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The negative feedback regulation of epidermal growth factor receptor (EGFR) and other tyrosine kinase receptors, including receptor dephosphorylation and endocytosis followed by degradation, is becoming recognized as a major determinant of receptor function. To evaluate the significance of the negative regulation of EGFR during carcinogenesis in vivo, we subjected the mutant mouse line Dsk5, in which the intrinsic activation of the receptor due to a point mutation is normally counterbalanced by increased posttranslational receptor down-regulation, to skin chemical carcinogenesis. Dsk5 mice showed reduced tumor numbers and tumor burden compared with control littermates, and Dsk5-derived tumors showed a reduction in the activation and total levels of EGFR. Furthermore, the transcript levels of several molecules known to act as negative regulators of EGFR were significantly increased in Dsk5-derived tumors. Another intriguing observation was the appearance of tumors with sebaceous differentiation in the ears of Dsk5 mice after chemical carcinogenesis. Further studies are necessary to reveal whether these tumors represent a cell type-specific evasion from EGFR negative feedback machinery. In conclusion, this study reveals that several negative feedback regulators contribute to suppression of the intrinsic activation of mutant EGFR during skin carcinogenesis, stressing the potential exploitation of negative regulators as either therapeutic targets or diagnostic tools in cancer and other diseases., (Copyright © 2012 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Background: Radiofrequency-induced thermotherapy has shown promising results in the palliative treatment of various tumor entities. The purpose of this study was to investigate the effectiveness of bipolar radiofrequency volumetric tissue reduction (VTR) on lymph node (LN) metastases in the VX2 SCC model., Materials and Methods: Six male New Zealand white rabbits, with palpable metastatic disease within the parotid lymph nodes, were treated using the Celon-ProSurge probe, needle length 10 mm, diameter of 2.3 mm. The animals were sacrificed on the 4th, 8th, 11th, 14th, 18th and 22nd postoperative days respectively., Results and Conclusion: Bipolar radiofrequency VTR could prevent progression of local metastatic disease in one-third of the animals compared to the control group of untreated VX2 carcinoma rabbits. These results encourage further studies, directed at whether this treatment modality could play a role in the palliative therapy of metastatic LN. Future studies should concentrate on the refinement of the treatment parameters and optimization of the treatment duration.

Acrylonitrile, a high volume organic chemical, was tested for reproductive effects in a three generation drinking water study with two matings per generation. Sprague-Dawley rats were exposed to acrylonitrile in drinking water at 0, 100, or 500 ppm. This corresponds to 0, 11+/-5 and 37+/-10 mg/kg, respectively, for males and 0, 20+/-3 and 40+/-8 mg/kg per day for the females, respectively. Water consumption was reduced in F0 rats in the 100 and 500 ppm groups. At 500 ppm, acrylonitrile reduced body weight gain and food intake of the first generation parental rats (F0). These parameters were not investigated at subsequent generations. The pup survival (both viability and lactation indices) was reduced at the 500 ppm treatment level in both matings of all three generations. Fostering the 500 ppm pups onto untreated mothers following the second mating lessened mortality, suggesting a maternal effect consistent with decreased water consumption. There was no remarkable change in the reproductive capacity in any of matings in rats at the 100 ppm concentration. In contrast, in all three generations, the body weights of the pups of the 500 ppm treatment level were reduced on Day 21 at both matings. No adverse findings were observed in the tissues of a limited number of third generation weanlings (F3b) upon gross and microscopic evaluation. No effect on the sciatic nerve was evident among the adult female rats held for 20 weeks after weaning of the second litter. There was a dose-related effect of acrylonitrile on gross masses in female rats at each parental generation held 20 weeks after the weaning of the second litter. Histopathological evaluation of these dams showed an increase in astrocytomas and zymbal gland tumors.

Fermented milk products might be used for cancer chemoprevention due to their putative anticarcinogenic and antitumor activities. The diet was supplemented with freeze-dried milk fermented by Lactobacillus bulgaricus strain LBB.B 144 (product FFM.B 144) added throughout the experiment at doses of 1.3 g and 2.5 g per rat, 5 times a week starting 3 weeks before the first carcinogen injection. This treatment significantly inhibited, by 26.2-28.6% and by 34.2%, the total intestinal carcinogenesis induced by 1,2-dimethylhydrazine (DMH, 21 mg/kg, s.c., once per week for 20 weeks) in male and female BD6 rats, respectively. FFM.B144 decreased the tumor incidence and multiplicity in large bowel, caecum, and duodenum. Protective effects were better expressed in female animals, with exception of that observed in duodenum. Supplementation of diet with freeze-dried milk fermented by Lactobacillus bulgaricus strain LBB.B5 (product FFM.B5) inhibited DMH-induced carcinogenesis only in the large bowel, but had no significant protective effect when all intestinal tumors were taken into account. However, both freeze-dried products favorably shifted the differentiation of large bowel tumors by increasing the proportion of benign and highly differentiated malignant tumors and decreasing in parallel the number of poorly differentiated carcinomas without influencing the tumor size. A lower number of cases with visible mesenterial metastasis was also observed in FFM-treated rats. In addition, both FFM.B 144 and FFM.B5 significantly inhibited, by 26-33%, the induction in the same rats of ear-duct tumors. FFM.B144 but not FFM.B5 was also effective in inhibiting the tracheal carcinogenesis induced in Syrian golden hamsters by diethylnitrosamine (DEN, 100 mg/kg, two s.c. injections), the protective effect being better expressed in female animals. The anticarcinogenic potential of some fermented milk products might be exploited in chemoprevention of cancer in humans.

We report three patients who developed unusually aggressive squamous cell carcinomas after receiving long-term azathioprine treatment for dermatological disorders. Two patients gave a history suggestive of moderate to excessive sun exposure, and the third suffered from chronic actinic dermatitis. Hence, ultraviolet light damage may have been a significant cofactor in the development of these malignancies. Careful follow-up is necessary in patients who are taking azathioprine long term, and who have previously been excessively exposed to ultraviolet light (UVL), or in whom future exposure is likely to be excessive. We suggest that strict sun avoidance measures are followed by patients on long-term azathioprine, or that alternatives to azathioprine therapy are considered, especially in individuals inherently at risk of UVL damage, and in those already showing clinical signs of such damage.

The effects of topical application of geniposide on 12-o-tetradecanoylphorbol-13-acetate(TPA)-induced promotion of skin tumors, hyperplasia, ornithine decarboxylase (ODC) and inflammation were evaluated in female CD-1 mice. Topical application of geniposide (0.2 to 1.0 mumol) with TPA (15 nmol) twice weekly for 20 weeks to mice previously initiated with benzo[a]pyrene (B[a]P) inhibited the number of TPA-induced tumor per mouse by 84 or 89%, respectively. Pre-application of the same amount of geniposide also afforded significant protection against TPA-induced hyperplasia in the ear skin. Topical application of geniposide inhibited tumor promoter-caused induction of epidermal ODC activity by TPA (5 nmol). The topical application of geniposide (0.2 or 1.0 mumol) inhibited TPA-induced edema of mouse ears by 41 or 43%, respectively. Pretreatment of mouse skin with various amounts of geniposide caused inhibition of hydrogen peroxide (H2O2) and myeloperoxidase (MPO) formation by TPA. These results indicate that geniposide possesses potential as a cancer chemopreventive agent against tumor promotion.

Effects of the naturally occurring antioxidants on mammary gland carcinogenesis were examined in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[alpha]anthracene (DMBA). Groups of 15-16 7-week-old rats received a 50 mg/kg body weight intra-gastric dose of DMBA, and starting one week thereafter placed on diet containing 0.4% catechol, 1.0% gamma-oryzanol, 2.0% phytic acid, 1.0% green tea catechins (GTC), 1.0% tannic acid or basal diet alone for 35 weeks. Although the final incidences and multiplicities of mammary tumors were not significantly different between DMBA-treated groups, the numbers of survivors in the antioxidant-treated groups at the end of the experiment at week 36 were significantly higher than in the basal diet group. In particular, the survival rate of the GTC group at 93.8% strongly contrasted with that of only 33.3% for rats on the basal diet. At the end of week 18, when all the animals were still alive, the average size of palpable mammary tumors was significantly smaller in the catechol, phytic acid and catechins groups. These results indicate that antioxidants, and GTC in particular, inhibit rat mammary gland carcinogenesis after DMBA initiation.

1,2-dimethylhydrazine (DMH) is widely used to induce colorectal tumours in rodents. Some of the animals develop ear as well as colorectal tumours. Rats with large, ulcerated ear tumours are usually sacrificed before the completion of the experiment. In this experiment, fourty-six male Spraque-Dawley rats were injected with 1,2-dimethylhydrazine (21 mg/kg body weight) once a week for 27 weeks to study the histogenesis of colorectal carcinoma. Thirty-six developed ear tumours. Fourteen of the 36 tumours were larger than 2 cm in diameter. These developed between 20-26 weeks and were surgically excised 1-5 weeks later. Four rats died postoperatively. The surgical removal of large ear tumours permitted the completion of the large bowel experiment on schedule (i.e. 27 weeks) in 10 (28%) of the 36 rats with ear tumours.

The activating mutations of all three ras genes in rat Zymbal's gland tumors induced by a food mutagen, 2-amino-3-methylimidazo[4,5- f]quinoline (IQ) were analyzed. DNA fragments of the Ha-ras, Ki-ras and N-ras oncogenes were amplified from formalin-fixed and paraffin-embedded tissues by the polymerase chain reaction (PCR) and analyzed for activating mutations involving codons 12, 13 and 61 by oligonucleotide differential hybridization. All nine Zymbal's gland tumors examined, including three papillomas, were found to contain either an Ha-ras or Ki-ras mutation. These mutations were located in either codon 13 or 61 of Ha-ras, and in either codon 12 or 13 of Ki-ras. Of the nine mutations, three were G-->T, three were G-->C, two were G-->A and one was A-->T. Of the nine mutations, eight occurred at guanine bases and seven were transversions. There was no correlation between the types of mutations and the histological types of the tumors. These results suggest that ras gene activation is an important early event in the tumorigenesis induced by IQ in rat Zymbal's gland and that mutations at guanine bases are frequent, though the locations and types of the mutations are not highly specific.

One of the models of colon carcinogenesis in rats is produced by s.c. injections of 1,2-dimethylhydrazine (DMH). This specific colon carcinogen provokes other tumors in the rat, notably intestinal tumors. Ear tumors are just marginally mentioned in the literature. We have studied the appearance and histologic characteristics of ear tumors produced by 19 s.c. injections of 21 mg/kg of DMH in 18 Sprague-Dawley rats: 15 tumors appeared in 13 ears of 10 rats (55% of the animals). Simultaneously there were 23 colonic tumors: four (26.6%) of the tumors were carcinomas, 10 (66.6%) papillomas and one (6.6%) pseudoepitheliomatous hyperplasia. We conclude that ear tumors induced by DMH appear in 55% of the rats and that it is not possible to distinguish macroscopically in terms of size and aspect between benign and malignant lesions.

The activation of the c-Ha-ras gene and its carcinogen specificity were examined in squamous cell carcinomas (SCCs) induced by the mutagenic heterocyclic amines 2-amino-3-methylimidazo [4,5-f]quinoline (IQ),2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in the Zymbal gland in rats. DNA fragments of the c-Ha-ras gene were amplified from formalin-fixed and paraffin-embedded tissues by polymerase chain reaction and analyzed for activating mutations involving codons 12, 13, and 61 by oligonucleotide differential hybridization and sequencing. c-Ha-ras mutations were found in four of seven and two of six Zymbal gland SCCs induced by IQ and MeIQx, respectively. These mutations were located in either codon 13 or 61. In the case of MeIQ, point mutations at the second nucleotide of codon 13 were found in nine of the total 14 Zymbal gland SCCs and in one papilloma. Of the nine SCCs that had mutations in codon 13, two possessed mutations at the second nucleotide of codon 12 as well. Most reported mutations in c-Ha-ras are located at codon 12 or 61, but the heterocyclic amines in this study induced mutations not only at codons 12 and 61 but also in codon 13. Transversions were the dominant mutation induced by these heterocyclic amines.

The effects of diet supplemented with perilla oil, which contains a large amount of n-3 alpha-linolenic acid, and n-6 linoleic acid rich soybean and safflower oil supplemented diets on 7,12-dimethylbenz[a]anthracene (DMBA)- and 1,2-dimethylhydrazine (DMH)-induced mammary gland and colon carcinogenesis were investigated in female SD rats. Groups of 23 or 24, 5 week old animals were first given three s.c. injections of 40 mg/kg body wt DMH followed by a single intragastric administration of 50 mg/kg body wt DMBA within 2 weeks of the commencement. Starting 1 week after the DMBA treatment, they were administered pellet diet containing 10% perilla oil, soybean oil or safflower oil for the succeeding 33 weeks. Histological examination revealed that the resultant numbers of mammary tumors per rat were significantly lower in rats given perilla oil diet (4.4 +/- 2.5) than in the soybean oil diet group (6.5 +/- 3.9). Furthermore, colon tumor incidence was significantly lower in animals receiving the perilla oil supplement (18.2%) than in those given safflower oil diet (47.4%), and the numbers of colon tumors per rat tended to be lowest in rats administered perilla oil. Also the incidence of nephroblastomas in rats receiving perilla oil diet (0%) was significantly lower than that for the soybean oil diet group (23.8%). The results thus indicate that the alpha-linolenic acid (n-3)-rich perilla oil diet inhibits development of mammary gland, colon and kidney tumors as compared to linoleic acid (n-6)-rich safflower or soybean oil diet.

Male Sprague-Dawley rats were given 10 weekly intravenous injections of acetoxymethyl-methylnitrosamine (AMMN = N-nitroso-acetoxymethyl-methylamine). One group was also treated with disulfiram (DSF) by gavage twice daily five times per week. DSF markedly reduced the rate of heart and lung tumors but not of tumors at other organ sites. In animals treated with the combination of DSF and AMMN a significant incidence of neurogenic tumors was observed. No neurogenic neoplasms occurred in animals treated with AMMN alone. During the observation period DSF showed no carcinogenic potential.

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.

Thirty female Sprague-Dawley rats were fed 0.535 per cent phenacetin in the diet for up to 110 weeks. Twenty-six of these rats developed urothelial hyperplasia, partly papillary, of the renal papillae. Twenty-eight rats showed dilatation of the vasa recta frequently associated with thrombus formation and calcification. One phenacetin fed rat had epithelial hyperplasia associated with chronic pyelitis. In 2 of the 30 control rats urothelial hyperplasia was found to be associated with chronic pyelitis. The hyperplastic urothelial changes and vascular changes were often, but not always, present simultaneously. One control rat developed a mammary carcinoma, as compared with 5 rats in the phenacetin group. Four phenacetin fed rats developed carcinoma of the ear duct. The results of the present investigation provide evidence that phenacetin can induce proliferative lesions of the urothelium of the rat renal pelvis with weak carcinogenic activity in the ear duct and mammary glands.

Effects of hydroperoxides, autoxidation products of linolic acid (HPO) and secondary oxidative products of HPO (SOP) (5% each in diet) were examined in female Sprague-Dawley rats. HPO and SOP administration was carried out during or subsequent to two injections of dimethylhydrazine (DMH) (40 mg/kg body wt s.c.), and a single i.g. dose of 7,12-dimethylbenz[a]anthracene (DMBA) (50 mg/kg body wt). No significant differences in the incidences of tumors in the mammary gland, colon, ear duct and hematopoietic system associated with HPO or SOP treatment were evident, during or after carcinogen exposure. The present results therefore indicate that the environmental contaminants, HPO and SOP, lack any potential for modification of mammary gland or colon carcinogenesis under the conditions of the investigation.

Both subcutaneous and hepatic hemangiosarcomas were induced in mice exposed to vinyl chloride monomer, and for the first time, the ultrastructure of hemangiosarcomas related to vinyl chloride exposure has been described. The subcutaneous hemangiosarcoma developed in a mouse's ear 29 weeks after exposure to 10 ppm vinyl chloride for 4 weeks, and the hepatic hemangiosarcoma was found in a mouse's liver at necropsy 56 weeks after exposure to 600 ppm vinyl chloride for 4 weeks. Both tumors showed a localized, cystic nodular appearance with a dark red tone. Histologically, an angiomatous architecture, the presence of neoplastic mesenchymal cell aggregates, focal necrosis, and hemorrhagic foci were common. Ultrastructurally, two neoplastic cell types, a mesenchymal and a well-differentiated endothelial cell type, were identified in both tumors. In addition, in the hepatic tumor, a pericyte-like neoplastic cell was also present. The incidence of hemangiosarcoma was much lower than that of lung tumors (alveologenic tumor) in mice exposed to vinyl chloride at the same concentrations for the same duration. This study suggests that there is no basic difference in ultrastructure between the vinyl chloride-induced hemangiosarcomas and hemangiosarcomas not related to this chemical exposure.

Rats of 3 inbred strains (DA, HS and AS2) were dosed with 1,2-dimethylhydrazine 2HCl (DMH) or saline by gavage weekly for 10 wk. DA and HS rats showed little overt toxic reaction but all AS2 rats died following DMH doses of 30 mg/kg. However, at 10 mg/kg 60% of AS2 rats survived the 30 wk experiment. All DA rats developed a high yield of adenocarcinoma of the bowel (means: males 6.8 tumours/large bowel and 0.8/small bowel; females 2.8/large and 0.08/small bowel) and one-third of the males developed tumours of the ear canal. A smaller proportion (52%) of HS rats developed tumours, specifically bowel tumours (means: male 1.4/large and 0.2/small bowel; females 0.4/large and 0.1/small bowel). Even on the lower dose of DMH AS2 rats showed extensive liver changes including cystic cholangioma (58%), angiosarcoma (25%) and hepatocellular carcinoma (8%) and 83% developed bowel tumours (means: males 2.3/large and 1.5/small bowel; females 3.5/large and 1.0/small bowel). The rapid induction and high yield of bowel tumours, the different toxicity of DMH in AS2 rats, and the differences in relative tumour density both between sexes and in the various segments of the bowel indicate the potential of these strains for studies of carcinogenesis in the bowel.

Tumor incidence was studied in 1,2-dimethylhydrazine (DMH) injected male rats assigned at weaning to isoenergetic casein-sucorse deits containing 7.5%, 15%, or 22.5% protein with or without 2.5% urea. Twenty rats fed each diet were given weekly intraperitoneal injections of DMH (15 mg/kg body weight/week) for the first 24 weeks and 20 were given saline. Of 96 DMH-injected rats necropsied after 28 weeks, 88 were necropsied during the 32nd or final week of the experiment. Adenocarcinomas of the small and large intestine were larger and significantly more numberous in rats fed 15% and 22.5% dietary protein. Keratin producing papillomas of the sebaceous glands of the external ear were observed first at 21 weeks in DMH-injected rats fed 22.5% protein. These were subsequently observed in some rats from all DMH-treated groups. As time progressed, the ear tumors increased in size and number in all groups but the greatest incidence was in the group fed 22.5% protein. No tumors were observed in saline-injected rats. Urea feeding did not increase the number of tumors nor cause changes in pH, urease activity or ammonia concentration of contents of the colon or cecum, or blood cholesterol. As dietary protein increased, cecal ammonia concentrations rose while both colon and cecal pH dropped. Portal blood urea and cholesterol reose as dietary protein was increased. DMH-treated rats had significantly higher concentrations of colon and cecal ammonia and lower blood cholesterol. Altough the rats fed 7.5% protein gained significantly less weight during 0 to 6 weeks of feeding, their weight gain was significantly higher during 6 to 26 weeks. No tumors were found in rats necropsied at 16 weeks.

Three groups of Donryu rats, each consisting of 36 females, were continuously given solutions of 1-butyl-3,3-dimethyl-1-nitrosourea as drinking water (400 ppm for group A, 200 ppm for group B 100 ppm for group C). Of the 100 rats that survived at least 122 experimental days, 64 developed leukemia and 38 had vaginal tumors. Leukemias were preponderant in animals of groups A and B; vaginal tumors appeared in group C.

Subcutaneous injections of the carcinogen dimethylhydrazine in inbred Fischer 344 male rats induced squamous-cell carcinomas in the ear canal, adenocarcinomas in the small bowel and duodenum, and adenomas and adenocarcinomas in the large bowel. The incidences of the tumors induced in the large bowel and ear canal were dose-related. As for tumors of the large bowel, the average size of adenomas was less than that of adenocarcinomas with massive infiltration beyond the muscularis mucosa. The average size of early adenocarcinomas was greater than that of adenomas but less than that of adenocarcinomas with massive infiltration beyond the muscularis mucosa.

Feeding 1,4-bis(fluorophenyl)-2-propynyl-N-cyclooctyl carbamate to F344 or Sprague-Dawley male rats at 125-500 ppm in the diet led to many carcinomas of the small intestine and ear duct (Zymbal's gland tumors) in addition to lymphomas and leukemias. A high incidence of mammary adenocarcinomas was found in the Sprague-Dawley rats. Only a few colon or liver tumors were observed in each strain.

A variety of established skin tumorigenesis protocols were tested for efficacy on athymic nu/nu mice (BALB/c background) and compared on euthymic nu/+ counterparts. Chemical carcinogens and UV light were applied to the ears of 10 mice of each sex and genotype for each group. Treatments were: 0.5 mg 7,12-dimethylbenz[a]anthracene [(DMBA) CAS: 57-97-6] to each ear; 0.125 mg DMBA to each ear, followed by 0.1 microgram 12-O-tetradecanoylphorbol-13-acetate [(TPA) CAS: 16561-29-8] twice weekly for 56 weeks; 0.2 mg N-nitroso-N-methylurea [(NMU) CAS: 684-93-5; 1% in acetone, 20 microliter] to each ear; 0.1 mg NMU to each ear weekly for 30 weeks; 0.2 mg NMU to each ear, followed by TPA twice weekly for 56 weeks; two ip doses of N-nitroso-N-ethylurea [(NEU) CAS: 759-73-9; 25 mg/kg each], followed by TPA twice weekly topically for 56 weeks; and exposure to sunlamps (250- to 400-nm emission) two or three times per week for 20 weeks, for a total dose of 3.7 X 10(5) J/m2. The chemical treatments caused mainly squamous papillomas and carcinomas, sebaceous adenomas and adenocarcinomas, and basal cell tumors, which appeared both on the skin of the ears and elsewhere. UV light caused squamous tumors, basal cell tumors, and sarcomas. Ear skin of the nu/nu mice developed significantly more squamous tumors than those of nu/+ mice after DMBA-TPA, NMU-TPA, NEU-TPA, repeated NMU, or UV light. Similar results were obtained for the skin of the heads and bodies. Even a single dose of NMU caused a few tumors on the nude, but not the euthymic, mice. A single dose of DMBA caused primarily sebaceous adenomas, distributed at random over the entire bodies. These results show that, contrary to previous reports, nude mice are sensitive to skin tumorigenesis, more so than euthymic nu/+ mice similarly exposed to diverse types of carcinogen and treatment protocols.

The effect of intestinal microflora on the sensitivity of the colon to the carcinogenic effect of azoxymethane and a large dose of 1,2-dimethylhydrazine was studied using germ-free and conventional female Fischer rats. Injection s. c. of 1,2-dimethylhydrazine-induced tumors of the ear duct, kidney, and small intestine of conventional rats but none in germ-free animals. Only 20% germ-free rats showed 1,2-dimethylhydrazine-induced colonic tumors, whereas 93% of conventional rats developed multiple colonic tumors. Intrarectal instillation of azoxymethane appreciably increased the multiplicity of colonic tumors in germ-free rats and in gnotobiotic rats contaminated with Clostridium perfringens, as compared to conventional controls. None of the germ-free rats showed ear duct tumors. The incidence of kidney tumors was lower in germ-free rats than in other groups. It is concluded than the intestinal microbial populations alter the effect of carcinogens in the large intestine.

Male and female F344/DuCrj rats were administered N-butyl-N-nitrosourea at a concentration of 400 ppm in their drinking water. By the 50th week of the experiment, the cumulative incidence of upper-digestive-tract tumors was as high as 35/39 (90%) and 34/39 (87%) in male and female rats, respectively. Among these, esophageal and forestomach tumors occurred most frequently. Except one female rat with fibroma, upper-digestive-tract neoplasms were of the epithelial type -- papilloma, squamous-cell carcinoma or adenocarcinoma. In female rats, vaginal tumors were induced in 16 (41%) animals. Ear-duct tumors and hematopoietic neoplasms were also induced in both sexes of rats, with incidence of less than 21%.

Female SD rats were maintained for approximately 1 year on diets containing 300 ppm N-2-fluorenylacetamide (2-FAA), 50 ppm polybrominated biphenyls (PBB), or a combination of these chemicals (PBB + 2-FAA). Ingestion of 2-FAA significantly reduced the average survival time of the rats; this effect was virtually blocked by the simultaneous ingestion of PBB. Simultaneous ingestion of PBB also significantly reduced the overall incidence of 2-FAA-induced tumors during the examination period. The lower incidence of tumorigenesis was accompanied by an increase in the latency time for tumor induction; tumors were found in 100% of the animals given 2-FAA after 29 weeks of carcinogen ingestion, whereas only 50% of the PBB + 2-FAA-fed animals had tumors at the end of the experiment (53 wk of carcinogen ingestion). PBB significantly reduced the incidence of 2-FAA-induced tumors at nonhepatic locations (mammary gland and ear duct) but did not affect the incidence of hepatic tumors to a statistically significant extent. PBB ingestion did not significantly increase the incidence of tumors when compared with controls; 1 tumor was found in 1 of 12 rats fed 50 ppm PBB for 57 weeks, and no tumors were detected in 8 controls.

The temporal bones of a newborn infant with hydantoin syndrome showed multiple middle ear and inner ear anomalies. There was a constellation of bony and membranous defects involving the oval and round windows, cochlear ducts, cochlear aqueducts, endolymphatic ducts and sacs, and vestibular labyrinths. To the authors' knowledge, supernumerary vestibular sensory epithelial structures and an inner ear epidermoid cyst have not been previously reported. Wide communications between the subarachnoid space and inner ear were of surgical relevance.

A series of administration of 7,12-dimethylbenz[a]anthracene given at biweekly intervals by gastric intubation of juvenile male rats of the Sprague-Dawley strain elicited considerable number of mammary carcinomas, leukemias, and ear duct tumors. The evoked leukemia shared two main types; 51.6% of erythroblastic stem cell and 48.4% of myelogenous.

One hundred and seventy-nine male Wistar rats were divided into 6 groups and fed with a standard diet supplemented with 0.05% 2-acetylaminofluorene (2AAF) and/or 0.1% glutathione (GSH) or N-acetyl-L-cysteine (NAC). Each treatment cycle lasted for 3 weeks, followed by 1 week of standard meal. After 4 cycles, survival was 100% in the 3 control groups, and 86.0, 100 and 91.7%, in the groups receiving 2AAF, 2AAF plus GSH, and 2AAF plus NAC, respectively. After an additional 4-8 weeks, all the 5 surviving rats fed with 2AAF exhibited deforming ear tumors, which on histological examination were classified as sebaceous squamocellular carcinomas of Zymbal glands. No such tumors were detectable in control groups, nor in the 16 surviving rats fed with 2AAF plus GSH or NAC. In the liver, 2AAF produced significant DNA damage at the 3rd week of each cycle, which was partially repaired during the week of standard meal feeding. Moreover, 2AAF determined the appearance of gamma-glutamyl transpeptidase-positive foci, which tended to increase with time both in number and in size. GSH and NAC exerted similar protective effects on these phenomena, but only at early stages of the experimental model used.

Histoacryl-induced cholesteatomas were produced in guinea pigs at the posterosuperior part of the external ear canal adjacent to the tympanic membrane. Semithin and ultrathin tissue sections were used to study primary formation of the cholesteatoma as well as the influence of the altered epithelium upon the bordering zone of connective tissue. Quantitative and qualitative tissue changes were analyzed by electron microscopy and showed degradation and new formation of collagen and activation of fibroblasts. Our findings are similar to those previously reported on human cholesteatomas and indicate that the bordering subepithelial tissue seems to be influenced through the basilar membrane.

The effect of dietary fat and intestinal microflora on colon and small intestinal carcinogenesis was studied in weanling male F344 germfree and conventional rats fed semipurified diets containing low and high fat. At 7 weeks of age, all animals, except vehicle-treated groups, received weekly s.c. injections of 50 mg 3,2'-dimethyl-4-aminobiphenyl (DMAB) per kg body weight for 20 weeks. The DMAB- and vehicle-treated germfree and conventional rats fed high- and low-fat diets were autopsied 20 weeks after the last injection of DMAB. The incidence of colon, small intestinal, ear duct, and skin tumors was lower in germfree rats than in the conventional animals. The incidence and multiplicity of DMAB-induced colon tumors were higher in conventional rats fed the high-fat diet than in the conventional animals fed the low-fat diet; however, the tumor incidence did not differ significantly between the high- and low-fat-fed germfree animals. Dietary fat had no effect on the incidence of small intestinal tumors in both germfree and conventional rats.

The effects of the antioxidants tetramethyl-p-phenylenediamine (TMPD), propyl gallate (PG), quercetin (QC), 2-tert-butyl-4-methylphenol (TBMP), tert-butylhydroquinone (TBHQ), 3,3'-thiodipropionic acid (TDPA), guaiac gum (GG) and caffeic acid (CA) on 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mammary gland, ear duct and forestomach carcinogenesis were examined in female Sprague--Dawley rats. Fifty-day-old rats were treated with 2.5 mg/100 g body wt of DMBA and, commencing 1 week thereafter, were given diets supplemented with 0.1% TMPD, 1.0% PG, 1.0% QC, 1% TBMP, 0.8% TBHQ, 1.0% TDPA, 1.0% GG or 0.5% CA for 51 weeks and then killed. Mammary tumor development was reduced by diet containing TMPD, PG, TBMP, TBHQ or GG, although this could be partly due to antioxidant treatment-associated decrease in body wt gain. The incidence of ear duct tumors was not affected by any of the antioxidant treatments. Development of forestomach tumors was enhanced in the group given DMBA followed by CA.

The effects of antioxidants on mammary gland carcinogenesis pretreated with 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats were examined. The antioxidants used were butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), sodium L-ascorbate, alpha-tocopherol, ethoxyquin and p,p'-diaminodiphenylmethane (DDPM), which is an inhibitor of carcinogenesis in the liver, kidney and urinary bladder. Female Sprague-Dawley rats of 50 days old were treated with 2.5 mg/100 g body weight of DMBA, and from 1 week later were given diet supplemented with 1% BHA, 0.7% BHT, 5% sodium L-ascorbate, 1.5% alpha-tocopherol, 0.5% ethoxyquin or 0.1% DDPM for 33 weeks and then killed. The incidences of mammary tumors, carcinomas and fibroadenomas in DMBA-treated animals were reduced by diet containing BHA or ethoxyquin. Diet containing BHT or DDPM inhibited the induction of only fibroadenomas. The incidence of ear duct tumors in DMBA-treated animals was reduced by diet containing BHT, alpha-tocopherol or ethoxyquin.

Three groups of female Donryu rats were given continuously 1-ethyl-1-nitrosourea, 400, 200, or 100 mg/liter, in their drinking water. Leukemias developed in 94 of 104 (92%) rats surviving more than 6 experimental weeks. Of the leukemias, the erythroleukemias were induced most frequently, rapidly, and selectively. Other types of leukemias were found in a few rats of the high-dose group and, in some cases, in rats of the low-dose group. Tumors were also induced in the digestive tract, mammary glands, ear duct, and other organs, but their incidences were lower than 24%.

The carcinogenicity of the mutagenic compound 2-amino-3-methylimidazo[4,5-f]-quinoline (IQ), identified in fried and broiled foods, was investigated in female Sprague-Dawley rats. Administration by gavage of IQ (0.4 mmol/kg body weight) on a weekly regimen for 31 weeks starting with 6-week-old animals induced a high yield of multiple mammary gland carcinomas in a limited bioassay lasting a total of 52 weeks. In a positive control group receiving 4-aminobiphenyl (4-AB), the expected carcinomas in the mammary gland developed. IQ, but not 4-AB, also yielded neoplasms in the ear duct and to a lesser degree, in the liver, pancreas, and urinary bladder. In addition, with IQ, a high incidence of preneoplastic lesions in the pancreas was observed. Vehicle and untreated controls did not have any lesions. These findings demonstrate that IQ is a powerful multipotent carcinogen in the rat.

2-Acetylaminofluorene induced mammary and ear duct carcinomata and spontaneously arising mammary carcinomata and sarcomata were shown to express embryonic antigens at the cell surface by their reaction with serum from multiparous female rats. These observations with essentially non-immunogenic tumours are comparable with early findings showing that embryonic antigens are also expressed on aminoazo dye induced rat hepatomata, and sarcomata induced with 3-methylcholanthrene. Re-expression of embryonal components, therefore, may be a concomitant of neoplastic transformation.

After ten times monthly, subcutaneous, injections of 30 mg/kg 1,2-dimethylhydrazine (DMH) to Sprague-Dawley-rats, malignant tumors were found in approximately 90% of the animals after a mean induction period of approximately 330 days. Injections were started on the 2nd day of life and maintained during 10 months. 72% of the tumors induced were formed in the colon, 17% were squamous cell carcinomas of the ear duct, adenosarcomas of the kidney and hepatocellular carcinomas were found in 13 and 11% of the animals, respectively. Additional treatment with immunodepressive (cyclophosphamide, methotrexat, hydrocortisone) and immunostimulating substances (BCG, albumin, vitamin A-acid) as well as an enzyme-stimulating agent (Luminal) did not alter incidences and induction periods of tumors. After application of a vegetarian diet, the rate of liver and kidney tumors was diminished significantly and induction periods of intestinal and ear duct tumors increased.

Chlorambucil was linked to prednisolone to improve the therapeutic and toxic properties of this potent alkylating agent, which is known to induce second tumors in humans. To compare the carcinogenic potency of the linked compound with that of the respective individual agents and of their unlinked mixture, prednimustine (I), chlorambucil (II), prednisolone (III), chlorambucil plus prednisolone (IV), or vehicle were administered to groups of 120 female Sprague-Dawley rats for 18 months. The following doses were administered nine, four, five, two times, or once a month per subgroup of 30 rats: I, 12 mg/kg; II, 3 mg/kg; III, 3 mg/kg; IV, 3 mg/kg. After natural death of animals, median survival times were analyzed, and percentages of malignant tumors were recorded. An increased tumor risk was found in the following organs compared with those of vehicle-treated controls: I, external auditory canal (EAC); II, mammary gland (MG), central and peripheral nervous tissue (CPNT), hematopoietic and lymphatic tissue (HLT), and EAC; III, none; and IV, MG, CPNT, and EAC. There is evidence of carcinogenic activity of prednimustine compared with untreated controls, but the cancer-inducing potential of the linked compound is distinctly lower than that of the unlinked mixture of chlorambucil plus prednisolone or that of chlorambucil.