Fig. 2: PLK1 inhibition increased the expression level of tumor suppressor genes.

A DU145 cells were transfected with PLK1 siRNA, and the genomic DNA was isolated. The global DNA methylation profiling was performed by Illumina Infinium Methylation EPIC arrays. All array probes for each group were used to generate density plots (left) and boxplots (right). In density plots, X-axis indicates β value; The scores in the range between 0 and 1 indicate the level of DNA methylation. Y axis indicates the probability densities which describe the distribution of β values for all probes. Whisker boxplots (right) represent the 25th–75th percentiles, with midlines indicating the median values. Whiskers extend to the minimum/maximum values. B Heatmaps shows β values of probe in the promoter regions of tumor suppressor genes. The TSGs marked in red were selected for further validation. C DU145 were treated with DMSO or different doses of BI6727 for 48 h. The mRNA levels of tumor suppressor genes were analyzed by RT-PCR, ACTIN was used as an internal control. D DU145 cells were transfected with scrambled or two different PLK1 siRNAs, and then cell cycle was synchronized at S phase. The cell cycle phase distribution was analyzed by flow cytometry. The mRNA levels of tumor suppressor genes were analyzed by RT-PCR, ACTIN was used as an internal control. Data were expressed as mean ± SD from three separate experiments, and were analyzed for statistical significance *P < 0.05, **P < 0.01.