Development of a CD8 co-receptor independent T-cell receptor specific for tumor-associated antigen MAGE-A4 for next generation T-cell-based immunotherapy

BACKGROUND

The cancer-testis antigen MAGE-A4 is an attractive target for T-cell-based immunotherapy, especially for indications with unmet clinical need like non-small cell lung or triple-negative breast cancer.

METHODS

An unbiased CD137-based sorting approach was first used to identify an immunogenic MAGE-A4-derived epitope (GVYDGREHTV) that was properly processed and presented on human leukocyte antigen (HLA)-A2 molecules encoded by the HLA-A*02:01 allele. To isolate high-avidity T cells via subsequent multimer sorting, an in vitro priming approach using HLA-A2-negative donors was conducted to bypass central tolerance to this self-antigen. Pre-clinical parameters of safety and activity were assessed in a comprehensive set of in vitro and in vivo studies.

RESULTS

A MAGE-A4-reactive, HLA-A2-restricted T-cell receptor (TCR) was isolated from primed T cells of an HLA-A2-negative donor. The respective TCR-T-cell (TCR-T) product bbT485 was demonstrated pre-clinically to have a favorable safety profile and superior in vivo potency compared with TCR-Ts expressing a TCR derived from a tolerized T-cell repertoire to self-antigens. This natural high-avidity TCR was found to be CD8 co-receptor independent, allowing effector functions to be elicited in transgenic CD4+ T helper cells. These CD4+ TCR-Ts supported an anti-tumor response by direct killing of MAGE-A4-positive tumor cells and upregulated hallmarks associated with helper function, such as CD154 expression and release of key cytokines on tumor-specific stimulation.

CONCLUSION

The extensive pre-clinical assessment of safety and in vivo potency of bbT485 provide the basis for its use in TCR-T immunotherapy studies. The ability of this non-mutated high-avidity, co-receptor-independent TCR to activate CD8+ and CD4+ T cells could potentially provide enhanced cellular responses in the clinical setting through the induction of functionally diverse T-cell subsets that goes beyond what is currently tested in the clinic.

Hepatic Temporal Gene Expression Profiling in Helicobacter hepaticus-Infected A/JCr Mice

Helicobacter hepaticus infection of A/JCr mice is a model of infectious liver cancer. We monitored hepatic global gene expression profiles in H. hepaticus infected and control male A/JCr mice at 3 months, 6 months, and 1 year of age using an Affymetrix-based oligonucleotide microarray platform on the premise that a specific genetic expression signature at isolated time points would be indicative of disease status. Model based expression index comparisons generated by dChip yielded consistent profiles of differential gene expression for H. hepaticus infected male mice with progressive liver disease versus uninfected control mice within each age group. Linear discriminant analysis and principal component analysis allowed segregation of mice based on combined age and lesion status, or age alone. Up-regulation of putative tumor markers correlated with advancing hepatocellular dysplasia. Transcriptionally down-regulated genes in mice with liver lesions included those related to peroxisome proliferator, fatty acid, and steroid metabolism pathways. In conclusion, transcriptional profiling of hepatic genes documented gene expression signatures in the livers of H. hepaticus infected male A/JCr mice with chronic progressive hepatitis and preneoplastic liver lesions, complemented the histopathological diagnosis, and suggested molecular targets for the monitoring and intervention of disease progression prior to the onset of hepatocellular neoplasia.

Global Gene Expression Profiling: A Complement to Conventional Histopathologic Analysis of Neoplasia

Transcriptional profiling of entire tumors has yielded considerable insight into the molecular mechanisms of heterogeneous cell populations within different types of neoplasms. The data thus acquired can be further refined by microdissection methods that enable the analyses of subpopulations of neoplastic cells. Separation of the various components of a neoplasm (i.e., stromal cells, inflammatory infiltrates, and blood vessels) has been problematic, primarily because of a paucity of tools for accurate microdissection. The advent of laser capture microdissection combined with powerful tools of linear amplification of RNA and high-throughput microarray-based assays have allowed the transcriptional mapping of intricate and highly complex networks within pure populations of neoplastic cells. With this approach, specific “molecular signatures” can be assigned to tumors of distinct or even similar histomorphology, thereby aiding the desired objective of pattern recognition, tumor classification, and prognostication. This review highlights the potential benefits of global gene expression profiling of tumor cells as a complement to conventional histopathologic analyses.

Regulatory Forum Commentary* Counterpoint: Dose Selection for rasH2 Mouse Carcinogenicity Studies

Dose selection for the 6-month rasH2 mouse carcinogenicity studies depends heavily on the maximum tolerated dose (MTD) obtained from 1-month range-finding studies. A retrospective evaluation of range-finding studies and pivotal 6 month rasH2 mouse studies for 11 compounds demonstrated that the MTD based on at least a 10% decrease in body weight gain, mortality, and target organ toxicity in range-finding studies appropriately identified high doses for pivotal studies for 8 of 11 compounds. Two of the selected high doses were based on decreased body weight gain alone, while 7 were based on mortality at higher doses in shorter duration range-finding studies. High-dose selection was based on the maximum feasible dose for one study. The Center for Drug Evaluation and Research, U.S. Food and Drug Administration Executive Carcinogenicity Assessment Committee often suggested different doses than those proposed by the sponsor. High mortality was observed in only one pivotal study and the high dose was lowered during the course of that study.

Two-year Carcinogenicity Study in Rats with a Nonnucleoside Reverse Transcriptase Inhibitor

Administration of lersivirine, a nonnucleotide reverse transcriptase inhibitor, daily by oral gavage to Sprague-Dawley rats for up to 2 yr was associated with decreased survival, decreased body weights, and an increase in neoplasms and related proliferative lesions in the liver, thyroid, kidney, and urinary bladder. Thyroid follicular adenoma and carcinoma, the associated thyroid follicular hypertrophy/hyperplasia, hepatocellular adenoma/adenocarcinoma, altered cell foci, and hepatocellular hypertrophy were consistent with lersivirine-related induction of hepatic microsomal enzymes. Renal tubular adenoma and renal tubular hyperplasia were attributed to the lersivirine-related exacerbation of chronic progressive nephropathy (CPN), while urinary bladder hyperplasia and transitional cell carcinoma in the renal pelvis and urinary bladder were attributed to urinary calculi. Renal tubular neoplasms associated with increased incidence and severity of CPN, neoplasms of transitional epithelium attributed to crystalluria, and thyroid follicular and hepatocellular neoplasms related to hepatic enzyme induction have low relevance for human risk assessment.

Toxicities Associated with 1-month Treatment with Propylthiouracil (PTU) and Methimazole (MMI) in Male Rats

Thionamides such as propylthiouracil (PTU) and methimazole (MMI) have been used for more than 50 years to treat the more common causes of thyrotoxicosis/hyperthyroidism such as Graves’ disease. Serious adverse effects associated with thionamides in humans include idiosyncratic liver damage, agranulocytosis, aplastic anemia, and vasculitis. Both prospective and retrospective clinical studies with these drugs have failed to identify predictive biomarker for these adverse effects. To assess whether rat is a good model for predicting drug-related adverse events in the liver and in the bone marrow, we conducted a comprehensive study in male rats with multiple doses of PTU and MMI. As expected, euthyroid animals became hypothyroid along with several secondary changes associated with hypothyroidism. There were slight reductions in red blood cell parameters along with some marginal effects on the bone marrow elements. However, there was no evidence of significant neutropenia and liver injury in both PTU-treated and MMI-treated cohorts. MMI-related effects were noted in the seminiferous tubules of the testes. Overall, 1-month daily treatment of euthyroid rats with PTU or MMI resulted in hypothyroidism, minor bone marrow effects, and several secondary effects associated with hypothyroidism, but without any evidence of adverse effects reported in humans including liver injury and agranulocytosis.

Regulatory Forum Commentary

International regulatory and pharmaceutical industry scientists are discussing revision of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) S1 guidance on rodent carcinogenicity assessment of small molecule pharmaceuticals. A weight-of-evidence approach is proposed to determine the need for rodent carcinogenicity studies. For compounds with high human cancer risk, the product may be labeled appropriately without conducting rodent carcinogenicity studies. For compounds with minimal cancer risk, only a 6-month transgenic mouse study (rasH2 mouse or p53+/− mouse) or a 2-year mouse study would be needed. If rodent carcinogenicity testing may add significant value to cancer risk assessment, a 2-year rat study and either a 6-month transgenic mouse or a 2-year mouse study is appropriate. In many cases, therefore, one rodent carcinogenicity study could be sufficient. The rasH2 model predicts neoplastic findings relevant to human cancer risk assessment as well as 2-year rodent models, produces fewer irrelevant neoplastic outcomes, and often will be preferable to a 2-year rodent study. Before revising ICH S1 guidance, a prospective evaluation will be conducted to test the proposed weight-of-evidence approach. This evaluation offers an opportunity for a secondary analysis comparing the value of alternative mouse models and 2-year rodent studies in the proposed ICH S1 weight-of-evidence approach for human cancer risk assessment.

The rasH2 Mouse Model for Assessing Carcinogenic Potential of Pharmaceuticals

A factor limiting widespread use of the transgenic rasH2 mouse model for carcinogenicity testing of pharmaceuticals is the paucity of published data on actual drug candidates in rasH2 mice. This report addresses this gap by highlighting rasH2 mouse study data for 10 pharmaceutical candidates. These results were compared with findings in the 2-year studies in Sprague-Dawley rats for the same 10 compounds. In the 6-month rasH2 studies, only 2 of the 10 compounds tested positive for carcinogenicity and these correlated with positive findings in the companion 2-year rat studies. One compound, sunitinib, produced gastroduodenal carcinoma in both sexes and increased hemangiosarcoma in spleen and uterus in female rasH2 mice; in rats it produced gastroduodenal carcinoma and increased pheochromocytoma (males only). The second compound, bazedoxifene, produced ovarian granulosa cell neoplasms in rasH2 mice and rats, and renal tubular neoplasms associated with increased chronic progressive nephropathy only in rats. The higher percentage of carcinogenicity positive rat bioassays could be attributed to rat-specific phenomena with little or low relevance to man. Thus, this article confirms previous reports that rasH2 mice develop rodent-specific neoplasms less frequently than rats and positive findings, when present, are accompanied by similar positive results in the rat.

Expression of TMPRSS4 in non-small cell lung cancer and its modulation by hypoxia

Overexpression of TMPRSS4, a cell surface-associated transmembrane serine protease, has been reported in pancreatic, colorectal and thyroid cancers, and has been implicated in tumor cell migration and metastasis. Few reports have investigated both TMPRSS4 gene expression levels and the protein products. In this study, quantitative RT-PCR and protein staining were used to assess TMPRSS4 expression in primary non-small cell lung carcinoma (NSCLC) tissues and in lung tumor cell lines. At the transcriptional level, TMPRSS4 message was significantly elevated in the majority of human squamous cell and adenocarcinomas compared with normal lung tissues. Staining of over 100 NSCLC primary tumor and normal specimens with rabbit polyclonal anti-TMPRSS4 antibodies confirmed expression at the protein level in both squamous cell and adenocarcinomas with little or no staining in normal lung tissues. Human lung tumor cell lines expressed varying levels of TMPRSS4 mRNA in vitro. Interestingly, tumor cell lines with high levels of TMPRSS4 mRNA failed to show detectable TMPRSS4 protein by either immunoblotting or flow cytometry. However, protein levels were increased under hypoxic culture conditions suggesting that hypoxia within the tumor microenvironment may upregulate TMPRSS4 protein expression in vivo. This was supported by the observation of TMPRSS4 protein in xenograft tumors derived from the cell lines. In addition, staining of human squamous cell carcinoma samples for carbonic anhydrase IX (CAIX), a hypoxia marker, showed TMPRSS4 positive cells adjacent to CAIX positive cells. Overall, these results indicate that the cancer-associated TMPRSS4 protein is overexpressed in NSCLC and may represent a potential therapeutic target.

Spontaneous tumor incidence in rasH2 mice: review of internal data and published literature

Alternate transgenic mouse models are accepted as replacements for the standard carcinogenicity mouse bioassay by regulatory agencies with a companion 2-year rat bioassay. The slower rate of industry acceptance of these shorter transgenic mouse cancer bioassays has been due to lack of historical data and diagnostic criteria, and the use of nonstandardized terminologies in published data. To address these issues, especially that of generating a large historical database, a retrospective analysis of the spontaneous tumor incidences in rasH2 mice from internally sponsored 6-month carcinogenicity studies was compared to the published literature. Incidences of common spontaneous tumors (incidences > 1%) observed in these studies were lung bronchiolo-alveolar adenomas (mean 3.9-9.9%; range 0-18%), lung bronchiolo-alveolar adenocarcinomas (mean 1.4-2.4%; range 0-5%), splenic hemangiosarcomas (mean 3.0-3.9%; range 0-17%), cutaneous squamous cell papillomas (mean 1.1-1.2%; range 0-4%), Harderian gland adenoma (mean 0.8-1.2%; range 0-4%), and hepatocellular adenomas (mean 1.8%; 0-9% in males only). The remarkable similarity in the tumor incidences in multiple rasH2 studies over a decade and the observed stability of the inserted human gene are important indicators of the minimal drift in this model. Overall, the historical control data for spontaneous neoplasms should assist in the interpretation of future rasH2 mouse studies.

Staphylococcal meningoencephalitis, nematodiasis, and typhlocolitis in a squirrel monkey (Saimiri sciureus)

BACKGROUND

Seizures were observed in a 16-year old male Guyanese squirrel monkey with a history of inappetence and weakness.

METHODS AND RESULTS

Complete blood count, biochemical profile, and urinalysis indicated systemic disease. Nematode larvae were detected in the feces. Cerebrospinal fluid (CSF) analysis revealed leukocytes and gram-positive cocci. Staphylococcus aureus was isolated from the CSF. Histopathological evaluation revealed systemic lesions with inflammation and nematodes in the small and large intestine.

CONCLUSION

This is the first report describing spontaneous staphylococcal CNS infection in a squirrel monkey.

Abstract C166: Cancer cells expressing TMPRSS4 colocalized with carbonic anhydrase IX (CAIX)-positive cells in lung and pancreatic carcinomas

TMPRSS4, a cell surface transmembrane serine protease, is over expressed at the transcriptional level in pancreatic, colorectal and thyroid cancers compared with normal tissues. Recent studies have indicated a role for TMPRSS4 in tumor cell migration and tumor metastasis. We examined TMPRSS4 expression in dissected non-small cell lung cancer (NSCLC) tissues by quantitative RT-PCR and immunohistochemisty. At the transcriptional level, TMPRSS4 expression was elevated in adeno and squamous cell (SC) carcinomas when compared to the matching normal tissues (p=0.0035). At the protein level, over 100 tumor and normal specimens were examined with rabbit polyclonal anti-TMPRSS4 antibodies via immunohistochemistry. Adeno and SC carcinomas were positive for TMPRSS4 (p<0.05), while little or no staining observed on the normal tissue sections. TMPRSS4 protein expression in tumor samples correlated with mRNA qRT-PCR results. When similar experiments were performed on lung cancer cell lines, six out of 16 lines expressed TMPRSS4 mRNA, particularly NCI-H358 and NCI-H596 cells which exhibited high TMPRSS4 message with an average of 6000 and 5000 copies, respectively, relative to the 18S rRNA; however, no TMPRSS4 protein was detected either by Western blot or flow cytometry. When NCI-H358 cells were implanted into nude mice, TMPRSS4 was detected in the xenograft tumors via immunohistochemistry. When lung SC carcinoma and pancreatic adenocarcinoma were stained for TMPRSS4 and for the hypoxia marker, CAIX, TMPRSS4 positive cells were found to be adjacent to CAIX positive cells; however, no co-staining in the same cell was observed, suggesting that TMPRSS4 has a significant function with the adjacent hypoxic cancer cells in tumor tissues, and hypoxia may induce TMPRSS4 expression in xenograft tumors of NCI-H358 in which protein is not detectable under normal cell culture environment.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C166.

Obesity and non-insulin-dependent diabetes mellitus in Swiss-Webster mice associated with late-onset hepatocellular carcinoma

Genetic mutations resulting in obesity and type 2 diabetes mellitus (T2D) are described for both inbred and outbred mice. However, no known mouse model completely recapitulates human T2D and its comorbidities. We identified a cohort of obese, male, outbred Swiss-Webster (SW) mice as polyuric, polydipsic, glucosuric, and hyperglycemic. Prevalence of glucosuria in the SW colony reached 60% (n=70) in males 8 weeks to 6 months of age. Despite severe obesity in some females, no females were diabetic. Pathologic findings in affected males included cachexia, dilated gastrointestinal tracts with poor muscular tone, pancreatic islet degeneration and atrophy with compensatory metaplasia and/or neogenesis, bacterial pyelonephritis, membranous glomerulopathy, and late-onset hepatic tumors with macrosteatosis, microsteatosis, and hydropic change in aged males. Serum insulin correlated with blood glucose in a nonlinear pattern, suggestive of islet exhaustion. Circulating leptin levels showed a weak inverse correlation with glucose. Diabetic males were bred with obese colony females to produce 20 male and 20 female offspring. Prevalence of diabetes in male offspring was 80% (16/20) with a median age of onset of 18 weeks. By contrast, no diabetic females were identified, despite being significantly more obese than males. Male predominance is likewise a feature of T2D in humans. To our knowledge, this is the first documentation of hepatocellular carcinoma and islet metaplasia and/or neogenesis in a spontaneous outbred mouse model of T2D. The SW availability and histopathologic features represent a promising new model for the study of T2D.

Diarrhea as a cause of mortality in a mouse model of infectious colitis

Analysis of gene expression in the colons of Citrobacter rodentium-infected susceptible and resistant mice suggests that mortality is associated with impaired intestinal ion transport.

Background

Comparative characterization of genome-wide transcriptional changes during infection can help elucidate the mechanisms underlying host susceptibility. In this study, transcriptional profiling of the mouse colon was carried out in two cognate lines of mice that differ in their response to Citrobacter rodentium infection; susceptible inbred FVB/N and resistant outbred Swiss Webster mice. Gene expression in the distal colon was determined prior to infection, and at four and nine days post-inoculation using a whole mouse genome Affymetrix array.

Results

Computational analysis identified 462 probe sets more than 2-fold differentially expressed between uninoculated resistant and susceptible mice. In response to C. rodentium infection, 5,123 probe sets were differentially expressed in one or both lines of mice. Microarray data were validated by quantitative real-time RT-PCR for 35 selected genes and were found to have a 94% concordance rate. Transcripts represented by 1,547 probe sets were differentially expressed between susceptible and resistant mice regardless of infection status, a host effect. Genes associated with transport were over-represented to a greater extent than even immune response-related genes. Electrolyte analysis revealed reduction in serum levels of chloride and sodium in susceptible animals.

Conclusion

The results support the hypothesis that mortality in C. rodentium-infected susceptible mice is associated with impaired intestinal ion transport and development of fatal fluid loss and dehydration. These studies contribute to our understanding of the pathogenesis of C. rodentium and suggest novel strategies for the prevention and treatment of diarrhea associated with intestinal bacterial infections.

Genetic deletion of mPGES-1 suppresses intestinal tumorigenesis

Elevated levels of prostaglandin E(2) (PGE(2)) are often found in colorectal cancers. Thus, nonsteroidal anti-inflammatory drugs, including selective cyclooxygenase-2 (COX-2) inhibitors, are among the most promising chemopreventive agents for colorectal cancer. However, their long-term use is restricted by the occurrence of adverse events believed to be associated with a global reduction in prostaglandin production. In the present study, we evaluated the chemopreventive efficacy of targeting the terminal synthase microsomal PGE(2) synthase 1 (mPGES-1), which is responsible for generating PGE(2), in two murine models of intestinal cancer. We report for the first time that genetic deletion of mPGES-1 in Apc-mutant mice results in marked and persistent suppression of intestinal cancer growth by 66%, whereas suppression of large adenomas (>3 mm) was almost 95%. This effect occurred despite loss of Apc heterozygosity and beta-catenin activation. However, we found that mPGES-1 deficiency was associated with a disorganized vascular pattern within primary adenomas as determined by CD31 immunostaining. We also examined the effect of mPGES-1 deletion on carcinogen-induced colon cancer. The absence of mPGES-1 reduced the size and number of preneoplastic aberrant crypt foci (ACF). Importantly, mPGES-1 deletion also blocked the nuclear accumulation of beta-catenin in ACF, confirming that beta-catenin is a critical target of PGE(2) procarcinogenic signaling in the colon. Our data show the feasibility of targeting mPGES-1 for cancer chemoprevention with the potential for improved tolerability over traditional nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors.

Infestation of wild-caught American bullfrogs (Rana catesbeiana) by multiple species of metazoan parasites

The American bullfrog (Rana catesbeiana) is an aquatic, carnivorous member of the family Ranidae that is used extensively in physiology education programs and in various physiology, toxicology, sensorineural, and genetics research. Eleven bullfrogs purchased from a vendor distributing wild-caught frogs for use in a physiology research protocol were emaciated but otherwise showed no apparent clinical signs of illness. Necropsies performed on selected emaciated frogs indicated heavy infestation with multiple species of endoparasites. Identified helminths included Gorgodera amplicava, Haematolechus breviplexus, Clinostomum spp, Contracaecum spp, Cosmocercoides dukae, and Eustrongyloides spp. Grossly, parasitized bullfrogs showed encysted trematode larvae within skeletal muscle, nematode impaction of the intestinal tract, and lack of coelemic fat stores. Histopathologic lesions were restricted primarily to the gastrointestinal tract and consisted of parasitic granulomas associated with Contracaecum spp. The parasitic lesions may have been associated with the poor body condition of the bullfrogs. Food crickets maintained in-house were negative for parasite larvae or ova. Heavy parasitism of wild-caught bullfrogs may confound research protocols and markedly impair animal health. We encourage researchers to purchase laboratory-bred and -reared bullfrogs and to routinely monitor the parasite status of colony frogs.

Rapid reversal of interleukin-6-dependent epithelial invasion in a mouse model of microbially induced colon carcinoma

Chronic inflammation of mucosal surfaces renders them increasingly susceptible to epithelial cancers both in humans and mice. We have previously shown that anti-inflammatory CD4(+)CD45RB(lo)CD25(+) regulatory (Treg or T(R)) lymphocytes down-regulate inflammation and block development of bacteria-triggered colitis and colorectal cancer (CRC) in 129/SvEv Rag2-/- mice. Interestingly, T(R) cells collected from Interleukin (IL)-10-deficient cell donors not only failed to suppress carcinogenesis but instead promoted invasive mucinous colonic carcinoma with a strong gender bias expressing in male mice. We found we show that peritoneal invasion in this model is dependent on pleiotropic cytokine IL-6. Mucinous carcinoma arose rapidly and consistently after treatment with IL10-/- T(R) cells, which were found to express Foxp3+ and localize throughout tumor tissue. Carcinogenesis was rapidly reversible with transfer of wild type IL10-competent T(R) cells. Likewise, treatment with IL10-Ig fusion protein was sufficient to revert the lesions histologically, and restore inflammatory cytokine and oncogene expression to base line levels. These studies indicate an essential role for IL 6 in this CRC phenotype. Furthermore, immune-competent T(R) cells were important not only for preventing pathology but also for constructive remodeling of bowel following tumorigenic microbial insults. These data provide insights into etiopathogenesis of inflammation-associated epithelial invasion and maintenance of epithelial homeostasis.

Development of fatal colitis in FVB mice infected with Citrobacter rodentium

Citrobacter rodentium is the causative agent of transmissible murine colonic hyperplasia. The disease is characterized by severe but temporary epithelial hyperplasia with limited inflammation in the descending colon of adult mice on a variety of genetic backgrounds. The natural history of infection with this murine pathogen has been characterized in outbred Swiss Webster (SW) mice but not in the cognate inbred FVB strain. In contrast to subclinical infection in SW mice, 12-week-old FVB mice developed overt disease with significant weight loss and mortality beginning by 9 days postinoculation (dpi). By 21 dpi, more than 75% of infected FVB mice died or had to be euthanized, whereas no mortality developed in SW mice. Mortality in FVB mice was fully prevented by fluid therapy. Fecal shedding of bacteria was similar in both groups through 9 dpi; however, a slight but significant delay in bacterial clearance was observed in FVB mice by 12 to 18 dpi. SW mice developed hyperplasia with minimal inflammation in the descending colon. FVB mice developed epithelial cell hyperproliferation, severe inflammation with erosions and ulcers, and epithelial atypia by 6 dpi in the descending colon. In the majority of surviving FVB mice, colonic lesions, including epithelial atypia, were reversible, although a small percentage (5 to 7%) exhibited chronic colitis through 7 months postinoculation. The existence of susceptible and resistant lines of mice with similar genetic backgrounds will facilitate the identification of host factors responsible for the outcome of infection and may lead to the development of novel strategies for preventing and treating infectious colitis.

Inhibition of Helicobacter hepaticus-induced colitis by IL-10 requires the p50/p105 subunit of NF-kappa B

Defects within the innate immune system sensitize NF-kappaB-deficient (p50(-/-); p65(+/-)) mice to Helicobacter hepaticus (Hh)-induced colitis. Because IL-10 plays a central role in the inhibition of Hh-induced colitis, we hypothesized that the ability of IL-10 to inhibit the innate inflammatory response to Hh may be compromised in NF-kappaB-deficient mice. To test this hypothesis, we evaluated the ability of an IL-10-Ig fusion protein with IL-10-like properties to inhibit Hh-induced colitis in RAG-2(-/-) (RAG) and p50(-/-); p65(+/-); RAG-2(-/-) (3X/RAG) mice. As expected, IL-10-Ig efficiently inhibited the development of colitis in RAG mice. In contrast, the ability of IL-10-Ig to inhibit colitis was compromised in 3X/RAG mice. The defect in response to IL-10-Ig appeared to be primarily the result of the absence of the p50/p105 subunit, because the ability of IL-10-Ig to inhibit colitis was also compromised in p50(-/-); RAG-2(-/-) (p50/RAG) mice. Radiation chimeras demonstrated that the presence of p50/p105 within hemopoietic cells of the innate immune system was necessary for efficient inhibition of colitis by IL-10-Ig. Consistent with a defect in the suppressive effects of IL-10 in the absence of p50/p105, we found that the ability of IL-10 to control LPS-induced expression of IL-12 p40 was significantly compromised in macrophages lacking p50/p105. These results suggest that the absence of the p50/p105 subunit of NF-kappaB within hemopoietic cells of the innate immune system interferes with the ability of IL-10 to suppress inflammatory gene expression and Hh-induced colitis.

Trefoil family factor 2 is expressed in murine gastric and immune cells and controls both gastrointestinal inflammation and systemic immune responses

Trefoil family factor 2 (TFF2), also known as spasmolytic peptide, is a low-molecular-weight protein that is upregulated in gastric tissues infected with Helicobacter or having other inflammatory conditions, but a precise function is yet to be elucidated. The role of TFF2 in the development of gastritis, colitis, and inflammatory cytokine responses was examined both in vivo and in vitro using wild-type and TFF2 knockout mice. TFF2 knockout and wild-type mice were infected with Helicobacter felis (H. felis) to induce gastritis. Colitis was induced in TFF2 knockout and wild-type mice by administering dextran sodium sulfate (DSS) in drinking water. Histopathology, clinical disease (colitis), and antibody levels (H. felis) were examined. TFF2 expression in tissues was determined by reverse transcriptase PCR, and the inflammatory and proliferative responses of TFF2-expressing macrophages and spleen cells were examined by cytokine enzyme-linked immunosorbent assay, thymidine incorporation, and gene array studies. TFF2 knockout mice have increased susceptibility to H. felis-induced gastritis, with enhanced gastric inflammation. They were also more susceptible to DSS-induced colitis, with prolonged colonic hemorrhage and persistent weight loss. Remarkably, TFF2 expression was not limited to the gastrointestinal tract, as suggested in previous studies, but was also present in macrophages and lymphocytes. The inflammatory and proliferative responses of these immune cell types were dysregulated in TFF2 knockout mice. TFF2-/- cells were hyperresponsive to interleukin 1 beta stimulation but showed normal responses to lipopolysaccharide, suggesting a specific role for TFF2 in interleukin 1 receptor but not Toll-like receptor 4 signaling via their Toll-interleukin 1 resistance domains. TFF2-/- lymphocytes also produced higher levels of interleukin 2 than wild-type cells. Thus, TFF2 was expressed in the gastrointestinal cells and in immune cells and was a negative regulator of gastrointestinal inflammation and immune cell cytokine responses. Our studies suggest that TFF2 not only controls gastrointestinal repair but also regulates mononuclear cell inflammatory responses.

Enterohepatic Helicobacter species isolated from the ileum, liver and colon of a baboon with pancreatic islet amyloidosis

Microaerobic bacteria were isolated from a baboon with pancreatic islet amyloidosis and hepatitis. Phenotypic and molecular analyses identified two distinct helicobacters. Analyses of 16S rRNA demonstrated "Helicobacter macacae" in the ileum and liver, and Helicobacter cinaedi in the colon. To the best of the authors' knowledge, this is the first report describing the isolation of enterohepatic Helicobacter species from a baboon.

Progressive proliferative and dysplastic typhlocolitis in aging syrian hamsters naturally infected with Helicobacter spp.: a spontaneous model of inflammatory bowel disease

Helicobacter spp. have been implicated in a variety of gastrointestinal tract diseases, including peptic ulcer disease, gastric cancer, and inflammatory bowel disease (IBD), in humans and animals. Although most models of IBD are experimentally induced, spontaneous or natural models of IBD are rare. Herein, we describe a long-term study of chronic, progressive lesions that develop in the distal portion of the large bowel of unmanipulated Syrian hamsters naturally infected with Helicobacter spp. Twenty-four Syrian hamsters of three age groups (group A, 1 month [n = 4], group B, 7-12 months [n = 12], group C, 18-24 months [n = 12]), underwent complete postmortem examination. Results of microbial isolation and polymerase chain reaction and restriction fragment length polymorphism analyses confirmed the presence of Helicobacter spp. infection in the distal portion of the large bowel of all animals. Additionally, confounding pathogens, such as Clostridium difficile, Lawsonia intracellularis, and Giardia spp. that can cause proliferative enteritis, were absent in the hamsters of this study. Histopathologic scores for inflammation (P < 0.01), hyperplasia (P < 0.01), and dysplasia (P < 0.05) were significantly higher in the ileocecocolic (ICC) junction of animals in group C, relative to group A. Dysplastic lesions of various grades were detected in 5 of 11 hamsters in group C. Interestingly, the segment of the bowel that is usually colonized by Helicobacter spp. in hamsters had the most severe lesions. One hamster of group C developed a malignant fibrous histiocytoma, whereas another hamster developed a round cell sarcoma originating from the ICC junction. Thus, lesions in the distal portion of the large bowel of aging hamsters naturally colonized with Helicobacter spp. warrants developing the hamster as an animal model of IBD and potentially IBD-related cancer.

Circumvention and reactivation of the p53 oncogene checkpoint in mouse colon tumors

The p53 tumor suppressor protein is sequence-normal in azoxymethane (AOM)-induced mouse colon tumors, making them a good model for human colon cancers that retain a wild type p53 gene. Cellular localization and co-immunoprecipitation experiments using a cell line derived from an AOM-induced colon tumor (AJ02-NM(0) cells) pointed to constitutively expressed Mdm2 as being an important negative regulator of p53 in these cells. Although the Mdm2 inhibitory protein p19/ARF was expressed in AJ02-NM(0) cells, its level of expression was not sufficient for p53 activation. We tested the response of AJ02-NM(0) cells to the recently developed Mdm2 inhibitor, Nutlin-3. Nutlin-3 was found to activate p53 DNA binding in AJ02-NM(0) cells, to a level comparable to doxorubicin and 5-fluorouracil (5-FU). In addition, Nutlin-3 increased expression of the p53 target genes Bax and PERP to a greater extent than doxorubicin or 5-FU, and triggered a G2/M phase arrest in these cells, compared to a G1 arrest triggered by doxorubicin and 5-FU. The differences in the cellular response may be related to differences in the kinetics of p53 activation and/or its post-translational modification status. In an ex vivo experiment, Nutlin-3 was found to activate p53 target gene expression and apoptosis in AOM-induced tumor tissue, but not in normal adjacent mucosa. Our data indicate that Mdm2 inhibitors may be an effective means of selectively targeting colon cancers that retain a sequence-normal p53 gene while sparing normal tissue and that the AOM model is an appropriate model for the preclinical development of these drugs.

Innate Immune Inflammatory Response against Enteric Bacteria Helicobacter hepaticus Induces Mammary Adenocarcinoma in Mice

Inflammation associated with bacterial infections is a risk factor for cancers in humans, yet its role in breast cancer remains poorly understood. We have previously shown that innate immune inflammatory response against intestinal bacteria is sufficient to induce colon cancer. Here we report that infecting Rag2-deficient C57BL/6 Apc(Min/+) mice with an intestinal bacterial pathogen, Helicobacter hepaticus, significantly promotes mammary carcinoma in females and enhances intestinal adenoma multiplicity by a tumor necrosis factor alpha (TNFalpha)-dependent mechanism. The mammary and intestinal tumor development as well as the increase in proinflammatory mediators is suppressed by adoptive transfer of interleukin 10-competent CD4+CD45RB(lo)CD25+ regulatory (T(R)) cells. Furthermore, prior exposure of donor mice to H. hepaticus significantly enhances antitumor potency of their T(R) cells. Interestingly, these microbially experienced T(R) cells suppress tumorigenesis more effectively in recipient mice irrespective of their tumor etiology. These data suggest that infections with enteric pathogens enhance T(R)-cell potency and protect against epithelial cancers later in life, potentially explaining paradoxical increases in cancer risk in developed countries having more stringent hygiene practices. The possibility that dysregulated gut microbial infections in humans may lead to cancer in anatomically distant organs, such as breast, highlights the need for novel immune-based strategies in cancer prevention and treatment.

Immunomodulatory effects of in vitro exposure to organochlorines on T-cell proliferation in marine mammals and mice

Marine mammals bioaccumulate various environmental contaminants such as organochlorines (OCs), which biomagnify via the food web. While the immunomodulatory effects of individual OCs have been studied, the effects of mixtures are not well understood. The immunomodulatory effects of polychlorinated biphenyl (PCB) 138, 153, 169, and 180 as well as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and all possible mixtures were examined in marine mammals and mice. Lymphocyte proliferation was significantly modulated by OCs in all species tested, mostly by non-coplanar PCBs, as shown using regression analyses. Correlation analyses showed significant correlations (interpreted as additive effects) between OCs in mice, killer whales, and Steller sea lions. Nonadditive synergistic and antagonistic interactions between OCs were detected in most of the species tested. Toxic equivalency (TEQ) values used for OC toxicity assessment failed to predict the immunomodulatory effects measured in mice and marine mammals. The commonly used mouse model failed to predict immunomodulatory effects in other species. Clustering data suggested that phylogeny does not predict toxicity of OCs. Overall, our data suggest the presence of species-specific sensitivities to different mixtures, in which OCs interactions may be complex and that may exert their effects through dioxinlike or dioxin-independent pathways. Lastly, lymphocyte proliferation, an important part of adaptive immunity, was significantly modulated in mice and marine mammals, suggesting the possibility of increased susceptibility to diseases. These findings will be useful to better characterize the risk associated with OC exposure and possibly lead to new conservation and management strategies.

Proinflammatory CD4+CD45RBhi Lymphocytes Promote Mammary and Intestinal Carcinogenesis in ApcMin/+ Mice

Cancers of breast and bowel are increasingly frequent in humans. Chronic inflammation is known to be a risk factor for these malignancies, yet cellular and molecular mechanisms linking inflammation and carcinogenesis remain poorly understood. Here, we apply a widely used T-cell transfer paradigm, involving adoptive transfer of proinflammatory CD4+ CD45RB(hi) (T(E)) cells to induce inflammatory bowel disease (IBD) in mice, to investigate roles of inflammation on carcinogenesis in the Apc(Min/+) mouse model of intestinal polyposis. We find that transfer of T(E) cells significantly increases adenoma multiplicity and features of malignancy in recipient Apc(Min/+) mice. Surprisingly, we find that female Apc(Min/+) recipients of T(E) cells also rapidly develop mammary tumors. Both intestinal polyposis and mammary adenocarcinoma are abolished by cotransfer of anti-inflammatory CD4+ CD45RB(lo) regulatory lymphocytes or by neutralization of key proinflammatory cytokine tumor necrosis factor-alpha. Lastly, down-regulation of cyclooxygenase-2 and c-Myc expression is observed coincident with tumor regression. These findings define a novel mouse model of inflammation-driven mammary carcinoma and suggest that epithelial carcinogenesis can be mitigated by anti-inflammatory cells and cytokines known to regulate IBD in humans and mice.

Non-coplanar PCB-mediated modulation of human leukocyte phagocytosis: a new mechanism for immunotoxicity

Organochlorine (OC) contaminants, notably polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are ubiquitous in all ecosystems and found in the tissues of humans and wildlife. Although the immunotoxicity of coplanar, dioxinlike PCBs is well documented, the adverse effects exerted by non-coplanar, non-dioxinlike PCBs have received little attention. Direct causal relationship between PCB and dioxin exposure and the observed detrimental effects on the immune system has yet to be fully established in humans. The immunomodulatory potential of toxic coplanar PCB 169 and TCDD and abundant non-coplanar PCBs 138, 153, and 180 on human leukocyte phagocytosis, an important innate immune function that initiates the clearance of pathogens, was tested upon in vitro exposure. Mixture and concentration-response experiments demonstrated a suppression of phagocytosis by non-coplanar PCBs suggesting a previously unrecognized aryl hydrocarbon receptor (AhR)-independent pathway. Regression analysis revealed that reduction of phagocytosis was mostly explained by the non-coplanar congeners. The effects on phagocytosis could not be accurately predicted by either the currently used toxic equivalence (TEQ) approach or the mouse model, thus undermining the use of the traditional models in the risk assessment for OC mixtures containing non-coplanar congeners. Our results are cause for concern as they suggest an AhR-independent pathway through which non-coplanar PCBs modulate phagocytosis, the immune system's first line of defense, possibly increasing the risk to developing infectious disease.

Acute paraplegia in a young adult long-evans rat resulting from T-cell lymphoma

We describe an unusual case of acute paraplegia in a young adult (7.5-month-old) Long-Evans rat that resulted from a spontaneous T-cell lymphoma. At presentation, a neurologic exam revealed normal pelvic limb flexor reflexes, the absence of an anal reflex, and deep pain recognition. Radiographs did not identify any obvious spinal abnormality or osseous trauma, although the liver and spleen were prominent. Hematologic analysis disclosed leukocytosis with atypical lymphocytes. At necropsy, red, friable to gelatinous masses were found associated with the ventral aspect of the vertebral column at the levels of the thoracic and lumbar vertebrae. Impression smears of the mass revealed a monocytic cell population with cells averaging 7 to 10 microm in diameter and having scant cytoplasm and pleomorphic nuclei, characteristics consistent with a lymphoid neoplasm. Histologically, the neoplasm was unencapsulated, poorly demarcated and highly infiltrative, invading and effacing the bone marrow and epidural space of the vertebral column. Neoplastic cells also were identified in the femoral bone marrow, spleen, liver, iliac and sacral lymph nodes, and lung. Immunophenotyping showed the neoplasm to be of T-cell origin. Although the lymphoma did not invade the meninges of the spinal cord, its impingement on the central and peripheral nervous systems resulted in foci of Wallerian degeneration that contributed to the paraplegia. This case report highlights the importance of having lymphoma and leukemia among the differential diagnoses in cases of acute paralysis in rodents.

Effect of tissue preservation on imaging using ultrahigh resolution optical coherence tomography

Ultrahigh resolution optical coherence tomography (OCT) is an emerging imaging modality that enables noninvasive imaging of tissue with 1- to 3-microm resolutions. Initial OCT studies have typically been performed using harvested tissue specimens (ex vivo). No reports have investigated postexcision tissue degradation on OCT image quality. We investigate the effects of formalin fixation and commonly used cell culture media on tissue optical scattering characteristics in OCT images at different times postexcision compared to in vivo conditions. OCT imaging at 800-nm wavelength with 1.5-mum axial resolution is used to image the hamster cheek pouch in vivo, followed by excision and imaging during preservation in phosphate-buffered saline (PBS), Dulbecco's Modified Eagle's Media (DMEM), and 10% neutral-buffered formalin. Imaging is performed in vivo and at sequential time points postexcision from 15 min to 10 to 18 h. Formalin fixation results in increases in scattering intensity from the muscle layers, as well as shrinkage of the epithelium, muscle, and connective tissue of approximately 50%. PBS preservation shows loss of optical contrast within two hours, occurring predominantly in deep muscle and connective tissue. DMEM maintains tissue structure and optical scattering characteristics close to in vivo conditions up to 4 to 6 h after excision and best preserved tissue optical properties when compared to in vivo imaging.

Gastritis-associated adenocarcinoma and intestinal metaplasia in a Syrian hamster naturally infected with Helicobacter species

The objective of this study was to evaluate stomachs of 2-year-old Syrian hamsters that were naturally colonized by multiple Helicobacter species including Helicobacter aurati. A previous report on 7- to 12-month-old Syrian hamsters described chronic gastritis and intestinal metaplasia, a putative preneoplastic lesion in the stomach, without cancer. This report describes an invasive adenocarcinoma at the pyloric-duodenal junction in one of nine hamsters at a site of helicobacter-associated inflammation and marked intestinal metaplasia. Ceca of nine of nine animals were culture positive and polymerase chain reaction positive for Helicobacter spp. Furthermore, immunohistochemical analysis of the stomach using a H. pylori polyclonal antibody detected positive-staining bacteria within the pyloric region of three of nine hamsters including the neoplastic glands. However, argyrophilic bacteria were demonstrated only within the stomach of the hamster with gastric adenocarcinoma. This is a first report of gastric adenocarcinoma in helicobacter-infected hamsters. Syrian hamsters appear suitable as potential model for studying development of helicobacter-associated gastric adenocarcinomas.

Vascular endothelial growth factor and enhanced angiogenesis do not promote metastatic conversion of a newly established azoxymethane-induced colon cancer cell line

The organo-specific carcinogen, azoxymethane (AOM), produces colon tumors in mice that share many pathological features with sporadic human colorectal cancer (CRC). An important distinction between AOM-induced CRC and human CRC is lack of mucosal invasion in the murine model. To assess the role of the microenvironment in preventing the invasive phenotype, multiple benign in situ adenocarcinomas were harvested from AOM-treated mice and cultured in vitro. However, tumor cell growth was extremely limiting under standard culturing conditions. Thus, we injected tumor cells directly into nude mice and performed two serial transplants, and successfully explanted a rapidly growing epithelial tumor cell line (AJ02nm(0)). When injected subcutaneously (sc) into nude mice, AJ02nm(0) cells formed well-differentiated adenocarcinomas with minimal tumor invasive capacity. To define whether metastatic and invasive potential were related to lack of angiogenic stimuli, the AJ02nm(0) cells were transfected to overexpress murine vascular endothelial growth factor-164 (VEGF(164)). AJ02nm-VEGF cells produced rapidly growing tumors in nude mice that exhibited extensive pseudo-epithelial ductal architecture and supporting vasculature, but without increased invasive potential compared to controls. The established murine colon epithelial cell line provides a useful experimental model to further elaborate genetic and epigenetic factors that may promote or inhibit colon tumorigenesis and metastasis.

CD4+CD25+ regulatory lymphocytes induce regression of intestinal tumors in ApcMin/+ mice

Colorectal cancer in humans results from sequential genetic changes in intestinal epithelia commencing with inactivation of the APC tumor suppressor gene. Roles for host immunity in epithelial tumorigenesis are poorly understood. It has been previously shown that CD4+CD25+ lymphocytes inhibit colitis-associated epithelial tumors in Rag-deficient mice. Here we show that addition of CD4+CD25+ lymphocytes in ApcMin/+ mice reduces multiplicity of epithelial adenomas. Interleukin-10 was required in regulatory cells for therapeutic effect. Recipients of regulatory cells showed increased apoptosis and down-regulation of cyclooxygenase-2 within tumors coincident with tumor regression. These data suggest a role for regulatory lymphocytes in epithelial homeostasis in the ApcMin/+ mouse model of intestinal polyposis. Similarities with cancer of the breast, prostate, lung, and other sites raise the possibility of broader roles for regulatory lymphocytes in prevention and treatment of epithelial cancers in humans.

Cytolethal distending toxin is essential for Helicobacter hepaticus colonization in outbred Swiss Webster mice

Helicobacter hepaticus, which induces chronic hepatitis and typhlocolitis in susceptible mouse strains, produces a cytolethal distending toxin (CDT) consisting of CdtA, CdtB, and CdtC. A cdtB-deficient H. hepaticus isogenic mutant (HhcdtBm7) was generated and characterized for colonization parameters in four intestinal regions (jejunum, ileum, cecum, and colon) of outbred Swiss Webster (SW) mice. Inactivation of the cdtB gene abolished the ability of HhcdtBm7 to colonize female mice at both 8 and 16 weeks postinfection (wpi), whereas HhcdtBm7 colonized all of four intestinal regions of three of five males at 8 wpi and then was eliminated by 16 wpi. Wild-type (WT) H. hepaticus was detected in the corresponding intestinal regions of both male and female mice at 8 and 16 wpi; however, colonization levels of WT H. hepaticus in the cecum and colon of male mice were approximately 1,000-fold higher than in females (P < 0.0079) at 16 wpi. Infection with WT H. hepaticus, but not HhcdtBm7, at 8 wpi was associated with significantly increased mRNA level of ileal and cecal gamma interferon (IFN-gamma) in females (P < 0.016 and 0.031 between WT H. hepaticus-infected and sham-dosed females, respectively). In contrast, the mRNA levels of IFN-gamma were significantly higher in the colon (P < 0.0079) and trended to be higher in the cecum (P < 0.15) in the HhcdtBm7-colonized male mice versus the sham-dosed controls at 8 wpi. In addition, mRNA levels of ileal IFN-gamma were significantly higher in the control females than males at 8 wpi (P < 0.016). There were significantly higher Th1-associated immunoglobulin G2a (IgG2a), Th2-associated IgG1 and mucosal IgA (P < 0.002, 0.002, 0.002, respectively) responses in the mice infected with WT H. hepaticus when compared to HhcdtBm7 at 16 wpi. Colonic interleukin-10 (IL-10) expressions at 16 wpi were significantly lower in both female and male mice colonized by WT H. hepaticus or in males transiently colonized through 8 wpi by HhcdtBm7 versus control mice (P < 0.0159). These lines of evidence indicate that (i) H. hepaticus CDT plays a crucial role in the persistent colonization of H. hepaticus in SW mice; (ii) SW female mice are more resistant to H. hepaticus colonization than male mice; (iii) there was persistent colonization of WT H. hepaticus in cecum, colon, and jejunum but only transient colonization of H. hepaticus in the ileum of female mice; (iv) H. hepaticus colonization was associated with down-regulation of colonic IL-10 production.

Eradication of enteric helicobacters in Mongolian gerbils is complicated by the occurrence of Clostridium difficile enterotoxemia

Outbred Mongolian gerbils from a United States commercial source were examined for colonization with naturally occurring enterohepatic Helicobacter spp. Helicobacter spp. were identified in the cecum and colon by culture and by using genus-specific primers in polymerase chain reaction (PCR) assays. Nutritionally balanced triple-antibiotic wafers (containing amoxicillin, metronidazole, and bismuth) used previously to eliminate helicobacter infections in mice were administered in an attempt to eradicate the naturally occurring novel helicobacters in the gerbils. After 7 days of antibiotic treatment, two of the experimental animals died due to Clostridium difficile-associated enterotoxemia. However, at 3 weeks after antibiotic cessation, the surviving three animals had no Helicobacter spp. in the cecum or colon according to PCR analysis. Eradication of Helicobacter spp. using dietary administration of antibiotics was complicated by the presence of toxin-producing C. difficile. An alternate method to develop helicobacter-free gerbils (such as Caesarian rederivation) may be necessary.

PCBs and TCDD, alone and in mixtures, modulate marine mammal but not B6C3F1 mouse leukocyte phagocytosis

Increasing evidence has supported the general hypothesis that organochlorines (OC) can produce immunotoxic effects in marine mammals. One important innate defense mechanism is phagocytosis, the ability of cells to ingest extracellular macromolecules. The present study is aimed at characterizing the immunomodulatory potential of mixtures of OCs on phagocytosis compared to that of individual compounds in different species of marine mammals and mice, the traditional model to study mammalian immunotoxicity. The ability of peripheral blood neutrophils and monocytes to engulf fluorescent microspheres was evaluated using flow cytometry. The immunomodulatory effects of three non-coplanar polychlorinated biphenyl (PCB) congeners, 138, 153, 180, one coplanar PCB, 169, as well as 2,3,7,8-TCDD, and all possible mixtures (26) were tested upon in vitro exposure. All species were not equally sensitive to the adverse effects of OCs on either neutrophils or monocytes phagocytosis. With the exception of harbor seals, all mixtures that significantly modulated neutrophil or monocyte phagocytosis contained at least one non-coplanar PCB. Regression analysis revealed that the non-coplanar congeners, more than the coplanar congeners, explained the variability in phagocytosis. Dendrograms revealed that phylogeny could not predict immunotoxicity. The currently used toxic equivalency (TEQ) approach and the traditional mouse model both failed to predict experimentally induced immunomodulatory effects in marine mammals tested, leading us to question the reliability of both TEQs and mouse model in risk assessment of OC mixtures. Testing the relative sensitivity to immunomodulatory effects of contaminants and contaminant mixtures between different species of marine mammals may have important implications for risk assessment as well as conservation and management strategies.

Microgenomics: Identification of new expression profiles via small and single-cell sample analyses

BACKGROUND

Since the sequencing of the human genome has been finished, microgenomics has been booming, employing highly sophisticated, high-throughput platforms. But these mainly chip-based methods can only generate biologically relevant data if the samples investigated consist of homogeneous cell populations, in which no unwanted cells of different specificity and/or developmental stage obscure the results.

METHODS

Different sampling methods have been routinely applied to overcome the problem presented by heterogeneous samples, e.g., global surveys, cell cultures, and microdissection. Various methods of laser-assisted microdissection, employing either positive or negative selection of tissue areas or even single cells, are available.

RESULTS

These laser-assisted microdissection methods allow for fast and precise procurement of extremely small samples. Through subsequent application of recently developed methods of linear mRNA amplification in a pool of isolated total RNA, it has now become possible to perform complex high-throughput RNA expression profiling by microdissecting and processing even single-cell samples.

CONCLUSIONS

Studies using the tools and methods of microgenomics have shed light on how those new approaches will eventually aid in the development of a new generation of diagnostics, e.g., leading to new patient-specific drugs tailored to the requirements assessed by assaying only a few biopsy cells.

Genetic signatures of high- and low-risk aberrant crypt foci in a mouse model of sporadic colon cancer

To determine whether cancer risk is related to histopathological features of preneoplastic aberrant crypt foci (ACF), gene expression analysis was performed on ACF from two mouse strains with differing tumor sensitivity to the colonotropic carcinogen, azoxymethane. ACF from sensitive A/J mice were considered at high risk, whereas ACF from resistant AKR/J mice were considered at low risk for tumorigenesis. A/J and AKR/J mice received weekly injections of azoxymethane (10 mg/kg body weight), and frozen colon sections were prepared 6 weeks later. Immunohistochemistry was performed using biomarkers associated with colon cancer, including adenomatous polyposis coli, beta-catenin, p53, c-myc, cyclin D1, and proliferating cell nuclear antigen. Hyperplastic ACF, dysplastic ACF, microadenomas, adjacent normal-appearing epithelium, and vehicle-treated colons were laser captured, and RNA was linearly amplified (LCM-LA) and subjected to cDNA microarray-based expression analysis. Patterns of gene expression were identified using adaptive centroid algorithm. ACF from low- and high-risk colons were not discriminated by immunohistochemistry, with the exception of membrane staining of beta-catenin. To develop genetic signatures that predict cancer risk, LCM-LA RNA from ACF was hybridized to cDNA arrays. Of 4896 interrogated genes, 220 clustered into six broad clusters. A total of 226 and 202 genes was consistently altered in lesions from A/J and AKR/J mice, respectively. Although many alterations were common to both strains, expression profiles stratified high- and low- risk lesions. These data demonstrate that ACF with distinct tumorigenic potential have distinguishing molecular features. In addition to providing insight into colon cancer promotion, our data identify potential biomarkers for determining colon cancer risk in humans.

Azoxymethane-induced pre-adipocyte factor 1 (Pref-1) functions as a differentiation inhibitor in colonic epithelial cells

Inbred mice differ dramatically in their sensitivity to the colon carcinogen, azoxymethane (AOM). Identifying genes associated with this differential susceptibility in mice may ultimately reveal molecular mechanisms responsible for colon carcinogenesis. A cDNA array approach was taken to study gene expression changes induced by AOM in the colons of sensitive (A/J) and resistant (AKR) mice. Among the genes represented on the array, pre-adipocyte factor 1 (Pref-1), associated previously with suppression of adipocyte differentiation, was induced specifically by AOM in the distal colons of sensitive A/J mice (5.4-fold). Reverse transcription-PCR followed by sequence analysis revealed the presence of four alternative splice variants of Pref-1 mRNA in the colon. The potential significance of Pref-1 in colon tumorigenesis was explored in colon cancer cells infected with a retroviral construct containing the major splice variant. Over-expression of Pref-1A in HT-29 cells led to a marked resistance to butyrate-induced differentiation and growth inhibition. Our data indicate that Pref-1, a protein that suppresses differentiation and promotes colonocyte growth, may account in part for the sensitivity of A/J mice to AOM-induced carcinogenesis. In addition, detection of Pref-1 in a human colon tumor cell line suggests that it may also participate in human colon tumorigenesis.

Preliminary analysis of azoxymethane induced colon tumors in inbred mice commonly used as transgenic/knockout progenitors

Azoxymethane (AOM) is a colon carcinogen that is used to study the pathogenesis of sporadic colorectal cancer. We have evaluated differential susceptibility to AOM in inbred mice used as progenitors of recombinant/transgenic lines. In experiment 1, male FVB/N, 129/SvJ, C57Bl/6J mice were treated i.p. with 10 mg/kg AOM once per week for 4 weeks and sacrificed after 20 weeks. Only AOM-treated FVB/N mice developed tumors (3.6 tumors/mouse) in distal colon. In experiment 2, A/J, AKR/J, Balb/CJ mice were treated with AOM for 6 weeks and sacrificed after 24 weeks. AOM-treated A/J and Balb/CJ mice developed 9.2 and 1 tumor/mouse, respectively. Despite these differences, tumors had similar morphology regardless of strain. Immunohistochemistry with beta-catenin resulted in marked nuclear and cytoplasmic staining of tumor cells in FVB/N. However, fainter and heterogeneous beta-catenin staining was observed in A/J tumors, suggesting distinct pathways of tumorigenesis in different strains. Irrespective of cytological features of malignancy, tumor cells rarely breached the muscularis mucosa and showed no evidence of distant metastasis. Lack of invasiveness and metastasis in even the most sensitive strains provides a model system for studying the potential role of 'metastasis genes' in imparting a malignant phenotype.

Defective processing of the transforming growth factor-beta1 in azoxymethane-induced mouse colon tumors

High levels of the cell growth inhibitor transforming growth factor-beta1 (TGF-beta1) are often found in a variety of human cancers. However, the physiological significance of this overexpression depends on the availability of the biologically active form of TGF-beta1 within the extracellular matrix of the tumor microenvironment. To determine the expression and activation status of TGF-beta1 in chemically induced tumors, 6-wk-old A/J mice were injected intraperitoneally with either azoxymethane (AOM) (10 mg/kg body weight, once a week for 6 wk) or normal saline solution, and colon tumors were isolated 24 wk following the last injection. An enzyme-linked immunosorbent assay for TGF-beta1 revealed a significant increase (1.7-fold, P < 0.05) in total TGF-beta1 protein in tumors. Interestingly, while 80% of the total TGF-beta1 in the control colon tissues was in the active form, only 50% was found to be active in tumors. Together with our earlier observations that TGF-beta1 mRNA levels are unchanged in A/J tumors, these data further support a mechanism whereby elevated TGF-beta1 levels result from a defective activation and turnover of this protein. Because plasmin is known to be a major activator of TGF-beta1 in vivo, we hypothesized that reduced plasmin activity may be responsible for the observed dysregulation of TGF-beta1 processing in these behaviorally benign tumors. With a fluorogenic peptide substrate for serine proteases, a deficiency in plasmin activity was found in the tumors. Furthermore, semiquantitative reverse transcription (RT)-polymerase chain reaction (PCR) analysis of a panel of genes involved in the plasminogen activation system, including plasminogen activator inhibitor-1 (PAI-1), urokinase-plasminogen activator (u-PA), and urokinase-receptor (u-PAR-1), demonstrated a significant upregulation (approximately fourfold to sixfold, P < 0.05) in the expression of each of these genes in the tumor tissue. In addition, no significant changes were observed in the expression levels of thrombospondin-1 (TSP-1) and insulin-like growth factor type II receptor (IGF-IIR), which also mediate the activation of latent TGF-beta1. To gain further insight into the functionality of the TGF-beta1 pathway, cDNA microarrays were performed and the expression levels of a panel of 21 TGF-beta1-specific target genes were determined in AOM-induced tumors that overexpress the ligand. A significant dysregulation in the expression of each of these targets was observed, providing evidence of aberrant TGF-beta1 signaling in tumors. Overall, the present study demonstrates a very low plasmin activity in A/J colon tumors, possibly as a result of the potent inhibitory effect of PAI-1 on the plasminogen activation cascade. The observed deficiency in plasmin activity may not be sufficiently compensated for by other mechanisms of latent TGF-beta1 activation, including TSP-1 and IGF-IIR, thereby resulting in a decreased fraction of the biologically active form of TGF-beta1 and subsequent aberration in TGF-beta1-specific gene regulation in A/J tumors.

Multistage gene expression profiling in a differentially susceptible mouse colon cancer model

The DNA alkylating agent, azoxymethane (AOM), induces tumor formation in the distal colon of susceptible mice. Differential susceptibility to this colonotropic carcinogen has been well characterized in A/J (sensitive) and AKR/J (resistant) mice. However, the reasons underlying the differential response to AOM and the molecular mechanisms involved in colon tumor progression remain unclear. To address these issues, we used a cDNA microarray approach to determine time-related changes in gene expression patterns in A/J and AKR/J colons following carcinogen treatment. In the present study, mice were injected intraperitoneally with either AOM (10mg/kg body weight once a week for 6 weeks) or 0.9% NaCl solution (vehicle controls). Total RNA was isolated from the distal colons at 1, 4, and 24 weeks post-AOM exposure. RNA was reverse transcribed and cDNA samples labeled with Cy3 and Cy5 were hybridized to a glass chip containing 4608 mouse cDNA duplicate clones. The resulting mRNA expression levels were analyzed using GLEAMS 3.0, a Unix/Linux-based software program. Genes with more than twofold variations in expression levels were considered significant. Further clustering analysis was performed based on gene expression patterns at different time points using a novel adaptive centroid algorithm (ACA). Of the 4608 genes, 118 clustered into 11 significant groups that displayed similar and distinct expression patterns between the strains following carcinogen treatment. Nine clusters were selected for further analysis based on their divergence in response between A/J and AKR/J and their potential role in tumorigenesis. Overall, our data indicate time- and strain-specific genetic alterations during different stages of colon tumorigenesis following AOM treatment.

Inverse association between phospholipase A2 and COX-2 expression during mouse colon tumorigenesis

Cytosolic phospholipase A(2) (cPLA(2)) releases arachidonic acid (AA) from intracellular phospholipids. We evaluated the status of cPLA(2) in azoxymethane (AOM)-induced mouse colon tumors. Despite increased expression of cyclooxygenase 2 (3.7-fold) and PGE(2) (3.4-fold) production in tumors, cPLA(2) mRNA levels and enzyme activity were significantly reduced (3.6- and 3-fold, respectively). Reduced levels of cPLA(2) were also observed in pre-neoplastic aberrant crypt foci (ACF), a distinct morphological alteration that represents an early stage in the pathogenesis of colon tumors. Furthermore, the reciprocal expression patterns of these two genes were found to occur in human colorectal cancers (CRC). Examination of the activity of the secretory phospholipases A(2) (sPLA(2)) and expression of the groups V and X sPLA(2)s revealed no compensatory increase in tumor tissue. As cPLA(2) has been shown to be involved in TNF-alpha-induced apoptosis in certain cell types, and TNF-alpha expression is significantly enhanced in AOM-induced tumors (2.8-fold), we examined the role of cPLA(2) in TNF-alpha-induced apoptosis of cultured mouse colonocytes (YAMC). The specific cPLA(2) inhibitor, AACOCF(3) (arachidonoyl trifluoromethyl ketone), was able to protect colonocytes from TNF-alpha-induced apoptosis in vitro. In summary, our data demonstrate an inverse relationship between COX-2 and cPLA(2) expression in both AOM-induced mouse colon tumors and human CRC and suggest that down regulation of cPLA(2) may attenuate TNF-alpha mediated apoptosis during tumorigenesis and facilitate tumor progression.

Preliminary analysis of azoxymethane induced colon tumors in inbred mice commonly used as transgenic/knockout progenitors

Azoxymethane (AOM) is a colon carcinogen that is used to study the pathogenesis of sporadic colorectal cancer. We have evaluated differential susceptibility to AOM in inbred mice used as progenitors of recombinant/transgenic lines. In experiment 1, male FVB/N, 129/SvJ, C57Bl/6J mice were treated i.p. with 10 mg/kg AOM once per week for 4 weeks and sacrificed after 20 weeks. Only AOM-treated FVB/N mice developed tumors (3.6 tumors/mouse) in distal colon. In experiment 2, A/J, AKR/J, Balb/CJ mice were treated with AOM for 6 weeks and sacrificed after 24 weeks. AOM-treated A/J and Balb/CJ mice developed 9.2 and 1 tumor/mouse, respectively. Despite these differences, tumors had similar morphology regardless of strain. Immunohistochemistry with beta-catenin resulted in marked nuclear and cytoplasmic staining of tumor cells in FVB/N. However, fainter and heterogeneous beta-catenin staining was observed in A/J tumors, suggesting distinct pathways of tumorigenesis in different strains. Irrespective of cytological features of malignancy, tumor cells rarely breached the muscularis mucosa and showed no evidence of distant metastasis. Lack of invasiveness and metastasis in even the most sensitive strains provides a model system for studying the potential role of 'metastasis genes' in imparting a malignant phenotype.

Role of the alternating reading frame (P19)-p53 pathway in an in vivo murine colon tumor model

Considering the importance of the oncogene checkpoint function of the alternating reading frame(ARF)-p53 pathway, studies were undertaken to evaluate the status of this pathway in azoxymethane (AOM)-induced mouse colon tumors. A PCR-based analysis of ARF and p53 cDNAs in normal colon tissues and AOM-induced colon tumors failed to detect mutations in either of these two critical tumor suppressor genes. In addition, laser capture microdissection of tumors followed by PCR-based sequencing of exons 5-7 of genomic p53 showed that even the most pleomorphic cancer cells were p53 normal. A marked increase in ARF mRNA and protein levels was observed in colon tumors, indicating activation of the ARF-p53 pathway in these tumors. High levels of ARF protein stabilized p53 protein in the tumors, but the p53 protein showed little biochemical activity. Compared with a mouse colonocyte cell line that expresses high levels of wild-type p53 (YAMC), the p53 protein in tumors had no detectable DNA binding activity nor did it activate p21 expression. In fact, p21 levels were lower in tumor tissue relative to normal mucosa, even though p53 levels were approximately 30-fold higher in tumors relative to control. Within the A/J tumors, we also used a cDNA microarray approach to screen a panel of genes that are transcriptionally up- or down-regulated by functional p53. The expression patterns of these p53-regulated genes were consistent with a lack of functional p53. This work demonstrates that the ARF-p53 oncogene checkpoint can be overcome without p53 mutations and that the mechanism used to overcome this checkpoint involves the suppression of p53 transcriptional activating activity. The AOM colon cancer model may be well suited for studying tumor promotion events that precede p53 disruption.

Immunohistochemical detection of tumor suppressor gene p53 protein in feline injection site-associated sarcomas

Sarcomas associated with injection sites are a rare but important problem in cats. Immunohistochemical detection of p53 protein may correlate to mutation of the p53 tumor suppressor gene, a gene known to be important in oncogenesis. The expression of nuclear p53 protein in 40 feline injection site-assocated sarcomas was examined by immunohistochemical staining. In 42.5% (17/40), tumor cell nuclei were stained darkly; in 20% (8/40), tumor cell nuclei were stained palely; and in 37.5% (15/40), tumor cell nuclei were unstained. Immunohistochemical detection of p53 protein in a proportion of injection site-associated sarcomas suggests that mutation of the p53 gene may play a role in the pathogenesis of these tumors.

Mutational analysis of tumor suppressor gene p53 in feline vaccine site-associated sarcomas

OBJECTIVES

To investigate the role of tumor suppressor gene p53 mutation in feline vaccine site-associated sarcoma (VSS) development and to evaluate the relationship between p53 nucleotide sequence and protein expression.

SAMPLE POPULATION

Formalin-fixed paraffin-embedded tissues of 8 feline VSS with dark p53 immunostaining (high p53 expression) and 13 feline VSS with faint or no staining (normal p53 expression).

PROCEDURE

DNA was extracted from neoplastic and normal tissue from each paraffin block. The following 3 regions of the p53 gene were amplified by polymerase chain reaction: 379 base pair (bp) region of exon 5, intron 5, and exon 6, 108 bp region of exon 7, and 140 bp region of exon 8. Amplified p53 products were sequenced and compared with published feline p53. The p53 mutations identified were correlated with p53 mutations predicted by immunostaining.

RESULTS

Neoplastic cells of 5 of 8 (62.5%) VSS that had high p53 expression harbored single missense mutations within the p53 gene regions examined. The p53 gene mutations were not detected in the 13 tumors with normal p53 immunostaining. Nonneoplastic tissues adjacent to all 21 VSS lacked mutations of these p53 gene regions.

CONCLUSIONS

The p53 gene mutations were restricted to neoplastic tissue and, therefore, were unlikely to predispose to VSS. However, p53 mutations may have contributed to cancer progression in 5 of the 21 VSS. There was very good (kappa quotient = 0.67 with a confidence limit of 0.3 to 1.0), although not complete, agreement between prediction of mutation by p53 immunostaining and identification of mutations by sequencing of key p53 gene regions.

Differential expression of p16(INK4a) in azoxymethane-induced mouse colon tumorigenesis

Alterations in the p16(INK4a) gene have been implicated in the pathogenesis of different human cancers and animal tumors. We postulated that alterations in the p16(INK4a) gene may also be involved in mouse colon tumorigenesis induced by the chemical carcinogen azoxymethane (AOM). In the present study, p16(INK4a) deletion status and its expression were examined in an AOM-induced mouse colon tumor model. Polymerase chain reaction-based deletion analysis of p16(INK4a) exon 2 showed no deletions in the colon tumors. The expression and localization of p16(INK4a) and its gene product were examined by reverse transcription-polymerase chain reaction and immunohistochemical analyses, respectively. The p16(INK4a) mRNA levels were low, and in some cases undetectable, in control colon tissue. However, colon tumors exhibited an eightfold increase in p16(INK4a) mRNA level when compared with control colon tissue (P < 0.01). Whereas control colon epithelium was uniformly negative for p16(INK4a) immunoreactivity, p16(INK4a)-immunoreactive cells were markedly increased in preneoplastic lesions and adenomas isolated from AOM-treated mice. To further examine the p16(INK4a) regulatory pathway, the retinoblastoma tumor-suppressor protein (Rb) was also examined immunohistochemically in these tissues. A heterogeneous Rb immunostaining was observed in preneoplastic lesions and adenomas. Immunohistochemical analysis also showed a reciprocal relationship between p16(INK4a) and Rb protein expression. These findings suggest that alterations in the p16(INK4a)/Rb pathway may play an important role in AOM-induced mouse colon tumorigenesis. Mol. Carcinog. 28:139-147, 2000.