[Animal models of bladder cancer]

Treatment with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) or N-ethyl-N-(4-hydroxybutyl)nitrosamine (EHBN) in the drinking water induces bladder cancer of rats or mice with high incidence. Induced bladder cancers of rats are mostly papillary, non-invasive type, whereas those of mice are non-papillary, invasive type. Histologically, most of BBN-induced bladder cancers are transitional cell carcinoma in both rats and mice. On the other hand, the incidences of squamous cell carcinoma increased in cases of mice, especially in mice treated with EHBN. Metastases and invasions of bladder cancers are more common in mice than in rats. There are strain and species differences in the bladder response to BBN and EHBN. In addition, a putative preneoplastic lesion, papillary or nodular hyperplasia of the epithelium is a good marker for early detection of bladder cancer development.