Acute Gastric Dilatation in Nonhuman Primates: Review and Case Studies

Acute gastric dilatation occurs sporadically in laboratory-housed nonhuman primates. Clinical histories often include chronic drug administration, food restriction, accidental overfeeding, and prior anesthesia. Monkeys may be found dead or may have clinical signs of colic, abdominal distention, and dyspnea. Death in untreated cases is due to impaired venous return and cardiopulmonary failure. Gastric distention with fermented gaseous ingesta and congestion of the abdominal viscera are the predominant lesions. The cause of acute gastric dilatation is unknown, but it probably is multifactorial. Two principal factors seem to be intragastric fermentation associated with Clostridium perfringens, and abnormal gastric function.

Preclinical testing using tumors from genetically engineered mouse mammary models

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Background: Mouse models have been used extensively in preclinical testing of anticancer drugs. However, few of these models reflect the progression of human disease, and even fewer predict the performance of these drugs in clinical trials. Testing anticancer therapies in genetically engineered mouse (GEM) holds the promise of improving preclinical models and guiding the design of clinical trials. Unfortunately, the use of tumor-bearing GEM is hampered by the difficulty in simultaneously obtaining sufficient numbers of animals with the same stage of tumor development. The additional complexity in testing breast cancer therapies in the mouse is that all 10 mammary glands can develop tumors, frequently at different times. Methods: To circumvent the variable tumor latency and lack of synchrony in GEM, we transplanted tumor fragments or cell suspensions from multiple mammary tumor-bearing GEM into the mammary fat pad or subcutaneously into naïve syngeneic, immunodeficient athymic nude, or scid mice. Results: Tumors transplanted as fragments or cell suspensions derived from anterior mammary gland grew faster than the posterior tumors for serial passages without any significant morphologic differences. Cell suspensions using fresh or frozen cells were equally effective in generating tumors, and increasing the numbers of transplanted cells resulted in faster tumor growth. The transplantation strategy was reproducible in multiple breast cancer mouse models, including MMTV-PyMT, -Her2/neu, -wnt1/p53, BRCA1/p53, and others. Metastatic disease in the lungs was evident after removing the primary tumors at different rates for each mouse model. The transplanted primary tumors and the tumors arising in the original GEM had similar morphologic appearance and sensitivity to several chemotherapeutic and novel molecular targeted agents. Conclusions: We have established transplantable synchronous mammary tumors from GEM which also develop metastatic disease. These valuable mouse models are suitable for studying tumor-host interactions, tumor progression, and preclinical testing in a well-characterized molecular and genetic background. Testing these GEM tumors for conventional and novel molecular targeted therapies will be discussed.

No significant financial relationships to disclose.

Gadd45a acts as a modifier locus for lymphoblastic lymphoma

GADD:45a-/- and p53-/- mice and cells derived from them share similar phenotypes, most notably genomic instability. However, p53-/- mice rapidly develop a variety of neoplasms, while Gadd45a-/- mice do not. The two proteins are involved in a regulatory feedback loop, whereby each can increase the expression or activity of the other, suggesting that common phenotypes might result from similar molecular mechanisms. Mice lacking both genes were generated to address this issue. Gadd45a-/-p53-/- mice developed tumors with a latency similar to that of tumor-prone p53-/- mice. However, while p53-/- mice developed a variety of tumor types, nearly all Gadd45a-/-p53-/- mice developed lymphoblastic lymphoma (LBL), often accompanied by mediastinal masses as is common in human patients with this tumor type. Deletion of Gadd45a in leukemia/lymphoma-prone AKR mice decreased the latency for LBL. These results indicate that Gadd45a may act as modifier locus for T-cell LBL, whereby deletion of Gadd45a enhances development of this tumor type in susceptible mice. Gadd45a is localized to 1p31.1, and 1p abnormalities have been described in T-cell lymphomas. Related human tumor samples did not show Gadd45a deletion or mutation, although changes in expression could not be ruled out.

Identification of dynamically distinct subpopulations of T lymphocytes that are differentially affected by HIV

We examined the effects of human immunodeficiency virus infection on the turnover of CD4 and CD8 T lymphocytes in 17 HIV-infected patients by 30 min in vivo pulse labeling with bromodeoxyuridine (BrdU). The percentage of labeled CD4 and CD8 T lymphocytes was initially higher in lymph nodes than in blood. Labeled cells equilibrated between the two compartments within 24 h. Based on mathematical modeling of the dynamics of BrdU-labeled cells in the blood, we identified rapidly and slowly proliferating subpopulations of CD4 and CD8 T lymphocytes. The percentage, but not the decay rate, of labeled CD4 or CD8 cells in the rapidly proliferating pool correlated significantly with plasma HIV RNA levels for both CD4 (r = 0.77, P < 0.001) and CD8 (r = 0.81, P < 0.001) T cells. In six patients there was a geometric mean decrease of greater than 2 logs in HIV levels within 2 to 6 mo after the initiation of highly active antiretroviral therapy; this was associated with a significant decrease in the percentage (but not the decay rate) of labeled cells in the rapidly proliferating pool for both CD4 (P = 0.03) and CD8 (P < 0.001) T lymphocytes. Neither plasma viral levels nor therapy had an effect on the decay rate constants or the percentage of labeled cells in the slowly proliferating pool. Monocyte production was inversely related to viral load (r = -0.56, P = 0.003) and increased with therapy (P = 0.01). These findings demonstrate that HIV does not impair CD4 T cell production but does increase CD4 and CD8 lymphocyte proliferation and death by inducing entry into a rapidly proliferating subpopulation of cells.

2-difluoromethylornithine and dehydroepiandrosterone inhibit mammary tumor progression but not mammary or prostate tumor initiation in C3(1)/SV40 T/t-antigen transgenic mice

Female transgenic mice that express SV40 T/t antigens under the regulatory control of the rat C3(1) gene spontaneously develop multifocal mammary lesions that predictably evolve into invasive, hormone-independent carcinomas, whereas male mice are prone to develop prostate cancer. Chemopreventive agents were administered to female C3(1)/SV40 large T-antigen mice from 7 to 19 weeks of age, during which time the mammary lesions developed and progressed to invasive carcinomas. No significant differences in the numbers of preinvasive mammary intraepithelial neoplasia lesions (histologically similar to human ductal carcinoma in situ) were observed after 2 or 8 weeks of treatment between mice receiving either vehicle alone, dehydroepiandrosterone (DHEA), or 2-difluoromethylornithine (DFMO). However, a dose-response reduction in invasive carcinoma growth was observed for both DFMO, an inhibitor of ornithine decarboxylase, and DHEA, the primary steroid precursor to both androgens and estrogens in primates. Despite unaltered expression of the transgene, tumor incidence was reduced approximately 20% by DFMO (8000 mg/kg) and 30% by DHEA (4000 mg/kg; P < 0.05). Tumor multiplicity was reduced by approximately 50% by both DFMO and DHEA (P < 0.05). DFMO had a dose-dependent effect on total tumor burden, which was reduced by 25% at low doses (4000 mg/kg) and 70% at high doses (8000 mg/kg). DHEA reduced tumor burden by 50% and 66% at low (2000 mg/kg) and high (4000 mg/kg) doses, respectively. Interestingly, despite its inhibitory effects on tumor development, DHEA caused a dose-dependent increase of serum estradiol levels that we have previously shown to increase mammary tumor formation in this model. No effect on the development of the prostate cancer precursor lesions (prostate intraepithelial neoplasia) was observed when mice were treated with DHEA, DFMO, tocopherol acetate, selenomethionine, or 9-cis-retinoic acid, although the effects on late-stage prostate cancer development were not determined. These results demonstrate that despite the expression of the highly transforming C3(1)/SV40 large T-antigen transgene, this transgenic model can be used to study the effects of chemopreventive agents on mammary cancer progression. The tumor-inhibitory effects of DHEA and DFMO on mammary cancer growth appear to occur after the development of preinvasive lesions, suggesting that these agents inhibit tumor progression but not initiation.

Neonatal sunburn and melanoma in mice

Retrospective epidemiological data have indicated that cutaneous malignant melanoma may arise as a consequence of intense, intermittent exposure of the skin to ultraviolet radiation, particularly in children, rather than from the cumulative lifetime exposure that is associated with other forms of skin cancer. Here we use a genetically engineered mouse model to show that a single dose of burning ultraviolet radiation to neonates, but not adults, is necessary and sufficient to induce tumours with high penetrance which are reminiscent of human melanoma. Our results provide experimental support for epidemiological evidence that childhood sunburn poses a significant risk of developing this potentially fatal disease.

Antibodies to CD40 induce a lethal cytokine cascade after syngeneic bone marrow transplantation

CD40 stimulation, by either antibody or ligand, has been shown to inhibit the growth of a variety of neoplastic cells, both in vivo and in vitro. In this study, we assessed the effects of CD40 stimulation using a murine agonistic CD40 monoclonal antibody (MoAb) (FGK115) or a soluble recombinant murine CD40 ligand (srmCD40L) in both lethally irradiated and nonirradiated BALB/c mice. Toxicity after CD40 stimulation was not observed in nonirradiated animals receiving up to 100 microg of the agonist anti-CD40 MoAb. However, as little as 10 microg of the agonistic anti-CD40 MoAb induced acute toxicity resulting in 100% morbidity of lethally irradiated animals by 4 days after irradiation. Histological evaluation of animals receiving anti-CD40 MoAb revealed severe intestinal lesions with disruption of the villi, goblet cell depletion, and crypt hyperplasia of the small intestine, colon, and cecum. Delaying the administration of anti-CD40 MoAb or reducing the amount of irradiation given resulted in increased survival and less severe lesions. Analysis of serum cytokine levels in lethally irradiated mice receiving agonistic anti-CD40 showed a marked increase of interferon (IFN)-gamma. Lethally irradiated IFN-gamma knockout mice given the agonistic anti-CD40 MoAb demonstrated significant increases in survival and minimal gut lesions compared with wild-type mice receiving the same regimen, suggesting that IFN-gamma plays a major role in this toxic reaction. These results indicate that CD40 stimulation using agonistic antibodies following lethal irradiation leads to a fatal, cytokine-induced disease affecting the intestine.

Lsh, a SNF2 family member, is required for normal murine development

Lsh is a member of the SNF2 family of chromatin remodelers, that regulate diverse biological processes such as replication, repair and transcription. Although expression of Lsh is highly tissue specific in adult animals, Lsh mRNA is detectable in multiple tissues during embryogenesis. In order to determine the physiologic role of Lsh during murine development and to assess its unique function in adult mice, we performed targeted deletion of the Lsh gene using homologous recombination in murine embryonic stem cells. Lsh-/- embryos occurred with the expected Mendelian frequency after implantation and during embryogenesis. However, Lsh-/- mice died within a few hours after birth. Furthermore, newborn mice were 22% lower in weight in comparison with their littermates and showed renal lesions. Thus Lsh is a non-redundant member of the SNF2 family and is essential for normal murine development and survival.

Cyclooxygenase-2, P-glycoprotein-170 and drug resistance; is chemoprevention against multidrug resistance possible?

BACKGROUND

It is generally accepted that P-glycoprotein 170 (MDR1/Pgp170) expression in breast tumors results in poor response to chemotherapy due to its ability to export chemotherapeutic agents. Studies indicate that the use of non-steroidal anti-inflammatory drugs (NSAIDs) may enhance the anti-tumor activity of cancer chemotherapeutic agents and reduce the risk of many cancers. The best known function of NSAIDs is to block the enzyme cyclooxygenase (Cox), the rate limiting enzyme in the conversion of arachidonic acid to prostaglandins. In this study we investigated whether expression of the inducible isoform of Cox (Cox-2) is linked with the multidrug resistance phenotype in breast cancer.

METHODS

Expression of Cox-2 and MDR1/Pgp170 was investigated in tumor specimens along with normal epithelium in breast cancer patients using immunohistochemisrty. Expression of Cox-2, MDR1/Pgp170, Protein Kinase C (PKC), and Activator Protein 1 (AP1) were investigated in a series of increasingly resistant human MCF-7 breast cancer cells compared to wild type using immunohistochemistry, Western blots, Northern blots, RT-PCR, and Southern blots.

RESULTS

Immunohistochemical analyses of human breast tumor specimens revealed a strong correlation between expression of Cox-2 and MDR1/Pgp170. In drug resistant cell lines that over-express MDR1/Pgp170 there was also significant up-regulation of Cox-2 expression. In addition, PKC and AP1 subunits c-Jun and c-Fos were also upregulated. We hypothesized that increased prostaglandin production by Cox-2 induces PKC and the expression of transcriptional factor c-Jun, which in turn, induces the expression of MDR1/Pgp170.

CONCLUSION

We propose that pretreatment with selective Cox-2 inhibitors may be useful in the prevention of multidrug resistance in response to cancer chemotherapy and should be further evaluated.

Opposing roles of interferon-gamma on CD4+ T cell-mediated graft-versus-host disease: effects of conditioning

Although alloreactive T cells are required for the induction of graft-versus-host disease (GVHD), other factors can influence outcome in murine models of the disease. Lethal total body irradiation (TBI) conditioning regimens followed by reconstitution with allogeneic lymphohematopoietic cells results in the generation of donor anti-host cytotoxic T lymphocyte (CTL)-mediated solid organ (gut, liver, skin) destruction. In contrast, donor anti-host CTL-mediated hematopoietic failure is the primary cause of morbidity following sublethal TBI. To determine the role of interferon (IFN)-gamma in graft-versus-host reactions against hematopoietic and solid organ targets, we used IFN-gamma knockout mice as donors in both lethal TBI and bone marrow transplantation (BMT) rescue and sublethal TBI models. In this report, we show that CD4+ T cells from IFN-gamma knockout (KO) mice resulted in accelerated GVHD after lethal TBI/BMT using a single major histocompatibility class II mismatch model. In marked contrast, the use of these same IFN-gamma KO CD4+ donor cells in combination with sublethal TBI significantly ameliorated GVHD-associated mortality. In these recipients, severe anemia, bone marrow aplasia, and intestinal lesions were observed in the presence but not the absence of donor-derived IFN-gamma. Administration of anti-IFN-gamma antibodies to sublethally irradiated recipients of wild-type donor cells confirmed the role of IFN-gamma depletion in CD4+ T cell-mediated GVHD. In conclusion, the extent of conditioning markedly affects the role of IFN-gamma in GVHD lesions mediated by CD4+ T cells. In models using sublethal TBI, the absence of IFN-gamma is protective from GVHD, whereas in lethal TBI situations, the loss is deleterious.

Gastrointestinal cells of IL-7 receptor null mice exhibit increased sensitivity to irradiation

IL-7 is a critical cytokine in the development of T and B cells but little is known about its activity on nonhematopoietic cells. An unexpected finding was noted in allogeneic bone marrow transplant studies using IL-7 receptor null (IL-7R alpha(-/-)) mice as recipients. These mice exhibited a significantly greater weight loss after total body irradiation compared with wild type, IL-7R alpha(+/+), mice. Pathological assessment indicated greater intestinal crypt damage in IL-7R alpha(-/-) recipients, suggesting these mice may be predisposed to gut destruction. Therefore, we determined the effect of the conditioning itself on the intestinal tract of these mice. IL-7R alpha(-/-) mice and IL-7R alpha(+/+) mice were irradiated and examined for lesions and apoptosis within the small intestine. In moribund animals, IL-7R alpha(-/-) mice had extensive damage in the small intestine, including marked ablation of the crypts and extreme shortening of villi following 1500 cGy total body irradiation. In contrast, by 8 days after irradiation, the small intestines of IL-7R alpha(+/+) mice had regenerated as distinguished by normal villus length and hyperplastic crypts. Following 750 cGy irradiation, IL-7R alpha(-/-) mice had a higher proportion of apoptotic cells in the crypts and an accompanying increase in the pro-apoptotic protein Bak was expressed in intestinal epithelial cells. These results demonstrate the increased radiosensitivity of intestinal stem cells within the crypts in IL-7R alpha(-/-) mice and a role for IL-7 in the protection of radiation-induced apoptosis in these same cells. This study describes a novel role of IL-7 in nonhematopoietic tissues.

Hyalinosis and Ym1/Ym2 gene expression in the stomach and respiratory tract of 129S4/SvJae and wild-type and CYP1A2-null B6, 129 mice

The C57BL/6, 129, and B6,129 mouse strains or stocks have been commonly used to generate targeted mutant mice. The pathology of these mice is not well characterized. In studies of these aging mice, we found high incidences of hyalinosis (eosinophilic cytoplasmic change) in the glandular stomach, respiratory tract, bile duct, and gall bladder of B6,129 CYP1A2-null and wild-type mice as well as in both sexes of the background 129S4/SvJae strain. The gastric lesions of the glandular stomach were found in 95.7% of female CYP1A2-null mice as well as in 45.7% of female 129S4/SvJae animals. The eosinophilic protein isolated from characteristic hyaline gastric lesions was identified as Ym2, a member of the chitinase family. Immunohistochemistry, using rabbit polyclonal antibodies to oligopeptides derived from the Ym1 sequence, detected focal to diffuse reactivity within both normal and abnormal nasal olfactory and respiratory epithelium, pulmonary alveolar macrophages, bone marrow myeloid cells, and the squamous epithelium of the forestomach and epithelium of the glandular stomach. Alveolar macrophages in acidophilic pneumonia, a major cause of death of aging 129 mice, and in mice with the me mutation also were highly immunoreactive. The possible cause of this protein excess in gastric and other lesions and its possible functions are discussed.

Age-related alterations in 32P-postlabeled DNA adducts in livers of mice infected with the tumorigenic bacterial pathogen, Helicobacter hepaticus

Helicobacter hepaticus causes chronic active hepatitis and liver tumors in mice, with associated increase in reactive oxygen species. Indigenous (I)-compounds are bulky DNA adducts present at low levels and detected by 32P-post-labeling. Some may be caused by reactive oxygen species; others occur normally and decrease during liver tumorigenesis. The identity of most is unknown. We investigated whether mouse liver infection by H. hepaticus and resulting progression of hepatic lesions would be associated with qualitative or quantitative changes in I-compounds. Mice were 3, 6, 9, and 12 months of age; liver disease ranged from minimal through marked. In control A/J mice, up to 20 I-compounds were detected, and the total level of these did not change with age, whereas 11 individual I-compounds showed marked age-related differences. These appeared to be coordinately regulated, as the total of these 11 adducts was constant at 6-12 months. In A/JNCr mice naturally infected with H. hepaticus, up to 12 hepatic I-compounds were found. Total levels varied markedly with age and were high at 6 and 12 months. Neither total adduct levels, nor the amount of any individual adduct, correlated positively with severity of hepatic lesions; in some cases, highest levels were found in livers with least disease. Thus, liver infection and tumorigenesis by H. hepaticus was not associated with an increase in any 32P-postlabeled DNA adduct. Marked, and distinct, age-related changes in total or individual adducts in control and infected mice suggest a role in the physiological alterations of aging and in host response to infection.

Accelerated ultraviolet radiation-induced carcinogenesis in hepatocyte growth factor/scatter factor transgenic mice

The dramatic rise in incidence of malignant melanoma experienced by populations both within the United States and throughout the world over the last several decades has been attributed to enhanced exposure to the UV spectrum of sunlight radiation. This hypothesis can now be tested using genetically engineered mouse models predisposed to malignant melanoma. Here we use melanoma-prone transgenic mice inappropriately expressing hepatocyte growth factor/scatter factor (HGF/SF) in the skin as an experimental model system to ascertain the consequences of a chronic regimen of suberythemal UV radiation on melanoma genesis. HGF/SF is a multifunctional regulator capable of stimulating growth, motility, invasiveness, and morphogenetic transformation in cells, including melanocytes, expressing its receptor tyrosine kinase Met. HGF/SF transgenic mice demonstrate ectopic interfollicular localization and accumulation of melanocytes within the truncal dermis, epidermis, and junction and if untreated develop primary cutaneous melanoma with a mean onset age of approximately 21 months. Transgenic mice and their wild-type littermates subjected to UV radiation three times weekly using FS40 sunlamps (60% UVB and 40% UVA), with daily UV doses graded from 2.25 to 6.0 kJ/m2, developed skin tumors with a mean onset age of 26 and 37 weeks, respectively (P < 0.001, Kaplan-Meier log rank test). However, the repeated doses of suberythemal UV radiation used in this study failed to accelerate melanoma genesis, instead inducing the development of nonmelanoma tumors that included squamous cell carcinomas, squamous papillomas, and sarcomas. The conspicuous absence of melanocytic tumors occurred despite the immunohistochemical detection of a significant stimulation (P < 0.001) in melanocyte-specific bromodeoxyuridine incorporation in response to only 2 weeks of UV irradiation (total UV dose of 13.5 kJ/m2), resulting in 2.6- and 4.6-fold increases in the number of melanocytes in the dermis and epidermis, respectively. These data indicate that chronic suberythemal UV radiation preferentially favors the development of nonmelanocytic over melanocytic neoplasms in this transgenic animal, consistent with the pathogenesis proposed for sun exposure-associated skin cancer based on retrospective studies in the human population. Our findings suggest that the HGF/SF transgenic mouse will be useful as an experimental model for determining the consequences of exposure to various regimens of UV radiation and for elucidating the mechanisms by which such consequences are realized.

The p53 response to DNA damage in vivo is independent of DNA-dependent protein kinase

Ionizing radiation (IR) exposure causes mammalian cells to undergo p53-dependent cell cycle arrest and/or apoptosis. The in vivo role of DNA-dependent protein kinase (DNA-PK) in the transduction of the DNA damage signal to p53 remains unresolved. To determine the relationship between DNA-PK and p53, we studied the cell cycle and apoptotic responses to IR in mice deficient in DNA-PK. Using the slip mouse, which harbors an inactivating mutation of the DNA-PK catalytic subunit (DNA-PKcs), we demonstrated not only that these DNA-PKcs null mutants were highly radiosensitive but also that upon IR treatment, p53 accumulated in their cultured cells and tissue. Induced p53 was transcriptionally active and mediated the induction of p21 and Bax in slip cells. Examination of the thymic cell cycle response to IR treatment indicated that the slip G(1)/S-phase cell cycle checkpoint function was intact. We further show that slip mice exhibited a higher level of spontaneous thymic apoptosis as well as a more robust apoptotic response to IR than wild-type mice. Together, these data demonstrate that the p53-mediated response to DNA damage is intact in cells devoid of DNA-PK activity and suggest that other kinases, such as the product of the gene (ATM) mutated in ataxia telangiectasia, are better candidates for regulating IR-induced phosphorylation and accumulation of p53.

The mammary pathology of genetically engineered mice: the consensus report and recommendations from the Annapolis meeting

NIH sponsored a meeting of medical and veterinary pathologists with mammary gland expertise in Annapolis in March 1999. Rapid development of mouse mammary models has accentuated the need for definitions of the mammary lesions in genetically engineered mice (GEM) and to assess their usefulness as models of human breast disease. The panel of nine pathologists independently reviewed material representing over 90% of the published systems. The GEM tumors were found to have: (1) phenotypes similar to those of non-GEM; (2) signature phenotypes specific to the transgene; and (3) some morphological similarities to the human disease. The current mouse mammary and human breast tumor classifications describe the majority of GEM lesions but unique morphologic lesions are found in many GEM. Since little information is available on the natural history of GEM lesions, a simple morphologic nomenclature is proposed that allows direct comparisons between models. Future progress requires rigorous application of guidelines covering pathologic examination of the mammary gland and the whole animal. Since the phenotype of the lesions is an essential component of their molecular pathology, funding agencies should adopt policies ensuring careful morphological evaluation of any funded research involving animal models. A pathologist should be part of each research team.

The C3(1)/SV40 T-antigen transgenic mouse model of mammary cancer: ductal epithelial cell targeting with multistage progression to carcinoma

The 5' flanking region of the C3(1) component of the rat prostate steroid binding protein (PSBP) has been used to successfully target the expression of the SV40 large T-antigen (Tag) to the epithelium of both the mammary and prostate glands resulting in models of mammary and prostate cancers which histologically resemble the human diseases. Atypia of the mammary ductal epithelium develops at about 8 weeks of age, progressing to mammary intraepithelial neoplasia (resembling human ductal carcinoma in situ [DCIS]) at about 12 weeks of age with the development of invasive carcinomas at about 16 weeks of age in 100% of female mice. The carcinomas share features to what has been classified in human breast cancer as infiltrating ductal carcinomas. All FVB/N female mice carrying the transgene develop mammary cancer with about a 15% incidence of lung metastases. Approximately 10% of older male mice develop anaplastic mammary carcinomas. Unlike many other transgenic models in which hormones and pregnancy are used to induce a mammary phenotype, C3(1)/Tag mice develop mammary tumors in the mammary epithelium of virgin animals without hormone supplementation or pregnancy. Although mammary tumor development appears hormone-responsive at early stages, invasive carcinomas are hormone-independent, which corresponds to the loss of estrogen receptor-alpha expression during tumor progression. Molecular and biologic factors related to mammary tumor progression can be studied in this model since lesions evolve over a predictable time course. Genomic alterations have been identified during tumor progression, including an amplification of the distal portion of chromosome 6 containing ki-ras and loss of heterozygosity (LOH) in other chromosomal regions. We have demonstrated that stage specific alterations in the expression of genes which are critical regulators of the cell cycle and apoptosis are functionally important in vivo. C3(1)/Tag mice appear useful for testing particular therapies since growth of the mammary tumors can be reduced using chemopreventive agents, cytokines, and an anti-angiogenesis agent.

Chronic toxic and carcinogenic effects of oral cadmium in the Noble (NBL/Cr) rat: induction of neoplastic and proliferative lesions of the adrenal, kidney, prostate, and testes

Based on the occurrence of pulmonary cancers in exposed populations, cadmium is classified as a human carcinogen. More controversial target sites for cadmium in humans include the prostate and kidney, where some studies have shown a link between cadmium and cancer. In Wistar rats cadmium induces tumors in the ventral prostate. The relevance of such lesions to humans is debated since the rat ventral lobe, unlike the dorsolateral lobe, has no embryological homolog in the human prostate. Cadmium has not been linked with renal tumors in rodents but is a potent nephrotoxin. In this work we studied the effects of oral cadmium in the Noble (NBL/Cr) rat with particular attention to proliferative lesions of the prostate and kidneys. Cadmium (as CdCl2) was given ad libitum throughout the study in the drinking water at doses of 0, 25, 50, 100, and 200 ppm Cd to groups (initial n = 30) of male rats, which were observed for up to 102 wk. At the lower doses of cadmium (< or =50 ppm) a clear dose-related increase in total proliferative lesions of the prostate (ventral and dorsolateral lesions combined) occurred (0 ppm = 21% incidence, 25 ppm = 46%, 50 ppm = 50%; trend p < .03). These lesions were described as intraepithelial hyperplasia with occasional areas of atypical epithelial cells without stromal invasion. The lesions occurred primarily in the dorsolateral prostate with cadmium exposure and most frequently showed three or more foci within each specimen. At higher doses, prostatic proliferative lesions declined to control levels. The loss of prostatic response at the higher doses was likely due to diminished testicular function secondary to cadmium treatment. This was reflected in lesions indicative of testicular hypofunction at the highest cadmium dose, namely, interstitial cell hyperplasia, and a strong correlation between cadmium dose and total proliferative lesions of the testes (hyperplasias and tumors combined). Renal tumors (mainly mesenchymal and pelvic transitional cell), although few in number, showed a positive correlation with cadmium dose, as did pelvic transitional epithelial hyperplasia. Renal lesions were not associated with any cadmium-induced changes in age-related chronic nephropathy. The incidence of pheochromocytomas of the adrenal was increased by cadmium but only at the 50 ppm dose. Inflammatory lesions of the liver and spleen were common at higher doses and showed strong trends based on dose. These results indicate that oral cadmium can induce proliferative lesions in the prostate and kidney of the Noble rat. The finding of proliferative lesions of dorsolateral prostate in rats has presumed relevance to human prostate cancers.

Vascular endothelial growth factor and basic fibroblast growth factor induce expression of CXCR4 on human endothelial cells: In vivo neovascularization induced by stromal-derived factor-1alpha

The contribution of chemokines toward angiogenesis is currently a focus of intensive investigation. Certain members of the CXC chemokine family can induce bovine capillary endothelial cell migration in vitro and corneal angiogenesis in vivo, and apparently act via binding to their receptors CXCR1 and CXCR2. We used an RNAse protection assay that permitted the simultaneous detection of mRNA for various CXC chemokine receptors in resting human umbilical vein endothelial cells (HUVECs) and detected low levels of only CXCR4 mRNA. Stimulation of HUVECs with vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF) up-regulated levels of only CXCR4 mRNA. CXCR4 specifically binds the chemokine stromal-derived factor-1alpha (SDF-1alpha). Competitive binding studies using 125I-labeled SDF-1alpha with Scatchard analysis indicated that VEGF or bFGF induced an average number of approximately 16,600 CXCR4 molecules per endothelial cell, with a Kd = 1.23 x 10(-9) mol/L. These receptors were functional as HUVECs and human aorta endothelial cells (HAECs) migrated toward SDF-1alpha. Although SDF-1alpha-induced chemotaxis was inhibited by the addition of a neutralizing monoclonal CXCR4 antibody, endothelial chemotaxis toward VEGF was not altered; therefore, the angiogenic effect of VEGF is independent of SDF-1alpha. Furthermore, subcutaneous SDF-1alpha injections into mice induced formation of local small blood vessels that was accompanied by leukocytic infiltrates. To test whether these effects were dependent on circulating leukocytes, we successfully obtained SDF-1alpha-induced neovascularization from cross sections of leukocyte-free rat aorta. Taken together, our data indicate that SDF-1alpha acts as a potent chemoattractant for endothelial cells of different origins bearing CXCR4 and is a participant in angiogenesis that is regulated at the receptor level by VEGF and bFGF.

Expression of metallothionein protein in the lungs of Wistar rats and C57 and DBA mice exposed to cadmium oxide fumes

Chronic exposure to inhaled cadmium (Cd) has been shown to induce lung tumors in rats (Wistar strain) but not in mice (NMRI strain). The protein metallothionein (MT) plays an important role in Cd detoxification, and it has been suggested that differential inducibility of pulmonary MT may lead to interspecies susceptibility differences to inhaled Cd. Interstrain differences in the pulmonary response of the MT gene to Cd stimuli have not been examined in rats or mice. We compared pulmonary MT expression in Wistar Furth (WF) rats with that in DBA and C57 mice, following a single 3-h exposure to CdO fumes containing 1 mg Cd/m3. Induction of the MT gene was assessed by the levels of MT-I and MT-II transcripts, MT-protein content, and number of MT-labeled alveolar and bronchiolar epithelial cells immediately after Cd exposure and 1, 3, and 5 days later. Control animals were exposed to air/argon furnace gases. We observed differential intra- and interspecies inducibility of the MT gene in the lung following Cd inhalation. DBA mice exhibited greater levels of MT-mRNA, mainly for the MT-I isoform, MT-protein content, and number of MT positive cells relative to C57 mice. WF rats showed lower transcription and translation responses of the MT gene upon Cd stimuli than C57 mice. The present results, in concert with our previous findings of higher lung cell proliferation in Cd-exposed C57 relative to DBA mice, predict greater susceptibility of C57 to the carcinogenic effects of inhaled Cd. Furthermore, the low transcriptional and translation responses of the MT gene to Cd stimuli in WF rats might explain the higher susceptibility of this rat strain to develop malignant lung tumors after chronic exposure to Cd via inhalation. Parallel to our findings in mice, differences in the responsiveness of lung MT gene may exist across rat strains. Thus intraspecies genetic variability in pulmonary MT may influence the susceptibility of rats or mice to lung carcinogenesis induced by inhalation of Cd compounds.

Transforming growth factor-beta1 is a new form of tumor suppressor with true haploid insufficiency

Components of the transforming growth factor-beta (TGF-beta) signal pathway function as classic tumor suppressors, but the role of the TGF-betas themselves is less clear. Here we show that mice heterozygous for deletion of the TGF-beta1 gene express only 10-30% of wild-type TGF-beta1 protein levels. Although grossly normal, these mice have a subtly altered proliferative phenotype, with increased cell turnover in the liver and lung. Treatment of these mice with chemical carcinogens resulted in enhanced tumorigenesis when compared with wild-type littermates. However, tumors in the heterozygous mice did not lose the remaining wild-type TGF-beta1 allele, indicating that the TGF-beta1 ligand is a new form of tumor suppressor that shows true haploid insufficiency in its ability to protect against tumorigenesis.

Inflammatory large bowel disease in immunodeficient rats naturally and experimentally infected with Helicobacter bilis

Proliferative and ulcerative typhlitis, colitis, and proctitis were found incidentally in a breeding colony of male athymic nude (Cr:NIH-rnu) rats. Within the crypts of the large intestine, modified Steiner's silver stain revealed spiral organisms that were identified by culture, polymerase chain reaction, and sequencing to be Helicobacter bilis. The large bowel disease was reproduced in H. bilis-free male athymic nude rats that were injected intraperitoneally with a culture of H. bilis from the affected colony. The organism was isolated from the feces and cecum of the experimentally infected rats. H. bilis should be considered a potential pathogen in immunocompromised rats. The infection in immunocompromised rats may serve as an animal model for inflammatory large bowel disease.

Distinct time courses of increase in cytochromes P450 1A2, 2A5 and glutathione S-transferases during the progressive hepatitis associated with Helicobacter hepaticus

Mice naturally infected by Helicobacter hepaticus develop a chronic active hepatitis leading to hepatocellular carcinoma. This mouse model of liver cancer was used to examine the impact of bacterial infection on the hepatic expression and activity of enzymes involved in carcinogen bioactivation (phase I enzymes) and detoxification (phase II enzymes). No major differences in total cytochrome P450 (CYP) content were found between control and infected mice during the course of the study. The most striking modulations of individual isoenzymes were the increases in immunohistochemical staining observed for CYP1A and CYP2A5 in relation to increasing age and liver lesions. The increase in CYP2A5 in mice aged over 12 months was confirmed by the observed increases in coumarin 7-hydroxylation (CYP2A5 substrate) in vitro and CYP2A5 mRNA levels by Northern blot analysis. Immunoblotting confirmed the specific induction of CYP1A2 in infected mice 12 and 18 months of age. Perfusion of liver with nitroblue tetrazolium, an indicator for superoxide formation, demonstrated that in livers of infected mice, hepatocytes often co-expressed CYP2A5 and formazan deposition. Concerning phase II enzymes, an enhancement of glutathione S-transferase (GST) activities, related to the disease process, was observed in infected mice. An age-specific increase of GSTpi and A4.4 (early stage of disease) and GST YaYa (>9 months) expression was also demonstrated by immunohistochemical staining. In contrast, catalase and glutathione-peroxidase activities, as well as reduced glutathione content were decreased in the early stages of disease (3-9 months) in infected mice compared to age-matched control mice. Overall, these results suggest that alterations in CYP and GST expression may contribute to the aetiology of tumour incidence due to H. hepaticus infection via production of reactive oxygen species.

Immunologic and hematopoietic effects of CD40 stimulation after syngeneic bone marrow transplantation in mice

CD40 is a molecule present on multiple cell types including B lymphocyte lineage cells. CD40 has been shown to play an important role in B cell differentiation and activation in vitro, although little is known concerning the effects of CD40 stimulation in vivo. We therefore examined the effects of CD40 stimulation in mice using a syngeneic bone marrow transplantation (BMT) model in an effort to augment B cell recovery after high dose therapy with hematopoietic reconstitution. After the BMT, mice were treated with or without 2-6 microg of a soluble recombinant murine CD40 ligand (srmCD40L) given intraperitoneally twice a week. A significant increase in B cell progenitors (B220+/ surface IgM-) was observed in the bone marrow of mice receiving the srmCD40L. The treated recipients also demonstrated improved B-cell function with increases in total serum immunoglobulin and increased splenic mitogen responsiveness to LPS being noted. Additionally, srmCD40L treatment promoted secondary lymphoid organ repopulation, accelerating germinal center formation in the lymph nodes. Total B cell numbers in the periphery were not significantly affected even with continuous srmCD40L administration. Lymphocytes obtained from mice treated with the ligand also had increases in T cell mitogen and anti-CD3 mAb responsiveness and acquired the capability to produce IL-4. Surprisingly, treatment with srmCD40L also produced hematopoietic effects in mice, resulting in an increase of BM and splenic hematopoietic progenitor cells in the mice after BMT. Treatment with srmCD40L significantly increased granulocyte and platelet recovery in the peripheral blood. Incubation of BMC with srmCD40L in vitro also resulted in increased progenitor proliferation, demonstrating that the hematopoietic effects of the ligand may be direct. Thus, stimulation of CD40 by its ligand may be beneficial in accelerating both immune and hematopoietic recovery in the setting of bone marrow transplantation.

Lack of p53 and ras mutations in Helicobacter hepaticus-induced liver tumors in A/JCr mice

Helicobacter hepaticus is a recently discovered bacterium that invades mouse liver causing chronic active hepatitis followed by development of preneoplastic hepatocellular foci, hepatocellular adenomas and carcinomas. This establishes a unique animal model for study of the mechanisms of cancer development due to a chronic bacterial infection. A possible mechanism of bacteria-associated tumorigenesis is mutation of oncogenes or tumor suppressor genes. Since mutations in ras oncogenes have been widely detected in a variety of chemically induced and spontaneous mouse liver tumors and specific mutations in the p53 tumor suppressor gene have been associated with human bladder cancers attributed to chronic schistosomal infection, we studied exons 1 and 2 of the N-, K- and H-ras genes and exons 5-8 of the p53 gene for the presence of point mutations in 25 liver tumors from 10 naturally infected A/JCr mice, ranging in age from 16 to 24 months. The 20 adenomas and five carcinomas varied in size from 0.1 to 2.3 cm and arose in livers characterized by a wide assortment of pathological profiles, including hepatitis, inflammation, hyperplasia, hypertrophy, leukocyte infiltration, necrosis and focal phenotypic alteration. DNA samples extracted from formalin-fixed paraffin-embedded tissues were screened by PCR/SSCP analysis and showed no mutations in the analyzed genes. Complete absence of mutations in ras genes in 25 mouse liver tumors is unusual. Other genes may be targeted or H. hepaticus infection causes liver cancer through other pathways than direct damage to DNA.

Adoptive immunotherapy involving recombinant human M-CSF and R24 anti-melanoma antibody induces human T-cell infiltration into human melanoma xenografts

Directed motion toward and infiltration of tumor masses by effector cells is essential for successful adoptive immunotherapy. A human/SCID mouse chimeric system was used to examine whether an antitumor antibody and recombinant human monocyte colony-stimulating factor (rhM-CSF) could promote human T-cell infiltration of a human tumor in vivo. Fourteen days after subcutaneous injection of the human melanoma cell line M-14 into SCID recipients, several adoptive immunotherapy regimens were initiated using activated human T cells, an anti-melanoma monoclonal antibody (MoAb) (R24), and rhM-CSF. Effects on tumor growth and human T-cell infiltration into the tumor were assessed. Compared with other treatment groups, only mice treated with the combination of activated human T cells, anti-tumor MoAb, and rhM-CSF demonstrated a significant cellular infiltrate in the melanoma. Immunohistology demonstrated human T cells present in the tumor up to 7 days after injection. Groups treated with rhRANTES or rmGM-CSF in place of rhM-CSF exhibited markedly less human T-cell infiltration. Additionally, only mice treated with human T cells, R24, and rhM-CSF demonstrated a significant antitumor response in vivo. This model suggests that activated human T cells can be specifically targeted to in vivo tumor sites by combined treatment with an antitumor antibody and rhM-CSF.

Inflammatory large bowel disease in immunodeficient mice naturally infected with Helicobacter hepaticus

Large bowel disease detected clinically by rectal prolapse was studied in 64 immunodeficient mice (37 athymic NCr-nu/nu, 12 BALB/c AnNCr-nu/nu, 9 C57BL/6NCr-nu/nu, and 6 C.B17/Icr-scid/NCr) naturally infected with Helicobacter hepaticus. Rectal prolapse was found in approximately 5% of immunodeficient mice maintained in a research facility over a period of 3.5 years. All mice had various degrees of chronic proliferative typhlitis, colitis, and proctitis, usually without concomitant hepatitis. Some mice had severe proliferative proctitis with cystic hyperplasia. Histologic study of the large bowel of 48 athymic NCr-nu/nu mice without H. hepaticus infection and housed in another clean facility revealed only 12% of the mice with minimal-to-mild large bowel inflammation. Helicobacter hepaticus infection is associated with large bowel disease in immunodeficient mice but is not seen in H. hepaticus-infected immunocompetent mice. This new pathogenic bacterial infection should be considered as another potential cause or co-factor for rectal prolapse and large bowel disease in mice.

Chemopreventive activity of tamoxifen, N-(4-hydroxyphenyl)retinamide, and the vitamin D analogue Ro24-5531 for androgen-promoted carcinomas of the rat seminal vesicle and prostate

We evaluated the ability of dietary N-(4-hydroxyphenyl)retinamide; 1 alpha,25-dihydroxy-16-ene-23-yne-26,27-hexafluorocholecalcifero l (Ro24-5531); and tamoxifen to inhibit the development of androgen-promoted carcinomas of the accessory sex organs of male Lobund-Wistar rats. Invasive carcinomas of the seminal vesicle (SV) and anterior prostate (AP) were induced in Lobund-Wistar rats with three different combinations of initiator [N-nitroso-N-methylurea (NMU)] and promoter [testosterone propionate (TP)]: (a) high-dose NMU (30 mg/kg) + high-dose TP (20 mg via implant every 2 months); (b) high-dose NMU + low-dose TP (10 mg implanted every 2 months); or (c) low-dose NMU (15 mg/kg) + low-dose TP. During the period of TP administration, rats were fed a diet supplemented with either N-(4-hydroxyphenyl)retinamide (1 or 2 mmol/kg diet), Ro24-5531 (1.25 or 2.5 nmol/kg diet), tamoxifen (0.5 or 5 mg/kg diet), or vehicle alone. After sacrifice at 8.5 or 11 months, the prostate-seminal vesicle complex from each rat was processed in toto and histologically staged as to the extent of tumor involvement. In animals given low-dose TP, all three agents were significantly effective at reducing the incidence of invasive carcinomas of the SV and, to a lesser degree, the AP. Of the three agents, tamoxifen given in high dose (5 mg/kg) had the strongest activity, reducing the occurrence of invasive SV carcinomas from 72-83% in controls to 6% (P = 0.0001) and the occurrence of invasive AP carcinomas from 50-72% to 18-22% (P < 0.05).

Promotion of N-nitrosodiethylamine-initiated hepatocellular tumors and hepatoblastomas by 2,3,7,8-tetrachlorodibenzo-p-dioxin or Aroclor 1254 in C57BL/6, DBA/2, and B6D2F1 mice

To investigate the hypothesis that tumor promotion by chlorinated aromatic hydrocarbons involves Ah receptor occupation and subsequent induction of cytochromes P-450 1a-1, effects of Aroclor 1254 or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were examined in N-nitrosodiethylamine-initiated mice with different Ah receptor phenotype. Levels of cytochromes P-450 1a and 2b were measured by enzyme assay and Western immunoblots. Males of the C57BL/6, DBA/2, or (C57BL/6 x DBA/2)F1 (hereafter referred to as "B6D2F1") strain were initiated with a single i.p. dose of N-nitrosodiethylamine (90 mg/kg body weight), followed by either multiple doses of TCDD (0.05 micrograms/kg) weekly or Aroclor 1254 chronically in the diet (100 ppm) for 20 weeks, and then no treatment for 24 weeks. Lung tumor incidence or multiplicity was not altered by either of the promoters. Liver tumor incidence was similar among the three strains after N-nitrosodiethylamine alone (14, 21, and 21%, respectively). In DBA/2 mice, TCDD neither induced Cyp 1a nor promoted liver tumors. Aroclor caused an 8-fold induction of hepatic Cyp 2b, which was its maximum at the 12-week time point but did not promote tumors. Inductions of hepatic Cyp 1a by TCDD and 1a and 2b by Aroclor were similar in C57BL/6 and B6D2F1 mice, but tumor promotion responses were quite different. Dietary Aroclor significantly promoted liver tumors in C57BL/6 mice (59 versus 14%) but not in B6D2F1 mice (24 versus 21%). Repeated TCDD promoted only in B6D2F1 mice (52 versus 21%) and not in C57BL/6 mice (19 versus 14%). Thus, whereas these data confirm that a functional Ah receptor is required for liver tumor promotion, the degree of activation as measured by induction of Cyp 1a is not directly related to the degree of tumor-promoting capability. Other genetic factors must play a role in mediating the final tumor outcome.

Use of antibiotics to prevent hepatitis and typhlitis in male scid mice spontaneously infected with Helicobacter hepaticus

The use of antibiotic combinations to prevent acute and progressive chronic hepatitis and proliferative typhlitis associated with Helicobacter hepaticus infection in male scid/NCr mice was evaluated. The drug combinations used were amoxicillin-metronidazole-bismuth, tetracycline-metronidazole-bismuth, amoxicillin-neomycin, neomycin alone, and amoxicillin alone. Treatments were administered per os for 14 days beginning at 4 weeks of age. All mice remained clinically normal throughout the study. Specimens from mice were evaluated histologically at 21, 60, 90, and 120 days after initiation of the antibiotic treatments. Results of histologic examination and use of special stains indicated that the antibiotic regimens containing amoxicillin prevented progressive chronic hepatitis and typhlitis. Helical bacteria were not observed histologically in the liver or cecum of amoxicillin-treated mice. Helical bacteria were observed in the liver and cecum of untreated mice and in the cecum of mice treated with antibiotic regimens not containing amoxicillin. Untreated mice and those treated with amoxicillin were evaluated by culture for presence of H. hepaticus at 60 and 90 days and by polymerase chain reaction at 90 days after initiation of the antibiotic treatment. All untreated mice were test-positive by fecal/cecal culture, and three of five were positive by polymerase chain reaction. All mice treated with amoxicillin were negative for H. hepaticus by results of culture and polymerase chain reaction. The oral administration of amoxicillin to young scid mice via the drinking water prevents hepatitis and typhlitis caused by H. hepaticus.

Promotion of N-nitrosodimethylamine-initiated mouse lung tumors following single or multiple low dose exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin

The environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is highly toxic to several rodent species and may have adverse health effects in exposed human populations. Further, TCDD has been shown to be a potent liver tumor promoter in the rat after repeated administration. These studies were conducted to determine the tumor promoting capability of TCDD in the Swiss mouse following single or multiple exposures. Following tumor initiation with N-nitrosodimethylamine (NDMA; 25 mg/kg), animals were given either a single dose (1.6, 16 or 48 micrograms/kg) or repeated injections (0.05 microgram/kg/week for 20 weeks) of TCDD and sacrificed at 52 weeks of age. Neither NDMA nor TCDD caused an increase in incidence of liver tumors. NDMA induced lung tumors in 100% of animals, with 12 +/- 0.1 tumors/mouse. The multiplicity of lung tumors was significantly increased by low dose TCDD treatment, with 20 +/- 2.6 tumors/mouse following a single 1.6 micrograms/kg dose (P = 0.016) and 18 +/- 1.7 (P = 0.031) following repeated 0.05 microgram/kg doses (x 20). Higher doses of TCDD did not increase multiplicity of lung tumors and, in fact, may have been toxic to the lungs of NDMA-treated mice, as evidenced by the infiltration of pigmented macrophages. These data demonstrate the potent tumor promoting capability of TCDD in mouse lung.

Defective lymphoid development in mice lacking expression of the common cytokine receptor gamma chain

The common gamma chain (gamma c) of the IL-2, IL-4, IL-7, IL-9, and IL-15 receptors is defective in humans with XSCID. Mice lacking gamma c expression had hypoplastic thymuses; the thymocytes responded to gamma c-independent mitogens, but not gamma c-dependent stimuli. Splenic T cells were diminished at 3 weeks of age, but CD4+ T cells markedly increased by 4 weeks. B cells were greatly diminished in contrast with the situation in XSCID. NK cells, gamma delta intestinal intraepithelial lymphocytes, dendritic epidermal T cells, peripheral lymph nodes, and gut-associated lymphoid tissue were absent. These findings underscore the importance of gamma c in lymphoid development. Moreover, differences in humans and mice lacking gamma c expression indicate species-specific differences in the roles of gamma c-dependent cytokines or in the existence of redundant pathways. These mice provide an important model for studying the pathophysiology provide an important model for studying the pathophysiology of and gene therapy for human XSCID.

Chronic active hepatitis in mice caused by Helicobacter hepaticus

Helicobacter infections cause chronic gastroenteritis in humans and several animal species. We recently discovered a new Helicobacter (H. hepaticus) that is the etiological agent of a unique chronic active hepatitis in mice. Natural infection appeared to be acquired early in life in enzootically infected colonies. Liver lesions arose as focal necrosis and focal nonsuppurative inflammation by 1 to 4 months of age in susceptible mouse strains. By 6 to 8 months, extensive liver involvement included hepatocytomegaly, bile ductular (oval cell) hyperplasia, and cholangitis. There was an age-related increase in proliferating cell nuclear antigen hepatocyte nuclear labeling index. The bacteria were usually found within bile canaliculi as determined by ultrastructural evaluation of liver lesions, the Steiner modification of the Warthin-Starry stain and immunohistochemistry with a rabbit antibody to Helicobacter pylori. Naturally infected mice showed an age-related increase in serum IgG antibodies to Helicobacter hepaticus proteins. The disease was experimentally reproduced by intraperitoneal injection of liver suspensions from affected livers or bacteria cultivated in vitro. The earliest lesions of the experimental disease appeared 4 weeks after injection. The course of spontaneous and experimental infection was slow and insidious and resulted in high titers of antibodies to bacterial proteins. This chronic bacterial infection represents a new model of chronic liver disease.

Chronic active hepatitis and associated liver tumors in mice caused by a persistent bacterial infection with a novel Helicobacter species

BACKGROUND

In the autumn of 1992, a novel form of chronic, active hepatitis of unknown etiology was discovered in mice at the National Cancer Institute-Frederick Cancer Research and Development Center (NCI-FCRDC), Frederick, Md. A high incidence of hepatocellular tumors occurred in affected animals. The disease entity was originally identified in A/JCr mice that were untreated controls in a long-term toxicologic study.

PURPOSE

Our original purpose was to determine the origin and etiology of the chronic hepatitis and to quantify its association with hepatocellular tumors in mice of low liver tumor incidence strains. After a helical microorganism was discovered in hepatic parenchyma of diseased mice, we undertook characterization of the organism and investigation of its relationship to the disease process.

METHODS

Hepatic histopathology of many strains of mice and rats, as well as guinea pigs and Syrian hamsters, in our research and animal production facilities was reviewed. Steiner's modification of the Warthin-Starry stain and transmission electron microscopy were used to identify bacteria in the liver. We transmitted the hepatitis with liver suspensions from affected mice and by inoculation with bacterial cultures. Bacteria were cultivated on blood agar plates maintained under anaerobic or microaerophilic conditions and characterized morphologically, biochemically, and by 16S rRNA sequence.

RESULTS

We report here the isolation of a new species of Helicobacter (provisionally designated Helicobacter hepaticus sp. nov.) that selectively and persistently colonizes the hepatic bile canaliculi of mice (and possibly the intrahepatic biliary system and large bowel), causing a morphologically distinctive pattern of chronic, active hepatitis and associated with a high incidence of hepatocellular neoplasms in infected animals.

CONCLUSIONS

The novel Helicobacter is a likely candidate for the etiology of hepatocellular tumors in our mice. The Helicobacter-associated chronic active hepatitis represents a new model to study mechanisms of carcinogenesis by this genus of bacteria.

IMPLICATIONS

Adenocarcinoma of the stomach, the second most prevalent of all human malignancies world-wide, is associated with infection at an early age with Helicobacter pylori. Infection leads to several distinctive forms of gastritis, including chronic atrophic gastritis, which is a precursor of adenocarcinoma. H. hepaticus infection in mice constitutes the only other parallel association between a persistent bacterial infection and tumor development known to exist naturally. Study of the H. hepaticus syndrome of chronic active hepatitis and liver tumors in mice may yield insights into the role of H. pylori in human stomach cancer and gastric lymphoma.

Induction of T cell differentiation and lymphomagenesis in the thymus of mice with severe combined immune deficiency (SCID)

Severe combined immune deficiency (SCID) mice have a defect in their recombinase system and cannot productively rearrange their immune receptor genes. Thus, SCID thymocytes are arrested at the immature "triple negative" phase, not expressing CD3, CD4, or CD8 surface markers. Whole body irradiation of SCID mice induced maturation of their thymocytes to the CD4+/CD8+ double positive, CD3+low stage of differentiation, and resulted in the generation of a thymic cortical region on histologic examination. No mature single positive T cells were detected in the thymus or the periphery. VDJ rearrangements of TCR-beta with restricted clonality were observed in the double positive cells from a given individual. The CD3 complex was expressed on some of these cells, but the cells failed to mobilize intracellular calcium after cross-linking with CD3 Abs. The double positive cells appeared several weeks after irradiation, persisted for many months in the thymus, and by 6 mo generally developed into metastatic lymphoma. Retroviral activation was undetectable in both the preneoplastic and transformed thymocytes. Thus, it appears that the earliest steps in T cell development can be induced in SCID mice by inducing DNA breaks with radiation. This system represents a model of early thymic development, preneoplasia, and neoplasia.

Induction of T cell differentiation and lymphomagenesis in the thymus of mice with severe combined immune deficiency (SCID)

Severe combined immune deficiency (SCID) mice have a defect in their recombinase system and cannot productively rearrange their immune receptor genes. Thus, SCID thymocytes are arrested at the immature "triple negative" phase, not expressing CD3, CD4, or CD8 surface markers. Whole body irradiation of SCID mice induced maturation of their thymocytes to the CD4+/CD8+ double positive, CD3+low stage of differentiation, and resulted in the generation of a thymic cortical region on histologic examination. No mature single positive T cells were detected in the thymus or the periphery. VDJ rearrangements of TCR-beta with restricted clonality were observed in the double positive cells from a given individual. The CD3 complex was expressed on some of these cells, but the cells failed to mobilize intracellular calcium after cross-linking with CD3 Abs. The double positive cells appeared several weeks after irradiation, persisted for many months in the thymus, and by 6 mo generally developed into metastatic lymphoma. Retroviral activation was undetectable in both the preneoplastic and transformed thymocytes. Thus, it appears that the earliest steps in T cell development can be induced in SCID mice by inducing DNA breaks with radiation. This system represents a model of early thymic development, preneoplasia, and neoplasia.

Effects of inhibition of O6-alkylguanine-DNA alkyltransferase in rats on carcinogenesis by methylnitrosourea and ethylnitrosourea

Many alkylating agents are potent carcinogens and there is considerable evidence that the formation of O6-alkylguanine in DNA can lead to mutations and the initiation of neoplastic growth. The repair of O6-methyl- or O6-ethylguanine in DNA is known to be brought about by the action of a protein termed O6-alkylguanine-DNA alkyltransferase. In order to investigate the role of this activity in the carcinogenic action of methylnitrosourea and ethylnitrosourea, O6-benzylguanine, a potent inhibitor of the alkyltransferase, was used. Groups of 20 female F344 rats were treated with the nitrosourea (0.2 mmol) by gavage in 10 weekly doses and a parallel group was also treated with 4 mg of O6-benzylguanine, 2 h prior to each dose of the nitrosourea. This dose of O6-benzylguanine was sufficient to reduce the alkyltransferase activity to zero in the liver for at least 8 h but activity had returned to about 60% of normal within 24 h. Animals were maintained until they became moribund, when they were killed, or until death related to tumors. The median week of death in the animals receiving methylnitrosourea was reduced from 60 wk to 52 wk by co-treatment with O6-benzylguanine. There was a smaller reduction from 55 to 50 wk in the rats receiving ethylnitrosourea. The treatment with O6-benzylguanine caused no significant change in the incidence of the principal tumors induced by the alkylnitrosoureas and there were no liver tumors produced by the combined treatments. These results show that the level of inactivation of alkyltransferase produced by this dose of O6-benzylguanine was not sufficient to greatly alter the potent carcinogenic effect of these doses of alkylnitrosoureas in this system.

Collaboration between growth factors and diverse chemical carcinogens in hepatocarcinogenesis of transforming growth factor alpha transgenic mice

Transforming growth factor alpha (TGF-alpha) has been shown to induce liver tumors within 1 year in transgenic male mice in which this potent mitogen is overexpressed. To determine more precisely how TGF-alpha participates in multistep tumorigenesis of the liver, genotoxic (diethylnitrosamine or dimethylnitrosamine) and nongenotoxic (phenobarbital) chemical carcinogens were administered independently to TGF-alpha transgenic mice [line MT42 on a Crl:CD-1(ICR)BR background]. TGF-alpha overexpression dramatically accelerated carcinogen-induced hepatocarcinogenesis in MT42 males but not females. Interestingly, all three chemical agents were found to enhance strongly both hepatic tumor formation and progression in TGF-alpha transgenic male mice. In this study 100%, 90%, and 78% of transgenic males exposed to diethylnitrosamine, dimethylnitrosamine or phenobarbital, respectively, developed tumors between 24 and 32 weeks of age. Moreover, approximately 70% of tumor-bearing transgenic mice from each treatment group had hepatocellular carcinomas; no malignant lesions were found in any carcinogen-treated or untreated nontransgenic mice or in untreated MT42 mice at this age. These results demonstrate that chemical agents as diverse as nitrosamines and phenobarbital act as cocarcinogens with TGF-alpha in the livers of these transgenic mice, indicating that TGF-alpha possesses the unique ability to complement both initiation and promotion in hepatocarcinogenesis. Furthermore, because carcinogen-induced malignant conversion was restricted to transgenic mice, constitutive TGF-alpha overexpression may promote liver tumor progression as well.

Hypercoagulable state associated with a deficiency of protein C in a thoroughbred colt

Protein C is a vitamin K-dependent serine protease with anticoagulant and profibrinolytic activity which is synthesized in the liver. Decreased protein C activity was detected in a Thoroughbred colt with clinical and histopathologic evidence of recurrent venous thrombosis. Although protein C activity was reduced, protein C antigen concentration was normal. Consumptive coagulopathies produce a decrease in both the functional and antigenic concentrations of protein C, thus a defect in protein C synthesis was suspected. Inhibition of gamma-carboxylation secondary to vitamin K antagonism results in the synthesis of a protein C molecule with antigenicity, but without biological activity. However, there was no evidence of vitamin K antagonism. The hypercoaguable state resulting from the reduced activity of protein C in this colt was associated with uncomplicated renal disease, rather than a protein C consumptive process such as endotoxemia. A primary hypercoagulable state due to a deficiency of protein C activity was diagnosed. Primary deficiencies of protein C activity have not been previously documented in horses.

Amphibian tumors: a comparison of anurans and urodeles

Anuran and urodele amphibians develop spontaneous neoplasms in all major organ systems with the integumentary system a frequent target. Anurans and urodeles have spontaneous viral-associated tumors, the biological behavior of which is temperature-related. Anurans seem to have a greater frequency of spontaneous neoplasms than do urodeles and respond to chemical carcinogens in a manner analogous to mammalian species. Urodeles have greater cell regenerative capabilities than do anurans and paradoxically, are more refractory than anurans or mammalian species to chemical carcinogens in their proliferating regenerative blastema.

Immunologic and hematologic effects of neuroendocrine hormones. Studies on DW/J dwarf mice

DW/J dwarf mice lack acidophilic anterior pituitary cells and are deficient in growth hormone and other neuroendocrine mediators. These mice were examined to determine the effects of these deficiencies on hematopoietic and immune system development. Previous studies have suggested that these mice had immunologic defects primarily involving T cell development. However, we have found that these mice exhibit decreased peripheral blood cell counts affecting all lineages (erythrocytic, leukocytic, and platelets). Examination of lymphoid tissues of dwarf mice indicated that their spleens were hypoplastic. Treatment of these mice with recombinant human growth hormone resulted in a significant improvement of peripheral blood counts and spleen cell number. Analysis of the bone marrow indicated a profound deficiency of B cell progenitors in the dwarf mice. However, in untreated dwarf mice, mature B cells and T cells were observed in the spleens. Although treatment with recombinant human growth hormone could correct the hematopoietic deficiencies in these mice, it did not restore the B cell progenitor populations, suggesting that an absence of growth hormone is not solely responsible for this deficiency. Thus, these mice display significant myeloid and lymphoid deficiencies that have been previously undetected.

Immunologic and hematologic effects of neuroendocrine hormones. Studies on DW/J dwarf mice

DW/J dwarf mice lack acidophilic anterior pituitary cells and are deficient in growth hormone and other neuroendocrine mediators. These mice were examined to determine the effects of these deficiencies on hematopoietic and immune system development. Previous studies have suggested that these mice had immunologic defects primarily involving T cell development. However, we have found that these mice exhibit decreased peripheral blood cell counts affecting all lineages (erythrocytic, leukocytic, and platelets). Examination of lymphoid tissues of dwarf mice indicated that their spleens were hypoplastic. Treatment of these mice with recombinant human growth hormone resulted in a significant improvement of peripheral blood counts and spleen cell number. Analysis of the bone marrow indicated a profound deficiency of B cell progenitors in the dwarf mice. However, in untreated dwarf mice, mature B cells and T cells were observed in the spleens. Although treatment with recombinant human growth hormone could correct the hematopoietic deficiencies in these mice, it did not restore the B cell progenitor populations, suggesting that an absence of growth hormone is not solely responsible for this deficiency. Thus, these mice display significant myeloid and lymphoid deficiencies that have been previously undetected.

Human-mouse lymphoid chimeras: host-vs.-graft and graft-vs.-host reactions

Human peripheral blood lymphocytes (huPBL) were injected into mice with severe combined immune deficiency (SCID). It was ascertained that murine natural killer (NK) cells were capable of affecting engraftment of human lymphocytes in SCID mice. The presence of host NK cells resulted in the clearance of the human lymphocytes. Human T lymphocytes were the primary cell to engraft in the SCID recipients, with human T cells being detected in the spleen, lymph nodes, bone marrow and peritoneal cavity of the mice up to several months after transfer. No human T cells were detected in the murine thymus and the level of engraftment in the periphery could be highly variable. Additionally, there appeared to be significant reactions between the human lymphocytes and the murine host resulting in a xenogeneic graft-vs.-host reaction (XGVHR). The predominant manifestation involved splenomegaly resulting from an expansion of murine hematopoietic cells in the spleens of these xenogeneic chimeras. The severity of the XGVHR could be correlated with the extent of human T cell engraftment and the recovered human T cells were found to be in a proliferative state. Thus, there appear to be significant host-vs.-graft and graft-vs.-host interactions occurring in human/mouse lymphocyte chimeras.

Intestinal myxosarcoma in a thoroughbred mare

A large fibrotic mass originating from the cecal base was discovered upon surgical exploration of the abdomen in a Thoroughbred mare with a history of chronic colic and weight loss. The mass protruded intraluminally resulting in partial obstruction. Surgical excision was not feasible due to the location of the mass and the inability to exteriorize it adequately from the abdominal cavity. The mass was fibrous with a shiny, gelatinous material present throughout the neoplasm. Histologically, large confluent spaces filled with mucopolysaccharides were identified by staining with Alcian blue. The diagnosis of myxosarcoma was based upon finding of atypical fibroblastic cells, mucinous stroma, local invasiveness, and metastasis to the regional lymph nodes. Myxomatous tumors have not previously been documented to occur in the equine intestinal tract.

Evaluation of sodium hyaluronate therapy in induced septic arthritis in the horse

This study was conducted to determine the efficacy of sodium hyaluronate (SH) with antibiotic therapy and joint lavage for reducing acute inflammatory and degenerative changes induced by septic arthritis. Septic arthritis was induced in six adult horses by inoculating the tarsocrural joints with 1 x 10(4) colony-forming units of Staphylococcus aureus. When clinical signs appeared, trimethoprim-sulphamethoxazole (30 mg/kg bodyweight [bwt] daily) and phenylbutazone (4.4 mg/kg bwt sid) were administered and continued until termination of the study (Treatment Day 18). Twenty-four hours post inoculation, all joints were lavaged with sterile lactated Ringer's solution. Following lavage, one joint of each horse was injected with 10 mg of SH, and the contralateral joint served as the control. Sodium hyaluronate treated joints showed significant reductions in lameness, tarsal circumference and synovial fluid protein and WBC concentrations. The synovial membrane of the SH-treated joints contained less cellular infiltrate, less granulation tissue formation and retained a more normal villous structure compared with controls. The total glycosaminoglycan loss from the articular cartilage in the SH treated joints was consistently less than that from the control joints; however, this difference was not statistically significant. Sodium hyaluronate with joint lavage appears to be more beneficial than lavage alone for treatment of septic arthritis.

High incidence of neoplasms in female NZB/NZW mice treated with pulse doses of cyclophosphamide

The immunosuppressive properties of cyclophosphamide prevent formation of anti-DNA antibodies and prolong lifespans in autoimmune NZB/NZW mice, an animal model of systemic lupus erythematosus. In the current study, NZB/NZW mice were treated with weekly doses of cyclophosphamide to determine if intermittent pulses of the drug were effective therapy. Life-long treatment with cyclophosphamide, 56 mg/kg/week, was started at the mean age of 6 weeks; results were compared with saline-injected control mice. Pulse therapy with cyclophosphamide suppressed anti-DNA antibody levels, prevented severe glomerulonephritis and prolonged longevity. Seventeen of 19 treated mice developed neoplasms; 7 of these immunosuppressed animals had 2 to 4 separate neoplasms. Examination of earlier studies in this laboratory in which NZB/NZW mice were treated each day with cyclophosphamide showed that daily and weekly therapeutic regimens had similar immunosuppressive and oncogenic effects.

Isolation of Chlamydia psittaci from naturally infected African clawed frogs (Xenopus laevis)

An inclusion-forming agent was isolated from the livers of commercially raised African clawed frogs (Xenopus laevis) involved in an epizootic of high morbidity and mortality. Original isolation was made in McCoy cells. This agent was identified as Chlamydia psittaci based on the formation of typical intracytoplasmic inclusions which developed within 48 h, were not stained by iodine, and were resistant to sulfadiazine. The isolate from one particular frog (designated as strain 178) was further studied and found to be lethal for 7-day-old embryonated chicken eggs after intra-yolk sac inoculation. This strain was demonstrated not to be pathogenic for mice when inoculated intraperitoneally. The cell culture isolate of C. psittaci was transmitted to uninfected X. laevis, causing disease and death.