Magnolol targets CCND1 to suppress the proliferation of cholangiocarcinoma cells by inhibiting the Akt and STAT3 pathways.

Most cases of cholangiocarcinoma (CCA) are diagnosed at the middle or advanced stages and show insensitivity to chemotherapy, radiotherapy, as well as targeted therapy and immunotherapy. Magnolol, featuring anti-inflammatory and antioxidant properties, can inhibit the growth of CCA. This study aimed to analyze the effects of magnolol on cyclin D1 (CCND1) in CCA. Two CCA cell lines, RBE and HuCC-T1, were treated with escalating concentrations of magnolol for 24 h. Cell viability and CCND1 expression were measured in these two cell lines. The binding activity of magnolol to CCND1 was analyzed by molecular docking. The interaction of cyclin-dependent (CDK)2/4 and CCND1 was evaluated using Co-immunoprecipitation (Co-IP). Subsequently, pcDNA-CCND1 was transfected into both cell lines to explore the impacts of magnolol on cell cycle, cell viability, CDK2/4, and the phosphorylation of Akt (s473) and STAT3 (s727). Moreover, RBE cells were employed to induce xenograft tumors. The effects of magnolol on tumor growth and CCND1-mediated Akt and STAT3 pathways were observed. The results showed that magnolol inhibited cell viability and CCND1 expression with increasing concentrations in the two CCA cell lines. A good binding activity of magnolol to CCND1 was found (score = -7.1 kcal/mol). Overexpression of CCND1 attenuated magnolol's suppression of cell-cycle progression, cell viability, the expression of CDK2/4, and the phosphorylation of Akt (S473) and STAT3 (S727). In nude mouse models, magnolol suppressed tumor growth, as well as the expressions of CCND1, and the phosphorylation of Akt (s473) and STAT3 (s727). Nevertheless, CCND1 overexpression attenuated the aforementioned inhibitory effects of magnolol in vivo. This study demonstrated that magnolol exerted its effect on arresting the cell cycle at the G0-G1 phase through suppressing CCND1, suggesting that magnolol holds potential as a novel anti-CCA agent.