Emodin Induced Necroptosis and Inhibited Glycolysis in the Renal Cancer Cells by Enhancing ROS

Background: Renal cell carcinoma (RCC) is a tumor with unpredictable presentation and poor clinical outcome. RCC is always resistant to chemotherapy, radiation, and weakly sensitive to immunotherapeutic agents. Therefore, novel agents and approaches are urgently needed for the treatment of RCC. Emodin, an anthraquinone compound extracted from rhubarb and other traditional Chinese herbs, has been implicated in a wide variety of pharmacological effects, such as anti-inflammatory, antiviral, and antitumor activities. However，its role in RCC remains unkown. Methods: Flow cytometry assay and lactate dehydrogenase release assay were used to detect the cell death. Reactive oxygen species was tested by the dye MitoSox and DCFH-DA. Glucose-6-phosphate, pyruvate and ATP level were measured to evaluate the glycolysis process. Western blot was used to detect protein expression. Results: Emodin effectively killed renal cancer cells without significant toxicity to normal renal tubular epithelial cell. Flow cytometry assay with Annexin V-FITC and PI demonstrated that emodin induces necroptosis, but not apoptosis, in renal cancer cells. Meanwhile, the phosphorylation levels of RIP1 and MLKL, the key necroptosis-related proteins, were significantly increased. To explore how emodin inhibits kidney tumor growth, reactive oxygen species (ROS) levels were tested and the levels of ROS increased upon emodin treatment in a dose-dependent manner. Further studies demonstrated that emodin induced necroptosis through ROS-mediated activation of JNK signaling pathway, and also inhibited glycolysis by down-regulation GLUT1 by ROS-mediated inactivation of PI3K/AKT signaling pathway. Conclusion: These findings revealed the potential mechanisms by which emodin suppresses renal cancer cell growth, and will help develop novel therapeutic approaches for patients with JNK- or PI3K/AKT-dysregulated renal cancer.