Aim: To study the mechanism of differentiation-inducing action of 10-hydroxycamptothecin (HCPT) on human hepatoma Hep G2 cells.
Methods: The proliferating cell nuclear antigen (PCNA) expression was studied by immunocytochemical staining method. The cell cycle distribution and the wild-type protein p53 expression were measured by flow cytometry. Telomerase activity was assayed with telomeric repeat amplification protocol (TRAP).
Results: After treatment with HCPT at differentiation-inducing concentrations 5-20 micrograms.L-1 for 6 d, Hep G2 cells were mainly arrested at G2/M phase and the PCNA expression rate was lower than that of control cells. When Hep G2 cells grew in a medium containing HCPT 5 micrograms.L-1 for 6 d, the p53 expression level markedly increased in comparison with the control cells. The telomerase activity did not change in Hep G2 cells treated with HCPT 5-20 micrograms.L-1 for 8 d.
Conclusion: The differentiation-inducing effect of HCPT on Hep G2 cells is related with the cell cycle arrest at G2/M phase, down-regulation of PCNA and up-regulation of wild-type protein p53.