| In vitro: |
| 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. |
|
| In vivo: |
| 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. |
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