Catalpol synergistically potentiates the anti-tumour effects of regorafenib against hepatocellular carcinoma via dual inhibition of PI3K/Akt/mTOR/NF-κB and VEGF/VEGFR2 signaling pathways

Background Hepatocellular carcinoma (HCC) is the most common primary liver cancer characterized by dysregulation of several crucial cellular signaling pathways such as PI3K/p-Akt/mTOR/NF-κB and VEGF/VEGFR2 pathways. Novel therapies targeting these pathways have been discovered such as regorafenib which is small molecular multi-kinase inhibitor mainly targets VEGF/VEGFR2. Catalpol is an iridoid glycoside richly found in rehmannia glutinosa which is a fundamental herb used extensively in traditional Chinese medicine. It is evidenced that catalpol has many pharmacological effects on nervous and cardiovascular systems, in addition to exhibiting hypoglycemic, anti-inflammatory, anti-proliferative and anti-tumour activities. However, its effect on HCC isn’t clear enough. So, this study aimed to investigate the anti-tumour effects of catalpol either alone or in combination with regorafenib on HCC. Methods and results In vitro experiments were performed using HepG2 and HUH-7 hepatocellular carcinoma cell lines. MTT assays evaluated anti-proliferative effects of catalpol and/or regorafenib. Combination index was calculated via compusyn software to detect synergism. Tumour biomarkers were measured using ELISA technique. Results showed that catalpol has anti-tumour effects against HCC via targeting PI3K/p-Akt/mTOR/NF-κB and VEGF/VEGFR2 pathways. In addition, results revealed that our novel combination of catalpol and regorafenib showed potent synergistic anti-tumour effect via suppressing both of PI3K/p-Akt/mTOR/NF-κB and VEGF/VEGFR2 signaling pathways and their downstreams. Conclusion Catalpol and/or regorafenib markedly suppressed PI3K/p-Akt/mTOR/NF-κB and VEGF/VEGFR2 signaling pathways and consequently showed potent anti-tumour effects against HCC. Results encourage further pre-clinical and clinical studies of this novel combination as a promising targeted therapy for HCC management. Graphic abstract