Lack of oxidative DNA damage or initiation of carcinogenesis in the kidneys of male F344 rats given subchronic exposure to p-dichlorobenzene (pDCB) at a carcinogenic dose.

p-Dichlorobenzene (pDCB) is a male rat kidney carcinogen believed to act through alpha2u-globulin nephropathy. Recent data on metabolism, however, suggest a potential for generating oxidative stress. To examine possible mechanisms of kidney carcinogenesis, pDCB was studied for ability to produce 8-oxodeoxyguanosine (8-oxodG) in kidney nuclear DNA and for initiating activity in a two-stage renal carcinogenesis model. F344 male rats were given pDCB by intragastric instillation, 5 days/week for 13 weeks at 300 mg/kg per day, which is a carcinogenic dose with chronic administration. To assess initiation after exposure, trisodium nitrilotriacetic acid (NTA), a kidney tumor promoter was given in the drinking water at 1,000 ppm for 39 weeks. At the end of the exposure segment, pDCB did not produce an increase of 8-oxodG levels in the kidney nuclear DNA in contrast to potassium bromate (KBrO3). Following NTA promotion, no neoplastic lesions occurred in rats given pDCB, although diethylnitrosamine carcinogenesis was enhanced. Thus, pDCB did not produce oxidative DNA damage in the rat kidney or effect initiation of kidney carcinogenesis. These data suggest that oxidative stress is not involved in pDCB-induced renal carcinogenesis. The alpha2u-globulin-mediated chronic nephropathy probably acts as a promoter, not an initiation of renal carcinogenesis. Accordingly, pDCB is assessed to have no cancer hazard to humans who are not susceptible to the alpha2u-globulin nephropathy.

The induction of benign epithelial neoplasms of the ovaries of guinea pigs by testosterone stimulation: a potential animal model.

We studied the effects of different hormones on the epithelial cells of the ovaries of 11 guinea pigs. Three received testosterone, two received estrone, three megestrol, and three chorionic gonadotropin. Three control guinea pigs received sterile water. Benign epithelial cysts larger than 1.5 mm were found in six guinea pigs, three who received testosterone, one who received megestrol, and two who received chorionic gonadotropin. In one of the three guinea pigs who received testosterone, 2.5-cm bilateral cysts were grossly identified. Papillary excrescences were found on the ovarian surface in four guinea pigs, three who received testosterone and one who received megestrol. The proliferating epithelial cells also formed benign glands in the ovarian stroma in two guinea pigs who received testosterone, the most exuberant epithelial proliferations, including large bilateral cystadenomas, papillary excrescence that formed a small papillary neoplasm, and glands in the ovarian stroma that formed adenomatous areas, were seen in the guinea pig who received an intermediate dose of testosterone for the longest time. By radioimmunoassay, the serum level of testosterone was 22 ng/dL in one of the controls and 10,000, 12,000, and 15,000 ng/dL in the three guinea pigs who received testosterone. In the guinea pig with the most exuberant epithelial proliferation, the level of testosterone in the uterus was similar to that in the serum (13,860 ng/mg), but in the wall of the ovarian epithelial cyst, it was three times higher than it was in the serum (44,000 ng/mg). Our study shows that testosterone stimulates the growth of epithelial cells in the ovaries of guinea pigs, resulting in benign cysts, small adenomas in the ovarian parenchyma, and papillomas on the ovarian surface. The study also shows that guinea pigs can be used as an animal model for epithelial tumors of the human ovary.

Dissimilar frequency of hepatoblastomas and hepatic cystadenomas and adenocarcinomas arising in hepatocellular neoplasms of D2B6F1 mice initiated with N-nitrosodiethylamine and subsequently given Aroclor-1254, dichlorodiphenyltrichloroethane, or phenobarbital.

Aroclor-1254 (Ar-1254) and dichlorodiphenyltrichloroethane (DDT) were compared to phenobarbital (PB) for their ability to promote hepatocellular proliferative lesions to hepatocellular adenomas and carcinomas and to hepatoblastomas in D2B6F1 male mice initiated with N-nitrosodiethylamine (NDEA). Hepatocellular neoplasms developed in all mice given NDEA and were more numerous in mice fed promoters. Multiplicities decreased in the order Ar-1254 > PB > DDT, indicating that Ar-1254 was more potent than either PB or DDT at the dosage levels used. PB was the most effective of the 3 agents in stimulating the evolution of hepatocellular neoplasms to hepatoblastoma. The incidence of hepatoblastomas in the NDEA.PB group was 72% but was only 27% in NDEA-initiated, DDT-promoted mice and 33% in low-dose and only 9% in high-dose Ar-1254-promoted mice. In contrast, lesions resembling benign and malignant cholangiocellular neoplasms were frequently found within hepatocellular tumors in Ar-1254-promoted mice but not in mice fed PB or DDT, either alone or after NDEA. Some cystic glandular structures in Ar-1254-promoted mice contained mucous cells, argentaffin cells, and Paneth cells and thus constituted intestinal metaplasia. Hepatoblastoma and intestinal metaplasia/cholangiocellular tumor morphology appear to constitute different patterns of genetic programming induced by certain promoters in expanding clones of initiated hepatocytes, on favorable genetic backgrounds such as that of D2B6F1 male mice.

Promotion of cholangiocarcinogenesis in the hamster liver by bile duct ligation after dimethylnitrosamine initiation.

Administration of hepatocarcinogenic nitrosamines before or after infection with the liver fluke, Opisthorchis viverrini (OV), results in marked development of cholangiocellular and hepatocellular precancerous and cancerous lesions in the hamster liver. The promoting effects of OV are believed to be exerted either mechanically, chemically or immunologically. To test the influence of possible mechanical effects, Syrian hamsters were initiated with a single i.p. injection of dimethylnitrosamine (DMN) 20 mg/kg and subjected 2 weeks later either to a sham operation or to complete ligation of the extrahepatic bile duct to the left lateral lobe. At the end of week 40, the animals receiving DMN-initiation and ligation had a 60.9% incidence of cholangiofibrosis, 21.7% of mucous cystadenomas and 39.1% of cholangiocarcinomas, whereas the group given DMN alone only developed cholangiofibrosis, limited to 5% of the animals. In the latter case neither cystadenomas nor cholangiocarcinomas were observed. The incidence of hepatocellular nodules did not differ between the two groups and no tumorous lesions developed in either the ligated or the untreated groups without DMN pretreatment. Complete ligation of the bile duct itself led to a series of events; obstruction of bile flow being followed by dilatation, cyst formation, and necrosis of the bile duct epithelium and surrounding affected areas leading to regenerative proliferation. The results are in line with the conclusion that parasite-associated proliferation in target cell populations is, at least in part, responsible for the influence of OV on liver tumor development.

Hemorrhagic ovarian cysts in patients on anticoagulation therapy: CT findings.

OBJECTIVE: Hemorrhage into ovarian cysts is a frequent and potentially life-threatening complication in women on chronic anticoagulation therapy. This article presents the CT findings of three surgically confirmed cases of symptomatic hemorrhagic ovarian cysts associated with anticoagulation therapy. MATERIALS AND METHODS: There were two cases of unruptured hemorrhagic ovarian cysts: a patient with two corpus luteum cysts of menstruation and a patient with a serous cystadenoma. RESULTS: Each mass had a rounded central region of high attenuation (76, 62, and 50 HU) representing blood that was surrounded by fluid density. The third case was a hemorrhagic corpus luteum cyst of menstruation with rupture and hemoperitoneum. CONCLUSION: Hemorrhagic ovarian cysts should be included in the differential diagnosis of high-attenuation adnexal masses, especially in patients on anticoagulation therapy and in those with abrupt onset of pelvic pain.

Tumors in rat kidney generated by initiation with trans-4-acetylaminostilbene and several promoting treatments.

trans-4-Acetylaminostilbene (AAS) is a complete carcinogen in rats and produces quite selectively tumors in Zymbal's glands. On the basis of DNA adduct formation, it has been proposed that this model arylamine initiates neoplastic transformation of cells in many tissues, particularly liver and kidney, which, in the classical sense are considered to be non-target tissues for this chemical. In the present study an initiating treatment with AAS was followed by unilateral nephrectomy and the application of two nephrotoxic substances, gentamycin or beta-cyclodextrin which, among other activities, stimulate cell proliferation specifically in kidney. The initiating dose of AAS, given alone, gave rise to Zymbal's gland and mammary tumors in female Wistar rats within 88 weeks but not to liver or kidney tumors. When the initiation treatment was followed by unilateral nephrectomy, alone or in combination with gentamycin, or by beta-cyclodextrin, four tumors in two out of ten animals, eight tumors in three/ten, and seven tumors in three/ten, respectively, were observed in the kidney. The administered dose of gentamycin was not sufficient to induce tumors on its own. The results support the view that the genotoxic effects of AAS produce promotable lesions in rat kidney. None of the animals that had been treated with AAS, with or without other treatments, developed tumors or the predominant types of preneoplastic lesions in the liver within 88 weeks; this supports the notion that liver, like kidney, is not a target for complete carcinogenesis for this chemical.

Morphology of nasal lesions induced in Osborne-Mendel rats and B6C3F1 mice by chronic inhalation of allyl glycidyl ether.

Chronic (24-month) inhalation exposure to 5 or 10 ppm allyl glycidyl ether (AGE) induced nasal lesions in Osborne-Mendel rats and B6C3F1 mice. Inflammation, degeneration, regeneration, metaplasia, hyperplasia, and neoplasia were observed in the nasal mucosa. Squamous metaplasia and hyperplasia of the respiratory epithelium and degeneration and regeneration with subsequent squamous and/or respiratory metaplasia of the olfactory epithelium were observed in many AGE-exposed animals. Three primary nasal neoplasms (1 papillary adenoma, 1 squamous cell carcinoma, and 1 olfactory epithelial carcinoma) were observed in rats exposed to 10 ppm AGE, and 1 nasal papillary adenoma was observed in a rat exposed to 5 ppm. Four papillary adenomas and 2 hemangiomas were observed in the noses of mice exposed to 10 ppm AGE. Although the incidence of primary nasal tumors in AGE-exposed rats or mice was not statistically significant compared to the incidence in concurrent controls, the relative rarity of primary nasal tumors in historical controls and the concurrent presence of metaplastic and hyperplastic nasal lesions similar to those reported to be associated with induced tumors of nasal epithelia by other chemicals suggest that the nasal tumors observed may be related to AGE exposure. It was concluded that, in addition to lesions indicating a toxic effect on the nasal mucosa, inhalation exposure to AGE for 24 months resulted in some evidence of carcinogenicity of AGE for male mice, equivocal evidence of carcinogenicity for female mice and male rats, and no evidence of carcinogenicity for female rats.

Genetic studies on lung tumor susceptibility and histogenesis in mice.

The probability that a mouse develops a pulmonary tumor, as well as the structure of that tumor, are dependent on several genes. Three pulmonary adenoma susceptibility (pas) genes predispose some inbred strains to develop lung tumors, even in the absence of carcinogen exposure, and cause others to be resistant. One pas gene is K-ras, which may also be overexpressed in these tumors in a mutated form capable of transforming cells. Mice with activated Ha-ras transgenes override the resistant pas alleles and are born with lung cancer. Susceptible strains have a higher turnover rate of alveolar type II and bronchiolar Clara cells, those cells from which lung tumors arise, than more resistant strains. A high precursor cell turnover rate correlates with a propensity to neoplasia in other animal models as well, possibly due to low concentrations of endogenous growth regulatory molecules such as corticosterone and protein kinase C (PKC). Neoplastic lung epithelial cells are relatively resistant to glucocorticoids and have low PKC levels. A set of genes other than the pas genes governs the response to tumor modulation by butylated hydroxytoluene (BHT). The genes that determine whether lung tumor multiplicity is enhanced by chronic BHT exposure may regulate the ability to hydroxylate BHT at a tert-butyl position to form BHT-OH, a metabolite with greater tumor-promoting potency than BHT. Inbred and recombinant inbred strain variations in adenoma growth patterns indicate that another set of genes, which we have designated pah for pulmonary adenoma histogenesis, may determine which cell type becomes neoplastic and whether adenomas will undergo malignant conversion.

Cells of origin of primary pulmonary neoplasms in mice: morphologic and histochemical studies.

Urethane-induced pulmonary adenomas in mice have two distinct histologic growth patterns--solid and papillary. The development of these tumors between 14 and 56 weeks was investigated in A/J mice. Solid tumor multiplicity remained constant from 14 to 56 weeks, whereas papillary and total tumor multiplicities increased in parallel between 14 and 28 weeks and remained constant through 56 weeks. The simplest explanation of these results is that solid and papillary adenomas arise independently, possibly from different cell types. The cell type of origin of these primary mouse lung tumors was investigated histochemically. Succinate dehydrogenase (SDH) histochemistry readily stained bronchiolar epithelial cells, but alveolar epithelial cells exhibited only slight enzymatic activity. Urethane-induced papillary adenomas exhibited intense SDH staining, whereas solid adenomas stained very lightly. Since Clara cells and type II pneumocytes are the only cells capable of proliferation in the bronchiolar and alveolar epithelia, respectively, the relative SDH activities of these adenomas is consistent with a hypothesis that solid tumors arise from type II pneumocytes and papillary tumors arise from Clara cells.

[Lung tumors induction short-term test of chloroprene in mice].

In a previous report by the authors, positive results in both case-control study mouse lung tumor induction short-term test of chloroprene for carcinogenicity was conducted to determine whether chloroprene monomer itself could induce tumor. Kuangming albino mice weaned 2 wk were subjected to inhale 0.0, 2.9 +/- 0.34, 19.18 +/- 1.89, 189.00 +/- 13.26 mg/m3, chloroprene (GC purity 99.69%) 4 h daily (except Sunday) for 7 month. All survivors were killed at the end of the 8th month or when moribund. No lung tumor was found before the 6th month. Thus survivors at the 6th month were counted as effective animals. Most lung tumors observed were papillo-adenoma (50/57), and a few were adenoma (7/57). Tumor incidence of the 2.9 mg/m3 group increased to 8.1% in comparison with that of the control group (1.3%) at a significant level of P less than 0.05; and the higher the concentration the higher the incidence. Examination of the multiplicity of tumors also demonstrated the dose-response relationship, and the number of tumors per mouse in the 189 mg/m3 group was significant at P less than 0.01.

Primary liver tumors in beagle dogs exposed by inhalation to aerosols of plutonium-238 dioxide.

Primary liver tumors developed in Beagle dogs exposed by inhalation to aerosols of 238PuO2. Initial deposition of 238PuO2 in the respiratory tract was followed by translocation of a portion of the 238Pu to the liver and skeleton, which resulted in a large dose commitment and tumor risk to all three tissues. In a population of 144 dogs exposed to 238PuO2, 112 dogs died or were killed 4000 days after 238Pu exposure, 100 dogs had osteosarcoma, and 28 dogs had lung cancers. At increasing times after exposure, however, liver lesions have become more pronounced. Ten primary liver tumors in nine animals were diagnosed in the dogs dying before 4000 days after exposure. An additional five primary liver tumors in three dogs occurred in 9 animals killed after 4000 days after exposure. The majority of these tumors have been fibrosarcomas. The liver tumors were usually not the cause of death, and rarely metastasized. The occurrence of liver tumors in this study indicates that 238Pu is an effective hepatic carcinogen. Liver carcinogenesis is assuming an increasing importance in this study at late times after inhalation exposure. These results suggest that the liver may be an important organ at risk for the development of neoplasia in humans at time periods long after inhalation of 238Pu.

Oral contraceptives and intrahepatic biliary cystadenoma having an increased level of estrogen receptor.

We report a case of intrahepatic biliary cystadenoma in a young woman who had no prior history of liver disease and who had taken oral contraceptives for one year. A 27-year-old woman was admitted to our hospital with a firm epigastric mass. At laparotomy, a large cystic mass was resected from the left hepatic lobe, and diagnosed as biliary cystadenoma. In the tumor tissue, the estrogen receptor content was 14.0 fmol/mg cytosol protein, which was much higher than the 3.0 fmol/mg cytosol protein in the surrounding liver tissue. This is the first case of biliary cystadenoma in which the estrogen receptor content was increased.

PIP: A 27-year-old woman with a 1-year history of oral contraceptive (OC) use presented to a Japanese medical center with a firm epigastric mass. The patient had no prior history of liver disease. Biliary cystadenoma was diagnosed on the basis of the cystic nature of the mass, several mural nodules, and the presence of large amounts of mucinous fluid. At laparotomy, a cystic mass 7.2 x 5.8 x 6.2 cm was rejected from the left hepatic lobe. Several smaller cysts, lined by a layer of columnar mucinous epithelium, were contained within the wall of the larger cyst. The estrogen receptor content of the tumor tissue was 14 fmol/mg cytosol protein compared to less than 3 fmol/mg in the surrounding liver tissue. Biliary cystadenoma accounts for under 5% of all solitary cysts of biliary origin. This is the 4th known case of such a tumor in an OC user. Although the precise etiology of this woman's biliary cystadenoma cannot be ascertained, the high estrogen receptor content in her cystadenoma suggests that these tumors are sensitive to estrogen and that estrogen-containing OCs may serve as tumor promoters.

Effect of propylthiouracil on the thyroid tumorigenesis induced by N-bis(2-hydroxypropyl)nitrosamine in rats.

The effect of 0.15% propylthiouracil (PTU) on thyroid tumorigenesis was studied in male Wistar rats given a single i.p. injection of 280 mg of N-bis(-2-hydroxypropyl)nitrosamine (DHPN) per 100 g body weight. The mean weights of the thyroid of rats treated with DHPN followed by PTU and with PTU alone were significantly higher than those of rats treated with DHPN only and control rats. The incidences of follicular adenoma at the end of week 20 of the experiment were 100% (21/21) in rats treated with DHPN followed by PTU, and 19% (4/21) in rats given DHPN alone. Papillary adenoma was observed in one rat treated with DHPN followed by PTU. The incidence of follicular carcinomas with invasive growth into the capsule, adipose tissues or blood vessels was 52% (11/21) in rats given DHPN and then PTU. No papillary carcinomas or solid tumors were found in any rats. Rats given PTU alone and untreated rats had no thyroid tumors. The serum concentration of T4 in rats treated with PTU alone was significantly lower than that in the control group. The serum concentration of T4 in rats treated with DHPN followed by PTU was slightly, but not significantly, lower than that in control rats. The serum concentrations of T3 in rats treated with DHPN followed by PTU, DHPN alone and PTU alone were also slightly, but not significantly, lower than that in controls.

Upper genital tract abnormalities in the Syrian hamster as a result of in utero exposure to diethylstilbestrol. I. Uterine cystadenomatous papilloma and hypoplasia.

Prenatal exposure to diethylstilbestrol (DES) causes a significant increase in the carcinogenic response of the hamster's reproductive tract to subsequent DES treatment. Uteri from DES treated females from untreated- and DES treated mothers (C.D & D.D) have abnormal hyperplasia with characteristic finger-like structures projecting into the lumen of the uteri. Inside these papillae along with the rest of the stroma are cystic glands. We found that these glands had no openings into the uterine lumen and that they "begin" and "end" in the stroma. In addition there are two types of cells lining the cystic gland i.e., pale cells and acidophilic cells. Capillary beds surround the cystic glands. We have named these uterine structures "cystadenomatous papilloma". In addition, we found a spectrum of hyperplastic abnormalities in C.D and D.D uteri and carcinoma in situ in D.D uteri. Similar neoplasms have been described in human pathology. Ultrasound observations have demonstrated that in utero exposure to DES may result in uterine hypoplasia and because it appears to be similar to the changes seen in prenatally DES treated (D.C) hamsters, cross sectional areas of C.C (untreated control), D.C, C.D and D.D uteri were compared. Our results show that later in life uterine hypoplasia also occurs in the 100 days old D.C hamsters and since D.C uteri present hyperplasia with cystic structures, our data support the hypothesis that in utero DES-treated human females may later in life develop benign and malignant lesions in their reproductive tract. Much of these data corresponds to what has been found in humans, and consequently warrants further investigation into the use of Syrian hamster as a model to understand the uterine abnormal morphogenesis in regards to hypoplasia, adenocarcinoma and carcinoma development in the human.

Histogenesis of the papillary Clara cell adenoma.

Mouse lung adenomas have two characteristic histologic patterns, alveolar and bronchiolar or papillary. Differences in biologic behavior have been noted in tumors of different histologic form, in that papillary tumors were said to grow faster and become larger and possibly malignant. Progressive development from the alveolar to the papillary tumors has been proposed, involving a step-wise transformation from benign to malignant tumors. The author recently presented evidence from ultrastructural studies that the different histologic patterns were related to the cell of origin; the bronchiolar tumors consisted of Clara cells, while the alveolar tumors were made up of Type II alveolar epithelium. In the present study, designed to evaluate the histologic patterns of tumors during their development, multiple lung adenomas were induced in fetal Bagg-Webster mice on the sixteenth day of gestation by a single transplacental exposure to ethyl-nitrosourea. The animals were killed from the seventh postnatal day to 185 days of age; their tumors were counted and categorized histologically. Analysis of serial-step sections of the right lower lobes of young postnatal mice showed tumors with either an alveolar (37%) or a bronchiolar pattern (63%). Two forms of the latter were recognized, tubular and papillary. Between Day 80 and Day 186 papillary adenomas increased, tubular tumors decreased, and alveolar adenomas remained relatively constant in number. At the end of the 6-month observation period the overall proportion of alveolar and Clara cell tumors was similar to that found in the first 3 weeks of life. These data support the concept that alveolar and papillary tumors arise from different cell lines, the papillary tumors exclusively from Clara cells.

Enhanced development of mammary tumors in rats following transplacental and neonatal exposure to ethylnitrosourea.

Transplacental and neonatal induction of mammary tumors (MT's) with ethylnitrosourea (ENU) was studied in Sprague-Dawley rats. A low transplacental ENU dose (10 mg/kg) did not increase the number of MT's or shorten their latency period. High ENU doses (30 mg/kg neonatal, 60 mg/kg transplacental, or 120 mg/kg transplacental) when corrected for differences in life span caused a significant shortening of the tumor induction period and an overall increase in the tumor incidence. With high ENU doses, the MT's were frequently multiple in the same animal and were more often malignant. Tumors developed mostly in females; only a few were observed in males. It is concluded that with a sufficient dose of the carcinogen in susceptible animals, transplacental and neonatal ENU mammary carcinogenesis takes place. The experiment was originally designed to evaluate ENU-induced neurogenic tumors; the results on MT's were obtained incidentally.