Update on Prostate Cancer Chemoprevention

The andrologist's contribution to a better life for ageing men: part 2

The long-term intake of a judiciously composed nutriceutical containing low-dose vitamins, antioxidants, minerals and particular herbal preparations seems justified for older persons who take medication, or who consume an unbalanced diet, or who are exposed to environmental toxins. Recent reports suggest these nutriceuticals may delay age-related diseases and the occurrence of cancer, and reduce mortality in apparently healthy ageing men. Food supplementation with a nutriceutical that was formulated particularly for ageing men should result in an increase of at least one quality-adjusted life year and may lower the financial and social burden of disease in elderly people.

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.

Vitamin d, sunlight and prostate cancer risk

Prostate cancer is the second common cancer in men worldwide. The prevention of prostate cancer remains a challenge to researchers and clinicians. Here, we review the relationship of vitamin D and sunlight to prostate cancer risk. Ultraviolet radiation of the sunlight is the main stimulator for vitamin D production in humans. Vitamin D's antiprostate cancer activities may be involved in the actions through the pathways mediated by vitamin D metabolites, vitamin D metabolizing enzymes, vitamin D receptor (VDR), and VDR-regulated genes. Although laboratory studies including the use of animal models have shown that vitamin D has antiprostate cancer properties, whether it can effectively prevent the development and/or progression of prostate cancer in humans remains to be inconclusive and an intensively studied subject. This review will provide up-to-date information regarding the recent outcomes of laboratory and epidemiology studies on the effects of vitamin D on prostate cancer prevention.

Vitamins and prostate cancer risk

Prostate cancer (PC) is the second most common cancer in men worldwide. Its prevention and treatment remain a challenge to clinicians. Here we review the relationship of vitamins to PC risk. Many vitamins and related chemicals, including vitamin A, retinoids, several B vitamins, vitamin C, vitamin D and vitamin E have shown their anti-cancer activities as anti-oxidants, activators of transcription factors or factors influencing epigenetic events. Although laboratory tests including the use of animal models showed these vitamins may have anti-PC properties, whether they can effectively prevent the development and/or progression of PC in humans remains to be intensively studied subjects. This review will provide up-to-date information regarding the recent outcomes of laboratory, epidemiology and/or clinical trials on the effects of vitamins on PC prevention and/or treatment.

Effects of selenite and genistein on G2/M cell cycle arrest and apoptosis in human prostate cancer cells

Combination of chemopreventive agents with distinct molecular mechanisms is considered to offer a potential for enhancing cancer prevention efficacy while minimizing toxicity. Here we report two chemopreventive agents, selenite and genistein, that have synergistic effects on apoptosis, cell cycle arrest, and associated signaling pathways in p53-expressing LNCaP and p53-null PC3 prostate cancer cells. We show that selenite induced apoptosis only, whereas genistein induced both apoptosis and G2/M cell cycle arrest. Combination of these two agents exhibited enhanced effects, which were slightly greater in LNCaP than PC3 cells. Selenite or genistein alone upregulated protein levels of p53 in LNCaP cells only and p21(waf1) and Bax in both cell lines. Additionally, genistein inhibited AKT phosphorylation. Downregulation of AKT by siRNA caused apoptosis and G2/M cell cycle arrest and masked the effects of genistein. Treatment with insulin-like growth factor I (IGF-I) elevated levels of total and phosphorylated AKT and suppressed the effects of genistein. Neither downregulation of AKT nor IGF-I treatment altered the cellular effects of selenite. Our study demonstrates that selenium and genistein act via different molecular mechanisms and exhibit enhanced anticancer effects, suggesting that a combination of selenium and genistein may offer better efficacy and reduction of toxicity in prostate cancer prevention.

Whole blood selenium levels (WBSL) in patients with prostate cancer (PC), benign prostatic hyperplasia (BPH) and healthy male inhabitants (HMI) and prostatic tissue selenium levels (PTSL) in patients with PC and BPH

BACKGROUND

The aim of this exploratory study was to evaluate whether significant differences exist between whole blood selenium levels (WBSL) in patients with prostate cancer (PC), benign prostatic hyperplasia (BPH), healthy male inhabitants (HMI) in northern Bavaria and the normal value. Furthermore, we investigated whether differences exist between prostatic tissue selenium levels (PTSL) in patients with PC, BPH and the benign tissue surrounding the PC.

MATERIAL AND METHODS

We prospectively evaluated WBSL in 24 patients with PC, 21 patients with BPH, and 21 HMI. Measurements of PTSL were performed in 17 patients with PC and 22 patients with BPH. In 9 cases with PC, measurements were also done in the benign tissue surrounding the carcinoma. Measurements were performed using automated graphite furnace atomic absorption spectrophotometry.

RESULTS

In patients with PC, there is a significantly lower WBSL in comparison to HMI (p=0.04). There is no significant difference in WBSL between BPH-patients and HMI (p=0.13) and between PC- and BPH-patients (p=0.67). In all patients and the HMI, there is a significantly lower WBSL in comparison to the recommended normal value of 85-162 microg/l (p<0.01). There is no significant difference in PTSL between PC and BPH (p=0.49), and between PC and the tissue compartment surrounding the PC (p=0.56). PTSL seemed to be reduced in the compartment surrounding the PC in comparison to BPH (p=0.03). In PC-patients, there is no significant correlation between WBSL and prostate specific antigen (PSA) (? = -0.20; p=0.36), Gleason score (? = 0.32, p=0.13), and T-stage (? = 0.22; p=0.23).

CONCLUSION

Since the WBSL measured in all men with PC and BPH, and in HMI participating in our study were significantly lower than the recommended normal range, our findings may support the recommendation of selenium supplementation.

Delayed cytotoxic effects of methyl jasmonate and cis-jasmone induced apoptosis in prostate cancer cells

Advanced prostate cancer cells are typically hormone independent, resistant to apoptosis and do not respond to chemotherapeutic agents. The ability of methyl jasmonate (MJ) and cis-jasmone (CJ) to inhibit growth in hormone independent prostate cancer cell lines, PC-3 and DU-145, was evaluated. CJ and MJ inhibited cell growth, induced cell cycle arrest and apoptosis. Detailed studies with the PC-3 cell line revealed that 2 mM CJ or MJ treatment resulted in caspase 3 activation and Tumor Necrosis Factor Receptor 1 (TNFR1) activation, all hallmarks of apoptosis. These phytochemicals could be useful in the management of advanced prostate cancer.

Extraction conditions affecting supercritical fluid extraction (SFE) of lycopene from watermelon

Lycopene, a carotenoid linked to protection against certain forms of cancer, is found in produce such as papaya, red-fleshed tomatoes, grapefruit and watermelon. The preparation of a supercritical CO2 (SC-CO2) watermelon-lycopene extract could serve as a food grade source of this carotenoid. This study established preliminary conditions for enhancing SC-CO2 extraction of lycopene from watermelon. Freeze-dried watermelon was extracted with SC-CO2 and ethanol as an organic co-solvent. The lycopene concentration was determined by HPLC, with absorbance measured at 503 nm. In an initial set of experiments, the effects of extraction temperature (70-90 degrees C), pressure (20.7-41.4 MPa) and co-solvent ethanol addition (10-15%) were evaluated. A lycopene yield of 38 microg per gram of wet weight was obtained at 70 degrees C, 20.7 MPa, and 15% by volume ethanol. The extraction of fresh (non-freeze-dried) watermelon yielded 103+/-6 microg lycopene per gram fresh fruit weight. Of the parameters tested, temperature had the most effect on lycopene yield. Thus, in another set of experiments, the temperature was varied from 60-75 degrees C at an extraction pressure of 20.7 MPa in the presence of 15% ethanol. Studies showed that freeze-dried watermelon flesh loses lycopene in storage. In accounting for lycopene storage losses, lycopene yields at 60 degrees C extraction temperature were 14% greater than those obtained at 70 degrees C.

Induction of apoptosis by lupeol and mango extract in mouse prostate and LNCaP cells

Prostate cancer (PCA) is one of the most invasive malignancy and second leading cause of cancer related deaths in United States and some other countries. Long latency period makes PCA an ideal disease for pharmacologic or nutritional chemoprevention. Lupeol, a triterpene present in mango and other fruits, has shown to possess anticancer properties in in vivo and in vitro assays. Here, we recorded the apoptogenic activity in mouse prostate by lupeol and mango pulp extract (MPE). Testosterone was injected subcutaneously (5 mg/kg body weight) for 14 consecutive days to male Swiss albino mice. Lupeol/MPE supplementation resulted in arrest of prostate enlargement in testosterone-treated animals. In mouse prostate tissue, lupeol and MPE supplementation resulted in a significantly high percentage of apoptotic cells in the hypodiploid region. The induction of apoptosis in mouse prostate cells was preceded by the loss of mitochondrial transmembrane potential and DNA laddering. In testosterone-induced mouse prostate, upregulation of antiapoptotic B-cell non-Hodgkin lymphoma-2 and downregulation of proapoptotic Bcl-2-associated X protein and caspase-3 were also recorded. We further observed apoptogenic activities of lupeol in an in vitro model using human prostate cancer cells [lymph node carcinoma of the prostate (LNCaP)]. The apoptogenic response of lupeol-induced changes in LNCaP cells can be summarized as early increase of reactive oxygen species followed by induction of mitochondrial pathway leading to cell death. Thus, the results of this study demonstrate that lupeol/MPE is effective in combating testosterone-induced changes in mouse prostate as well as causing apoptosis by modulating cell-growth regulators.

Low-Activity V89L Variant in SRD5A2 Is Associated with Aggressive Prostate Cancer Risk: An Explanation for the Adverse Effects Observed in Chemoprevention Trials Using 5-Alpha-Reductase Inhibitors

OBJECTIVE

The 5-alpha-reductase type 2 (5A2) enzyme catalyses the irreversible conversion of testosterone to dihydrotestosterone, the most active androgen in the prostate. This key enzyme in prostate gland physiopathology has recently been targeted by using inhibitors for chemoprevention of prostate cancer. However, some controversies have arisen by the observation of greater than expected high-grade tumours in men diagnosed with prostate cancer in the finasteride chemoprevention trial. To help understand the impact of prolonged exposure to low 5A2 activity on prostate cancer risk, we analysed the rather common genetic V89L polymorphism, which has previously been well characterised functionally for determining low enzymatic activities.

METHODS

The study was performed on 1605 white Caucasian French men categorised in 803 patients with prostate adenocarcinoma and 802 matched healthy male controls. The different alleles and genotypes were analysed according to case-control status and the aggressiveness pattern of the tumours.

RESULTS

The V89L amino acid substitution leading to the homozygous genotype LL increased the risk of clinically significant disease (odds ratio [OR]=1.89, 95% confidence interval (%95 CI), 1.07-2.74; p=0.0017) and was also associated with the most aggressive patterns of the disease (OR=2.56, 95%CI, 1.41-4.63; p=0.002).

CONCLUSIONS

Our data confirm in a large and homogeneous Caucasian French population that the low-activity V89L variant is associated with an increased risk of aggressive prostate cancer. These results corroborate that long-term exposure to 5A2 inhibitors (chemoprevention) must be evaluated in terms of risk of prostate cancer adverse effects.

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.