Preclinical efficacy evaluation of potential chemopreventive agents in animal carcinogenesis models: methods and results from the NCI Chemoprevention Drug Development Program

Synthesis of 4,5-Dihydro-1H-[1,2]dithiolo[3,4-c]quinoline-1-thione Derivatives and Their Application as Protein Kinase Inhibitors

This study represents the design and synthesis of a new set of hybrid and chimeric derivatives of 4,5-dihydro-4,4-dimethyl-1H-[1,2]dithiolo[3,4-c]quinoline-1-thiones, the structure of which the tricyclic fragment linearly bound or/and condensed with another heterocyclic fragment. Using the PASS Online software, among the previously synthesized and new derivatives of 1,2-dithiolo[3,4-c]quinoline-1-thione we identified 12 substances with pleiotropic activity, including chemoprotective and antitumor activity. All the synthesized derivatives were screened for their inhibitory assessment against a number of kinases. Compounds which exhibited prominent inhibition percentage in cells (>85%) were also examined for their inhibitory efficiency on human kinases via ELISA utilizing sorafenib as a reference standard to estimate their IC50 values. It was revealed that compounds 2a, 2b, 2c, and 2q displayed a significant inhibition JAK3 (IC50 = 0.36 μM, 0.38 μM, 0.41 μM, and 0.46 μM, respectively); moreover, compounds 2a and 2b displayed excellent activities against NPM1-ALK (IC50 = 0.54 μM, 0.25 μM, respectively), against cRAF[Y340D][Y341D], compound 2c showed excellent activity, and compound 2q showed weak activity (IC50 = 0.78 μM, 5.34 μM, respectively) (sorafenib IC50 = 0.78 μM, 0.43 μM, 1.95 μM, respectively). Thus, new promising preferred structures for the creation of drugs for the treatment of cancer and other multifactorial diseases in the future have been found.

An organoid-based carcinogenesis model induced by in vitro chemical treatment

Animal carcinogenesis models induced by environmental chemicals have been widely used for basic and applied cancer research. However, establishment of in vitro or ex vivo models is essential for molecular mechanistic elucidation of early events in carcinogenesis, leading to clarification of the total mode of action. In the present study, to establish an organoid-based chemical carcinogenesis model, mouse organoids were treated in vitro with 4 genotoxic chemicals, e.g. ethyl methanesulfonate (EMS), acrylamide (AA), diethylnitrosamine (DEN) and 7,12-dimethylbenz[a]anthracene (DMBA) to examine their tumorigenicity after injection to nude mice. The four chemicals were reported to induce lung, liver or mammary carcinomas in mouse models. DMBA-treated mammary tissue-derived organoids with Trp53 heterozygous knockout exhibited tumorigenicity, but not those with wild-type Trp53, reflecting previous reports of corresponding animal models. Treatment of lung organoids with or without Trp53 knockout with EMS or AA resulted in carcinogenic histopathological characteristics, and the activation of oncogenic kinases was demonstrated in the nodules from the nude mouse subcutis. DEN-treated liver (biliary tract) organoids also had an increased number of similar changes. In conclusion, an ex vivo model for chemical carcinogenesis was established using normal mouse tissue-derived organoids. This model will be applied to detect early molecular events, leading to clarification of the mode of action of chemical carcinogenesis.

Molecular insight into isoform specific inhibition of PI3K-α and PKC-η with dietary agents through an ensemble pharmacophore and docking studies

Dietary compounds play an important role in the prevention and treatment of many cancers, although their specific molecular mechanism is not yet known. In the present study, thirty dietary agents were analyzed on nine drug targets through in silico studies. However, nine dietary scaffolds, such as silibinin, flavopiridol, oleandrin, ursolic acid, α-boswellic acid, β-boswellic acid, triterpenoid, guggulsterone, and oleanolic acid potentially bound to the cavity of PI3K-α, PKC-η, H-Ras, and Ras with the highest binding energy. Particularly, the compounds silibinin and flavopiridol have been shown to have broad spectrum anticancer activity. Interestingly, flavopiridol was embedded in the pockets of PI3K-α and PKC-η as bound crystal inhibitors in two different conformations and showed significant interactions with ATP binding pocket residues. However, complex-based pharmacophore modeling achieved two vital pharmacophoric features namely, two H-bond acceptors for PI3K-α, while three are hydrophobic, one cat-donor and one H-bond donor and acceptor for PKC-η, respectively. The database screening with the ChemBridge core library explored potential hits on a valid pharmacophore query. Therefore, to optimize perspective lead compounds from the hits, which were subjected to various constraints such as docking, MM/GBVI, Lipinski rule of five, ADMET and toxicity properties. Henceforth, the top ligands were sorted out and examined for vital interactions with key residues, arguably the top three promising lead compounds for PI3K-α, while seven for PKC-η, exhibiting binding energy from - 11.5 to - 8.5 kcal mol^-1. Therefore, these scaffolds could be helpful in the development of novel class of effective anticancer agents.

Randomized Phase II Trial of Polyphenon E versus Placebo in Patients at High Risk of Recurrent Colonic Neoplasia

Polyphenon E (Poly E) is a green tea polyphenol preparation whose most active component is epigallocatechin gallate (EGCG). We studied the cancer preventive efficacy and safety of Poly E in subjects with rectal aberrant crypt foci (ACF), which represent putative precursors of colorectal cancers. Eligible subjects had prior colorectal advanced adenomas or cancers, and had ≥5 rectal ACF at a preregistration chromoendoscopy. Subjects (N = 39) were randomized to 6 months of oral Poly E (780 mg EGCG) daily or placebo. Baseline characteristics were similar by treatment arm (all P >0.41); 32 of 39 (82%) subjects completed 6 months of treatment. The primary endpoint was percent reduction in rectal ACF at chromoendoscopy comparing before and after treatment. Among 32 subjects (15 Poly E, 17 placebo), percent change in rectal ACF number (baseline vs. 6 months) did not differ significantly between study arms (3.7% difference of means; P = 0.28); total ACF burden was also similar (-2.3% difference of means; P = 0.83). Adenoma recurrence rates at 6 months were similar by arm (P > 0.35). Total drug received did not differ significantly by study arm; 31 (79%) subjects received ≥70% of prescribed Poly E. Poly E was well tolerated and adverse events (AE) did not differ significantly by arm. One subject on placebo had two grade 3 AEs; one subject had grade 2 hepatic transaminase elevations attributed to treatment. In conclusion, Poly E for 6 months did not significantly reduce rectal ACF number relative to placebo. Poly E was well tolerated and without significant toxicity at the dose studied. PREVENTION RELEVANCE: We report a chemoprevention trial of polyphenon E in subjects at high risk of colorectal cancer. The results show that polyphenon E was well tolerated, but did not significantly reduce the number of rectal aberrant crypt foci, a surrogate endpoint biomarker of colorectal cancer.

Inflammation, immunosuppressive microenvironment and breast cancer: opportunities for cancer prevention and therapy

Breast cancer is the most commonly diagnosed malignancy and a leading cause of cancer-related death in women worldwide. It also exhibits pronounced racial disparities in terms of incidence and clinical outcomes. There has been a growing interest in research community to better understand the role of the microenvironment in cancer. Several lines of evidence have highlighted the significance of chronic inflammation at the local and/or systemic level in breast tumor pathobiology. Inflammation can influence breast cancer progression, metastasis and therapeutic outcome by establishing a tumor supportive immune microenvironment. These processes are mediated through a variety of cytokines and hormones that exert their biological actions either locally or distantly via systemic circulation. Targeting of immune and inflammatory pathways has met tremendous success in some cancers underscoring the importance of research to further our understanding of these systems in breast cancer. This knowledge can be helpful not only in the development of novel prevention and therapeutic strategies, but also help in better prediction of therapeutic responses in patients. This review summarizes some of the significant findings on the role of inflammation in breast cancer to gain collective molecular and mechanistic insights. We also discuss ongoing efforts and future outlook to exploit the existing knowledge for improved breast cancer management.

Canine mammary tumors as a model for human disease

Animal models for examining human breast cancer (HBC) carcinogenesis have been extensively studied and proposed. With the recent advent of immunotherapy, significant attention has been focused on the dog as a model for human cancer. Dogs develop mammary tumors and other cancer types spontaneously with an intact immune system, which exhibit a number of clinical and molecular similarities to HBC. In addition to the spontaneous tumor presentation, the clinical similarities between human and canine mammary tumors (CMT) include the age at onset, hormonal etiology and course of the diseases. Furthermore, factors that affect the disease outcome, including tumor size, stage and lymph node invasion, are similar in HBC and CMT. Similarly, the molecular characteristics of steroid receptor, epidermal growth factor, proliferation marker, metalloproteinase and cyclooxygenase expression, and the mutation of the p53 tumor suppressor gene in CMT, mimic HBC. Furthermore, ductal carcinomas in situ in human and canine mammary glands are particularly similar in their pathological, molecular and visual characteristics. These CMT characteristics and their similarities to HBC indicate that the dog could be an excellent model for the study of human disease. These similarities are discussed in detail in the present review, and are compared with the in vitro and other in vivo animal models available.

Intermittent Dosing with Sulindac Provides Effective Colorectal Cancer Chemoprevention in the Azoxymethane-Treated Mouse Model

Sulindac is an NSAID that can provide effective chemoprevention for colorectal cancer. In this study, alternative dosing regimens of sulindac were evaluated for their chemoprevention effectiveness in the azoxymethane-treated A/J mouse model of colorectal cancer. High-resolution endoscopic optical coherence tomography was utilized to time-serially measure tumor number and tumor burden in the distal colon as the biological endpoints. Four treatment groups were studied: (i) daily for 20 weeks (sulindac-daily); (ii) for 2 weeks, then no sulindac for 2 weeks, cycle repeated 5 times (sulindac-2); (iii) for 10 weeks ("on"), then no sulindac for 10 weeks ("off"; sulindac-10); and (iv) no sulindac (sulindac-none). Sulindac-2 and sulindac-daily had statistically significantly lower final tumor counts and slopes (change in number of tumors per week) when compared with sulindac-none (P < 0.0001). All of the treatment groups had statistically significantly lower final tumor burdens and slopes when compared with sulindac-none (P < 0.001). There was a prolonged latency period in the sulindac-10 group, with no significant difference between the "off" portion of this treatment and sulindac-none. These results suggest that, although daily doses of sulindac provide the most optimal effects, intermittent doses of sulindac in a 50% duty cycle with an overall 4-week period (sulindac-2 model) can provide highly effective chemoprevention of colorectal cancer in this model. After cessation of sulindac treatment (sulindac-10 "off"), there is no evidence of either a persistent chemopreventive effect or a rebound effect. Cancer Prev Res; 10(8); 459-66. ©2017 AACR.

Citrus fruits as a treasure trove of active natural metabolites that potentially provide benefits for human health

Citrus fruits, which are cultivated worldwide, have been recognized as some of the most high-consumption fruits in terms of energy, nutrients and health supplements. What is more, a number of these fruits have been used as traditional medicinal herbs to cure diseases in several Asian countries. Numerous studies have focused on Citrus secondary metabolites as well as bioactivities and have been intended to develop new chemotherapeutic or complementary medicine in recent decades. Citrus-derived secondary metabolites, including flavonoids, alkaloids, limonoids, coumarins, carotenoids, phenolic acids and essential oils, are of vital importance to human health due to their active properties. These characteristics include anti-oxidative, anti-inflammatory, anti-cancer, as well as cardiovascular protective effects, neuroprotective effects, etc. This review summarizes the global distribution and taxonomy, numerous secondary metabolites and bioactivities of Citrus fruits to provide a reference for further study. Flavonoids as characteristic bioactive metabolites in Citrus fruits are mainly introduced.

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.

Skin Carcinogenesis Studies Using Mouse Models with Altered Polyamines

Nonmelanoma skin cancer (NMSC) is a major health concern worldwide. With increasing numbers in high-risk groups such as organ transplant recipients and patients taking photosensitizing medications, the incidence of NMSC continues to rise. Mouse models of NMSC allow us to better understand the molecular signaling cascades involved in skin tumor development in order to identify novel therapeutic strategies. Here we review the models designed to determine the role of the polyamines in NMSC development and maintenance. Elevated polyamines are absolutely required for tumor growth, and dysregulation of their biosynthetic and catabolic enzymes has been observed in NMSC. Studies using mice with genetic alterations in epidermal polyamines suggest that they play key roles in tumor promotion and epithelial cell survival pathways, and recent clinical trials indicate that pharmacological inhibitors of polyamine metabolism show promise in individuals at high risk for NMSC.

Aspirin and serum estrogens in postmenopausal women: a randomized controlled clinical trial

Epidemiologic studies suggest a reduced risk of breast cancer among women who use aspirin. A plausible mechanism is through aspirin's effect on estrogens, possibly mediated through interference with estrogen synthesis via reduction in inflammation, which is increased in adipose tissues, including breast. In a randomized placebo-controlled trial, we evaluated the effects of six-month administration of 325 mg/day aspirin on serum estrogens (estradiol, estrone, free estradiol, and bioavailable estradiol) and sex hormone-binding globulin (SHBG) in 144 healthy postmenopausal women. Eligible participants, recruited 2005-2007, were not taking nonsteroidal anti-inflammatory medication, including aspirin >2 times/week or menopausal hormone therapy, and had a Breast Imaging-Reporting and Data System (BI-RADS) mammographic density classification of 2, 3, or 4. The intervention effects (intent-to-treat) were evaluated by differences in the geometric mean outcome changes at six months between aspirin and placebo groups using generalized estimating equations (GEE). Participants were a mean 59.4 (SD, 5.4) years of age, with a mean body mass index (BMI) of 26.4 (SD, 5.4) kg/m(2). Between baseline and six months, none of the serum estrogens or SHBG changed substantially and there were no differences between groups. Stratifying by BMI did not change results. In conclusion, a single daily administration of 325 mg of aspirin for six months had no effect on serum estrogens or SHBG in postmenopausal women. Larger doses or longer duration of aspirin administration may be needed to affect circulating estrogens. Alternately, if aspirin influences breast cancer risk in postmenopausal women, it may do so through direct breast tissue effects, or through pathways other than estrogens.

Chemoprevention of gastrointestinal neoplasia

Cancer chemoprevention is defined as the pharmacologic intervention, by drugs or nutrient-components, with the process of carcinogenesis, in order to prevent the development of invasive malignant neoplasms. This preventive attempt is particularly challenging in cancer types, which have a long subclinical developmental phase, because of their low cellular proliferation rate and their slow pre-clinical evolution, until they become clinically detectable and therapeutically as well as prognostically relevant. Therefore, only certain specific cancer types are presently in the focus of clinical chemoprevention. Among the GI tract cancer, colorectal (CRC) as well as esophageal cancer have raised the most attention over the past decades, as they both share a long precancerous stage (the adenoma in CRC and Barrett's esophagus in the case of esophageal adenocarcinoma) which provides a window of opportunity to intervene and prevent development of cancer.In this review, we will focus on both CRC as well as esophageal adenocarcinoma (EAC).

Targeted expression of ornithine decarboxylase antizyme prevents upper aerodigestive tract carcinogenesis in p53-deficient mice

Upper aerodigestive tract (UADT) cancers of the oral cavity and esophagus are a significant global health burden, and there is an urgent need to develop relevant animal models to identify chemopreventive and therapeutic strategies to combat these diseases. Antizyme (AZ) is a multifunctional negative regulator of cellular polyamine levels, and here, we evaluate the susceptibility of keratin 5 (K5)-AZ transgenic mice to tumor models that combine chemical carcinogenesis with dietary and genetic risk factors known to influence human susceptibility to UADT cancer and promote UADT carcinogenesis in mice. First, p53(+/-) and K5-AZ/p53(+/-) (AZ/p53(+/-)) mice were placed on a zinc-deficient (ZD) or zinc-sufficient (ZS) diet and chronically exposed to 4-nitroquinoline 1-oxide. Tongue tumor incidence, multiplicity and size were substantially reduced in both ZD and ZS AZ/p53(+/-) mice compared with p53(+/-). AZ expression also reduced progression to carcinoma in situ or invasive carcinoma and decreased expression of the squamous cell carcinoma biomarkers K14, cyclooxygenase-2 and metallothionein. Next, AZ-expressing p53(+/-) and p53 null mice were placed on the ZD diet and treated with a single dose of N-nitrosomethylbenzylamine. Regardless of p53 status, forestomach (FST) tumor incidence, multiplicity and size were greatly reduced with AZ expression, which was also associated with a significant decrease in FST epithelial thickness along with reduced proliferation marker K6 and increased differentiation marker loricrin. These studies demonstrate the powerful tumor suppressive effects of targeted AZ expression in two distinct and unique mouse models and validate the polyamine metabolic pathway as a target for chemoprevention of UADT cancers.

Dose-response on the chemopreventive effects of sarcophine-diol on UVB-induced skin tumor development in SKH-1 hairless mice

Sarcophine-diol (SD) is a lactone ring-opened analogue of sarcophine. It has shown chemopreventive effects on chemically-induced skin tumor development in female CD-1 mice, as well as in a UVB-induced skin tumor development model in hairless SKH-1 mice at a dose of 30 μg SD applied topically and 180 mJ/cm² UVB. The objective of this study was to determine the dose-response on the chemopreventive effects of SD on SKH-1 hairless mice when exposed to a UVB radiation dose of 30 mJ/cm². This UVB dose better represents chronic human skin exposure to sunlight leading to skin cancer than previous studies applying much higher UVB doses. Carcinogenesis was initiated and promoted by UVB radiation. Female hairless SKH-1 mice were divided into five groups. The control group was topically treated with 200 μL of acetone (vehicle), and the SD treatment groups were topically treated with SD (30 μg, 45 μg, and 60 μg dissolved in 200 μL of acetone) 1 h before UVB radiation (30 mJ/cm²). The last group of animals received 60 μg SD/200 μL acetone without UVB exposure. These treatments were continued for 27 weeks. Tumor multiplicity and tumor volumes were recorded on a weekly basis for 27 weeks. Weight gain and any signs of toxicity were also closely monitored. Histological characteristics and the proliferating cell nuclear antigen (PCNA) were evaluated in the mice skin collected at the end of the experiment. The dose-response study proved a modest increase in chemopreventive effects with the increase in SD dose. SD reduced the number of cells positively stained with PCNA proliferation marker in mice skin. The study also showed that SD application without UVB exposure has no effect on the structure of skin. The results from this study suggest that broader range doses of SD are necessary to improve the chemopreventive effects.

Reversal by RARα agonist Am580 of c-Myc-induced imbalance in RARα/RARγ expression during MMTV-Myc tumorigenesis

INTRODUCTION

Retinoic acid signaling plays key roles in embryonic development and in maintaining the differentiated status of adult tissues. Recently, the nuclear retinoic acid receptor (RAR) isotypes α, β and γ were found to play specific functions in the expansion and differentiation of the stem compartments of various tissues. For instance, RARγ appears to be involved in stem cell compartment expansion, while RARα and RARβ are implicated in the subsequent cell differentiation. We found that over-expressing c-Myc in normal mouse mammary epithelium and in a c-Myc-driven transgenic model of mammary cancer, disrupts the balance between RARγ and RARα/β in favor of RARγ.

METHODS

The effects of c-Myc on RAR isotype expression were evaluated in normal mouse mammary epithelium, mammary tumor cells obtained from the MMTV-Myc transgenic mouse model as well as human normal immortalized breast epithelial and breast cancer cell lines. The in vivo effect of the RARα-selective agonist 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)carboxamido]benzoic acid (Am580) was examined in the MMTV-Myc mouse model of mammary tumorigenesis.

RESULTS

Modulation of the RARα/β to RARγ expression in mammary glands of normal mice, oncomice, and human mammary cell lines through the alteration of RAR-target gene expression affected cell proliferation, survival and tumor growth. Treatment of MMTV-Myc mice with the RARα-selective agonist Am580 led to significant inhibition of mammary tumor growth (~90%, P<0.001), lung metastasis (P<0.01) and extended tumor latency in 63% of mice. Immunocytochemical analysis showed that in these mice, RARα responsive genes such as Cyp26A1, E-cadherin, cellular retinol-binding protein 1 (CRBP1) and p27, were up-regulated. In contrast, the mammary gland tumors of mice that responded poorly to Am580 treatment (37%) expressed significantly higher levels of RARγ. In vitro experiments indicated that the rise in RARγ was functionally linked to promotion of tumor growth and inhibition of differentiation. Thus, activation of the RARα pathway is linked to tumor growth inhibition, differentiation and cell death.

CONCLUSIONS

The functional consequence of the interplay between c-Myc oncogene expression and the RARγ to RARα/β balance suggests that prevalence of RARγ over-RARα/β expression levels in breast cancer accompanied by c-Myc amplification or over-expression in breast cancer should be predictive of response to treatment with RARα-isotype-specific agonists and warrant monitoring during clinical trials.

COX inhibitors Indomethacin and Sulindac derivatives as antiproliferative agents: synthesis, biological evaluation, and mechanism investigation

Cyclooxygenase (COX) inhibitors Indomethacin and its structural analogs Sulindac exhibit cell growth inhibition and apoptosis inducing activities in various cancer cell lines via COX independent mechanisms. In this study, the molecular structures of Indomethacin and Sulindac were used as starting scaffolds to design novel analogs and their effects on the proliferation of human cancer cells were evaluated. Compared to Indomethacin and Sulindac inhibiting cancer cell proliferation with IC(50)s of more than 1 mM, the derivatives displayed significantly increased activities. Especially, one of the Indomethacin analogs inhibited the growth of a series of cancer cell lines with IC(50)s around 0.5 μM-3 μM. Mechanistic investigation revealed that the new analog was in fact a tubulin inhibitor, although the parental compound Indomethacin did not show any tubulin inhibitory activity. Tubulin polymerization assay indicated this compound inhibited tubulin assembly at high concentrations, but promoted this process at low concentrations which is a very unique mechanism. The binding mode of this compound in tubulin was predicted using the molecular docking simulation.

Efficacy of EGFR inhibition is modulated by model, sex, genetic background and diet: implications for preclinical cancer prevention and therapy trials

Molecule-targeted therapies are being widely developed and deployed, but they are frequently less effective in clinical trials than predicted based upon preclinical studies. Frequently, only a single model or genetic background is utilized using diets that are not relevant to that consumed by most cancer patients, which may contribute to the lack of predictability of many preclinical therapeutic studies. Inhibition of epidermal growth factor receptor (EGFR) in colorectal cancer was used to investigate potential causes for low predictive values of many preclinical studies. The efficacy of the small molecule EGFR inhibitor AG1478 was evaluated using two mouse models, Apc^Min/+ and azoxymethane (AOM), both sexes on three genetic backgrounds, C57BL/6J (B6) and A/J (A) inbred strains and AB6F1 hybrids, and two diets, standard chow (STD) or Western-style diet (WD). AG1478 has significant anti-tumor activity in the B6-Apc^Min/+ model with STD but only moderately on the WD and in the AOM model on an A background with a WD but not STD. On the F1 hybrid background AG1478 is effective in the Apc^Min/+ model with either STD or WD, but has only moderate efficacy in the AOM model with either diet. Sex differences were also observed. Unexpectedly, the level of liver EGFR phosphorylation inhibition by AG1478 was not positively correlated with inhibition of tumor growth in the AOM model. Model-dependent interactions between genetic background and diet can dramatically impact preclinical results, and indicate that low predictive values of preclinical studies can be attributed to study designs that do not account for the heterogeneous patient population or the diets they consume. Better-designed preclinical studies should lead to more accurate predictions of therapeutic response in the clinic.

Chemoprevention of mouse lung and colon tumors by suberoylanilide hydroxamic acid and atorvastatin

Atorvastatin and suberoylanilide hydroxamic acid (SAHA) were evaluated for chemoprevention of mouse lung tumors. In Experiment 1, lung tumors were induced by vinyl carbamate in strain A/J mice followed by 500 mg/kg SAHA, 60 or 180 mg/kg atorvastatin, and combinations containing SAHA and atorvastatin administered in their diet. SAHA and both combinations, but not atorvastatin, decreased the multiplicity of lung tumors, including large adenomas and adenocarcinomas with the combinations demonstrating the greatest efficacy. In Experiment 2, lung tumors were induced by 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanol in strain A/J mice followed by 180 mg/kg atorvastatin, 500 mg/kg SAHA, or both drugs administered in the diet. SAHA and the combination of both drugs, but not atorvastatin alone, decreased the multiplicity of lung tumors and large tumors, with the combination demonstrating greater efficacy. In Experiment 3, lung tumors were induced by 1,2-dimethylhydrazine in Swiss-Webster mice followed by 160 mg/kg atorvastatin, 400 mg/kg SAHA, or a combination of both drugs administered in the diet. SAHA and the combination, but not atorvastatin, decreased the multiplicity of lung tumors with the combination demonstrating greater efficacy. The multiplicity of colon tumors was decreased by SAHA, atorvastatin, and the combination, without any significant difference in their efficacy. mRNA expression analysis of lung tumor bearing mice suggested that the enhanced chemopreventive activity of the combination is related to atorvastatin modulation of DNA repair, SAHA modulation of angiogenesis, and both drugs modulating invasion and metastasis pathways. Atorvastatin demonstrated chemoprevention activity as indicated by the enhancement of the efficacy of SAHA to prevent mouse lung tumors.

Evaluation of difluoromethylornithine for the chemoprevention of Barrett's esophagus and mucosal dysplasia

Patients with Barrett's esophagus (BE) and dysplasia are candidates for chemopreventive strategies to reduce cancer risk. We determined the effects of difluoromethylornithine (DMFO) on mucosal polyamines, gene expression, and histopathology in BE. Ten patients with BE and low-grade dysplasia participated in a single-arm study of DFMO (0.5 g/m(2)/d) given continuously for 6 months. Esophagoscopy with biopsies was conducted at baseline, 3, 6, and 12 months. Dysplasia was graded by a gastrointestinal pathologist. Audiology was assessed (at baseline and at 6 months). Mucosal polyamines were measured by high-performance liquid chromatography. Microarray-based gene expression was analyzed using a cDNA two-color chip. DFMO suppressed levels of the polyamines putrescine (P = 0.02) and spermidine (P = 0.02) and the spermidine/spermine ratio (P < 0.01) in dysplastic BE (6 months vs. baseline) that persisted at 6 months following drug cessation. Among the top 25 modulated genes, we found those regulating p53-mediated cell signaling (RPL11), cell-cycle regulation (cyclin E2), and cell adhesion and invasion (Plexin1). DFMO downregulated Krüppel-like factor 5 (KLF5), a transcription factor promoting cell proliferation, and suppressed RFC5 whose protein interacts with proliferating cell nuclear antigen. Histopathology showed regression of dysplasia (n = 1), stable disease (n = 8), and progression to high-grade dysplasia (n = 1). Polyamines were suppressed in the responder to a greater extent than in stable cases. DFMO was well tolerated, and one patient had subclinical, unilateral ototoxicity. DFMO suppressed mucosal polyamines and modulated genes that may be mechanistically related to its chemopreventive effect. Further study of DFMO for the chemoprevention of esophageal cancer in BE patients is warranted.

Establishment of a mammary carcinoma cell line from Syrian hamsters treated with N-methyl-N-nitrosourea

Clearly new breast cancer models are necessary in developing novel therapies. To address this challenge, we examined mammary tumor formation in the Syrian hamster using the chemical carcinogen N-methyl-N-nitrosourea (MNU). A single 50mg/kg intraperitoneal dose of MNU resulted in a 60% incidence of premalignant mammary lesions, and a 20% incidence of mammary adenocarcinomas. Two cell lines, HMAM4A and HMAM4B, were derived from one of the primary mammary tumors induced by MNU. The morphology of the primary tumor was similar to a high-grade poorly differentiated adenocarcinoma in human breast cancer. The primary tumor stained positively for both HER-2/neu and pancytokeratin, and negatively for both cytokeratin 5/6 and p63. When the HMAM4B cell line was implanted subcutaneously into syngeneic female hamsters, tumors grew at a take rate of 50%. A tumor derived from HMAM4B cells implanted into a syngeneic hamster was further propagated in vitro as a stable cell line HMAM5. The HMAM5 cells grew in female syngeneic hamsters with a 70% take rate of tumor formation. These cells proliferate in vitro, form colonies in soft agar, and are aneuploid with a modal chromosomal number of 74 (the normal chromosome number for Syrian hamster is 44). To determine responsiveness to the estrogen receptor (ER), a cell proliferation assay was examined using increasing concentrations of tamoxifen. Both HMAM5 and human MCF-7 (ER positive) cells showed a similar decrease at 24h. However, MDA-MB-231 (ER negative) cells were relatively insensitive to any decrease in proliferation from tamoxifen treatment. These results suggest that the HMAM5 cell line was likely derived from a luminal B subtype of mammary tumor. These results also represent characterization of the first mammary tumor cell line available from the Syrian hamster. The HMAM5 cell line is likely to be useful as an immunocompetent model for human breast cancer in developing novel therapies.

Soybean peptide lunasin suppresses in vitro and in vivo 7,12-dimethylbenz[a]anthracene-induced tumorigenesis

Lunasin is a novel peptide identified in soybean and other seeds. This study evaluated the anti-tumorigenic effects of lunasin on 7,12-dimethylbenz(a)anthracene (DMBA) and 3-methylcholanthrene-treated (MCA) fibroblast NIH/3T3 cells. Lunasin significantly inhibited cell proliferation and cancerous foci formation in these 2 chemical carcinogens-treated cells. An in vivo SENCAR mouse model induced with DMBA was used to study the mammary cancer preventive properties of dietary lunasin contained in soy protein. Tumor incidence was 67% and 50%, and the tumor generation was 1.88 ± 0.48 and 1.17 ± 0.17, respectively, for the mice fed control diet and experimental diet obtained after AIN-93G supplementation with lunasin-enriched soy protein concentrate (containing 0.23% lunasin). However, no effects were observed in mice fed AIN-93G supplemented with soy protein concentrate (containing 0.15% lunasin). The data provided illustrate the anticancer potential of lunasin both in vitro and in vivo and supports the recommendation of soy protein as a dietary component that may aid in the prevention of mammary cancer.

RARα1 control of mammary gland ductal morphogenesis and wnt1-tumorigenesis

INTRODUCTION

Retinoic acid signaling pathways are disabled in human breast cancer suggesting a controlling role in normal mammary growth that might be lost in tumorigenesis. We tested a single receptor isotype, RARα1, for its role in mouse mammary gland morphogenesis and MMTV-wnt1-induced oncogenesis.

METHODS

The role of RARα1 in mammary morphogenesis was tested in RARα1-knockout (KO) mice and in mammary tumorigenesis in bi-genic (RARα1/KO crossed with MMTV-wnt1) mice. We used whole mounts analysis, stem cells/progenitor quantification, mammary gland repopulation, Q-PCR, test of tumor-free survival, tumor fragments and cell transplantation.

RESULTS

In 2 genetic backgrounds (129/Bl-6 and FVB) the neo-natal RARα1/KO-mammary epithelial tree was 2-fold larger and the pubertal tree had 2-fold more branch points and 5-fold more mature end buds, a phenotype that was predominantly epithelial cell autonomous. The stem/progenitor compartment of the RARα1/KO mammary, defined as CD24(low)/ALDH(high activity) was increased by a median 1.7 fold, but the mammary stem cell (MaSC)-containing compartment, (CD24(low)/CD29(high)), was larger (~1.5 fold) in the wt-glands, and the mammary repopulating ability of the wt-gland epithelium was ~2-fold greater. In MMTV-wnt1 transgenic glands the progenitor (CD24(low)/ALDH(high activity)) content was 2.6-fold greater than in the wt and was further increased in the RARα1/KO-wnt1 glands. The tumor-free survival of RARα1/KO-wnt1 mice was significantly (p=0.0002, Kaplan Meier) longer, the in vivo growth of RARα1/KO-wnt1 transplanted tumor fragments was significantly (p=0.01) slower and RARα1/KO-wnt1 tumors cell suspension produced tumors after much longer latency.

CONCLUSIONS

In vitamin A-replete mice, RARα1 is required to maintain normal mammary morphogenesis, but paradoxically, also efficient tumorigenesis. While its loss increases the density of the mammary epithelial tree and the content of luminal mammary progenitors, it appears to reduce the size of the MaSC-containing compartment, the mammary repopulating activity, and to delay significantly the MMTV-wnt1-mammary tumorigenesis. Whether the delay in tumorigenesis is solely due to a reduction in wnt1 target cells or due to additional mechanisms remains to be determined. These results reveal the intricate nature of the retinoid signaling pathways in mammary development and carcinogenesis and suggest that a better understanding will be needed before retinoids can join the armament of effective anti- breast cancer therapies.

Aberrant crypt foci: the case for inclusion as a biomarker for colon cancer

Aberrant crypt foci (ACF) are one of the earliest histopathological manifestations of colon cancer. In this review, we critically present the molecular, cellular, histopathological, and chemopreventive evidence that ACF are relevant biomarkers for colon cancer. The laboratory and clinical evidence are highly suggestive that ACF are in the pathway leading to colon cancer, but not all ACF will do so. The possible fate and outcome of ACF in the progression toward colon cancer may be dependent on a number of features that define their predictive power for the prevention or progression of cancer.

Cancer chemoprevention locks onto a new polyamine metabolic target

Ornithine decarboxylase has a relatively long history as a target for cancer chemoprevention and chemotherapy. Plym Forshell et al. report new evidence (beginning on p. 140 in this issue of the journal) indicating that spermidine synthase, a fellow enzyme of ornithine decarboxylase in polyamine metabolism, is transactivated in part by the MYC gene and is a potential target for chemoprevention of B-cell lymphomas.

DHEA, important source of sex steroids in men and even more in women

A major achievement from 500 million years of evolution is the establishment of a high secretion rate of dehydroepiandrosterone (DHEA) by the human adrenal glands coupled with the indroduction of menopause which stops secretion of estrogens by the ovary. Cessation of estrogen secretion at menopause eliminates the risks of endometrial hyperplasia and cancer which would result from non-opposed estrogen stimulation during the post-menopausal years. In fact, from the time of menopause, DHEA becomes the exclusive and tissue-specific source of sex steroids for all tissues except the uterus. Intracrinology, a term coined in 1988, describes the local formation, action and inactivation of sex steroids from the inactive sex steroid precursor DHEA. Over the past 25 years most, if not all, the genes encoding the human steroidogenic and steroid-inactivating enzymes have been cloned and sequenced and their enzymatic activity characterized. The problem with DHEA, however, is that its secretion decreases from the age of 30 years and is already decreased, on average, by 60% at time of menopause. In addition, there is a large variability in the circulating levels of DHEA with some post-menopausal women having barely detectable serum concentrations of the steroid while others have normal values. Since there is no feedback mechanism controlling DHEA secretion within 'normal' values, women with low DHEA will remain with such a deficit of sex steroids for their remaining lifetime. Since there is no other significant source of sex steroids after menopause, one can reasonably believe that low DHEA is involved, in association with the aging process, in a series of medical problems classically associated with post-menopause, namely osteoporosis, muscle loss, vaginal atrophy, fat accumulation, hot flashes, skin atrophy, type 2 diabetes, memory loss, cognition loss and possibly Alzheimer's disease. A recent randomized, placebo-controlled study has shown that all the signs and symptoms of vaginal atrophy, a classical problem recognized to be due to the hormone deficiency of menopause, can be rapidly improved or corrected by local administration of DHEA without systemic exposure to estrogens. In addition, the four domains of sexual dysfucntion are improved. For the other problems of menopause, although similar large scale, randomized and placebo-controlled studies usually remain to be performed, the available evidence already strongly suggests that they could be improved, corrected or even prevented by exogenous DHEA. In men, the contribution of adrenal DHEA to the total androgen pool has been measured at 40% in 65-75-year-old men. Such data stress the necessity of blocking both the testicular and adrenal sources of androgens in order to achieve optimal benefits in prostate cancer therapy. On the other hand, the comparable decrease in serum DHEA levels observed in both sexes has less consequence in men who continue to receive a practically constant supply of testicular sex steroids during their whole life. In fact, in men, the appearance of hormone-deficiency symptoms common to women is observed at a later age and with a lower degree of severity. Consequently, DHEA replacement has shown much more easily measurable beneficial effects in women. Most importantly, despite the non-scientific and unfortunate availability of DHEA as a food supplement in the United States, a situation that discourages rigorous clinical trials on the crucial physiological and therapeutic role of DHEA, no serious adverse event related to DHEA has ever been reported in the world literature (thousands of subjects exposed) or in the monitoring of adverse events by the FDA (millions of subjects exposed), thus indicating, as expected from its known physiology, the excellent safety profile of DHEA. With today's knowledge, one can reasonably suggest that DHEA offers the promise of a safe and efficient replacement therapy for the multiple problems related to hormone deficiency after menopause without the risks associated with estrogen-based or any other treatments.

Mastitis and the risk of breast cancer

BACKGROUND

Many cancers arise from sites of infection and inflammation. Results from animal studies indicate that inflammatory cells may facilitate neoplastic processes by orchestrating the tumor microenvironment. Little is known about the role of inflammation in the etiology of breast cancer. The aim of this study was to examine possible associations between a history of mastitis requiring hospitalization and subsequent risk of breast cancer.

METHODS

This cohort study of 2,577,565 women used data from several Swedish population-based registers, including the Inpatient Register and the Cancer Register. The risk of breast cancer was assessed by Poisson regression modeling.

RESULTS

We identified 8411 women in the Inpatient Register with a discharge diagnosis of mastitis. Of these, 106 had a subsequent diagnosis of breast cancer recorded in the Cancer Register. Compared with women who had no recorded mastitis, the incidence rate of breast cancer (regardless of laterality) was higher in women with mastitis, with an incidence rate ratio of 1.23 (95% confidence interval [CI] = 1.02-1.49) following adjustment for age, calendar time, age at first birth and parity. In the group of women among whom information on laterality was available for both the mastitis and the malignancy (n = 87), side of lesions corresponded for 52% (95% CI = 41%-62%), which is what could be expected by chance.

CONCLUSIONS

The overall risk of breast cancer was slightly elevated in women with a history of mastitis recorded in the Inpatient Register. The absence of a correlation between laterality of lesions, however, does not support a causal association between inflammation and the development of breast cancer.

Citrus auraptene suppresses cyclin D1 and significantly delays N-methyl nitrosourea induced mammary carcinogenesis in female Sprague-Dawley rats

BACKGROUND

Breast cancer is a major problem in the United States leading to tens of thousands of deaths each year. Although citrus auraptene suppresses cancer in numerous rodent models, its role in breast cancer prevention previously has not been reported. Thus, our goal was to determine the anticarcinogenic effects of auraptene against breast cancer.

METHODS

The effects of auraptene on cell proliferation of MCF-7 and MDA-MB-231 human breast carcinoma cells in culture was assessed by measuring metabolism of a substrate to a formazan dye. Dietary effects of auraptene on tumor incidence, multiplicity and latency were studied in the N-methyl nitrosourea (MNU) induced mammary carcinogenesis model in female Sprague Dawley rats. The concentration of auraptene in rat tissues was analyzed by reverse phase HPLC. Cyclin D1 expression in MCF-7 cells and rat tumors was measured by western blot.

RESULTS

Auraptene (500 ppm) significantly delayed median time to tumor by 39 days compared to the MNU only group (p < 0.05, n = 24-26). Auraptene (10 microM) reduced Insulin like Growth Factor-1 (IGF-1, 10 ng/mL)-induced cyclin D1 expression by 40% in MCF-7 cells. In comparison, western blot analysis of rat mammary tumors (n = 10 per group) confirmed that auraptene (500 ppm) significantly reduced (p < 0.05) cyclin D1 expression by 49% compared to the MNU only group. Analysis of rat mammary tissue extract by HPLC with fluorescence detection indicated an average concentration (means +/- S.E.) of 1.4 +/- 0.5 microM and 1.8 +/- 0.3 microM in the normal mammary glands of the auraptene 200 ppm and 500 ppm groups, respectively. The concentration (means +/- S.E.) of auraptene in the mammary tumors of the auraptene 200 ppm group was 0.31 +/- 0.98 microM.

CONCLUSION

Overall, these observations suggest that the predominant effect of auraptene was to delay the development of tumors possibly through the suppression of cyclin D1 expression. These results point to the potential chemopreventive effects of auraptene in mammary carcinogenesis.

CHEMOPREVENTION: MOUSE COLON AND LUNG TUMOR BIOASSAY AND MODULATION OF DNA METHYLATION AS A BIOMARKER

Lung and colon tumors were induced in A/J, C3H, and A/J X C3H (AC3) mice by administering 16 mg/kg vinyl carbamate followed by 6 weekly doses of 12 mg/kg azoxymethane (AOM). Beginning 1 week after carcinogen treatment, the mice received chemopreventive agents, dexamethasone or piroxicam, at 0.1 and 75 mg/kg in the diet, respectively. Both AOM and vinyl carbamate induces lung tumors, but only AOM induced colon tumors. The strain sensitivity for both colon and lung tumors was A/J > AC3 > C3H mice. Dexamethasone and piroxicam reduced the multiplicity of colon and lung tumors in A/J and AC3 mice, demonstrating the advantage of a combined colon and lung bioassay. The ability of budesonide, a drug that prevents mouse lung tumors, to modulate DNA methylation in vinyl carbamate-induced lung tumors was also determined. Budesonide administered for only 7 days prior to sacrifice caused a dose-dependent (0.6 to 2.4 mg/kg diet) reversal in tumors of DNA hypomethylation and hypomethylation of the insulin-like growth factor (IGF)-II gene in the differentially methylated region (DMR) 2 region of exons 4 to 5. Longer treatment with budesonide reversed hypomethylation when administered up to the time of sacrifice. These results indicate that reversal of the hypomethylation of DNA and of specific genes in lung tumors may be applicable as a surrogate end-point biomarker for chemoprevention.

No effect of aspirin on mammographic density in a randomized controlled clinical trial

BACKGROUND

Epidemiologic studies suggest a reduced risk of breast cancer among women who regularly use aspirin; a plausible mechanism is through aspirin effect on mammographic breast density, a breast cancer risk factor, possibly mediated through aspirin interference with estrogen synthesis.

METHODS

In a 2-arm randomized placebo-controlled clinical trial, we evaluated the effects of 6-month administration of 325 mg/day aspirin on total mammographic breast dense area and percent of the mammographic breast image occupied by dense areas (% density) in 143 postmenopausal women. Eligible women, recruited from 2005 to 2007, were healthy, not taking hormone therapy, with elevated mammographic breast density (American College of Radiology Breast Imaging Reporting and Data System density category 2, 3, or 4) within 6 months before enrollment.

RESULTS

Women were a mean (SD) 59.5 (5.5) years. Geometric mean baseline percent density was 17.6% (95% confidence interval, 14.8-20.9) in women randomized to aspirin and 19.2% (95% confidence interval, 16.3-22.7) in women randomized to placebo. Percent density decreased in women randomized to aspirin by an absolute 0.8% versus an absolute decrease of 1.2% in controls (P = 0.84). Total breast area and dense area decreased to a similar degree in women assigned to aspirin and in those assigned to placebo, with no statistically significant differences between trial arms.

CONCLUSIONS

A single daily administration of adult-dose aspirin for 6 months had no effect on mammographic density in postmenopausal women. If aspirin affects breast cancer risk in postmenopausal women, it may do so through alternative pathways than mammographic breast density.

Dithiolethiones for cancer chemoprevention: where do we stand?

Dithiolethiones are a well-known class of cancer chemopreventive agents; the key mechanism of action of dithiolethiones involves activation of Nrf2 signaling and induction of phase II enzymes. In the past, attention has been focused mainly on 4-methyl-5-pyrazinyl-3H-1,2-dithiole-3-thione (oltipraz), which showed ability as a wide-spectrum inhibitor of chemical carcinogenesis in preclinical models. However, clinical trials of oltipraz have shown questionable efficacy, and at the high doses employed in such studies, significant side effects were observed. Dithiolethiones that are markedly more effective and potent than oltipraz in both induction of phase II enzymes and inhibition of chemical carcinogenesis in preclinical studies have been identified, and these compounds have shown pronounced organ specificity in vivo. Further investigation of these compounds may lead to development of effective and safe agents for cancer prevention in humans.

Beta-sitosterol induces anti-proliferation and apoptosis in human leukemic U937 cells through activation of caspase-3 and induction of Bax/Bcl-2 ratio

Beta-sitosterol is the main dietary phytosterol found in plants and has been shown to inhibit proliferation and induce apoptosis in human solid tumors such as colon and breast cancers. However, the mechanism by which beta-sitosterol induces apoptosis is not completely understood in leukemic cells. This study investigated the mechanism of apoptosis induced by beta-sitosterol in human leukemic U937 cells. beta-Sitosterol induced cytotoxicity and apoptosis in U937 cells in a concentration dependent manner, as measured by hemocytometer counts, fluorescence microscopy, agarose gel electrophoresis, and flow cytometry analysis. The increase in apoptosis induced by beta-sitosterol was associated with down-regulation of Bcl-2, degradation of poly-(ADP-ribose) polymerase (PARP) and phospholipase C (PLC)-gamma1 protein, and activation of caspase-3. beta-Sitosterol induced apoptosis was not associated with changes in the expression of Bcl-xL, Bax, or inhibitor of apoptosis proteins (IAPs). z-DEVD-fmk, a caspase-3 specific inhibitor, blocked caspase-3 activation and PARP degradation, and significantly attenuated beta-sitosterol-induced apoptosis. This suggests that caspase-3 activation is partially essential for beta-sitosterol-induced apoptosis. Bcl-2 overexpression also significantly blocked caspase-3 activation and the decrease in PARP cleavage by beta-sitosterol, and effectively attenuated the apoptotic response to beta-sitosterol. These results show that beta-sitosterol potently induces apoptosis in U937 cells and that beta-sitosterol-induced apoptosis is related to the selective activation of caspase-3 and induction of Bax/Bcl-2 ratio.

Cancer chemoprevention by cyclooxygenase 2 (COX-2) blockade: results of case control studies

Significant use of selective cyclooxygenase-2 (COX-2) blocking agents prescribed for the treatment of arthritis during 1999 to 2005 facilitates epidemiologic investigations to illuminate their chemopreventive effects against human cancer. We therefore conducted a set of case control studies of selective COX-2 blocking agents to determine their chemopreventive potential for the four major cancers: breast, prostate, colon, and lung. Newly diagnosed cases (323 breast cancer patients, 229 prostate cancer patients, 326 colon cancer patients, and 486 lung cancer patients) were ascertained during 2002 to September 30, 2004, at The James Cancer Hospital and Solove Research Institute, The Ohio State University Medical Center, Columbus, Ohio. All cases of invasive cancer were confirmed by examination of the pathology report. Healthy controls without cancer were ascertained from hospital screening clinics during the same time period. Controls were frequency matched at a rate of 2:1 to the cases by age, gender, and county of residence. We collected information on type, frequency, and duration of use of selective COX-2 inhibitors and nonselective nonsteroidal anti-inflammatory drugs (NSAIDs). Other potentially important risk factors (smoking, drinking, body mass, medical history, blood pressure and cholesterol medications, family history of cancer, occupational history, and reproductive history for women) were also recorded for each subject. Estimates of odds ratios were obtained with adjustment for age and other potential confounders using logistic regression analysis. Use of selective COX-2 inhibitors resulted in a significant risk reduction for each type of cancer (71% for breast cancer, 55% for prostate cancer, 70% for colon cancer, and 79% for lung cancer) and an overall 68% risk reduction for all four cancers. This investigation demonstrates that COX-2 blocking agents have strong potential for the chemoprevention of cancers of the breast, prostate, colon and lung.

Selenised casein protects against AOM-induced colon tumors in Sprague Dawley rats

Selenium (Se) has been shown to be protective against cancers in animal models at concentrations exceeding those considered essential for normal nutritional requirements. Organic forms of Se provided as dairy proteins were obtained from cows fed diets supplemented with yeast Se. The casein extracted from milk was found to contain approximately half the Se of the Se-enriched milk. This casein was included in a semi-purified AIN rodent diet so as to provide 1 ppm Se and 25% protein and was compared with AIN diets containing no added Se (control, 0.05 ppm), 1 ppm and 4 ppm Se as selenised yeast (Sel-Plex) Their influence on colon tumor expression was examined in rats induced with azoxymethane, the diets being introduced post-induction. The selenised casein diet at this concentration was effective in reducing colon tumor incidence (by 29%) and burden (decreased 52%, P < 0.05) relative to the control in rats 26 wk post-induction. Selenised yeast, when added at similar (1 ppm) and increased Se concentration (4 ppm), did not influence significantly colon tumor expression. However, in a second study, with Se yeast providing Se at 1 ppm, 4 ppm, and 8 ppm throughout the experiment, a significant reduction in tumors was observed with 8 ppm Se (colon tumor incidence was 15% lower and colon tumor burden was 35% lower, P < 0.05). However this was associated with a significantly lower body weight in the rats (down 10.5%, P < 0.05) indicating a possible disturbance with normal energy intake or metabolism. The form in which Se is presented in the diet may influence significantly its bioavailability and/or anticancer potential at given concentrations within a safe range. The efficacy of selenised casein and indeed other potential dietary sources deserve further investigation with regard to their ability to prevent colon tumors at concentrations considered safe in the diet.

Endometriosis as a model for inflammation–hormone interactions in ovarian and breast cancers

Chronic inflammation has been implicated in a variety of cancers. In this review, we consider associations between endometriosis and cancers both local (ovarian) and distant (breast). We review the epidemiological data linking endometriosis to ovarian and breast cancers. We then consider evidence for a role for sex steroid hormones and for inflammation in the aetiology of each of these cancers. Finally, we consider that endometriosis may promote alterations in sex steroid hormones and inflammatory mediators. A possible explanation for the association between endometriosis and these reproductive cancers may then be local and systemic enhancement of aberrant inflammatory and hormonal mediators. If this hypothesis is true, endometriosis may need to be considered as a risk factor for ovarian and breast cancers, triggering increasingly intensive surveillance. Moreover, treatments for endometriosis may require consideration of the impact on long-term cancer risk.

Comparative effects of RRR-alpha- and RRR-gamma-tocopherol on proliferation and apoptosis in human colon cancer cell lines

Background

Mediterranean societies, with diets rich in vitamin E isoforms, have a lower risk for colon cancer than those of northern Europe and the Americas. Vitamin E rich diets may neutralize free radicals generated by fecal bacteria in the gut and prevent DNA damage, but signal transduction activities can occur independent of the antioxidant function. The term vitamin E represents eight structurally related compounds, each differing in their potency and mechanisms of chemoprevention. The RRR-γ-tocopherol isoform is found primarily in the US diet, while RRR-α-tocopherol is highest in the plasma.

Methods

The effectiveness of RRR-α- and RRR-γ-tocopherol at inhibiting cell growth and inducing apoptosis in colon cancer cell lines with varying molecular characteristics (SW480, HCT-15, HCT-116 and HT-29) and primary colon cells (CCD-112CoN, nontransformed normal phenotype) was studied. Colon cells were treated with and without RRR-α- or RRR-γ-tocopherol using varying tocopherol concentrations and time intervals. Cell proliferation and apoptosis were measured using the trypan blue assay, annexin V staining, DNA laddering and caspase activation.

Results

Treatment with RRR-γ-tocopherol resulted in significant cell death for all cancer cell lines tested, while RRR-α-tocopherol did not. Further, RRR-γ-tocopherol treatment showed no cytotoxicity to normal colon cells CCD-112CoN at the highest concentration and time point tested. RRR-γ-tocopherol treatment resulted in cleavage of PARP, caspase 3, 7, and 8, but not caspase 9. Differences in the percentage cell death and apoptosis were observed in different cell lines suggesting that molecular differences in these cell lines may influence the ability of RRR-γ-tocopherol to induce cell death.

Conclusion

This is the first study to demonstrate that multiple colon cancer cell lines containing varying genetic alterations will under go growth reduction and apoptosis in the presence of RRR-γ-tocopherol without damage to normal colon cells. The amount growth reduction was dependent upon the molecular signatures of the cell lines. Since RRR-γ-tocopherol is effective at inhibition of cell proliferation at both physiological and pharmacological concentrations dietary RRR-γ-tocopherol may be chemopreventive, while pharmacological concentrations of RRR-γ-tocopherol may aid chemotherapy without toxic effects to normal cells demonstrated by most chemotherapeutic agents.

Lifestyle and medical approaches to cancer prevention

Cancer risk can be reduced by adopting a healthy lifestyle and by medical means. Tobacco control is central to public policies for cancer prevention. Overweight and obesity in the United States may contribute to 20% of cancer deaths in women and 14% in men. Cancer prevention strategies have progressed from a predominant lifestyle approach to a model that combines clinical investigations in a medical setting with public health interventions. This change stems from advances in identifying, developing, and testing agents with the potential either to prevent cancer initiation, or to inhibit or reverse the progression of premalignant lesions to invasive cancer. Encouraging laboratory and epidemiologic studies, along with secondary endpoints in treatment trials, have provided a strong scientific rationale for the hypothesis that a pharmacologic approach--chemoprevention--can reduce cancer risk. Numerous chemopreventive agents, including naturally occurring vitamins, minerals, phytochemicals, and synthetic compounds, have proved to be safe and effective in preclinical and clinical studies. Promising results have been reported for cancers of the prostate, breast, colon, lung, bladder, cervix, oral cavity, esophagus, skin, and liver. The use of emerging technologies, identification of biomarkers of risk, and advances in genetic research are being applied to chemoprevention research. An interdisciplinary research approach to investigate molecular and genetic markers--as well as chemoprevention and lifestyle strategies--that affect cancer risk is being applied to the most common types of cancer in the United States in women (breast) and men (prostate).

Prevention of mouse lung tumors by targretin

Targretin has indicated chemotherapeutic activity against nonsmall-cell lung cancer and chemoprevention in rat mammary gland. Therefore, targretin was evaluated for the prevention of 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanol (NNK) and vinyl carbamate-induced lung tumors in female strain A mice. Three experiments were performed: (i) a dose-response study with vinyl carbamate-induced tumors; (ii) a limited treatment study also with vinyl carbamate and (iii) prevention of NNK-induced tumors. In the dose-response study, 0, 10, 30, 100 and 300 mg/kg targretin were administered after vinyl carbamate. Dose levels of 30 mg/kg and greater significantly decreased tumor multiplicity by >19%. However, the efficacy of 30 and 300 mg/kg was not significantly different demonstrating a shallow dose-response relationship. In the limited treatment study, 200 mg/kg targretin was administered to the mice from 4-13, 4-19, 4-25 and 23-25 weeks after vinyl carbamate. Administering targretin from weeks 4-19 and 4-25 decreased the multiplicity of tumors from 35.3 +/- 1.43 to 29.1 +/- 1.51 and 25.0 +/- 0.93, respectively, and along with administering it from weeks 23-25 decreased tumor size. In the third study, when targretin (100 and 300 mg/kg) was administered for 3 weeks after NNK followed by a 20 weeks holding period, tumor multiplicity was reduced from 10.6 +/- 1.13 to 6.38 +/- 0.75 and 4.60 +/- 0.70, respectively. Hence, targretin demonstrated both preventive and therapeutic activity with respect to mouse lung tumors supporting its further development as a preventive and therapeutic agent for lung cancer.

Naturally occurring coumarins inhibit 7,12-dimethylbenz[a]anthracene DNA adduct formation in mouse mammary gland

Naturally occurring coumarins (NOCs) are anti-carcinogenic in the mouse skin model. To characterize the chemopreventive potential of NOCs against breast cancer, we first examined their effects on 7,12-dimethylbenz[a]anthracene (DMBA)-DNA adduct formation in mouse mammary gland. We hypothesized that those NOCs that both inhibited cytochrome P450 1A1/1B1 and induced hepatic glutathione S-transferases (GSTs) would be the most effective in blocking DMBA-DNA adduct formation in mouse mammary gland. To address this hypothesis, simple coumarins (e.g. coumarin and limettin, which induced mouse hepatic GSTs but had little effect on P4501A1/1B1) and linear furanocoumarins (e.g. imperatorin and isopimpinellin, which induced hepatic GSTs and were potent inhibitors of P4501A1/1B1) were compared. Mice were pretreated with NOCs (150 mg/kg body wt, by gavage) prior to either a single dose of DMBA (50 microg) or multiple doses of DMBA (20 microg daily for 3 and 6 weeks). Mammary DMBA-DNA adduct formation was quantitated by the nuclease P1-enhanced 32P-postlabeling assay. With the single dose of DMBA, coumarin, limettin, imperatorin and isopimpinellin inhibited DMBA-DNA adduct formation by 50, 41, 79 and 88%, respectively. Coumarin, limettin and imperatorin blocked DMBA-DNA adduct formation by 36, 60, and 66% at 3 weeks, and by 0, 49 and 55% at 6 weeks of DMBA dosing, respectively. In a 6 week dose-response study of select NOCs and 7,8-benzoflavone (a potent P4501 inhibitor that had little effect on GSTs), DMBA-DNA adduct formation was inhibited by 0, 43 and 24% in the limettin groups; by 26, 26 and 69% in the isopimpinellin groups; and by 80, 96 and 97% in the 7,8- benzoflavone groups at 35, 70 and 150 mg/kg, respectively. Taken together, these results suggest that linear furanocoumarins had a greater inhibitory effect on DMBA-DNA adduct formation in mouse mammary glands compared with simple coumarins, and that the predominant effect may be P4501 inhibition.

The chemopreventive agent development research program in the Division of Cancer Prevention of the US National Cancer Institute: an overview

Chemoprevention is an innovative area of cancer research that focuses on the development of pharmacological, biological, and nutritional interventions to prevent, reverse, or delay carcinogenesis. Over the past two decades the Division of Cancer Prevention of the US National Cancer Institute has organized a research and development program to provide resources and infrastructure to the research community for the clinical evaluation of potential cancer preventive agents. This program now encompasses preclinical agent and molecular target identification, in vitro and in vivo screening, efficacy and intermediate endpoint testing, pharmacology and toxicology assessments, and finally chemical synthesis and manufacturing leading to Investigational New Drug applications and clinical studies. In this review, examples of agents currently in development, preclinical testing models, and phase 1 and 2 clinical studies are described. Continued commitment to cancer prevention will significantly reduce the economic and medical burden of cancer.

Induction of cell proliferation, micronuclei and hyperdiploidy/polyploidy in the mammary cells of DDT- and DMBA-treated pubertal rats

The environmental estrogen, dichlorodiphenyltrichloroethane (DDT), and its metabolites have been implicated in the development of breast cancer through mechanisms that remain to be elucidated. It has been hypothesized that exposure to DDT and its metabolites, during critical periods of development, can contribute to an elevated risk for breast cancer in adults. In the present study, we have investigated the effect of o,p'-DDT on mammary gland cell proliferation and chromosomal alterations, in a rat mammary cancer model (commonly used to study human cancer), to gain insights into its potential role in the development of breast cancer. Twenty-one-day-old female Sprague-Dawley (SD) rats were administered o,p'-DDT, 7,12-dimethylbenz[a]anthracene (DMBA), genistein, DDT+DMBA, or DDT+DMBA+genistein, over a 14-day period. To determine changes in chromosome number and structure, we used the micronucleus assay as well as multicolor fluorescence in situ hybridization (FISH) region-specific DNA probes for rat chromosomes 4 and 19. Cell proliferation was evaluated using 5-bromo-2'-deoxyuridine (BrdU). Significant increases in BrdU-incorporated cells were seen in the rats treated with DDT+DMBA. Although micronucleus frequencies were somewhat elevated in several of the treatment groups, significant increases were not seen in any of them. Significant increases in numerical chromosomal aberrations were detected in all of the DDT- and DMBA-treated groups. Genistein significantly reduced BrdU incorporation and polyploidy in the DDT+DMBA-treated rats. These initial studies indicate that DDT and DMBA can induce cellular and chromosomal alterations in the rat mammary gland, which is consistent with the hypothesis that these agents can induce early events in mammary carcinogenesis.

Role of aberrant crypt foci detected using high-magnification-chromoscopic colonoscopy in human colorectal carcinogenesis

Abstract Liaison between gastrointestinal endoscopists and histopathologists is essential to provide the highest standards of diagnostic accuracy and patient management. The histopathologist needs to be aware of the endoscopic findings when interpreting endoscopic biopsies. High-magnification-chromoscopic-colonoscopy (HMCC) is a new technology that provides the endoscopists with much greater resolution and functional staining of the gastrointestinal tract. Using HMCC, the endoscopist is now able to identify subtle changes in the colorectal luminal openings or crypts. Changes in crypt appearances now allow detection of aberrant crypt foci (ACF) in the colon, which might themselves be precancerous lesions but additionally might serve as a valid biomarker of subsequent adenoma and colorectal cancer formation. This article describes the role of the aberrant crypt focus in colorectal carcinogenesis and discusses the clinical impact of HMCC techniques as applicable to ACF.

Modulation of DNA hypomethylation as a surrogate endpoint biomarker for chemoprevention of colon cancer

Surrogate end-point biomarkers are being developed as indicators of the efficacy of chemopreventive agents. These biomarkers are molecular and biological end-points that can be modulated by chemopreventive agents in accordance with their efficacy to prevent cancer. DNA hypomethylation is a common alteration found in colon tumors that has the potential of being modulated by chemopreventive agents and thus being useful as a surrogate end-point biomarker. Agents that were either effective or ineffective in preventing colon cancer were evaluated for the ability to modulate DNA hypomethylation in azoxymethane-induced colon tumors in male F344 rats. DNA methylation was determined by Dot Blot Analysis using a mouse monoclonal anti-5-methylcytosine antibody. Colon tumors had a 70% reduction in DNA methylation relative to normal colonic mucosa. DNA methylation in the tumors was increased by 7 days of treatment with agents that have been shown to prevent colon cancer (calcium chloride, alpha-diflouromethylornithine [DFMO], piroxicam, and sulindac), whereas agents shown not to prevent colon cancer in rats (low dose aspirin, 2-carboxyphenyl retinamide [2-CPR], quercetin, 9-cis retinoic acid, and rutin) did not increase DNA methylation. The results suggest that the ability to reverse the DNA hypomethylation in colon tumors could be useful as a surrogate end-point biomarker for chemoprevention of colon cancer.

Development of gamma (gamma)-tocopherol as a colorectal cancer chemopreventive agent

Nutritional factors play an important role in the prevention and promotion of colorectal cancer. Vitamin E is a generic term that describes a group of lipid-soluble chain-breaking antioxidants that includes tocopherols and tocotrienols. Vitamin E occurs in nature as eight structurally related forms that include four tocopherols and four tocotrienols. Vitamin E is a potent membrane-soluble antioxidant. Antioxidants like vitamin E (tocopherols) may prevent colon cancer through several different cellular and molecular mechanisms. Vitamin E in the American diet is primarily available in plant-oil rich foods such as vegetable oils, seeds and nuts and these foods vary widely in their content of alpha-tocopherol and gamma-tocopherol. Vitamin E may help prevent colon cancer by decreasing the formation of mutagens arising from the oxidation of fecal lipids, by decreasing oxidative stress in the epithelial cells of the colon and by molecular mechanisms that influence cell death, cell cycle and transcriptional events. Most epidemiological, experimental and clinical studies have evaluated the alpha-isoform and not the gamma-isoform of vitamin E. Recent epidemiological, experimental and mechanistic evidence suggests that gamma-tocopherol may be a more potent cancer chemopreventive agent than alpha-tocopherol. The differences in chemical reactivity, metabolism and biological activity may contribute to these differences in the effects of gamma-tocopherol when compared with alpha-tocopherol. The rationale supporting the development of gamma-tocopherol as a colorectal cancer preventive agent is reviewed here.

Inhibition of ultraviolet light B-induced cutaneous inflammation by a specific cyclooxygenase-2 inhibitor

Ultraviolet B (UVB) radiation is responsible for the majority of cutaneous damage following both acute and long-term exposure, and is believed to be the most important etiologic agent in human skin cancer. UVB carcinogenesis initially induces an inflammatory response characterized by edema, dermal infiltration of leukocytes, as well as the production and release of prostaglandins, which may be critical to the observed damaging effects of UVB light on skin. Recently, a specific cyclooxygenase-2 (COX-2) inhibitor, Celecoxib, was developed, which inhibits COX-2-induced inflammation without inhibiting the cytoprotective function of cyclooxygenase-1 (COX-1). Studies have demonstrated that oral administration of Celecoxib decreased the incidence of skin and colon tumors. Recently, the process of inflammation has been linked to tumor formation. The present study examined the effects of a topical application of Celecoxib on the acute UVB-induced cutaneous inflammatory response. We show that topical Celecoxib treatment effectively reduced many parameters of UVB-mediated inflammation, including edema, dermal myeloperoxidase activity, neutrophil infiltration, and prostaglandin E2 (PGE2) levels. By inhibiting this inflammatory response, topical Celecoxib treatment could ultimately be effective in preventing tumor development and progression in the skin, which is known to result from long-term UV exposure.