Quercetin induces the apoptosis of human ovarian carcinoma cells by upregulating the expression of microRNA-145

Therapeutic effects and molecular mechanisms of quercetin in gynecological disorders

Quercetin is a representative flavonoid that is widely present in fruits, herbs, and vegetables. It is also an important active core component in traditional Chinese medicines. As an important flavonoid, quercetin has various properties and exerts antioxidant, anti-inflammatory, and cardioprotective effects. The public interest in quercetin is increasing, and quercetin has been used to prevent or treat numerous of diseases, such as polycystic ovary syndrome (PCOS), cancer, autoimmune diseases and chronic cardiovascular diseases, in clinical experiments and animal studies due to its powerful antioxidant properties and minimal side effects. Quercetin exerts marked pharmacological effects on gynecological disorders; however, there have been no reviews about the potential health benefits of quercetin in the context of gynecological disorders, including PCOS, premature ovary failure (POF), endometriosis (EM), ovarian cancer (OC), cervical cancer (CC) and endometrial carcinoma (EC). Thus, this review aimed to summarize the biological effects of quercetin on gynecological disorders and its mechanisms.

Plant-Derived Epi-Nutraceuticals as Potential Broad-Spectrum Anti-Viral Agents

Although the COVID-19 pandemic appears to be diminishing, the emergence of SARS-CoV-2 variants represents a threat to humans due to their inherent transmissibility, immunological evasion, virulence, and invulnerability to existing therapies. The COVID-19 pandemic affected more than 500 million people and caused over 6 million deaths. Vaccines are essential, but in circumstances in which vaccination is not accessible or in individuals with compromised immune systems, drugs can provide additional protection. Targeting host signaling pathways is recommended due to their genomic stability and resistance barriers. Moreover, targeting host factors allows us to develop compounds that are effective against different viral variants as well as against newly emerging virus strains. In recent years, the globe has experienced climate change, which may contribute to the emergence and spread of infectious diseases through a variety of factors. Warmer temperatures and changing precipitation patterns can increase the geographic range of disease-carrying vectors, increasing the risk of diseases spreading to new areas. Climate change may also affect vector behavior, leading to a longer breeding season and more breeding sites for disease vectors. Climate change may also disrupt ecosystems, bringing humans closer to wildlife that transmits zoonotic diseases. All the above factors may accelerate the emergence of new viral epidemics. Plant-derived products, which have been used in traditional medicine for treating pathological conditions, offer structurally novel therapeutic compounds, including those with anti-viral activity. In addition, plant-derived bioactive substances might serve as the ideal basis for developing sustainable/efficient/cost-effective anti-viral alternatives. Interest in herbal antiviral products has increased. More than 50% of approved drugs originate from herbal sources. Plant-derived compounds offer diverse structures and bioactive molecules that are candidates for new drug development. Combining these therapies with conventional drugs could improve patient outcomes. Epigenetics modifications in the genome can affect gene expression without altering DNA sequences. Host cells can use epigenetic gene regulation as a mechanism to silence incoming viral DNA molecules, while viruses recruit cellular epitranscriptomic (covalent modifications of RNAs) modifiers to increase the translational efficiency and transcript stability of viral transcripts to enhance viral gene expression and replication. Moreover, viruses manipulate host cells' epigenetic machinery to ensure productive viral infections. Environmental factors, such as natural products, may influence epigenetic modifications. In this review, we explore the potential of plant-derived substances as epigenetic modifiers for broad-spectrum anti-viral activity, reviewing their modulation processes and anti-viral effects on DNA and RNA viruses, as well as addressing future research objectives in this rapidly emerging field.

Selected Flavonols in Breast and Gynecological Cancer: A Systematic Review

The consumption of foods that are rich in phenolic compounds has chemopreventive effects on many cancers, including breast cancer, ovarian cancer, and endometrial cancer. A wide spectrum of their health-promoting properties such as antioxidant, anti-inflammatory, and anticancer activities, has been demonstrated. This paper analyzes the mechanisms of the anticancer action of selected common flavonols, including kemferol, myricetin, quercetin, fisetin, galangin, isorhamnetin, and morin, in preclinical studies, with particular emphasis on in vitro studies in gynecological cancers and breast cancer. In the future, these compounds may find applications in the prevention and treatment of gynecological cancers and breast cancer, but this requires further, more advanced research.

Quercetin modulates signal transductions and targets non-coding RNAs against cancer development

In recent decades, various investigations have indicated that natural compounds have great potential in the prevention and treatment of different chronic disorders including different types of cancer. As a bioactive flavonoid, Quercetin (Qu) is a dietary ingredient enjoying high pharmacological values and health-promoting effects due to its antioxidant and anti-inflammatory characterization. Conclusive in vitro and in vivo evidence has revealed that Qu has great potential in cancer prevention and development. Qu exerts its anticancer influences by altering various cellular processes such as apoptosis, autophagy, angiogenesis, metastasis, cell cycle, and proliferation. In this way, Qu by targeting numerous signaling pathways as well as non-coding RNAs regulates several cellular mechanisms to suppress cancer occurrence and promotion. This review aimed to summarize the impact of Qu on the molecular pathways and non-coding RNAs in modulating various cancer-associated cellular mechanisms.

The polymorphism rs4705342 in the promoter of miR-143/145 is related to the risk of epithelial ovarian cancer and patient prognosis

Objective

To evaluate the effects of two genetic variants in the promoter of the miR-143/145 cluster on the risk of epithelial ovarian cancer (EOC) and the prognosis of EOC patients.

Study design

Genotypes were determined by the polymerase chain reaction and ligase detection reaction method in 563 EOC patients and 576 healthy women. The expression of miR-143 and miR-145 were detected by quantitative real-time polymerase chain reaction (qRT-PCR) in fifty-two EOC tissues.

Results

The rs4705342 CC genotype frequencies in EOC patients were higher than those in the controls (P = 0.014). Furthermore, the CC genotype of rs4705342 was associated with an advanced FIGO stage of EOC patients (P = 0.046). Patients with the rs4705342 CC genotype had shorter progression-free survival (PFS) and overall survival (OS) times than those carrying the TT genotype in multivariable analysis adjusting for clinical variables (HR = 1.30, 95% CI = 1.04-1.62, P = 0.020; HR = 1.33, 95% CI = 1.05-1.70, P = 0.020). In addition, the miR-145 levels were lower in EOC tissues with the rs4705342 CC genotype than in those with the TT genotype (P = 0.005).

Conclusion

The CC genotype of rs4705342 was related to an increased risk of EOC and poor prognosis of EOC patients, and rs4705342 may serve as a molecular marker for predicting the development of EOC and the clinical outcome of EOC patients.

The Involvement of Natural Polyphenols in Molecular Mechanisms Inducing Apoptosis in Tumor Cells: A Promising Adjuvant in Cancer Therapy

Various literature data show how a diet rich in vegetables could reduce the incidence of several cancers due to the contribution of the natural polyphenols contained in them. Polyphenols are attributed multiple pharmacological actions such as anti-inflammatory, anti-oxidant, antibiotic, antiseptic, anti-allergic, cardioprotective and even anti-tumor properties. The multiple mechanisms involved in their anti-tumor action include signaling pathways modulation associated with cell proliferation, differentiation, migration, angiogenesis, metastasis and cell death. Since the dysregulation of death processes is involved in cancer etiopathology, the natural compounds able to kill cancer cells could be used as new anticancer agents. Apoptosis, a programmed form of cell death, is the most potent defense against cancer and the main mechanism used by both chemotherapy agents and polyphenols. The aim of this review is to provide an update of literature data on the apoptotic molecular mechanisms induced by some representative polyphenol family members in cancer cells. This aspect is particularly important because it may be useful in the design of new therapeutic strategies against cancer involving the polyphenols as adjuvants.

Natural flavonoids exhibit potent anticancer activity by targeting microRNAs in cancer: A signature step hinting towards clinical perfection

Cancer prevalence and its rate of incidence are constantly rising since the past few decades. Owing to the toxicity of present-day antineoplastic drugs, it is imperative to explore safer and more effective molecules to combat and/or prevent this dreaded disease. Flavonoids, a class of polyphenols, have exhibited multifaceted implications against several diseases including cancer, without showing significant toxicity towards the normal cells. Shredded pieces of evidence suggest that flavonoids can enhance drug sensitivity and suppress proliferation, metastasis, and angiogenesis of cancer cells by modulating several oncogenic or oncosuppressor microRNAs (miRNAs, miRs). They play pivotal roles in regulation of various biological and pathological processes, including various cancers. In the present review, the structure, chemistry and miR targeting efficacy of quercetin, luteolin, silibinin, genistein, epigallocatechin gallate, and cyanidin against several cancer types are comprehensively discussed. miRs are considered as next-generation medicine of recent times, and their targeting by naturally occurring flavonoids in cancer cells could be deemed as a signature step. We anticipate that our compilations related to miRNA-mediated regulation of cancer cells by flavonoids might catapult the clinical investigations and affirmation in the future.

Contribution of Non-Coding RNAs to Anticancer Effects of Dietary Polyphenols: Chlorogenic Acid, Curcumin, Epigallocatechin-3-Gallate, Genistein, Quercetin and Resveratrol

Growing evidence has been accumulated to show the anticancer effects of daily consumption of polyphenols. These dietary polyphenols include chlorogenic acid, curcumin, epigallocatechin-3-O-gallate, genistein, quercetin, and resveratrol. These polyphenols have similar chemical and biological properties in that they can act as antioxidants and exert the anticancer effects via cell signaling pathways involving their reactive oxygen species (ROS)-scavenging activity. These polyphenols may also act as pro-oxidants under certain conditions, especially at high concentrations. Epigenetic modifications, including dysregulation of noncoding RNAs (ncRNAs) such as microRNAs, long noncoding RNAs, and circular RNAs are now known to be involved in the anticancer effects of polyphenols. These polyphenols can modulate the expression/activity of the component molecules in ROS-scavenger-triggered anticancer pathways (RSTAPs) by increasing the expression of tumor-suppressive ncRNAs and decreasing the expression of oncogenic ncRNAs in general. Multiple ncRNAs are similarly modulated by multiple polyphenols. Many of the targets of ncRNAs affected by these polyphenols are components of RSTAPs. Therefore, ncRNA modulation may enhance the anticancer effects of polyphenols via RSTAPs in an additive or synergistic manner, although other mechanisms may be operating as well.

Using ncRNAs as Tools in Cancer Diagnosis and Treatment-The Way towards Personalized Medicine to Improve Patients' Health

Although the first discovery of a non-coding RNA (ncRNA) dates back to 1958, only in recent years has the complexity of the transcriptome started to be elucidated. However, its components are still under investigation and their identification is one of the challenges that scientists are presently facing. In addition, their function is still far from being fully understood. The non-coding portion of the genome is indeed the largest, both quantitatively and qualitatively. A large fraction of these ncRNAs have a regulatory role either in coding mRNAs or in other ncRNAs, creating an intracellular network of crossed interactions (competing endogenous RNA networks, or ceRNET) that fine-tune the gene expression in both health and disease. The alteration of the equilibrium among such interactions can be enough to cause a transition from health to disease, but the opposite is equally true, leading to the possibility of intervening based on these mechanisms to cure human conditions. In this review, we summarize the present knowledge on these mechanisms, illustrating how they can be used for disease treatment, the current challenges and pitfalls, and the roles of environmental and lifestyle-related contributing factors, in addition to the ethical, legal, and social issues arising from their (improper) use.

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.

Anti-Cancer Effects of Dietary Polyphenols via ROS-Mediated Pathway with Their Modulation of MicroRNAs

Consumption of coffee, tea, wine, curry, and soybeans has been linked to a lower risk of cancer in epidemiological studies. Several cell-based and animal studies have shown that dietary polyphenols like chlorogenic acid, curcumin, epigallocatechin-3-O-gallate, genistein, quercetin and resveratrol play a major role in these anticancer effects. Several mechanisms have been proposed to explain the anticancer effects of polyphenols. Depending on the cellular microenvironment, these polyphenols can exert double-faced actions as either an antioxidant or a prooxidant, and one of the representative anticancer mechanisms is a reactive oxygen species (ROS)-mediated mechanism. These polyphenols can also influence microRNA (miR) expression. In general, they can modulate the expression/activity of the constituent molecules in ROS-mediated anticancer pathways by increasing the expression of tumor-suppressive miRs and decreasing the expression of oncogenic miRs. Thus, miR modulation may enhance the anticancer effects of polyphenols through the ROS-mediated pathways in an additive or synergistic manner. More precise human clinical studies on the effects of dietary polyphenols on miR expression will provide convincing evidence of the preventive roles of dietary polyphenols in cancer and other diseases.

The Targeting of Noncoding RNAs by Quercetin in Cancer Prevention and Therapy

The dietary flavonoid quercetin is ubiquitously distributed in fruits, vegetables, and medicinal herbs. Quercetin has been a focal point in recent years due to its versatile health-promoting benefits and high pharmacological values. It has well documented that quercetin exerts anticancer actions by inhibiting cell proliferation, inducing apoptosis, and retarding the invasion and metastasis of cancer cells. However, the exact mechanism of quercetin-mediated cancer chemoprevention is still not fully understood. With the advances in high-throughput sequencing technologies, the intricate oncogenic signaling networks have been gradually characterized. Increasing evidence on the close association between noncoding RNA (ncRNAs) and cancer etiopathogenesis emphasizes the potential of ncRNAs as promising molecular targets for cancer treatment. Available experimental studies indicate that quercetin can dominate multiple cancer-associated ncRNAs, hence repressing carcinogenesis and cancer development. Thus, modulation of ncRNAs serves as a key mechanism responsible for the anticancer effects of quercetin. In this review, we focus on the chemopreventive effects of quercetin on cancer pathogenesis by targeting cancer-relevant ncRNAs, supporting the viewpoint that quercetin holds promise as a drug candidate for cancer chemoprevention and chemotherapy. An in-depth comprehension of the interplay between quercetin and ncRNAs in the inhibition of cancer development and progression will raise the possibility of developing this bioactive compound as an anticancer agent that could be highly efficacious and safe in clinical practice.

Role of Flavonoids as Epigenetic Modulators in Cancer Prevention and Therapy

Epigenetic regulation involves reversible changes in histones and DNA modifications that can be inherited without any changes in the DNA sequence. Dysregulation of normal epigenetic processes can lead to aberrant gene expression as observed in many diseases, notably cancer. Recent insights into the mechanisms of DNA methylation, histone modifications, and non-coding RNAs involved in altered gene expression profiles of tumor cells have caused a paradigm shift in the diagnostic and therapeutic approaches towards cancer. There has been a surge in search for compounds that could modulate the altered epigenetic landscape of tumor cells, and to exploit their therapeutic potential against cancers. Flavonoids are naturally occurring phenol compounds which are abundantly found among phytochemicals and have potentials to modulate epigenetic processes. Knowledge of the precise flavonoid-mediated epigenetic alterations is needed for the development of epigenetics drugs and combinatorial therapeutic approaches against cancers. This review is aimed to comprehensively explore the epigenetic modulations of flavonoids and their anti-tumor activities.

Natural products in the reprogramming of cancer epigenetics

Owing to the technological advancements, including next generation sequencing, the significance of deregulated epigenetic mechanisms in cancer initiation, progression and treatment has become evident. The accumulating knowledge relating to the epigenetic markers viz. DNA methylation, Histone modifications and non-coding RNAs make them one of the most interesting candidates for developing anti-cancer therapies. The reversibility of deregulated epigenetic mechanisms through environmental and dietary factors opens numerous avenues in the field of chemoprevention and drug development. Recent studies have proven that plant-derived natural products encompass a great potential in targeting epigenetic signatures in cancer and numerous natural products are being explored for their possibility to be considered as "epi-drug". This review intends to highlight the major aberrant epigenetic mechanisms and summarizes the essential functions of natural products like Resveratrol, Quercetin, Genistein, EGCG, Curcumin, Sulforaphane, Apigenin, Parthenolide and Berberine in modulating these aberrations. This knowledge along with the challenges and limitations in this field has potential and wider implications in developing novel and successful therapeutic strategies. The increased focus in the area will possibly provide a better understanding for the development of dietary supplements and/or drugs either alone or in combination. The interaction of epigenetics with different hallmarks of cancer and how natural products can be utilized to target them will also be interesting in the future therapeutic approaches.

Flavonoid display ability to target microRNAs in cancer pathogenesis

MicroRNAs (miRNAs) are non-coding, conserved, single-stranded nucleotide sequences involved in physiological and developmental processes. Recent evidence suggests an association between miRNAs' deregulation with initiation, promotion, progression, and drug resistance in cancer cells. Besides, miRNAs are known to regulate the epithelial-mesenchymal transition, angiogenesis, autophagy, and senescence in different cancer types. Previous reports proposed that apart from the antioxidant potential, flavonoids play an essential role in miRNAs modulation associated with changes in cancer-related proteins, tumor suppressor genes, and oncogenes. Thus, flavonoids can suppress proliferation, help in the development of drug sensitivity, suppress metastasis and angiogenesis by modulating miRNAs expression. In the present review, we summarize the role of miRNAs in cancer, drug resistance, and the chemopreventive potential of flavonoids mediated by miRNAs. The potential of flavonoids to modulate miRNAs expression in different cancer types demonstrate their selectivity and importance as regulators of carcinogenesis. Flavonoids as chemopreventive agents targeting miRNAs are extensively studied in vitro, in vivo, and pre-clinical studies, but their efficiency in targeting miRNAs in clinical studies is less investigated. The evidence presented in this review highlights the potential of flavonoids in cancer prevention/treatment by regulating miRNAs, although further investigations are required to validate and establish their clinical usefulness.

MicroRNA-145 plays a role in mitochondrial dysfunction in alveolar epithelial cells in lipopolysaccharide-induced acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome (ARDS) causes substantial mortalities. Alveolar epithelium is one of the main sites of cell injuries in ARDS. As an important kind of microRNAs (miRNAs), microRNA-145 (miR-145) has been studied in various diseases, while its role in ARDS has not been investigated.

METHODS

Lipopolysaccharide (LPS) was intratracheally instilled to establish a rat ARDS model. Cytokines from bronchoalveolar lavage fluid (BALF) were measured using rat tumor necrosis factor-α and interleukin-6 enzyme-linked immunosorbent assay kits (R&D Systems), and the pathological structures were evaluated using hematoxylin and eosin (H&E) staining and transmission electron microscope; the lung miR-145 messenger RNA (mRNA) was detected using quantitative polymerase chain reaction. Bioinformatics focused on the target genes and possible pathways of gene regulation.

RESULTS

A rat model of LPS-induced ARDS was successfully established. The miR-145 was down-regulated in the LPS-induced ARDS lung, and mitochondrial dysfunction was observed in alveolar epithelial cells, most obviously at 72 hours after LPS. TargetScan and miRDB databases were used to predict the target genes of miR-145. A total of 428 overlapping genes were identified, seven genes were associated with mitochondrial function, and Ogt, Camk2d, Slc8a3, and Slc25a25 were verified. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched in the mitogen-activated protein kinase (MAPK) signaling pathway, and Gene Ontology (GO) biological process was mainly enriched in signal transduction and transcription regulation.

CONCLUSIONS

The miR-145 is down-regulated in LPS-induced ARDS, and affects its downstream genes targeting mitochondrial functions.

Quercetin and MicroRNA Interplay in Apoptosis Regulation in Ovarian Cancer

The multifaceted nature of ovarian cancer has severely hampered the development of effective therapeutics over the years. The complicate nature of ovarian cancer makes it therapeutically challenging, therefore, there has been a renewed interest in phytochemistry. Phytochemicals have emerged as a potential therapeutic option due to less side effects. Moreover, the signaling inhibition properties have also been studied extensively in recent times. A growing number of data obtained via high-throughput technologies has started to delineate the complex oncogenic signaling networks, thus broadening the therapeutic opportunities. Within the network, microRNAs (miRNAs) have been shown to play a versatile role in the regulation of cancer. Quercetin has been in the spotlight over the years because of its high pharmacological values and substantial evidence has demonstrated its anti-proliferative effect against various types of cancers. Despite the versatility of quercetin, little is known about its anti-proliferative potential towards ovarian cancer. This review sheds some light on quercetin as an alternative therapeutic approach to cancer. Furthermore, we also addresss the interplay between miRNAs and quercetin in the regulation of apoptosis in ovarian cancer.

Antitumor effects and molecular mechanisms of action of natural products in ovarian cancer

Ovarian cancer is a common malignancy and the second leading cause of mortality among females with genital tract cancer. At present, postoperative platinum drugs and paclitaxel-based chemotherapy is the gold standard treatment for ovarian cancer. However, patients who receive this chemotherapy often develop cumulative toxic effects and are prone to chemotherapy resistance. Therefore, it is necessary to determine more effective treatment options that would be better tolerated by patients. Recent studies have reported the therapeutic effects of numerous natural products in patients with ovarian cancer. Notably, these natural ingredients do not induce adverse effects in healthy cells and tissues, suggesting that natural products may serve as a safe alternative treatment for ovarian cancer. The antitumor effects of natural products are attributed to suppression of cell proliferation and metastasis, stimulation of autophagy, improved chemotherapy sensitivity, and induction of apoptosis. The present review focused on the antitumor effects of several natural products, including curcumin, resveratrol, ginsenosides, (-)-epigallocatechin-3-gallate and quercetin, which are increasingly being investigated as therapeutic options in ovarian cancer, and discussed the molecular mechanisms involved in cell proliferation, apoptosis, autophagy, metastasis and sensitization.

Overview of biological effects of Quercetin on ovary

Over the last few decades, using natural products has been increased to treat different diseases. Today, great attention has been pointed toward the usage of natural products such as flavonoids, especially Quercetin (QUR), in the treatment of diseases. QUR as a natural antioxidant has been traditionally used to prevent or treat a variety of diseases such as cancer, cardiovascular disease, polycystic ovary syndrome (PCOS), obesity, chronic inflammation, and reproductive system dysfunction. Several studies demonstrated that QUR acts as an anti-inflammatory, anti-apoptotic, antioxidant, and anticancer agent. With this in view, in this study, we intended to describe an overview of the biological effects of QUR on the ovary. QUR improves the quality of oocytes and embryos. It affects the proliferation and apoptosis and decreases the oxidative stress in granulosa cells (GCs). Furthermore, QUR can be used as a complementary and alternative therapy in ovarian cancer and it has beneficial effects in the treatment of PCOS patients. It seems that QUR as a supplementary factor has different activities for the treatment of different disorders and it also has bidirectional activities. However, further investigations are needed for understanding the efficacy of QUR in the treatment and improvement of gynecological patients.

Targeting epigenetics in cancer: therapeutic potential of flavonoids

Irrespective of sex and age, cancer is the leading cause of mortality around the globe. Therapeutic incompliance, unwanted effects, and economic burdens imparted by cancer treatments, are primary health challenges. The heritable features in gene expression that are propagated through cell division and contribute to cellular identity without a change in DNA sequence are considered epigenetic characteristics and agents that could interfere with these features and are regarded as potential therapeutic targets. The genetic modification accounts for the recurrence and uncontrolled changes in the physiology of cancer cells. This review focuses on plant-derived flavonoids as a therapeutic tool for cancer, attributed to their ability for epigenetic regulation of cancer pathogenesis. The epigenetic mechanisms of various classes of flavonoids including flavonols, flavones, isoflavones, flavanones, flavan-3-ols, and anthocyanidins, such as cyanidin, delphinidin, and pelargonidin, are discussed. The outstanding results of preclinical studies encourage researchers to design several clinical trials on various flavonoids to ascertain their clinical strength in the treatment of different cancers. The results of such studies will define the clinical fate of these agents in future.

Modulation of Mitochondrial Metabolic Reprogramming and Oxidative Stress to Overcome Chemoresistance in Cancer

Metabolic reprogramming, carried out by cancer cells to rapidly adapt to stress such as hypoxia and limited nutrient conditions, is an emerging concepts in tumor biology, and is now recognized as one of the hallmarks of cancer. In contrast with conventional views, based on the classical Warburg effect, these metabolic alterations require fully functional mitochondria and finely-tuned regulations of their activity. In turn, the reciprocal regulation of the metabolic adaptations of cancer cells and the microenvironment critically influence disease progression and response to therapy. This is also realized through the function of specific stress-adaptive proteins, which are able to relieve oxidative stress, inhibit apoptosis, and facilitate the switch between metabolic pathways. Among these, the molecular chaperone tumor necrosis factor receptor associated protein 1 (TRAP1), the most abundant heat shock protein 90 (HSP90) family member in mitochondria, is particularly relevant because of its role as an oncogene or a tumor suppressor, depending on the metabolic features of the specific tumor. This review highlights the interplay between metabolic reprogramming and cancer progression, and the role of mitochondrial activity and oxidative stress in this setting, examining the possibility of targeting pathways of energy metabolism as a therapeutic strategy to overcome drug resistance, with particular emphasis on natural compounds and inhibitors of mitochondrial HSP90s.

Quercetin, Epigallocatechin Gallate, Curcumin, and Resveratrol: From Dietary Sources to Human MicroRNA Modulation

Epidemiologic studies suggest that dietary polyphenol intake is associated with a lower incidence of several non-communicable diseases. Although several foods contain complex mixtures of polyphenols, numerous factors can affect their content. Besides the well-known capability of these molecules to act as antioxidants, they are able to interact with cell-signaling pathways, modulating gene expression, influencing the activity of transcription factors, and modulating microRNAs. Here we deeply describe four polyphenols used as nutritional supplements: quercetin, resveratrol, epigallocatechin gallate (ECGC), and curcumin, summarizing the current knowledge about them, spanning from dietary sources to the epigenetic capabilities of these compounds on microRNA modulation.

The effect of quercetin on microRNA expression: A critical review

Quercetin, a flavonoid with multiple proven health benefits to both man and animals, displays a plethora of biological activities, collectively referred to as pleiotropic. The most studied of these are antioxidant and anti-inflammatory but modulation of signalling pathways is important as well. One of the lesser-known and recently discovered roles of quercetin, is modulation of microRNA (miRNA) expression. miRNAs are important posttranscriptional modulators that play a critical role in health and disease and many of these non-coding oligonucleotides are recognized as oncogenic or tumor suppressor miRNAs. This review is an evaluation of the recent relevant literature on the subject, with focus on the ability of quercetin to modulate miRNA expression. It includes a summary of recent knowledge on miRNAs deregulated by quercetin, an overview of quercetin pharmacokinetics and miRNA biogenesis, for the interested reader.

DNA damage response and repair in ovarian cancer: Potential targets for therapeutic strategies

Ovarian cancer is among the most lethal gynecologic malignancies with a poor survival prognosis. The current therapeutic strategies involve surgery and chemotherapy. Research is now focused on novel agents especially those targeting DNA damage response (DDR) pathways. Understanding the DDR process in ovarian cancer necessitates having a detailed knowledge on a series of signaling mediators at the cellular and molecular levels. The complexity of the DDR process in ovarian cancer and how this process works in metastatic conditions is comprehensively reviewed. For evaluating the efficacy of therapeutic agents targeting DNA damage in ovarian cancer, we will discuss the components of this system including DDR sensors, DDR transducers, DDR mediators, and DDR effectors. The constituent pathways include DNA repair machinery, cell cycle checkpoints, and apoptotic pathways. We also will assess the potential of active mediators involved in the DDR process such as therapeutic and prognostic candidates that may facilitate future studies.

RETRACTED: Quercetin ameliorates lipopolysaccharide-caused inflammatory damage via down-regulation of miR-221 in WI-38 cells

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Given the comments of Dr Elisabeth Bik regarding this article “… the Western blot bands in all 400+ papers are all very regularly spaced and have a smooth appearance in the shape of a dumbbell or tadpole, without any of the usual smudges or stains. All bands are placed on similar looking backgrounds, suggesting they were copy/pasted from other sources, or computer generated”, the journal requested the authors to provide the raw data. However, the authors were not able to fulfil this request and therefore the Editor-in-Chief decided to retract the article.

Antiproliferative potential from aqueous Viscum album L. preparations and their main constituents in comparison with ricin and purothionin on human cancer cells

ETHNOPHARMACOLOGICAL RELEVANCE

Mistletoe has been used since ancient times in Europe mostly for medicinal purposes. Since 1917, mistletoe preparations have been applied in cancer therapy and today are the most frequently used complementary medicine in tumor treatment. The main cytotoxic constituents of Viscum album are lectins and viscotoxins.

AIM OF THE STUDY

The aim of this in vitro study was to investigate the antiproliferative potential of Viscum album preparations from different host trees and to assess the impact of mistletoe lectin 1 (ML-1) and viscotoxin A (VT-A) in comparison to a structurally similar lectin and thionin.

MATERIALS AND METHODS

By means of widely accepted 2D Alamar Blue Assay, based on population counting of living cells using a fluorescent cell viability dye, the potential impact to inhibit tumor cell of the mistletoe preparations (Iscucin^®) and their single compounds (ML-1 and VT-A) on the cell growth of six human cancer cell lines were evaluated. Also the mixture of ML-1 and VT-A corresponding to the contents in the specific mistletoe preparations were monitored. Ricin and purothionin were used as reference lectin and reference thionin, respectively.

RESULTS

The lung carcinoma cell line HCC827 was very sensitive to the Iscucin^® preparations. Very strong antiproliferative effects were found with Iscucin^®Salicis and Tiliae and a strong with Iscucin^®Crataegi, Mali and Populi. The IC₅₀ concentrations of the Iscucin^® preparations correlated with their respective ML-1 contents, but the ML-1 levels were much lower than the IC₅₀ concentration of isolated ML-1 (1 ng/ml - 56 ng/ml). ML-1 was much more effective than ricin. Iscucin^® preparations, ML-1 and ricin showed antiproliferative activity on human tumor cells. VT-A and purothionin had no effect on cell viability in the concentration ranges tested.

CONCLUSION

The complete mistletoe extract is more potent to inhibit tumor cell proliferation than isolated ML-1 at an equivalent concentration level. Phenolic compounds found in all Iscucin^® preparations might contribute to uphold the cytotoxic activity of ML-1 by antioxidative action. However, further studies are necessary to evaluate the role of VT-A and possible synergistic actions to the antiproliferative effect of aqueous mistletoe extracts.

Effect of Turkish Propolis on miRNA Expression, Cell Cycle, and Apoptosis in Human Breast Cancer (MCF-7) Cells

Enriched in flavonoid compounds, phenol acids, and terpene derivatives, propolis has been shown to regulate apoptosis signaling pathways and alter the expression of microRNAs (miRNAs). In the present study, it has been aimed to examine the effects of Turkish propolis on miRNA levels of breast cancer (MCF-7) cells, and its relationship with cell proliferation and apoptosis. Cytotoxic activity of ethanolic propolis extract (EEP) was evaluated using MTT assay. Mechanisms involved in the cytotoxic action of Turkish propolis in MCF-7 cells were investigated with regard to apoptosis and cell cycle using flow cytometry and western blot. Mitochondrial membrane potential (MMP) were evaluated by spectrofluorometric method. miRNA levels were detected by qRT-PCR method. EEP exhibited selective toxicity against MCF-7 cells compared to normal fibroblast cells. EEP increased the cell cycle arrest at the G₁ phase. EEP elevated the apoptotic cell death through increasing pro-apoptotic protein levels (p21, Bax, p53, p53-Ser46, and p53-Ser15), decreasing MMP and altering the expression levels of specific tumor suppressors (miR-34, miR-15a, and miR-16-5p) and oncogenic (miR-21) miRNAs. These data support that Turkish propolis may be evaluated as a potential natural agent for new anticancer drugs in future.

Effects of quercetin on microRNAs: A mechanistic review

MicroRNA (miRNA)-dependent pathways are one of the newest gene regulation mechanisms in various diseases, particularly in cancers. miRNAs are endogenous noncoding RNAs with about 18 to 25 nucleotide length, which can regulate the expression of at least 60% of human total genome posttranscriptionally. Quercetin is the most abundant flavonoid in a variety of fruits, flowers, and medical herbs, known as a strong free radical scavenger that could show antioxidant, anti-inflammatory, and antitumor activities. Recent studies also reported its strong impact on various miRNA expressions in different abnormalities. In this review, we aimed to summarize the studies focused on the effects of quercetin on different miRNA expressions to more clear the main possible mechanisms of quercetin influences and introduce it as a beneficial agent for regulation of miRNAs in various biological directions.

Enhancing the anti-ovarian cancer activity of quercetin using a self-assembling micelle and thermosensitive hydrogel drug delivery system

Ovarian cancer, as one of the killers that threaten women’s health, has been studied extensively. As a natural bioflavonoid with prospective effects, quercetin is highly recognized for its anti-cancer applications. However, one of the major challenges that quercetin faces is its poor water solubility, instability in physiological media, and subsequent poor bioavailability. Thus, optimizing the ideal drug delivery options is necessary to facilitate the harnessing of the maximum benefits from quercetin. In this study, a quercetin-loaded thermosensitive injectable hydrogel system (Qu-M–hydrogel composites) was constructed based on nanotechnology. Quercetin was encapsulated into MPEG-PCL (with a high drug loading of 7% and minor particle size of 32 nm) and then added into the blank thermosensitive hydrogel Pluronic F-127. The Qu-M–hydrogel composites showed a much slower release than Qu-M in vivo. Moreover, the cytotoxicity, apoptosis induction, and anti-tumor effects of the Qu-M–hydrogel composites on the abdominal SKOV-3 ovarian cancer mouse models were investigated in vivo. Compared with other groups, the Qu-M–hydrogel composites exhibited improved apoptosis induction and cell growth inhibition effects and in vivo trials showed a better balance between the anti-tumor efficacy in the Qu-M–hydrogel composite group than in other groups at an equal drug dose. In conclusion, the prepared Qu-M–hydrogel composites enhanced the anti-tumor activity by providing a high local quercetin concentration, sustained and stable drug release, extended drug retention inside the tumor, and low toxicity to normal tissues. The Qu-M–hydrogel composites might have great potential for clinical application in anti-ovarian cancer activity.

In this study, a quercetin-loaded thermosensitive injectable hydrogel system (Qu-M–hydrogel composites) was constructed based on nanotechnology.

Nutrigenomics in cancer: Revisiting the effects of natural compounds

Nutrigenomics effects have an important role in the manipulation of dietary components for human benefit, particularly in cancer prevention or treatment. The impact of dietary components, including phytochemicals, is largely studied by nutrigenomics, looking at the gene expression and molecular mechanisms interacting with bioactive compounds and nutrients, based on new 'omics' technologies. The high number of preclinical studies proves the relevant role of nutrigenomics in cancer management. By deciphering the network of nutrient-gene connections associated with cancer, relevant data will be transposed as therapeutic interventions for this devastating pathology and for fulfilling the concept of personalized nutrition. All these are presented under the nutrigenomics canopy for a better comprehension of the relation between ingested phytochemicals and chemoprevention or chemotherapy. The profits from the nutrigenomics progress, with a particular focus on the coding and noncoding genes related to the exposure of natural compounds need to be validated. A precise attention receives the evaluation of the role of natural compounds in tandem with conventional therapy using genomic approaches, with emphasis on the capacity to inhibit drug resistance mechanisms. All these relevant nutrigenomics aspects are summarized in the present review paper. It is concluded that further nutrigenomics studies are required to improve our understanding related to the complex mechanisms of action of the natural compounds and for their appropriate application as gears in cancer therapy.

Novel Investigations of Flavonoids as Chemopreventive Agents for Hepatocellular Carcinoma

We would like to highlight the application of natural products to hepatocellular carcinoma (HCC). We will focus on the natural products known as flavonoids, which target this disease at different stages of hepatocarcinogenesis. In spite of the use of chemotherapy and radiotherapy in treating HCC, patients with HCC still face poor prognosis because of the nature of multidrug resistance and toxicity derived from chemotherapy and radiotherapy. Flavonoids can be found in many vegetables, fruits, and herbal medicines that exert their different anticancer effects via different intracellular signaling pathways and serve as antioxidants. In this review, we will discuss seven common flavonoids that exert different biological effects against HCC via different pathways.