Lack of carcinogenicity of phenytoin in (C57BL/6 x C3H)F1 mice.

Groups of 50 B6C3F1 mice of each sex were given 0.012% or 0.006% phenytoin in their powdered diet for 78 wk and were then fed a basal diet for 8 wk. Control groups of 50 mice of each sex were fed powdered basal diet for 86 wk. Mean total intakes of phenytoin per mouse were 301 and 150 mg in males, and 292 and 154 mg in females, respectively. The survival rates of each group at week 86 were 72-86% in males, and 86-94% in females. Liver-cell tumors, alveolar tumors, and Harderian-gland adenomas in male mice, malignant lymphomas and/or leukemias in female mice, and a few tumors in other organs of both sexes were found. The total number of hepatocellular tumors in mice treated with the high dose of phenytoin was significantly smaller than that of control mice in males (p less than 0.05). However, hepatocellular carcinomas developed 15 to 3 wk earlier in a few mice of phenytoin-treated males than in the controls. In other organs, no significant increase of any particular tumor type was observed in the treated groups of both sexes. Thus, phenytoin was not carcinogenic in B6C3F1 mice in this study.

Macroregenerative nodule of the liver. A clinicopathologic study of 345 autopsy cases of chronic liver disease.

The livers of 345 autopsy cases of chronic liver disease were examined for macroregenerative nodule (MRN), a large nodular lesion more than 10 mm in diameter. A total of 86 lesions of MRN was found in 49 cases (14.2%): 32 were from 191 cases of hepatocellular carcinoma (HCC), 16 were from 148 cases of cirrhosis only, and one was from six cases of chronic hepatitis. The incidence (19.6%) and the size (12.1 mm) of MRN in macronodular type of cirrhosis were significantly higher and larger than those in other types of cirrhosis. Also, the average size of MRN lesions of cases with HCC (12 mm) was significantly larger than that of cases with cirrhosis only (10.5 mm). The incidence of liver cell dysplasia (LCD) in cases of MRN (67.3%) was significantly higher than that in cases without MRN (40.9%). The MRN lesions were divided into Type I and Type II, the latter having proliferative foci distinguishable from the surrounding tissue. Three of them contained atypical cells regarded as cancer. Type II lesions were larger in size, and cases with multiple MRN lesions were seen more frequently in cases of HCC. The average age of the patients with Type II lesion was 5 years older than those with Type I lesions. These findings suggest that MRN should not be ignored in the morphogenesis of HCC.

Carcinogenicity of bucetin in (C57BL/6 X C3H)F1 mice.

The carcinogenicity of bucetin [(3-hydroxy-p-butyrophenetidide) CAS: 1083-57-4], an antipyretic analgesic drug, was examined in 300 (C57BL/6 X C3H)F1 mice. Groups of 50 mice of each sex were treated with 1.5 or 0.75% bucetin in their basal diet for 76 weeks and then fed a basal diet for 8 weeks. Control groups were given a basal diet for 84 weeks. In 10 of 46 (22%) male mice given the high dose of bucetin and in 6 of 45 (13%) given the low dose, renal cell tumors were induced. Dysplastic lesions of the proximal tubules were frequently seen in the males given bucetin in a dose-related fashion. Neither tumorous nor preneoplastic lesions developed in the kidneys of bucetin-treated female mice and control animals. Papilloma of the urinary bladder in 1 male mouse and papillary or nodular hyperplasia in 9 mice of both sexes were observed in groups given the high dose of bucetin.

Effects of 12-O-tetradecanoylphorbol-13-acetate on carcinogenesis in the heterotopically transplanted rat urinary bladder.

12-O-Tetradecanoylphorbol-13-acetate (TPA), a potent promoter of mouse skin carcinogenesis, was tested for possible tumor-enhancing effects on urinary bladder carcinogenesis using the heterotopically transplanted bladder (HTB) model. Weekly administration of TPA at 1.0 microgram/week to N-methyl-N-nitrosourea-initiated HTBs did not increase tumor incidence, but instead, resulted in a significantly high incidence of nodulopapillary hyperplasia, an early neoplastic lesion, suggesting possible tumor enhancement by TPA. In addition, administration of a high dose of TPA with or without a carcinogen treatment led to the development of numerous finger-like epithelial projections on the luminal surface of the HTBs. Evidence indicates that epithelial projections are formed as a result of proliferation of intermediate cells. Whether these structures evolve into true neoplastic lesions is at present unknown.