The use of animal models for cancer chemoprevention drug development

Evaluation of antioxidant, anti-inflammatory, anticancer activities and molecular docking of Moringa oleifera seed oil extract against experimental model of Ehrlich ascites carcinoma in Swiss female albino mice

The current research intended to evaluate the antitumor properties of Moringa oleifera oil extract (MOE). Fifty-six female Swiss albino mice were employed in this study. Animals were assigned into four groups: control (C) group, moringa oil extract (MOE) group administered (500 mg/kg b. wt) MOE daily via gavage, Ehrlich ascites carcinoma (EAC) group and EAC group administered daily with (500 mg/kg b.wt) MOE for two weeks (EAC/MOE). The results showed that MOE significantly ameliorated the EAC increase in body weight and reduced the EAC cell viability. In addition, they upgraded the levels of hepatic and renal functions, inflammatory cytokines, oxidative stress markers and EAC-induced hepatic and renal histopathological changes. Treatment of EAC with MOE induced antitumor, anti-inflammatory and antioxidant effects and normalized most of the tested parameters besides the histopathological alterations in both renal and hepatic tissues. HPLC for the MOE identified Cinnamic acid, Ellagic acid, Quercetin, Gallic acid, Vanillin and Hesperidin as major compounds. The molecular docking study highlighted the virtual binding of the identified compounds inside the GSH and SOD proteins, especially for Quercetin which exhibited promising binding affinity with good interactive binding mode with the key amino acids. These results demonstrate that the antitumor constituents of MOE against EAC induced oxidative stress and inflammation by preventing oxidative damage and controlling EAC increase.

The interplay of cells, polymers, and vascularization in three-dimensional lung models and their applications in COVID-19 research and therapy

Millions of people have been affected ever since the emergence of the corona virus disease of 2019 (COVID-19) outbreak, leading to an urgent need for antiviral drug and vaccine development. Current experimentation on traditional two-dimensional culture (2D) fails to accurately mimic the in vivo microenvironment for the disease, while in vivo animal model testing does not faithfully replicate human COVID-19 infection. Human-based three-dimensional (3D) cell culture models such as spheroids, organoids, and organ-on-a-chip present a promising solution to these challenges. In this report, we review the recent 3D in vitro lung models used in COVID-19 infection and drug screening studies and highlight the most common types of natural and synthetic polymers used to generate 3D lung models.

Fibroblast Activation Protein Inhibitor Theranostics

Fibroblast activation protein (FAP) was first reported in 1986. However, FAP is not expressed in normal fibroblasts, normal or malignant epithelial cells, or the stroma of benign epithelial tumors. FAP is a cell membrane-bound serine peptidase overexpressed on the surface of cancer-associated fibroblasts and, as such, is a novel target for molecular imaging of several tumors. FAP inhibitors (FAPI) are potential theranostic molecular probes for various cancers. A tumor model expressing FAP was used to verify or confirm the usefulness of FAPI experimentally.

Gamma-ray Irradiation of Rodent Diets Alters the Urinary Metabolome in Rats with Chemically Induced Mammary Cancer

In this study, a comparative, untargeted metabolomics approach was applied to compare urinary metabolite profiles of rats fed irradiated and non-irradiated diets. γ-Irradiated and non-irradiated NIH 7001 diet was given orally to animals beginning 5 days after exposure to the carcinogen N-methyl-N-nitrosourea and continued for 120 days. There was a 36% reduction in mammary tumor incidence in rats consuming the γ-irradiated diet, compared to rats receiving the non-irradiated form of the same diet. Urine samples from rats fed with γ-irradiated and non-irradiated diets were analyzed using nanoLC-MS/MS on a Q-TOF mass spectrometer, collecting positive and negative ion data. Data processing involved feature detection and alignment with MS-DIAL, normalization, mean-centering and Pareto scaling, and univariate and multivariate statistical analysis using MetaboAnalyst, and pathway analysis with Mummichog. Unsupervised Principal Component Analysis and supervised Partial Least Squares-Discriminant Analysis of both negative and positive ions revealed separation of the two groups. The top 25 metabolites from variable importance in projection scores >1 showed their contributions in discriminating urines the γ-irradiated diet fed group from non-irradiated control diet group. Consumption of the γ-irradiated diet led to alteration of several gut microbial metabolites such as phenylacetylglycine, indoxyl sulfate, kynurenic acid, hippurate and betaine in the urine. This study provides insights into metabolic changes in rat urine in response to a γ-irradiated diet which may be associated with mammary cancer prevention.

Association of Diabetes Mellitus and Alcohol Abuse with Cancer: Molecular Mechanisms and Clinical Significance

Diabetes mellitus (DM), one of the metabolic diseases which is characterized by sustained hyperglycemia, is a life-threatening disease. The global prevalence of DM is on the rise, mainly in low- and middle-income countries. Diabetes is a major cause of blindness, heart attacks, kidney failure, stroke, and lower limb amputation. Type 2 diabetes mellitus (T2DM) is a form of diabetes that is characterized by high blood sugar and insulin resistance. T2DM can be prevented or delayed by a healthy diet, regular physical activity, maintaining normal body weight, and avoiding alcohol and tobacco use. Ethanol and its metabolites can cause differentiation defects in stem cells and promote inflammatory injury and carcinogenesis in several tissues. Recent studies have suggested that diabetes can be treated, and its consequences can be avoided or delayed with proper management. DM has a greater risk for several cancers, such as breast, colorectal, endometrial, pancreatic, gallbladder, renal, and liver cancer. The incidence of cancer is significantly higher in patients with DM than in those without DM. In addition to DM, alcohol abuse is also a risk factor for many cancers. We present a review of the recent studies investigating the association of both DM and alcohol abuse with cancer incidence.

Transcending toward Advanced 3D-Cell Culture Modalities: A Review about an Emerging Paradigm in Translational Oncology

Cancer is a disorder characterized by an uncontrollable overgrowth and a fast-moving spread of cells from a localized tissue to multiple organs of the body, reaching a metastatic state. Throughout years, complexity of cancer progression and invasion, high prevalence and incidence, as well as the high rise in treatment failure cases leading to a poor patient prognosis accounted for continuous experimental investigations on animals and cellular models, mainly with 2D- and 3D-cell culture. Nowadays, these research models are considered a main asset to reflect the physiological events in many cancer types in terms of cellular characteristics and features, replication and metastatic mechanisms, metabolic pathways, biomarkers expression, and chemotherapeutic agent resistance. In practice, based on research perspective and hypothesis, scientists aim to choose the best model to approach their understanding and to prove their hypothesis. Recently, 3D-cell models are seen to be highly incorporated as a crucial tool for reflecting the true cancer cell microenvironment in pharmacokinetic and pharmacodynamics studies, in addition to the intensity of anticancer drug response in pharmacogenomics trials. Hence, in this review, we shed light on the unique characteristics of 3D cells favoring its promising usage through a comparative approach with other research models, specifically 2D-cell culture. Plus, we will discuss the importance of 3D models as a direct reflector of the intrinsic cancer cell environment with the newest multiple methods and types available for 3D-cells implementation.

Targeting breast cancer using pirarubicin-loaded vasoactive intestinal peptide grafted sterically stabilized micelles

In this study the chemotherapeutic agent Pirarubicin (PRB) which is known for its serious side effects was actively targeted to the breast cancer cells by uploading it to the biocompatible and biodegradable Sterically Stabilized Micelles (SSMs) made of 1,2- Distearoyl- sn- glycero‑3- phosphoethanolamine- N- methoxy‑ polyethylene glycol 2000 (DSPE-PEG₂₀₀₀) to enhance efficacy and reduce toxicity. Vasoactive intestinal peptide (VIP), the receptors of which are overexpressed on the breast cancer cells, was grafted on the surface of the micelles. To the best of our knowledge this is the first report on active targeting of PRB to tumor site. For this purpose, PRB loaded VIP grafted SSMs (PRB-SSM-VIP) were synthesized and characterized. The in vitro efficiency of PRB-SSM-VIP along with SSM and free PRB was investigated on the MCF-7 breast cancer cells and the in vivo effects were studied on the 4T1 breast cancer bearing nude mice. Solubilizing 300 µg of PRB using 2.81 mg of DSPE-PEG₂₀₀₀ resulted in obtaining monodispersed particles of 12.16 ± 2.7 nm with slow drug release profile. Incorporation of PRB within the hydrophobic DSPE core of SSM was confirmed using differential scanning calorimetry (DSC) and the spherical shape of the synthesized particles was demonstrated using atomic force microscope (AFM). Both in vitro and in vivo studies showed significantly higher activity of PRB-SSM-VIP compared to free PRB. In vivo imaging showed successful accumulation of PRB-SSM-VIP at the tumor site and 98.8% tumor eradication was obtained with no signs of side effects. Current study suggests that SSM-VIP could be used as new drug delivery system for targeting PRB to the breast cancer cells.

Norcantharidin Suppresses YD-15 Cell Invasion Through Inhibition of FAK/Paxillin and F-Actin Reorganization

Norcantharidin (NCTD), a demethylated derivative of cantharidin, has been reported to exhibit activity against various types of cancers. However, the anti-invasive effects of NCTD and its molecular mechanism in human mucoepidermoid carcinoma (MEC) remain incompletely elucidated. Clonogenic, wound healing, invasion, zymography, western blotting and immunocytochemistry assays were performed in YD-15 cells to investigate the anti-invasive effect of NCTD and its molecular mechanism of action. The inhibitory effects of NCTD on invasiveness were compared with those of a novel focal adhesion kinase (FAK) kinase inhibitor, PF-562271. NCTD markedly suppressed the colony formation, migration, and invasion of YD-15 cells as well as the activities of MMP-2 and MMP-9. It disrupted F-actin reorganization through suppressing the FAK/Paxillin axis. Moreover, NCTD exhibited a powerful anti-invasive effect compared with that of PF-562271 in YD-15 cells. Collectively, these results suggest that NCTD has a potential anti-invasive activity against YD-15 cells. This study may clarify the impact of NCTD on migration and invasion of human MEC cells.

Mouse models in endocrine tumors

Endocrine and neuroendocrine tumors comprise a highly heterogeneous group of neoplasms that can arise from (neuro)endocrine cells, either from endocrine glands or from the widespread diffuse neuroendocrine system, and, consequently, are widely distributed throughout the body. Due to their diversity, heterogeneity and limited incidence, studying in detail the molecular and genetic alterations that underlie their development and progression is still a highly elusive task. This, in turn, hinders the discovery of novel therapeutic options for these tumors. To circumvent these limitations, numerous mouse models of endocrine and neuroendocrine tumors have been developed, characterized and used in pre-clinical, co-clinical (implemented in mouse models and patients simultaneously) and post-clinical studies, for they represent powerful and necessary tools in basic and translational tumor biology research. Indeed, different in vivo mouse models, including cell line-based xenografts (CDXs), patient-derived xenografts (PDXs) and genetically engineered mouse models (GEMs), have been used to delineate the development, progression and behavior of human tumors. Results gained with these in vivo models have facilitated the clinical application in patients of diverse breakthrough discoveries made in this field. Herein, we review the generation, characterization and translatability of the most prominent mouse models of endocrine and neuroendocrine tumors reported to date, as well as the most relevant clinical implications obtained for each endocrine and neuroendocrine tumor type.

Screening of Chemopreventive Agents in Animal Models: Results on Reproducibility, Agents of a Given Class, and Agents Tested During Tumor Progression

Because of the importance of testing reproducibility of results, we present our findings regarding screening agents in preclinical chemoprevention studies in rodent models performed by the Chemopreventive Agent Development Research Group (CADRG) of the Division of Cancer Prevention of the NCI. These studies were performed via contracts to various commercial and academic laboratories. Primarily, results with positive agents are reported because positive agents may progress to the clinics. In testing reproducibility, a limited number of direct repeats of our standard screening assays were performed; which entailed initiating treatment shortly after carcinogen administration or in young transgenic mice and continuing treatment until the end of the study. However, three additional protocols were employed relating to reproducibility: (i) testing agents at lower doses to determine efficacy and reduced toxicity; (ii) testing agents later in tumor progression when microscopic lesions existed and, (iii) testing multiple agents of the same mechanistic class. Data with six models that were routinely employed are presented: MNU-induced ER-positive mammary cancer in rats; MMTV-Neu ER-negative mammary cancers in transgenic mice; AOM-induced colon tumors in rats; intestinal adenomas in Min mice; OH-BBN-induced invasive rat urinary bladder cancers in rats; and UV-induced skin squamous carcinomas in mice. It was found that strongly positive results were highly reproducible in the preclinical models evaluated. Cancer Prev Res; 11(10); 595-606. ©2018 AACR.

Asteriscus graveolens Extract in Combination with Cisplatin/Etoposide/Doxorubicin Suppresses Lymphoma Cell Growth through Induction of Caspase-3 Dependent Apoptosis

Chemotherapy drugs action against cancer is not selective, lead to adverse reactions and drug resistance. Combination therapies have proven more effective in defeating cancers. We hypothesize that plant extract/fraction contains many/several compounds and as such can target multiple pathways as cytotoxic agent and may also have chemo sensitizing activities. We designed a study in which, Asteriscus graveolens (Forssk.) Less (A. graveolens)-derived fraction that contains sesquiterpene lactone asteriscunolide isomers (AS) will be tested in combination with known chemotherapy drugs. Successful combination will permit to reduce chemotherapy drugs concentration and still get the same impact on cancer cells. Sesquiterpene lactone such as asteriscunolide isomers is a naturally occurring compound found in a variety of fruits, vegetables, and medicinal plants with anti-cancer properties. The experiments presented here showed that adding plant fraction containing AS permit reducing the concentration of cisplatin/etoposide/doxorubicin in order to reduce mouse BS-24-1 lymphoma cells (BS-24-1 cells) survival. It involved enhancing the production of Reactive Oxygen Species (ROS), activation of caspase-3 and inhibition of Topoisomerase I activity. Taken together, the results suggest that A. graveolens fraction sensitized BS-24-1 cells to cisplatin/etoposide/doxorubicin through induction of ROS and caspase-3-dependent apoptosis.

Mouse models in squamous cell lung cancer: impact for drug discovery

INTRODUCTION

Squamous cell lung cancer (SQCLC) is the second most common subtype of non-small cell lung cancer (NSCLC) and has limited therapeutic options. Its development is likely a result of a multistep process in response to chronic tobacco exposure, involving sequential metaplasia, dysplasia and invasive carcinoma. Its complex genomic landscape has recently been revealed but no driver mutations have been validated that could lead to molecularly targeted therapy as have emerged in lung adenocarcinoma. Few preclinical murine models exist for testing and developing novel therapeutics in SQCLC. Areas covered: This review discusses the pathophysiology and molecular underpinnings of SQCLC that have limited the development of animal models. It then explores the advantages and limitations of a variety of existing mouse models and illustrates their potential application in drug discovery and chemoprevention. Expert opinion: There are several challenges in the development of mouse models for SQCLC, such as lack of validated driver genetic alterations, unclear cell of origin, and difficulty in reproducing the sophisticated tumor microenvironment of human disease. Nevertheless, several successful SQCLC murine models have emerged, especially Patient Derived Xenografts (PDXs) and Genetically Engineered Mouse Models (GEMMs). Continued efforts are needed to generate more SQCLC animal models to better understand its carcinogenesis and metastasis and to further test novel therapeutic strategies.

Preclinical mouse solid tumour models: status quo, challenges and perspectives

Oncology research in humans is limited to analytical and observational studies for obvious ethical reasons, with therapy-focused clinical trials being the one exception to this rule. Preclinical mouse tumour models therefore serve as an indispensable intermediate experimental model system bridging more reductionist in vitro research with human studies. Based on a systematic survey of preclinical mouse tumour studies published in eight scientific journals in 2016, this Analysis provides an overview of how contemporary preclinical mouse tumour biology research is pursued. It thereby identifies some of the most important challenges in this field and discusses potential ways in which preclinical mouse tumour models could be improved for better relevance, reproducibility and translatability.

Inhibition of Pro-inflammatory and Anti-apoptotic Biomarkers during Experimental Oral Cancer Chemoprevention by Dietary Black Raspberries

Oral cancer continues to be a significant public health problem worldwide. Recently conducted clinical trials demonstrate the ability of black raspberries (BRBs) to modulate biomarkers of molecular efficacy that supports a chemopreventive strategy against oral cancer. However, it is essential that a preclinical animal model of black raspberry (BRB) chemoprevention which recapitulates human oral carcinogenesis be developed, so that we can validate biomarkers and evaluate potential mechanisms of action. We therefore established the ability of BRBs to inhibit oral lesion formation in a carcinogen-induced rat oral cancer model and examined potential mechanisms. F344 rats were administered 4-nitroquinoline 1-oxide (4NQO) (20 µg/ml) in drinking water for 14 weeks followed by regular drinking water for 6 weeks. At week 14, rats were fed a diet containing either 5 or 10% BRB, or 0.4% ellagic acid (EA), a BRB phytochemical. Dietary administration of 5 and 10% BRB reduced oral lesion incidence and multiplicity by 39.3 and 28.6%, respectively. Histopathological analyses demonstrate the ability of BRBs and, to a lesser extent EA, to inhibit the progression of oral cancer. Oral lesion inhibition by BRBs was associated with a reduction in the mRNA expression of pro-inflammatory biomarkers Cxcl1, Mif, and Nfe2l2 as well as the anti-apoptotic and cell cycle associated markers Birc5, Aurka, Ccna1, and Ccna2. Cellular proliferation (Ki-67 staining) in tongue lesions was inhibited by BRBs and EA. Our study demonstrates that, in the rat 4NQO oral cancer model, dietary administration of BRBs inhibits oral carcinogenesis via inhibition of pro-inflammatory and anti-apoptotic pathways.

Experimental mammary carcinogenesis - Rat models

Mammary cancer is one of the most common cancers, victimizing more than half a million of women worldwide every year. Despite all the studies in this field, the current therapeutic approaches are not effective and have several devastating effects for patients. In this way, the need to better understand the mammary cancer biopathology and find effective therapies led to the development of several rodent models over years. With this review, the authors intended to provide the readers with an overview of the rat models used to study mammary carcinogenesis, with a special emphasis on chemically-induced models.

Bringing 3D tumor models to the clinic - predictive value for personalized medicine

Current decision-guiding algorithms in cancer drug treatment are based on decades of research and numerous clinical trials. For the majority of patients, this data is successfully applied for a systemic disease management. For a number of patients however, treatment stratification according to clinically based risk criteria will not be sufficient. The most effective treatment options are ideally identified prior to the start of clinical drug therapy. This review will discuss the implementation of three-dimensional (3D) cell culture models as a preclinical testing paradigm for the efficacy of clinical cancer treatment. Patient tumor-derived cells in 3D cultures duplicate the individual tumor microenvironment with a minimum of confounding factors. Clinical implementation of such personalized tumor models requires a high quality of methodological and clinical validation comparable to other biomarkers. A non-systematic literature search demonstrated the small number of prospective studies that have been conducted in this area of research. This may explain the current reluctance of many physicians and insurance providers in implementing this type of assay into the clinical diagnostic routine despite potential benefit for patients. Achieving valid and reproducible results with a high level of evidence is central in improving the acceptance of preclinical 3D tumor models.

Translation of a Tissue-Selective Rexinoid, UAB30, to the Clinic for Breast Cancer Prevention

This review focuses on our efforts to translate a low-toxicity retinoid X receptor-selective agonist, UAB30, to the clinic for the prevention of breast cancers. The review is divided into several sections. First, the current status of breast cancer prevention is discussed. Next, preclinical studies are presented that support translation of rexinoids to the clinic for cancer prevention. While current FDAapproved retinoids and rexinoids demonstrate profound effects in treating cancers, they lack sufficient safety for long term use in the high risk population that is otherwise disease free. The review stresses the need to identify cancer preventive drugs that are effective and safe in order to gain wide use in the clinic. Due to the heterogeneity of the disease, UAB30 is evaluated for the prevention of ER-positive and ER-negative mammary cancers. Since selective estrogen receptor modulators and aromatase inhibitors are used clinically to prevent and treat ER-positive breast cancers, preclinical studies also must demonstrate efficacy of UAB30 in combination with existing drugs under use in the clinic. To support an Investigational New Drug Application to the FDA, data on pharmacology and toxicity as well as mutagenicity is gathered prior to human trials. The review concludes with a discussion of the outcomes of human Phase 0/1 clinical trials that determine the safety and pharmacology of UAB30. These studies are essential before this agent is evaluated for efficacy in phase 2 trials. Success in phase 2 evaluation is critical before long-term and costly phase 3 trials are undertaken. The lack of surrogate biomarkers as endpoints for phase 2 evaluation of rexinoid preventive agents is discussed.

EMODIN EFFICACY ON THE AKT, MAPK, ERK AND DNMT EXPRESSION PATTERN DURING DMBA-INDUCED ORAL CARCINOMA IN GOLDEN SYRIAN HAMSTERS

Background:

The present study has evaluated the Emodin efficacy on the Akt, MAPK, ERK and DNMT expression pattern during 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral carcinoma in golden Syrian hamsters, in order to explore its antitumor potential.

Materials and methods:

Oral tumors were developed in the buccal pouches of golden Syrian hamsters using the carcinogen, DMBA.

Results:

While the incidence of tumor formation was 100% in hamsters treated with DMBA alone, the tumor formation was not noticed in DMBA+ Emodin treated hamsters. Also, Emodin reduced the severity of precancerous pathological lesions such as dysplasia, in the hamsters treated with DMBA. Emodin administration corrected the abnormalities in the expression pattern of Akt, MAPK, ERK and DNMT in the buccal mucosa of hamsters treated with DMBA.

Conclusions:

The present study thus suggests that the tumor preventive potential of Emodin is partly related to its modulating effect on the Akt, MAPK, ERK and DNMT expression pattern, as these molecular markers have a pivotal role in the process of cell proliferation, inflammation, invasion, and apoptosis.

Sex differences and pathology status correlated to the toxicity of some common carcinogens in experimental skin carcinoma

The increased susceptibility of men as compared to women to develop different types of cancer, including skin cancer, is well known; however, the mechanisms involved in this process are still a matter of debate. This study aimed to obtain animal models of photo-chemically-induced skin carcinogenesis by exposure to ultraviolet radiation B (UVB) coupled with topical applications of a tumor initiator (7,12-dimethylbenz(a)anthracene, DMBA) and a tumor promoter (12-O-tetradecanoylphorbol-13-acetate, TPA) in order to characterize the gender disparities regarding the skin lesions developed by the female and male SKH-1 hairless mice included in this study. Histopathological analysis confirmed the presence of malignant lesions in both cases, in female and male mice, following chronic exposure (24 weeks) to the noxious effects of the carcinogens applied, whereas the tumors in male mice had a more severe histological grade. In addition, tumor incidence, size and multiplicity were higher in male mice than in female mice.

Cancer Prevention: Obstacles, Challenges and the Road Ahead

Approaches to reduce the global burden of cancer include two major strategies: screening and early detection and active preventive intervention. The latter is the topic of this Commentary and spans a broad range of activities. The genetic heterogeneity and complexity of advanced cancers strongly support the rationale for early interruption of the carcinogenic process and an enhanced focus on prevention as a priority strategy to reduce the burden of cancer; however, the focus of cancer prevention management should be on individuals at high risk and on primary localized disease in which screening and detection should also play a vital role. The timing and dose of (chemo-)preventive intervention also affects response. The intervention may be ineffective if the target population is very high risk or already presenting with preneoplastic lesions with cellular changes that cannot be reversed. The field needs to move beyond general concepts of carcinogenesis to targeted organ site prevention approaches in patients at high risk, as is currently being done for breast and colorectal cancers. Establishing the benefit of new cancer preventive interventions will take years and possibly decades, depending on the outcome being evaluated. We also propose that comparative effectiveness research designs and the value of information obtained from large-scale prevention studies are necessary in order for preventive interventions to become a routine part of cancer management.

Predictive Value Tools as an Aid in Chemopreventive Agent Development

BACKGROUND

Over 25 years, the National Cancer Institute's Division of Cancer Prevention has entered some 800 agents into a chemopreventive agent testing program. Two critical steps involve: 1) in vitro/in vivo morphologic assays and 2) animal tumor assays (incidence/multiplicity reduction). We sought to determine how accurately the earlier-stage (morphologic) assays predict efficacy in the later-stage (animal tumor) assays.

METHODS

Focusing on 210 agents tested in both morphologic and animal tumor assays, we carried out statistical modeling of how well the six most commonly used morphologic assays predicted drug efficacy in animal tumor assays. Using multimodel inference, three statistical models were generated to evaluate the ability of these six morphologic assays to predict tumor outcomes in three different sets of animal tumor assays: 1) all tumor types, 2) mammary cancer only, and 3) colon cancer only. Using this statistical modeling approach, each morphologic assay was assigned a value reflecting how strongly it predicted outcomes in each of the three different sets of animal tumor assays.

RESULTS

We demonstrated differences in the predictive value of specific morphologic assays for positive animal tumor assay results. Some of the morphologic assays were strongly predictive of meaningful positive efficacy outcomes in animal tumor assays representing specific cancer types, particularly the aberrant crypt focus (ACF) assay for colon cancer. Moreover, less strongly predictive assays can be combined and sequenced, resulting in enhanced composite predictive ability.

CONCLUSIONS

Predictive models such as these could be used to guide selection of preventive agents as well as morphologic and animal tumor assays, thereby improving the efficiency of our approach to chemopreventive agent development.

N-Methyl-N-nitrosourea as a mammary carcinogenic agent

The administration of chemical carcinogens is one of the most commonly used methods to induce tumors in several organs in laboratory animals in order to study oncologic diseases of humans. The carcinogen agent N-methyl-N-nitrosourea (MNU) is the oldest member of the nitroso compounds that has the ability to alkylate DNA. MNU is classified as a complete, potent, and direct alkylating compound. Depending on the animals' species and strain, dose, route, and age at the administration, MNU may induce tumors' development in several organs. The aim of this manuscript was to review MNU as a carcinogenic agent, taking into account that this carcinogen agent has been frequently used in experimental protocols to study the carcinogenesis in several tissues, namely breast, ovary, uterus, prostate, liver, spleen, kidney, stomach, small intestine, colon, hematopoietic system, lung, skin, retina, and urinary bladder. In this paper, we also reviewed the experimental conditions to the chemical induction of tumors in different organs with this carcinogen agent, with a special emphasis in the mammary carcinogenesis.

Three-dimensional cell culture: a breakthrough in vivo

Cell culture is an important tool for biological research. Two-dimensional cell culture has been used for some time now, but growing cells in flat layers on plastic surfaces does not accurately model the in vivo state. As compared to the two-dimensional case, the three-dimensional (3D) cell culture allows biological cells to grow or interact with their surroundings in all three dimensions thanks to an artificial environment. Cells grown in a 3D model have proven to be more physiologically relevant and showed improvements in several studies of biological mechanisms like: cell number monitoring, viability, morphology, proliferation, differentiation, response to stimuli, migration and invasion of tumor cells into surrounding tissues, angiogenesis stimulation and immune system evasion, drug metabolism, gene expression and protein synthesis, general cell function and in vivo relevance. 3D culture models succeed thanks to technological advances, including materials science, cell biology and bioreactor design.

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.

Future directions in cancer prevention

Prevention of cancer remains the most promising strategy for reducing both its incidence and the mortality due to this disease. For more than four decades, findings from epidemiology, basic research and clinical trials have informed the development of lifestyle and medical approaches to cancer prevention. These include selective oestrogen receptor modulators and aromatase inhibitors for breast cancer, the 5-α-reductase inhibitors finasteride and dutasteride for prostate cancer, and the development of vaccines for viruses that are associated with specific cancers. Future directions include genetic, proteomic and other molecular approaches for identifying pathways that are associated with cancer initiation and development, as well as refining the search for immunologically modifiable causes of cancer.

Abstract CN04-03: Development of NSAID eflornithine combinations for treating cancer risk factors

Nonsteroidal anti-inflammatory drugs (NSAIDS) have been found to be potent inhibitors of carcinogenesis in both preclinical models and in randomized controlled prospective clinical trials in humans. NSAIDS exert their anti-carcinogenic effects by inhibiting cyclooxygenases (COXs) involved in arachidonic acid metabolism and by COX-independent mechanisms. Empirical data indicates eflornithine (difluoromethylornithine or DFMO), an enzyme-activated inhibitor of ornithine decarboxylase (ODC) (Meyskens and Gerner, 1999), is one of the most potent agents known acting in combination with NSAIDS to inhibit carcinogenesis in rodent models (Steele and Lubet, 2010). At least part of the rationale for combining NSAIDS with eflornithine for inhibition of carcinogenesis is that eflornithine inhibits the activity of ODC, the first enzyme in polyamine synthesis, while NSAIDS activate the spermidine/spermine acetyltransferase (SAT1), which targets polyamines for export by specific solute carrier transporters (Gerner and Meyskens, 2009). Thus, NSAIDS and eflornithine both reduce tissue levels of the growth-associated polyamines, but by complementary mechanisms. A clinical trial of the combination of eflornithine and the NSAID sulindac showed dramatic treatment-associated reductions of metachronous colorectal adenomas in patients with prior sporadic colorectal polyps (Meyskens et al., 2008). Several clinical trials in progress or soon to commence will further test the hypothesis that NSAID eflornithine combinations can successfully treat cancer risk factors in patients with specific cancers, or risk of cancer. One group of clinical trials involves patients with neuroblastoma (NB). Patients with poor prognosis NB often have tumors in which MYCN is overexpressed. Preclinical data indicates that MYCN as well as c-MYC drive expression of ODC and other genes in the polyamine pathway, and that inhibiting this pathway with eflornithine suppressed carcinogenesis in mouse models of NB (Hogarty et al., 2008). Likewise, COX-2 is expressed in NB tumors and cell lines, and COX-2 inhibitors such as celecoxib can suppress the growth of NB xenografts (Ponthan et al., 2007). The Neuroblastoma and Medulloblastoma Translational Research Consortium (NMTRC) and the New Approaches to Neuroblastoma Therapy (NANT) group are conducting clinical trials to evaluate the safety and efficacy of eflornithine alone or in combination with NSAIDS and other agents in patients with high risk NB. The NMTRC is conducting an especially novel prevention trial of eflornithine in patients with high risk NB in remission (NCT01586260). Eflornithine NSAID combinations are also being evaluated in other MYC-associated diseases. Familial adenomatous polyposis (FAP) is a genetic syndrome associated with increased risk of colon cancer and other neoplasia and is caused by mutation/deletions in the adenomatous polyposis coli (APC) tumor suppressor gene. MYC mediates intestinal tumorigenesis (Ignatenko et al., 2006) and combinations of eflornithine and NSAIDS are potent inhibitors of intestinal carcinogenesis (Ignatenko et al., 2008) in murine models of FAP. Notable is the change in clinical management of FAP patients over the past two decades. FAP is now managed primarily by surgery, with duodenal polyposis and desmoid disease constituting two current significant clinical problems. An international consortium will be evaluating the combination of eflornithine and sulindac in adult patients with FAP, using time to FAP-related events as the primary outcome (NCT01483144). This same combination will be evaluated in patients with prior sporadic colon cancer in a study to be conducted by a national cooperative group (S0820, Adenoma and second primary prevention trial, NCT01349881) (Rial et al., 2012). These and other trials have been designed to include assessment of a range of biological correlates, including genetic (Zell et al., 2010), tissue (Thompson et al., 2010) and urinary markers (Hiramatsu et al., 2005) of disease prognosis and prediction of treatment responses, including therapy-associated toxicities.

Citation Format: Eugene W. Gerner. Development of NSAID eflornithine combinations for treating cancer risk factors. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr CN04-03.

The role of Nrf2 and apoptotic signaling pathways in oroxylin A-mediated responses in HCT-116 colorectal adenocarcinoma cells and xenograft tumors

Oroxylin A is a flavonoid found in the roots of Scutellaria baicalensis Georgi, a herbal medicine commonly used as an antipyretic, analgesic, antitumor, and anti-inflammatory agent. It has recently been investigated for its anticancer activities in hepatoma, gastric, and breast tumors. Here, we investigated the antitumor effects of oroxylin A in human colon carcinoma HCT-116 cells in vitro and in vivo. We characterized the proapoptotic effect of oroxylin A using diamidino-phenyl-indole (DAPI) and annexin V/PI staining. We then found that both caspase-3 and caspase-9 were activated, the expression of Bcl-2 protein decreased, and the expression of Bax protein increased after treatment with oroxylin A. In addition, oroxylin A increased nuclear transcription factor erythroid-related factor 2 (Nrf2) expression and induced Nrf2 translocation into the nucleus. Furthermore, we found that oroxylin A treatment elevated intracellular reactive oxygen species levels and increased the protein expression level of two of the Nrf2 target genes heme oxygenase-1 and NADP(H):quinone oxidoreductase-1 in HCT-116 cells. Finally, our study demonstrated that oral administration of oroxylin A significantly decreased tumor volume and weight in immunodeficient mice that were inoculated with HCT-116 cells. The in-vivo chemopreventive efficacy of oroxylin A against HCT-116 human colon cancer was accompanied by its proapoptotic and Nrf2-inducing activities, which correlates with the in-vitro study. This is the first demonstration of oroxylin A-dependent chemoprevention in colon cancer and may offer a potential mechanism for its anticancer action in vivo.

Inhibition of mouse urinary bladder carcinogenesis by açai fruit (Euterpe oleraceae Martius) intake

Açai, fruit from Euterpe oleraceae Martius, is consumed in natura and in a variety of beverages and food preparations and possesses several potential antioxidant compounds. In a first study for anticarcinogenicity screening, male Swiss mice (n = 20/per group) were chemically-induced to urothelial bladder carcinogenesis for 10 weeks and received a standard diet or a standard diet containing 2.5 and 5 % spray-dried açai pulp (AP) for 10 weeks. At week 20, the incidence of simple and nodular hyperplasia and the incidence and multiplicity of transitional cell carcinoma (TCC) were evaluated. In a second study for antigenotoxicity screening, male Swiss mice (n = 6/per group) were fed standard diet or standard diet containing 5 % AP for three weeks. Urothelial cell suspensions were obtained and challenged with H(2)O(2) for induction of DNA damage and analyzed by comet assay. Overall, dietary 5 % AP reduced TCC incidence and multiplicity (p = 0.019 and p = 0.015, respectively) and tumor cell proliferation and p63 expression (p = 0.02 and p = 0.007, respectively), Furthermore, the group fed the 5 % AP presented a significant reduction (p < 0.01) in DNA damage induced by H(2)O(2), a notable oxidant agent. The results suggest that the spray-dried açai pulp used here inhibits the TCC development in male Swiss mice, probably due to its potential antioxidant action.

Cancer stem cell targeting: the next generation of cancer therapy and molecular imaging

Cancer stem cells (CSCs) have the capacity to generate the heterogeneous lineages of all cancer cells comprising a tumor and these populations of cells are likely to be more relevant in determining prognosis. However, these cells do not operate in isolation, but instead rely upon signals co-opted from their microenvironment, making the targeting and imaging of CSCs within a cancer mass a daunting task. A better understanding of the molecular cell biology underlying CSC pathology will facilitate the development of new therapeutic targets and novel strategies for the successful eradication of cancer. In addition, the continued investigation of sensitive molecular-imaging modalities will enable more accurate staging, treatment planning and the ability to monitor the effectiveness of CSC-targeted therapies in vivo. In this review, we explore the possibilities and limitations of CSC-directed therapies and molecular imaging modalities.