Licoricidin Hinders Proliferation and Induces Cell Cycle Arrest and Apoptosis in Hepatocellular Carcinoma Cells by Regulating the PDK1/AKT/P21 Pathway

Abstract

Background: Licoricidin (LCD) is a bioactive compound isolated from licorice with anticancer properties. This study aimed to investigate the effect of LCD on the biological behaviors of hepatocellular carcinoma (HCC) and to explore its underlying molecular mechanisms. Methods: The effect of LCD, at gradient concentrations (0, 5, 10, 15 and 20 μM), on the viability of human normal liver epithelial cells (THLE-3) and HCC cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, the impacts of LCD, at different concentrations (0, 5 and 10 μM), on the HCC cell cycle, apoptosis, proliferation, and migration were evaluated using flow cytometry, colony formation experiment, and Transwell assay. Furthermore, the levels of cell cycle-related proteins, protein kinase B (AKT)/p21 pathway-related proteins, and pyruvate dehydrogenase kinase isoform 1 (PDK1)-related proteins were assessed using western blot assay and quantitative real-time polymerase chain reaction (qRT-PCR). Rescue experiments were performed to conform whether the LCD works through PDK1. Results: It was found that cell viability remained unaffected in THLE-3 cells but reduced in HCC cells (p < 0.001) following LCD treatment. Furthermore, LCD hampered the proliferation and migration, boosted apoptosis, and induced cell cycle arrest in the G0/G1 phase of HCC cells (p < 0.05). Moreover, LCD reduced the expression levels of B-cell lymphoma-2 (Bcl-2), cyclin A, cyclin-dependent kinase 2 (CDK2), and phosphorylated-AKT (p-AKT) while elevating Bcl-2 associated X protein (Bax) and p21 levels (p < 0.05). Additionally, LCD decreased PDK1 expression level, but overexpression of PDK1 reversed its regulatory impacts on the AKT/p21 pathway (p < 0.001). Moreover, overexpressed PDK1 counteracted the impacts of LCD on repressing the proliferation and migration and boosting cell cycle arrest in the G0/G1 phase and apoptosis of HCC cells (p < 0.05). Conclusion: LCD hinders the proliferation and migration of HCC cells and enhances the apoptosis and cycle arrest at the G0/G1 phase by modulating the PDK1/AKT/p21 pathway.