Dependence of DPPH radical scavenging activity of dietary flavonoid quercetin on reaction environment

Many of nowadays diseases are due to the oxidative stress resulting from imbalance between formation and neutralization of free radicals. Intake of dietary antioxidants is therefore crucial to maintain good health. As the safety of synthetic antioxidants has raised several questions the search for natural efficient antioxidants from chemicals produced by plants has gained increased popularity in recent years. Quercetin is an abundant dietary flavonoid with well-known radical scavenging properties being often used as a reference compound in many antioxidant tests. Its reaction with 1,1- diphenyl-2-picrylhydrazyl (artificial DPPH radical) is rapid and stoichiometric; however the published inhibitory constants vary in a very wide range, from 95 nM to 226 µM. The analysis indicates the dependence of antiradical capacity of quercetin on the composition of solvent systems where the reactions are performed and also on the surrounding temperature showing somewhat higher scavenging ability at body temperature compared to room conditions. At the same time, this activity is generally independent on the initial DPPH concentration. These data highlight the importance to consider the reaction environment and conditions when predicting the redox behavior of quercetin in a certain cellular context. Moreover, due to the changes in cellular environment accompanying with different pathogeneses the redox action of polyphenols can essentially vary leading even to the situations where the well-known antioxidant quercetin may reveal prooxidant properties.

NOTCH signaling: Journey of an evolutionarily conserved pathway in driving tumor progression and its modulation as a therapeutic target

Notch signaling, an evolutionarily conserved signaling cascade, is critical for normal biological processes of cell differentiation, development, and homeostasis. Deregulation of the Notch signaling pathway has been associated with tumor progression. Thus, Notch presents as an interesting target for a variety of cancer subtypes and its signaling mechanisms have been actively explored from the therapeutic viewpoint. However, besides acting as an oncogene, Notch pathway can possess also tumor suppressive functions, being implicated in inhibition of cancer development. Given such interesting dual and dynamic role of Notch, in this review, we discuss how the evolutionarily conserved Notch signaling pathway drives hallmarks of tumor progression and how it could be targeted for a promising treatment and management of cancer. In addition, the up-to-date information on the inhibitors currently under clinical trials for Notch targets is presented along with how NOTCH inhibitors can be used in conjunction with established chemotherapy/radiotherapy regimes.

Phloretin, as a Potent Anticancer Compound: From Chemistry to Cellular Interactions

Phloretin is a natural dihydrochalcone found in many fruits and vegetables, especially in apple tree leaves and the Manchurian apricots, exhibiting several therapeutic properties, such as antioxidant, antidiabetic, anti-inflammatory, and antitumor activities. In this review article, the diverse aspects of the anticancer potential of phloretin are addressed, presenting its antiproliferative, proapoptotic, antimetastatic, and antiangiogenic activities in many different preclinical cancer models. The fact that phloretin is a planar lipophilic polyphenol and, thus, a membrane-disrupting Pan-Assay Interference compound (PAIN) compromises the validity of the cell-based anticancer activities. Phloretin significantly reduces membrane dipole potential and, therefore, is expected to be able to activate a number of cellular signaling pathways in a non-specific way. In this way, the effects of this minor flavonoid on Bax and Bcl-2 proteins, caspases and MMPs, cytokines, and inflammatory enzymes are all analyzed in the current review. Moreover, besides the anticancer activities exerted by phloretin alone, its co-effects with conventional anticancer drugs are also under discussion. Therefore, this review presents a thorough overview of the preclinical anticancer potential of phloretin, allowing one to take the next steps in the development of novel drug candidates and move on to clinical trials.

Molecular mechanisms underlying chemopreventive potential of butein: Current trends and future perspectives

Despite extensive efforts, cancer is still often considered as an incurable disease and initiation of novel drug development programs is crucial to improve the prognosis and clinical outcome of patients. One of the major approaches in designing the novel cancer drugs has historically comprised studies of natural agents with diverse anticancer properties. As only a marginal part of natural compounds has been investigated, this approach still represents an attractive source of new potential antitumor molecules. In this review article, different anticancer effects of plant-derived chalcone, butein, are discussed, including its growth inhibitory action, proapoptotic, antiangiogenic and antimetastatic activities in a variety of cancer cells. The molecular mechanisms underlying these effects are presented in detail, revealing interactions of butein with multiple cellular targets (Bcl-2/Bax, caspases, STAT3, cyclins, NF-κB, COX-2, MMP-9, VEGF/R etc.) and regulation of a wide range of intracellular signal transduction pathways. These data altogether allow a good basis for initiating further in vivo studies as well as clinical trials. Along with the efforts to overcome low bioavailability issues generally characteristic to plant metabolites, butein can be considered as a potential lead compound for safe and more efficient cancer drugs in the future.

Radiosensitizing Potential of Curcumin in Different Cancer Models

Over the past decades, studies of phytochemicals as modifiers of radiotherapeutic efficacy have become increasingly popular to improve the treatment outcome of human malignancies. In the current comprehensive review article, radiosensitizing effects of curcumin, a yellow-colored polyphenolic constituent of turmeric, in various preclinical cancer models, both In Vitro and In Vivo, are presented. Attenuation of radioadaptation and augmentation of irradiation-induced cancer cell killing are achieved through multifaceted action of curcumin on suppression of prosurvival and antiapoptotic factors. Most importantly, curcumin can block radiation-triggered NF-κB signaling pathway and downregulate downstream effector proteins, thereby conferring potentiation of radioresponses. Based on the elucidated molecular mechanisms but also due to its safety profile and low cost, curcumin might be considered a promising adjuvant agent to enhance radiotherapeutic efficacy in the treatment of various cancer types formed in different human organ systems. Further efforts to translate the current preclinical knowledge to the real application of curcumin in combinatorial radiotherapeutic strategies in clinical settings are necessary.AbbreviationsAKTprotein kinase BARMSalveolar rhabdomyosarcomaATMataxia telangiectasia mutatedBaxBcl-2-associated X proteinBcl-2B-cell lymphoma 2CDC2cyclin-dependent kinase 2Bcl-xLB-cell lymphoma-extra largec-FLIPcellular FLICE-like inhibitory proteinCDDPcisplatinCOX-2cyclooxygenase-2cyt ccytochrome cDNA-PKcsDNA-dependent protein kinaseEGFRepidermal growth factor receptorEMTepithelial-mesenchymal transitionERKextracellular signal-regulated kinaseESEwing`s sarcomaETS2erythroblastosis virus transcription factor 2GBMglioblastoma multiformeHCChepatocellular carcinomaHNSCChead and neck squamous cell carcinomaIAPinhibitor of apoptosis proteinIκBαinhibitor of κB alphaIKKinhibitor of κB kinaseIRionizing radiationlncRNAlong non-coding RNAlucluciferaseMcl-1myeloid cell leukemia-1MDR1multidrug resistance protein 1miRmicroRNAMMP-9matrix metalloproteinase-9mTORmammalian target of rapamycinNBneuroblastomaNF-κBnuclear factor-κBNPCnasopharyngeal carcinomaNSCLCnon-small cell lung cancerOSCCoral squamous cell carcinomaPARPpoly-(ADP-ribose)-polymerasepH2AXphosphorylated histone 2AX-immunoreactivePI3Kphosphatidylinositol 3-kinasePrp4KPre-mRNA processing factor 4 kinaseRCCrenal cell carcinomaROSreactive oxygen speciesSCCsquamous cell carcinomaSLNsolid lipid nanoparticleSOD2superoxide dismutase 2TERTtelomerase reverse transcriptaseTNF-αtumor necrosis factor-αTxnRd1thioredoxin reductase-1VEGFvascular endothelial growth factorXIAPX-linked inhibitor of apoptosis proteinΔΨmmitochondrial membrane potential.

Apoptotic Mechanisms of Quercetin in Liver Cancer: Recent Trends and Advancements

Due to rising incidence rates of liver cancer and worries about the toxicity of current chemotherapeutic medicines, the hunt for further alternative methods to treat this malignancy has escalated. Compared to chemotherapy, quercetin, a flavonoid, is relatively less harmful to normal cells and is regarded as an excellent free-radical scavenger. Apoptotic cell death of cancer cells caused by quercetin has been demonstrated by many prior studies. It is present in many fruits, vegetables, and herbs. Quercetin targets apoptosis, by upregulating Bax, caspase-3, and p21 while downregulating Akt, PLK-1, cyclin-B1, cyclin-A, CDC-2, CDK-2, and Bcl-2. Additionally, it has been reported to increase STAT3 protein degradation in liver cancer cells while decreasing STAT3 activation. Quercetin has a potential future in chemoprevention, based on substantial research on its anticancer effects. The current review discusses quercetin's mechanisms of action, nanodelivery strategies, and other potential cellular effects in liver cancer.

Application of curcumin nanoformulations to target folic acid receptor in cancer: Recent trends and advances

Curcumin, derived from turmeric, has a strong anticancer potential known for millennia. The development of this phytochemical as a medicine has been hampered by several significant deficiencies, including its poor water solubility and low bioavailability. This review article discusses possibilities to overcome these bottlenecks by focusing on this natural polyphenol's nanoformulation. Moreover, preparation of curcumin conjugates containing folates as ligands for folic acid receptors can add a new important dimension in this field, allowing specific targeting of cancer cells, considering the significantly higher expression of these receptors in malignant tissues compared to normal cells. It is highly expected that simultaneous improvement of different aspects of curcumin in fighting against such a complex and multifaceted disease like cancer. Therefore, we can better comprehend cancer biology by developing a mechanistic understanding of curcumin, which will also inspire the scientific community to develop new pharmacological models, and exploration of emerging directions to revitalize application of natural products in cancer therapy.

Suppression of Taxanes Cytotoxicity by Citrus Flavonoid Hesperetin in PPC-1 Human Prostate Cancer Cells

BACKGROUND/AIM

More than half of prostate cancer patients use, in addition to conventional therapies, some kind of complementary medicine, including flavonoid-rich products. However, knowledge about the co-effects of flavonoids with cytotoxic chemotherapies is still rather poor. Therefore, this study was undertaken to assess the cytotoxic activity of flavonoids and their interactions with taxanes in human advanced prostate cancer cells.

MATERIALS AND METHODS

Cytotoxicity of different flavonoids and their effects on the efficacy of docetaxel and cabazitaxel were studied in the human metastatic prostate cancer cell line PPC-1, using MTT colorimetric assay.

RESULTS

Both taxanes suppressed the viability of PPC-1 cells with IC50 values in the nanomolar range. Tested flavonoids exerted cytotoxic activity only at high micromolar concentrations or revealed no remarkable effect on cell survival. Simultaneous treatment of cells with taxanes and flavonoids baicalein, chrysin, luteolin, fisetin, quercetin, genistein or daidzein did not lead to any change in chemotherapy-induced cytotoxicity. However, simultaneous exposure of cells to hesperetin and taxanes resulted in 9.8- and 13.1-fold reduction in cytotoxicity of docetaxel and cabazitaxel, respectively.

CONCLUSION

Flavonoid hesperetin remarkably suppressed the cytotoxic efficacy of taxanes in prostate cancer cells. Therefore, caution is required from prostate cancer patients who take hesperetin-containing oral supplements.

A new lignan glycoside from the aerial parts and cytotoxic investigation of Uvaria rufa

Chemical investigation of the aerial parts of Uvaria rufa (Dunal) Blume collected from Vietnam yielded one new lignan glycoside, ufaside (1), along with six known compounds, oxoanolobine (2), ergosta-4,6,8(14),22-tetraen-3-one (3), catechin (4), epicatechin (5), daucosterol (6) and glutin-5-en-3-one (7). Their chemical structures were determined by using NMR, HR-MS spectroscopic analyses and in comparison with the reported data. A cytotoxic analysis of U. rufa herb extracts was performed for the first time using nine human cancer cell lines (MCF-7, MDA-MB-231, LNCaP, MKN7, SW480, KB, LU-1, HepG2 and HL-60) derived from different tumour types. Of these seven constituents, compounds 2 and 3 displayed moderate cytotoxicity against the human lung adenocarcinoma cell line (LU-1) with IC50 values of 9.22 ± 1.02 μg/mL and 10.21 ± 1.16 μg/mL, respectively.

Galangin: A metabolite that suppresses anti-neoplastic activities through modulation of oncogenic targets

With the dramatic increase in cancer incidence all over the world in the last decades, studies on identifying novel efficient anti-cancer agents have been intensified. Historically, natural products have represented one of the most important sources of new lead compounds with a wide range of biological activities. In this article, the multifaceted anti-cancer action of propolis-derived flavonoid, galangin, is presented, discussing its antioxidant, anti-inflammatory, antiproliferative, pro-apoptotic, anti-angiogenic, and anti-metastatic effects in various cancer cells. In addition, co-effects with standard chemotherapeutic drugs as well as other natural compounds are also under discussion, besides highlighting modern nanotechnological advancements for overcoming the low bioavailability issue characteristic of galangin. Although further studies are needed for confirming the anti-cancer potential of galangin in vivo malignant systems, exploring this natural compound might open new perspectives in molecular oncology.

Intake of Individual Flavonoids and Risk of Carcinogenesis: Overview of Epidemiological Evidence

Several epidemiological findings have demonstrated that specific flavonoids can be responsible for reduction of the risk of certain cancer types. However, these results are still rather limited, inconclusive and controversial. Therefore, in this comprehensive review article the findings reported to date about the associations between dietary intake of individual flavonoid compounds and cancer incidence are compiled and analyzed. Also, the possible reasons for inconsistencies are brought forth and discussed. As diet is a potentially modifiable factor in our behavioral choices, further large-scale prospective studies with longer follow-up times, different populations, various doses and exposure timing as well as diverse well-controlled confounders are highly needed to confirm or disprove the current epidemiological knowledge about the role of flavonoids on cancer risk. Regarding the promising data to date, more research on bioavailability, metabolism and biological action mechanisms of these plant secondary metabolites is also encouraged.

Pharmacological characterisation of pyrimidinoceptor responses in NG108-15 cells

In the present study, the P2Y receptor(s) mediating the effects of the pyrimidines UTP and UDP on phospholipase C activation in the mouse neuroblastoma x rat glioma hybrid cell line NG108-15 was investigated. Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) analysis detected transcripts for the P2Y(6) and P2Y(2) receptors, but not for P2Y(1) and P2Y(4.) UTP and UDP were equipotent agonists and their effects were partially additive. Suramin, reactive blue 2 and pyridoxal phosphate-6-azophenyl-2',4'disulfonic acid (PPADS) antagonised the phospholipase C response to both UTP and UDP. High micromolar concentrations of adenosine, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS-21680), 2',3'-O-isopropylideneadenosine (iPAdo) and adenosine 3':5'-cyclic monophosphate (3',5'-cAMP) were able to antagonise the effect of UTP on phospholipase C but not that of UDP. The additivity of the UTP and UDP responses, novel P2 receptor antagonist profile and the distinguishing action of adenosine may indicate the expression of a pyrimidine selective P2Y receptor in addition to the P2Y(6) type in these cells.

STAT signaling as a target for intervention: from cancer inflammation and angiogenesis to non-coding RNAs modulation

As a landmark, scientific investigation in cytokine signaling and interferon-related anti-viral activity, signal transducer and activator of transcription (STAT) family of proteins was first discovered in the 1990s. Today, we know that the STAT family consists of several transcription factors which regulate various molecular and cellular processes, including proliferation, angiogenesis, and differentiation in human carcinoma. STAT family members play an active role in transducing signals from cell membrane to nucleus through intracellular signaling and thus activating gene transcription. Additionally, they are also associated with the development and progression of human cancer by facilitating inflammation, cell survival, and resistance to therapeutic responses. Accumulating evidence suggests that not all STAT proteins are associated with the progression of human malignancy; however, STAT3/5 are constitutively activated in various cancers, including multiple myeloma, lymphoma, breast cancer, prostate hepatocellular carcinoma, and non-small cell lung cancer. The present review highlights how STAT-associated events are implicated in cancer inflammation, angiogenesis and non-coding RNA (ncRNA) modulation to highlight potential intervention into carcinogenesis-related cellular processes.

Analysis of NADP+-dependent isocitrate dehydrogenase-1/2 gene mutations in pediatric brain tumors: report of a secondary anaplastic astrocytoma carrying the IDH1 mutation

Somatic mutations of the isocitrate dehydrogenase-1 gene (IDH1), most commonly resulting in replacement of arginine at position 132 by histidine (p.R132H), have been reported for WHO grade II and III diffuse gliomas and secondary glioblastomas. We investigated IDH1/2 mutations in a retrospective series of 165 pediatric brain tumors, including atypical teratoid/rhabdoid tumors (AT/RT) and choroid plexus tumors, which had not previously been investigated. Mutation analysis was performed by use of pyrosequencing and, additionally, data were validated for a cohort of 70 gliomas from among the series by use of the arrayed primer extension technique. We identified one tumor which harbored mutation of IDH1 at codon 132 and no alteration was identified in the matched-germline DNA. No IDH2 mutations were detected. Most noteworthy, the IDH1 mutant tumor was an anaplastic astrocytoma involving the cortex in the left frontal lobe which appeared seven years after radiation treatment for an extensive sellar/suprasellar craniopharyngioma. This anaplastic astrocytoma was regarded as secondary to radiation treatment because it seemed to originate within the irradiation field that received a dose varying from a maximum of 30.6 Gy of 4 MV X-rays down to very few Gy of lower-energy scattered radiation. In this work our observations agree with those in previous reports showing the rarity of IDH1/2 mutations in childhood tumors. The interesting identification of an IDH1 mutation in a radiation-induced secondary malignant glioma raises the likelihood that these types of tumor may develop IDH1/2 mutations. Thus, caution is needed when dealing with these tumors, and further genetic analysis is warranted.

Adenosine-derived non-phosphate antagonists for P2Y(1) purinoceptors

Novel type antagonists for P2Y(1) adenine nucleotide receptors were synthesized by coupling of adenosine 5'-OH group with oligo-aspartate chain via a carbonyl linker. All these conjugates (AdoOC(O)Asp(n), n = 1-4) inhibited the 2MeSADP-stimulated synthesis of inositol phosphates in 1321N1 human astrocytoma cells stably expressing human P2Y(1) receptors. This inhibitory effect followed the rank order AdoOC(O)Asp(2)> AdoOC(O)Asp(3)> AdoOC(O)Asp(1)> AdoOC(O)Asp(4) with antagonistic constant pA(2) = 5.4 for AdoOC(O)Asp(2). Potency of this non-phosphate inhibitor was comparable with the previously known adenosine 3',5'- and 2', 5'-bisphosphates. Chemical and biological stabilities of these novel adenosine derived antagonists of the nucleotide receptor provide perspectives of their pharmacological implication.

Current epidemiological knowledge about the role of flavonoids in prostate carcinogenesis

Numerous experimental studies have demonstrated anticancer action of polyphenolic plant metabolites. However, data about associations between dietary intake of plant-derived flavonoids and prostate cancer risk are still sparse and inconsistent. This minireview compiles the epidemiological findings published to date on the role of flavonoids in prostate tumorigenesis, discusses the reasons of inconsistencies and elicits the promising results for chemoprevention of this malignancy. Long-term consumption of high doses of soy isoflavones can be the reason of markedly lower clinically detectable prostate cancer incidence among Asian men compared to their counterparts in the Western world. The ability to metabolize daidzein to equol, the most biologically active isoflavone, by the certain intestinal bacteria also seems to contribute to this important health benefit. The increasing incidence rate of prostate cancer related to adoption of westernized lifestyle and dietary habits makes the issue of chemoprevention ever more important and directs the eyes to specific food components in the Eastern diet. If further large-scale epidemiological studies will confirm the protective effects of isoflavones against prostate cancer, this could provide an important way for prostate cancer prevention, as diet is a potentially modifiable factor in our behavioral pattern.

Nanoformulations of quercetin for controlled delivery: a review of preclinical anticancer studies

One of the well-studied older molecules, quercetin, is found in large quantities in many fruits and vegetables. Natural anti-oxidant quercetin has demonstrated numerous pharmacological properties in preclinical and clinical research, including anti-inflammatory and anti-cancer effects. Due to its ability to control cell signaling pathways, including NF-κB, p53, activated protein-1 (AP-1), STAT3, and epidermal growth response-1 (Egr-1), which is essential in the initiation and proliferation of cancer, it has gained a lot of fame as an anticancer molecule. Recent research suggests that using nanoformulations can help quercetin to overcome its hydrophobicity while also enhancing its stability and cellular bioavailability both in vitro and in vivo. The main aim of this review is to focus on the comprehensive insights of several nanoformulations, including liposomes, nano gels, micelles, solid lipid nanoparticles (SLN), polymer nanoparticles, gold nanoparticles, and cyclodextrin complexes, to transport quercetin for application in cancer.

Epidemiological Evidences on Dietary Flavonoids and Breast Cancer Risk: A Narrative Review

Epidemiological studies on associations between intake of flavonoids and breast cancer risk are highly needed to assess the actual effects of flavonoids in humans. Experimental investigations in vitro conditions cannot detect and model the real action of these phytochemicals due to the limitations to consider absorption and metabolic biotransformation as well as several complex interactions. Therefore, the data about association findings between intake of flavonoids and breast cancer risk are compiled and analyzed in the current review by evaluating both the results obtained using food composition databases as well as different biomarkers. Although several case-control studies demonstrate some reduction in breast cancer risk related to high consumption of flavones and flavonols, large-scale prospective cohort studies with follow-up times of many years do not confirm these findings. Intake of isoflavones can be associated with a decrease in breast tumorigenesis only in Asian countries where the consumption of soy foods is high but not among Western women with significantly lower ingestion amounts, suggesting the presence of so-called threshold level of effect. Besides doses, the timing of exposure to isoflavones seems also to be a significant factor as childhood and prepubertal age can be critical periods. Although women may need to consume high amounts of isoflavones typical to Asian diets to gain beneficial effects and protection against mammary carcinogenesis, it is still too early to give any specific recommendations to prevent breast tumors by diet rich in certain flavonoids.

Licorice (Glycyrrhiza glabra L.)-Derived Phytochemicals Target Multiple Signaling Pathways to Confer Oncopreventive and Oncotherapeutic Effects

Cancer is a highly lethal disease, and its incidence has rapidly increased worldwide over the past few decades. Although chemotherapeutics and surgery are widely used in clinical settings, they are often insufficient to provide the cure for cancer patients. Hence, more effective treatment options are highly needed. Although licorice has been used as a medicinal herb since ancient times, the knowledge about molecular mechanisms behind its diverse bioactivities is still rather new. In this review article, different anticancer properties (antiproliferative, antiangiogenic, antimetastatic, antioxidant, and anti-inflammatory effects) of various bioactive constituents of licorice (Glycyrrhiza glabra L.) are thoroughly described. Multiple licorice constituents have been shown to bind to and inhibit the activities of various cellular targets, including B-cell lymphoma 2, cyclin-dependent kinase 2, phosphatidylinositol 3-kinase, c-Jun N-terminal kinases, mammalian target of rapamycin, nuclear factor-κB, signal transducer and activator of transcription 3, vascular endothelial growth factor, and matrix metalloproteinase-3, resulting in reduced carcinogenesis in several in vitro and in vivo models with no evident toxicity. Emerging evidence is bringing forth licorice as an anticancer agent as well as bottlenecks in its potential clinical application. It is expected that overcoming toxicity-related obstacles by using novel nanotechnological methods might importantly facilitate the use of anticancer properties of licorice-derived phytochemicals in the future. Therefore, anticancer studies with licorice components must be continued. Overall, licorice could be a natural alternative to the present medication for eradicating new emergent illnesses while having just minor side effects.

Xanthohumol: A Metabolite with Promising Anti-Neoplastic Potential

The overwhelming global burden of cancer has posed numerous challenges and opportunities for developing anti-cancer therapies. Phytochemicals have emerged as promising synergistic compounds with potential anti-cancer effects to supplement chemo- and immune-therapeutic regimens. Anti cancer synergistic effects have been investigated in the interaction between phytocompounds derived from flavonoids such as quercetin, apigenin, kaempferol, hesperidin, emodin, etc., and conventional drugs. Xanthohumol is one of the prenylated phytoflavonoid that has demonstrated key anti-cancer activities in in vitro (anti proliferation of cancer cell lines) and in vivo (animal models of xenograft tumours) studies, and has been explored from different dimensions for targeting cancer subtypes. In the last decade, xanthohumol has been investigated how it induces the anti- cancer effects at cellular and molecular levels. The different signalling cascades and targets of xanthohumol are summarized in this review. Overall, this review summarizes the current advances made in the field of natural compounds with special reference to xanthohumol and its promising anti-cancer effects to inhibit tumour progression. The present review has also discussedthe potential of xanthohumol transitioning into a leadingcandidate from nano-therapy viewpoint along with the challenges which need to be addressed for extensive preclinical and clinical anti-cancer studies.

Adenosine triphosphate is full antagonist at human P2Y(1) purinoceptors

Both agonistic and antagonistic effects have been reported for ATP at P2Y(1) purinoceptors at micromolar ligand concentrations. These conflicting data hamper specification of the true pharmacological profile as well as structural requirements for antagonistic ligands of this receptor. In this report the type of ATP activity at human P2Y(1) receptors in hP2Y(1)-1321N1 cells was revisited. In parallel, kinetics of degradation of ATP in the assay mixture was analysed. It was found that transformation of this ligand to ADP was responsible for initiation of synthesis of inositol phosphates, observed in the presence of ATP in hP2Y(1)-1321N1 cells. This agonistic effect was abolished in the presence of the triphosphate regeneration system (CP/CPK). On the other hand, if the agonistic effect caused by degradation product of ATP was taken into consideration, this ligand behaved as a full antagonist at P2Y(1) receptors and was characterized by the apparent inhibitory constant 5 microM.

Multi-Target Cytotoxic Actions of Flavonoids in Blood Cancer Cells

To date, cytotoxic effects of flavonoids in various cancer cells are well accepted. However, the intracellular signaling cascades triggered by these natural compounds remain largely unknown and elusive. In this mini- review, the multiplicity of molecular targets of flavonoids in blood cancer cells is discussed by demonstrating the involvement of various signaling pathways in induction of apoptotic responses. Although these data reveal a great potential of flavonoids for the development of novel agents against different types of hematological malignancies, the pleiotropic nature of these compounds in modulation of cellular processes and their interactions certainly need unraveling and further investigation.