Chemoprevention of Prostate Cancer through Dietary Agents: Progress and Promise

Natural Polyphenols in Cancer Management: Promising Role, Mechanisms, and Chemistry

BACKGROUND

Although cancers emerge rapidly and cancer cells divide aggressively, which affects our vital organ systems. Recently, cancer treatments are targeted immune systems mediating intrinsic cellular mechanisms. Natural efficacious polyphenols have been exhibited to help prevent most cancers and reverse the progression of cancers.

METHODS

Many resources have been used to know the promising role of polyphenols in preventing and treating cancers. The electronic databases include Science Direct, Google, Google Scholar, PubMed, and Scopus. The search was limited to the English language only.

RESULTS

Polyphenols have been reported as anti-metastatic agents that explore the promising role of these compounds in cancer prevention. Such agents act through many signaling pathways, including PI3K/Akt and TNF-induced signaling pathways. The chemical modifications of polyphenols and the structure-activity relationships (SARs) between polyphenols and anticancer activities have also been discussed.

CONCLUSION

Many research papers were reported to explain the anti-cancer potential of Polyphenols, The SARs between polyphenols and anti-cancer activities, which correlate structures of polyphenols with significant chemotherapeutic action. The mechanism of anti-cancer potential is to be added for searching for new anti-cancer natural products.

The efficacy of natural bioactive compounds against prostate cancer: Molecular targets and synergistic activities

Globally, prostate cancer (PCa) is regarded as a challenging health issue, and the number of PCa patients continues to rise despite the availability of effective treatments in recent decades. The current therapy with chemotherapeutic drugs has been largely ineffective due to multidrug resistance and the conventional treatment has restricted drug accessibility to malignant tissues, necessitating a higher dosage resulting in increased cytotoxicity. Plant-derived bioactive compounds have recently attracted a great deal of attention in the field of PCa treatment due to their potent effects on several molecular targets and synergistic effects with anti-PCa drugs. This review emphasizes the molecular mechanism of phytochemicals on PCa cells, the synergistic effects of compound-drug interactions, and stem cell targeting for PCa treatment. Some potential compounds, such as curcumin, phenethyl-isothiocyanate, fisetin, baicalein, berberine, lutein, and many others, exert an anti-PCa effect via inhibiting proliferation, metastasis, cell cycle progression, and normal apoptosis pathways. In addition, multiple studies have demonstrated that the isolated natural compounds: d-limonene, paeonol, lanreotide, artesunate, and bicalutamide have potential synergistic effects. Further, a significant number of natural compounds effectively target PCa stem cells. However, further high-quality studies are needed to firmly establish the clinical efficacy of these phytochemicals against PCa.

Chemopreventive Effect of Cinnamon and Its Bioactive Compounds in a Rat Model of Premalignant Prostate Carcinogenesis

Cinnamon and its bioactive compounds inhibit prostate cancer cell proliferation in vitro. The aim of the current study was to assess the chemopreventive efficacy of cinnamon (CN) and its bioactive compounds in vivo using N-methyl-N-nitrosourea (MNU) and testosterone (T) to induce prostate carcinogenesis in male Wistar/National Institute of Nutrition rats. Cancer-induced (CI) rats (n = 10) developed prostatic hyperplasia and prostatic intraepithelial neoplasia. These histopathologic changes were diminished in CI rats fed for 4 months with diets supplemented with either CN (n = 20) or its bioactive compounds (cinnamaldehyde, n = 10 and procyanidin B2, n = 10). Androgen receptor (AR) expression was lower in the prostates of CI rats than in control, but the AR target gene, probasin, was robustly upregulated. Treatment of CI rats with CN or its bioactive compounds upregulated AR expression but inhibited the expression of the 5-alpha reductase genes (Srd5a1 and Srd5a2) and did not further increase probasin expression, suggesting blunted transcriptional activity of AR due to the limited availability of dihydrotestosterone. MNU+T induced an altered oxidant status in rat prostate, which was reflected by an increase in lipid peroxidation and DNA oxidation. These changes were completely or partially corrected by treatment with CN or the bioactive compounds. CN and its active components increased the activity of the apoptotic enzymes caspase-8 and caspase-3 in the prostates of CI rats. In conclusion, our data demonstrate that CN and its bioactive compounds have inhibitory effects on premalignant prostate lesions induced by MNU + T and, therefore, may be considered for the chemoprevention of prostate cancer.

PREVENTION RELEVANCE

The research work presented in this article demonstrates the chemopreventive efficacy of CN and its bioactive compounds in a rat model of premalignant prostate cancer.

Chemical Composition of Reichardia tingitana Methanolic Extract and Its Potential Antioxidant, Antimicrobial, Cytotoxic and Larvicidal Activity

The biggest challenges are locating effective, reasonably priced, and eco-friendly compounds to treat diseases caused by insects and microbes. The aim of this study was to employ GC-MS to assess the biological potency and chemical composition of the aerial parts of Reichardia tingitana (L.) Roth. Using this technique, 17 components were interpreted from the extracted plant, accounting for around 100% of total volatile compounds. Commonly, 6,10,14-trimethylpentadecan-2-one (21.98%) and methyl oleate (27.26%) were positioned as the major components, which were ascertained after 19.25, and 23.34 min, respectively. The major components were classified as hydrocarbons (23.82%), fatty acids, esters of fatty acids (57.46%), steroids (17.26%), and terpenes (1.48%). The DPPH antioxidant activity of the R. tingitana extracted components revealed that the shoot extract is the most powerful, with an IC50 value of 30.77 mg L−1 and a radical scavenging activity percentage of 71.91%. According to the current result, methanolic extract of R. tingitana had the maximum zone of inhibition against Salmonella typhimurium and Bacillus cereus (25.71 ± 1.63 and 24.42 ± 0.81 mm, respectively), while Clostridium tetani and Staphylococcus xylosus were the main resistant species. In addition, the 50% methanol crude shoot extract of R. tingitana showed greater potential anticancer activity with high cytotoxicity for two tumor cells HepG-2 and PC3 cells (IC50 = 29.977 and 40.479 µg mL−1, respectively) and noncytotoxic activity for WI-38 normal cells (IC50 = >100 µg mL−1). The MeOH extract of plant sample was more effective against Aedes aegypti larvae with LC50 of extract being 46.85, 35.75, and 29.38 mg L−1, whereas the LC90 is 82.66, 63.82, and 53.30 mg L−1 for the various time periods of 24, 48, and 72 h, respectively. R. tingitana is a possible biologically active plant. Future study will include pure chemical isolation and individual component bioactivity evaluation.

Anticancer activity of linalool: comparative investigation of ultrastructural changes and apoptosis in breast cancer cells

Breast cancer is the most common cancer in women ın the world. Many anticancer drugs are currently used clinically have been isolated from plant species or are based on such substances. Linalool is aromatic compounds from the monoterpene group. It is the main constituents of essential oils and show antiproliferative, antioxidant, and antiseptic properties. The aim of this study was to investigate the antiproliferativeand apoptotic, effects of linalool in MCF-7 and MDA-MB-231 human breast cancer cells. MCF-7 and MDA-MB-231 human breast cancer cells were treated with different concentrations of linalool (100, 200, 400, 600, 800, 1000 µM) at 24 h and 48 h. MTT assay for cell proliferation and Annexin V assay for apoptosis was done. The morphology of breast cancer cells was investigated by lıght mıcroscope and scanning electron microscope (SEM). The study show that linalool significantly induced apoptosis in all groups as dose and time-dependent (p < .05). Linalool has apoptotic and antiproliferative properties in a concentration and time-dependent manner in breast cancer cells. The cytotoxic effects of linalool on MCF-7 and MDA-MB-231 human breast cancer cells was found to be associated with apoptotic cell death. Linalool was more effective on MCF-7 human breast cancer cells in smaller amounts.

Natural Products for the Management of Castration-Resistant Prostate Cancer: Special Focus on Nanoparticles Based Studies

Prostate cancer is the most common type of cancer among men and the second most frequent cause of cancer-related mortality around the world. The progression of advanced prostate cancer to castration-resistant prostate cancer (CRPC) plays a major role in disease-associated morbidity and mortality, posing a significant therapeutic challenge. Resistance has been associated with the activation of androgen receptors via several mechanisms, including alternative dehydroepiandrosterone biosynthetic pathways, other androgen receptor activator molecules, oncogenes, and carcinogenic signaling pathways. Tumor microenvironment plays a critical role not only in the cancer progression but also in the drug resistance. Numerous natural products have shown major potential against particular or multiple resistance pathways as shown by in vitro and in vivo studies. However, their efficacy in clinical trials has been undermined by their unfavorable pharmacological properties (hydrophobic molecules, instability, low pharmacokinetic profile, poor water solubility, and high excretion rate). Nanoparticle formulations can provide a way out of the stalemate, employing targeted drug delivery, improved pharmacokinetic drug profile, and transportation of diagnostic and therapeutic agents via otherwise impermeable biological barriers. This review compiles the available evidence regarding the use of natural products for the management of CRPC with a focus on nanoparticle formulations. PubMed and Google Scholar search engines were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical studies. The results of our study suggest the efficacy of natural compounds such as curcumin, resveratrol, apigenin, quercetin, fisetin, luteolin, kaempferol, genistein, berberine, ursolic acid, eugenol, gingerol, and ellagic acid against several mechanisms leading to castration resistance in preclinical studies, but fail to set the disease under control in clinical studies. Nanoparticle formulations of curcumin and quercetin seem to increase their potential in clinical settings. Using nanoparticles based on betulinic acid, capsaicin, sintokamide A, niphatenones A and B, as well as atraric acid seems promising but needs to be verified with preclinical and clinical studies.

The effect of green tea on prostate specific antigen (PSA): A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Prostate cancer is a major malignancy, affecting men, worldwide. The protective effect of green tea consumption on prostate cancer has been reported in several studies; however, the findings are equivocal.

OBJECTIVE

The aim of this study was to evaluate the effects of green tea on PSA level, by conducting a systematic review and meta-analysis of randomized controlled trials.

METHODS

We searched online databases, including PubMed, Scopus, and Web of Science, up to 11 Aug 2020, to obtain relevant publications. The publication search was not limited by language or date.

RESULTS

A total of 2488 records were identified in the systematic search; from these, seven were included in the meta-analysis. The overall analysis showed no significant changes in PSA levels in subjects treated with green tea, (WMD: ‒0.60 ng/mL; 95 % CI: ‒1.32, 0.12 ng/mL; P = 0.104, I² = 93.80 %, P heterogeneity<0.001). Subgroup analysis based on geographical location showed that green tea significantly reduced PSA level in the USA population (WMD: ‒1.02 pg/mL, 95 % CI: ‒1.30, ‒0.73, P < 0.001) compared to non-USA populations (WMD: ‒0.22 pg/mL, 95 % CI: ‒0.95, 0.50, P = 0.539) (P < 0.001).

CONCLUSION

The results of this review show that green tea has no significant effect on PSA level. However, due to the heterogeneity among studies more consistent clinical trials, with larger sample sizes are required.

Therapeutic Potential of Gnetin C in Prostate Cancer: A Pre-Clinical Study

Natural stilbenes have gained significant attention in the scientific community owing to their potential anticancer effects against prostate cancer. We recently reported that Gnetin C, a resveratrol (Res) dimer, demonstrated more potent inhibition of metastasis-associated protein 1/v-ets avian erythroblastosis virus E26 oncogene homolog 2 (MTA1/ETS2) axis in prostate cancer cell lines than other stilbenes. In this study, we investigated in vivo antitumor effects of Gnetin C in two doses (50 and 25 mg/kg, i.p.) using PC3M-Luc subcutaneous xenografts and compared these to Res and pterostilbene (Pter). We found that while vehicle-treated mice revealed rapid tumor progression, compounds-treated mice showed noticeable delay in tumor growth. Gnetin C in 50 mg/kg dose demonstrated the most potent tumor inhibitory effects. Gnetin C in 25 mg/kg dose exhibited tumor inhibitory effects comparable with Pter in 50 mg/kg dose. Consistent with the effective antitumor effects, Gnetin C-treated tumors showed reduced mitotic activity and angiogenesis and a significant increase in apoptosis compared to all the other groups. The data suggest that Gnetin C is more potent in slowing tumor progression in prostate cancer xenografts than Res or Pter. Taken together, we demonstrated, for the first time, that Gnetin C is a lead compound among stilbenes for effectively blocking prostate cancer progression in vivo.

Dietary Factors and Supplements Influencing Prostate Specific-Antigen (PSA) Concentrations in Men with Prostate Cancer and Increased Cancer Risk: An Evidence Analysis Review Based on Randomized Controlled Trials

The quest for dietary patterns and supplements efficient in down-regulating prostate-specific antigen (PSA) concentrations among men with prostate cancer (PCa) or increased PCa risk has been long. Several antioxidants, including lycopene, selenium, curcumin, coenzyme Q10, phytoestrogens (including isoflavones and flavonoids), green tea catechins, cernitin, vitamins (C, E, D) and multivitamins, medicinal mushrooms (Ganoderma lucidum), fruit extracts (saw palmetto, cranberries, pomegranate), walnuts and fatty acids, as well as combined supplementations of all, have been examined in randomized controlled trials (RCTs) in humans, on the primary, secondary, and tertiary PCa prevention level. Despite the plethora of trials and the variety of examined interventions, the evidence supporting the efficacy of most dietary factors appears inadequate to recommend their use.

Triterpenoid saponins in tea (Camellia sinensis) plants: biosynthetic gene expression, content variations, chemical identification and cytotoxicity

Very little is known about saponins in tea and their biosynthesis in tea plants despite of the importance. Here, we studied tea saponins and their biosynthesis genes. Saponins were promptly recovered in tea infusions. Cytotoxicity of tea saponin extracts on human tongue squamous and hepatocellular carcinoma lines showed respective IC50 values of 29.2 and 17.5 μg/mL, which may be attributable to over 40 saponins identified in green tea. Saponin contents varied in shoot tips of 42 tea plant varieties but did not change drastically during tea processing. Saponin biosynthetic gene expression was consistent with its contents in plant tissues. Thus, plant tips produce significant amounts of saponins, which are stable during tea processing, and ready to be recovered to tea infusions to provide potent health benefits to consumers. This study paves a road towards clarifying the biosynthesis and genetic improvement of saponins in tea plants.

Comparison of ultrastructural changes and the anticarcinogenic effects of thymol and carvacrol on ovarian cancer cells: which is more effective?

Ovarian cancer is the seventh most common cancer worldwide in women. Many anticancer drugs are currently used clinically have been isolated from plant species or are based on such substances. Thymol (5-methyl-2-isopropylphenol) and carvacrol are oxygenated aromatic compounds from the monoterpene group. They are the main constituents of thyme essential oil and show antiproliferative, antioxidant, and antiseptic properties. The aim of this study is to compare the antiproliferative and apoptotic effects of thymol and carvacrol on SKOV-3 ovarian cancer cell line. The cancer cells were treated with different concentrations of thymol and carvacrol (100, 200, 400, 600 µM) at 24 h and 48 h durations. The cell viability was investigated by MTT assay and analysis of apoptosis with annexin V assay was determined. The study show that thymol and carvacrol significantly induced apoptosis in all groups as dose and time-dependent (p < .05). The data in the present study demonstrated that thymol and carvacrol have apoptotic and antiproliferative properties in a concentration-dependent manner toward ovarian cancer cells. SKOV-3 cancer cell line was much more sensitive to the toxic effect of thymol than carvacrol.

Lajis N, Abas F, Othman I, Naidu R. Mechanism of Anti-Cancer Activity of Curcumin on Androgen-Dependent and Androgen-Independent Prostate Cancer

Prostate cancer (PCa) is a heterogeneous disease and ranked as the second leading cause of cancer-related deaths in males worldwide. The global burden of PCa keeps rising regardless of the emerging cutting-edge technologies for treatment and drug designation. There are a number of treatment options which are effectively treating localised and androgen-dependent PCa (ADPC) through hormonal and surgery treatments. However, over time, these cancerous cells progress to androgen-independent PCa (AIPC) which continuously grow despite hormone depletion. At this particular stage, androgen depletion therapy (ADT) is no longer effective as these cancerous cells are rendered hormone-insensitive and capable of growing in the absence of androgen. AIPC is a lethal type of disease which leads to poor prognosis and is a major contributor to PCa death rates. A natural product-derived compound, curcumin has been identified as a pleiotropic compound which capable of influencing and modulating a diverse range of molecular targets and signalling pathways in order to exhibit its medicinal properties. Due to such multi-targeted behaviour, its benefits are paramount in combating a wide range of diseases including inflammation and cancer disease. Curcumin exhibits anti-cancer properties by suppressing cancer cells growth and survival, inflammation, invasion, cell proliferation as well as possesses the ability to induce apoptosis in malignant cells. In this review, we investigate the mechanism of curcumin by modulating multiple signalling pathways such as androgen receptor (AR) signalling, activating protein-1 (AP-1), phosphatidylinositol 3-kinases/the serine/threonine kinase (PI3K/Akt/mTOR), wingless (Wnt)/ß-catenin signalling, and molecular targets including nuclear factor kappa-B (NF-κB), B-cell lymphoma 2 (Bcl-2) and cyclin D1 which are implicated in the development and progression of both types of PCa, ADPC and AIPC. In addition, the role of microRNAs and clinical trials on the anti-cancer effects of curcumin in PCa patients were also reviewed.

Effect of green tea and lycopene on the insulin-like growth factor system: the ProDiet randomized controlled trial

Whether prostate cancer (PCa) may be preventable by dietary interventions can be assessed in randomized trials using intermediate biomarkers of cancer risk or progression. We investigated whether lycopene or green tea modify circulating insulin-like growth factor (IGF) peptides in men at increased risk of PCa. Participants (aged 50-69 years) in one centre in the UK wide PCa testing and treatment trial (ProtecT) with prostate specific antigen between 2.0 and 2.95 ng/ml or negative biopsies, were randomized to daily lycopene (n = 44 assigned 15 mg capsules/day; 44 assigned a lycopene-rich diet; 45 assigned placebo) and green tea (n = 45 assigned 600 mg/day epigallocatechin gallate; 45 assigned green tea drink; 43 assigned placebo) for 6 months. The interventions significantly elevated the primary outcomes, serum epigallocatechin gallate and lycopene at 6 months of follow-up. We report here an exploratory analysis in which serum IGF-I, IGF-II, IGF binding protein (BP)-2 and IGFBP-3 were measured at baseline and 6 months of postintervention. A total of 133 men were randomized (34% of eligible men approached) and 130 had follow-up IGF peptides (98%). In intention-to-treat analyses, there was only weak evidence that lycopene or green tea influenced some aspects of serum IGF-I, IGF-II, IGFBP-2 or IGFBP-3. In men randomized to lycopene supplements, IGFBP-2 was nonsignificantly (50.9 ng/ml; 95% confidence interval: -51.2-152.9, P = 0.3) higher in comparison to placebo, whereas in men randomized to green tea supplements, IGFBP-3 was nonsignificantly (205.2 ng/ml; 95% confidence interval: -583.3-172.9, P = 0.3) lower than with placebo. In this small, pilot randomized controlled trial, there was little evidence that lycopene or green tea interventions influenced serum levels of IGF-I, IGF-II, IGFBBP-3 and IGFBP-2. However, the effects were imprecisely estimates and some observed trends may justify larger trials.

Role of Unani Medicines in Cancer Control and Management

Background:

Cancer is a havoc and killer disease. Several ways including allopathic chemotherapy have been used in the cancer treatment. Allopathic chemotherapy has several limitations and side effects. Unani medicine is also one of the therapies to cure cancer.

Objective:

In this type of treatment, herbal drugs are used for the treatment and prevention of cancer. The main attractive thing about herbal drug is no side effect as compared to allopathic chemotherapy.

Methods:

Actually, herbal drugs are the extracts of medicinal plants. The plant extracts are obtained by crushing and heating the main part of the plants; showing anticancer activity. The main plants used in the treatment of cancer are oroxylum indicum, dillenia indica, terminalia arjuna etc.

Results:

Mainly the cancers treated are of digestive system, breast, cervical, brain, blood, bone, lungs, thyroid, uterine, bladder, throat etc.

Conclusion:

The present review article discusses the importance of Unani system of medicine for the treatment of cancer. Besides, the future perspectives of Unani medicine in cancer treatment are also highlighted.

Antiproliferative Effects of Ellagic Acid on DU145 Cells

Background:

Prostate Cancer (PC) represents a leading cause of tumor-related death among men in the Western world. Above all, DU145 cell line represents the most particular cells model of PC, derived from a central nervous system metastasis. In recent years, functional and healthy diet has gained a pivotal role in society, allowing the possibility to deal with cancer before its emergence or progression, profiting by anti-tumor properties of dietary phytochemicals. Among them, Ellagic Acid (EA) is found in several fruits and vegetables, whose juice demonstrated antioxidant, anti-carcinogenic and anti-fibrotic properties.

Methods:

DU145 prostate cancer cell line was used to determine the effects of ellagic acid on cell viability. In order to evaluate metastatic feature of DU145, VEGF-A and OPG levels by ELISA assay were assessed. Expression of β-catenin, HO-1, HO-2 and SIRT1, markers of proliferative and defense capacities, were determined by western blotting. To strengthen the study, cell transfection with siRNA β-catenin was performed.

Results:

In the presence of EA, the viability of DU145 cells was reduced by about 40 and 50%, respectively after the exposure to 50 and 100 μM concentrations. We also observed a reduction of both levels of VEGF-A and OPG, confirming the important role of EA in facing the metastasis development. EA treatment (50 μM) induced a significant reduction of β-catenin and SIRT1 levels and, similarly, there was a decrease of HO protein expression, more pronounced for HO-2, showing EA activity on the proliferative feature of DU145 cells. Knockdown of β-catenin by siRNA, in the presence of EA treatment, inhibited cell proliferation.

Conclusion:

Ellagic acid exhibits significant antiproliferative effects in ourin vitromodel of prostate cancer’s metastasis, suggesting that, the use of EA as a multitarget natural compound, may represent a possible strategy for cancer chemoprevention.

Inhibition of Tumor Growth by Dietary Indole-3-Carbinol in a Prostate Cancer Xenograft Model May Be Associated with Disrupted Gut Microbial Interactions

Accumulated evidence suggests that the cruciferous vegetables-derived compound indole-3-carbinol (I3C) may protect against prostate cancer, but the precise mechanisms underlying its action remain unclear. This study aimed to verify the hypothesis that the beneficial effect of dietary I3C may be due to its modulatory effect on the gut microbiome of mice. Athymic nude mice (5–7 weeks old, male, Balb c/c nu/nu) with established tumor xenografts were fed a basal diet (AIN-93) with or without 1 µmoles I3C/g for 9 weeks. The effects of dietary I3C on gut microbial composition and microbial species interactions were then examined by 16s rRNA gene-based sequencing and co-occurrence network analysis. I3C supplementation significantly inhibited tumor growth (p < 0.0001) and altered the structure of gut microbiome. The abundance of the phylum Deferribacteres, more specifically, Mucispirillum schaedleri, was significantly increased by dietary I3C. Additionally, I3C consumption also changed gut microbial co-occurrence patterns. One of the network modules in the control group, consisting of seven bacteria in family S-27, was positively correlated with tumor size (p < 0.009). Moreover, dietary I3C disrupted microbial interactions and altered this association between specific microbial network and tumor development. Our results unraveled complex relationships among I3C ingestion, gut microbiota, and prostate tumor development and may provide a novel insight into the mechanism for the chemopreventive effect of dietary I3C on prostate cancer.

Prostate Cancer Disparity, Chemoprevention, and Treatment by Specific Medicinal Plants

Prostate cancer (PC) is one of the most common cancers in men. The global burden of this disease is rising. Its incidence and mortality rates are higher in African American (AA) men compared to white men and other ethnic groups. The treatment decisions for PC are based exclusively on histological architecture, prostate-specific antigen (PSA) levels, and local disease state. Despite advances in screening for and early detection of PC, a large percentage of men continue to be diagnosed with metastatic disease including about 20% of men affected with a high mortality rate within the African American population. As such, this population group may benefit from edible natural products that are safe with a low cost. Hence, the central goal of this article is to highlight PC disparity associated with nutritional factors and highlight chemo-preventive agents from medicinal plants that are more likely to reduce PC. To reach this central goal, we searched the PubMed Central database and the Google Scholar website for relevant papers. Our search results revealed that there are significant improvements in PC statistics among white men and other ethnic groups. However, its mortality rate remains significantly high among AA men. In addition, there are limited studies that have addressed the benefits of medicinal plants as chemo-preventive agents for PC treatment, especially among AA men. This review paper addresses this knowledge gap by discussing PC disparity associated with nutritional factors and highlighting the biomedical significance of three medicinal plants (curcumin, garlic, and Vernonia amygdalina) that show a great potential to prevent/treat PC, as well as to reduce its incidence/prevalence and mortality, improve survival rate, and reduce PC-related health disparity.

Muscadine grape skin extract inhibits prostate cancer cells by inducing cell-cycle arrest, and decreasing migration through heat shock protein 40

Previously we demonstrated that muscadine grape skin extract (MSKE), a natural product, significantly inhibited androgen-responsive prostate cancer cell growth by inducing apoptosis through the targeting of survival pathways. However, the therapeutic effect of MSKE on more aggressive androgen-independent prostate cancer remains unknown. This study examined the effects of MSKE treatment in metastatic prostate cancer using complementary PC-3 cells and xenograft model. MSKE significantly inhibited PC-3 human prostate cancer cell tumor growth in vitro and in vivo. The growth-inhibitory effect of MSKE appeared to be through the induction of cell-cycle arrest. This induction was accompanied by a reduction in the protein expression of Hsp40 and cell-cycle regulation proteins, cyclin D1 and NF-kBp65. In addition, MSKE induced p21 expression independent of wild-type p53 induced protein expression. Moreover, we demonstrate that MSKE significantly inhibited cell migration in PC-3 prostate cancer cells. Overall, these results demonstrate that MSKE inhibits prostate tumor growth and migration, and induces cell-cycle arrest by targeting Hsp40 and proteins involved in cell-cycle regulation and proliferation. This suggests that MSKE may also be explored either as a neo-adjuvant or therapeutic for castration resistant prostate cancer.

Combination Effect of δ-Tocotrienol and γ-Tocopherol on Prostate Cancer Cell Growth

Tocotrienols (T3s) and tocopherols (Tocs) are both members of the vitamin E family. It is known that δ-tocotrienol (δ-T3) has displayed the most potent anti-cancer activity amongst the tocotrienols. On the other hand, γ-tocopherol (γ-Toc) is reported to have a protective effect against prostate cancer. Therefore, we investigated whether the combination of γ-Toc and δ-T3 could strengthen the inhibitory effect of δ-T3 on prostate cancer cell growth. In this study the effect of combined δ-T3 (annatto T3 oil) and γ-Toc (Tmix, γ-Toc-rich oil) therapy was assessed against human androgen-dependent prostate cancer cells (LNCaP). We found that combined treatment of δ-T3 (10 μM) and γ-Toc (5 μM) resulted in reinforced anti-prostate cancer activity. Specifically, cell cycle phase distribution analysis revealed that in addition to G1 arrest caused by the treatment with δ-T3, the combination of δ-T3 with γ-Toc induced G2/M arrest. Enhanced induction of apoptosis by the combined treatment was also observed. These findings indicate that combination of δ-T3 and γ-Toc significantly inhibits prostate cancer cell growth due to the simultaneous cell cycle arrest in the G1 phase and G2/M phase.

The mutagenic and antimutagenic activity of Sutherlandia frutescens extracts and marker compounds

BACKGROUND

Sutherlandia frutescens (L.) R. Br is endemic to Southern Africa where it has been traditionally used for cancer and diabetes. In recent times it has been marketed for its reputed (but not proven) anticancer, antidiabetic and anti-HIV properties. Little is known about the mutagenic and antimutagenic potential of extracts and common marker compounds of Sutherlandia frutescens. Therefore this study aimed to investigate the putative efficacy and possible long-term adverse effects of using this herb.

METHODS

Ethylacetate (EA) and 50% Methanol (MeOH) extracts were screened for mutagenic and antimutagenic activity using the Ames assay utilising TA97a, TA98, TA100 and TA102 in the presence and absence of metabolic activation. Four compounds, L-arginine, L-canavanine, GABA and D-pinitol known to occur in sutherlandia were also included. The total polyphenolic content of the both extracts was determined using the Folin-Ciocalteau method and FRAP and ABTS were used to determine the anti-oxidant potential of the extracts.

RESULTS

The extracts and the standards did not show any cytotoxicity except in TA97a. The EA extract exhibited antimutagenicity against all the bacterial strains at all concentrations tested. The MeOH extract showed both pro-mutagenic and antimutagenic activities with 2-acetamidofluorene and aflatoxin B1 in the presence of metabolic activation of TA98 and TA100, respectively. All compounds, except L-canavanine exhibited antimutagenic activity against all strains. L-canavanine, on the other hand showed co-mutagenicity with 9-aminoacridine on TA97a, at all test concentrations. The extracts and pure compounds exhibited their antimutagenic activity in a dose response manner. L-arginine and GABA showed an some antimutagenic response. EA extract had three times the total phenolic content (12.56 μg GE / mg) observed in the MeOH extract. There was correlation between total phenolic content, antioxidant potential and antimutagenicity.

CONCLUSION

Both extracts exhibited a protective effect, with the EA extract exhibiting greater potency. L-canavanine acted as a co-mutagen in a dose response manner without metabolic activation. It is suggested that the EA extract be priotized for future development work as it showed a better risk profile and activity.

Combinatorial treatment with natural compounds in prostate cancer inhibits prostate tumor growth and leads to key modulations of cancer cell metabolism

High-throughput screening of a natural compound library was performed to identify the most efficacious combinatorial treatment on prostate cancer. Ursolic acid, curcumin and resveratrol were selected for further analyses and administered in vivo via the diet, either alone or in combination, in a mouse allograft model of prostate cancer. All possible combinations of these natural compounds produced synergistic effects on tumor size and weight, as predicted in the screens. A subsequent untargeted metabolomics and metabolic flux analysis using isotopically labeled glutamine indicated that the compound combinations modulated glutamine metabolism. In addition, ASCT2 levels and STAT3, mTORC1 and AMPK activity were modulated to a greater extent by the combinations compared to the individual compounds. Overall, this approach can be useful for identifying synergistic combinations of natural compounds for chemopreventive and therapeutic interventions.

The bounty of nature for changing the cancer landscape

The landscape of cancer has changed considerably in past several years, due mainly to aggressive screening, accumulation of data from basic and epidemiological studies, and the advances in translational research. Natural anticancer agents have always been a part and parcel of cancer research. The initial focus on natural anticancer agents was in context of their cancer chemopreventive properties but their ability to selectively target oncogenic signaling pathways has also been recognized. In light of the rapid advancements in our understanding of the role of microRNAs, cancer stem cells, and epigenetic events in cancer initiation and progression, a number of natural anticancer agents are showing promise in vitro, in vivo as well as in preclinical studies. Moreover, parent structures of natural agents are being extensively modified with the hope of improving efficacy, specificity, and bioavailability. In this article, we focus on two natural agents, 3,3'-diindolylmethane and garcinol, along with 3,4-difluorobenzo curcumin, a synthetic analog of natural agent curcumin. We showcase how these anticancer agents are changing cancer landscape by modulating novel microRNAs, epigenetic factors, and cancer stem cell markers. These activities are relevant and being appreciated for overcoming drug resistance and inhibition of metastases, the two overarching clinical challenges in modern medicine.

Antitumor Activity of Garcinol in Human Prostate Cancer Cells and Xenograft Mice

Garcinol, which is isolated from fruit rinds of Garcinia indica, is a polyisoprenylated benzophenone. It has been studied for its antitumor activity by inducing apoptosis and inhibiting autophagy in human prostate cancer cells. The Bax/Bcl-2 ratio increased when garcinol was applied to PC-3 cells indicating a presence of apoptosis. Meanwhile, procaspases-9 and -3 were suppressed with attenuating PARP and DFF-45. Autophagy was inhibited through activating p-mTOR and p-PI3 Kinase/AKT by garcinol, which as a result induced the cells to apoptosis directly. In addition, the apoptosis effect of garcinol in a xenograft mouse model was also tested, suggesting a consistent result with PC-3 cell model. The tumor size was reduced more than 80 percent after the mouse accepted the garcinol treatment. Garcinol was demonstrated to have a strong antitumor activity through inhibiting autophagy and inducing apoptosis, which was discovered for the first time. Based on these findings, our data suggests that garcinol deserves further investigation as a potent chemopreventive agent.

Dietary, supplement, and adipose tissue tocopherol levels in relation to prostate cancer aggressiveness among African and European Americans: The North Carolina-Louisiana Prostate Cancer Project (PCaP)

BACKGROUND

Controversies remain over the safety and efficacy of vitamin E (i.e., α-tocopherol) supplementation use for the prevention of prostate cancer (CaP); however, associations of different tocopherol forms and CaP aggressiveness have yet to be examined.

METHODS

This study examined whether food intake of tocopherols, vitamin E supplement use, and adipose tissue biomarkers of tocopherol were associated with CaP aggressiveness among African-American (AA, n = 1,023) and European-American (EA, n = 1,079) men diagnosed with incident CaP. Dietary tocopherols were estimated from a food frequency questionnaire, supplement use from questionnaire/inventory, and biomarkers from abdominal adipose samples measured using high-performance liquid chromatography. Odds ratios (ORs) and 95% confidence intervals (95%CIs) were estimated from logistic regression comparing high-aggressive CaP to low/intermediate aggressive CaP, adjusting for covariates.

RESULTS

Dietary intakes of α-and δ-tocopherol were related inversely to CaP aggressiveness among EAs [OR (95%CI), highest versus lowest quartile: α-tocopherol, 0.34 (0.17-0.69), P(trend)  = 0.006; δ-tocopherol, 0.45 (0.21-0.95) P(trend)  = 0.007]. Inverse associations between dietary and supplemental α-tocopherol and CaP aggressiveness were observed among AAs, though these did not reach statistical significance [OR (95%CI), highest versus lowest quartile: dietary α-tocopherol, 0.58 (0.28-1.19), P(trend)  = 0.20; supplemental α-tocopherol, 0.64 (0.31-1.21) P(trend)  = 0.15]. No significant association was observed between adipose tocopherol levels and CaP aggressiveness [OR (95%CI), highest versus lowest quartiles of α-tocopherol for EAs 1.43 (0.66-3.11) and AAs 0.66 (0.27-1.62)].

CONCLUSIONS

The inverse associations observed between dietary sources of tocopherols and CaP aggressiveness suggests a beneficial role of food sources of these tocopherols in CaP aggressiveness.

Inhibition of prostate cancer cell growth by 3',4',5'-trimethoxyflavonol (TMFol)

PURPOSE

TMFol (3',4',5'-trimethoxyflavonol) is a synthetic analogue of the naturally occurring flavonol fisetin and quercetin, which have been considered of potential usefulness in the management of prostate cancer. We investigated whether TMFol may have preclinical features superior to those of its two flavonol congeners.

METHODS

The ability of the three flavonols to compromise prostate cancer cell survival was tested in four prostate cancer cell types 22Rv1, TRAMP C2, PC-3 and LNCaP. The effect of TMFol on prostate cancer development in vivo was investigated in nude mice bearing the 22Rv1 or TRAMP C2 tumours.

RESULTS

TMFol inhibited cell growth in vitro in all four prostate cancer cell types more potently than fisetin and quercetin. It also interfered with TRAMP C2 tumour development in vivo, while fisetin and quercetin at equivalent doses were without activity in this model. Likewise, TMFol slowed the growth of the 22Rv1 tumour in vivo. Efficacy in either model was accompanied by induction of apoptosis, although in vitro only TRAMP C2 cells, but not 22Rv1, underwent apoptosis when exposed to TMFol.

CONCLUSIONS

The results support the notion that among the three congeneric flavonols, quercetin, fisetin and TMFol, the latter may be the most suitable candidate agent for potential development in prostate cancer management.

Effect of Metformin, Rapamycin, and Their Combination on Growth and Progression of Prostate Tumors in HiMyc Mice

In this study, we compared the effect of oral administration of metformin (MET) and rapamycin (RAPA) alone or in combination on prostate cancer development and progression in HiMyc mice. MET (250 mg/kg body weight in the drinking water), RAPA (2.24 mg/kg body weight microencapsulated in the diet), and the combination inhibited progression of prostatic intraepithelial neoplasia lesions to adenocarcinomas in the ventral prostate (VP). RAPA and the combination were more effective than MET at the doses used. Inhibition of prostate cancer progression in HiMyc mice by RAPA was associated with a significant reduction in mTORC1 signaling that was further potentiated by the combination of MET and RAPA. In contrast, treatment with MET alone enhanced AMPK activation, but had little or no effect on mTORC1 signaling pathways in the VP of HiMyc mice. Further analyses revealed a significant effect of all treatments on prostate tissue inflammation as assessed by analysis of the expression of cytokines, the presence of inflammatory cells and NFκB signaling. MET at the dose used appeared to reduce prostate cancer progression primarily by reducing tissue inflammation whereas RAPA and the combination appeared to inhibit prostate cancer progression in this mouse model via the combined effects on both mTORC1 signaling as well as on tissue inflammation. Overall, these data support the hypothesis that blocking mTORC1 signaling and/or tissue inflammation can effectively inhibit prostate cancer progression in a relevant mouse model of human prostate cancer. Furthermore, combinatorial approaches that target both pathways may be highly effective for prevention of prostate cancer progression in men.

Ethanol extract of Remotiflori radix induces endoplasmic reticulum stress-mediated cell death through AMPK/mTOR signaling in human prostate cancer cells

Remotiflori radix is the root of Mosidae, which has long been used as a traditional medicine to treat chills, fever, and phlegm discharge. The ethanol extract of Mosidae leaves (MLE) possesses strong antioxidant and chemopreventive activities. However, the anti-cancer effects of the Remotiflori radix have not been examined. We used the ethanol extract of Remotiflori radix (ERR) and the PC-3 and DU145 prostate cancer cell lines in this study. We found that > 100 μg/mL ERR caused dose- and time-dependent cell death. Autophagic and apoptotic cell numbers increased in a dose-dependent manner as incubation time was prolonged, and LC3 punctuation, YO-PRO-1 uptake, DNA fragmentation, activation of caspases, and PARP cleavage were induced. Phosphorylation of AMPK, ULK, and p38 was increased after ERR treatment, and the level of the ER stress marker CHOP was also elevated. AMPK knockdown dramatically blocked ERR-mediated CHOP expression and cell death, suggesting that AMPK activation and ER stress play a critical role in ERR-induced cell death. Furthermore, oral administration of ERR at 50 mg/kg efficiently suppressed tumorigenic growth of PC-3 cells with no adverse effects. These results suggest that the ERR can be used as a safe and potent alternative therapy for patients with prostate cancer.

Dietary polyphenols in prevention and treatment of prostate cancer

Prostate cancer is the most prevalent disease affecting males in many Western countries, with an estimated 29,480 deaths in 2014 in the US alone. Incidence rates for prostate cancer deaths have been decreasing since the early 1990s in men of all races/ethnicities, though they remain about 60% higher in African Americans than in any other group. The relationship between dietary polyphenols and the prevention of prostate cancer has been examined previously. Although results are sometimes inconsistent and variable, there is a general agreement that polyphenols hold great promise for the future management of prostate cancer. Various dietary components, including polyphenols, have been shown to possess anti-cancer properties. Generally considered as non-toxic, dietary polyphenols act as key modulators of signaling pathways and are therefore considered ideal chemopreventive agents. Besides possessing various anti-tumor properties, dietary polyphenols also contribute to epigenetic changes associated with the fate of cancer cells and have emerged as potential drugs for therapeutic intervention. Polyphenols have also been shown to affect post-translational modifications and microRNA expressions. This article provides a systematic review of the health benefits of selected dietary polyphenols in prostate cancer, especially focusing on the subclasses of polyphenols, which have a great effect on disease prevention and treatment.

Men's knowledge and attitudes towards dietary prevention of a prostate cancer diagnosis: a qualitative study

Background

Prostate cancer (PC) incidence and progression may be influenced by dietary factors, but little is known about the acceptability of dietary modification to men at increased risk of PC. Qualitative interviews with men participating in the ProDiet study were undertaken to explore the feasibility of implementing dietary interventions for the prevention of prostate cancer.

Methods

An interview study nested within the ProDiet randomised feasibility trial of dietary interventions to prevent a PC diagnosis. Men (n = 133) who previously participated in community based prostate specific antigen (PSA) testing without PC but who were at increased risk of the disease were randomly allocation to both lycopene (lycopene or placebo capsules or lycopene rich diet) and green tea (green tea or placebo capsules or green tea drink) for 6 months. Semi-structured interviews were conducted with participants shortly after randomisation, to investigate attitudes towards dietary modification for PC prevention and dietary information. Interviews were audio-recorded, transcribed and analysed to identify common themes.

Results

Interviews were conducted with 21 participants aged 52-72 years with PSA levels between 2.5 and 2.95 ng/ml, or a negative prostate biopsy result. Most men identified the major causes of cancer in general to include diet, environment, ageing and genetic factors. This contrasted sharply with men’s uncertainty about PC aetiology, and the function of the prostate. Men were confused by conflicting messages in the media about dietary practices to promote health overall, but were positive about the potential of lycopene and green tea in relation to PC prevention, valuing their natural components. Furthermore these men wanted tailored dietary advice for PC prevention from their clinicians, whom they considered a trusted source of information.

Conclusion

Men at elevated risk of PC reported uncertainty about PC aetiology and the role of diet in PC prevention, but enthusiasm for dietary modifications that were perceived as ‘simple’ and ‘natural’. The men looked to clinicians to provide consistent disease specific dietary advice. These factors should be taken into consideration by clinicians discussing elevated PSA results with patients and those planning to embark on future trials investigating dietary modification interventions for the prevention of a PC diagnosis.

Comparative effects of two different forms of selenium on oxidative stress biomarkers in healthy men: a randomized clinical trial

Epidemiologic and laboratory studies indicate that dietary selenium protects against prostate cancer. Results from clinical trials suggest that selenium-enriched yeast (SY) but not selenomethionine (SeMet) may be effective at reducing prostate cancer risk. Our objectives were to directly compare for the first time the effects of SeMet and SY on prostate cancer relevant biomarkers in men. We performed a randomized double blind, placebo-controlled trial of SY (200 or 285 μg/day) and SeMet (200 μg/day) administered for 9 months in 69 healthy men. Primary endpoints included blood levels of selenium-containing compounds and oxidative stress biomarkers [urine 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-iso-prostaglandin-F2α (8-iso-PGF2α) and blood glutathione (GSH)]. Secondary endpoints included plasma glucose and PSA levels. Compliance was high in all groups (>95%). Plasma selenium levels were increased 93%, 54%, and 86% after 9 months in SeMet and low- and high-dose SY groups, respectively, and returned to baseline levels after a 3-month washout (P < 0.05). Levels of 8-OHdG and 8-iso-PGF2α were decreased 34% and 28%, respectively, after 9 months in the high-dose SY group (P < 0.05). These decreases were greatest in individuals with low baseline plasma levels of selenium (<127 ng/mL). No changes in serum PSA or blood glucose and GSH were observed. Overall, we showed for the first time, reductions in biomarkers of oxidative stress following supplementation with SY but not SeMet in healthy men. These findings suggest that selenium-containing compounds other than SeMet may account for the decrease in oxidative stress.

Safety and chemopreventive effect of Polyphenon E in preventing early and metastatic progression of prostate cancer in TRAMP mice

Prostate cancer treatment is often accompanied by untoward side effects. Therefore, chemoprevention to reduce the risk and inhibit the progression of prostate cancer may be an effective approach to reducing disease burden. We investigated the safety and efficacy of Polyphenon E, a green tea extract, in reducing the progression of prostate cancer in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice. A total of 119 male TRAMP and 119 C57BL/6J mice were treated orally with one of 3 doses of Polyphenon E (200, 500, and 1,000 mg/kg/day) in drinking water ad libitum replicating human achievable doses. Baseline assessments were performed before treatments. Safety and efficacy assessments during treatments were performed when mice were 12, 22, and 32 weeks old. The number and size of tumors in treated TRAMP mice were significantly decreased compared with untreated animals. In untreated 32 weeks old TRAMP mice, prostate carcinoma metastasis to distant sites was observed in 100% of mice (8/8), compared with 13% of mice (2/16) treated with high-dose Polyphenon E during the same period. Furthermore, Polyphenon E treatment significantly inhibited metastasis in TRAMP mice in a dose-dependent manner (P = 0.0003). Long-term (32 weeks) treatment with Polyphenon E was safe and well tolerated with no evidence of toxicity in C57BL/6J mice. Polyphenon E is an effective chemopreventive agent in preventing the progression of prostate cancer to metastasis in TRAMP mice. Polyphenon E showed no toxicity in these mouse models. Our findings provide additional evidence for the safety and chemopreventive effect of Polyphenon E in preventing metastatic progression of prostate cancer.

Use of selenium-silymarin mix reduces lower urinary tract symptoms and prostate specific antigen in men

The aim of this double-blind, placebo controlled clinical trial was to assess the effects of a combination of selenium and silymarin in men with lower urinary tract symptoms, benign prostatic hyperplasia and a prostate specific antigen (PSA) ≤2.5ng/ml. The volunteers were randomized to two groups: the first one (n=26) received 240μg selenium (in the form of yeast l-selenomethionine) plus 570mg silymarin daily for 6 months and the second (n=29) received placebo. Outcome measures were changes in the International Prostate Symptom Score (IPSS), bladder volume (V), urinary flow rate, ultrasound estimated postvoid residual urine volume (RV), serum PSA, testosterone and selenium levels, safety clinical biochemistry, hematology and oxidative stress parameters at baseline and on day 180. The results showed statistically significant differences (p<0.05) between treatment and control groups for the following parameters: IPSS score, urodynamic parameters: maximal rate of urine flow (Qmax), average flow (Qave), V and RV, total PSA value and serum selenium levels. There was a significant reduction in PSA in the selenium-silymarin group but no effect on blood testosterone level. Overall the treatment was well-tolerated with no adverse effects.

Related flavonoids cause cooperative inhibition of the sarcoplasmic reticulum Ca²⁺ ATPase by multimode mechanisms

Flavonoids are group of plant-derived hydroxylated polycyclic molecules found in fruit and vegetables. They are known to bio-accumulate within humans and are considered to have beneficial health effects, including cancer chemoprotection. One mechanism proposed to explain this is that they are able to induce apoptosis in cancer cells by inhibiting a variety of kinases and also the Ca²⁺ ATPase. An investigation was undertaken with respect to the mechanism of inhibition for three flavonoids: quercetin, galangin and 3,6 dihydroxyflavone (3,6-DHF). Each inhibited the Ca²⁺ ATPase with K(i) values of 8.7, 10.3 and 5.4 μM, respectively, showing cooperative inhibition with n ~ 2. Given their similar structures, the flavonoids showed several differences in their mechanisms of inhibition. All three flavonoids stabilized the ATPase in the E₁ conformation and reduced [³²P]-ATP binding. However, both galangin and 3,6-DHF increased the affinity of Ca²⁺ for the ATPase by decreasing the Ca²⁺-dissociation rate constant, whereas quercetin had little effect. Ca²⁺-induced changes in tryptophan fluorescence levels were reduced in the presence of 3,6-DHF and galangin (but not with quercetin), indicating that Ca²⁺-associated changes within the transmembrane helices are altered. Both galangin and quercetin reduced the rates of ATP-dependent phosphorylation and dephosphorylation, whereas 3,6-DHF did not. Modelling studies suggest that flavonoids could potentially bind to two sites: one directly where nucleotides bind within ATP binding site and the other at a site close by. We hypothesize that interactions of these two neighbouring sites may account for both the cooperative inhibition and the multimode mechanisms of action seen with related flavonoids.

Chemopreventive effect of quercetin in MNU and testosterone induced prostate cancer of Sprague-Dawley rats

Prostate cancer becomes an ideal target for chemoprevention because of its high incidence and extended natural history. The consumption of quercetin (plant flavonoid) in diet is associated with decreased risk of disease and many cancers but then this was not elucidated in prostate malignancy. Hence, a study in which the male Sprague-Dawley rats were induced prostate cancer by hormone (testosterone) and carcinogen (MNU) and simultaneously supplemented with quercetin (200 mg/Kg body weight) thrice a week, was conducted. After the treatment period, rats were killed; ventral and dorsolateral lobes of the prostate were dissected. Histology and oxidative stress markers LPO, H2O2, and antioxidant GSH level were measured in both lobes. The lipid peroxidation, H2O2, in (MNU+T) treated rats were increased and GSH level was decreased, whereas simultaneous quercetin-treated rats reverted back to normal level in both ventral and dorsolateral regions. The different patterns of PIN were observed with associated hyperplasia and dysplasia; changes in these regions and the occurrence of this lesion were reduced in simultaneous quercetin-treated rats. The study concluded that dietary quercetin prevented MNU + T-induced prostate carcinogenesis on both ventral and dorsolateral lobes of Sprague-Dawley rats.

Combination of low dose of genistein and daidzein has synergistic preventive effects on isogenic human prostate cancer cells when compared with individual soy isoflavone

The reduced incidence of prostate cancer (PCa) in Asia countries has been attributed to high soy diets, and major soy isoflavones, in particular daidzein and genistein, are thought to be the source of the beneficial and anti-cancer effects of soy foods. However, attention has been drawn to the safety of using high levels of soy isoflavones in humans, which is especially the concern for consumers taking regular soy isoflavone dietary supplements. The main objective of this study is thus to identify a soy isoflavone combination with lower levels of daidzein and genistein to be a more efficacious and safer chemo-preventive agent for PCa. The anticancer effects of daidzein and genistein, and their combinations on early-stage androgen-dependent PCa cells (LNCaP) and bone metastatic LNCaP-derivative PCa cells (C4-2B) were compared. Cells were treated with varying concentrations of daidzein, genistein (25-200 μM) or their combinations (25 or 50 μM) and cell proliferation, apoptosis, cell cycles and cellular uptakes of the isoflavones were measured after 48 h. Daidzein and genistein showed a synergistic effect on inhibiting cell proliferation and inducing apoptosis of both PCa cells. Twenty-five μM daidzein/50 μM genistein and 50 μM daidzein/50 μM genistein significantly increased the apoptotic effects on C4-2B cells although they did not show any effect when used individually. Except 50 μM daidzein/50 μM genistein, all other combinations had no impacts on cell cycles. For treatment with soy isoflavone combination, genistein was always better taken up than daidzein by both LNCaP and C4-2B cells.

Protective effect of γ-tocopherol-enriched diet on N-methyl-N-nitrosourea-induced epithelial dysplasia in rat ventral prostate

Despite recent advances in understanding the biological basis of prostate cancer (PCa), the management of this disease remains a challenge. Chemoprotective agents have been used to protect against or eradicate prostate malignancies. Here, we investigated the protective effect of γ-tocopherol on N-methyl-N-nitrosourea (MNU)-induced epithelial dysplasia in the rat ventral prostate (VP). Thirty-two male Wistar rats were divided into four groups (n = 8): control (CT): healthy control animals fed a standard diet; control+γ-tocopherol (CT+γT): healthy control animals without intervention fed a γ-tocopherol-enriched diet (20 mg/kg); N-methyl-N-nitrosourea (MNU): rats that received a single dose of MNU (30 mg/kg) plus testosterone propionate (100 mg/kg) and were fed a standard diet; and MNU+γ-tocopherol (MNU+γT): rats that received the same treatment of MNU plus testosterone and were fed with a γ-tocopherol-enriched diet (20 mg/kg). After 4 months, the VPs were excised to evaluate morphology, cell proliferation and apoptosis, as well as cyclooxygenase-2 (Cox-2), glutathione-S-transferase-pi (GST-pi) and androgen receptor (AR) protein expression, and matrix metalloproteinase-9 (MMP-9) activity. An increase in the incidence of epithelial dysplasias, such as stratified epithelial hyperplasia and squamous metaplasia, in the MNU group was accompanied by augmented cell proliferation, GST-pi and Cox-2 immunoexpression and pro-MMP-9 activity. Stromal thickening and inflammatory foci were also observed. The administration of a γ-tocopherol-enriched diet significantly attenuated the adverse effects of MNU in the VP. The incidence of epithelial dysplasia decreased, along with the cell proliferation index, GST-pi and Cox-2 immunoexpression. The gelatinolytic activity of pro-MMP-9 returned to the levels observed for the CT group. These results suggest that γ-tocopherol acts as a protective agent against MNU-induced prostatic disorders in the rat ventral prostate.

Influence of lycopene on cell viability, cell cycle, and apoptosis of human prostate cancer and benign hyperplastic cells

Prostate cancer is the most common malignancy in men and the second leading cause of cancer-related mortality in men of the Western world. Lycopene has received attention because of its expcted potential to prevent cancer. In the present study, we evaluated the influence of lycopene on cell viability, cell cycle, and apoptosis of human prostate cancer cells and benign prostate hyperplastic cells. Using MTT assay, we observed a decrease of cell viability in all cancer cell lines after treatment with lycopene, which decreased the percentage of cells in G0/G1 phase and increased in S and G2/M phases after 96 h of treatment in metastatic prostate cancer cell lineages. Flow citometry analysis of cell cycle revealed lycopene promoted cell cycle arrest in G0/G1 phase after 48 and 96 h of treatment in a primary cancer cell line. Using real time PCR assay, lycopene also induced apoptosis in prostate cancer cells with altered gene expression of Bax and Bcl-2. No effect was observed in benign prostate hyperplasia cells. These results suggest an effect of lycopene on activity of human prostate cancer cells.

Trimethoxy-resveratrol and piceatannol administered orally suppress and inhibit tumor formation and growth in prostate cancer xenografts

BACKGROUND

Resveratrol (Res) is recognized as a promising cancer chemoprevention dietary polyphenol with antioxidative, anti-inflammatory, and anticancer properties. However, the role of its analogues in prostate cancer (PCa) chemoprevention is unknown.

METHODS

We synthesized several natural and synthetic analogues of Res and characterized their effects on PCa cells in vitro using a cell proliferation assay. A colony formation assay and in vitro validation of luciferase (Luc) activity was done for LNCaP-Luc cells that were consequently used for in vivo studies. The efficacy of Res, trimethoxy-resveratrol (3M-Res) and piceatannol (PIC) was studied in a subcutaneous (s.c.) model of PCa using oral gavage. Tumor progression was monitored by traditional caliper and bioluminescent imaging. The levels of cytokines in serum were examined by ELISA, and the levels of compounds in serum and tumor tissues were determined by gas chromatography-mass spectrometry.

RESULTS

We examined the anti-proliferative activities of Res/analogues in three PCa cell lines. We further compared the chemopreventive effects of oral Res, 3M-Res, and PIC in LNCaP-Luc-xenografts. We found that 2 weeks pretreatment with the compounds diminished cell colonization, reduced tumor volume, and decreased tumor growth in the xenografts. Both 3M-Res and PIC demonstrated higher potency in inhibiting tumor progression compared to Res. Notably, 3M-Res was the most active in inhibiting cell proliferation and suppressing colony formation, and its accumulation in both serum and tumor tissues was the highest.

CONCLUSIONS

Our findings offer strong pre-clinical evidence for the utilization of dietary stilbenes, particularly 3M-Res, as novel, potent, effective chemopreventive agents in PCa.

Therapeutic applications of herbal medicines for cancer patients

Medicinal herbs and their derivative phytocompounds are being increasingly recognized as useful complementary treatments for cancer. A large volume of clinical studies have reported the beneficial effects of herbal medicines on the survival, immune modulation, and quality of life (QOL) of cancer patients, when these herbal medicines are used in combination with conventional therapeutics. Here, we briefly review some examples of clinical studies that investigated the use of herbal medicines for various cancers and the development of randomized controlled trials (RCTs) in this emerging research area. In addition, we also report recent studies on the biochemical and cellular mechanisms of herbal medicines in specific tumor microenvironments and the potential application of specific phytochemicals in cell-based cancer vaccine systems. This review should provide useful technological support for evidence-based application of herbal medicines in cancer therapy.