[CANCER RESEARCH 29, 2219-2228, December 1969]

Pathogenesis, Histology, and Transplantability of Urinary BladderCarcinomas Induced in Albino Rats by Oral Administration ofN-[4-(5-Nitro-2-furyl)-2-thiazolyl] formamide1

E. Ertürk,S. M. Cohen 2, J. M. Price, and George T. Bryan3

The Division of Clinical Oncology, University of Wisconsin Medical School, Madison, Wisconsin 53706 [E. E., S. M. C., G. T. B.J and ScientificDivisions, Abbott Laboratories, North Chicago, Illinois 60064 [J. M. P.]

SUMMARY

Thirty-five male Sprague-Dawley rats were fed 0.188% ofN- [4-(5-nitro-2-furyl)-2-thiazolyl] formamide for 26 or 46

weeks. All of the rats survived 24 weeks or more anddeveloped gross bladder carcinomas. Severe hyperplasia of therenal pelvis was observed in 19 rats, and carcinomas of therenal pelvis which invaded the kidney developed in 4 rats.

The pathogenesis of these bladder carcinomas was studied in70 female Sprague-Dawley rats fed 0.188% of 7V-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide for 26 or 46 weeks. At frequentintervals, one rat from each group was sacrificed, andhistologie comparisons of the bladder mucosa were made withbladders of rats fed the control diet. Hyperplasia of thetransitional epithelium of the urinary bladder, developing inseveral areas of the mucosa, was observed 3 weeks afterinitiation of feeding the test compound. Squamous metaplasiaand increased mucosal mitotic activity was seen after 8 weeks.Microscopic papillary or sessile transitional cell carcinomaswere detected within 9 weeks, and small tumors localized allover the bladder mucosa were detectable grossly after 12weeks. After 25 weeks the gross bladder tumors were 2 cm indiameter, and after 45 weeks they were 3—7cm in diameter.One rat developed a metastatic pulmonary transitional cellcarcinoma.

Urinary bladder carcinomas which developed in male ratswere transplanted s.c. into weanling female Sprague-Dawleyrats. Grossly palpable tumors were present 3 weeks aftertransplantation, and the presence of squamous metaplasiaincreased the degree of transplantability. One recipient ratdeveloped a metastatic pulmonary transitional cell carcinoma.jV-[4-(5-Nitro-2-furyl>2-thiazolyl] formamide appears to be

'Supported in part by Grant No. CA-10017 and Contract No. PH

43-66-888 from the National Cancer Institute and by a grant from theWisconsin Division of the American Cancer Society.

2Medical Scientist Trainee of the National Institute of GeneralMedical Sciences (GM-01932).

3Career Development Awardee of the National Cancer Institute

(CA-8245-01A1).

Received March 6,1969; accepted April 24, 1969.

one of the most effective urinary bladder carcinogens for bothmale and female Sprague-Dawley rats, providing carcinomasexhibiting all criteria of malignancy.

INTRODUCTION

N- [4-(5-Nitro-2-furyl)-2-thiazolyl] formamide was reportedpreviously (8) to be carcinogenic for the urinary bladder offemale Sprague-Dawley rats. Additional studies have beenconducted to investigate the bladder carcinogenicity of thischemical in male rats, to ascertain the pathogenesis of bladdertumors in female rats, and to determine the transplantabilityof chemically induced bladder carcinomas. These observationsconstitute the basis of this report.

MATERIALS AND METHODS

To investigate the bladder carcinogenicity of N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide in male rats, 65 Sprague-Dawley rats weighing from 71 to 96 gm were fed powderedWayne Lab-Blox (Allied Mills, Inc., Chicago, Illinois). Fifteenrats received 0.188% of JV-[4-(5-nitro-2-furyl>2-thiazolyl]-formamide mixed with the diet for 26 weeks (Group A), and20 rats were fed the test compound for 46 weeks (Group B)(Chart 1), while 30 rats served as untreated controls. After 26or 46 weeks of receiving the diet containing the testcompound, all surviving animals were fed the control diet untilthe termination of the experiment at 52 weeks. The rats wereweighed frequently, and food consumption was determinedbiweekly for the first few months and then at monthlyintervals.

To study the pathogenesis of bladder tumors in female rats,110 Sprague-Dawley rats weighing from 54 to 72 gm were fedpowdered Wayne Lab-Blox. Thirty-four rats (Group A) received 0.188% of JV-[4-(5-nitro-2-furyl>2-thiazolyl] formamidemixed with the diet for 26 weeks, and 36 rats (Group B) werefed the test compound for 46 weeks (Chart 2), while 40 ratsserved as untreated controls. After 26 or 46 weeks of receivingthe diet containing the test compound, all surviving rats werefed the control diet until the termination of the experiment.Rats fed the test compound or the control diet were sacrificedat the time periods indicated in Chart 2, and histologie

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E. Ertùrk, S. M. Cohen, J. M. Price, and G. T. Bryan

MALE SPRAGUE-DAWLEY RATS

GROUPSABCONTROLTIME

(WEEKS) AFTER FEEDINGSTARTED24•

•26•27•O30•3133•(38>39•O4l43•O45•4648O49O50•

•51••O52•i«23OTOTAL

RATS152030

A:26 WEEKS FEEDING

B' 46 WEEKS FEEDING

O NORMAL URINARY BLADDER

•TRANSITIONAL CELL CARCINOMA

Chart 1. Temporal distribution of the occurrence of urinary bladdercarcinomas in male Sprague-Dawley rats fed 7v"-[4-(5-nitro-2-

furyl)-2-thiazolyl] formamide for 26 weeks (Group A) or 46 weeks(Group B). Urinary bladders of control rats sacrificed or dying with nohyperplasia, metaplasia, or bladder carcinomas are représentaby (O);urinary bladders of rats fed carcinogen sacrificed or dying with bladdercarcinomas are represented by (•).Twenty-three control rats weresacrificed at the end of the 52nd week. Each symbol represents one rat.

FEMALE SPRAGUE-DAWLEY RATS

GROUPSABCONTROLTIME

(WEEKS) AFTER FEEDINGSTARTED2OOO3•O5•®«O79®«O

O8®•O9OOoIO«9o129«014Oo990o01799O20•

••

••Oo26•

••

••0o

o30•

••

•O035•

••040••O46••

•O

OSO••

•o

o70»13•«9•iMOTOTAL

RATS343640

A'26 WEEKS FEEDING

B:46 WEEKS FEEDING

O:NORMAL URINARY BLADDER

®: EPITHELIAL HYPERPLASIA

(J: PAPILLARY CARCINOMA^•TRANSITIONAL CELL CARCINOMA

Chart 2. Temporal development and progression of urinary bladderhistologie changes induced by feeding jV-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide to female Sprague-Dawley rats for 26 weeks(Group A) or 46 weeks (Group B). The bladder histology observed isdesignated as follows: O, no histologie alterations from normal; 8 mildto severe epithelial hyperplasia; 3 papillary carcinoma; •, largecarcinoma nearly occluding bladder lumen. Each symbol represents onerat

comparisons of the bladders of rats fed the test compoundwere made with those of control rats. The rats were weighedfrequently, and food consumption was determined biweeklyfor the first few months and then at monthly intervals.

Bladder carcinomas induced in male Sprague-Dawley ratswere excised from the primary hosts under sterile conditionsand transplanted s.c. into the lateral chest wall of weanlingfemale Sprague-Dawley rats (Table 1). The donor rats wereanesthetized with ether and the tumors were removed,transferred to a dish containing sterile physiologic saline

solution, and cut into very small pieces to obtain a turbulentcellular suspension. Inoculations of 0.5 ml of the suspensionbilaterally into each rat were made with a 16-gauge needleattached to a 10-ml syringe. Twenty-six rats received inoculaprepared from the bladder of a donor that had a transitionalcell carcinoma (Group 1), and 12 rats received inoculaprepared from the bladder of a donor that had a squamous cellcarcinoma (Group 2). Eight control rats received 0.5 ml ofsterile saline s.c. (Group 3). The sites of inoculation wereobserved at weekly intervals for the presence of tumorformation. As palpable nodules were found, these weremeasured at weekly intervals. Ten weeks after inoculation, therats with tumors in Group 2 were sacrificed. Those rats inGroup 1 which developed tumors were sacrificed between the10th and 30th weeks. The control rats (Group 3) and all ratswithout palpable tumors in Groups 1 and 2 were sacrificed 56weeks after inoculation. All tumor nodules were prepared forhistologie examination.

A^-[4-(5-Nitro-2-furyl)-2-thiazolyl] formamide was obtainedas a gift from Abbott Laboratories, North Chicago, Illinois (8).Respiratory infections in the rat colony were controlled by theadministration of Bicillin Long-Acting (Wyeth Laboratories,Inc., Phila., Pa.) (8). The autopsy procedures and histologiepreparation were described (8).

RESULTS

Bladder carcinomas were observed in all male rats thatingested N- [4-(5-nitro-2-furyl)-2-thiazolyl] formamide. Thecarcinogen appeared to be slightly toxic at the level at which itwas fed, as the mean weight of the animals receiving thechemical was nearly 30 gm less than the mean weight of thecontrols after 46 weeks of feeding. The average animalingested 14.5 gm of the chemical in 46 weeks. Macrohematuriaoccurred initially during the 23rd week of feeding and wasintermittent for the duration of the experiment. Occasionallya mass was palpable anterior to the pelvis. The first grossbladder tumor was observed in a rat dying during the 24thweek. The gross and histologie appearances of these bladdercarcinomas were identical to those reported previously (8).

Bladder carcinomas were observed in all female rats thatsurvived for more than 9 weeks following ingestion ofjV-[4-{5-nitro-2-furyl)-2-thiazolyl] formamide (Chart 2). Asrats were sacrificed at frequent intervals during the earlier partof this experiment, the pathogenesis of these bladdercarcinomas could be observed. The normal distended raturinary bladder contains a mucosal epithelium that is 1-3 cellsthick (Fig. 1). After three weeks of feeding the carcinogen, thecell layer of the mucosa demonstrated slight hyperplasia with athickness of 3-5 cells (Fig. 2). This hyperplastic response wasobserved in several areas of the bladder and became very severeafter the 5th week of the experiment. At this same timemarked turbidity of the urine was observed due to exfoliatingmucosal epithelial cells (Fig. 3). At the end of the 7th week offeeding, numerous epithelial mitotic figures were present and

Tereaccompanied by severe epithelial hyperplasia (Figs. 3,4).

At the end of the 8th week, extreme epithelial hyperplasia(Fig. 5) and squamous metaplasia were observed. Thesechanges were followed by the formation of sessile (Figs. 6, 7)

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Table 1

Group123Histology

ofchemically inducedbladdercarcinomaTransitional

cellcarcinomaSquamous

cellcarcinomaNo.

ofrecipients26128No.

ofsurvivors at

4 weeks26128No.

of rats withpalpable4

weeks19010 weeks590

Transplantability into female recipient rats of rat urinary bladder carcinomas induced by7V-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide in male rats.

or papillary (Figs. 8—10) transitional cell carcinomas whichappeared during the 9th week of feeding. These tumors weregrossly detectable as white spots on the bladder mucosa duringthe postmortem examination and became easily detectable bythe end of the 12th week of feeding. By the 14th week, thecarcinomas tended to infiltrate into the subepithelial andmuscular layers of the bladder and markedly projected intothe bladder lumen (Figs. 9-14). After 20 weeks, large tumorswere present in the urinary bladder that were easily detectable.These neoplasms seemed to arise in any location of the bladdermucosa, and each bladder always contained several tumors ofvarious sizes, ranging from 2 mm to 1 cm in diameter. By the30th week of the experiment the tumors averaged 2 cm indiameter and by the 45th week of the experiment were 3—7cm in diameter. No bladder parasites were observed in eithermale or female rats.

The histologie characteristics of the well-developed urinarybladder carcinomas observed in both male and female ratsvaried. The observed squamous metaplastic response wasfollowed by the development of carcinomas consisting entirelyof squamous cell elements (Fig. 12) or partially squamous(Figs. 10, 11) cell elements that contained other types ofmetaplastic cellular variations such as adenocarcinoma-like,solid cellular (Figs. 10, 15), or pseudostratified carcinomas(Fig. 16). These latter carcinomas consisted of small, roundtransitional cells with frequent mitoses, ranging from 3 to 5mitotic figures per high-power field. In some instancesmesoderma! connective tissue elements participated in theformation of neoplasms which appeared as carcinosarcomas(Fig. 17), with frequent mitotic figures in both the connectivetissue and epithelial elements of these tumors (Fig. 18). In thelatter stages of the development of the carcinomas, the bladderlumen was filled with tumor masses, causing chronic urinaryretention resulting in obstructive uropathy. Urinary bladdercarcinomas were found capable of metastasizing to the lungsfrom the sites of primary origin (Figs. 19, 20), but distantmétastaseswere surprisingly rare considering the extent ofdevelopment of the bladder carcinomas observed.

The renal pelvis of both male and female rats were involvedin a similar manner. The renal pelvic urothelium demonstratedmild to severe hyperplasia in most animals. A transitional cellcarcinoma was found in a male rat which survived more than46 weeks (Figs. 21, 22). All of the kidney tumors were foundin animals surviving the full extent of the experiment. The

tumors seemed to be related to the high degree of partialurinary obstruction.

One huge tumor found in the pelvic cavity of a male rat wasdiagnosed as a bladder carcinoma which invaded the prostate.However, the prostate gland itself gave rise to a carcinomaarising from both glandular and ductal epithelial elements(Figs. 23, 24).

Bladder carcinomas originating in male rats were trans-plantable. Three weeks after transplantation some palpablenodules were present (Table 1). These lesions grew rapidly andat the end of 4 weeks were 1 cm in diameter. At 10 weeksthey had reached a diameter of 5 cm. At autopsy these s.c.masses occasionally contained a yellowish-green nonpurulentliquid in various quantities-. These lesions appeared grossly as

medullary tumors. Transitional cell carcinomas (Fig. 12) weredetected in 5 rats after 10 weeks of observation. Thesetransplanted tumors developed a partly squamous cell appearance (Fig. 25) at the injection sites. The tumor, whichoriginally contained significant degrees of squamous cellcarcinoma (Figs. 11, 12), grew well in 9 rats, and thetransplanted tumors were almost pure squamous cell carcinomas (Fig. 26) (Table 1). Many mitotic figures were seen inthese transplanted carcinomas. Tumor tissues that originallycontained significant amounts of connective tissue (Figs. 17,18) retained their cellular characteristics in recipient animals(Fig. 27). One recipient rat developed a metastatic pulmonarytransitional cell carcinoma (Figs. 28, 29). Thus, these urinarybladder carcinomas, though quite variable in histologie appearance, exhibited all criteria of malignancy.

DISCUSSION

Though numerous attempts have been made to induceurinary bladder carcinomas in rats with a variety of chemicalsthat produce bladder carcinomas in man and other species,these effects generally have been disappointing (3,4,7,10,13,14, 20, 22-25, 27, 28). Bladder carcinomas have beenproduced in rats by feeding 2-acetylaminofluorene (7, 10, 23,28), 3,2 -dimethyl-4-aminobiphenyl (25), or 3-methoxy-4-aminobiphenyl (20), but the yield of malignant tumors hasbeen low. The tabulation of observations reported by severalworkers (1, 2,4,7, 10,13, 14, 23,24, 28) reveals that the oraladministration of 2-acetylaminofluorene to 670 male orfemale rats of a variety of strains at dosage levels ranging from

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E. Ertürk,S. M. Cohen, J. M. Price, and G. T. Bryan

0.031% to 0.125%, and with observation periods lasting aslong as 693 days, resulted in the production of 19 benign(2.8%), 22 malignant (3.3%), and 7 histologically undefined(1.0%) bladder lesions. Similarly, the administration of3,2'-dimethyl-4-aminobiphenyl to 84 rats resulted in the

formation of 9 benign (1%) and 5 malignant (0.6%) bladdertumors (27), and the feeding of 2-methoxy-3-aminodibenzofuran to 72 rats resulted in the development of13 transitional cell bladder papillomas (18%) and 11 transitional cell carcinomas (15%) (20). Conversely, the oraladministration of 2-naphthy lamine (4), benzidine (4, 22), or4-aminobiphenyl (25) to rats has failed to elicit a singlebladder tumor.

2-Naphthylamine (6), benzidine (6), and 4-aminobiphenyl(12) have been associated as etiologic in the production ofbladder carcinomas arising in workmen exposed to thesechemicals in an industrial environment. Additionally, thesethree compounds, as well as 2-acetylaminofluorene, haveproduced bladder carcinomas when fed to dogs (9,11, 22, 26).The paucity of bladder carcinomas produced in rats, contrasted with other species, has suggested that: (a) a differencein the metabolism between the rat and other species exists, (ft)the rat bladder may have a low level of susceptibility tocarcinogens, or (c) the rat may possess too brief a life-span todevelop chemically induced bladder carcinomas (20). Theobserved bladder carcinogenicity in male and female Sprague-Dawley rats after feeding N-[4-(5-nitro-2-furyl)-2-thiazolyl] -formamide with a latent period of only 9 weeks and anincidence of 100% would not support the latter 2 possibilities.These data would seem to strengthen the alternative suggestionthat differences in species metabolism is related to differencesin bladder carcinogenic response.

Several of these results are worthy of comment. Within 3weeks after initiation of feeding of A^-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide, early mucosal hyperplasia was seen.This response progressed to severe hyperplasia, and after 9weeks sessile or papillary carcinomas were observed. Theselesions were progressive in both female and male rats, for noevidence of regression of the bladder carcinomas was detectedwhen TV-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide was removed from their diet. The urothelial response was notrestricted to the bladder since late in the experiment severehyperplasia accompanied by a low incidence of carcinomasarising in the renal pelvis was detected. Métastasesfrom theprimary bladder lesions occurred late and in very lowincidence. This sequence of events mirrors the clinical coursereported for man (15) and cattle (16, 17) with bladdercarcinomas.

The histologie characteristics of the bladder lesions inducedby N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide in rats seemto be identical to those described in humans (15), cattle(16-'18), dogs (9, 11, 22, 26), and mice exposed to bladdercarcinogenic stimuli by the pellet implantation technic (5, 19,21). The bladder epithelial surface of the rat exhibited a widevariety of responses including hyperplasia; squamous, pseu-dostratified, and adenomatous metaplasia; and transitionalcell, squamous cell, mixed, adenocarcinoma, and carcino-sarcoma. Thus, 7V-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide

administration to rats appears to provide an acceptable modelfor investigating the pathogenesis of urinary bladder cancer.

Additional evidence of the malignancy of the bladder lesionswas provided by the demonstration that these carcinomascould be transplanted into rats of the same strain but of theopposite sex. No pretreatment with immunosuppressive agentswas necessary to permit the successful implantation andgrowth of the carcinomas in these rats of heterogenous geneticcomposition. Lesions composed of a predominant squamouscell element appeared to be more amenable to transplantation.This enhanced malignant agressiveness of squamous cellcarcinoma of the bladder has also been observed for patientsharboring this lesion (15). The demonstration of a pulmonarymetastasis in the secondary transplant host unequivocallyestablishes the malignant character of these chemically induced bladder carcinomas.

Preliminary studies suggest that the urinary bladder of otherspecies, in addition to the rat, is susceptible to the carcinogenic activity of TV-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide

E. Ertürk, S. M. Cohen, 0. Yoshida, and G. T. Bryan,unpublished observations). Studies of the metabolism of thischemical are in progress in an attempt to ascertain the basis ofits urothelial carcinogenicity It appears that this compound isone of the most potent rat urinary bladder carcinogens and, assuch, may provide a useful tool for investigators interested inthis subject.

ACKNOWLEDGMENTS

We thank Miss R. S. Leith for providing expert assistance with thefeeding and care of the rats, and Mrs. C. Schlotthauer and Miss S.Wagner for the preparation of the figures and the manuscript.

REFERENCES

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2. Bielschowsky, F. Comparison of the Tumours Produced by2-Acetyl-Amino-Fluorene in Piebald and Wistar Rats. Brit. J. Exptl.Pathol., 27. 135-139,1946

3. Bonser, G. M., Clayson, D. B., lull, J. W., and Pyrah, L. N. TheCarcinogenic Properties of 2-Amino-l-Naphthol Hydrochloride andIts Parent Amine 2-Naphthylamine. Brit. J. Cancer, 6: 412-424,1952.

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7. Dunning, W. F., Curtis, M. R., and Madsen, M. E. The Induction ofNeoplasms in Five Strains of Rats with Acetylaminofluorene.Cancer Res., 7: 134-140, 1947.

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8. Erturk, E., Price, J. M. Morris, J. E., Cohen S., Leith, R. S., VonEsch, A. M., and dovetti, A. J. The Production of Carcinoma ofthe Urinary Bladder in Rats by Feeding jV-[4-(5-Nitro-2-furyl)-2-thiazolyl] formamide. Cancer Res., 27: 1998-2002,1967.

9. Eyestone, W. H., and Morris, H. P. The Development of BladderTumors in the Dog Following the Ingestion of 2-Acetylamino-fluorene. Proc. 2nd Nati. Cancer Conf., 1: 360, 1952.

10. Harris, P. N. Production of Tumors in Rats by 2-Aminofluoreneand 2-Acetylaminofluorene: Failure of Liver Extract and ofDietary Protein Level to Influence Liver Tumor Production. CancerRes., 7: 88-94. 1947.

11. Hueper, W. C, Wiley, F. H., and Wolfe, H. D. ExperimentalProduction of Bladder Tumors in Dogs by Administration ofBeta-Naphthylamine. J. Ind. Hyg. Toxicol., 20: 46-84, 1938.

12. Melick, W. F., Escue, H. M., Naryka, J. J., Mezera, R. A., andWheeler, E. P. The First Reported Cases of Human Bladder Tumorsdue to a New Carcinogen-Xenylamine. J. Urol., 74: 760-766,1955.

13. Morris, H. P., Sidransky, H., and Wagner, B. P. Bladder Tumors inRats Ingesting Diets Low in Vitamin Bg and Containing A^-2-Flu-orenylacetamide. Proc. Am. Assoc. Cancer Res., 3: 136, 1960.

14. Morris, H. P., Wagner, B. P., Ray, F. E., Snell, K. C., and Stewart,H. L. Comparative Study of Cancer and Other Lesions of Rats FedN,N'-2,7-Fluorenylenebisacetamide or N-2-Fluorenylacetamide.Nati. Cancer Inst. Monograph, 5: 1-53, 1961.

15. Mostofi, F. K. Pathology of Cancer of Bladder. Acta UnióIntern.Contra Cancrum, 18: 611-615,1962.

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Neoplasms Induced by Feeding Bracken Fern (Pteris aquilina) toCows. Cancer Res., 27: 917-924,1967.

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20. Radomski, J. L., Brill, E., and Glass, E. M. Induction of BladderTumors and Other Malignancies in Rats with 2-Methoxy-3-Amino-dibenzofuran. J. Nati. Cancer Inst., 39: 1069-1080,1967.

21. Roe, F. J. C. An Illustrated Classification of the Proliferative andNeoplastic Changes in Mouse Bladder Epithelium in Response toProlonged Irritation. Brit. J. Urol., 34: 238-253, 1964.

22. Spitz, S., Maguigan, W. H., and Dobriner, K. The CarcinogenicAction of Benzidine. Cancer, 3: 789-804, 1950.

23. Stasney, J., Paschkis, K. E., Cantarow, A., and Rothenberg, M. S.Neoplasms in Rats with 2-Acetylaminofluorene and Sex Hormones.II. Cancer Res., 7: 356-362. 1947.

24. Strombeck, J. P., and Ekman, B. Effect of 2-Acetylaminofluorene(AAF) in Inducing Tumors of the Bladder. Acta Pathol. Microbiol.Scand., 26: 480-495, 1949.

25. Walpole, A. L., Williams, M. H. C., and Roberts, D. C. TheCarcinogenic Action of 4-Aminodiphenyl and 3:2'-Dimethyl-4-Aminodiphenyl. Brit. J. Ind. Med., 9: 255-263, 1952.

26. Walpole, A. L., Williams, M. H. C., and Roberts, D. C. Tumours ofthe Urinary Bladder in Dogs After Ingestion of 4-Aminodiphenyl.Brit. J. Ind. Med., 11: 105-109, 1954.

27. Walpole, A. L., Williams, M. H. C., and Roberts, D. C. BladderTumours Induced in Rats of Two Strains with 3:2'-Dimethyl-

4-Aminodiphenyl. Brit. J. Cancer, 9: 170-176,1955.28. Wilson, R. H., DeEds, F., and Cox, A. J., Jr. The Toxicity and

Carcinogenic Activity of 2-Acetaminofluorene. Cancer Res., 1:595-608, 1941.

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Fig. 1. Normal features of epithelium of rat urinary bladder. X 50.Fig. 2. Mild hyperplasia of the bladder epithelium 3 weeks after initiation of feeding. X 150.Fig. 3. Hyperplasia with exfoliating cells at the end of the 5th week. X 150.Fig. 4. Severe hyperplasia with mitoses after 7 weeks of feeding. X 200.Fig. 5. Very severe hyperplasia at the end of the 8th week of feeding. X 150.Fig. 6. Squamous metaplasia and mitoses from a sessile carcinoma (Grade 1). X 150.Fig. 7. Sessile carcinoma (Grade 1) at the end of the 9th week. X 75.Fig. 8. Papillary carcinoma with irregular basement membrane and exfoliating cell clumps at the end of the 12th week of feeding. X 150.Fig. 9. Papillary carcinoma at the end of the 20th week. X 60.Fig. 10. Papillary carcinoma showing variations of epithelial cells at the end of the 30th week. X 100.Fig. 11. Advanced urinary bladder carcinoma with infiltration. X 50.Fig. 12. Same carcinoma as in Fig. 11 under higher magnification. X 125.Fig. 13. Carcinoma invading muscular wall of the bladder (Grade 2). X 75.Fig. 14. Grade 3 bladder carcinoma with invasion of the bladder wall through the muscular layers to the serosa. X 50.Fig. 15. Mitotic figures in a carcinoma. X 150.Fig. 16. Pseudostratified metaplastic carcinoma with adenocarcinoma-like formations. X 125.Fig. 17. Carcinosarcoma composed of epithelial and connective tissue elements. X 100.Fig. 18. Carcinosarcoma with mitoses in both epithelial and connective tissue portions of tumor. X 150.Fig. 19. Metastasis of a urinary bladder carcinoma to lung alveoli. X 125.Fig. 20. Metastatic squamous cell carcinoma in the lung of same rat as seen in Fig. 19. X 125.Fig. 21. Early transitional cell carcinoma of renal pelvis. X 110.Fig. 22. Transitional cell carcinoma of renal pelvis. X 110.Fig. 23. Squamous cell carcinoma originating from the glandular area of prostate. X 175.Fig. 24. Same carcinoma as seen in Fig. 23 arising from a duct. X 75.Fig. 25. Mixed squamous and transitional cell carcinoma which developed in s.c. tissue of female Sprague-Dawley rat 3 weeks after

transplantation of a chemically induced urinary bladder transitional cell carcinoma. The tumor cells started to form a partially squamous cellcarcinoma. Note the resemblance of this tumor to that shown in Figs. 10 and 16. X 50.

Fig. 26. Squamous cell carcinoma which developed in the recipient's s.c. tissue 3 weeks after transplantation. The structure of this tumor is

similar to that in Fig. 12, but note the increase in mitotic figures. X 125.Fig. 27. Fibrocarcinoma after transplantation of a tumor sample that contained epithelial and connective tissue elements. Note the similarity to

Fig. 17. X 100.Fig. 28. A metastatic carcinoma to the lung from the injection site of a recipient rat. Note the compression of the surrounding alveoli by the

rapidly growing tumor tissue, the atelectesis, and the disruption of the pulmonary tissues. X 50.Fig. 29. Same metastatic squamous cell carcinoma as in Fig. 28 under higher magnification. X 150.

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1969;29:2219-2228. Cancer Res   E. Ertürk, S. M. Cohen, J. M. Price, et al.  

-[4-(5-Nitro-2-furyl)-2-thiazolyl]formamideNAdministration of Bladder Carcinomas Induced in Albino Rats by Oral Pathogenesis, Histology, and Transplantability of Urinary

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