ObjectiveTo explore the in vitro anti-tumor effect of clove extracts (CEs) on radioresistant esophageal cancer cell KYSER and its mechanism.MethodsEthanol extracts of clove bud were prepared. Gas chromatography was used to identify the main active components of CEs. In vitro cell culture method was used to observe the effect of CEs at different concentrations on KYSER cell growth. Methyl thiazolyl tetrazolium (MTT) method was used to detect the effect of different concentration CEs on KYSER’s survival and its’ manner. Transmission electron microscope (TEM) was used to observe the changes of KYSER’s organelle microstructure after CEs treated. Transwell chamber method was used to detect the impact of CEs on KYSER’s migration ability. The apoptosis rate and cell cycle distribution of KYSER treated by CEs were quantitatively determined by flow cytometry. Clone formation experiment was used to detect the clone formation ability of KYSER treaded by CEs.ResultsThe main components of CEs were eugenol, eugenol hydrocarbon, and eugenol acetate. In vitro cell culture showed that 0.4% CEs could inhibit KYSER growth. MTT assay showed that the concentration of CEs≥0.5% could inhibit the survival of KYSER in a dose-dependent manner. TEM assay showed that after treated by 0.5% CEs, KYSER’s microvilli became shorter and wider, ribosomes in the cytoplasm decreased, mitochondria atrophied, and a large number of autophagosomes were formed. Transwell migration assay showed that relative migration rates of KYSER after treated by 0.5% CEs and 0.6% CEs were (65±4)% and (41±3)%, respectively. Compared with the control group, the differences were statistically significant (P<0.001). Flow cytometry showed that the apoptosis rates of the control group, the 0.5% CEs treated group, and the 0.6% CEs treated group were (5.63±0.50)%, (11.77±0.42)%, and (19.44±0.19)%, respectively, and the differences between the control group and the two CEs treated groups were statistically significant (P<0.001). Flow cytometry showed that the G1 phase ratios of cells in the control group, the 0.5% CEs treatment group, and the 0.6% CEs treatment group were (61.99±1.20)%, (75.38±1.50)%, and (78.81±1.00)%, respectively, and the differences between the control group and the two CEs treated groups were statistically significant (P<0.001). The clonal formation experiment showed that after 24 h of CEs treatment, the clonal formation rates of the control group, the 0.5% CEs treatment group, and the 0.6% CEs treatment group were (80.5±1.0)%, (18.1±0.8)%, and (5.0±0.5)%, respectively, and the differences between the control group and the two CEs treated groups were statistically significant (P<0.001).ConclusionCEs can exert anti-tumor effect on radioresistant esophageal cancer cells by inducing autophagy and apoptosis, promoting cell cycle arrest, inhibiting cell energy metabolism, and inhibiting migration.