Objective:To investigate the effects of resveratrol on proliferation and apoptosis of human papillary thyroid carcinoma IHH4 cells and its possible mechanisms. Methods:The inhibition rate of resveratrol on IHH4 cells proliferation was detected by CCK-8 assay. Morphological changes of IHH4 cells were observed by inverted microscope,transmission electron microscope and DAPI staining,respectively. The expression of cleaved caspase-3 was detected by immunofluorescence cytochemistry and Western blot. The change of cell apoptosis and cell cycle distribution were analyzed by flow cytometry. Results:Resveratrol inhibited the growth of IHH4 cells in a time- and dose-dependent manner. Compared with normal control,after resveratrol treatment,IHH4 cells shrank,turned round and began to shed off,various sizes of vacuoles appeared in the cytoplasm,intracytoplasmic content increased under optical microscope. The transmission electron microscope examination showed pyknosis and margination of apoptotic cell nucleus chromatin. DAPI staining showed that the normal nucleichromatin was relatively dispersed with regular shape and smooth surface,while cells treated with resveratrol displayed condensed and fragmented nuclei,which were typical features of apoptosis. Immunofluorescence cytochemistry and Western blot revealed that the expression of cleaved caspase-3 increased significantly in a time- and dose-dependent manner. Resveratrol induced apoptosis of IHH4 cells in a dose-dependent manner with S phase cycle arrest. Conclusion:Resveratrol could inhibit proliferation and induce apoptosis of human IHH4 cells in vitro. One of the possible mechanisms is related to S phase cycle arrest.