Rodent Models Of Carcinogenesis Research Articles

Biochemical and molecular aspects of 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis: a review.

1,2-dimethylhydrazine (DMH) is a member in the class of hydrazines, strong DNA alkylating agent, naturally present in cycads. DMH is widely used as a carcinogen to induce colon cancer in animal models. Exploration of DMH-induced colon carcinogenesis in rodent models provides the knowledge to perceive the biochemical, molecular, and histological mechanisms of different stages of colon carcinogenesis. The procarcinogen DMH, after a series of metabolic reactions, finally reaches the colon, there produces the ultimate carcinogen and reactive oxygen species (ROS), which further alkylate the DNA and initiate the development of colon carcinogenesis. The preneolpastic lesions and histopathological observations of DMH-induced colon tumors may provide typical understanding about the disease in rodents and humans. In addition, this review discusses about the action of biotransformation and antioxidant enzymes involved in DMH intoxication. This understanding is essential to accurately identify and interpret alterations that occur in the colonic mucosa when evaluating natural or pharmacological compounds in DMH-induced animal colon carcinogenesis.

Chemically induced carcinogenesis in rodent models of aging: assessing organismal resilience to genotoxic stressors in geroscience research.

There is significant overlap between the cellular and molecular mechanisms of aging and pathways contributing to carcinogenesis, including the role of genome maintenance pathways. In the field of geroscience analysis of novel genetic mouse models with either a shortened, or an extended, lifespan provides a unique opportunity to evaluate the synergistic roles of longevity assurance pathways in cancer resistance and regulation of lifespan and to develop novel targets for interventions that both delay aging and prevent carcinogenesis. There is a growing need for robust assays to assess the susceptibility of cancer in these models. The present review focuses on a well-characterized method frequently used in cancer research, which can be adapted to study resilience to genotoxic stress and susceptibility to genotoxic stress-induced carcinogenesis in geroscience research namely, chemical carcinogenesis induced by treatment with 7,12-dimethylbenz(a)anthracene (DMBA). Recent progress in understanding how longer-living mice may achieve resistance to chemical carcinogenesis and how these pathways are modulated by anti-aging interventions is reviewed. Strain-specific differences in sensitivity to DMBA-induced carcinogenesis are also explored and contrasted with mouse lifespan. The clinical relevance of inhibition of DMBA-induced carcinogenesis for the pathogenesis of mammary adenocarcinomas in older human subjects is discussed. Finally, the potential role of insulin-like growth factor-1 (IGF-1) in the regulation of pathways responsible for cellular resilience to DMBA-induced mutagenesis is discussed.

Inherent aerobic capacity-dependent differences in breast carcinogenesis.

Although regular physical activity is associated with improvement in aerobic capacity and lower breast cancer risk, there are heritable sets of traits that affect improvement in aerobic capacity in response to physical activity. Although aerobic capacity segregates risk for a number of chronic diseases, the effect of the heritable component on cancer risk has not been evaluated. Therefore, we investigated breast carcinogenesis in rodent models of heritable fitness in the absence of induced physical activity. Female offspring of N:NIH rats selectively bred for low (LIAC) or high (HIAC) inherent aerobic capacity were injected intraperitoneally with 1-methyl-1-nitrosurea (70 mg/kg body wt). At study termination 33 weeks post-carcinogen, cancer incidence (14.0 versus 47.3%; P < 0.001) and multiplicity (0.18 versus 0.85 cancers per rat; P < 0.0001) were significantly decreased in HIAC versus LIAC rats, respectively. HIAC had smaller visceral and subcutaneous body fat depots than LIAC and activity of two proteins that regulated the mammalian target of rapamycin, protein kinase B (Akt), and adenosine monophosphate-activated protein kinase were suppressed and activated, respectively, in HIAC. Although many factors distinguish between HIAC and LIAC, it appears that the protective effect of HIAC against breast carcinogenesis is mediated, at least in part, via alterations in core metabolic signaling pathways deregulated in the majority of human breast cancers.

Abstract 2585: Bioactive compounds or metabolites from black raspberries modulate T lymphocyte function, myeloid cell differentiation and Jak/STATsignaling

Abstract Bioactive phyotochemicals from natural products, such as black raspberries have direct anti-cancer properties on malignant cells in culture and in xenograft models. In addition, black raspberry components inhibit cancer progression in more complex rodent carcinogenesis models. Although mechanistic targets for black raspberry phytochemicals in cancer cells are beginning to emerge, the potential role in modulating host immune processes impacting cancer have not been systematically examined. We hypothesized that black raspberries contain compounds capable of eliciting potent immunomodulatory properties that impact cellular mediators relevant to chronic inflammation and tumor progression. In the present report, we studied both an ethanol extract from black raspberries (BRB-E) containing a diverse mixture of phytochemicals and two abundant phytochemical metabolites of black raspberries produced upon ingestion (Cyanidin-3-Rutinoside, C3R; Quercitin-3-rutinoside, Q3R). BRB-E inhibited proliferation of CD3/CD28 activated human CD4+ and CD8+ T lymphocytes. BRB-E also limited the viability of CD3+ T cells cultured in IL-2, and were potent inhibitors of IL-2-induced STAT5 phosphorylation. Conversely, BRB-E significantly enhanced the monokine-induced by gamma (MIG)-mediated chemotaxis of CD8+ T lymphocytes in transwell assays. This enhanced chemotaxis was associated with upregulated expression of CXCR3 on T lymphocytes. BRB-E also inhibited the in vitro expansion of myeloid-derived suppressor cells (MDSC). Consistent with the reduction in MDSC, pre-treatment of immune cells with BRB E attenuated IL-6-mediated signal transducer and activator of transcription-3 (STAT3) phosphorylation. Finally, the C3R and Q3R metabolites were also found to be immunomodulatory, as C3R inhibited proliferation of CD3/CD28 activated T lymphocytes and STAT5 phosphorylation, while Q3R inhibited MDSC expansion and STAT3 signaling but not STAT5. Together these data indicate that black raspberries or their physiologically-relevant metabolites contain phytochemicals that affect immune processes relevant to carcinogenesis. Furthermore, specific components and their metabolites may be a source of lead compounds for drug development that exhibit targeted immunological outcomes or inhibition of specific STAT-regulated signaling pathways. Citation Format: Thomas A. Mace, Samantha King, Zeenath Ameen, Omar Elnaggar, Gregory Young, Kenneth Riedl, Steven Schwartz, Steven Clinton, Thomas Knobloch, Christopher Weghorst, Gregory B. Lesinski. Bioactive compounds or metabolites from black raspberries modulate T lymphocyte function, myeloid cell differentiation and Jak/STATsignaling. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2585. doi:10.1158/1538-7445.AM2014-2585

Abstract 1246: Development and validation of a global proteomics approach for identifying novel binding partners of resveratrol

Abstract The dietary constituent resveratrol (trans-3,5,4′-trihydroxystilbene) has received a great deal of scientific attention and publicity due to its broad ranging pharmacological effects in preclinical systems, including cancer chemoprevention in a variety of rodent carcinogenesis models. It has been hypothesized that resveratrol exerts its effects by interacting directly with specific proteins such as cyclooxygenase 2 (COX2) and NAD(P)H dehydrogenase quinone 2 (NQO2). Nevertheless the key targets which may mediate its anticancer activity in humans have not yet been identified. An affinity purification (pull-down) assay coupled with global LC-MS/MS analysis was developed to identify proteins that bind directly to resveratrol. Resveratrol was synthetically linked via one of its phenol moieties to agarose beads using a short amine linker, generating two resveratrol bead species. Resveratrol beads were incubated with cell lysate from human-derived colon adenocarcinoma (HCA7) or adenoma cells (AAC1) and then washed to remove unbound proteins. Resveratrol-bound proteins were eluted from the beads by heat denaturation in SDS buffer. Control beads end-capped with ethanolamine were used to identify non-specific protein binding. Proteins were eluted from the beads and identified in trypsinised gel slices by PAGE coupled with either LC-MS/MS to identify all proteins bound to resveratrol or immunoblotting to identify known target proteins. More than 30 proteins were identified by LC-MS/MS that were reproducibly ‘pulled’ from cell lysates by resveratrol beads. The proteins identified fall into five main groups, including enzymes and proteins associated with nuclear transport, apoptosis, DNA repair, prostaglandin and fatty acid synthesis. Following MS/MS, 30 proteins were confirmed as selective binding partners of resveratrol by Western blotting, with 97% agreement between the two detection methods. Among the proteins identified were COX2, NQO2, fatty acid synthase (FAS) and Exportin 1 (CRM1). The first two are known resveratrol targets, which supports the validity of the method. Resveratrol at clinically achievable concentrations (0.001-10 μM) did not change the expression of the proteins identified in the pull-down assay. It is conceivable that resveratrol modulates the function of the proteins to which it binds. To test this hypothesis the effects of resveratrol on FAS activity and on Exportin 1 and its cargoes is currently under investigation. In conclusion, the protein pull-down assay described here may help discover mechanism-related protein biomarkers that can be used to monitor the efficacy of multi-targeted cancer chemopreventive diet constituents in individuals in chemoprevention trials. Citation Format: Christina J. Kovoor, Robert G. Britton, Emma Horner-Glister, Catherine Andreadi, Raj Singh, Rebekah Jukes-Jones, Kelvin Cain, William P. Steward, Andreas Gescher, Karen Brown. Development and validation of a global proteomics approach for identifying novel binding partners of resveratrol. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1246. doi:10.1158/1538-7445.AM2014-1246

Bioactive compounds or metabolites from black raspberries modulate T lymphocyte proliferation, myeloid cell differentiation and Jak/STAT signaling

Bioactive phytochemicals from natural products, such as black raspberries (BRB; Rubus occidentalis), have direct anticancer properties on malignant cells in culture and in xenograft models. BRB components inhibit cancer progression in more complex rodent carcinogenesis models. Although mechanistic targets for BRB phytochemicals in cancer cells are beginning to emerge, the potential role in modulating host immune processes impacting cancer have not been systematically examined. We hypothesized that BRB contain compounds capable of eliciting potent immunomodulatory properties that impact cellular mediators relevant to chronic inflammation and tumor progression. We studied both an ethanol extract from black raspberries (BRB-E) containing a diverse mixture of phytochemicals and two abundant phytochemical metabolites of BRB produced upon ingestion (Cyanidin-3-Rutinoside, C3R; Quercitin-3-Rutinoside, Q3R). BRB-E inhibited proliferation, and viability of CD3/CD28 activated human CD4(+) and CD8(+) T lymphocytes. BRB-E also limited in vitro expansion of myeloid-derived suppressor cells (MDSC) and their suppressive capacity. Pre-treatment of immune cells with BRB-E attenuated IL-6-mediated phosphorylation of signal transducer and activator of transcription-3 (STAT3) and IL-2-induced STAT5 phosphorylation. In contrast, pre-treatment of immune cells with the C3R and Q3R metabolites inhibited MDSC expansion, IL-6-mediated STAT3 signaling, but not IL-2-induced STAT5 phosphorylation and were less potent inhibitors of T cell viability. Together these data indicate that BRB extracts and their physiologically relevant metabolites contain phytochemicals that affect immune processes relevant to carcinogenesis and immunotherapy. Furthermore, specific BRB components and their metabolites may be a source of lead compounds for drug development that exhibits targeted immunological outcomes or inhibition of specific STAT-regulated signaling pathways.

Novel analogues of resveratrol: metabolism and inhibition of colon cancer cell proliferation

Resveratrol is a phytochemical present in the skin of red grapes, and hence red wine as well as a variety of berries and nuts. It is an anti-oxidant, which has shown cancer chemopreventive properties in preclinical rodent models of carcinogenesis. The bioavailability of resveratrol is low, as it is rapidly metabolised to glucuronides and sulfates. The pharmacological activities of conjugate metabolites of phenols are often much lower than those of their metabolic progenitors. Therefore chemical synthetic manipulations aimed at slowing the rate of metabolic conjugation of phenols may generate analogues with increased bioavailability and efficacy. Here we describe the synthesis using the Wittig–Horner–Emmons reaction of a new series of resveratrol analogues in which the phenol moieties were systematically replaced by hydroxymethyl and/or methoxy groups. Incubation of analogues, which lack phenol groups with phase II metabolising enzyme preparations generated hardly any, or only small amounts of, conjugates. Four of the new analogue inhibited the growth of human-derived HCA-7 colon cancer cells, but with much less potency than resveratrol.

Why Cancer &amp; Metabolism? Why now?

Why Cancer &amp; Metabolism? Why now?

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

Abstract 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.

Helicobacter pylori infection and gastric carcinogenesis in rodent models

Helicobacter pylori infection is an important factor for gastric carcinogenesis in human. In carcinogen-treated Mongolian gerbils, H. pylori infection enhances stomach carcinogenesis, while infection alone induced severe hyperplasia called heterotopic proliferative glands. A high-salt diet or early acquisition of the bacteria exacerbates inflammation and carcinogenesis. Oxygen radical scavengers or anti-inflammatory chemicals as well as eradication of H. pylori are effective to prevent carcinogenesis. H. pylori-associated inflammation induces intestinal metaplasia and intestinalization of stomach cancers independently. It is necessary to control cancer development not only in H. pylori-positive cases but also in H. pylori-negative metaplastic gastritis.

Cell signaling pathways associated with a reduction in mammary cancer burden by dietary common bean ( Phaseolus vulgaris L.)

Emerging evidence indicates that common bean (Phaseolus vulgaris L.) is associated with reduced cancer risk in human populations and rodent carcinogenesis models. This study sought to identify cancer-associated molecular targets that mediate the effects of bean on cancer burden in a chemically induced rat model for breast cancer. Initial experiments were conducted using a high dietary concentration of bean (60% wt/wt) where carcinoma burden in bean-fed rats was reduced 62.2% (P < 0.001) and histological and western blot analyses revealed that the dominant cellular process associated with reduced burden was induction of apoptosis. Further analysis of mammary carcinomas revealed changes in the phosphorylation states of mammalian target of rapamycin (mTOR) substrates (4E-binding protein 1 and p70S6 kinase) and mTOR regulators adenosine monophosphate-activated protein kinase and protein kinase B (Akt) (P < 0.001). Effects on mTOR signaling in carcinomas were also found at lower dietary concentrations of bean (7.5-30% wt/wt). Liquid chromatography-time of flight-mass spectrometry analysis of plasma provided evidence of altered lipid metabolism consistent with reduced mTOR network activity in the liver (P < 0.001). Plasma concentrations of insulin and insulin-like growth factor-1 were reduced by 36.3 and 38.9%, respectively, (P < 0.001), identifying a link to Akt regulation. Plasma C-reactive protein, a prognostic marker for long-term survival in breast cancer patients, was reduced by 23% (P < 0.001) in bean-fed rats. Identification of a role for the mTOR signaling network in the reduction of cancer burden by dietary bean is highly relevant given that this pathway is deregulated in the majority of human breast cancers.

Resveratrol in human cancer chemoprevention – Choosing the ‘right’ dose

There is now robust preclinical evidence to suggest that resveratrol possesses cancer chemopreventive properties. A series of clinical pilot studies has provided insights into its pharmacokinetics, and data on its human antineoplastic pharmacodynamics start to emerge. It is likely that resveratrol will be developed further in the clinic as a putative cancer chemopreventive agent. The question that remains unresolved is: What is the most suitable dose of resveratrol for effective cancer preventive intervention? Mechanistic studies in cells in vitro have almost invariably used concentrations of resveratrol in the 10(-5) to 10(-4) M range, which is much higher than those which can be achieved in the human biophase after consumption of doses up to 1 g. Many of the preclinical efficacy studies in rodent models of carcinogenesis have employed doses which are dramatically above those which can be ingested with the diet. New experimental paradigms need to be used to obtain information on pharmacological changes elicited by resveratrol when present at very low concentrations or when administered at dietary-relevant doses.

Nrf2: control of sensitivity to carcinogens

Induction of enzymes that enhance the detoxication of chemical carcinogens has been a broadly effective strategy for chemoprevention of experimental carcinogenesis in rodent models. Several inducing agents are now in clinical trials to evaluate utility for prevention of cancers associated with unavoidable high exposures to environmental carcinogens. The successes of these pre-clinical and clinical interventions lead to studies to define the molecular basis for protection by these agents, which now include phenolic antioxidants, dithiolethiones, isothiocyanates, and triterpenoids. In the mid-1990s, the NF-E2-related factor 2 (Nrf2) transcription factor was identified as a key regulator of the inducible expression of enzymes such as glutathione S-transferases and NAD(P)H: quinone oxidoreductase in catalyzing the detoxication of reactive electrophiles and oxidants that contribute to the formation of mutations and ultimately cancers. Nrf2 is now recognized to regulate a broad cytoprotective, transcriptional response leading to prevention of damage to DNA, proteins and lipids; recognition, repair and removal of macromolecular damage; and tissue renewal following toxic assaults. Highlighting the importance of this pathway as a determinant of susceptibility to carcinogenesis, multiple studies now demonstrate enhanced incidence, multiplicity, and/or tumor burden in Nrf2-disrupted mice compared to wild-type in models of inflammation and colon cancer, bladder cancer, lung disease and cancer, stomach cancer, mammary cancer, skin cancer, and hepatocarcinogenesis.

Enhanced Mammary Progesterone Receptor-A Isoform Activity in the Promotion of Mammary Tumor Progression by Dietary Soy in Rats

Dietary contribution to breast cancer risk, recurrence, and progression remains incompletely understood. Increased consumption of soy and soy isoflavones is associated with reduced mammary cancer susceptibility in women and in rodent models of carcinogenesis. In rats treated with N-methyl-N-nitrosourea, dietary intake of soy protein isolate (SPI) reduced mammary tumor occurrence but increased incidence of more invasive tumors in tumored rats, relative to the control diet casein. Here we evaluated whether mammary tumor progression in tumor-bearing rats lifetime exposed to SPI is associated with deregulated progesterone receptor (PR) isoform expression. In histologically normal mammary glands of rats with invasive ductal carcinoma lesions, PR-A protein levels were higher for SPI- than casein-fed rats, whereas PR-B was undetectable for both groups. Increased mammary PR-A expression was associated with higher transforming growth factor-β1, stanniocalcin-1, and CD44 transcript levels; lower E-cadherin and estrogen receptor-α expression; and reduced apoptotic status in ductal epithelium. Serum progesterone (ng/ml) (CAS: 25.94 ± 3.81; SPI: 13.19 ± 2.32) and estradiol (pg/ml) (CAS: 27.9 ± 4.49; SPI: 68.48 ± 23.87) levels differed with diet. However, sera from rats of both diet groups displayed comparable mammosphere-forming efficiency in human MCF-7 cells. Thus, soy-rich diets may influence the development of more aggressive tumors by enhancing PR-A-dependent signaling in premalignant breast tissues.

Abstract 2867: Anthocyanin and carotenoid rich fresh vs. processed colored potatoes suppress human colon cancer cell proliferation and elevate apoptosis via suppression of inducible nitric oxide synthase (iNOS) pathway

Abstract The potato (Solanum tuberosum L.) is the world's 3rd largest food crop and the leading vegetable crop in the United States, with per capita consumption of about 126 lbs annually. Specialty/colored potatoes rich in anti-proliferative, pro-apoptotic and anti-inflammatory anthocyanins and/or carotenoids can be an attractive “delivery system” for these bioactive compounds in humans. Unlike other carotenoid- or anthocyanin-rich sources such as blueberries or pears, potatoes are stored and processed before consumption (80 lbs industrially processed potatoes/capita/year in the US). We previously demonstrated that colored potato extracts suppress cancer cell proliferation and induce apoptosis via both caspase-dependent and independent pathways; however, the effect of processing methods on these functional compounds is unknown. We hypothesized that potato bioactive compounds retain their chemoprotective properties against human colon cancer cells even after processing (chipping and baking) compared to the DMSO solvent controls. To test this hypothesis the anti-proliferative (WST assay), pro-apoptotic (cell death detection ELISA) and anti-inflammatory (iNOS pathway; immunoblots) properties of Atlantic (white; phenolics), Yukon Gold (yellow; carotenoids) and Purple Majesty (purple; anthocyanins) potato extracts before and after processing were determined using HCT116 p53+/+ and p53−/− human colon cancer cells. Potato extracts from processed potatoes (5 −15μg/ml) suppressed both p53+/+ and p53−/− human colon cancer cell proliferation and elevated apoptosis compared to the DMSO control after 24 hr incubation period. Similar results were observed after 48 and 72 hr of incubation. However, processing suppressed (p &amp;lt; 0.05) anti-proliferative and pro-apoptotic properties of potato bioactive compounds compared to the fresh potato extracts. Purple potato extracts were more potent in suppressing (p &amp;lt; 0.05) colon cancer cell proliferation and elevating apoptosis compared to the white and yellow colored potatoes. Potato extracts suppressed inducible nitric oxide synthase (iNOS) levels, a critical pro-inflammatory enzyme. Our results suggest that it is important to consider the processing effects on bioactive compounds in foods while conducting nutritional and epidemiological studies. We plan to determine whether colored potatoes suppress chemically-induced colon carcinogenesis in rodent models via suppression of inflammation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2867.

Do anthocyanins and anthocyanidins, cancer chemopreventive pigments in the diet, merit development as potential drugs?

Anthocyanins, plant pigments in fruits and berries, have been shown to delay cancer development in rodent models of carcinogenesis, especially those of the colorectal tract. Anthocyanins and anthocyanidins, their aglycons, especially cyanidin and delphinidin, have been subjected to extensive mechanistic studies. In cells in vitro, both glycosides and aglycons engage an array of anti-oncogenic mechanisms including anti-proliferation, induction of apoptosis and inhibition of activities of oncogenic transcription factors and protein tyrosine kinases. Anthocyanins and anthocyanidins exist as four isomers, interconversion between which depends on pH, temperature and access to light. Anthocyanidins are much more prone to avid chemical decomposition than the glycosides, and they only survive for minutes in the biophase. These pharmaceutical issues are very important determinants of the suitability of these flavonoids for potential development as cancer chemopreventive drugs, and they have hitherto not received adequate attention. In the light of their robust cancer chemopreventive efficacy in experimental models and their superior stability as compared to that of the aglycons, the anthocyanins seem much more suitable for further drug development than their anthocyanidin counterparts.

Radiation-Induced Mammary Carcinogenesis in Rodent Models: What's Different from Chemical Carcinogenesis?

Ionizing radiation is one of a few well-characterized etiologic factors of human breast cancer. Laboratory rodents serve as useful experimental models for investigating dose responses and mechanisms of cancer development. Using these models, a lot of information has been accumulated about mammary gland cancer, which can be induced by both chemical carcinogens and radiation. In this review, we first list some experimental rodent models of breast cancer induction. We then focus on several topics that are important in understanding the mechanisms and risk modification of breast cancer development, and compare radiation and chemical carcinogenesis models. We will focus on the pathology and natural history of cancer development in these models, genetic changes observed in induced cancers, indirect effects of carcinogens, and finally risk modification by reproductive factors and age at exposure to the carcinogens. In addition, we summarize the knowledge available on mammary stem/progenitor cells as a potential target of carcinogens. Comparison of chemical and radiation carcinogenesis models on these topics indicates certain similarities, but it also indicates clear differences in several important aspects, such as genetic alterations of induced cancers and modification of susceptibility by age and reproductive factors. Identification of the target cell type and relevant translational research for human risk management may be among the important issues that are addressed by radiation carcinogenesis models.JRRS Incentive Award in 2009.

Dietary Cancer Chemopreventive Agents – Targeting Inflammation and Nrf2 Signaling Pathway

Accumulating epidemiological and clinical evidence shows that chronic inflammation plays a critical role in neoplastic transformation and progression. Long-term users of selective cycloxygenase-2 (Cox-2) inhibitors (coxibs) and non-steroidal anti-inflammatory drugs (NSAIDs) have been reported to have a reduced risk of developing colorectal cancer. However, the adverse gastrointestinal and cardiovascular side effects associated with these drugs have limited their routine use for cancer chemoprevention. Basic leucine zipper (bZIP) protein Nrf2, a key transcription factor mediating the antioxidant response is an important modulator of tumor susceptibility in mouse models. Mice lacking Nrf2 are more susceptible to carcinogenesis induced by carcinogens. Moreover, induction of the Nrf2 signaling pathway is essential for many food phytochemicals to exert their cancer chemopreventive activity as demonstrated in many preclinical studies. It has been recently shown that the combination of coxibs or NSAIDs and natural phytochemicals can synergistically inhibit carcinogenesis in rodent models. This review will focus on the role of chronic inflammation and the Nrf2 signaling pathway in carcinogenesis and the feasibility of targeting these signaling pathways with dietary cancer chemopreventive agents and for cancer chemoprevention.

Evaluation of the cancer chemopreventive efficacy of silibinin in genetic mouse models of prostate and intestinal carcinogenesis: Relationship with silibinin levels

Silibinin, a flavonolignan from milk thistle seeds, possesses cancer chemopreventive properties in rodent models of carcinogenesis. We tested the hypotheses that silibinin or silipide, silibinin formulated with phospholipids, delays tumour development in TRAMP or ApcMin mice, genetic models of prostate or intestinal malignancies, respectively. Mice received silibinin or silipide with their diet (0.2% silibinin equivalents) from weaning. Intervention with silipide reduced the size of well differentiated TRAMP adenocarcinomas by 31%. Silipide and silibinin decreased the incidence of poorly differentiated carcinomas by 61% compared to mice on control diet. Silipide decreased plasma levels of insulin-like growth factor (IGF)-1 by 36%. Levels of circulating IGF binding protein (IGFBP)-3 in mice on silipide or silibinin were 3.9- or 5.9-fold, respectively, elevated over those in control TRAMP mice. In ApcMin mice silibinin, but not silipide, had only a marginal adenoma number-reducing effect. The results cautiously support the advancement of silipide to the stage of clinical investigation in prostate cancer.

Chemoprevention of Familial Adenomatous Polyposis by Natural Dietary Compounds Sulforaphane and Dibenzoylmethane Alone and in Combination in ApcMin/+ Mouse

Cancer chemopreventive agent sulforaphane (SFN) and dibenzoylmethane (DBM) showed antitumorigenesis effects in several rodent carcinogenesis models. In this study, we investigated the cancer chemopreventive effects and the underlying molecular mechanisms of dietary administration of SFN and DBM alone or in combination in the ApcMin/+ mice model. Male ApcMin/+ mice (12 per group) at age of 5 weeks were given control AIN-76A diet, diets containing 600 ppm SFN and 1.0% DBM, or a combination of 300 ppm SFN and 0.5% DBM for 10 weeks. Mice were then sacrificed, and tumor numbers and size were examined. Microarray analysis, Western blotting, ELISA, and immunohistochemical staining were done to investigate the underlying molecular mechanisms of cancer chemopreventive effects of SFN and DBM. Dietary administrations of SFN and DBM alone or in combination significantly inhibited the development of intestinal adenomas by 48% (P=0.002), 50% (P=0.001), and 57% (P<0.001), respectively. Dietary administration of 600 ppm SFN and 1.0% DBM also reduced colon tumor numbers by 80% (P=0.016) and 60% (P=0.103), respectively, whereas the combination of SFN and DBM treatment blocked the colon tumor development (P=0.002). Both SFN and DBM treatments resulted in decreased levels of prostaglandin E2 or leukotriene B4 in intestinal polyps or apparently normal mucosa. Treatments also led to the inhibition of cell survival and growth-related signaling pathways (such as Akt and extracellular signal-regulated kinase) or biomarkers (such as cyclooxygenase-2, proliferating cell nuclear antigen, cleaved caspases, cyclin D1, and p21). In conclusion, our results showed that both SFN and DBM alone as well as their combination are potent natural dietary compounds for chemoprevention of gastrointestinal cancers.