Quantitative chemical proteomics reveals anti-cancer targets of Celastrol in HCT116 human colon cancer cells.

BACKGROUND:Celastrol (Cel) is a naturally-derived compound with anti-cancer properties and exerts beneficial effects against various diseases. Although an extensive body of research already exists for Cel, the vast majority are inductive studies with limited validation of specific pathways and functions. The cellular targets that bind to Cel remain poorly characterized, which limits attempts to uncover its mechanism of action. PURPOSE:The present study aims to comprehensively identify the protein targets of Cel in HCT116 cells in an unbiased manner, and elucidate the mechanism of the anti-cancer activity of Cel based on target information. METHODS:A comprehensive analysis of protein targets that bind to Cel was performed in HCT116 colon cancer cells using a quantitative chemical biology method. A Cel probe (Cel-P) was synthesized to allow in situ monitoring of treatment in living HCT116 cells, and specific targets were identified with a quantitative chemical biology method (isobaric tags for relative and absolute quantitation) using mass spectrometry. RESULTS:In total, 100 protein targets were identified as specific targets of Cel. Pathways associated with the targets were investigated. Multiple pathways were demonstrated to be potential effectors of Cel. These pathways included the suppression of protein synthesis, deregulation of cellular reactive oxygen species, and suppression of fatty acid metabolism, and they were validated with in vitro experiments. CONCLUSION:The extensive information on the protein targets of Cel and their functions uncovered by this study will enhance the current understanding of the mechanism of action of Cel and serve as a valuable knowledge base for future studies.