(1/112) Chronic inhalation carcinogenicity study of commercial hexane solvent in F-344 rats and B6C3F1 mice.

The carcinogenic and chronic toxicity potential of commercial hexane solvent was evaluated in F-344 rats and B6C3F1 mice (50/sex/concentration/species) exposed by inhalation for 6 h/day, 5 days/week for 2 years. Target hexane vapor concentrations were 0, 900, 3000, and 9000 ppm. There were no significant differences in survivorship between control and hexane-exposed groups, and clinical observations were generally unremarkable. Small, but statistically significant decreases in body weight gain were seen in rats of both sexes in the mid- and high-exposure groups and in high-expsoure female mice. The only noteworthy histopathological finding in rats was epithelial cell hyperplasia in the nasoturbinates and larynx of exposed groups. This response was judged to be indicative of upper respiratory tract tissue irritation. No significant differences in tumor incidence between control and hexane-exposed rats were found. In mice, uterine tissue from the high-exposure females exhibited a significant decrease in the severity of cystic endometrial hyperplasia compared to controls. An increase in the combined incidence of hepatocellular adenomas and carcinomas was observed in high-exposure female mice. The incidence of liver tumors was not increased in the mid- or low-exposure female mice or in male mice exposed to hexane. An increased incidence of pituitary adenomas was observed in female, but not male mice. This finding was not believed to have been treatment-related because the incidence in the control group was unusually low, and the incidence in exposed groups was not dose-related and was within the historical control range. No other neoplastic changes judged to be treatment-related were observed in tissues from male or female mice. In conclusion, chronic exposure to commercial hexane solvent at concentrations up to 9000 ppm was not carcinogenic to F-344 rats or to male B6C3F1 mice, but did result in an increased incidence of liver tumors in female mice.  (+info)

(2/112) Mutation of beta-catenin is an early event in chemically induced mouse hepatocellular carcinogenesis.

beta-catenin activation, and subsequent upregulation of Wnt-signaling, is an important event in the development of certain human and rodent cancers. Recently, mutations in the beta-catenin gene in the region of the serine-threonine glycogen kinase (GSK)-3beta phosphorylation target sites have been identified in hepatocellular neoplasms from humans and transgenic mice. In this study we examined 152 hepatocellular neoplasms from B6C3F1 mice included in five chemical treatment groups and controls for mutations in the beta-catenin gene. Twenty of 29 hepatocellular neoplasms from mice treated with methyleugenol had point mutations at codons 32, 33, 34 or 41, sites which are mutated in colon and other cancers. Likewise, nine of 24 methylene chloride-induced hepatocellular neoplasms and 18 of 42 oxazepam-induced neoplasms exhibited similar mutations. In contrast, only three of 18 vinyl carbamate-induced liver tumors, one of 18 TCDD-induced liver tumors, and two of 22 spontaneous liver neoplasms had mutations in beta-catenin. Thus, there appears to be a chemical specific involvement of beta-catenin activation in mouse hepatocellular carcinogenesis. Expression analyses using Western blot and immunohistochemistry indicate that beta-catenin protein accumulates along cell membranes following mutation. The finding of mutations in both adenomas and carcinomas from diverse chemical treatment groups and the immunostaining of beta-catenin protein in an altered hepatocellular focus suggest that these alterations are early events in mouse hepatocellular carcinogenesis.  (+info)

(3/112) Liver adenomatosis: reappraisal, diagnosis, and surgical management: eight new cases and review of the literature.

OBJECTIVE: Liver adenomatosis (LA) is a rare disease originally defined by Flejou et al in 1985 from a series of 13 cases. In 1998, 38 cases were available for analysis, including eight personal cases. The aim of this study was to review and reappraise the characteristics of this rare liver disease and to discuss diagnosis and therapeutic options. BACKGROUND: LA was defined as the presence of >10 adenomas in an otherwise normal parenchyma. Neither female predominance nor a relation with estrogen/progesterone intake has been noted. Natural progression is poorly known. METHODS: The clinical presentation, evolution, histologic characteristics, and therapeutic options and results were analyzed based on a personal series of eight new cases and an updated review of the literature. RESULTS: From a diagnostic standpoint, two forms of liver adenomatosis with different presentations and evolution can be defined: a massive form and a multifocal form. The role of estrogen and progesterone is reevaluated. The risks of hemorrhage and malignant transformation are of major concern. In the authors' series, liver transplantation was indicated in two young women with the massive, aggressive form, and good results were obtained. CONCLUSION: Liver adenomatosis is a rare disease, more common in women, where outcome and evolution vary and are exacerbated by estrogen intake. Most often, conservative surgery is indicated. Liver transplantation is indicated only in highly symptomatic and aggressive forms of the disease.  (+info)

(4/112) Hepatocellular adenomatosis associated with hereditary haemochromatosis.

A young healthy man presented with abdominal pain following an accidental fall. Imaging studies and laparoscopy revealed multiple yellowish well-defined hepatic lesions. Liver biopsies showed hepatic adenomas and iron overload. Laboratory investigation confirmed a diagnosis of hereditary haemochromatosis. To our knowledge this represents the first report of an association of hepatic adenomatosis and primary haemochromatosis.  (+info)

(5/112) Enhancement of chemical hepatocarcinogenesis by the HIV-1 tat gene.

The human immunodeficiency virus-1 Tat protein is suspected to be involved in the neoplastic pathology arising in AIDS patients. tat-transgenic (TT) mice, which constitutively express Tat in the liver, develop liver cell dysplasia (LCD) that may represent a preneoplastic lesion. To test if TT mice are predisposed to liver carcinogenesis, we treated them with diethylnitrosamine, a hepatotropic carcinogen. Diethylnitrosamine-treated TT mice developed both preneoplastic and neoplastic lesions in the liver. They showed an enhancement of LCD and developed basophilic liver cell nodules (BLCN), hepatocellular adenomas (HA), and hepatocellular carcinomas (HC). Both preneoplastic (LCD and BLCN) and neoplastic (HA and HC) lesions were significantly more frequent in TT than in control mice: 29.7% versus 12.7% for LCD, 57.9% versus 23.3% for BLCN, 40.6% versus 10.0% for HA, and 50.0% versus 12.7% for HC. These results indicate that Tat expression in the liver predisposes to both initiation of hepatocarcinogenesis and to malignant progression of liver tumors. This study supports a role for Tat in enhancing the effect of endogenous and exogenous carcinogens in human immunodeficiency virus-1-infected patients, thereby contributing to tumorigenesis in the course of AIDS.  (+info)

(6/112) Diagnostic impact of fluorescence in situ hybridization in the differentiation of hepatocellular adenoma and well-differentiated hepatocellular carcinoma.

Histopathological differentiation between hepatocellular adenoma and well differentiated hepatocellular carcinoma (HCC) may be a difficult task in small biopsies and occasionally in resected tumor specimens. Whether the analysis of chromosome aberrations can contribute to a more precise discrimination has not been analyzed systematically up to now. Therefore, fluorescence in situ hybridization was applied to 28 cases of adenoma and well differentiated carcinoma, using centromeric probes for chromosomes 1, 6, 7, 8, and X. None of 14 adenomas revealed an aberrant count in the analyses performed. By contrast, 13/14 carcinomas demonstrated aberrations for 2-5 chromosomes/case. Chromosome 1 was aberrant in 8/12 cases informative for this probe (67%), chromosomes 6 and 7 were aberrant in 9/14 cases (64%), chromosome 8 was aberrant in 11/14 cases (79%), and chromosome X in 7/14 cases (50%). Taking results for chromosomes 1 and 8 together, 13/14 HCC revealed aberrations for at least one of these chromosomes. Probes for 6, 7, and X revealed no additional aberrant cases.Thus, FISH for chromosomes 1 and 8, extended by probes for chromosomes 6, 7 and X, represents a promising approach toward a more accurate differentiation between hepatocellular adenoma and carcinoma.  (+info)

(7/112) An in vivo method for using 5-bromo-2'-deoxyuridine (BrdU) as a marker of chemically-induced hepatocellular proliferation in the Japanese medaka (Oryzias latipes).

Japanese medaka fish (Oryzias latipes) were used to develop an in vivo method to assess hepatocellular proliferation in a nonmammalian model. Proliferative responses were assessed in medaka at 7, 17, 24, and 94 days after a 48-hour exposure to 10 or 100 mg/L diethylnitrosamine (DEN). Subgroups of medaka were exposed to 50 or 75 mg/L of 5-bromo-2'-deoxyuridine (BrdU) in water for 72 hours, sacrificed, and then processed for immunohistochemical staining. Proliferative indices of BrdU-labeled hepatocytes were quantified and compared using both count and area measurements. There was a significant increase (p < 0.05) in hepatocellular proliferation in the 100 mg/L DEN-treated fish as compared to controls and 10 mg/L DEN-treated fish for the first 3 time points. Hepatocarcinogenicity was evaluated 26 weeks post-DEN exposure. There was a significant increase (p < 0.0001) in hepatocellular neoplasms in 100 mg/L DEN-treated fish compared to other fish. Effective BrdU-labeling of S-phase hepatocytes in medaka was achieved by adding BrdU to the aquarium water, and an increase in hepatocellular proliferation using this method was detected 7 days after exposure to a carcinogenic concentration of DEN. Additionally, the new method of area measurement indices of proliferation were as precise as count indices (R2 > or = 0.92).  (+info)

(8/112) Di(2-ethylhexyl)phthalate induces hepatocellular adenoma in transgenic mice carrying a human prototype c-Ha-ras gene in a 26-week carcinogenicity study.

To evaluate the transgenic mouse carrying a human prototype c-Ha-ras gene (rasH2 mouse) as a model for 26-week carcinogenicity tests, Di(2-ethylhexyl)phthalate (DEHP), a peroxisome proliferator, was administered to 15 rasH2 mice/sex/group at concentrations of 1,500, 3,000 or 6,000 ppm, and to 15 wild-type (non-Tg) mice/sex/group at a concentration of 6,000 ppm in their diets for 26 weeks. Survival rates and food consumption in the groups treated with DEHP and in the control group were similar. Body weight gain in rasH2 and non-Tg mice at 6,000 ppm in the terminal week decreased about 10% as compared to the control group. Common findings related to treatment with DEHP in rasH2 and non-Tg mice included hypertrophy with coarse granules and deposit of pigment in the liver, hydronephrosis and tubular regeneration in the kidney, focal atrophy in the testis, and increased eosinophilic body in the nasal cavity. Hepatocellular adenoma was induced by treatment with DEHP, and was confined to male rasH2; mice the incidence being 7%(1/15), 13%(2/15), and 27%(4/15) in the 1,500-, 3,000-, and 6,000-ppm group, respectively. Point mutation was not detected in codon 12 and 61 of human c-Ha-ras transgene upon DNA analyses on frozen samples taken from these hepatocellular adenomas. From the results obtained in this 26-week carcinogenicity study, it is concluded that DEHP is a hepato-carcinogen for transgenic mouse carrying a human prototype c-Ha-ras gene.  (+info)