['To investigate the effect of aquaporin 9 (AQP9) expression level on the apoptosis and biological behaviors of HepG2 cells induced by arsenic trioxide (As2O3).', 'The effects of different concentration As2O3 on the cell proliferation were measured by MTT assay, and IC50 was calculated. The recombinant plasmids pEGFP-N1-AQP9 and pshRNA-AQP9 were transfected into HepG2 cells. The expression of AQP9 mRNA and protein were detected by reverse transcription PCR and Western blotting, respectively. Then As2O3 was added to plasmid-transfected cells and untreated HepG2 cells. Cell proliferation was detected by MTT assay, cell cycle and apoptosis rate were determined by flow cytometry, and cell invasion and migration ability were examined by Transwell(TM) (Boyden Chamber) assay. The activity of caspase-3 was detected by microplate reader.', 'The recombinant plasmids remarkably influenced the expression of AQP9. Compared with the group treated with As2O3 alone (control group), the cell proliferation, invasion and migration of HepG2 cells transfected with pEGFP-N1-AQP9 were attenuated significantly, while the cells transfected with pshRNA-AQP9 increased. The increasing population of apoptotic cells, augmented caspase 3 activity and highest percentage of cells stagnating at G0/G1 phase were observed in HepG2 cells transfected with pEGFP-N1-AQP9 as compared with the control HepG2 cells; in contrast, the HepG2 cells transfected with pshRNA-AQP9 presented with lower caspase 3 activity and stronger invasion and migration ability than the control HepG2 cells did.'] Does [ The expression of AQP9 in HepG2 cells affect cell biological behaviors and sensitivity to As2O3 ]?