Analysis of genetic alterations in normal bladder urothelium.

Objectives: To determine whether normal mucosa had already acquired genetic changes, we analyzed the loss of heterozygosity (LOH) and chromosomal changes in normal urothelium from patients with bladder cancer and those without any history of bladder cancer.

Methods: Sixteen patients with bladder cancer and 15 patients with benign prostatic hyperplasia were included in this study. Tumor tissue, as well as macroscopically normal mucosa, was examined histopathologically. We performed comparative genomic hybridization according to standard protocols to detect chromosomal alterations. Furthermore, we analyzed LOH using four markers on chromosome 9 according to standard protocols for polymerase chain reaction.

Results: In 75% of tumor samples, LOH or shifts were detected at least with one marker on chromosome 9. Comparative genomic hybridization revealed chromosomal alterations in 12 (75%) of 16 tumors. The loss of chromosome 9 was seen frequently (56%). LOH was observed in normal mucosa in 5 of 16 patients with tumor and 1 of 15 patients with benign prostatic hyperplasia. Chromosomal alterations were also seen in the normal mucosa of 1 patient with tumor and 2 patients with benign prostatic hyperplasia (chromosomes 1, 2, 6, 14, and 17).

Conclusions: Our results indicated that no general genetic instability is present in the bladder urothelium. Therefore, in most patients with bladder cancer, it seems that multifocality and recurrence are not caused by genetic instability of normal urothelial cells but develop owing to cell migration or intraluminal spread.