Allelotyping and promoter hypermethylation of urinary bladder cancer.

摘要

Bladder cancer is the ninth most common cancer in the world and eighth most common in Hong Kong. Urothelial carcinoma (UC) comprised the majority of bladder cancer. Genetic and epigenetic alterations played a very important role of bladder cancer development, however detailed high resolution mapping of genetic and epigenetic abnormalities are lacking. We aimed to investigate the genetic and epigenetic alterations in bladder urothelial carcinoma (UC) by allelotyping analysis and gene promoter hypermethylation respectively. Moreover, the diagnostic potential of epigenetic alterations in urine were also assessed.; In allelotyping analysis, high frequency of allelic imbalance was observed in chromosome arm 1q (61.9%), 3p (61.9%), 4q (66.67%), 8p (57.14%), 9p (76.2%), and 9q (66.67%). Allelic imbalance with frequency above average was also observed in chromosome arm 2q, 10p, 10q, 11p, 11q, 12q, 13q, 15q, 17p, and 19q. The allelic imbalance of each case and fractional allelic loss (FAL) for each chromosome was associated with higher tumor grade and stage. We have also delineated several minimal deletion regions (MDR) on chromosome 3p, 4q, 5q, 8p, 9p, 9q, 11p, 13q, 16q, 17p, and 19p. MDR on 4q, 11p, 16q, and 19p were first described in bladder cancer.; In methylation study, frequent methylation was detected in RAR β (87.8%), 14-3-3σ (76.9%), E-cadherin (63.3%), DAPK (58.2%), hMLH1 (48.7%), RASSF1A (46.2%), p14 (35.9%), APC (30.8%), and p16 (26.5%). Methylation was also detected in HLTF (20.5%), p15 (13.3%), SOCS-1 (12.8%) and HIC-1 (12.8%) of the tumor cases. However, methylation of GSTP1 (5.1%), MGMT (5.1%) and TSLC1 (0%) was rare in bladder UC. Normal bladder epithelium did not show any aberrant hypermethylation except for RARβ (42.9%), and 14-3-3σ (16.6%). Methylation index of each case was significantly correlated with tumor grade, stage and muscle invasiveness. Meanwhile, methylation of 14-3-3σ, HLTF, SOCS-1, and HIC-1 was first reported in bladder cancer.; In voided urine samples, methylation can be detected in DAPK, RARβ, E-cadherin, RASSF1A and p16. The sensitivity of methylation analysis (95.5%) was higher than that of urine cytology (45.5%) in cancer detection. Moreover, we are the first group to demonstrate the potential diagnostic value of methylation detection in urine of bladder cancer patients.; In conclusion, we have demonstrated a distinct genetic and epigenetic pattern in bladder cancer that a progressive increase in genetic and epigenetic alterations was observed. Detection of gene methylation in routine voided urine using selected markers appeared to be more sensitive than conventional urine cytology. The potential application of such observations may be explored in both diagnosis and detection, as well as in monitoring relapse in patient treated for urothelial carcinoma.