Quercetin and ovarian cancer: An evaluation based on a systematic review

The Role of Natural Flavonoids as Telomerase Inhibitors in Suppressing Cancer Growth

Cancer is a complex and multifaceted group of diseases characterized by the uncontrolled growth and spread of abnormal cells. While cancer can be challenging and life-altering, advances in research and development have led to the identification of new promising anti-cancer targets. Telomerase is one such target that is overexpressed in almost all cancer cells and plays a critical role in maintaining telomere length, which is essential for cell proliferation and survival. Inhibiting telomerase activity can lead to telomere shortening and eventual cell death, thus presenting itself as a potential target for cancer therapy. Naturally occurring flavonoids are a class of compounds that have already been shown to possess different biological properties, including the anti-cancer property. They are present in various everyday food sources and richly present in fruits, nuts, soybeans, vegetables, tea, wine, and berries, to name a few. Thus, these flavonoids could inhibit or deactivate telomerase expression in cancer cells by different mechanisms, which include inhibiting the expression of hTERT, mRNA, protein, and nuclear translocation, inhibiting the binding of transcription factors to hTERT promoters, and even telomere shortening. Numerous cell line studies and in vivo experiments have supported this hypothesis, and this development could serve as a vital and innovative therapeutic option for cancer. In this light, we aim to elucidate the role of telomerase as a potential anti-cancer target. Subsequently, we have illustrated that how commonly found natural flavonoids demonstrate their anti-cancer activity via telomerase inactivation in different cancer types, thus proving the potential of these naturally occurring flavonoids as useful therapeutic agents.

Quercetin and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a reproductive endocrine disease, and results to opsomenorrhea or amenorrhea, hairy, acne, acanthosis, infertility, abortion. In the long term, PCOS may also increase the risk of endometrial cancer, diabetes, hypertension, dyslipidemia and other diseases. Till now there is no specific drug for PCOS due to the unclearness of the cause and pathogenesis, as current treatments for PCOS only target certain symptoms. Quercetin (QUR) is a flavonoid drug widely found in Chinese herbal medicines, fruits, leaves, vegetables, seeds and plants roots. Studies on other diseases have found that QUR has anti-oxidant, anti-inflammatory, anti-insulin resistance, anti-cancer and other effects. Some studies have shown that serum testosterone (T), luteinizing hormone (LH), the LH/follicule-stimulating hormone (FSH) ratio, fasting glucose, fasting insulin, HOMA-IR and lipid levels are reduced in PCOS patients with QUR treatment. However, the mechanisms of QUR in PCOS patients have not been completely elucidated. In this review, we retrospect the basic characteristics of QUR, and in vitro studies, animal experiments and clinical trials of QUR and plant extracts containing QUR in the treatment of PCOS. We also summarized the effects and mechanism of QUR in ovarian cells in vitro and PCOS model rats, the changes in relevant parameters after QUR administration in PCOS patients, and its potentially therapeutic applications.

Therapeutic and Nutraceutical Effects of Polyphenolics from Natural Sources

The prevalence of cardiovascular disease, oxidative stress-related complications, and chronic age-related illnesses is gradually increasing worldwide. Several causes include the ineffectiveness of medicinal treatment therapies, their toxicity, their inability to provide radical solutions in some diseases, and the necessity of multiple drug therapy in certain chronic diseases. It is therefore necessary for alternative treatment methods to be sought. In this review, polyphenols were identified and classified according to their chemical structure, and the sources of these polyphenol molecules are indicated. The cardioprotective, ROS scavenging, anti-aging, anticancer properties of polyphenolic compounds have been demonstrated by the results of many studies, and these natural antioxidant molecules are potential alternative therapeutic agents.

Role of Ginseng, Quercetin, and Tea in Enhancing Chemotherapeutic Efficacy of Colorectal Cancer

As the most common gastrointestinal malignancy, colorectal cancer (CRC) remains a leading cause of cancer death worldwide. Although multimodal chemotherapy has effectively improved the prognosis of patients with CRC in recent years, severe chemotherapy-associated side effects and chemoresistance still greatly impair efficacy and limit its clinical application. In response to these challenges, an increasing number of traditional Chinese medicines have been used as synergistic agents for CRC administration. In particular, ginseng, quercetin, and tea, three common dietary supplements, have been shown to possess the potent capacity of enhancing the sensitivity of various chemotherapy drugs and reducing their side effects. Ginseng, also named “the king of herbs”, contains a great variety of anti-cancer compounds, among which ginsenosides are the most abundant and major research objects of various anti-tumor studies. Quercetin is a flavonoid and has been detected in multiple common foods, which possesses a wide range of pharmacological properties, especially with stronger anti-cancer and anti-inflammatory effects. As one of the most consumed beverages, tea has become particularly prevalent in both West and East in recent years. Tea and its major extracts, such as catechins and various constituents, were capable of significantly improving life quality and exerting anti-cancer effects both in vivo and in vitro. In this review, we mainly focused on the adjunctive effects of the three herbs and their constituents on the chemotherapy process of CRC.

Beneficial Actions of Orostachys japonica and Its Compounds against Tumors via MAPK Signaling Pathways

Tumors are one of the most life-threatening diseases, and a variety of cancer treatment options have been continuously introduced in order to overcome cancer and improve conventional therapy. Orostachys japonica (O. japonica), which is a perennial plant belonging to the genus Orostachys of the Crassulaceae family, has been revealed to exhibit pharmacological properties against various tumors in numerous studies. The present review aimed to discuss the biological actions and underlying molecular mechanisms of O. japonica and its representative compounds-kaempferol and quercetin-against tumors. O. japonica reportedly has antiproliferative, anti-angiogenic, and antimetastatic activities against various types of malignant tumors through the induction of apoptosis and cell cycle arrest, a blockade of downstream vascular endothelial growth factor (VEGF)-VEGFR2 pathways, and the regulation of epithelial-to-mesenchymal transition. In addition, emerging studies have highlighted the antitumor efficacy of kaempferol and quercetin. Interestingly, it was found that alterations of the mitogen-activated protein kinase (MAPK) signaling cascades are involved in the pivotal mechanisms of the antitumor effects of O. japonica and its two compounds against cancer cell overgrowth, angiogenesis, and metastasis. In summary, O. japonica could be considered a preventive and therapeutic medicinal plant which exhibits antitumor actions by reversing altered patterns of MAPK cascades, and kaempferol and quercetin might be potential components that can contribute to the efficacy and underlying mechanism of O. japonica.

Network Pharmacology-Based and Clinically Relevant Prediction of the Potential Targets of Chinese Herbs in Ovarian Cancer Patients

Reports increasingly suggest that Chinese herbal medicine (CHM) has been used to treat ovarian cancer (OvCa) with a good curative effect; however, the molecular mechanisms underlying CHM are still unclear. In this retrospective study, we explored CHM's molecular targets for the treatment of OvCa based on clinical data and network pharmacology. We used the Kaplan-Meier method and Cox regression analysis to verify the survival rate of 202 patients with CHM-treated OvCa. The association between CHM and survival time was analyzed by bivariate correlation. A target network of CHM active ingredients against OvCa was established via network pharmacology. Cox regression analysis showed that CHM is an independent favorable prognostic factor. The median survival time was 91 months in the CHM group and 65 months in the non-CHM group. The survival time of FIGO stage III patients in the two groups was 91 months and 52 months, and the median survival period of FIOG stage IV patients was 60 months and 22 months, respectively (p < 0.001). Correlation analysis demonstrated that 12 herbs were closely associated with prognosis, especially in regard to the long-term benefits. Bioinformatics analysis indicated that the anti-OvCa activity of these 12 herbs occurs mainly through the regulation of apoptosis-related protein expression, which promotes OvCa cell apoptosis and inhibits OvCa development. They also regulate the progress of OvCa treatment by promoting or inhibiting protein expression on the p53 signaling pathway and by inhibiting the NF-κB signaling pathway by directly inhibiting NF-κB.

Physician Attitudes and Perceptions of Complementary and Alternative Medicine (CAM): A Multicentre Italian Study

Purpose: Complementary and Alternative Medicine (CAM) interventions are widely used by patients with chronic disorders, including cancer, and may interact with cancer treatment. Physicians are often unaware of this, probably due to poor patient-physician communication on CAM. The purpose of this study was to evaluate physicians' knowledge, attitudes and practice patterns regarding CAM in a survey conducted in Italy. Methods: A questionnaire was administered to 438 physicians (11 Italian hospitals) who predominantly treat patients with chronic disease, to collect personal and professional data and information on attitudes toward CAM and its possible role in Conventional Medicine (CM). Results: Of the 438 participants, most were specialists in oncology (18%), internal medicine (17%), surgery (15%), and radiotherapy (11%). Most worked at university (44%) or research hospitals (31%). Forty-two percent of participants believed that CAM could have an integrative role within CM. Oncologists were the physicians who were best informed on CAM (58%). Physicians working at research institutes or university hospitals had a greater knowledge of CAM than those employed at general hospitals (p < 0.0001), and those who were also involved in research activity had a greater knowledge of CAM than those who were not (p < 0.003). Length of work experience was significantly related to CAM knowledge. Moreover, 55% of participants suggest CAM interventions to their patients and 44% discuss CAM with them. The best-known interventions were acupuncture, Aloe vera and high-dose vitamin C. Conclusion: CAM use by patients with chronic disease and/or cancer has become a topical issue for the scientific community and for physicians. Knowing the reasons that prompt these patients to use CAM and guiding them in their decisions would improve treatment and outcomes and also benefit healthcare systems. Our findings contribute to a greater understanding of CAM knowledge, attitudes, and practice among Italian physicians. Further research is needed to identify the more effective CAM treatments and to work toward an integrated healthcare model.

Effect of Dietary Doses of Quercetin on Hepatic Drug Metabolizing Enzymes in Spontaneously Hypertensive Rats

BACKGROUND

Administration of quercetin (QR) has shown several health benefits in clinical and pre-clinical studies.

OBJECTIVE

This study investigates the effect of dietary doses of QR on hepatic drug metabolizing enzymes in spontaneously hypertensive rats in order to investigate the potential for herb-drug interactions.

METHODS

The activity and/or protein expression of selected cytochrome P450 (CYP) enzymes and microsomal epoxide hydrolase were measured in hepatic microsomes using specific probe substrates and/or polyclonal antibodies. Cytosolic fraction was utilized to measure protein level and activity of major antioxidant systems.

RESULTS

The doses employed in our study did not cause any significant alterations in the activity and/or protein level of CYP1A1, CYP2A6, CYP2E, and glutathione (GSH). While the activity and apoprotein levels of CYP1A2 and CYP2B1/2 were significantly reduced by the medium and high doses of QR, the activity and/or protein level of microsomal CYP3A and cytosolic GSH-S-transferase, GSH reductase, and GSH peroxidase were significantly enhanced. Activity and protein level of CYP2C9 were significantly inhibited by all doses. Only the high-dose QR resulted in significant inhibition of both microsomal and soluble epoxide hydrolase as well as induction of the antioxidant enzymes, catalase and superoxide dismutase.

CONCLUSION

This study demonstrates that dietary doses of QR may offer chemoprevention through stimulation of the endogenous antioxidant systems and inhibition of CYP enzymes involved in bioactivation of procarcinogens. However, modulation of drug metabolizing enzymes by QR could have potential for herb-drug interactions with the possibility of serious complications.

Quercetin and cancer: new insights into its therapeutic effects on ovarian cancer cells

Ovarian cancer is known as a serious malignancy that affects women's reproductive tract and can considerably threat their health. A wide range of molecular mechanisms and genetic modifications have been involved in ovarian cancer pathogenesis making it difficult to develop effective therapeutic platforms. Hence, discovery and developing new therapeutic approaches are required. Medicinal plants, as a new source of drugs, could potentially be used alone or in combination with other medicines in the treatment of various cancers such as ovarian cancer. Among various natural compounds, quercetin has shown great anti-cancer and anti-inflammatory properties. In vitro and in vivo experiments have revealed that quercetin possesses a cytotoxic impact on ovarian cancer cells. Despite obtaining good results both in vitro and in vivo, few clinical studies have assessed the anti-cancer effects of quercetin particularly in the ovarian cancer. Therefore, it seems that further clinical studies may introduce quercetin as therapeutic agent alone or in combination with other chemotherapy drugs to the clinical setting. Here, we not only summarize the anti-cancer effects of quercetin but also highlight the therapeutic effects of quercetin in the ovarian cancer.

Competitive glucose metabolism as a target to boost bladder cancer immunotherapy

Bladder cancer - the tenth most frequent cancer worldwide - has a heterogeneous natural history and clinical behaviour. The predominant histological subtype, urothelial bladder carcinoma, is characterized by high recurrence rates, progression and both primary and acquired resistance to platinum-based therapy, which impose a considerable economic burden on health-care systems and have substantial effects on the quality of life and the overall outcomes of patients with bladder cancer. The incidence of urothelial tumours is increasing owing to population growth and ageing, so novel therapeutic options are vital. Based on work by The Cancer Genome Atlas project, which has identified targetable vulnerabilities in bladder cancer, immune checkpoint inhibitors (ICIs) have arisen as an effective alternative for managing advanced disease. However, although ICIs have shown durable responses in a subset of patients with bladder cancer, the overall response rate is only ~15-25%, which increases the demand for biomarkers of response and therapeutic strategies that can overcome resistance to ICIs. In ICI non-responders, cancer cells use effective mechanisms to evade immune cell antitumour activity; the overlapping Warburg effect machinery of cancer and immune cells is a putative determinant of the immunosuppressive phenotype in bladder cancer. This energetic interplay between tumour and immune cells leads to metabolic competition in the tumour ecosystem, limiting nutrient availability and leading to microenvironmental acidosis, which hinders immune cell function. Thus, molecular hallmarks of cancer cell metabolism are potential therapeutic targets, not only to eliminate malignant cells but also to boost the efficacy of immunotherapy. In this sense, integrating the targeting of tumour metabolism into immunotherapy design seems a rational approach to improve the therapeutic efficacy of ICIs.

Effect of quercetin on ovarian cells of pigs and cattle

The bioflavonoid quercetin is a component of food with numerous biological effects, but its function in reproductive processes and mechanisms in various species remain unclear. The aim of this study was to examine the effect of quercetin on ovarian cells isolated from ovaries of two phytophagous mammalian species (i.e. pigs and cattle). There was analysis of the effect of quercetin (0, 1, 10, and 100 ng/mL) on cultured granulosa cells of pigs and cattle. Proliferation (PCNA) and apoptosis (bax) markers and release of progesterone (P4), testosterone (T), estradiol (E2), and IGF-I were quantified using quantitative immunocytochemistry, enzyme immunoassay, or radioimmunoassay. Treatments with quercetin reduced PCNA and bax accumulation and decreased P4 release from both granulosa cells of pigs and cattle. In cells of pigs, treatment with quercetin reduced T output, however, in cells of cattle quercetin increased T release. In cells of pigs, quercetin reduced IGF-I release. In cells of cattle, quercetin at smaller doses (1 or 10 ng/mL), promoted and at a large dose (100 ng/mL) reduced IGF-I secretions. There was no substantial E2 release from granulosa cells of pigs or cattle. These observations are the first to indicate there is a direct action of quercetin on basic ovarian cell functions (proliferation, apoptosis, and hormones release) which can be species-specific.

Dietary bioflavonoid quercetin modulates porcine ovarian granulosa cell functions in vitro

Quercetin is a dietary bioflavonoid used widely as a food supplement and is generally recognized as safe. The aim of this in vitro study was to examine the steroid hormone (progesterone and 17- β estradiol) release, proliferation (PCNA and cyclin B1) and apoptosis (caspase 3 and p53) of porcine ovarian granulosa cells after the addition of quercetin at concentrations 0.01, 0.1, 1, 10 and 100 μmol L^-1. Progesterone release was stimulated at the concentration 10 μmol L^-1. Quercetin neither had any impact on 17-β estradiol secretion nor on the presence of PCNA. However, a significant enhancement of the occurrence of cyclin B1 was noted except for the lowest concentration 0.01 μmol L^-1. Quercetin did not have any influence on the number of granulosa cells containing caspase 3, but at the concentration 10 μmol L^-1 it inhibited p53 occurrence. Results confirm the safety of quercetin in porcine ovarian granulosa cell model and further suggest its possible concentration-dependent influence on ovarian functions through pathway that may involve progesterone, cyclin B1 and p53.

Quercetin inhibits glucose transport by binding to an exofacial site on GLUT1

Quercetin, a common dietary flavone, is a competitive inhibitor of glucose uptake and is also thought to be transported into cells by GLUT1. In this study, we confirm that quercetin is a competitive inhibitor of GLUT1 and also demonstrate that newly synthesized compounds, WZB-117 and BAY-876 are robust inhibitors of GLUT1 in L929 cells. To measure quercetin interaction with L929 cells, we develop a new fluorescent assay using flow cytometry. The binding of quercetin and its inhibitory effects on 2-deoxyglucose (2DG) uptake showed nearly identical dose dependent effects, with both having maximum effects between 50 and 100 μM and similar half maximum effects at 8.9 and 8.5 μM respectively. The interaction of quercetin was rapid with t_1/2 of 54 s and the onset and loss of its inhibitory effects on 2DG uptake were equally fast. This suggests that either quercetin is simply binding to surface GLUT1 or its transport in and out of the cell reaches equilibrium very quickly. If quercetin is transported, the co-incubation of quercetin with other glucose inhibitors should block quercetin uptake. However, we observed that WZB-117, an exofacial binding inhibitor of GLUT1 reduced quercetin interaction, while cytochalasin B, an endofacial binding inhibitor, enhanced quercetin interaction, and BAY-876 had no effect on quercetin interaction. Taken together, these data are more consistent with quercetin simply binding to GLUT1, but not actually being transported into L929 cells via the glucose channel in GLUT1.

Studying the Inhibitory Effect of Quercetin and Thymoquinone on Human Cytochrome P450 Enzyme Activities

BACKGROUND

Quercetin (QR) and thymoquinone (TQ) are herbal remedies that are currently extensively used by the general population to prevent and treat various chronic conditions. Therefore, investigating the potential of pharmacokinetic interactions caused by the concomitant use of these herbal remedies and conventional medicine is warranted to ensure patient safety.

PURPOSE OF THE STUDY

This study was conducted to determine the inhibitory effect of QR and TQ, two commonly used remedies, on the activities of selected cytochrome P450 (CYP) enzymes that play an important role in drug metabolism and/or toxicology.

MATERIALS AND METHODS

The in vitro studies were conducted using fluorescence-based high throughput assays using human c-DNA baculovirus expressed CYP enzymes. For measuring CYP2E1 activity, a validated High-performance liquid chromatography (HPLC) assay was utilized to measure the formation of 6-hydroxychlorzoxazone.

RESULTS

The obtained half-maximum inhibitory concentration values with known positive control inhibitors of this study were comparable to the published values indicating accurate experimental techniques. Although QR did not show any significant effect on CYP1A2 and CYP2E1, it exhibited a strong inhibitory effect against CYP2D6 and a moderate effect against CYP2C19 and CYP3A4. On the other hand, TQ demonstrated a strong and a moderate inhibitory effect against CYP3A4 and CYP2C19, respectively.

CONCLUSIONS

The findings of this study may indicate that consumption of QR or TQ, in the form of food or dietary supplements, with drugs that are metabolized by CYP2C19, CYP2D6, or CYP3A4 may cause significant herb-drug interactions.

SUMMARY

Neither QR nor TQ has any significant inhibitory effect on the activity of CYP1A2 or CYP2E1 enzymesBoth QR and TQ have a moderate to strong inhibitory effect on CYP3A4 activityQR has a moderate inhibitory effect on CYP2C19 and a strong inhibitory effect on CYP2D6Both QR and TQ are moderate inhibitors of the CYP2C9 activity. Abbreviations used: ABT: Aminobenztriazole, BZF: 7,8 Benzoflavone, CYP: Cytochrome P450, GB: Gingko Biloba, IC50: Half-maximum inhibitory concentration, KTZ: Ketoconazole, QND: Quinidine, QR: Quercetin, TCP: Tranylcypromine, TQ: Thymoquinone.

Telomerase Inhibitors from Natural Products and Their Anticancer Potential

Telomeres and telomerase are nowadays exploring traits on targets for anticancer therapy. Telomerase is a unique reverse transcriptase enzyme, considered as a primary factor in almost all cancer cells, which is mainly responsible to regulate the telomere length. Hence, telomerase ensures the indefinite cell proliferation during malignancy—a hallmark of cancer—and this distinctive feature has provided telomerase as the preferred target for drug development in cancer therapy. Deactivation of telomerase and telomere destabilization by natural products provides an opening to succeed new targets for cancer therapy. This review aims to provide a fundamental knowledge for research on telomere, working regulation of telomerase and its various binding proteins to inhibit the telomere/telomerase complex. In addition, the review summarizes the inhibitors of the enzyme catalytic subunit and RNA component, natural products that target telomeres, and suppression of transcriptional and post-transcriptional levels. This extensive understanding of telomerase biology will provide indispensable information for enhancing the efficiency of rational anti-cancer drug design.

Cytochrome P450 CYP1 metabolism of hydroxylated flavones and flavonols: Selective bioactivation of luteolin in breast cancer cells

Natural flavonoids with methoxy substitutions are metabolized by CYP1 enzymes to yield the corresponding demethylated products. The present study aimed to characterize the metabolism and further antiproliferative activity of the hydroxylated flavonoids apigenin, luteolin, scutellarein, kaempferol and quercetin in CYP1 recombinant enzymes and in the CYP1 expressing cell lines MCF7 and MDA-MB-468, respectively. Apigenin was converted to luteolin and scutellarein, whereas kaempferol was metabolized only to quercetin by recombinant CYP1 enzymes. Luteolin metabolism yielded 6 hydroxyluteolin only by recombinant CYP1B1, whereas CYP1A1 and CYP1A2 were not capable of metabolizing this compound. Molecular modeling demonstrated that CYP1B1 favored the A ring orientation of apigenin and luteolin to the heme group compared with CYP1A1. The IC50 of the compounds luteolin, scutellarein and 6 hydroxyluteolin was significantly lower in MDA-MB-468, MCF7 and MCF10A cells compared with that of apigenin. Similarly, the IC50 of quercetin in MDA-MB-468 cells was significantly lower compared with that of kaempferol. The most potent compound was luteolin in MDA-MB-468 cells (IC50 = 2 ± 0.3 μM). In the presence of the CYP1-inhibitors α-napthoflavone and/or acacetin, luteolin activation was lessened. Taken collectively, the data demonstrate that the metabolism of hydroxylated flavonoids by cytochrome P450 CYP1 enzymes, notably CYP1A1 and CYP1B1, can enhance their antiproliferative activity in breast cancer cells. In addition, this antiproliferative activity is attributed to the combined action of the parent compound and the corresponding CYP1 metabolites.

Evaluation of ovarian function after hysterectomy with or without salpingectomy: A feasible study

BACKGROUND

Prophylactic salpingectomy for the prevention of ovarian cancer has been recommended strongly. The aim of this study was to compare ovarian function in patients who undergo hysterectomy for benign reasons with or without bilateral salpingectomy.

MATERIALS AND METHODS

This was a clinical-trial study on patients undergone hysterectomy with/without bilateral salpingectomy in Al-Zahra Hospital, in 2015-2016. Demographic information (age, height, and weight) were recorded. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured in 2-5 days of menstrual cycle before operation. Patients were asked to refer in 6 months for follow-up, including FSH and LH re-measurement and also menopausal status examination. Patients were divided into age groups of 39-45, 46-50, and ≥51 and also groups of body mass index including 18.5-24.9, 25-29.9, and 30-34.9.

RESULTS

A total of 37 patients divided into two groups, including 22 patients undergone hysterectomy without salpingectomy (H) and 15 undergone hysterectomy with bilateral salpingectomy (H-bS). The mean age (standard deviation) of Group H was 47.77 (3.03) and Group H-bS was 48.47 (2.03) (P > 0.05). Furthermore, the mean level of FSH and LH before surgery was not significantly different (P > 0.05). The mean level of FSH and LH changes was not significant between H and H-bS groups (P = 0.17), (P = 0.16).

CONCLUSION

Bilateral salpingectomy during hysterectomy did not increase the risk of ovarian dysfunction after 6 months follow-up.