Novel mouse model for Gardner syndrome generated by a large-scale N-ethyl-N-nitrosourea mutagenesis program.

Mutant mouse models are indispensable tools for clarifying the functions of genes and elucidating the underlying pathogenic mechanisms of human diseases. We carried out large-scale mutagenesis using the chemical mutagen N-ethyl-N-nitrosourea. One specific aim of our mutagenesis project was to generate novel cancer models. We screened 7012 animals for dominant traits using a necropsy test and thereby established 17 mutant lines predisposed to cancer. Here, we report on a novel cancer model line that developed osteoma, trichogenic tumor, and breast cancer. Using fine mapping and genomic sequencing, we identified a point mutation in the adenomatous polyposis coli (Apc) gene. The Apc1576 mutants bear a nonsense mutation at codon 1576 in the Apc gene. Although most Apc mutant mice established thus far have multifocal intestinal tumors, mice that are heterozygous for the Apc1576 mutation do not develop intestinal tumors; instead, they develop multifocal breast cancers and trichogenic tumors. Notably, the osteomas that develop in the Apc1576 mutant mice recapitulate the lesion observed in Gardner syndrome, a clinical variant of familial adenomatous polyposis. Our Apc1576 mutant mice will be valuable not only for understanding the function of the Apc gene in detail but also as models of human Gardner syndrome.

Multiple miliary osteoma cutis of the face after initiation of alendronate therapy for osteoporosis.

A 62-year-old Asian woman presented with multiple small, rock-hard papular lesions on her face (Figure). She had no previous history of acne vulgaris or cutaneous malignancy. She had been diagnosed with breast cancer in 1995 and was treated with left lumpectomy followed by combination chemotherapy consisting of cyclophosphamide, 5-fluorouracil, and methotrexate. In 1995, at age 50, she also began therapy with systemic alendronate to treat osteoporosis. Within 1 year, she noticed the development of asymptomatic indurated dermal papules on her cheeks. Topical treatment with 12% lactic acid lotion did not improve her condition. Clinical examination revealed numerous 1- to 2-mm, brown dermal nodules on the malar cheeks bilaterally. Normal laboratory data included complete blood cell count, alkaline phosphatase, serum calcium, and serum phosphate. A lesional punch biopsy from the left cheek revealed lamellar bone within the dermis. Correlation of the clinical presentation, laboratory data, and pathology established the diagnosis of multiple miliary osteoma cutis of the face.

Skeletal changes in rats given daily subcutaneous injections of recombinant human parathyroid hormone (1-34) for 2 years and relevance to human safety.

Fischer 344 rats (60/sex/group) were given daily subcutaneous injections of recombinant human parathyroid hormone (PTH)(1-34) for 2 years at doses of 0, 5, 30, or 75 microg/kg. Treatment caused substantial increases in bone mass consistent with the known pharmacologic effects of once-daily administration. As determined by quantitative computed tomography (QCT) and histomorphometry, bone mass was markedly increased. Substantial new bone formation resulted in a large decrease in marrow space accompanied by altered bone architecture. Bone proliferative lesions were observed in all PTH( 1-34)-treated groups. Osteosarcoma occurred in 3, 21, and 31 male rats and in 4, 12, and 23 female rats in the 5-, 30-, and 75-microg/kg treatment groups, respectively. Focal osteoblast hyperplasia, osteoma, and osteoblastoma were much less frequent. Although the specific cellular or molecular mechanisms responsible for the rat bone tumors have not been fully elucidated, the data suggest that these lesions resulted from the long duration of treatment and the exaggerated pharmacologic response of the rat skeleton to daily treatment with PTH(1-34). Important differences between the rat study and clinical use in adult humans suggest that the increased incidence of bone neoplasia in rats treated for 2 years is likely not predictive of an increased risk of bone cancer in skeletally mature adult humans being given PTH(1-34) for a limited period of time in the treatment of osteoporosis.

[Multiple miliary osteomas of the face]. / Multiple miliare Osteome des Gesichts.

Osteoma cutis is a single or multiple ectope calcification with development of bony structures in the skin. We distinguish between primary and secondary ossification. Multiple miliary osteoma in the face has mostly been described secondary to preexisting acne vulgaris. We present a 62-year-old woman who developed multiple miliary osteoma in the face together with repeated doses of estrogen and discuss pathogenesis and therapeutic possibilities.

Phenobarbital promotes multistage pulmonary carcinogenesis in MNU-inoculated L-W rats.

Lobund-Wistar (L-W) rats develop adenocarcinomas spontaneously in the accessory sex glands (prostate-seminal vesicles) (P-SV) in the livers and in the lungs-all after long periods of latency. This report addresses (a) the multistage pattern of induced lung carcinomas in L-W rats and (b) the role(s) of two putative promotional agents (testosterone propionate (TP) and phenobarbital (PB) in the development of carcinomas in the lungs of L-W rats. Lung cancer is a rare slow-growing spontaneous neoplasm in L-W rats. Their incidence increased from 4.4% in avg 25.6 months (spontaneously) to 23.8% in avg 19 months following a single IV inoculation of methylnitrosourea (MNU), and further increased to 57% in avg 15 months by adding phenobarbital to the diet of MNU-inoculated rats. Three stages of lung tumorigenesis were manifested in L-W rats following treatments with MNU, or MNU + PB: hyperplasia, adenoma, and carcinoma.

Proliferative bone lesions in rats fed a diet containing glucocorticoid for up to two years.

A glucocorticoid was fed in the diet to 50 Sprague-Dawley rats/sex at 0, 0.03, 0.06, 0.12, 0.25, 0.50, and 1.0 mg/kg/day for up to 2 yr. A total of 1,400 rats were examined. Bone neoplasms (5 osteosarcomas and 2 osteomas), involving the head, occurred in 7 males that were fed the test compound at the highest dose (0.25 mg/kg) with long-term survivors. One osteoma and 1 hyperostotic lesion were seen in 2 males receiving lower doses (0.06 mg/kg and 0.12 mg/kg, respectively); 1 female rat that received the highest dose (1 mg/kg) had an osteosarcoma. The results suggest, but do not confirm, a relationship between glucocorticoid exposure and bone proliferations in male Sprague-Dawley rats. Other proliferative bone lesions included hyperostosis in a 0.12-mg/kg male, osteoma in a 0.06-mg/kg male, and osteosarcoma in 1 female at 1.0 mg/kg. The purpose of this report is to characterize the incidence and morphology of primary bone proliferative lesions found in rats of 1-yr glucocorticoid toxicity and 2-yr carcinogenicity studies conducted in our laboratory.

Confounded carcinogenicity study of sodium fluoride in CD-1 mice.

To determine its carcinogenic potential, sodium fluoride (NaF) was fed to CD-1 mice for up to 97 weeks. Mice given NaF at a dose of 4, 10, or 25 mg/kg of body weight per day added to a low-fluoride diet were compared to controls given either an unsupplemented low-fluoride diet or laboratory chow. Nonneoplastic changes consistent with those previously recognized from fluoride toxicity were observed in teeth, bones, and joints. Unexpectedly, osteomas occurred in all groups. The incidence of osteomas was similar in groups given the low-fluoride control diet, laboratory chow, or NaF doses of 4 or 10 mg/kg per day. The incidence of osteomas in these groups was increased over that historically experienced at the laboratory and reported in the literature for CD-1 mice. The incidence of osteomas in the mice given 25 mg NaF/kg per day added to a low-fluoride diet was increased over that in the other groups. Osteomas were first observed at Week 55. No malignant bone tumors were observed during the course of the study. The locations, multiplicity, and morphologic features of the osteomas in all groups were similar to those associated with virus-induced bone tumors. Electron microscopic examination revealed abundant retrovirus particles in all osteomas examined from control and test mice. It was concluded that the study was confounded by a retrovirus which contributed to the induction of the osteomas. Because the study was confounded, it cannot be considered a valid bioassay to be used for risk assessment.

Osteomas in OF-1 mice: no alteration in biologic behavior during long-term treatment with cyclosporine.

During the course of a long-term oral study in OF-1 mice for the assessment of any carcinogenic potential of the immunosuppressive agent cyclosporine (CS-A), a high incidence of osteomas was found in all treatment groups as well as in controls. The incidences of osteoma-bearing mice were 20% in control male and 30% in control female mice; the respective incidences in all treated mice were 14.7% for males and 38% for females. The osteomas were found to occur in multiple sites in 70% of control males, in 73.3% of control females, and from all treated groups in 54.5% of males and 64.9% of females. The pelvis and sacrum were most frequently involved (42%), followed by the hindlimbs (32%), the skull (14.5%), the vertebral column (6.5%), the forelimbs (4%), and the sternum and ribs (1%) in control animals. The distribution of osteomas was similar in treated mice and did not differ significantly from controls. Histologic and ultrastructural analysis confirmed benign osteomas with abundant C-type viral particles. Thus a previously unobserved spontaneous high incidence of osteomas was reported in OF-1 mice. Immunosuppressive treatment with CS-A did not change the incidence or the biologic behavior of these osteomas.

Osteoma cutis: a case of probable exacerbation following treatment of severe acne with isotretinoin.

A florid case of osteoma cutis was observed following isotretinoin treatment of severe cystic acne in which a few scattered osteomata of the skin were observed prior to the treatment with isotretinoin.