The Heat Shock Proteins are Novel Targets For Nobiletin in Human Cancer Cells

Abstract

Nobiletin is a major bioactive flavonoid found in citrus fruits that has been shown to have many bioactivities such as anti-cancer and anti-inflammation effects. However, the underlying molecular mechanism of these bioactivities is poorly understood. We hypothesize that nobiletin may exert its diverse biological effects by interacting with specific target proteins. Nobiletin was derivatized so that it can be covalently bound and immobilized to sepharose. Whole cell lysates of human colon cancer cells were subject to affinity chromatography with nobiletin-bound sepharose as stationary matrix. Proteins with high binding affinity to nobiletin was selectively eluted by high ion strength buffers, and then resolved by two-dimensional electrophoresis. The identities of proteins were determined by mass spectroscopy after digestion with trypsin. Heat shock proteins (HSPs) were identified as major high-affinity binding proteins of nobiletin, which was further confirmed by Western blot analysis using specific anti-HSP antibodies. HSPs play critical roles in various signaling pathways important for carcinogenesis. Our results provide a solid basis to further investigate the implication of the interaction between nobiletin and HSPs in cancer chemoprevention. This study was supported by funding from NIH, AICR and USDA.