High susceptibility of an analbuminemic congenic strain of rats with an F344 genetic background to induced bladder cancer and its possible mechanism

Preclinical models of bladder cancer: BBN and beyond

Preclinical modelling is a crucial component of advancing the understanding of cancer biology and therapeutic development. Several models exist for understanding the pathobiology of bladder cancer and evaluating therapeutics. N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN)-induced bladder cancer is a commonly used model that recapitulates many of the features of human disease. Particularly in mice, BBN is a preferred laboratory model owing to a high level of reproducibility, high genetic fidelity to the human condition, and its relative ease of use. However, important aspects of the model are often overlooked in laboratory studies. Moreover, the advent of new models has yielded a variety of methodologies that complement the use of BBN. Toxicokinetics, histopathology, molecular genetics and sex can differ between available models and are important factors to consider in bladder cancer modelling.

Ideal Experimental Rat Models for Liver Diseases

There are many limitations for conducting liver disease research in human beings due to the high cost and potential ethical issues. For this reason, conducting a study that is difficult to perform in humans using appropriate animal models, can be beneficial in ascertaining the pathological physiology, and in developing new treatment modalities. However, it is difficult to determine the appropriate animal model which is suitable for research purposes, since every patient has different and diverse clinical symptoms, adverse reactions, and complications due to the pathological physiology. Also, it is not easy to reproduce identically various clinical situations in animal models. Recently, the Guide for the Care and Use of Laboratory Animals has tightened up the regulations, and therefore it is advisable to select the appropriate animals and decide upon the appropriate quantities through scientific and systemic considerations before conducting animal testing. Therefore, in this review article the authors examined various white rat animal testing models and determined the appropriate usable rat model, and the pros and cons of its application in liver disease research. The authors believe that this review will be beneficial in selecting proper laboratory animals for research purposes.

F344 rat liver nonparenchymal cell transplantation can increase the number of albumin-positive hepatocytes in the liver following hematopoietic reconstitution in irradiated analbuminemic rats

The adult liver contains hematopoietic stem cells that can reconstitute the bone marrow. We tested whether bone marrow cells (BMCs) derived from liver nonparenchymal cells (LNPCs) can increase the number of hepatocytes within livers. LNPCs from Fischer 344 rats (F344) were infused into the penile veins of F344 congenic Nagase's analbuminenic rats (F344alb) immediately after whole-body irradiation, and the recipients were sacrificed 8 weeks later. Eleven of 15 (73.3%) F344alb that received the LNPC transplantation after irradiation survived, while only 1 of 8 (12.5%) F344alb that received irradiation alone was alive after 8 weeks. Normal albumin gene sequences were detected by PCR in BMCs of the recipient F344alb that received LNPC transplantation after irradiation, indicating that F344alb bone marrow was reconstituted by F344 LNPCs. Although single or pairs of albumin-positive (Alb+) hepatocytes were seen in the liver of untreated F344alb and those with irradiation or LNPC transplantation alone, clusters consisting of >3 Alb+ hepatocytes were detected in the livers of F344alb with the LNPC or BMC transplantation after irradiation together with single or double Alb+ cells. Normal albumin gene sequences were detected by PCR in the DNA isolated from such Alb+ hepatocyte clusters microdissected from the immunostained sections. The data indicate that BMCs derived from F344 LNPCs could increase the number Alb+ hepatocytes within the F344alb liver.

Strain differences in sensitivity to the promoting effect of sodium L-ascorbate in a two-stage rat urinary bladder carcinogenesis model

Rat strain differences in sensitivity to the promoting effect of sodium L-ascorbate (SA) on the development of urinary bladder tumors were investigated. In experiment 1, WS/Shi (WS), ODS/Shiod/od (ODS), and LEW/Crj (LEW) rats were initiated with 0.05% N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) in their drinking water and subsequently given basal Oriental MF diet (M) with or without a 5% SA supplement. In LEW rats the SA treatment increased the induction of neoplastic lesions in the urinary bladder, whereas WS and ODS animals proved unresponsive to its promoting effects. In experiment 2, WS and F344 rats were maintained on two kinds of commercial basal diets, M and CLEA CA-1 (C), during administration of SA, since dietary factors can influence promoting effects. Feeding M during the promotion period in F344 rats yielded significantly more neoplastic lesions than feeding C, but in WS rats no such dietary influence was apparent. In experiment 3, strain differences in biosynthesis of alpha-2u-globulin (alpha 1a-g) were assessed because both alpha 2a-g in the urine and administration of sodium salts of organic acids such as SA have been reported to be involved in tumor promotion. Immunohistochemical analysis of renal tubules and Western blotting analysis of urine revealed the presence of alpha 2a-g in all three strains examined. These data suggest that differences in susceptibility to promotion are due to genetic factors rather than dietary factors and the ability to synthesize alpha 2a-g.

Modifying effects of chemicals on the development of liver preneoplastic placental glutathione S-transferase positive foci in analbuminemic and Sprague-Dawley rats

Nagase analbuminemic rats (NARs) were compared to the Sprague-Dawley (SD) stock in a medium-term assay system for hepatocarcinogenesis regarding their susceptibilities to the influence of chemicals on the development of glutathione S-transferase, placental form, positive (GST-P+) foci. Two weeks after initiation with diethylnitrosamine (DEN), the animals were exposed alternatively to 0.06% 3'-methyl-4-dimethyl-aminoazobenzene (3'-Me-DAB), 50 ppm DEN, 0.25% ethionine, 1% clofibrate, and 1% butylated hydroxyanisole (BHA) for a 6-wk period. Adequate controls included groups only initiated with DEN or treated with each test compound alone. For evaluation of the modifying potential of the chemicals, indices were generated by using the mean values obtained for number and area of GST-P+ foci after each treatment. Comparison between these indices suggests that SD rats were relatively more sensitive than NARs to the modifying effects of complete carcinogens (3'-Me-DAB and DEN). The strains were similarly-susceptible to the promoting influence of ethionine, a nongenotoxic carcinogen. The inhibitory influence of BHA was more intense in NARs, whereas in both strains clofibrate was associated to similarly reduced values for number and area of GST-P+ foci. The degree of susceptibility of each strain to the modifying influence of chemicals on foci development depended on the chemical agent investigated.

High susceptibility of analbuminemic rats to neurogenic tumor induction by transplacental administration of N-ethyl-N-nitrosourea

The susceptibilities of Nagase analbuminemic rats (NAR) and control Sprague-Dawley rats (SDR) to N-ethyl-N-nitrosourea (ENU) were compared. In Experiment I, the rats were given daily subcutaneous injections of 10 mg/kg of ENU for a week from 4 weeks of age. In Experiment II, mother rats were given a single subcutaneous injection of 60 mg/kg of ENU on day 17 of pregnancy and tumor development in their offspring was examined. In Experiment I, the incidence of neurogenic tumors was slightly, but not significantly, higher in NAR than in control rats. In Experiment II, the incidence of total tumors including neurogenic tumors was significantly higher in NAR (40/43, 93.0%) than in SDR (13/61, 21.3%). NAR showed particularly high susceptibility to induction of neurogenic tumors (34/43, 79.1%) and renal tumors (15/43, 34.9%). In an attempt to elucidate the underlying mechanisms of the increased susceptibility of NAR to ENU, O6-ethylguanine, a major premutagenic ethylated DNA adduct, was quantitated in fetal brain DNA of NAR and SDR after a pulse exposure to 60 mg/kg ENU. No significant difference in the initial formation or subsequent repair of O6-ethylguanine was observed in the two strains, indicating that abnormality at some later stage(s) of chemical carcinogenesis may lead to the increased susceptibility of NAR to induction of neurogenic tumors.

Time- and dose-dependent induction of invasive urinary bladder cancers by N-ethyl-N-(4-hydroxybutyl)nitrosamine in B6C3F1 mice

A sequential investigation of N-ethyl-N-(4-hydroxybutyl)nitrosamine (EHBN) bladder carcinogenesis was performed in male B6C3F1 mice maintained ad libitum on tap water containing 0.025% EHBN for 4, 12, 20, 28 and 36 weeks. A total of 81 invasive tumors, comprising 55 squamous cell carcinomas (SCCs) (68%), 25 transitional cell carcinomas (TCCs) (31%) and 1 adenocarcinoma (1%) were found. Of these, 23 (22 SCCs and 1 TCC) demonstrated invasion to the prostate, 3 metastasized to the lung, and 2 spread by peritoneal seeding. The anaplastic grade and extent of invasion of the SCCs significantly exceeded those of the TCCs. The results suggested a histogenetic pathway from simple dysplasia through papillary or nodular dysplasia and/or carcinoma in situ to eventual development of invasive carcinomas.

Lack of bladder carcinogenicity of dietary sodium saccharin in analbuminaemic rats, which are highly susceptible to N-nitroso-n-butyl-(4-hydroxybutyl)amine

A previous 1-wk study measuring the agglutinability of bladder epithelial cells by concanavalin A had suggested a high susceptibility of analbuminaemic rats to bladder carcinogenesis by sodium saccharin (Honma et al., Cancer Letters 1983, 19, 7). A long-term study was conducted to confirm the results of this short-term assay. Sodium saccharin was administered at 5% in the diet to groups of 35 male analbuminaemic rats and 36 male rats of the Sprague-Dawley strain. No bladder carcinomas nor precancerous lesions were observed in any of the rats exposed to sodium saccharin. The discrepancy between the results of the agglutination assay and the long-term experiment might be attributable to a sharp increase in urine volume in analbuminaemic rats during the first week of treatment. The resultant distension of the bladder wall might make the epithelial cells more susceptible to concanavalin A agglutination. The results indicated no demonstrable bladder carcinogenicity of sodium saccharin in analbuminaemic rats and excluded the possibility that these particular mutant rats could be useful animals for shorter-duration screening for bladder carcinogens.

Fluorometric assay for polyamines in urine and tissues using electrophoresis on Titan III cellulose acetate

A simple, rapid assay method for polyamines (putrescine, spermidine, and spermine) in urine and tissues using electrophoresis on Titan III cellulose acetate was developed. In this procedure, polyamines are preliminarily extracted from a hydrolysate of urine or from supernatants of tissue homogenates by use of a Bio-Rex 70 minicolumn. After electrophoretic separation, polyamines are fluorometrically detected by the reaction with o-phthalaldehyde and 2-mercaptoethanol. Six extracts and two external standards of polyamines can be separated and detected in 11 min on a cellulose acetate strip. This method permits the determination of polyamines in a range of 0.1 mM (25 pmol) to 1.0 mM (250 pmol).