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Biochanin-A, a major dietary isoflavone in soy and red clover, possesses anticancer and chemopreventive properties. Induction of apoptosis by naturally occurring dietary agents is an important event for cancer chemoprevention. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis selectively in cancer cells but not in normal cells. Soluble or expressed in immune cells, molecules TRAIL plays a significant role in surveillance and defense mechanisms against tumours. Prostate cancer is an ideal disease for nutritional prevention. The TRAIL-mediated apoptosis pathway in prostate cancer cells is an attractive target for chemopreventive activities of dietary agents. LNCaP and DU145 prostate cancer cells are resistant to TRAIL-induced apoptosis. We showed that biochanin-A markedly augmented TRAIL-induced cytotoxicity and apoptosis in both prostate cancer cell lines. Then, we investigated the mechanisms by which biochanin-A enhanced TRAIL-mediated apoptosis using the LNCaP cell line. The isoflavone sensitized the TRAIL-resistant LNCaP cells through the inhibition of transcription factor NF-κB(p65) activity, increased the expression of the death receptor TRAIL-R2 (DR5), and disrupted mitochondrial membrane potential (ΔΨm). Our study confirmed that biochanin-A overcame TRAIL-resistance by engaging both intrinsic and extrinsic apoptotic pathways and by regulating the NF-κB activity. The results suggested a potential role of biochanin-A in prostate cancer chemoprevention through the enhancement of TRAIL-mediated apoptosis., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Naturally occurring phenolic compounds have been shown to sensitize prostate cancer cells to tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. TRAIL is a potent stimulator of apoptosis in cancer cells and an important immune effector molecule in the surveillance and elimination of developing tumours. However, many cancer cells are resistant to TRAIL-mediated death. In this study, we aimed to determine the mechanisms by which TRAIL resistance can be overcome in prostate cancer cells by 3,5-diprenyl-4-hydroxycinnamic acid (artepillin C). Artepillin C is a bioactive component of Brazilian green propolis that possesses antitumour and chemopreventive activities. TRAIL-resistant LNCaP prostate cancer cells were treated with TRAIL and artepillin C. Cytotoxicity was measured by MTT and lactate dehydrogenase (LDH) assays. Apoptosis was detected using Annexin V-FITC staining by flow cytometry and fluorescence microscopy. Death receptor (DR) (TRAIL-R1/DR4 and TRAIL-R2/DR5) expression was analyzed using flow cytometry. Mitochondrial membrane potential (∆ψm) was evaluated using DePsipher staining by fluorescence micro-scopy. The inhibition of NF-κB (p65) activation was confirmed with the ELISA-based TransAM NF-κB kit. Caspase-8 and caspase-3 activities were determined by colorimetric protease assays. The results showed that artepillin C sensitized the TRAIL-resistant LNCaP cells by engaging the extrinsic (receptor-mediated) and intrinsic (mitochondrial) apoptotic pathways. Artepillin C increased the expression of TRAIL-R2 and decreased the activity of NF-κB. Co-treatment with TRAIL and artepillin C induced the significant activation of caspase-8 and caspase-3, as well as the disruption of ∆ψm. These findings show that prostate cancer cells can be sensitized to TRAIL-mediated immunoprevention by artepillin C and confirm the role of phenolic compounds in prostate cancer immunochemoprevention.

Background: Photodynamic therapy (PDT) is an attractive, emerging therapeutic procedure suitable for the treatment of non-muscle-invasive bladder cancer. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a death ligand that belongs to the TNF superfamily of cytokines. The ability of TRAIL to selectively induce apoptosis in cancer cells but not in normal cells promotes the development of TRAIL-based cancer therapy. However, many tumor cells are resistant to TRAIL-induced apoptosis. The purpose of the study was to overcome TRAIL-resistance in bladder cancer cells by photodynamic therapy (PDT)., Material/methods: Three human bladder transitional cancer cell lines - T24, 647V and SW780 - were treated with TRAIL and/or chlorin-based PDT. The cytotoxicity was measured by MTT and LDH assays and apoptosis was detected using annexin V by flow cytometry., Results: Our test confirmed that T24 and 647V bladder cancer cells are resistant to TRAIL, whereas SW780 cells are sensitive to TRAIL. Then we examined the cytotoxic and apoptotic effects of TRAIL in combination with chlorin e6-polyvinylpyrrolidone (Ce6-PVP)-mediated PDT on bladder cancer cells. We showed for the first time that pretreatment with a low dose of PDT significantly sensitizes bladder cancer cells to TRAIL-induced apoptosis. Chlorin-based PDT augments the effect of TRAIL on bladder cancer cells., Conclusions: PDT with Ce6-PVP photosensitizer enhances the cytotoxic and apoptotic effects of TRAIL on bladder cancer cells. The obtained results suggest that combined treatment by TRAIL and PDT may provide the basis for a new therapeutic approach to induce cell death in bladder cancer.

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is an endogenous agent that induces apoptosis selectively in cancer cells. Soluble or expressed in immune cells, TRAIL plays an important role in the defense against tumour cells. The resistance of cancer cells to TRAIL immune surveillance is implicated in tumour development. Naturally occurring flavonoids can sensitize TRAIL-resistant cancer cells and augment their apoptotic activity. Fisetin, a dietary flavonol has cancer preventive properties. This study was designed to investigate the effect of fisetin on the TRAIL-induced apoptosis potential in prostate cancer cells. Prostate cancer cell lines represent an ideal model for research in chemoprevention. Cytotoxicity was measured by MTT and LDH assays. Apoptosis was detected using Αnnexin V-FITC by flow cytometry and fluorescence microscopy. Mito-chondrial membrane potential (ΔΨm) was evaluated using DePsipher staining by fluorescence microscopy. Death receptor (TRAIL-R1 and TRAIL-R2) expression was analysed by flow cytometry. Inhibition of NF-κB (p65) activation was confirmed with an ELISA-based TransAM NF-κB kit. Caspase-8 and caspase-3 activities were determined by colorimetric protease assays. Our study demonstrates that fisetin sensitizes the TRAIL-resistant androgen-dependent LNCaP and the androgen-independent DU145 and PC3 prostate cancer cells to TRAIL-induced death. Fisetin augmented TRAIL-mediated cytotoxicity and apoptosis in prostate cancer LNCaP cells by engaging the extrinsic (receptor-mediated) and intrinsic (mitochondrial) apoptotic pathways. Fisetin increased the expression of TRAIL-R1 and decreased the activity of NF-κB. Co-treatment of cancer cells with TRAIL and fisetin caused significant activation of caspase-8 and caspase-3 and disruption of ΔΨm. Our data indicate the usefulness of fisetin in prostate cancer chemoprevention through enhancement of TRAIL-mediated apoptosis.

Prostate cancer represents an ideal disease for chemopreventive intervention. Genistein, daidzein and equol, the predominant soy isoflavones, have been reported to lower the risk of prostate cancer. Isoflavones exert their chemopreventive properties by affecting apoptosis signalling pathways in cancer cells. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is an endogenous anticancer agent that induces apoptosis selectively in tumour cells. Soluble or expressed in immune cells, TRAIL molecules play an important role in immune surveillance and defense mechanisms against tumour cells. However, various types of cancer cells are resistant to TRAIL-mediated apoptosis. We examined the cytotoxic and apoptotic effects of genistein, daidzein and equol in combination with TRAIL in LNCaP cells. Cytotoxicity was measured by MTT and LDH assays. Apoptosis was analyzed by flow cytometry and fluorescence microscopy using Annexin V-FITC. Mitochondrial membrane potential (ΔΨm) was evaluated by fluorescence microscopy using DePsipher staining. Flow cytometry detected the expression of death receptor TRAIL-R1 (DR4) and TRAIL-R2 (DR5) on cell surfaces. The soy isoflavones sensitized TRAIL-resistant prostate cancer cells to apoptotic death. The isoflavones did not alter death receptor expression, but significantly augmented TRAIL-induced disruption of ΔΨm in the LNCaP cells. We showed for the first time that the chemopreventive effects of soy foods on prostate cancer are associated with isoflavone-induced support of TRAIL-mediated apoptotic death.

Prostate cancer represents an ideal disease for chemopreventive intervention. Propolis possesses immuno-modulatory, anti-tumour and chemopreventive properties. The tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is an important endogenous anti-cancer agent that induces apoptosis selectively in tumour cells. However, some cancer cells are resistant to TRAIL-mediated apoptosis. Naturally occurring phenolic and polyphenolic compounds sensitize TRAIL-resistant cancer cells and augment the apoptotic activity of TRAIL. The ethanolic extract of Brazilian green propolis (EEP) is rich in phenolic components. Our in vitro results indicate the potential targets in the TRAIL-induced apoptotic pathway for the cancer chemopreventive activity of Brazilian propolis. We examined the cytotoxic and apoptotic effects of Brazilian EEP and its bioactive components in combination with TRAIL on LNCaP prostate cancer cells. The chemical composition of Brazilian green propolis was determined by high performance liquid chromatography-diode array detection. The cytotoxicity was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl-tetrazolium and lactate dehydrogenase assays. Apoptosis was detected using annexin V-FITC by flow cytometry and fluorescence microscopy. The mitochondrial membrane potential (∆Ψm) was evaluated using DePsipher staining by fluorescence microscopy. Flow cytometry was used to analyse death receptor (TRAIL-R1 and TRAIL-R2) expression in LNCaP cells. The inhibition of nuclear factor-κB (NF-κB) (p65) activation in cancer cells was confirmed by the ELISA-based TransAM NF-κB kit. The LNCaP cells were shown to be resistant to TRAIL-induced apoptosis. Our study demonstrates that EEP sensitizes TRAIL-resistant prostate cancer cells. The main phenolic components detected in Brazilian green propolis are artepillin C, quercetin, kaempferol and p-coumaric acid. Brazilian propolis and its bioactive components markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells. Brazilian EEP enhanced the expression of TRAIL-R2 and the activity of NF-κB in LNCaP cells. The co-treatment of prostate cancer cells with 100 ng/ml TRAIL and 50 µg/ml EEP increased the percentage of apoptotic cells to 65.8 ± 1.2% and caused a significant disruption of ∆Ψm in LNCaP cells. We show that Brazilian EEP helped cells overcome TRAIL resistance by engaging both intrinsic and extrinsic apoptotic pathways and regulating NF-κB activity. The data demonstrate the important role of Brazilian green propolis and its bioactive compounds in prostate cancer chemoprevention through the enhancement of TRAIL-mediated apoptosis.

Polyphenols, occurring in vegetables, fruits, herbs, spices, propolis, tea, beer, and wine play an important role in cancer chemoprevention. Dietary polyphenols exert their chemopreventive effect by multiple molecular mechanisms of action on apoptosis signaling pathways in cancer cells. In this review, we describe dietary polyphenols targeting the tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptotic pathway. TRAIL is a natural potent anticancer agent that preferentially induces apoptosis in cancer cells and is not toxic to normal cells. Soluble or expressed on immune cells, molecules of TRAIL take part in immune surveillance and defense mechanisms against tumor cells. However, some cancer cells are resistant to TRAIL-mediated cytotoxicity. The decreased expression of death receptors (TRAIL-R1, TRAIL-R2) and proapoptotic proteins or increased expression of antiapoptotic proteins in cancer cells is involved in TRAIL resistance. There is a growing body of experimental evidence showing that polyphenols sensitize TRAIL-resistant cancer cells and markedly augment TRAIL-induced programmed death in cancer cells. These in-vitro and in-vivo studies indicate the significance of dietary polyphenols in cancer chemoprevention strategies through enhancing the apoptosis-inducing potential of TRAIL.

Chalcones and dihydrochalcones exhibit chemopreventive and antitumor activity. TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is a natural endogenous anticancer agent. We examined the cytotoxic and apoptotic effect of chalcones and dihydrochalcones on TRAIL-mediated apoptosis in LNCaP prostate cancer cells. The cytotoxicity was evaluated by the MTT and LDH assays. The apoptosis was detected using annexin V-FITC by flow cytometry and fluorescence microscopy. The DeltaPsim was evaluated using DePsipher staining by fluorescence microscopy. Our study showed that two tested chalcones (chalcone and 2',6'dihydroxy-4'-methoxychalcone) and three dihydrochalcones (2',6'-dihydroxy-4'4-dimethoxydihydrochalcone, 2',6'-dihydroxy-4'-methoxydihydro- chalcone, and 2',4',6'-trihydroxydihydrochalcone, called phloretin) markedly augmented TRAIL-induced apoptosis and cytotoxicity in LNCaP cells and confirmed the significant role of chalcones in chemoprevention of prostate cancer.

Isoflavones are a class of bioactive polyphenols with cancer chemopreventive properties. TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is a naturally occurring antitumor agent that selectively induces programmed death (apoptosis) in cancer cells. Polyphenols can modulate TRAIL-mediated apoptosis in cancer cells. We examined the cytotoxic and apoptotic activities of isoflavones in combination with TRAIL on HeLa cancer cells. The apoptosis was detected by fluorescence microscopy with annexin V-FITC. The cytotoxicity was evaluated by MTT and LDH assays. The tested isoflavones: genistein, biochanin-A and neobavaisoflavone enhance TRAIL-induced apoptosis in HeLa cells. Our study indicated that isoflavones augmented TRAIL-cytotoxicity against cancer cells and confirmed potential role of those polyphenols in chemoprevention.

Chalcones exhibit chemopreventive and antitumor effects. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a naturally occurring anticancer agent that induces apoptosis in cancer cells and is not toxic to normal cells. We examined the cytotoxic and apoptotic effect of five chalcones in combination with TRAIL on prostate cancer cells. The cytotoxicity was evaluated by the MTT and LDH assays. The apoptosis was determined using flow cytometry with annexin V-FITC. Our study showed that all five tested chalcones: chalcone, licochalcone-A, isobavachalcone, xanthohumol, butein markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells and confirmed the significant role of chalcones in chemoprevention of prostate cancer.

Ethanolic extract of propolis (EEP) is one of the richest sources of phenolic acids and flavonoids. EEP and its phenolic compounds have been known for various biological activities including immunopotentiation, chemopreventive and antitumor effects. Tumor necrosis factor related apoptosis inducing ligand (TRAIL) is a naturally occurring anticancer agent that preferentially induces apoptosis in cancer cells and is not toxic toward normal cells. We examined the cytotoxic and apoptotic effect of EEP and phenolic compounds identified in propolis in combination with TRAIL on HeLa cancer cells. HeLa cells were resistant to TRAIL-induced apoptosis. Our study demonstrated that EEP and its components significantly sensitize to TRAIL induced death in cancer cells. The percentage of the apoptotic cell after exposure to 50 microg/mL EEP and 100 ng/mL TRAIL increased to 71.10 +/- 1.16%. The strongest cytotoxic effect in combination with TRAIL on HeLa cells exhibited apigenin and CAPE at the concentration of 50 microM (58.87 +/- 0.75% and 49.59 +/- 0.39%, respectively). In this report, we show for the first time that EEP markedly augmented TRAIL mediated apoptosis in cancer cells and confirmed the importance of propolis in chemoprevention of malignant tumors.