Update on chemoprevention of prostate cancer

An Integrative Approach to Prostate Cancer

OBJECTIVES

The mostly indolent natural history and long overall survival associated with a diagnosis of prostate cancer provides a unique opportunity for men to explore diet and lifestyle interventions to alter the trajectory of their disease. As many patients may be appropriate for postponing conventional therapy, the effects of various integrative interventions can be investigated. In addition, treatment of prostate cancer with surgery, radiation, or androgen deprivation therapy, all may produce physical or psychological side effects that could be amenable to complementary therapies. This article serves to review salient information in the published literature.

DESIGN

A review of published research was conducted.

RESULTS

A plant-based antioxidant-rich diet with an emphasis on cruciferous vegetables, tomatoes, soy, pomegranate, and marine omega 3 fatty acids while avoiding saturated fats, including dairy products is the best option. Supplementation with vitamin D3, omega 3, and some nutraceutical-based preparations may be advised. It is likely prudent to avoid vitamin E and selenium supplements. Physical activity has been shown to have multiple benefits in men diagnosed with all stages of prostate cancer from strengthening bones, improving body habitus, and enhancing overall wellbeing. Yoga, combining physical activity with a mind-body component, has been shown to have a salutogenic effect in both prostate cancer patients and their caregivers. Traditional Chinese Medicine may be particularly useful in managing side effects of conventional treatments, especially the hot flashes associated with androgen deprivation therapy. Although the long natural history, availability of a useful blood marker of disease progression and prolonged survival are overall positive features, they also combine to allow men to live for a long time with diagnosed cancer, fear of progression, or recurrence and fixation on changes in their prostate-specific antigen level. The resultant stress can be deleterious to general health as well as possibly the natural history of their disease. Mind-body interventions to reduce stress, including mindfulness-based stress reduction and support groups may be useful adjunctive therapies.

CONCLUSION

Men with prostate cancer may benefit from lifestyle and complementary interventions integrated with their conventional care.

The versatile role of curcumin in cancer prevention and treatment: A focus on PI3K/AKT pathway

Despite significant advances in treatment modalities, millions of cancer-related deaths continue to occur annually, often as a consequence of developing resistance against the range of available chemotherapeutic drugs. Furthermore, available anti-cancer chemotherapeutic agents show limited efficacy, often have severe side effects, and are expensive. Thus, the discovery of pharmacological agents that do not have these disadvantages is necessary. Curcumin, a polyphenolic compound derived from turmeric (Curcumin longa L.), is one such agent that has been widely studied for its anti-inflammatory and/or anti-cancer effects. Curcumin exerts its anti-cancer effect by suppressing the initiation, progression, and metastasis of a variety of cancers and appears to inhibit carcinogenesis by affecting two main processes: angiogenesis and tumor growth. These anti-cancer effects are largely mediated via negative regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other oncogenic molecules. The PI3K/AKT pathway is commonly activated in cancer initiation and progression. Considered to be the key signaling pathway, the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) pathway therefore represents a key target for cancer therapeutics. In the current review, we focus upon curcumin's targeting of PI3K/AKT in different malignancies to effect inhibition of cancer development and progression.

Five-alpha reductase inhibitor influences expression of androgen receptor and HOXB13 in human hyperplastic prostate tissue

OBJECTIVES

Five-alpha reductase inhibitors (5ARIs) are known as chemopreventive agents in prostate cancer with a risk of high-grade disease. This study evaluated the effects of 5ARI on androgen receptor (AR) and proteins involved in prostate cell growth such as HOXB13 expression in human prostate tissue and LNCaP prostate cancer cells.

MATERIALS AND METHODS

We retrospectively selected 21 patients who underwent TURP between March 2007 and February 2010 for previously confirmed BPH by prostate biopsy. They were grouped into control (group 1, n = 9) and 5ARI treatment (group 2, n = 12) before TURP. AR and HOXB13 expression in prostate tissue was evaluated by immunohistochemical staining. We tested the effect of 5ARI on the expression of AR, prostate specific antigen (PSA) and HOXB13 in LNCaP cells. Cells were assessed by Western blot analysis, MTT in vitro proliferation assay, and ELISA.

RESULTS

Group 2 showed stronger reactivity for AR and HOXB13 than those of the group 1. MTT assay showed death of LNCaP cells at 25uM of 5ARI. At the same time, ELISA assay for PSA showed that 5ARI inhibited secretion of PSA in LNCaP cells. Western blot analysis showed that 5ARI did not greatly alter AR expression but it stimulated the expression of HOXB13.

CONCLUSIONS

These results demonstrated that 5ARI influences AR and HOXB13 expression in both LNCaP cells and human prostate tissue. In order to use 5ARI in chemoprevention of prostate cancer, we still need to clarify the influence of 5ARI in ARs and oncogenic proteins and its regulation pathway.

Management of prostate cancer. Part 1: chemoprevention

Numerous agents have been investigated in prostate cancer prevention. Many manipulate sex steroid levels or function, some regulate response to oxidative stress and others affect tumor proliferation and/or apoptosis. Some are postulated to even affect downstream targets, such as cyclooxygenase-2, which has been shown to be elevated in prostate cancer by most investigators. The evidence for all these potential chemopreventive agents is critically reviewed. While the current information base is vast, level 1 evidence is lacking, and ongoing trials are not due to provide such evidence for many years to come. In addition, the current lack of ability to accurately differentiate clinically important prostate cancer from latent disease makes chemoprevention in this setting even more challenging. Currently, no reliable biomarkers that can act as surrogate endpoints for the development of clinically relevant prostate cancer exist, which makes performing large chemoprevention trials expensive. At present, there is little to suggest that the urologist or General Practitioner should be recommending any particular chemopreventive agent to either the general population or those deemed to be at higher risk of contracting prostate cancer.

Androgen-deprivation therapy versus radical prostatectomy as monotherapy among clinically localized prostate cancer patients

BACKGROUND

The most recent randomized controlled trial in a predominantly prostate-specific antigen-detected prostate cancer (PC) population found a nonsignificant reduction in mortality from radical prostatectomy (RP) compared to conservative management. The optimal treatment for clinically localized prostate cancer is anything but clear. The PC-specific mortality and all-cause mortality were compared between primary androgen-deprivation treatment (PADT) and RP, both as monotherapy, among clinically localized PC patients.

METHODS

A retrospective cohort study among PC patients in Surveillance, Epidemiology and End Results-Medicare data with a median follow up of 2.87 years in the PADT cohort and 2.95 years in the RP cohort. Propensity score-matching was employed to adjust for the observed selection bias. PC-specific mortality and all-cause mortality were modeled using the Fine and Gray competing risk model and Cox proportional hazards model, respectively. The independent variables in these models included age, race, Gleason score risk groups, T-score, prostate-specific antigen, Charlson comorbidity, and index year of treatment initiation.

RESULTS

After propensity score-matching, there were 1624 in the PADT cohort and 1624 in the RP cohort. All baseline values were comparable (all P-values >0.35). There were a total of 266 deaths (16.38%) and 60 (3.69%) PC-specific deaths among PADT recipients, while there were 56 (3.45%) deaths and four (0.25%) PC-specific deaths among RP recipients. According to the Kaplan-Meier estimation, the 8-year survival rate was 43.39% in the PADT cohort and 79.62% in the RP cohort. PADT was associated with increased risk of overall mortality (hazard ratio = 2.98, 95% confidence interval 2.35-3.79; P < 0.001) and increased risk of PC-specific mortality (hazard ratio = 12.47, 95% confidence interval 4.48-34.70; P < 0.001).

CONCLUSION

With adjustment for the observed selection bias, PADT was associated with increased all-cause mortality and PC-specific mortality when compared to RP.

Perifosine sensitizes UVB-induced apoptosis in skin cells: new implication of skin cancer prevention?

We demonstrate here that a relative low dose of perifosine significantly enhanced UVB-induced apoptosis in skin cells (keratinocytes and fibroblasts), associated with a significant increase of reactive oxygen species (ROS) and ceramide production as well as multiple perturbations of diverse cell signaling pathways, shifting to a significant pro-apoptosis outcomes. Perifosine inhibited UVB-induced pro-survival Akt/mammalian target of rapamycin (mTOR) and ERK activation, while facilitating pro-apoptotic AMP-activated protein kinas (AMPK), c-Jun-NH(2)-kinase (JNK), and p53 activation; these signaling changes together promoted a striking increase in skin cell apoptosis and a significantly reduced amount of DNA damages. Our results suggest that perifosine may represent a novel skin cancer prevention strategy.

Lycopene for the prevention of prostate cancer

BACKGROUND

Prostate cancer is a common cause of death in developed countries, yet the benefits of screening for prostate cancer still remain controversial. A prostate-specific antigen (PSA) test result greater than 4 ng/mL (nanograms/millilitre) has commonly been used as the cut-off level for seeking further tests to diagnose the presence (or absence) of prostate cancer. An increase in PSA levels may not necessarily be associated with an increased risk of prostate cancer, as PSA levels may also be increased in men with benign prostatic hyperplasia and prostatitis. Despite the uncertainty of the net benefit of early detection and treatment, safe and effective methods to prevent prostate cancer are of value. Consumers, seeking greater involvement in their healthcare, are increasingly turning to lifestyle modification and complementary and alternative medicines (CAMs) to maintain their health and prevent disease. Lycopene is a member of the carotenoid family, which is found abundantly in tomatoes, tomato-based products, strawberries, and watermelon. It has been hypothesised that lycopene is a strong antioxidant, which may lower the risk of cancer (including prostate cancer) in people who have diets rich in lycopene.

OBJECTIVES

To determine whether lycopene reduces the incidence of prostate cancer and prostate cancer-specific mortality. Secondary objectives include changes in PSA levels, prostate symptoms and the nature of adverse events associated with lycopene use.

SEARCH METHODS

Electronic searches were conducted across MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL) databases. No language or other limitations were imposed.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that investigated the use of lycopene for the prevention of prostate cancer were eligible for inclusion in this review.

DATA COLLECTION AND ANALYSIS

A search of electronic databases, performed in August 2011, identified 64 citations. All articles were selected for full-text review. From these citations, three studies were identified as meeting the inclusion criteria. Handsearching did not provide any additional studies.

MAIN RESULTS

Three RCTs, with a total of 154 participants were included in this review. None of the studies reported data on prostate cancer mortality. All of the included studies differed with respect to design, participants included and allocation of lycopene. This clinical heterogeneity limits the value on the pooled estimated of the meta-analyses. The methodological quality of two of the three included studies was assessed as posing a 'high' risk of bias. Meta-analysis indicated no statistical difference in PSA levels between men randomised to receive lycopene and the comparison group (MD (mean difference) -0.34, 95% CI (confidence interval) -2.01, 1.32). Only one study reported incidence of prostate cancer (10% in the lycopene group versus 30% in control group). The level of lycopene was also not statistically different in men randomised to receive lycopene and the comparison group (MD 0.39 µg/mL (micrograms/millilitre), 95% CI -0.19, 0.98). No other meta-analyses were possible since other outcomes assessed only had one study contributing data.

AUTHORS' CONCLUSIONS

Given that only three RCTs were included in this systematic review, and the high risk of bias in two of the three studies, there is insufficient evidence to either support, or refute, the use of lycopene for the prevention of prostate cancer. Similarly, there is no robust evidence from RCTs to identify the impact of lycopene consumption upon the incidence of prostate cancer, prostate symptoms, PSA levels or adverse events.

Strategies for prostate cancer prevention: Review of the literature

The goal of primary chemoprevention is to decrease the incidence of a given cancer, simultaneously reducing treatment-related adverse events, cost of treatment of the disease and mortality. Prostate cancer is an attractive and appropriate target for primary prevention because of its high incidence and prevalence, increased disease-related mortality, long latency and molecular pathogenesis and epidemiological data indicating that modifiable environmental factors may decrease risk. Various agents have been suggested to prevent prostate cancer and many clinical trials are currently on. Ultimately the adoption of a preventive strategy hinges on its potential benefits weighed against the potential risks of the specific agents used. This article is aimed to examine the experimental and epidemiological data spanning a period of 1998 to 2007, demonstrating the chemopreventive activity, safety and toxicity of various nutritional elements and other agents that can help prevent prostate cancer and/or slow disease progression.

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.

Finasteride upregulates expression of androgen receptor in hyperplastic prostate and LNCaP cells: implications for chemoprevention of prostate cancer

BACKGROUND

Although finasteride is recognized for its role as a chemopreventive agent for prostate cancer, higher grades of malignancy have been reported. It is questioned whether blocking of testosterone conversion to dihydrotestosterone (DHT) by finasteride in prostate tissue will change expression of androgen receptor (AR). Therefore, this study evaluated the effects of finasteride on AR expression in prostate tissue and in the LNCaP cell line.

METHODS

Between January and December 2006, we retrospectively selected and evaluated 47 cases of benign prostatic hyperplasia treated with variable duration of finasteride (5 mg QD) before transurethral resection of the prostate. AR expression in prostate tissue was semiquantified by immunostaining and compared with duration of finasteride treatment. An androgen-dependent prostate cancer cell line (LNCaP) was cultured in charcoal/dextran-treated FBS with DHT or testosterone, and treated with finasteride for 1-3 weeks. Samples of total RNA were collected to analyze expression of AR by real-time quantitative reverse transcription polymerase chain reaction.

RESULTS

Immunohistochemical study revealed significant upregulation of ARs by finasteride treatment for 30-180 days. In cell line study, quantitative real-time reverse transcription polymerase chain reaction revealed significant upregulation of ARs treated by finasteride.

CONCLUSIONS

In our study, finasteride influenced AR expression in benign prostate tissue and prostate cancer cell. Before we can use finasteride in chemoprevention with confidence, we still need to clarify the influence of finasteride in ARs and its regulation pathway.

Infection, inflammation and prostate carcinogenesis

Several reports have shown that the incidence of prostate cancer is on the increase and that more men would be diagnosed of prostate cancer in the next decades. Many approaches are being applied towards reducing the cases of prostate cancer, especially in the very rich countries. However, these have not been effective due to the poor current understanding of the pathophysiology of prostate carcinogenesis. The current work presents a review of how chronic infection and inflammation may contribute to prostate carcinogenesis.

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

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

Significance of S100A2 and S100A4 Expression in the Progression of Prostate Adenocarcinoma

Purpose

The aim of this study was to investigate the expression pattern of calcium-binding proteins S100A2 and S100A4. We also sought to determine the prognostic value of these markers for patients with prostate adenocarcinoma.

Materials and Methods

Immunohistochemical staining was performed to detect S100A2 and S100A4 expression in 26 tissue samples obtained during transurethral resection from patients with benign prostatic hyperplasia (BPH) and in 67 tissue samples obtained during prostate biopsy and radical prostatectomy from patients with prostate carcinoma. The immunoreactivity of these proteins was stratified on a scale of 0 to 3 and was correlated with the pathologic features of prostate adenocarcinoma.

Results

High expression of S100A2 was observed in the tissue of patients with BPH, whereas low or no expression was observed in prostate cancer (CaP) cells. The protein level of S100A4 was significantly higher in CaP than in BPH cells. The higher level of S100A4 observed in CaP tissue correlated with increasing tumor grade.

Conclusions

Decreased expression of S100A2 and increased expression of S100A4 may be important in the progression of CaP. This finding could aid in identifying aggressive CaP. The simultaneous analysis of S100A2 and S100A4 expression in prostate tissues may be a useful prognostic marker for CaP.

Current issues of selenium in cancer chemoprevention

The element selenium (Se) was identified, nearly 40 years ago, as being essential in the nutrition of animals and humans. In addition, antitumorigenic effects of Se compounds have been described in a variety of in vitro and animal models, suggesting that supplemental Se in human diets may reduce cancer risk. Apparent mechanisms underlying the potential of Se compounds as cancer chemopreventive agents have been suggested. Some recent clinical trials, however, have shed doubt on the anticancer effects of Se. The contradictory findings and consequent controversy might be due to the lack of understanding of the mechanisms underlying Se biology. This article reviews current knowledge on this topic and addresses the disparate viewpoints on the chemopreventive effects of Se, the human populations.

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.

A meta-analysis of the NAT1 and NAT2 polymorphisms and prostate cancer: a huge review

Studies revealing conflicting results on the role of NAT1 or NAT2 phenotypes on prostate cancer risk led us to perform a meta-analysis to investigate the association of these polymorphisms and prostate cancer risk. The meta-analysis included six studies with NAT1 genotyping (610 prostate cancer cases and 713 controls), and 10 studies with NAT2 genotyping (1,253 cases and 1,722 controls). The fixed effects odds ratio was 0.96 [95% confidence interval (95% CI): 0.75, 1.21; I(2) = 32.9%, P for heterogeneity = 0.189] for the NAT1 genotype, and the random effects odds ratio was 1.10 (95% CI: 0.87, 1.39; I(2) = 49.1%, P for heterogeneity = 0.039) for the NAT2 genotype. For NAT2 polymorphism, a statistically significant association between NAT2 polymorphism and prostate cancer appeared in Asians, but not in Caucasians. In conclusion, the NAT1 or NAT2 phenotypes detoxify carcinogens and their reactive intermediates are unlikely to be the cause of PCa development.

Herbal extract of Wedelia chinensis attenuates androgen receptor activity and orthotopic growth of prostate cancer in nude mice

PURPOSE

Wedelia chinensis is a common ingredient of anti-inflammatory herbal medicines in Taiwan and southern China. Inflammation is involved in promoting tumor growth, invasion, and metastasis. This study aims to test the biological effects in vivo of W. chinensis extract on prostate cancer.

EXPERIMENTAL DESIGN

The in vivo efficacy and mechanisms of action of oral administration of a standardized extract of W. chinensis were analyzed in animals bearing a subcutaneous or orthotopic prostate cancer xenograft.

RESULTS

Exposure of prostate cancer cells to W. chinensis extract induced apoptosis selectively in androgen receptor (AR)-positive prostate cancer cells and shifted the proportion in each phase of cell cycle toward G(2)-M phase in AR-negative prostate cancer cells. Oral herbal extract (4 or 40 mg/kg/d for 24-28 days) attenuated the growth of prostate tumors in nude mice implanted at both subcutaneous (31% and 44%, respectively) and orthotopic (49% and 49%, respectively) sites. The tumor suppression effects were associated with increased apoptosis and lower proliferation in tumor cells as well as reduced tumor angiogenesis. The antitumor effect of W. chinensis extract was correlated with accumulation of the principle active compounds wedelolactone, luteolin, and apigenin in vivo.

CONCLUSION

Anticancer action of W. chinensis extract was due to three active compounds that inhibit the AR signaling pathway. Oral administration of W. chinensis extract impeded prostate cancer tumorigenesis. Future studies of W. chinensis for chemoprevention or complementary medicine against prostate cancer in humans are thus warranted.

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.

The relation of alpha-linolenic acid to the risk of prostate cancer: a systematic review and meta-analysis

BACKGROUND

alpha-Linolenic acid (ALA; 18:3n-3) has been associated inconsistently with an increased risk of prostate cancer. Additional studies have become available since the publication of 2 previous meta-analyses.

OBJECTIVE

The objective was to review the published data on the relation between ALA and prostate cancer.

DESIGN

We conducted a systematic review to identify studies that included data on ALA and risk of prostate cancer. Data were pooled from studies that compared the highest ALA quantile with the lowest ALA quantile, and risk estimates were combined by using a random-effects model.

RESULTS

The relation between ALA and prostate cancer is inconsistent across studies. We pooled data from 8 case-control and 8 prospective studies. The summary estimate revealed that high ALA dietary intakes or tissue concentrations are weakly associated with prostate cancer risk (relative risk [RR]: 1.20; 95% CI: 1.01, 1.43). When examined by study type (ie, retrospective compared with prospective or dietary ALA compared with tissue concentration) or by decade of publication, only the 6 studies examining blood or tissue ALA concentrations revealed a statistically significant association. With the exception of these studies, there was significant heterogeneity and evidence of publication bias. After adjustment for publication bias, there was no association between ALA and prostate cancer (RR: 0.96; 95% CI: 0.79, 1.17).

CONCLUSIONS

Studies examining the relation between ALA and prostate cancer have produced inconsistent findings. High ALA intakes or high blood and adipose tissue concentrations of ALA may be associated with a small increased risk of prostate cancer. However, these conclusions are qualified because of the heterogeneity across studies and the likelihood of publication bias.

A combination of micronutrients is beneficial in reducing the incidence of prostate cancer and increasing survival in the Lady transgenic model

We have previously shown that administration of a combination of micronutrients (selenium, vitamin E, and lycopene) inhibits prostate cancer (PCa) development in the Lady transgenic model. In the present study, we examine timing of initiation of micronutrients, and the effect of micronutrient combinations, on PCa development in Lady transgenic model. Transgenic males were randomized to either a control diet; control diet supplemented with human equivalent doses of vitamin E, selenium, and lycopene (E+S+L); or control diet supplemented with vitamin E and selenium (E+S). In separate experiments, the combination of E+S+L was initiated at varying time points (4, 8, 20, and 36 weeks of age). A combination of E+S+L resulted in a significant reduction in PCa and liver metastasis when intervention was commenced within 8 weeks of age (P < 0.0001). Immunohistochemical analysis revealed a strong correlation between disease-free state with up-regulation of the prognostic marker p27(Kip1) (P < 0.0001) and decreased expression of proliferating cell nuclear antigen and significantly increased apoptotic index (P < 0.0001). On the contrary, a combination of E+S was not effectual in preventing PCa, with a high proportion (84.6%) of animals developing PCa and a small proportion (11.5%) developing high-grade PIN. Early commencement of micronutrients (E+S+L) is beneficial in reducing PCa. Lycopene is an essential component of the combination and effective (when used with E+S) for PCa prevention. These observations provide support for their chemopreventive effect and some clues about their mechanism of action. These key findings will be complementary to the outcome from the Selenium and Vitamin E Chemoprevention Trial.

Diets high in selenium and isoflavones decrease androgen-regulated gene expression in healthy rat dorsolateral prostate

BACKGROUND

High dietary intake of selenium or soybean isoflavones reduces prostate cancer risk. These components each affect androgen-regulated gene expression. The objective of this work was to determine the combined effects of selenium and isoflavones on androgen-regulated gene expression in rat prostate.

METHODS

Male Noble rats were exposed from conception until 200 days of age to diets containing an adequate (0.33-0.45 mg/kg diet) or high (3.33-3.45 mg/kg) concentration of selenium as Se-methylselenocysteine and a low (10 mg/kg) or high (600 mg/kg) level of isoflavones in a 2 x 2 factorial design. Gene expression in the dorsolateral prostate was determined for the androgen receptor, for androgen-regulated genes, and for Akr1c9, whose product catalyzes the reduction of dihydrotestosterone to 5alpha-androstane-3alpha, 17beta-diol. Activity of hepatic glutathione peroxidise 1 and of prostatic 5alpha reductase were also assayed.

RESULTS

There were no differences due to diet in activity of liver glutathione peroxidase activity. Total activity of 5alpha reductase in prostate was significantly lower (p = 0.007) in rats fed high selenium/high isoflavones than in rats consuming adequate selenium/low isoflavones. High selenium intake reduced expression of the androgen receptor, Dhcr24 (24-dehydrocholesterol reductase), and Abcc4 (ATP-binding cassette sub-family C member 4). High isoflavone intake decreased expression of Facl3 (fatty acid CoA ligase 3), Gucy1a3 (guanylate cyclase alpha 3), and Akr1c9. For Abcc4 the combination of high selenium/high isoflavones had a greater inhibitory effect than either treatment alone. The effects of selenium on gene expression were always in the direction of chemoprevention

CONCLUSION

These results suggest that combined intake of high selenium and high isoflavones may achieve a greater chemopreventive effect than either compound supplemented individually.

Lupeol: connotations for chemoprevention

The perception of chemoprevention lies still in its infancy. Intervention, to slow down, arrest or reverse the process of carcinogenesis, by the use of either natural or synthetic substances individually or in combination therapy has emerged as a promising and pragmatic medical approach to reduce cancer risk. Pentacyclic lupane-type triterpenes exemplified by lupeol [lup-20(29)-en-3b-ol], are principally found in common fruit plants such as olive, mango, fig, etc. Although, lupeol exhibits an array of biological activities like anti-inflammatory, anti-arthritic, anti-mutagenic and anti-malarial activity both in in vitro and in vivo systems yet, extensive exploration in regard to establish its role as chemopreventive compound is warranted. Interest in developing lupeol based potent anti-neoplastic agents, has led to the discovery of a host of highly active derivatives exhibiting greater potencies and better therapeutic indices. This review asserts on the chemopreventive prospects of lupeol and reveals potential chemoprevention drug targets, central to which are the cell cycle regulatory pathway genes and tries to explain the mechanism operating behind its action.

Toxicity and mutagenicity of selenium compounds in Saccharomyces cerevisiae

Selenium (Se) is an essential trace element for humans, animals and some bacteria which is important for many cellular processes. Se's bio-activity is mainly influenced by its chemical form and dose. The use of Se supplements in the human diet emphasizes the need to establish both the beneficial and detrimental doses of each Se compound. We have evaluated three different Se compounds, sodium selenite (SeL), selenomethionine (SeM) and Se-methylselenocysteine (SeMC), with respect to their potential DNA damaging effects. The budding yeast Saccharomyces cerevisiae was used as a model system to test the toxic and mutagenic effects as well as the DNA double-strand breakage potency of these Se compounds in both exponentially growing and stationary yeast cells. Only SeL manifested any significant toxic effects in the yeast which were more pronounced in the exponentially growing cells than in those cells in the stationary phase of growth. The toxic effects of SeL were however accompanied with the pro-mutagenic effects in the stationary cell phase of growth. The toxic and mutagenic effects of SeL are likely associated with the ability of this compound to generate DNA double-strand breaks (DSB). We also show that SeL significantly increased frame-shift mutations, especially 1-4 bp deletions, in the CAN1 mutational spectrum of the yeast genome when compared to untreated control. We propose that SeL is acting as an oxidizing agent in S. cerevisiae producing superoxide and oxidative damage to DNA accounting for the observed DSB and cell death.

Prostate Cancer - What's New?

Research has shown that prostate specific antigen (PSA) is a tumour marker for diagnosis of cancer prostate with significant prognostic value. Screening studies in North America and Europe have revealed that carcinoma prostate is common. Early detection and treatment improves the quality of life besides preventing deaths due to metastatic prostate cancer. Radical prostatectomy and laparoscopic radical prostatectomy has become the standard treatment for localized prostate cancer in all major uro-oncological centres resulting in reduced mortality. Magnetic resonance imaging and positron emission tomography have helped in detecting local and distant spread of cancer prostate. Revised approach to reduce occurrence of prostate cancer by the use of 5 alpha reductase inhibitors like finasteride and dietary supplements has been instituted. The World Health Organisation (WHO) has recommended lifestyle changes to promote men's health and reduce the incidence of prostate cancer.

Estrogen receptor activation and estrogen-regulated gene expression are unaffected by methylseleninic acid in LNCaP prostate cancer cells

Prostate cancer is the most frequently diagnosed cancer and a leading cause of cancer deaths in American men. High dietary intake and status of the essential trace element selenium (Se) have been consistently correlated with reduced risk for prostate cancer. One molecular mechanism by which Se may reduce prostate cancer risk is by catalyzing disulfide bond formation or, otherwise, complexing with reactive sulfhydryl groups in transcription factors, thus altering their binding to DNA and regulation of gene expression. Estrogen plays a role in the etiology of prostate cancer. Estrogen receptors contain cysteines in zinc fingers that are susceptible to oxidation and internal disulfide bond formation, which can prevent DNA binding. We hypothesized that Se alteration of estrogen receptor (ER) binding to DNA and estrogen-regulated gene expression may be one mechanism by which it exerts its chemopreventive effects. LNCaP human prostate cancer cells were treated with 0.05 mumol/L (control) or 5.0 mumol/L (high) Se as methylseleninic acid (MSA). Electrophoretic mobility shift assays showed that binding of ER-beta to the estrogen response element was a nonsignificant 14% lower in cells treated with high MSA. Run-on transcription assays showed no significant changes in transcription rates for estrogen-regulated genes, and steady-state mRNA levels for those genes, assayed by reverse transcription-polymerase chair reaction, were likewise unaffected by MSA. These results suggest that the well-documented chemopreventive effects of Se against prostate cancer may be mediated by mechanisms other than inhibition by monomethylated Se compounds of ER-beta activation or estrogen-regulated gene expression.

Detection bias due to the effect of finasteride on prostate volume: a modeling approach for analysis of the Prostate Cancer Prevention Trial

BACKGROUND

The Prostate Cancer Prevention Trial (PCPT) demonstrated a 24.8% reduction in the 7-year prevalence of prostate cancer among patients treated with finasteride (5 mg daily) compared with that among patients treated with placebo; however, a 25.5% increase in the prevalence of high-Gleason grade tumors was observed, the clinical significance of which is unknown. One hypothesized explanation for this increase is that finasteride reduced prostate volume, leading to detection of more high-grade tumors due to increased sampling density. This possibility was investigated in an observational reanalysis of the PCPT data, with adjustment for sampling density.

METHODS

A logistic model for the association of high-grade (Gleason score 7-10) prostate cancer with baseline covariates and/or baseline covariates plus prostate volume and number of cores obtained at biopsy was developed using the placebo group (n = 4775) of the PCPT. This model was then applied to the finasteride group (n = 5123) to compare the predicted and observed numbers of high-grade tumors in that group. In a second approach, odds ratios (ORs) for prostate cancer in the finasteride versus placebo groups calculated from binary and polytomous logistic regression models that contained or excluded covariates for gland volume and number of needle cores were compared.

RESULTS

Median prostate volume was 25% lower in the finasteride group (median = 25.1 cm3) than in the placebo group (median = 33.5 cm3). The logistic model developed in the placebo group showed that the likelihood of detection of high-grade prostate cancer decreased as volume increased (for each 10 cm3 increase in prostate volume, OR = 0.81, 95% confidence interval [CI] = 0.74 to 0.90). Based on this model, 239 high-grade prostate cancers were predicted in the finasteride group, whereas 243 were observed, a non-statistically significant difference. Among all participants, the odds ratios for high-grade cancer in the finasteride versus placebo groups decreased from 1.27 (95% CI = 1.05 to 1.54) with adjustment for baseline covariates to 1.03 (95% CI = 0.84 to 1.26) following additional adjustment for gland volume and number of biopsy cores in binary outcome models and from 1.14 (95% CI = 0.94 to 1.38) to 0.88 (95% CI = 0.72 to 1.09) following these adjustments in the polytomous models.

CONCLUSIONS

Although analyses using postrandomization data require cautious interpretation, these results suggest that sampling density bias alone could explain the excess of high-grade cancers among the finasteride-assigned participants in the PCPT.

Tea beverage in chemoprevention and chemotherapy of prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed malignancy and the second leading cause of cancer-related deaths in American males with similar trends in many western countries. The existing treatment approaches and surgical intervention have not been able to effectively cope with this dreaded disease. For these reasons, it is necessary to intensify our efforts for a better understanding of the disease process and for the development of novel approaches for its prevention and treatment. Based on considerable evidence from in vivo and in vitro data and epidemiological studies, in recent years the beverage tea has gained considerable attention for reducing the risk of several cancers. Much of the cancer preventive effects of tea, especially green tea appear to be mediated by the polyphenols present therein. Geographical evidence suggests that the incidence and occurrence of PCa is lower in populations that consume tea regularly. This evidence suggests that tea polyphenols could be extrapolated to optimize their chemopreventive properties against PCa. PCa represents an excellent candidate disease for chemoprevention because it is typically diagnosed in men over 50 years of age and therefore, even a modest delay in neoplastic development achieved through pharmacological or nutritional intervention could result in a substantial reduction in the incidence of clinically detectable disease. In this review we address the issue of possible use of tea, especially green tea, for the prevention as well as treatment of PCa.

Chemoprävention des Prostatakarzinoms

Fueled by the results from recently published large interventional trials the topic of chemoprevention of prostate cancer has increasingly attracted the interest of practicing urologists. In this analysis the term"chemoprevention" comprises all agents not included in regular food intake. If possible, the results from interventional studies were considered. Today, it must be accepted as evidence-based that chemoprevention of prostate cancer by 5alpha-reductase inhibition using finasteride is possible. Furthermore, there is increasing evidence that selective estrogen receptor modulators (SERMs) may also have preventive potential. Prospective interventional trials investigating these substances are currently underway. Considering the high incidence and the fact that the diagnosis of prostate cancer has serious impact on the future life of the respective individuals further scientific evaluation of chemoprevention of prostate cancer is mandatory.

Prevention of prostate cancer through custom tailoring of chemopreventive regimen

One practical way to control cancer is through chemoprevention, which refers to the administration of synthetic or naturally occurring agents to block, reverse or delay the process of carcinogenesis. For a variety of reasons, the most important of which is human acceptance, for chemopreventive intervention naturally occurring diet-based agents are preferred over synthetic agents. For a long time, the prevailing mantra of cancer chemoprevention has been: "Find effective agents with acceptable or no toxicity and use them in preventing cancer in relatively healthy people or individuals at high risk for developing cancer". In pursuing this goal many naturally occurring phytochemicals capable of affording protection against carcinogenesis in preclinical settings in experimental animals have been described. However, clinical trials of single agents have yielded disappointing results. Since carcinogenesis is a multistage phenomenon in which many normal cellular pathways become aberrant, it is unlikely that one agent could prove effective in preventing cancer. This review underscores the need to build an armamentarium of naturally occurring chemopreventive substances that could prevent or slow down the development and progression of prostate cancer. Thus, the new effective approach for cancer prevention "building a customized mechanism-based chemoprevention cocktail of naturally occurring substances" is advocated.

Modulation of aflatoxin toxicity and biomarkers by lycopene in F344 rats

Modulation by lycopene of aflatoxin B(1) (AFB(1))-induced toxic effects, metabolism, and metabolic activations was studied in young F344 rats. Animals were pretreated orally with either corn oil (control group) or lycopene [100 mg/kg body weight (b.w.), intervention group] 5 days/week for 2 weeks. Control animals were then treated daily with AFB(1) (250 microg/kg b.w) alone. Intervention animals were administered lycopene (100 mg/kg b.w.) at 1 h following a daily treatment with AFB(1) (250 mug/kg b.w.). Pretreatment and intervention with lycopene significantly reduced the toxic effect caused by AFB(1) and greatly modulated AFB(1) metabolism and metabolic activation. Urinary excretion of AFB(1) phase 1 metabolites, AFM(1), AFQ(1), and AFP(1), was significantly decreased in lycopene-treated animals. Formation of serum AFB(1)-albumin adducts was also significantly reduced. The rate of reduction was from approximately 30% on day 1 (p<0.05) to 67.7% on day 15 (p<0.001). Lycopene intervention also significantly reduced formation of AFB(1)-DNA adducts in liver compared to control animals, with the highest reduction (52.7%) occurring on day 3 (p<0.05). Levels of AFB(1)-N(7)-guanine excreted in urine were also significantly decreased. Urinary excretion of the phase 2 detoxification metabolite, AFB(1)-mecapturic acid, was significantly increased in lycopene-intervened animals. AFB(1)-induced urinary excretion of 8-hydroxydeoxyguanosine was also reduced to 50% on day 7 after lycopene intervention. Collectively, these results suggest that inhibition of phase 1 metabolism and metabolic activation, as well as induction of phase 2 detoxification enzyme activity are the potential mechanisms for the chemopreventive effects of lycopene.

Looking Back at PCPT: Looking Forward to New Paradigms in Prostate Cancer Screening and Prevention

OBJECTIVES

Provide a critical summary of the latest interpretation of findings from the Prostate Cancer Prevention Trial (PCPT).

METHODS

Findings from PCPT and recently published post-hoc analyses are reviewed.

RESULTS

PCPT demonstrated that finasteride can reduce the prevalence of prostate cancer, permitted the first large-scale assessment of the performance characteristics of prostate-specific antigen for prostate cancer screening, and identified new-onset erectile dysfunction as an early predictor of cardiovascular events.

CONCLUSIONS

PCPT has and will continue to yield valuable information regarding future strategies for prostate cancer prevention and detection, benign prostatic hyperplasia, and other matters of public health importance.

S100A4 accelerates tumorigenesis and invasion of human prostate cancer through the transcriptional regulation of matrix metalloproteinase 9

We previously showed that the calcium-binding protein S100A4 is overexpressed during the progression of prostate cancer (CaP) in humans and in the TRAMP (transgenic adenocarcinoma of the mouse prostate) mouse model. We tested a hypothesis that the S100A4 gene plays a role in the invasiveness of human CaP and may be associated with its metastatic spread. We observed that siRNA-mediated suppression of the S100A4 gene significantly reduced the proliferative and invasive capability of the highly invasive CaP cells PC-3. We evaluated the mechanism through which the S100A4 gene controls invasiveness of cells by using a macroarray containing 96 well characterized metastatic genes. We found that matrix metalloproteinase 9 (MMP-9) and its tissue inhibitor (TIMP-1) were highly responsive to S100A4 gene suppression. Furthermore, S100A4 suppression significantly reduced the expression and proteolytic activity of MMP-9. By employing an MMP-9-promoter reporter, we observed a significant reduction in the transcriptional activation of the MMP-9 gene in S100A4-siRNA-transfected cells. Cells overexpressing the S100A4 gene (when transfected with pcDNA3.1-S100A4 plasmid) also significantly expressed MMP-9 and TIMP-1 genes with increased proteolytic activity of MMP-9 concomitant to increased transcriptional activation of the MMP-9 gene. S100A4-siRNA-transfected cells exhibited a reduced rate of tumor growth under in vivo conditions. Our data demonstrate that the S100A4 gene controls the invasive potential of human CaP cells through regulation of MMP-9 and that this association may contribute to metastasis of CaP cells. We suggest that S100A4 could be used as a biomarker for CaP progression and a novel therapeutic or chemopreventive target for human CaP treatment.

Melanoma chemoprevention

BACKGROUND

Despite efforts to promote sun protection behaviors, melanoma incidence continues to increase. The prognosis of advanced melanoma remains extremely poor in spite of treatment advances, emphasizing the importance of exploring additional preventive measures.

OBJECTIVE

We sought to summarize the results of published research on candidate chemoprevention agents for melanoma.

METHODS

We conducted a narrative review of the literature.

RESULTS

Investigation into a possible role in melanoma chemoprevention continues for multiple agents, including sunscreen, lipid-lowering medications, nonsteroidal anti-inflammatory drugs, dietary nutrients, immunomodulators, and other drugs, including retinoids, difluoromethylornithine, and T4 endonuclease V.

LIMITATIONS

Systematic review of the literature was not performed.

CONCLUSION

Because no agent yet emerges as a clear choice for effective melanoma chemoprevention, sun avoidance and sun protection remain the mainstay of melanoma prevention for persons at high risk.

Use of selenium in chemoprevention of bladder cancer

The anticarcinogenic potential of selenium was first identified nearly 40 years ago in geographical studies that reported lower death rates for cancer in regions with high levels of selenium. Cancer of the bladder was one of the body sites found to share this inverse association. Although many subsequent studies have been done on selenium and cancer, only a few have specifically assessed the relation with bladder cancer. However, the high recurrence rate and ability to monitor bladder urothelial-cell carcinoma make selenium a good candidate for chemoprevention. Evidence suggests that selenium is a biologically plausible, safe, and efficacious potential chemoprevention agent for bladder cancer. Large tertiary chemoprevention trials are needed to further investigate the role of selenium in the prevention of bladder cancer. Future studies should assess the best dose and form of selenium, and whether the protective effect of selenium differs between the sexes.

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.

Selenoprotein deficiency accelerates prostate carcinogenesis in a transgenic model

Considerable animal and human data have indicated that selenium is effective in reducing the incidence of several different types of cancer, including that of the prostate. However, the mechanism by which selenium inhibits carcinogenesis remains unknown. One possibility is that dietary selenium influences the levels of selenium-containing proteins, or selenoproteins. Selenoproteins contain selenium in the form of selenocysteine and perform a variety of cellular functions, including antioxidant defense. To determine whether the levels of selenoproteins can influence carcinogenesis independent of selenium intake, a unique mouse model was developed by breeding two transgenic animals: mice with reduced selenoprotein levels because of the expression of an altered selenocysteine-tRNA (i6A-) and mice that develop prostate cancer because of the targeted expression of the SV40 large T and small t oncogenes to that organ [C3(1)/Tag]. The resulting bigenic animals (i6A-/Tag) and control WT/Tag mice were assessed for the presence, degree, and progression of prostatic epithelial hyperplasia and nuclear atypia. The selenoprotein-deficient mice exhibited accelerated development of lesions associated with prostate cancer progression, implicating selenoproteins in cancer risk and development and raising the possibility that selenium prevents cancer by modulating the levels of these selenoproteins.

Enhancement of UVB radiation-mediated apoptosis by sanguinarine in HaCaT human immortalized keratinocytes

In this article, we studied the chemopreventive effects of sanguinarine on UVB-mediated responses in human HaCaT immortalized keratinocytes. For our studies, HaCaT cells were treated with a low dose (50 nmol/L) of sanguinarine for 24 hours followed by irradiation with UVB (15 or 30 mJ/cm2). Our data showed that UVB exposure, at both doses, resulted in decreased cell viability and increased apoptosis. Interestingly, pretreatment of the cells with sanguinarine caused a significant enhancement in the antiproliferative response of UVB. These responses on UVB and/or sanguinarine treatments were associated with (a) decrease in Bcl-2 and Bcl-X(L) and (b) increase in Bax, Bid, and Bak protein levels. Bax knockdown and Bcl-2 overexpression resulted in a rescue of HaCaT cells from sanguinarine-mediated apoptosis. DNA cell cycle analysis revealed that UVB treatment resulted in an accumulation of cells in the G2-M phase of the cell cycle, whereas pretreatment of sanguinarine resulted in a significant shift of cells in the S phase at a low UVB dose and a further accumulation of cells in the G2-M phase at a higher UVB dose. These effects on cell cycle were accompanied with modulations in the protein levels of cyclin (B1, E, and A) and cdc2 and cyclin-dependent kinase 1. Furthermore, sanguinarine treatment was found to result in significant modulations in p53, p66Shc, MsrA, and superoxide dismutase levels. Based on our data, we suggest the sanguinarine may protect skin cells from UVB-mediated damages via apoptotic elimination of damaged cells that escape programmed cell death and therefore possess a potential of clonal expansion.

Beneficial effects of tea and its polyphenols against prostate cancer

Tea, next to water, is the most widely consumed beverage in the world. Depending upon the level of fermentation, tea can be categorized into three types: green (unfermented), oolong (partially fermented), and black (highly to fully fermented). In general, green tea has been found to be superior to black and oolong tea in terms of antioxidant and health promoting benefits owing to the higher content of (-)-epigallocatechin-3-gallate. Tea polyphenols comprise about one-third of the weight of the dried leaf, and they exhibit biochemical and pharmacological activities including antioxidant activities, inhibition of cell proliferation, induction of apoptosis, cell cycle arrest and modulation of carcinogen metabolism. Several studies demonstrate that most tea polyphenols exert their effects by scavenging reactive oxygen species (ROS) since excessive production of ROS has been implicated in the development of a variety of ailments including cancer of the prostate gland (CaP). Using cell culture and animal model systems, molecular targets for these remarkable beneficial effects of green tea drinking on CaP prevention and therapy have been defined. Geographical and case-control studies are showing that green tea drinking could afford CaP chemopreventive effects in human population. In this review we attempt to summarize the experimental as well as the epidemiological basis for the possible role of tea and its polyphenols for chemoprevention and chemotherapy of CaP.

Update on Prostate Cancer Chemoprevention

BACKGROUND

Prostate cancer is the most common type of cancer and the second leading cause of cancer-related deaths in American men. Its high rate of occurrence and long lead time to clinically significant disease make prostate cancer an ideal disease for pharmacologic or nutritional chemoprevention.

METHODS

To identify the various chemoprevention strategies for prostate cancer, a MEDLINE search (from 1967-2005) and bibliographic search of the English-language literature were conducted.

RESULTS

Epidemiologic and retrospective studies have assessed the effect of carotenoids (e.g., lycopene), vitamins, selenium, and nonsteroidal antiinflammatory drugs (NSAIDs) on the rate of occurrence of prostate cancer. The few published prospective trials evaluated prostate cancer as a secondary end point. Lycopene (as beta-carotene) and selenium supplementation have been associated with a reduced risk of prostate cancer in nested case-control studies, but only in subgroups of men with low baseline plasma lycopene (or beta-carotene) and selenium levels respectively. The Prostate Cancer Prevention Trial prospectively evaluated finasteride, a 5-alpha-reductase inhibitor, as chemoprevention. The results showed a 25% relative risk reduction in prostate cancer, albeit at an increased risk of invasive tumors.

CONCLUSION

Data regarding lycopene, vitamin E, and selenium as chemoprevention for prostate cancer appear promising. Prospective trials such as the Selenium and Vitamin E Cancer Prevention Trial (SELECT) will clarify the role of these agents in prostate cancer prevention. The role of NSAIDs is unclear, and the long-term toxicity associated with NSAIDs may limit their usefulness. Although finasteride has decreased overall prostate cancer occurrence, the risk of invasive tumors may outweigh the benefit of this agent. The continuing Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial may help define a role for the 5-alpha-reductase inhibitors in cancer chemoprevention. At this time, nothing has been proven effective as chemoprevention against clinically significant prostate cancer.

Design of clinical trials in advanced prostate cancer: avoiding the dead ends

Despite more than 30 years of clinical trials, investigations in prostate cancer have not succeeded in making advances comparable to those in other branches of research, such as breast cancer. Indeed, prostate cancer trials have repeatedly run into a series of "dead ends", as investigators face the problems of inadequate funding for research, treatments that result in only minimal improvements in survival, and lack of treatment options that have sufficient prospects for success. This article briefly reviews the strategies behind clinical investigations into prostate cancer over the last three decades, evaluates the pitfalls that have hindered research, and makes suggestions for the appropriate design of clinical trials that are safe and beneficial to patients while maintaining cost-effectiveness and accountability to patients and society.

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.