Discovery of Myricetin as a Potent Inhibitor of Human Flap Endonuclease 1, Which Potentially Can Be Used as Sensitizing Agent against HT-29 Human Colon Cancer Cells

Highly Sensitive Flow Cytometry Biosensor with a High Signal-to-Background Ratio for FEN1 Analysis via Solid-Phase Interface-Mediated Primer Exchange Reaction Amplification

Flap endonuclease 1 (FEN1) is a specific enzyme capable of recognizing and cleaving triplex DNA structures and releasing 5'-flap fragments. It plays a crucial role in the DNA metabolism of cells, participating in DNA replication and the repair of damaged DNA. Additionally, FEN1 is overexpressed in various tumor tissues, promoting tumor progression and drug resistance through different regulatory mechanisms. However, few significant advancements have been made in sensitive analytical methods for detecting FEN1. Herein, in this study, we present a highly sensitive flow cytometry biosensor with solid-phase interface-mediated primer exchange reaction amplification (FCsperA) for FEN1 analysis. By comparing homogeneous PER amplification (h-PER), we found that solid-phase interface-mediated PER amplification (s-PER) effectively suppressed background signals, leading to a higher signal-to-background (S/B) ratio exceeding ∼46-fold when FEN1 was at 1 × 10-3 U/μL. Combining the high efficiency of s-PER, the strong suppression of background signals, and the highly precise flow cytometry assay, FCsperA showed high sensitivity, with a limit of detection (LOD) for FEN1 of 2.53 × 10-6 U/μL. Notably, FCsperA exhibited high selectivity and exceptional anti-interference ability, making it applicable for detecting FEN1 in cells and serum samples. The outstanding performance of FCsperA allowed for sensing FEN1 in ∼10 cancer cells. Additionally, FCsperA demonstrated the potential for screening inhibitors of FEN1.

A simple "mix-and-detection" method based on template-free amplification for sensitive measurement of human cellular FEN1

Flap endonuclease 1 (FEN1) is a structure-specific nuclease that can specially identify and cleave 5' flap of branched duplex DNA, and it plays a critical role in DNA metabolic pathways and human diseases. Herein, we propose a simple "mix-and-detection" strategy for sensitive measurement of human cellular FEN1 on basis of template-free amplification. We design a dumbbell probe with 5' flap as a substrate of FEN1 and a NH2-labeled 3' termini to prevent nonspecific amplification. When FEN1 is present, the 5' flap is cleaved to release a free 3'-OH termini, initiating Ribonuclease HII (RNase HII)-assisted terminal deoxynucleotidyl transferase (TdT)-induced amplification for the production of a significant fluorescence signal. Due to the high exactitude of TdT-mediated extension reaction and RNase HII-induced single ribonucleotide excise, this assay shows excellent specificity and high sensitivity with a detection limit of 5.64 × 10-6 U/μL. Importantly, it can detect intracellular FEN1 activity with single-cell sensitivity under isothermal condition in a "mix-and-detection" manner, screen the FEN1 inhibitors, and even discriminate tumor cells from normal cells, offering a new platform for disease diagnosis and drug discovery.

Cellulose nanocrystals/cellulose nanofibrils-combined astaxanthin nanoemulsion for reinforcement of targeted tumor delivery of gastric cancer cells

Nanoemulsion based nanomaterial (NE) was carried out in the present study to evaluate the efficacy and its antitumor potential of the gastric cancer cells. NE was prepared with astaxanthin/alpha-tocopherol- cellulose nanocrystals/cellulose nanofibrils based nanoemulsions for gastric cancer treatment. The cytotoxic potential was tested against cancer cells and evaluated in terms of its cell proliferation, migration, and cellular uptake by the standard methods. NE was examined for its synergetic effect with photodynamic therapy (PDT) in a xenograft mouse model. The results confirmed the synergetic effect of PDT and NEs in the in vivo animal model. The regulated expression of proteins manifested the reduced toxicity and inhibition of cell proliferation and migration. The antitumor study showed that NE inhibited the growth of human colon cancer in vivo. Immunohistological analysis confirmed the regulation of PI3K/AKT signaling pathway. The present study demonstrates that NEs can enhance anti-cancer effect against human gastric cancer through the immunomodulatory signaling pathway.

Argonaute-Based Nucleic Acid Detection Technology: Advantages, Current Status, Challenges, and Perspectives

Rapid and accurate detection is a prerequisite for precise clinical diagnostics, ensuring food safety, and facilitating biotechnological applications. The Argonaute system, as a cutting-edge technique, has been successfully repurposed in biosensing beyond the CRISPR/Cas system (clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins), which has been extensively researched, but recognition of PAM sequences remains restricted. Argonaute, as a programmable and target-activated nuclease, is repurposed for fabricating novel detection methods due to its unparalleled biological features. In this comprehensive review, we initially elaborate on the current methods for nucleic acid testing and programmable nucleases, followed by delving into the structure and nuclease activity of the Argonaute system. The advantages of Argonaute compared with the CRISPR/Cas system in nucleic acid detection are highlighted and discussed. Furthermore, we summarize the applications of Argonaute-based nucleic acid detection and provide an in-depth analysis of future perspectives and challenges. Recent research has demonstrated that Argonaute-based biosensing is an innovative and rapidly advancing technology that can overcome the limitations of existing methods and potentially replace them. In summary, the implementation of Argonaute and its integration with other technologies hold promise in developing customized and intelligent detection methods for nucleic acid testing across various aspects.

Endogenous Telomerase-Activated Fluorescent Probes for Specific Detection and Imaging of Flap Endonuclease 1 in Cancer Cells and Tissues

Flap endonuclease 1 (FEN1) is a structure-specific DNA repair enzyme that has emerged as a potential target for cancer diagnosis and treatment. However, existing FEN1 assays often suffer from complicated reaction schemes and laborious procedures, and only a few methods are available for the detection and imaging of FEN1 in living cells. Especially, FEN1 is not exclusive to cancer cells, but it is also shared by normal cells. Consequently, the specific detection of FEN1 in cancer cells remains a challenge. Herein, we develop a simple and selective fluorescent biosensor for the specific imaging of FEN1 in cancer cells and tissues by engineering a FEN1 detection probe with a telomerase-responsive unit. In the presence of telomerase, it induces an extension reaction and subsequent intramolecular reconfiguration of the detection probe, generating a suitable branched DNA structure for FEN1 recognition and facilitating the cleavage of the flap by FEN1 for the recovery of fluorescence signal. Because telomerase is undetectable in normal cells but highly upregulated in cancer cells, the detection probe can only be activated in cancer cells to generate a high signal. This assay is quite simple, with the requirement of merely a single probe for dual enzyme recognition and signal output. With the integration of the single-molecule counting technology, this biosensor can achieve a detection limit of 1.2 × 10-5 U/μL, and it can accurately detect FEN1 in living cells and clinical tissues, providing a new avenue for FEN1-associated fundamental research and clinical diagnosis.

Effect and mechanism of polyphenols containing m-dihydroxyl structure on 2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) formation in chemical models and roast pork patties

2-amino-1-methyl-6-phenylimidazole [4, 5-b] pyridine (PhIP) is a prevalent heterocyclic amine (HAA) found in heated processed meat. This study investigated the inhibitory impact of eight different types of polyphenols containing m-dihydroxyl structure on PhIP formation through a chemical model system. The structure-activity relationship and potential sites of action of polyphenols containing m-dihydroxyl structure were also analyzed. Then, the mechanism of inhibiting PhIP formation by kaempferol, naringenin and quercetin was speculated by UPLC-MS. Results showed that 8 kinds of polyphenols containing m-dihydroxyl structure had significant (P < 0.05) inhibition on the formation of PhIP in the chemical model system in a dose-dependent manner. In addition, PhIP was most significantly inhibited by naringenin at the same concentration, followed by kaempferol and quercetin (83.27%, 80.81% and 79.26%, respectively). UPLC-MS results speculated that kaempferol, naringenin, and quercetin formed a new admixture via an electrophilic aromatic substitution reaction with the intermediate product phenylacetaldehyde, preventing the formation of PhIP.

Myricetin Induces Ferroptosis and Inhibits Gastric Cancer Progression by Targeting NOX4

Ferroptosis holds great potential as a therapeutic approach for gastric cancer (GC), a prevalent and deadly malignant tumor associated with high rates of incidence and mortality. Myricetin, well-known for its multifaceted biomedical attributes, particularly its anticancer properties, has yet to be thoroughly investigated regarding its involvement in ferroptosis. The aim of this research was to elucidate the impact of myricetin on ferroptosis in GC progression. The present study observed that myricetin could trigger ferroptosis in GC cells by enhancing malondialdehyde production and Fe2+ accumulation while suppressing glutathione levels. Mechanistically, myricetin directly interacted with NADPH oxidase 4 (NOX4), influencing its stability by inhibiting its ubiquitin degradation. Moreover, myricetin regulated the inhibition of ferroptosis induced by Helicobacter pylori cytotoxin-associated gene A (CagA) through the NOX4/NRF2/GPX4 pathway. In vivo experiments demonstrated that myricetin treatment significantly inhibited the growth of subcutaneous tumors in BALB/c nude mice. It was accompanied by increased NOX4 expression in tumor tissue and suppression of the NRF2/GPX4 antioxidant pathway. Therefore, this research underscores myricetin as a novel inducer of ferroptosis in GC cells through its interaction with NOX4. It is a promising candidate for GC treatment.

Myricetin, a natural inhibitor of CD147, increases sensitivity of cisplatin in ovarian cancer

BACKGROUND

Ovarian cancer (OC) is the most lethal gynecological tumor, but it currently lacks effective therapeutic targets. CD147, which is overexpressed in OC, plays a crucial role in promoting malignant progression and is associated with poor prognosis in patients. Therefore, CD147 has been identified as a potential therapeutic target. However, there is a limited amount of research on the development of CD147 inhibitors.

METHODS

Surface plasmon resonance (SPR) assay and virtual molecular docking analysis were performed to identify potential natural compounds targeting CD147. The anti‑tumor effects of myricetin were evaluated using various assays, including CCK8, Alkaline comet, immunofluorescence and xenograft mouse models. The underlying mechanism was investigated through western blot analysis and lentivirus short hairpin RNA (LV-shRNA) transfection.

RESULTS

Myricetin, a flavonoid commonly found in plants, was discovered to be a potent inhibitor of CD147. Our findings demonstrated that myricetin exhibited a strong affinity for CD147 and down-regulated the protein level of CD147 by facilitating its proteasome-dependent degradation. Additionally, we observed synergistic antitumor effects of myricetin and cisplatin both in vivo and in vitro. Mechanistically, myricetin suppressed the expression of FOXM1 and its downstream DNA damage response (DDR) genes E×O1and BRIP1, thereby enhancing the DDR induced by cisplatin.

CONCLUSION

Our data demonstrate that myricetin, a natural inhibitor of CD147, may have clinical utility in the treatment of OC due to its ability to increase genomic toxicity when combined with cisplatin.

Colorimetric and photothermal dual readout biosensor for flap endonuclease 1 based on target-prevented gold nanoparticles aggregation

A colorimetric and photothermal dual readout biosensor for Flap endonuclease 1 (FEN1) quantification was developed on the basis of target-prevented gold nanoparticles (AuNPs) aggregation. The exposed 5'-flap of double-flap DNA substrate modified on SAMBs was firstly cleaved by FEN1. Large amount of cleaved 5'-flap remained in the supernatant after simple magnetic separation, which can adsorb on the surface of AuNPs and effectively prevent the dispersed AuNPs from aggregation under high ionic concentration, accompanied with the color changing of the system, which can be recognized by nake eyes easily. The absorption intensity at 528 nm shows a good linear relationship with the increasing FEN1 concentration from 5.0 × 10-3 to 3.1 × 10-2 U μL-1 with a LOD of 1.6 × 10-3 U μL-1 (S/N = 3). Given the aggregated AuNPs have higher photothermal effect than that of the dispersed AuNPs, the target-prevented AuNPs aggregation avoids a sharp increase of temperature for the system under the laser radiation. The temperature change is linearly correlated with the FEN1 concentration in the range of 3.1 × 10-3-6.1 × 10-2 U μL-1 with a LOD of 1.1 × 10-3 U μL-1. The whole detection process can be completed within 1 h. The proposed system had been applied to detect FEN1 concentration in serum samples with satisfied results, which can be applied in resource-limited area easily and quickly.

Flavonoids as promising anticancer therapeutics: Contemporary research, nanoantioxidant potential, and future scope

Flavonoids are natural polyphenolic compounds considered safe, pleiotropic, and readily available molecules. It is widely distributed in various food products such as fruits and vegetables and beverages such as green tea, wine, and coca-based products. Many studies have reported the anticancer potential of flavonoids against different types of cancers, including solid tumors. The chemopreventive effect of flavonoids is attributed to various mechanisms, including modulation of autophagy, induction of cell cycle arrest, apoptosis, and antioxidant defense. Despite of significant anticancer activity of flavonoids, their clinical translation is limited due to their poor biopharmaceutical attributes (such as low aqueous solubility, limited permeability across the biological membranes (intestinal and blood-brain barrier), and stability issue in biological systems). A nanoparticulate system is an approach that is widely utilized to improve the biopharmaceutical performance and therapeutic efficacy of phytopharmaceuticals. The present review discusses the significant anticancer potential of promising flavonoids in different cancers and the utilization of nanoparticulate systems to improve their nanoantioxidant activity further to enhance the anticancer activity of loaded promising flavonoids. Although, various plant-derived secondary metabolites including flavonoids have been recommended for treating cancer, further vigilant research is warranted to prove their translational values.

Myricetin: a potential plant-derived anticancer bioactive compound-an updated overview

The globe is currently confronting a global fight against the deadliest cancer sickness. Chemotherapy, hormonal therapy, surgery, and radiation therapy are among cancer treatment options. Still, these treatments can induce patient side effects, including recurrence, multidrug resistance, fever, and weakness. As a result, the scientific community is always working on natural phytochemical substances. Numerous phytochemical compounds, including taxol analogues, vinca alkaloids such as vincristine and vinblastine, and podophyllotoxin analogues, are currently undergoing testing and have shown promising results against a number of the deadliest diseases, as well as considerable advantages due to their safety and low cost. According to research, secondary plant metabolites such as myricetin, a flavonoid in berries, herbs, and walnuts, have emerged as valuable bio-agents for cancer prevention. Myricetin and its derivatives have antiinflammatory, anticancer, apoptosis-inducing, and anticarcinogenic properties and can prevent cancer cell proliferation. Multiple studies have found that myricetin has anticancer characteristics in various malignancies, including colon, breast, prostate, bladder, and pancreatic cancers. Current knowledge of the anticancer effects of myricetin reveals its promise as a potentially bioactive chemical produced from plants for the prevention and treatment of cancer. This review aimed to study the numerous bioactivities, mode of action, and modification of several cellular processes that myricetin possesses to impede the spread of cancer cells. This review also addresses the challenges and future prospects of using myricetin as a anticancer drug.

Construction of dual exponential amplification accompanied by multi-terminal signal output method for convenient detection of tumor biomarker FEN1 activity

As an important 5'-nuclease in DNA replication and damage repair, Flap endonuclease 1 (FEN1) has been considered as a potential tumor biomarker due to its overexpression in different human cancer cells. Here, we developed a convenient fluorescent method based on dual enzymatic repairing exponential amplification accompanied by multi-terminal signal output to realize the rapid and sensitive detection of FEN1. In the presence of FEN1, the double-branched substrate could be cleaved to produce 5' flap single strand DNA (ssDNA) which subsequently was used as a primer to initiate the dual exponential amplification (EXPAR) to generate abundant ssDNAs (X' and Y'), then the ssDNAs can respectively hybridize with the 3' and 5' ends of the signal probe to form partially complementary double strands (dsDNAs). Subsequently, the signal probe on the dsDNAs could be digested under the assistance of Bst. polymerase and T7 exonuclease, as well as releasing the fluorescence signals. The method displayed high sensitivity with the detection limit of 9.7 × 10^-3 U mL^-1 (1.94 × 10^-4 U) and also exhibited good selectivity towards FEN1 under the challenge from complicated samples including extracts of normal and cancer cells. Furthermore, it was successfully applied to screen FEN1 inhibitors, holding great promise in the screening of potential drugs targeting FEN1. This sensitive, selective and convenient method could be used for FEN1 assay without the complicated nanomaterial synthesis/modification, showing great potential in FEN1- related prediction and diagnosis.

Lighting-up aptamer transcriptional amplification for highly sensitive and label-free FEN1 detection

Specific and sensitive detection of flap endonuclease 1 (FEN1), an enzyme biomarker involved in DNA replications and several metabolic pathways, is of high values for the diagnosis of various cancers. In this work, a fluorescence strategy based on transcriptional amplification of lighting-up aptamers for label-free, low background and sensitive monitoring of FEN1 is developed. FEN1 cleaves the 5' flap of the DNA complex probe with double flaps to form a notched dsDNA, which is ligated by T4 DNA ligase to yield fully complementary dsDNA. Subsequently, T7 RNA polymerase binds the promoter region to initiate cyclic transcriptional generation of many RNA aptamers that associate with the malachite green dye to yield highly amplified fluorescence for detecting FEN1 with detection limit as low as 0.22 pM in a selective way. In addition, the method can achieve diluted serum monitoring of low concentrations of FEN1, exhibiting its potential for the diagnosis of early-stage cancers.

Myricetin-Loaded Nanomicelles Protect against Cisplatin-Induced Acute Kidney Injury by Inhibiting the DNA Damage-cGAS-STING Signaling Pathway

Acute kidney injury (AKI) is the most common side effect of the anti-cancer drug cisplatin, and currently, no effective preventive measures are available in clinical practice. Oxidative stress and DNA damage mechanisms may be involved in cisplatin-induced AKI. In this study, we prepared Kolliphor HS15-based myricetin-loaded (HS15-Myr) nanomicelles and explored the mechanism of protection against cisplatin-induced AKI. In vitro results showed that the HS15-Myr nanomicelles enhanced the antioxidant activity of myricetin (Myr) and inhibited cisplatin-induced proliferation inhibition of HK-2 cells. Moreover, the HS15-Myr nanomicelles inhibited cisplatin-induced reactive oxygen species accumulation, mitochondrial membrane potential reduction, and DNA damage, which might be related to the inhibition of the cyclic GMP-AMP synthase (cGAS)─stimulating interferon gene (STING) signaling pathway. In vivo results in mice showed that the significant reductions in body weight and renal indices and the increased blood urea nitrogen and serum creatinine levels induced by cisplatin could be significantly reversed by pretreating with the HS15-Myr nanomicelles. Furthermore, nanomicelle pretreatment significantly altered the activities of antioxidant enzymes (e.g., GSH, MDA, and SOD) induced by cisplatin. In addition, cisplatin-induced inflammatory responses in mouse kidney tissue were found to be inhibited by pretreatment with HS15-Myr nanomicelles, such as IL-1β and TNF-α expression. The nanomicelles also significantly inhibited cisplatin-induced activation of the DNA damage-cGAS-STING pathway in kidney tissues. Together, our findings suggest that Myr-loaded nanomicelles are potential nephroprotective drugs.

Crosstalk between xanthine oxidase (XO) inhibiting and cancer chemotherapeutic properties of comestible flavonoids- a comprehensive update

Gout is an inflammatory disease caused by metabolic disorder or genetic inheritance. People throughout the world are strongly dependent on ethnomedicine for the treatment of gout and some receive satisfactory curative treatment. The natural remedies as well as established drugs derived from natural sources or synthetically made exert their action by mechanisms that are closely associated with anticancer treatment mechanisms regarding inhibition of xanthine oxidase, feedback inhibition of de novo purine synthesis, depolymerization and disappearance of microtubule, inhibition of NF-ĸB activation, induction of TRAIL, promotion of apoptosis, and caspase activation and proteasome inhibition. Some anti-gout and anticancer novel compounds interact with same receptors for their action, e.g., colchicine and colchicine analogues. Dietary flavonoids, i.e., chrysin, kaempferol, quercetin, fisetin, pelargonidin, apigenin, luteolin, myricetin, isorhamnetin, phloretinetc etc. have comparable IC₅₀ values with established anti-gout drug and effective against both cancer and gout. Moreover, a noticeable number of newer anticancer compounds have already been isolated from plants that have been using by local traditional healers and herbal practitioners to treat gout. Therefore, the anti-gout plants might have greater potentiality to become selective candidates for screening of newer anticancer leads.

Controllable crRNA Self-Transcription Aided Dual-Amplified CRISPR-Cas12a Strategy for Highly Sensitive Biosensing of FEN1 Activity

A controllable crRNA self-transcription aided dual-amplified CRISPR-Cas12a strategy (termed CST-Cas12a) was developed for highly sensitive and specific biosensing of flap endonuclease 1 (FEN1), a structure-selective nuclease in eukaryotic cells. In this strategy, a branched DNA probe with a 5' overhanging flap was designed to serve as a hydrolysis substrate of FEN1. The flap cut by FEN1 was annealed with a template probe and functioned as a primer for an extension reaction to produce a double-stranded DNA (dsDNA) containing a T7 promoter and crRNA transcription template. Assisting the T7 RNA polymerase, abundant crRNA was generated and assembled with Cas12a to form a Cas12a/crRNA complex, which can be activated by a dsDNA trigger and unlock the indiscriminate fluorophore-quencher reporter cleavage. The highly efficient dual signal amplification and near-zero background enabled CST-Cas12a with extraordinarily high sensitivity. Under optimized conditions, this method allowed highly sensitive biosensing of FEN1 activity in the range of 1 × 10^-5 U μL^-1 to 5 × 10^-2 U μL^-1 with a detection limit of 5.2 × 10^-6 U μL^-1 and achieved excellent specificity for FEN1 in the presence of other interfering enzymes. The inhibitory capabilities of chemicals on FEN1 were also investigated. Further, the newly established CST-Cas12a strategy was successfully applied to FEN1 biosensing in complex biological samples, which might be a reliable biosensing platform for highly sensitive and specific detection of FEN1 activity in clinical applications.

Synthesis of Silver Nano Particles Using Myricetin and the In-Vitro Assessment of Anti-Colorectal Cancer Activity: In-Silico Integration

The creation of novel anticancer treatments for a variety of human illnesses, including different malignancies and dangerous microbes, also potentially depends on nanoparticles including silver. Recently, it has been successful to biologically synthesize metal nanoparticles using plant extracts. The natural flavonoid 3,3′, 4′, 5,5′, and 7 hexahydroxyflavon (myricetin) has anticancer properties. There is not much known about the regulatory effects of myricetin on the possible cell fate-determination mechanisms (such as apoptosis/proliferation) in colorectal cancer. Because the majority of investigations related to the anticancer activity of myricetin have dominantly focused on the enhancement of tumor cell uncontrolled growth (i.e., apoptosis). Thus, we have decided to explore the potential myricetin interactors and the associated biological functions by using an in-silico approach. Then, we focused on the main goal of the work which involved the synthesis of silver nanoparticles and the labeling of myricetin with it. The synthesized silver nanoparticles were examined using UV-visible spectroscopy, dynamic light scattering spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. In this study, we have investigated the effects of myricetin on colorectal cancer where numerous techniques were used to show myricetin’s effect on colon cancer cells. Transmission Electron Microscopy was employed to monitor morphological changes. Furthermore, we have combined the results of the colorectal cancer gene expression dataset with those of the myricetin interactors and pathways. Based on the results, we conclude that myricetin is able to efficiently kill human colorectal cancer cell lines. Since, it shares important biological roles and possible route components and this myricetin may be a promising herbal treatment for colorectal cancer as per an in-silico analysis of the TCGA dataset.

Myricetin: targeting signaling networks in cancer and its implication in chemotherapy

The gaps between the complex nature of cancer and therapeutics have been narrowed down due to extensive research in molecular oncology. Despite gathering massive insight into the mysteries of tumor heterogeneity and the molecular framework of tumor cells, therapy resistance and adverse side effects of current therapeutic remain the major challenge. This has shifted the attention towards therapeutics with less toxicity and high efficacy. Myricetin a natural flavonoid has been under the spotlight for its anti-cancer, anti-oxidant, and anti-inflammatory properties. The cutting-edge molecular techniques have shed light on the interplay between myricetin and dysregulated signaling cascades in cancer progression, invasion, and metastasis. However, there are limited data available regarding the nano-delivery platforms composed of myricetin in cancer. In this review, we have provided a comprehensive detail of myricetin-mediated regulation of different cellular pathways, its implications in cancer prevention, preclinical and clinical trials, and its current available nano-formulations for the treatment of various cancers.

Small-Molecule Inhibitors Targeting FEN1 for Cancer Therapy

DNA damage repair plays a key role in maintaining genomic stability and integrity. Flap endonuclease 1 (FEN1) is a core protein in the base excision repair (BER) pathway and participates in Okazaki fragment maturation during DNA replication. Several studies have implicated FEN1 in the regulation of other DNA repair pathways, including homologous recombination repair (HRR) and non-homologous end joining (NHEJ). Abnormal expression or mutation of FEN1 in cells can cause a series of pathological responses, leading to various diseases, including cancers. Moreover, overexpression of FEN1 contributes to drug resistance in several types of cancers. All this supports the hypothesis that FEN1 could be a therapeutic target for cancer treatment. Targeting FEN1 has been verified as an effective strategy in mono or combined treatment of cancer. Small-molecule compounds targeting FEN1 have also been developed and detected in cancer regression. In this review, we summarize the recent development of small-molecule inhibitors targeting FEN1 in recent years, thereby expanding their therapeutic potential and application.

Anticancer effects of natural phytochemicals in anaplastic thyroid cancer (Review)

Anaplastic thyroid cancer (ATC) is an aggressive and lethal malignancy having a dismal prognosis. Phytochemicals are bioactive components obtained from plants that have been proven useful to treat numerous diseases. Phytochemicals are also an important source of novel anticancer drugs and an important area of research due to the numerous available candidates that can potentially treat cancers. This review discusses naturally occurring phytochemicals and their derivatives that show promising anticancer effects in anaplastic thyroid cancer. Anticancer effects include cell growth inhibition, induction of apoptosis, promoting cell cycle arrest, suppressing angiogenesis, modulating autophagy, and increasing the production of reactive oxygen species. Phytochemicals are not only prospective candidates in the therapy of anaplastic thyroid cancer but also exhibit potential as adjuvants to improve the anticancer effects of other drugs. Although some phytochemicals have excellent anticancer properties, drug resistance observed during the use of resveratrol and artemisinin in different anaplastic thyroid cancer cell lines is still a problem. Anaplastic thyroid cancer cells have several biological, clinical, and drug-resistance features that differ from differentiated thyroid cancer cells. Phytochemicals such as resveratrol and quercetin exhibit different biological effects in anaplastic thyroid cancer and differentiated thyroid cancer. Tumor cells depend on increased aerobic glycolysis by mitochondrial oxidative phosphorylation to provide energy for their rapid growth, invasiveness, and drug resistance. Phytochemicals can alter signaling cascades, modulate the metabolic properties of cancer cells, and influence the mitochondrial membrane potential of anaplastic thyroid cancer cells. These findings enrich our knowledge of the anticancer effects of phytochemicals and highlight alternative therapies to prevent drug resistance in anaplastic thyroid cancer.

Label-Free and Homogeneous Electrochemical Biosensor for Flap Endonuclease 1 Based on the Target-Triggered Difference in Electrostatic Interaction between Molecular Indicators and Electrode Surface

Target-induced differences in the electrostatic interactions between methylene blue (MB) and indium tin oxide (ITO) electrode surface was firstly employed to develop a homogeneous electrochemical biosensor for flap endonuclease 1 (FEN1) detection. In the absence of FEN1, the positively charged methylene blue (MB) is free in the solution and can diffuse onto the negatively charged ITO electrode surface easily, resulting in an obvious electrochemical signal. Conversely, with the presence of FEN1, a 5′-flap is cleaved from the well-designed flapped dumbbell DNA probe (FDP). The remained DNA fragment forms a closed dumbbell DNA probe to trigger hyperbranched rolling circle amplification (HRCA) reaction, generating plentiful dsDNA sequences. A large amount of MB could be inserted into the produced dsDNA sequences to form MB-dsDNA complexes, which contain a large number of negative charges. Due to the strong electrostatic repulsion between MB-dsDNA complexes and the ITO electrode surface, a significant signal drop occurs. The signal change (ΔCurrent) shows a linear relationship with the logarithm of FEN1 concentration from 0.04 to 80.0 U/L with a low detection limit of 0.003 U/L (S/N = 3). This study provides a label-free and homogeneous electrochemical platform for evaluating FEN1 activity.

Myricetin Induces Apoptosis and Protective Autophagy through Endoplasmic Reticulum Stress in Hepatocellular Carcinoma

Myricetin, a natural flavonoid, exhibits diverse biological activities, including antitumor effects. The present study aimed to investigate the effects of myricetin on hepatocellular carcinoma (HCC) cells and explore the underlying molecular mechanisms. Our results showed that myricetin significantly inhibited cell proliferation and induced apoptosis in HCC cells. The apoptosis induced by myricetin was associated with the activation of endoplasmic reticulum (ER) stress. In addition, autophagy was enhanced in response to ER stress. Inhibition of autophagy by RNA interference or chemical inhibitors resulted in increased apoptosis in myricetin-treated HCC cells. The in vivo experiment also showed that myricetin effectively reduced tumor growth in an HCC xenograft model and that combination treatment with an autophagy inhibitor significantly enhanced this effect. These results indicated that myricetin induced apoptosis in HCC cells through the activation of ER stress. Protective autophagy was also upregulated during this process. Simultaneous inhibition of autophagy enhanced the anti-HCC activity of myricetin. Myricetin might be a promising drug candidate for HCC therapy, and the combined use of myricetin with autophagy inhibitors could be an effective therapeutic strategy.

A highly sensitive homogeneous electrochemiluminescence biosensor for flap endonuclease 1 based on branched hybridization chain reaction amplification and ultrafiltration separation

A sensitive homogeneous electrochemiluminescence (ECL) biosensor for flap endonuclease 1 (FEN1) detection was developed by combining highly sensitive ECL detection, high efficiency of branched hybridization chain reaction (BHCR) amplification, a convenient homogeneous strategy, and simple ultrafiltration separation. Magnetic beads were first modified with well-designed double flap DNAs containing 5'-flaps. In the presence of FEN1, the 5'-flap can be cleaved, and a large amount of single-stranded DNA can be produced, which can be separated easily from the double-flap DNA-modified beads by a magnet. Then, the cleaved 5'-flap can be used to initiate BHCR amplification to produce a large amount of long-strand dsDNA. Ru(phen)₃²⁺ can insert dsDNA to form Ru-dsDNAs, which can be easily separated from the main solution through ultrafiltration. The ECL signal from the separated Ru-dsDNAs has a good linear relationship with the logarithm of the FEN1 concentration ranging from 6.5 × 10^-2 ∼ 6.5 × 10³ U/L with a detection limit of 2.2 × 10^-2 U/L. The proposed biosensor was used to evaluate FEN1 activity in real samples with satisfactory results.

Molecular Pathways Involved in the Anti-Cancer Activity of Flavonols: A Focus on Myricetin and Kaempferol

Natural compounds have always represented valuable allies in the battle against several illnesses, particularly cancer. In this field, flavonoids are known to modulate a wide panel of mechanisms involved in tumorigenesis, thus rendering them worthy candidates for both cancer prevention and treatment. In particular, it was reported that flavonoids regulate apoptosis, as well as hamper migration and proliferation, crucial events for the progression of cancer. In this review, we collect recent evidence concerning the anti-cancer properties of the flavonols myricetin and kaempferol, discussing their mechanisms of action to give a thorough overview of their noteworthy capabilities, which are comparable to those of their most famous analogue, namely quercetin. On the whole, these flavonols possess great potential, and hence further study is highly advised to allow a proper definition of their pharmaco-toxicological profile and assess their potential use in protocols of chemoprevention and adjuvant therapies.

Evidence for Anticancer Effects of Chinese Medicine Monomers on Colorectal Cancer

Colorectal cancer is one of the most commonly occurring cancers worldwide. Although clinical reports have indicated the anticancer effects of Chinese herbal medicine, the multiple underlying molecular and biochemical mechanisms of action remain to be fully characterized. Chinese medicine (CM) monomers, which are the active components of CM, serve as the material basis of the functional mechanisms of CM. The aim of this review is to summarize the current experimental evidence from in vitro, in vivo, and clinical studies for the effects of CM monomers in colorectal cancer prevention and treatment, providing some useful references for future research.

Myricetin Induces Autophagy and Cell Cycle Arrest of HCC by Inhibiting MARCH1-Regulated Stat3 and p38 MAPK Signaling Pathways

Myricetin is a type of natural flavonol known for its anticancer activity. However, the molecular mechanism of myricetin in anti-hepatocellular carcinoma (HCC) is not well defined. Previous studies indicated that downregulation of membrane-associated RING-CH finger protein 1 (MARCH1) contributed to the treatment of a variety of cancers. Whether the anticancer property of myricetin is associated with MARCH1 expression remains to be investigated. This research explored the anti-HCC mechanism of myricetin. Our results indicate that myricetin induces autophagy and arrests cell cycle at the G2/M phase to suppress the proliferation of HCC cells by downregulating MARCH1. Myricetin reduces MARCH1 protein in Hep3B and HepG2 cells. Interestingly, myricetin upregulates the MARCH1 mRNA level in Hep3B cells but downregulates it in HepG2 cells. The knockdown of MARCH1 by siRNAs (small interfering RNAs) decreases the phosphorylated p38 MAPK (p-p38 MAPK) and Stat3 (p-Stat3), and inhibits HCC cell viability. Moreover, myricetin inhibits p38 MAPK and Stat3 signaling pathways by downregulating MARCH1 to repress HCC growth both in vitro and in vivo. Bafilomycin A1 (BafA1), an autophagy inhibitor, has synergetic effect with myricetin to inhibit HCC growth. Taken together, our results reveal that myricetin inhibits the proliferation of HCC cells by inhibiting MARCH1-regulated p38 MAPK and Stat3 signaling pathways. This research provides a new molecular mechanism for myricetin in anti-HCC and suggests that targeting MARCH1 could be a novel treatment strategy in developing anticancer therapeutics.

The Clinical Significance of the Expression of FEN1 in Primary Osteosarcoma

PURPOSE

The aim of this research was to investigate the clinical significance of the expression of flap structure-specific endonuclease 1 (FEN1) in primary osteosarcoma.

METHODS

The expression of FEN1 was detected by immunohistochemistry analysis. The association of the expression of FEN1 in osteosarcoma with clinicopathological parameters was analyzed by using χ 2 test or Fisher's exact test. Survival analyses were performed by Kaplan-Meier method and Cox proportional hazards regression model.

RESULTS

Of the 40 osteosarcoma patients, 19 (47.5%) patients presented with FEN1 high expression, while in the non-neoplastic bone specimens, the FEN1 high expression was observed in 10% (3/30), the positive expression rate in osteosarcoma patients was significantly higher than that of non-neoplastic bone specimens (P< 0.01). Univariate analysis indicated that the progression-free survival (PFS) and overall survival (OS) were correlated with the expression level of FEN1 (PFS, P < 0.001; OS, P = 0.002), Enneking staging (PFS, P = 0.026; OS, P = 0.044) and chemotherapy response (PFS, P = 0.019; OS, P = 0.031). Multivariate analysis demonstrated that FEN1 expression was an independent prognostic factor for the PFS (HR = 4.73, P = 0.002) and OS (HR = 4.01, P = 0.038) of osteosarcoma patients.

CONCLUSION

This study showed that FEN1 was overexpressed in osteosarcoma patients and positively associated with poor prognosis of osteosarcoma patients. Further studies should focus on the relative mechanisms and the targeted FEN1 therapies for osteosarcoma.

Precision Spherical Nucleic Acids Enable Sensitive FEN1 Imaging and Controllable Drug Delivery for Cancer-Specific Therapy

Accurate diagnosis and targeted therapy are essential to precision theranostics. However, nonspecific response of theranostic agents in healthy tissues impedes their practical applications. Here, we design an activatable DNA nanosphere for specifically in situ sensing of cancer biomarker flap endonuclease 1 (FEN1) and spatiotemporally modulating drug release. The gold nanostar-conjugated FEN1 substrate acts as spherical nucleic acid and induces a fluorescence signal upon a FEN1 stimulus for diagnosis. Guided by the nanoflare, external NIR light then triggers a controlled release of carried drugs at desired sites. This DNA nanosphere not only exhibits good stability, sensitivity, and specificity toward FEN1 assay but also serves as a precision theranostic agent for targeted and controlled drug delivery. Our study provides a reliable method for FEN1 imaging in vitro and in vivo and suggests a powerful strategy for precision medicine.

Myricetin prevents high molecular weight Aβ1-42 oligomer-induced neurotoxicity through antioxidant effects in cell membranes and mitochondria

Excessive accumulation of amyloid β-protein (Aβ) is one of the primary mechanisms that leads to neuronal death with phosphorylated tau in the pathogenesis of Alzheimer's disease (AD). Protofibrils, one of the high-molecular-weight Aβ oligomers (HMW-Aβo), are implicated to be important targets of disease modifying therapy of AD. We previously reported that phenolic compounds such as myricetin inhibit Aβ1-40, Aβ1-42, and α-synuclein aggregations, including their oligomerizations, which may exert protective effects against AD and Parkinson's disease. The purpose of this study was to clarify the detailed mechanism of the protective effect of myricetin against the neurotoxicity of HMW-Aβo in SH-SY5Y cells. To assess the effect of myricetin on HMW-Aβo-induced oxidative stress, we systematically examined the level of membrane oxidative damage by measuring cell membrane lipid peroxidation, membrane fluidity, and cell membrane potential, and the mitochondrial oxidative damage was evaluated by mitochondrial permeability transition (MPT), mitochondrial reactive oxygen species (ROS), and manganese-superoxide dismutase (Mn-SOD), and adenosine triphosphate (ATP) assay in SH-SY5Y cells. Myricetin has been found to increased cell viability by suppression of HMW-Aβo-induced membrane disruption in SH-SY5Y cells, as shown in reducing membrane phospholipid peroxidation and increasing membrane fluidity and membrane resistance. Myricetin has also been found to suppress HMW-Aβo-induced mitochondria dysfunction, as demonstrated in decreasing MPT, Mn-SOD, and ATP generation, raising mitochondrial membrane potential, and increasing mitochondrial-ROS generation. These results suggest that myricetin preventing HMW-Aβo-induced neurotoxicity through multiple antioxidant functions may be developed as a disease-modifying agent against AD.

Targeting FEN1 Suppresses the Proliferation of Chronic Myeloid Leukemia Cells Through Regulating Alternative End-Joining Pathways

Chronic myeloid leukemia (CML) is characterized by the formation of the BCR-ABL fusion gene. The BCR-ABL protein leads to an increased level of reactive oxygen species, which is a major cause of endogenous DNA double-strand breaks (DSBs). CML cells are prone to rely on a highly mutagenic alternative end-joining (Alt-EJ) pathway to cope with enhanced DSBs, which aggravates chromosomal instability. Hence, targeting dysregulated DNA repair proteins provides new insights into cancer treatment. In this study, we discovered the abnormal upregulation of Flap endonuclease 1 (FEN1) in CML, as well as FEN1's participation in the error-prone Alt-EJ repair pathway and its interplay with DNA Ligase1 and proliferating cell nuclear antigen in DSB repair. Knockdown of FEN1 by shRNA not only inhibited the proliferation and induced apoptosis but also enhanced the efficacy of imatinib (IM) in drug-resistant CML cell K562/G01. Moreover, excessive DSB accumulation was detected after FEN1 inhibition. In summary, our results demonstrated that FEN1 is a promising therapeutic target in CML treatment. This work extends the understanding of regulating abnormal DSB repair for cancer treatment.

Evaluation of Indonesian mangrove Xylocarpus granatum leaves ethyl acetate extract as potential anticancer drug

Local Xylocarpus granatum leaves were extracted by ethyl acetate solvent and characterized by TLC fingerprinting and 2D 1H NMR spectroscopy to contain phenolic compounds as well as several organic and amino acids as metabolic byproducts, such as succinic acid and acetic acid. Traces of flavonoids and other non-categorized phenolic compounds exhibited intermediate antioxidant activity (antioxidant IC50 84.93 ppm) as well as anticancer activity against HeLa, T47D, and HT-29 cell lines; which the latter being most effective against HT-29 with Fraction 5 contained the strongest activity (anticancer IC50 23.12 ppm). Extracts also behaved as a natural growth factor and nonlethal towards brine shrimps as well as human adipose-derived stem cell hADSC due to antioxidative properties. A stability test was performed to examine how storage conditions factored in bioactivity and phytochemical structure. Extracts were compared with several studies about X. granatum leaves extracts to evaluate how ethnogeography and ecosystem factored on biologically active compounds. Further research on anticancer or antioxidant mechanism on cancer cells is needed to determine whether the extract is suitable as a candidate for an anticancer drug.

Polyphenol-Rich Extract from Litchi chinensis Seeds Alleviates Hypertension-Induced Renal Damage in Rats

Litchi chinensis seed is a valuable byproduct of the subtropical fruit litchi (L. chinensis Sonn.), whose extract (LSE) has been confirmed to ameliorate dyslipidemia, hyperglycemia, and oxidative stress caused by type 2 diabetes. However, if LSE exerts an effect on anti-hypertension and hypertensive renal damage remains unknown. In this study, 13 polyphenols and one fatty acid were identified by UPLC-Q/TOF-MS. Network pharmacological analysis revealed that the therapeutic effects of LSE may be involved in multitargets and multipathways, such as the TNF signaling pathway, interleukin (IL)-6-mediated signaling pathway, NF-kappa B signaling pathway, removal of superoxide radicals, negative regulation of blood pressure, and so forth. Moreover, spontaneously hypertensive rats (SHRs) were daily gavaged with LSE (60 mg/kg) for 10 weeks. LSE remarkably reduced systolic blood pressure (SBP). The hypertension-induced renal damage was improved by suppressing inflammation and oxidative stress, which was consistent with the prediction of network pharmacology. In addition, LSE treatment remarkably increased the relative abundances of Lactobacillus and the production of short-chain fatty acids in the intestine. Our study indicated that a byproduct of litchi, namely, litchi seed, may be effective in reducing SBP and alleviating hypertensive renal damage.

Signal-Amplified Detection of the Tumor Biomarker FEN1 Based on Cleavage-Induced Ligation of a Dumbbell DNA Probe and Rolling Circle Amplification

Flap endonuclease 1 (FEN1), an endogenous nuclease with the ability to cleave the 5' overhang of branched dsDNA, is of significance in DNA replication and repair. The overexpression of FEN1 is common in cancer because of the ubiquitous upregulation of DNA replication; thus, FEN1 has been recognized as a potential biomarker in oncological investigations. However, few analytical methods targeting FEN1 with high sensitivity and simplicity have been developed. This work developed a signal-amplified detection of FEN1 based on the cleavage-induced ligation of a dumbbell DNA probe and rolling circle amplification (RCA). A flapped dumbbell DNA probe (FDP) was rationally designed with a FEN1 cleavable flap at the 5' end. The cleavage generated a nick site with juxtaposed 5' phosphate and 3' hydroxyl ends, which were linkable by T4 DNA ligase to form a closed dumbbell DNA probe (CDP) with a circular conformation. The CDP functioned as a template for RCA, which produced abundant DNA that could be probed using SYBR Green I. The highly sensitive detection of FEN1 with a limit of detection of 15 fM was achieved, and this method showed high specificity, which enabled the quantification of FEN1 in real samples. The inhibitory effects of chemicals on FEN1 were also evaluated. This study represents the first attempt to develop an FEN1 assay that involves signal amplification, and the novel biosensor method enriches the tools for FEN1-based diagnostics.

Total flavone extract from Ampelopsis megalophylla induces apoptosis in the MCF‑7 cell line

Ampelopsis megalophylla has been found to demonstrate anticancer activities in human cancer cells; however, the effect of total flavone extract (TFE), commonly used in Traditional Chinese Medicine, remains unclear. Furthermore, there is limited information on its effects on breast cancer cell lines. The present study aimed to investigate the inhibitory effects of TFE in different human cancer cell lines. In addition, the underlying mechanisms and the signaling pathways involved were also investigated by determining tumor cell morphological changes, and differences in the cell cycle, apoptosis, mitochondrial transmembrane potential, and related protein expression levels in a breast cancer cell line. It was found that TFE inhibited proliferation in seven cancer cell lines (HeLa, A549, MCF-7, HepG2, A2780, SW620 and MDA-MB-231 and demonstrated a strong inhibitory effect on MCF-7 cell proliferation. Cell morphological changes were also observed and arrested at the G₂/M phase following treatment with TFE at different concentrations. In addition, TFE disrupted the mitochondrial membrane potential and upregulated the expression level of apoptotic proteins, including caspase-3, -8 and -9, the Bax/Bcl-2 ratio, and Apaf-1 in time-dependent manner. These results indicated that TFE induced apoptosis of the MCF-7 cells via a mitochondrial-mediated apoptotic pathway. In conclusion, TFE is potentially effective in treating breast cancer.

Myricetin: A review of the most recent research

Myricetin(MYR) is a flavonoid compound widely found in many natural plants including bayberry. So far, MYR has been proven to have multiple biological functions and it is a natural compound with promising research and development prospects. This review comprehensively retrieved and collected the latest pharmacological abstracts on MYR, and discussed the potential molecular mechanisms of its effects. The results of our review indicated that MYR has a therapeutic effect on many diseases, including tumors of different types, inflammatory diseases, atherosclerosis, thrombosis, cerebral ischemia, diabetes, Alzheimer's disease and pathogenic microbial infections. Furthermore, it regulates the expression of Hippo, MAPK, GSK-3β, PI3K/AKT/mTOR, STAT3, TLR, IκB/NF-κB, Nrf2/HO-1, ACE, eNOS / NO, AChE and BrdU/NeuN. MYR also enhances the immunomodulatory functions, suppresses cytokine storms, improves cardiac dysfunction, possesses an antiviral potential, can be used as an adjuvant treatment against cancer, cardiovascular injury and nervous system diseases, and it may be a potential drug against COVID-19 and other viral infections. Generally, this article provides a theoretical basis for the clinical application of MYR and a reference for its further use.

Dual Processing of R-Loops and Topoisomerase I Induces Transcription-Dependent DNA Double-Strand Breaks

Although accumulation of DNA damage and genomic instability in resting cells can cause neurodegenerative disorders, our understanding of how transcription produces DNA double-strand breaks (DSBs) is limited. Transcription-blocking topoisomerase I cleavage complexes (TOP1ccs) are frequent events that prime DSB production in non-replicating cells. Here, we report a mechanism of their formation by showing that they arise from two nearby single-strand breaks (SSBs) on opposing DNA strands: one SSB from the removal of transcription-blocking TOP1ccs by the TDP1 pathway and the other from the cleavage of R-loops by endonucleases, including XPF, XPG, and FEN1. Genetic defects in TOP1cc removal (TDP1, PNKP, and XRCC1) or in the resolution of R-loops (SETX) enhance DSB formation and prevent their repair. Such deficiencies cause neurological disorders. Owing to the high frequency of TOP1cc trapping and the widespread distribution of R-loops, these persistent transcriptional DSBs could accumulate over time in neuronal cells, contributing to the neurodegenerative diseases.

Myricetin bioactive effects: moving from preclinical evidence to potential clinical applications

Several flavonoids have been recognized as nutraceuticals, and myricetin is a good example. Myricetin is commonly found in plants and their antimicrobial and antioxidant activities is well demonstrated. One of its beneficial biological effects is the neuroprotective activity, showing preclinical activities on Alzheimer, Parkinson, and Huntington diseases, and even in amyotrophic lateral sclerosis. Also, myricetin has revealed other biological activities, among them as antidiabetic, anticancer, immunomodulatory, cardiovascular, analgesic and antihypertensive. However, few clinical trials have been performed using myricetin as nutraceutical. Thus, this review provides new insights on myricetin preclinical pharmacological activities, and role in selected clinical trials.

Jianpi-yangwei decoction inhibits DNA damage repair in the drug resistance of gastric cancer by reducing FEN1 expression

Background

Flap Endonuclease 1(FEN1) has been considered as a new tumor marker in recent years and Jianpi Yangwei Decoction (JPYW) is a basic Traditional Chinese Medicine (TCM) for the treatment of gastric cancer. This study aimed to explore the role of FEN1-mediated DNA damage repair in the drug resistance of gastric cancer and the effect of JPYW on it by employing BGC823/5-Fu drug-resistant cell model.

Methods

The DNA repair efficiency of BGC823 and BGC823/5-Fu was compared intracellularly and extracellularly using an extrachromosomal assay system and the reconstituted base excision repair assay. By comparing gene and protein expression and identifying cell survival rates after knockdown or high expression of FEN1, the correlation between FEN1 high expression and 5-Fluorouracil (5-Fu) drug resistance was revealed. The effect of JPYW on DNA damage repair and FEN1 expression was observed by the degree of γ-H2AX phosphorylation in the cells, DNA repair efficiency and enzyme activity, et al.

Results

BGC823/5-Fu had a higher DNA repair efficiency than BGC823(P < 0.001), which proved to be both intracellular and extracellular. FEN1 was highly expressed in BGC823/5-Fu regardless of gene level(P < 0.001) or protein level. Furthermore, manipulating FEN1 altered the sensitivity of cancer cells to chemotherapeutic drug 5-Fu. Different concentrations of JPYW were used to investigate the inhibitory effect on the expression of FEN1 and DNA damage repair. JPYW inhibited DNA damage repair both intracellularly and extracellularly: the phosphorylation of γ-H2AX increased, with more DNA damage in the cells; the synthetic 8-oxo dG damage repair was reduced; and the ability of cell lysates to repair DNA damage decreased. The decrease of FEN1 expression in BGC823/5-Fu had a concentration dependent relationship with JYPW. In addition, JPYW inhibited the activity of FEN1 at the enzymatic level, as the amount of cut-off synthetic ³²p labeled DNA substrates were decreased.

Conclusion

FEN1 was highly expressed in drug-resistance gastric cancer cells BGC823/5-Fu, which leading to BGC823 resistant to (5-Fu) by acting on DNA damage repair. JPYW inhibited DNA damage repair and reversed 5-Fu drug resistance by reducing FEN1 expression and inhibiting FEN1 functional activity.

A review on myricetin as a potential therapeutic candidate for cancer prevention

Myricetin, one of the most extensively studied polyphenols, is present abundantly in various fruits and vegetables and exhibits diverse pharmacological properties. The multifaceted biological action of myricetin against tumor heterogeneity makes it an impressive anticancer agent whose efficacy has been confirmed by an overwhelming number of studies. Myricetin shows its therapeutic potential by targeting and modulating the expression of various molecular target which are involved in inflammation, cell proliferation, apoptosis, angiogenesis, invasion, and metastasis. Myricetin deters tumor progression by inducing apoptosis via both intrinsic and extrinsic pathway, activating/inactivating several signaling pathways, and reactivating various tumor suppressor genes. This comprehensive review represents the effect of myricetin on various hallmarks of cancer with insight into the molecular mechanism employed by myricetin to mitigate cell proliferation, angiogenesis, metastasis, and induce apoptosis. In addition, enhanced bioavailability of myricetin through conjugation and its increased efficacy as an anticancer agent when used in combination are also highlighted.

Anti-cancer activity of Conyza blinii saponin against cervical carcinoma through MAPK/TGF-β/Nrf2 signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Conyza blinii H.Lév. is a type of natural plant distributed in southwest of China. Its dried overground section can be used in traditional Chinese medicine (TCM) for treating infections, inflammations and occasionally cancers. CBS (Conyza blinii saponin), mainly composed of triterpenoidal saponins of Conyza blinii H.Lév. CBS is considered as the major active fraction of this species. The current investigation have focused on the mechanisms of CBS with regard to its anti-cancer activity. Hence it is of high relevance of identifying the anti-cancer efficacy of ethnomedicine.

AIM OF THE STUDY

To understand the anti-cancer mechanism of CBS using both in vitro and in vivo experiments.

MATERIALS AND METHODS

CBS (Conyza blinii saponin) was obtained as described previously. We tested the anti-cancer activity of CBS using in vitro HeLa cell models and in vivo animal models. We adopted immunoblot, RT-PCR (reverse transcription polymerase chain reaction), luciferase reporter assay and flow cytometry to study relevant proteins, genes, pathways and cellular ROS (reactive oxygen species) responsible for anti-cancer activity of CBS. More, 24 tumour-xenografted mice were grouped randomly as 'control', 'cisplatin' (as positive control), 'low dose' and 'high dose' groups. The IL-1β, TNF-α, PGE2 and IL-2 in the blood serum and the tumour tissue of mice were measured.

RESULTS AND CONCLUSIONS

We have found that CBS is capable of inducing apoptotic cancer cell death via both caspase-dependent and -independent pathways. CBS inhibits the activation of TGF-β signaling pathway in a dose- and time-dependent manner. Phospho-ERK, phospho-JNK and phospho-p38 MAPK are significantly suppressed by CBS. Furthermore, some inflammation mediators including IL-1β, TNF-α and PGE2 from animal samples were found decreased in CBS-treated mice models. In contrast, the level of IL-2, a cytokine commonly used for treating cancers, increased reversely. Last, we have discovered that CBS is able to decrease the expression of Nrf2, inhibit the activation of ARE and increase ROS level in HeLa cells. In summary, we have confirmed that the anti-cancer activity of CBS is possibly related to its TGF-β, MAPK, Nrf2 signaling pathways as well as some cancer related inflammation mediators and cytokines.

miR-193b Increases the Chemosensitivity of Osteosarcoma Cells by Promoting FEN1-Mediated Autophagy

Background

Osteosarcoma (OS) is one of the most common malignant bone tumors and specific microRNAs (miRNAs) are closely associated with malignant OS progression. In this study, we examined the role of microRNA-193b-3p (miR-193b) and the involvement of autophagy and apoptosis in the chemosensitivity of OS cells.

Methods

We employed qRT-PCR, Western blot, and immunohistochemistry to examine the expression levels of miR-193b, flap endonuclease 1 (FEN1), and autophagy-related proteins. Apoptosis was determined by flow cytometry using an Annexin V-FITC/PI apoptosis detection kit. Luciferase reporter assays confirmed the relationship between miR-193b and FEN1.

Results

miR-193b was downregulated in OS compared to adjacent normal tissues (p < 0.05). miR-193b overexpression in the OS cell lines induced autophagy and apoptosis, as shown by Western blotting and flow cytometry. Knockdown of FEN1, a structure-specific nuclease overexpressed in OS tissues (p < 0.001), induced apoptosis through activation of autophagy. Luciferase reporter assays confirmed that FEN1 is a direct target of miR-193b, FEN1 knockdown reinforced miR-193b induced apoptosis. Moreover, miR-193b expression enhanced epirubicin-induced autophagy and apoptosis.

Conclusion

Collectively, the results showed that miR-193b/FEN1 may serve as a novel therapeutic target for OS aimed mainly at the induction of autophagy and apoptosis. The miR-193b/FEN1 axis increased the chemosensitivity of OS cells, while activation of autophagy enhanced the anticancer effects of epirubicin.

Cardiac Glycoside Compound Isolated from Helleborus thibetanus Franch Displays Potent Toxicity against HeLa Cervical Carcinoma Cells through ROS-Independent Autophagy

The current study aimed to examine the anticancer activity of HTF-1, a cardiac glycoside (CG) isolated from Helleborus thibetanus Franch, using a cell-based model and to discover the underlying mechanisms with specific focus on autophagy. We found that HTF-1 was able to potently decrease the viability of several cancer cell lines especially for HeLa cervical carcinoma cells. It was discovered that HTF-1 dose dependently induced overproduction of ROS in HeLa cells, and the cell viability can be rescued when adding ROS scavenger N-acetyl-l-cysteine (NAC). More, we found that HTF-1 induced ROS-independent autophagy in concentration- and time-dependent manners in HeLa cells. This can be collectively verified by LC3-II and p62 abundance and also eGFP-LC3 puncta assay, bafilomycin clamp experiment, and acidotropic dye fluorescent labeling experiment. Additionally, TEM examination showed more autophagic vacuoles for HTF-1-treated HeLa cells. In HeLa cells, pretreatment with wortmannin (an inhibitor of the initial stages of autophagy to block autophagosome formation, thus, it should weaken the autophagy induction effect of HTF-1) decreased the autophagic flux and partially antagonized cell death induced by HTF-1, indicating that autophagy induced by HTF-1 played a cancer-suppressing role. Furthermore, coadministration of BAF (as a distal inhibitor of autophagy) with HTF-1 demonstrated a synergistic anticancer effect against HeLa cells. We believe that our work will enrich the understanding of CGs and especially anticarcinoma activity, also, pave the way for natural-product-based anticancer drug development.

Anti-tumor effects and associated molecular mechanisms of myricetin

Myricetin (3, 5, 7, 3', 4', 5'-hexahydroxyflavone) is a natural flavonol compound found in a large variety of plants, including berries, oranges, grapes, herbs, teas, and wine. In the last decade, a convergence of evidence has demonstrated that myricetin has good biological activity as an anti-tumor, anti-inflammatory, and anti-oxidation agent. In studies involving various types of cancer cells, myricetin has been shown to suppress cancer cell invasion and metastasis, to induce cell cycle arrest and apoptosis of cancer cells, and to inhibit their proliferation. These findings have raised interest in myricetin as a potential tumor inhibitor in human patients. In this review, evidence of myricetin's anti-tumor activity and its underlying molecular mechanisms published in the last decade are summarized.