Chemistry Central Journal

© Keppner et al; licensee BioMed Central Ltd. 2009

This article is published under license to BioMed Central Ltd.

10.1186/1752-153X-3-S1-P65

Poster presentation

Identification of Plk1 type II inhibitors by structure-based virtual screening

S Keppner1 , E Proschak¹, G Schneider¹ and B Spänkuch¹

(1)

Johann Wolfgang Goethe University, Beilstein Endowed Chair for Cheminformatics, Siesmayerstr. 70, 60323 Frankfurt/Main, Germany

Published online: 05 June 2009

Protein kinases are targets for drug development [1]. Dysregulation of kinase activity leads to various diseases [2], e.g. cancer, inflammation, diabetes [1]. Human polo-like kinase 1 (Plk1), a serine/threonine kinase, is a cancer-relevant gene and a potential drug target which attracts increasing attention in the field of cancer therapy. Plk1 is a key player in mitosis and modulates entry into mitosis and the spindle checkpoint at the meta-/anaphase transition. Plk1 overexpression is observed in various human tumors, and it is a negative prognostic factor for cancer patients [3].

The same catalytical mechanism and the same co-substrate (ATP) lead to the problem of inhibitor selectivity. A strategy to solve this problem is represented by targeting the inactive conformation of kinases [2]. Kinases undergo conformational changes between active and inactive conformation and thus an additional hydrophobic pocket is created in the inactive conformation where the surrounding amino acids are less conserved [2].

A "homology model" of the inactive conformation of Plk1 was constructed, as the crystal structure in its inactive conformation is unknown. A crystal structure of Aurora A kinase served as template structure. With this homology model a receptor-based pharmacophore search was performed using SYBYL7.3 software. The raw hits were filtered using physico-chemical properties. The resulting hits were docked using Gold3.2 software, and 13 candidates for biological testing were manually selected.

Three compounds of the 13 tested exhibit anti-proliferative effects in HeLa cancer cells. The most potent inhibitor, SBE13, was further tested in various other cancer cell lines of different origins and displayed EC50 values between 12 μM and 39 μM. Cancer cells incubated with SBE13 showed induction of apoptosis, detected by PARP (Poly-Adenosyl-Ribose-Polymerase) cleavage, caspase 9 activation and DAPI staining of apoptotic nuclei.

References

1.

Thaimattam R, Banerjee R, Miglani R, Iqbal J: Protein kinase inhibitors: structural insights into selectivity. Curr Pharm Des. 2007, 13: 2751-2765. 10.2174/138161207781757042.CrossRef

2.

Liu Y, Gray NS: Rational design of inhibitors that bind to inactive kinase conformations. Nat Chem Biol. 2006, 2: 358-364. 10.1038/nchembio799.CrossRef

3.

Strebhardt K, Ullrich A: Targeting polo-like kinase 1 for cancer therapy. Nat Rev Cancer. 2006, 6: 321-330. 10.1038/nrc1841.CrossRef