Mutagenicity of 3,4-diphenyl-5-nitrofuran analogs in Salmonella typhimurium

A new series of chemicals comprising eight different 3,4-diphenyl-substituted furan analogs, namely, methyl-3,4-diphenyl-2-furoate, methyl-3,4-diphenyl-5-nitro-2-furoate, 3,4-diphenyl-5-nitro-2-furoic acid, 3,4-diphenyl-5-nitro-2-acetylfuran, 3,4-diphenyl-5-nitro-2-bromoacetylfuran, 2-amino-4-(3,4-diphenyl-5-nitro-2-furyl)thiazole, 2-acetyl-amino-4-(3,4-diphenyl-5-nitro-2-furyl)thiazole and 2-formyl-amino-4-(3,4-diphenyl-5-nitro-2-furyl)thiazole were synthesized and their mutagenic activities tested in Salmonella typhimurium. The structure--activity relationship studies revealed that for mutagenic activity the nitro group is essential and that the potency of activity is greatly altered by the nature of the substituent at the 2-position of the furan ring. The mutagenic activities of these chemicals were generally much higher in TA100 compared to TA98. The relative order of activities for 2-substituted, 3,4-diphenyl-5-nitrofurans were COOCH3 greater than COCH2BR greater than COCH3 greater than COOH in S. typhimurium TA100. 3,4-Diphenyl-5-nitro-2-bromoacetylfuran was equally active in nitroreductase-proficient (TA98, TA100) and in nitroreductase-deficient (TA98NR, TA100NR) strains. In contrast, the acetyl and carboxymethyl ester analogs were relatively less active in nitroreductase-deficient strains. Mutagenic activities of 3,4-diphenyl-substituted furylthiazoles in comparison with the unsubstituted analogs of N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide, N-[4-(5-nitro-2-furyl)-2-thiazolyl]-acetamide and 2-amino-4-(5-nitro-2-furyl)thiazole revealed that the phenyl groups drastically reduced their mutagenic activities. However, the relative order of activities formylamino greater than or equal to acetylamino greater than amino were the were the same between phenyl-substituted and unsubstituted analogs.

Inhibitory effects of interferon-inducing pyrimidinones on the growth of transplantable mouse bladder tumors

Pyrimidinones are low-molecular-weight compounds which are inducers of interferon in several animal species. They have established antiviral, immunomodulatory, and antitumor effects. Four pyrimidinones as well as another potent interferon inducer, polyriboinosinic-polyribocytidylic acid, and beta-interferon were tested for effects on growth of the transplantable mouse bladder tumor (MBT-2). The pyrimidinones 2-amino-5-bromo-6-phenyl-4(3H)pyrimidinone (ABPP) and 2-amino-5-bromo-6-(3-fluorophenyl)-4(3H)pyrimidinone (ABMFPP) significantly inhibited MBT-2 growth in a dose-dependent manner and with equal potency when injected i.p. every 4 days starting 1 day after tumor cell inoculation. Administration of ABPP p.o. was as effective as i.p. injections. Direct intravesical application of ABPP to transplantable tumors growing in the bladder may be more effective in inhibiting MBT-2 growth than the same dose introduced p.o. Although ABPP (100 mg/kg) has an inhibitory effect comparable to 5000 units of beta-interferon, both pyrimidinones even at 500 mg/kg were less inhibitory of tumor growth than 10 mg of polyriboinosinic-polyribocytidylic acid per kg. The pyrimidinones 2-amino-5-bromo-6-(2,5-difluorophenyl)pyrimidine-4(3H)one (ABDFPP) and 2-amino-5-iodo-6-(2,3-difluorophenyl)pyrimidin-4(3H)one (AIDFPP) were also of comparable potency in inhibiting MBT-2 growth and were more effective on mg/kg basis than both ABPP and ABMFPP. Treatment with ABDFPP or AIDFPP also resulted in long-term cures of up to 40% of mice. In this respect these latter two compounds were superior to treatment with 10 mg of polyriboinosinic-polyribocytidylic acid per kg, a treatment which reduced tumor size but had no effects on tumor incidence. The data suggest that tumors of bladder origin may be particularly sensitive to treatment with pyrimidinones.

Identification of 4-(5-amino-2-furyl)thiazole (AFT) as a reductive metabolite of the carcinogen 4-(5-nitro-2-furyl)thiazole (NFT)

The chemical synthesis of 4-(5-amino-2-furyl)thiazole (AFT) and its formation during the in vitro reductive metabolism of 4-(5-nitro-2-furyl)thiazole (NFT) by rat liver tissues on anaerobic incubation with NADPH were examined. AFT was synthesized by catalytic reduction of NFT with 5% palladium on activated carbon. Purified AFT, a pale yellow powder, melted at 105 degrees C and had an extinction coefficient of 16.3 mM-1 cm-1 at 297 nm in methanol. The proton n.m.r. spectrum, i.r. and mass spectra were consistent with the assigned structure. Analysis of the ethyl acetate extract, following incubation of NFT with rat liver tissue preparations, revealed a metabolite whose chromatographic and mass spectral characteristics were the same as those obtained with synthetic AFT, thus establishing the structural identity of the metabolite as AFT. These data show that AFT is formed on reduction and could act as a precursor for the formation of 1-(4-thiazolyl)-3-cyano-1-propanone as postulated earlier.

A protocol for the combined biochemical and serological identification of the Ames mutagen tester strains as Salmonella typhimurium

Previously published reports have noted biochemical reactions atypical of Salmonella among the Ames tester strains of Salmonella typhimurium, and an inability to assign the strains to a specific Salmonella O (heat-stable cell wall) antigen group. We studied the biochemistry and serology of strains TA97, 98, 100, 102, 104, 1535, 1537, and 1538 in an attempt to develop a protocol to correctly speciate the strains. Biochemical reactions of all eight strains using standard media supplemented with histidine and biotin were consistent with those of the genus Salmonella. Strains TA100, 104, and 1535 were assigned to Salmonella O groups using bacteria treated with hot ethanol (White schema). H (flagellar) antigen assignments were performed successfully with seven of the eight strains. Two H antigen assignments required the use of the Craigie tube test for selection of motile revertants. Combining our biochemical and serological results obtained by this protocol, we were able to correctly speciate TA100, 104, and 1535 as Salmonella typhimurium. Our results demonstrate that representatives of the tester strains can be correctly speciated provided that procedures are followed that allow for the unusual nutrient requirements, the deep rough cell wall mutation, and the variably deficient motility of these organisms.

Urine recovery experiments with quercetin and other mutagens using the Ames test

Recovery from urine of the mutagenic activity of 2-anthramine, cyclophosphamide, 7,12-dimethylbenz[a]anthracene, 6-chloro-9-((3-(2-chloroethylamino)-propyl)amino)-2-methoxyacridin e dihydrochloride (ICR-191), mitomycin-C, nitrofurantoin, and quercetin was studied with several of the Ames tester strains using acetone-extracted XAD-2 columns with yields ranging from 27% to 79%. Dose responses of the pure chemicals were also studied, and results showed TA 97 to be far more susceptible to quercetin mutagenesis than TA 1537. Reducing pour plate agar volume enhanced mutagenesis.

The influence of niacin and nicotinamide on in vivo carcinogenesis

Data concerning effects of the essential vitamin niacin and its active form nicotinamide were evaluated. Dietary deficiencies and excesses of these nutrients by themselves do not appear to exert any influence on in vivo carcinogenesis in animals. Varying results were produced when nicotinamide was administered at pharmacologic doses concurrently with or following carcinogen administration to mice or rats. Some investigators found significantly increased tumor formation, whereas others reported a decreased effect or no effect. Epidemiologic studies have not investigated the relationship between niacin deficiency or excess and carcinogenesis in humans.

Serial cultivation of normal rat bladder epithelial cells in vitro

Recent advances in culture techniques for human urothelial cells have led to the development of an improved method for growing primary rat bladder epithelial cells. We report here the conditions developed for large-scale in vitro growth and serial cultivation of normal diploid rat bladder epithelial cells. Primary cultures were initiated by attachment of bladder mucosal explants to type I collagen gels. A rapid outgrowth of epithelial cells from the explants occurred when cultured in a hormone-supplemented medium with epidermal growth factor. These primary outgrowths were passaged by nonenzymatic dispersion with 0.1 per cent ethylenediaminetetracetic acid and replating onto new gels. The capacity for routine serial passaging and maintenance of rat bladder epithelial cells required the presence of epidermal growth factor, a requirement not observed with human urothelial cells. The characteristics of the cultured rat bladder epithelial cells were similar to human urothelial cells in: ultrastructural and phase-contrast morphologic properties, showing junctional complexes, desmosomes, stratification and an apical glycocalyx; the absence of stromal cell contamination; and the ability to be serially passaged. Spontaneous cell-line formation was observed with the rat bladder epithelial cells, but has not been found with the human urothelial cells. With the method that we have developed, the number of rat bladder epithelial cells generated from a single bladder of a 4 to 6 week old rat was increased 100-fold from about 7 X 10(5) cells to 7 X 10(7) viable cells within 3 weeks of culture. The capability of culturing normal, primary rat bladder epithelial cells on this scale has not been reported previously and will facilitate comparative studies of the biological and molecular characteristics of the mammalian urothelium. Furthermore, this culture system will be useful for carcinogenesis studies, including metabolic activation of carcinogens and cellular transformation in vitro.

Chemical induction of ovarian tumors in rats

The production and pathogenesis of ovarian cancer was investigated in noninbred albino weanling female rats by surgical fixation into the left ovaries of sutures chemically impregnated with the chemical carcinogens formic acid 2-[4-(5-nitro-2-furyl)-2-thiazolyl]hydrazide (FNT), a nitrofuran antibiotic; N-methyl-N'-nitrosourea (MNU), a direct-acting alkylating agent; or 7,12-dimethylbenz[a]anthracene (DMBA). Rats living more than 30 days following surgery were subjected to complete necropsy of external, thoracic, and abdominal tissues when they died or were killed at 407 days, the study termination. Mean survival of rats in treated and control groups was comparable. All carcinogen-treated rats exposed to FNT, MNU, or DMBA developed one or more ovarian, uterine, or mammary neoplasms with a total of 31 tumors in 22 rats as compared with no tumors in 5 control rats. All carcinogen-treated rats (22) developed ovarian adenomas (18) or adenocarcinomas (4); 3 developed uterine fibroadenomas (1) or squamous cell carcinomas (2); and 6 developed mammary adenocarcinomas. No neoplasms were present in the right ovaries of carcinogen-treated rats. These data suggest that direct application of carcinogens to ovarian tissue is a satisfactory way to develop ovarian adenoma and adenocarcinoma.

Tumor promoter 12-O-tetradecanoylphorbol-13-acetate receptors in normal human transitional epithelial cells

As a prelude to study the promotion with TPA of in vitro transformation of human urothelial cells (HUC) in culture, we characterized tumor promoter TPA receptors in primary cultures of HUC. [3H]TPA bound specifically to intact living HUC; maximum specific binding was attained in approximately 30 min at 37 degrees C. [3H]TPA bound to HUC in a saturable and competitive manner. Scatchard analysis of specific binding to intact cells displayed a single slope corresponding to an equilibrium dissociation constant (Kd) of 0.56 nM; at saturation TPA-binding capacity was 2.37 pmol/10(6) HUC (1.43 X 10(6) sites per cell). [3H]TPA bound specifically and with high affinity to the particulate fractions of HUC; binding was both saturable and reversible. Saturation of the specific binding of [3H]TPA occurred at approximately 1 nM at 4 degrees C. Scatchard analysis of specific binding to the particulate fraction displayed a single slope corresponding to a Kd of 1.08 nM; at saturation TPA-binding capacity was 2.05 pmol/mg protein (750 000 molecules per HUC). [3H]TPA binding was inhibited by the biologically active phorbol ester, phorbol didecanoate, whereas inactive phorbol did not compete for TPA binding. Binding was not affected by sodium saccharin, epidermal growth factor, retinoic acid or dexamethasone. [3H]TPA bound specifically to the HUC cytosolic fraction but only in the presence of calcium and phosphatidylserine. Calcium-activated and phospholipid-sensitive protein kinase activity was detected in HUC fractions. These results indicate the presence of high-affinity specific receptors for TPA in HUC.

Factors affecting the mutagenic activity of quercetin for Salmonella typhimurium TA98: metal ions, antioxidants and pH

The mutagenic activity of quercetin for Salmonella typhimurium TA98 was inhibited by addition of metal salts. MnCl2 was a potent inhibitor, followed by CuCl2, FeSO4, and FeCl3, the probable mechanism being facilitated catalytic oxidation of quercetin. With quercetin incorporated at a level of 100 nmoles/plate, approximate doses (nmoles/plate) to give 50% inhibition of mutagenic activity were: MnCl2 less than 10 (-S9), 18 (+S9); CuCl2 65 (-S9), greater than 100 (+S9); FeSO4 190 (-S9), greater than 300 (+S9); or FeCl3 275 (-S9), greater than 300 (+S9). Ascorbate, superoxide dismutase, and, to a lesser extent, NADH and NADPH, all enhanced the mutagenic activity of quercetin in the absence of the mammalian-microsome (S9) system, but had no significant effect in the presence of the S9 mix. The maximum enhancement of activity by ascorbate or superoxide dismutase was approximately 87% of the increase achieved by addition of the S9 mix. Tyrosinase (catechol oxidase) substantially reduced the mutagenic activity of quercetin in the absence of the S9 mix. At lower levels of tyrosinase, activity was restored by incorporation of the S9 mix. It is proposed that the S9 mix enhances the mutagenic activity of quercetin by scavenging superoxide radicals, thus inhibiting the autoxidation of quercetin, and possibly by reducing quinone oxidation products of quercetin. The mutagenic activity of quercetin increased substantially when the pH of the media was decreased. This may be due in part to a decrease in ionization of quercetin at lower pH, thereby increasing its absorption by the tester strain, to a decrease in the rate of autoxidation of quercetin at lower pH, or to a combination of these.

Antitumor effects of polyribonucleotides for mouse transitional cell carcinoma enhanced by cyclophosphamide

Mouse bladder tumor (MBT-2), derived from a carcinogen-induced transitional cell carcinoma of the bladder, has proven a useful model for study of pathogenesis and prediction of cytotoxic drug sensitivity of human bladder carcinoma. To define optimal conditions for activity of the potent interferon inducer polyriboinosinic-polyribocytidylic acid [poly(I) X poly(C)] in this model, studies of dose, timing, and combinations with a cytotoxic drug were initiated. Poly(I) X poly(C) inhibited MBT-2 growth when 10(5) or 10(6) tumor cells were implanted. Tumor growth reduction was relatively more pronounced in mice inoculated with higher numbers of MBT-2 cells (10(6] than in mice inoculated with an intermediate dose (10(5] or small dose (10(4]. In mice inoculated with 10(5) MBT-2 tumor cells, poly(I) X poly(C) (2.5 or 10 mg/kg i.p.) on Days 5 to 19 every other day reduced tumor size markedly. It had no effect, however, on tumor incidence or the time of their first detection. Treatment for a shorter period (alternate days from Days 11 to 19) resulted in less inhibition of tumor growth. Once treatment was discontinued, tumors grew progressively. Polyriboadenylic:polyribouridylic acid [poly(A) X poly(U)] (10 mg/kg) which inhibited tumor growth but to a lesser degree than poly(I) X poly(C) induced lower, less sustained levels of serum interferon. Cyclophosphamide, injected i.p. on Day 1, resulted in inhibition of tumor incidence and growth in direct proportion to the dose administered (25 to 200 mg/kg), but it was curative only at greater than or equal to 30% lethal doses. When combined with poly(I) X poly(C) (2.5 or 10 mg/kg), cyclophosphamide (50 mg/kg) had an additive antitumor effect. Optimal inhibition of MBT-2 tumor growth occurred by combining cyclophosphamide (100 mg/kg) with poly(I) X poly(C) (2.5 mg/kg); eight of 14 mice were tumor free on Day 60.

Augmented antiproliferative effects of interferons at elevated temperatures against human bladder carcinoma cell lines

The in vitro antiproliferative effects of interferons (IFN) against the human bladder carcinoma cell lines T24, RT4, HT1197, and 647V were evaluated at temperatures ranging from 37-41 degrees. At 37 degrees, the antiproliferative activities of IFN, either naturally produced or produced by recombinant DNA technology, were different against different cell lines. An increase in temperature markedly enhanced the antimitotic effect of IFN for all cells. For example, T24 cells grown at 37 degrees and treated with 200 units naturally produced IFN-alpha or IFN-beta per ml for 7 days were inhibited 50 to 60%. No change in cell proliferation occurred in untreated T24 cells grown at 39.5 degrees. Treatment with 200 units IFN-alpha or IFN-beta per ml at 39.5 degrees inhibited these cells 80 to 90%. Similar results were obtained with IFN produced by recombinant DNA technology and purified to homogeneity. Colony formation by the RT4 cell line, at 37 degrees, was decreased less than 10% with 200 units IFN-alpha per ml and 63% by 200 units IFN-beta per ml. At 39.5 degrees, colony formation by untreated RT4 cells was inhibited 48%. Treatment with IFN-beta at 39.5 degrees did not result in an enhancement of the antiproliferative effect; however, treatment with IFN-alpha enhanced the inhibition from less than 10% to 98%. These results suggest that a supraadditive relationship exists between antiproliferative effects of IFN and temperature elevation. The differences seen between IFN-alpha and IFN-beta may be due to the different stabilities of these two molecules. In order to probe the mechanism of the enhanced antiproliferative effect, activity of an IFN-induced enzyme, 2'-5'-oligoadenylate synthetase, was measured. IFN-alpha treatment resulted in significantly greater 2'-5'-oligoadenylate synthetase induction at 39.5 degrees than at 37 degrees. Thus, two cellular effects resulting from IFN were augmented by increased temperature.

Bioconversion and macromolecular binding of 2-amino-4-(5-nitro-2-furyl)thiazole by cultured rat urothelial cells

Bioconversion and binding of 2-amino-4-(5-nitro-2-furyl)-thiazole (ANFT) were examined using cultured rat bladder epithelial cells from weanling male F344 rats. Bladder cells were obtained in large quantities from outgrowths of dissected explants which were grown on collagen gels. Metabolic potential of rat urothelial cells to activate ANFT was evaluated by incubating primary culture cells with [2-14C]ANFT for 48 hr. Metabolites were subsequently analyzed by chromatographic and spectroscopic methods. Thin-layer chromatography of the ethyl acetate:diethyl ether (1:1, v/v) extract of the culture medium revealed two regions of radioactivity with Rf values of 0.12 and 0.60, the former corresponding to ANFT and the latter to one of its metabolites. High-pressure liquid chromatography of the solvent extract revealed two major peaks, with retention times of about 4 and 9 min, corresponding with the metabolite and ANFT, respectively. Low-resolution mass spectrum of the isolated metabolite showed a molecular ion at m/e 181. The metabolite was identified as 1-[4-(2-aminothiazolyl)]-3-cyano-1-propanone based on its chromatographic and spectral characteristics in comparison with the synthetic compound. About 24% of the recovered radioactivity from the culture medium was extractable into the organic phase, a majority of which was identified as 1-[4-(2-aminothiazolyl)]-3-cyano-1-propanone. Analysis of binding to proteins and nucleic acids prepared following exposure of [2-14C]ANFT revealed a 15- and 9-fold greater amount of binding, respectively, in cultures incubated with bladder cells than their corresponding heat-inactivated controls. Furthermore, homogenates of cultured bladder cells reduced ANFT on anaerobic incubation with reduced nicotinamide adenine dinucleotide phosphate to generate 1-[4-(2-aminothiazolyl)]-3-cyano-1-propanone. On reduction of [2-14C]ANFT with rat bladder or liver homogenates, about 23 and 11%, respectively, of the initial amounts of radioactivity were bound to the trichloracetic acid-insoluble fraction. These data demonstrate that rat bladder cells possess the metabolic capability to reduce ANFT and to generate reactive intermediate(s) that bind to cellular macromolecules.

Antiproliferative activities of interferons against human bladder carcinoma cell lines in vitro

The antiproliferative effect of interferons against 5 human bladder carcinoma cell lines, RT112, T24, RT4, 647V and HT1197, was determined in vitro. Each of these human bladder carcinoma cell lines except 647V was sensitive to human interferons in liquid media. The antiproliferative effect of interferons was observed only upon continuous exposure, not after 1 hour. Partially purified, naturally produced interferon beta was more inhibitory of cell growth than naturally produced interferon alpha. Interferon alpha 54, 76, 61, 6L and 1 purified to homogeneity were as effective as naturally produced, partially pure interferon alpha. Although interferon beta, produced by recombinant DNA technology and purified to homogeneity, was not equivalent in effectiveness to naturally produced interferon beta, its antiproliferative activity was greater than interferon alpha 54 for 3 of 4 cell lines tested. Antimitotic effects may underlie, at least in part, the potential therapeutic activity of interferons for bladder carcinoma.

Biotransformation of the bladder carcinogen N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide in mice

The biotransformation of N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT), a potent urinary bladder carcinogen, was studied in mice. About 82% of radioactivity was excreted as 14CO2 within 36 hr after intragastric administration of N-[4-(5-nitro-2-furyl)-2-thiazolyl]-[14C]formamide, suggesting its deformylation to 2-amino-4-(5-nitro-2-furyl)thiazole ( ANFT ). The latter was formed in vitro as a product following incubation of FANFT with mouse liver homogenates. Chromatographic analysis of mouse urine obtained 24 hr after the i.p. administration of N-[4-(5-nitro-2-furyl)-[2-14C]thiazolyl]formamide revealed excretion of ANFT and unmetabolized FANFT, suggesting the prevalence of the deformylation reaction in vivo. In addition, at least two more metabolites were present in urine. One of these metabolites exhibited chromatographic properties similar to those exhibited by a compound derived from the in vitro nitroreduction of ANFT . This metabolite was isolated from urine of FANFT-fed animals and from in vitro enzymatic reduction of ANFT with mouse liver homogenates. The isolated products had chromatographic and spectral properties and a mass spectral fragmentation pattern similar to that of a compound obtained by catalytic reduction of ANFT with palladium and activated carbon. Spectroscopic analyses established the structural identity of the chemical reduction product as 1-[4-(2-aminothiazolyl)]-3-cyano-1-propanone ( ATCP ). Since the chromatographic properties of the enzymatically derived product and the urinary metabolite were identical to those of a compound obtained by chemical reduction, they must be structurally the same and thus correspond to ATCP . About 5% of the urinary metabolites of FANFT is ATCP , and thus ATCP is quantitatively a minor excretory product. ATCP was far less active than was ANFT of FANFT in the Ames mutagenicity assay with Salmonella typhimurium TA.

Tumor production in germ-free rats fed 5-nitrofurans

Weanling female germ-free Sprague-Dawley rats were divided into 3 groups: the control group rats were fed an autoclaved 5010C diet for 2 years; the nitrofurantoin (NF) group rats were fed this diet supplemented with 0.188% NF for 2 years; and the N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide (FANFT) group rats were fed this diet supplemented with 0.188% FANFT for 20 weeks followed by 20 additional weeks of the control diet. The FANFT-group rats were killed following the early appearance of bladder tumors. Six of 11 control rats had tumors: 2 with mammary fibroadenomas, 1 with adrenal adenoma, 1 with leukemic spleen, and 2 with mesenchymal sarcoma of the colon. Ten of 12 NF-group rats had tumors: 9 with mammary fibroadenomas, 1 with adrenal adenoma, and 1 each with leukemic spleen and cervical squamous cell carcinoma. Eight of 12 FANFT-group rats had tumors: 7 with bladder and 1 with renal pelvis transitional cell carcinoma. The incidences of mammary fibroadenoma in the NF group and of lower urinary tract tumors in the FANFT group were significantly greater (P less than 0.01) than those of these tumors in the control group.

Stimulation of ornithine decarboxylase activity and DNA synthesis by phorbol esters or bile acids in rat colon

The changes of colonic epithelial ornithine decarboxylase (ODC) activity and DNA synthesis following intrarectal administration of a tumor-promoting agent, 12-O-tetradecanoylphorbol-13-acetate (TPA), or various bile acids to male noninbred rats were studied. A single instillation of TPA, at a dose as low as 16 nmol, led to a significant (about 10-fold) increase in colonic ODC activity. Peak ODC activity was observed at 4 hr, and the enzyme activity returned to the control level about 24 hr after intrarectal TPA. This pattern was almost the same as that observed after sodium deoxycholate treatment. TPA showed more potent induction of ODC activity than deoxycholate, although the maximal induction was greater in the case of deoxycholate treatment. Both TPA and deoxycholate stimulated DNA synthesis at 2 days after intrarectal instillation, after an initial depression at 4-12 hr. A structure-activity study of 26 bile acids revealed that 5 beta-cholanoic acid with alpha-hydroxy groups in two of the 3 alpha, 7 alpha, 12 alpha positions and 5 beta-cholanoic acid with a 3 alpha-hydroxy group induced colonic ODC activity significantly, while the 3 alpha, 6 alpha-dihydroxy acid did not. Replacement of hydroxy groups by keto groups or a change from alpha to beta configuration decreased the ODC-inducing activities. Tri-substituted 5 beta-cholanoic acid derivatives, whether hydroxy or keto, did not stimulate ODC. These data indicate that a specific bile acid structure with a definite spatial relationship of the hydroxy groups is required for induction of colonic ODC activity.

Specific binding, stimulation of rodent urinary bladder epithelial ornithine decarboxylase, and induction of transitional cell hyperplasia by the skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate

The effects of intraurethral or i.p. administration of a mouse skin tumor promoter phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), on rodent urinary bladder transitional epithelium were studied. TPA, when instilled into the urinary bladder of inbred rats (female Fischer, F344) or mice (C3H, ICR, C57BL X DBA/2 F1) at a dose as low as 0.16 nmol, led to a significant (about 10-fold) increase in bladder ornithine decarboxylase (EC 4.1.1.17) (ODC) activity. Peak ODC activity was observed at about 6 hr, and enzyme activity returned to base levels about 14 hr after intravesical TPA. Administration of TPA i.p. in dimethyl sulfoxide also induced vesical ODC at 4 hr after treatment. The magnitude of vesical ODC induction correlated well with the ability of a series of phorbol esters to promote mouse skin tumor formation (TPA greater than phorbol didecanoate greater than phorbol dibenzoate, and phorbol diacetate or phorbol did not induce bladder ODC activity). Mezerein, a second stage mouse skin tumor promoter, induced urinary bladder ODC as much as TPA did. Increased ODC activity by TPA was the result of an increased amount of ODC protein localized mostly (greater than 60%) in urinary bladder mucosa. Intraurethrally administered TPA induced transitional cell hyperplasia starting at Day 2, and it persisted for about 7 days. The urothelium regained normal histology 13 days after TPA treatment. TPA bound specifically and with high affinity to murine bladder mucosa and muscularis particulate preparations. Scatchard analysis of mucosal binding revealed a Kd of 0.82 nM; at saturation, 2.43 pmol were bound per mg protein. Since TPA binds specifically to urinary bladder epithelium, and the induction of ODC activity is one of the properties of tumor promoters, one may conclude that TPA may promote urinary bladder carcinogenesis. Intravesical saccharin also induced urinary bladder ODC activity, but TPA at equimolar quantity was far more potent than saccharin. Thus TPA, being a structurally well-defined molecule, may be a useful compound to study the phenomenon of the tumor promotion stage in urinary bladder carcinogenesis.

Altered growth patterns in vitro of human papillary transitional carcinoma cells

In vitro growth patterns and morphologic characteristics of five low-grade human papillary transitional cell carcinomas (TCCs) were compared and contrasted with those of normal human urothelial cells in culture. Biopsies of TCC were performed by transurethral resection. Specimens of normal human ureters were obtained surgically. Singly dispersed TCC cells grew in 0.3% agarose semisolid medium with a cloning efficiency ranging from 0.02% to 0.71%. Singly dispersed normal ureteral urothelial cells under the same conditions did not form colonies in 0.3% agarose. Neither singly dispersed TCC nor normal urothelial cells formed colonies when plated on collagen-gel substrates. In primary explant culture, normal human urothelial cells grew rapidly, to form tightly adherent flat sheets of apparently nonmotile cells. Autoradiographic labeling with 3H-thymidine of growing cultures of normal urothelial cells showed cell division primarily in the zones of growth near the explant. Outgrowth of TCC from primary explants was loosely adherent. One TCC explant culture gave rise to a continuous suspension culture. Numerous multilayered cellular formations of fronds, nodules, and "walls" were seen around the periphery of TCC explant colonies. Autoradiography showed that these multilayered areas of TCC growth contained actively dividing cells. The altered ability of papillary TCC to form superficial multilayered formations in vitro distinguishes them from normal human urothelium and reflects the morphologic characteristic of this tumor type in vivo.

Azathioprine induction of lymphomas and squamous cell carcinomas in rats

The carcinogenicity of azathioprine was evaluated in weaning female noninbred Sprague-Dawley rats by feeding it in the diet. Due to toxicity, the dose had to be changed during the course of the experiments and ranged from 0.015 to 0.04% of the diet by weight. In the first experiment, the estimated maximal cumulative consumption of azathioprine was 1.5 g/rat. Of the 14 rats evaluated, six developed thymic lymphomas, and four developed squamous cell carcinomas of the ear duct. When the experiment was repeated with a slightly lower daily consumption but with a cumulative total dose of 2.2 g/rat, there were seven of 19 rats with thymic lymphoma and two rats with ear duct carcinoma. These data support the hypothesis that azathioprine is a carcinogen.

Growth and characterization of normal human urothelium in vitro

A method for initiating rapidly growing cultures of normal human transitional cells from ureter and embryonic bladder specimens has been developed and quantified. A new microdissection technique was used to nonenzymatically separate the urothelium. The use of enriched medium containing 10 micrograms/ml insulin, 5 micrograms/ml transferrin, and 1 microgram/ml hydrocortisone resulted in improved growth. The use of thin collagen gel substrates (0.6 ml/60 mm petri dish) resulted in 97% attachment of explants compared to 77% attachment on plastic. Explants grown on thicker collagen (2 ml/60 mm petri dish) showed, in addition to better attachment, enhanced growth of cells as determined both by measurements of colony size and cell density. Cultures of transitional cells that were initiated using explants could be passed three to five times using 0.1% EDTA for dispersion. Autoradiography of [3H]thymidine-labeled cells showed an initial phase of rapid cell division in primary explant cultures and restimulation of cell division in passaged cultures. Transmission electron microscopy showed that the cells growing out from the explants were continuous with the stratified urothelium maintained in the original explant. Stratification of transitional cells occurred in cultures of both ureter and embryonic bladder cells. Surface cells were joined near their apices by junctional complexes. Desmosomes and Golgi vesicles were present in all cells. Passage in culture did not alter the morphological characteristics of cells.

Pathogenesis of human urinary bladder cancer

The pathogenesis of bladder cancer is being analyzed at several levels of biological organization, i.e., population groups, individual whole animal, tissue, cell, molecule, etc. Each of these levels provides opportunities for mechanistic studies. Yet the integration of these several levels into a cohesive fabric is incomplete. From a clinical point of view, the following seem of importance to human bladder cancer pathogenesis. The initiation, promotion, and progression of bladder cancer involves several factors acting concurrently or sequentially. These factors appear to be naturally occurring or synthetically created chemicals present in the external environment. Human exposures to these agents may begin in utero, and varying, dynamic qualitative and quantitative exposure patterns continue through developmental and adult life. Apparent latent periods of development of clinical bladder cancer may be as short as one, or as long as 50 years or more. Individuals may exhibit differential susceptibility to vesical carcinogens, perhaps through phenotypic differences in quantitative biotransformation routes. Differences in bladder epithelial cell susceptibilities probably also occur, as well as varying local tissue and generalized resistance to neoplasia formation. Older individuals do not appear to be more resistant to bladder carcinogenesis. A number of animal model systems have been developed for the study of the in vivo, cellular, and molecular pathogenesis of bladder cancer. These models replicate many of the known salient features of human bladder cancer. Through use of appropriate whole animal models in conjunction with investigations of human and animal bladder cells and tissues in culture, controlled mechanistic and quantitative studies of bladder cancer pathogenesis should rapidly develop.