Serotonin receptor type 7 (5-HT7) promotes colorectal cancer progression by activating Wnt/β-catenin signaling via interacting with CK1ε.

5-hydroxytryptamine (5-HT; serotonin), a well-known neurotransmitter, can promote the development of colorectal cancer (CRC). 5-HT exerts distinct physiological and pathological effects through engagement with specific 5-HT receptors. However, the receptors mediating tumor-promoting effects in CRC remain largely unknown. Here, we found that 5-HT receptor 7 (5-HT7) was significantly upregulated in CRC tumor tissues. Elevated 5-HT7 protein levels correlated positively with tumor burden, pathological grade, and lymph node metastasis, and negatively with overall survival in CRC patients. In CRC cells, lentivirus-mediated 5-HT7 overexpression enhanced proliferation, migration, and invasion, whereas RNA interference-mediated knockdown suppressed these processes. 5-HT (10 μM) increased 5-HT7 expression and had similar tumor-promoting effects in CRC cells, which were suppressed by 5-HT7 knockdown. In nude mice, 5-HT7 overexpression increased tumor size and lung metastasis, while knockdown produced the opposite effects. Mechanistically, 5-HT7 interacted with CK1ε, leading to Dishevelled (Dvl) phosphorylation, β-catenin accumulation, and activation of the Wnt/β-catenin signaling pathway. CK1ε knockdown or treatment with the CK1ε-specific inhibitor PF4800567 blocked 5-HT7-induced Wnt/β-catenin activation and reduced tumor growth and metastasis. Molecular docking and mutagenesis assays identified R13 and R372 in CK1ε and R427 and W472 in 5-HT7 as key residues mediating their interaction. These sites were essential for 5-HT7-driven Wnt/β-catenin activation. Collectively, this study identifies 5-HT7 as a functional receptor promoting CRC progression via Wnt/β-catenin signaling. These findings support the therapeutic potential of targeting 5-HT7 and its interaction with CK1ε in CRC.