Heat shock cognate 70 protein is a novel target of nobiletin and its colonic metabolites in inhibiting colon carcinogenesis

Nobiletin (NBT) is a unique flavonoid mainly found in citrus fruits and has been reported to inhibit colon carcinogenesis in multiple rodent models. However, the direct molecular targets of NBT are unknown, which greatly limits its utilization in cancer prevention and treatment. In this study, using affinity chromatography, proteomics, computer modeling and various biochemical analyses, for the first time we identified HSC70 as a direct protein target of NBT in colon cancer cells. Moreover, NBT bound to HSC70 at its ATP-binding site and inhibited its ATPase activity. Importantly, our results also demonstrated that the major colonic metabolites of NBT (generated in the colon of NBT-fed mice) produced similar inhibitory effects against HSC70-mediated pro-carcinogenic events to those of NBT. Overall, our results provide a solid basis to further investigate the implication of the interaction between NBT/NBT metabolites and HSC70 in cancer chemoprevention. HSC70 has been identified as a direct protein target of nobiletin (NBT), and the interaction between NBT and HSC70 triggers cancer cell death.