Potential role of flavonoids in the prevention of intestinal neoplasia: a review of their mode of action and their clinical perspectives

Effect of a Flavonoid Combination of Apigenin and Epigallocatechin-3-Gallate on Alleviating Intestinal Inflammation in Experimental Colitis Models

Inflammatory bowel disease (IBD) is an autoimmune disease that leads to severe bowel symptoms and complications. Currently, there is no effective treatment, and the exact cause of IBD remains unclear. In the last decades, numerous studies have confirmed that flavonoids can have a positive impact on the treatment of IBD. Therefore, this study investigated the protective effect of a flavonoid combination of apigenin and epigallocatechin-3-gallate (EGCG) on IBD. In vitro studies in which Caco-2 cell monolayers were incubated with different concentrations of flavonoids found that the flavonoid-treated group exhibited increased transepithelial electrical resistance (TEER) at high concentrations, indicating a protective effect on the barrier function of the intestinal epithelium. In vivo studies showed that flavonoids significantly attenuated inflammatory levels in both chronic and acute hapten-mediated experimental colitis models in a time- and dose-dependent manner. In addition, the activity of myeloperoxidase (MPO) and the level of proinflammatory cytokines in the colon tissue were significantly reduced. Interestingly, the levels of anti-inflammatory cytokines were also dramatically increased. Finally, flavonoids were found to positively modulate the composition of the gut microbiota in the colon. Therefore, a combination of flavonoids could be a promising therapeutic agent for the future adjunctive treatment of IBD.

Targeting lipid metabolism with natural products: A novel strategy for gastrointestinal cancer therapy

Gastrointestinal cancer (GIC), including gastric cancer and colorectal cancer, is a common malignant tumor originating from gastrointestinal epithelial cells. Although the pathogenesis of GIC remains unclear, aberrant lipid metabolism has emerged as a hallmark of cancer. Several enzymes, proteins, and transcription factors are involved in lipid metabolism reprogramming in GIC, and their abnormal expression can promote lipid synthesis and accumulation of lipid droplets through numerous mechanisms, thereby affecting the growth, proliferation, and metastasis of GIC cells. Studies show that some natural compounds, including flavonoids, alkaloids, and saponins, can inhibit the de novo synthesis of lipids in GIC, reduce the level of lipid accumulation, and subsequently, inhibit the occurrence and development of GIC by regulating Sterol regulatory element-binding protein 1 (SREBP-1), adenosine monophosphate-activated protein kinase (AMPK), 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), phosphatidylinositol-3-kinase/Akt and the mammalian target of rapamycin PI3K/Akt/mTOR, amongst other targets and pathways. Therefore, targeting tumor lipid metabolism is the focus of anti-gastrointestinal tumor therapy. Although most natural products require further high-quality studies to firmly establish their clinical efficacy, we review the potential of natural products in the treatment of GIC and summarize the application prospect of lipid metabolism as a new target for the treatment of GIC, hoping to provide a reference for drug development for gastrointestinal tumors.

The influence of dietary vegetables and fruits on endometrial cancer risk: a meta-analysis of observational studies

Fruits and vegetables store many bioactive compounds and micronutrients, making their consumption ideal for maintaining good health. A previous meta-analysis in 2007 provided evidence that high vegetable and cruciferous vegetable intake might help prevent endometrial cancer (EC) development. The current study purposely explored the favorable effects of vegetables, fruits, and their other specific types using a review of the most recent papers. We conducted a systematic search through August 2021 in the PubMed and EMBASE databases on this topic, through which twenty-seven studies, consisting of 21 case-control and 6 cohort studies, were obtained. The results showed that vegetables (pooled odds ratio [OR], relative risk [RR], hazard ratio [HR] = 0.76, 95% confidence interval [CI] 0.63-0.91), cruciferous vegetables (pooled OR = 0.81, 95% CI 0.70-0.94), dark green and yellow/orange combined vegetables (pooled OR = 0.64, 95% CI 0.42-0.97), and fruits (pooled OR = 0.81, 95% CI 0.70-0.92) were strongly associated with a reduced risk of EC. These results were primarily based on studies of high quality and exhibited either by case-control only or a combination of case-control and cohort studies. Additionally, the results varied by geographic location, such as Western areas, the US, and Italy. This meta-analysis suggested that the consumption of fruits and vegetables has beneficial effects on EC risk and that specific kinds of fruits and vegetables should be recommended differently due to their outstanding bioactive components.

Supercritical Carbon Dioxide Extracts of Cordyceps sinensis: Chromatography-based Metabolite Profiling and Protective Efficacy Against Hypobaric Hypoxia

The toxicity and disposal concerns of organic solvents used in conventional extraction purposes has entailed the need for greener alternatives. Among such techniques, supercritical fluid extraction (SFE) has gained popularity by yielding extracts of high purity in a much faster manner. Carbon dioxide (CO₂) is generally preferred as a supercritical solvent because of its lower temperature requirements, better diffusivity and easy removal. The present study describes the characterization of supercritical CO₂ extracts of Indian variety of Cordyceps sinensis (CS)- a high-altitude medicinal mushroom widely revered in traditional medicine for its extensive anti-hypercholesterolemic, anti-inflammatory, anti-proliferative and energy-enhancing properties. Experimental parameters viz. 300 and 350 bar of extraction pressure, 60°C of temperature, 0.4°L/h CO₂ of flow rate and use of 1% (v/v) of ethanol as entrainer were optimized to prepare three different extracts namely, CSF1, CSF2 and CSF3. High-performance thin-layer chromatography (HPTLC) was used for assessing the quality of all the extracts in terms of cordycepin, the pivot biomarker compound in CS. Characterization by HPTLC and GC-MS confirmed the presence of flavonoids and nucleobases and, volatile organic compounds (VOCs), respectively. The chromatographic data acquired from metabolite profiling were subjected to chemometric analysis in an open source R studio which illustrated interrelatedness between CSF1 and CSF2 in terms of two major principal components. i.e. Dim 1 and Dim 2 whose values were 40.33 and 30.52% in variables factor map plotted using the HPTLC-generated retardation factor values. The factor maps based on retention times of the VOCs exhibited a variance of Dim 1 = 43.95% and Dim 2 = 24.85%. Furthermore, the extracts demonstrated appreciable antibacterial activity against Escherichia coli and Salmonella typhi by generation of reactive oxygen species (ROS), protein leakage and efflux pump inhibition within bacterial pathogens. CSFs were elucidated to be significantly cytoprotective (p < 0.05) in a simulated hypobaric hypoxia milieu (0.5% oxygen). CSF2 showed the best results by effectively improving the viability of human embryonic kidney (HEK 293) cells to 82.36 ± 1.76% at an optimum dose of 100 µg/ml. Levels of hypoxia inducible factor-1 alpha (HIF-1α) were modulated four-fold upon supplementation with CSF2. The results collectively evinced that the CSF extracts are substantially bioactive and could be effectively utilized as mycotherapeutics for multiple bioeffects.

Characterizing Demographic and Geographical Differences in Health Beliefs and Dietary Habits Related to Colon Cancer Risk in US Adults

Background: Colon cancer (CC) risk is increased by behavioral factors including a diet high in red meat (RM) and processed meat; excess adiposity has contributed to a rise in CC in younger adults. The willingness of at-risk adults to modify behaviors to reduce CC risk warrants further investigation.

Methods: The previously validated Dietary Habits and Colon Cancer Beliefs Survey (DHCCBS) was used to assess attitudes and beliefs related to CC risk and diet behavior. An abbreviated food frequency questionnaire was included in the survey to quantify RM and green leafy vegetable (GLV) intake over the previous 30 days. Independent samples t-tests compared RM and GLV intake and DHCCBS responses. One-way analysis of variance with post-hoc LSD correction was completed to assess these differences within three age groups (<35, 35–44, and 45–54 years old) and between U.S. Census Bureau geographical regions.

Results: Eight hundred and thirty eight survey responses were analyzed. Perceived severity of CC diagnosis was significantly lower in younger adults (<35) compared to older adults (35–44, p = 0.042; 45–54, p = 0.003). Furthermore, younger adults (<35) perceived fewer barriers (i.e., taste preference) to GLV consumption than their older adult counterparts (35–44, p = 0.019; 45–54, p = 0.002). Few regional differences in habitual RM consumption were observed, however, several disparities were observed with GLV.

Conclusion: These findings from the DHCCBS indicate health beliefs toward CC risk are influenced by an individual's age and dietary habits. Additionally, regional differences in GLV consumption indicate opportunities for risk-reduction-focused health messages, particularly in the southern United States where CC incidence and mortality are highest.

Regulation of the intestinal immune system by flavonoids and its utility in chronic inflammatory bowel disease

Flavonoids are phytochemicals which can regulate the activity of the intestinal immune system. In patients with chronic inflammatory bowel disease (IBD) there is an overexpression and imbalance of the components of the inflammatory immune reactions which are chronically activated. Suppression of inflammation can be achieved by anti-inflammatory drugs which are used in clinical medicine but these can cause serious side effects. Flavonoids can have natural immunosuppressive properties and inhibit the activation of immune cells and its effectors (chemokines, TNF-, cytokines). Phytochemicals such as flavonoids bind to the nuclear Ah (aryl hydrocarbon) -receptor thereby stimulating protective enzyme activities. As shown by clinical evidence in patients and by experimental work some flavonoids (apigenin, epigallocatechin gallate) were effective in the inhibition of inflammation. Instead of or additionally to anti-inflammatory drugs flavonoids can be used in IBD patients to treat the over-reactive immunologic system. This is accomplished by upregulation of the Ah-receptor. Flavonoids interact with toll-like receptors expressing on the surface of immune cells, then they were internalized to the cytosol and transferred into the nucleus, where they were attached to the Ah-receptor. The Ah-receptor binds to the Ah-R nuclear translocator and via Ah response element beneficial protective enzymes and cytokines are induced, leading to upregulation of the anti-inflammatory system.

Intake of Individual Flavonoids and Risk of Carcinogenesis: Overview of Epidemiological Evidence

Several epidemiological findings have demonstrated that specific flavonoids can be responsible for reduction of the risk of certain cancer types. However, these results are still rather limited, inconclusive and controversial. Therefore, in this comprehensive review article the findings reported to date about the associations between dietary intake of individual flavonoid compounds and cancer incidence are compiled and analyzed. Also, the possible reasons for inconsistencies are brought forth and discussed. As diet is a potentially modifiable factor in our behavioral choices, further large-scale prospective studies with longer follow-up times, different populations, various doses and exposure timing as well as diverse well-controlled confounders are highly needed to confirm or disprove the current epidemiological knowledge about the role of flavonoids on cancer risk. Regarding the promising data to date, more research on bioavailability, metabolism and biological action mechanisms of these plant secondary metabolites is also encouraged.

Dietary Flavonoids, CYP1A1 Genetic Variants, and the Risk of Colorectal Cancer in a Korean population

The role of dietary flavonoid intake in colorectal carcinogenesis might differ according to flavonoid subclasses and individual genetic variants related to carcinogen metabolism. Therefore, we examined whether greater dietary intake of flavonoid subclasses was associated with a lower risk of colorectal cancer and whether CYP1A1 genetic variants altered this association. A semi-quantitative food frequency questionnaire was used to assess the dietary intake of six flavonoid subclasses (flavonols, flavones, flavanones, flavan-3-ols, anthocyanidins, and isoflavones) in 923 patients with colorectal cancer and 1,846 controls; furthermore, CYP1A1 genetic variants (rs4646903 and rs1048943) were genotyped. Among the subclasses of flavonoids, higher intake of flavonols and flavan-3-ols showed a stronger association with a reduced risk of colorectal cancer after adjusting for potential confounding factors. Carriers of the CYP1A1 rs4646903 CC homozygous variant showed a reduced risk of rectal cancer compared with that in TT carriers. The inverse association between dietary flavonol intake and colorectal cancer risk was stronger among carriers of the CC homozygous variant than among T allele carriers (P for interaction = 0.02), particularly for rectal cancer (P for interaction = 0.005). In conclusion, the effect of dietary flavonoid intake on colorectal cancer risk differs according to flavonoid subclasses and CYP1A1 genetic variants.

Iberis amara Extract Induces Intracellular Formation of Reactive Oxygen Species and Inhibits Colon Cancer

Massively increasing global incidences of colorectal cancer require efficient treatment and prevention strategies. Here, we report unexpected anticancerogenic effects of hydroethanolic Iberis amara extract (IAE), which is known as a widely used phytomedical product for treating gastrointestinal complaints. IAE significantly inhibited the proliferation of HT-29 and T84 colon carcinoma cells with an inhibitory concentration (IC₅₀) of 6 and 9 μg/ml, respectively, and further generated inhibitory effects in PC-3 prostate and MCF7 breast cancer cells. Inhibition of proliferation in HT-29 cells was associated with a G2/M phase cell cycle arrest including reduced expression of various regulatory marker proteins. Notably, in HT-29 cells IAE further induced apoptosis by intracellular formation of reactive oxygen species (ROS). Consistent with predictions derived from our in vitro experiments, bidaily oral gavage of 50 mg/kg of IAE over 4 weeks resulted in significant inhibition of tumor growth in a mouse HT-29 tumor xenograft model. Taken together, Iberis amara extracts could become useful alternatives for preventing and treating the progression of colon cancer.

Kaempferol Induces Cell Cycle Arrest in HT-29 Human Colon Cancer Cells

Background:

A greater intake of vegetables and fruits has been linked to a reduced incidence of colon cancer. Flavonoids are polyphenolic compounds which are broadly distributed in fruits and vegetables and display a remarkable spectrum of physiological activities, including anti-carcinogenic effects. The objective of this study was to determine the mechanisms by which kaempferol, a flavonol present in tea, apples, strawberries, and beans, inhibits the growth of HT-29 human colon cancer cells.

Methods:

To examine the effects of kaempferol on cell cycle progression in HT-29 cells, cells were treated with various concentrations (0–60 μmol/L) of kaempferol. Cell proliferation and DNA synthesis were evaluated by MTT assay and [³H]thymidine incorporation assay, respectively. Fluorescence-activated cell sorting analyses were conducted to calculate cell cycle phase distribution. Western blot analyses and in vitro kinase assays were used to estimate the expression of proteins involved in the regulation of cell cycle progression and the activity of cyclin-dependent kinase (CDK)s, respectively.

Results:

Kaempferol decreased viable cell numbers and [³H]thymidine incorporation into DNA of HT-29 cells in a dose-dependent manner. Kaempferol induced G1 cell cycle arrest within 6 h and G2/M arrest at 12 h. Kaempferol inhibited the activity of CDK2 and CDK4 as well as the protein expression of CDK2, CDK4, cyclins D1, cyclin E, and cyclin A, and suppressed the phosphorylation of retinoblastoma protein. Additionally, kaempferol decreased the levels of Cdc25C, Cdc2, and cyclin B1 proteins, as well as the activity of Cdc2.

Conclusions:

The present results indicate that kaempferol induces G1 and G2/M cell cycle arrest by inhibiting the activity of CDK2, CDK4, and Cdc2. The induction of cell cycle arrest may be one of the mechanisms by which kaempferol exerts anti-carcinogenic effects in colon cancer cells.

Kaempferol Downregulates Insulin-like Growth Factor-I Receptor and ErbB3 Signaling in HT-29 Human Colon Cancer Cells

BACKGROUND

Novel dietary agents for colon cancer prevention and therapy are desired. Kaempferol, a flavonol, has been reported to possess anticancer activity. However, little is known about the molecular mechanisms of the anticancer effects of kaempferol. The aim of this study was to determine the inhibitory effect of kaempferol on growth factor-induced proliferation and to elucidate its underlying mechanisms in the HT-29 human colon cancer cell line.

METHODS

To assess the effects of kaempferol and/or growth factors [insulin-like growth factor (IGF)-I and heregulin (HRG)-β], cells were cultured with or without 60 μmol/L kaempferol and/or 10 nmol/L IGF-I or 20 μg/L HRG-β. Cell proliferation, DNA synthesis, and apoptosis were determined by a cell viability assay, a [(3)H]thymidine incorporation assay, and Annexin-V staining, respectively. Western blotting, immunoprecipitation, and an in vitro kinase assay were conducted to evaluate expression and activation of various signaling molecules involved in the IGF-I receptor (IGF-IR) and ErbB3 signaling pathways.

RESULTS

IGF-I and HRG-β stimulated HT-29 cell growth but did not abrogate kaempferol-induced growth inhibition and apoptosis. Kaempferol reduced IGF-II secretion, HRG expression and phosphorylation of Akt and extracellular signal-regulated kinase (ERK)-1/2. Kaempferol reduced IGF-I- and HRG-β-induced phosphorylation of the IGF-IR and ErbB3, their association with p85, and phosphatidylinositol 3-kinase (PI3K) activity. Additionally, kaempferol inhibited IGF-I- and HRG-β-induced phosphorylation of Akt and ERK-1/2.

CONCLUSIONS

The results demonstrate that kaempferol downregulates activation of PI3K/Akt and ERK-1/2 pathways by inhibiting IGF-IR and ErbB3 signaling in HT-29 cells. We suggest that kaempferol could be a useful chemopreventive agent against colon cancer.

Kaempferol Downregulates Insulin-like Growth Factor-I Receptor and ErbB3 Signaling in HT-29 Human Colon Cancer Cells

Background:

Novel dietary agents for colon cancer prevention and therapy are desired. Kaempferol, a flavonol, has been reported to possess anticancer activity. However, little is known about the molecular mechanisms of the anticancer effects of kaempferol. The aim of this study was to determine the inhibitory effect of kaempferol on growth factor-induced proliferation and to elucidate its underlying mechanisms in the HT-29 human colon cancer cell line.

Methods:

To assess the effects of kaempferol and/or growth factors [insulin-like growth factor (IGF)-I and heregulin (HRG)-β], cells were cultured with or without 60 μmol/L kaempferol and/or 10 nmol/L IGF-I or 20 μg/L HRG-β. Cell proliferation, DNA synthesis, and apoptosis were determined by a cell viability assay, a [³H]thymidine incorporation assay, and Annexin-V staining, respectively. Western blotting, immunoprecipitation, and an in vitro kinase assay were conducted to evaluate expression and activation of various signaling molecules involved in the IGF-I receptor (IGF-IR) and ErbB3 signaling pathways.

Results:

IGF-I and HRG-β stimulated HT-29 cell growth but did not abrogate kaempferol-induced growth inhibition and apoptosis. Kaempferol reduced IGF-II secretion, HRG expression and phosphorylation of Akt and extracellular signal-regulated kinase (ERK)-1/2. Kaempferol reduced IGF-I- and HRG-β-induced phosphorylation of the IGF-IR and ErbB3, their association with p85, and phosphatidylinositol 3-kinase (PI3K) activity. Additionally, kaempferol inhibited IGF-I- and HRG-β-induced phosphorylation of Akt and ERK-1/2.

Conclusions:

The results demonstrate that kaempferol downregulates activation of PI3K/Akt and ERK-1/2 pathways by inhibiting IGF-IR and ErbB3 signaling in HT-29 cells. We suggest that kaempferol could be a useful chemopreventive agent against colon cancer.

Chemopreventive properties of raisins originating from Greece in colon cancer cells

Colorectal cancer is one of the major causes of cancer-related mortality in humans in both developed and developing countries. Dietary patterns influence the risk of colon cancer development, while plant-derived foods have gained great interest, due to the high content of antioxidants. Corinthian raisins (Currants, CR) and Sultanas (S) (Vitis vinifera L., Vitaceae) are dried vine fruits produced in Greece with many culinary uses in both the Mediterranean and the Western nutrition. In the present study, we investigated the effects of CR and S on human colon cancer cells. Methanol extracts of CR and S were used at different concentrations. The total polyphenol content and anti-radical activity were measured by Folin-Ciocalteu and DPPH, respectively. Antioxidant, anti-inflammatory and anti-proliferative effects on HT29 cell culture were evaluated. All extracts exhibited DPPH˙ scavenging activity in a dose-dependent manner. Both products suppressed cell proliferation, while the levels of glutathione and cyclooxygenase 2 were significantly decreased. A significant reduction in IL-8 levels and NF-kappaB p65 activation was also observed. Both antioxidant and anti-inflammatory effects were dependent on the duration of exposure. Results indicate that the methanol extracts of CR and S exhibit anti-radical activity in vitro, as well as cancer preventive efficacy on colon cancer cells, with S having slightly higher activity. The beneficial properties of these unique dried grapes are attributed to their high content of phenolic compounds.

Vigna unguiculata modulates cholesterol induced cardiac markers, genotoxicity and gene expressions profile in an experimental rabbit model

Vigna unguiculata (VU) leaves are edible and used as a leafy vegetable in cuisine from traditional times in India. This study was designed to investigate the cardioprotective effect of VU in cholesterol fed rabbits. The animals were randomly divided into 4 groups of 6 animals each and the experimental period was 3 months. Group I-ND [normal diet 40 g feed], Group II-ND + FVU [flavanoid fraction of Vigna unguiculata (150 mg kg (-1) per body weight)], Group III-ND + CH [cholesterol (400 mg)] and Group IV-ND + CH (400 mg) +FVU (150 mg kg(-1) per body weight). After the experimental period, animals were sacrificed and the various parameters, such as cardiac markers, toxicity parameters, genotoxicity and gene expression, were investigated. Cholesterol feeding causes a significant increase in the levels of cardiac marker enzymes, namely lactate dehydrogenase (LDH) and creatine phospokinase (CPK), atherogenic index, toxicity parameters like serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) were elevated. Antioxidant enzyme levels were decreased, lipid peroxidation products in heart tissue and inflammatory markers, namely cyclooxygenase (COX2) and lipooxygenase (LOX15) in peripheral blood monocytes (PBMCs), were significantly increased. A genotoxicity study using a Comet assay and gene expression by reverse transcriptase-polymerase chain reaction (RT-PCR) of transforming growth factor-b1 (TGF-b1) and heme oxygenase-1 (HO-1) from heart tissue showed an altered expression in the disease group. The supplementation of the flavonoid fraction of Vigna unguiculata leaves (FVU) in the CH + FVU group caused the reversal of the above parameters and cardiotoxicity to near normal when compared with the CH group and FVU. This study revealed the cardioprotective nature of Vigna unguiculata in preventing cardiovascular diseases and this effect is attributed to the presence of antioxidants and the antihyperlipidemic properties of the flavonoid fraction of Vigna unguiculata leaves.

Tea phenols in bulk and nanoparticle form modify DNA damage in human lymphocytes from colon cancer patients and healthy individuals treated in vitro with platinum-based chemotherapeutic drugs

BACKGROUND

Tea catechin epigallocatechin-3-gallate (EGCG) and other polyphenols, such as theaflavins (TFs), are increasingly proving useful as chemopreventives in a number of human cancers. They can also affect normal cells. The polyphenols in tea are known to have antioxidant properties that can quench free radical species, and pro-oxidant activities that appear to be responsible for the induction of apoptosis in tumor cells. The bioavailability of these natural compounds is an important factor that determines their efficacy. Nanoparticle (NP)-mediated delivery techniques of EGCG and TFs have been found to improve their bioavailability to a level that could benefit their effectiveness as chemopreventives.

AIM

The present study was conducted to compare the effects of TFs and EGCG, when used in the bulk form and in the polymer (poly[lactic-co-glycolic acid])-based NP form, in oxaliplatin- and satraplatin-treated lymphocytes as surrogate cells from colorectal cancer patients and healthy volunteers.

MATERIALS & METHODS

NPs were examined for their size distribution, surface morphology, entrapment efficiency and release profile. Lymphocytes were treated in the Comet assay with oxaliplatin and satraplatin, washed and treated with bulk or NP forms of tea phenols, washed and then treated with hydrogen peroxide to determine single-strand breaks after crosslinking.

RESULTS

The results of DNA damage measurements by the Comet assay revealed opposite trends in bulk and NP forms of TFs, as well as EGCG. Both the compounds in the bulk form produced statistically significant concentration-dependent reductions in DNA damage in oxaliplatin- or satraplatin-treated lymphocytes. In contrast, when used in the NP form both TFs and EGCG, although initially causing a reduction, produced a concentration-dependent statistically significant increase in DNA damage in the lymphocytes.

DISCUSSION

These observations support the notion that TFs and EGCG act as both antioxidants and pro-oxidants, depending on the form in which they are administered under the conditions of investigation.

Silibinin, a natural flavonoid, modulates the early expression of chemoprevention biomarkers in a preclinical model of colon carcinogenesis

The flavonolignan silibinin, the major biologically active compound of the milk thistle (Silybum marianum), has been shown to possess anticancer properties in a variety of epithelial cancers. The present study investigated the potential of silibinin as a chemopreventive agent in colon carcinogenesis. The rat azoxymethane (AOM)-induced colon carcinogenesis model was used because of its molecular and clinical similarities to sporadic human colorectal cancer. One week after AOM injection (post-initiation), Wistar rats received daily intragastric feeding of 300 mg silibinin/kg body weight per day until their sacrifice after 7 weeks of treatment. Silibinin-treated rats exhibited a 2-fold reduction in the number of AOM-induced hyperproliferative crypts and aberrant crypt foci in the colon compared to AOM-injected control rats receiving the vehicle. Silibinin-induced apoptosis in the colon mucosal cells was demonstrated by flow cytometry after propodium iodide staining and by colorimetric measurement of caspase-3 activity. Mechanisms involved in silibinin-induced apoptosis included the downregulation of the anti-apoptotic protein Bcl-2 and upregulation of the pro-apoptotic protein Bax, inverting the Bcl-2/Bax ratio to <1. This modulation already takes place at the mRNA expression level as shown by real-time RT-PCR. Furthermore, silibinin treatment significantly (P<0.01) decreased the genetic expression of biomarkers of the inflammatory response such as IL1β, TNFα and their downstream target MMP7, all of them shown to be upregulated during colon carcinogenesis. The downregulation of MMP7 protein was confirmed by western blot analysis. The present findings show the ability of silibinin to shift the disturbed balance between cell renewal and cell death in colon carcinogenesis in rats previously injected with the carcinogen AOM. Silibinin administered via intragastric feeding exhibited potent pro-apoptotic, anti-inflammatory and multi-targeted effects at the molecular level. The effective reduction of preneoplastic lesions by silibinin supports its use as a natural agent for colon cancer chemoprevention.

Association between habitual dietary flavonoid and lignan intake and colorectal cancer in a Spanish case-control study (the Bellvitge Colorectal Cancer Study)

BACKGROUND

Flavonoid-rich foods, such as fruits, vegetables, and tea, may have a protective effect upon colorectal cancer. However, current epidemiological evidence for a protective effect of flavonoid intake upon colorectal cancer is promising but not conclusive.

OBJECTIVE

To examine the relation between dietary flavonoid and lignan intakes and the risk of colorectal cancer within a Spanish population.

DESIGN

Data from the Bellvitge Colorectal Cancer Study, a case-control study (424 cases with incident colorectal cancer and 401 hospital-based controls), were used. A reproducible and validated food frequency questionnaire was administered in personal interviews. An ad hoc food composition database on flavonoids and lignans was compiled, mainly using data from the US Department of Agriculture and Phenol-Explorer databases. Adjusted odds ratios (ORs) and 95 % confidence intervals (CIs) were estimated using unconditional logistic regression models.

RESULTS

An inverse association was found between intake of total flavonoids (OR, 0.59; 95 % CI, 0.35-0.99 for the highest vs. the lowest quartile; p for trend = 0.04), lignans (OR, 0.59; 95 % CI, 0.34-0.99; p for trend = 0.03), and some individual flavonoid subgroups (flavones, proanthocyanidins) and the risk of colorectal cancer. Separate analyses by cancer site showed similar results.

CONCLUSIONS

Intake of total dietary flavonoids (particularly certain flavonoid subgroups) and lignans was inversely associated with colorectal cancer risk in a Spanish population.

Emerging role of bioflavonoids in gastroenterology: Especially their effects on intestinal neoplasia

Flavonoids, secondary plant products which could be essential for normal physiology in humans and animals, may be the vitamins of the next century. Flavonoids belong to the polyphenols and possess antioxidative, anti-inflammatory, antimutagenic and anticarcinogenic properties. Among the various flavonoid species, tea flavonoids such as apigenin (from camomile) and epigallocatechin gallate (EGCG from green tea) can be used for the prevention of intestinal neoplasia, especially for adenoma and cancer prevention in the gastrointestinal tract. Numerous experimental studies with molecular and biological end points support the therapeutic efficacy of bioflavonoids. Clinical studies with cohorts and case-control trials suggest that flavonoids are effective in tertiary bioprevention but, as yet, there are no controlled randomized clinical trials. Flavonoids can inhibit inflammatory pathways and could be useful for chronic inflammatory bowel diseases. Flavonoid deficiency syndromes could be therapeutic targets in the future.

[Colorectal cancer prevention by flavonoids]

BACKGROUND

Valid, sustained and safe clinical means of colorectal cancer prevention are still lacking, but they are urgently needed to lower the incidence of colorectal cancer. Dietary factors and phytochemicals such as flavonoids play an important role for prevention.

METHODS

A selective search of the literature using PubMed was performed with the following key words: flavonoids, cancer, therapy, colorectal cancer focused on clinical queries. Results of clinical studies including the authors' own were compared.

RESULTS

In vivo and in vitro studies with animals, cell cultures and subcellular components provide ample evidence for antimutagenic and anticarcinogenic effects of flavonoids as shown for multiple biological and molecular endpoints. Isoflavonoids in vitro have been shown to induce proliferation of breast cancer cells. Epidemiologic trials (cohort, case-control and cross-sectional studies) yielded inconsistent results for flavonoid protection. Systematic reviews and meta-analyses support the protective role of tea flavonoids on adenoma incidence. An interventional pilot study with sustained flavonoid supplementation was shown to reduce the rate of neoplasia in patients with resected colorectal cancer.

CONCLUSION

Selected flavonoids possess antimutagenic and anticarcinogenic properties and could reduce the incidence of colorectal neoplasias as shown in epidemiologic trials. Randomized controlled clinical studies with flavonoid intervention are necessary to provide evidence for their role in colorectal cancer prevention.

In vitro antiproliferative and antiangiogenic effects of synthetic chalcone analogues

As flavonoids, chalcones possess a wide variety of biological activities including anticancer properties. In the present study we have investigated the in vitro antiproliferative and antiangiogenic effects of four synthetic chalcones. E-2-(4'-methoxybenzylidene)-1-benzosuberone (3) was the most active compound with IC(50)=10(-7)mol l(-1) in Jurkat cells. In both Jurkat and HeLa chalcone 3-treated cells we found a significant increase in the proportion of cancer cells in the G(2)/M phase of the cell cycle as well as an increase in cells having sub-G(0)/G(1) DNA content which is considered to be a marker of apoptotic cell death. Apoptosis was also confirmed by annexin V staining and DNA fragmentation. These effects were associated with reduced expression of the anti-apoptotic gene, Bcl-2, and increased expression of the pro-apoptotic gene, Bax. Furthermore, chalcone 3 was selected to evaluate its effect on some angiogenic events. In non-toxic concentrations, chalcone 3 inhibited VEGF-induced migration of human umbilical vein endothelial cells. Moreover, it also decreased secretion of matrix metalloproteinase (mainly MMP-9) and vascular endothelial growth factor (VEGF). In conclusion, the present study has assessed the in vitro antiproliferative/antiangiogenic potential of chalcone 3. This results generate a rationale for in vivo efficacy studies with this compound in preclinical cancer models.

Proanthocyanidins and the risk of colorectal cancer in Italy

Proanthocyanidins are a group of polymers of flavanols. Animal and in vitro studies suggest they decrease cancer risk, particularly of colorectal cancer. We used data from an Italian case-control study to investigate whether proanthocyanidins are related to colorectal cancer risk. Cases were 1,953 patients with incident, histologically confirmed colorectal cancer (1,225 colon cancers, 728 rectal cancers). Controls were 4,154 patients admitted for acute, non-neoplastic conditions. A reproducible and valid food frequency questionnaire was used. We estimated odds ratios (ORs) through multiple logistic regression models, including terms for potential confounding factors, and energy intake. A trend of decreasing risk with increasing intake of proanthocyanidins emerged for all classes except monomers. The OR for the highest vs. the lowest quintile of intake was 0.82 for monomers and dimers combined, 0.88 for monomers, 0.75 for dimers, 0.74 for all polymers with three or more mers, 0.84 for trimers, 0.80 for 4-6 mers, 0.79 for 7-10 mers, 0.69 for more than 10 mers, and 0.74 for total proanthocyanidins. The associations were apparently stronger for rectal than for colon cancer, in the absence of significant heterogeneity. These results may explain the protective effect of vegetables and fruit on colorectal cancer.

Citrus fruit and cancer risk in a network of case-control studies

BACKGROUND

Citrus fruit has shown a favorable effect against various cancers. To better understand their role in cancer risk, we analyzed data from a series of case-control studies conducted in Italy and Switzerland.

PATIENTS AND METHODS

The studies included 955 patients with oral and pharyngeal cancer, 395 with esophageal, 999 with stomach, 3,634 with large bowel, 527 with laryngeal, 2,900 with breast, 454 with endometrial, 1,031 with ovarian, 1,294 with prostate, and 767 with renal cell cancer. All cancers were incident and histologically confirmed. Controls were admitted to the same network of hospitals for acute, nonneoplastic conditions. Odds ratios (OR) were estimated by multiple logistic regression models, including terms for major identified confounding factors for each cancer site, and energy intake.

RESULTS

The ORs for the highest versus lowest category of citrus fruit consumption were 0.47 (95% confidence interval, CI, 0.36-0.61) for oral and pharyngeal, 0.42 (95% CI, 0.25-0.70) for esophageal, 0.69 (95% CI, 0.52-0.92) for stomach, 0.82 (95% CI, 0.72-0.93) for colorectal, and 0.55 (95% CI, 0.37-0.83) for laryngeal cancer. No consistent association was found with breast, endometrial, ovarian, prostate, and renal cell cancer.

CONCLUSIONS

Our findings indicate that citrus fruit has a protective role against cancers of the digestive and upper respiratory tract.

Inhibition of azoxymethane-induced colonic aberrant crypt foci formation by silibinin in male Fisher 344 rats

Chemoprevention is a practical approach to control colorectal cancer, which is one of the major causes of cancer mortality in the United States. Based on our recent silibinin efficacy studies in human colorectal cancer cells, we investigated the effects of its dietary feeding on azoxymethane (AOM)-induced aberrant crypt foci (ACF) formation and associated biomarkers in male Fisher 344 rats. Five-week-old male Fisher 344 rats were fed control or silibinin-supplemented (0.033%, 0.1%, 0.33%, or 1%, w/w) diet. After 2 weeks, AOM was injected once a week for 2 weeks while silibinin treatments were continued. In another protocol, identical silibinin treatments were done but started 2 weeks post-AOM initiation. All rats were sacrificed at 16 weeks of age, and colon samples were evaluated for ACF, followed by proliferation, apoptosis, and inducible nitric oxide synthase and cyclooxygenase-2, by immunohistochemistry and/or immunoblotting. Silibinin significantly (P < 0.001) reduced dose-dependently the number and multiplicity of AOM-induced ACF formation. Silibinin feeding in pre- and post-AOM initiation decreased mean number of ACF by 39% to 65% and in post-AOM initiation by 29% to 55%. Silibinin dose-dependently decreased AOM-induced colonic cell proliferation, evidenced by proliferative cell nuclear antigen and cyclin D1 immunohistochemical staining, and induced apoptosis in these colon tissues, evidenced by terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining and cleaved poly(ADP-ribose) polymerase. Furthermore, silibinin significantly decreased AOM-induced inducible nitric oxide synthase- and cyclooxygenase-2-positive cells in colon tissues. The present findings show possible beneficial activity of silibinin at least in early stage of colon tumorigenesis, suggesting that silibinin might be an effective natural agent for colorectal cancer chemoprevention.

Kaempferol, a mutagenic flavonol from Helichrysum simillimum

Helichrysum simillimum is native to South Africa. It is used for the treatment of coughs, colds, fever, infections, headache, and menstrual pain. Extracts of this species showed mutagenic effects in the Salmonella/microsome assay. The aim of this study was to isolate and determine the mutagenic constituents of H. simillimum. Bioassay-guided fractionation of 90% aqueous methanol extracts, using Salmonella typhimurium TA98, led to the isolation of the flavonol kaempferol.

Prospective cohort comparison of flavonoid treatment in patients with resected colorectal cancer to prevent recurrence

AIM: To investigate biological prevention with flavonoids the recurrence risk of neoplasia was studied in patients with resected colorectal cancer and after adenoma polypectomy.

METHODS: Eighty-seven patients, 36 patients with resected colon cancer and 51 patients after polypectomy, were divided into 2 groups: one group was treated with a flavonoid mixture (daily standard dose 20 mg apigenin and 20 mg epigallocathechin-gallat, n = 31) and compared with a matched control group (n = 56). Both groups were observed for 3-4 years by surveillance colonoscopy and by questionnaire.

RESULTS: Of 87 patients enrolled in this study, 36 had resected colon cancer and 29 of these patients had surveillance colonoscopy. Among the flavonoid-treated patients with resected colon cancer (n = 14), there was no cancer recurrence and one adenoma developed. In contrast the cancer recurrence rate of the 15 matched untreated controls was 20% (3 of 15) and adenomas evolved in 4 of those patients (27%). The combined recurrence rate for neoplasia was 7% (1 of 14) in the treated patients and 47% (7 of 15) in the controls (P = 0.027).

CONCLUSION: Sustained long-term treatment with a flavonoid mixture could reduce the recurrence rate of colon neoplasia in patients with resected colon cancer.

Dietary flavonoids and the risk of colorectal cancer

In vitro and in vivo laboratory data point to chemoprotective effects of flavonoids on colorectal cancer. However, there has been limited epidemiologic research on the dietary intake of flavonoids and risk of colorectal cancer. Recent expansions of dietary databases to include flavonoid data now make such studies feasible. Association between the six main classes of flavonoids and the risk of colorectal cancer was examined using data from a national prospective case-control study in Scotland, including 1,456 incident cases and 1,456 population-based controls matched on age, sex, and residence area. Dietary, including flavonoid data, were obtained from a validated, self-administered food frequency questionnaire. Risk of colorectal cancer was estimated using conditional logistic regression models in the whole sample and stratified by sex, smoking status, and cancer site and adjusted for established and putative risk factors. After energy adjustment, reductions in colorectal cancer risk associated with the highest quartiles of intake (versus the lowest quartile) were 27% for flavonols [odds ratio (OR), 0.73; P(trend) = 0.012], 32% for quercetin (OR, 0.68; P(trend) = 0.001), 32% for catechin (OR, 0.68; P(trend) < 0.0005); 26% for epicatechin (OR, 0.74; P(trend) = 0.019), and 22% for procyanidins (OR, 0.78; P(trend) = 0.031). The significant dose-dependent reductions in colorectal cancer risk that were associated with increased consumption of flavonols, quercetin, catechin, and epicatechin remained robust after controlling for overall fruit and vegetable consumption or for other flavonoid intake. The risk reductions were greater among nonsmokers, but no interaction beyond a multiplicative effect was present. Sex-specific or cancer-type differences were not observed. No risk reductions were associated with intake of flavones (P(trend) = 0.64), flavonones (P(trend) = 0.22), and phytoestrogens (P(trend) = 0.26). This was the first of several a priori hypotheses to be tested in this large study and showed strong and linear inverse associations of flavonoids with colorectal cancer risk.

Flavonoids and laryngeal cancer risk in Italy

BACKGROUND

Flavonoids may play an important role in explaining the protective effect of vegetables and fruit against cancer.

PATIENTS AND METHODS

To investigate the relation between flavonoids and laryngeal cancer risk, we have applied data on the composition of foods and beverages in terms of six principal classes of flavonoids to a case-control study of laryngeal cancer conducted from 1992 to 2000 in Italy. Cases were 460 subjects with incident, histologically confirmed laryngeal cancer; controls were 1088 patients admitted for acute, non-neoplastic diseases. Odds ratios (OR) were estimated through multiple logistic regression models, including terms for sociodemographic and lifestyle factors, tobacco smoking, alcohol consumption and energy intake.

RESULTS

Significant inverse relations were found for the highest versus the lowest quintile of intake for flavan-3-ols (OR = 0.64), flavanones (OR = 0.60), flavonols (OR = 0.32) and total flavonoids (OR = 0.60), although the overall trends in risk were significant only for flavanones and flavonols. No consistent associations were observed for isoflavones, anthocyanidins and flavones. The estimates did not differ substantially across strata of alcohol drinking, tobacco smoking, body mass index and education, and tended to persist even after controlling for vegetable and fruit intake.

CONCLUSION

This study provides support for a beneficial effect of selected flavonoids on laryngeal cancer risk.

Zapotin, a Phytochemical Present in a Mexican Fruit, Prevents Colon Carcinogenesis

Zapotin (5,6,2',6'-tetramethoxyflavone), found in the tropical fruit zapote blanco (Casimiroa edulis), is consumed in many parts of the world, including Central America and Asia. Previously, we have demonstrated in vitro chemopreventive activity of extracts derived from the seeds of C. edulis. In the present study, we examined the effects of natural and synthetic zapotin in SW480, SW620, and HT-29 colon cancer cell lines and on the generation of aberrant crypt foci (ACF) using mice. Zapotin treatment (IC50=2.74x10(-7 M)) resulted in a marked suppression of cell proliferation in the HT-29 cells. Cell cycle analysis demonstrated a significant accumulation of cells in the G2-M phase, with a concomitant decrease of cells in the G0-G1 phase, after treatment with zapotin (molecular weight=342.35 g/mol; 1 microM for 18, 24, and 48 h). Zapotin treatment enhanced apoptosis in all of the colon cancer cell lines studied. For the study of ACF, 5-wk-old CF-1 mice were given subcutaneous injections of azoxymethane (AOM; 10 mg/kg body weight, BW) weekly for 2 wk, and zapotin (5 or 10 mg/kg BW; 46 or 92 pmol/kg BW) or vehicle was administered intragastrically 7 days/wk. The mean number of ACF for the control group was 14.0+/-2.3, whereas the mean numbers of ACF in the zapotin-treated groups were 6.2+/-1.7 and 4.6+/-1.4 at doses of 5.0 and 10.0 mg/kg BW, respectively. Loss of hexosaminidase, a lysosomal enzyme active in normal colonic crypts but decreased in up to 95% of ACF, was used as a second biomarker for colon carcinogenesis. Zapotin was found to significantly (P<0.01) prevent loss of hexosaminidase in the colon of AOM-treated mice. The present study is the first to report the potent anticancer activity of zapotin and suggests a role for zapotin both as a chemopreventive and a chemotherapeutic agent against colon cancer.

Flavonoids and risk of squamous cell esophageal cancer

The relation between 5 classes of flavonoids (flavanones, flavan-3-ols, flavonols, flavones and anthocyanidines) and esophageal cancer was investigated using data from a case-control study conducted between 1992 and 1997 in 3 areas of northern Italy. The study included 304 cases (275 men, 29 women) with a first diagnosis of squamous-cell carcinoma of the esophagus and 743 controls (593 men, 150 women) with no history of cancer, admitted for acute illnesses, unrelated to tobacco and alcohol consumption, to major hospitals of the areas under surveillance. Dietary habits were investigated using a validated food frequency questionnaire. Odds ratios (ORs) and 95% confidence intervals (CI) were computed after allowance for age, sex, study centre, years of education, alcohol drinking, tobacco smoking, body mass index and energy intake. An inverse association emerged between flavanone intake and esophageal cancer risk (OR=0.38 for the highest vs. the lowest quintile, 95% CI=0.23-0.66). The inverse relation between flavanones and esophageal cancer tended to be stronger in those who drank >or=6 drinks/day. In conclusion, this study suggests that flavanone intake is inversely associated with esophageal cancer risk and may account, with vitamin C, for the protective effect of fruit, especially citrus fruit, on esophageal cancer.

Flavonoids and colorectal cancer in Italy

Because of their several biological activities, flavonoids may have an important role in explaining the protective effects of vegetables, fruit, and, possibly, tea against cancer. The potential relation between flavonoids and colorectal cancer risk was investigated using data from a multicentric Italian case-control study, including 1,953 cases of colorectal cancers (1,225 colon cancers and 728 rectal cancers) and 4,154 hospital controls admitted for acute nonneoplastic diseases. We have applied recently published data on the composition of foods and beverages, in terms of six principal classes of flavonoids, on dietary information collected through a validated food-frequency questionnaire. Odds ratios (OR) were estimated by multiple logistic regression models, including terms for sex, age, study center, family history of colorectal cancer, education, alcohol consumption, body mass index, physical activity, and energy intake. A reduced risk of colorectal cancer was found for increasing intake of isoflavones (OR, 0.76, for the highest versus the lowest quintile, P(trend) = 0.001), anthocyanidins (OR, 0.67, P(trend) < 0.001), flavones (OR, 0.78, P(trend) = 0.004), and flavonols (OR, 0.64, P(trend) < 0.001). No significant association was found for flavan-3-ols (OR, 0.98), flavanones (OR, 0.96), and total flavonoids (OR, 0.97). The estimates did not substantially differ for colon and rectal cancers, as well as in strata of sex, age, and body mass index. The findings of this large study provide support for an inverse association of selected classes of flavonoids with colorectal cancer risk.

Chronic malnutrition does not influence the development of ethylnitrosourea-induced brain tumors

There is controversy over the subject of malnutrition as a potential risk factor for cancer; we studied the effect of chronic malnutrition on the development of tumors in rats prenatally exposed to the carcinogenic ethylnitrosourea. Twelve pregnant Wistar rats were administered on the 19th day of gestation with a single i.v. dose of 30 mg/kg of ethylnitrosourea. Immediately after weaning, at 23 days of age, half of the offspring were nourished with a protein-deficient diet (less than 6%), which consisted mostly of a corn-based diet with high calorie and low fiber contents. In the adult age, 83 rats (74%) developed a tumor of the nervous system; in comparison with controls, we found no differences in time of development, site and histological characteristics of the tumors that developed in animals subjected to chronic malnutrition.