Figure 4

Ratio of cancerous PHD3 mRNA level to histopathologically unchanged tissue PHD3 mRNA level in three ranges of PHD3 methylation status: 0–1%; 1–10% and 10–100%. Methylation percentage of three DNA fragments within the PHD3 CpG island (Additional file 1, Additional file 2) was determined by Real Time PCR amplification of bisulfite treated standard and patient DNA, followed by comparison of their HRM profiles. The methylation for each patient was calculated as an average percentage of methylation in amplified fragments located in the CpG island of PHD3. The samples were divided into three groups for statistical analysis: 0–1% methylation, 1–10% methylation and 10–100% methylation (Table 2) [28–30]. To evaluate the statistically significant difference in the ratio of cancerous PHD3 mRNA level to histopathologically unchanged tissue PHD3 mRNA level between the three DNA methylation ranges (0–1% methylation, 1–10% methylation and 10–100% methylation), the non-parametric Kruskal-Wallis test was employed.