Broad-Spectrum Anticancer Activity and Pharmacokinetic Properties of a Prenyloxy-Substituted Indeno[1,2-b]indole Derivative, Discovered as CK2 Inhibitor.

Ehab El-Awaad,Zouhair Bouaziz,Christelle Marminon,Marc Le Borgne,Joachim Jose,Dagmar Aichele,Laurens Ballentin,Robin Birus

doi:10.3390/ph14060542

Abstract

Protein kinase CK2 is involved in regulating cellular processes, such as cell cycle, proliferation, migration, and apoptosis, making it an attractive anticancer target. We previously described a prenyloxy-substituted indeno[1,2-b]indole (5-isopropyl-4-(3-methylbut-2-enyloxy)-5,6,7,8-tetrahydroindeno[1,2-b]indole-9,10-dione (4p)) as a very potent inhibitor of CK2 holoenzyme (IC50 = 25 nM). Here, we report the broad-spectrum anticancer activity of 4p and provide substantial progress on its pharmacokinetic properties. Using a cell-based CK2 activity assay and live-cell imaging of cultured A431, A549, and LNCaP cancer cell lines, cellular CK2 target engagement was shown as well as strong antiproliferative, anti-migratory and apoptosis-inducing effects of 4p. Furthermore, evidence was found for the ability of 4p to disrupt A549 spheroid cohesion. A series of LC-MS/MS experiments revealed high and rapid cellular uptake (intracellular concentration is approximately 5 µM after 1 h incubation) and low metabolic stability of 4p. These results point to the value of 4p as a potent CK2 inhibitor with promising anticancer activities and should trigger future medicinal chemistry efforts to improve the drug-like properties of this compound.

Highlights

Human protein kinase CK2, originally named “Casein Kinase II” [1], is a ubiquitously expressed serine/threonine kinase that phosphorylates several hundreds of substrates in eukaryotic cells [2,3,4]
To determine the cellular target engagement of protein kinase CK2 by 4p, cultured cells from A431, A549, and LNCaP cell lines were treated with 4p at 1 and 20 μM or vehicle (1% dimethyl sulfoxide (DMSO)) for 24 h followed by harvesting and lysing the cells
CK2 activity in the soluble fraction of the cell lysates was determined in a capillary electrophoresis-based CK2 activity assay as described before [35] utilizing the fluorescently labeled CK2 substrate FITC-RRRDDDSDD-NH2 (A representative electropherogram is shown in the Supplementary Materials, Figure S1)

Summary

Introduction

Human protein kinase CK2, originally named “Casein Kinase II” [1], is a ubiquitously expressed serine/threonine kinase that phosphorylates several hundreds of substrates in eukaryotic cells [2,3,4]. This highly pleiotropic kinase is involved in the regulation of numerous cellular processes, including, among others, cell proliferation, cell survival, as well as gene transcription and translation [5,6,7,8,9,10]. Upregulation of CK2 expression/activity allows them to proliferate strongly and circumvent apoptosis, and thereforewith these malignant dependon high CK2 activity for their survival.

Methods

Results

Conclusion