PI-273, a Substrate-Competitive, Specific Small-Molecule Inhibitor of PI4KIIα, Inhibits the Growth of Breast Cancer Cells

While phosphatidylinositol 4-kinase (PI4KII alpha) has been identified as a potential target for antitumor therapy, the clinical applications of PI4KII alpha are limited by a lack of specific inhibitors. Here we report the first small-molecule inhibitor (SMI) of human PI4KII alpha. Docking-based and ligand-based virtual screening strategies were first employed to identify promising hits, followed by two rounds of kinase activity inhibition validation. 2-(3-(4-Chlorobenzoyl) thioureido)-4-ethyl-5-methylthiophene-3-carboxamide (PI-273) exhibited the greatest inhibitory effect on PI4KII alpha kinase activity (IC50 = 0.47 mmol/L) and suppressed cell proliferation. Surface plasmon resonance and thermal shift assays indicated that PI-273 interacted directly with PI4KII alpha. Kinetic analysis identified PI-273 as a reversible competitive inhibitor with respect to the substrate phosphatidylinositol (PI), which contrasted with most other PI kinase inhibitors that bind the ATP binding site. PI-273 reduced PI4P content, cell viability, and AKT signaling in wild typeMCF-7 cells, but not in PI4KII alpha knockout MCF-7 cells, indicating that PI-273 is highly selective for PI4KII alpha. Mutant analysis revealed a role of palmitoylation insertion in the selectivity of PI-273 for PI4KII alpha. In addition, PI-273 treatment retarded cell proliferation by blocking cells in G(2)-M, inducing cell apoptosis and suppressing colony-forming ability. Importantly, PI-273 significantly inhibited MCF-7 cell-induced breast tumor growth without toxicity. PI-273 is the first substrate-competitive, subtype-specific inhibitor of PI4KII alpha, the use of which will facilitate evaluations of PI4KII alpha as a cancer therapeutic target. (C) 2017 AACR.