Emerging evidence suggests that autophagic modulators have therapeutic potential. This study aims to identify novel autophagic inducers from traditional Chinese medicinal herbs as potential antitumor agents. Using an image-based screen and bioactivity-guided purification, we identified alisol B 23-acetate, alisol A 24-acetate, and alisol B from the rhizome of Alisma orientale as novel inducers of autophagy, with alisol B being the most potent natural product. Across several cancer cell lines, we showed that alisol B-treated cells displayed an increase of autophagic flux and formation of autophagosomes, leading to cell cycle arrest at the G 1 phase and cell death. Alisol B induced calcium mobilization from internal stores, leading to autophagy through the activation of the CaMKK-AMPK-mammalian target of rapamycin pathway. Moreover, the disruption of calcium homeostasis induces endoplasmic reticulum stress and unfolded protein responses in alisol B-treated cells, leading to apoptotic cell death. Finally, by computational virtual docking analysis and biochemical assays, we showed that the molecular target of alisol B is the sarcoplasmic/endoplasmic reticulum Ca 2+ ATPase. This study provides detailed insights into the cytotoxic mechanism of a novel antitumor compound. Mol Cancer Ther; 9(3); 718-30. ©2010 AACR.

Gold(III) complexes have shown promise as antitumor agents, but their clinical usefulness has been limited by their poor stability under physiological conditions. A novel gold(III) porphyrin complex [5-hydroxyphenyl-10,15,20-triphenylporphyrinato gold(III) chloride (gold-2a)] with improved aqueous stability showed 100-fold to 3,000-fold higher cytotoxicity than platinum-based cisplatin and IC 50 values in the nanomolar range in a panel of human breast cancer cell lines. Intraductal injections of gold-2a significantly suppressed mammary tumor growth in nude mice. These effects are attributed, in part, to attenuation of Wnt/β-catenin signaling through inhibition of class I histone deacetylase (HDAC) activity. These data, in combination with computer modeling, suggest that gold-2a may represent a promising class of anticancer HDAC inhibitor preferentially targeting tumor cells with aberrant Wnt/β-catenin signaling.

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