Kinase experiment:

Briefly, final assay concentrations for CK1δ, Ulight peptide substrate (ULight-Topo-Ila(Thr1342) peptide) and ATP are 2 nM, 200 nM and 20 μM respectively. The reaction is performed at room temperature in a 10 μL final volume (384-well low volume plate) containing the following: 50 mM Hepes, pH 7.5, 5 mM MgCl2, 0.1 mg/mL bovine serum albumin, 1 mM dl-dithiothreitol, 0.01% Triton X-100 and 1% DMSO. After 10 min, the reaction is terminated by addition of 10 μL of 4 nM Eu-anti-p-Topo-Ila in Lance Detection Buffer. The fluorescent signal is detected using a plate reader. 10 point does-response curves with 3-fold dilutions starting from 10 μM for each compound (SR-3029) is generated in duplicate and data fit to a four parameter logistic[1].

Cell experiment:

Human A375 melanoma cells are cultured in Dulbecco's Modified Eagle Medium (DMEM) supplemented with 10% fetal bovine serum, 1% penicillin/streptomycin and 1× MEM Non-Essential Amino Acids at 37℃, 5% CO2. To evaluate the anti-proliferative activity of newly synthesized CK1δ/ε inhibitors, each compound (SR-3029) is subjected to MTT assays against A375 melanoma cells and their EC50 values are determined. Briefly, A375 melanoma cells are plated into a 96-well plate and treated with a series of concentrations of each new inhibitor, vehicle (DMSO) or with SR-3029 or SR-1277 (positive controls). MTT assays are performed four days after treatment and data are analyzed using the GraphPad Prism5[1].

Animal experiment:

Stable pools of MDA-MB-231-Luc, MDA-MB-231, MDA-MB-468, SKBR3, or BT474 cells are established by injection of 2 × 106 cancer cells into the mammary fat pads of 6-week-old female athymic nude mice. Establishment of BCM-4013 patient-derived xenografts is performed. Briefly, fresh xenograft tumor fragments (~1 mm3) are transplanted into the cleared mammary fat pad of recipient SCID/Bg mice. Mice are treated with SR-3029 or vehicle (10:10:80, DMSO:Tween-80:Water) at 20 mg/kg daily by i.p. injection. Tumor volumes are measured as the indicated intervals using calipers or by luminescence imaging with the IVIS 100 imager after subcutaneous injection of luciferin (15 mg/mL). Average radiance (p/s/cm2/sr) is determined from tumor region-of-interest (ROI) using Living-Image analysis software[2].

SR-3029 is a potent and ATP competitive CK1δ and CK1ε inhibitor, with IC50s of 44 nM and 260 nM, respectively, and Kis of 97 nM for both kinases.

SR-3029 is a potent CK1δ/CK1ε inhibitor, with IC50s of 44 nM and 260 nM, respectively. SR-3029 is ATP competitive, with Kis of 97 nM for CK1δ/CK1ε. SR-3029 also blocks CDK6/cyclin D3, CDK6/cyclin D1, CDK4/cyclin D3, CDK4/cyclin D1 and FLT3, with IC50s of 427, 428, 368, 576, and 3000 nM, respectively. SR-3029 shows inhibitory effects on A375 cells, with an EC50 of 86 nM[1]. CK1δ is a necessary and sufficient driver of Wnt/β-catenin signaling in human breast cancer. SR-3029 shows less potent activities against MCF7 and T47D breast cancer cells and the MCF10A cell line, which express low amounts of CK1δ[2].

SR-3029 (20 mg/kg daily i.p.) exibits anti-tumor effects in rthotopic MDA-MB-231, MDA-MB-468 (TNBC), SKBR3 and BT474 (HER2+) tumor xenografts with no overt toxicity in mice. SR-3029 (20 mg/kg daily i.p.) also effectively inhibits the growth of tumor in primary patient-derived xenograft (PDX) models. In addition, SR-3029 (20 mg/kg, i.p.) strongly reduces the expression of nuclear β-catenin in tumors of mice[2].

References:
[1]. Bibian M, et al. Development of highly selective casein kinase 1δ/1ε (CK1δ/ε) inhibitors with potent antiproliferative properties. Bioorg Med Chem Lett. 2013 Aug 1;23(15):4374-80.
[2]. Rosenberg LH, et al. Therapeutic targeting of casein kinase 1δ in breast cancer. Sci Transl Med. 2015 Dec 16;7(318):318ra202.