Estriol prevention of mammary carcinoma induced by 7,12-dimethylbenzanthracene and procarbazine.

The concentration of estrogenic, androgenic, progestational, and adrenocortical steroid hormones in body fluids of mature intact Sprague-Dawley female rats was increased by s.c. implantation of 5 to 7 mg NaCl pellets containing 1 to 20% steroid 48 hr before administration p.o. of either 7,12-dimethylbenz(a) anthracene or procarbazine. The incidence of rats developing one or more mammary carcinomas in each treated group was compared to that ovserved in simultaneously treated groups receiving only the carcinogen, steroid, or no treatment whatsoever, with weekly observation of all rats until palpably growing tumors were biopsied and proven carcinomatous or until death occurred from other causes determined by autopsy. A total of 105 untreated or steroid-implanted rats followed to death (234 to 256 days median observation) developed no breast carcinomas. Rats fed either of the carcinogens developed initial evidence of breast carcinoma, after 136 to 156 days median observation, in 51 to 57% of 318 total treated rats. Nonbreast carcinomas and sarcomas developed in 5 to 10% of the carcinogen-treated rats.     

Spontaneous ECL cell carcinomas in cotton rats: natural course and prevention by a gastrin receptor antagonist

In our inbred strain of cotton rats (Sigmodon hispidus) 50% of the females develop spontaneous ECL cell-derived tumors in the acid-producing part of the stomach due to hypergastrinemia secondary to gastric hypoacidity. Although the mechanism behind the hypoacidity is unknown, the female cotton rat is an excellent model for studying ECL cell-related tumorigenesis. In this study we wanted to explore the malignancy potential of these tumors and the ability of a gastrin receptor antagonist (YF476) to prevent their development. First, nine hypergastrinemic female cotton rats (10 months of age) were diagnosed by laparotomy as having gastric tumors. They were killed 6 months later. Second, 18 female cotton rats (2 months of age) were dosed monthly for 6 months with YF476 (500 micro mol/kg body wt) by s.c. injection, while 21 age-matched animals received vehicle. Samples from each stomach were collected for histology, immunohistochemistry and northern blot analysis. The gastric tumors harbored cells with immunohistochemical features of ECL cells. The tumors were found at times to invade and penetrate the stomach wall and to metastasize to perigastric sites. ECL-derived tumor cells were discovered in peritoneal fluid. At death only 1 out of 18 animals given YF476 displayed carcinomas (invasive growth), compared with 7 out of 21 in the vehicle dosed control group (P = 0.048). The spontaneous gastric tumors in cotton rats derived from ECL cells. The tumors were able to penetrate the stomach wall and to metastasize by intracavital seeding. Gastrin receptor blockade lowered the incidence of such tumors. We propose that the tumors are ECL cell carcinomas and that gastrin is the driving force behind the transformation from normal to malignant ECL cells.     

Enhanced ATPase activity in liver cell nuclei induced by administration of mitomycin C to rats

Intraperitoneal administration of mitomycin C (40 micrograms/100 g body weight) to male Wistar rats increased the ATPase activity in hypotonic extracts of liver cell nuclei for 4 days after injection. Partially purified ATPase, obtained by the DEAE-cellulose column chromatography of these extracts, showed a 14 times higher specific activity than that found in normal rat liver nuclei. The enzymatic activity was strongly enhanced by the addition of polynucleotides, especially poly A and poly I, to the assay mixture, but was inhibited by GTP, a chelating agent, heparin and thiol-group inhibitors. Quercetin and oligomycin were less effective, and ouabain showed no inhibitory effect. Mg2+ ions were essential, but neither Ca2+, Na+ nor K+ ions were required for the manifestation of the activity. These characteristic properties of the enzyme are similar to those of a nucleoside triphosphatase found in the nuclear matrix and envelope, suggesting that some energy-providing mechanisms involved in the repair processes of DNA damage or cellular injury are induced by mitomycin C administration.     

Adenocarcinomas of the prostate induced by N-nitroso-N-methylurea in rats pretreated with cyproterone acetate and testosterone

Prostatic adenocarcinomas were induced in 5 out of 20 Wistar rats upon a single administration of 50 mg/kg N-nitroso-N-methylurea (NMU). The rats were pretreated with a daily dose of 50 mg/kg cyproterone acetate for 3 weeks followed by 3 daily injections of 100 mg/kg testosterone. All tumours developed in the dorsolateral prostate and were invasively growing. In 2 cases distant metastases were found. Three proliferative lesions classified as carcinomas in situ were also found in the dorsolateral prostate. A total of 7/20 animals (35%) carried an adenocarcinoma and/or a carcinoma in situ. In addition, 6 epithelial hyperplasias were observed in the dorsolateral and 1 in the ventral prostate of non-tumour-bearing rats. The method described may provide a good animal model for cancer of the prostate and lead to a better understanding of prostatic carcinogenesis.     

Stomach tumors in rats induced by a single administration of N-methyl-N-nitro-N-nitrosoguanidine and N-methyl-N-nitrosourea

The pathologic characteristics of gastric tumors induced by single injections of N-methyl-N'-nitro-N-nitrosoguanidine (15 mg) solution and N-methyl-N-nitrosourea (10 mg) solution in 0.1 ml dimethylformamide were studied in 23 noninbred rats. The chemicals were injected into the antropyloric segment of the stomach. By months 11-15, specific changes in the glandular epithelium had developed at that site in 20 rats: dysplasia--in 6, precancer--7, and adenocarcinoma in 7 animals. Also, there were papillomas (6), squamous cell carcinoma (3), precancer and sarcoma (4) in various segments of the organ.     

Enzyme deviation patterns in primary rat hepatomas induced by sequential administration of two chemically different carcinogens

Enzyme deviation patterns were examined in primary rat hepatomas induced by short-term sequential administration of two chemical carcinogens from among 2-fluorenylacetamide (FAA), diethylnitrosamine (DENA), and 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) or by FAA or 3'-Me-DAB followed by phenobarbital as a promoter. The purpose was to discern how the patterns are influenced by different administration schedules of carcinogens and which of the two carcinogens in the sequence affects the pattern more. Biochemical differentiation of hyperplastic hepatic nodules and hepatomas was determined by simultaneous assays of activities and isozyme composition of glucose-adenosine triphosphate phosphotransferase, pyruvate kinase, glucose-6-phosphatase, fructose-1,6-bisphosphatase, and gamma-glutamyltransferase with consideration of histological classification of nodules and tumors. Poorly differentiated hepatomas were predominantly induced by 3'-Me-DAB followed by FAA or DENA except for hepatomas induced by 3'-Me-DAB followed by phenobarbital, which were mainly well and moderately differentiated; well and moderately differentiated hepatomas were predominantly induced by FAA followed by 3'-Me-DAB or phenobarbital. The degree of enzyme deviation of the hepatomas induced by DENA as the first carcinogen was intermediate between those of hepatomas induced by FAA or 3'-Me-DAB, although the degree tended to increase with increased dose or term of DENA. These results indicate that deviations of some enzymes, such as pyruvate kinase and fructose-1,6-bisphosphatase, as well as histological differentiation of the primary hepatomas are more strongly influenced by the first carcinogen than by the second under our administration schedules and that the degree of enzyme deviation shown by hepatomas produced by a particular carcinogen treatment regimen principally related to the potential of that regimen to induce the more anaplastic tumors.     

Carcinogenic effects of sequential administration of two nitrosamines in Fischer 344 rats

The carcinogenic effects of sequential treatment of female F344 rats with two nitrosamines were studied. The animals received either methylethylnitrosamine (NMEA), a strong liver carcinogen, N-nitrosomethylaniline (NMA), a moderately strong esophageal carcinogen, or N-nitrosopyrrolidine, (NPyr), a weaker liver carcinogen. The sequentially treated groups were given NMEA followed by NMA and vice versa, NPyr followed by NMEA and vice versa. The dose and duration for each chemical in the sequentially treated groups were identical for the individual treatments. The animals were allowed to die or were killed when moribund. The animals surviving longer than 110 weeks were sacrificed. The NMEA-NPyr and NPyr-NMEA groups had a tumor spectrum characteristic for NMEA alone (a mixture of hepatic carcinomas and sarcomas with extensive metastases to the lungs). The survival was reduced in the NMEA-NPyr group compared to the NMEA alone group. The time to death of the NMA-NMEA group was not affected by the NMA treatment, but many of the animals had esophageal neoplasms. The NMEA-NMA group survival was reduced when compared to the NMEA alone group but the tumor spectrum was dominated by NMEA. The data indicate that when the target organ is the same, the effect of two nitrosamines is additive with the stronger carcinogen dominating the tumor spectrum. When the target organs are different, the initial exposure influences the tumor spectrum, although the treatment with the second nitrosamine enhances the tumorigenicity of the initial nitrosamine.     

Increased biopterin production in rats with tumors induced by radon inhalation and benzonaphthoflavone administration

Serial determinations of urinary biopterin were performed in rats during the development of lung tumors induced by radon inhalation and 5,6-benzonaphtoflavone administration. A striking increase in biopterin levels was observed in animals which developed single or multiple epidermoid carcinoma of the lung and this increase occurred several weeks before tumors could be detected radiographically.     

Prevention of rectal cancer induced by N-nitrosobis(2-oxopropyl)-amine by exogenous testosterone in MRC rats

Rectal carcinogenicity of N-nitrosobis(2-oxopropyl)amine (BOP)in male MRC Wistar rats was shown to be inhibited by exogenoustestosterone (T) when the hormone was given during, but notafter, administration of the carcinogen. This effect was independentof the dose and frequency of BOP, which was given either weeklyfor 20 weeks orally or daily for 3 days subcutaneously. Since,except for prostatic cancer, the incidence and the patternsof other BOP-induced tumors were not altered by T, this hormoneseems to play a specific role in the rectal carcinogenesis ofBOP.     

Influence of sodium selenite on carcinogenesis of the prostate and other organs induced by methylnitrosourea and testosterone in rats

Influence of selenium on induced carcinogenesis of the prostate and other organs was studied in male Wistar rats. Carcinogenesis was induced (68) by using our modification of a combined double-stage model including surgical castration, single administration of N-methyl-N-nitrosourea (MNU) and long-term promotion by a mix of testosterone ethers (MTE). Seven days after MNU injection the rats were randomized to form 2 groups. Controls were fed drinking water while the study group - water containing sodium selenite 4mg/l, daily - till the end of the experiment. Controls (12) were not exposed to any treatment. They were followed up for 55 weeks until sacrificed. Apparent benign prostatic hyperplasia developed in rats subjected to castration, MNU and MTE. Also, such precancerous lesions as prostatic intraepithelial neoplasia (PIN) and prostate cancer including metastatic one were detected. Malignant lymphoma, other than in target tissues, was the most frequent. Prostate pathological changes and lymphomas were not registered in intact rats. Unlike rats treated with MNU and MTE and fed untreated drinking water, selenium did not influence significantly the development of prostate intraepithelial neoplasia but reduced multiplicity of prostate cancer by 44.6%. Simultaneously, the incidence of induced malignant lymphomas decreased by 26.4%.     

Genetics of susceptibility of rats to trigeminal schwannomas induced by neonatal administration of N-ethyl-N-nitrosourea

A genetic analysis was done on the induction of trigeminal schwannomas by N-ethyl-N-nitrosourea [(ENU) CAS: 759-73-9] in susceptible LE rats, resistant WF rats, and their F1, F2, and reciprocal backcross hybrids. Both sexes of all strains were given a neonatal sc injection of 40 mg ENU/kg body weight and were sacrificed at 6 months after treatment. Many neurogenic tumors were induced in the central nervous system of all strains of rats. However, the incidence of trigeminal schwannomas in LE rats was 93% in males and 86% in females, whereas in WF rats the incidence was 24% in males and 20% in females. F1 and F2 hybrids showed an intermediate susceptibility (62 and 82% in F1 males, 79 and 86% in F2 males, 26 and 38% in F1 females, and 65 and 77% in F2 females). The incidence in hybrids backcrossed to LE was high (90 and 100% in males and 77 and 83% in females), and the incidence in hybrids backcrossed to WF was low (35 and 38% in males and 11 and 7% in females). The findings suggest that susceptibility to the induction of trigeminal schwannomas by ENU does not result from the expression of genes that are simple dominant or recessive genes. A genetic model involving three independently segregating loci may explain the experimental results. In all strains of rats, particularly the F1 hybrids, males were more susceptible than females to the induction of trigeminal schwannomas by ENU.     

The role of testosterone in the nasal cavity tumors induced by N-nitrosobis(2-oxopropyl)amine in rats

In a previous study in rats we have shown that castration priorto weekly administration of N-nitrosobis(2-oxopropyl)amine (BOP)prevents induction of nasal and paranasal cavity (NPNC) tumors,indicating androgen dependency of these neoplasms. To investigatethe possible inhibitory effect of testosterone withdrawal onthe growth of NPNC tumors, in the present study rats were castratedfollowing weekly treatment with BOP for 10, 20 or 30 weeks.This treatment did not alter the incidence, type, location,latency or multiplicity of NPNC tumors. However, simultaneoustreatment of castrated rats with BOP and testosterone (T) yieldedNPNC tumors in an incidence and patterns comparable to thatseen in BOP-treated intact and BOP-plus-T-treated intact rats.Serological examination revealed abnormally high levels of Tand 17-beta estradiol (E) in rats, which were killed immediatelyafter 10, 20 or 30 weekly BOP administrations. The overall resultssuggest that the initiation but not the promotional stage ofNPNC carcinogenesis is governed by androgens.     

Carcinogenesis induced by a single administration of 1,2-diethylhydrazine in female rats of various ages.

Three- or fourteen-month-old female L10 rats were exposed to a single intravenous injection of 1,2-diethylhydrazine (SDEH) at 150 mg/kg of body weight. At the 95th week after carcinogen treatment when the experiment was stopped, 30.7% and 4.5% of rats from the younger and older groups survived, respectively. Total tumor incidences were 68.8% and 84.6%, respectively, in rats treated with SDEH at the age of 3 or 14 months vs. 18.2% and 34.5% in corresponding young and old controls (P < 0.01). Leukemias, thyroid adenomas, uterine tumors and mammary malignancies developed more frequently in animals exposed to carcinogens than in control groups. No age-related differences in tumor incidence or localization between rats exposed to SDEH at various ages were observed, but tumors developed earlier in older groups than in younger groups. The results supported the suggestion that the accumulation of initiated cells in some tissues during natural aging is a cause of the age-related increase in cancer incidence.     

Diagnosis and management of red cell aplasia in children

The vast majority of pediatric RBC hypoplastic anemias are accounted for by red blood cell aplasia associated with chronic hemolysis, Diamond-Blackfan anemia, and transient erythroblastopenia of childhood. However, other causes of hypoplastic anemia occur in children, and some of these are similar to what is seen in adult RBC aplasia. For example, it has been reported that a 5-year-old girl with an aregenerative anemia had a thymoma and later developed pancytopenia. RBC aplasia also has been seen in children receiving anticonvulsant drug therapy, children recovering from severe protein malnutrition, children with hepatitis, and in children with leukemia during maintenance therapy. In addition, it is not uncommon for pediatric hematologists to observe children with RBC aplasia where there is no obvious diagnosis, although many are considered to be variants of Diamond-Blackfan anemia. Several important questions about RBC hypoplastic anemias in children need to be resolved; it is hoped that this will be accomplished in the next decade. Do RBC hypoplastic crises associated with hemolytic anemia occur with viral infections other than HPV? What is the cellular pathophysiology in DBA and TEC? Does the apparent heterogeneity of these disorders reflect limitations of laboratory techniques or are we looking at several different diseases? Is acute leukemia a real complication of Diamond-Blackfan anemia? Is TEC a completely benign entity or will we see other long-term problems in these children? Is the incidence of TEC actually increasing? Will TEC-like problems be seen in other aged children? As a case in point, we recently observed a 16-year-old girl who presented with pure RBC aplasia that required RBC transfusion support for 5 months; she also received prednisone therapy. After 7 months, however, this young lady had a spontaneous remission, and now 4 years later she is normal and free of any hematologic abnormalities. This was a most unusual event in our experience and, in view of the apparent increasing incidence of TEC in young children, we queried whether we were observing an adolescent equivalent of this disorder. During the next several years the answer to this and the other questions posed herein should be available.