Chemoprevention by indomethacin of tumor promotion in a rat urinary bladder carcinogenesis model

Prostaglandin E2 as a therapeutic target in bladder cancer: From basic science to clinical trials

Bladder cancer (BCa) is a common solid tumor marked by high rates of recurrence, especially in non-muscle invasive disease. Prostaglandin E₂ (PGE₂) is a ubiquitously present lipid mediator responsible for numerous physiological actions. Inhibition of cyclooxygenase (COX) enzymes by the non-steroidal anti-inflammatory (NSAID) class of drugs results in reduced PGE₂ levels. NSAID usage has been associated with reductions in cancers such as BCa. Clinical trials using NSAIDs to prevent recurrence have had mixed results, but largely converge on issues with cardiotoxicity. The purpose of this review is to understand the basic science behind how and why inhibitors of PGE₂ may be effective against BCa, and to explore alternate therapeutic modalities for addressing the role of PGE₂ without the associated cardiotoxicity. We will address the role of PGE₂ in a diverse array of cancer-related functions including stemness, immunosuppression, proliferation, cellular signaling and more.

Carbonic anhydrase 2 is a novel invasion-associated factor in urinary bladder cancers

Rat bladder cancer is nearly always papillary non-invasive urothelial carcinoma (UC). To establish an animal model mimicking invasive UC that arises from papillary non-invasive UC in the bladder, male human c-Ha-ras proto-oncogene transgenic rats (Hras128) were treated with 0.05% N-butyl-N-(hydroxybutyl)nitrosameine (BBN) in their drinking water and/or 0.1% phenylethyl isothiocyanate (PEITC) in their diet as follows: BBN (8 weeks)→PEITC (8 weeks); PEITC (8 weeks)→BBN (8 weeks); BBN alone (16 weeks); PEITC alone (16 weeks); and no treatment. At the end of week 16, the highest incidence of invasive UC was observed in the BBN→PEITC group. Therefore, we used Hras128 rats treated with BBN followed by PEITC as a model of invasive bladder cancer to identify invasion-associated proteins. Proteome analysis was performed to compare the protein profiles of invasive and non-invasive UC in Hras128 rats. We identified 49 proteins that were either overexpressed or underexpressed in invasive UC but not in non-invasive UC. Immunohistochemical analysis of carbonic anhydrase 2 (CA2), an overexpressed protein, showed that the relative number of CA2-positive UC was significantly higher for invasive UC compared to non-invasive UC in rats. Moreover, the incidence of CA2-positive cancers was also significantly higher for human muscle-invasive bladder cancer (MIBC) compared to non-MIBC (NMIBC) and was positively associated with the progression of NMIBC. Our findings indicate that CA2 is an invasion-associated factor and suggest that it could serve as a potential therapeutic molecular target for bladder cancers.

Chemoprevention of urothelial cell carcinoma growth and invasion by the dual COX-LOX inhibitor licofelone in UPII-SV40T transgenic mice

Epidemiologic and clinical data suggest that use of anti-inflammatory agents is associated with reduced risk for bladder cancer. We determined the chemopreventive efficacy of licofelone, a dual COX-lipoxygenase (LOX) inhibitor, in a transgenic UPII-SV40T mouse model of urothelial transitional cell carcinoma (TCC). After genotyping, six-week-old UPII-SV40T mice (n = 30/group) were fed control (AIN-76A) or experimental diets containing 150 or 300 ppm licofelone for 34 weeks. At 40 weeks of age, all mice were euthanized, and urinary bladders were collected to determine urothelial tumor weights and to evaluate histopathology. Results showed that bladders of the transgenic mice fed control diet weighed 3 to 5-fold more than did those of the wild-type mice due to urothelial tumor growth. However, treatment of transgenic mice with licofelone led to a significant, dose-dependent inhibition of the urothelial tumor growth (by 68.6%-80.2%, P < 0.0001 in males; by 36.9%-55.3%, P < 0.0001 in females) compared with the control group. The licofelone diet led to the development of significantly fewer invasive tumors in these transgenic mice. Urothelial tumor progression to invasive TCC was inhibited in both male (up to 50%; P < 0.01) and female mice (41%-44%; P < 0.003). Urothelial tumors of the licofelone-fed mice showed an increase in apoptosis (p53, p21, Bax, and caspase3) with a decrease in proliferation, inflammation, and angiogenesis markers (proliferating cell nuclear antigen, COX-2, 5-LOX, prostaglandin E synthase 1, FLAP, and VEGF). These results suggest that licofelone can serve as potential chemopreventive for bladder TCC.

Non-steroidal anti-inflammatory drugs in the treatment of genitourinary malignancies: focus on clinical data

The antitumour activity of NSAIDs in preclinical trials has lead to their evaluation in the management of various malignancies in humans. Evidence regarding their use in the treatment of genitourinary tumours is reviewed here, focusing primarily on clinical data. The majority of available evidence comes from meeting abstracts and only a few published manuscripts were detected. The efficacy of selective COX-2 inhibitors, a subcategory of anti-inflammatory drugs, is promising in prostate cancer, in either biochemical recurrence after initial treatment or advanced disease. This does not seem to be the case for renal tumours in which efficacy in the advanced disease setting is not satisfactory. Despite the well-documented rationale for the application of NSAIDs in bladder cancer management, clinical evidence is not available. More studies are needed to assess the efficacy of anti-inflammatory agents in bladder cancer treatment and further clarify their therapeutic benefit in patients with prostate cancer, in which initial results are encouraging.

Analgesic therapy and the prevention of bladder cancer

The aim of this study was to measure the association between analgesic use and risk of bladder cancer among patients seen at the James A. Haley Veterans' Administration (VA) Hospital in Tampa, FL. A total of 330 cases were obtained using a combination of computerized pathology records, and inpatient and outpatient diagnoses. Controls were randomly selected from the VA computerized administrative database, and 1293 controls were included for analysis. Unconditional logistic regression analysis was performed to assess the risk of bladder cancer after adjusting for age, gender, and cigarette smoking. Among analgesic users, we were able to identify a nearly 20% reduction in risk potentially consistent with a protective role (OR = 0.81, 95% CI = 0.63, 1.05). Nonsmokers had a 43% decrease in risk (OR = 0.57, 95% CI = 0.33, 0.98). While smoking is a strong and recognized cause of bladder cancer, 50% of bladder cancer cases are not attributable to tobacco consumption. Given that nonsmokers prescribed nonsteroidal anti-inflammatory drugs (NSAIDs) were observed to have a 43% reduction in risk, it is important to study whether nonsmokers may benefit from therapy with NSAIDs.

COX-2 inhibitors and other nonsteroidal anti-inflammatory drugs in genitourinary cancer

Selective cyclooxygenase (COX)-2-inhibiting and other nonsteroidal anti-inflammatory drugs (NSAIDs) show promise for preventing and treating bladder and prostate cancers. In contrast to the strong NSAID epidemiology in colorectal cancer, the epidemiologic data on NSAIDs and genitourinary (GU) cancers are limited and mixed. However, a substantial body of preclinical in vitro and in vivo animal model data shows consistent NSAID activity in treating, and in some cases preventing, GU cancers and begins to address the mechanisms behind this activity (eg, involving Akt and ERK2 in the prostate). Many preclinical and clinical NSAID studies currently under way are helping to resolve the best type (selective or nonselective COX inhibitors or non-COX inhibitors), dose and duration of NSAID treatment for prevention in the GU setting. Future studies likely will focus on clarifying the NSAID mechanisms behind and developing NSAID combinations for both treating and preventing GU cancers.

Antiproliferative effect of nitrosulindac (NCX 1102), a new nitric oxide-donating non-steroidal anti-inflammatory drug, on human bladder carcinoma cell lines

Non-steroidal anti-inflammatory drugs (NSAIDs) are potent antitumoral agents but their side effects limit their clinical use. A novel class of drugs, nitric oxide-donating NSAIDs (NO-NSAIDs), was found to be safer and more active than classical NSAIDs. This study explored the effect of the NO-donating sulindac derivative, NCX 1102, on three human urothelial epithelial carcinoma cell lines (T24, 647V, and 1207) and primary cultures of normal urothelial cells. Cytotoxicity, antiproliferative effect, cell cycle alterations, morphological changes, and apoptosis were investigated after treatment with NCX 1102 in comparison with the native molecule. After treatment, there was a cytotoxic effect (with IC50 at 48 h of 23.1 μm on 647V, 19.4 μm on T24, and 14.5 μm on 1207) and an antiproliferative effect on all three cell lines with NCX 1102 but not with sulindac. No effect was detected on normal urothelial cells. Flow cytometric analysis showed a differential NCX 1102-induced accumulation of cells in various phases of the cell cycle, depending on cell line and concentration. NCX 1102 induced an occurrence of multinucleated cells in all cell lines and mitotic arrest in 647V and 1207. NCX 1102-treated T24 and 647V cell lines showed a significant difference of apoptotic cell amount when compared to controls. Our results demonstrated a greater antiproliferative potency of NCX 1102 compared to its parent molecule sulindac, and suggested that this new NO-NSAID may have therapeutic impact in the management of bladder cancer.

Bladder cancer prevention. Part I: what do I tell my patients about lifestyle changes and dietary supplements?

PURPOSE OF REVIEW

Comprehensive reviews of lifestyle changes and dietary supplements that may prevent bladder cancer are needed in order to facilitate discussions between clinicians and patients.

RECENT FINDINGS

Novel data exist that numerous lifestyle/diet and dietary supplements may lower the risk of this disease. For example, reducing arsenic exposure, incorporating dietary changes, and vitamin E supplements continue to accumulate research that supports their use with some patients at a higher risk for this disease. Regardless, smoking cessation seems to have the largest impact on reducing risk and incorporating these other changes after smoking cessation may reduce an individual's risk to an even greater extent.

SUMMARY

However, a large percentage of cases of individuals diagnosed with this cancer apparently have no known etiology. Diets lower in calories or possibly specific sub-types of fat, and higher in fruits and especially vegetables, seem to provide some protection. Other dietary/supplement options may affect risk, but these benefits could be seriously attenuated by smoking. Dietary selenium, but currently not selenium supplements, may also affect risk, especially in non-smokers. Dietary vitamin E, and vitamin E supplements, may provide some protection. Non-selective (e.g. non-steroidal anti-inflammatory drugs) and selective cyclooxygenase-2 inhibitors are generating interest because bladder tumors seem to contain higher concentrations of this enzyme. Drinking-water quality, especially arsenic concentrations, may seriously affect risk. Providing recommendations for patients with regard to some of these lifestyle modifications is currently recommended because the majority of these alterations are also recommended currently for cardiovascular or general oncology disease reduction.

Chemoprevention of superficial bladder cancer

Patients who have bladder cancer with superficial disease are at high risk for recurrence but low risk for progression to muscle invasive disease and are regularly monitored with cystoscopy to detect recurrent tumors. This clinical setting (high recurrence rate, excellent surveillance, and low risk of progression in stage) provides an ideal setting for secondary chemoprevention. Vitamins, difluoromethylornithine, and cyclooxygenase inhibitors have demonstrated activity in preclinical models of bladder cancer. Limited clinical data suggests that vitamins and their analogs may be useful for decreasing the rate of tumor recurrence in patients with superficial bladder cancer. Ongoing clinical trials are exploring the roles of fenretinide, difluoromethylornithine, and celecoxib in the treatment of patients with a history of superficial bladder cancer.

Suppression of lung metastasis by aspirin but not indomethacin in an in vivo model of chemically induced hepatocellular carcinoma

To examine the effect of non-steroidal anti-inflammatory drugs on metastasis formation, aspirin (ASP, 0.5% in diet) and indomethacin (IM, 0.005% in drinking water) were applied to an in vivo highly metastatic rat hepatocellular carcinoma (HCC) model in F344 male rats. Administration for 8 weeks after induction of highly metastatic HCC by sequential treatment with diethylnitrosamine and N-nitrosomorpholine did not cause any significant change in survival rate or body weight. Multiplicity of HCC in the liver increased during ASP or IM treatment without any significant histological alteration. Although absent in the rats killed at the end of the period of carcinogen exposure, lung metastasis at the end of the experiment was found in 100%, 89% and 100% of rats in the control, ASP and IM groups, respectively. Degree of metastasis was classified into three groups according to the number of metastatic nodules, i.e., slight (1 - 5 nodules), moderate (6 - 50) and severe (more than 51), which amounted to 0%, 43% and 57% in the control group. ASP significantly reduced the degree of metastasis, the incidences being 33%, 44%, and 11%, respectively, whereas IM was without significant influence. Both agents suppressed cell proliferation in HCCs, without any alteration of pan-cadherin expression. However, expression in HCC of mRNAs for intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, both of which are considered to play key roles in attachment of cancer cells to the endothelium, was significantly suppressed by ASP. Thus, the present study demonstrated that ASP, but not IM, has the potential to inhibit lung metastasis of rat HCC in vivo, possibly via reduced attachment of tumor cells to the vascular endothelium. Moreover, these data indicate this in vivo model for induction of rat highly metastatic HCC to be a useful tool for the assessment of the efficacy of therapeutic treatments to block metastasis formation.

Potential lifestyle and dietary supplement options for the prevention and postdiagnosis of bladder cancer

Apart from smoking, certain occupational exposures, and schistosomiasis, little is known about other potential lifestyle risk factors for bladder cancer. Other investigations thus far have also been important because of the large number of individuals who are diagnosed with this cancer that apparently have no known risk factors. Preventing the recurrence of bladder cancer has generated some interest because several preliminary trials have found that a combination dietary supplement of vitamins and minerals or a probiotic agent (Lactobacillus casei) may impact this outcome favorably. Advising patients on some of these lifestyle modifications is currently recommended because the majority of them are also currently recommended for cardiovascular disease reduction.

Stimulation of DNA synthesis by tumor promoters in primary rat hepatocytes is not mediated by arachidonic acid metabolites

Studies in vivo using inhibitors of eicosanoid synthesis suggested that prostaglandins may play a role in mediating tumor promotion in liver by agents such as phenobarbital (PB). However, it is not clear whether any stimulation of arachidonic acid metabolism/prostaglandin formation results directly from the action of tumor promoters on hepatocytes or indirectly from effects of promoters on Kupffer cells or other non-hepatocytes. Our laboratory has been utilizing relatively pure populations of rat hepatocytes under the defined conditions of primary cultures, to investigate growth-stimulatory actions of tumor promoters, an important element in the promotion stage of carcinogenesis. It has been shown that most if not all liver tumor promoters tested stimulate hepatocyte DNA synthesis when added in combination with factors such as EGF, insulin, and glucocorticoid. In the present study, we sought evidence for a role of prostaglandins (PGs) in the direct growth-stimulatory actions of tumor promoters on hepatocytes. PGE(2), PGF(2 alpha), and PGD(2) cause concentration-dependent stimulation of hepatocyte DNA synthesis, while arachidonic acid was without any effect. PGE(2) and PGF(2 alpha) required the presence of dexamethasone to exert significant effects. These PGs did not further augment the stimulatory effect of EGF. In contrast, PGD(2) stimulated DNA synthesis in the presence or absence of insulin, dexamethasone, or EGF. The effect of tumor promoters on arachidonic acid metabolism, as measured by [(3)H]arachidonic acid release and PGE(2) production, was determined. The phorbol ester TPA significantly increased [(3)H]arachidonic acid release as well as PGE(2) formation in hepatocytes in line with known effects in other cell types. However, liver tumor promoters phenobarbital (PB), alpha-hexachlorocycohexane (HCH), 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT), and pregnenolone-16 alpha-carbonitrile (PCN) were without effects. Finally, inhibitors of arachidonic acid metabolism were tested for effects on the ability of TPA or liver tumor promoters to stimulate DNA synthesis by direct action on cultured hepatocytes. In all cases, lack of selective inhibition was observed. Taken together, the results show that while prostaglandins may directly stimulate DNA synthesis in hepatocytes, they are unlikely to mediate the direct growth-stimulatory actions of liver tumor promoters.

Comparison of the effect of fish oil and corn oil on chemical-induced hepatic enzyme-altered foci in rats

The effects of fish oil and corn oil diets on diethylnitrosamine initiation/phenobarbital promotion of hepatic enzyme-altered foci in female Sprague-Dawley rats were investigated. Groups of 12 rats were initiated with diethylnitrosamine (15 mg/kg) at 24 h of age. After weaning, they received diets containing either 13.5% fish oil plus 1. 5% corn oil or 15% corn oil for 24 weeks. Rats fed fish oil had significantly greater liver weight, relative liver weight, spleen weight, and relative spleen weight than rats fed corn oil (p < 0.05). Hepatic phospholipid fatty-acid profile was significantly affected by the type of dietary lipid. The rats fed fish oil had significantly greater hepatic phospholipid 20:5 and 22:6 than rats fed corn oil; in contrast, the rats fed corn oil had significantly greater hepatic phospholipid 18:2 and 20:4 than rats fed fish oil (p < 0.05). Rats fed fish oil had significantly lower hepatic vitamin E and PGE(2) content but significantly greater hepatic lipid peroxidation than rats fed corn oil (p < 0.05). The hepatic levels of antioxidant enzymes (GSH reductase and GST) were significantly greater in rats fed fish oil than in rats fed corn oil (p < 0.05). Except for PGST-positive foci (foci area/tissue area), all the other foci parameters (GGT-positive foci area/tissue area, GGT-positive foci no./cm(2), GGT-positive foci no./cm(3), PGST-positive foci no. /cm(2), and PGST-positive foci no./cm(3)) measured in the fish oil group were 10-30% of those in the corn oil group (p < 0.05). Analyses of Pearson correlation coefficient revealed a positive correlation between hepatic GGT- or PGST-positive foci number (no. /cm(2)) and PGE(2) content (r = 0.66, P = 0.01; r = 0.56, P = 0.02, respectively) but a negative correlation between GGT- and PGST-positive foci (no./cm(2)) and lipid peroxidation (r = -0.8, P = 0.0006; r = -0.58, P = 0.01, respectively), GSH/(GSH + GSSG) ratio (r = -0.61, P = 0.05; r = -0.4, P = 0.14, respectively), GSH reductase (r = -0.75, P = 0.002; r = -0.53, P = 0.02, respectively), and GST activities (r = -0.65, P = 0.01; r = -0.44, P = 0.07, respectively). Similar correlation between foci number (no./cm(3)) and PGE(2), lipid peroxidation, GSH/(GSH + GSSG) ratio, GSH reductase, and GST activities were obtained. The results of this study show that dietary fish oil significantly inhibited hepatic enzyme-altered foci formation compared with corn oil in rats. These results suggest that the possible mechanisms involved in this process are the stimulation of hepatic detoxification system, changes in membrane composition, inhibition of PGE(2) synthesis, the enhancement of GSH-related antioxidant capacity, and the enhancement of lipid peroxidation by fish oil.

Non-steroidal anti-inflammatory drugs and bladder cancer prevention

Inclusion of phenacetin among 'proven' human carcinogens by the IARC in 1987, raised concerns about the carcinogenic potential of acetaminophen, its major metabolite. Acetaminophen has been implicated as a possible causal agent in the development of cancer of the renal pelvis. The bladder and renal pelvis, which derive from the same embryological structure, share the same transitional type of epithelium. Past studies have been inconclusive on the possible relationship among these analgesics and bladder cancer but no large, highly detailed study of this association has been conducted. A population-based case-control study conducted in Los Angeles, California, involved 1514 incident bladder cancer cases and an equal number of controls who were matched to the index cases by sex, date of birth (within 5 years) and race. Detailed information on medication use and prior medical conditions was collected through in-person interviews. Regular use of analgesics was not associated with an increased risk of bladder cancer in either men or women. In fact, compared with non- or irregular users, regular analgesic users were at a decreased risk of bladder cancer overall (odds ratio (OR) = 0.81, 95% confidence interval (CI) = 0.68-0.96). However, there were clear differences in both the direction and strength of the associations between the different formulation classes of analgesics and bladder cancer risk. Intake of phenacetin was positively related to bladder cancer risk in a dose-dependent manner while intake of its major metabolite in humans, acetaminophen, was unrelated to risk. Intake of all classes of NSAIDs, except pyrazolon derivatives, were negatively associated with bladder cancer risk, with suggestive evidence that the protective effect varies in strength by subcategories of formulation. Acetic acids seemed to exhibit the strongest protective effect, whereas aspirin/other salicylic acids and oxicam showed the weakest protection.

Role of prostaglandins in the urinary bladder: an update

Our knowledge of prostanoids is rapidly increasing. In this review we survey the factors governing the synthesis of prostanoids by the urinary bladder, their role in the maintenance of normal bladder function, the pattern of their secretion in bladder disease and the possible use of prostanoids in the treatment of bladder pathology.

Modulation of prostaglandin H synthase-2 mRNA expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice

Prostaglandin endoperoxide H synthases (PGHS-1 and PGHS-2) catalyze an intermediate step in the biosynthesis of prostaglandins and thromboxanes. Recently, it was observed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) modulates the expression of PGHS-2 mRNA in different cell lines. The main aim of this study was to examine whether PGHS-2 mRNA expression can be changed by acute TCDD in vivo and, second, we were also interested in whether modulation of PGHS-2 is mediated by the aryl hydrocarbon receptor (AhR) which is known to be involved in the transcriptional control of TCDD-induced phase 1 and phase 2 enzymes. Initially C57BL/6J mice were treated with a single dose of 10,000 ng TCDD/kg and the PGHS-1 and PGHS-2 mRNAs were analyzed in liver, lung, thymus, kidney, and spleen. In all tissues examined the expression of PGHS-1 mRNA was not affected by TCDD. However, TCDD treatment enhanced the PGHS-2 mRNA levels in lung and spleen. No effect of TCDD on PGHS-2 expression was found in liver and kidney. For dose-response studies C57BL/6J and DBA/2J mice were treated for 24 h with various doses of TCDD (1-50,000 ng/kg) and the PGHS-2 mRNA increases were analyzed in lungs and spleens. A significant increase of PGHS-2 mRNA in lungs of C57BL/6J mice was found at a dose of 100 ng TCDD/kg, whereas a nearly 100-fold higher TCDD dose was needed to increase PGHS-2 in DBA/2J mice. A similar dose-dependent induction of PGHS-2 was found in spleens of C57BL/6J mice; however, no significant increase of PGHS-2 was found in spleens of DBA/2 mice. These results indicate an involvement of AhR in TCDD-mediated changes of PGHS-2 expression. This suggestion is supported by studies in AhR-deficient animals which showed that TCDD had no effect on PGHS-2 mRNA. When changes of PGHS-2 mRNA expression are compared with those of CYP1A1 between 4 and 72 h after TCDD, it is noteworthy that TCDD led to a delayed and more transient increase of PGHS-2. These data suggest that the mechanism of modulation of both genes by TCDD may be different.

Growth regulation of primary human keratinocytes by prostaglandin E receptor EP2 and EP3 subtypes

We examined the contribution of specific EP receptors in regulating cell growth. By RT-PCR and northern hybridization, adult human keratinocytes express mRNA for three PGE2 receptor subtypes associated with cAMP signaling (EP2, EP3, and small amounts of EP4). In actively growing, non-confluent primary keratinocyte cultures, the EP2 and EP4 selective agonists, 11-deoxy PGE1 and 1-OH PGE1, caused complete reversal of indomethacin-induced growth inhibition. The EP3/EP2 agonist (misoprostol), and the EP1/EP2 agonist (17-phenyl trinor PGE2), showed less activity. Similar results were obtained with agonist-induced cAMP formation. The ability of exogenous dibutyryl cAMP to completely reverse indomethacin-induced growth inhibition support the conclusion that growth stimulation occurs via an EP2 and/or EP4 receptor-adenylyl cyclase coupled response. In contrast, activation of EP3 receptors by sulprostone, which is virtually devoid of agonist activity at EP2 or EP4 receptors, inhibited bromodeoxyuridine uptake in indomethacin-treated cells up to 30%. Although human EP3 receptor variants have been shown in other cell types to markedly inhibit cAMP formation via a pertussis toxin sensitive mechanisms, EP3 receptor activation and presumably growth inhibition was independent of adenylyl cyclase, suggesting activation of other signaling pathways.

Chemopreventive efficacy of piroxicam administered alone or in combination with lycopene and beta-carotene on the development of rat urinary bladder carcinoma after N-butyl-N-(4-hydroxybutyl)nitrosamine treatment

The effects of the non-steroidal anti-inflammatory drug (NSAID) piroxicam and the carotenoids lycopene and beta-carotene, alone or in combination, on the development of rat superficial urinary bladder carcinomas induced by N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) were studied. Male Fischer 344 rats, 6 weeks old, were given 0.05% BBN in the drinking water for 8 weeks followed by administration of piroxicam (0.0075% in the diet), lycopene (0.0025% in the drinking water) and/or beta-carotene (0.0025% in the drinking water) for 12 weeks, then killed for histological analysis of urinary bladder lesions. Cell proliferation potential was analyzed by immunohistochemical staining of the proliferative cell nuclear antigen (PCNA). Piroxicam alone, piroxicam+lycopene, and piroxicam +lycopene+ beta-carotene all significantly decreased the incidences and numbers of transitional cell carcinomas (TCCs), but the combination of piroxicam with carotenoids did not result in a clear improvement in the preventive potential of piroxicam. Piroxicam+ beta-carotene also caused a significant reduction and lycopene alone a slight but not significant reduction in the number of TCCs. In contrast, beta-carotene alone and lycopene+ beta-carotene were without inhibitory influence on any of the lesion categories examined, and the latter significantly increased the proportion of high-grade TCCs. Nevertheless, all of the chemopreventive agents, either alone or in combination, significantly decreased the TCC PCNA index, the effect extending to the surrounding epithelium in the piroxicam+lycopene and piroxicam+lycopene+beta-carotene groups. These results indicate that the NSAID piroxicam may be a more effective chemopreventive agent than lycopene and beta-carotene for superficial urinary bladder carcinogenesis.

Decrease of prostaglandin E2 and 5-bromo-2'-deoxyuridine labeling but not prostate tumor development by indomethacin treatment of rats given 3,2'-dimethyl-4-aminobiphenyl and testosterone propionate

The modifying effects of indomethacin (IM) on rat prostate carcinogenesis induced by 3,2'-dimethyl-4-aminobiphenyl (DMAB) were investigated. F344 rats were given 50 mg/kg body weight of DMAB at 2-week intervals for 20 weeks and then received IM at a dose of 20 ppm in the drinking water for 37 weeks. Separate groups additionally received testosterone propionate (TP) in Silastic tubes throughout the experiment. DMAB alone induced carcinomas in situ in the ventral lobe and in combination with TP caused invasive carcinomas of the dorso-lateral and anterior lobes and seminal vesicles. No clear suppression by IM of development of in situ carcinomas or invasive carcinomas was observed. In a short-term satellite experiment, it was revealed that prostaglandin E2 (PGE2) levels in the dorso-lateral prostate and seminal vesicles, but not the ventral prostate, were significantly reduced by IM and that TP itself also suppressed PGE2 levels. The 5-bromo-2'-deoxyuridine labeling index in the ventral prostate was significantly decreased by IM administration. These results indicate that while IM can efficiently suppress tissue PGE2 levels, it does not inhibit tumor development in the prostate or seminal vesicles of rats in the present model.

Progressive growth of rat bladder carcinomas after exposure to prolonged uracil-induced urolithiasis

Dietary uracil at the 3% level induces urinary bladder tumors in rats through urolithiasis-dependent mechanical irritation. In the present study, comparison of lesions induced by uracil administration over the different periods of 36 weeks (middle-term) and up to 103 weeks (long-term) revealed significant elevation of both incidences and multiplicity of transitional cell carcinomas (TCCs) in the long-term group. Histopathological assessment in terms of tumor biology further demonstrated significantly higher grading on the basis of the degree of cellular and structural atypia, and greater depth of invasion in the long-term group. Application of markers for cell proliferation activities including proliferating cell nuclear antigen (PCNA) and silver-binding nucleolar organizer regions (AgNORs) also revealed significantly elevated AgNOR counts in the long-term group TCC. AgNOR counts and PCNA rates in TCCs showed relation to the histological grades. Thus the present study demonstrated that prolonged uracil-induced urolithiasis causes more biologically aggressive bladder carcinomas with invasive potential. Continuous stimulation of cell proliferation presumably has the potential to facilitate multiple genetic alterations leading to development of more malignant carcinomas. However, it should be borne in mind that the difference in bladder cancer development might also be related to the fact that the animals survived longer and that the early lesions therefore had more time to progress to more advanced stages.