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Bioorg Med Chem. 2014 Sep 1;22(17):4553-65. doi: 10.1016/j.bmc.2014.07.037. Epub 2014 Jul 30.

Ethyl 2-(benzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate analogues as a new scaffold for protein kinase casein kinase 2 inhibitor.

Author information

1
Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul 120-750, Republic of Korea.
2
College of Pharmacy, Ewha Womans University, Seoul 120-750, Republic of Korea.
3
Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul 120-750, Republic of Korea; Integrated Genomic Research Center for Metabolic Regulation, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea.
4
Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul 120-750, Republic of Korea; Integrated Genomic Research Center for Metabolic Regulation, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. Electronic address: kimkh34@yuhs.ac.
5
College of Pharmacy, CHA University, Pocheon 487-010, Republic of Korea. Electronic address: yna7315@cha.ac.kr.

Abstract

Protein kinase casein kinase 2 (PKCK2) is a constitutively active, growth factor-independent serine/threonine kinase, and changes in PKCK2 expression or its activity are reported in many cancer cells. To develop a novel PKCK2 inhibitor(s), we first performed cell-based phenotypic screening using 4000 chemicals purchased from ChemDiv chemical libraries (2000: randomly selected; 2000: kinase-biased) and performed in vitro kinase assay-based screening using hits found from the first screening. We identified compound 24 (C24)[(Z)-ethyl 5-(4-chlorophenyl)-2-(3,4-dihydroxybenzylidene)-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a] pyrimidine-6-carboxylate] as a novel inhibitor of PKCK2 that is more potent and selective than 4,5,6,7-tetrabromobenzotriazole (TBB). In particular, compound 24 [half maximal inhibitory concentration (IC50)=0.56μM] inhibited PKCK2 2.2-fold more efficiently than did TBB (IC50=1.24μM), which is quite specific toward PKCK2 with respect to ATP binding, in a panel of 31 human protein kinases. The Ki values of compound 24 and TBB for PKCK2 were 0.78μM and 2.70μM, respectively. Treatment of cells with compound 24 inhibited endogenous PKCK2 activity and showed anti-proliferative and pro-apoptotic effects against stomach and hepatocellular cancer cell lines more efficiently than did TBB. As expected, compound 24 also enabled tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-resistant cancer cells to be sensitive toward TRAIL. In comparing the molecular docking of compound 24 bound to PKCK2α versus previously reported complexes of PKCK2 with other inhibitors, our findings suggest a new scaffold for specific PKCK2α inhibitors. Thus, compound 24 appears to be a selective, cell-permeable, potent, and novel PKCK2 inhibitor worthy of further characterization.

KEYWORDS:

ATP binding site; Protein kinase casein kinase 2 (PKCK2); Selective PKCK2 inhibitor

PMID:
25131958
DOI:
10.1016/j.bmc.2014.07.037
[Indexed for MEDLINE]
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