Tea beverage in chemoprevention of prostate cancer: a mini-review

Anti-Obesity Drug Delivery Systems: Recent Progress and Challenges

Obesity has reached an epidemic proportion in the last thirty years, and it is recognized as a major health issue in modern society now with the possibility of serious social and economic consequences. By the year 2030, nearly 60% of the global population may be obese or overweight, which emphasizes a need for novel obesity treatments. Various traditional approaches, such as pharmacotherapy and bariatric surgery, have been utilized in clinical settings to treat obesity. However, these methods frequently show the possibility of side effects while remaining ineffective. There is, therefore, an urgent need for alternative obesity treatments with improved efficacy and specificity. Polymeric materials and chemical strategies are employed in emerging drug delivery systems (DDSs) to enhance therapy effectiveness and specificity by stabilizing and controlling the release of active molecules such as natural ingredients. Designing DDSs is currently a top priority research objective with an eye towards creating obesity treatment approaches. In reality, the most recent trends in the literature demonstrate that there are not enough in-depth reviews that emphasize the current knowledge based on the creation and design of DDSs for obesity treatment. It is also observed in the existing literature that a complex interplay of different physical and chemical parameters must be considered carefully to determine the effectiveness of the DDSs, including microneedles, for obesity treatment. Additionally, it is observed that these properties depend on how the DDS is synthesized. Although many studies are at the animal-study stage, the use of more advanced DDS techniques would significantly enhance the development of safe and efficient treatment approaches for obese people in the future. Considering these, this review provides an overview of the current anti-obesity treatment approaches as well as the conventional anti-obesity therapeutics. The article aims to conduct an in-depth discussion on the current trends in obesity treatment approaches. Filling in this knowledge gap will lead to a greater understanding of the safest ways to manage obesity.

Preventive Effects of Green Tea Extract against Obesity Development in Zebrafish

Various natural products (NPs) have been used to treat obesity and related diseases. However, the best way to fight obesity is preventive, with accurate body weight management through exercise, diet, or bioactive NPs to avoid obesity development. We demonstrated that green tea extract (GTE) is an anti-obesity NP using a zebrafish obesity model. Based on a hypothesis that GTE can prevent obesity, the objective of this study was to assess GTE's ability to attenuate obesity development. Juvenile zebrafish were pretreated with GTE for seven days before obesity induction via a high-fat diet; adult zebrafish were pretreated with GTE for two weeks before obesity induction by overfeeding. As a preventive intervention, GTE significantly decreased visceral adipose tissue accumulation in juveniles and ameliorated visceral adiposity and plasma triglyceride levels in adult zebrafish obesity models. RNA sequencing analysis was performed using liver tissues from adult obese zebrafish, with or without GTE administration, to investigate the underlying molecular mechanism. Transcriptome analysis revealed that preventive GTE treatment affects several pathways associated with anti-obesity regulation, including activation of STAT and downregulation of CEBP signaling pathways. In conclusion, GTE could be used as a preventive agent against obesity.

RNA-seq Based Transcriptome Analysis of the Anti-Obesity Effect of Green Tea Extract Using Zebrafish Obesity Models

Green tea is a popular beverage that is rich in polyphenolic compounds such as catechins. Its major content, (-)-epigallocatechin-3-gallate, has been shown to have beneficial effects on several diseases including cancer, metabolic syndrome, cardiovascular diseases, and neurodegenerative diseases. The aim of this study was to assess the anti-obesity effects and the underlying molecular mechanisms of green tea extract (GTE) using zebrafish larva and adult obesity models. We administered 100 μg/mL GTE to zebrafish larvae and performed a short-term obesogenic test. GTE significantly decreased the visceral adipose tissue volume induced by a high-fat diet. Oral administration (250 µg/g body weight/day) of GTE to adult diet-induced obese zebrafish also significantly reduced their visceral adipose tissue volume, with a reduction of plasma triglyceride and total cholesterol levels. To investigate the molecular mechanism underlying the GTE effects, we conducted RNA sequencing using liver tissues of adult zebrafish and found that GTE may ameliorate the obese phenotypes via the activation of Wnt/β-catenin and adenosine monophosphate-activated protein kinase (AMPK) pathway signaling. In addition, the comparative transcriptome analysis revealed that zebrafish and mammals may share a common molecular response to GTE. Our findings suggest that daily consumption of green tea may be beneficial for the prevention and treatment of obesity.

Lupeol suppresses migration and invasion via p38/MAPK and PI3K/Akt signaling pathways in human osteosarcoma U-2 OS cells

Lupeol, one of the common components from the fruits and natural foods, has been reported to exert antitumor activities in many human cancer cell lines; however, its effects on osteosarcoma cell metastasis were not elucidated. In the present study, lupeol at 10–25 μM induced cell morphological changes and decreased total viable cell number in U-2 OS cells. Lupeol (5–15 μM) suppressed cell mobility, migration, and invasion by wound healing and transwell chamber assays, respectively. Lupeol inhibited the activities of MMP-2 and −9 in U-2 OS cells by gelatin zymography assay. Lupeol significantly decreased PI3K, pAKT, β-catenin, and increased GSK3β. Furthermore, lupeol decreased the expressions of Ras, p-Raf-1, p-p38, and β-catenin. Lupeol also decreased uPA, MMP-2, MMP-9, and N-cadherin but increased VE-cadherin in U-2 OS cells. Based on these observations, we suggest that lupeol can be used in anti-metastasis of human osteosarcoma cells in the future.

Anti-Cancer Effects of Green Tea Polyphenols Against Prostate Cancer

Prostate cancer is the most common cancer among men. Green tea consumption is reported to play an important role in the prevention of carcinogenesis in many types of malignancies, including prostate cancer; however, epidemiological studies show conflicting results regarding these anti-cancer effects. In recent years, in addition to prevention, many investigators have shown the efficacy and safety of green tea polyphenols and combination therapies with green tea extracts and anti-cancer agents in in vivo and in vitro studies. Furthermore, numerous studies have revealed the molecular mechanisms of the anti-cancer effects of green tea extracts. We believe that improved understanding of the detailed pathological roles at the molecular level is important to evaluate the prevention and treatment of prostate cancer. Therefore, in this review, we present current knowledge regarding the anti-cancer effects of green tea extracts in the prevention and treatment of prostate cancer, with a particular focus on the molecular mechanisms of action, such as influencing tumor growth, apoptosis, androgen receptor signaling, cell cycle, and various malignant behaviors. Finally, the future direction for the use of green tea extracts as treatment strategies in patients with prostate cancer is introduced.

Magnetic solid-phase extraction of pyrethroid insecticides from tea infusions using ionic liquid-modified magnetic zeolitic imidazolate framework-8 as an adsorbent

A MSPE-GC-MS/MS method was developed for the analysis of pyrethroids from tea infusions using Fe₃O₄/ZIF-8/IL as an adsorbent.

A review of pomegranate in prostate cancer

Background

Preclinical studies showing that pomegranate juice and its components inhibit prostate cancer led to multiple clinical trials to determine whether pomegranate products could slow the growth of prostate cancer. This review summarizes the preclinical data and discusses the results of the clinical trials.

Methods

Trials targeted patients on active surveillance, neoadjuvant patients, patients with biochemical recurrence (BCR) following local therapy for prostate cancer, and patients with metastatic castration-resistant prostate cancer (mCRPC).

Results

In the BCR patient population, early phase II trials of both pomegranate juice and extract showed significant lengthening of PSA doubling time (PSADT), and confirmed the safety of pomegranate products. While a placebo-controlled phase III trial determined that pomegranate extract did not significantly prolong PSADT in BCR patients, a preplanned subset analysis of patients with the manganese superoxide dismutase (MnSOD) AA genotype showed greater PSADT lengthening on the pomegranate extract arm. In the neoadjuvant population, a large trial demonstrated a significant increase in urolithin A and a non-significant reduction in 8-OHdG, a marker of oxidation in prostate cancer tissue, on the pomegranate arm vs. the placebo arm. In addition, a randomized clinical trial of a polyphenol-rich multi-component food supplement tablet, including 31.25% pomegranate extract, found significant slowing of PSA increase in the food supplement arm vs. placebo in men on active surveillance and those experiencing biochemical recurrence.

Conclusions

Pomegranate juice and extract are safe but did not significantly improve outcomes in BCR patients in a large placebo controlled trial. However a subset of BCR patients with the MnSOD AA genotype appear to respond positively to the antioxidant effects of pomegranate treatment. Phase II trials of 100% pomegranate products in neoadjuvant patients and patients with mCRPC were negative. A multi-component food supplement showed promising results in a phase II study in active surveillance and BCR patients.

Targeted nanoparticles encapsulating (-)-epigallocatechin-3-gallate for prostate cancer prevention and therapy

Earlier we introduced the concept of ‘nanochemoprevention’ i.e. the use of nanotechnology to improve the outcome of cancer chemoprevention. Here, we extended our work and developed polymeric EGCG-encapsulated nanoparticles (NPs) targeted with small molecular entities, able to bind to prostate specific membrane antigen (PSMA), a transmembrane protein that is overexpressed in prostate cancer (PCa), and evaluated their efficacy in preclinical studies. First, we performed a molecular recognition of DCL- and AG-PEGylation on ligand binding on PSMA active site. Next, the biocompatible polymers PLGA-PEG-A were synthesized and used as base to conjugate DCL or AG to obtain the respective copolymers, needed for the preparation of targeted NPs. The resulting EGCG encapsulating NPs led to an enhanced anti-proliferative activity in PCa cell lines compared to the free EGCG. The behavior of EGCG encapsulated in NPs in modulating apoptosis and cell-cycle, was also determined. Then, in vivo experiments, in mouse xenograft model of prostatic tumor, using EGCG-loaded NPs, with a model of targeted nanosystems, were conducted. The obtained data supported our hypothesis of target-specific enhanced bioavailability and limited unwanted toxicity, thus leading to a significant potential for probable clinical outcome.

Association between green tea/coffee consumption and biliary tract cancer: A population-based cohort study in Japan

Green tea and coffee consumption may decrease the risk of some types of cancers. However, their effects on biliary tract cancer (BTC) have been poorly understood. In this population‐based prospective cohort study in Japan, we investigated the association of green tea (total green tea, Sencha, and Bancha/Genmaicha) and coffee consumption with the risk for BTC and its subtypes, gallbladder cancer, and extrahepatic bile duct cancer. The hazard ratios and 95% confidence intervals were calculated using the Cox proportional hazard model. A total of 89 555 people aged 45–74 years were enrolled between 1995 and 1999 and followed up for 1 138 623 person‐years until 2010, during which 284 cases of BTC were identified. Consumption of >720 mL/day green tea was significantly associated with decreased risk compared with consumption of ≤120 mL/day (hazard ratio = 0.67 [95% confidence interval, 0.46–0.97]), and a non‐significant trend of decreased risk associated with increased consumption was observed (P‐trend = 0.095). In the analysis according to the location of the primary tumor, consuming >120 mL green tea tended to be associated with decreased risk of gallbladder cancer and extrahepatic bile duct cancer. When Sencha and Bancha/Genmaicha were analyzed separately, we observed a non‐significant trend of decreased risk of BTC associated with Sencha but no association with Bancha/Genmaicha. For coffee, there was no clear association with biliary tract, gallbladder, or extrahepatic bile duct cancer. Our findings suggest that high green tea consumption may lower the risk of BTC, and the effect may be attributable to Sencha consumption.

Lupeol: An antioxidant triterpene in Ficus pseudopalma Blanco (Moraceae)

OBJECTIVE

To assess the antioxidant activity of Ficus pseudopalma Blanco (Moraceae) (F. pseudopalma) and characterize the active components present in it.

METHODS

Column chromatography of crude ethanol leaf extract of F. pseudopalma was performed and seven fractions were obtained, labeled as F1, F2, F3, F4, F5, F6, F7. DPPH, FRAP, Griess, Fenton and superoxide radical scavenging assays were performed to assess the antioxidant ability of the fractions. Thin layer chromatography (TLC), high performance liquid chromatography and Fourier transfer infrared spectroscopy (FTIR) were performed to identify and characterize the bioactive component present in each fractions of F. pseudopalma.

RESULTS

DPPH and FRAP assay showed that F5, F6 and F7 exhibited the good proton accepting ability and reducing power as compared to the other fractions. All fractions exhibited a good nitric oxide radical scavenging activity wherein F1, F2 and F3 showed the highest inhibition. However, all of the fractions exhibited a stimulatory activity on hydroxyl and superoxide radicals. Lupeol matched one of the spots on the thin layer chromatography chromatogram of the fractions. Linear gradient high performance liquid chromatography and spiking of lupeol with the fraction revealed the presence of 5.84 mg/L lupeol in F6. Infrared spectra of the fractions revealed the presence of C-C, OH, aromatic C=C and C=O groups.

CONCLUSIONS

The identified lupeol in F. pseudopalma may be responsible for the exhibited antioxidant property of the plant. Furthermore, knowing the antioxidant capability of the plant, F. pseudopalma can be developed into products which can help prevent the occurrence of oxidative stress related diseases.

Kallikrein 3 and vitamin D receptor polymorphisms: potentials environmental risk factors for prostate cancer

Objective

To investigate the relationship and interaction of the single nucleotide polymorphisms (SNPs) of KLK3 and VDR and environmental factors with the predisposition to prostate cancer within Chinese population.

Methods

The comparison between 108 patients and 242 healthy people was carried out by using the TaqMan/MGB Probe Technology to determine the genotypes of KLK3(rs2735839 is located between KLK2 and KLK3) and VDR (rs731236 is located exon 9). Univariate and multivariate logistic regression model were used to assess the connection of genetic polymorphisms and environmental risk factors with PCa by collecting demographic information, as well as BMI, consumption of cigarettes, alcohol, and tea, exercise, and other environmental risk factors.

Results

The appearing frequencies of AA, AG, and GG genotypes at the SNPs rs2735839 (A/G) for KLK3 were 13.89%, 62.96% and 23.15% in PCa and 37.19%, 44.63%, 18.18% in control, respectively; these two groups are statistically different (P = 0.00). While the appearing frequencies of TT, TC, and CC genotypes at the SNPs rs731236 (T/C) for VDR were 88.89%, 9, 26%, 1.85% and 90.50%, 9.10%, 0.40% in control, respectively, with no significant statistical difference between the two group. The study confirmed decreasing risk in tea drinkers (OR = 0.58, 95% CI = 0.35-0.96).

Conclusions

Our studies indicate that environmental factor-tea drinking is associated with the development of PCa. The habit of drinking tea is a protective factor against PCa. The SNPs rs2735839 for KLK3 is strongly related to the development of PCa, while the SNPs rs731236 for VDR is not.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/9759981571058803.

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.

Suppression of urinary bladder urothelial carcinoma cell by the ethanol extract of pomegranate fruit through cell cycle arrest and apoptosis

Background

Pomegranate possesses many medicinal properties such as antioxidant, anti-inflammation and antitumor. It has been extensively used as a folk medicine by many cultures. Pomegranate fruit has been shown to have the inhibitory efficacy against prostate cancer and lung cancer in vitro and in vivo. It can be exploited in chemoprevention and chemotherapy of prostate cancer. In this study we examined the anti-cancer efficacy of pomegranate fruit grown in Taiwan against urinary bladder urothelial carcinoma (UBUC) and its mechanism of action.

Methods

Edible portion of Taiwanese pomegranate was extracted using ethanol and the anti-cancer effectiveness of ethanol extract was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometry and western immunoblotting were exploited to uncover the molecular pathways underlying anti-UBUC activity of Taiwanese pomegranate ethanol extract.

Results

This study demonstrated that Taiwanese pomegranate fruit ethanol extract (PEE) could effectively restrict the proliferation of UBUC T24 and J82 cells. Cell cycle analyses indicated that the S phase arrest induced by PEE treatment might be caused by an increase in cyclin A protein level and a decrease in the expression of cyclin-dependent kinase 1. The results of western immunoblotting demonstrated that PEE treatment could not only evoke the activation of pro-caspase-3, -8,-9 but also increase Bax/Bcl-2 ratio in T24 cells. The above observations implicated that PEE administration might trigger the apoptosis in T24 cells through death receptor signaling and mitochondrial damage pathway. Besides we found that PEE exposure to T24 cells could provoke intensive activation of procaspase-12 and enhance the expressions of CHOP and Bip, endoplasmic reticulum (ER) stress marker, suggesting that ER stress might be the cardinal apoptotic mechanism of PEE-induced inhibition of bladder cancer cell.

Conclusions

The analytical results of this study help to provide insight into the molecular mechanism of induced bladder cancer cell apoptosis by pomegranate and to develop novel mechanism-based chemopreventive strategy for bladder cancer.

New insights into the mechanisms of green tea catechins in the chemoprevention of prostate cancer

Prostate cancer is the most commonly diagnosed cancer and second most common cause of cancer deaths in American men. Its long latency, slow progression, and high incidence rate make prostate cancer ideal for targeted chemopreventative therapies. Therefore, chemoprevention studies and clinical trials are essential for reducing the burden of prostate cancer on society. Epidemiological studies suggest that tea consumption has protective effects against a variety of human cancers, including that of the prostate. Laboratory and clinical studies have demonstrated that green tea components, specifically the green tea catechin (GTC) epigallocatechin gallate, can induce apoptosis, suppress progression, and inhibit invasion and metastasis of prostate cancer. Multiple mechanisms are involved in the chemoprevention of prostate cancer with GTCs; understanding and refining models of fundamental molecular pathways by which GTCs modulate prostate carcinogenesis is essential to apply the utilization of green tea for the chemoprevention of prostate cancer in clinical settings. The objective of this article is to review and summarize the most current literature focusing on the major mechanisms of GTC chemopreventative action on prostate cancer from laboratory, in vitro, and in vivo studies, and clinical chemoprevention trials.

d -Limonene sensitizes docetaxel-induced cytotoxicity in human prostate cancer cells: Generation of reactive oxygen species and induction of apoptosis

BACKGROUND

Clinical trials have shown that docetaxel combined with other novel agents can improve the survival of androgen-independent prostate cancer patients. d -Limonene, a non-nutrient dietary component, has been found to inhibit various cancer cell growths without toxicity. We sought to characterize whether a non-toxic dose of d -limonene may enhance tumor response to docetaxel in an in vitro model of metastatic prostate cancer.

MATERIALS AND METHODS

Human prostate carcinoma DU-145 and normal prostate epithelial PZ-HPV-7 cells were treated with various concentrations of d -limonene, docetaxel or a combination of both, and cell viability was determined by MTT assay. Intracellular reactive oxygen species (ROS), reduced glutathione (GSH) and caspase activity were measured. Apoptosis and apoptosis-related proteins were studied by enzyme-linked immunosorbent assay and Western blotting, respectively.

RESULTS

d -Limonene and docetaxel in combination significantly enhanced the cytotoxicity to DU-145 cells than PZ-HPV-7 cells. Exposure of DU-145 cells to a combined d -limonene and docetaxel resulted in higher ROS generation, depletion of GSH, accompanied by increased caspase activity than docetaxel alone. It also triggered a series of effects involving cytochrome c , cleavages of caspase-9, 3 and poly (ADP-ribose) polymerase, and a shift in Bad:Bcl-xL ratio in favor of apoptosis. Apoptotic effect was significantly blocked on pretreatment with N -acetylcystein, indicating that antitumor effect is initiated by ROS generation, and caspase cascades contribute to the cell death.

CONCLUSION

Our results show, for the first time, that d -limonene enhanced the antitumor effect of docetaxel against prostate cancer cells without being toxic to normal prostate epithelial cells. The combined beneficial effect could be through the modulation of proteins involved in mitochondrial pathway of apoptosis. d -Limonene could be used as a potent non-toxic agent to improve the treatment outcome of hormone-refractory prostate cancer with docetaxel.

Targeted biocompatible nanoparticles for the delivery of (-)-epigallocatechin 3-gallate to prostate cancer cells

Molecular targeted cancer therapy mediated by nanoparticles (NPs) is a promising strategy to overcome the lack of specificity of conventional chemotherapeutic agents. In this context, the prostate-specific membrane antigen (PSMA) has demonstrated a powerful potential for the management of prostate cancer (PCa). Cancer chemoprevention by phytochemicals is emerging as a suitable approach for the treatment of early carcinogenic processes. Since (-)-epigallocatechin 3-gallate (EGCG) has shown potent chemopreventive efficacy for PCa, we designed and developed novel targeted NPs in order to selectively deliver EGCG to cancer cells. Herein, to explore the recent concept of "nanochemoprevention", we present a study on EGCG-loaded NPs consisting of biocompatible polymers, functionalized with small molecules targeting PSMA, that exhibited a selective in vitro efficacy against PSMA-expressing PCa cells. This approach could be beneficial for high risk patients and would fulfill a significant therapeutic need, thus opening new perspectives for novel and effective treatment for PCa.

Nanochemoprevention: sustained release of bioactive food components for cancer prevention

Chemoprevention, especially through the use of naturally occurring phytochemicals capable of impeding the process of carcinogenesis at one or more steps, is an ideal approach for cancer management. Despite accomplished outcomes in preclinical settings, its applicability to humans has met with limited success for many reasons including inefficient systemic delivery and bioavailability of promising chemopreventive agents. We have recently introduced a novel concept of "nanochemoprevention" that utilizes nanotechnology for enhancing the outcome of chemoprevention (Cancer Res 69, 1712-1716, 2009). To establish the usefulness of nanochemoprevention in cancer management, we studied the efficacy of a well identified chemopreventive agent epigallocatechin-3-gallate (EGCG) encapsulated in polylactic acid (PLA) and polyethylene glycol (PEG) nanoparticles (hereafter referred to as nano-EGCG) in preclinical settings. Nano-EGCG was found to retain its biological effectiveness, with over 10-fold dose advantage compared to nonencapsulated EGCG for exerting its cell growth inhibition, proapoptotic, and angiogenic inhibitory effects. Nano-EGCG was also observed to be effective in inhibiting tumor cell growth in athymic nude mice, with over 10-fold dose advantage compared to nonencapsulated EGCG. The rate of degradation of nonencapsulated EGCG was rapid, with a complete degradation within 4 h, whereas nano-EGCG had a significantly longer half-life. This study provides a foundation for the use of nanoparticle-mediated delivery of natural products to enhance the bioavailability of active agents for their enhanced effective and chemopreventive potential. In doing this, it is hoped that perceived toxicity concerns associated with prolonged use of agents could also be minimized. Oral consumption is the most desirable and acceptable form of delivery of chemopreventive agents. One disadvantage of using PLA-PEG nanoparticles is its unstable nature in acidic environment; and therefore, it is not recommended for oral consumption. To overcome this obstacle, it will be important to develop nanoparticles encapsulating phytochemicals that are suitable for oral consumption.

Modeling prostate cancer: a perspective on transgenic mouse models

Despite considerable success in treatment of early stage localized prostate cancer (PC), acute inadequacy of late stage PC treatment and its inherent heterogeneity poses a formidable challenge. Clearly, an improved understanding of PC genesis and progression along with the development of new targeted therapies are warranted. Animal models, especially, transgenic immunocompetent mouse models, have proven to be the best ally in this respect. A series of models have been developed by modulation of expression of genes implicated in cancer-genesis and progression; mainly, modulation of expression of oncogenes, steroid hormone receptors, growth factors and their receptors, cell cycle and apoptosis regulators, and tumor suppressor genes have been used. Such models have contributed significantly to our understanding of the molecular and pathological aspects of PC initiation and progression. In particular, the transgenic mouse models based on multiple genetic alterations can more accurately address the inherent complexity of PC, not only in revealing the mechanisms of tumorigenesis and progression but also for clinically relevant evaluation of new therapies. Further, with advances in conditional knockout technologies, otherwise embryonically lethal gene changes can be incorporated leading to the development of new generation transgenics, thus adding significantly to our existing knowledge base. Different models and their relevance to PC research are discussed.

Nanochemoprevention by bioactive food components: a perspective

Chemoprevention through the use of bioactive food components is a practical approach for cancer control. Despite abundant efficacy data under preclinical settings, this strategy has resulted in limited success for human cancer control. Amongst many reasons, inefficient systemic delivery and bioavailability of promising chemopreventive agents are considered to significantly contribute to such a disconnect. We recently introduced a novel concept in which we utilized nanotechnology for enhancing the outcome of chemoprevention (Cancer Res. 2009; 69:1712-6) and termed it nanochemoprevention. To establish the proof-of-principle of nanotechnology for cancer management, we determined the efficacy of a well-known chemopreventive agent epigallocatechin-3-gallate (EGCG) encapsulated in polylactic acid (PLA)-polyethylene glycol (PEG) nanoparticles in preclinical settings and observed that, compared to non-encapsulated EGCG, nano-EGCG retained its biological efficacy with over 10-fold dose advantage both in cell culture system and in vivo settings in athymic nude mice implanted with human prostate cancer cells. This study laid the foundation of nanochemoprevention by bioactive food components. Since oral consumption is the most desirable and acceptable form of delivery of bioactive food components, it will be important to develop nanoparticles containing bioactive food components that are suitable for oral consumption for which experiments are underway in this laboratory.

Pomegranate extract induces apoptosis in human prostate cancer cells by modulation of the IGF-IGFBP axis

The IGF axis is critical for the regulation of apoptosis in many human cancer cell lines. Recently, potent anti-tumorigenic effects of pomegranate juice and extracts have been reported. Consequently, pomegranate has potential not only as a treatment but also as a preventative measure against certain types of cancer, including prostate. In this study, we investigated the relationship between pomegranate-induced apoptosis in human prostate cancer cells and the IGF/IGFBP system. Treatment of LAPC4 prostate cancer cells with 10microg/ml POMx, a highly potent pomegranate extract prepared from skin and arils minus seeds and standardized to ellagitannin content (37% punicalagins by HPLC), resulted in inhibition of cell proliferation and induction of apoptosis. Interestingly, co-treatment with POMx and IGFBP-3 revealed synergistic stimulation of apoptosis and additive inhibition of cell growth. Western blot analysis revealed that treatment with POMx or POMx/IGFBP-3 combination resulted in increased JNK phosphorylation, and decreased Akt and mTOR activation, consistent with a growth inhibitory, pro-apoptotic function. We also investigated the relationship between IGF-1 and pomegranate-induced apoptosis in 22RV1 prostate cancer cells. Co-treatment with 100ng/ml IGF-1 completely blocked apoptosis induction by POMx. In contrast, IGF-I failed to inhibit POMx-induced apoptosis in R(-) cells, suggesting the importance of IGF-IR. POMx-treatment decreased Igf1 mRNA expression in a dose-dependent manner indicating that its actions also involve tumor-specific suppression of IGF-1. These studies revealed novel interactions between the IGF system and pomegranate-induced apoptosis.

Polyphenols from green tea and pomegranate for prevention of prostate cancer

Prostate cancer (PCa) is the most common non-cutaneous cancer diagnosed in North America with similar trends in many Western countries. Geographic, epidemiological and laboratory studies suggest a role for dietary constituents in the etiology as well as prevention of PCa. The rising incidence of PCa in several countries appears to be coincidental with adoption of western lifestyle. Increase in the incidence of PCa has also been found in Asian populations migrating to the west. These facts give numerous leads to explore testable PCa prevention strategies. There is growing evidence in support of use of dietary ingredients in prevention and treatment of PCa. While substantial data exists in favor of use of polyphenols from tea as PCa chemopreventive agent, interest in anti-cancer properties of polyphenols from pomegranate has recently emerged. This review summarizes current literature on the effects of polyphenols from green tea and pomegranate against PCa.

Green tea catechins suppress the DNA synthesis marker MCM7 in the TRAMP model of prostate cancer

Green tea catechins (GTCs) exert chemopreventive effects in many cancer models. Several studies implicate the DNA synthesis marker minichromosome maintenance protein 7 (MCM7) in prostate cancer progression, growth and invasion; representing a novel therapeutic target. In this study, we investigated the effect of GTCs on MCM7 expression in the transgenic adenocarcinoma mouse prostate model (TRAMP). DNA microarray, immunohistochemistry and western blot analysis showed that GTCs significantly suppressed MCM7 in the TRAMP mice treated with GTCs. Our study indicates that the cellular DNA replication factor MCM7 is involved in prostate cancer (CaP) and MCM7 gene expression was reduced by GTCs. Together, these results suggest a possible role of GTCs in CaP chemoprevention in which MCM7 plays a critical role.

Introducing nanochemoprevention as a novel approach for cancer control: proof of principle with green tea polyphenol epigallocatechin-3-gallate

Chemoprevention, especially through the use of naturally occurring phytochemicals capable of impeding the process of one or more steps of carcinogenesis process, is a promising approach for cancer management. Despite promising results in preclinical settings, its applicability to humans has met with limited success largely due to inefficient systemic delivery and bioavailability of promising chemopreventive agents. Here, we introduce the concept of nanochemoprevention, which uses nanotechnology for enhancing the outcome of chemoprevention. We encapsulated green tea polyphenol epigallocatechin-3-gallate (EGCG) in polylactic acid-polyethylene glycol nanoparticles and observed that encapsulated EGCG retains its biological effectiveness with over 10-fold dose advantage for exerting its proapoptotic and angiogenesis inhibitory effects, critically important determinants of chemopreventive effects of EGCG in both in vitro and in vivo systems. Thus, this study could serve as a basis for the use of nanoparticle-mediated delivery to enhance bioavailability and limit any unwanted toxicity of chemopreventive agents, such as EGCG.

Bioavailability issues in studying the health effects of plant polyphenolic compounds

Polyphenolic compounds are common in the diet and have been suggested to have a number of beneficial health effects including prevention of cancer, cardiovascular disease, diabetes, and others. For some dietary polyphenols, certain benficial effects are suggested by epidemiological studies, some are supported by studies in animal models, and still others are extrapolated from studies in vitro. Because of the relatively poor bioavailability of many of these compounds, the molecular basis of these beneficial effects is not clear. In the present review, we discuss the potential health benefits of dietary polyphenols from the point of view of bioavailability. Tea catechins, curcumin, and proanthocyanidins are used as examples to illustrate some of the problems that need to be resolved. Further research on both the biological activity and bioavailability of dietary polyphenols is needed to properly assess their usefulness for the prevention and treatment of disease.

Ellagic acid, pomegranate and prostate cancer -- a mini review

There is currently a shifting focus towards finding natural compounds that may prevent or treat cancer, due to the problems that exist with current chemotherapeutic regimens. The fruit of the Punica granatum (pomegranate) contains hundreds of phytochemicals and pomegranate extracts have recently been shown to exhibit antioxidant properties, thought to be due to the action of ellagic acid, the main polyphenol in pomegranate. In this mini review the effects of pomegranate extracts and ellagic acid on the proliferation of prostate cancer cells and their future potential are discussed.

Tea or coffee? A case study on evidence for dietary advice

The present paper explores the level of evidence required to justify giving dietary advice to the public. There are important practical differences between the development of public health nutrition guidelines and guidelines for clinical practice. While the gold standard for evidence for clinical practice guidelines is a meta-analysis of a number of randomised controlled trials, this is often unrealistic and sometimes unethical for the evaluation of public health nutrition interventions. Hence, epidemiological studies make up the bulk of evidence for nutrition guidelines. Tea and coffee are an interesting case study in relation to this issue. They are two of the most commonly consumed beverages worldwide, yet there is little dietary advice on their use. The evidence for a relationship between coffee or tea consumption and several diseases is discussed. The available studies, predominantly epidemiological, together with animal and in vitro studies, indicate that coffee and tea are both safe beverages. However, tea is the healthier option because it has a possible role in the prevention of several cancers and CVD. While the evidence for such relationships is not strong, the public will continue to drink both tea and coffee, and will continue to ask nutritionists to make recommendations. It is therefore argued that advice should be given on the best available data, as waiting for complete data to become available could have severe consequences for public health.

Epigallocatechin-3-Gallate suppresses early stage, but not late stage prostate cancer in TRAMP mice: mechanisms of action

BACKGROUND

Prostate cancer (PCa) is the second leading cause of cancer-related death in men in the United States. Many men have implemented purported chemopreventive agents into their daily diet in an attempt to delay the early onset of a PCa. Green tea polyphenols, one such agent, has been shown to be chemopreventive in skin, breast, and prostate cancers. We hypothesized that Epigallocatechin-3-Gallate (EGCG), the major polyphenol found in green tea, will exert its chemopreventive effect in the prostate via regulation of sex steroid receptor, growth factor-signaling, and inflammatory pathways.

METHODS

Five-week-old male TRAMP (Transgenic Adenocarcinoma Mouse Prostate) offspring were fed AIN-76A diet and 0.06% EGCG in tap water. Animals were sacrificed at 28 weeks of age and the entire prostates were scored histopathologically. In addition, animals were sacrificed at 12 weeks of age and ventral (VP) and dorsolateral (DLP) prostates were removed for histopathological evaluation and immunoblot analyses or ELISA.

RESULTS

EGCG, inhibited early but not late stage PCa in the current study. In the VP, EGCG significantly reduced cell proliferation, induced apoptosis, and decreased androgen receptor (AR), insulin-like growth factor-1 (IGF-1), IGF-1 receptor (IGF-1R), phospho-extracellular signal-regulated kinases 1 and 2 (phospho-ERKs 1 and 2), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS).

CONCLUSIONS

The attenuation of the AR, the down-regulation of potent growth factor IGF-1, modulation of inflammation biomarkers, and decrease in the MAPK signaling may contribute to the reduction in cell proliferation and induction of apoptosis and hence provide a biochemical basis for EGCG suppressing PCa without toxicity.

Lupeol Suppresses Cisplatin-Induced Nuclear Factor-κB Activation in Head and Neck Squamous Cell Carcinoma and Inhibits Local Invasion and Nodal Metastasis in an Orthotopic Nude Mouse Model

A poor prognosis in head and neck squamous cell carcinoma (HNSCC) patients is commonly associated with the presence of regional metastasis. Cisplatin-based chemotherapy concurrent with radiation therapy is commonly used in the treatment of locally advanced HNSCC. However, the result is dismal due to common acquisition of chemoresistance and radioresistance. Epidemiologic studies have shown the importance of dietary substances in the prevention of HNSCC. Here, we found that lupeol, a triterpene found in fruits and vegetables, selectively induced substantial HNSCC cell death but exhibited only a minimal effect on a normal tongue fibroblast cell line in vitro. Down-regulation of NF-kappaB was identified as the major mechanism of the anticancer properties of lupeol against HNSCC. Lupeol alone was not only found to suppress tumor growth but also to impair HNSCC cell invasion by reversal of the NF-kappaB-dependent epithelial-to-mesenchymal transition. Lupeol exerted a synergistic effect with cisplatin, resulting in chemosensitization of HNSCC cell lines with high NF-kappaB activity in vitro. In in vivo studies, using an orthotopic metastatic nude mouse model of oral tongue squamous cell carcinoma, lupeol at a dose of 2 mg/animal dramatically decreased tumor volume and suppressed local metastasis, which was more effective than cisplatin alone. Lupeol exerted a significant synergistic cytotoxic effect when combined with low-dose cisplatin without side effects. Our results suggest that lupeol may be an effective agent either alone or in combination for treatment of advanced tumors.

Inhibition of carcinogenesis by tea constituents

The possible cancer preventive activity of tea has received much attention in recent years. The inhibitory activities of tea and tea constituents against carcinogenesis at different organ sites have been demonstrated in many animal models. The effect of tea consumption on human cancers, however, remains inconclusive. The mechanisms of action of tea polyphenols, especially EGCG, the most abundant and active catechin, have been extensively investigated. Most of the studies, however, were based on cell culture systems, and these mechanisms need to be evaluated and verified in animal models or humans in order to gain more understanding on the effect of tea consumption on human cancer. Human intervention trials are warranted to determine the possible prevention of cancer of specific sites by preparation of tea constituents.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

Pannarin inhibits cell growth and induces cell death in human prostate carcinoma DU-145 cells

In the course of our continuing search for new natural anticancer compounds for treatment and/or prevention of prostate cancer, our laboratory has focused its search on poorly investigated lichen metabolites, sphaerophorin, pannarin and epiphorellic acid-1. To this end, we treated DU-145, a cell line resembling the last stage of prostate carcinoma, with different concentrations (6-50 micromol/l) of these compounds for 72 h. Our data clearly evidenced that these lichen metabolites inhibit the growth of human prostate carcinoma DU-145 cells, but pannarin exhibits a higher effect. Our data show an induction of apoptotic death of advanced prostate cancer cells by sphaerophorin, pannarin and epiphorellic acid-1. In fact, a significant (P<0.001) increase in caspase-3 enzyme activity occurred in DU-145 cells treated with all lichen compounds at 12 and 25 micromol/l concentrations, correlated to a high DNA fragmentation, but without the disruption of the plasma membrane, as evaluated by the percentage of lactic dehydrogenase release. Alternatively, we found a low, but significant (P<0.01) lactic dehydrogenase release at higher concentrations (50 micromol/l), suggesting that in these experimental conditions sphaerophorin, pannarin and epiphorellic acid-1 induce necrosis in DU-145 cells, through the increase in reactive oxygen species generation. The experimental evidence is further confirmed by caspase-3 activity results, evidencing a reduction in the activity of this protease at a higher concentration, 50 micromol/l.

Differential protein expression of peroxiredoxin I and II by benzo(a)pyrene and quercetin treatment in 22Rv1 and PrEC prostate cell lines

Mechanisms of benzo(a)pyrene (BaP)-mediated toxicity and chemopreventative potential of quercetin in prostate cancer are poorly understood. Two-dimensional gel electrophoresis was used to map the differences in protein expression in BaP (1 microM)- and quercetin (5 microM)-treated 22Rv1 human prostate cancer cells. As compared to DMSO, 26 proteins in BaP and 41 proteins in quercetin were found to be differentially expressed (+/-2-fold). Western blots confirmed that BaP increased peroxiredoxin (Prx) Prx I and decreased Prx II in 22Rv1 cells. Similar results were found in PrEC normal prostate epithelial cells. Quercetin (up to 10 microM) upregulated Prx II without altering Prx I levels in 22Rv1 cells whereas in PrEC cells, it did not alter the constitutive protein expression of Prx I or II. The lack of quercetin-mediated changes in Prx expression suggests that quercetin does not interfere with H(2)O(2) levels, and thus may have no deleterious effect in normal prostate cells. Quercetin inhibited both BaP-mediated effects on Prx I and II in 22Rv1 cells. In PrEC cells, quercetin inhibited BaP-mediated upregulation of Prx I and had tendency to neutralize BaP-mediated downregulation of Prx II. Quercetin also inhibited BaP-induced concentrations of reactive oxygen species in both 22Rv1 and PrEC cells. These results suggest that Prx I and II may be involved in BaP-mediated toxicity and the potential chemopreventative mechanisms of quercetin.

Annexin-I as a potential target for green tea extract induced actin remodeling

Using a multistep human urothelial model, we previously showed that green tea extract (GTE) selectively modulates actin remodeling in transformed cells (MC-T11), which resulted in increased cell adhesion and reduced cell motility (Lu et al., Clin Cancer Res 2005;11:1675-83). This study further analyzed which actin binding proteins (ABPs) might be involved in this process. Proteomic profiles of GTE treated and untreated MC-T11 cells using two-dimensional gel electrophoresis coupled with liquid chromatography tandem mass spectrometry (LC/MS/MS) and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) identified 20 GTE-induced proteins. Among them, 3 were ABPs (tropomodulin, cofilin and annexin-I), and only annexin-I showed a dose- and time-dependent expression. The increased annexin-I correlated with actin remodeling, and was the result of transcription level up-regulation, as determined by RT-PCR, pull-down immunoblot and siRNA analyses. 5-Azacytidine, a DNA methylation inhibitor, exhibited no effect on annexin-I expression when used alone, but had an additive effect for GTE-induced annexin-I expression. Immunohistochemistry of bladder cancer tissue array showed a decrease of annexin-I expression in carcinoma in situ and low grade papillary carcinoma (n = 32, 0% positive) compared to nontumor urothelium (n = 18, 89% positive) (p < 0.001 by Fisher exact test), but increased in some (6 of 15, 40%) high-grade tumors. Together, GTE induced annexin-I expression plays a role in regulating actin remodeling and decreased annexin-I expression is a common event in early stage of bladder cancer development.

Putrescine-1,4-dicinnamide from Pholiota spumosa (Basidiomycetes) inhibits cell growth of human prostate cancer cells

Previously, it was isolated from the fruiting bodies of the gilled mushroom Pholiota spumosa (Basidiomycetes, Strophariaceae), putrescine-1,4-dicinnamide, a phenylpropanoid derivative conjugated with polyamine putrescine never isolated before as a natural compound. Recently, polyamine analogs that are similar in structure to the natural polyamines but that cannot mimic their functions that are essential for cellular growth and differentiation, have shown antitumor activity in several types of human cancer cells. Therefore, we have now investigated the response of DU-145 cells, a well characterized androgen-independent human prostate cancer (PCA) cell line, to this phenylpropanoid derivative. The results presented here demonstrate that putrescine-1,4-dicinnamide, as suggested for polyamine analogs synthesized artificially, inhibits the cell growth of cancer cells inducing apoptosis cell death, mediated, at least in part, by the activation of caspase cascades, that at higher doses shift to necrosis, through the increase of reactive oxygen species (ROS) generation.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

Modulation of activator protein-1 (AP-1) and MAPK pathway by flavonoids in human prostate cancer PC3 cells

In last couple of decades the use of natural compounds like flavonoids as chemopreventive agents has gained much attention. Our current study focuses on identifying chemopreventive flavonoids and their mechanism of action on human prostate cancer cells. Human prostate cancer cells (PC3), stably transfected with activator protein 1 (AP-1) luciferase reporter gene were treated with four main classes of flavonoids namely flavonols, flavones, flavonones, and isoflavones. The maximum AP-1 luciferase induction of about 3 fold over control was observed with 20 microM concentrations of quercetin, chrysin and genistein and 50 microM concentration of kaempferol. At higher concentrations, most of the flavonoids demonstrated inhibition of AP-1 activity. The MTS assay for cell viability at 24 h showed that even at a very high concentration (500 microM), cell death was minimal for most of the flavonoids. To determine the role of MAPK pathway in the induction of AP-1 by flavonoids, Western blot of phospho MAPK proteins was performed. Four out of the eight flavonoids namely kaempferol, apigenin, genistein and naringenin were used for the Western Blot analysis. Induction of phospho-JNK and phospho-ERK activity was observed after two hour incubation of PC3-AP1 cells with flavonoids. However no induction of phospho-p38 activity was observed. Furthermore, pretreating the cells with specific inhibitors of JNK reduced the AP-1 luciferase activity that was induced by genistein while pretreatment with MEK inhibitor reduced the AP-1 luciferase activity induced by kaempferol. The pharmacological inhibitors did not affect the AP-1 luciferase activity induced by apigenin and naringenin. These results suggest the possible involvement of JNK pathway in genistein induced AP-1 activity while the ERK pathway seems to play an important role in kaempferol induced AP-1 activity.

No association between green tea and prostate cancer risk in Japanese men: the Ohsaki Cohort Study

In a prospective study of 19 561 Japanese men, green-tea intake was not associated with a lower risk of prostate cancer (110 cases), the multivariate hazard ratio for men drinking ≥5 cups compared with <1 cup per day being 0.85 (95% confidence interval 0.50–1.43, trend P=0.81).

A novel biomarker for staging human prostate adenocarcinoma: overexpression of matriptase with concomitant loss of its inhibitor, hepatocyte growth factor activator inhibitor-1

BACKGROUND

Matriptase, a type II transmembrane serine protease is involved in angiogenesis, degradation of extracellular matrix, and in the progression of some epithelial cancers. Here, we establish the clinical significance of matriptase and its inhibitor, hepatocyte growth factor activator inhibitor-1 (HAI-1), during the progression of human prostate cancer (CaP).

METHODS

The expression patterns of matriptase and HAI-1 were determined in primary cultures of normal human prostate epithelial (NHPE) cells, human CaP cells LNCaP, DU-145, CWR22Rnu1, and PC-3, and in tissue samples of 172 patients with normal prostate, benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia (PIN), and adenocarcinoma of different tumor grades.

RESULTS

The protein and mRNA levels of matriptase were significantly higher in all carcinoma cells as compared with NHPE cells. Conversely, all CaP cells exhibited a reduced expression of HAI-1 as compared with NHPE cells. A progressive increase in the protein levels of matriptase was observed with increasing tumor grade in CaP specimens as compared with normal and BPH tissue specimens. Tissue samples of normal prostate exhibited a high constitutive protein level of HAI-1 compared with BPH and low-grade cancer with a progressive loss with increasing tumor grade.

CONCLUSION

The increased expression of matriptase and loss of HAI-1 may be an important event during the progression of CaP in humans. We suggest that the ratio of these two gene products may serve as a promising biomarker for CaP progression and a potential marker for establishing the efficacy of therapeutic and chemopreventive interventions.

Dietary agents in the chemoprevention of prostate cancer

Nutritional factors have been estimated to contribute 20-60% of cancers around the globe, and almost one-third of deaths are being reported in Western countries. According to estimates by the American Cancer Society, during the year 2005 about 232,090 new cases of prostate cancer will be diagnosed alone in the United States and 30,350 men will die of this disease. The high incidence and long latency period of prostate cancer offer plenty of time to pursue strategies toward prevention and/or treatment to suppress or revert this disease. Epidemiological evidence suggests that plant-based dietary agents decrease the risk of some types of human cancer, including prostate cancer. Intake of 400-600 g/day of fruits and vegetables is associated with reduced risk of several cancers. The use of micronutrients and/or other phenolic agents in the diet or synthetic exogenous supplements to prevent neoplastic transformation of normal cells or to slow the progression of established malignant changes in cancer cells is termed "chemoprevention." Considerable attention has been devoted to identify plant-based dietary agents that may serve as natural inhibitors of prostate carcinogenesis. Much progress has been made in the last decade in this area of investigation through identification of pathways that play important roles in prostate tumorigenesis. This article summarizes epidemiological, clinical, and mechanistic studies and the significance of plant-derived dietary agents such as flavonoids, indoles, isothiocyanates, phenolics, monoterpenes, and complementary and alternative agents in the management of prostate cancer with recommendations for future studies to advance this area of research.

Tea, hormone-related cancers and endogenous hormone levels

Tea is one of the most popular beverages consumed around the world, second only to water. There has been substantial interest in the potential role of tea in cancer prevention, particularly in respiratory and gastrointestinal tract cancers. Recent epidemiological data have linked tea intake to reduced risk of hormone-related cancers, including breast, ovarian and prostate cancers. Based on sparse data, there is suggestion that tea intake may influence circulating hormone levels, providing a plausible mechanism whereby tea intake may influence risk of hormone-related cancers. The major objectives of this paper are to review the epidemiological evidence on tea and risk of breast, ovarian, and prostate cancers as well as the human and non-human studies on tea and circulating hormone levels. We pay special attention to some of the limitations of the human studies and discuss future research needs.

Green tea polyphenols modulate secretion of urokinase plasminogen activator (uPA) and inhibit invasive behavior of breast cancer cells

Many epidemiological studies have suggested that consumption of green tea may decrease the risk of cancer. The chemopreventive effect of green tea polyphenols (GTP) has been demonstrated through the inhibition of cell proliferation and angiogenesis in cell culture and animal models of breast cancer. Metastasis of breast cancer is the major reason for the high mortality of breast cancer patients and is directly linked to the invasive behavior of breast cancer cells. Cancer metastasis consists of several interdependent processes including cancer cell adhesion, cancer cell migration, and invasion of cancer cells. In this study, we evaluated the effect of GTP on human breast cancer cells, and we show that in addition to inhibiting cell growth, GTP also suppressed the invasive behavior of MDA-MB-231 cells. These anti-invasive effects of GTP were the result of the inhibition of constitutively active transcription factors AP-1 and NF-kappaB, which further suppressed secretion of urokinase plasminogen activator (uPA) from breast cancer cells. Based on these results, it can be hypothesized that GTP treatment resulted in the inhibition of formation of signaling complexes responsible for cell adhesion and migration (uPA, uPA receptor, vitronectin, integrin receptor) and cell invasion (uPA, uPA receptor). Our results indicate that GTP may contribute to the anticancer effects of green tea by inhibiting the invasive behavior of cancer cells.

A novel dietary triterpene Lupeol induces fas-mediated apoptotic death of androgen-sensitive prostate cancer cells and inhibits tumor growth in a xenograft model

In prostate cancer, a fine balance between cell proliferation and apoptotic death is lost, resulting in increased cellular mass and tumor progression. One approach to redress this imbalance and control this malignancy is its preventive intervention through the use of dietary natural agents. Here, we investigated the growth-inhibitory effect and associated mechanisms of Lupeol, a triterpene present in fruits and vegetables, in androgen-sensitive human prostate cancer cells. Lupeol treatment resulted in significant inhibition of cell viability in a dose-dependent manner and caused apoptotic death of prostate cancer cells. Lupeol was found to induce the cleavage of poly(ADP-ribose) polymerase protein and degradation of acinus protein with a significant increase in the expression of FADD protein. Among all death receptor targets examined, Lupeol specifically caused a significant increase in the expression of Fas receptor. The small interfering RNA-mediated silencing of the Fas gene and inhibition of caspase-6, caspase-8, and caspase-9 by their specific inhibitors confirmed that Lupeol specifically activates the Fas receptor-mediated apoptotic pathway in androgen-sensitive prostate cancer cells. The treatment of cells with a combination of anti-Fas monoclonal antibody and Lupeol resulted in higher cell death compared with the additive effect of the two compounds alone, suggesting a synergistic effect. Lupeol treatment resulted in a significant inhibition in growth of tumors with concomitant reduction in prostate-specific antigen secretion in athymic nude mice implanted with CWR22Rnu1 cells. Because early clinical prostate cancer growth is an androgen-dependent response, the results of the present study suggest that Lupeol may have a potential to be an effective agent against prostate cancer.

Differential attenuation of oxidative/nitrosative injuries in early prostatic neoplastic lesions in TRAMP mice by dietary antioxidants

BACKGROUND

Dietary antioxidants with yet unproven efficacies in averting prostate cancer (PCa) are widely used in the United States as preventives. Experimental evidence establishing a causal relationship between oxidative and nitrosative stress (OS/NS) and PCa development and showing its modulation by dietary antioxidants would help justify their usage.

METHODS

The TRAMP (Transgenic Adenocarcinoma of the Mouse Prostate) mouse model was used to demonstrate the OS/NS-associated damage, as evident by 8-hydroxy-2'-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE)-protein-adducts and nitrotyrosine (Ntyr), in prostatic premalignant lesions, and to evaluate the antioxidant efficacy of various dietary supplements [natural antioxidant (NAO) from spinach extracts, (-) epigallocatechin-3-gallate (EGCG), or N-acetylcystein (NAC)] during the early PCa development.

RESULT

We show, for the first time, that oxidative/nitrosative damages of genomic DNA and cellular proteins were discretely localized in premalignant lesions, but not in adjacent morphologically normal epithelia, of TRAMP prostates; these injuries were absent in age-matched nontransgenic littermates. The extent of OS/NS-related injuries correlated well with the tempo of development and prevalence of premalignant lesions in various prostatic lobes and exhibited a clear trend of increase from 12 to 20 weeks of age. Treatment of TRAMP mice with various antioxidants as dietary supplements resulted in differential alleviation of OS/NS-related prostatic injuries. The antioxidant potencies of the dietary supplements did not fully correlate with their documented antiPCa actions, suggest that they may exert additional "nonantioxidant," antitumor effects in this model.

CONCLUSIONS

Our data indicate that in TRAMP mice, OS/NS injuries are likely involved in early prostatic tumorigenesis and can be modulated by various antioxidants.