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

Abstract

While phosphatidylinositol 4-kinase (PI4KIIa) has been identified as a potential target for antitumor therapy, the clinical applications of PI4KIIa are limited by a lack of specific inhibitors. Here we report the first small-molecule inhibitor (SMI) of human PI4KIIa. 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 PI4KIIa kinase activity (IC 50 ¼ 0.47 mmol/L) and suppressed cell proliferation. Surface plasmon resonance and thermal shift assays indicated that PI-273 interacted directly with PI4KIIa. 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-type MCF-7 cells, but not in PI4KIIa knockout MCF-7 cells, indicating that PI-273 is highly selective for PI4KIIa. Mutant analysis revealed a role of palmitoylation insertion in the selectivity of PI-273 for PI4KIIa. 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 substratecompetitive, subtype-specific inhibitor of PI4KIIa, the use of which will facilitate evaluations of PI4KIIa as a cancer therapeutic target. Cancer Res; 77(22); 6253-66. Ó2017 AACR.

The Many Roles of Type II Phosphatidylinositol 4‐Kinases in Membrane Trafficking: New Tricks for Old Dogs

“…Historically, the two PI4KII activities could not be distinguished in cell and tissue extracts and, unsurprisingly, the structure of the conserved core of PI4KIIβ is very similar to that of PI4KIIα . Recently an isoform‐selective small molecule inhibitor, PI‐273, has been developed that is approximately 30 times more potent against PI4KIIα than PI4KIIβ . This compound is capable of differentiating the two isoforms and is likely to become an important experimental tool.…”

A large scale high-throughput screen identifies chemical inhibitors of phosphatidylinositol 4-kinase type II alpha

“…S1). Importantly, there was no structural similarity between PI-273 (35) and any of the active compounds identified in this study.…”

“…Based on all of these data linking type II PI4Ks to many physiological processes relevant to a variety of diseases, it would be desirable to find inhibitors for PI4K2A, the class of PI4Ks for which inhibitors are not available as yet. A recent study described an inhibitor (PI-273) of PI4K2A (35), which showed promise in inhibiting cancer cell growth. That study used docking-based and ligand-based screening strategy to identify PI-273, which was found to interfere with substrate binding or substrate access and not with ATP binding (35).…”

“…A recent study described an inhibitor (PI-273) of PI4K2A (35), which showed promise in inhibiting cancer cell growth. That study used docking-based and ligand-based screening strategy to identify PI-273, which was found to interfere with substrate binding or substrate access and not with ATP binding (35). Our studies have used a different strategy, namely, the screening of a small molecule library of compounds using a recombinant PI4K2A.…”

Therapeutic targeting of the PI4K2A/PKR lysosome network is critical for misfolded protein clearance and survival in cancer cells

“…PI4K2A is targeted to the trans-Golgi network and lysosomes [29][30][31]. Recently, an increasing number of studies have identified PI4K2A as a potential target for breast cancer therapy [32][33][34]. These results improved our understanding of PI4K2A/PKR lysosome networks may lead to the development of unique and highly specific targeted therapies for cancer.…”