| Summary: | 碩士 === 國防醫學院 === 生物化學研究所 === 92 === Proplis, a honeybee-hive products, exhibits anti-inflammatory, antiviral, immunostimulatory and carcinostatic activities. Known for the variety of its beneficial effects, it has been a popular folk medicine through the ages. The active ingredient of propolis was identified as caffeic acid phenylether ester ( CAPE). CAPE was shown to involved in many cellular processes to induce differential toxicity to cancer cells versus normal cell lines. Despite the knows properties of these compounds in modulation of cellular processes, the molecular basis of their action remains to be clarified. Previous studies in our lab indicated that CAPE-mediated its action through lowering intracellular hydrogen peroxide levels, activation of caspase 8 and decrease Mcl-1 protein level. To investigate the action mechanism of CAPE, we analyzed the effect if this compound on cell cycle progression and found that the CAPE arrested human cervical ME180 cells at S-phase. In addition, the S-phase arrest is associated with increased expression of E2F1, p21 and Apaf-1 proteins and decreased expression of Mcl-1 protein. To verify the role of E2F1 in CAPE-mediated cell growth arrest, we constructed E2F1, Apaf-1 and Mcl-1 promoter-luciferase reporters and analyzed by transient transfection studies. Ours results indicated that the presence of E2F1 binding sequence (EBS) in the reporters is essential for alteration of promoter activity in CAPE-treated cells. Using electrophoretic mobility shift assay (EMSA), we showed that the exposures of cells to CAPE resulted in enhanced E2F1 binding to the wild type EBS but not to the mutated EBS oligos. Further studies using RNAi techniques to suppress endogenous expression with the inhibitory effect of CAPE on the transcriptional activity of E2F1 overexperssion with the inhibitory effect of CAPE on the transcriptional activity of NF-kB factor. Taken together, our study presents evidence that indicated the crucial role of E2F1 protein factor in the cellular actions of CAPE. We hope that our study would help to elucidate the molecular basis and therapeutic potential of this agent.
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