Fig. 1. CK1δ is a clinically relevant and effective target for select breast cancer subtypes.

(A) CK1δ mRNA expression in invasive ductal breast carcinomas (IDC) vs. adjacent normal tissue (***, p=6.78e–15). (B) Expression of CK1α1, CK1δ, and CK1ε across PAM50 breast cancer subtypes based on RNA-Seq data (n=972 tumor samples, 113 solid tissue normal). Log2 normalized read count (RSEM) is shown. (C) CSNK1D DNA copy number analysis in invasive breast carcinomas clustered according to CK1δ expression (n=303). Gene-level copy number estimates (GISTIC2 threshold) of −2 (dark blue), −1 (light blue), 0 (white), 1 (light red), 2 (dark red), representing homozygous deletion, single copy deletion, diploid normal copy, low-level copy number amplification, or high-level copy number amplification are shown. (D) Scatter plot of CSNK1D Log₂ mRNA expression vs. Log₂ copy number values (972 breast cancer patients). (E) CK1δ and CK1ε protein expression in indicated breast cancer cell lines and MCF10A mammary epithelial cells. (F) Chemical structure of SR-3029. (G) Anti-proliferative potency of SR-3029 in the indicated breast cancer cell lines. Data are plotted as % proliferation vs. vehicle (n=6). (H) Clonogenic growth and survival of the indicated cells in the presence of SR-3029 or vehicle (n=3; p=0.0008). (I) Percent apoptosis by PI /Annexin V FACS after 72 hours of treatment with indicated doses of SR-3029 (n=3; ***, left to right p=0.0007 and 0.0001). (J) Left, Clonogenic growth of MDA-MB-231 cells overexpressing CK1δ or GFP +/− SR-3029 (n=3; ***, p=0. 001, **, p=0.0035). Right, western blot confirming CK1δ overexpression +/− 30 nM SR-3029 at 48 hours. (K) Relative growth (left; n=3, siδ1; p=0.01, siδ2; p=0.003) and percent cell death by trypan blue dye exclusion (right; n=3, siδ1; p=0.01, siδ2 p=0.027) 5 days after transfection of MDA-MB-231 with non-targeting (NT) or CK1δ siRNAs. (L) qPCR data and immunoblot confirming knockdown of CK1δ but not CK1ε (n=3; ***, p<0.0001).