Significant overexpression of metallothionein and cyclin D1 and apoptosis in the early process of rat urinary bladder carcinogenesis induced by treatment with N-butyl-N-(4-hydroxybutyl)nitrosamine or sodium L-ascorbate

Abstract

Effects of a genotoxic bladder carcinogen, N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) and a non-genotoxic bladder promoter, sodium L-ascorbate (Na-AsA), on protein expression, cell proliferation and apoptosis of the bladder epithelium with or without the influence of testicular castration were investigated. Male F344 rats were divided into six groups (groups 1-6). BBN was given with 0.05% drinking water to groups 1 and 4 for 8 weeks, groups 2 and 5 received diet with 5% Na-AsA. Then the animals were treated without any chemicals. Groups 3 and 6 were non-treated controls. Testicular castration was carried out 2 weeks before commencement of chemical treatment on groups 4-6. The total observation period was 18 weeks. Overexpression of cyclin D1 was induced by BBN but not Na-AsA and the degree of overexpression was higher in the order simple hyperplasia, papillary or nodular hyperplasia, papilloma and carcinoma. Metallothionein (MT) was also overexpressed in bladder epithelium treated with BBN but not Na-AsA, but was decreased in papillomas and never found in a carcinoma. Cyclin D1-positive cells were essentially MT-negative. Therefore, it is speculated that MT protects genes from insult by genotoxic carcinogens and its lack is associated with tumor development. Apoptotic cell death occurred during treatment with BBN and Na-AsA and after their withdrawal. Chromatin condensation of many G0/G(1) cells was particularly marked on flow cytometry analysis 1 week after cessation of treatment, this being considered as an early apoptotic change. Although testicular castration had no influence on the above events, it resulted in decreased tumor formation as compared with the case of similarly treated intact animals. Our data demonstrate that overexpression of MT and cyclin D1 is specific for treatment with a genotoxic carcinogen, and suggest that MT overexpression may play an important suppressive role in the early stages of rat urinary bladder carcinogenesis.

Accelerated Induction of Bladder Cancer in Patched Heterozygous Mutant Mice

“…Between 0 and 3% of intensely stained nuclei were observed, mostly in the upper layer of normal and hyperplastic urothelia and in TCCs, as was reported by Takaba et al (16) in BBN-treated rat bladders. However, we found no difference in the proportion of apoptotic cells between wt and Ptc ϩ/Ϫ mice at any time (0.17 Ͻ P Ͻ 0.89; data not shown).…”

Modulation of Gene Expression in Precancerous Rat Esophagus by Dietary Zinc Deficit and Replenishment

“…Metallothionein overexpression in ESCC is often positively correlated with the metastatic and proliferative activities of the cancer (36). In animal tumor models, overexpression of metallothionein has been shown in chemically induced rat and mouse bladder tumors (39,40). Our results show that metallothionein overexpression occurs in precancerous zinc-deficient esophagus (Tables 1 and 2; Fig.…”

Suppressive effect of 1,4-phenylene diisothiocyanate onN-butyl-N-(4-hydroxybutyl)nitrosamine-induced urinary bladder carcinogenesis in male ICR mice

“…This is consistent with the data reported previously. 37,[48][49][50][51][52] In this study, DITC effectively suppressed cyclin D1-positive cell ratios of urinary bladder, implying that reduction in the incidence of tumors and preneoplastic lesions of urinary bladder is related to effectively suppressed cell cycle progression by the treatment with DITC. In our recent study, another selective cyclin D1 inhibitor, silymarin have also been demonstrated to possess chemopreventive potential on BBN-induced urinary bladder carcinogenesis in male ICR mice.…”