Chalcone-based compounds, both natural and synthetic, have shown a wide spectrum of biological activities with therapeutic potentials, including cytotoxicity, anti-inflammation, anti-microbial, and others. Among these bioactivities, cytotoxicity is of particular interest due to its anti-cancer potential. Although chalcones' bioactivities have been studied extensively, the mechanistic insights and particularly the responsible cellular targets surprisingly remain largely unsettled, which significantly limits the development of chalcone-based compounds into potent and selective therapeutic agents.<br/><br/>In this study, we aimed to identify the cellular target responsible for chalcones' cytotoxicity via photoaffinity labeling approach, and to further elucidate the cytotoxic mechanisms. We first developed a chalcone compound library targeting cytotoxicity. Guided by the sharp structure-activity relationship (SAR) obtained within our library, positive and negative photoaffinity probes were designed and synthesized for direct target labeling and pull-down experiments from cells. Various cell-based photoaffinity labeling experiments unambiguously identified a 52 kD protein as the responsible cellular target for chalcone’s cytotoxicity, which was revealed as β-tubulin by mass spectrometry. Furthermore, cytotoxic chalcones were shown to inhibit tubulin polymerization, disrupt the microtubule network in cells, and cause M-phase cell cycle arrest. These tubulin-related effects not only further supported β-tubulin as chalcones' direct cellular target responsible for cytotoxicity, but also provided a comprehensive view of the cellular mechanisms by which chalcones exert their cytotoxicity.<br/><br/>Altogether, our results provided a target-level mechanistic insight into chalcones' cytotoxicity, which would be important for further development of chalcone-based compounds as potential anti-cancer agents. The methodology applied here could be adapted for the target identification and mechanism elucidation of chalcones' other biological activities.

Target identification and mechanism elucidation of chalcones’ cytotoxicity via photoaffinity probes

249th National Meeting (2015)

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