Flavonoids suppress androgen-independent human prostate tumor proliferation

The Pros and Cons of Estrogens in Prostate Cancer: An Update with a Focus on Phytoestrogens

The role of estrogens in prostate cancer (PCa) is shrouded in mystery, with its actions going from angelic to devilish. The findings by Huggins and Hodges establishing PCa as a hormone-sensitive cancer have provided the basis for using estrogens in therapy. However, despite the clinical efficacy in suppressing tumor growth and the panoply of experimental evidence describing its anticarcinogenic effects, estrogens were abolished from PCa treatment because of the adverse secondary effects. Notwithstanding, research work over the years has continued investigating the effects of estrogens, reporting their pros and cons in prostate carcinogenesis. In contrast with the beneficial therapeutic effects, many reports have implicated estrogens in the disruption of prostate cell fate and tissue homeostasis. On the other hand, epidemiological data demonstrating the lower incidence of PCa in Eastern countries associated with a higher consumption of phytoestrogens support the beneficial role of estrogens in counteracting cancer development. Many studies have investigated the effects of phytoestrogens and the underlying mechanisms of action, which may contribute to developing safe estrogen-based anti-PCa therapies. This review compiles the existing data on the anti- and protumorigenic actions of estrogens and summarizes the anticancer effects of several phytoestrogens, highlighting their promising features in PCa treatment.

Effects and Mechanisms of Luteolin, a Plant-Based Flavonoid, in the Prevention of Cancers via Modulation of Inflammation and Cell Signaling Molecules

Luteolin, a flavonoid, is mainly found in various vegetables and fruits, including carrots, cabbages, onions, parsley, apples, broccoli, and peppers. Extensive research in vivo and in vitro has been performed to explore its role in disease prevention and treatment. Moreover, this compound possesses the ability to combat cancer by modulating cell-signaling pathways across various types of cancer. The studies have confirmed that luteolin can inhibit cancer-cell survival and proliferation, angiogenesis, invasion, metastasis, mTOR/PI3K/Akt, STAT3, Wnt/β-catenin, and cell-cycle arrest, and induce apoptosis. Further, scientific evidence describes that this compound plays a vital role in the up/down-regulation of microRNAs (miRNAs) in cancer therapy. This review aims to outline the anti-cancer mechanisms of this compound and its molecular targets. However, a knowledge gap remains regarding the studies on its safety and efficacy and clinical trials. Therefore, it is essential to conduct more research based on safety, efficacy, and clinical trials to explore the beneficial role of this compound in disease management, including cancer.

Apolipoprotein E3 Containing Nanodiscs as Vehicles for Transport and Targeted Delivery of Flavonoid Luteolin

Luteolin is a flavonoid that possesses multiple beneficial biological properties, such as anticancer, antioxidant, and anti-inflammatory effects. The objective of this study is to test the hypothesis that luteolin can be transported across a cell via a nanodisc delivery system and delivered to intracellular sites. Luteolin was incorporated into reconstituted high-density lipoprotein complexes made up of apolipoprotein E3 (apoE3) N-terminal domain (apoE3NT) and 1,2-dimystrioyl-sn-glycero-3-phosphocholine. ApoE3NT confers the ability on nanodiscs to traverse the plasma membrane via low-density lipoprotein receptor or scavenger receptor-B1. Physicochemical characterization revealed that the nanodiscs were 17-22 nm in diameter as demonstrated by native polyacrylamide gel electrophoresis and dynamic lightering analysis and ∼660 kDa in size, with a luteolin content of ∼4 luteolin molecules/nanodisc. Luteolin appeared to be embedded in the nonpolar core of nanodiscs, as revealed by fluorescence quenching and polarization analysis and spectroscopic characterization. The presence of luteolin did not affect the ability of apoE3NT to mediate binding and cellular uptake of luteolin containing nanodiscs in macrophages, as inferred from immunofluorescence analysis that revealed apoE- and lipid-related fluorescence as punctate perinuclear vesicles and from flow cytometry studies. Lastly, luteolin appeared to be localized in the nucleus, having escaped the lysosomes following disassembly of the nanodiscs as suggested by fluorescence spectroscopy and microscopy analyses. Taken together, nanodiscs offer the potential to effectively transport luteolin and potentially therapeutic drugs into perinuclear sites in cells, where they can be available to enter the nucleus.

Therapeutic Importance of Kaempferol in the Treatment of Cancer through the Modulation of Cell Signalling Pathways

Plant-derived flavonoids are considered natural nontoxic chemo-preventers and have been widely studied for cancer treatment in recent decades. Mostly all flavonoid compounds show significant anti-inflammatory, anticancer and antioxidant properties. Kaempferol (Kmp) is a well-studied compound and exhibits remarkable anticancer and antioxidant potential. Kmp can regulate various cancer-related processes and activities such as cell cycle, oxidative stress, apoptosis, proliferation, metastasis, and angiogenesis. The anti-cancer properties of Kmp primarily occur via modulation of apoptosis, MAPK/ERK1/2, P13K/Akt/mTOR, vascular endothelial growth factor (VEGF) signalling pathways. The anti-cancer property of Kmp has been recognized in several in-vivo and in-vitro studies which also includes numerous cell lines and animal models. This flavonoid possesses toxic activities against only cancer cells and have restricted toxicity on healthy cells. In this review, we present extensive research investigations about the therapeutic potential of Kmp in the management of different types of cancers. The anti-cancer properties of Kmp are discussed by concentration on its capability to target molecular-signalling pathway such as VEGF, STAT, p53, NF-κB and PI3K-AKT signalling pathways. The anti-cancer property of Kmf has gained a lot of attention, but the accurate action mechanism remains unclear. However, this natural compound has a great pharmacological capability and is now considered to be an alternative cancer treatment.

The Role of Heat Shock Protein 27 in Carcinogenesis and Treatment of Colorectal Cancer

The incidence of colorectal cancer (CRC) has significantly increased in recent decades, which has made this disease an important global health issue. Despite many efforts, there is no useful prognostic or diagnostic biomarker for CRC. Heat shock protein 27 (Hsp27) is one of the most studied members of the Hsp family. It has attracted particular attention in CRC pathogenesis since it is involved in fundamental cell functions for cell survival. Evidence shows that Hsp27 plays important role in CRC progression and metastasis. Hsp27 overexpression has been observed in CRC and is suggested to be associated with CRC's poor prognosis. In the present review, we focus on the current knowledge of the role of Hsp27 in CRC carcinogenesis and the underlying mechanisms. In addition, we discuss the value of targeting Hsp27 in CRC treatment.

Kaempferol, Myricetin and Fisetin in Prostate and Bladder Cancer: A Systematic Review of the Literature

Prostate and bladder cancer represent the two most frequently diagnosed genito-urinary malignancies. Diet has been implicated in both prostate and bladder cancer. Given their prolonged latency and high prevalence rates, both prostate and bladder cancer represent attractive candidates for dietary preventive measures, including the use of nutritional supplements. Flavonols, a class of flavonoids, are commonly found in fruit and vegetables and are known for their protective effect against diabetes and cardiovascular diseases. Furthermore, a higher dietary intake of flavonols was associated with a lower risk of both bladder and prostate cancer in epidemiological studies. In this systematic review, we gathered all available evidence supporting the anti-cancer potential of selected flavonols (kaempferol, fisetin and myricetin) against bladder and prostate cancer. A total of 21, 15 and 7 pre-clinical articles on bladder or prostate cancer reporting on kaempferol, fisetin and myricetin, respectively, were found, while more limited evidence was available from animal models and epidemiological studies or clinical trials. In conclusion, the available evidence supports the potential use of these flavonols in prostate and bladder cancer, with a low expected toxicity, thus providing the rationale for clinical trials that explore dosing, settings for clinical use as well as their use in combination with other pharmacological and non-pharmacological interventions.

Heat Shock Proteins 27, 70, and 110: Expression and Prognostic Significance in Colorectal Cancer

Heat shock proteins (HSPs) are evolutionarily conserved chaperones occurring in virtually all living organisms playing a key role in the maintenance of cellular homeostasis. They are constitutively expressed to prevent and repair protein damage following various physiological and environmental stressors. HSPs are overexpressed in various types of cancers to provide cytoprotective function, and they have been described to influence prognosis and response to therapy. Moreover, they have been used as a tumor marker in blood serum biochemistry and they represent a potentially promising therapeutic target. To clarify prognostic significance of two canonical HSPs (27 and 70) and less known HSP110 (previously known as HSP105) in colorectal carcinoma (CRC), we retrospectively performed HSP immunohistochemistry on tissue microarrays from formalin-fixed paraffin-embedded tumor tissue from 297 patients with known follow-up. Survival analysis (univariate Kaplan-Meier analysis with the log-rank test and multivariate Cox regression) revealed significantly shorter overall survival (OS, mean 5.54 vs. 7.07, p = 0.033) and borderline insignificantly shorter cancer specific survival (CSS, mean 6.3 vs. 7.87 years, p = 0.066) in patients with HSP70+ tumors. In the case of HSP27+ tumors, there was an insignificantly shorter OS (mean 6.36 vs. 7.13 years, p = 0.2) and CSS (mean 7.17 vs. 7.95 years, p = 0.2). HSP110 showed no significant impact on survival. Using Pearson's chi-squared test, there was a significant association of HSP27 and HSP70 expression with advanced cancer stage. HSP27+ tumors were more frequently mismatch-repair proficient and vice versa (p = 0.014), and they occurred more often in female patients and vice versa (p = 0.015). There was an enrichment of left sided tumors with HSP110+ compared to the right sided (p = 0.022). In multivariate Cox regression adjusted on the UICC stage, grade and right/left side; both HSPs 27 and 70 were not independent survival predictors (p = 0.616 & p = 0.586). In multivariate analysis, only advanced UICC stage (p = 0) and right sided localization (p = 0.04) were independent predictors of worse CSS. In conclusion, from all three HSPs examined in our study, only HSP70 expression worsened CRC prognosis, although stage-dependent. The contribution of this article may be seen as a large survival analysis of HSPs 27 and 70 and the largest analysis of HSP110 described in CRC.

Bioassay-Guided Identification of the Antiproliferative Compounds of Cissus trifoliata and the Transcriptomic Effect of Resveratrol in Prostate Cancer Pc3 Cells

The bioassay-guided fractionation of a CHCl₃-MeOH extract from the stems of Cissus trifoliata identified an active fraction against PC3 prostate cancer cells. The treatment for 24 h showed an 80% reduction in cell viability (p ≤ 0.05) by a WST-1 assay at a concentration of 100 μg/mL. The HPLC-QTOF-MS analysis of the fraction showed the presence of coumaric and isoferulic acids, apigenin, kaempferol, chrysoeriol, naringenin, ursolic and betulinic acids, hexadecadienoic and octadecadienoic fatty acids, and the stilbene resveratrol. The exposure of PC3 cells to resveratrol (IC₂₅ = 23 μg/mL) for 24 h induced significant changes in 847 genes (Z-score ≥ ±2). The functional classification tool of the DAVID v6.8 platform indicates that the underlying molecular mechanisms against the proliferation of PC3 cells were associated (p ≤ 0.05) with the process of differentiation and metabolism. These findings provide experimental evidence suggesting the potential of C. trifoliata as a promising natural source of anticancer compounds.

Small molecule inhibitors and stimulators of inducible nitric oxide synthase in cancer cells from natural origin (phytochemicals, marine compounds, antibiotics)

Nitric oxide synthases (NOS) are a family of isoforms, which generate nitric oxide (NO). NO is one of the smallest molecules in nature and acts mainly as a potent vasodilator. It participates in various biological processes ranging from physiological to pathological conditions. Inducible NOS (iNOS, NOS2) is a calcium-independent and inducible isoform. Despite high iNOS expression in many tumors, the role of iNOS is still unclear and complex with both enhancing and prohibiting actions in tumorigenesis. Nature presents a broad variety of natural stimulators and inhibitors, which may either promote or inhibit iNOS response. In the present review, we give an overview of iNOS-modulating agents with a special focus on both natural and synthetic molecules and their effects in related biological processes. The role of iNOS in physiological and pathological conditions is also discussed.

The Natural Flavonoid Naringenin Elicits Analgesia through Inhibition of NaV1.8 Voltage-Gated Sodium Channels

Naringenin (2S)-5,7-dihydroxy-2-(4-hydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-4-one is a natural flavonoid found in fruits from the citrus family. Because (2S)-naringenin is known to racemize, its bioactivity might be related to one or both enantiomers. Computational studies predicted that (2R)-naringenin may act on voltage-gated ion channels, particularly the N-type calcium channel (CaV2.2) and the NaV1.7 sodium channel-both of which are key for pain signaling. Here we set out to identify the possible mechanism of action of naringenin. Naringenin inhibited depolarization-evoked Ca²⁺ influx in acetylcholine-, ATP-, and capsaicin-responding rat dorsal root ganglion (DRG) neurons. This was corroborated in electrophysiological recordings from DRG neurons. Pharmacological dissection of each of the voltage-gated Ca²⁺ channels subtypes could not pinpoint any selectivity of naringenin. Instead, naringenin inhibited NaV1.8-dependent and tetrodotoxin (TTX)-resistant while sparing tetrodotoxin sensitive (TTX-S) voltage-gated Na⁺ channels as evidenced by the lack of further inhibition by the NaV1.8 blocker A-803467. The effects of the natural flavonoid were validated ex vivo in spinal cord slices where naringenin decreased both the frequency and amplitude of sEPSC recorded in neurons within the substantia gelatinosa. The antinociceptive potential of naringenin was evaluated in male and female mice. Naringenin had no effect on the nociceptive thresholds evoked by heat. Naringenin's reversed allodynia was in mouse models of postsurgical and neuropathic pain. Here, driven by a call by the National Center for Complementary and Integrative Health's strategic plan to advance fundamental research into basic biological mechanisms of the action of natural products, we advance the antinociceptive potential of the flavonoid naringenin.

Targeting Heat Shock Protein 27 in Cancer: A Druggable Target for Cancer Treatment?

Heat shock protein 27 (HSP27), induced by heat shock, environmental, and pathophysiological stressors, is a multi-functional protein that acts as a protein chaperone and an antioxidant. HSP27 plays a significant role in the inhibition of apoptosis and actin cytoskeletal remodeling. HSP27 is upregulated in many cancers and is associated with a poor prognosis, as well as treatment resistance, whereby cells are protected from therapeutic agents that normally induce apoptosis. This review highlights the most recent findings and role of HSP27 in cancer, as well as the strategies for using HSP27 inhibitors for therapeutic purposes.

Effect of Aslagh Capsule, a Traditional Compound Herbal Product on Oligomenorrhea in Patients with Polycystic Ovary Syndrome: A Three-Arm, Open-label, Randomized, Controlled Trial

Background:

Oligomenorrhea is a common complaint in patients with polycystic ovary syndrome (PCOS). There are some useful medicinal recommendations such as Aslagh product (include fennel fruits, carrot seeds, chaste tree fruits) in Iranian traditional medicine for the treatment of oligomenorrhea in PCOS. Hence, the present investigation was designed to compare Aslagh capsule with metformin on the oligomenorrhea.

Materials and Methods:

One hundred fifty women aged between 18-43 years with oligomenorrhea due to PCOS were randomly divided into Aslagh, metformin, and Aslagh + metformin groups. The occurrence of menstrual bleeding was considered as the primary outcome. Menstrual cyclicity, duration, and volume of the bleeding were also evaluated.

Results:

Occurrence of menstrual bleeding was 87.2% in all patients, with no significant difference between the three groups (P> 0.05). Menstrual cyclicity significantly improved from baseline in Aslagh and Aslagh + metformin groups (P=0.02). Duration of menstrual bleeding was significantly higher in Aslagh group in the first and the second menstrual bleeding cycle compared to the other two groups (P<0.05). No significant change was observed in the volume of the bleeding after the intervention in any of the three groups. The occurrence of menstrual bleeding in Aslagh group was significantly (P=0.03) higher than the other two groups in the fourth month (drug-free period).

Conclusion:

Aslagh capsule showed beneficial effects similar to metformin in the treatment of oligomenorrhea in PCOS women and could be suggested for use as an alternative treatment in these patients.

Synthesis, Cancer-Selective Antiproliferative and Apoptotic Effects of Some (±)-Naringenin Cycloaminoethyl Derivatives

Naringenin is a naturally occurring flavonoid and due to its broad spectrum of biological activities, including anticancer properties, has attracted scientific attention in recent years. To contribute to these studies, we synthesized some new (±)-naringenin cyclic aminoethyl derivatives, analyzed the cytotoxic and anti-proliferative properties of them via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, and mitochondrial apoptosis signaling response and gene expressions belong to caspase-3 depended apoptosis as biomarkers in both healthy and cancer cell lines. Our results suggest that some of our naringenin derivatives are potential anticancer agents with a selective death potential and targeting properties for mitochondrial apoptosis signaling against at least human cervix and breast cancer.

Plant flavone apigenin: An emerging anticancer agent

Research in cancer chemoprevention provides convincing evidence that increased intake of vegetables and fruits may reduce the risk of several human malignancies. Phytochemicals present therein provide beneficial anti-inflammatory and antioxidant properties that serve to improve the cellular microenvironment. Compounds known as flavonoids categorized anthocyanidins, flavonols, flavanones, flavonols, flavones, and isoflavones have shown considerable promise as chemopreventive agents. Apigenin (4', 5, 7-trihydroxyflavone), a major plant flavone, possessing antioxidant, anti-inflammatory, and anticancer properties affecting several molecular and cellular targets used to treat various human diseases. Epidemiologic and case-control studies have suggested apigenin reduces the risk of certain cancers. Studies demonstrate that apigenin retain potent therapeutic properties alone and/or increases the efficacy of several chemotherapeutic drugs in combination on a variety of human cancers. Apigenin's anticancer effects could also be due to its differential effects in causing minimal toxicity to normal cells with delayed plasma clearance and slow decomposition in liver increasing the systemic bioavailability in pharmacokinetic studies. Here we discuss the anticancer role of apigenin highlighting its potential activity as a chemopreventive and therapeutic agent. We also highlight the current caveats that preclude apigenin for its use in the human trials.

Targeting Heat Shock Proteins in Cancer: A Promising Therapeutic Approach

Heat shock proteins (HSPs) are a large family of chaperones that are involved in protein folding and maturation of a variety of "client" proteins protecting them from degradation, oxidative stress, hypoxia, and thermal stress. Hence, they are significant regulators of cellular proliferation, differentiation and strongly implicated in the molecular orchestration of cancer development and progression as many of their clients are well established oncoproteins in multiple tumor types. Interestingly, tumor cells are more HSP chaperonage-dependent than normal cells for proliferation and survival because the oncoproteins in cancer cells are often misfolded and require augmented chaperonage activity for correction. This led to the development of several inhibitors of HSP90 and other HSPs that have shown promise both preclinically and clinically in the treatment of cancer. In this article, we comprehensively review the roles of some of the important HSPs in cancer, and how targeting them could be efficacious, especially when traditional cancer therapies fail.

Quercetin Targets hnRNPA1 to Overcome Enzalutamide Resistance in Prostate Cancer Cells

Prostate cancer remains dependent on androgen receptor signaling even after castration. Aberrant androgen receptor signaling in castration-resistant prostate cancer is mediated by mechanisms such as alterations in the androgen receptor and activation of interacting signaling pathways. Clinical evidence confirms that resistance to the next-generation antiandrogen, enzalutamide, may be mediated to a large extent by alternative splicing of the androgen receptor to generate constitutively active splice variants such as AR-V7. The splice variants AR-V7 and AR^v567es have been implicated in the resistance to not only enzalutamide, but also to abiraterone and other conventional therapeutics such as taxanes. Numerous studies, including ours, suggest that splicing factors such as hnRNPA1 promote the generation of AR-V7, thus contributing to enzalutamide resistance in prostate cancer cells. In the present study, we discovered that quercetin, a naturally occurring polyphenolic compound, reduces the expression of hnRNPA1, and consequently, that of AR-V7. The suppression of AR-V7 by quercetin resensitizes enzalutamide-resistant prostate cancer cells to treatment with enzalutamide. Our results indicate that quercetin downregulates hnRNPA1 expression, downregulates the expression of AR-V7, antagonizes androgen receptor signaling, and resensitizes enzalutamide-resistant prostate cancer cells to enzalutamide treatment in vivo in mouse xenografts. These findings demonstrate that suppressing the alternative splicing of the androgen receptor may have important implications in overcoming the resistance to next-generation antiandrogen therapy. Mol Cancer Ther; 16(12); 2770-9. ©2017 AACR.

Expression of prostate stem cell antigen is downregulated during flavonoid-induced cytotoxicity in prostate cancer cells

Prostate stem cell antigen (PSCA) is expressed in the majority of prostate cancer cases and may be a potential therapeutic target in the treatment of prostate cancer. The present study evaluated the cytotoxicity of three flavonoids (genistein, luteolin and quercetin) towards DU145 prostate cancer cells, and investigated the effect of these flavonoids on PSCA expression. The results demonstrated that genistein, luteolin and quercetin inhibited the growth of DU145 cells in a dose-dependent manner (P<0.05) and induced morphological changes characteristic of apoptosis in DU145 cells. Flow cytometry analysis also indicated that the flavonoids induced S phase cycle arrest in DU145 cells. Notably, it was observed that expression of PSCA was inhibited at the mRNA (P<0.05) and protein levels in DU145 cells following flavonoid treatment compared with the control. These results suggest that flavonoids may be potential therapeutic agents in the treatment and prevention of prostate cancer.

Identification of androgen receptor antagonists: In vitro investigation and classification methodology for flavonoid

A tremendous gap exists between the number of potential endocrine disrupting chemicals (EDCs) possibly in the environment and the limitation of traditional regulatory testing. In this study, the anti-androgenic potencies of 21 flavonoids were analyzed in vitro, and another 32 flavonoids from the literature were selected as additional chemicals. Molecular dynamic simulations were employed to obtain four different separation approaches based on the different behaviors of ligands and receptors during the process of interaction. Specifically, ligand-receptor complex which highlighted the discriminating features of ligand escape or retention via "mousetrap" mechanism, hydrogen bonds formed during simulation times, ligand stability and the stability of the helix-12 of the receptor were investigated. Together, a methodology was generated that 87.5% of flavonoids could be discriminated as active versus inactive antagonists, and over 90% inactive antagonists could be filtered out before QSAR study. This methodology could be used as a "proof of concept" to identify inactive anti-androgenic flavonoids, as well could be beneficial for rapid risk assessment and regulation of multiple new chemicals for androgenicity.

Synergistic Effects of Dietary Natural Products as Anti-Prostate Cancer Agents

This review is to describe synergistic effects of various combinations of dietary natural products including curcumin, quercetin, soybean isoflavones, silibinin, and EGCG that have potential for the treatment of prostate cancer. These data can provide valuable insights into the future rational design and development of synergistic and/or hybrid agents for potential treatment of prostate cancer.

New Sulphated Flavonoids from Wissadula periplocifolia (L.) C. Presl (Malvaceae)

Wissadula periplocifolia (L.) C. Presl (Malvaceae) is commonly used in Brazil to treat bee stings and as an antiseptic. The antioxidant properties of its extracts have been previously demonstrated, thus justifying a phytochemical investigation for its bioactive phenolic constituents. This has yielded five new sulphated flavonoids: 8-O-sulphate isoscutellarein (yannin) (1a); 4′-O-methyl-7-O-sulphate isoscutellarein (beltraonin) (1b); 7-O-sulphate acacetin (wissadulin) (2a); 4′-O-methyl-8-O-sulphate isoscutellarein (caicoine) (2b) and 3′-O-methyl-8-O-sulphate hypolaetin (pedroin) (3b) along with the known flavonoids 7,4′-di-O-methyl-8-O-sulphate isoscutellarein (4), acacetin, apigenin, isoscutellarein, 4′-O-methyl isoscutellarein, 7,4′-di-O-methylisoscutellarein, astragalin and tiliroside. The compounds were isolated by column chromatography and identified by NMR (¹H, ¹³C, HMQC, HMBC and COSY) and LC-HRMS. A cell based assay was carried out to evaluate the preliminary cytotoxic properties of the flavonoids against UVW glioma and PC-3M prostate cancer cells as well as non-tumour cell lines. The obtained results showed that acacetin, tiliroside, a mixture of acacetin + apigenin and the sulphated flavonoids 2a + 2b exhibited inhibitory activity against at least one of the cell lines tested. Among the tested flavonoids acacetin and tiliroside showed lower IC₅₀ values, presenting promising antitumor effects.

Anti-androgenic effects of flavonols in prostate cancer

Dietary-derived agents, such as the flavonoids, are of particular interest for prostate cancer (PCa) chemoprevention as they may offer a favourable safety and side-effect profile. An agent that demonstrates action on the androgen receptor (AR) axis may have value for preventing or treating castrate-resistant PCa. Four main flavonols - quercetin, myricetin, kaempferol, and fisetin - have been demonstrated in laboratory studies to have chemopreventive action in both castrate-resistant and castrate-sensitive PCa models. Mechanisms of flavonol action on the AR axis in PCa have been proposed to be inhibition of the 5α-reductase enzymes, direct androgen competition, suppression of the AR complex and transactivation by coregulators such as c-Jun, Sp1, and the PI3K/Akt pathway. It is, however, still unclear with current levels of evidence whether AR axis-mediated effects can fully account for the flavonols' chemopreventive action.

FV-429 induces apoptosis and inhibits glycolysis by inhibiting Akt-mediated phosphorylation of hexokinase II in MDA-MB-231 cells

In this study, the anticancer effect of a newly synthesized flavonoid FV-429, against human breast cancer MDA-MB-231 cells, and the underlying mechanisms were investigated. FV-429 triggered the apoptosis and simultaneously inhibited the glycolysis of MDA-MB-231 cells. Both the HK II activity and its level in mitochondria were significantly down regulated by FV-429. Moreover, FV-429 weakened the interaction between HKII and VDAC, stimulated the detachment of HK II from the mitochondria, and resulted in the opening of the mitochondrial permeability transition pores. Thus FV-429 induced the mitochondrial-mediated apoptosis, showing increased Bax/Bcl-2 ratio, loss of mitochondrial membrane potential (MMP) and activation of caspase-3 and -9, cytochrome c (Cyt c) release, and apoptosis inducing factor (AIF) transposition. Further research revealed that the phosphorylation of mitochondrial HKII via Akt was responsible for the dissociation of HKII and the decreased HKII activity induced by FV-429. Taken together, FV-429 inhibited the phosphorylation of HKII, down-regulated its activity, and stimulated the release of HKII from the mitochondria, resulting the inhibited glycolysis and mitochondrial-mediated apoptosis. The studies provide a molecular basis for the development of flavonoid compounds as novel anticancer agents for breast cancer. © 2015 Wiley Periodicals, Inc.

Isolation, purification and identification of etiolation substrate from fresh-cut Chinese water-chestnut (Eleocharis tuberosa)

Fresh cut Chinese water-chestnut is a popular ready-to-eat fresh-cut fruit in China. However, it is prone to etiolation and the chemicals responsible for this process are not known yet. To address this problem, we extracted phytochemicals from etiolated Chinese water-chestnut and separated them using MPLC and column chromatography. Four compounds were obtained and their structures were determined by interpretation of UV, TLC, HPLC and NMR spectral data and by comparison with reported data. We identified these compounds as eriodictyol, naringenin, sucrose and ethyl D-glucoside. Among those, eriodictyol and naringenin were both isolated for the first time in fresh-cut Chinese water-chestnut and are responsible for the yellowing of this fruit cutting.

Luteolin is effective in the non-small cell lung cancer model with L858R/T790M EGF receptor mutation and erlotinib resistance

BACKGROUND AND PURPOSE

Non-small cell lung cancer (NSCLC) is one of the most commonly diagnosed malignancies in the world. Small-molecule inhibitors of the EGF receptor's tyrosine kinase domain (TKIs), including gefitinib and erlotinib, have been widely used for treating NSCLC. Unfortunately, nearly all patients after initially experiencing a marked improvement while on these drugs, eventually progress to acquire resistance to TKIs. Because there is no effective therapeutic strategy to treat TKI-resistant NSCLC, we evaluated the effects of luteolin, a naturally occurring flavanoid, on T790M mutant NSCLC cells.

EXPERIMENTAL APPROACH

The effect of luteolin on the viability of NSCLC and normal cell lines was investigated using the Cell Counting Kit-8 (CCK-8) assay. Luteolin-induced apoptosis was assessed by bivariate FITC-annexin V/PI assay, and Western blots were used to measured apoptotic proteins. Co-immunoprecipitation was used to determine the effect of luteolin on the interaction between Hsp90 and mutant EGF receptors. The effect of luteolin on the Akt/mTOR pathway was studied using Western blotting analysis. Its anti-tumour efficacy in vivo was examined in a mouse xenograft model.

KEY RESULTS

Luteolin exerted significant anti-tumourigenic effects on the EGF receptor L858R/T790M mutation and erlotinib-resistant NSCLC both at the cellular and animal levels. Mechanistically, luteolin induced degradation of the EGF receptor by inhibiting the association of Hsp90 with the mutant EGF receptor, and, therefore, prevented PI3K/Akt/mTOR signalling, which resulted in NSCLC cell apoptosis.

CONCLUSION AND IMPLICATIONS

Luteolin may be a potential candidate for NSCLC therapy, especially for treatment of patients with acquired erlotinib-resistant NSCLC.

Cytotoxicity of dietary flavonoids on different human cancer types

Flavonoids are ubiquitous in nature. They are also in food, providing an essential link between diet and prevention of chronic diseases including cancer. Anticancer effects of these polyphenols depend on several factors: Their chemical structure and concentration, and also on the type of cancer. Malignant cells from different tissues reveal somewhat different sensitivity toward flavonoids and, therefore, the preferences of the most common dietary flavonoids to various human cancer types are analyzed in this review. While luteolin and kaempferol can be considered as promising candidate agents for treatment of gastric and ovarian cancers, respectively, apigenin, chrysin, and luteolin have good perspectives as potent antitumor agents for cervical cancer; cells from main sites of flavonoid metabolism (colon and liver) reveal rather large fluctuations in anticancer activity probably due to exposure to various metabolites with different activities. Anticancer effect of flavonoids toward blood cancer cells depend on their myeloid, lymphoid, or erythroid origin; cytotoxic effects of flavonoids on breast and prostate cancer cells are highly related to the expression of hormone receptors. Different flavonoids are often preferentially present in certain food items, and knowledge about the malignant tissue-specific anticancer effects of flavonoids could be purposely applied both in chemoprevention as well as in cancer treatment.

Kaempferol, a potential cytostatic and cure for inflammatory disorders

Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many edible plants (e.g., tea, broccoli, cabbage, kale, beans, endive, leek, tomato, strawberries, and grapes) and in plants or botanical products commonly used in traditional medicine (e.g., Ginkgo biloba, Tilia spp, Equisetum spp, Moringa oleifera, Sophora japonica and propolis). Its anti-oxidant/anti-inflammatory effects have been demonstrated in various disease models, including those for encephalomyelitis, diabetes, asthma, and carcinogenesis. Moreover, kaempferol act as a scavenger of free radicals and superoxide radicals as well as preserve the activity of various anti-oxidant enzymes such as catalase, glutathione peroxidase, and glutathione-S-transferase. The anticancer effect of this flavonoid is mediated through different modes of action, including anti-proliferation, apoptosis induction, cell-cycle arrest, generation of reactive oxygen species (ROS), and anti-metastasis/anti-angiogenesis activities. In addition, kaempferol was found to exhibit its anticancer activity through the modulation of multiple molecular targets including p53 and STAT3, through the activation of caspases, and through the generation of ROS. The anti-tumor effects of kaempferol have also been investigated in tumor-bearing mice. The combination of kaempferol and conventional chemotherapeutic drugs produces a greater therapeutic effect than the latter, as well as reduces the toxicity of the latter. In this review, we summarize the anti-oxidant/anti-inflammatory and anticancer effects of kaempferol with a focus on its molecular targets and the possible use of this flavonoid for the treatment of inflammatory diseases and cancer.

Synthesis and anticancer activity of new flavonoid analogs and inconsistencies in assays related to proliferation and viability measurements

Flavonoids have been studied intensely for their ability to act as anti-carcinogenic, anti-inflammatory, anti-viral and anti-aging agents and are often marketed as supplements related to their anti-inflammatory activity. Previous studies have primarily focused on the effects of polar natural flavonoids. We examined the activity of novel hydrophobic and lipophilic flavonols against human DU-145 and PC-3 prostate cancer cell lines. All flavonol analogs were more active than the naturally occurring flavonols quercetin, kaempferol, kaempferide and galangin. The most potent analogs were 6.5-fold more active against DU-145 and PC-3 cells than quercetin and fell within the biologically relevant concentration range (low micromolar). We also evaluated the potential toxic effects of flavonol analogs on normal cells, an assessment that has frequently been ignored when studying the anticancer effects of flavonoids. During these analyses, we discovered that various metabolic and DNA staining assays were unreliable methods for assessing cell viability of flavonoids. Flavonoids reduce colorimetric dyes such as MTT and Alamar Blue in the absence of cells. We showed that flavonol-treated prostate cancer cells were stained less intensely with crystal violet than untreated cells at non-toxic concentrations. The trypan blue exclusion assay was selected as a reliable alternative for measuring cell viability.

Site-specific anticancer effects of dietary flavonoid quercetin

Food-derived flavonoid quercetin, widely distributed in onions, apples, and tea, is able to inhibit growth of various cancer cells indicating that this compound can be considered as a good candidate for anticancer therapy. Although the exact mechanism of this action is not thoroughly understood, behaving as antioxidant and/or prooxidant as well as modulating different intracellular signalling cascades may all play a certain role. Such inhibitory activity of quercetin has been shown to depend first of all on cell lines and cancer types; however, no comprehensive site-specific analysis of this effect has been published. In this review article, cytotoxicity constants of quercetin measured in various human malignant cell lines of different origin were compiled from literature and a clear cancer selective action was demonstrated. The most sensitive malignant sites for quercetin revealed to be cancers of blood, brain, lung, uterine, and salivary gland as well as melanoma whereas cytotoxic activity was higher in more aggressive cells compared to the slowly growing cells showing that the most harmful cells for the organism are probably targeted. More research is needed to overcome the issues of poor water solubility and relatively low bioavailability of quercetin as the major obstacles limiting its clinical use.

Alleviation of podophyllotoxin toxicity using coexisting flavonoids from Dysosma versipellis

Podophyllotoxin (POD) is a lignan-type toxin existing in many herbs used in folk medicine. Until now, no effective strategy is available for the management of POD intoxication. This study aims to determine the protective effects of flavonoids (quercetin and kaempferol) on POD-induced toxicity. In Vero cells, both flavonoids protected POD-induced cytotoxicity by recovering alleviating G2/M arrest, decreasing ROS generation and changes of membrane potential, and recovering microtubule structure. In Swiss mice, the group given both POD and flavonoids group had significantly lower mortality rate and showed less damages in the liver and kidney than the group given POD alone. As compared to the POD group, the POD plus flavonoids group exhibited decreases in plasma transaminases, alkaline phosphatase, lactate dehydrogenase, plasma urea, creatinine and malondialdehyde levels, and increases in superoxide dismutase and glutathione levels. Histological examination of the liver and kidney showed less pathological changes in the treatment of POD plus flavonoids group. The protective mechanisms were due to the antioxidant activity of flavonoids against the oxidative stress induced by POD and the competitive binding of flavonoids against POD for the same colchicines-binding sites. The latter binding was confirmed by the tubulin assembly assay in combination with molecular docking analyses. In conclusion, this study for the first time demonstrated that the coexisting flavonoids have great protective effects against the POD toxicity, and results of this study highlighted the great potential of searching for effective antidotes against toxins based on the pharmacological clues.

Luteolin induced-growth inhibition and apoptosis of human esophageal squamous carcinoma cell line Eca109 cells in vitro

Luteolin is a plant flavonoid which exhibits anti-oxidative, anti-inflammatory and anti-tumor effects. However, the antiproliferative potential of luteolin is not fully understood. In this study, we investigated the effect of luteolin on cell cycling and apoptosis in human esophageal squamous carcinoma cell line Eca109 cells. MTT assays showed that luteolin had obvious cytotoxicity on Eca109 with an IC50 of 70.7±1.72 μM at 24 h. Luteolin arrested cell cycle progression in the G0/G1 phase and prevented entry into S phase in a dose- and time-dependent manner. as assessed by FCM. Luteolin induced apoptosis of Eca109 cells was demonstrated by AO/EB staining assay and annexin V-FITC/PI staining. Moreover, luteolin downregulated the expression of cyclin D1, survivin and c-myc, and it also upregulated the expression of p53, in line with the fact that luteolin was able to inhibit Eca109 cell proliferation.

Naringenin (citrus flavonone) induces growth inhibition, cell cycle arrest and apoptosis in human hepatocellular carcinoma cells

Search for new substances with antiproliferative activity and apoptosis inducing potential towards HepG2 cells is important since HCC is notoriously resistant to conventional chemotherapy. Dietary phytochemicals with significant anti-proliferative and apoptosis inducing potential are considered as agents promising for cancer therapy. Naringenin, a common dietary flavonoid abundantly present in fruits and vegetables, is believed to possess strong cytotoxic activity in numerous types of cancer cells. However, the detailed molecular mechanisms of its antiproliferative effects and apoptosis induction are still unclear. In this study, we investigated antiproliferative and apoptosis-inducing effect of naringenin in human hepatocellular carcinoma HepG2 cells. Naringenin was shown to inhibit the proliferation of HepG2 cells resulted partly from an accumulation of cells in the G0/G1 and G2/M phase of the cell cycle. Naringenin induced a rapid accumulation of p53, which might account for the naringenin-induced G0/G1 and G2/M phase arrests in Hep G2 cells. In addition, naringenin have been shown to induce apoptosis as evidenced by nuclei damage and increased proportion of apoptotic cells detected by flow cytometry analysis. Naringenin triggered the mitochondrial-mediated apoptosis pathway as shown by an increased ratio of Bax/Bcl-2, subsequent release of cytochrome C, and sequential activation of caspase-3. Our results showed that naringenin had inhibitory effect on the growth of HepG2 cell line through inhibition of cell proliferation and apoptosis induction. The elucidation of the drug targets of naringenin on inhibition of tumor cells growth should enable further development of naringenin for liver cancer therapy.

Heat shock proteins 27, 40, and 70 as combinational and dual therapeutic cancer targets

The heat shock proteins are essential players in the development of cancer and they are prime therapeutic targets. Targeting multiple hsps in dual therapies decreases the likelihood of drug resistance compared to utilizing mono-therapies. Further, employing an hsp inhibitor in combination with another therapy has proven clinically successful. Examples of efficacious strategies include the inhibition of hsp27, which prevents protein aggregation, controlling hsp40's role as an ATPase modulator, and inhibiting hsp70 from acting as a molecular chaperone. While hsp40 therapies are just in the beginning stages, hsp27 and hsp70 therapies have been successfully used in dual inhibition treatments with hsp90 inhibitors and in combinational therapy with antineoplastic drugs. Both dual and combinatorial therapies show encouraging results when used in treating chemotherapeutically resistant diseases.

Tebrophen--an old polyphenol drug with anticancer potential

In vitro high-throughput screening was carried out in order to detect new activities for old drugs and to select compounds for the drug development process comprising new indications. Tebrophen, a known antiviral drug, was found to inhibit activities on inflammation and cancer related targets. In primary screening this semisynthetic halogenated polyphenol was identified to inhibit the activities of kinases ZAP-70 and Lck (IC₅₀ 0.34 µM and 16 µM, respectively), as well as hydrolase DPPIV (at 80 µM 41% inhibition). Next, it showed no cytotoxic effects on standard cell lines within 24 h. However, tebrophen slowed propagation of breast cancer (MDA-MB-231), osteosarcoma (U2OS) and cervical carcinoma (HeLa), through at least 35 population doublings in a dose-dependent manner. It completely stopped the division of the prostate cancer (PC3) cell line at 50 µM concentration and the cells entered massive cell death in less than 20 days. On the other hand, tebrophen did not influence the growth of normal fibroblasts. According to the measured oxidative burst and estimated in silico parameters its direct antioxidative ability is limited. The obtained results indicate that tebrophen can be considered a promising lead molecule for generating more soluble derivatives with specific anticancer efficacy.

Quercetin increased the antiproliferative activity of green tea polyphenol (-)-epigallocatechin gallate in prostate cancer cells

We previously demonstrated that 50% of (-)-epigallocatechin gallate (EGCG) was present in methylated form (4″-MeEGCG) in human prostate tissue, which is less bioactive. We therefore investigated whether quercetin, a natural inhibitor of catechol-O-methyl transferase (COMT), will inhibit EGCG methylation leading to enhanced antiproliferative activity of EGCG in prostate cancer cells. Incubation with both quercetin and EGCG for 2 h increased the cellular concentrations of EGCG by 4- to 8-fold and 6- to 10-fold in androgen-independent PC-3 cells and androgen-dependent LNCaP cells, respectively. Concurrently, the percent of 4″-MeEGCG in the total EGCG was decreased from 39% to 15% in PC-3 cells and from 61% to 38% in LNCaP cells. Quercetin and EGCG in combination synergistically inhibited cell proliferation, caused cell cycle arrest, and induced apoptosis in PC-3 cells. In LNCaP cells, EGCG and quercetin exhibited a stronger antiproliferative activity leading to an additive effect. The synergistic effect of these 2 agents in PC-3 cells could be based on the fact that EGCG primarily inhibited COMT activity, whereas quercetin reduced the amount of COMT protein. In summary, quercetin combined with EGCG in vitro demonstrated enhanced inhibition of cell proliferation by increasing the intracellular concentration of EGCG and decreasing EGCG methylation.

Flavonoids: A versatile source of anticancer drugs

An exponential increase in the number of studies investigating how different components of the diet interact at the molecular and cellular level to determine the fate of a cell has been witnessed. In search for anticancer drugs compelling data from laboratories, epidemiologic investigations, and human clinical trials showed that flavonoids have important effects on cancer chemoprevention and chemotherapy. In many molecular mechanisms of action for prevention against cancer, flavonoids play a major role by interacting between different types of genes and enzymes. Many mechanisms of action have been identified, including carcinogen inactivation, antiproliferation, cell cycle arrest, induction of apoptosis, inhibition of angiogenesis, antioxidation, and reversal of multidrug resistance or a combination of these mechanisms. This review focuses on the anticancer activity of flavonoids as well as their molecular mechanisms, including the treatment of mammary and prostate cancer. This review also highlights some advanced derivatives of flavonoids, which play an important role against cancer.