Pomegranate Juice Metabolites, Ellagic Acid and Urolithin A, Synergistically Inhibit Androgen Independent Prostate Cancer Cell Growth via Distinct Effects on Cell Cycle Control and Apoptosis Roberto Vicinanza1, Yanjun Zhang1, Susanne M.Henning1 and David Heber1§ 1Center for Human Nutrition, David Geffen School of Medicine, University of California, Los Angeles, California, UCLA.
Abstract Ellagitannins (ET) from pomegranate juice (PJ) are bioactive polyphenols with chemopreventive potential against prostate cancer (PCa). ET are not absorbed intact, but are partially hydrolyzed in the gut to ellagic acid (EA). Colonic microflora can convert EA to urolithin A (UA), and EA and UA enter the circulation after PJ consumption. Here, we studied the effects of EA and UA on cell proliferation, cell cycle and apoptosis in DU-145 and PC-3 androgen-independent PCa cells, and whether combinations of EA and UA affected cell proliferation. EA demonstrated greater dose-dependent antiproliferative effects in both cell lines compared to UA. EA induced cell cycle arrest in S-phase associated with decreased cyclin B1 and cyclin D1 levels. UA induced a G2/M arrest and increased cyclin B1 and cdc2 phosphorylation at tyrosine-15, suggesting inactivation of the cyclin B1/cdc2 kinase complex. EA induced apoptosis in both cell lines, while UA had a less pronounced pro-apoptotic effect only in DU- 145. Co-treatment with low concentrations of EA and UA dramatically decreased cell proliferation, exhibiting synergism in PC-3 cells evaluated by isobolographic analysis and combination index. These data provide information on pomegranate metabolites for the prevention PCa recurrence, supporting the role of gut flora-derived metabolites for cancer prevention.
Pomegranate extract induces apoptosis in human prostate cancer cells by modulation of the IGF-IGFBP axis Satomi Koyama,1 Laura J Cobb,1 Hemal H Mehta,1 Navindra P. Seeram,2 David Heber,2 Allan J. Pantuck,3 and Pinchas Cohen11
Division of Pediatric Endocrinology, Mattel Children's Hospital, David Geffen School of Medicine, University of California, Los Angeles 2Center for Human Nutrition, David Geffen School of Medicine, UCLA 3 Department of Urology, David Geffen School of Medicine, UCLA
Abstract 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 10 μg/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 100 ng/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.
In conclusion, these studies reveal novel interactions between the IGF system and pomegranate-induced apoptosis, and suggest that pomegranate products modulate the tumor production and responsiveness to IGFs and the IGFBPs. As IGFBP-3 is currently being tested in humans as a treatment for prostate cancer and pomegranate supplements are becoming popular as adjuvant nutritional treatments for this disease, we propose that these agents may emerge as useful in the management of prostate cancer.
Pomegranate extract inhibits androgen-independent prostate cancer growth through a nuclear factor-κB-dependent mechanism Matthew B. Rettig 25,David Heber4, Jiabin An5,Navindra P. Seeram4,Jian Y. Rao3, Huiren Liu1,Tobias Klatte2,Arie Belldegrun2,Aune Moro4,Susanne M. Henning4, Deqiong Mo5,William J. Aronson26 and Allan Pantuck2
Abstract Constitutive nuclear factor-κB (NF-κB) activation is observed in androgen-independent prostate cancer and represents a predictor for biochemical recurrence after radical prostatectomy. Dietary agents such as pomegranate extract (PE) have received increasing attention as potential agents to prevent the onset or progression of many malignancies, including prostate cancer. Here, we show that PE inhibited NF-κB and cell viability of prostate cancer cell lines in a dose-dependent fashion in vitro. Importantly, maximal PE-induced apoptosis was dependent on PE-mediated NF-κB blockade. In the LAPC4 xenograft model, PE delayed the emergence of LAPC4 androgen-independent xenografts in castrated mice through an inhibition of proliferation and induction of apoptosis. Moreover, the observed increase in NF-κB activity during the transition from androgen dependence to androgen independence in the LAPC4 xenograft model was abrogated by PE. Our study represents the first description of PE as a promising dietary agent for the prevention of the emergence of androgen independence that is driven in part by heightened NF-κB activity.
.....Extending the duration of the androgen-dependent state could potentially prolong life expectancy of prostate cancer patients and delay or prevent the need for additional hormonal therapy or chemotherapy. In this regard, our finding that PE delayed the growth and emergence of androgen independence in our xenograft model may be particularly germane. Of importance, our group showed previously that dietary fat reduction delayed the emergence of androgen independence and prolonged survival using a similar xenograft model (36). Future research will focus on potential additive and/or synergistic effects of combining a low-fat diet with PE. Based on our results, we propose that PJ could have potential as a dietary agent to prevent the emergence of androgen independence and suggest that this may be a high priority area for future clinical investigation.