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December 2013

Growth Inhibitory, Antiandrogenic, and Pro-apoptotic Effects of Punicic Acid in LNCaP Human Prostate Cancer Cells.

Prostate cancer is a commonly diagnosed cancer in men, and dietary chemoprevention by pomegranate (Punica granatum) extracts has shown noticeable benefits. In this study, we investigated the growth inhibitory, antiandrogenic, and pro-apoptotic effects of 13 pure compounds found in the pomegranate in androgen-dependent LNCaP human prostate cancer cells. Cells deprived of steroid hormones were exposed to increasing concentrations (1-100 µM) of pomegranate compounds in the presence of 0.1 nM dihydrotestosterone (DHT), and the inhibition of cell growth was measured by WST-1 colorimetric assay after a 4 day exposure. Four compounds, epigallocatechin gallate (EGCG), delphinidin chloride, kaempferol, and punicic acid, were found to inhibit DHT-stimulated cell growth at concentrations of 10 µM and above. These four pomegranate compounds inhibited DHT-stimulated androgen receptor nuclear accumulation and the expression of the androgen receptor-dependent genes prostate specific antigen and steroid 5a-reductase type 1 at concentrations ≥10 µM. We determined the possible contribution of apoptosis to the observed decrease in cell growth and found that three compounds, EGCG, kaempferol, and, in particular, punicic acid, induced DNA fragmentation after a 24 h treatment, at concentrations in the 10-100 µM range. Punicic acid, an important fatty acid in pomegranate seeds, was further found to induce intrinsic apoptosis via a caspase-dependent pathway. In conclusion, punicic acid, the main constituent of pomegranate seed (70-80%), exhibited potent growth inhibitory activities in androgen-dependent LNCaP cells, which appear to be mediated by both antiandrogenic and pro-apoptotic mechanisms.

J Agric Food Chem . 2010 Nov 10

Cancer chemoprevention by pomegranate: laboratory and clinical evidence.

Pomegranate fruit from the tree Punica granatum has been dubbed as the “nature’s power fruit.” Dating back to Biblical times, the tree itself is attributed to possess extraordinary medicinal properties. The geographical distribution of the tree, being native to the Middle East and some Asian countries, is generally attributed to a lack of interest in its medicinal properties by many western scientists. However, the unique biochemical composition of the pomegranate fruit being rich in antioxidant tannins and flavonoids has recently drawn attention of many investigators to study its exceptional healing qualities. Recent research has shown that pomegranate extracts selectively inhibit the growth of breast, prostate, colon and lung cancer cells in culture. In preclinical animal studies, oral consumption of pomegranate extract inhibited growth of lung, skin, colon and prostate tumors. An initial phase II clinical trial of pomegranate juice in patients with prostate cancer reported significant prolongation of prostate specific antigen doubling time. This review focuses on recent investigations into the effects of pomegranate fruit on cancer.

Nutr Cancer. 2009;61(6):811-5

A randomized phase II study of pomegranate extract for men with rising PSA following initial therapy for localized prostate cancer.

BACKGROUND: Pomegranate juice has been associated with PSA doubling time (PSADT) elongation in a single-arm phase II trial. This study assesses biological activity of two doses of pomegranate extract (POMx) in men with recurrent prostate cancer, using changes in PSADT as the primary outcome. METHODS: This randomized, multi-center, double-blind phase II, dose-exploring trial randomized men with a rising PSA and without metastases to receive 1 or 3 g of POMx, stratified by baseline PSADT and Gleason score. Patients (104) were enrolled and treated for up to 18 months. The intent-to-treat (ITT) population was 96% white, with median age 74.5 years and median Gleason score 7. This study was designed to detect a 6-month on-study increase in PSADT from baseline in each arm. RESULTS: Overall, median PSADT in the ITT population lengthened from 11.9 months at baseline to 18.5 months after treatment (P < 0.001). PSADT lengthened in the low-dose group from 11.9 to 18.8 months and 12.2 to 17.5 months in the high-dose group, with no significant difference between dose groups (P = 0.554). PSADT increases >100% of baseline were observed in 43% of patients. Declining PSA levels were observed in 13 patients (13%). In all, 42% of patients discontinued treatment before meeting the protocol-definition of PSA progression, or 18 months, primarily due to a rising PSA. No significant changes occurred in testosterone. Although no clinically significant toxicities were seen, diarrhea was seen in 1.9% and 13.5% of patients in the 1- and 3-g dose groups, respectively. CONCLUSIONS: POMx treatment was associated with ≥ 6 month increases in PSADT in both treatment arms without adverse effects. The significance of this on-study slowing of PSADT remains unclear, reinforcing the need for placebo-controlled studies in this patient population.

Prostate Cancer Prostatic Dis. 2013 Mar;16(1):50-5

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.

Nutr Cancer. 2012;64(1):4-22

Green tea and prostate cancer: from bench to clinic.

Green tea, the most popular beverage next to water, is a rich source of tea catechins and has potential to be developed as a chemopreventive agent for prostate cancer. For centuries it has been used in traditional medicine in Far-East countries. Male populations in these countries where large quantities of green tea are consumed on regular basis have the lowest incidence of prostate cancer. In this review, after a description of prostate cancer and several risk factors associated with the disease, we evaluated studies reported with green tea or its major constituent, (-)-epigallocatechin-3-gallate in inhibition of prostate cancer. This review provides an in-depth overview of various biochemical and signaling pathways affected by green tea in in vivo and in vitro models of prostate cancer. This is followed by a comprehensive discussion of the epidemiological studies and some ongoing clinical trials with green tea catechins. The review concludes with a brief discussion of the future direction and development of clinical trials employing green tea catechins which could be developed for prevention and/or intervention of prostate cancer.

Front Biosci (Elite Ed). 2009 Jun 1;1:13-25

Tea and lycopene protect against prostate cancer.

Prostate cancer is the most common male cancer in developed countries and is increasing in the developing world. Its long latency and geographical variation suggest the possibility of prevention or postponement of onset by dietary modification. To investigate the possible joint effect of lycopene and green tea on prostate cancer risk, a case-control study was conducted in Hangzhou, China, with 130 prostate cancer patients and 274 hospital controls. Information on tea and dietary intakes, and possible confounders was collected using a structured questionnaire. The risk of prostate cancer for the intake of tea and lycopene and their joint effect were assessed using multivariate logistic regression models. Prostate cancer risk was reduced with increased consumption of green tea. The protective effect of green tea was significant (odds ratio 0.14, 95% CI: 0.06-0.35) for the highest quartile relative to the lowest after adjusting for total vegetables and fruits intakes and other potential confounding factors. Intakes of vegetables and fruits rich in lycopene were also inversely associated with prostate cancer risk (odds ratio 0.18, 95% CI 0.08-0.39). Interaction analysis showed that the protective effect from tea and lycopene consumption was synergistic (p<0.01). This study suggests that habitual drinking tea and intakes of vegetables and fruits rich in lycopene could lead to a reduced risk of prostate cancer in Chinese men. Together they have a stronger preventive effect than either component taken separately. This is the first epidemiological study to investigate the joint effect between tea drinking and lycopene intake.

Asia Pac J Clin Nutr. 2007;16 Suppl 1:453-7.

Curcumin blocks CCL2-induced adhesion, motility and invasion, in part, through down-regulation of CCL2 expression and proteolytic activity.

Expression and activity of CC motif ligand 2 (CCL2) is down-regulated by curcumin, the active phytochemical ingredient of turmeric (Curcuma longa), a dietary supplement often self-prescribed to promote prostate health. CCL2 is a potent chemotactic factor of prostate cancer (PCa) with important roles in development of bone metastasis. The relationship between CCL2 and curcumin, however, has not been studied in PCa. Adhesion, invasion and motility of PC-3 cells were measured in response to exposure to curcumin (30 microM; 18 h), CCL2 (100 ng/ml; 18 h) or PMA (100 ng/ml; 18 h). CCL2 mRNA expression and protein secretion levels were measured by real-time PCR and ELISA respectively. Curcumin significantly blocked CCL2 induced adhesion, invasion and motility. Curcumin also significantly suppressed the mRNA expression and secreted CCL2 protein levels. The addition of PMA, a protein kinase C (PKC) activator, blocked the effects of curcumin, leading to an increase in CCL2 expression as well as an increase in PC-3 cell adhesion, invasion and motility. The introduction of a PKC inhibitor, however, blocked the effects of CCL2. We also found that curcumin, CCL2 and PMA, in part, function through the differential regulation of the proteolytic protein matrix metalloproteinase (MMP)-9. These data indicate a potential mechanism; by which curcumin can block the chemotactic effects of CCL2 on PCa. Curcumin exerts potential anti-metastatic effects in bone-derived PCa cells by blocking CCL2 mediated actions on invasion, adhesion and motility, in part through differential regulation of PKC and MMP-9 signaling.

Int J Oncol. 2009 May;34(5):1319-27

Curcumin-targeting pericellular serine protease matriptase role in suppression of prostate cancer cell invasion, tumor growth, and metastasis.

Curcumin has been shown to possess potent chemopreventive and antitumor effects on prostate cancer. However, the molecular mechanism involved in curcumin’s ability to suppress prostate cancer cell invasion, tumor growth, and metastasis is not yet well understood. In this study, we have shown that curcumin can suppress epidermal growth factor (EGF)- stimulated and heregulin-stimulated PC-3 cell invasion, as well as androgen-induced LNCaP cell invasion. Curcumin treatment significantly resulted in reduced matrix metalloproteinase 9 activity and downregulation of cellular matriptase, a membrane-anchored serine protease with oncogenic roles in tumor formation and invasion. Our data further show that curcumin is able to inhibit the induction effects of androgens and EGF on matriptase activation, as well as to reduce the activated levels of matriptase after its overexpression, thus suggesting that curcumin may interrupt diverse signal pathways to block the protease. Furthermore, the reduction of activated matriptase in cells by curcumin was also partly due to curcumin’s effect on promoting the shedding of matriptase into an extracellular environment, but not via altering matriptase gene expression. In addition, curcumin significantly suppressed the invasive ability of prostate cancer cells induced by matriptase overexpression. In xenograft model, curcumin not only inhibits prostate cancer tumor growth and metastasis but also downregulates matriptase activity in vivo. Overall, the data indicate that curcumin exhibits a suppressive effect on prostate cancer cell invasion, tumor growth, and metastasis, at least in part via downregulating matriptase function.

Cancer Prev Res (Phila). 2013 May;6(5):495-505

Demethoxycurcumin Modulates Prostate Cancer Cell Proliferation via AMPK-Induced Down-regulation of HSP70 and EGFR.

Curcumin (Cur), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) are major forms of curcuminoids found in the rhizomes of turmeric. This study examined the effects of three curcuminoid analogues on prostate cancer cells. The results revealed that DMC demonstrated the most efficient cytotoxic effects on prostate cancer PC3 cells. DMC activated AMPK and in turn decreased the activity and/or expression of lipogenic enzymes, such as fatty acid synthase (FASN) and acetyl-CoA carboxylase (ACC). AICAR, an AMPK activator, and DMC down-regulated heat shock protein (HSP) 70 and increased the activity of the pro-apoptotic effector, caspase-3. In addition, DMC sustained epidermal growth factor receptor (EGFR) activation by suppressing the phosphatases PP2a and SHP-2. DMC also increased the interaction between EGFR and Cbl and induced the tyrosine phosphorylation of Cbl. The results suggest that DMC may have antitumor effects on prostate cancer cells via AMPK-induced down-regulation of HSP70 and EGFR.

J Agric Food Chem. 2012 Aug 16

Cruciferous vegetables, genetic polymorphisms in glutathione S-transferases M1 and T1, and prostate cancer risk.

Cruciferous vegetables contain anticarcinogenic isothiocyanates (ITCs), particularly the potent sulforaphane, which may decrease risk of prostate cancer through induction of phase II enzymes, including glutathione S-transferases (GSTs). We evaluated this hypothesis in a population-based, case-control study of prostate cancer, including 428 men with incident prostate cancer and 537 community controls. An in-person interview included an extensive food-frequency questionnaire. Genotyping for deletions in GSTM1 and GSTT1 was performed in a subset of men who provided blood. Intakes of cruciferous vegetables and of broccoli, the greatest source of sulforaphane, were associated with decreased prostate cancer risk at all levels above the lowest consumers [adjusted 4th quartile odds ratio (OR)=0.58; 95% confidence interval (CI)=0.38, 0.89, and 0.72 (95% CI=0.49, 1.06)], respectively. In relation to genotypes, there was a nonsignificant increase in risk with the GSTT1 null genotype (OR=1.51; 95% CI=0.98, 2.31) but no effects of GSTM1 genotype. However, men with GSTM1-present genotype and high broccoli intake had the greatest reduction in risk (OR=0.49; 95% CI=0.27, 0.89). Our findings provide evidence that two or more servings per month of cruciferous vegetables may reduce risk of prostate cancer, especially among men with GSTM1-present alleles, and are consistent with a role of dietary ITCs as chemopreventive agents against prostate cancer.

Nutr Cancer. 2004;50(2):206-13

Sulforaphane retards the growth of human PC-3 xenografts and inhibits HDAC activity in human subjects.

Sulforaphane (SFN) is an isothiocyanate found in cruciferous vegetables such as broccoli. This anticarcinogen was first identified as a potent inducer of Phase 2 enzymes, but evidence is mounting that SFN acts through other cancer chemopreventive mechanisms. We recently reported on a novel mechanism of chemoprotection by SFN in human colon cancer cells and prostate epithelial cells, namely the inhibition of histone deacetylase (HDAC). In the present investigation, we sought to test whether SFN also might inhibit HDAC activity in vivo. When consumed in the diet at an average daily dose of 7.5 mumol per animal for 21 days, SFN suppressed the growth of human PC-3 prostate cancer cells by 40% in male nude mice. There was a significant decrease in HDAC activity in the xenografts, as well as in the prostates and mononuclear blood cells (MBC), of mice treated with SFN, compared to controls. There also was a trend towards increased global histone acetylation in the xenografts, prostates, and MBC. In human subjects, a single dose of 68 g BroccoSprouts inhibited HDAC activity significantly in peripheral blood mononuclear cells (PBMC) 3 and 6 hrs following consumption. These findings provide evidence that one mechanism through which SFN acts as a cancer chemopreventive agent in vivo is through the inhibition of HDAC activity. Moreover, the data suggest that HDAC activity in PBMC may be used as a biomarker for assessing exposure to novel dietary HDAC inhibitors in human subjects.

Exp Biol Med (Maywood). 2007 Feb;232(2):227-34

Sulforaphane inhibits constitutive and interleukin-6-induced activation of signal transducer and activator of transcription 3 in prostate cancer cells.

D,L-sulforaphane (SFN), a synthetic analogue of broccoli-derived L-isomer, inhibits viability of human prostate cancer cells and prevents development of prostate cancer and distant site metastasis in a transgenic mouse model. However, the mechanism underlying the anticancer effect of SFN is not fully understood. We now show that SFN inhibits constitutive and interleukin-6 (IL-6)-inducible activation of signal transducer and activator of transcription 3 (STAT3), which is an oncogenic transcription factor activated in many human malignancies, including prostate cancer. Growth-suppressive concentrations of SFN (20 and 40 micromol/L) decreased constitutive (DU145 cells) and IL-6-induced (DU145 and LNCaP cells) phosphorylation of STAT3 (Tyr(705)) as well as its upstream regulator Janus-activated kinase 2 (Tyr(1007/1008)). Exposure of DU145 and LNCaP cells to SFN resulted in suppression of (a) IL-6-induced transcriptional activity of STAT3 as judged by luciferase reporter assay and (b) nuclear translocation of phospho-STAT3 as revealed by immunofluorescence microscopy. Levels of many STAT3-regulated gene products, including Bcl-2, cyclin D1, and survivin, were also reduced in SFN-treated cells. The IL-6-mediated activation of STAT3 conferred partial but marked protection against SFN-induced apoptosis as evidenced by cytoplasmic histone-associated DNA fragmentation and cleavage of poly(ADP-ribose) polymerase and procaspase-3. Furthermore, knockdown of STAT3 protein using small interfering RNA resulted in a modest yet statistically significant increase in SFN-induced apoptotic DNA fragmentation in DU145 cells. Suppression of STAT3 activation was also observed in cells treated with naturally occurring analogues of SFN. In conclusion, the present study indicates that inhibition of STAT3 partially contributes to the proapoptotic effect of SFN.

Cancer Prev Res (Phila). 2010 Apr;3(4):484-94