Global
DNA hypomethylation is a common phenomenon in
bladder cancer. Therefore we investigated whether it is possible to detect and assess global
DNA hypomethylation in
bladder cancer using a specific
monoclonal antibody for 5-methyl-cytosine. Cytospins from exfoliative urine cytology specimens of patients with
bladder cancer or a history of
bladder cancer, control patients with benign
urological diseases and of young healthy volunteers were analyzed. Urothelial
carcinoma (UC) cells showed various degrees of nuclear destaining indicating global
DNA hypomethylation whereas all specimens from healthy volunteers showed granular nuclear staining indicating regular methylation of repeated DNA sequences. Lowest
5-methylcytosine immunostaining scores were observed in
carcinoma cells and a statistically significant difference was observed between urothelial cells of healthy controls or patients with benign disease compared to
bladder cancer patients (p<0.01, p<0.05, respectively). In UC cases even morphologically normal urothelial cells often displayed evident hypomethylation. Likewise, in patients with a history of UC, but no cystoscopic evidence of recurrence, morphologically non-malignant urothelial cells presented with some degree of demethylation. Our results strongly support the hypothesis of early global demethylation in
bladder cancer. Immunocytochemical staining with the
5-methylcytosine antibody allows simultaneous individual assessment of nuclear morphology and methylation status of a given sample.