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 1 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 1 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 1 promoter methylation in 23 (47%). Methylation of the 1 gene did not correlate with tumor stage (p = 0.2097) but with high grade transitional cell carcinoma (p = 0.0416). 1 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 1 gene promoter methylation is strongly associated with bladder transitional cell carcinoma comprising carcinoma in situ.