Hypermethylation of an E-cadherin (CDH1) promoter region in high grade transitional cell carcinoma of the bladder comprising carcinoma in situ

Purpose: We elucidated the role of methylation in the promoter region of the CDH1 gene in bladder carcinogenesis, particularly in those comprising carcinoma in situ. Materials and Methods: A total of 49 cases of transitional cell carcinoma of the bladder obtained from transurethral resection were examined. Methylation status of the CDH1 promoter region was analyzed by methylation specific polymerase chain reaction from chemically modified DNA after Na-bisulfite treatment. Loss of heterozygosity on 16q was examined by blunt end single strand DNA conformation polymorphism using 4 tetranucleotide repeat microsatellite markers assigned on 16q13 to 22.1. E-cadherin expression was evaluated by immunostaining on formalin fixed, paraffin embedded tissue sections using anti E-cadherin murine monoclonal antibody, HECD1 and standard avidin-biotin immunoperoxidase complex technique. Results: Analysis of the 49 bladder transitional cell carcinoma samples showed CDH1 promoter methylation in 23 (47%). Methylation of the CDH1 gene did not correlate with tumor stage (p = 0.2097) but with high grade transitional cell carcinoma (p = 0.0416). CDH1 promoter methylation was observed at a significantly higher frequency in the carcinoma in situ positive group than in the carcinoma in situ negative group (16 of 18 cases or 89% versus 7 of 31 or 23%, p <0.0001) and it strongly correlated with abnormal E-cadherin expression (p <0.0001). We found 16q loss of heterozygosity in 16 of 47 cases (34%), which correlated with higher histological grade (p = 0.0069) but not with the presence of the carcinoma in situ component (p = 0.1235). Conclusions: This study showed that CDH1 gene promoter methylation is strongly associated with bladder transitional cell carcinoma comprising carcinoma in situ.