AIM:To investigate effects of arsenic trioxide(As₂O₃)on the proliferation and apoptosis of on adenoid cystic carcinoma-2(ACC-2)cells and detect the expression of MDM2 gene from gene and protein level and to explore detailed mechanism of As₂O₃ inducing ACC-2 cells apoptosis.

METHODS: ACC-2 cells were cultured in vitro and divided into the experiment group and control group. Different concentrations of As₂O₃(2, 4, 6, 8μmol/L)were applied to cells in logarithmic growth phase at different time as experiment group, the control group was given the same amount of cell culture fluid, after added As₂O₃, the cells were cultured at different times, respectively. The effect of different As₂O₃ concentrations at each point time on inhibition and metamorphoses of ACC-2 cells was observed under inverted phase contrast microscope. Expression changes of MDM2 mRNA(24, 48h)and protein(24, 48, 72h)were determined by reverse transcription polymerase chain reaction(RT-PCR)and immunohistochemistry test(IHCT)respectively.

RESULTS: Cells shrinkage, nuclear chromatin condensation, apoptotic cells increased and the number of viable cells significantly reduced after being cultured with different concentrations of As₂O₃. The results of RT-PCR and IHCT were showed consistent the expression of MDM2 in experiment group decreased gradually with the increase of As₂O₃ concentrations and extension of action time, which was significantly different to that in the control group(P<0.05). Campared with each other, it was statistically significant between the different concentration and time of two groups(P<0.05). MDM2 expression was negatively correlated with concentration and time(r<-0.7, P<0.05), that was, it presented in dose- and time-dependent manner.

CONCLUSION: As₂O₃ has the inhibitory and apoptosis-inducing effect on ACC-2 cells, and it can downregulate the expression of MDM2 mRNA and protein in ACC-2 cell line. This may be the mechanism of As₂O₃ induced ACC-2 cells apoptosis.