Hypermethylation of cell-free serum DNA indicates worse outcome in patients with bladder cancer

Purpose: CpG island hypermethylation is a frequent event in bladder carcinogenesis and progression. We investigated the diagnostic and prognostic value of hypermethylation in cell-free serum DNA of patients with bladder cancer. Materials and Methods: The study cohort consisted of 45 patients with bladder cancer undergoing cystectomy and 45 with histologically confirmed benign prostatic hyperplasia serving as controls. Hypermethylation at APC, DAPK, GSTP1, PTGS2, TIG1 and Reprimo was analyzed using real-time polymerase chain reaction following methylation sensitive restriction endonuclease treatment. Results: Hypermethylation at the APC and GSTP1 promoter was detected in 59% of cases, whereas TIG1 (32%, PTGS2 (24%) and DAPK (2%) were less frequently hypermethylated. In the benign prostatic hyperplasia group 3 patients also harbored methylated GSTP1 DNA, whereas none of the other gene sites was methylated. Hypermethylation at APC, GSTP1 or TIG1 distinguished patients with bladder cancer and controls most accurately with 80% sensitivity and 93% specificity. Hypermethylation significantly correlated with prognostic unfavorable clinicopathological parameters, including A-PC with pT stage, GSTP1, or GSTP1 or TIG1 with multifocal bladder cancer and A-PC, or A-PC or TIG1 with surgical margin positivity. Bladder cancer specific mortality was significantly increased in patients with APC hypermethylation. Conclusions: The detection of hypermethylation in cell-free serum DNA provides valuable diagnostic and prognostic information that can still be improved by combining the results of 3 gene sites (APC, GSTP1 and TIG1). The presence of hypermethylated DNA in the serum of patients with bladder cancer is associated with a worse outcome. Our results suggest that measuring hypermethylation in the serum of patients with bladder cancer is a useful biomarker.