Abstract: Objective To determine the sensitization of Nicotinamide (NA) on None Focused Ultrasound (NFU) on GLC-82 cells in vitro. Methods The experiments were divided into A、B、C and D four groups, group A was negative control, group B was treated with NA, group C was irradiated with NFU, group D was treated with both NFU and NA; MTT assay was used to evaluate the cytotoxicity of NA and its sensitivity for NFU on GLC-82 cells quantified by calculating the sensitive enhancement ratios (SER); Morphologic change of cells were observed with light microscope, fluorescence microscope and scanning electron microscope；Flow cytometry was performed to determine the percentage changes of apoptosis and distributional percentage of the cell cycle of GLC-82 cells in response to NFU, NA and the effect of its intervention to NFU. Results The cytotoxicity of NA increased in a dose-dependent manner after 24-hour treatment, with the optimal dose range of 1 mg/ml-5 mg/ml. A sub-toxic dose of NA at 3 mg/ml was used in the subsequent experiments; After treatment with NA plus NFU, microvilli and filipodium of GLC-82 cells reduced, shortened and shrunk into corpuscule-shape; The apoptosis rate of group D was more than group B and C, with cell cycle arrested at phase S and G2；Conclusion NA can obviously enhance the effect of NFU on GLC-82 cells, which provided evidence for NA as a sensitization to NFU in clinic.

Key words: NFU, Nicotinamide, GLC-82, SER