6-Gingerol induces cell-cycle G1-phase arrest through AKT–GSK 3β–cyclin D1 pathway in renal-cell carcinoma

Purpose: 6-Gingerol, a major biochemical and pharmacological active ingredient of ginger, has shown anti-inflammatory and antitumor activities against various cancers. Searching for natural products with fewer side effects for developing adjunctive therapeutic options is necessary. Methods: The effects of 6-gingerol on proliferation, colony formation, and cell cycle in RCC cells were detected by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, colony formation assay, and propidium iodide (PI) staining, respectively. Western blotting, an immunofluorescence assay, and immunohistochemical staining were performed to assess the expression of relevant proteins. A subcutaneous tumor model was set up to investigate the 6-gingerol effects on tumor growth in vivo, and the pharmacokinetics of 6-gingerol in mice were detected by LC/MS assays. Results: 6-Gingerol treatment exerted time- and dose-dependent inhibition of the growth and colony formation of ACHN, 786-O, and 769-P cells, leading to a concomitant induction of cell-cycle G1-phase arrest and decrease in Ki-67 expression in the cell nucleus. Western-blotting results showed that 6-gingerol reduces phosphorylation of protein kinase B (AKT) Ser 473, cyclin-dependent kinases (CDK4), and cyclin D1 and, meanwhile, increases glycogen synthase kinase (GSK 3β) protein amount. Furthermore, the efficacy of 6-gingerol was demonstrated in an in vivo murine model of 786-O. Conclusion: The above results indicate that 6-gingerol can induce cell-cycle arrest and cell-growth inhibition through the AKT–GSK 3β–cyclin D1 signaling pathway in vitro and in vivo, suggesting that 6-gingerol should be useful for renal-cell carcinoma treatment.