Quercetin as a potential modulator of P-glycoprotein expression and function in cells of human pancreatic carcinoma line resistant to daunorubicin

Phytochemicals for the prevention and treatment of pancreatic cancer: Current progress and future prospects

Pancreatic cancer is the third leading cause of cancer-related deaths in the United States, owing to its aggressive nature and suboptimal treatment options, emphasizing the need for novel therapeutic approaches. Emerging studies have exhibited promising results regarding the therapeutic utility of plant-derived compounds (phytochemicals) in pancreatic cancer. The purpose of this review is to evaluate the potential of phytochemicals in the treatment and prevention of pancreatic cancer. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses was applied to collect articles for this review. Scholarly databases, including PubMed, Scopus and ScienceDirect, were queried for relevant studies using the following keywords: phytochemicals, phenolics, terpenoids, alkaloids, sulfur-containing compounds, in vitro, in vivo, clinical studies, pancreatic cancer, tumour, treatment and prevention. Aggregate results pooled from qualified studies indicate phytochemicals can inhibit pancreatic cancer cell growth or decrease tumour size and volume in animal models. These effects have been attributed to various mechanisms, such as increasing proapoptotic factors, decreasing antiapoptotic factors, or inducing cell death and cell cycle arrest. Notable signalling pathways modulated by phytochemicals include the rat sarcoma/mitogen activated protein kinase, wingless-related integration site/β-catenin and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signal transduction pathways. Clinically, phytochemicals have been found to increase survival while being well-tolerated and safe, though research is scarce. While these promising results have produced great interest in this field, further in-depth studies are required to characterize the anticancer activities of phytochemicals before they can be utilized to prevent or treat pancreatic cancer in clinical practice.

A New ABCB1 Inhibitor Enhances the Anticancer Effect of Doxorubicin in Both In Vitro and In Vivo Models of NSCLC

In tumors, the multi drug resistance phenomenon may occur through the efflux of chemotherapeutic drugs out of cancer cells, impeding their accumulation, and eventually reducing their toxicity. This process is mediated by transporters overexpressed in the plasma membranes of tumor cells, among which is the P-glycoprotein/multidrug resistance 1/ATP-binding cassette B1 (P-gp/MDR1/ABCB1). The aim of this study was to explore the effect of a new molecule, called AIF-1, on ABCB1 activity. In a cellular model of non-small cell lung cancer (NSCLC), AIF-1 significantly inhibited ABCB1 activity, which was evaluated by the fluorimetric measurement of the intracellular accumulation of calcein. AIF-1 also significantly increased the intracellular content of doxorubicin, which was evaluated by confocal microscopy and LC-MS/MS analysis. This effect translated to higher cytotoxicity of doxorubicin and reduced cellular proliferation. Finally, in a murine xenograft model, the tumor volume increased by 267% and 148% on average in mice treated with vehicle and doxorubicin alone, respectively. After the co-administration of doxorubicin with AIF-1, tumor volume increased by only 13.4%. In conclusion, these results suggest enhancement of the efficacy of the chemotherapeutic drug doxorubicin by AIF-1, laying the basis for the future development of new ABCB1 inhibitors for tumor treatment.

Why Do Dietary Flavonoids Have a Promising Effect as Enhancers of Anthracyclines? Hydroxyl Substituents, Bioavailability and Biological Activity

Anthracyclines currently play a key role in the treatment of many cancers, but the limiting factor of their use is the widespread phenomenon of drug resistance and untargeted toxicity. Flavonoids have pleiotropic, beneficial effects on human health that, apart from antioxidant activity, are currently considered small molecules-starting structures for drug development and enhancers of conventional therapeutics. This paper is a review of the current and most important data on the participation of a selected series of flavonoids: chrysin, apigenin, kaempferol, quercetin and myricetin, which differ in the presence of an additional hydroxyl group, in the formation of a synergistic effect with anthracycline antibiotics. The review includes a characterization of the mechanism of action of flavonoids, as well as insight into the physicochemical parameters determining their bioavailability in vitro. The crosstalk between flavonoids and the molecular activity of anthracyclines discussed in the article covers the most important common areas of action, such as (1) disruption of DNA integrity (genotoxic effect), (2) modulation of antioxidant response pathways, and (3) inhibition of the activity of membrane proteins responsible for the active transport of drugs and xenobiotics. The increase in knowledge about the relationship between the molecular structure of flavonoids and their biological effect makes it possible to more effectively search for derivatives with a synergistic effect with anthracyclines and to develop better therapeutic strategies in the treatment of cancer.

Quercetin improves pancreatic cancer chemo-sensitivity by regulating oxidative-inflammatory networks

Chemotherapy is the main method for controlling pancreatic cancer metastasis but the prevalent chemotherapy resistance limits its utilization. The response of oxidation and inflammation often promotes pancreatic cancer progression and chemo-resistance. It is critical to explore the potential natural products with few side effects to control inflammatory responses and understand the related mechanisms. Quercetin is a flavonoid widely found in numerous vegetables, fruits, and foods and is thought to have antioxidant and anti-inflammatory properties, which may be associated with improvement of chemotherapy sensitivity during pancreatic cancer treatment. Quercetin may sensitize pancreatic cancer cells to the chemotherapeutic agents, including bromodomain and extraterminal domain inhibitors (BETI), daunorubicin, gemcitabine, sulforaphane, doxorubicin, and tumor necrosis factor-related signaling apoptosis-inducing ligand (TRAIL). Meanwhile, during the chemo-resistance therapy, many signaling molecules are involved with toll-like receptor 4 (TLR4)-mediated oxidative and inflammatory pathway. The effects of quercetin on other oxidative and inflammatory pathways were also explored. Quercetin may exert antitumor activity during the prevention of pancreatic cancer progression by regulating oxidative and inflammatory networks, which can promote immune escape of cancer cells by inducing immunosuppressive cytokines. Studying these patterns will help us to better understand the functional role of quercetin in the improvement of pancreatic cancer chemo-sensitivity. PRACTICAL APPLICATIONS: Chemotherapy is the major way for treating pancreatic cancer metastasis but the prevalent chemotherapy resistance caused by oxidative and inflammatory responses limits its utilization. It is necessary to explore the potential natural products with few side effects to prevent the oxidative and inflammatory responses. Quercetin is a flavonoid widely found in numerous vegetables, fruits, and foods and is thought to have antioxidant and anti-inflammatory properties, which may be associated with improvement of chemotherapy sensitivity of pancreatic cancer treatment by sensitizing pancreatic cancer cells to various chemotherapeutic agents via the regulation of oxidative and inflammatory networks. Studying these patterns will help us to better understand the functional role of quercetin in the improvement of pancreatic cancer chemo-sensitivity.

Potential mechanisms of quercetin in cancer prevention: focus on cellular and molecular targets

Over the past few years, the cancer-related disease has had a high mortality rate and incidence worldwide, despite clinical advances in cancer treatment. The drugs used for cancer therapy, have high side effects in addition to the high cost. Subsequently, to reduce these side effects, many studies have suggested the use of natural bioactive compounds. Among these, which have recently attracted the attention of many researchers, quercetin has such properties. Quercetin, a plant flavonoid found in fresh fruits, vegetables and citrus fruits, has anti-cancer properties by inhibiting tumor proliferation, invasion, and tumor metastasis. Several studies have demonstrated the anti-cancer mechanism of quercetin, and these mechanisms are controlled through several signalling pathways within the cancer cell. Pathways involved in this process include apoptotic, p53, NF-κB, MAPK, JAK/STAT, PI3K/AKT, and Wnt/β-catenin pathways. In addition to regulating these pathways, quercetin controls the activity of oncogenic and tumor suppressor ncRNAs. Therefore, in this comprehensive review, we summarized the regulation of these signalling pathways by quercetin. The modulatory role of quercetin in the expression of various miRNAs has also been discussed. Understanding the basic anti-cancer mechanisms of these herbal compounds can help prevent and manage many types of cancer.

Sensitive and valid assay for reliable evaluation of drug interactions mediated by human organic anion transporter 1 and 3 using 5-carboxyfluorescein

Drug interactions can induce significant clinical impacts, either by increasing adverse effects or by decreasing the therapeutic effect of drugs, and thus, need to be explored thoroughly. Clinically significant drug interactions can be induced by organic anion transporter 1 (OAT1) and OAT3 when concomitant medications competitively interact with the transporters. The purposes of this study were to develop and validate a sensitive and selective analytical method for 5-carboxyfluorescein (5-CF) and optimize the experimental conditions for interaction studies. An analytical method using high-performance liquid chromatography (HPLC) equipped with a fluorescence detector was validated for accuracy, precision, matrix effect, recovery, stability, dilutional integrity, and carry-over effect. In addition, the 5-CF concentration, incubation period, and washing conditions for interaction study were optimized. Using a valid analytical method and optimized conditions, we performed an interaction study for OAT1 and OAT3 using 26 test articles. Some of the test articles showed strong inhibitory potency for the transporters, with IC₅₀ values close to or less than 10 μM. The valid analysis method and optimized systems developed in this study can be utilized to improve the predictability of drug interactions in humans and consequently aid in successful disease treatment by maintaining appropriate systemic exposures.

The potential biological effects of quercetin based on pharmacokinetics and multi-targeted mechanism in vivo

Quercetin is a plant-derived polyphenol flavonoid that has been proven to be effective for many diseases. However, the mechanism and in vivo metabolism of quercetin remains to be clarified. It achieves a wide range of biological effects through various metabolites, gut microbiota and its metabolites, systemic mediators produced by inflammation and oxidation, as well as by multiple mechanisms. The all-round disease treatment of quercetin is achieved through the organic combination of multiple channels. Therefore, this article clarifies the metabolic process of quercetin in the body, and explores the new pattern of action of quercetin in the treatment of diseases.

Synthesis, characterization, and pharmacological evaluation of some metal complexes of quercetin as P-gp inhibitors

Background

Six different metal complexes of quercetin (Cu, Zn, Co, Vd, Mo, Ni) were synthesized, purified, and characterized by their physical and spectral (UV, IR) data. They were evaluated for their P-gp (permeability glycoprotein) inhibitory activity by in vitro everted sac method in rats. The apparent permeability of atorvastatin (P-gp substrate) from everted sac of the rat intestine was determined in control, standard (verapamil), and groups treated with quercetin-metal complexes. The drug contents were analyzed by validated RP-HPLC method using a mixture of acetonitrile and water (60:40 v/v) adjusted to pH 2.8 with phosphate buffer as mobile phase.

Results

In vitro studies revealed that the apparent permeability of atorvastatin (P-gp substrate) across the small intestine is much affected by the treatment with Cu/Co/Ni complexes of quercetin. The mean ± SD and apparent permeability of atorvastatin decreased after pre-treatment with these metal complexes.

Conclusions

The quercetin Cu/Co/Ni complexes could inhibit P-gp and increase the atorvastatin absorption. Hence, they could be considered P-gp inhibitors.

Determination of effective concentrations of drug absorption enhancers using in vitro and ex vivo models

BACKGROUND

Achievement of an effective concentration of the pharmaceutically active ingredient in the blood and/or at the target site is an important aspect in the formulation of drugs and therefore needs to be quantified. Any concentration above therapeutic levels can cause toxic effects whereas low concentrations can be sub-therapeutic. This paper investigated different concentrations of selected commercially sourced analytical-grade pure chemicals as potential drug absorption enhancers in vitro and ex vivo to determine the lowest effective concentrations for optimizing drug absorption in oral dosage forms.

METHODS

Recombinant cytochrome (CYP) 3A4 enzyme and recombinant p-glycoprotein membrane models were utilized for the investigation of in vitro inhibitory effects of drug absorption enhancers. Promega (2015) protocols were adopted for both assays. The everted porcine intestinal ex vivo model was employed for assessing effects of the drug absorption enhancers on the absorption of propranolol.

RESULTS

The lowest effective CYP3A4 inhibitory concentrations were observed for curcumin (75µM and 100 µM), quercetin (75 and 100 µM) and glycyrrhizic acid (50 µM) while the most effective p-glycoprotein (P-gp) inhibition concentrations were curcumin (10, 15, 25, 50, 75 and 100 µM), sinomenine (50, 75, and 100 µM), quercetin (75 and 100 µM) and naringin (50 µM). Additive effects were observed between combinations of quercetin (75 µM) and curcumin (100 µM); quercetin (75 µM) and curcumin (75 µM); quercetin (75 µM) and curcumin (50 µM), and quercetin (75 µM) with curcumin (10 µM), which increased the basal ex vivo absorption of propranolol from 1.24 ± 0.03 µg/mL to 5.19 ± 0.12 µg/mL, 4.17 ± 0.05 µg/mL, 3.86 ± 0.10 µg/mL, and 4.07± 0.05 µg/mL respectively, after 2 hours.

CONCLUSION

Incorporation of the drug absorption enhancers (e.g., curcumin and quercetin), at specific concentrations, in dosage forms could improve the bioavailability of the BCS Class III and IV drugs that are substrates of CYP3A4 and p-glycoprotein.

Lipid nanocarrier of selegiline augmented anti-Parkinson's effect via P-gp modulation using quercetin

In the present study, SEL was loaded in a lipid nanocarrier (LNC) formulation with a P-gp pump inhibitor i.e., Quercetin (QUR) for improving the bioavailability of the SEL in the brain via the oral route. SEL-QUR LNC was formulated using modified emulsiosonication method and optimized using central composite rotatable design (CCRD) design. The results showed that optimized SEL-QUR LNC formulation was spherical with globule size, polydispersity index, entrapment efficiency and zeta potential within the range of 92.46-95.34 nm, 0.239-0.248, 88.94-91.26%, and -6.21 to -7.75 mV respectively. A 4-fold and 6-fold increase was observed in the permeation of SEL from SEL-QUR LNC across the gut sac in comparison with SEL-QUR and SEL suspensions respectively. CLSM images showed 2-fold deeper permeation of SEL across intestinal membrane demonstrating excellent in vivo prospect of the formulation. The behavioural studies including forced swimming, muscle coordination, locomotor activity, akinesia, and catalepsy were performed in the haloperidol-induced PD rats that demonstrated increased efficacy of the formulation in contrast to the SEL-QUR and SEL suspensions. These studies concluded that developed LNC formulation loaded SEL with P-gp inhibitor had the potential in improving bioavailability of SEL in the brain via oral route.

Quercetin Impact in Pancreatic Cancer: An Overview on Its Therapeutic Effects

Pancreatic cancer (PC) is a lethal malignancy cancer, and its mortality rates have been increasing worldwide. Diagnosis of this cancer is complicated, as it does not often present symptoms, and most patients present an irremediable tumor having a 5-year survival rate after diagnosis. Regarding treatment, many concerns have also been raised, as most tumors are found at advanced stages. At present, anticancer compounds-rich foods have been utilized to control PC. Among such bioactive molecules, flavonoid compounds have shown excellent anticancer abilities, such as quercetin, which has been used as an adjunctive or alternative drug to PC treatment by inhibitory or stimulatory biological mechanisms including autophagy, apoptosis, cell growth reduction or inhibition, EMT, oxidative stress, and enhancing sensitivity to chemotherapy agents. The recognition that this natural product has beneficial effects on cancer treatment has boosted the researchers' interest towards more extensive studies to use herbal medicine for anticancer purposes. In addition, due to the expensive cost and high rate of side effects of anticancer drugs, attempts have been made to use quercetin but also other flavonoids for preventing and treating PC. Based on related studies, it has been found that the quercetin compound has significant effect on cancerous cell lines as well as animal models. Therefore, it can be used as a supplementary drug to treat a variety of cancers, particularly pancreatic cancer. This review is aimed at discussing the therapeutic effects of quercetin by targeting the molecular signaling pathway and identifying antigrowth, cell proliferation, antioxidative stress, EMT, induction of apoptotic, and autophagic features.

Advanced Bioinformatics Tools in the Pharmacokinetic Profiles of Natural and Synthetic Compounds with Anti-Diabetic Activity

Diabetes represents a major health problem, involving a severe imbalance of blood sugar levels, which can disturb the nerves, eyes, kidneys, and other organs. Diabes management involves several synthetic drugs focused on improving insulin sensitivity, increasing insulin production, and decreasing blood glucose levels, but with unclear molecular mechanisms and severe side effects. Natural chemicals extracted from several plants such as Gymnema sylvestre, Momordica charantia or Ophiopogon planiscapus Niger have aroused great interest for their anti-diabetes activity, but also their hypolipidemic and anti-obesity activity. Here, we focused on the anti-diabetic activity of a few natural and synthetic compounds, in correlation with their pharmacokinetic/pharmacodynamic profiles, especially with their blood-brain barrier (BBB) permeability. We reviewed studies that used bioinformatics methods such as predicted BBB, molecular docking, molecular dynamics and quantitative structure-activity relationship (QSAR) to elucidate the proper action mechanisms of antidiabetic compounds. Currently, it is evident that BBB damage plays a significant role in diabetes disorders, but the molecular mechanisms are not clear. Here, we presented the efficacy of natural (gymnemic acids, quercetin, resveratrol) and synthetic (TAK-242, propofol, or APX3330) compounds in reducing diabetes symptoms and improving BBB dysfunctions. Bioinformatics tools can be helpful in the quest for chemical compounds with effective anti-diabetic activity that can enhance the druggability of molecular targets and provide a deeper understanding of diabetes mechanisms.

Phytochemicals reverse P-glycoprotein mediated multidrug resistance via signal transduction pathways

P-glycoprotein, encoded by ATP-binding cassette transporters B1 gene (ABCB1), renders multidrug resistance (MDR) during cancer chemotherapy. Several synthetic small molecule inhibitors affect P-glycoprotein (P-gp) transport function in MDR tumor cells. However, inhibition of P-gp transport function adversely accumulates chemotherapeutic drugs in non-target normal tissues. Moreover, most small-molecule P-gp inhibitors failed in the clinical trials due to the low therapeutic window at the maximum tolerated dose. Therefore, downregulation of ABCB1-gene expression (P-gp) in tumor tissues seems to be a novel approach rather than inhibiting its transport function for the reversal of multidrug resistance (MDR). Several plant-derived phytochemicals modulate various signal transduction pathways and inhibit translocation of transcription factors, thereby reverses P-gp mediated MDR in tumor cells. Therefore, phytochemicals may be considered an alternative to synthetic small molecule P-gp inhibitors for the reversal of MDR in cancer cells. This review discussed the role of natural phytochemicals that modulate ABCB1 expression through various signal transduction pathways in MDR cancer cells. Therefore, modulating the cell signaling pathways by phytochemicals might play crucial roles in modulating ABCB1 gene expression and the reversal of MDR.

Structure-activity relationship and mechanism of flavonoids on the inhibitory activity of P-glycoprotein (P-gp)-mediated transport of rhodamine123 and daunorubicin in P-gp overexpressed human mouth epidermal carcinoma (KB/MDR) cells

This study was aimed to investigate the inhibitory activity of flavonoids on P-glycoprotein (P-gp). Effects of 39 flavonoids on the cellular uptake (CU) of rhodamine123 (Rho) and daunomycin (DNR) were investigated in both parental KB and P-gp overexpressed KB/MDR cells. The inhibition mechanism of selected flavonoids was further investigated by measuring the ATPase activity and expression level of P-gp. Twelve flavonoids improved the uptake of Rho (↑Rho_F) and nineteen flavonoids increased the uptake of DNR (↑DNR_F) in KB/MDR cells with nine flavonoids overlapped. Structure-activity relationship (SAR) indicated that 8-OCH₃, and 2'-OH have a negative effect on Rho and DNR transport. Whereas 5-OH, 5-OCH₃, 6-OH, 7-OCH₃, 3'-OH, and 4'-OH, are essential for inhibition of flavonoids on P-gp and reversing the resistance of Rho and DNR. Eleven selected flavonoids significantly induced the basal P-gp-ATPase activity but much lower than that induced by verapamil. Tangeretin, galangin, kaempferol, quercetin, and morin significantly reversed the ATPase activity stimulated by verapamil. Six of eleven flavonoids significantly decreased P-gp expression, whereas three flavonoids slightly increased P-gp expression. These results provide valuable information that flavonoids can effectively reverse multidrug resistance of P-gp-mediated transport of nutraceutical and drugs by co-administration.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Dietary Polyphenols in Cancer Chemoprevention: Implications in Pancreatic Cancer

Naturally occurring dietary agents present in a wide variety of plant products, are rich sources of phytochemicals possessing medicinal properties, and thus, have been used in folk medicine for ages to treat various ailments. The beneficial effects of such dietary components are frequently attributed to their anti-inflammatory and antioxidant properties, particularly in regards to their antineoplastic activities. As many tumor types exhibit greater oxidative stress levels that are implicated in favoring autonomous cell growth activation, most chemotherapeutic agents can also enhance tumoral oxidative stress levels in part via generating reactive oxygen species (ROS). While ROS-mediated imbalance of the cellular redox potential can provide novel drug targets, as a consequence, this ROS-mediated excessive damage to cellular functions, including oncogenic mutagenesis, has also been implicated in inducing chemoresistance. This remains one of the major challenges in the treatment and management of human malignancies. Antioxidant-enriched natural compounds offer one of the promising approaches in mitigating some of the underlying mechanisms involved in tumorigenesis and metastasis, and therefore, have been extensively explored in cancer chemoprevention. Among various groups of dietary phytochemicals, polyphenols have been extensively explored for their underlying chemopreventive mechanisms in other cancer models. Thus, the current review highlights the significance and mechanisms of some of the highly studied polyphenolic compounds, with greater emphasis on pancreatic cancer chemoprevention.

Quercetin overcomes colon cancer cells resistance to chemotherapy by inhibiting solute carrier family 1, member 5 transporter

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) remains a significant impediment to the success of cancer chemotherapy. The natural flavonoid Quercetin (Que) has been reported to be able to inhibit P-gp-mediated MDR in various cancer cells. However, the MDR reversal effect of Que on human colon cancer cells and its mechanism at the metabolic level requires further clarification. This study was designed to provide a better understanding of the MDR reversal effect of Que. Our present results showed that 33 μM of Que significantly improved the cytotoxicity of doxorubicin (Dox) to P-gp-overexpressed SW620/Ad300 cells by proliferation and apoptpsis assay. Further mechanism studies demonstrated that Que inhibited the ATP-driven transport activity of P-gp, which in turn increased the intracellular accumulation of Dox. The metabolomics studies based on UPLC-MS/MS analysis revealed that Que could reverse the MDR by significantly blocking D-glutamine and D-glutamate metabolism, and the underlying mechanism is that Que down-regulated the expression of the glutamine transporter solute sarrier family 1, member 5 (SLC1A5) in SW620/Ad300 cells. This is the first time to report that Que was a SLC1A5 inhibitor, which could be served as a template compound to potentially develop novel P-gp-mediated MDR reversal modulators in cancer chemotherapy.

Influence of the Phenological State of in the Antioxidant Potential and Chemical Composition of Ageratina havanensis. Effects on the P-Glycoprotein Function

Ageratina havanensis (Kunth) R. M. King & H. Robinson is a species of flowering shrub in the family Asteraceae, native to the Caribbean and Texas. The aim of this work was to compare the quantitative chemical composition of extracts obtained from Ageratina havanensis in its flowering and vegetative stages with the antioxidant potential and to determine the effects on P-glycoprotein (P-gp) function. The quantitative chemical composition of the extracts was determined quantifying their major flavonoids by UPLC-ESI-MS/MS and by PCA analysis. The effects of the extracts on P-gp activity was evaluated by Rhodamine 123 assay; antioxidant properties were determined by DPPH, FRAP and inhibition of lipid peroxidation methods. The obtained results show that major flavonoids were present in higher concentrations in vegetative stage than flowering stage. In particular, the extracts obtained in the flowering season showed a significantly higher ability to sequester free radicals compared to those of the vegetative season, meanwhile, the extracts obtained during the vegetative stage showed a significant inhibitory effect against brain lipid peroxidation and a strong reductive capacity. This study also showed the inhibitory effects of all ethanolic extracts on P-gp function in 4T1 cell line; these effects were unrelated to the phenological stage. This work shows, therefore, the first evidence on: the inhibition of P-gp function, the antioxidant effects and the content of major flavonoids of Ageratina havanensis. According to the obtained results, the species Ageratina havanensis (Kunth) R. M. King & H. Robinson could be a source of new potential inhibitors of drug efflux mediated by P-gp. A special focus on all these aspects must be taking into account for future studies.

Quantitative Structure⁻Activity Relationships for the Flavonoid-Mediated Inhibition of P-Glycoprotein in KB/MDR1 Cells

P-glycoprotein (P-gp) serves as a therapeutic target for the development of inhibitors to overcome multidrug resistance (MDR) in cancer cells. In order to enhance the uptake of chemotherapy drugs, larger amounts of P-gp inhibitors are required. Besides several chemically synthesized P-gp inhibitors, flavonoids as P-gp inhibitors are being investigated, with their advantages including abundance in our daily diet and a low toxicity. The cytotoxicity of daunorubicin (as a substrate of P-gp) to KB/MDR1 cells and the parental KB cells was measured in the presence or absence of flavonoids. A two-dimensional quantitative structure–activity relationship (2D-QSAR) model was built with a high cross-validation coefficient (Q²) value of 0.829. Descriptors including vsurf_DW23, E_sol, Dipole and vsurf_G were determined to be related to the inhibitory activity of flavonoids. The lack of 2,3-double bond, 3′-OH, 4′-OH and the increased number of methoxylated substitutions were shown to be beneficial for the inhibition of P-gp. These results are important for the screening of flavonoids for inhibitory activity on P-gp.

Co-Encapsulation of EGCG and Quercetin in Liposomes for Optimum Antioxidant Activity

Although different delivery systems have been developed to overcome the limits of Epigallocatechin-3-gallate (EGCG) and quercetin in food application, none have referred to their simultaneous encapsulation. In this study, these two polyphenols were successfully co-loaded into liposomes. Under the optimal conditions (lecithin-total polyphenols ratio 25:1, lecithin-cholesterol ratio 6:1, lecithin-Tween 80 ratio 8:1 and ultrasonic time 2 min), the mean size, polydispersity index (PDI) and zeta potential of liposomes were 111.10 ± 0.52 nm, 0.259 ± 0.006 and -19.83 ± 0.45 mV, with an encapsulation efficiency of 64.05 ± 1.56% and 61.73 ± 2.55% for EGCG and quercetin, respectively. After 30-day storage, an increase of 4.05% was observed in the mean size with no significant change (P ≥ 0.05) in the PDI and zeta potential. Moreover, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay revealed a synergistic antioxidant effect of the two compounds in liposomal system. These results demonstrated that co-encapsulation of EGCG and quercetin enhances their effectiveness. PRACTICAL APPLICATION: EGCG and quercetin are natural polyphenols abound in the human diet with diverse biological activities. These two polyphenols were successfully co-encapsulated into a homogeneous and stable liposomal system. Interestingly, a synergistic antioxidant effect of the two polyphenols was observed due to co-encapsulation. This indicated that the simultaneous delivery of EGCG and quercetin was an attractive approach to improve their functionality for expanding their application in food, cosmetic and pharmaceutical industries.

Taxifolin Resensitizes Multidrug Resistance Cancer Cells via Uncompetitive Inhibition of P-Glycoprotein Function

P-glycoprotein (P-gp) effluxes lots of chemotherapeutic agents and leads to multidrug resistance (MDR) in cancer treatments. The development of P-gp inhibitors from natural products provide a potential strategy for the beneficial clinical outcomes. This study aimed to evaluate the effects of the natural flavonoid taxifolin, luteolin, (-)-gallocatechin, and (-)-catechin on human P-gp activity. The kinetic interactions and underlying mechanisms of taxifolin-mediated transporter inhibition were further investigated. The transporter inhibition ability was evaluated in human P-gp stable expression cells (ABCB1/Flp-InTM-293) by calcein-AM uptake assays. The kinetics study for P-gp inhibition was evaluated by doxorubicin and rhodamine123 efflux assays. The MDR reversal ability of taxifolin were performed by SRB assays to detect the cell viability in sensitive cancer cell line (HeLaS3), and resistant cancer cell line (KB-vin). Cell cycle analysis and ABCB1 real-time RT-PCR were used for mechanical exploration. The results demonstrated that taxifolin decreased ABCB1 expression in a concentration-dependent manner. The function of P-gp was inhibited by taxifolin through uncompetitive inhibition of rhodamine 123 and doxorubicin efflux. The combination of taxifolin significantly resensitized MDR cancer cells to chemotherapeutic agents. These results suggested that taxifolin may be considered as a potential P-gp modulator for synergistic treatment of MDR cancers.

An ABCG2 non-substrate anticancer agent FL118 targets drug-resistant cancer stem-like cells and overcomes treatment resistance of human pancreatic cancer

Background

Pancreatic cancer is a deadly disease with a very low 5-year patient survival rate of 6–8%. The major challenges of eliminating pancreatic cancer are treatment resistance and stromal barriers to optimal drug access within the tumor. Therefore, effective molecular targeting drugs with high intra-tumor access and retention are urgently needed for managing this devastating disease in the clinic.

Methods

This study has used the following in vitro and in vivo techniques for the investigation of exceptional anticancer drug FL118’s efficacy in treatment of resistant pancreatic cancer: cell culture; immunoblotting analysis to test protein expression; DNA sub-G1 flow cytometry analyses to test cell death; MTT assay to test cell viability; pancreatic cancer stem cell assays (fluorescence microscopy tracing; matrigel assay; CD44-positive cell colony formation assay); human luciferase-labeled pancreatic tumor orthotopic animal model in vivo imaging; pancreatic cancer patient-derived xenograft (PDX) animal models; and toxicology studies with immune-competent BALB/cj mice and beagle dogs.

Results

Our studies found that FL118 alone preferentially killed cisplatin-resistant cancer cells, while a combination of FL118 with cisplatin synergistically killed resistant pancreatic cancer cells and reduced spheroid formation of treatment-resistant pancreatic cancer stem-like cells. Furthermore, using in vivo-imaging, we found that FL118 in combination with cisplatin strongly inhibited both drug-resistant pancreatic xenograft tumor growth and metastasis. In PDX model, we demonstrated that FL118 alone effectively eliminated PDX tumors, while FL118 in combination with gemcitabine eliminated PDX tumors that showed relative resistance (less sensitivity) to treatment with FL118. These FL118 efficacy results are consistent with our molecular-targeting data showing that FL118 inhibited the expression of multiple antiapoptotic proteins (survivin, Mcl-1, XIAP, cIAP2) and ERCC6, a critical regulator of DNA repair, in treatment-resistant pancreatic stem-like cancer cells. Furthermore, FL118 toxicity studies in BALB/cj mice and beagle dogs indicated that FL118 exhibits favorable hematopoietic and biochemical toxicities.

Conclusion

Together, our studies suggest that FL118 is a promising anticancer drug for further clinical development to effectively treat drug-resistant pancreatic cancer alone or in combination with other pancreatic cancer chemotherapeutic drugs.

Quercetin and doxorubicin co-encapsulated biotin receptor-targeting nanoparticles for minimizing drug resistance in breast cancer

The combination of a chemotherapeutic drug with a chemosensitizer has emerged as a promising strategy for cancers showing multidrug resistance (MDR). Herein we describe the simultaneous targeted delivery of two drugs to tumor cells by using biotin-decorated poly(ethylene glycol)-b-poly(ε-caprolactone) nanoparticles encapsulating the chemotherapeutic drug doxorubicin and the chemosensitizer quercetin (BNDQ). Next, the potential ability of BNDQ to reverse MDR in vitro and in vivo was investigated. Studies demonstrated that BNDQ was more effectively taken up with less efflux by doxorubicin-resistant MCF-7 breast cancer cells (MCF-7/ADR cells) than by the cells treated with the free drugs, single-drug–loaded nanoparticles, or non-biotin–decorated nanoparticles. BNDQ exhibited clear inhibition of both the activity and expression of P-glycoprotein in MCF-7/ADR cells. More importantly, it caused a significant reduction in doxorubicin resistance in MCF-7/ADR breast cancer cells both in vitro and in vivo, among all the groups. Overall, this study suggests that BNDQ has a potential role in the treatment of drug-resistant breast cancer.

Natural flavonoids silymarin and quercetin improve the brain distribution of co-administered P-gp substrate drugs

P-glycoprotein (P-gp), a well known efflux transporter in the blood brain barrier inhibits the uptake of substrate drugs into brain. The main aim of this study is to evaluate the effect of natural product based P-gp inhibitors on brain penetration of various CNS drugs which are P-gp substrates. In this study, we have evaluated the inhibitory effects of natural bioflavonoids (quercetin and silymarin) on P-gp by using digoxin and quinidine as model P-gp model substrate drugs. In vitro inhibitory effects were evaluated in Caco-2 cell lines using digoxin as a model drug and in vivo P-gp inhibiting effect was evaluated in mice model using quinidine as model drug. The accumulation and bidirectional transport of digoxin in Caco-2 cells was determined in presence and absence of quercetin and silymarin. Elacridar was used as standard P-gp inhibitor and used to compare the inhibitory effects of test compounds. The apical to basolateral transport of digoxin was increased where as basolateral to apical transport of digoxin was decreased in concentration dependent manner in the presence of elacridar, quercetin and silymarin. After intravenous administration of P-gp inhibitors, brain levels of quinidine were estimated using LC-MS method. Increased brain uptake was observed with quercetin (2.5-fold) and silymarin (3.5-fold). Though the brain penetration potential of P-gp substrates was lower than that observed in elacridar, both quercetin and silymarin improved plasma quinidine levels. Caco-2 permeability studies and brain uptake indicate that both quercetin and silymarin can inhibit P-gp mediated efflux of drug into brain. Our results suggest that both silymarin and quercetin could potentially increase the brain distribution of co-administered drugs that are P-gp substrates.

Classical and atypical resistance of cancer cells as a target for resveratrol

The phenomenon of cancer cell resistance to chemotherapeutics is the main cause of insensitivity to anticancer therapy. Thus, the current challenge remains searching for substances sensitising the activity of cytostatic drugs. In this respect, resveratrol is a very promising therapeutic agent. It has pleiotropic effect on cancer cells, which can play a key role in numerous resistance mechanisms, both classical and atypical. The purpose of the present study was to assess the effect of resveratrol on the inhibition of human pancreatic cancer cell proliferation and on the level of cytostatic resistance-associated proteins. The study was performed on human pancreatic cancer cell lines EPP85-181P (control), EPP85-181RDB (daunorubicin resistance) and EPP85-181PRNOV (mitoxantrone resistance). The effect of resveratrol on the viability and proliferation of the studied cell lines was evaluated by SRB assay, whereas cell cycle arrest and cytostatic accumulation by FACS. Western blot analysis was used to determine the level of P-glycoprotein, topoisomerase II α and β and immunofluorescence technique to visualise the proteins in the cells. Resveratrol inhibited proliferation of all studied cell lines. Phase-specific cell cycle arrest depended on the type of cancer cells. Resveratrol decreased the level and activity of P-gp in EPP85-181RDB cells. In EPP85-181PRNOV cells, expression of both TopoII isoforms increased in a statistically significant manner. The results of in vitro studies support the possibility of potential use of resveratrol in breaking cancer cell resistance to chemotherapeutic drugs.

Natural products-friends or foes?

A trend in the general population has been observed in recent years regarding the orientation toward preventive measures in health; in this context the increased interest from the users and researchers concerning the active effect of food supplements on the health state and on longevity, is noticeable. All over the world, the consumption of natural foods and of vegetal supplements has increased spectacularly over the last 5-10 years. The decreased prevalence of cardio-vascular diseases associated with Mediterranean diet, as well as the French paradox convinced researchers to scientifically document the beneficial outcomes pointed out by traditional use of plants, and to try to develop supplements that would have the same positive effects as these noticed for diet components. The intense research dedicated to this topic revealed the fact that food supplements are linked to some problematic aspects, such as toxicological side effects when associated with classical synthetic drugs. The food supplement-drug interactions are submitted to complex issues regarding pharmacokinetic interactions leading to changes in absorption, distribution, metabolism and excretion processes with direct impact on effect and toxicological potential. The present review based on recent literature aims at discussing the food-drug interactions with direct impact on efficacy and toxicity of drugs.

The flavonoid quercetin: possible solution for anthracycline-induced cardiotoxicity and multidrug resistance

Anthracycline chemotherapy is often used in the treatment of various malignancies. Its application, however, encounters several limitations due to development of serious side effects, mainly cardiotoxicity and may be ineffective due to multidrug resistance (MDR). Many different compounds have been evaluated as poorly effective in the protection against anthracycline side effects and in the prevention from MDR. Thus, continuous investigational efforts are necessary to find valuable protectants and the flavonoid quercetin (Q) seems to be a promising candidate. It is present in relatively high amounts in a human diet and the lack of its toxicity, including genotoxicity has been confirmed. The structure of Q favours its high antioxidant activity, the potential to inhibit the activity of oxidative enzymes and to interact with membrane transporter proteins responsible for development of MDR, e.g. P-glycoprotein. Furthermore, Q can influence cellular signalling and gene expression, and thus, alter response to exogenous genotoxicants and oxidative stress in normal cells. It accounts for its chemopreventive and anticancer properties. Overall, these properties might indicate the possibility of application of Q as cardioprotectant during anthracycline chemotherapy. Moreover, numerous biological properties displayed by Q might possibly result in the reversal of MDR in tumour cells and improve the efficacy of chemotherapy. However, these beneficial effects towards anthracycline-induced complications of chemotherapy have to be further explored and confirmed both in animal and clinical studies. Concurrently, investigations aimed at improvement of the bioavailability of Q and further elucidation of its metabolism after application in combination with anthracyclines are needed.

Hesperidin as a preventive resistance agent in MCF-7 breast cancer cells line resistance to doxorubicin

OBJECTIVE

To evaluate of hesperidin to overcome resistance of doxorubicin in MCF-7 resistant doxorubicin cells (MCF-7/Dox) in cytotoxicity apoptosis and P-glycoprotein (Pgp) expression in combination with doxorubicin.

METHODS

The cytotoxic properties, 50% inhibition concentration (IC50) and its combination with doxorubicin in MCF-7 cell lines resistant to doxorubicin (MCF-7/Dox) cells were determined using MTT assay. Apoptosis induction was examined by double staining assay using ethidium bromide-acridine orange. Immunocytochemistry assay was performed to determine the level and localization of Pgp.

RESULTS

Single treatment of hesperidin showed cytotoxic activity on MCF-7/Dox cells with IC50 value of 11 µmol/L. Thus, combination treatment from hesperidin and doxorubicin showed addictive and antagonist effect (CI>1.0). Hesperidin did not increase the apoptotic induction, but decreased the Pgp expressions level when combined with doxorubicin in low concentration.

CONCLUSIONS

Hesperidin has cytotoxic effect on MCF-7/Dox cells with IC50 of 11 µmol/L. Hesperidin did not increased the apoptotic induction combined with doxorubicin. Co-chemotherapy application of doxorubicin and hesperidin on MCF-7/Dox cells showed synergism effect through inhibition of Pgp expression.

Novel flavonoid-based biodegradable nanoparticles for effective oral delivery of etoposide by P-glycoprotein modulation: an in vitro, ex vivo and in vivo investigations

A receptor level interaction of etoposide with P-glycoprotein (P-gp) and subsequent intestinal efflux has an adverse effect on its oral absorption. The present work is aimed to enhance the bioavailability of etoposide by co-administering it with quercetin (a P-gp inhibitor) in dual-loaded polymeric nanoparticle formulation. Poly-lactic-co-glycolic acid (PLGA) nanoparticles were optimized for various parameters like o/w phase volume ratio, poly-vinyl alcohol concentration, PLGA concentration and sonication time. The cytotoxicity studies (MTT assay) revealed a 9- and 11-fold decrease in the IC 50 values for etoposide-loaded nanoparticles (ENP) and etoposide + quercetin dual-loaded nanoparticles (EQNP) when compared to that of free etoposide, respectively, and the results were further supported by florescent-activated cell sorter studies. The confocal imaging of the intestinal sections treated with ENP and EQNP containing fluorescent probe (rhodamine) showed the superiority of the EQNP to permeate deeper. Furthermore, pharmacokinetic studies on rats revealed that EQNP exhibited a 2.4-fold increase in bioavailability of etoposide than ENP with no quercetin. The developed loaded nanoparticles have the high potential to enhance the bioavailability of the etoposide and sensitize the resistant cells.

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.

Reversal effect of bufalin on multidrug resistance in human hepatocellular carcinoma BEL-7402/5-FU cells

Multidrug resistance (MDR) is a major obstacle to chemotherapy in patients with hepatocellular carcinoma (HCC). To overcome MDR and improve chemotherapeutic efficacy, novel reversal agents with higher efficacy and lower toxicity are urgently needed for HCC. The present study was designed to examine the potential reversal activity of bufalin, a toxic ligand isolated from the traditional Chinese medicine 'Chansu' and to elucidate the possible related mechanisms. A multidrug-resistant HCC cell line, BEL-7402/5-FU, was used as the cell model. The working concentration of bufalin as an effective reversal agent, and the cell viability in the reversal experiments were determined by MTT assay. The effects of bufalin at a non-cytotoxic dose on cell cycle distribution, apoptosis and drug efflux pump activity were measured by flow cytometry. Qualitative observation of apoptosis was also carried out by confocal microscopy. Furthermore, the effects of bufalin on the expression of potential genes involved in MDR of BEL-7402/5-FU cells, including thymidylate synthase (TS), P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1), B-cell lymphoma-extra large (Bcl-xL) and Bcl-2-associated X protein (Bax), were determined using real-time PCR and western blot analysis. The results showed that bufalin at a concentration of 1 nM enhanced the chemosensitivity of BEL-7402/5-FU cells to 5-FU with a reversal fold of 3.8 which was similar to that of 1 µM verapamil. Bufalin significantly arrested the cell cycle at the G₀/G₁ phase, induced apoptosis through an increase in the Bax/Bcl-xL ratio, inhibited drug efflux pump activity via downregulation of MRP1, and reduced the expression of TS in BEL-7402/5-FU cells. The present study revealed that bufalin effectively reversed MDR in BEL-7402/5-FU cells through multiple pathways. The combination of bufalin with cytotoxic drugs may serve as a promising strategy for the chemotherapy of HCC.

Natural polyphenols in cancer therapy

Natural polyphenols are secondary metabolites of plants involved in defense against different types of stress. Extracts containing these compounds have been used for thousands of years in traditional eastern medicine. Polyphenols act on multiple targets in pathways and mechanisms related to carcinogenesis, tumor cell proliferation and death, inflammation, metastatic spread, angiogenesis, or drug and radiation resistance. Nevertheless, reported effects claimed for polyphenols are controversial, since correlations between in vitro effects and in vivo evidence are poorly established. The main discrepancy between health claims versus clinical observations is the frequent use of nonphysiologically relevant concentrations of these compounds and their metabolites in efficacy and mechanistic studies. The present review will discuss how in vivo administration correlates with polyphenol metabolism, toxicity, and bioavailability. Analysis of the general application of polyphenols in cancer therapy will be complemented by potential applications in the therapy of specific tumors, including melanoma, colorectal and lung cancers. Possible pharmaceutical formulations, structural modifications, combinations, and delivery systems aimed to increase bioavailability and/or biological effects will be discussed. Final remarks will include recommendations for future research and developments.

Quercetin and rutin reduced the bioavailability of cyclosporine from Neoral, an immunosuppressant, through activating P-glycoprotein and CYP 3A4

Quercetin and rutin are popular flavonoids in plant foods, herbs, and dietary supplements. Cyclosporine (CSP), an immunosuppressant with a narrow therapeutic window, is a substrate of P-glycoprotein (P-gp) and cytochrome P-450 3A4 (CYP3A4). This study investigated the effects of quercetin and rutin on CSP pharmacokinetics from Neoral and relevant mechanisms. Rats were orally administered Neoral with and without quercetin or rutin. The blood CSP concentration was assayed by a specific monoclonal fluorescence polarization immunoassay. The results showed that quercetin and rutin significantly decreased the C(max) of CSP by 67.8 and 63.2% and reduced the AUC(0-540) by 43.3 and 57.2%, respectively. The in vitro studies indicated that the quercetin and rutin induced the functions of P-gp and CYP3A4. In conclusion, quercetin and rutin decreased the bioavailability of CSP through activating P-gp and CYP3A. Transplant patients treated with Neoral should avoid concurrent consumption of quercetin or rutin to minimize the risk of allograft rejection.

Membrane drug transporters and chemoresistance in human pancreatic carcinoma

Pancreatic cancer ranks among the tumors most resistant to chemotherapy. Such chemoresistance of tumors can be mediated by various cellular mechanisms including dysregulated apoptosis or ineffective drug concentration at the intracellular target sites. In this review, we highlight recent advances in experimental chemotherapy underlining the role of cellular transporters in drug resistance. Such contribution to the chemoresistant phenotype of tumor cells or tissues can be conferred both by uptake and export transporters, as demonstrated by in vivo and in vitro data. Our studies used human pancreatic carcinoma cells, cells stably transfected with human transporter cDNAs, or cells in which a specific transporter was knocked down by RNA interference. We have previously shown that 5-fluorouracil treatment affects the expression profile of relevant cellular transporters including multidrug resistance proteins (MRPs), and that MRP5 (ABCC5) influences chemoresistance of these tumor cells. Similarly, cell treatment with the nucleoside drug gemcitabine or a combination of chemotherapeutic drugs can variably influence the expression pattern and relative amount of uptake and export transporters in pancreatic carcinoma cells or select for pre-existing subpopulations. In addition, cytotoxicity studies with MRP5-overexpressing or MRP5-silenced cells demonstrate a contribution of MRP5 also to gemcitabine resistance. These data may lead to improved strategies of future chemotherapy regimens using gemcitabine and/or 5-fluorouracil.

Dietary factors and pancreatic cancer: the role of food bioactive compounds

Pancreatic cancer is the fourth leading cause of cancer mortality among both men and women in the United States with a 5-year survival rate of only 4%. Several dietary factors may influence the risk of developing pancreatic cancer and its recurrence. Some of these factors may offer innovative therapies for prevention of this disease. The goal of this review is to provide an overview of pancreatic cancer, as well as current knowledge on the epidemiological, in vitro, in vivo, and clinical studies conducted about this disease using various dietary agents. The main focus is on food-based approaches for preventing this disease particularly, citrus fruits, and foods containing flavonoids, curcumin, folate and vitamin D.

The dietary bioflavonoid quercetin synergizes with epigallocathechin gallate (EGCG) to inhibit prostate cancer stem cell characteristics, invasion, migration and epithelial-mesenchymal transition

Background

Much attention has been recently focused on the role of cancer stem cells (CSCs) in the initiation and progression of solid malignancies. Since CSCs are able to proliferate and self-renew extensively due to their ability to express anti-apoptotic and drug resistant proteins, thus sustaining tumor growth. Therefore, the strategy to eradicate CSCs might have significant clinical implications. The objectives of this study were to examine the molecular mechanisms by which epigallocathechin gallate (EGCG) inhibits stem cell characteristics of prostate CSCs, and synergizes with quercetin, a major polyphenol and flavonoid commonly detected in many fruits and vegetables.

Results

Our data indicate that human prostate cancer cell lines contain a small population of CD44⁺CD133⁺ cancer stem cells and their self-renewal capacity is inhibited by EGCG. Furthermore, EGCG inhibits the self-renewal capacity of CD44⁺α2β1⁺CD133⁺ CSCs isolated from human primary prostate tumors, as measured by spheroid formation in suspension. EGCG induces apoptosis by activating capase-3/7 and inhibiting the expression of Bcl-2, survivin and XIAP in CSCs. Furthermore, EGCG inhibits epithelial-mesenchymal transition by inhibiting the expression of vimentin, slug, snail and nuclear β-catenin, and the activity of LEF-1/TCF responsive reporter, and also retards CSC's migration and invasion, suggesting the blockade of signaling involved in early metastasis. Interestingly, quercetin synergizes with EGCG in inhibiting the self-renewal properties of prostate CSCs, inducing apoptosis, and blocking CSC's migration and invasion. These data suggest that EGCG either alone or in combination with quercetin can eliminate cancer stem cell-characteristics.

Conclusion

Since carcinogenesis is a complex process, combination of bioactive dietary agents with complementary activities will be beneficial for prostate cancer prevention and/ortreatment.