Progress in cancer chemoprevention

The ethanolic extract of Gomphrena celosioides is not carcinogenic and has antigenotoxic effects and chemopreventive Properties

Gomphrena celosioides, popularly known as perpétua, perpétua brava, bachelor´s button and prostate globe amarahth, is used for the treatment of urinary tract disorders, kidney stones, for skin diseases, infectious diseases, gastrointestinal and respiratory conditions. Rich in phenolic acids and flavonoids, this plant has therefore a potential for use in cancer prevention. Given the above, the present research aimed to evaluate the carcinogenic effect of the ethanolic extract of G. celosioides (EEGc) in an alternative model of Drosophila melanogaster and the genotoxic and antigenotoxic effects in Swiss mice. The larval survival test and the detection of epithelial tumor clones were performed in D. melanogaster. The tested EEGc concentrations were 0.96, 1.92, 3.85 and 7.70 mg/mL. In Swiss mice, the genotoxicity and antigenotoxicity of doses of 100, 1,000 and 2,000 mg/Kg were evaluated. The results showed that EEGc at a concentration of 7.70 mg/mL reduced (p<0.05) larval survival. However, EEGc was not carcinogenic, and the lowest concentration (0.96 mg/mL) prevented (p<0.05) the basal occurrence of epithelial tumors. In mice, EEGc at the highest dose (2,000mg/Kg) increased the frequency of genomic lesions (p<0.05). Yet, none of the doses caused chromosomal lesions (p>0.05). When associated with cyclophosphamide, EEGc was antigenotoxic (p<0.05). The percentages of reduction of genomic damage ranged from 33.39 to 63.23% and of chromosomal damage from 20.00 to 77.19%. In view of the above, it is suggested that EEGc is not carcinogenic, has an antigenotoxic effect and chemopreventive properties.

Comparative study between in vivo- and in vitro-derived extracts of cactus (Opuntis ficus-indica L. Mill) against prostate and mammary cancer cell lines

Opuntia ficus-indica L. Mill cladodes are considered to be a source of an abundance of bioactive compounds. To identify a natural product that can be used in the chemoprevention and treatment of cancer, this study was conducted to produce an anticancer agent extracted from in vitro-derived cladodes of prickly pear cactus. Toward this goal, assays of seed germination and micropropagation revealed that the highest seed germination rate was 66% and that the highest shoot number per explant was obtained with benzyl adenine (BA) (2 mg/l) and kinetin (Kin) (1 mg/l) within 2 months, at 22.6. In addition, the maximum length of shoots was obtained with BA (3 mg/l) and Kin (0.5 mg/l), at 7.44 cm. The in vitro-derived cladode extract showed higher total phenolic and kaempferol contents than the in vivo-derived cladode extract (total phenolics 156.5 mg/g and 86 mg/g DW; kaempferol 2.807 mg/g and 1.304 mg/g DW, respectively). These remarkable results reflected the anticancer activity on the viability and proliferation/migration of PC3 prostate and mammary Mcf7-7 cells. In terms of cytotoxicity, the IC50 values on PC3 and Mcf7 cells were 5775.7 and 6311.3 μg/ml, respectively, showing dose-dependent increases. Meanwhile, from in vivo analyses of the plants, the IC50 values were 5927.93 and 6825.6 μg/ml, respectively, again showing dose-dependent increases.

Mechanism underlying nephroprotective property of curcumin against sodium nitrite-induced nephrotoxicity in male Wistar rat

The current work examined the outcome of curcumin (20 mg/kg body weight/day) administration on arginase and adenosine deaminase (ADA) activities and other kidney markers, as well as markers of oxidative stress, in Wistar rats exposed to sodium nitrite (NaNO₂ ) (60 mg/kg of body weight, single dose) for 28 days. The results revealed that the NaNO₂ exposed rats had significantly altered the ADA activities, arginase activities alongside other biomarkers of kidney function, and oxidative stress. However, pretreatment with curcumin significantly mitigated the altered activities ADA and arginase as well as other parameters. This was supported by the histopathological examination of the kidney tissues. Our findings suggest that the alteration in the activities of ADA and arginase could be involved in the mechanism of action employed by NaNO₂ and curcumin in the respective induction and prevention of nephrotoxicity. PRACTICAL APPLICATIONS: These results suggest that moderate exposure to the acceptable daily dose of curcumin can improve food-related kidney damage through regulations of ADA and arginase activities, enhancement in the antioxidant system, and suppression of lipid peroxidation.

Cancer Chemoprevention and Piperine: Molecular Mechanisms and Therapeutic Opportunities

Cancer is a genetic disease characterized by unregulated growth and dissemination of malignantly transformed neoplastic cells. The process of cancer development goes through several stages of biochemical and genetic alterations in a target cell. Several dietary alkaloids have been found to inhibit the molecular events and signaling pathways associated with various stages of cancer development and therefore are useful in cancer chemoprevention. Cancer chemoprevention has long been recognized as an important prophylactic strategy to reduce the burden of cancer on health care system. Cancer chemoprevention assumes the use of one or more pharmacologically active agents to block, suppress, prevent, or reverse the development of invasive cancer. Piperine is an active alkaloid with an excellent spectrum of therapeutic activities such as anti-oxidant, anti-inflammatory, immunomodulatory, anti-asthmatic, anti-convulsant, anti-mutagenic, antimycobacterial, anti-amoebic, and anti-cancer activities. In this article, we made an attempt to sum up the current knowledge on piperine that supports the chemopreventive potential of this dietary phytochemical. Many mechanisms have been purported to understand the chemopreventive action of piperine. Piperine has been reported to inhibit the proliferation and survival of many types of cancer cells through its influence on activation of apoptotic signaling and inhibition of cell cycle progression. Piperine is known to affect cancer cells in variety of other ways such as influencing the redox homeostasis, inhibiting cancer stem cell (CSC) self-renewal and modulation of ER stress and autophagy. Piperine can modify activity of many enzymes and transcription factors to inhibit invasion, metastasis, and angiogenesis. Piperine is a potent inhibitor of p-glycoprotein (P-gp) and has a significant effect on the drug metabolizing enzyme (DME) system. Because of its inhibitory influence on P-gp activity, piperine can reverse multidrug resistance (MDR) in cancer cells and acts as bioavailability enhancer for many chemotherapeutic agents. In this article, we emphasize the potential of piperine as a promising cancer chemopreventive agent and the knowledge we collected in this review can be applied in the strategic design of future researches particularly human intervention trials with piperine.

Chemopreventive Strategies for Inflammation-Related Carcinogenesis: Current Status and Future Direction

A sustained and chronically-inflamed environment is characterized by the presence of heterogeneous inflammatory cellular components, including neutrophils, macrophages, lymphocytes and fibroblasts. These infiltrated cells produce growth stimulating mediators (inflammatory cytokines and growth factors), chemotactic factors (chemokines) and genotoxic substances (reactive oxygen species and nitrogen oxide) and induce DNA damage and methylation. Therefore, chronic inflammation serves as an intrinsic niche for carcinogenesis and tumor progression. In this article, we summarize the up-to-date findings regarding definitive/possible causes and mechanisms of inflammation-related carcinogenesis derived from experimental and clinical studies. We also propose 10 strategies, as well as candidate agents for the prevention of inflammation-related carcinogenesis.

Antioxidant capacity of phytochemicals and their potential effects on oxidative status in animals - A review

Oxidative stress suppresses animal health, performance, and production, subsequently impacting economic feasibility; hence, maintaining and improving oxidative status especially through natural nutrition strategy are essential for normal physiological process in animals. Phytochemicals are naturally occurring antioxidants that could be considered as one of the most promising materials used in animal diets in various forms. In this review, their antioxidant effects on animals are discussed as reflected by improved apparent performance, productivity, and the internal physiological changes. Moreover, the antioxidant actions toward animals further describe a molecular basis to elucidate their underlying mechanisms targeting signal transduction pathways, especially through the antioxidant response element/nuclear factor (erythroid-derived 2)-like 2 transcription system.

Biological activity of terpene compounds produced by biotechnological methods

CONTEXT

Biotransformation systems are profitable tools for structural modification of bioactive natural compounds into valuable biologically active terpenoids.

OBJECTIVE

This study determines the biological effect of (R)-(+)-limonene and (-)-α-pinene, and their oxygenated derivatives, (a) perillyl alcohol and (S)-(+)- and (R)-(-)-carvone enantiomers and (b) linalool, trans-verbenol and verbenone, respectively, on human colon tumour cells and normal colonic epithelium.

MATERIALS AND METHODS

Biotransformation procedures and in vitro cell culture tests were used in this work. Cells were incubated for 24 h with terpenes at concentrations of 5-500 μg/mL for NR, MTT, DPPH, and NO assays. IL-6 was determined by ELISA with/without 2 h pre-activation with 10 μg/mL LPS.

RESULTS

trans-Verbenol and perillyl alcohol, obtained via biotransformation, produced in vitro effect against tumour cells at lower concentrations (IC50 value = 77.8 and 98.8 μg/mL, respectively) than their monoterpene precursors, (R)-(+)-limonene (IC50 value = 171.4 μg/mL) and (-)-α-pinene (IC50 value = 206.3 μg/mL). They also showed lower cytotoxicity against normal cells (IC50 > 500 and > 200 μg/mL, respectively). (S)-(+)-Carvone was 59.4% and 27.1% more toxic to tumour and normal cells, respectively, than the (R)-(-)-enantiomer. (R)-(+)-limonene derivatives decreased IL-6 production from normal cells in media with or without LPS (30.2% and 13.9%, respectively), while (-)-α-pinene derivatives induced IL-6 (verbenone had the strongest effect, 60.2% and 29.1% above control, respectively). None of the terpenes had antioxidative activity below 500 μg/mL.

DISCUSSION AND CONCLUSIONS

Bioactivity against tumour cells decreased in the following order: alcohols > ketones > hydrocarbons. (R)-(+)-limonene, (-)-α-pinene, and their derivatives expressed diverse activity towards normal and tumour cells with noticeable enantiomeric differences.

Chemoprevention of Breast Cancer by Dietary Polyphenols

The review will discuss in detail the effects of polyphenols on breast cancer, including both the advantages and disadvantages of the applications of these natural compounds. First, we focus on the characterization of the main classes of polyphenols and then on in vitro and in vivo experiments carried out in breast cancer models. Since the therapeutic effects of the administration of a single type of polyphenol might be limited because of the reduced bioavailability of these drugs, investigations on combination of several polyphenols or polyphenols with conventional therapy will also be discussed. In addition, we present recent data focusing on clinical trials with polyphenols and new approaches with nanoparticles in breast cancer. Besides the clinical and translational findings this review systematically summarizes our current knowledge about the molecular mechanisms of anti-cancer effects of polyphenols, which are related to apoptosis, cell cycle regulation, plasma membrane receptors, signaling pathways and epigenetic mechanisms. At the same time the effects of polyphenols on primary tumor, metastasis and angiogenesis in breast cancer are discussed. The increasing enthusiasm regarding the combination of polyphenols and conventional therapy in breast cancer might lead to additional efforts to motivate further research in this field.

Anticancer and multidrug-resistance reversing potential of traditional medicinal plants and their bioactive compounds in leukemia cell lines

Multidrug resistance remains a serious clinical problem in the successful therapy of malignant diseases. It occurs in cultured tumor cell lines, as well as in human cancers. Therefore, it is critical to develop novel anticancer drugs with multidrug-resistance modulating potential to increase the survival rate of leukemia patients. Plant-derived natural products have been used for the treatment of various diseases for thousands of years. This review summarizes the anticancer and multidrug-resistance reversing properties of the extracts and bioactive compounds from traditional medicinal plants in different leukemia cell lines. Further mechanistic studies will pave the road to establish the anticancer potential of plant-derived natural compounds.

Chemo-predictive assay for targeting cancer stem-like cells in patients affected by brain tumors

Administration of ineffective anticancer therapy is associated with unnecessary toxicity and development of resistant clones. Cancer stem-like cells (CSLCs) resist chemotherapy, thereby causing relapse of the disease. Thus, development of a test that identifies the most effective chemotherapy management offers great promise for individualized anticancer treatments. We have developed an ex vivo chemotherapy sensitivity assay (ChemoID), which measures the sensitivity of CSLCs as well as the bulk of tumor cells to a variety of chemotherapy agents. Two patients, a 21-year old male (patient 1) and a 5-month female (patient 2), affected by anaplastic WHO grade-III ependymoma were screened using the ChemoID assay. Patient 1 was found sensitive to the combination of irinotecan and bevacizumab, which resulted in a prolonged disease progression free period of 18 months. Following recurrence, the combination of various chemotherapy drugs was tested again with the ChemoID assay. We found that benzyl isothiocyanate (BITC) greatly increased the chemosensitivity of the ependymoma cells to the combination of irinotecan and bevacizumab. After patient 1 was treated for two months with irinotecan, bevacizumab and supplements of cruciferous vegetable extracts containing BITC, we observed over 50% tumoral regression in comparison with pre-ChemoID scan as evidenced by MRI. Patient 2 was found resistant to all treatments tested and following 6 cycles of vincristine, carboplatin, cyclophosphamide, etoposide, and cisplatin in various combinations, the tumor of this patient rapidly progressed and proton beam therapy was recommended. As expected animal studies conducted with patient derived xenografts treated with ChemoID screened drugs recapitulated the clinical observation. This assay demonstrates that patients with the same histological stage and grade of cancer may vary considerably in their clinical response, suggesting that ChemoID testing which measures the sensitivity of CSLCs as well as the bulk of tumor cells to a variety of chemotherapy agents could lead to more effective and personalized anticancer treatments in the future.

Crystal structure elucidation and anticancer studies of (-)-pseudosemiglabrin: a flavanone isolated from the aerial parts of Tephrosia apollinea

Tephrosia apollinea is a perennial shrublet widely distributed in Africa and is known to have medicinal properties. The current study describes the bio-assay (cytotoxicity) guided isolation of (-)-pseudosemiglabrin from the aerial parts of T. apollinea. The structural and stereochemical features have been described using spectral and x-ray crystallographic techniques. The cytotoxicity of isolated compound was evaluated against nine cancer cell lines. In addition, human fibroblast was used as a model cell line for normal cells. The results showed that (-)-pseudosemiglabrin exhibited dose-dependent antiproliferative effect on most of the tested cancer cell lines. Selectively, the compound showed significant inhibitory effect on the proliferation of leukemia, prostate and breast cancer cell lines. Further studies revealed that, the compound exhibited proapoptotic phenomenon of cytotoxicity. Interestingly, the compound did not display toxicity against the normal human fibroblast. It can be concluded that (-)-pseudosemiglabrin is worthy for further investigation as a potential chemotherapeutic agent.

Selenium compounds induced ROS-dependent apoptosis in myelodysplasia cells

Several authors have demonstrated the chemoprotective and anti-carcinogenic role of selenium. However, the therapeutic potential of selenium in myelodysplastic syndrome (MDS) as single agent and as co-adjuvant of the current therapies has not been previously studied. Sodium selenite and selenomethionine, alone and in combination with cytarabine, induce a decrease in cell viability in a time-, dose- and administration-dependent manner inducing cell death by apoptosis in F36P cells (MDS cell line). These compounds increased superoxide production and induced mitochondrial membrane depolarization. The increase in BAX/BCL-2 ratio and in the activated caspase 3 expression levels, the decrease in mitochondria membrane potential, as well as the increase in superoxide production, supports the mitochondria contribution on selenium-induced apoptosis. These findings suggest that selenium may offer a new therapeutic approach in myelodysplastic syndrome in monotherapy and/or as co-adjuvant therapy to conventional anti-carcinogenic.

Effects of sophorae radix on human gastric and colorectal adenocarcinoma cells: sophorae radix and cancer cells

The purpose of this study was to investigate the anti-cancer effects of Sophorae Radix (SR) and doxorubicin (DOX) in human gastric and colorectal adenocarcinoma cells. We used the human gastric and colorectal adenocarcinoma cell lines (MKN-45 and WIDR cells, respectively). We examined cell death by using the MTT(3-[4, 5-dimethylthiazol-2-yl]-2, 5- diphenyltetrazolium bromide) assay and the caspase 3 assay with SR. To examine the inhibitory effects of SR, we performed a cell cycle (sub G1) analysis for the MKN-45 and WIDR cells after three days with SR. The reversibility of SR was examined for one-day to five-day treatments with SR. SR inhibited the growth of MKN-45 and WIDR cells in a dosedependent manner. Also, we showed that SR induced apoptosis in MKN-45 and WIDR cells by using the MTT assay, the caspase 3 assay and the sub-G1 analysis. SR combined with DOX markedly inhibited the growth of MKN-45 and WIDR cells compared to SR or DOX alone. After 3 days of treating MKN-45 and WIDR cells with SR, the fraction of cells in the sub-G1 phase was much higher than that of the control group. Our findings provide insights into unraveling the effects of SR on human gastric and colorectal adenocarcinoma cells and into developing therapeutic agents for use against gastric and colorectal adenocarcinomas.

Up-regulation of p53 and mitochondrial signaling pathway in apoptosis by a combination of COX-2 inhibitor, Celecoxib and Dolastatin 15, a marine mollusk linear peptide in experimental colon carcinogenesis

Programmed cell death, also known as apoptosis, is an active process occurring in eukaryotic cells and it depends on various sets of pro and anti-apoptotic proteins. Chemoprevention of colorectal cancer can be achieved by inducing apoptosis using synthetic compound, Celecoxib and natural peptide, Dolastatin 15 in an effective manner. But the apoptotic signaling by these two drugs remain unclear. The present study was thus focused on the role of Bcl2 family of proteins and their interplay with p53 in rats during the chemoprevention by these two drugs. After treatment for 6 wk with 1, 2-dimethylhydrazine (DMH), animals showed a marked occurrence of multiple plaque lesions. However, a simultaneous treatment with Celecoxib and Dolastatin 15 decreases such number to a significant level. DMH treatment also decreases the number of apoptotic cells in the colonic enterocytes which were corrected to the normal level by Celecoxib and Dolastatin 15. An increased expression of Bcl2 while other proteins like Bax, Apaf-1, cyt c, and caspases in the apoptotic pathway, and the tumor suppressor proteins, p53 and p21 get down-regulated after DMH treatment which were reverted back to normal with Celecoxib and Dolastatin 15. Also, cells having high mitochondrial membrane potential had been seen to increase to significant levels which were reduced after the administration of these anti-inflammatory drugs. In silico molecular docking studies also showed that Dolastatin 15 and Celecoxib may bind to the active site pocket of Bcl2 , thus revealing the direct target of Dolastatin 15 and Celecoxib apart from binding to COX-2.

Kuguacin J, a triterpeniod from Momordica charantia leaf, modulates the progression of androgen-independent human prostate cancer cell line, PC3

In this study, we focused on the in vitro effects of Kuguacin J (KuJ), a purified component of bitter melon (Momordica charantia) leaf extract (BMLE), on the androgen-independent human prostate cancer cell line PC3 and the in vivo effect of dietary BMLE on prostate carcinogenesis using a PC3-xenograph model. KuJ exerted a strong growth-inhibitory effect on PC3 cells. Growth inhibition was mainly through G1-arrest: KuJ markedly decreased the levels of cyclins (D1 and E), cyclin-dependent kinases (Cdk2 and Cdk4) and proliferating cell nuclear antigen. Interestingly, KuJ also dramatically decreased the levels of survivin expressed by PC3 cells. In addition, KuJ exerted anti-invasive effects on PC3 cells, significantly inhibiting migration and invasion: KuJ inhibited secretion of the active forms of MMP-2, MMP-9 and uPA by PC3 cells. In addition, KuJ treatment significantly decreased the expression of membrane type 1-MMP (MT1-MMP) by PC3 cells. In vivo, 1% and 5% BMLE in the diet resulted in 63% and 57% inhibition of PC3 xenograft growth without adverse effect on host body weight. Our results suggest that KuJ is a promising new candidate chemopreventive and chemotherapeutic agent for prostate cancer.

Quantitative assessment of mammary gland density in rodents using digital image analysis

Background

Rodent models have been used extensively to study mammary gland development and for studies of toxicology and carcinogenesis. Mammary gland gross morphology can visualized via the excision of intact mammary gland chains following fixation and staining with carmine using a tissue preparation referred to as a whole mount. Methods are described for the automated collection of digital images from an entire mammary gland whole mount and for the interrogation of digital data using a "masking" technique available with Image-Pro^® plus image analysis software (Mediacybernetics. Silver Spring, MD).

Results

Parallel to mammographic analysis in humans, measurements of rodent mammary gland density were derived from area-based or volume-based algorithms and included: total circumscribed mammary fat pad mass, mammary epithelial mass, and epithelium-free fat pad mass. These values permitted estimation of absolute mass of mammary epithelium as well as breast density. The biological plausibility of these measurements was evaluated in mammary whole mounts from rats and mice. During mammary gland development, absolute epithelial mass increased linearly without significant changes in mammographic density. Treatment of rodents with tamoxifen, 9-cis-retinoic acid, or ovariectomy, and occurrence of diet induced obesity decreased both absolute epithelial mass and mammographic density. The area and volumetric methods gave similar results.

Conclusions

Digital image analysis can be used for screening agents for potential impact on reproductive toxicity or carcinogenesis as well as for mechanistic studies, particularly for cumulative effects on mammary epithelial mass as well as translational studies of mechanisms that explain the relationship between epithelial mass and cancer risk.

Induction of G1 arrest and apoptosis in androgen-dependent human prostate cancer by Kuguacin J, a triterpenoid from Momordica charantia leaf

In this study, we focused on the effects of a bitter melon (Momordica charantia) leaf extract (BMLE) and a purified component, Kuguacin J (KuJ), on androgen-dependent LNCaP human prostate cancer cells. Both treatments exerted growth inhibition through G1 arrest and induction of apoptosis. In addition, KuJ markedly decreased the levels of cyclins (D1 and E), cyclin-dependent kinases (Cdk2 and Cdk4) and proliferating cell nuclear antigen, and caused an increase in p21 and p27 levels. Its induction of apoptosis was accompanied by an increase in cleavage of caspase-3 and poly (ADP-ribose) polymerase, attributable to augment of Bax/Bcl-2 and Bad/Bcl-xL and reduction of survivin levels. BMLE and KuJ also reduced the expression of androgen receptor (AR), prostate-specific antigen (PSA) while induced P53 protein level. Down-regulation of p53 by RNA interference indicated that BMLE and KuJ inhibited cell growth partly through p53-dependent cell cycle arrest and apoptotic pathways. Both BMLE and KuJ caused less toxicity in a normal prostate cell line, PNT1A. Our results suggest that BMLE and a purified component, KuJ, from its diethyl ether fraction could be promising candidate new antineoplastic and chemopreventive agents for androgen-dependent prostate cancer and carcinogenesis.

Phytochemicals: cancer chemoprevention and suppression of tumor onset and metastasis

Carcinogenesis is a multi-step process which could be prevented by phytochemicals. Phytochemicals from dietary plants and other plant sources such as herbs are becoming increasingly important sources of anticancer drugs or compounds for cancer chemoprevention or adjuvant chemotherapy. Phytochemicals can prevent cancer initiation, promotion, and progression by exerting anti-inflammatory and anti-oxidative stress effects which are mediated by integrated Nrf2, NF-kappaB, and AP-1 signaling pathways. In addition, phytochemicals from herbal medicinal plants and/or some dietary plants developed in recent years have been shown to induce apoptosis in cancer cells and inhibition of tumor growth in vivo. In advanced tumors, a series of changes involving critical signaling molecules that would drive tumor cells undergoing epithelial-mesenchymal transition and becoming invasive. In this review, we will discuss the potential molecular targets and signaling pathways that mediate tumor onset and metastasis. In addition, we will shed light on some of the phytochemicals that are capable of targeting these signaling pathways which would make them potentially applicable to cancer chemoprevention, treatment and control of cancer progression.

Regulation of NF-E2-related factor 2 signaling for cancer chemoprevention: antioxidant coupled with antiinflammatory

Cancer chemoprevention is a process of using either natural or synthetic compounds to reduce the risk of developing cancer. Observations that NF-E2-related factor 2 (Nrf2)-deficient mice lack response to some chemopreventive agents point to the important role of Nrf2 in chemoprevention. Nrf2 is a member of basic-leucine zipper transcription factor family and has been shown to regulate gene expression by binding to a response element, antioxidant responsive element. It is generally believed that activation of Nrf2 signaling is an adaptive response to the environmental and endogenous stresses. Under homeostatic conditions, Nrf2 is suppressed by association with Kelch-like ECH-associated protein 1 (Keap1), but is stimulated upon exposure to oxidative or electrophilic stress. Once activated, Nrf2 translocates into nuclei and upregulates a group of genes that act in concert to combat oxidative stress. Nrf2 is also shown to have protective function against inflammation, a pathological process that could contribute to carcinogenesis. In this review, we will discuss the current progress in the study of Nrf2 signaling, in particular, the mechanisms of Nrf2 activation by chemopreventive agents. We will also discuss some of the potential caveats of Nrf2 in cancer treatment and future opportunity and challenges on regulation of Nrf2-mediated antioxidant and antiinflammatory signaling in the context of cancer prevention.

Cactus pear extracts induce reactive oxygen species production and apoptosis in ovarian cancer cells

The protective effect of natural products such as fruits and vegetables against cancer has attracted great attention because of their fewer side effects and therefore, potentially greater safety. We have previously reported that cactus pear mixture aqueous extract (CME) reduces gynecologic cancer cells growth by inducting apoptosis. This study aimed to elucidate the cellular pathway(s) triggered by CME in cancer cells. Normal, immortalized ovarian and ovarian cancer cells (OVCA420, SKOV3) were treated with 5 and 10% CME. After 2 days of treatment, immortalized cells treated with 10% CME accumulated more ROS than untreated cells, whereas cancer cells cultured with 5% and 10% CME exhibited a dramatic increase of reactive oxygen species (ROS). Greater levels of DNA fragmentation, together with a perturbed expression of apoptotic-related (Bax, Bad, caspase 3, Bcl2, p53, and p21) and ROS-sensitive (NF-kappaB, c-jun/c-fos) genes were observed in the treated cancer cells. After three days of treatment, the NF-kappaB and p-/SAPK/JNK expressions were decreased, whereas p-AKT was upregulated. The CME significantly induced apoptosis in cancer cells. The results suggest an inhibitory effect of Arizona CME on cancer cell growth through the accumulation of intracellular ROS, which may activate a cascade of reactions leading to the apoptosis.

Evaluation of chemopreventive activity of glutamine by the comet and the micronucleus assay in mice's peripheral blood

This research has evaluated the effects of enteral supplementation of glutamine in clastogens and genotoxic damages caused by the acute administration of cisplatin. For this, it was utilized Swiss mice distributed in eight experimental groups: control, cisplatin, glutamine, in three different doses and the combination of these with cisplatin. The results show that the glutamine was present in neither genotoxic nor mutagenic activity. When in association with glutamine and cisplatin, in simultaneous treatment, it was verified the frequency decreased of micronuclei and comets. The damage reduction percentages to the micronucleus ranged from 95.4 to 91.8% after 24h of administration of these compounds and 76.7 to 56.8% after 48h. In the same time the damage reduction percentages to the comet test ranged from 117.0 to 115.0%. The results suggest that glutamine is capable of preventing genotoxic and mutagenic damage according to the experimental design proposed.

New structural analogues of curcumin exhibit potent growth suppressive activity in human colorectal carcinoma cells

BACKGROUND

Colorectal carcinoma is one of the major causes of morbidity and mortality in the Western World. Novel therapeutic approaches are needed for colorectal carcinoma. Curcumin, the active component and yellow pigment of turmeric, has been reported to have several anti-cancer activities including anti-proliferation, anti-invasion, and anti-angiogenesis. Clinical trials have suggested that curcumin may serve as a potential preventive or therapeutic agent for colorectal cancer.

METHODS

We compared the inhibitory effects of curcumin and novel structural analogues, GO-Y030, FLLL-11, and FLLL-12, in three independent human colorectal cancer cell lines, SW480, HT-29, and HCT116. MTT cell viability assay was used to examine the cell viability/proliferation and western blots were used to determine the level of PARP cleavages. Half-Maximal inhibitory concentrations (IC50) were calculated using Sigma Plot 9.0 software.

RESULTS

Curcumin inhibited cell viability in all three of the human colorectal cancer cell lines studied with IC50 values ranging between 10.26 microM and 13.31 microM. GO-Y030, FLLL-11, and FLLL-12 were more potent than curcumin in the inhibition of cell viability in these three human colorectal cancer cell lines with IC50 values ranging between 0.51 microM and 4.48 microM. In addition, FLLL-11 and FLLL-12 exhibit low toxicity to WI-38 normal human lung fibroblasts with an IC-50 value greater than 1,000 microM. GO-Y030, FLLL-11, and FLLL-12 are also more potent than curcumin in the induction of apoptosis, as evidenced by cleaved PARP and cleaved caspase-3 in all three human colorectal cancer cell lines studied.

CONCLUSION

The results indicate that the three curcumin analogues studied exhibit more potent inhibitory activity than curcumin in human colorectal cancer cells. Thus, they may have translational potential as chemopreventive or therapeutic agents for colorectal carcinoma.

Dietary reference intake (DRI) value for dietary polyphenols: are we heading in the right direction?

Dietary Reference Intake (DRI) values exist for vitamins and minerals, and provide a guideline on the optimal dose range to avoid deficiency and prevent toxicity. Polyphenols are widely distributed in plant foods, and have been linked to improved human health through reduced risk of chronic diseases, especially cardiovascular. Although they do not cause classical deficiencies, recently they have been discussed as 'lifespan essentials because they are needed to achieve a full lifespan by reducing the risk of a range of chronic diseases. A recent meta analysis shows promising actions of polyphenols from cocoa, soya and tea on flow mediated dilation, blood pressure and LDL cholesterol. Many epidemiological studies support the action of polyphenols or polyphenol-rich foods on health, but there are still many gaps in our knowledge. More adequately powered, randomised, placebo controlled human studies are needed on polyphenols. There is a large number of structurally different polyphenols which are relevant for health, and obtaining enough information to set a DRI for each of these will not be feasible in the foreseeable future. A new approach is needed, and a new way of thinking, which would apply not only to polyphenols but also to other phytochemicals. Today, a target intake value of polyphenols as 'lifespan essentials' needs to be based on the amount of polyphenols in '5-a-day'. We are heading in the right direction towards a DRI, but bioavailability and dose-effects, including toxic levels, need to be established before DRIs can be considered.

ATP depletion alters the mode of cell death induced by benzyl isothiocyanate

Pro-inflammatory death is presumably an undesirable event in cancer prevention process, thus biochemical comprehension and molecular definition of this process could have important clinical implications. In the present study, we examined the cytophysiological conversion of cell death mode by benzyl isothiocyanate (BITC) in human cervical cancer HeLa cells. The detailed studies using flow cytometric and morphological analyses demonstrated that the cells treated with appropriate concentration (25 microM) of BITC showed apoptotic feature, such as chromatin condensation, DNA fragmentation, and preserved plasma membrane integrity, whereas these features were disappeared by treatment with higher concentration (100 microM). The treatment with 2-deoxyglucose, an inhibitor of ATP synthesis, drastically increased in the ratio of necrotic dead cells, while it influences little that of apoptotic cells. Moreover, an analysis using the mitochondrial DNA-deficient HeLa cells demonstrated that the rho degrees cells were more susceptible to the BITC-induced necrosis-like cell death compared to the wild-type (rho(+)) cells, whereas the ROS production was significantly inhibited in the rho degrees cells. It is likely that the BITC-induced ROS is derived from mitochondrial respiratory chain and ruled out the contribution to the mechanism of cell death mode switching. In addition, the BITC treatment resulted in a more rapid depletion of ATP in the rho degrees cells than in the rho(+) cells. Furthermore, a caspase inhibitor, Z-VAD-fmk counteracted not only apoptosis, but also necrosis-like cell death induced by BITC, suggesting that increment in this cell death pattern might be due to the interruption of events downstream of a caspase-dependent pathway. The obtained data suggested that the decline in the intracellular ATP level plays an important role in tuning the mode of cell death by BITC.

Curcumin: from ancient medicine to current clinical trials

Curcumin is the active ingredient in the traditional herbal remedy and dietary spice turmeric (Curcuma longa). Curcumin has a surprisingly wide range of beneficial properties, including anti-inflammatory, antioxidant, chemopreventive and chemotherapeutic activity. The pleiotropic activities of curcumin derive from its complex chemistry as well as its ability to influence multiple signaling pathways, including survival pathways such as those regulated by NF-kappaB, Akt, and growth factors; cytoprotective pathways dependent on Nrf2; and metastatic and angiogenic pathways. Curcumin is a free radical scavenger and hydrogen donor, and exhibits both pro- and antioxidant activity. It also binds metals, particularly iron and copper, and can function as an iron chelator. Curcumin is remarkably non-toxic and exhibits limited bioavailability. Curcumin exhibits great promise as a therapeutic agent, and is currently in human clinical trials for a variety of conditions, including multiple myeloma, pancreatic cancer, myelodysplastic syndromes, colon cancer, psoriasis and Alzheimer's disease.

Mechanisms of colorectal and lung cancer prevention by vegetables: a genomic approach

Colorectal cancer (CRC) and lung cancer (LC) occur at high incidence, and both can be effectively prevented by dietary vegetable consumption. This makes these two types of cancer highly suitable for elucidating the underlying molecular mechanisms of cancer chemoprevention. Numerous studies have shown that vegetables exert their beneficial effects through various different mechanisms, but effects on the genome level remain mostly unclear. This review evaluates current knowledge on the mechanisms of CRC and LC prevention by vegetables, thereby focusing on the modulation of gene and protein expressions. The majority of the effects found in the colon are changes in the expression of genes and proteins involved in apoptosis, cell cycle, cell proliferation and intracellular defense, in favor of reduced CRC risk. Furthermore, vegetables and vegetable components changed the expression of many more genes and proteins involved in other pathways for which biologic meaning is less clear. The number of studies investigating gene and protein expression changes in the lungs is limited to only a few in vitro and animal studies. Data from these studies show that mostly genes involved in biotransformation, apoptosis and cell cycle regulation are affected. In both colon and lungs, genomewide analyses of gene and protein expression changes by new genomics and proteomics technologies, as well as the investigation of whole vegetables, are few in number. Further studies applying these 'omics' approaches are needed to provide more insights on affected genetic/biologic pathways and, thus, in molecular mechanisms by which different chemopreventive compounds can protect against carcinogenesis. Particularly studies with combinations of phytochemicals and whole vegetables are needed to establish gene expression changes in the colon, but especially in the lungs.

CURCUMIN: THE INDIAN SOLID GOLD

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

Mechanisms of fenretinide-induced apoptosis

Fenretinide, a synthetic retinoid, has emerged as a promising anticancer agent based on numerous in vitro and animal studies, as well as chemoprevention clinical trials. In vitro observations suggest that the anticancer activity of fenretinide may arise from its ability to induce apoptosis in tumor cells. Diverse signaling molecules including reactive oxygen species, ceramide, and ganglioside GD3 can mediate apoptosis induction by fenretinide in transformed, premalignant, and malignant cells. In many cell types, these signaling intermediates appear to be induced by mechanisms that are independent of retinoic acid receptor activation, and ultimately initiate the intrinsic or mitochondrial-mediated pathway of cell elimination. Numerous investigations conducted during the past 10 years have discovered a great deal about the apoptogenic activity of fenretinide. In this review we explore the mechanisms associated with fenretinide-induced apoptosis and highlight certain mechanistic underpinnings of fenretinide-induced cell death that remain poorly understood and thus warrant further characterization.

Evaluation of antimutagenic activity and mechanisms of action of β-glucan from barley, in CHO-k1 and HTC cell lines using the micronucleus test

Due to the need to identify new antimutagenic agents and to determine their mechanism of action, the present study examined the mechanism of action of the beta-glucan with regard to antimutagenicity using the micronucleus assay in CHO-k1 and HTC cell lines. The mutagenicity experiments were performed with three different concentrations of beta-glucan (5, 10, and 20 microg/mL), in wich only the highest dose showed mutagenic activity. In the antimutagenicity experiments, the same concentrations of beta-glucan were combined with a mutagenic agent, methylmethane sulfonate, or 2-aminoanthracene, using four different treatment protocols: pre-treatment, simultaneous treatment (simple and with pre-incubation), and post-treatment. The results indicate that the CHO-k1 cell line treated with MMS presented a chemopreventive activity for all the doses of beta-glucan in the different treatment protocols, except for the lowest dose in post-treatment. When HTC cell line treated with MMS is analysed, a chemopreventive activity can be verified for the highest dose in both pre- and post-treatment. For the simple simultaneous treatment, the three doses demonstrated efficacy, while for the simultaneous treatment with pre-incubation only the intermediate concentration was effective. In HTC treated with 2AA both the lowest dose in the pre-treatment protocol and the post-treatment protocol did not show efficacy in preventing DNA damage. The evaluation of the different protocols and the damage decrease percentages observed suggest that beta-glucan has both desmutagenic and bioantimutagenic activity. It is necessary, however, to note that efficacy and mechanism of action are subject to variation when compared the two cell lines, since in HTC, representing a drug-metabolizing system, this substance can show a diminished chemopreventive capacity.

Neu-induced retroviral rat mammary carcinogenesis: a novel chemoprevention model for both hormonally responsive and nonresponsive mammary carcinomas

Clinically relevant animal models of mammary carcinogenesis are crucial for the development and evaluation of new breast cancer chemopreventive agents. The neu-induced retroviral rat mammary carcinogenesis model is based on the direct in situ transfer of the activated neu oncogene into the mammary epithelium using a replication-defective retroviral vector. The resulting mammary carcinomas in intact Wistar-Furth rats exhibit a mixed hormonal response in the same proportion as has been observed in women. In intact rats, approximately 50% of mammary carcinomas can be prevented by tamoxifen treatment. In ovariectomized animals, the mammary carcinomas are hormonally nonresponsive and cannot be prevented by tamoxifen. We evaluated the efficacy of retinoic X receptor-selective retinoids (rexinoids) in this novel model of mammary carcinogenesis. The rexinoids LG100268 and bexarotene (LG1069, Targretin) were highly efficacious in the prevention of neu-induced mammary carcinomas. Dietary LG100268 at 100 mg/kg diet decreased tumor multiplicity by 32% (P = 0.0114) in intact rats and 50% (P < 0.0001) in ovariectomized rats. Bexarotene treatment at a dose of 250 mg/kg diet was associated with reductions in tumor multiplicity of 84% (P < 0.0001) and 86% (P < 0.0001) in intact and ovariectomized animals, respectively. In addition to tumor multiplicity, proliferation and apoptosis were modulated by bexarotene treatment independently of estrogen signaling. The neu-induced retroviral rat mammary carcinogenesis model represents a valuable addition to existing rodent chemoprevention models. The model is useful for assessing the efficacy of chemopreventive agents, specifically those compounds that target hormonally nonresponsive tumors.

Grape seed extract induces anoikis and caspase-mediated apoptosis in human prostate carcinoma LNCaP cells: possible role of ataxia telangiectasia mutated–p53 activation

Prostate cancer is the second leading cancer diagnosed in elderly males in the Western world. Epidemiologic studies suggest that dietary modifications could be an effective approach in reducing various cancers, including prostate cancer, and accordingly cancer-preventive efficacy of dietary nutrients has gained increased attention in recent years. We have recently shown that grape seed extract (GSE) inhibits growth and induces apoptotic death of advanced human prostate cancer DU145 cells in culture and xenograft. Because prostate cancer is initially an androgen-dependent malignancy, here we used LNCaP human prostate cancer cells as a model to assess GSE efficacy and associated mechanisms. GSE treatment of cells led to their detachment within 12 hours, as occurs in anoikis, and caused a significant decrease in live cells mostly due to their apoptotic death. GSE-induced anoikis and apoptosis were accompanied by a strong decrease in focal adhesion kinase levels, but an increase in caspase-3, caspase-9, and poly(ADP-ribose) polymerase cleavage; however, GSE caused both caspase-dependent and caspase-independent apoptosis as evidenced by cytochrome c and apoptosis-inducing factor release into cytosol. Additional studies revealed that GSE causes DNA damage-induced activation of ataxia telangiectasia mutated kinase and Chk2, as well as p53 Ser(15) phosphorylation and its translocation to mitochondria, suggesting this to be an additional mechanism for apoptosis induction. GSE-induced apoptosis, cell growth inhibition, and cell death were attenuated by pretreatment with N-acetylcysteine and involved reactive oxygen species generation. Together, these results show GSE effects in LNCaP cells and suggest additional in vivo efficacy studies in prostate cancer animal models.

Opposing action of curcumin and green tea polyphenol in human keratinocytes

Persistent environmental insult can convert a normal cell into a cancer cell. However, various natural chemopreventive agents called antioxidants can retard this progression. We have recently explored the effects of several chemopreventive agents, including green tea polyphenol and curcumin, on normal human keratinocyte function. Our findings suggest that a bioactive polyphenol from green tea, (-)-epigallocatechin-3-gallate (EGCG), acts to increase involucrin gene expression, suggesting that EGCG treatment enhances normal human keratinocyte differentiation. Mechanistic studies indicate that EGCG alters mitogen-activated protein kinase cascade function to activate involucrin gene transcription via a Ras, MEKK1, MEK3, ERK1/2-p38delta cascade that targets AP1 and CAATT enhancer binding protein transcription factors. These findings suggest that EGCG may inhibit disease progression by promoting keratinocyte differentiation. Parallel studies indicate that not all antioxidants produce a similar response. Curcumin, an antioxidant derived from the turmeric, antagonizes the EGCG-dependent response by interfering in this signaling pathway. These studies suggest that different antioxidant may produce antagonistic effects in tissues.

Selective cytotoxicity of benzyl isothiocyanate in the proliferating fibroblastoid cells

In the present study, experiments using presynchronization culture cells demonstrated that benzyl ITC (BITC), previously isolated from a tropical papaya fruit extract, induced the cytotoxic effect preferentially in the proliferating human colon CCD-18Co cells to the quiescent ones. Quiescent CCD-18Co cells were virtually unaffected by BITC and marginal cytotoxicity was observed at 15 microM. We observed that BITC dramatically induced the p53 phosphorylation and stabilization only in the quiescent (G(0)/G(1) phase-arrested) cells, but not significantly in the proliferating human colon CCD-18Co cells when compared with quiescent ones. We also observed ataxia telangiectasia-mutated (ATM) phosphorylation in the quiescent cells. The BITC-induced p53 phosphorylation was counteracted by caffeine treatment, implying the involvement of an ATM/ataxia telangiectasia and Rad3-related kinase signaling pathway. Moreover, downregulation of p53 by a siRNA resulted in the enhancement of susceptibility to undergo apoptosis by BITC. We also showed here that depletion of p53 abrogated G(0)/G(1) arrest accompanied by the declined expression of p21(waf1/cip1) and p27(kip1) in CCD-18Co cells. In conclusion, we identified p53 as a potential negative regulator of the apoptosis induction by BITC in the normal colon CCD-18Co cells through the inhibition of cell-cycle progression at the G(0)/G(1) phase.

Chemopreventive agent-induced modulation of death receptors

The goals of chemoprevention of cancer are to inhibit the initiation or suppress the promotion and progression of preneoplastic lesions to invasive cancer through the use specific natural or synthetic agents. Therefore, a more desirable and aggressive approach is to eliminate aberrant clones by inducing apoptosis rather than merely slowing down their proliferation. The increased understanding of apoptosis pathways has directed attention to components of these pathways as potential targets not only for chemotherapeutic but also for chemopreventive agents. Activation of death receptors triggers an extrinsic apoptotic pathway, which plays a critical role in tumor immunosurveillance. An increasing number of previously identified chemopreventive agents were found to induce apoptosis in a variety of premalignant and malignant cell types in vitro and in a few animal models in vivo. Some chemopreventive agents such as non-steroidal anti-inflammatory drugs, tritepenoids, and retinoids increase the expression of death receptors. Thus, understanding the modulation of death receptors by chemopreventive agents and their implications in chemoprevention may provide a rational approach for using such agents alone or in combination with other agents to enhance death receptor-mediated apoptosis as a strategy for effective chemoprevention of cancer.

Cactus pear: a natural product in cancer chemoprevention

BACKGROUND

Cancer chemoprevention is a new approach in cancer prevention, in which chemical agents are used to prevent cancer in normal and/or high-risk populations. Although chemoprevention has shown promise in some epithelial cancers, currently available preventive agents are limited and the agents are costly, generally with side effects. Natural products, such as grape seed, green tea, and certain herbs have demonstrated anti-cancer effects. To find a natural product that can be used in chemoprevention of cancer, we tested Arizona cactus fruit solution, the aqueous extracts of cactus pear, for its anti-cancer effects in cultured cells and in an animal model.

METHOD

Aqueous extracts of cactus pear were used to treat immortalized ovarian and cervical epithelial cells, as well as ovarian, cervical, and bladder cancer cells. Aqueous extracts of cactus pear were used at six concentrations (0, 0.5, 1, 5, 10 or 25%) to treat cells for 1, 3, or 5 days. Growth inhibition, apoptosis induction, and cell cycle changes were analyzed in the cultured cells; the suppression of tumor growth in nude mice was evaluated and compared with the effect of a synthetic retinoid N-(4-hydroxyphernyl) retinamide (4-HPR), which is currently used as a chemoprevention agent. Immunohistochemistry staining of tissue samples from animal tumors was performed to examine the gene expression.

RESULTS

Cells exposed to cactus pear extracts had a significant increase in apoptosis and growth inhibition in both immortalized epithelial cells and cancer cells in a dose- and time-dependent manner. It also affected cell cycle of cancer cells by increasing G1 and decreasing G2 and S phases. Both 4-HPR and cactus pear extracts significantly suppressed tumor growth in nude mice, increased annexin IV expression, and decreased VEGF expression.

CONCLUSION

Arizona cactus pear extracts effectively inhibited cell growth in several different immortalized and cancer cell cultures, suppressed tumor growth in nude mice, and modulated expression of tumor-related genes. These effects were comparable with those caused by a synthetic retinoid currently used in chemoprevention trials. The mechanism of the anti-cancer effects of cactus pear extracts needs to be further studied.

Mitochondria: A novel target for the chemoprevention of cancer

The mitochondria have emerged as a novel target for anticancer chemotherapy. This tenet is based on the observations that several conventional and experimental chemotherapeutic agents promote the permeabilization of mitochondrial membranes in cancerous cells to initiate the release of apoptogenic mitochondrial proteins. This ability to engage mitochondrial-mediated apoptosis directly using chemotherapy may be responsible for overcoming aberrant apoptosis regulatory mechanisms commonly encountered in cancerous cells. Interestingly, several putative cancer chemopreventive agents also possess the ability to trigger apoptosis in transformed, premalignant, or malignant cells in vitro via mitochondrial membrane permeabilization. This process may occur through the regulation of Bcl-2 family members, or by the induction of the mitochondrial permeability transition. Thus, by exploiting endogenous mitochondrial-mediated apoptosis-inducing mechanisms, certain chemopreventive agents may be able to block the progression of premalignant cells to malignant cells or the dissemination of malignant cells to distant organ sites as means of modulating carcinogenesis in vivo. This review will examine cancer chemoprevention with respect to apoptosis, carcinogenesis, and the proapoptotic activity of various chemopreventive agents observed in vitro. In doing so, I will construct a paradigm supporting the notion that the mitochondria are a novel target for the chemoprevention of cancer.

Sensitization of cervical cancer cell lines to low-dose radiation by retinoic acid does not require functional p53

OBJECTIVE

Current therapy for cervical cancer includes radiation therapy. Retinoic acid (RA) can increase the sensitivity of cervical cancer cell lines to radiation. The mechanism of this sensitization may not involve the p53 protein because the human papillomavirus (HPV) E6 protein, which is present in the majority of cervical cancers, promotes p53 degradation. The objective of this study was to determine if p53 is involved in the mechanism of RA radiosensitization.

METHOD

The effects of radiation on cervical (SiHa, CC-1, and C33a) and vulvar (SW962) cancer cell lines under various experimental conditions were evaluated using clonogenic, Coulter Counter, electrophoretic mobility shift (EMSA) and a multi-probe RNase protection assay of p53-inducible genes.

RESULTS

RA (5 microM 9-cis-RA) radiosensitized the SiHa and CC-1 cell lines that contain HPV-degraded p53, but did not radiosensitize the SW962 cell line, which is HPV negative and contains wild-type p53, nor the C33a cell line, which contains mutant p53 (R273C). Expression of mutant p53 (R273H) in SiHa cells increased the growth rate, but did not prevent RA-induced differentiation or radiosensitization at clinically relevant doses. Inhibition of p53 transactivation with pifithirin alpha did not prevent RA radiosensitization of SiHa at 5 Gy. RA repressed c-fos mRNA expression in control and irradiated SiHa cultures, but did not repress bcl-x(L), p53, GADD45, p21, bax, bcl-2, or mcl-1 mRNA expression.

CONCLUSIONS

The mechanism of RA radiosensitization does not require functional p53 and may involve c-fos in cervical cancer cell lines.

Inhibition of prostate cancer cell growth by an avocado extract: role of lipid-soluble bioactive substances

Although the avocado is known as a rich source of monounsaturated fatty acids, there has been far less attention given to its content of other bioactive substances including carotenoids, which might contribute to cancer preventive properties similar to those attributed to other fruits and vegetables. The yellow-green color of the avocado prompted us to study the carotenoid content of this fruit using established methods in our laboratory. The California Hass avocado (Persea americana Mill.) was selected for study, because it is the most commonly consumed variety in the southwest United States. These avocados were found to contain the highest content of lutein among commonly eaten fruits as well as measurable amounts of related carotenoids (zeaxanthin, alpha-carotene, and beta-carotene). Lutein accounted for 70% of the measured carotenoids, and the avocado also contained significant quantities of vitamin E. An acetone extract of avocado containing these carotenoids and tocopherols was shown to inhibit the growth of both androgen-dependent (LNCaP) and androgen-independent (PC-3) prostate cancer cell lines in vitro. Incubation of PC-3 cells with the avocado extract led to G(2)/M cell cycle arrest accompanied by an increase in p27 protein expression. Lutein alone did not reproduce the effects of the avocado extract on cancer cell proliferation. In common with other colorful fruits and vegetables, the avocado contains numerous bioactive carotenoids. Because the avocado also contains a significant amount of monounsaturated fat, these bioactive carotenoids are likely to be absorbed into the bloodstream, where in combination with other diet-derived phytochemicals they may contribute to the significant cancer risk reduction associated with a diet of fruits and vegetables.

Role of lycopene and tomato products in prostate health

Epidemiological evidence associating the decreased risk of prostate cancer with frequent consumption of tomato products inspired us to conduct a small intervention trial among patients diagnosed with prostate adenocarcinoma. Tomato sauce pasta was consumed daily for 3 weeks before their scheduled prostatectomy, and biomarkers of tomato intake, prostate cancer progression and oxidative DNA damage were followed in blood and the available prostate tissue. The whole food intervention was so well accepted by the subjects that the blood lycopene (the primary carotenoid in tomatoes responsible for their red color) doubled and the prostate lycopene concentration tripled during this short period. Oxidative DNA damage in leukocytes and prostate tissues was significantly diminished, the latter mainly in the tumor cell nuclei, possibly due to the antioxidant properties of lycopene. Quite surprising was the decrease in blood prostate-specific antigen, which was explained by the increase in apoptotic death of prostate cells, especially in carcinoma regions. Prostate cancer cell cultures (LNCaP) were also sensitive to lycopene in growth medium, which caused an increased apoptosis and arrested the cell cycle. A possible explanation of these promising results may reside in lycopene effects on the genes governing the androgen stimulation of prostate growth, cytokines and on the enzymes producing reactive oxygen species, all of which were recently discovered by nutrigenomic techniques. Other phytochemicals in tomato may act in synergy with lycopene to potentiate protective effects and to help in the maintenance of prostate health.

Dietary exposure to soy or whey proteins alters colonic global gene expression profiles during rat colon tumorigenesis

BACKGROUND

We previously reported that lifetime consumption of soy proteins or whey proteins reduced the incidence of azoxymethane (AOM)-induced colon tumors in rats. To obtain insights into these effects, global gene expression profiles of colons from rats with lifetime ingestion of casein (CAS, control diet), soy protein isolate (SPI), and whey protein hydrolysate (WPH) diets were determined.

RESULTS

Male Sprague Dawley rats, fed one of the three purified diets, were studied at 40 weeks after AOM injection and when tumors had developed in some animals of each group. Total RNA, purified from non-tumor tissue within the proximal half of each colon, was used to prepare biotinylated probes, which were hybridized to Affymetrix RG_U34A rat microarrays containing probes sets for 8799 rat genes. Microarray data were analyzed using DMT (Affymetrix), SAM (Stanford) and pair-wise comparisons. Differentially expressed genes (SPI and/or WPH vs. CAS) were found. We identified 31 induced and 49 repressed genes in the proximal colons of the SPI-fed group and 44 induced and 119 repressed genes in the proximal colons of the WPH-fed group, relative to CAS. Hierarchical clustering identified the co-induction or co-repression of multiple genes by SPI and WPH. The differential expression of I-FABP (2.92-, 3.97-fold down-regulated in SPI and WPH fed rats; P = 0.023, P = 0.01, respectively), cyclin D1 (1.61-, 2.42-fold down-regulated in SPI and WPH fed rats; P = 0.033, P = 0.001, respectively), and the c-neu proto-oncogene (2.46-, 4.10-fold down-regulated in SPI and WPH fed rats; P < 0.001, P < 0.001, respectively) mRNAs were confirmed by real-time quantitative RT-PCR. SPI and WPH affected colonic neuro-endocrine gene expression: peptide YY (PYY) and glucagon mRNAs were down-regulated in WPH fed rats, whereas somatostatin mRNA and corresponding circulating protein levels, were enhanced by SPI and WPH.

CONCLUSIONS

The identification of transcripts co- or differentially-regulated by SPI and WPH diets suggests common as well as unique anti-tumorigenesis mechanisms of action which may involve growth factor, neuroendocrine and immune system genes. SPI and WPH induction of somatostatin, a known anti-proliferative agent for colon cancer cells, would inhibit tumorigenesis.

Antioxidants regulate normal human keratinocyte differentiation

Cancer begins with a normal cell that, due to persistent environmental insult, is transformed, via a series of progressively more insidious steps, into a cancer cell. A major goal of chemopreventive therapy is to alter the normal cell response to the environmental agent with the goal of inhibiting disease progression. (-)-Epigallocatechin-3-gallate (EGCG) is an important bioactive green tea antioxidant that possesses remarkable cancer chemopreventive properties. We have recently explored the hypothesis that EGCG prevents cancer by promoting keratinocyte differentiation. Based on our findings, we argue that EGCG acts to enhance the differentiation of normal keratinocytes. This is a potentially important finding, as it represents a novel mechanism of disease inhibition by EGCG--cancer preventive "differentiation therapy". However, not all antioxidant chemopreventive agents work by this mechanism. Curcumin, for example, inhibits the differentiation-promoting activity of EGCG. This report discusses the mechanism of EGCG and curcumin action in regulating expression of involucrin, a marker of keratinocyte differentiation.

Curcumin impairs tumor suppressor p53 function in colon cancer cells

Curcumin (diferuloylmethane) is being considered as a potential chemopreventive agent in humans. In vitro it inhibits transcription by NF-kappaB, and the activity of lipoxygenase or cyclooxygenase enzymes, which facilitate tumor progression. In vivo it is protective in rodent models of chemical carcinogenesis. Curcumin contains an alpha,beta-unsaturated ketone, a reactive chemical substituent that is responsible for its repression of NF-kappaB. In compounds other than curcumin this same electrophilic moiety is associated with inactivation of the tumor suppressor, p53. Here we report that curcumin behaves analogously to these compounds. It disrupts the conformation of the p53 protein required for its serine phosphorylation, its binding to DNA, its transactivation of p53-responsive genes and p53-mediated cell cycle arrest.