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. Author manuscript; available in PMC: 2011 Feb 1.
Published in final edited form as: Growth Horm IGF Res. 2009 Oct 22;20(1):55. doi: 10.1016/j.ghir.2009.09.003

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, Pinchas Cohen 1
PMCID: PMC2815223  NIHMSID: NIHMS154342  PMID: 19853487

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.

Keywords: Prostate cancer, Pomegranate, IGF-I, IGFBP-3

Introduction

Prostate cancer (CaP) is the leading cause of cancer in American men (1). Treatment of recurrent CaP commonly involves hormone ablation therapy, however given sufficient time, tumors uniformly progress to a state of insensitivity to hormonal ablation. Once the disease is castrate-resistant and metastatic, the prognosis for the patient is poor. On the other hand, the protracted period of prostate carcinogenesis provides an ideal opportunity for chemoprevention, the administration of natural or synthetic agents to inhibit this process before the invasive phenotype is established (2,3,4,5). This approach is ideally suited for CaP since it is typically diagnosed in men over 50 years of age, and therefore even a modest delay in disease onset or progression could significantly impact the quality of life of these patients (6). In this regard, several naturally occurring antioxidants including lycopene, tea polyphenols and pomegranate as potential modulators of prostate carcinogenesis are currently being evaluated (7, 8, 9), and are demonstrating positive effects in CaP patients (6, 10, 11,12, 13).

Pomegranate (punica granatum L.) fruits are widely consumed fresh and in beverage forms such as juice and wines (14). Commercial pomegranate juice (PJ) shows potent antioxidant and anti-atherosclerotic properties attributed to its high content of polyphenols including ellagic acid (EA), gallotannins and anthocyanins (cyanidin, delphynidin, and pelargonidin glycosides), and other flavonoids (quercetin, kaempferol and luteolin glycosides) (13, 15, 16, 17, 18, 19). The most abundant of these polyphenols is punicalagin, an ellagitannin implicated as the bioactive constituent responsible for >50% of the potent antioxidant activity of the pomegranate (13). Punicalagin is abundant in the fruit husk and is extracted into PJ in significant quantities during processing, reaching levels of >2 g/L juice (13, 17, 18,20). POMx is a highly potent pomegranate extract that was developed for use as a dietary ingredient, has received Generally Recognized as Safe status, is prepared from skin and arils minus seeds, and is standardized to ellagitannin content (37% punicalagins by HPLC) (21).

The activity of insulin-like growth factor (IGF)-I and -II are regulated by a family of six high-affinity binding proteins. IGF-I is upregulated in a variety of cancers including prostate cancer, and functions as a potent mitogen and survival factor as well as being epidemiologically related to CaP incidence (22). IGF binding protein (IGFBP)-3 is the most abundant of the IGFBPs in serum, where it forms a ternary complex with acid labile subunit and IGF (23). In addition to its role in regulating IGF action, IGFBP-3 exerts many IGF-independent effects to inhibit cell proliferation and enhance apoptosis in many cell types, including prostate (24) and breast (25,26,27) cancers. As recent reports demonstrate that pomegranate juice and its extracts have potent anti-tumorigenic effects in prostate cancer, the purpose of this study was to evaluate the effects of pomegranate extracts on the IGF-IGFBP axis in prostate cancer cell lines.

Materials and methods

Reagents

Recombinant non-glycosylated IGFBP-3 was provided by Insmed (Glen Allen, VA). The mouse anti-β-actin was purchased from Sigma (St. Louis, MO). I-Block™ was purchased from Applied Biosystems (Foster City, CA). SDS-PAGE precast gels and blotting equipment were purchased from Bio-Rad (Hercules, CA). CellTiter 96 Aqueous One Solution Cell Proliferation Assay was purchased from Promega (Madison, WI). Cell Death Detection ELISAPLUS kit was purchased from Roche Applied Science (Germany). Phospho-SAPK/JNK (Thr183/Tyr185) (G9) Mouse mAb, SAPK/JNK (56G8) Rabbit mAb, Phospho-Akt (Thr308) antibody, Phospho-Akt (Ser473) antibody, Akt antibody, Phospho-mTOR (Ser2448) antibody, Phospho-mTOR (Ser2481) antibody and mTOR antibody were purchased from Cell Signaling (Danvers, MA). IGF-I was provided by Tercica (Brisbane, CA)

Cell Culture

The LAPC4 prostate cancer cell line was a generous gift from Charles Sawyers ( 28 ). LAPC4 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 1% penicillin/streptomycin, and 10 nmol/L R1881 (Perkin-Elmer Life Sciences, Wellesley, MA). 22RV1 prostate carcinoma cell line (American Type Culture Collection, Manassas, VA) was maintained in RPMI 1640 supplemented with 10% FBS and 1% penicillin/streptomycin. The R- cell line were generously provided by Renato Baserga (Thomas Jefferson University, Philadelphia, PA); briefly, fibroblasts from an IGF-I receptor knock-out mouse was generated from 18-day embryos as described previously (29). R- cells were maintained in DMEM containing 10% fetal bovine serum and 1% penicillin/streptomycin. For individual experiments, cells were seeded at a final density of 1 × 105/cm2 (24-well and six-well), or 2× 105/cm2 (96-well) in plates and grown to 80% or 50% confluence, respectively. Cells were maintained in a humidified atmosphere of 5% CO2 at 37°C. All treatments were carried out as indicated in serum-free medium.

Cell Proliferation Assay

Cells were seeded on 96-well plates, and were allowed to attach overnight. Cells were incubated with 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 72 hours in SF media. CellTiter 96® AQueous One Solution Cell Proliferation Assay (Promega) was performed according to manufacturer's instructions. Mean ± SE values of the absorbance at 490 nm were plotted.

Analysis of Apoptosis

Apoptosis was assessed in cells growing on 24 well plates using Cell Death Detection ELISAPLUS for the determination of cytoplasmic histone-associated DNA fragments (Roche Applied Science) following the manufacturer's instructions.

Immunoblotting

Cell lysates containing 50 μg protein were resolved by SDS-PAGE and transferred to PVDF membrane (Bio-Rad). Membranes were blocked on 0.2% I-Block™ in PBS containing 0.1% Tween 20 for 3 hours at room temperature and then probed with the appropriate primary and secondary antibodies. Antibody-antigen complexes were visualized by Immobilon Western Chemilluminescence reagents (Millipore, Billerica, MA) and autoradiography.

mRNA Extraction and Reverse Transcription Polymerase Chain Reaction

Total RNA was prepared using TRIzol Reagent (Invitrogen, Carlsbad, CA) and was reverse transcribed to cDNA (Bio-Rad Laboratories, Hercules, CA) as per manufacturer's instructions. PCR reactions were performed in 20 μl containing 1 μl cDNA and 5′ HotMasterMix (Eppendorf, Ontario, CA). Oligonucleotide primers (Invitrogen, Carlsbad, CA) were included in the reactions with sequences as follows: IGF-1: 5′TGG ATG CTC TTC AGT TCG TG 3′ (forward), 5′CCT GCA CTC CCT CTA CTT GC 3′ (reverse); IGF-1: 5′ GGA CCG GAG ACG CTC TGC GGG 3′ (forward), 5′ AGC TGA CTT GGC AGG CTT GAG 3′ (reverse); β-actin: 5′ CAC CTT CTA CAA TGA GCT GC 3′ (forward), 5′ AAG GTA GTT TCG TGG ATG CC 3′ (reverse). Cycling conditions were as follows; denaturing at 95 °C for 1 min, annealing at 60 °C for 1 min, extension at 72 °C for 1 min for 30 cycles.

Densitometrical and Statistical analysis

Densitmetric measurements of autoradiographs was performed by using computer-scanned densitometry. Experiments are means of triplicates, and each experiment was performed three times. Data are expressed as mean ± SEM. Statistical analysis were performed with by using an unpaired nonparametric Mann-Whitney test. Differences were considered statistically significant when p < 0.05.

Results

POMx and IGFBP-3 inhibit proliferation of LAPC4 prostate cancer cells and demonstrate additive effects

Recent reports demonstrate that pomegranate juice and its extracts have potent anti-tumorigenic effects. Since IGFBP-3 functions as a negative regulator of cell proliferation in cultured prostate cancer cells, we investigated the effects of co-incubation with POMx and IGFBP-3 on cell proliferation. LAPC4 human prostate cancer cells were treated with 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 72 h in SF media. POMx and IGFBP-3 independently inhibited cell proliferation by 20% and 30% (Fig. 1), respectively. However, co-treatment with both IGFBP-3 and POMx had an additive effect of growth inhibition, suggesting that co-treatment may have the potential for more potent inhibition of cancer growth.

Figure 1. IGFBP-3 and POMx additively inhibit the growth of LAPC4 cells.

Figure 1

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LAPC4 prostate cancer cells were incubated in the presence and absence of 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 72 h in SF media. Cell proliferation was assessed by enzymatic reduction of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), to a formazan product. n=3; significance that mean is difference from untreated control: *P<0.05, **P<0.01, ***P<0.001.

Synergistic apoptosis induction by IGFBP-3 and POMx

Pomegranate extracts and IGFBP-3 have been reported to enhance apoptosis in many cell lines (9, 19, 22, 23, 24, 25,30, 31,32). Since co-treatment with IGFBP-3 and POMx additively inhibited the growth of prostate cancer cells, we evaluated the effects of co-treatment on apoptosis induction in LAPC4 cells. As previously demonstrated, treatment with 1 μg/ml IGFBP-3 for 24 h in SF media results in enhanced apoptosis induction by 25% in LAPC4 cells (33) (Fig 2). Similarly, incubation of LAPC4 cells with 10 μg/ml POMx resulted in a 60% increase in apoptosis, as assessed by ELISA for cytoplasmic histone-associated DNA-fragments. Importantly, co-treatment of POMx and IGFBP-3 revealed synergistic induction of apoptosis (Fig. 2), an effect which was more pronounced than that seen for cell growth inhibition in Figure 1.

Figure 2. Synergistic apoptosis induction by IGFBP-3 and POMx.

Figure 2

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LAPC4 cells were incubated in the presence and absence of 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 24 h in SF media. Apoptosis was assessed by ELISA for cytoplasmic histone-associated–DNA fragments. n=3; significance that mean is different from 1 (untreated control): *P<0.05, **P<0.01

POMx increases JNK phosphorylation in a dose-dependent manner in LAPC4 cells

It has been reported that pomegranate extracts reduce phosphorylation of a variety of different MAP kinases, including ERK1/2, JNK and p38, in human lung carcinoma A549 cells (34). We investigated the influence of POMx and IGFBP-3 treatment on the key signaling pathways known to be important in cell proliferation and apoptosis in prostate cancer cells. LAPC4 cells were incubated with increasing concentrations of POMx in SF media for 24 h. Levels of total and phospho-JNK were determined by immunoblotting. POMx increased JNK phosphorylation in a dose-dependent manner (Fig. 3A). LAPC4 cells were also treated with 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 24 h in SF media. IGFBP-3 and POMx independently increase JNK phosphorylation. However, co-treatment resulted in no additional activation of JNK (Fig. 3B). This suggests that POMx and IGFBP-3 may activate JNK by the same mechanism, or that maximal phosphorylation is achieved after IGFBP-3-treatment.

Figure 3. Dose-dependent increase in JNK phosphorylation by POMx.

Figure 3

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A, LAPC4 cells were incubated with increasing concentrations of POMx in SF media for 24 h. Levels of total and phospho-JNK were determined by immunoblotting, n=3. B, LAPC4 cells were treated in the presence or absence of 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 24 h in SF media. Levels of total and phospho-JNK were determined by immunoblotting, n=3 (upper panel).

Inhibition of Akt and mTOR phosphorylation by POMx and POMx/IGFBP-3 combination in LAPC4 cells

Recently, Khan et al demonstrated reduced phosphorylation of Akt (Thr308) in A549 human lung carcinoma cells treated with pomegranate (33). To further elucidate the mechanism of POMx and IGFBP-3/POMx-induced apoptosis in LAPC4 cells, we assessed total and phospho-Akt and mTOR levels by immunoblotting. LAPC4 cells were incubated with 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 24 h in SF media. Akt phosphorylation at position Thr308 and Ser473 is decreased by POMx. (Fig. 4A). Interestingly, co-treatment with IGFBP-3 and POMx led to a synergistic decrease in Ser-473 phosphorylation, suggesting that this may be one of the mechanisms by which the synergistic induction of apoptosis occurs. mTOR is a downstream target of PI3 kinase/Akt signaling, and its regulation is frequently altered in tumorigenesis. PI3 kinase/Akt activity is also required for an autophosphorylation event at Ser-2481 of mTOR. POMx treatment reduced mTOR phosphorylation at Ser2448, and slightly reduced at Ser2481. In contrast, IGFBP-3 slightly increased phosphorylation at both sites. Co-treatment with POMx and IGFBP-3 nullified the individual actions each, giving no overall change in mTOR phosphorylation at either serine residue. These data suggest that IGFBP-3 and POMx have differing effects on the PI3 kinase/Akt/mTOR signaling pathway, confirming the likelihood of distinct mechanisms of action for apoptosis induction.

Figure 4. Modulation of PI3 kinase/Akt/mTOR signaling by POMx.

Figure 4

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LAPC4 cells were treated in the presence or absence of 10 μg/ml POMx and/or 1 μg/ml IGFBP-3 for 24 h in SF media. A, Total and phospho-Akt (Thr308 and Ser473) were assessed by immunoblotting, n=3. B, Total and phospho-mTOR (Ser2448 and Ser2481) were assessed by immunoblotting, n=3.

IGF-I and POMx have opposing effects on apoptosis induction in prostate cancer cells

While IGFBP-3 is known to play an important inhibitory role in the regulation of many types of cancer, IGF-I is recognized to be a potent mitogen and survival factor. We therefore investigated the relationship between IGF-1 and pomegranate-induced apoptosis in prostate cancer cells. Apoptosis was assessed by ELISA for histone-DNA-fragments in 22RV1 cells incubated with 10 μg/ml POMx and/or 100 ng/ml IGF-I for 24 h in SF media. Treatment with POMx increases apoptosis by 20% in 22RV1 cells and 3 fold induction in R- cells (Fig 5). IGF-I reduced the apoptosis induced by serum withdrawal, however when added in combination with POMx, IGF-I completely antagonized the apoptosis induced by POMx in 22RV1 cells (Fig. 5A). In contrast, IGF-I failed to inhibit POMx-induced apoptosis in R- (IGF-IR null MEFs) cells (Fig. 5B), suggesting the importance of the IGF-IR in antagonizing the effects of POMx.

Figure 5. IGF-I antagonizes POMx-induced apoptosis.

Figure 5

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A, 22RV1 human prostate cancer cells were incubated in the presence or absence of 10 μg/ml POMx and/or 100 ng/ml IGF-I for 24 h in SF media. Apoptosis was assessed by ELISA for histone-associated DNA fragments. n=3; significance that mean is different from 1 (untreated control): *P<0.05, **P<0.01. B, Apoptosis was assessed by ELISA for histone-associated –DNA-fragments in R- cells (IGF-IR null MEFs) incubated in the presence and absence of 10 μg/ml POMx and/or 100 ng/ml IGF-I for 24 h in SF media. n=3; significance that mean is different from 1 (untreated control): *P<0.05, **P<0.01.

IGF-I and POMx increase JNK phosphorylation in 22RV1 cells

Since POMx-treatment leads to a dose-dependent increase in JNK phosphorylation, we decided to investigate whether co-incubation with IGF-I could modulate this effect. 22RV1 cells were treated with 10 μg/ml POMx and/or 100 ng/ml IGF-I for 24 h in SF media, and total and phospho-JNK were assessed by immunoblotting. As demonstrated previously for LAPC4 cells (Fig 3A), treatment with POMx increases JNK phosphorylation in a dose dependent manner in 22RV1 cells (Fig 6A). Interestingly, IGF-I treatment alone also caused a 1.5-fold increase in JNK phosphorylation (Fig 6B). Co-treatment of 22RV1 cells with IGF-I and POMx synergistically enhance JNK phosphorylation (Fig 6B), suggesting that the antagonistic actions of IGF-I on POMx-induced apoptosis are exerted via alternative pathways.

Figure 6. Synergistic activation of JNK phosphorylation by IGF-I and POMx.

Figure 6

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A, 22RV1 cells were incubated with increasing concentrations POMx in SF media for 24 h. Levels of total and phospho-JNK were determined by immunoblotting, Blots are representative of 3 independent experiments. B, 22RV1 cells were treated in the presence and absence of 10 μg/ml POMx and/or 100 ng/ml IGF-I for 24 h in SF media. Levels of total and phospho-JNK were determined by immunoblotting (upper panel). Blots are representative of 3 independent experiments.

POMx decreases Igf1 mRNA expression in a dose-dependent manner

To elucidate additional mechanisms by which POMx modulate IGF-axis regulation of death and survival in prostate cancer cells, we investigated the effects of POMx treatment on Igf1 mRNA expression by RT-PCR in 22RV1 cells. POMx-treatment caused a dose-dependent reduction in Igf1 mRNA levels (Fig 7A). Treatment with either IGF-I or IGFBP-3 alone had no effect on Igf1 levels (Fig 7B) and neither was unable to antagonize the inhibitory effect of POMx alone. This suggests that inhibition of Igf1 expression may be one of the mechanisms by which POMx causes reduced cell survival in prostate cancer.

Figure 7. POMx decreases Igf1 mRNA expression in a dose-dependent manner.

Figure 7

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A, 22RV1 cells were incubated with increasing concentrations POMx in SF media for 24 h. Total RNA was prepared using TRIzol Reagent. Levels of Igf1 and β-actin mRNA were determined by RT-PCR. B, 22RV1 cells were incubated with and without 1 μg/ml IGFBP-3, 100 ng/ml IGF-I and/or 10 μg/ml POMx for 24 h in SF media. Total RNA was prepared using TRIzol Reagent. Levels of Igf1 and β-actin mRNA were determined by RT-PCR.

Discussion

Multiple lines of evidence, including both in vitro and clinical studies, have demonstrated the centrality of the IGF system in cancers such as prostatic carcinoma, and point to IGFBP-3 as an anti-cancer molecule (35). Furthermore, different pomegranate extracts have been shown to inhibit cell growth in a variety of human cancer cell lines. In 2005, Malik et al. demonstrated that pomegranate fruit extract (PFE) inhibits cell growth in PC3 cell lines in a dose dependent manner. Recently, Kahn et al. also reported that PFE inhibits cell growth in A549 human lung carcinoma cells (33). We have previously shown that punicalagin, ellagic acid (EA), total pomegranate tannin (TPT) and pomegranate juice (PJ) inhibit cell growth in RWPE-1 and 22RV1 prostate cancer cells, KB and CAL27 human oral cancer cells and HT-29, HCT116, SW480 and SW620 human colon cancer cells (19). In addition, oral consumption of PFE inhibits the growth and progression of lung carcinoma in mice after chemically-induced tumor initiation (36). In prostate cancer clinical studies, treatment with pomegranate juice was associated with significant prolongation of patients' PSA doubling time, and a decrease in cell proliferation and increase in apoptosis in prostate cancer cell lines grown in the presence of treated patients' serum (X). Here, we report that POMx and IGFBP-3 can additively reduce the proliferation of LAPC4 human prostate cancer cells. In addition to inhibiting cancer cell proliferation, we also previously reported that punicalagin, EA, TPT and PJ can induce apoptosis in HT-29 and HCT116 human colon cancer cells (19). Interestingly, although POMx and IGFBP-3 individually function as apoptotic factors, co-treatment leads to a synergistic induction of apoptosis in LAPC4 human prostate cancer cells. In addition to highlighting the potential of pomegranate and its extracts as possible therapeutics, these data also suggest that combination therapy of POMx with other therapeutics may have beneficial effects in the treatment of tumors. To analyze the synergistic mechanism of apoptosis induction by POMx and IGFBP-3, we investigated the signaling pathways known to be important in cell proliferation and apoptosis. Afaq et al. reported that PFE treatment in normal human epidermal keratinocytes (NHEK) prior to be UVB irradiation significantly inhibited UVB-mediated phosphorylation of ERK1/2, JNK1/2 and p38 in a time-dependent manner (37). Khan et al. also reported reduced MAPK and PI3-kinase/Akt signaling after PFE treatment in A549 human lung carcinoma cells (32). Here, we demonstrate reduced Akt/mTOR phosphorylation after POMx treatment in LAPC4 human prostate cancer cell lines, but increased phosphorylation of JNK in both LAPC4 and 22RV1 human prostate cancer cell lines. This suggests that POMx has cell specific effects on JNK phosphorylation in different tumor models. We have previously demonstrated enhanced JNK phosphorylation in prostate cancer cells after treatment with IGFBP-3 (38). Interestingly, however, co-incubation with POMx led to no further increase in JNK activation, suggesting that POMx and IGFBP-3 may activate JNK by the same mechanism, or that maximal phosphorylation is achieved after IGFBP-3-treatment. Surprisingly, IGF-I and POMx activated JNK synergistically. Since the two factors have opposing effects on cell proliferation and apoptosis, and as JNK phosphorylation can lead to both pro- and anti-apoptotic events, this would suggest that the activation of JNK by the different factors leads to the activation of distinct targets.

Intriguingly, POMx induced a 3-fold increase in apoptosis in R- cells, compared with only a 20% induction in 22RV1 prostate cancer cells. This suggests that endogenous, in addition to exogenously added, IGF-I plays a key role in blocking POMx-induced apoptosis. Since POMx treatment leads to a dose-dependent down-regulation of Igf1 mRNA, this would suggest that some of the effects of POMx may involve suppression of endogenous tumor production of IGF-I. It is well established that manipulations of the IGF axis to promote apoptotic events in cancer may have beneficial therapeutic effects (39). However, since POMx also induced apoptosis in MEF cells lacking the IGF-IR, it is unlikely that manipulation of Igf1 levels is the only mechanism by which POMx induces apoptosis. Rather, it appears that pomegranate extracts act via multiple mechanisms, including enhancement of IGFBP-3 pro-apoptotic activity and through inhibition of the NFkB pathway (40). It is possible that the IGFBP3-related activities of POMx are both IGF-dependent and –independent.

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.

Acknowledgments

Supported in part by grants: 1R01CA100938, R01HD047013, P50CA92131, DOD idea development award (to PC) and a DOD fellowship award (to LJC)

Footnotes

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