OBJECTIVE: To explore the relationship between the changes in the activity of caspase-8 and apoptosisof HepG2 cells induced by 5-fluorouracil (5-Fu).METHODS: Human hepatoma HepG2 cells were treated with 5-Fu at the concentrations of 1×10~(-1),1×10~(-2), 1×10~(-3), 1×10~(-4), 1×10~(-5) mol/L and for 1, 2, 4, 8, 16, 24 hours, respectively. Thecaspase-8 activity was detected using caspase-8 fluorescent assay kit. The apoptotic rate of HepG2 cellsinduced by 5-Fu with or without the caspase-8 inhibitor IETD-FMK was measured by flow cytometry.RESULTS: Afer the HepG2 cells were trealed with 10~(-2) mol/L 5-Fu, the caspase-8 activity increasedgradually and reached the peak level (313.9±6.9) at 16 hours, then fell down. Compared with thecontrol group, the activity was still significantly higher (274.2±3.9 vs 68.3±3.6, P<0.01). With theincreasing concentraion of 5-Fu, the caspase-8 activity was also increased; the activity in highconcentration 5-Fu was significantly higher than that in low concentration 5-Fu (370.5±4.7 vs313.7±6.9; 225.7±5.4 vs 183.3±4.8; 183.3±4.8 vs 124.0±6.2, P<0.01). The caspase-8activity was the highest at 1×10~(-1) mol/L 5-Fu (370.5±4.7). The caspase-8 activity in lowconcentration 5-Fu was higher than in the blank control group and inhibitor group (124.0±6.2 vs68.5±3.4; 124.0±6.2 vs 41.0±2.1, P<0.01). IETD-FMK could block the activation of caspase-8and reduce the apoptosis of HepG2 cells induced by 5-Fu. The apoptotic rate of HepG2 cells in the 5-Fugroup was significantly different from that in the inhibitor group (P<0.01).CONCLUSIONS: 5-Fu can induce apoptosis of HepG2 cells via caspase-8 signal transduction pathway,which can be blocked by IETD-FMK. 5-Fu promotes the increase of caspase-8 activity in a time- orconcentration-dependent manner. OBJECTIVE: To explore the relationship between the changes in the activity of caspase-8 and apoptosis of HepG2 cells induced by 5-fluorouracil (5-Fu). METHODS: Human hepatoma HepG2 cells were treated with 5-Fu at the concentrations of 1 × 10 1 × 10 ~ (-2), 1 × 10 -3, 1 × 10 -4, 1 × 10 -5 mol / L and for 1, 2, 4, 8, 16, 24 hours, respectively. The caspase-8 activity was detected using caspase-8 fluorescent assay kit. The apoptotic rate of HepG2 cells induced by 5-Fu with or without the caspase-8 inhibitor IETD-FMK was measured by flow The cytometry. RESULTS: Afer the HepG2 cells were trealed with 10 ~ (-2) mol / L 5-Fu, the caspase-8 activity increasedgradually and reached the peak level (313.9 ± 6.9) at 16 hours, then fell down. the activity was still significantly higher (274.2 ± 3.9 vs 68.3 ± 3.6, P <0.01). With the increase in concentraion of 5-Fu, the caspase-8 activity was also increased; the activity in high concentration 5-Fu was significantly higher than that in l ow concentration 5-Fu (370.5 ± 4.7 vs 313.7 ± 6.9; 225.7 ± 5.4 vs 183.3 ± 4.8; 183.3 ± 4.8 vs 124.0 ± 6.2, P <0.01). The caspase-8 activity was the highest at 1 × 10 ~ 1) mol / L 5-Fu (370.5 ± 4.7). The caspase-8 activity in lowconcentration 5-Fu was higher than in the blank control group and inhibitor group (124.0 ± 6.2 vs68.5 ± 3.4; 124.0 ± 6.2 vs 41.0 ± 2.1, P <0.01). IETD-FMK could block the activation of caspase-8 and reduce the apoptosis of HepG2 cells induced by 5-Fu. The apoptotic rate of HepG2 cells in the 5-Fugroup was significantly different from that in inhibitor group (P <0.01) .CONCLUSIONS: 5-Fu can induce apoptosis of HepG2 cells via caspase-8 signal transduction pathway, which can be blocked by IETD-FMK. 5-Fu promotes the increase of caspase-8 activity in a time- orconcentration-dependent manner.