Imiquimod targets tankyrase 2 to suppress wnt-active colorectal cancer

The Wnt/beta-catenin signaling pathway is frequently upregulated in colorectal cancer (CRC), driving tumor progression and therapeutic resistance. Tankyrase (TNKS), a key regulator of this pathway, has emerged as a promising therapeutic target. XAV939, a small-molecule inhibitor of TNKS, has been widely used to study Wnt pathway inhibition. TNKS inhibitors suppress Wnt signaling by stabilizing Axin, a key component of the beta-catenin destruction complex, which leads to enhanced degradation and thus a reduction in the cellular and nuclear levels of beta-catenin. We investigated the anticancer potential of Imiquimod (IMQ), a Toll-like receptor 7 (TLR7) agonist, through its interaction with TNKS2. Molecular docking and dynamics simulations revealed that IMQ binds stably to the PARP catalytic domain of TNKS2, with a higher docking score than the co-crystallized ligand. Notably, IMQ formed critical interactions with residues Tyr1060 and Glu1138, located within the catalytic core of TNKS2, suggesting its ability to modulate Wnt/beta-catenin signaling. Cytotoxicity and cell cycle analysis demonstrated differential sensitivity to IMQ and XAV939, across colorectal cancer and normal cell lines. Interestingly, confocal microscopy revealed that IMQ significantly reduced beta-catenin expression in DLD1 CRC cells harboring wild-type beta-catenin, while no significant decrease was observed in HCT116 CRC cells with mutant beta-catenin. This study reveals a novel potential route for repurposing a clinically approved agent to suppress Wnt-driven oncogenesis. This is the first study to propose a mechanism by which IMQ may inhibit Wnt/beta-catenin signaling.