Frequentp53 mutations and occasional loss of chromosome 4 in invasive bladder carcinoma induced byN-butyl-N-(4-hydroxybutyl)nitrosamine in B6D2F1 mice

Abstract

B6D2F1 mice (45/group) were treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) or uracil as follows: Group 1 received 0.05% BBN in drinking water for the entire experiment, Group 2 received 5 mg of BBN by gastric gavage in 0.1 mL of 20% ethanol twice per week for 10 wk, Group 3 received a 2.5% uracil-containing diet for the entire experiment, and Group 4 was controls (received 0.1 ml of 20% ethanol by gavage twice per week for 10 wk). The surviving mice in Group 1 were killed after week 26 and those in the other groups after week 30. By week 15, three of 11 Group 1 and one of 15 Group 2 mice had bladder carcinoma. By 26 and 30 wk, respectively, invasive carcinomas were observed in 33 of 34 and six of 21 mice in Groups 1 and 2 and renal pelvic carcinomas in 11 of 34 and three of 21 mice in Groups 1 and 2. Four of 19 uracil-treated mice had bladder nodular hyperplasia. By polymerase chain reaction-single-strand conformation polymorphism and sequence analyses, 16 of 20 and two of five bladder carcinomas from Groups 1 and 2, respectively, showed mutations in the p53 gene. Ha-ras mutation was present in one case. Loss of heterozygosity analysis with simple-sequence length polymorphism markers for chromosome 4 showed that 10 of 21, two of 15, and nine of 13 mice in Groups 1-3, respectively, had heterozygous or homozygous deletions. B6D2F1 mice are therefore susceptible to the urothelial carcinogenic effects of BBN and develop frequent p53 mutations and chromosome 4 deletions. Chromosome 4 deletions were also seen with uracil.

p53 Heterozygosity Results in an Increased 2-Acetylaminofluorene-Induced Urinary Bladder but not Liver Tumor Response in DNA Repair-Deficient Xpa Mice

“…The conclusion that p53 plays an important role in urinary bladder tumor suppression has also been made by others (45)(46)(47)(48), but in the present study we show for the first time in vivo that this is most likely because of the induction of p53-mediated death of cells with DNA damage by triggering apoptosis. We found a relatively high number of apoptotic cells in Xpa mice, which was clearly reduced in Xpa mice carrying only one functional p53 allele.…”

Role of Ha-ras activation in superficial papillary pathway of urothelial tumor formation

“…An interesting phenomenon in chemical carcinogenesis models of bladder cancer is that the same carcinogens appear to cause di erent bladder tumors in rats than in mice (Oyasu, 1995;Ogawa et al, 1998). In rats, bladder tumors are frequently of the papillary type, irrespective of the carcinogens used, and they are rarely invasive unless large doses of carcinogens was used for a prolonged period (Kunze and Chowaniec, 1990).…”

“…In rats, bladder tumors are frequently of the papillary type, irrespective of the carcinogens used, and they are rarely invasive unless large doses of carcinogens was used for a prolonged period (Kunze and Chowaniec, 1990). In mice, however, the same carcinogens can cause primarily urothelial dysplasia and CIS, the latter of which readily becomes invasive (Ohtani et al, 1986;Ogawa et al, 1998). The reason for this species variability is not entirely clear, but existing data suggest that it is the speci®c genetic defects, rather than the genetic background per se, that determine the di erent phenotypes.…”

“…In carcinogen-induced rat bladder tumors, there is a high frequency of Ha-ras mutation and low frequency of p53 mutation (Enomoto et al, 1990;Masui et al, 1993). In contrast, the same carcinogen-induced mouse bladder tumors contain a high frequency of p53 mutations and a low frequency of Ha-ras mutations (Yamamoto et al, 1995;Ogawa et ., 1998). Therefore, the di erent genetic background in rats and mice may contribute indirectly to the varying types of genetic defects that will occur in response to the same carcinogen treatment, i.e., either Ha-ras activation, which produces super®cial papillary tumors, or p53 mutation, which produces CIS/invasive tumors.…”

“…Notably, deletions involving chromosomes 9p and 9q are frequently found in super®cial papillary tumors, whereas dysfunction of p53 and pRb is primarily associated with CIS and invasive tumors (Dalbagni et al, 1993;Spruck et al, 1994;Rosin et al, 1995;Wagner et al, 1995). However, with the exception of several chemical carcinogenesis models (Oyasu, 1995;Ogawa et al, 1998), most of the clinical data are correlative in nature. Moreover, since multiple genetic alterations are simultaneously present in human bladder cancer, the role of a single genetic defect in inducing urothelial tumorigenesis has been di cult to ascertain.…”