Abstract: BACKGROUND ＆ AIM: To study the effect of LaCl3 on the expression of CyclinD1 and CDK4 in hepatocellular carcinoma cells. MATERIALS AND METHODS: The in vitro growth of CBRH-7919 cells was observed following treatment with 0.01, 0.10, 1.00 mmol/L LaCl3 for 1,3,5 days, the changes of cell cycle were assessed by flow cytometry. At the same time,changes of CyclinD1 and CDK4 were studied by immunocytochemical analysis. CBRH-7919 cells without LaCl3 were used as control groups. RESULTS: The growth of CBRH-7919 cells was markedly inhibited by 0.10 and 1.00 mmol/L LaCl3 treatment for 3, 5 days,with a time-depentent effect in 1.00 mmol/L group, as compared with control group, the difference was statistically significant(P<0.01). The percentage of CBRH-7919 cells in G0/ G1 phase was significantly increased by 0.10 and 1.00 mmol/L LaCl3 groups for 3, 5 days, as compared with control group (P<0.01). However the expression of CyclinD1 and CDK4 was significantly decreased in 0.10 and 1.00 mmol/L LaCl3 groups for 3, 5 days as compared with control group(P<0.01). CONCLUSION: LaCl3 could obviously inhibit the growth of CBRH-7919 cells by down-regulating CyclinD1 and CDK4 and blocking the cell cycle progression from G1 to S.

Key words: rare earth elements, LaCl3, hepatocellular carcinoma cells, cell cycle, Cyclin D1, CDK4