Potassium-3-beta-hydroxy-20-oxopregn-5-en-17-alpha-yl sulfate: a novel inhibitor of 78 kDa glucose-regulated protein

BACKGROUND Previous studies have shown the central role of 78 kDa glucose-regulated protein (GRP78) in colorectal cancer (CRC) survival and chemoresistance. In the present study, we aimed to design a GRP78 inhibitor and test its potential to inhibit CRC cells growth. MATERIALS AND METHODS Computer-aided drug design was used to establish novel compounds as potential inhibitors of GRP78. Discovery Studio 3.5 software was used to evaluate a series of designed compounds and assess their mode of binding to the active site of the protein. The cytotoxicity of the designed compounds was evaluated using the MTT assay and the propidium iodide method. The effect of the inhibitor on the expression of GRP78 was evaluated by immunoblotting. RESULTS Among the designed compounds, only potassium-3-beta-hydroxy-20-oxopregn-5-en-17-alpha-yl sulfate (PHOS) has a potential to inhibit the growth of CRC cells. Inhibition of cellular growth was largely attributed to downregulation of GRP78 and induction of apoptotic cell death. CONCLUSION These results introduce PHOS as a promising GRP78 inhibitor that could be used in future studies as a combination with chemotherapy in the treatment of CRC patients. Our ongoing studies aim to characterize PHOS safety profile as well as its mechanism of action.