Analysis of Plk1 CpG island methylation status and expression, global methylation, and expression levels for p53 and p21 in normal and liver tumour tissue samples. (a) Plk1 CpG island methylation status for HCC samples compared to normal tissue as determined by MSP for aged-matched littermates. U = unmethylated, M = methylated. (b) Graphical representation summarizing the percentage of methylated Plk1 promoters in both normal liver tissue and tumours. (c) Plk1 transcript levels in normal liver and HCC samples as determined by qPCR. RQ values were normalized to the level of Plk1 transcripts in Plk4
+/+livers. The error bars represent the upper and lower limit of the standard error from the mean expression level (RQ) (d) Plk1 protein levels were examined by Western blot analysis. GAPDH protein levels were used as a loading control. N = normal, T = tumour. (e) The percent of global methylation of genomic DNA extracted from liver was determined by an ELISA assay specific for methylated DNA. (*p < 0.05), **p < 0.001, ***p < 0.05). The error bars represent the upper and lower limit of the standard error (f) p53 and p21 protein levels as detected by Western blot analysis. GAPDH levels were used as a loading control. N = normal, T = Tumour.