Phenoxodiol

Cancer Cell Int . 2014 Nov 8;14(1):110.

The effects of phenoxodiol on the cell cycle of prostate cancer cell lines[Pubmed: 25400509]

Background: Prostate cancer is associated with a poor survival rate. The ability of cancer cells to evade apoptosis and exhibit limitless replication potential allows for progression of cancer from a benign to a metastatic phenotype. The aim of this study was to investigate in vitro the effect of the isoflavone Phenoxodiol on the expression of cell cycle genes. Methods: Three prostate cancer cell lines-LNCaP, DU145, and PC3 were cultured in vitro, and then treated with Phenoxodiol (10 μM and 30 μM) for 24 and 48 h. The expression of cell cycle genes p21(WAF1), c-Myc, Cyclin-D1, and Ki-67 was investigated by Real Time PCR. Results: Here we report that Phenoxodiol induces cell cycle arrest in the G1/S phase of the cell cycle, with the resultant arrest due to the upregulation of p21(WAF1) in all the cell lines in response to treatment, indicating that activation of p21(WAF1) and subsequent cell arrest was occurring via a p53 independent manner, with induction of cytotoxicity independent of caspase activation. We found that c-Myc and Cyclin-D1 expression was not consistently altered across all cell lines but Ki-67 signalling expression was decreased in line with the cell cycle arrest. Conclusions: Phenoxodiol demonstrates an ability in prostate cancer cells to induce significant cytotoxicity in cells by interacting with p21(WAF1) and inducing cell cycle arrest irrespective of p53 status or caspase pathway interactions. These data indicate that Phenoxodiol would be effective as a potential future treatment modality for both hormone sensitive and hormone refractory prostate cancer.

Anticancer Res . Sep-Oct 2002;22(5):2581-2585.

Phenoxodiol (2H-1-benzopyran-7-0,1,3-(4-hydroxyphenyl)), a novel isoflavone derivative, inhibits DNA topoisomerase II by stabilizing the cleavable complex[Pubmed: 12529967]

Cancer therapeutic drugs that inhibit DNA topoisomerase (topo) II by stabilizing the cleavable complex are collectively known as topo II poisons. Phenoxodiol is a synthetic derivative of the plant isoflavone daidzein and is currently undergoing clinical testing as a cancer therapeutic drug. The development of this agent as an antitumor drug was based to a large extent on its low toxicity in normal tissues but potent topo II inhibitory effects in rapidly dividing tumor cells. To evaluate Phenoxodiol as a potential inhibitor of topoisomerases, we used the relaxation and nicking assays that can identify topo I inhibitors, and the unknotting and DNA cleavage assays that can identify topo II inhibitors. Phenoxodiol inhibited the catalytic activity of topo II in a dose-dependent manner and it stabilized the topo II-mediated cleavable complex, demonstrating that this agent is a topo II poison. Phenoxodiol's topo II inhibitory effects were comparable to those of other antitumor agents such as VP-16 and were stronger than those of genistein. Phenoxodiol did not inhibit topo I catalytic activity nor did it stabilize the topo I-mediated cleavable complex. These results demonstrate that Phenoxodiol is a topo II-specific poison and suggest that this novel agent may find applications in cancer chemotherapy.

J Cell Mol Med. 2009 Sep;13(9B):3929-3938.

Phenoxodiol, an anticancer isoflavene, induces immunomodulatory effects in vitro and in vivo[Pubmed: 19220577]

Phenoxodiol (PXD) is a synthetic analogue of the plant isoflavone genistein with improved anticancer efficacy. Various properties and mechanisms of action have been attributed to the drug, the most important being its ability to sensitize resistant tumour cells to chemotherapy, which led to its fast track FDA approval for phase II/III clinical trials. In this study, we examined the effects of PXD on human peripheral blood mononuclear cells (PBMC) and its potential role in regulating immune responses. We show that PXD, at concentrations >or=1 microg/ml (4 microM), inhibited proliferation and reduced the viability of healthy donor-derived PBMC. In contrast, lower PXD concentrations (0.05-0.5 microg/ml) augmented, upon 3-day incubation, PBMC cytotoxicity. Experiments with purified CD56(+) lymphocytes revealed that PXD enhanced the lytic function of natural killer (NK) cells by directly stimulating this lymphocytic subpopulation. Furthermore, in an in vivo colon cancer model, Balb/C mice administered low-dose PXD, exhibited significantly reduced tumour growth rates and prolonged survival (in 40% of the animals). Ex vivo results showed that PXD stimulated both NK and tumour-specific cell lytic activity. We conclude that PXD, when administered at low concentrations, can act as an immunomodulator, enhancing impaired immune responses, often seen in cancer-bearing individuals.

Biochim Biophys Acta . 2011 Aug;1810(8):784-789.

Metabolite modulation of HeLa cell response to ENOX2 inhibitors EGCG and phenoxodiol[Pubmed: 21571040]

Background: Constituents and inhibitors of intermediary metabolism resulting in alterations in levels of cytosolic NADH, stimulation of sphingomyelinase and inhibition of sphingosine kinase were evaluated for effects on growth inhibition and induction of apoptosis by the ENOX2 inhibitors EGCG, the principal catechin of green tea, and Phenoxodiol, a naturally occurring isoflavone. Methods: Responses were evaluated from dose-response curves of the metabolites and metabolic inhibitors in which growth of HeLa cells, apoptosis based on DAPI fluorescence and cytosolic NADH levels were correlated with sphingomyelinase and spingosine kinase activities and levels of ceramide and sphingosine1-phosphate. Results: Growth inhibition correlated with the modulation of localized cytosolic NADH levels by metabolites and metabolic inhibitors, the response of sphingomyelinase and sphingosine kinase located near the inner surface of the plasma membrane, and apoptosis. Conclusions: Based on findings with metabolites, we conclude that apoptosis in cancer cell lines caused by ENOX2 inhibitors such as EGCG and Phenoxodiol is a direct response to elevated levels of cytosolic NADH that result from ENOX2 inhibition. General significance: The findings help to explain why increased NADH levels resulting from ENOX2 inhibition result in decreased prosurvival sphingosine-1-phosphate and increased proapoptotic ceramide, both of which may be important to initiation of the ENOX2 inhibitor-induced apoptotic cascade

Biofactors . 2008;34(3):253-260.

Downstream targets of altered sphingolipid metabolism in response to inhibition of ENOX2 by phenoxodiol[Pubmed: 19734127]

Phenoxodiol, an ENOX2 inhibitor, alters cytosolic NADH levels to initiate a regulatory cascade linking sphingolipid metabolism and the PI3K/Akt pathway to programmed cell death. Specifically, the pyridine nucleotide products of plasma membrane redox, NAD+ and NADH, directly modulate in a recriprocal manner two key plasma membrane enzymes. NADH stimulation of sphingomyelinase and NADH inhibition of sphingosine kinase potentially lead to G1 arrest (increase in ceramide) and apoptosis (loss of sphingosine-1-phosphate). The findings link plasma membrane electron transport and the anticancer action of several clinically-relevant anticancer agents targeted to ENOX2 such as Phenoxodiol. Growth inhibition by Phenoxodiol is unaffected by inhibitors of protein or mRNA synthesis. Findings with okadiaic acid, an inhibitor of serine/threonine phosphatases, suggest that hyperphosphorylation of intracellular substrates does not affect the action of Phenoxodiol on ENOX2. Our findings and those of others are consistent with operation of the FAS signaling pathway of apoptosis and its suppression by sphingosine-1-phosphate. The prevailing hypothesis is that products of Akt activation, c-FLIP and XIAP, which exhibit anticaspase activities to block FAS signaling when sphingosine-1-phospate is elevated, are down regulated to permit apoptosis when sphingosine-1-phosphate is decreased by inhibition of sphingosine kinase under conditions of elevated cytosolic NADH associated with anticancer drug inhibition of ENOX2.

J Cell Mol Med. 2009 Sep;13(9B):3929-3938.

Phenoxodiol, an anticancer isoflavene, induces immunomodulatory effects in vitro and in vivo[Pubmed: 19220577]

Phenoxodiol (PXD) is a synthetic analogue of the plant isoflavone genistein with improved anticancer efficacy. Various properties and mechanisms of action have been attributed to the drug, the most important being its ability to sensitize resistant tumour cells to chemotherapy, which led to its fast track FDA approval for phase II/III clinical trials. In this study, we examined the effects of PXD on human peripheral blood mononuclear cells (PBMC) and its potential role in regulating immune responses. We show that PXD, at concentrations >or=1 microg/ml (4 microM), inhibited proliferation and reduced the viability of healthy donor-derived PBMC. In contrast, lower PXD concentrations (0.05-0.5 microg/ml) augmented, upon 3-day incubation, PBMC cytotoxicity. Experiments with purified CD56(+) lymphocytes revealed that PXD enhanced the lytic function of natural killer (NK) cells by directly stimulating this lymphocytic subpopulation. Furthermore, in an in vivo colon cancer model, Balb/C mice administered low-dose PXD, exhibited significantly reduced tumour growth rates and prolonged survival (in 40% of the animals). Ex vivo results showed that PXD stimulated both NK and tumour-specific cell lytic activity. We conclude that PXD, when administered at low concentrations, can act as an immunomodulator, enhancing impaired immune responses, often seen in cancer-bearing individuals.

Oncogene . 2003 May 1;22(17):2611-2620.

Phenoxodiol--an isoflavone analog--induces apoptosis in chemoresistant ovarian cancer cells[Pubmed: 12730675]

Interference with the innate apoptotic activity is a hallmark of neoplastic transformation and tumor formation. In this study we characterize the cytotoxic effect of Phenoxodiol, a synthetic anticancer drug analog of genestein, and demonstrate the mechanism of action by which Phenoxodiol affects the components of the Fas apoptotic pathway on ovarian cancer cells. Primary ovarian cancer cells, isolated from ascitic fluids of ovarian cancer patients, resistant to conventional chemotherapy, undergo apoptosis following Phenoxodiol treatment. This effect is dependent upon the activation of the caspase system, inhibiting XIAP, an inhibitor of apoptosis, and disrupting FLICE inhibitory protein (FLIP) expression through the Akt signal transduction pathway. We suggest that Phenoxodiol is an efficient inducer of cell death in ovarian cancer cells and sensitizes the cancer cells to Fas-mediated apoptosis. We identified FLIP and XIAP signalling pathways as key factors regulating the survival of ovarian cancer cells. These findings demonstrate a novel nontoxic drug that controls FLIP/XIAP function and has the potential to eliminate tumor cells through Fas-mediated apoptosis.

Anticancer Res . 2018 Oct;38(10):5709-5716.

Evaluation of Therapeutic Potential of Phenoxodiol, a Novel Isoflavone Analog, in Renal Cancer Cells[Pubmed: 30275191]

Background/aim: In the present study, the antineoplastic activity and mechanism of action of Phenoxodiol, a novel isoflavone analog, was investigated in renal cancer cells. Materials and methods: A panel of renal cancer cells (769-P, 786-O, Caki-2) was treated with Phenoxodiol in vitro, and the efficacy of treatment was evaluated. Results: MTS assay results showed that Phenoxodiol decreased renal cancer viability in a dose-dependent manner. In addition, it inhibited colony formation significantly and perturbed the cell cycle. Treatment with Phenoxodiol increased the number of annexin-V-positive cells as well as the expression of cleaved poly ADP ribose polymerase, demonstrating that Phenoxodiol induced apoptosis in renal cancer cells. Phenoxodiol also inhibited Akt pathway via dephosphorylation of Akt. Conclusion: Phenoxodiol inhibited Akt pathway and induced apoptosis of renal cancer cells. The present study provides a theoretical basis for future development of a novel therapy effective against renal cancer.

Anticancer Res . 2018 Jan;38(1):301-306.

Phenoxodiol Increases Cisplatin Sensitivity in Ovarian Clear Cancer Cells Through XIAP Down-regulation and Autophagy Inhibition[Pubmed: 29277787]

Background/aim: To investigate whether XIAP down-regulation and autophagy inhibition sensitize ovarian clear cell cancer cells to cisplatin. Materials and methods: The ovarian clear cancer cell line KK was used for in vitro analysis. Hydroxychloroquine (HCQ) and Phenoxodiol (PXD) or embelin were used as autophagy and XIAP inhibitors, respectively. Non-specific and XIAP-specific siRNAs were transfected using Lipofectamine. Cytotoxicity was assessed by MTT assays. Protein expression was confirmed by western blotting. Results: In KK, down-regulation of XIAP using specific siRNAs together with HCQ treatment enhanced the anti-tumor effect of cisplatin. Although embelin sensitized KK to cisplatin through XIAP down-regulation, it induced autophagy. However, PXD increased cisplatin sensitivity through XIAP down-regulation and autophagy inhibition. Expression of Atg7, Atg12, and Beclin 1 was decreased after PXD treatment. Conclusion: PXD increased cisplatin sensitivity through XIAP down-regulation and autophagy inhibition and could be a new candidate for ovarian clear cell carcinoma treatment. Keywords: Ovarian clear cell carcinoma; X-chromosome-linked inhibitor of apoptosis (XIAP); autophagy; Phenoxodiol; platinum resistance.

Biochem Pharmacol . 2007 Dec 3;74(11):1587-1595.

The antiproliferative effects of phenoxodiol are associated with inhibition of plasma membrane electron transport in tumour cell lines and primary immune cells[Pubmed: 17904534]

Although the redox-active synthetic isoflavene, Phenoxodiol, is in Phase 3 clinical trials for drug-resistant ovarian cancer, and in early stage clinical trials for prostate and cervical cancer, its primary molecular target is unknown. Nevertheless, Phenoxodiol inhibits proliferation of many cancer cell lines and induces apoptosis by disrupting FLICE-inhibitory protein, FLIP, expression and by caspase-dependent and -independent degradation of the X-linked inhibitor of apoptosis, XIAP. In addition, Phenoxodiol sensitizes drug-resistant tumour cells to anticancer drugs including paclitaxel, carboplatin and gemcitabine. Here, we investigate the effects of Phenoxodiol on plasma membrane electron transport (PMET) and cell proliferation in human leukemic HL60 cells and mitochondrial gene knockout HL60rho(o) cells that exhibit elevated PMET. Phenoxodiol inhibited PMET by both HL60 (IC(50) 32 microM) and HL60rho(o) (IC(50) 70 microM) cells, and this was associated with inhibition of cell proliferation (IC(50) of 2.8 and 6.7 microM, respectively), pan-caspase activation and apoptosis. Unexpectedly, Phenoxodiol also inhibited PMET by activated murine splenic T cells (IC(50) of 29 microM) as well as T cell proliferation (IC(50) of 2.5 microM). In contrast, proliferation of WI-38 cells and HUVECs was only weakly affected by Phenoxodiol. These results indicate that PMET may be a primary target for Phenoxodiol in tumour cells and in activated T cells.

Int J Cancer . 2006 May 15;118(10):2412-2420.

Phenoxodiol, an experimental anticancer drug, shows potent antiangiogenic properties in addition to its antitumour effects[Pubmed: 16353157]

Phenoxodiol (2H-1-benzopyran-7-0,1, 3-[4-hydroxyphenyl], PXD) is a synthetic analogue of the naturally-occurring plant isoflavone and anticancer agent, genistein. PXD directly induces mitotic arrest and apoptosis in most cancer cells and is currently undergoing clinical trials, as a chemotherapeutic in ovarian and prostate cancers. We show here that PXD also exhibits potent antiangiogenic properties. Thus, it inhibited endothelial cell proliferation, migration and capillary tube formation and inhibited expression of the matrix metalloproteinase MMP-2, a major matrix degrading enzyme. Importantly, we demonstrate that PXD is functional in vivo since it inhibited the extent of capillary tube invasion in an in vivo model of angiogenesis. We show that Phenoxodiol inhibits hallmarks of endothelial cell activation, namely TNF or IL-1 induced E-selectin and VCAM-1 expression and IL-8 secretion. However, PXD had no effect on unstimulated endothelial cells. We also describe that PXD inhibits the lipid kinase sphingosine kinase, which recently has been implicated in endothelial cell activation and angiogenesis as well as oncogenesis. Thus, our results suggest that PXD may be an effective anticancer drug targeting the two drivers of tumour growth--the proliferation of the tumour cells themselves and the angiogenic and inflammatory stimulation of the vasculature.