Docosahexaenoic Acid-mediated Inhibition of Heat Shock Protein 90-p23 Chaperone Complex and Downstream Client Proteins in Lung and Breast Cancer.

The molecular chaperone, heat shock protein 90 (Hsp90), is a critical regulator for the proper folding and stabilization of several client proteins, and is a major contributor to carcinogenesis. Specific Hsp90 inhibitors have been designed to target the ATP-binding site in order to prevent Hsp90 chaperone maturation. The current study investigated the effects of docosahexaenoic acid (DHA; C22:6 n-3) on Hsp90 function and downstream client protein expression. In vitro analyses of BT-474 human breast carcinoma and A549 human lung adenocarcinoma cell lines revealed dose-dependent decreases in intracellular ATP levels by DHA treatment, resulting in a significant reduction of Hsp90 and p23 association in both cell lines. Attenuation of the Hsp90-p23 complex led to the inhibition of Hsp90 client proteins, epidermal growth factor receptor 2 (ErbB2), and hypoxia-inducible factor 1 (HIF-1). Similar results were observed when employing 2-deoxyglucose (2-DG), confirming that DHA and 2-DG, both independently and combined, can disturb Hsp90 molecular chaperone function. In vivo A549 xenograft analysis also demonstrated decreased expression levels of Hsp90-p23 association and diminished protein levels of ErbB2 and HIF-1 in mice supplemented with dietary DHA. These data support a role for dietary intervention to improve cancer therapy in tumors overexpressing Hsp90 and its client proteins.