Focal loss of alkaline phosphatase and increase of proliferation in preneoplastic areas of the rat urothelium after administration of n-butyl-n-(4-hydroxybutyl)-nitrosamine and n-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide

Chemoprevention of BBN-Induced Bladder Carcinogenesis by the Selective Estrogen Receptor Modulator Tamoxifen

Bladder cancer is the fifth most frequent tumor in men and ninth in women in the United States. Due to a high likelihood of recurrence, effective chemoprevention is a significant unmet need. Estrogen receptors (ERs), primarily ERβ, are expressed in normal urothelium and urothelial carcinoma, and blocking ER function with selective ER modulators such as tamoxifen inhibits bladder cancer cell proliferation in vitro. Herein, the chemoprotective potential of tamoxifen was evaluated in female mice exposed to the bladder-specific carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Carcinogen treatment resulted in a 76% tumor incidence and increased mean bladder weights in comparison to controls. In contrast, mice receiving tamoxifen concurrent (8-20 weeks) or concurrent and subsequent (8-32 weeks) to BBN administration had no change in bladder weight and only 10% to 14% incidence of tumors. Non-muscle-invasive disease was present in animals treated with tamoxifen before (5-8 weeks) or after (20-32 weeks) BBN exposure, while incidence of muscle-invasive bladder carcinoma was reduced. ERβ was present in all mice and thus is a potential mediator of the tamoxifen chemoprotective effect. Surprisingly, ERα expression, which was detected in 74% of the mice exposed to BBN alone but not in any controlmice, was correlated with tumor incidence, indicating a possible role for this receptor in carcinogen-induced urothelial tumorigenesis. Thus, these data argue that both ERα and ERβ play a role in modulating carcinogen-induced bladder tumorigenesis. Administration of tamoxifen should be tested as a chemopreventive strategy for patients at high risk for bladder cancer recurrence.

Control of alkaline phosphatase activity in C3H10T1/2 cells: role of retinoic acid and cell density

The enzyme alkaline phosphatase (AP) has been shown to be lost or inappropriately expressed during carcinogenesis in some tissues. Because retinoic acid (RA) appears to play a role in the normal regulation of the enzyme (RA up-regulates AP in a variety of cell types) we have suggested that altered AP expression in some cancers may be caused by a defect in the ability of the cells to respond normally to retinoid. We have begun to use the chemically transformable mouse embryo fibroblast cell, C3H10T1/2, to investigate this possibility. In this initial study we characterized AP regulation in normal C3H10T1/2 cells and show that: (1) 10(-7) M RA increases AP activity within 3-4 h in serum-free medium; (2) serum inhibits short-term induction (0-8 h) in a concentration-dependent manner (10% serum causes complete inhibition); (3) during long-term RA exposure (24 h and 48 h), induction can be detected in serum-containing medium; (4) AP induction is dose related at RA concentrations from 10(-10) M to 10(-6) M in serum-free medium; (5) 10(-5) M RA is ineffective at inducing AP in serum-free medium during 8 h but is the most effective concentration in serum-containing medium during 24 h and 48 h exposures; (6) AP inducibility by RA requires near-confluent cell densities; and (7) when cultures become confluent, cells become constitutive for AP and no longer require RA for enzyme expression. The effects of serum and cell density on AP inducibility by RA and implications of the RA up-regulation of AP for teratogenesis are discussed.

Comparison of enzyme phenotypes in human bladder tumours and experimentally induced hyperplastic and neoplastic lesions of the rat urinary bladder. A combined histochemical and immunohistochemical approach

The expression of a number of enzymes involved in drug metabolism, membrane function etc. was compared in hyperplastic and neoplastic lesions of the rat bladder and in human bladder tumours. Transitional cell carcinomas (TCC) in both rat and Man were characterized by decreased alkaline phosphatase (ALP) and increased gamma-glutamyl transpeptidase (GGT), beta-glucuronidase (beta-G1), succinate dehydrogenase (SD) and glucose-6-phosphate dehydrogenase (G6PD) activities. In addition, binding for antibodies specific for different cytochrome P-450 species (UT50, PB3a, MC1, MC2) and microsomal epoxide hydrolase (mEHb) was elevated in both murine and human tumours. Comparison of the enzyme phenotype in hyperplastic lesions induced by freeze ulceration or uracil administration with that in preneoplastic papillary or nodular hyperplasia (PNH) and TCC suggested, however, that most of the alteration in enzyme content or activity was non-specific and related to requirements for epithelial cell proliferation. On the other hand, the decreased ALP, and increased GGT and beta-G1 activity appeared more directly related to neoplastic transformation. The results suggested that qualitative differences exist between reactive hyperplasia and preneoplastic or neoplastic lesions in the urinary bladder. The finding of increased cytochrome P-450, in clear contrast to the reduction characteristic of preneoplastic hepatic lesions, may be important with regard to the observed difference in neoplastic transformation between the bladder and liver in response to drug metabolising enzyme inducers.

Epithelial-mesenchymal interactions in prostatic development. I. morphological observations of prostatic induction by urogenital sinus mesenchyme in epithelium of the adult rodent urinary bladder

Tissue recombinants of embryonic urogenital sinus mesenchyme (UGM) and epithelium of the urinary bladder (urothelium, BLE) of adult rats and mice were grown for 3-30 d in male syngeneic hosts. Short-term in vivo growth indicated that prostatic morphogenesis is initiated as focal outgrowths from the basal aspect of the adult urothelium. The solid epithelial buds elongate, branch, and subsequently canalize, forming prostatic acini. After 30 d of growth in the male hosts, prostatic acini exhibit secretory activity. The marked changes in urothelial morphology induced by the UGM are accompanied by the expression of fine-structural features indicative of secretory function (rough endoplasmic reticulum, Golgi apparatus, and secretory granules). During this process, urothelial cells express prostatic histochemical markers (alkaline phosphatase, nonspecific esterase, glycosaminoglycans) and prostate-specific antigens. The expression within BLE of prostatic characteristics is associated with the loss of urothelial characteristics. These data indicate that adult urothelial cells retain a responsiveness to embryonic mesenchymal inductors. Furthermore, mesenchyme-induced changes in urothelial cytodifferentiation appear to be coupled to changes in functional activity.

Keratin, luminal epithelial antigen and carcinoembryonic antigen in human urinary bladder carcinomas. An immunohistochemical study

14 urinary bladder carcinomas of all main types were investigated with antisera to "broad spectrum keratin" (aK), "luminal epithelial antigen" (aLEA) and carcinoembryonic antigen (aCEA), using an indirect immunoperoxidase method on formalin fixed paraffin embedded sections. Keratin and LEA were both present in normal transitional epithelium, papilloma and carcinoma in situ whereas CEA was absent. Transitional cell carcinomas reacted with both aK and aLEA whereas CEA was seen only in a few foci. In squamous metaplasia and squamous carcinoma reaction with aK was particularly strong, while LEA was almost lacking and CEA was present in necrotic centres. In adenocarcinomas aK and aLEA reacted equally while aCEA reacted only on the surface.

The modification of rat liver regeneration by carcinogens and its reflection by extrahepatic tissues

Liver regeneration is distinctly influenced by the treatment of male Sprague-Dawley rats with 2-acetylaminofluorene or N-methyl-N-nitrosourea on three successive days immediately prior to partial hepatectomy. The latter compound modulates the restorative liver growth, whereas it is strongly inhibited by the hepato-carcinogen 2-acetylaminofluorene. According to their influence on the regenerating liver, both carcinogens delay the post-operative decrease as well as the recovery of the physiological cell renewal in the jejunal and esophageal epithelium. Beside this, the circadian mitotic fluctuation of the esophagus is also altered by the carcinogens after partial hepatectomy like that of the regenerating liver. In contrast to the behaviour of the jejunum and the esophagus, the adrenocortical cell division is temporally elevated by the growth stimulus after partial hepatectomy. This effect is also found after carcinogen pretreatment only. For that reason one can assume that carcinogens produce a growth stimulating response like partial hepatectomy, which is displayed by an increased cell replication in the adrenal cortex. Possibly this phenomenon reflects common systemic mechanisms which indicate the promotory action of partial hepatectomy and chemical promotors as well as that of carcinogens.

[Stimulating effect of partial cystectomy on regeneration of rat bladder urothelium and its significance for carcinogenesis (author's transl)]

Cell proliferation kinetics of the urinary bladder urothelium have been analyzed in a total of 218 female Wistar rats after partial cystectomy. After one-third resection of the bladder DNA synthesis started 15 h postoperatively in the bladder stump and reached its maximum at 25 h with a mean 3H-TdR index of 10.1%. In the area of resection the proliferative activity increased after 20 h and the highest 3H-TdR index was found to be 24.7% after 45 h. In the case of hemicystectomy the labeling index in the stump increased 15 h postoperatively and the highest 3H-T-dR index was determined at 20 h with 16.6%. The urothelial cells in the area of resection began to proliferate synchronously with those in the stump and the maximum of DNA synthesis was measured 35 h postoperatively with an 3H-TdR index of 24.2%. After 2 weeks the proliferative activity within the stump and operative region corresponded to that of the control urothelium. The basal cells showed absolutely the highest proliferative activity, the suprabasal cells exhibited on the other side the highest regenerative potential compared with the control urothelium. Partial cystectomy might possibly serve as an experimental model for testing low potential carcinogens, in the case where carcinogenic effects would be initiated, potentiated and accelerated via stimulation of the DNA synthesis.

A rationale for the loss of growth control during experimental bladder carcinogenesis

A rationale is presented which provides an explanation for the loss of growth control which is associated with the early phase of experimentally-induced bladder cancer. Two early events which occur in the urothelium following exposure to carcinogen, the focal loss of alkaline phosphatase activity and the initiation of cell proliferation, are both proposed to be the result of a defect in the interaction between glucocorticoid hormone and urothelium. The possible causes for this defect are discussed in terms of a defect in, or an interference with, the glucocorticoid-receptor mechanism.

Induction of transitional cell carcinoma of the urinary bladder in rats by feeding N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide. Histological and ultrastructural findings

After feeding with 0.188% N-[4-(5-nitro-2 furyl)-2-thiazolyl] formamide (FANFT), transitional cell carcinoma of the urinary bladder was induced in all female Wistar rats tested. Histological changes of the urothelium consisted of various degrees of hyperplasia and dysplasia. An infiltrating transitional cell carcinoma first appeared after 8 months. These results are compared with the findings of other authors, and divergencies of the tumour induction rates are discussed with respect to strain, sex and weight of experimental animals as well as concentration and amount of ingested carcinogen. Electron microscopy shows microvillous transformation of the luminal plasma membrane and appearance of a thick fluffy cell coat (glycocalyx). These changes are explained by an altered function of the Golgi complex occurring during malignancy and leading to a loss of the specific discoid vesicles of the urothelial cells.

Biological behavior of N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide induced carcinoma of the transitional epithelium in the rat

30 female Wistar rats weighing between 70 and 90 g were fed for 8 months with 0,188% N-[4-(5-nitro-2-furyl)-2-thiazolyl] Formamide (FANFT). After this period a papillary tumor of the urinary bladder was demonstrable in each animal. Histological examination always revealed a transitional cell carcinoma with prevailing medium tumor stages; no distant metastases were found. The grade of malignancy was classified as medium and high. No significant statistical relationship could be ascertained between tumor stage and grade or between grade and weight, but a correlation was established between tumor stage and weight. After 12 months, 36/60 kidneys were found to be normal, whereas in 20/60 dysplasias and in 2/60 transitional cell carcinomas of the renal pelvis were observed; secondary hydronephrosis due to bladder tumors occured 4 times. Other organ changes were not noticeable.

Stages of transformation in the development of N-butyl-N-(4-hydroxybutyl)-nitrosamine-induced transitional cell carcinomas in the urinary bladder of rats

The histogenesis of papillary and nonpapillary transitional cell carcinomas were studied morphologically and autoradiographically in 177 female Wistar rats after oral application of N-butyl-N-(4-hydroxybutyl)-nitrosamine with varying exposure and induction times. By far the largest proportion of carcinomas developed by a malignant transformation of preexisting papillomas or their precursors, the papillary hyperplasias. The transition into a focally malignant growth did not take place abruptly, but occurred stepwise through different successive stages of transformation, each having its own distinct morphological character. The first stage consisted of a focal, sharpely defined cellular atypia. In a further stage carcinomata in situ developed out of the atypical foci and progressed finally in a last stage of transformation into a circumscript infiltrative growth. The successive development of each stage occurred independent of any further carcinogen application after transformation was initiated at the molecular level. The number of papillomas with transformation stages increased with a lengthening of the exposure and induction time. 74.4% of all the registered papillomas had been transformed. Consequently papillomas must be considered potentially highly malignant. The 3H-TdR index was 4.2 times higher in atypical urothelial areas (7.6%) and 7.5 times higher in carcinomata in situ (14.3%) than in the surrounding papillomatous structures which appeared light microscopically benign. The latter demonstrated a rather constant 3H-TdR index, whether they bordered on atypical foci (1.8%) or carcinomata in situ (1.9%). The length of exposure and induction time exercised no significant influence on the degree of proliferative activity. The development of transitional cell carcinomas from a primary carcinoma in situ (intraurothelial carcinoma) played a much less significant role.