The promise of genetically engineered mice for cancer prevention studies

Hyaluronic Acid Nanoparticles for Immunogenic Chemotherapy of Leukemia and T-Cell Lymphoma

Ratiometric delivery of combination chemotherapy can achieve therapeutic efficacy based on synergistic interactions between drugs. It is critical to design such combinations with drugs that complement each other and reduce cancer growth through multiple mechanisms. Using hyaluronic acid (HA) as a carrier, two chemotherapeutic agents-doxorubicin (DOX) and camptothecin (CPT)-were incorporated and tested for their synergistic potency against a broad panel of blood-cancer cell lines. The pair also demonstrated the ability to achieve immunogenic cell death by increasing the surface exposure levels of Calreticulin, thereby highlighting its ability to induce apoptosis via an alternate pathway. Global proteomic profiling of cancer cells treated with HA-DOX-CPT identified pathways that could potentially predict patient sensitivity to HA-DOX-CPT. This lays the foundation for further exploration of integrating drug delivery and proteomics in personalized immunogenic chemotherapy.

Cancer models in preclinical research: A chronicle review of advancement in effective cancer research

Cancer is a major stress for public well-being and is the most dreadful disease. The models used in the discovery of cancer treatment are continuously changing and extending toward advanced preclinical studies. Cancer models are either naturally existing or artificially prepared experimental systems that show similar features with human tumors though the heterogeneous nature of the tumor is very familiar. The choice of the most fitting model to best reflect the given tumor system is one of the real difficulties for cancer examination. Therefore, vast studies have been conducted on the cancer models for developing a better understanding of cancer invasion, progression, and early detection. These models give an insight into cancer etiology, molecular basis, host tumor interaction, the role of microenvironment, and tumor heterogeneity in tumor metastasis. These models are also used to predict novel cancer markers, targeted therapies, and are extremely helpful in drug development. In this review, the potential of cancer models to be used as a platform for drug screening and therapeutic discoveries are highlighted. Although none of the cancer models is regarded as ideal because each is associated with essential caveats that restraint its application yet by bridging the gap between preliminary cancer research and translational medicine. However, they promise a brighter future for cancer treatment.

Cancer pharmacoprevention: Targeting polyamine metabolism to manage risk factors for colon cancer

Cancer is a set of diseases characterized by uncontrolled cell growth. In certain cancers of the gastrointestinal tract, the adenomatous polyposis coli (APC) tumor suppressor gene is altered in either germline or somatic cells and causes formation of risk factors, such as benign colonic or intestinal neoplasia, which can progress to invasive cancer. APC is a key component of the WNT pathway, contributing to normal GI tract development, and APC alteration results in dysregulation of the pathway for production of polyamines, which are ubiquitous cations essential for cell growth. Studies with mice have identified nonsteroidal anti-inflammatory drugs (NSAIDs) and difluoromethylornithine (DFMO), an inhibitor of polyamine synthesis, as potent inhibitors of colon carcinogenesis. Moreover, gene expression profiling has uncovered that NSAIDs activate polyamine catabolism and export. Several DFMO-NSAID combination strategies are effective and safe methods for reducing risk factors in clinical trials with patients having genetic or sporadic risk of colon cancer. These strategies affect cancer stem cells, inflammation, immune surveillance, and the microbiome. Pharmacotherapies consisting of drug combinations targeting the polyamine pathway provide a complementary approach to surgery and cytotoxic cancer treatments for treating patients with cancer risk factors. In this Minireview, we discuss the role of polyamines in colon cancer and highlight the mechanisms of select pharmacoprevention agents to delay or prevent carcinogenesis in humans.

Translational models of tumor angiogenesis: A nexus of in silico and in vitro models

Emerging evidence shows that endothelial cells are not only the building blocks of vascular networks that enable oxygen and nutrient delivery throughout a tissue but also serve as a rich resource of angiocrine factors. Endothelial cells play key roles in determining cancer progression and response to anti-cancer drugs. Furthermore, the endothelium-specific deposition of extracellular matrix is a key modulator of the availability of angiocrine factors to both stromal and cancer cells. Considering tumor vascular network as a decisive factor in cancer pathogenesis and treatment response, these networks need to be an inseparable component of cancer models. Both computational and in vitro experimental models have been extensively developed to model tumor-endothelium interactions. While informative, they have been developed in different communities and do not yet represent a comprehensive platform. In this review, we overview the necessity of incorporating vascular networks for both in vitro and in silico cancer models and discuss recent progresses and challenges of in vitro experimental microfluidic cancer vasculature-on-chip systems and their in silico counterparts. We further highlight how these two approaches can merge together with the aim of presenting a predictive combinatorial platform for studying cancer pathogenesis and testing the efficacy of single or multi-drug therapeutics for cancer treatment.

Mucin-1-Antibody-Conjugated Mesoporous Silica Nanoparticles for Selective Breast Cancer Detection in a Mucin-1 Transgenic Murine Mouse Model

Mucin-1 (MUC1), a transmembrane glycoprotein is aberrantly expressed on ~90% of breast cancer and is an excellent target for nanoparticulate targeted imaging. In this study, the development of a dye-doped NIR emitting mesoporous silica nanoparticles platform conjugated to tumor-specific MUC1 antibody (ab-tMUC1-NIR-MSN) for in vivo optical detection of breast adenocarcinoma tissue is reported. The structural properties, the in vitro and in vivo performance of this nanoparticle-based probe were evaluated. In vitro studies showed that the MSN-based optical imaging nanoprobe is non-cytotoxic and targets efficiently mammary cancer cells overexpressing human tMUC1 protein. In vivo experiments with female C57BL/6 mice indicated that this platform accumulates mainly in the liver and did not induce short-term toxicity. In addition, we demonstrated that the ab-tMUC1-NIR-MSN nanoprobe specifically detects mammary gland tumors overexpressing human tMUC1 in a human MUC1 transgenic mouse model.

Functional imaging of the angiogenic switch in a transgenic mouse model of human breast cancer by dynamic contrast enhanced magnetic resonance imaging

Tumour progression depends on several sequential events that include the microenvironment remodelling processes and the switch to the angiogenic phenotype, leading to new blood vessels recruitment. Non-invasive imaging techniques allow the monitoring of functional alterations in tumour vascularity and cellularity. The aim of this work was to detect functional changes in vascularisation and cellularity through Dynamic Contrast Enhanced (DCE) and Diffusion Weighted (DW) Magnetic Resonance Imaging (MRI) modalities during breast cancer initiation and progression of a transgenic mouse model (BALB-neuT mice). Histological examination showed that BALB-neuT mammary glands undergo a slow neoplastic progression from simple hyperplasia to invasive carcinoma, still preserving normal parts of mammary glands. DCE-MRI results highlighted marked functional changes in terms of vessel permeability (K(trans) , volume transfer constant) and vascularisation (vp , vascular volume fraction) in BALB-neuT hyperplastic mammary glands if compared to BALB/c ones. When breast tissue progressed from simple to atypical hyperplasia, a strong increase in DCE-MRI biomarkers was observed in BALB-neuT in comparison to BALB/c mice (K(trans)  = 5.3 ± 0.7E-4 and 3.1 ± 0.5E-4; vp  = 7.4 ± 0.8E-2 and 4.7 ± 0.6E-2 for BALB-neuT and BALB/c, respectively) that remained constant during the successive steps of the neoplastic transformation. Consistent with DCE-MRI observations, microvessel counting revealed a significant increase in tumour vessels. Our study showed that DCE-MRI estimates can accurately detect the angiogenic switch at early step of breast cancer carcinogenesis. These results support the view that this imaging approach is an excellent tool to characterize microvasculature changes, despite only small portions of the mammary glands developed neoplastic lesions in a transgenic mouse model.

Optimizing mouse models for precision cancer prevention

As cancer has become increasingly prevalent, cancer prevention research has evolved towards placing a greater emphasis on reducing cancer deaths and minimizing the adverse consequences of having cancer. 'Precision cancer prevention' takes into account the collaboration of intrinsic and extrinsic factors in influencing cancer incidence and aggressiveness in the context of the individual, as well as recognizing that such knowledge can improve early detection and enable more accurate discrimination of cancerous lesions. However, mouse models, and particularly genetically engineered mouse (GEM) models, have yet to be fully integrated into prevention research. In this Opinion article, we discuss opportunities and challenges for precision mouse modelling, including the essential criteria of mouse models for prevention research, representative success stories and opportunities for more refined analyses in future studies.

Critical roles of specimen type and temperature before and during fixation in the detection of phosphoproteins in breast cancer tissues

The most efficient approach for therapy selection to inhibit the deregulated kinases in cancer tissues is to measure their phosphorylation status prior to the treatment. The aim of our study was to evaluate the influence of pre-analytical parameters (cold ischemia time, temperature before and during tissue fixation, and sample type) on the levels of proteins and phosphoproteins in breast cancer tissues, focusing on the PI3 kinase/AKT pathway. The BALB-neuT mouse breast cancer model expressing HER2 and pAKT proteins and human biopsy and resection specimens were analyzed. By using quantitative reverse phase protein arrays (RPPA), 9 proteins and 16 phosphoproteins relevant to breast cancer biology were assessed. Cold temperatures before and during fixation resulted in a marked improvement in the preservation of the reactivity of biological markers (eg, ER, HER2) in general and, specifically, pHER2 and pAKT. Some phosphoproteins, eg, pHER2 and pAKT, were more sensitive to prolonged cold ischemia times than others (eg, pS6RP and pSTAT5). By comparing the phosphoprotein levels in core needle biopsies with those in resection specimens, we found a marked decrease in many phosphoproteins in the latter. Cold conditions can improve the preservation of proteins and phosphoproteins in breast cancer tissues. Biopsies ≤ 1 mm in size are the preferred sample type for assessing the activity of deregulated kinases for personalized cancer treatments because the phosphoprotein levels are better preserved compared with resection specimens. Each potential new (phospho)protein biomarker should be tested for its sensitivity to pre-analytical processing prior to the development of a diagnostic assay.

Targeting HER2 Positive Breast Cancer with Chemopreventive Agents

Human epidermal growth factor receptor 2-positive (HER2+) breast cancer is a subtype of breast cancer that is exhibited in approximately 20-30% of breast cancer cases. The overexpression of HER2 is typically associated with a more aggressive disease and poor prognosis. Currently, the therapeutic drugs trastuzumab and lapatinib are the most commonly used to combat HER2+ breast cancer. However, tumors can develop resistance to these drugs. A better understanding of the mechanism of how HER2+ breast cancer works will help aid the development for new therapeutic approaches which more closely target the source of the signaling dysfunction. This review summarizes four major points in the context of HER2 over-expressing breast cancer (i) HER2 as a molecular target in breast cancer therapy, (ii) current treatment options as well as ongoing clinical studies, (iii) animal and cellular models for the study of HER2 over-expressing breast cancer, and (iv) future therapies and chemopreventive agents used to target HER2+ breast cancer.

Tazarotene: randomized, double-blind, vehicle-controlled, and open-label concurrent trials for basal cell carcinoma prevention and therapy in patients with basal cell nevus syndrome

Sporadic human basal cell carcinomas (BCC) are generally well managed with current surgical modalities. However, in the subset of high-risk patients predisposed to developing large numbers of BCCs, there is an unmet need for effective, low-morbidity chemoprevention. This population includes fair-skinned patients with extensive sun exposure and those with genodermatoses such as the basal cell nevus (Gorlin) syndrome (BCNS). Tazarotene (Tazorac, Allergan) is a topical retinoid with relative specificity for RAR-β and RAR-γ receptors. We previously demonstrated tazarotene's robust anti-BCC efficacy in Ptch1(+/-) mice, a murine equivalent of BCNS, and others have found it to have some efficacy against sporadic human BCCs. We report here results of a randomized, double-blind, vehicle-controlled study in patients with BCNS evaluating the efficacy of topically applied tazarotene for BCC chemoprevention (N = 34 subjects), along with an open-label trial evaluating tazarotene's efficacy for chemotherapy of BCC lesions (N = 36 subjects) for a maximum follow-up period of 3 years. We found that only 6% of patients had a chemopreventive response and that only 6% of treated BCC target lesions were clinically cured. Our studies provide no evidence for either chemopreventive or chemotherapeutic effect of tazarotene against BCCs in patients with BCNS.

Monitoring therapy with MEK inhibitor U0126 in a novel Wilms tumor model in Wt1 knockout Igf2 transgenic mice using 18F-FDG PET with dual-contrast enhanced CT and MRI: early metabolic response without inhibition of tumor growth

PURPOSE

The understanding of the role of genetic alterations in Wilms tumor development could be greatly advanced using a genetically engineered mouse models that can replicate the development and progression of this disease in human patients and can be monitored using non-invasive structural and molecular imaging optimized for renal tumors.

PROCEDURES

Repetitive dual-contrast computed tomography (CT; intravenous and intraperitoneal contrast), T2-weighted magnetic resonance imaging (MRI), and delayed 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG) positron emission tomography (PET) were utilized for characterization of Igf2 biallelic expression/Wt1 knockout mouse model of Wilms tumor. For CT imaging, Ioversol 678 mg/ml in 200 μl was administered i.p. followed by 100 μl injected intravenously at 20 and 15 min prior to imaging, respectively. Static PET imaging studies were acquired at 1, 2, and 3 h after i.v. administration of (18)F-FDG (400 μCi). Coronal and sagittal T1-weighted images (TE/TR 8.5/620 ms) were acquired before and immediately after i.v. injection of 0.4 ml/kg gadopentetate dimeglumine followed by T2-weighted images (TE/TR 60/300 ms). Tumor tissue samples were characterized by histopathology and immunohistochemistry for Glut1, FASN, Ki67, and CD34. In addition, six Wt1-Igf2 mice were treated with a mitogen-activated protein kinase (MEK) inhibitor U0126 (50 μmol/kg i.p.) every 4 days for 6 weeks. (18)F-FDG PET/CT imaging was repeated at different days after initiation of therapy with U0126. The percent change of initial tumor volume and SUV was compared to non-treated historic control animals.

RESULTS

Overall, the best tumor-to-adjacent kidney contrast as well as soft tissue contrast for other abdominal organs was achieved using T2-weighted MRI. Delayed (18)F-FDG PET (3-h post (18)F-FDG administration) and dual-contrast CT (intravenous and intraperitoneal contrast) provided a more accurate anatomic and metabolic characterization of Wilms tumors in Wt1-Igf2 mice during early development and progression of renal tumors. Over the 8-month period, 46 Wt1-Igf2 mice and 8 littermate control mice were studied. Renal tumors were identified in 54.3 % of Wt1-Igf2 mice between post-natal 50-100 days. In 35.6 % of Wt1-Igf2 mice, tumors were localized in the right kidney; in 24 %, in the left kidney, while 40.4 % of Wt1-Igf2 mice had bilateral kidney tumors. Metastatic lesions were identified in 15.4 % of Wt1-Igf2 mice. Increased levels of Glut1 and IGF1R expression, high Ki67 labeling index, and a dense network of CD34+ microvessels in renal tumors was consistent with increased (18)F-FDG accumulation. Treatment with a MEK 1/2 inhibitor U0126 did not cause the inhibition of tumor growth as compared to untreated animals. However, after the first three to four doses (~2 weeks of treatment), a decrease in (18)F-FDG SUV was observed, as compared to pre-treatment levels (p < 0.05, paired Student t test), which constitutes a metabolic response. Six weeks later, despite continuing therapy, the (18)F-FDG SUV increased again to previous levels.

CONCLUSIONS

The optimized dual contrast PET/CT imaging with early post i.v. and i.p. contrast CT and 3 h delayed PET imaging after (18)F-FDG administration provides a sensitive and reliable method for detecting early tumor lesions in this endogenous mouse model of Wilms tumor and for monitoring their growth in response to targeted therapies. Therapy with MEK inhibitor U0126 produces only a transient inhibition of tumor glycolytic activity but does not inhibit tumor growth, which is due to continuing IGF2-induced signaling from IGF1R through the PI3K-AKT-mTOR pathway.

Rodent intestinal epithelial carcinogenesis: pathology and preclinical models

Colon cancer is a major human malignancy that afflicts millions of people throughout the world each year. Genetics and diet play large roles in colon carcinogenesis although chemicals may also contribute. For the past 40 years, scientists have studied experimentally induced intestinal carcinogenesis in rodents in order to elucidate the etiology and mechanisms involved. Comparative histopathology has revealed many similarities of rodent and human intestinal cancers. Comparative molecular pathology has also shown genetic similarities. More recently, genetically engineered mice and inflammatory colon cancer models have been used for investigating mechanisms and potential chemopreventive and treatment modalities. This review will focus on comparative histopathology and nonclinical models.

Early onset and enhanced growth of autochthonous mammary carcinomas in C3-deficient Her2/neu transgenic mice

Aside from its classical role in fighting infections, complement is an important, although poorly understood, component of the tumor microenvironment. In particular, the tumor growth-regulatory activities of complement remain under debate. To assess the role of the complement system in the progression of autochthonous mammary carcinomas, we have crossed complement component 3 (C3)-deficient (C3^−/−) BALB/c male mice with BALB/c females expressing the activated rat Her2/neu oncogene (neuT). Although neuT transgenic mice develop spontaneous mammary cancers with 100% penetrance, a significantly shorter tumor latency (i.e., earlier onset of the first palpable tumor), a higher frequency of multiple tumors (multiplicity), and a dramatic increase in the tumor growth rate were found in neuT-C3^−/− animals. The accelerated tumor onset observed in neuT-C3^−/− mice was paralleled by an earlier onset of spontaneous lung metastases and by an increase in Her2 expression levels, primarily on the surface of tumor cells. The percentage of immune cells infiltrating neuT carcinomas was similar in C3-deficient and C3-proficient mice, with the exception of a significant increase in the frequency of regulatory T cells in neuT-C3^−/− tumors. Of particular interest, the enhanced immunosuppression imparted by C3 deficiency clearly influenced the immunogenic phenotype of autochthonous mammary tumors as neuT-C3^−/− malignant cells transplanted into syngeneic immunocompetent hosts gave rise to lesions with a significantly delayed kinetics and reduced incidence as compared with cells obtained from neuT C3-proficient tumors. Finally, increased blood vessel permeability was evident in neuT-C3^−/− tumors, although a similar number of tumor vessels was found in neuT and neuT-C3^−/− lesions. Altogether, these data suggest that complement plays a crucial role in the immunosurveillance and, possibly, the immunoediting of Her2-driven autochthonous mammary tumors.

The cryobiology of spermatozoa

The impact of successful cryopreservation of spermatozoa can be found in many fields, including agriculture, laboratory animal medicine, and human assisted reproduction, providing a cost-effective and efficient method to preserve genetic material for decades. The success of any cryobiologic protocol depends critically on understanding the fundamentals that underlie the process. In this review, we summarize the biophysical fundamentals critical to much of the research in sperm cryobiology, provide a synopsis of the development of sperm cryobiology as a discipline, and present the current state and directions for future research in sperm cryobiology in the three major areas outlined above-agriculture, laboratory animal medicine, and human clinical assisted reproduction. There is much room for new research, both empiric and fundamental, in all areas, including refinement of mathematical models, optimization of cryoprotective agent addition and removal procedures for spermatozoa from many species, development of effective, efficient, and facile cryopreservation protocols and freezing containers for agricultural sperm cryopreservation, and tailoring cryopreservation protocols for individual human samples.

p53 cooperates with DNA methylation and a suicidal interferon response to maintain epigenetic silencing of repeats and noncoding RNAs

Large parts of mammalian genomes are transcriptionally inactive and enriched with various classes of interspersed and tandem repeats. Here we show that the tumor suppressor protein p53 cooperates with DNA methylation to maintain silencing of a large portion of the mouse genome. Massive transcription of major classes of short, interspersed nuclear elements (SINEs) B1 and B2, both strands of near-centromeric satellite DNAs consisting of tandem repeats, and multiple species of noncoding RNAs was observed in p53-deficient but not in p53 wild-type mouse fibroblasts treated with the DNA demethylating agent 5-aza-2'-deoxycytidine. The abundance of these transcripts exceeded the level of β-actin mRNA by more than 150-fold. Accumulation of these transcripts, which are capable of forming double-stranded RNA (dsRNA), was accompanied by a strong, endogenous, apoptosis-inducing type I IFN response. This phenomenon, which we named "TRAIN" (for "transcription of repeats activates interferon"), was observed in spontaneous tumors in two models of cancer-prone mice, presumably reflecting naturally occurring DNA hypomethylation and p53 inactivation in cancer. These observations suggest that p53 and IFN cooperate to prevent accumulation of cells with activated repeats and provide a plausible explanation for the deregulation of IFN function frequently seen in tumors. Overall, this work reveals roles for p53 and IFN that are key for genetic stability and therefore relevant to both tumorigenesis and the evolution of species.

Spontaneous transformation of murine epithelial cells requires the early acquisition of specific chromosomal aneuploidies and genomic imbalances

Human carcinomas are defined by recurrent chromosomal aneuploidies, which result in a tissue-specific distribution of genomic imbalances. In order to develop models for these genome mutations and to determine their role in tumorigenesis, we generated 45 spontaneously transformed murine cell lines from normal epithelial cells derived from bladder, cervix, colon, kidney, lung, and mammary gland. Phenotypic changes, chromosomal aberrations, centrosome number, and telomerase activity were assayed in control uncultured cells and in three subsequent stages of transformation. Supernumerary centrosomes, binucleate cells, and tetraploidy were observed as early as 48 hr after explantation. In addition, telomerase activity increased throughout progression. Live-cell imaging revealed that failure of cytokinesis, not cell fusion, promoted genome duplication. Spectral karyotyping demonstrated that aneuploidy preceded immortalization, consisting predominantly of whole chromosome losses (4, 9, 12, 13, 16, and Y) and gains (1, 10, 15, and 19). After transformation, focal amplifications of the oncogenes Myc and Mdm2 were frequently detected. Fifty percent of the transformed lines resulted in tumors on injection into immunocompromised mice. The phenotypic and genomic alterations observed in spontaneously transformed murine epithelial cells recapitulated the aberration pattern observed during human carcinogenesis. The dominant aberration of these cell lines was the presence of specific chromosomal aneuploidies. We propose that our newly derived cancer models will be useful tools to dissect the sequential steps of genome mutations during malignant transformation, and also to identify cancer-specific genes, signaling pathways, and the role of chromosomal instability in this process.

Antioxidants for prostate cancer chemoprevention: challenges and opportunities

Extensive research has led to the firm conclusion that antioxidants protect cells from damage caused by oxidative stress and its associated pathological conditions including inflammation. It has also been established that inflammation is a precursor in neoplastic transformation of the prostate. Although, a vast body of experimental and clinical evidence shows efficacy of antioxidants as preventive strategies for prostate cancer, there is a lack of consistent agreement in outcomes especially from recent large-scale randomized clinical trials. Despite these concerns, our understanding of the preventive mechanisms as well as clinical efficacy and safety data indicate that novel antioxidant therapeutics still hold great promise for prostate cancer chemoprevention. We propose that for effective use of antioxidants for prostate cancer prevention, further high impact translational research is needed with special attention on selecting those patients who will benefit from such intervention. Therefore, it is important to validate predictive biomarkers from successful trials and combine this with knowledge of preclinical characterization of antioxidants (and combinations) that will eventually facilitate the development of 'personalized prostate cancer chemoprevention'. In this review, we briefly describe some common and emerging antioxidants that have shown benefits in preclinical and clinical settings. Above all, we focus on summarizing the progress we made thus far in prostate cancer chemoprevention using antioxidants, the heightened interest and challenges in the future.

Targeting the tumor microenvironment: focus on angiogenesis

Tumorigenesis is a complex multistep process involving not only genetic and epigenetic changes in the tumor cell but also selective supportive conditions of the deregulated tumor microenvironment. One key compartment of the microenvironment is the vascular niche. The role of angiogenesis in solid tumors but also in hematologic malignancies is now well established. Research on angiogenesis in general, and vascular endothelial growth factor in particular, is a major focus in biomedicine and has led to the clinical approval of several antiangiogenic agents including thalidomide, bevacizumab, sorafenib, sunitinib, pazopanib, temesirolimus, and everolimus. Indeed, antiangiogenic agents have significantly changed treatment strategies in solid tumors (colorectal cancer, renal cell carcinoma, and breast cancer) and multiple myeloma. Here we illustrate important aspects in the interrelationship between tumor cells and the microenvironment leading to tumor progression, with focus on angiogenesis, and summarize derived targeted therapies.

Human tumor cells killed by anthracyclines induce a tumor-specific immune response

Immunogenic cell death is characterized by the early surface exposure of chaperones including calreticulin and HSPs, which affect dendritic cell (DC) maturation and the uptake and presentation of tumor antigens. It has also been shown that it is characterized by the late release of high mobility group box 1 (HMGB1), which acts through Toll-like receptor 4 (TLR4) and augments the presentation of antigens from dying tumor cells to DCs. Most of the data on immunogenic tumor cell death were obtained using mouse models. In this study, we investigated the capacity of clinically used chemotherapeutics to induce immunogenic cell death in human tumor cell lines and primary tumor cells. We found that only anthracyclines induced a rapid translocation of calreticulin, HSP70, and HSP90 to the cell surface and the release of HMGB1 12 hours after the treatment. The interaction of immature DCs with immunogenic tumor cells led to an increased tumor cell uptake and induces moderate phenotypic maturation of DCs. Killed tumor cell-loaded DCs efficiently stimulated tumor-specific IFN-γ-producing T cells. DCs pulsed with killed immunogenic tumor cells also induced significantly lower numbers of regulatory T cells than those pulsed with nonimmunogenic tumor cells. These data indicate that human prostate cancer, ovarian cancer, and acute lymphoblastic leukemia cells share the key features of immunogenic cell death with mice tumor cells. These data also identify anthracyclines as anticancer drugs capable of inducing immunogenic cell death in sensitive human tumor cells.

A Western-type diet accelerates tumor progression in an autochthonous mouse model of prostate cancer

Epidemiological studies have provided evidence suggesting an important role for diet and obesity in the development of cancer. Specifically, lipid nutrients of the diet have been identified as important regulators of tumor development and progression. In the present study, we have examined the role of dietary fat and cholesterol in the initiation and progression of prostate cancer using the well-characterized TRAMP mouse model. Consumption of a Western-type diet--that is, enriched in both fat and cholesterol--accelerated prostate tumor incidence and tumor burden compared to mice fed a control chow diet. Furthermore, we also show that this diet increased the extent and the histological grade of prostate tumors. These findings were confirmed by the presence of increased levels of protein markers of advanced tumors in prostates obtained from animals fed a Western-type diet compared to those obtained from control animals. Increased lung metastases in animals fed a Western-type diet were also observed. In addition, we found that with a Western diet, animals bearing tumors presented with reduced plasma cholesterol levels compared with animals fed a control diet. Finally, we show that tumors obtained from animals fed a Western-type diet displayed increased expression of the high-density lipoprotein receptor SR-BI and increased angiogenesis. Taken together, our data suggest that dietary fat and cholesterol play an important role in the development of prostate cancer.

Ethyl acetate fraction of adlay bran ethanolic extract inhibits oncogene expression and suppresses DMH-induced preneoplastic lesions of the colon in F344 rats through an anti-inflammatory pathway

Adlay ( Coix lachryma-jobi L. var. ma-yuen Stapf) is a grass crop and was reported to possess anti-inflammatory activity and an antiproliferative effect in cancer cell lines. The purpose of this study was to evaluate the effects of the ethyl acetate fraction of an adlay bran ethanolic extract (ABE-Ea) on colon carcinogenesis in an animal model and investigate its mechanism. Male F344 rats received 1,2-dimethylhydrazine (DMH) and consumed different doses of ABE-Ea. The medium-dose group (17.28 mg of ABE-Ea/day) exhibited the best suppressive effect on colon carcinogenesis and prevented preneoplastic mucin-depleted foci (MDF) formation. Moreover, RAS and Ets2 oncogenes were significantly down-regulated in this group compared to the negative control group, whereas Wee1, a gene involved in the cell cycle, was up-regulated. Cyclooxygenase-2 (COX-2) protein expression was significantly suppressed in all colons receiving the ABE-Ea, indicating that ABE-Ea delayed carcinogenesis by suppressing chronic inflammation. ABE-Ea included considerable a proportion of phenolic compounds, and ferulic acid was the major phenolic acid (5206 microg/g ABE-Ea) on the basis of HPLC analysis. Results from this study suggest that ABE-Ea suppressed DMH-indued preneoplastic lesions of the colon in F344 rats and that ferulic acid may be one of the active compounds.

Mouse models for breast cancer metastasis

Metastasis of cancer cells is the main cause of death in most breast cancer patients. Although markers for early diagnosis and drugs that limit the spread of cancer to other organs have been developed, it is difficult to prevent the relapse of breast cancer. Recent research has highlighted the importance of tumor environment in which communication between tumor cells and the body system occurs. Emerging data have suggested that animal models are a good system to investigate this communication. Therefore, studies with mouse models have been developed as a reasonable method for a systemic approach to understand breast cancer metastasis. In this review, we summarize mouse models of breast cancer and their applications to the study of human breast cancers, and discuss limitation of model system and advanced techniques to overcome it.

Promises and Limitations of Murine Models in the Development of Anticancer T-Cell Vaccines

Murine models have been instrumental in defining the basic mechanisms of antitumor immunity. Most of these mechanisms have since been shown to operate in humans as well. Based on these similarities, active vaccination strategies aimed at eliciting antitumor T-cell responses have been elaborated and successfully implemented in various mouse models. However, the results of human antitumor vaccination trials have been rather disappointing thus far. This review summarizes the different experimental approaches used in mice to induce antitumor T-cell responses and identifies some critical parameters that should be considered when evaluating results from murine models.

Review Paper: Implications of the “Cancer Stem Cell” Hypothesis on Murine Models of Colon Cancer and Colitis-associated Cancer

The use of murine models to investigate human diseases has been an invaluable tool. In the areas of inflammation and oncogenesis, such models have provided unique insights into pathogenesis and mechanisms to evaluate potential therapy. As such, one facet of these disease processes links inflammation and cancer. Inflammation is associated with at least 15% of the world's malignancies. One example of this relationship is documented in the association between colitis and colorectal cancer. To date, the precise molecular events linking inflammation and cancer remain unclear. A new paradigm that may bridge these processes includes the cancer stem cell hypothesis. In this review, murine models of colitis, colon cancer, and colitis-associated cancer are discussed in reference to the potential of this paradigm to clarify the relationship of these devastating diseases.

A short-term rat mammary carcinogenesis model for the prevention of hormonally responsive and nonresponsive in situ carcinomas

Preclinical models that accurately reproduce specific aspects of human disease etiology are invaluable for the initial development and evaluation of chemopreventive agents. We developed a novel, short-term prevention model, which is particularly useful for assessing the efficacy of a compound to prevent hormonally responsive and nonresponsive in situ carcinomas. In this model, carcinogenesis is induced by a high titer of neu-containing, replication-defective retrovirus. The multiplicity and size of the resulting in situ carcinomas are scored in whole-mounted, aluminum carmine-stained mammary glands at 15 days postinfusion. These in situ carcinomas represent a distinct biological time point in the development of neu-induced mammary cancer in the rat. They are characterized by high rates of proliferation (40.0%; P < 0.0001) and apoptosis (2.8%; P < 0.005) compared with mammary carcinomas. The majority of in situ carcinomas regress spontaneously after 20 days postinfusion. The in situ carcinomas at 15 days postinfusion exhibit hormonal responsiveness. The effects of the chemoprevention agents tamoxifen, celecoxib, and targretin on hormonally responsive and nonresponsive in situ carcinomas recapitulate those observed on mammary carcinomas at 12 and 18 weeks postinfusion for intact and ovariectomized rats, respectively. Neu-induced in situ carcinomas in the rat represent etiologically relevant intermediate time points of mammary carcinogenesis. Our prevention model represents a cost-efficient in vivo system to determine whether the preventive effects of a compound extend to hormonally nonresponsive mammary lesions, for which new chemoprevention approaches are needed.

The untapped potential of genetically engineered mouse models in chemoprevention research: opportunities and challenges

The past decade has witnessed the unveiling of a powerful new generation of genetically engineered mouse (GEM) models of human cancer, which are proving to be highly effective for elucidating cancer mechanisms and interrogating novel experimental therapeutics. This new generation of GEM models are well suited for chemoprevention research, particularly for investigating progressive stages of carcinogenesis, identifying biomarkers for early detection and intervention, and preclinical assessment of novel agents or combinations of agents. Here we discuss opportunities and challenges for the application of GEM models in prevention research, as well as strategies to maximize their relevance for human cancer.

Organotypic modelling as a means of investigating epithelial-stromal interactions during tumourigenesis

The advent of co-culture approaches has allowed researchers to more accurately model the behaviour of epithelial cells in cell culture studies. The initial work on epidermal modelling allowed the development of reconstituted epidermis, growing keratinocytes on top of fibroblasts seeded in a collagen gel at an air-liquid interface to generate terminally differentiated 'skin equivalents'. In addition to developing ex vivo skin sheets for the treatment of burns victims, such cultures have also been used as a means of investigating both the development and repair of the epidermis, in more relevant conditions than simple two-dimensional culture, but without the use of animals. More recently, by varying the cell types used and adjusting the composition of the matrix components, this physiological system can be adapted to allow the study of interactions between tumour cells and their surrounding stroma, particularly with regards to how such interactions regulate invasion. Here we provide a summary of the major themes involved in tumour progression and consider the evolution of the approaches used to study cancer cell behaviour. Finally, we review how organotypic models have facilitated the study of several key pathways in cancer development and invasion, and speculate on the exciting future roles for these models in cancer research.

Genetically modified mouse models in cancer studies

Genetically modified animals represent a resource of immense potential for cancer research. Classically, genetic modifications in mice were obtained through selected breeding experiments or treatments with powerful carcinogens capable of inducing random mutagenesis. A new era began in the early 1980s when genetic modifications by inserting foreign DNA genes into the cells of an animal allowed for the development of transgenic mice. Since that moment, genetic modifications have been able to be made in a predetermined way. Gene targeting emerged later as a method of in vivo mutagenesis whereby the sequence of a predetermined gene is selectively modified within an intact cell. In this review we focus on how genetically modified mice can be created to study tumour development, and how these models have contributed to an understanding of the genetic alterations involved in human cancer. We also discuss the strengths and weaknesses of the different mouse models for identifying cancer genes, and understanding the consequences of their alterations in order to obtain the maximum benefit for cancer patients.

ErbB2 transgenic mice: a tool for investigation of the immune prevention and treatment of mammary carcinomas

The epidermal growth factor receptor belongs to a superfamily of receptor tyrosine kinases (RTK) that includes ErbB2. ErbB2 is involved in normal physiological processes, such as embryogenesis, cell proliferation, differentiation, adhesion motility, and apoptosis, while its malfunction or overexpression is responsible for development defects, diabetes, and cancer. The human ortholog of ErbB2 is referred as Her-2 (human ErbB2) while the rat ortholog is referred as neu (rat ErbB2). As ErbB2 is directly involved in carcinogenesis, mice transgenic for the rat neu oncogene allow straightforward assessment of the ability of drugs and vaccines to inhibit the progression of neu-driven cancer. Information from this model may provide indications on the efficacy of similar treatments in patients. This commentary provides key information regarding the use of these transgenic mouse models for evaluation of the efficacy of anti-tumor strategies.

Dual inhibition of VEGFR and EGFR signaling reduces the incidence and size of intestinal adenomas in Apc(Min/+) mice

Both the epidermal growth factor (EGF) and the vascular endothelial growth factor (VEGF) pathways are associated with intestinal cancer, and therapeutic approaches targeting either EGF receptor (EGFR) or VEGF receptor (VEGFR) signaling have recently been approved for patients with advanced colorectal cancer. The Apc(Min/+) mouse is a well-characterized in vivo model of intestinal tumorigenesis, and animals with this genetic mutation develop macroscopically detectable adenomas from approximately 6 weeks of age. Previous work in the Apc(Min/+) mouse has shown that therapeutic approaches targeting either VEGFR or EGFR signaling affect predominantly the size or number of adenomas, respectively. In this study, we have assessed the effect of inhibiting both these key pathways simultaneously using ZD6474 (Vandetanib, ZACTIMA), a selective inhibitor of VEGFR and EGFR tyrosine kinases. To assess the effects of ZD6474 on early- and later-stage disease, treatment was initiated in 6- and 10-week-old Apc(Min/+) mice for 28 days. ZD6474 markedly reduced both the number and the size of polyps when administered at either an early or a later stage of polyp development. This reduction in both adenoma number and size resulted in a total reduction in tumor burden in the small intestine of nearly 75% in both studies (P < 0.01). The current data build on the concept that EGFR-dependent tumor cell proliferation and VEGF/VEGFR2-dependent angiogenesis and survival are distinct key mechanisms in polyp development. Pharmacologic inhibition of both signaling pathways has significant antitumor effects at both early and late stages of polyp development. Therefore, targeting both VEGFR- and EGFR-dependent signaling may be a beneficial strategy in early intestinal cancer.

Primer: first do no harm--when is it appropriate to plan a cancer prevention clinical trial?

Abundant preclinical and clinical data suggest that cancer is a preventable disease; however, few, if any, of the medical interventions available are completely without adverse effects or risk to the patient. This statement is especially true with regard to phenotypically healthy but high-risk populations. Balancing the risks from interventions with the risk of future life-threatening disease is particularly challenging because no standardized methodologies to perform such calculations exist. It is critical, therefore, to establish a framework for determining when interventions show sufficient promise of efficacy and sufficient safety to justify their testing in clinical trials. Systematic review of all available preclinical, epidemiological, and clinical data, along with a mechanistic understanding of the biology of the disease under study, is mandatory before clinical trials are embarked upon. This Review identifies the issues that are critical for decision-making when clinical trials in human beings are being contemplated and provides a framework that can be applied in making these decisions.

Transgenic models to study actions of prolactin in mammary neoplasia

Transgenic models to explore the role of prolactin and its interactions with other factors in mammary oncogenesis have begun to reveal the dynamic contributions of prolactin to the development and progression of this disease. Targeting prolactin to mammary epithelial cells mimics the local production of this hormone that is prominent in women, and permits studies in the absence of effects on the ovarian steroid milieu. These models have demonstrated that local production of prolactin is sufficient to induce mammary tumors after a long latency. Prolactin also can potentiate actions of other oncogenic stimuli, decreasing tumor latency and increasing incidence in several models. Augmented proliferation, without alteration of apoptosis, is a consistent feature. Pathways in addition to the well-characterized Jak2-Stat5 pathway, including ERK1/2 and Akt1/2, are implicated in these actions. These studies have also revealed a complex relationship with estrogen; while prolactin increases ERalpha expression, it does not require estrogenic ligand for lesion development, and indeed, in combination with the EGFR ligand, TGFalpha, prolactin can contribute to estrogen insensitivity. These studies highlight the utility of these models to decipher the interplay between prolactin and other oncogenic factors in breast cancer, with implications for preventative and therapeutic strategies.

Valproic Acid prolongs survival time of severe combined immunodeficient mice bearing intracerebellar orthotopic medulloblastoma xenografts

PURPOSE

To develop novel orthotopic xenograft models of medulloblastoma in severe combined immunodeficient mice and to evaluate the in vivo antitumor efficacy of valproic acid.

EXPERIMENTAL DESIGN

Orthotopic xenografts were developed by injecting 10(3) to 10(5) tumor cells from four medulloblastoma cell lines (D283-MED, DAOY, MHH-MED-1, and MEB-MED-8A) into the right cerebellum of severe combined immunodeficient mice. Animals were then examined for reproducibility of tumorigenicity, cell number-survival time relationship, and histopathologic features. Tumor growth was monitored in vivo by serially sectioning the xenograft brains at 2, 4, 6, and 8 weeks postinjection. Valproic acid treatment, administered at 600 microg/h for 2 weeks via s.c. osmotic minipumps, was initiated 2 weeks after injection of 10(5) medulloblastoma cells, and treated and untreated animals were monitored for differences in survival. Changes in histone acetylation, proliferation, apoptosis, differentiation, and angiogenesis in xenografts were also evaluated.

RESULTS

Tumorigenicity was maintained at 100% in D283-MED, DAOY, and MHH-MED-1 cell lines. These cerebellar xenografts displayed histologic features and immunohistochemical profiles (microtubule-associated protein 2, glial fibrillary acidic protein, and vimentin) similar to human medulloblastomas. Animal survival time was inversely correlated with injected tumor cell number. Treatment with valproic acid prolonged survival time in two (D283-MED and MHH-MED-1) of the three models and was associated with induction of histone hyperacetylation, inhibition of proliferation and angiogenesis, and enhancement of apoptosis and differentiation.

CONCLUSION

We have developed intracerebellar orthotopic models that closely recapitulated the biological features of human medulloblastomas and characterized their in vivo growth characteristics. Valproic acid treatment of these xenografts showed potent in vivo anti-medulloblastoma activity. These xenograft models should facilitate the understanding of medulloblastoma pathogenesis and future preclinical evaluation of new therapies against medulloblastoma.

Precancer in mice: animal models used to understand, prevent, and treat human precancers

We present a status report from the NCI Mouse Models of Human Cancers Consortium (MMHCC) Precancers Workshop held November 8 and 9, 2004. An expert panel, the Mouse Models Group (MMG) evaluated the status of mouse models of precancer emphasizing genetically engineered mouse models, especially of lining epithelium and their utilitarian value to human carcinogenesis. An outline of the background for the panel's considerations is provided with examples of past and current precancerous lesions in mice. The experimental use of oncogenic viruses and chemical carcinogens in mice led to operational definitions of initiation, promotion, and preneoplasia Preneoplastic and precancerous lesions are found in these models. In this precancer concept, most preneoplastic lesions are considered as potentially precancerous or at least an earlier stage in cancer development than typical pre-invasive epithelial lesions, which are often seen in these mouse models. Genetically engineered mice, used to test the oncogenicity of individual genes, develop precancers that are initiated by defined molecular and histopathologic changes. The mouse can be used to isolate and study precancers in detail, thereby providing a level of biological understanding not readily available in clinical disease. These studies suggest that genetically engineered mice are very useful preclinical models for chemoprevention and therapy.

Mouse Mammary Tumor Biology: A Short History

For over a century, mouse mammary tumor biology and the associated Mouse mammary tumor virus (MMTV) have served as the foundation for experimental cancer research, in general, and, in particular, experimental breast cancer research. Spontaneous mouse mammary tumors were the basis for studies of the natural history of neoplasia, oncogenic viruses, host responses, endocrinology, and neoplastic progression. However, lacking formal proof of a human mammary tumor virus, the preeminence of the mouse model faded in the 1980s. Since the late 1980s, genetically engineered mice (GEM) have proven extremely useful for studying breast cancer and have become the animal model for human breast cancer. Hundreds of mouse models of human breast cancer have been developed since the first demonstration, in 1984, that the mouse mammary gland could be molecularly targeted and used to test the oncogenicity of candidate human genes. Now, very few scientists can avoid using a mouse model to test the biology of their favorite gene. The GEM have attracted a new generation of molecular and cellular biologists eager to apply their skills to these surrogates of the human disease. Newcomers often enter the field without an appreciation of the origins of mouse mammary tumor biology and the basis for many of the prevailing concepts. Our purpose in writing this short history of mouse mammary tumor biology is to provide a historical perspective for the benefit of the newcomers. If Einstein was correct in that "we stand on the shoulders of giants," the neophytes should meet their giants.

Mammary carcinogenesis is preceded by altered epithelial cell turnover in transforming growth factor-alpha and c-myc transgenic mice

Identification of biomarkers that indicate an increased risk of breast cancer or that can be used as surrogates for evaluating treatment efficacy is paramount to successful disease prevention and intervention. An ideal biomarker would be identifiable before lesion development. To test the hypothesis that changes in cell turnover precede mammary carcinogenesis, we evaluated epithelial cell proliferation and apoptosis in mammary glands from transgenic mice engineered to develop mammary cancer due to expression in mammary epithelia of transforming growth factor alpha (TGF-alpha) or c-myc. In transgenic glands, before lesion development, epithelial cell turnover was enhanced overall compared with nontransgenic glands, indicating that aberrant cell turnover in normal epithelia may contribute to tumorigenesis. In addition, in tumor-containing glands, proliferation in normal epithelia was higher than in tumor-free transgenic glands, suggesting these cell populations influence one another. Finally, although c-myc glands displayed a uniformly high epithelial cell turnover regardless of age, cell turnover was reduced with aging in nontransgenic and TGF-alpha mice, indicating that some growth and death regulatory mechanisms remain intact in TGF-alpha epithelia. These observations support the evaluation of cell turnover as a biomarker of cancer risk and indicator of prevention/treatment efficacy in preclinical models and warrant validation in human breast cancer.

Using genetically engineered mouse models of cancer to aid drug development: an industry perspective

Recent developments in the generation and characterization of genetically engineered mouse models of human cancer have resulted in notable improvements in these models as platforms for preclinical target validation and experimental therapeutics. In this review, we enumerate the criteria used to assess the accuracy of various models with respect to human disease and provide some examples of their prognostic and therapeutic utility, focusing on models for cancers that affect the largest populations. Technological advancements that allow greater exploitation of genetically engineered mouse models, such as RNA interference in vivo, are described in the context of target and drug validation. Finally, this review discusses stratagems for, and obstacles to, the application of these models in the drug development process.

Vitamin D inhibits the formation of prostatic intraepithelial neoplasia in Nkx3.1;Pten mutant mice

PURPOSE

Epidemiologic studies have shown that reduced levels of vitamin D represent a major risk factor for prostate cancer. In this report, we have examined the efficacy of 1alpha,25-dihydroxyvitamin D(3) (1,25 D(3)) as a chemopreventive agent using Nkx3.1; Pten mutant mice, which recapitulate stages of prostate carcinogenesis from prostate intraepithelial neoplasia (PIN) to adenocarcinoma.

EXPERIMENTAL DESIGN

1,25 D(3) (or vehicle) was delivered continuously to Nkx3.1; Pten mutant or control mice for a 4-month period beginning before (precancerous cohort) or after (cancerous cohort) these mice developed PIN. At the conclusion of the study, the mice were analyzed for the occurrence of PIN and/or cancer phenotypes by histologic analyses and immunostaining using known markers of cancer progression in these mice.

RESULTS

We found that sustained delivery of 1,25 D(3) to the Nkx3.1; Pten mutant mice resulted in a significant reduction in the formation of PIN while having no apparent effect on the control mice. Furthermore, 1,25 D(3) was maximally effective when delivered before, rather than subsequent to, the initial occurrence of PIN. We further show that this 1,25 D(3)-mediated inhibition of PIN was coincident with up-regulation of vitamin D receptor expression in the prostatic epithelium of the mutant mice, as well as in CASP prostate epithelial cell lines developed from these mice, while having no effect on androgen receptor expression or androgen receptor signaling.

CONCLUSION

Our findings show the value of chemoprevention studies using Nkx3.1; Pten mutant mice, particularly for evaluating the efficacy and underlying mechanisms of potential agents and to gain insights about the optimal timing of their delivery. In particular, our study predicts that vitamin D may have differential effects during early-stage versus late-stage disease and that it is more likely to be beneficial if delivered either before the overt manifestation of clinically detectable disease or during the earliest disease stages, rather than in advanced disease. Thus, our findings support the assessment of vitamin D analogues for chemoprevention in clinical trials targeting patients with early-stage disease and also establish molecular markers that can be used in such trials to determine biological activity and to optimize further clinical trials.

Introduction of oncogenes into mammary glands in vivo with an avian retroviral vector initiates and promotes carcinogenesis in mouse models

We have adapted the avian leukosis virus RCAS (replication-competent avian sarcoma-leukosis virus LTR splice acceptor)-mediated somatic gene transfer technique to introduce oncogenes into mammary cells in mice transgenic for the avian subgroup A receptor gene, tva, under control of the mouse mammary tumor virus (MMTV) promoter. Intraductal instillation of an RCAS vector carrying the polyoma middle T antigen (PyMT) gene (RCAS-PyMT) induced multiple, oligoclonal tumors within 3 weeks in infected mammary glands of MMTV-tva transgenic mice. The rapid appearance of these tumors from a relatively small pool of infected cells (estimated to be approximately 2 x 10(3) cells per gland by infection with RCAS carrying a GFP gene; RCAS-GFP) was accompanied by a high fraction of cells positive for Ki67, Cyclin D1, and c-Myc, implying strong proliferation competence. Furthermore, the tumors displayed greater cellular heterogeneity than did tumors arising in MMTV-PyMT mice, suggesting that RCAS-PyMT transforms a relatively immature cell type. Infection of mice transgenic for both MMTV-Wnt-1 and MMTV-tva with RCAS virus carrying an activated Neu oncogene dramatically enhanced tumor formation over what is observed in uninfected bitransgenic animals. We conclude that infection of mammary glands with retrovirus vectors is an efficient means to screen candidate oncogenes for their capacity to initiate or promote mammary carcinogenesis in the mouse.

Mammary tumorigenesis and metastasis caused by overexpression of insulin receptor substrate 1 (IRS-1) or IRS-2

Insulin receptor substrates (IRSs) are signaling adaptors that play a major role in the metabolic and mitogenic actions of insulin and insulin-like growth factors. Reports have recently noted increased levels, or activity, of IRSs in many human cancers, and some have linked this to poor patient prognosis. We found that overexpressed IRS-1 was constitutively phosphorylated in vitro and in vivo and that transgenic mice overexpressing IRS-1 or IRS-2 in the mammary gland showed progressive mammary hyperplasia, tumorigenesis, and metastasis. Tumors showed extensive squamous differentiation, a phenotype commonly seen with activation of the canonical beta-catenin signaling pathway. Consistent with this, IRSs were found to bind beta-catenin in vitro and in vivo. IRS-induced tumorigenesis is unique, given that the IRSs are signaling adaptors with no intrinsic kinase activity, and this supports a growing literature indicating a role for IRSs in cancer. This study defines IRSs as oncogene proteins in vivo and provides new models to develop inhibitors against IRSs for anticancer therapy.

Immunoprevention of cancer

This article discusses the current understanding of the interactions between tumors and cells of the immune system, particularly at the early stages of carcinogenesis. A growing body of data suggests that these interactions help shape the eventual development of tumors. Inflammation is a common feature of several cancers, and the immune system can serve as a two-edged sword against cancer, capable of supporting and suppressing cancer. Data from human studies show that the immune system is capable of detecting the smallest expansions of transformed cells, well before the development of clinical cancer. These advances suggest a need to change the current emphasis for harnessing antitumor immunity from therapy to prevention of cancers.

MMP-9 is differentially expressed in primary human colorectal adenocarcinomas and their metastases

Matrix metalloproteinase-9 (MMP-9) is up-regulated in macrophages in various human cancer types. In human colon cancer, MMP-9 is expressed in a macrophage subpopulation located at the tumor edge, indicating a specific induction of MMP-9 in macrophages in direct association with cancer invasion. To test whether MMP-9 is also induced in tumor edge macrophages in metastases from colorectal adenocarcinomas, we have compared the expression pattern of MMP-9 in primary colorectal adenocarcinomas (n = 15) with that in liver metastases (n = 15) and local lymph node metastases (n = 7) from the same patients by in situ hybridization and immunohistochemistry. In all the colorectal adenocarcinomas, the expression of MMP-9 mRNA and immunoreactivity in macrophages was located at the invasive front. In contrast, only 3 of the 15 liver metastases had MMP-9 mRNA and immunoreactivity at the periphery, and this expression was confined to small foci of macrophages located either among lymphocytes or in a dense desmoplastic stroma. Expression of MMP-9 mRNA and immunoreactivity was in all liver metastases seen in macrophages located in the lumen of malignant glandular structures and in central necrotic tissue. In all the 7 lymph node metastases, MMP-9 mRNA and immunoreactivity was seen in macrophages located in the stromal tissue surrounding the metastases. We conclude that MMP-9 is not up-regulated in tumor edge macrophages in liver metastases like in their primary tumor and local lymph node metastases, suggesting that disseminating colorectal cancer cells can adopt alternative proteolytic mechanisms for invasion depending on the local microenvironment.

A methodologic analysis of chemoprevention and cancer prevention strategies for gastrointestinal cancer

Gastroenterology lags behind other specialties such as cardiology in the quality of its evidence base for clinical practice. One area where this is particularly evident is in cancer prevention, despite developments in chemoprevention strategies for high-risk patients. For chemoprevention strategies to be successful, we need appropriate clinical networks and translational science infrastructures, model chemoprevention agents and multiple, large, flexible and randomized clinical trials. Translational science must also be embedded into large-scale, long-term, randomized clinical trials that have hard endpoints, so that irrefutable evidence of the longevity of treatment efficacy can be gathered. We also need to be able to identify an individual's cancer risk using valid global patient populations, so that medical benefits can be applied to all, regardless of ethnicity, sex, economic status, age and comorbidities. The future success of gastrointestinal chemoprevention relies on fostering a closer link between basic pharmaceutical research and clinical applications, in a 'bench to bedside and back' manner. In this review we systematically assess the evidence for various cancer prevention strategies, especially chemoprevention, and highlight the obstacles to further exploitation of this knowledge base.

Interferon regulatory factor-5-regulated pathways as a target for colorectal cancer therapeutics

Colorectal cancer is the second most common cause of cancer-related death. A significant obstacle to successful management of patients with colorectal cancer is intrinsic drug resistance or, in patients who initially responded to chemotherapy, acquired drug resistance. Failure in normal apoptotic pathways often contributes to resistance to anticancer drugs or radiotherapy. As a result, the identification of genes that control cell death and apoptosis has come to the forefront of cancer research, leading to new targets and novel therapeutic strategies in the treatment of colorectal cancer. To this effect, the authors have recently identified a new apoptotic signaling pathway that occurs through the transcription factor interferon regulatory factor-5. Here, the different strategies for targeting the interferon regulatory factor-5 signaling pathway in colorectal cancer are discussed. These strategies can be applied to a new generation of cytotoxic agents, as well as to novel biological compounds that are directed at inducing and/or activating interferon regulatory factor-5 or key components of this pathway.

Vaccines for tumour prevention

Despite tremendous progress in basic and epidemiological research, effective prevention of most types of cancer is still lacking. Vaccine use in cancer therapy remains a promising but difficult prospect. However, new mouse models that recapitulate significant features of human cancer progression show that vaccines can keep precancerous lesions under control and might eventually be the spearhead of effective and reliable ways to prevent cancer.

How good are rodent models of carcinogenesis in predicting efficacy in humans? A systematic review and meta-analysis of colon chemoprevention in rats, mice and men

Tumours in rodent and human colon share many histological and genetic features. To know if rodent models of colon carcinogenesis are good predictors of chemopreventive efficacy in humans, we conducted a meta-analysis of aspirin, beta-carotene, calcium, and wheat bran studies. Controlled intervention studies of adenoma recurrence in human volunteers were compared with chemoprevention studies of carcinogen-induced tumours in rats, and of polyps in Min (Apc(+/-)) mice: 6714 volunteers, 3911 rats and 458 mice were included in the meta-analyses. Difference between models was small since most global relative risks were between 0.76 and 1.00. A closer look showed that carcinogen-induced rat studies matched human trials for aspirin, calcium, carotene, and were compatible for wheat bran. Min mice results were compatible with human results for aspirin, but discordant for calcium and wheat bran (no carotene study). These few results suggest that rodent models roughly predict effect in humans, but the prediction is not accurate for all agents. Based on three cases only, the carcinogen-induced rat model seems better than the Min mouse model. However, rodent studies are useful to screen potential chemopreventive agents, and to study mechanisms of carcinogenesis and chemoprevention.

An animal model for the rapid induction of tongue neoplasms in human c-Ha-ras proto-oncogene transgenic rats by 4-nitroquinoline 1-oxide: its potential use for preclinical chemoprevention studies

Oral squamous cell carcinoma is one of the most common human neoplasms, and prevention of this malignancy requires a better understanding of its carcinogenesis process. To this end, we tried to establish an animal model using the human c-Ha-ras proto-oncogene-carrying transgenic (Tg) rats and the carcinogen 4-nitroquinoline 1-oxide (4-NQO). 4-NQO (20 p.p.m.) was administered to Tg and non-Tg rats for 8 weeks in their drinking water, and then the occurrence of tongue carcinogenesis was compared during the experimental period of 22 weeks. In addition, we determined the DNA ploidy in tongue lesions and examined the immunohistochemical expression of five biomarkers such as cyclin D1, glutathione S-transferase placental form, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) and beta-catenin. Next, the cancer chemopreventive effects of nimesulide, pioglitazone and a synthetic geranylated derivative, which have been reported to be inhibitors of tongue carcinogenesis, were examined in Tg rats treated with 4-NQO. Either during or after treatment with 4-NQO in the drinking water, tongue dysplasia and tumors were observed on the tongues of both Tg and non-Tg rats, with a greater incidence and multiplicity in Tg rats. Histopathologically, squamous cell dysplasia, papilloma and carcinoma with or without invasion were present in the tongue. Immunohistochemistry revealed that expression levels against five biomarkers increase with disease progression, and the changes correlated with those of the DNA ploidy pattern. Interestingly, a strong expression of COX-2, iNOS and beta-catenin was observed on the invasive front of squamous cell carcinomas. A subsequent chemoprevention study using Tg rats showed that the chemicals tested suppressed the occurrence of tongue carcinomas when they were administered after 4-NQO-exposure. These results may thus indicate that our 4-NQO-induced Tg rat tongue carcinogenesis model simulates many aspects of human oral carcinogenesis and it can be applied for an analysis of oral cancer development while also helping to identify potentially effective cancer chemopreventive agents against oral cancer.