Objective: To observe the effect of honokiol combined with artemisinin on cell cycle in nasopharyngeal carcinoma cell lines(CNE-2) cells and to explore its possible mechanism. Method: After treating with thymidine deoxyribonucleoside (TdR

the final concentration was 2 mmol· L-1) for 16 h

the CNE-2 cells were washed with PBS twice then cultured in RPMI-1640 medium for 10 h and then treated with TdR at same final contentration for 16 h.Aftter the thymidine released

the CNE-2 cells were collected for further experimental studies.The CNE-2 cells were treated with honokiol 7.5 mg· L-1 or/and artemisinin 7.5 mg· L-1 for 24 h

at the same time

the control group was established. Flow cytometric analysis was performed to analyze the change of the cell cycle distrubtion and RT-PCR analysis were used to examine the expression level of cyclin D1

cyclin E1and p27gene. Result: After the CNE-2 cells were released from TdR

the flow cytometric analysis indiacted that the cell percentage of Gl

S

G2 phase was (72.64±5.01)%

(24.60±4.35)%

(0.00%) respectively

which meant that the CNE-2 cells were at the G1/S boundary. The cells percentage of Gl phase in the combined group

the honokiol group and the artemisinin group was (90.78±9.49)%

( 67.86±1.59 )%

( 66.77±2.25)% respectively

which showed that compared with either honokiol or artemisinin alone

the combined group could cause the CNE-2 cells arrest at G1 phase significantly (P<0.05). RT-PCR analysis indicated that the cyclin D1mRNA expression in combined group

the honokiol group and the group was (0.237±0.014)

(0.328±0.002)

(0.368±0.007) respectively

the cyclin E1mRNA expression in above groups was (0.445±0.027)

(0.572±0.005)

(0.542±0.006)respectively

which indicated that the combined group could downregulate the mRNA expression of both cyclin D1and cyclin E1

compared to either honokiol or artemisinin alone(P<0.05).The RT-PCR showed that the p27 mRNA expression in combined group

the honokiol group and the artemisinin group was (1.069±0.046)

(0.543±0.022)and (0.388±0004)respectively

which showed that the combined group could upregulate the expression of p27mRNA. Conclusion: The combination of the honokiol with the artemisinin yields synergistic effect on induction of G1 phase arrest in CNE-2 cells. The cooperative effect of honokiol with artemisinin may be associated with the downregulate the expression of both cyclin D1mRNA and cyclin E1mRNA and upregulate expression of p27 mRNA.