三氧化二砷抗肿瘤血管形成研究

Expression of p15INK4B gene induced by arsenic trioxide in esophageal cancer cell line EC109

AIM: To investigate the effects of arsenic trioxide (As₂O₃) on the expression of cyclin dependent kinase inhibitor p15^INK4B (p15) gene in esophageal cancer cell line EC109.

METHODS: As₂O₃ was added to EC109 cells for succedent experiments (final concentration 2 μmol/L). Methylation of p15 gene in EC109 cells was detected by polymerase chain reaction (PCR) using a methylation specific primer (MSP), and the expression of p15 gene was detected by reverse transcription PCR (RT-PCR) and Western blot at the mRNA and protein level.

RESULTS: p15 gene failed to express in EC109 cells due to hypermethylation. As₂O₃ (2 μmol/L) significantly down-regulate the methylation of p15 gene at DNA level, and the difference between As₂O₃ action 72, 48, 24 h and no drug groups had statistical significance (37.11 ± 3.62 vs 50.92 ± 5.47 vs 72.07 ± 7.53 vs 97.23 ± 9.80, P < 0.05). After As₂O₃ action 24 h, p15 mRNA expression appeared. Along with the continuance of As₂O₃ action, the p15 mRNA expression became stronger. Except between no drug group and As₂O₃ action 24 h group as well as between As₂O₃ action 24 and 48 h group, the difference between all groups had statistical significance (0.72 ± 0.07, 0.58 ± 0.06, 0.48 ± 0.07 vs 0.41 ± 0.08, P < 0.05). After As₂O₃ action 24 h, the expression of p15 protein appeared. Along with the continuance of As₂O₃ action, the p15 protein expression became stronger. The differences between all the groups were significant (0.51 ± 0.02 vs 0.21 ± 0.01 vs 0.16 ± 0.02 vs 0.06 ± 0.01, P < 0.05).

CONCLUSION: As₂O₃ can activate the expression of the p15 gene by demethylation and inhibit the cell cycle progress of esophageal cancer cell line.

Inhibitory effect of arsenic trioxide on proliferation of hepatoma cells in mice

AIM: To explore the arsenic trioxide(As₂O₃)-induced inhibition of the proliferation of mouse hepatoma cells in vivo.

METHODS: The mice bearing H₂₂ solid and ascetic hepatoma cells were treated with different concentrations of arsenic trioxide. The growth of the solid tumor and the survival of the ascetic tumor-bearing mice were observed. The expression of proliferating cell nuclear antigen (PCNA) and cyclinD₁ of the tumor cells were examined by immunohistochemical methods. The changes of cell cycle were measured by flow cytometry. The ultra-structural changes of the cells were observed under electron microscope.

RESULTS: Both high and low concentration of As₂O₃ inhibited the growth of the solid tumor and prolonged the survival time of ascetic-tumor-bearing mice, and the inhibitory rates were 39.1% and 45.7%, respectively. The life prolonging rates were 57.2% and 97.7%, respectively. The positive rates of PCNA and cyclinD₁ expression in the As₂O₃-treated groups were significantly decreased from 57.9±6.6% to 44.0±5.0% (P <0.01), and from 49.2±9.3% to 37.6±6.3% (P <0.01), respectively. Flow cytometry showed that the percentage of G₀/G₁ phase cells was decreased and the percentage of G₂/M phase cells was increased. Electron microscopy showed the typical characteristics of cell apoptosis.

CONCLUSION: As₂O₃ can significantly inhibit the proliferation of mouse hepatoma cells.