Development of Dietary Phytochemical Chemopreventive Agents: Biomarkers and Choice of Dose for Early Clinical Trials: Fig. 1

HPLC-PDA-ESI-MS/MS Profiling and Anti-Biofilm Potential of Eucalyptussideroxylon Flowers

The development of multidrug-resistant bacterial strains is a worldwide emerging problem that needs a global solution. Exploring new natural antibiofilm agents is one of the most important alternative therapies in combating bacterial infections. This study aimed at testing the antimicrobial potential of Eucalyptus sideroxylon flowers extract (ESFE) against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans prior to testing the antibiofilm activity against S. aureus, P. aeruginosa and C. albicans. ESFE demonstrated antimicrobial activity and promising inhibition activity against methicillin-resistant S. aureus (MRSA) biofilm formation up to 95.9% (p < 0.05) at a concentration of 0.05 mg/mL and eradicated C. albicans biofilm formation up to 71.2% (p < 0.05) at a concentration of 0.7 mg/mL. LC-MS analysis allowed the tentative identification of eighty-three secondary metabolites: 21 phloroglucinol, 18 terpenes, 16 flavonoids, 7 oleuropeic acid derivatives, 7 ellagic acid derivatives, 6 gallic acid derivatives, 3 phenolic acids, 3 fatty acids and 2 miscellaneous. In conclusion, E. sideroxylon is a rich source of effective constituents that promote its valorization as a promising candidate in the management of multidrug-resistant bacterial infections.

Quercetin as an innovative therapeutic tool for cancer chemoprevention: Molecular mechanisms and implications in human health

Cancer is a life-threatening disease afflicting human health worldwide. Recent advances in drug discovery infrastructure and molecular approaches have helped a lot in identifying the novel drug targets for therapeutic intervention. Nevertheless, the morbidity and mortality rates because of this disease keep on rising at an alarming rate. Recently, the use of natural and synthetic molecules as innovative therapeutic tools for cancer prevention has lead to the development of cancer chemoprevention. Cancer chemoprevention is a prophylactic strategy that involves the chronic administration of one or more natural or synthetic agents to block, to inhibit, or to suppress the process of cancer development before it becomes an invasive disease. Quercetin, a dietary bioflavonoid, can specifically retard the growth of cancer cells and behaves as a potent cancer chemopreventive agent. Quercetin has multiple intracellular targets in a cancer cell. Therefore, many mechanisms have been postulated to explain its chemopreventive action. The chemopreventive effects elicited by this natural molecule in different model systems are believed to include antioxidant/pro-oxidant action, regulation of redox homeostasis, apoptosis, cell cycle arrest, anti-inflammatory action, modulation of drug metabolizing enzymes, alterations in gene expression patterns, inhibition of Ras gene expression, and modulation of signal transduction pathways. However, cell signaling networks have recently garnered attention as common molecular target for various chemopreventive effects of quercetin. In this review, we made an attempt to critically summarize the emerging knowledge on the role of quercetin in cancer chemoprevention and the underlying molecular mechanisms implicated in its chemopreventive and therapeutic effects.

Callistemon citrinus bioactive metabolites as new inhibitors of methicillin-resistant Staphylococcus aureus biofilm formation

ETHNOPHARMACOLOGICAL RELEVANCE

The development of new inhibitors of bacterial virulence factors from natural origin has recently received significant attention. Callistemon citrinus Skeels is an important plant of great medicinal value. Its antimicrobial activity is well documented. Although several compounds were isolated from this plant, the actual bioactive compounds responsible for its antimicrobial activity are still unrevealed.

AIM OF THE STUDY

To evaluate the effect of C. citrinus crude extract and isolated compounds on methicillin-resistant and sensitive Staphylococcus aureus.

MATERIALS AND METHODS

The methylene chloride-methanol extract (MME) of C. citrinus leaves was prepared by Soxhlet apparatus. Biologically guided fractionation of MME was accomplished using several normal and reversed phase silica gel columns. The potency of MME and its isolated compounds against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) was evaluated. In addition, the mechanism of resistance was studied using three virulence factors; antibiofilm activity, inhibition of staphyloxanthin biosynthesis and effect on acid tolerance. Ultrastructural changes in MRSA and MSSA were observed by TEM to understand mode of action of these compounds.

RESULTS

Pulverulentone A (C1), 8- desmethyl eucalyptin (C2) and eucalyptin (C3) were isolated from the most bioactive fraction of MME. Confocal scanning laser microscopy images revealed that C. citrinus isolated compounds destroyed the intact architecture of biofilm, thickness and reduced its biomass. Pulverulentone A (C1) showed the most potent anti-biofilm activity up to 71% and 62.3% against MRSA and MSSA, respectively. It also exhibited the highest inhibition of staphyloxanthin biosynthesis of MRSA and MSSA by 55.6% and 54.5%, respectively. The bacterial cell membrane was compromised, losing its integrity and releasing important cellular constituents when exposed to C1-C3 CONCLUSIONS: C. citrinus phenolics and acylphloroglucinols may serve as potential source of plant-based antibacterials and thus could be implicated to control MRSA biofilm formation.

Susceptibility Assessment of Methicillin-Resistant Staphylococcus aureus Strains to Lepidium sativum Extract

Many plant-derived compounds have been used to treat microbial infections. Staphylococcus aureus a common cause of many organ infections, has generated increasing concern due to its resistance to antibacterial drugs. This work was carried out to explore the susceptibility of 6 strains (LN872136, LN872137, LN871238, LN871239, LN872140, and LN871241) of methicillin-resistant Staphylococcus aureus to aqueous extract of Lepidium sativum seeds in vitro. Various concentrations (5-20 mg/mL) were used to evaluate the effect of the extract on bacteria growth via the assessment of the microbial biomass and the inhibition zone (IZ). The results showed that the plant extract at 15 or 20 mg/mL, significantly decreased the the biomass of S aureus strains after 24 or 48 hours exposure period. Staphylococcus aureus (LN871241) showed the largest IZ at 20 mg/mL and documented by scanning electron microscope. The current work may suggest that L sativum seed extract can be candidate as a promising antimicrobial agent to treat infection with methicillin-resistant S aureus.

Downregulation of Pro-Inflammatory and Pro-Angiogenic Pathways in Prostate Cancer Cells by a Polyphenol-Rich Extract from Olive Mill Wastewater

Dietary phytochemicals are particularly attractive for chemoprevention and are able to modulate several signal transduction pathways linked with cancer. Olive oil, a major component of the Mediterranean diet, is an abundant source of phenolic compounds. Olive oil production is associated with the generation of a waste material, termed 'olive mill wastewater' (OMWW) that have been reported to contain water-soluble polyphenols. Prostate cancer (PCa) is considered as an ideal cancer type for chemopreventive approaches, due to its wide incidence but relatively long latency period and progression time. Here, we investigated activities associated with potential preventive properties of a polyphenol-rich olive mill wastewater extract, OMWW (A009), on three in vitro models of PCa. A009 was able to inhibit PCa cell proliferation, adhesion, migration, and invasion. Molecularly, we found that A009 targeted NF-κB and reduced pro-angiogenic growth factor, VEGF, CXCL8, and CXCL12 production. IL-6/STAT3 axis was also regulated by the extract. A009 shows promising properties, and purified hydroxytyrosol (HyT), the major polyphenol component of A009, was also active but not always as effective as A009. Finally, our results support the idea of repositioning a food waste-derived material for nutraceutical employment, with environmental and industrial cost management benefits.

Detection of Plasma Curcuminoids from Dietary Intake of Turmeric-Containing Food in Human Volunteers

SCOPE

Curcumin (from turmeric), has been extensively investigated for potential beneficial properties in numerous diseases. Most work has focused on supra-dietary concentrations/doses that would necessitate curcumin supplementation. However, much evidence instigating curcumin research is underpinned by epidemiological data based on low dietary intake via turmeric consumption.

METHODS AND RESULTS

Here, a novel, highly sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS) method for detection of curcuminoids is described. Assay sensitivity is demonstrated in a pilot pharmacokinetic volunteer study following ingestion of foodstuffs containing a standardized mass of turmeric, representative of daily consumption by certain South Asian populations. Free parent curcumin was detectable in plasma from one individual, reaching maximal plasma concentrations (C_max ) of 3.2 nm. Curcumin conjugates were detected in all volunteers; C_max for curcumin glucuronide is 47.6 ± 28.5 nm 30 min post-food, while C_max for demethoxycurcumin glucuronide and curcumin sulfate is ≈2 nm. Curcumin and its major metabolites persist in plasma for at least 8 h.

CONCLUSION

Despite poor absorption and rapid conjugation, dietary intake of standard culinary turmeric within complex food matrices furnished human plasma with detectable levels of curcuminoids. Whether sustained low systemic concentrations of these non-nutritive, biologically active, dietary components may have pharmacological activity for human health benefit, warrants further research.

Integration of botanicals in contemporary medicine: road blocks, checkpoints and go-ahead signals

The use of botanicals for maintaining good health and preventing diseases is undisputed. The claimed health benefits of natural health products and herbal medicines are based on traditional claims, positive results obtained in preclinical studies and early phase clinical trials that are not backed by safety and efficacy evidences approved by regulatory agencies. Although, the popularity of botanicals is growing, health care practitioners of modern medicine seldom recommend their use because of ill equipped database of their safety and potency. This review discusses problems that preclude botanicals from integrating into the mainstream contemporary therapeutics and cues that provide impetus for their realisation.

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.

Hop derived flavonoid xanthohumol inhibits endothelial cell functions via AMPK activation

Angiogenesis, a process characterized by the formation of new blood vessels from pre-existing ones, is a crucial step in tumor growth and dissemination. Recently, increased attention has been addressed to the ability of flavonoids to prevent cancer by suppressing angiogenesis, strategy that we named "angioprevention". Several natural compounds exert their anti-tumor properties by activating 5' adenosine monophosphate-activated protein kinase (AMPK), a key regulator of metabolism in cancer cells. Drugs with angiopreventive activities, in particular metformin, regulate AMPK in endothelial cells. Here we investigated the involvement of AMPK in the anti-angiogenic effects of xanthohumol (XN), the major prenylated flavonoid of the hop plant, and mechanisms of action. The anti-angiogenic activity of XN was more potent than epigallocatechin-3-gallate (EGCG). Treatment of endothelial cells with XN led to increased AMPK phosphorylation and activity. Functional studies using biochemical approaches confirmed that AMPK mediates XN anti-angiogenic activity. AMPK activation by XN was mediated by CAMMKβ, but not LKB1. Analysis of the downstream mechanisms showed that XN-induced AMPK activation reduced nitric oxide (NO) levels in endothelial cells by decreasing eNOS phosphorylation. Finally, AKT pathway was inactivated by XN as part of its anti-angiogenic activity, but independently from AMPK, suggesting that these two signaling pathways proceed autonomously. Our study dissects the molecular mechanism by which XN exerts its potent anti-angiogenic activity, pointing out AMPK as a crucial signal transducer.

Chemopreventive Potential of Major Flavonoid Compound of Methanolic Bark Extract of Saraca asoca (Roxb.) in Benzene-induced Toxicity of Acute Myeloid Leukemia Mice

Background:

Saraca asoca (SA) (Roxb.) is one of the folk medicinal plants found in India, Bangladesh, and Sri Lanka. Its major biological activity appears due to the presence of flavonoid group of compounds in its bark extract.

Objective:

In this study, our research aims to analyze the chemopreventive effect of flavonoids, especially a natural phenol catechin present in the bark methanolic extract of SA on acute myeloid leukemia (AML) mice.

Materials and Methods:

The total bark extract was partitioned and analyzed on thin-layer chromatography (TLC) plate. The yellow-brown material of spot 4 was analyzed and identified as catechin. The yellowish brown material (YBM) was tested for their chemopreventive potential. An in vivo AML mice model was used to test the efficacy. Hematological parameters (Hb %, red blood cell, and white blood cell count), expression of cell cycle regulatory proteins, and DNA fragmentation analysis were performed.

Results:

After treatment of benzene-exposed mice with the major flavonoid compound, namely catechin, the above parameters increase significantly (P < 0.05). There was an upregulation of p53 and p21, caspase 11 myeloperoxidase, bcl2, and CYP2EI in catechin-treated group. DNA was less fragmented in flavonoid-treated group compared to that of control (P ≤ 0.05). The present study indicates that the secondary metabolites of SA methanolic bark extract, comprising flavonoid catechin as major constituents, have modulatory effect in cell cycle deregulation and hematological abnormalities induced by benzene in mice.

Conclusions:

Our data suggest that catechin from methanolic bark extract of SA effectively attenuates benzene-induced secondary AML in bone marrow, which is likely associated with the anticell cycle deregulation properties of this flavan-3-ol. This study was supported by the observation that catechin (YBM), like doxorubicin, can act as the neutralizer and protector of mortality in cancer cases.

SUMMARY

The catechin from methanolic bark extract of Saraca asoca has chemoprotective activity in benzene-induced secondary acute myeloid leukemia.(AML) in bone marrow

Hematological parameters, structural analysis of DNA showed that the purified catechin attenuates the conditions responsible for the development of AML

The purified flavonol, catechin has a modulatory effect on different cell cycle deregulations induced by benzene in AML model.

Chemoprevention in African American Men With Prostate Cancer

BACKGROUND

Recommendations for cancer screening are uncertain for the early detection or prevention of prostate cancer in African American men. Thus, chemoprevention strategies are needed to specifically target African American men.

METHODS

The evidence was examined on the biological etiology of disparities in African Americans related to prostate cancer. Possible chemopreventive agents and biomarkers critical to prostate cancer in African American men were also studied.

RESULTS

High-grade prostatic intraepithelial neoplasia may be more prevalent in African American men, even after controlling for age, prostate-specific antigen (PSA) level, abnormal results on digital rectal examination, and prostate volume. Prostate cancer in African American men can lead to the overexpression of signaling receptors that may mediate increased proliferation, angiogenesis, and decreased apoptosis. Use of chemopreventive agents may be useful for select populations of men.

CONCLUSIONS

Green tea catechins are able to target multiple pathways to address the underlying biology of prostate carcinogenesis in African American men, so they may be ideal as a chemoprevention agent in these men diagnosed with high-grade prostatic intraepithelial neoplasia.

Berberine affects osteosarcoma via downregulating the caspase-1/IL-1β signaling axis

Osteosarcoma is one of the most devastating cancers with associated poor prognosis. Chronic bone inflammation frequently predisposes to tumorigenesis and progression of osteosarcoma. In the tumor inflammatory microenvironment, caspase-1 and its processed cytokines such as interleukin 1β (IL-1β) play an important role in the occurrence and development of cancer. Berberine is an isoquinoline alkaloid extracted from the dry root of Coptidis Rhizoma, which has been found to exhibit significant anticancer effects on a wide spectrum of carcinomas including osteosarcoma. However, the mechanisms underlying the anticancer effects of berberine in osteosarcoma remain poorly understood and their elucidation is critical for developing improved therapies. In the present study, we investigated the potential mechanism underlying the anticancer effect of berberine in osteosarcoma. We found that the expression of caspase-1 and its downstream target IL-1β were higher in osteosarcoma cells compared with normal cells both in vitro and in vivo. Furthermore, administration of berberine is capable of reducing the expression of caspase-1 and IL-1β in osteosarcoma cells and inhibiting the growth of tumor cells. Based on the above, for the first time, we propose the hyposis that berberine could gengerate an anti-osteosarcoma property through downregulating caspase-1/IL-1β inflammatory signaling axis.

Synergic chemoprevention with dietary carbohydrate restriction and supplementation of AMPK-activating phytochemicals: the role of SIRT1

Calorie restriction or a low-carbohydrate diet (LCD) can increase life span in normal cells while inhibiting carcinogenesis. Various phytochemicals also have calorie restriction-mimetic anticancer properties. We investigated whether an isocaloric carbohydrate-restriction diet and AMP-activated protein kinase (AMPK)-activating phytochemicals induce synergic tumor suppression. We used a mixture of AMPK-activating phytochemical extracts including curcumin, quercetin, catechins, and resveratrol. Survival analysis was carried out in a B16F10 melanoma model fed a control diet (62.14% kcal carbohydrate, 24.65% kcal protein and 13.2% kcal fat), a control diet with multiple phytochemicals (MP), LCD (16.5, 55.2, and 28.3% kcal, respectively), LCD with multiple phytochemicals (LCDmp), a moderate-carbohydrate diet (MCD, 31.9, 62.4, and 5.7% kcal, respectively), or MCD with phytochemicals (MCDmp). Compared with the control group, MP, LCD, or MCD intervention did not produce survival benefit, but LCDmp (22.80±1.58 vs. 28.00±1.64 days, P=0.040) and MCDmp (23.80±1.08 vs. 30.13±2.29 days, P=0.008) increased the median survival time significantly. Suppression of the IGF-1R/PI3K/Akt/mTOR signaling, activation of the AMPK/SIRT1/LKB1pathway, and NF-κB suppression were the critical tumor-suppression mechanisms. In addition, SIRT1 suppressed proliferation of the B16F10 and A375SM cells under a low-glucose condition. Alterations in histone methylation within Pten and FoxO3a were observed after the MCDmp intervention. In the transgenic liver cancer model developed by hydrodynamic transfection of the HrasG12V and shp53, MCDmp and LCDmp interventions induced significant cancer-prevention effects. Microarray analysis showed that PPARα increased with decreased IL-6 and NF-κB within the hepatocytes after an MCDmp intervention. In conclusion, an isocaloric carbohydrate-restriction diet and natural AMPK-activating agents induce synergistic anticancer effects. SIRT1 acts as a tumor suppressor under a low-glucose condition.

Cancer chemoprevention: Evidence of a nonlinear dose response for the protective effects of resveratrol in humans and mice

Resveratrol is widely promoted as a potential cancer chemopreventive agent, but a lack of information on the optimal dose prohibits rationally designed trials to assess efficacy. To challenge the assumption that "more is better," we compared the pharmacokinetics and activity of a dietary dose with an intake 200 times higher. The dose-response relationship for concentrations generated and the metabolite profile of [(14)C]-resveratrol in colorectal tissue of cancer patients helped us to define clinically achievable levels. In Apc(Min) mice (a model of colorectal carcinogenesis) that received a high-fat diet, the low resveratrol dose suppressed intestinal adenoma development more potently than did the higher dose. Efficacy correlated with activation of adenosine monophosphate-activated protein kinase (AMPK) and increased expression of the senescence marker p21. Nonlinear dose responses were observed for AMPK and mechanistic target of rapamycin (mTOR) signaling in mouse adenoma cells, culminating in autophagy and senescence. In human colorectal tissues exposed to low dietary concentrations of resveratrol ex vivo, we measured enhanced AMPK phosphorylation and autophagy. The expression of the cytoprotective NAD(P)H dehydrogenase, quinone 1 (NQO1) enzyme was also increased in tissues from cancer patients participating in our [(14)C]-resveratrol trial. These findings warrant a revision of developmental strategies for diet-derived agents designed to achieve cancer chemoprevention.

Lessons learned from cancer prevention studies with nutrients and non-nutritive dietary constituents

Epidemiological studies have observed the association between dietary patterns and the risk of certain types of cancer. Extensive studies have been conducted on the cancer preventive activities of constituents from food and beverages. While laboratory research has shown impressive and promising results, such promising cancer preventive activities have not been demonstrated in many human intervention trials. This article analyzes the major differences between these different types of studies and the limitations of these studies. Animal and cell line studies usually use optimal conditions in order to demonstrate the hypothesized effects, sometimes without considering the human relevance. On the other hand, some clinical trials were designed without a good understanding of the biochemical and pharmacological properties of the agents used. Lessons learned from these studies will be illustrated using vitamin E, β-carotene and selenium as examples for nutrients, and green tea polyphenols as an example for non-nutritive dietary constituents. From the lessons learned, we believe that more interdisciplinary collaboration and integration of laboratory and human studies would effectively advance the field of cancer prevention.

Antibacterial Properties of Alkaloid Extracts from Callistemon citrinus and Vernonia adoensis against Staphylococcus aureus and Pseudomonas aeruginosa

The development of new antibiotics from new chemical entities is becoming more and more expensive, time-consuming, and compounded by emerging strains that are drug resistant. Alkaloids are plant secondary metabolites which have been shown to have potent pharmacological activities. The effect of alkaloids from Callistemon citrinus and Vernonia adoensis leaves on bacterial growth and efflux pump activity was evaluated on Staphylococcus aureus and Pseudomonas aeruginosa. At a concentration of 1.67 mg/mL, the alkaloids inhibited bacterial growth with comparable effects to ampicillin, a standard antibiotic. The alkaloids from C. citrinus were the most potent against S. aureus with an MIC of 0.0025 mg/mL and MBC of 0.835 mg/mL. It was shown that effects on P. aeruginosa by both plant alkaloids were bacteriostatic. P. aeruginosa was most susceptible to drug efflux pump inhibition by C. citrinus alkaloids which caused an accumulation of Rhodamine 6G of 121% compared to the control. Thus, C. citrinus alkaloids showed antibacterial activity as well as inhibiting ATP-dependent transport of compounds across the cell membrane. These alkaloids may serve as potential courses of compounds that can act as lead compounds for the development of plant-based antibacterials and/or their adjunct compounds.

New concepts and challenges in the clinical translation of cancer preventive therapies: the role of pharmacodynamic biomarkers

Implementation of therapeutic cancer prevention strategies has enormous potential for reducing cancer incidence and related mortality. Trials of drugs including tamoxifen and aspirin have led the way in demonstrating proof-of-principle that prevention of breast and colorectal cancer is feasible. Many other compounds ranging from drugs in widespread use for various indications, including metformin, bisphosphonates, and vitamin D, to dietary agents such as the phytochemicals resveratrol and curcumin, show preventive activity against several cancers in preclinical models. Notwithstanding the wealth of opportunities, major challenges have hindered the development process and only a handful of therapies are currently approved for cancer risk reduction. One of the major obstacles to successful clinical translation of promising preventive agents is a lack of pharmacodynamic biomarkers to provide an early read out of biological activity in humans and for optimising doses to take into large scale randomised clinical trials. A further confounding factor is a lack of consideration of clinical pharmacokinetics in the design of preclinical experiments, meaning results are frequently reported from studies that use irrelevant or unachievable concentrations. This article focuses on recent findings from investigations with dietary-derived agents to illustrate how a thorough understanding of the mechanisms of action, using models that mimic the clinical scenario, together with the development of compound-specific accompanying pharmacodynamic biomarkers could accelerate the developmental pipeline for preventive agents and maximise the chances of success in future clinical trials. Moreover, the concept of a bell-shaped dose-response curve for therapeutic cancer prevention is discussed, along with the need to rethink the traditional ‘more is better’ approach for dose selection.

Computer-aided discovery of biological activity spectra for anti-aging and anti-cancer olive oil oleuropeins

Aging is associated with common conditions, including cancer, diabetes, cardiovascular disease, and Alzheimer's disease. The type of multi-targeted pharmacological approach necessary to address a complex multifaceteddisease such as aging might take advantage of pleiotropic natural polyphenols affecting a wide variety of biological processes. We have recently postulated that the secoiridoids oleuropein aglycone (OA) and decarboxymethyl oleuropein aglycone (DOA), two complex polyphenols present in health-promoting extra virgin olive oil (EVOO), might constitute anew family of plant-produced gerosuppressant agents. This paper describes an analysis of the biological activity spectra (BAS) of OA and DOA using PASS (Prediction of Activity Spectra for Substances) software. PASS can predict thousands of biological activities, as the BAS of a compound is an intrinsic property that is largely dependent on the compound's structure and reflects pharmacological effects, physiological and biochemical mechanisms of action, and specific toxicities. Using Pharmaexpert, a tool that analyzes the PASS-predicted BAS of substances based on thousands of “mechanism-effect” and “effect-mechanism” relationships, we illuminate hypothesis-generating pharmacological effects, mechanisms of action, and targets that might underlie the anti-aging/anti-cancer activities of the gerosuppressant EVOO oleuropeins.

3,3'-diindolylmethane potentiates tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis of gastric cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) specifically kills cancer cells without destroying the majority of healthy cells. However, numerous types of cancer cell, including gastric cancer cells, tend to be resistant to TRAIL. The bioactive product 3,3'-diindolylmethane (DIM), which is derived from cruciferous vegetables, is also currently recognized as a candidate anticancer agent. In the present study, a Cell Counting Kit 8 cell growth assay and an Annexin V-fluorescein isothiocyanate apoptosis assay were performed to investigate the potentiating effect of DIM on TRAIL-induced apoptosis in gastric cancer cells, and the possible mechanisms of this potentiation. The results obtained demonstrated that, compared with TRAIL or DIM treatment alone, co-treatment with TRAIL (25 or 50 ng/ml) and DIM (10 µmol/l) induced cytotoxic and apoptotic effects in BGC-823 and SGC-7901 gastric cancer cells. Furthermore, western blot analysis revealed that the protein expression levels of death receptor 5 (DR5), CCAAT/enhancer binding protein homologous protein (CHOP) and glucose-regulated protein 78 (GRP78) were upregulated in the co-treated gastric cancer cells. To the best of our knowledge, the present study is the first to provide evidence that DIM sensitizes TRAIL-induced inhibition of proliferation and apoptosis in gastric cancer cells, accompanied by the upregulated expression of DR5, CHOP and GRP78 proteins, which may be involved in endoplasmic reticulum stress mechanisms.

Artemisinin triggers a G1 cell cycle arrest of human Ishikawa endometrial cancer cells and inhibits cyclin-dependent kinase-4 promoter activity and expression by disrupting nuclear factor-κB transcriptional signaling

Relatively little is known about the antiproliferative effects of artemisinin, a naturally occurring antimalarial compound from Artemisia annua, or sweet wormwood, in human endometrial cancer cells. Artemisinin induced a G1 cell cycle arrest in cultured human Ishikawa endometrial cancer cells and downregulated cyclin-dependent kinase-2 (CDK2) and CDK4 transcript and protein levels. Analysis of CDK4 promoter-luciferase reporter constructs showed that the artemisinin ablation of CDK4 gene expression was accounted for by the loss of CDK4 promoter activity. Chromatin immunoprecipitation demonstrated that artemisinin inhibited nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) subunit p65 and p50 interactions with the endogenous Ishikawa cell CDK4 promoter. Coimmunoprecipitation revealed that artemisinin disrupts endogenous p65 and p50 nuclear translocation through increased protein-protein interactions with IκB-α, an NF-κB inhibitor, and disrupts its interaction with the CDK4 promoter, leading to a loss of CDK4 gene expression. Artemisinin treatment stimulated the cellular levels of IκB-α protein without altering the level of IκB-α transcripts. Finally, expression of exogenous p65 resulted in the accumulation of this NF-κB subunit in the nucleus of artemisinin-treated and artemisinin-untreated cells, reversed the artemisinin downregulation of CDK4 protein expression and promoter activity, and prevented the artemisinin-induced G1 cell cycle arrest. Taken together, our results demonstrate that a key event in the artemisinin antiproliferative effects in endometrial cancer cells is the transcriptional downregulation of CDK4 expression by disruption of NF-κB interactions with the CDK4 promoter.

Berberine induces apoptosis and DNA damage in MG‑63 human osteosarcoma cells

Berberine, an isoquinoline alkaloid extracted from the dry root of Coptidis Rhizoma, has been found to exhibit marked anticancer effects on a panel of established cancer cells. Among the human osteosarcoma lines treated, MG-63 cells were found to be the most sensitive. The present study investigated the potential genotoxic effect of berberine on MG-63 human osteosarcoma cells. The effect of berberine on cell viability was determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cell apoptosis was analyzed by flow cytometry and a DNA ladder assay. γH2AX focus formation was used to detect DNA damage in MG-63 cells. Berberine induced a significant increase in apoptosis in MG-63 cells in a concentration- and time-dependent manner, as determined by DNA fragmentation analysis and flow cytometry. Furthermore, berberine induced significant concentration- and time-dependent increases in DNA damage compared with that in the negative control. In conclusion, these observations indicated that berberine induced apoptosis and DNA damage in MG-63 cells.

Chemoprevention in gastrointestinal physiology and disease. Natural products and microbiome

The human intestinal tract harbors a complex ecosystem of commensal bacteria that play a fundamental role in the well-being of their host. There is a general consensus that diet rich in plant-based foods has many advantages in relation to the health and well-being of an individual. In adults, diets that have a high proportion of fruit and vegetables and a low consumption of meat are associated with a highly diverse microbiota and are defined by a greater abundance of Prevotella compared with Bacteroides, whereas the reverse is associated with a diet that contains a low proportion of plant-based foods. In a philosophical term, our consumption of processed foods, widespread use of antibiotics and disinfectants, and our modern lifestyle may have forever altered our ancient gut microbiome. We may never be able to identify or restore our microbiomes to their ancestral state, but dietary modulation to manipulate specific gut microbial species or groups of species may offer new therapeutic approaches to conditions that are prevalent in modern society, such as functional gastrointestinal disorders, obesity, and age-related nutritional deficiency. We believe that this will become an increasingly important area of health research.

Cancer chemoprevention: current state of the art

The aim of cancer chemoprevention is disruption or delay of the molecular pathways that lead to carcinogenesis. Chemopreventive blocking and/or suppressing agents disrupt the molecular mechanisms that drive carcinogenesis such as DNA damage by reactive oxygen species, increased signal transduction to NF-κB, epigenomic deregulation, and the epithelial mesenchymal transition that leads to metastatic progression. Numerous dietary phytochemicals have been observed to inhibit the initiation phase of carcinogenesis, and therefore are useful in primary chemoprevention. Moreover, phytochemicals are capable of interfering with the molecular mechanisms of metastasis. Likewise, numerous synthetic compounds are relevant and clinically viable as chemopreventive agents during the fundamental stages of carcinogenesis. While molecularly targeted anti-cancer therapies are in constant stages of development, superior patient outcomes are observed if carcinogenic processes are prevented altogether. This article reviews the role of chemopreventive compounds in inhibition of cancer initiation and their ability to reduce cancer progression.

Qualitative and quantitative characterization of plasma proteins when incorporating traveling wave ion mobility into a liquid chromatography-mass spectrometry workflow for biomarker discovery: use of product ion quantitation as an alternative data analysis tool for label free quantitation

Discovery of protein biomarkers in clinical samples necessitates significant prefractionation prior to liquid chromatography-mass spectrometry (LC-MS) analysis. Integrating traveling wave ion mobility spectrometry (TWIMS) enables in-line gas phase separation which when coupled with nanoflow liquid chromatography and data independent acquisition tandem mass spectrometry, confers significant advantages to the discovery of protein biomarkers by improving separation and inherent sensitivity. Incorporation of TWIMS leads to a packet of concentrated ions which ultimately provides a significant improvement in sensitivity. As a consequence of ion packeting, when present at high concentrations, accurate quantitation of proteins can be affected due to detector saturation effects. Human plasma was analyzed in triplicate using liquid-chromatography data independent acquisition mass spectrometry (LC-DIA-MS) and using liquid-chromatography ion-mobility data independent acquisition mass spectrometry (LC-IM-DIA-MS). The inclusion of TWIMS was assessed for the effect on sample throughput, data integrity, confidence of protein and peptide identification, and dynamic range. The number of identified proteins is significantly increased by an average of 84% while both the precursor and product mass accuracies are maintained between the modalities. Sample dynamic range is also maintained while quantitation is achieved for all but the most abundant proteins by incorporating a novel data interpretation method that allows accurate quantitation to occur. This additional separation is all achieved within a workflow with no discernible deleterious effect on throughput. Consequently, TWIMS greatly enhances proteome coverage and can be reliably used for quantification when using an alternative product ion quantification strategy. Using TWIMS in biomarker discovery in human plasma is thus recommended.

Optimizing biomarkers and endpoints in oral cancer chemoprevention trials

Chemoprevention, defined as the use of natural, synthetic, or biologic compounds to halt, reverse, or prevent the initial phases of carcinogenesis or the progression of neoplastic cells to cancer, has produced successes, but progress has been slow. Notably, in the field of oral cancer prevention and despite extensive clinical investigations, a standard systemic therapy for patients with oral premalignant lesions is yet to be developed. In view of safety concerns surrounding the use of pharmaceuticals, the use of phytochemicals derived from the diet has been considered but has not yet translated into clinical success. The Bowman Birk Inhibitor (BBI) is a serine protease inhibitor isolated from soybeans possessing domains with trypsin and chymotrypsin inhibitory activity. Encouraging results were previously reported in a phase IIa trial of BBI complex in patients with oral leukoplakia with measurable clinical responses and favorable biomarker changes. In this issue of the journal, the less promising results of the randomized, placebo-controlled phase IIb trial are presented. In this commentary, the complexities involved in defining optimal biomarkers and endpoints for oral cancer prevention trials and the development of dietary chemoprevention agents are discussed.

Simultaneous inhibition of cell-cycle, proliferation, survival, metastatic pathways and induction of apoptosis in breast cancer cells by a phytochemical super-cocktail: genes that underpin its mode of action

Traditional chemotherapy and radiotherapy for cancer treatment face serious challenges such as drug resistance and toxic side effects. Complementary / Alternative medicine is increasingly being practiced worldwide due to its safety beneficial therapeutic effects. We hypothesized that a super combination (SC) of known phytochemicals used at bioavailable levels could induce 100% killing of breast cancer (BC) cells without toxic effects on normal cells and that microarray analysis would identify potential genes for targeted therapy of BC. Mesenchymal Stems cells (MSC, control) and two BC cell lines were treated with six well established pro-apoptotic phytochemicals individually and in combination (super cocktail), at bioavailable levels. The compounds were ineffective individually. In combination, they significantly suppressed BC cell proliferation (>80%), inhibited migration and invasion, caused cell cycle arrest and induced apoptosis resulting in 100% cell death. However, there were no deleterious effects on MSC cells used as control. Furthermore, the SC down-regulated the expression of PCNA, Rb, CDK4, BcL-2, SVV, and CD44 (metastasis inducing stem cell factor) in the BC cell lines. Microarray analysis revealed several differentially expressed key genes (PCNA, Rb, CDK4, Bcl-2, SVV, P53 and CD44) underpinning SC-promoted BC cell death and motility. Four unique genes were highly up-regulated (ARC, GADD45B, MYLIP and CDKN1C). This investigation indicates the potential for development of a highly effective phytochemical combination for breast cancer chemoprevention / chemotherapy. The novel over-expressed genes hold the potential for development as markers to follow efficacy of therapy.

Resveratrol in the management of human cancer: how strong is the clinical evidence?

Among the plethora of biochemical mechanisms engaged by resveratrol in preclinical systems, its anticarcinogenic effects represent some of the most convincing and intriguing. As outlined in this review, there is considerable interest in developing resveratrol for cancer prevention and treatment. The plasma pharmacokinetics of resveratrol in humans are now reasonably well defined, and studies have shown that repeated daily doses up to 1 g are safe and well tolerated, although gastrointestinal toxicity is observed at higher intakes. However, care is needed regarding underlying conditions in specific patient groups, and there is potential for drug interactions at doses greater than 1 gram. Little is known regarding the pharmacodynamic effects of resveratrol in humans, but the observation that it modulates components of the insulin-like growth factor system in the plasma of volunteers is encouraging. While the knowledge base that helps determine whether resveratrol may be useful in cancer management has increased substantially in recent years, important questions remain.

Cancer chemoprevention: a rapidly evolving field

Cancer chemoprevention involves the chronic administration of a synthetic, natural or biological agent to reduce or delay the occurrence of malignancy. The potential value of this approach has been demonstrated with trials in breast, prostate and colon cancer. The paradigm for developing new chemopreventive agents has changed markedly in the last decade and now involves extensive preclinical mechanistic evaluation of agents before clinical trials are instituted and a focus on defining biomarkers of activity that can be used as early predictors of efficacy. This review will summarise the current status of the field of chemoprevention and highlight potential new developments.

Early-phase development of cancer prevention agents: challenges and opportunities

Chemoprevention is the administration of agents (drugs, biologics, dietary supplements, or nutrients) to reduce the risk of developing cancer or prevent the recurrence of cancer. The National Cancer Institute, Division of Cancer Prevention (NCI, DCP), is a major sponsor of cancer preventive preclinical and clinical research. As such, it has developed a comprehensive drug development program specifically designed to meet the requirements needed for cancer preventive drugs to achieve initial regulatory approval. Clinical development of cancer prevention agents presents unique challenges that are not encountered with most cancer therapeutic agents. To meet these challenges, NCI, DCP has implemented new approaches and programs, including phase 0 clinical trial designs and microdose studies. In addition, the PREVENT Cancer Program was recently implemented by NCI, DCP to offer a formalized structure for moving drugs forward in the prevention pipeline using a continue/not continue decision process. Likewise, DCP has implemented a Clinical Trials Consortium to further develop these agents. These and other approaches will be discussed in this commentary.

Molecular Targeted Therapies Using Botanicals for Prostate Cancer Chemoprevention

In spite of the large number of botanicals demonstrating promise as potential cancer chemopreventive agents, most have failed to prove effectiveness in clinical trials. Critical requirements for moving botanical agents to recommendation for clinical use include adopting a systematic, molecular-target based approach and utilizing the same ethical and rigorous methods that are used to evaluate other pharmacological agents. Preliminary data on a mechanistic rationale for chemoprevention activity as observed from epidemiological, in vitro and preclinical studies, phase I data of safety in suitable cohorts, duration of intervention based on time to progression of pre-neoplastic disease to cancer and using a valid panel of biomarkers representing the hypothesized carcinogenesis pathway for measuring efficacy must inform the design of clinical trials. Botanicals have been shown to influence multiple biochemical and molecular cascades that inhibit mutagenesis, proliferation, induce apoptosis, suppress the formation and growth of human cancers, thus modulating several hallmarks of carcinogenesis. These agents appear promising in their potential to make a dramatic impact in cancer prevention and treatment, with a significantly superior safety profile than most agents evaluated to date. The goal of this paper is to provide models of translational research based on the current evidence of promising botanicals with a specific focus on targeted therapies for PCa chemoprevention.

Bioactivity and bioavailability of ginsenosides are dependent on the glycosidase activities of the A/J mouse intestinal microbiome defined by pyrosequencing

PURPOSE

To investigate the ability of bacteria in the intestinal microbiome to convert naturally occurring primary ginsenosides in red ginseng extract to active secondary ginsenosides.

METHODS

Anti-proliferative ginsenoside activity was tested using mouse lung cancer LM1 cells. Permeabilities were evaluated in Caco-2 cell monolayers. Systemic exposure of secondary ginsenosides was determined in A/J mice. 16S rRNA gene pyrosequencing was used to determine membership and abundance of bacteria in intestinal microbiome.

RESULTS

Secondary ginsenoside C-K exhibited higher anti-proliferative activity and permeability than primary ginsenosides. Significant amounts of secondary ginsenosides (F2 and C-K) were found in blood of A/J mice following oral administration of primary ginsenoside Rb1. Because mammalian cells did not hydrolyze ginsenoside, we determined the ability of bacteria to hydrolyze ginsenosides and found that Rb1 underwent stepwise hydrolysis to Rd, F2, and then C-K. Formation of F2 from Rd was the rate-limiting step in the biotransformation of Rb1 to C-K.

CONCLUSION

Conversion to F2 is the rate-limiting step in bioactivation of primary ginsenosides by A/J mouse intestinal microbiome, whose characterization reveals the presence of certain bacterial families capable of enabling the formation of F2 and C-K in vivo.

Anticancer effects of 3,3'-diindolylmethane are associated with G1 arrest and mitochondria-dependent apoptosis in human nasopharyngeal carcinoma cells

The antitumor effects of 3,3′-diindolylmethane (DIM) are exhibited in a number of human cancer cells. However, there have been few studies performed concerning the effect of DIM on nasopharyngeal cancer (NPC) cells. In the present study, we examined the in vitro antitumor activity of DIM on the poorly differentiated NPC cell line CNE-2. The potential molecular mechanisms of the activity were also explored. CNE-2 cells were treated with varying concentrations of DIM for different times. Cell proliferation and apoptosis were detected and the molecular mechanisms involved in these effects were characterized. The results demonstrated that DIM at concentrations of 15–100 μM caused dose- and time-dependent inhibition of CNE-2 cell proliferation. Flow cytometry analysis revealed a high sub-G1 cell peak following treatment with DIM, and the rate of apoptosis increased. DIM may elevate the levels of cleaved Bid and Bax and enhance mitochondrial membrane depolarization, allowing the efflux of cytochrome c, Smac and Omi into the cytosol. The levels of caspases-3, -8 and -9 and cleaved poly (ADP-ribose) polymerase (PARP) were upregulated following DIM treatment in a dose-dependent manner. DIM also inhibits the phosphorylation of IκB-α, and showed dose-dependent inhibition of Bcl-2, XIAP and NF-κB in CNE-2 cells in vitro. These results indicate that DIM inhibits cell proliferation by inducing cell cycle arrest at G0/G1 phase and induces the apoptosis of CNE-2 cells by regulating multiple molecules in a mitochondria-dependent pathway. DIM may be a preventive and therapeutic agent against NPC.

Associations between flavonoids and cardiovascular disease incidence or mortality in European and US populations

Twenty publications from twelve prospective cohorts have evaluated associations between flavonoid intakes and incidence or mortality from cardiovascular disease (CVD) among adults in Europe and the United States. The most common outcome was coronary heart disease mortality, and four of eight cohort studies reported significant inverse associations for at least one flavonoid class (multivariate adjusted p(trend) < 0.05). Three of seven cohorts reported that greater flavonoid intake was associated with lower risk of incident stroke. Comparisons among the studies were difficult because of variability in the flavonoid classes included, demographic characteristics of the populations, outcomes assessed, and length of follow-up. The most commonly examined flavonoid classes were flavonols and flavones combined (11 studies). Only one study examined all seven flavonoid classes. The flavonol and flavone classes were most strongly associated with lower coronary heart disease mortality. Evidence for protection from other flavonoid classes and CVD outcomes was more limited. The hypothesis that flavonoid intakes are associated with lower CVD incidence and mortality requires further study.

Antiproliferative effects of artemisinin on human breast cancer cells requires the downregulated expression of the E2F1 transcription factor and loss of E2F1-target cell cycle genes

Artemisinin, a sesquiterpene phytolactone derived from Artemisia annua, is a potent antimalarial compound with promising anticancer properties, although the mechanism of its anticancer signaling is not well understood. Artemisinin inhibited proliferation and induced a strong G1 cell cycle arrest of cultured MCF7 cells, an estrogen-responsive human breast cancer cell line that represents an early-stage cancer phenotype, and effectively inhibited the in-vivo growth of MCF7 cell-derived tumors from xenografts in athymic nude mice. Artemisinin also induced a growth arrest of tumorigenic human breast cancer cell lines with preneoplastic and late stage cancer phenotypes, but failed to arrest the growth of a nontumorigenic human mammary cell line. Concurrent with the cell cycle arrest of MCF7 cells, artemisinin selectively downregulated the transcript and protein levels of the CDK2 and CDK4 cyclin-dependent kinases, cyclin E, cyclin D1, and the E2F1 transcription factor. Analysis of CDK2 promoter-luciferase reporter constructs showed that the artemisinin ablation of CDK2 gene expression was accounted for by the loss of CDK2 promoter activity. Chromatin immunoprecipitation revealed that artemisinin inhibited E2F1 interactions with the endogenous MCF7 cell CDK2 and cyclin E promoters. Moreover, constitutive expression of exogenous E2F1 prevented the artemisinin-induced cell cycle arrest and downregulation of CDK2 and cyclin E gene expression. Taken together, our results demonstrate that the artemisinin disruption of E2F1 transcription factor expression mediates the cell cycle arrest of human breast cancer cells and represents a critical transcriptional pathway by which artemisinin controls human reproductive cancer cell growth.

Dietary intake of rosmarinic acid by Apc(Min) mice, a model of colorectal carcinogenesis: levels of parent agent in the target tissue and effect on adenoma development

SCOPE

Rosmarinic acid (RA), a constituent of culinary herbs is considered to possess cancer chemopreventive properties. It has been shown to inhibit the development of cancer in preclinical models but data are conflicting and whether it can protect against gastrointestinal malignancies in vivo has not been examined. This study aimed to investigate the effect of RA on the development of intestinal adenomas in the Apc(Min) mouse model of colorectal carcinogenesis, and to correlate efficacy with levels of RA achieved in the plasma and gastrointestinal tract.

METHODS AND RESULTS

RA inhibited the growth of APC10.1 cells derived from Apc(Min) mouse adenomas, with an IC₅₀ of 43 μM. Consumption of dietary RA (0.3%) by Apc(Min) mice for 8 weeks post weaning decreased adenoma burden by ∼35%, but the difference from controls was not significant. Although RA significantly decreased the frequency of large adenomas, the number of small ones increased. Using a novel validated HPLC assay, average levels of RA in the plasma and intestinal mucosa of these mice were found to be 1.1 μM and 38 nmol/g, respectively.

CONCLUSION

Chronic consumption of RA furnished quantifiable levels of parent compound in the plasma and intestinal tract of Apc(Min) mice and may slow adenoma development.

The dietary phytochemical 3,3'-diindolylmethane induces G2/M arrest and apoptosis in oral squamous cell carcinoma by modulating Akt-NF-κB, MAPK, and p53 signaling

In light of the growing incidence of oral cancer in Taiwan, this study is aimed at investigating the antitumor activity of 3,3'-diindolylmethane (DIM), an active metabolite of the phytochemical indole-3-carbinol (I3C), in oral squamous cell carcinoma (OSCC). DIM exhibited substantially higher antiproliferative potency than I3C in three OSCC cell lines with IC(50) values in SCC2095, SCC9, and SCC15 cells, respectively, of 22 versus 168μM, 25 versus 176μM, and 29versus 300μM. Flow cytometric analysis and Comet assay indicated that DIM suppressed the viability of SCC2095 cells by inducing apoptosis and G2/M arrest. Western blot analysis of various signaling markers revealed the ability of DIM to target pathways mediated by Akt, mitogen-activated protein (MAP) kinases, nuclear factor (NF)-κB, and p53, of which the concerted action underlined its antitumor efficacy. The concomitant inactivation of Akt and MAP kinases in response to DIM facilitated the dephosphorylation of the proapoptotic protein Bad at Ser-136 and Ser-112, respectively. Through endoplasmic reticulum (ER) stress, DIM stimulated the activation of p53 via Ser-15 phosphorylation, leading to increased expression of the BH3-only proapoptotic Bcl-2 members Puma and Noxa. Together, these changes decreased the mitochondrial threshold for apoptosis. G2/M arrest might be attributable to the suppressive effect of DIM on the expression of cyclin B1 and cdc25c. As many downstream effectors of the Akt-NF-κB pathway, including glycogen synthase kinase 3β, IκB kinase α, and cyclooxygenase-2, have been shown to promote oral tumorigenesis, the ability of DIM to inhibit this signaling axis underscores its chemopreventive potential in oral cancer.

Molecular pathways for cancer chemoprevention by dietary phytochemicals

Interest in dietary phytochemicals for potential cancer chemoprevention has increased substantially. Screening dietary compounds for chemopreventive activity however, requires a systematic and wide-ranging approach to encompass the complexity of carcinogenesis. We present some of the molecular pathways that underpin the broad biological processes involved in carcinogenesis. Oxidative stress, inflammation, and the evasion of apoptosis are important biological mechanisms by which carcinogenesis occurs. Subsequently, antioxidant, anti-inflammatory, and pro-apoptotic activity represent important activities for preventing, suppressing, or reversing the development of carcinogenesis. Ultimately, these mechanisms of action may provide a useful basis for screening novel phytochemicals for chemopreventive activity. In this review, we identify the important molecular processes that may be targeted in routine screenings of dietary phytochemicals to ultimately select the most effective potential candidates for cancer chemoprevention.

Phytochemicals and colorectal cancer prevention--myth or reality?

Chemoprevention of colorectal cancer has been the focus of intensive research for more than two decades. Epidemiological evidence has shown a small, but significant association between fruit and vegetable intake and a reduction in colorectal cancer risk. In vitro and animal data have also demonstrated that many dietary phytochemicals have potent chemopreventive activities. However, in humans, single-agent compounds have yielded conflicting results. A key concept is that dietary phytochemicals exert beneficial effects at low concentrations when working in synergy with each other. As the gut microflora evolved in an environment rich in dietary fiber and phytochemicals, the rapid shift towards a Western diet creates an environment in which the gut is more vulnerable to carcinogens, genetic alterations and inflammation. As enforcing dietary interventions on large populations is not realistic, we believe future chemopreventive work should focus on delivering phytochemical mixtures that target the multiple molecular events involved in colorectal carcinogenesis.

Clinical trials of antioxidants as cancer prevention agents: past, present, and future

The purpose of this review is to summarize the most important human clinical trials of antioxidants as cancer prevention agents conducted to date, provide an overview of currently ongoing studies, and discuss future steps needed to advance research in this field. To date there have been several large (at least 7000 participants) trials testing the efficacy of antioxidant supplements in preventing cancer. The specific agents (diet-derived direct antioxidants and essential components of antioxidant enzymes) tested in those trials included β-carotene, vitamin E, vitamin C, selenium, retinol, zinc, riboflavin, and molybdenum. None of the completed trials produced convincing evidence to justify the use of traditional antioxidant-related vitamins or minerals for cancer prevention. Our search of ongoing trials identified six projects at various stages of completion. Five of those six trials use selenium as the intervention of interest delivered either alone or in combination with other agents. The lack of success to date can be explained by a variety of factors that need to be considered in the next generation research. These factors include lack of good biological rationale for selecting specific agents of interest; limited number of agents tested to date; use of pharmacological, rather than dietary, doses; and insufficient duration of intervention and follow-up. The latter consideration underscores the need for alternative endpoints that are associated with increased risk of neoplasia (i.e., biomarkers of risk), but are detectable prior to tumor occurrence. Although dietary antioxidants are a large and diverse group of compounds, only a small proportion of candidate agents have been tested. In summary, the strategy of focusing on large high-budget studies using cancer incidence as the endpoint and testing a relatively limited number of antioxidant agents has been largely unsuccessful. This lack of success in previous trials should not preclude us from seeking novel ways of preventing cancer by modulating oxidative balance. On the contrary, the well demonstrated mechanistic link between excessive oxidative stress and carcinogenesis underscores the need for new studies. It appears that future large-scale projects should be preceded by smaller, shorter, less expensive biomarker-based studies that can serve as a link from mechanistic and observational research to human cancer prevention trials. These relatively inexpensive studies would provide human experimental evidence for the likely efficacy, optimum dose, and long-term safety of the intervention of interest that would then guide the design of safe, more definitive large-scale trials.

Curcumin suppresses growth of mesothelioma cells in vitro and in vivo, in part, by stimulating apoptosis

Malignant pleural mesothelioma (MPM) is an aggressive, asbestos-related malignancy of the thoracic pleura. Although, platinum-based agents are the first line of therapy, there is an urgent need for second-line therapies to treat the drug-resistant MPM. Cell cycle as well as apoptosis pathways are frequently altered in MPM and thus remain attractive targets for intervention strategies. Curcumin, the major component in the spice turmeric, alone or in combination with other chemotherapeutics has been under investigation for a number of cancers. In this study, we investigated the biological and molecular responses of MPM cells to curcumin treatments and the mechanisms involved. Flow-cytometric analyses coupled with western immunoblotting and gene-array analyses were conducted to determine mechanisms of curcumin-dependent growth suppression of human (H2373, H2452, H2461, and H226) and murine (AB12) MPM cells. Curcumin inhibited MPM cell growth in a dose- and time-dependent manner while pretreatment of MPM cells with curcumin enhanced cisplatin efficacy. Curcumin activated the stress-activated p38 kinase, caspases 9 and 3, caused elevated levels of proapoptotic proteins Bax, stimulated PARP cleavage, and apoptosis. In addition, curcumin treatments stimulated expression of novel transducers of cell growth suppression such as CARP-1, XAF1, and SULF1 proteins. Oral administration of curcumin inhibited growth of murine MPM cell-derived tumors in vivo in part by stimulating apoptosis. Thus, curcumin targets cell cycle and promotes apoptosis to suppress MPM growth in vitro and in vivo. Our studies provide a proof-of-principle rationale for further in-depth analysis of MPM growth suppression mechanisms and their future exploitation in effective management of resistant MPM.

Dietary fish oil promotes colonic apoptosis and mitochondrial proton leak in oxidatively stressed mice

An alteration of mitochondrial function can result in disruption of redox homeostasis and is associated with abnormal cancer cell growth. Manganese superoxide dismutase (SOD2) and glutathione peroxidase 4 (Gpx4) are two of the most important antioxidant defense enzymes that protect cells against oxidative stress. We had previously shown that n-3 polyunsaturated fatty acids (PUFA) promote colonocyte apoptosis, a marker of colon cancer risk, in part by enhancing phospholipid oxidation. To elucidate the mechanisms regulating oxidative stress-induced apoptosis in vivo, we fed heterozygous SOD2(Het), Gpx4(Het), and transgenic Gpx4(Tg) mice diets containing either 15% corn oil by weight (CO, enriched in n-6 PUFA) or 3.5% CO + 11.5% fish oil (FO, enriched in n-3 PUFA) for 4 weeks. Our data showed that (i) genetic predeposition to oxidative stress facilitates apoptosis in the mouse colon (Gpx4(Het) > SOD2(Het) > Wt > Gpx4(Tg)), (ii) dietary n-3 PUFA have an additive effect on the induction of apoptosis in Gpx4(Het) and SOD2(Het) mice; and (iii) dietary n-3 PUFA reverse the phenotype in oxidatively protected Gpx4(Tg) mice by elevating apoptosis to a level observed in wild-type (Wt; control) animals. Complimentary experiments examining colonic mitochondrial bioenergetic profiles indicate that FO-fed mice exhibit a significantly (P < 0.05) increased respiration-induced proton leak relative to control CO treatment. This finding was consistent with a loss of membrane potential in response to chronic oxidative stress and supports the contention that n-3 PUFA alter mitochondrial metabolic activity, thereby enhancing apoptosis and reducing colon cancer risk.

Clinical trials of resveratrol

An expanding body of preclinical evidence suggests resveratrol has the potential to impact a variety of human diseases. To translate encouraging experimental findings into human benefits, information is first needed on the safety, pharmacokinetics, pharmacodynamics, and, ultimately, clinical efficacy of resveratrol. Published clinical trials have largely focused on characterizing the pharmacokinetics and metabolism of resveratrol. Recent studies have also evaluated safety and potential mechanisms of activity following multiple dosing, and have found resveratrol to be safe and reasonably well-tolerated at doses of up to 5 g/day. However, the occurrence of mild to moderate side effects is likely to limit the doses employed in future trials to significantly less than this amount. This review describes the available clinical data, outlines how it supports the continuing development of resveratrol, and suggests what additional information is needed to increase the chances of success in future clinical trials.

Concurrent Sulforaphane and Eugenol Induces Differential Effects on Human Cervical Cancer Cells

Background. The concept of combination of chemoprevention holds great potential for cancer management as lower, clinically tolerable doses of individual agents could be achieved through therapeutic synergy. However, elucidation of their possible interactions—additive, synergistic, or antagonistic—must be thoroughly studied before considering for clinical use. Methods. To evaluate the effect of combination treatment of sulforaphane (SFN) and eugenol on HeLa cells, the authors performed cell viability assay, apoptosis assay, and reverse transcription polymerase chain reaction for gene expression analysis. Calculations of combination effects were expressed as a combination index (CI) with CI < 1, CI = 1, or CI > 1 representing synergism, additivity, or antagonism, respectively. Results. Simultaneous treatment with variable dose combinations of SFN and eugenol resulted in differential effects with an antagonistic effect at lower and synergistic at higher sub-lethal doses as reflected in cell cytotoxicity and apoptosis induction. Importantly, gemcitabine used in conjunction with the low- and high-dose combinations showed no significant cell death at lower doses suggesting that cell cytotoxicity is proportional to gemcitabine alone, whereas at higher sublethal doses of SFN and eugenol, it was found to act in a synergistic manner with gemcitabine. Furthermore, SFN and eugenol combinations at synergistic dose significantly downregulated the expression of Bcl-2, COX-2 and IL-β but not the antagonistic combinations. Conclusion. This study clearly indicates that 2 (or more) chemopreventive agents can act antagonistically or synergistically necessitating elucidation of possible mechanistic interactions for favorable and reliable outcomes of dietary components in the field of cancer prevention.

Salvianolic Acid B, a potential chemopreventive agent, for head and neck squamous cell cancer

Head and neck squamous cell cancer (HNSCC) is one of the top ten cancers in the United States. The survival rate of HNSCC has only marginally improved over the last two decades. In addition, African-American men bear a disproportionate burden of this preventable disease. Therefore, a critical challenge of preventive health approaches is warranted. Salvianolic acid B (Sal-B) isolated from Salvia miltiorrhiza Bge, which is a well-know Chinese medicines has been safely used to treat and prevent aging diseases for thousand of years. Recently, the anticancer properties of Sal-B have received more attention. Sal-B significantly inhibits or delays the growth of HNSCC in both cultured HNSCC cells and HNSCC xenograft animal models. The following anticancer mechanisms have been proposed: the inhibition of COX-2/PGE-2 pathway, the promotion of apoptosis, and the modulation of angiogenesis. In conclusion, Sal-B is a potential HNSCC chemopreventive agent working through antioxidation and anti-inflammation mechanisms.

Apigenin: a promising molecule for cancer prevention

Apigenin, a naturally occurring plant flavone, abundantly present in common fruits and vegetables, is recognized as a bioactive flavonoid shown to possess anti-inflammatory, antioxidant and anticancer properties. Epidemiologic studies suggest that a diet rich in flavones is related to a decreased risk of certain cancers, particularly cancers of the breast, digestive tract, skin, prostate and certain hematological malignancies. It has been suggested that apigenin may be protective in other diseases that are affected by oxidative process, such as cardiovascular and neurological disorders, although more research needs to be conducted in this regard. Human clinical trials examining the effect of supplementation of apigenin on disease prevention have not been conducted, although there is considerable potential for apigenin to be developed as a cancer chemopreventive agent.