Juniperus indica Bertol Extract Combined with 5-Fluorouracil Synergistically Suppresses the Growth of Esophageal Squamous Cell Carcinoma Cells

Background: Esophageal cancer is a prevalent malignancy of the digestive tract with a high incidence rate in Asia. Esophageal squamous cell carcinoma (ESCC) is the most common histological type, accounting for more than 90% of cases. JIB is a plant extract of Juniperus indica Bertol that has been shown to have anti-proliferation effects in nasopharyngeal carcinoma, oral cancer, and melanoma. Objectives: The aim of this study was to investigate the anti-cancer effects and underlying mechanisms of action of JIB in combination with 5-FU in ESCC cells. Methods: The effects of the combination of JIB and 5-FU on cytotoxicity, cell cycle arrest, apoptosis and drug resistance development were explored using CE81T/VGH human ESCC cells. Results: The results showed that JIB synergized the inhibitory effects of 5-FU on cell proliferation via downregulating the AKT/mTOR pathway in CE81T/VGH cells harboring the TP53 exon 8 R273C mutation. The combination treatment of JIB and 5-FU induced cell cycle arrest at G0/G1 and S phases via mediating the levels of CDK4/cyclin D1 and CDK2/cyclin A. Furthermore, JIB combined with 5-FU was more effective in inducing apoptosis by activation of extrinsic (Fas/caspase-8) and intrinsic (Bax/caspase-9) pathways than the use of a single drug. Additionally, JIB attenuated the development of resistance to 5-FU in long-term culture and exhibited enhanced cytotoxicity in bile acid environments. Conclusion: JIB combined with 5-FU synergistically inhibited the ESCC growth and triggered cell cycle arrest and apoptosis. These findings suggest that the combination of JIB and 5-FU may be a potential strategy for the treatment of esophageal cancer.