Periplocin Sensitizes Human Esophageal Squamous Cell Carcinoma to Trail-Induced Apoptosis via Upregulating Death Receptors and Inhibiting the Wnt/β-Catenin Pathway

Background: Esophageal cancer is one of the most common malignant tumors in the world. With currently available therapies, only 20% ~30% patients can survive this disease for more than 5 years. Although TRAIL, a natural ligand for death receptors that can induce the apoptosis of cancer cells, has been explored as a therapeutic agent for cancers, it has been reported that many cancer cells are resistant to TRAIL, limiting the potential clinical use of TRAIL as a cancer therapy. Meanwhile, Periplocin (CPP), a natural compound from dry root of Periploca sepium Bge, has been studied for its anti-cancer activity. It is not clear if CPP and TRAIL can have activity on esophageal squamous cell carcinoma (ESCC) cells, or if the combination of these two agents can have synergistic activity. Methods: We used MTS assay, flow cytometry and TUNEL assay to detect the effects of CPP alone and in combination with TRAIL in ESCC cells. The mechanism of CPP enhances the activity of TRAIL was analyzed by western blot, dual luciferase reporter gene assay and ChIP assay and so on. The anti-tumor effects and the potential toxic side effects of CPP alone and in combination with TRAIL were also evaluated in vivo. Findings: In our studies, we found that CPP alone and in combination with TRAIL could inhibit the proliferation ESCC cells and induce apoptosis. For the first time, we identified FoxP3 as a key transcriptional repressor for both DR4 and DR5. By down-regulating FoxP3, CPP increases the expression of DR4/DR5 and renders ESCC cells much more sensitive to TRAIL. We also showed that CPP reduced the expression of Survivin by inhibiting the activity of Wnt/β-catenin pathway. All these contribute to synergistic in vitro and in vivo activity of CPP and TRAIL on ESCC cells. Interpretation: Our data suggests that CPP and TRAIL can be further explored as potential therapeutic approach for esophageal cancer. Funding: This project was supported by the Natural Science Foundation of China (Grant No. 81673642, 81772550). Conflict of Interest: The authors declared no conflict of interest. Ethical Approval: All animal experiments were approved by the Animal Care Committee of the Fourth Hospital of Hebei Medical University.