Suppression of CBM complex activity/NFκB pathway via CK1α degradation by FPFT-2216. Western blot analysis of DLBCL cell lines (A) and RI-1 cells expressing CK1α G40N mutant (B) cultured for 24 hours in the presence of compounds at different concentrations. Open triangle: Uncleaved BCL10, closed triangle: Cleaved BCL10. C, MG-132 was added after OCI-Ly3 cells were cultured for 23 hours in the presence of compounds at the concentrations shown in the figure. After 1 hour, proteins were extracted from the cells, and Western blot analysis was performed. D, Jurkat cells were cultured for approximately 24 hours in the presence of compounds at the concentrations shown in the figure, and the cells were cultured for 15 minutes after adding PMA/ionomycin. Proteins were extracted from the cells, and Western blot analysis was performed. Representative results from two (B–D) or three (A) independent experiments are shown. GAPDH or α-tubulin was used as a loading control. 2216, FPFT-2216; Lena, lenalidomide; Iber, iberdomide; MALT1i, Z-VRPR-FMK; BAY, BAY 11-7082; Poma, pomalidomide.
ARTICLE ABSTRACT
Reducing casein kinase 1α (CK1α) expression inhibits the growth of multiple cancer cell lines, making it a potential therapeutic target for cancer. Herein, we evaluated the antitumor activity of FPFT-2216—a novel low molecular weight compound—in lymphoid tumors and elucidated its molecular mechanism of action. In addition, we determined whether targeting CK1α with FPFT-2216 is useful for treating hematopoietic malignancies. FPFT-2216 strongly degraded CK1α and IKAROS family zinc finger 1/3 (IKZF1/3) via proteasomal degradation. FPFT-2216 exhibited stronger inhibitory effects on human lymphoma cell proliferation than known thalidomide derivatives and induced upregulation of p53 and its transcriptional targets, namely, p21 and MDM2. Combining FPFT-2216 with an MDM2 inhibitor exhibited synergistic antiproliferative activity and induced rapid tumor regression in immunodeficient mice subcutaneously transplanted with a human lymphoma cell line. Nearly all tumors in mice disappeared after 10 days; this was continuously observed in 5 of 7 mice up to 24 days after the final FPFT-2216 administration. FPFT-2216 also enhanced the antitumor activity of rituximab and showed antitumor activity in a patient-derived diffuse large B-cell lymphoma xenograft model. Furthermore, FPFT-2216 decreased the activity of the CARD11/BCL10/MALT1 (CBM) complex and inhibited IκBα and NFκB phosphorylation. These effects were mediated through CK1α degradation and were stronger than those of known IKZF1/3 degraders. In conclusion, FPFT-2216 inhibits tumor growth by activating the p53 signaling pathway and inhibiting the CBM complex/NFκB pathway via CK1α degradation. Therefore, FPFT-2216 may represent an effective therapeutic agent for hematopoietic malignancies, such as lymphoma.
We found potential vulnerability to CK1α degradation in certain lymphoma cells refractory to IKZF1/3 degraders. Targeting CK1α with FPFT-2216 could inhibit the growth of these cells by activating p53 signaling. Our study demonstrates the potential therapeutic application of CK1α degraders, such as FPFT-2216, for treating lymphoma.
