Mechanisms of the antiangiogenic activity by the hop flavonoid xanthohumol: NF‐κB and Akt as targets

Versatile antitumor potential of isoxanthohumol: Enhancement of paclitaxel activity in vivo

Isoxanthohumol (IXN), a prenylated flavonoid from hops, exhibits diverse biological activities, e.g. antitumor, antiinflammatory, antioxidant and antiangiogenic. In this study, the effect of IXN is evaluated on two melanoma cell lines with dissimilar molecular background, B16 and A375. The treatment of both cell lines with IXN resulted in dose-dependent decrease of cell viability. Abolished viability was in correlation with changed morphology and loss of dividing potential indicating phenotypical alteration of both tested cell lines. While modified B16 cells underwent the process of non-classic differentiation followed by tyrosinase activity without enhancement of melanin content, inhibition of Notch 1, β-catenin and Oct-3/4 was observed in A375 cells indicating loss of their pluripotent characteristics. In parallel with this, distinct subpopulations in both cell cultures entered the process of programmed cell death-apoptosis in a caspase independent manner. The described changes in cultures upon exposure to IXN could be connected with the suppression of reactive oxygen (ROS) and nitrogen species (RNS) induced by the drug. Despite the differences in which IXN promoted modifications in the upper part of the PI3K/Akt and MEK-ERK signaling pathways between B16 and A375 cells, p70S6K and its target S6 protein in both types of melanoma cells, after transient activation, became inhibited. In addition to direct input of IXN on cell viability, this study for the first time shows that IXN strongly sensitizes melanoma cells to the treatment with paclitaxel in vivo, in concordance with data obtained in vitro on B16 cells as well as their highly invasive F10 subclone.

Molecular targeted approaches to cancer therapy and prevention using chalcones

There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy.

The hop constituent xanthohumol exhibits hepatoprotective effects and inhibits the activation of hepatic stellate cells at different levels

Xanthohumol is the principal prenylated flavonoid of the female inflorescences of the hop plant. In recent years, various beneficial xanthohumol effects including anti-inflammatory, antioxidant, hypoglycemic activities, and anticancer effects have been revealed. This review summarizes present studies indicating that xanthohumol also inhibits several critical pathophysiological steps during the development and course of chronic liver disease, including the activation and pro-fibrogenic genotype of hepatic stellate cells. Also the various mechanism of action and molecular targets of the beneficial xanthohumol effects will be described. Furthermore, the potential use of xanthohumol or a xanthohumol-enriched hop extract as therapeutic agent to combat the progression of chronic liver disease will be discussed. It is notable that in addition to its hepatoprotective effects, xanthohumol also holds promise as a therapeutic agent for treating obesity, dysregulation of glucose metabolism and other components of the metabolic syndrome including hepatic steatosis. Thus, therapeutic xanthohumol application appears as a promising strategy, particularly in obese patients, to inhibit the development as well as the progression of non-alcoholic fatty liver disease.

Xanthohumol-Mediated Suppression of Notch1 Signaling Is Associated with Antitumor Activity in Human Pancreatic Cancer Cells

Pancreatic cancer remains a lethal disease with limited treatment options. At the time of diagnosis, approximately 80% of these patients present with unresectable tumors caused by either locally advanced lesions or progressive metastatic growth. Therefore, development of novel treatment strategies and new therapeutics is needed. Xanthohumol (XN) has emerged as a potential compound that inhibits various types of cancer, but the molecular mechanism underlying the effects of XN remains unclear. In the present study, we have assessed the efficacy of XN on pancreatic cancer cell lines (AsPC-1, PANC-1, L3.6pl, MiaPaCa-2, 512, and 651) against cell growth in real time and using colony-forming assays. Treatment with XN resulted in reduction in cellular proliferation in a dose- and time-dependent manner. The growth suppression effect of XN in pancreatic cancer cell lines is due to increased apoptosis via the inhibition of the Notch1 signaling pathway, as evidenced by reduction in Notch1, HES-1, and survivin both at mRNA as well as protein levels. Notch1 promoter reporter analysis after XN treatment indicated that XN downregulates Notch promoter activity. Importantly, overexpression of active Notch1 in XN-treated pancreatic cancer cells resulted in negation of growth suppression. Taken together, these findings demonstrate, for the first time, that the growth suppressive effect of XN in pancreatic cancer cells is mainly mediated by Notch1 reduction.

Natural phenolic metabolites with anti-angiogenic properties - a review from the chemical point of view

Considering the many secondary natural metabolites available from plants, phenolic compounds play a particularly important role in human health as they occur in significant amounts in many fruits, vegetables and medicinal plants. In this review natural phenolic compounds of plant origin with significant anti-angiogenic properties are discussed. Thirteen representatives from eight different natural or natural-like phenolic subclasses are presented with an emphasis on their synthesis and methods to modify the parent compounds. When available, the consequence of structural variation on the pharmacological activity of the molecules is described.

Pharmacological profile of xanthohumol, a prenylated flavonoid from hops (Humulus lupulus)

The female inflorescences of hops (Humulus lupulus L.), a well-known bittering agent used in the brewing industry, have long been used in traditional medicines. Xanthohumol (XN) is one of the bioactive substances contributing to its medical applications. Among foodstuffs XN is found primarily in beer and its natural occurrence is surveyed. In recent years, XN has received much attention for its biological effects. The present review describes the pharmacological aspects of XN and summarizes the most interesting findings obtained in the preclinical research related to this compound, including the pharmacological activity, the pharmacokinetics, and the safety of XN. Furthermore, the potential use of XN as a food additive considering its many positive biological effects is discussed.

Xanthohumol modulates inflammation, oxidative stress, and angiogenesis in type 1 diabetic rat skin wound healing

Type 1 diabetes mellitus is responsible for metabolic dysfunction, accompanied by chronic inflammation, oxidative stress, and endothelium dysfunction, and is often associated with impaired wound healing. Phenol-rich food improves vascular function, contributing to diabetes prevention. This study has evaluated the effect of phenol-rich beverage consumption in diabetic rats on wound healing, through angiogenesis, inflammation, and oxidative stress modulation. A wound-healing assay was performed in streptozotocin-induced diabetic Wistar rats drinking water, 5% ethanol, and stout beer with and without 10 mg/L xanthohumol (1), for a five-week period. Wounded skin microvessel density was reduced to normal values upon consumption of 1 in diabetic rats, being accompanied by decreased serum VEGF-A and inflammatory markers (IL-1β, NO, N-acetylglucosaminidase). Systemic glutathione and kidney and liver H2O2, 3-nitrotyrosine, and protein carbonylation also decreased to healthy levels after treatment with 1, implying an improvement in oxidative stress status. These findings suggest that consumption of xanthohumol (1) by diabetic animals consistently decreases inflammation and oxidative stress, allowing neovascularization control and improving diabetic wound healing.

Isoxanthohumol modulates angiogenesis and inflammation via vascular endothelial growth factor receptor, tumor necrosis factor alpha and nuclear factor kappa B pathways

Angiogenesis and inflammation are becoming distinguished players in the pathogenesis of many heterogeneous diseases, such as diabetes, cardiovascular disease, and cancer. Therefore, it is crucial to study new compounds that are able to modulate these events. Isoxanthohumol (IXN) is a polyphenol with antioxidant, anti-inflammatory, and antiangiogenic properties. The aim of this study was to evaluate the effects of IXN on blood vessel proliferation and maturation and describe underlying molecular mechanisms in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs). Angiogenic profile of IXN was analyzed by retinal angiogenesis at different time points. IXN modulation of angiogenic and inflammatory signaling pathways was evaluated by Western blotting on EC and VSMC cultures. IXN inhibited by 20% sprouting angiogenesis and decreased vascular coverage by mural cells up to 39%. IXN of 10 µM also decreased inflammatory signals, namely tumor necrosis factor alpha (TNF-α) (26 and 40%) and factor nuclear kappa B (24 and 42%) in human aortic smooth muscle cells (HASMCs) and human umbilical vein endothelial cells (HUVECs). Angiogenic regulators, including vascular endothelial growth factor receptor 2 (HUVEC, 55%), angiopoietins 1 (HUVEC, 39%; HASMC, 35%), angiopoietin 2 (HUVEC, 38%), and Tie2 (HUVEC, 56%) were also inhibited by 10 µM of IXN treatments. Akt activation was reduced by 47% in HUVEC-treated cells and Erk activation was also reduced by 52 and 69% upon IXN treatment of HUVEC and HASMC. IXN seems to regulate in vivo vascular proliferation and stabilization and the EC-VSMC-inflammatory crosstalk, leaving this molecule as an interesting nutritional player for angiogenesis and inflammation-related diseases.

The antiangiogenic activity of Kushecarpin D, a novel flavonoid isolated from Sophora flavescens Ait

AIMS

Kushecarpin D (KD) is a novel flavonoid isolated from the traditional Chinese herbal medicine Kushen (the dried root of Sophora flavescens Ait). As part of our continuous effort to explore Chinese traditional medicinal herbs and to identify novel natural anticancer products, the antiangiogenic properties of KD were examined in vitro using a human umbilical vein endothelial cell line (ECV304).

MAIN METHODS

The SRB and Trypan Blue exclusion assays were used to evaluate the effect of KD on cell proliferation. The antiangiogenic activities of KD were evaluated through studies of cell migration, cell adhesion, and tube formation. DCFH-DA and DHE fluorescent assays were used to detect the reactive oxygen species (ROS) levels. Catalase activity was detected using the colorimetric ammonium molybdate method. Cell cycle and apoptosis were measured using flow cytometry and the Hoechst 33258 staining assay.

KEY FINDINGS

The results indicated that KD showed antiangiogenic activity via inhibitory effects on cell proliferation, cell migration, cell adhesion, and tube formation. ROS levels were down-regulated and catalase activity was up-regulated after treatment with KD. The cell cycle was arrested at the G2/M phase, while no apoptosis was observed using the Hoechst 33258 staining assay or following the flow cytometric analysis of the sub-G1 proportion.

SIGNIFICANCE

The antiangiogenic properties of KD, in combination with its anti-proliferative effect and ability to induce cell cycle arrest without inducing apoptosis, make it a good candidate for development as antitumor agent. However, further studies are essential to elucidate its mechanism of action.

Xanthohumol ameliorates atherosclerotic plaque formation, hypercholesterolemia, and hepatic steatosis in ApoE-deficient mice

SCOPE

Xanthohumol (XN), a prenylated antioxidative and anti-inflammatory chalcone from hops, exhibits positive effects on lipid and glucose metabolism. Based on its favorable biological properties, we investigated whether XN attenuates atherosclerosis in western-type diet-fed apolipoprotein-E-deficient (ApoE⁻/⁻) mice.

METHODS AND RESULTS

XN supplementation markedly reduced plasma cholesterol concentrations, decreased atherosclerotic lesion area, and attenuated plasma concentrations of the proinflammatory cytokine monocyte chemoattractant protein 1. Decreased hepatic triglyceride and cholesterol content, activation of AMP-activated protein kinase, phosphorylation and inactivation of acetyl-CoA carboxylase, and reduced expression levels of mature sterol regulatory element-binding protein (SREBP)-2 and SREBP-1c mRNA indicate reduced lipogenesis in the liver of XN-fed ApoE⁻/⁻ mice. Concomitant induction of hepatic mRNA expression of carnitine palmitoyltransferase-1a in ApoE⁻/⁻ mice-administered XN suggests increased fatty acid beta-oxidation. Fecal cholesterol concentrations were also markedly increased in XN-fed ApoE⁻/⁻ mice compared with mice fed western-type diet alone.

CONCLUSION

The atheroprotective effects of XN might be attributed to combined beneficial effects on plasma cholesterol and monocyte chemoattractant protein 1 concentrations and hepatic lipid metabolism via activation of AMP-activated protein kinase.

An update on antitumor activity of naturally occurring chalcones

Chalcones, which have characteristic 1,3-diaryl-2-propen-1-one skeleton, are mainly produced in roots, rhizomes, heartwood, leaves, and seeds of genera Angelica, Sophora, Glycyrrhiza, Humulus, Scutellaria, Parartocarpus, Ficus, Dorstenia, Morus, Artocarpus, and so forth. They have become of interest in the research and development of natural antitumor agents over the past decades due to their broad range of mechanisms including anti-initiation, induction of apoptosis, antiproliferation, antimetastasis, antiangiogenesis, and so forth. This review summarizes the studies on the antitumor activity of naturally occurring chalcones and their underlying mechanisms in detail during the past decades.

The involvement of xanthohumol in the expression of annexin in human malignant glioblastoma cells

Glioblastoma multiforme (GBM) is the most common malignant and resistant tumor of the central nervous system in humans and new therapeutic strategies are urgently required. Recently, we have shown that the potential chemotherapeutic polyphenol xanthohumol (XH), isolated from Humulus Lupulus, induces apoptosis of human T98G glioblastoma cells by increasing reactive oxygen species and activating MAPK pathways. Then we have found, by western blotting and microscopic analysis, that XH up-regulates cytosolic levels of ANXA1 and induces translocation of the protein on the cell membrane of T98G cells in a time-dependent manner with significant effects observed after 24 h. On the basis of the above evidence, the aim of this work was to investigate the role of intracellular and cell membrane localized ANXA1 in GBM cells. RT-PCR analysis has shown that XH up-regulates mRNA levels of ANXA1 after 16 h treatment. To demonstrate the involvement of ANXA1 in apoptosis of GBM cells we down-regulated ANXA1 expression with small interfering RNA (siRNA) and then analysed apoptosis in the presence and absence of apoptotic stimuli. Importantly, apoptosis induced by XH was reduced in siRNA-ANXA1 transfected cells where western blot analysis shows a significant reduction of ANXA1 protein levels. To investigate the role of ANXA1 expression on the cell membrane of T98G cells as potential "eat-me" signal we studied phagocytosis of apoptotic cells by human macrophages. We incubated apoptotic T98G cells with human blood monocyte derived macrophages (M=). After co-incubation period we analysed the percentage of M= phagocytosing the apoptotic cells by cytofluorimetric FACS analysis and by confocal microscopy. Our results show that XH induces phagocytosis of apoptotic T98G cells by human M= in a concentration-effect manner, a processes that is dependent on caspase mediated apoptosis. ANXA1 acts as an "eat-me" signal on the cell membrane of T98G cells, and interestingly, apoptotic siRNA-ANXA1 transfected cells are not completely ingested by M=. These results were confirmed by incubating apoptotic cells with a neutralizing anti-ANXA1 antiboby and ANXA1 membrane depletion by EDTA washing. ANXA1 was also detected in supernatants of apoptotic cells and the incubation of enriched supernatants enhanced the percentage of phagocytosis by M=. These results demonstrated that ANXA1 is involved both in the apoptosis and phagocytosis of glioblastoma cells. This study shows a possible role of ANXA1 in maintenance of brain homeostasis and may lead to novel therapeutic approaches for neuro-inflammatory diseases and chemotherapy targets in the treatment of glioblastoma multiforme.

Xanthohumol impairs human prostate cancer cell growth and invasion and diminishes the incidence and progression of advanced tumors in TRAMP mice

Despite recent advances in understanding the biological basis of prostate cancer, management of the disease, especially in the phase resistant to androgen ablation, remains a significant challenge. The long latency and high incidence of prostate carcinogenesis provides the opportunity to intervene with chemoprevention to prevent or eradicate prostate malignancies. In this study, we have used human hormone-resistant prostate cancer cells, DU145 and PC3, as an in vitro model to assess the efficacy of xanthohumol (XN) against cell growth, motility and invasion. We observed that treatment of prostate cancer cells with low micromolar doses of XN inhibits proliferation and modulates focal adhesion kinase (FAK) and AKT phosphorylation leading to reduced cell migration and invasion. Oxidative stress by increased production of reactive oxygen species (ROS) was associated with these effects. Transgenic adenocarcinoma of the mouse prostate (TRAMP) transgenic mice were used as an in vivo model of prostate adenocarcinoma. Oral gavage of XN, three times per week, beginning at 4 wks of age, induced a decrease in the average weight of the urogenital (UG) tract, delayed advanced tumor progression and inhibited the growth of poorly differentiated prostate carcinoma. The ability of XN to inhibit prostate cancer in vitro and in vivo suggests that XN may be a novel agent for the management of prostate cancer.

Anti-angiogenic activity of the flavonoid precursor 4-hydroxychalcone

Angiogenesis, the growth of new blood vessels, is necessary for cancerous tumors to keep growing and spreading. Suppression of abnormal angiogenesis may provide therapeutic strategies for the treatment of angiogenesis-dependent disorders. In the present study, we describe the in vitro and in vivo anti-angiogenic activities of the flavonoid precursor 4-hydroxychalcone (Q797). This chalcone (22μg/ml) suppressed several steps of angiogenesis, including endothelial cell proliferation, migration and tube formation without showing any signs of cytotoxicity. Moreover, we found a selective effect on activated endothelial cells, in particular with resting endothelial cells and the human epithelial tumor cell lines (HeLa, MCF-7, A549). In addition, Q797 was able to modulate both vascular endothelial growth factor (VEGF)- and basic fibroblast growth factor (FGF)- induced phosphorylation of extracellular signal-regulated kinase (ERK)-1/-2 and Akt kinase. It did not influence the nuclear translocation of p65 subunit of the nuclear factor-κB (NF-κB) when human endothelial cells were stimulated with tumor necrosis factor (TNF)-α. Taken together this indicates that the Q797-mediated inhibition of in vitro angiogenic features of endothelial cells is most likely caused by suppression of growth factor pathways. The potent inhibitory effect of Q797 on bFGF-driven neovascularization was also demonstrated in vivo using the chick chorioallantoic membrane (CAM) assay. In summary, this chalcone could serve as a new leading structure in the discovery of new potent synthetic angiogenesis inhibitors.

Xanthohumol-supplemented beer modulates angiogenesis and inflammation in a skin wound healing model. Involvement of local adipocytes

Angiogenesis and inflammation are two intermingled processes that play a role in wound healing. Nevertheless, whenever exacerbated, these processes result in nonhealing wounds. Xanthohumol (XN), a beer-derived polyphenol, inhibits these processes in many physiopathological situations. This study aimed at examining whether XN ingestion affects wound healing. Wistar rats drinking water, 5% ethanol, stout beer (SB) or stout beer supplemented with 10 mg/L XN (Suppl SB) for 4 weeks, were subjected to a 1.5 cm full skin-thickness longitudinal incision, and further maintained under the same beverage conditions for another week. No differences in beverage consumption or body weight were found throughout the study but food intake decreased in every group relative to controls. Consumption of Suppl SB resulted in decreased serum VEGF levels (18.42%), N-acetylglucosaminidase activity (27.77%), IL1β concentration (9.07%), and NO released (77.06%), accompanied by a reduced redox state as observed by increased GSH/GSSG ratio (to 198.80%). Also, the number of blood vessels within the wound granulation tissue seems to reduce in animals drinking Suppl SB (23.08%). Interestingly, SB and primarily Suppl SB showed a tendency to increase adipocyte number (to 194.26% and 156.68%, respectively) and reduce adipocyte size (4.60% and 24.64%, respectively) within the granuloma. Liver function and metabolism did not change among the animal groups as analyzed by plasma biochemical parameters, indicating no beverage toxicity. This study shows that XN intake in its natural beer context reduced inflammation, oxidative stress, and angiogenesis, ameliorating the wound healing process, suggesting that this polyphenol may exert beneficial effect as a nutritional supplement.

Xanthohumol suppresses inflammatory response to warm ischemia-reperfusion induced liver injury

Liver ischemia/reperfusion (I/R) leads to formation of reactive oxygen species (ROS), which cause hepatic injury and initiate an inflammatory response, which is a critical problem after liver surgery and transplantation. Xanthohumol, the major prenylated chalcone found in hops, has been discussed for its anti-inflammatory and ROS-scavenging properties, and thus, we aimed to investigate the effect of xanthohumol in a model of warm I/R liver injury. Xanthohumol was applied to BALB/c mice orally at a dose of 1 mg/g body weight for 5 days before I/R-injury was induced by clamping the vascular blood supply to the median and left lateral liver lobe for 1 h followed by a 6 h period of reperfusion. At this time, HPLC analysis revealed hepatic xanthohumol levels of approximately 2 μM, a concentration which has been shown to inhibit inflammatory effects in vitro. Assessment of hepatic HMOX1 expression, hepatic glutathione content and immunohistochemical analysis for proteins conjugated with the reactive aldehyde 4-hydroxynonenal indicated that I/R-induced oxidative stress was significantly inhibited in xanthohumol-fed compared to control mice. Histological analysis, TUNEL staining and determination of transaminase serum levels revealed no significant effects of xanthohumol on acute hepatocellular injury. However, at the same time point, pretreatment with xanthohumol almost completely blunted the I/R-induced AKT and NFκB activation and the expression of the proinflammatory genes IL-1alpha, IL-6, MCP-1 and ICAM-1, which are known to play a crucial role in the subacute phase of I/R-induced liver damage. In conclusion, these data indicate the potential of xanthohumol application to prevent adverse inflammatory responses to I/R-induced liver damage such as after surgical liver resection or transplantation.

Xanthohumol impairs autophagosome maturation through direct inhibition of valosin-containing protein

Autophagy is a bulk, nonspecific protein degradation pathway that is involved in the pathogenesis of cancer and neurodegenerative disease. Here, we observed that xanthohumol (XN), a prenylated chalcone present in hops (Humulus lupulus L.) and beer, modulates autophagy. By using XN-immobilized beads, valosin-containing protein (VCP) was identified as a XN-binding protein. VCP has been reported to be an essential protein for autophagosome maturation. Using an in vitro pull down assay, we showed that XN bound directly to the N domain, which is known to mediate cofactor and substrate binding to VCP. These data indicated that XN inhibited the function of VCP, thereby allowing the impairment of autophagosome maturation and resulting in the accumulation of microtubule-associated protein 1 light chain 3-II (LC3-II). This is the first report demonstrating XN as a VCP inhibitor that binds directly to the N domain of VCP. Our finding that XN bound to and inactivated VCP not only reveals the molecular mechanism of XN-modulated autophagy but may also explain how XN exhibits various biological activities that have been reported previously.

Xanthohumol, a Prenylated Flavonoid from Hops (Humulus lupulus), Prevents Platelet Activation in Human Platelets

Xanthohumol is the principal prenylated flavonoid in the hop plant (Humulus lupulus L.). Xanthohumol was found to be a very potent cancer chemopreventive agent through regulation of diverse mechanisms. However, no data are available concerning the effects of xanthohumol on platelet activation. The aim of this paper was to examine the antiplatelet effect of xanthohumol in washed human platelets. In the present paper, xanthohumol exhibited more-potent activity in inhibiting platelet aggregation stimulated by collagen. Xanthohumol inhibited platelet activation accompanied by relative [Ca²⁺]_i mobilization, thromboxane A₂ formation, hydroxyl radical (OH^●) formation, and phospholipase C (PLC)γ2, protein kinase C (PKC), mitogen-activated protein kinase (MAPK), and Akt phosphorylation. Neither SQ22536, an inhibitor of adenylate cyclase, nor ODQ, an inhibitor of guanylate cyclase, reversed the xanthohumol-mediated inhibitory effect on platelet aggregation. Furthermore, xanthohumol did not significantly increase nitrate formation in platelets. This study demonstrates for the first time that xanthohumol possesses potent antiplatelet activity which may initially inhibit the PI3-kinase/Akt, p38 MAPK, and PLCγ2-PKC cascades, followed by inhibition of the thromboxane A₂ formation, thereby leading to inhibition of [Ca²⁺]_i and finally inhibition of platelet aggregation. Therefore, this novel role of xanthohumol may represent a high therapeutic potential for treatment or prevention of cardiovascular diseases.

The AKT/NF-κB inhibitor xanthohumol is a potent anti-lymphocytic leukemia drug overcoming chemoresistance and cell infiltration

Although the vast majority of patients with acute lymphocytic leukemia (ALL) attain remission with modern therapies, relapsed leukemia will continue to be a common malignancy both in childhood and in adults, until new treatments are available. Therapeutic options for advanced B-cell acute lymphocytic leukemia are still limited and acquired drug resistance and extramedullary tissue infiltration are two major obstacles during treatment. The prenylflavonoid xanthohumol (XN) has shown in vitro and in vivo therapeutic potential against a range of tumors. In the present study we investigated the effects of XN on B-ALL cells in vitro and in an ALL-like xenograft mouse model. Treatment of ALL cell lines with XN resulted in growth arrest and apoptosis induction. XN retained its cytotoxicity when adriamycin resistant cells were examined while ALL cell clones adapted to long-term exposure to XN resulted highly responsive to cytotoxic drugs. Administration of 50μg XN/mouse (5 days/week) significantly increased animal life span by delaying the insurgence of neurological disorders due to leukemic cells dissemination. In agreement with a less invasive phenotype, cell migration and invasion were impaired by XN and basal levels of FAK, AKT and NF-κB signaling pathways were down-regulated in ALL cells upon XN exposure. Our data indicate that XN has significant antileukemic activity both in vitro and in vivo, which associates with impaired cell migration and invasion. Interestingly, this activity overcomes mechanisms leading to drug-resistance. XN represents a promising agent perspective for ALL therapy and recurrence prevention and would deserve clinical testing in the near future.

Neuroprotective effects of xanthohumol, a prenylated flavonoid from hops (Humulus lupulus), in ischemic stroke of rats

Xanthohumol is the principal prenylated flavonoid in hops (Humulus lupulus L.), an ingredient of beer. Xanthohumol was found to be a potent chemopreventive agent; however, no data are available concerning its neuroprotective effects. In the present study, the neuroprotective activity and mechanisms of xanthohumol in rats with middle cerebral artery occlusion (MCAO)-induced cerebral ischemia were examined. Treatment with xanthohumol (0.2 and 0.4 mg/kg; intraperitoneally) 10 min before MCAO dose-dependently attenuated focal cerebral ischemia and improved neurobehavioral deficits in cerebral ischemic rats. Xanthohumol treatment produced a marked reduction in infarct size compared to that in control rats. MCAO-induced focal cerebral ischemia was associated with increases in hypoxia-inducible factor (HIF)-1α, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), and active caspase-3 protein expressions in ischemic regions. These expressions were obviously inhibited by treatment with xanthohumol. In addition, xanthohumol (3-70 μM) concentration-dependently inhibited platelet aggregation stimulated by collagen (1 μg/mL) in human platelet-rich plasma. An electron spin resonance (ESR) method was used to examine the scavenging activity of xanthohumol on free radicals which had formed. Xanthohumol (1.5 and 3 μM) markedly reduced the ESR signal intensity of hydroxyl radical (OH•) formation in the H₂O₂/NaOH/DMSO system. In conclusion, this study demonstrates for the first time that in addition to its originally being considered an agent preventing tumor growth, xanthohumol possesses potent neuroprotective activity. This activity is mediated, at least in part, by inhibition of inflammatory responses (i.e., HIF-1α, iNOS expression, and free radical formation), apoptosis (i.e., TNF-α, active caspase-3), and platelet activation, resulting in a reduction of infarct volume and improvement in neurobehavior in rats with cerebral ischemia. Therefore, this novel role of xanthohumol may represent high therapeutic potential for treatment or prevention of ischemia-reperfusion injury-related disorders.

Xanthohumol induces apoptosis in human malignant glioblastoma cells by increasing reactive oxygen species and activating MAPK pathways

The effect of the biologically active prenylated chalcone and potential anticancer agent xanthohumol (1) has been investigated on apoptosis of the T98G human malignant glioblastoma cell line. Compound 1 decreased the viability of T98G cells by induction of apoptosis in a time- and concentration-dependent manner. Apoptosis induced by 1 was associated with activation of caspase-3, caspase-9, and PARP cleavage and was mediated by the mitochondrial pathway, as exemplified by mitochondrial depolarization, cytochrome c release, and downregulation of the antiapoptotic Bcl-2 protein. Xanthohumol induced intracellular reactive oxygen species (ROS), an effect that was reduced by pretreatment with the antioxidant N-acetyl-L-cysteine (NAC). Intracellular ROS production appeared essential for the activation of the mitochondrial pathway and induction of apoptosis after exposure to 1. Oxidative stress due to treatment with 1 was associated with MAPK activation, as determined by ERK1/2 and p38 phosphorylation. Phosphorylation of ERK1/2 and p38 was attenuated using NAC to inhibit ROS production. After treatment with 1, ROS provided a specific environment that resulted in MAPK-induced cell death, with this effect reduced by the ERK1/2 specific inhibitor PD98059 and partially inhibited by the p38 inhibitor SB203580. These findings suggest that xanthohumol (1) is a potential chemotherapeutic agent for the treatment of glioblastoma multiforme.

Anticancer drugs targeting the mitochondrial electron transport chain

SIGNIFICANCE

Mitochondria are emerging as highly intriguing organelles showing promise but that are yet to be fully exploited as targets for anticancer drugs.

RECENT ADVANCES

A group of compounds that induce mitochondrial destabilization, thereby affecting the physiology of cancer cells, has been defined and termed 'mitocans.' Based on their mode of action of targeting in and around mitochondria, we have placed these agents into several groups including hexokinase inhibitors, compounds targeting Bcl-2 family proteins, thiol redox inhibitors, VDAC/ANT targeting drugs, electron transport chain-targeting drugs, lipophilic cations targeting the inner membrane, agents affecting the tricarboxylic acid cycle, drugs targeting mtDNA, and agents targeting other presently unknown sites.

CRITICAL ISSUES

Mitocans have a potential to prove highly efficient in suppressing various malignant diseases in a selective manner. They include compounds that are currently in clinical trial and offer substantial promise to become clinically applied drugs. Here we update and redefine the individual classes of mitocans, providing examples of the various members of these groups with a particular focus on agents targeting the electron transport chain, and indicate their potential application in clinical practice.

FUTURE DIRECTIONS

Even though reactive oxygen species induction is important for the anticancer activity of many mitocans, the precise sequence of events preceding and following this pivotal event are not yet fully clarified, and warrant further investigation. This is imperative for effective deployment of these compounds in the clinic.

Xanthohumol decreases Notch1 expression and cell growth by cell cycle arrest and induction of apoptosis in epithelial ovarian cancer cell lines

OBJECTIVE

Notch1 signaling is active in ovarian cancer and is a promising pathway for new therapies in ovarian cancer. We have previously detected high Notch1 expression in ovarian tumors. Xanthohumol has been shown to inhibit cancer cell growth and invasion, including Kaposi's sarcoma, which also highly expresses Notch1. We hypothesized that the Notch1 signaling pathway is targeted by xanthohumol leading to decreased ovarian cancer cell growth.

METHODS

SKOV3 and OVCAR3 cells were utilized. MTT growth assays were conducted following treatment with xanthohumol. Quantitative RT-PCR and Western blot analyses were conducted to assess Notch1 down-regulation. Luciferase reporter assays were performed to assess functional down-regulation of Notch1. Cell cycle analysis was performed by flow cytometry.

RESULTS

Significant growth inhibition and down-regulation of Notch1 transcription and protein expression were found following xanthohumol treatment. In addition, xanthohumol increased Hes6 transcription and decreased Hes1 transcription, known downstream targets of Notch 1. These observations were associated with cell cycle inhibition as demonstrated by an increase in p21 expression and S and G2/M cell cycle arrest confirmed by an increase in phosphorylated cdc2. Furthermore, an increase in the apoptotic markers, cleaved caspase-3 and cleaved PARP were observed.

CONCLUSION

Xanthohumol was a potent inhibitor of ovarian cancer cell growth, and our results suggest that xanthohumol may be influencing the Notch1 pathway. These findings suggest that xanthohumol could be useful as a therapeutic agent in ovarian cancer.

Angiogenesis and inflammation signaling are targets of beer polyphenols on vascular cells

Emerging evidence indicates that chronic inflammation and oxidative stress cluster together with angiogenic imbalance in a wide range of pathologies. In general, natural polyphenols present health-protective properties, which are likely attributed to their effect on oxidative stress and inflammation. Hops used in beer production are a source of polyphenols such as xanthohumol (XN), and its metabolites isoxanthohumol (IXN) and phytoestrogen 8-prenylnaringenin (8PN). Our study aimed to evaluate XN, IXN, and 8PN effects on angiogenesis and inflammation processes. Opposite in vitro effects were observed between 8PN, stimulating endothelial and smooth muscle cell (SMC) growth, motility, invasion and capillary-like structures formation, and XN and IXN, which inhibited them. Mouse matrigel plug and rat skin wound-healing assays confirmed that XN and IXN treatments reduced vessel number as well as serum macrophage enzymatic activity, whereas 8PN increased blood vessels formation in both assays and enzyme activity in the wound-healing assay. A similar profile was found for serum inflammatory interleukin-1β quantification, in the wound-healing assay. Our data indicate that whereas 8PN stimulates angiogenesis, XN and IXN manifested anti-angiogenic and anti-inflammatory effects in identical conditions. These findings suggest that the effects observed for individual compounds on vascular wall cells must be carefully taken into account, as these polyphenols are metabolized after in vivo administration. The modulation of SMC proliferation and migration is also of special relevance, given the role of these cells in many pathological conditions. Furthermore, these results may provide clues for developing useful therapeutic agents against inflammation- and angiogenesis-associated pathologies.

Recovery and metabolism of xanthohumol in germ-free and human microbiota-associated rats

The impact of human intestinal bacteria on the bioavailability of the prenylflavonoid xanthohumol (XN) was studied by comparing germ-free (GF) and human microbiota-associated (HMA) rats. After XN application, XN, XN conjugates, and isoxanthohumol (IX) conjugates occurred in blood samples of GF and HMA rats, whereas IX was detected only in the blood of HMA rats. Overall excretion of XN and its metabolites within 48 h was only 4.6% of the ingested dose in GF rats and 4.2% in HMA rats, feces being the major route of excretion. While both GF and HMA rats excreted XN, IX, and their conjugates with urine and feces, 8-prenylnaringenin and its corresponding conjugates were exclusively observed in the feces of HMA rats. The microbial formation of 8-prenylnaringenin was confirmed by incubation of XN and IX with human fecal slurries. The amount of conjugates excreted in urine and feces was lower in HMA rats compared to GF rats indicating their hydrolysis by human intestinal microbiota. Thus, the impact of bacteria on the XN metabolism in the gut may affect the in vivo effects of ingested XN.

Dietary chalcones with chemopreventive and chemotherapeutic potential

Chalcones are absorbed in the daily diet and appear to be promising cancer chemopreventive agents. Chalcones represent an important group of the polyphenolic family, which includes a large number of naturally occurring molecules. This family possesses an interesting spectrum of biological activities, including antioxidative, antibacterial, anti-inflammatory, anticancer, cytotoxic, and immunosuppressive potential. Compounds of this family have been shown to interfere with each step of carcinogenesis, including initiation, promotion and progression. Moreover, numerous compounds from the family of dietary chalcones appear to show activity against cancer cells, suggesting that these molecules or their derivatives may be considered as potential anticancer drugs. This review will focus primarily on prominent members of the chalcone family with an 1,3-diphenyl-2-propenon core structure. Specifically, the inhibitory effects of these compounds on the different steps of carcinogenesis that reveal interesting chemopreventive and chemotherapeutic potential will be discussed.

Triggering of dendritic cell apoptosis by xanthohumol

Xanthohumol, a flavonoid from beer with anticancer activity is known to trigger apoptosis in a variety of tumor cells. Xanthohumol further has anti-inflammatory activity. However, little is known about the effect of xanthohumol on survival and function of immune cells. The present study thus addressed the effect of xanthohumol on dendritic cells (DCs), key players in the regulation of innate and adaptive immunity. To this end, mouse bone marrow-derived DCs were treated with xanthohumol with subsequent assessment of enzymatic activity of acid sphingomyelinase (Asm), ceramide formation determined with anti-ceramide antibodies in FACS and immunohistochemical analysis, caspase activity utilizing FITC conjugated anti-active caspase 8 or caspase 3 antibodies in FACS and by Western blotting, DNA fragmentation by determining the percentage of cells in the sub-G1 phase and cell membrane scrambling by annexin V binding in FACS analysis. As a result, xanthohumol stimulated Asm, enhanced ceramide formation, activated caspases 8 and 3, triggered DNA fragmentation and led to cell membrane scrambling, all effects virtually absent in DCs from gene targeted mice lacking functional Asm or in wild-type cells treated with sphingomyelinase inhibitor amitriptyline. In conclusion, xanthohumol stimulated Asm leading to caspase activation and apoptosis of bone marrow-derived DCs.

Xanthohumol, a chalcon derived from hops, inhibits hepatic inflammation and fibrosis

Xanthohumol (XN) is a major prenylated chalcone found in hops, which is used to add bitterness and flavor to beer. In this study, we first investigated the effects of XN on hepatocytes and hepatic stellate cells (HSC), the central mediators of liver fibrogenesis. XN inhibited the activation of primary human HSC and induced apoptosis in activated HSC in vitro in a dose dependent manner (0-20 microM). In contrast, XN doses as high as 50 microM did not impair viability of primary human hepatocytes. However, in both cell types XN inhibited activation of the transcription factor NFkappaB and expression of NFkappaB dependent proinflammatory genes. In vivo, feeding of XN reduced hepatic inflammation and expression of profibrogenic genes in a murine model of non-alcoholic steatohepatitis. These data indicate that XN has the potential as functional nutrient for the prevention or treatment of non-alcoholic steatohepatitis or other chronic liver disease.

alpha-Chaconine inhibits angiogenesis in vitro by reducing matrix metalloproteinase-2

alpha-Chaconine, a naturally occurring steroidal glycoalkaloid in potato sprouts, was found to possess anti-carcinogenic properties, such as inhibiting proliferation, migration, invasion, and inducing apoptosis of tumor cells. However, the effect of alpha-chaconine on tumor angiogenesis remains unclear. In the present study, we examined the effect of alpha-chaconine on angiogenesis in vitro. Data demonstrated that alpha-chaconine inhibited proliferation of bovine aortic endothelial cells (BAECs) in a dose-dependent manner. When treated with non-toxic doses of alpha-chaconine, cell migration, invasion and tube formation were markedly suppressed. Furthermore, alpha-chaconine reduced the expression and activity of matrix metalloproteinase-2 (MMP-2), which is involved in angiogenesis. Our biochemical assays indicated that alpha-chaconine potently suppressed the phosphorylation of c-Jun N-terminal kinase (JNK), phosphatidylinositide-3 kinase (PI3K) and Akt, while it did not affect phosphorylation of extracellular signal regulating kinase (ERK) and p38. In addition, alpha-chaconine significantly increased the cytoplasmic level of inhibitors of kappaBalpha (IkappaBalpha) and decreased the nuclear level of nuclear factor kappa B (NF-kappaB), suggesting that alpha-chaconine could inhibit NF-kappaB activity. Furthermore, the treatment of inhibitors specific for JNK (SP600125), PI3K (LY294002) or NF-kappaB (pyrrolidine dithiocarbamate) to BAECs reduced tube formation. Taken together, the results suggested that alpha-chaconine inhibited migration, invasion and tube formation of BAECs by reducing MMP-2 activities, as well as JNK and PI3K/Akt signaling pathways and inhibition of NF-kappaB activity. These findings reveal a new therapeutic potential for alpha-chaconine on anti-angiogenic therapy.

Methyl 2-cyano-3,11-dioxo-18-olean-1,12-dien-30-oate (CDODA-Me), a derivative of glycyrrhetinic acid, functions as a potent angiogenesis inhibitor

Methyl 2-cyano-3,11-dioxo-18-olean-1,12-dien-30-oate (CDODA-Me), a triterpenoid acid derived synthetically from glycyrrhetinic acid, has been characterized as a peroxisome proliferator-activated receptor γ agonist with a broad range of receptor-dependent and -independent anticancer activities. Although CDODA-Me decreases the expression of some angiogenic genes in cancer cells, the direct effects of this compound on angiogenesis have not been defined. In this study, we have extensively investigated the activities of CDODA-Me in multiple angiogenesis assays. Our results showed that this agent inhibited vascular endothelial growth factor (VEGF)-induced proliferation, migration, invasion, and lamellipodium and capillary-like structure formation of human umbilical endothelial cells (HUVECs) in a concentration-dependent manner. Moreover, CDODA-Me abrogated VEGF-induced sprouting of microvessels from rat aortic rings ex vivo and inhibited the generation of new vasculature in the Matrigel plugs in vivo, where CDODA-Me significantly decreased the number of infiltrating von Willebrand factor-positive endothelial cells. To understand the molecular basis of this antiangiogenic activity, we examined the signaling pathways in CDODA-Me-treated HUVECs. Our results showed that CDODA-Me significantly suppressed the activation of VEGF receptor 2 (VEGFR2) and interfered with the mammalian target of rapamycin (mTOR) signaling, including mTOR kinase and its downstream ribosomal S6 kinase (S6K), but had little effect on the activities of extracellular signal-regulated protein kinase and AKT. Taken together, CDODA-Me blocks several key steps of angiogenesis by inhibiting VEGF/VEGFR2 and mTOR/S6K signaling pathways, making the compound a promising agent for the treatment of cancer and angiogenesis-related pathologies.

Functional genomics of endothelial cells treated with anti-angiogenic or angiopreventive drugs

Angiogenesis is a highly regulated physiological process that has been studied in considerable detail given its importance in several chronic pathologies. Many endogenous factors and hormones intervene in the regulation of angiogensis and classical as well as targeted drugs have been developed for its control. Angiogenesis inhibition has come off the bench and entered into clinical application for cancer therapy, particularly for metastatic disease. While the clinical benefit is currently in terms of months, preclinical data suggest that novel drugs and drug combinations could lead to substantial improvement. The many targets of endogenous angiogenesis inhibitors reflect the complexity of the process; in contrast, current clinical therapies mainly target the vascular endothelial growth factor system. Cancer chemopreventive compounds can retard tumor insurgence and delay or prevent metastasis and many of these molecules hinder angiogenesis, a mechanism that we termed angioprevention. Angiopreventive drugs appear to prevalently act through the inhibition of the pro-inflammatory and anti-apoptotic player NFkappaB, thus contrasting inflammation dependent angiogenesis. Relatively little is known concerning the effects of these angiogenesis inhibitors on gene expression of endothelial cells, the main target of many of these molecules. Here we provide an exhaustive list of anti-angiogenic molecules, and summarize their effects, where known, on the transcriptome and functional genomics of endothelial cells. The regulation of specific genes can be crucial to preventive or therapeutic intervention. Further, novel targets might help to circumvent resistance to anti-angiogenic therapy. The studies we review are relevant not only to cancer but also to other chronic degenerative diseases involving endothelial cells, such as cardiovascular disorders, diabetes, rheumatoid arthritis and retinopaties, as well as vessel aging.

Xanthohumol inhibits IL-12 production and reduces chronic allergic contact dermatitis

Xanthohumol (XN) and its related compounds were evaluated for their effects on modulating the production of interleukin (IL)-12, the most important factor driving T helper 1 immune responses. XN showed the strongest inhibitory effect on IL-12 production in macrophages stimulated by lipopolysaccharide (LPS) or LPS/interferon-gamma. Xanthohumol 4'-O-beta-D-glucopyranoside (XNG) inhibited IL-12 production less effectively than XN. Isoxanthohumol and 8-prenylnaringenin showed comparatively lower inhibitory effects on IL-12 production than XNG. (2S)-5-methoxy-8-prenylnaringenin 7-O-beta-D-glucopyranoside did not exert any effect on IL-12 production. We then tested how these compounds affected NF-kappaB binding activity to the kappaB site in the nucleus. The compounds inhibited kappaB binding in macrophages with the same potency order as IL-12 inhibition. Furthermore, we investigated whether XN, which showed the most effective reduction of IL-12 production, attenuated skin inflammation. Chronic allergic contact dermatitis, an experimental model for psoriasis, was used to determine the anti-inflammatory effects of XN in vivo. XN treatment reduced the degree of ear thickening induced by oxazolone. Taken together, XN might be effective as an anti-inflammatory agent to reduce skin inflammation by inhibiting IL-12 production.

Cardiotoxicity of anticancer drugs: the need for cardio-oncology and cardio-oncological prevention

Due to the aging of the populations of developed countries and a common occurrence of risk factors, it is increasingly probable that a patient may have both cancer and cardiovascular disease. In addition, cytotoxic agents and targeted therapies used to treat cancer, including classic chemotherapeutic agents, monoclonal antibodies that target tyrosine kinase receptors, small molecule tyrosine kinase inhibitors, and even antiangiogenic drugs and chemoprevention agents such as cyclooxygenase-2 inhibitors, all affect the cardiovascular system. One of the reasons is that many agents reach targets in the microenvironment and do not affect only the tumor. Combination therapy often amplifies cardiotoxicity, and radiotherapy can also cause heart problems, particularly when combined with chemotherapy. In the past, cardiotoxic risk was less evident, but it is increasingly an issue, particularly with combination therapy and adjuvant therapy. Today's oncologists must be fully aware of cardiovascular risks to avoid or prevent adverse cardiovascular effects, and cardiologists must now be ready to assist oncologists by performing evaluations relevant to the choice of therapy. There is a need for cooperation between these two areas and for the development of a novel discipline, which could be termed cardio-oncology or onco-cardiology. Here, we summarize the potential cardiovascular toxicities for a range of cancer chemotherapeutic and chemopreventive agents and emphasize the importance of evaluating cardiovascular risk when patients enter into trials and the need to develop guidelines that include collateral effects on the cardiovascular system. We also discuss mechanistic pathways and describe several potential protective agents that could be administered to patients with occult or overt risk for cardiovascular complications.