Flavonoids modulate multidrug resistance through wnt signaling in P-glycoprotein overexpressing cell lines

Mechanism of multidrug resistance to chemotherapy mediated by P‑glycoprotein (Review)

Multidrug resistance (MDR) seriously limits the clinical application of chemotherapy. A mechanism underlying MDR is the overexpression of efflux transporters associated with chemotherapeutic drugs. P‑glycoprotein (P‑gp) is an ATP‑binding cassette (ABC) transporter, which promotes MDR by pumping out chemotherapeutic drugs and reducing their intracellular concentration. To date, overexpression of P‑gp has been detected in various types of chemoresistant cancer and inhibiting P‑gp‑related MDR has been suggested. The present review summarizes the mechanisms underlying MDR mediated by P‑gp in different tumors and evaluated the related signaling pathways, with the aim of improving understanding of the current status of P‑gp‑mediated chemotherapeutic resistance. This review focuses on the main mechanisms of inhibiting P‑gp‑mediated MDR, with the aim of providing a reference for the study of reversing P‑gp‑mediated MDR. The first mechanism involves decreasing the efflux activity of P‑gp by altering its conformation or hindering P‑gp‑chemotherapeutic drug binding. The second inhibitory mechanism involves inhibiting P‑gp expression to reduce efflux. The third inhibitory mechanism involves knocking out the ABCB1 gene. Potential strategies that can inhibit P‑gp include certain natural products, synthetic compounds and biological techniques. It is important to screen lead compounds or candidate techniques for P‑gp inhibition, and to identify inhibitors by targeting the relevant signaling pathways to overcome P‑gp‑mediated MDR.

Anticancer Potential of Flavonoids: An Overview with an Emphasis on Tangeretin

Natural compounds with pharmacological activity, flavonoids have been the subject of an exponential increase in studies in the field of scientific research focused on therapeutic purposes due to their bioactive properties, such as antioxidant, anti-inflammatory, anti-aging, antibacterial, antiviral, neuroprotective, radioprotective, and antitumor activities. The biological potential of flavonoids, added to their bioavailability, cost-effectiveness, and minimal side effects, direct them as promising cytotoxic anticancer compounds in the optimization of therapies and the search for new drugs in the treatment of cancer, since some extensively antineoplastic therapeutic approaches have become less effective due to tumor resistance to drugs commonly used in chemotherapy. In this review, we emphasize the antitumor properties of tangeretin, a flavonoid found in citrus fruits that has shown activity against some hallmarks of cancer in several types of cancerous cell lines, such as antiproliferative, apoptotic, anti-inflammatory, anti-metastatic, anti-angiogenic, antioxidant, regulatory expression of tumor-suppressor genes, and epigenetic modulation.

Leonurus japonicus Houttuyn induces reactive oxygen species-mediated apoptosis via regulation of miR-19a-3p/PTEN/PI3K/AKT in U937 and THP-1 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Leonurus japonicus Houttuyn is a medicinal ingredient in more than 300 prescriptions in traditional Korean medicine. It is especially important for women's health and blood-related diseases. Recent research revealed that Leonurus japonicus Houttuyn extracts have antioxidative, anticancer, analgesic, anti-inflammatory, and neuroprotective properties.

AIM OF THE STUDY

However, its underlying anti-cancerous mechanisms remain unclear. This study elucidated the anticancer mechanism of Leonurus japonicus Houttuyn in U937 and THP-1 cancer cells.

MATERIALS AND METHODS

High-performance liquid chromatography (HPLC) was used for detecting main compound of Leonurus japonicus Houttuyn, rutin. EZ-Cytox cell viability assay, Western blot analysis, live and dead cell assay, 2', 7' dichlorofluorescin diacetate (DCFDA) assay, quantitative real-time PCR (qRT-PCR) analysis, and microRNA (miR) mimic transfection assay were applied to further investigate anti-cancer efficacies and underlying mechanism in U937 and THP-1 cells.

RESULTS

The main compound of Leonurus japonicus Houttuyn, rutin was detected using HPLC. The cytotoxic effect of Leonurus japonicus Houttuyn was exerted in U937 and THP-1 cancer cells but not in MDBK and IEC-6 normal cells. Leonurus japonicus Houttuyn decreased mitochondria membrane potential (ΔΨm). Consistently, Leonurus japonicus Houttuyn reduced the expression of survivin and cleaved caspase-9, caspase-3, and poly (ADP-ribose) polymerase (PARP). Cell death was increased in Leonurus japonicus Houttuyn treated groups. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and CCAAT-enhancer-binding protein homologous protein (CHOP) was increased and phosphatidylinositol-3-kinase (PI3K) and Protein kinase B (AKT) were decreased by Leonurus japonicus Houttuyn. Reactive oxygen speices generation was elevated by Leonurus japonicus Houttuyn and its cytotoxicity was reversed by N-acetyl-l-cysteine (NAC) pretreatment. Moreover, onco-microRNA (miR), miR-19a-3p was suppressed by Leonurus japonicus Houttuyn and transfection of miR-19a-3p mimic reversed the regulated PTEN, p-AKT, CHOP expression, attenuating Leonurus japonicus Houttuyn induced apoptosis.

CONCLUSIONS

These findings indicated that Leonurus japonicus Houttuyn has anti-cancer effects by regulation of PTEN/PI3K/AKT signal pathway and ROS-related ER stress-induced apoptosis via regulation of miR-19a-3p. Leonurus japonicus Houttuyn may be an effective candidate for triggering PTEN-dependent apoptosis of cancer cells related to acute myeloid leukemia.

P-glycoprotein: new insights into structure, physiological function, regulation and alterations in disease

The multidrug resistance phenomenon presents a major threat to the pharmaceutical industry. This resistance is a common occurrence in several diseases and is mediated by multidrug transporters that actively pump substances out of the cell and away from their target regions. The most well-known multidrug transporter is the P-glycoprotein transporter. The binding sites within P-glycoprotein can accommodate a variety of compounds with diverse structures. Hence, numerous drugs are P-glycoprotein substrates, with new ones being identified every day. For many years, the mechanisms of action of P-glycoprotein have been shrouded in mystery, and scientists have only recently been able to elucidate certain structural and functional aspects of this protein. Although P-glycoprotein is highly implicated in multidrug resistant diseases, this transporter also performs various physiological roles in the human body and is expressed in several tissues, including the brain, kidneys, liver, gastrointestinal tract, testis, and placenta. The expression levels of P-glycoprotein are regulated by different enzymes, inflammatory mediators and transcription factors; alterations in which can result in the generation of a disease phenotype. This review details the discovery, the recently proposed structure and the regulatory functions of P-glycoprotein, as well as the crucial role it plays in health and disease.

Exploring the Protective Effect and Mechanism of Buddlejae Flos on Sodium Selenite-Induced Cataract in Rats by Network Pharmacology, Molecular Docking, and Experimental Validation

Objective

Buddlejae Flos has a long history of utilization by humans to treat ophthalmic diseases. Although in vitro study revealed that it can be used for treating cataract, the bioactive components and the mechanism of efficacy remained unclear. This study aims to discover the bioactive components and mode of efficacy of Buddlejae Flos in cataract treatment.

Methods

Several databases were screened for bioactive components and corresponding targets, as well as cataract-related targets. Using the String database, common targets were determined and utilized to construct protein-protein interactions (PPI). The drug-component-target-disease network map was drawn using Cytoscape software. R language was utilized to execute Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathway enrichment analysis. Molecular docking was done through Schrödinger Maestro software utilization. Luteolin's (LUT) effect on cataract induced by sodium selenite in rat pups was evaluated.

Results

Six bioactive components with 38 common targets were identified as being associated with cataract. TP53, AKT1, EGFR, CASP3, TNF, ESR1, INS, IL6, HIF1A, and VEGFA were identified as core targets in PPI analysis, and the binding energy of LUT with AKT was the lowest. LUT has been demonstrated to significantly lower MDA levels, raise glutathione (GSH) levels, and boost the activity of antioxidant enzymes like GST, SOD, GPx, and CAT. After LUT treatment, TNF-a, IL-2, and IL-6 levels were significantly lowered. Bcl-2 mRNA expression levels and p-PI3K and p-AKT protein expression were significantly elevated. In contrast, caspase-3 and Bax mRNA expression levels were significantly decreased.

Conclusion

This study demonstrates that LUT is a possible bioactive component that may be utilized for cataract treatment. Its mode of action includes oxidative stress suppression, reducing inflammation, and inhibiting apoptosis via regulating the PI3K/AKT single pathway.

Nobiletin Inhibits Non-Small-Cell Lung Cancer by Inactivating WNT/β-Catenin Signaling through Downregulating miR-15-5p

BACKGROUND

Nobiletin is a natural compound with anticancer activity; however, the mechanism is not clear.

METHODS

The inhibitory effect of nobiletin on non-small-cell lung cancer (NSCLC) cells was examined using soft agar, Transwell, and apoptosis analyses. Cancer stemness was measured by sphere assay. Genes and miRNAs regulated by nobiletin were identified by whole-genome sequencing. Protein levels were detected by western blot and immunofluorescence assays.

RESULTS

Nobiletin significantly inhibited NSCLC cell colony formation and sphere formation and induced apoptosis. Nobiletin upregulated negative regulators of WNT/β-catenin signaling, including NKD1, AXIN2, and WIF1, while it inhibited the expression of β-catenin and its downstream genes, including c-Myc, c-Jun, and cyclin D1. Furthermore, we identified that GN inhibits miR-15-5p expression in NSCLC cells and that NKD1, AXIN2, and WIF1 are the target genes of miR-15-5p.

CONCLUSIONS

Nobiletin has a strong inhibitory effect on NSCLC, and nobiletin plays an anticancer role by inhibiting miR-15-5p/β-catenin signaling in NSCLC.

The role of dietary flavonoids for modulation of ATP binding cassette transporter mediated multidrug resistance

Flavonoids are widely existing compounds with enormous pharmacological effects from food and medicine. However, the low bioavailability in intestinal absorption and metabolism limits their clinical application. Intestinal efflux ABC (ATP binding cassette) transporters, including P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), act as "pumping doors" to regulate the efflux of flavonoids from intestinal epithelial cells into the intestinal cavity or the systemic circulation. The present review describes the critical effect of ABC transporters involved in the efflux of flavonoids which depend on its efflux direction. And the role of flavonoids for modulation of intestinal ABC transporters was emphasized and several examples were given. We summarized that the resistance effect of flavonoid-mediated multidrug on ABC transporters may influence the bioavailability of drugs, bioactive ingredients and/or toxic compounds upon dietary uptake. Meanwhile, flavonoids functionalized as reversing agents of the ABC transporter may be an important mechanism for unexpected food-drug, food-toxin or food-food interactions. The overview also indicates that elucidation of the action and mechanism of the intestinal metabolic enzymes-efflux transporters coupling will lay a foundation for improving the bioavailability of flavonoids <i>in vivo</i> and increasing their clinical efficacy.

Cardamonin inhibits the expression of P-glycoprotein and enhances the anti-proliferation of paclitaxel on SKOV3-Taxol cells

Paclitaxel is widely used in the first-line treatment of ovarian cancer. Nevertheless, the development of acquired resistance to paclitaxel is a major obstacle for the therapy in clinic. Cardamonin is a novel anticancer chalcone which exhibits a wide range of pharmacological activities. However, the effect of cardamonin on paclitaxel-resistant ovarian cancer cells and its underlying molecular mechanisms are unknown. Here, we revealed whether cardamonin had a resensitivity for paclitaxel and furtherly explored the underlying mechanisms on SKOV3-Taxol cells. Our results showed that cardamonin combined with paclitaxel had a synergistic effect of anti-proliferation in SKOV3-Taxol cells, and CI was less than one. Cells apoptosis and G2/M phase arrest were enhanced by cardamonin with paclitaxel in a concentration-dependent way on SKOV3-Taxol cells (P < 0.05). Cardamonin significantly increased drug accumulation in SKOV3-Taxol cells (P < 0.05). Similar to verapamil, cardamonin decreased MDR1 mRNA and P-gp expression (P < 0.05). Cardamonin restrained NF-κB activation in SKOV3-Taxol cells (P < 0.05). Inhibitory effect of P-gp and NF-κB p65 (nuclear protein) expression was enhanced by cardamonin combined with PDTC, a NF-κB inhibitor. Cardamonin significantly inhibited the upregulation of NF-κB p65 (nuclear protein) and P-gp expression induced by TNF-α (P < 0.05). Taken together, cardamonin enhanced the effect of paclitaxel on inhibiting cell proliferation, inducing apoptosis and G2/M phase arrest, and then strengthened the cytotoxic effect of paclitaxel in SKOV3-Taxol cells. The mechanism might be involved in inhibition of P-gp efflux pump, reducing MDR1 mRNA and P-gp expression by cardamonin via suppression of NF-κB activation in SKOV3-Taxol cells.

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.

Celastrol Inhibits the Proliferation and Decreases Drug Resistance of Cisplatin-Resistant Gastric Cancer SGC7901/DDP Cells

BACKGROUND

This study aimed to determine the effect and mechanism of Celastrol inhibiting the proliferation and decreases drug resistance of cisplatin-resistant gastric cancer cells.

OBJECTIVE

To explore the effect and mechanism of Celastrol on proliferation and drug resistance of human gastric cancer cisplatin-resistant cells SGC7901/DDP.

METHODS

The thiazole blue (MTT) method was used to detect the sensitivity of human gastric cancer cisplatin-resistant cells SGC7901/DPP to cisplatin and Celastrol to determine the Drug resistance index (DRI). According to the half inhibitory concentration (IC50) value, the action concentration of the following experimental drugs was set to reduce the cytotoxicity; Annexin V-FITC/PI double staining method was used to detect the apoptosis of SGC7901/DDP cells induced by Celastrol; Western Blot was used to examine the expression levels of P-glycoprotein (P-gp), Multidrug Resistance Associated Protein 1 (MRP1), Breast Cancer Resistance Associated Protein (Breast Cancer Resistance)-relative protein (BCRP), and mechanistic Target of Rapamycin (mTOR) pathway related proteins; Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) was used to detect the mRNA expression levels of P-gp, MRP1, and BCRP.

RESULTS

(1) Compared with the control group (We set the untreated group as the control group), the proliferation of the SGC7901/DPP cells was significantly inhibited after treating with 0.1-6.4μmol/L Celastrol in a time- and concentration-dependent manner (P<0.05). The Drug resistance index DRI of the SGC7901/DPP cells to DDP was 5.64. (2) Compared with the control group, Celastrol could significantly inhibit the proliferation and induce the apoptosis of the SGC7901/DPP cells (P<0.05). (3) The mRNA and protein expression levels of P-gp, MRP1, and BCRP in the SGC7901/DPP cells were significantly higher than those in the SGC7901 cells. However, after treating with Celastrol, the expression levels of P-gp, MRP1, and BCRP in the SGC7901/DPP cells were significantly reduced (P<0.05). (4) Compared with the control group, the Celastrol treatment also reduced the expression of the mTOR signaling pathway related proteins, suggesting that the mTOR signaling pathway may be involved in the process of Celastrol inhibiting the proliferation of the SGC7901/DDP cells and reducing their drug resistance. (5) Significantly, the combination of Celastrol and DDP reduced the expression of P-gp, MRP1, and BCRP in the SGC7901/DPP cells.

CONCLUSION

Celastrol can inhibit the proliferation of the SGC7901/DDP cells, induce their apoptosis, and reduce the expression of drug resistance genes, probably by inhibiting the expression of the proteins related to the mTOR signaling pathway.

Molecular mechanisms of anticancer effect of rutin

Because of the extensive biological functions of natural substances such as bioflavonoids, and their high safety and low costs, they could have high priority application in the health care system. The antioxidant properties of rutin, a polyphenolic bioflavonoid, have been well documented and demonstrated a wide range of pharmacological applications in cancer research. Since chemotherapeutic drugs have a wide range of side effects and rutin is a safe anticancer agent with minor side effects so recent investigations are performed for study of mechanisms of its anticancer effect. Both in-vivo and in-vitro examinations on anticancer mechanisms of this natural agent have been widely carried out. Regulation of different cellular signaling pathways such as Wnt/β-catenin, p53-independent pathway, PI3K/Akt, JAK/STAT, MAPK, p53, apoptosis as well as NF-ĸB signaling pathways helps to mediate the anticancer impacts of this agent. This study tried to review the molecular mechanisms of rutin anticancer effect on various types of cancer. Deep exploration of these anticancer mechanisms can facilitate the development of this beneficial compound for its application in the treatment of different cancers.

Dietary polyphenols suppress chronic inflammation by modulation of multiple inflammation-associated cell signaling pathways

The high failure rate of the reductionist approach to discover effective and safe drugs to treat chronic inflammatory diseases has led scientists to seek alternative ways. Recently, targeting cell signaling pathways has been utilized as an innovative approach to discover drug leads from natural products. Cell signaling mechanisms have been identified playing key role in diverse diseases by inducing proliferation, cell survival and apoptosis. Phytochemicals are known to be able to modulate the cellular and molecular networks which are associated to chronic diseases including cancer-associated inflammation. In this review, the roles of dietary polyphenols (apigenin, kaempferol, quercetin, curcumin, genistein, isoliquiritigenin, resveratrol and gallic acid) in modulating multiple inflammation-associated cell signaling networks are deliberated. Scientific databases on suppressive effects of the polyphenols on chronic inflammation via modulation of the pathways especially in the recent five years are gathered and critically analyzed. The polyphenols are able to modulate several inflammation-associated cell signaling pathways, namely nuclear factor-kappa β, mitogen activated protein kinases, Wnt/β-catenin and phosphatidylinositol 3-kinase and protein kinase B via selective actions on various components of the networks. The suppressive effects of the polyphenols on the multiple cell signaling pathways reveal their potential use in prevention and treatment of chronic inflammatory disorders. Understanding the mechanistic effects involved in modulation of the signaling pathways by the polyphenols is necessary for lead identification and development of future functional foods for prevention and treatment of chronic inflammatory diseases.

Bioavailable wine pomace attenuates oxalate-induced type II epithelial mesenchymal transition and preserve the differentiated phenotype of renal MDCK cells

The functional renal epithelium is composed of differentiated and polarized tubular cells with a strong actin cortex and specialized cell-cell junctions. If, under pathological conditions, these cells have to resist higher kidney osmolarity, they need to activate diverse mechanisms to survive external nephrotoxic agents such as inflammation and oxidative stress. Wine pomace polyphenols exert protective effects on renal cells. In this study, two wine-pomace products and their protective effects upon promotion and preservation of normal cell differentiation and attenuation of oxalate-induced type II epithelial mesenchymal transition (EMT) are evaluated. Treatment with gastrointestinal and colonic bioavailable fractions from red (rWPP) and white (wWPP) wine pomaces, both in the presence and the absence of oxalate, showed similar cell numbers and nuclear size than the non-treated differentiated MDCK cells. Immunofluorescence analysis showed the reduction of morphological changes and the preservation of cellular junctions for the rWPP and wWPP pre-treatment of cells exposed to oxalate injury. Hence, both rWPP and wWPP attenuated oxalate type II EMT in MDCK cells that conserved their epithelial morphology and cellular junctions through the antioxidant activities of grape pomace polyphenols.

Flavonoids as Multi-Target Compounds: A Special Emphasis on their Potential as Chemo-adjuvants in Cancer Therapy

Flavonoids are low molecular weight, polyphenolic phytochemicals, obtained from secondary metabolism of various plant compounds. They have a spectrum of pharmacological efficacies, including potential anticancer efficacy. Natural flavonoids are present in fruits, vegetables, grains, bark, roots, stems, flowers, tea and wine. Flavonoids can attenuate or inhibit the initiation, promotion and progression of cancer by modulating various enzymes and receptors in diverse pathways that involve cellular proliferation, differentiation, apoptosis, inflammation, angiogenesis and metastasis. Furthermore, in vitro, flavonoids have been shown to reverse multidrug resistance when used as chemo-adjuvants. Flavonoids (both natural and synthetic analogues) interact with several oncogenic targets through dependent and independent mechanisms to mediate their anticancer efficacy in different types of cancer cells.

Role of flavonoids against adriamycin toxicity

Doxorubicin (DOX), or adriamycin, is an anthracycline antineoplastic drug widely used in the chemotherapy of a large variety of cancers due to its potency and action spectrum. However, its use is limited by the toxicity on healthy cells and its acute and chronic side effects. One of the developed strategies to attenuate DOX toxicity is the combined therapy with bioactive compounds such as flavonoids. This review embraces the role of flavonoids on DOX treatment side effects. Protective properties of some flavonoidss against DOX toxicity have been investigated and observed mainly in heart but also in liver, kidney, brain, testis or bone marrow. Protective mechanisms involve reduction of oxidative stress by decrease of ROS levels and/or increase antioxidant defenses and interferences with autophagy, apoptosis and inflammation. Studies in cancer cells have reported that the anticancer activity of DOX was not compromised by the flavonoids. Moreover, some of them increased DOX efficiency as anti-cancer drug even in multidrug resistant cells.

The anticancer potential of the dietary polyphenol rutin: Current status, challenges, and perspectives

Rutin is one of the most common dietary polyphenols found in vegetables, fruits, and other plants. It is metabolized by the mammalian gut microbiota and absorbed from the intestines, and becomes bioavailable in the form of conjugated metabolites. Rutin exhibits a plethora of bioactive properties, making it an extremely promising phytochemical. Numerous studies demonstrate that rutin can act as a chemotherapeutic and chemopreventive agent, and its anticancer effects can be mediated through the suppression of cell proliferation, the induction of apoptosis or autophagy, and the hindering of angiogenesis and metastasis. Rutin has been found to modulate multiple molecular targets involved in carcinogenesis, such as cell cycle mediators, cellular kinases, inflammatory cytokines, transcription factors, drug transporters, and reactive oxygen species. This review summarizes the natural sources of rutin, its bioavailability, and in particular its potential use as an anticancer agent, with highlighting its anticancer mechanisms as well as molecular targets. Additionally, this review updates the anticancer potential of its analogs, nanoformulations, and metabolites, and discusses relevant safety issues. Overall, rutin is a promising natural dietary compound with promising anticancer potential and can be widely used in functional foods, dietary supplements, and pharmaceuticals for the prevention and management of cancer.

Suaeda vermiculata Aqueous-Ethanolic Extract-Based Mitigation of CCl4-Induced Hepatotoxicity in Rats, and HepG-2 and HepG-2/ADR Cell-Lines-Based Cytotoxicity Evaluations

Suaeda vermiculata, an edible halophytic plant, used by desert nomads to treat jaundice, was investigated for its hepatoprotective bioactivity and safety profile on its mother liquor aqueous-ethanolic extract. Upon LC-MS (Liquid Chromatography-Mass Spectrometry) analysis, the presence of several constituents including three major flavonoids, namely quercetin, quercetin-3-O-rutinoside, and kaempferol-O-(acetyl)-hexoside-pentoside were confirmed. The aqueous-ethanolic extract, rich in antioxidants, quenched the DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals, and also showed noticeable levels of radical scavenging capacity in ABTS (2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid) assay. For the hepatoprotective activity confirmation, the male rat groups were fed daily, for 7 days (n = 8/group, p.o.), either carboxyl methylcellulose (CMC) 0.5%, silymarin 200 mg/kg, the aqueous-ethanolic extract of the plant Suaeda vermiculata (100, 250, and 500 mg/kg extract), or quercetin (100 mg/kg) alone, and on day 7 of the administrations, all the animal groups, excluding a naïve (250 mg/kg aqueous-ethanolic extract-fed), and an intact animal group were induced hepatotoxicity by intraperitoneally administering carbon tetrachloride (CCl₄). All the animals were sacrificed after 24 h, and aspartate transaminase and alanine transaminase serum levels were observed, which were noted to be significantly decreased for the aqueous-ethanolic extract, silymarin, and quercetin-fed groups in comparison to the CMC-fed group (p < 0.0001). No noticeable adverse effects were observed on the liver, kidney, or heart's functions of the naïve (250 mg/kg) group. The aqueous-ethanolic extract was found to be safe in the acute toxicity (5 g/kg) test and showed hepatoprotection and safety at higher doses. Further upon, the cytotoxicity testings in HepG-2 and HepG-2/ADR (Adriamycin resistant) cell-lines were also investigated, and the IC₅₀ values were recorded at 56.19±2.55 µg/mL, and 78.40±0.32 µg/mL (p < 0.001, Relative Resistance RR 1.39), respectively, while the doxorubicin (Adriamycin) IC₅₀ values were found to be 1.3±0.064, and 4.77±1.05 µg/mL (p < 0.001, RR 3.67), respectively. The HepG-2/ADR cell-lines when tested in a combination of the aqueous-ethanolic extract with doxorubicin, a significant reversal in the doxorubicin's IC₅₀ value by 2.77 folds (p < 0.001, CI = 0.56) was noted as compared to the cytotoxicity test where the extract was absent. The mode of action for the reversal was determined to be synergistic in nature indicating the role of the aqueous-ethanolic extract.

Targeting Multiple Signaling Pathways in Cancer: The Rutin Therapeutic Approach

Multiple dysregulated signaling pathways are implicated in the pathogenesis of cancer. The conventional therapies used in cancer prevention/treatment suffer from low efficacy, considerable toxicity, and high cost. Hence, the discovery and development of novel multi-targeted agents to attenuate the dysregulated signaling in cancer is of great importance. In recent decades, phytochemicals from dietary and medicinal plants have been successfully introduced as alternative anticancer agents due to their ability to modulate numerous oncogenic and oncosuppressive signaling pathways. Rutin (also known as rutoside, quercetin-3-O-rutinoside and sophorin) is an active plant-derived flavonoid that is widely distributed in various vegetables, fruits, and medicinal plants, including asparagus, buckwheat, apricots, apples, cherries, grapes, grapefruit, plums, oranges, and tea. Rutin has been shown to target various inflammatory, apoptotic, autophagic, and angiogenic signaling mediators, including nuclear factor-κB, tumor necrosis factor-α, interleukins, light chain 3/Beclin, B cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein, caspases, and vascular endothelial growth factor. A comprehensive and critical analysis of the anticancer potential of rutin and associated molecular targets amongst various cancer types has not been performed previously. Accordingly, the purpose of this review is to present an up-to-date and critical evaluation of multiple cellular and molecular mechanisms through which the anticancer effects of rutin are known to be exerted. The current challenges and limitations as well as future directions of research are also discussed.

Wnt-β-catenin Signaling Pathway, the Achilles' Heels of Cancer Multidrug Resistance

BACKGROUND

Most of the anticancer chemotherapies are hampered via the development of multidrug resistance (MDR), which is the resistance of tumor cells against cytotoxic effects of multiple chemotherapeutic agents. Overexpression and/or over-activation of ATP-dependent drug efflux transporters is a key mechanism underlying MDR development. Moreover, enhancement of drug metabolism, changes in drug targets and aberrant activation of the main signaling pathways, including Wnt, Akt and NF-κB are also responsible for MDR.

METHODS

In this study, we have reviewed the roles of Wnt signaling in MDR as well as its potential therapeutic significance. Pubmed and Scopus have been searched using Wnt, β-catenin, cancer, MDR and multidrug resistance as keywords. The last search was done in March 2019. Manuscripts investigating the roles of Wnt signaling in MDR or studying the modulation of MDR through the inhibition of Wnt signaling have been involved in the study. The main focus of the manuscript is regulation of MDR related transporters by canonical Wnt signaling pathway.

RESULT AND CONCLUSION

Wnt signaling has been involved in several pathophysiological states, including carcinogenesis and embryonic development. Wnt signaling is linked to various aspects of MDR including P-glycoprotein and multidrug resistance protein 1 regulation through its canonical pathways. Aberrant activation of Wnt/β- catenin signaling leads to the induction of cancer MDR mainly through the overexpression and/or over-activation of MDR related transporters. Accordingly, Wnt/β-catenin signaling can be a potential target for modulating cancer MDR.

Combination Therapy of Doxorubicin and Quercetin on Multidrug-Resistant Breast Cancer and Their Sequential Delivery by Reduction-Sensitive Hyaluronic Acid-Based Conjugate/d-α-Tocopheryl Poly(ethylene glycol) 1000 Succinate Mixed Micelles

The therapeutic efficacy of chemotherapy in many types of hematological malignancies and solid tumors is dramatically hindered by multidrug resistance (MDR). This work presents a combination strategy of pretreatment of MDA-MB-231/MDR1 cells with quercetin (QU) followed by doxorubicin (DOX) to overcome MDR, which can be delivered by mixed micelles composed of the reduction-sensitive hyaluronic acid-based conjugate and d-α-tocopheryl poly(ethylene glycol) 1000 succinate. The combination strategy can enhance the cytotoxicity of DOX on MDA-MB-231/MDR1 cells by increasing intracellular DOX accumulation and facilitating DOX-induced apoptosis. The probable MDR reversal mechanisms are that the pretreatment cells with QU-loaded mixed micelles downregulate P-glycoprotein expression to decrease DOX efflux as well as initiate mitochondria-dependent apoptotic pathways to accelerate DOX-induced apoptosis. In addition, this combination strategy can not only potentiate in vivo tumor-targeting efficiency but also enhance the antitumor effect in MDA-MB-231/MDR1-bearing nude mice without toxicity or side effects. This research suggests that the co-administration of natural compounds and chemotherapeutic drugs could be an effective strategy to overcome tumor MDR, which deserves further exploration.

Small Molecule Wnt Pathway Modulators from Natural Sources: History, State of the Art and Perspectives

The Wnt signaling is one of the major pathways known to regulate embryonic development, tissue renewal and regeneration in multicellular organisms. Dysregulations of the pathway are a common cause of several types of cancer and other diseases, such as osteoporosis and rheumatoid arthritis. This makes Wnt signaling an important therapeutic target. Small molecule activators and inhibitors of signaling pathways are important biomedical tools which allow one to harness signaling processes in the organism for therapeutic purposes in affordable and specific ways. Natural products are a well known source of biologically active small molecules with therapeutic potential. In this article, we provide an up-to-date overview of existing small molecule modulators of the Wnt pathway derived from natural products. In the first part of the review, we focus on Wnt pathway activators, which can be used for regenerative therapy in various tissues such as skin, bone, cartilage and the nervous system. The second part describes inhibitors of the pathway, which are desired agents for targeted therapies against different cancers. In each part, we pay specific attention to the mechanisms of action of the natural products, to the models on which they were investigated, and to the potential of different taxa to yield bioactive molecules capable of regulating the Wnt signaling.

Parkinson's disease, aging and adult neurogenesis: Wnt/β-catenin signalling as the key to unlock the mystery of endogenous brain repair

A common hallmark of age-dependent neurodegenerative diseases is an impairment of adult neurogenesis. Wingless-type mouse mammary tumor virus integration site (Wnt)/β-catenin (WβC) signalling is a vital pathway for dopaminergic (DAergic) neurogenesis and an essential signalling system during embryonic development and aging, the most critical risk factor for Parkinson's disease (PD). To date, there is no known cause or cure for PD. Here we focus on the potential to reawaken the impaired neurogenic niches to rejuvenate and repair the aged PD brain. Specifically, we highlight WβC-signalling in the plasticity of the subventricular zone (SVZ), the largest germinal region in the mature brain innervated by nigrostriatal DAergic terminals, and the mesencephalic aqueduct-periventricular region (Aq-PVR) Wnt-sensitive niche, which is in proximity to the SNpc and harbors neural stem progenitor cells (NSCs) with DAergic potential. The hallmark of the WβC pathway is the cytosolic accumulation of β-catenin, which enters the nucleus and associates with T cell factor/lymphoid enhancer binding factor (TCF/LEF) transcription factors, leading to the transcription of Wnt target genes. Here, we underscore the dynamic interplay between DAergic innervation and astroglial-derived factors regulating WβC-dependent transcription of key genes orchestrating NSC proliferation, survival, migration and differentiation. Aging, inflammation and oxidative stress synergize with neurotoxin exposure in "turning off" the WβC neurogenic switch via down-regulation of the nuclear factor erythroid-2-related factor 2/Wnt-regulated signalosome, a key player in the maintenance of antioxidant self-defense mechanisms and NSC homeostasis. Harnessing WβC-signalling in the aged PD brain can thus restore neurogenesis, rejuvenate the microenvironment, and promote neurorescue and regeneration.

Defying Multidrug Resistance! Modulation of Related Transporters by Flavonoids and Flavonolignans

Multidrug resistance (MDR) is a major challenge for the 21th century in both cancer chemotherapy and antibiotic treatment of bacterial infections. Efflux pumps and transport proteins play an important role in MDR. Compounds displaying inhibitory activity toward these proteins are prospective for adjuvant treatment of such conditions. Natural low-cost and nontoxic flavonoids, thanks to their vast structural diversity, offer a great pool of lead structures with broad possibility of chemical derivatizations. Various flavonoids were found to reverse both antineoplastic and bacterial multidrug resistance by inhibiting Adenosine triphosphate Binding Cassette (ABC)-transporters (human P-glycoprotein, multidrug resistance-associated protein MRP-1, breast cancer resistance protein, and bacterial ABC transporters), as well as other bacterial drug efflux pumps: major facilitator superfamily (MFS), multidrug and toxic compound extrusion (MATE), small multidrug resistance (SMR) and resistance-nodulation-cell-division (RND) transporters, and glucose transporters. Flavonoids and particularly flavonolignans are therefore highly prospective compounds for defying multidrug resistance.

Medicinal chemistry strategies to discover P-glycoprotein inhibitors: An update

The presence of multidrug resistance (MDR) in malignant tumors is one of the primary causes of treatment failure in cancer chemotherapy. The overexpression of the ATP binding cassette (ABC) transporter, P-glycoprotein (P-gp), which significantly increases the efflux of certain anticancer drugs from tumor cells, produces MDR. Therefore, inhibition of P-gp may represent a viable therapeutic strategy to overcome cancer MDR. Over the past 4 decades, many compounds with P-gp inhibitory efficacy (referred to as first- and second-generation P-gp inhibitors) have been identified or synthesized. However, these compounds were not successful in clinical trials due to a lack of efficacy and/or untoward toxicity. Subsequently, third- and fourth-generation P-gp inhibitors were developed but dedicated clinical trials did not indicate a significant therapeutic effect. In recent years, an extraordinary array of highly potent, selective, and low-toxicity P-gp inhibitors have been reported. Herein, we provide a comprehensive review of the synthetic and natural products that have specific inhibitory activity on P-gp drug efflux as well as promising chemosensitizing efficacy in MDR cancer cells. The present review focuses primarily on the structural features, design strategies, and structure-activity relationships (SAR) of these compounds.

WNT Signaling in Tumors: The Way to Evade Drugs and Immunity

WNT/β-catenin signaling is involved in many physiological processes. Its implication in embryonic development, cell migration, and polarization has been shown. Nevertheless, alterations in this signaling have also been related with pathological events such as sustaining and proliferating the cancer stem cell (CSC) subset present in the tumor bulk. Related with this, WNT signaling has been associated with the maintenance, expansion, and epithelial-mesenchymal transition of stem cells, and furthermore with two distinctive features of this tumor population: therapeutic resistance (MDR, multidrug resistance) and immune escape. These mechanisms are developed and maintained by WNT activation through the transcriptional control of the genes involved in such processes. This review focuses on the description of the best known WNT pathways and the molecules involved in them. Special attention is given to the WNT cascade proteins deregulated in tumors, which have a decisive role in tumor survival. Some of these proteins function as extrusion pumps that, in the course of chemotherapy, expel the drugs from the cells; others help the tumoral cells hide from the immune effector mechanisms. Among the WNT targets involved in drug resistance, the drug extrusion pump MDR-1 (P-GP, ABCB1) and the cell adhesion molecules from the CD44 family are highlighted. The chemokine CCL4 and the immune checkpoint proteins CD47 and PD-L1 are included in the list of WNT target molecules with a role in immunity escape. This pathway should be a main target in cancer therapy as WNT signaling activation is essential for tumor progression and survival, even in the presence of the anti-tumoral immune response and/or antineoplastic drugs. The appropriate design and combination of anti-tumoral strategies, based on the modulation of WNT mediators and/or protein targets, could negatively affect the growth of tumoral cells, improving the efficacy of these types of therapies.

Chemopreventive and anticancer activity of flavonoids and its possibility for clinical use by combining with conventional chemotherapeutic agents

Cancer is a diverse class of diseases characterized by uncontrolled cell growth with the potential to invade and spread to other parts of the body, and continues to be one of the leading causes of death worldwide. Conventional cancer treatment modalities include antitumor drugs, surgical resection, locally targeted therapies such as radiation therapy. Along with improved understanding of the molecular pathogenesis of various cancers, generation and the use of smart targeted anti-cancer drugs have been challenged. The need for novel therapeutic strategies remains paramount given the sustained development of drug resistance, tumor recurrence, and metastasis. Development of new strategies aimed at improving chemotherapy sensitivity and minimizing the adverse side effects is thus essential for obtaining satisfied therapeutic outcomes for patients and enhancing their quality of life. Emerging evidence has reported that many cancer patients use either herbs employed in complementary therapies or dietary agents that influence cellular signaling worldwide. Numerous components of edible plants, collectively termed phytochemicals that have beneficial effects for health, are being reported increasingly in the scientific literature. Of those, flavonoids have attracted much attention by virtue of its wide variety of biological functions including antioxidant, anti-inflammatory, and anticancer activity. In this review, we highlight the molecular mechanisms underlying its multiple pharmacological effects, especially focusing on cancer chemoprevention. We further discuss possible strategies to develop anticancer therapy by combining flavonoids nutraceuticals and conventional chemotherapeutic agents. We also highlight numerous pharmacokinetic challenges such as bioavailability, drug-drug interactions, which are still fundamental questions concerning its future clinical application.

Glabridin resensitizes p-glycoprotein-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic agents

Multidrug resistance (MDR) remains an obstacle to chemotherapy related with the overexpression of several efflux membrane proteins, and p-glycoprotein (P-gp) is the most studied among them. Thus, continuous investigational efforts are necessary to find valuable MDR reversal agents, and the flavonoid compound glabridin (GBD) seems to be a promising candidate. This study aimed to investigate the potential of GBD against MDR and explore the possible mechanisms. First, we found that GBD could decrease the half maximal inhibitory concentration of paclitaxel and doxorubicin (DOX) in breast cancer cells like MDA-MB-231/MDR1 cells and MCF-7/ADR cells. It was further explained that GBD enhanced the apoptosis of MDA-MB-231/MDR1 cells induced by DOX, due to the increased accumulation of DOX. Then, tests were performed to explore the possible MDR reversal mechanisms. On one hand, GBD can suppress the expression of P-gp. On the other hand, GBD can downregulate the activity of P-gp ATPase when cotreated with DOX or verapamil, revealing that GBD was a substrate of P-gp. Moreover, the obtained kinetic inhibition parameters proved that GBD was a competitive inhibitor of P-gp, and in molecular docking simulation modeling, GBD exhibited stronger binding affinity with P-gp than DOX. In conclusion, GBD can increase the accumulation of DOX in MDA-MB-231/MDR1 cells by suppressing the expression of P-gp and competitively inhibiting the P-gp efflux pump and enhance the apoptosis of MDA-MB-231/MDR1 cells induced by DOX, and thus realize reversal effects on MDR. Therefore, the combination therapy of anticancer drugs and flavonoid-like GBD is a promising strategy to overcome P-gp-mediated MDR.