Figure 3.

Benzethonium chloride accelerates protein degradation of cyclin D1 through ubiquitin-proteasome pathway. A. Expression levels of the G1 phase specific cyclin and CDK proteins were compared in BZN-treated A549 and H1299 cells by western blot. B. Immunoprecipitation assay was performed in the BZN-treated lung cancer cells, and ubiquitin expression was examined in the cyclin D1 immunoprecipitates. C. After pretreatment with cycloheximide (CHX; 50 μg/mL) for 12 h, A549 and H1299 cells were exposed to 10 μM BZN, and the cell lysates were collected at the indicated time points and compared for cyclin D1 expression using Western blotting. Cyclin D1 signals were quantified by densitometry, and the degradation rate was shown as the ratio of cyclin D1 level at each time point to the respective original level (0 min). D. MG132 could rescue the inhibitory effect of BZN on cyclin D1 expression. Bars, SD; *P < 0.05; **P < 0.01; ***P < 0.001 compared with DMSO-treated cells.