Abstract: Objective To investigate the effect of stress hormones on cell cycle re-entry of G₀ phase in mouse H22 hepatocarcinoma cells. Methods Flow cytometry antibody staining with CD44 and CD133 was used to determine the presence of cancer stem cells in H22 cells. In vitro, after treatment of H22 cells with stress hormone corticosterone (CORT), epinephrine (EPI) and norepinephrine (NE) for 48 h, the proportion changes of cells in G₀ phase and cell cycle distribution were detected by Ki-67 and PI flow cytometry staining. The hormone receptor antagonists were used to verify the receptor subtypes that mediated the cell cycle re-entry of G₀ phase cells. Results The proportion of cancer stem cells (CD44⁺CD133⁺) in H22 cells was 0.80%±0.15%. Compared with control group, the portion of G₀ phase cells was unchanged after corticosterone treatment, but was decreased by 62.50% and 53.00% respectively after EPI and NE treatment. Meanwhile, the total cells, proportion of G₂/M and S phase cells were increased compared to control group. The protein expression of Skp2 was increased and p27^kip1 decreased significantly after EPI and NE treatment(P＜0.05). In addition, α1-adrenergic receptor antagonists terazosin and prazosin blocked the G₀ phase cells cycle re-entry effect of EPI and NE. The protein expression of Skp2 was decreased and p27^kip1 was increased significantly after prazosin treatment compared to EPI or NE group(P＜0.05). Conclusions Catecholamine stress hormones mediate the cell cycle re-entry of G₀ phase cells in mouse H22 hepatocarcinoma cells by activating α1-adrenergic receptor,the mechanism of which may be associated with the Skp2 over-expression and the degradation of p27^kip1 protein.

Key words: hepatocellular carcinoma, G₀ phase cells, stress hormones, catecholamine, adrenergic receptor