with the control group with no significant difference in the mice body weights. In addition, the results of a cell-free system assay indicated that heteronemin could act as topoisomerase II (topo II) catalytic inhibitor through the elimination of essential enzymatic activity of topoisomerase IIα expression. We found that the use of heteronemin triggered apoptosis by 20.1%-68.3%, caused disruption of mitochondrial membrane potential (MMP) by 66.9%-99.1% and promoted calcium release by 1.8, 2.0 and 2.1 folds compared with the control group in a dose-dependent manner, as demonstrated by annexin-V/PI, rhodamine 123 and Fluo-3 staining assays, respectively. Moreover, our findings indicated that the pretreatment of LNcap cells with an inhibitor of protein tyrosine phosphatase (PTPi) diminished growth inhibition, oxidative and ER stress, as well as activation of Chop/Hsp70 induced by heteronemin, suggesting that PTP activation plays a crucial rule in the cytotoxic activity of heteronemin. Using molecular docking analysis, heteronemin exhibited more binding affinity to the N-terminal ATP-binding pocket of Hsp90 protein than 17-AAG, a standard Hsp90 inhibitor. The expression of Hsp90 client proteins, phosphorylation of Akt (Ser473), STAT 3 (Ser 727 and Tyr705), PCNA, Rb2, as well as XIAP were suppressed by the use of heteronemin. However, the expression of p-HSF1, Hsp70 and acetylated tubulin were induced after heteronemin treatment. Our results indicated that heteronemin significantly induced apoptotic and autophagic death of LNcap cells by modulating ER and oxidative stress combined with the inhibition of topo II catalytic activity and Hsp90 function. Finally, heteronemin promoted autophagy and apoptosis induction through inhibition of Hsp 90 and topo II as well as PTP activation in prostate cancer cells. Taken together, these multiple targets present heteronemin as an interesting candidate for its future development as an antiprostatic agent.