In vitro activity: CX-4945 is selective for CK2, as it only inhibits 7 of the 238 kinases by more than 90% at concentration of 0.5 μM, which is 500-fold greater than the IC50 of CK2. Although in cell-free systems CX-4945 inhibits FLT3, PIM1, and CDK1 with IC50 of 35 nM, 46 nM, and 56 nM, respectively, CX-4945 treatment at 10 μM is inactive against FLT3, PIM1, and CDK1 in cell-based functional assays. CX-4945 exhibits a broad spectrum of antiproliferative activity, and the breast cancer cell lines displays the widest range of sensitivity to CX-4945 with EC50 of 1.71-20.01 μM. The antiproliferative activity of CX-4945 correlates with CK2α mRNA and protein levels but not the CK2α' catalytic subunit, the regulatory CK2β subunit, and the PI3K/Akt or PTEN mutational status. CX-4945 inhibits PI3K/Akt signaling by directly blocking the phosphorylation of Akt at Serine 129 by CK2 rather than through activation of PTEN. CX-4945 treatment causes reduced phosphorylation of p21 (T145), increased levels of total p21 and p27, and induction of caspase 3/7 activity. CX-4945 treatment induces a G2/M cell-cycle arrest in BT-474 cells and a G1 arrest in BxPC-3 cells. CX-4945 inhibits HUVEC proliferation, migration, and tube formation with IC50 of 5.5 μM, 2 μM, and 4 μM, respectively. Under hypoxic conditions in BT-474 and BxPC-3 cells, CX-4945 treatment prevents downregulation of p53 and pVHL and reduces activation of HIF-1α transcription. CX-4945 potently inhibits endogenous intracellular CK2 activity with IC50 of 0.1 μM in Jurkat cells.

Kinase Assay: CX-4945 is added at a volume of 10 μL to a reaction mixture comprising 10 μL of assay dilution buffer (ADB; 20 mM MOPS, pH 7.2, 25 mM β-glycerolphosphate, 5 mM EGTA, 1 mM sodium orthovanadate, and 1 mM dithiothreitol), 10 μL of substrate peptide (RRRDDDSDDD, dissolved in ADB at a concentration of 1 mM), 10 μL of recombinant human CK2 (ααββ-holoenzyme, 25 ng dissolved in ADB). Reactions are initiated by the addition of 10 μL of ATP solution (90% 75 mM MgCl2, 75 μM ATP (final ATP concentration=15 μM) dissolved in ADB; 10% [γ-33P]ATP (stock 1 mCi/100 μL; 3000 Ci/mM and maintained for 10 minutes at 30 °C. The reactions are quenched with 100 μL of 0.75% phosphoric acid and then transferred to and filtered through a phosphocellulose filter plate. After washing each well five times with 0.75% phosphoric acid, the plate is dried under vacuum for 5 minutes and, following the addition of 15 μL of scintillation fluid to each well, the residual radioactivity is measured using a Wallac luminescence counter. The IC50 values are derived from eight concentrations of CX-4945 over a range of 0.0001 μM to 1 μM.

Cell Assay: Cells (SKBr3, MDA-MB-453, BT-474, ZR-75-1, MDA-MB-231, MDA-MB-468, T47D, MCF 7, Hs578T, MDA-MB-361, UACC-812, et al.) are seeded at a density of 3,000 cells per well 24 hours prior to treatment, in appropriate media, and then treated with various concentrations of CX-4945. Suspensions cells are seeded and treated on the same day. Following 4 days of incubation, Alamar Blue (20 μL, 10% of volume per well) is added and the cells are further incubated at 37 °C for 4-5 hours. Fluorescence with excitation wavelength at 530-560 nm and emission wavelength at 590 nm is measured.

Cancer Res. 2010 Dec 15;70(24):10288-98; J Med Chem. 2011 Jan 27;54(2):635-54.