Kaempferol Induces Cell Death Through ERK and Akt-Dependent Down-Regulation of XIAP and Survivin in Human Glioma Cells

Review: The PI3K-AKT-mTOR signal transduction pathway in canine cancer

Tumors in dogs and humans share many similar molecular and genetic features, incentivizing a better understanding of canine neoplasms not only for the purpose of treating companion animals, but also to facilitate research of spontaneously developing tumors with similar biologic behavior and treatment approaches in an immunologically competent animal model. Multiple tumor types of both species have similar dysregulation of signal transduction through phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB; AKT), and mechanistic target of rapamycin (mTOR), collectively known as the PI3K-AKT-mTOR pathway. This review aims to delineate the pertinent aspects of the PI3K-AKT-mTOR signaling pathway in health and in tumor development. It will then present a synopsis of current understanding of PI3K-AKT-mTOR signaling in important canine cancers and advancements in targeted inhibitors of this pathway.

The Anticancer Potential of Kaempferol: A Systematic Review Based on In Vitro Studies

Given the heterogeneity of different malignant processes, planning cancer treatment is challenging. According to recent studies, natural products are likely to be effective in cancer prevention and treatment. Among bioactive flavonoids found in fruits and vegetables, kaempferol (KMP) is known for its anti-inflammatory, antioxidant, and anticancer properties. This systematic review aims to highlight the potential therapeutic effects of KMP on different types of solid malignant tumors. This review was conducted following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Searches were performed in EMBASE, Medline/PubMed, Cochrane Collaboration Library, Science Direct, Scopus, and Google Scholar. After the application of study criteria, 64 studies were included. In vitro experiments demonstrated that KMP exerts antitumor effects by controlling tumor cell cycle progression, proliferation, apoptosis, migration, and invasion, as well as by inhibiting angiogenesis. KMP was also able to inhibit important markers that regulate epithelial-mesenchymal transition and enhanced the sensitivity of cancer cells to traditional drugs used in chemotherapy, including cisplatin and 5-fluorouracil. This flavonoid is a promising therapeutic compound and its combination with current anticancer agents, including targeted drugs, may potentially produce more effective and predictable results.

Kaempferol and Biomodified Kaempferol from Sophora japonica Extract as Potential Sources of Anti-Cancer Polyphenolics against High Grade Glioma Cell Lines

The enzymatic hydrolysis of the extract of Sophora japonica by two glycosyl hydrolases (hesperidinase and galactosidase) was performed in order to obtain kaempferol (KPF)-enriched extract with an enhanced anticancer activity. The current study examined the effectiveness of both Sophora japonica extracts (before (KPF-BBR) and after (KPF-ABR) bioconversion reactions) in reducing cell viability and inducing apoptosis in human high-degree gliomas in vitro. Cytotoxicity was determined using an MTT assay. The effects of both compounds on the proliferation of glioma cell lines were measured using trypan blue exclusion, flow cytometry for cell cycle, wound healing (WH), and neurosphere formation assays. Cellular apoptosis was detected by DNA fragmentation and phosphatidylserine exposure. qPCR and luciferase assays evaluated NF-kB pathway inhibition. The survival rate of NG-97 and U-251 cells significantly decreased in a time- and dose-dependent manner after the addition of KPF-BBR or KPF-ABR. Thus, a 50% reduction was observed in NG-97 cells at 800 µM (KPF-BBR) and 600 µM (KPF-ABR) after 72 h. Both compounds presented an IC50 of 1800 µM for U251 after 72 h. The above IC50 values were used in all of the following analyses. Neither of the KPF presented significant inhibitory effects on the non-tumoral cells (HDFa). However, after 24 h, both extracts (KPF-BBR and KPF-ABR) significantly inhibited the migration and proliferation of NG-97 and U-251 cells. In addition, MMP-9 was downregulated in glioma cells stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) plus KPF-BBR and TPA+KPF-ABR compared with the TPA-treated cells. Both KPF-BBR and KPF-ABR significantly inhibited the proliferation of glioma stem cells (neurospheres) after 24 h. DNA fragmentation assays demonstrated that the apoptotic ratio of KPF-ABR-treated cell lines was significantly higher than in the control groups, especially NG-97, which is not TMZ resistant. In fact, the flow cytometric analysis indicated that KPF-BBR and KPF-ABR induced significant apoptosis in both glioma cells. In addition, both KPF induced S and G2/M cell cycle arrest in the U251 cells. The qPCR and luciferase assays showed that both KPFs downregulated TRAF6, IRAK2, IL-1β, and TNF-α, indicating an inhibitory effect on the NF-kB pathway. Our findings suggest that both KPF-BBR and KPF-ABR can confer anti-tumoral effects on human cell glioma cells by inhibiting proliferation and inducing apoptosis, which is related to the NF-κB-mediated pathway. The KPF-enriched extract (KPF-ABR) showed an increased inhibitory effect on the cell migration and invasion, characterizing it as the best antitumor candidate.

Natural flavonols: actions, mechanisms, and potential therapeutic utility for various diseases

Background

Flavonols are phytoconstituents of biological and medicinal importance. In addition to functioning as antioxidants, flavonols may play a role in antagonizing diabetes, cancer, cardiovascular disease, and viral and bacterial diseases. Quercetin, myricetin, kaempferol, and fisetin are the major dietary flavonols. Quercetin is a potent scavenger of free radicals, providing protection from free radical damage and oxidation-associated diseases.

Main body of the abstract

An extensive literature review of specific databases (e.g., Pubmed, google scholar, science direct) were conducted using the keywords "flavonol," "quercetin," "antidiabetic," "antiviral," "anticancer," and "myricetin." Some studies concluded that quercetin is a promising antioxidant agent while kaempferol could be effective against human gastric cancer. In addition, kaempferol prevents apoptosis of pancreatic beta-cells via boosting the function and survival rate of the beta-cells, leading to increased insulin secretion. Flavonols also show potential as alternatives to conventional antibiotics, restricting viral infection by antagonizing the envelope proteins to block viral entry.

Short conclusion

There is substantial scientific evidence that high consumption of flavonols is associated with reduced risk of cancer and coronary diseases, free radical damage alleviation, tumor growth prevention, and insulin secretion improvement, among other diverse health benefits. Nevertheless, more studies are required to determine the appropriate dietary concentration, dose, and type of flavonol for a particular condition to prevent any adverse side effects.

Evaluation of Biological Activities of Twenty Flavones and In Silico Docking Study

This work aimed to evaluate the biological activities of 20 flavones (M1 to M20) and discuss their structure–activity relationships. In vitro assays were established to assess their numerous biological activities (anti-α-amylase, anti-acetylcholinesterase, anti-xanthine oxidase, anti-superoxide dismutase, and anticancer cell lines (HCT-116, MCF7, OVCAR-3, IGROV-1, and SKOV-3 cells lines)). An in silico docking study was also established in order to find the relationship between the chemical structure and the biological activities. In vitro tests revealed that M5 and M13 were the most active in terms of anti-α-amylase activity (IC50 = 1.2 and 1.4 µM, respectively). M17 was an inhibitor of xanthine oxidase (XOD) and performed better than the reference (allopurinol), at IC50 = 0.9 µM. M7 presented interesting anti-inflammatory (IC50 = 38.5 µM), anti-supriode dismutase (anti-SOD) (IC50 = 31.5 µM), and anti-acetylcholinesterase (IC50 = 10.2 µM) activities. Those abilities were in concordance with its high scavenging activity in antioxidant ABTS and DPPH assays, at IC50 = 6.3 and 5.2 µM, respectively. Selectivity was detected regarding cytotoxic activity for those flavones. M1 (IC50 = 35.9 µM) was a specific inhibitor to the MCF7 cancer cell lines. M3 (IC50 = 44.7 µM) and M15 (IC50 = 45.6 µM) were particularly potent for the OVCAR-3 cell line. M14 (IC50 = 4.6 µM) contributed more clearly to inhibiting the colon cancer cell line (HCT116). M7 (IC50 = 15.6 µM) was especially active against the ovarian SKOV human cancer cell line. The results of the biological activities were supported by means of in silico molecular docking calculations. This investigation analyzed the contribution of the structure–activity of natural flavones in terms of their biological properties, which is important for their future application against diseases.

Therapeutic Importance of Kaempferol in the Treatment of Cancer through the Modulation of Cell Signalling Pathways

Plant-derived flavonoids are considered natural nontoxic chemo-preventers and have been widely studied for cancer treatment in recent decades. Mostly all flavonoid compounds show significant anti-inflammatory, anticancer and antioxidant properties. Kaempferol (Kmp) is a well-studied compound and exhibits remarkable anticancer and antioxidant potential. Kmp can regulate various cancer-related processes and activities such as cell cycle, oxidative stress, apoptosis, proliferation, metastasis, and angiogenesis. The anti-cancer properties of Kmp primarily occur via modulation of apoptosis, MAPK/ERK1/2, P13K/Akt/mTOR, vascular endothelial growth factor (VEGF) signalling pathways. The anti-cancer property of Kmp has been recognized in several in-vivo and in-vitro studies which also includes numerous cell lines and animal models. This flavonoid possesses toxic activities against only cancer cells and have restricted toxicity on healthy cells. In this review, we present extensive research investigations about the therapeutic potential of Kmp in the management of different types of cancers. The anti-cancer properties of Kmp are discussed by concentration on its capability to target molecular-signalling pathway such as VEGF, STAT, p53, NF-κB and PI3K-AKT signalling pathways. The anti-cancer property of Kmf has gained a lot of attention, but the accurate action mechanism remains unclear. However, this natural compound has a great pharmacological capability and is now considered to be an alternative cancer treatment.

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.

A systematic review of anti-cancer roles and mechanisms of kaempferol as a natural compound

It has been shown in multiple experimental and biological investigations that kaempferol, an edible flavonoid generated from plants, may be used as an anti-cancer drug and has been shown to have anti-cancer properties. Many signaling pathways are altered in cancer cells, resulting in cell growth inhibition and death in various tumor types. Cancer is a multifaceted illness coordinated by multiple external and internal mechanisms. Natural extracts with the fewest side effects have piqued the attention of researchers in recent years, attempting to create cancer medicines based on them. An extensive array of natural product-derived anti-cancer agents have been examined to find a successful method. Numerous fruits and vegetables have high levels of naturally occurring flavonoid kaempferol, and its pharmacological and biological effects have been studied extensively. Certain forms of cancer are sensitive to kaempferol-mediated anti-cancer activity, although complete research is needed. We have endeavored to concentrate our review on controlling carcinogenic pathways by kaempferol in different malignancies. Aside from its extraordinary ability to modify cell processes, we have also discussed how kaempferol has the potential to be an effective therapy for numerous tumors.

Cancer Chemoprevention: A Strategic Approach Using Phytochemicals

Cancer chemoprevention approaches are aimed at preventing, delaying, or suppressing tumor incidence using synthetic or natural bioactive agents. Mechanistically, chemopreventive agents also aid in mitigating cancer development, either by impeding DNA damage or by blocking the division of premalignant cells with DNA damage. Several pre-clinical studies have substantiated the benefits of using various dietary components as chemopreventives in cancer therapy. The incessant rise in the number of cancer cases globally is an issue of major concern. The excessive toxicity and chemoresistance associated with conventional chemotherapies decrease the success rates of the existent chemotherapeutic regimen, which warrants the need for an efficient and safer alternative therapeutic approach. In this scenario, chemopreventive agents have been proven to be successful in protecting the high-risk populations from cancer, which further validates chemoprevention strategy as rational and promising. Clinical studies have shown the effectiveness of this approach in managing cancers of different origins. Phytochemicals, which constitute an appreciable proportion of currently used chemotherapeutic drugs, have been tested for their chemopreventive efficacy. This review primarily aims to highlight the efficacy of phytochemicals, currently being investigated globally as chemopreventives. The clinical relevance of chemoprevention, with special emphasis on the phytochemicals, curcumin, resveratrol, tryptanthrin, kaempferol, gingerol, emodin, quercetin genistein and epigallocatechingallate, which are potential candidates due to their ability to regulate multiple survival pathways without inducing toxicity, forms the crux of this review. The majority of these phytochemicals are polyphenols and flavanoids. We have analyzed how the key molecular targets of these chemopreventives potentially counteract the key drivers of chemoresistance, causing minimum toxicity to the body. An overview of the underlying mechanism of action of these phytochemicals in regulating the key players of cancer progression and tumor suppression is discussed in this review. A summary of the clinical trials on the important phytochemicals that emerge as chemopreventives is also incorporated. We elaborate on the pre-clinical and clinical observations, pharmacokinetics, mechanism of action, and molecular targets of some of these natural products. To summarize, the scope of this review comprises of the current status, limitations, and future directions of cancer chemoprevention, emphasizing the potency of phytochemicals as effective chemopreventives.

Anticancer activity of flavonoids accompanied by redox state modulation and the potential for a chemotherapeutic strategy

Since researchers began studying the mechanism of flavonoids' anticancer activity, little attention has been focused on the modulation of redox state in cells as a potential chemotherapeutic strategy. However, recent studies have begun identifying that the anticancer effect of flavonoids occurs both in their antioxidative activity which scavenges ROS and their prooxidative activity which generates ROS. Against this backdrop, this study attempts to achieve a comprehensive analysis of the individual and separate study findings regarding flavonoids' modulation of redox state in cancer cells. It focuses on the mechanism behind the anticancer effect, and mostly on the modulation of redox potential by flavonoids such as quercetin, hesperetin, apigenin, genistein, epigallocatechin-3-gallate (EGCG), luteolin and kaempferol in both in vitro and animal models. In addition, the clinical applications of and bioavailability of flavonoids were reviewed to help build a treatment strategy based on flavonoids' prooxidative potential.

Current Progress of Phytomedicine in Glioblastoma Therapy

Glioblastoma multiforme, an intrusive brain cancer, has the lowest survival rate of all brain cancers. The chemotherapy utilized to prevent their proliferation and propagation is limited due to modulation of complex cancer signalling pathways. These complex pathways provide infiltrative and drug evading properties leading to the development of chemotherapy resistance. Therefore, the development and discovery of such interventions or therapies that can bypass all these resistive barriers to ameliorate glioma prognosis and survival is of profound importance. Medicinal plants are comprised of an exorbitant range of phytochemicals that have the broad-spectrum capability to target intrusive brain cancers, modulate anti-cancer pathways and immunological responses to facilitate their eradication, and induce apoptosis. These phytocompounds also interfere with several oncogenic proteins that promote cancer invasiveness and metastasis, chemotherapy resistance and angiogenesis. These plants are extremely vital for promising anti-glioma therapy to avert glioma proliferation and recurrence. In this review, we acquired recent literature on medicinal plants whose extracts/bioactive ingredients are newly exploited in glioma therapeutics, and also highlighted their mode of action and pharmacological profile.

Anti-glioblastoma Activity of Kaempferol via Programmed Cell Death Induction: Involvement of Autophagy and Pyroptosis

Glioblastoma is one of the most common and lethal intracranial malignant, and is still lack of ideal treatments. Kaempferol is a major nutrient found in various edible plants, which has exhibited the potential for the treatment of glioblastoma. However, the specific anti-glioma mechanism of kaempferol is yet to be studied. Herein, we aim to explore the mechanisms underlying the anti-glioma activity of kaempferol. Our results demonstrated that kaempferol suppresses glioma cell proliferation in vitro and inhibits tumor growth in vivo. Moreover, kaempferol raises ROS and decreases mitochondrial membrane potential in glioma cells. The high levels of ROS induce autophagy then ultimately trigger the pyroptosis of glioma cells. Interestingly, when we used 3-MA to inhibit autophagy, we found that the cleaved form of GSDME was also decreased, suggesting that kaempferol induces pyroptosis through regulating autophagy in glioma cells. In conclusion, this study revealed kaempferol possesses good anti-glioma activity by inducing ROS, and subsequently leads to autophagy and pyroptosis, highlighting its clinical potentials as a natural nutrient against glioblastoma.

Tick-Borne Flaviviruses Depress AKT Activity during Acute Infection by Modulating AKT1/2

Tick-borne flaviviruses (TBFVs) are reemerging public health threats. To develop therapeutics against these pathogens, increased understanding of their interactions with the mammalian host is required. The PI3K-AKT pathway has been implicated in TBFV persistence, but its role during acute virus infection remains poorly understood. Previously, we showed that Langat virus (LGTV)-infected HEK 293T cells undergo a lytic crisis with a few surviving cells that become persistently infected. We also observed that AKT2 mRNA is upregulated in cells persistently infected with TBFV. Here, we investigated the virus-induced effects on AKT expression over the course of acute LGTV infection and found that total phosphorylated AKT (pAKT), AKT1, and AKT2 decrease over time, but AKT3 increases dramatically. Furthermore, cells lacking AKT1 or AKT2 were more resistant to LGTV-induced cell death than wild-type cells because they expressed higher levels of pAKT and antiapoptotic proteins, such as XIAP and survivin. The differential modulation of AKT by LGTV may be a mechanism by which viral persistence is initiated, and our results demonstrate a complicated manipulation of host pathways by TBFVs.

Antiproliferative and apoptogenic effects of Cassia fistula L. n-hexane fraction against human cervical cancer (HeLa) cells

The current study was performed to evaluate the antiproliferative and apoptosis-inducing potential of n-hexane fraction from Cassia fistula L. (Caesalpinioideae) fruits. The antiproliferative property of the fraction was determined by MTT assay against cancer cell lines including HeLa, MG-63, IMR-32, and PC-3 with GI50 value of 97.69, 155.2, 143, and 160.2 μg/ml respectively. The fraction was further explored for its apoptotic effect using confocal, SEM, and flow cytometry studies in HeLa cells. It was observed that the treatment of fraction revealed fragmentation of DNA, chromatin condensation, membrane blebbing, and formation of apoptotic bodies in a dose-dependent manner. The fraction also showed a remarkable increase in the level of ROS, mitochondrial depolarization and G0/G1 phase cell cycle arrest, and induction in the phosphatidylserine externalization analyzed using Annexin V-FITC/PI double staining assay in HeLa cells. Kaempferol, Ellagic acid, and Epicatechin are the major phytoconstituents present in the fraction as revealed by the HPLC. The treatment of n-hexane fraction showed downregulation in the gene expression of Bcl-2 and upregulation in the expression level of p53, Bad, and caspase-3 genes analyzed using semi-quantitative RT-PCR in HeLa cells. These results suggest that n-hexane fraction from C. fistula inhibited the proliferation of cervical cancer cells efficiently by the induction of apoptosis. Graphical abstract.

Antioxidant, Antiproliferative and Apoptosis-Inducing Efficacy of Fractions from Cassia fistula L. Leaves

: Cassia fistula L. is a highly admirable traditional medicinal plant used for the treatment of various diseases and disorders. The present study was performed to divulge the antioxidant, antiproliferative, and apoptosis-inducing efficacy of fractions from C. fistula leaves. The hexane (CaLH fraction), chloroform (CaLC fraction), ethyl acetate (CaLE fraction), n-butanol (CaLB fraction), and aqueous (CaLA fraction) were sequentially fractionated from 80% methanolic (CaLM extract) of C. fistula leaves. The CaLE fraction was fractionated using column chromatography to yield a pure compound, which was characterized as Epiafzelechin (CFL1) based on 1H, 13C, and DEPT135 NMR. Among these fractions, CaLE and isolated CFL1 fractions exhibited an effective antioxidant potential in Ferric ion reducing power, (2,2'-azino-bis (3-ethylbenzothiazoline -6-sulfonic acid)) cation radical scavenging, and nitric oxide radical scavenging assays. Epiafzelechin was investigated for its antiproliferative effects against MG-63 (osteosarcoma), IMR-32 (neuroblastoma), and PC-3 (prostate adenocarcinoma), and was found to inhibit cell proliferation with a GI50 value of 8.73, 9.15, and 11.8 μM respectively. MG-63 cells underwent apoptotic cell death on treatment with Epiafzelechin as the cells showed the formation of apoptotic bodies, enhanced reactive oxygen species (ROS) generation, mitochondrial membrane depolarization along with an increase in early apoptotic cell population analyzed using Annexin V-FITC/PI double staining assay. Cells showed cell cycle arrest at the G0/G1 phase accompanied by a downregulation in the expression levels of p-Akt (Protein kinase B), p-GSK-3β (Glycogen synthase kinase-3 beta), and Bcl-xl (B-cell lymphoma-extra large) proteins. RT-PCR (Real time-polymerase chain reaction) analysis revealed downregulation in the gene expression level of β-catenin and CDK2 (cyclin-dependent kinases-2) while it upregulated the expression level of caspase-8 and p53 genes in MG-63 cells.

Kaempferol: A Key Emphasis to Its Anticancer Potential

A marked decrease in human cancers, including breast cancer, bone cancer, and cervical cancer, has been linked to the consumption of vegetable and fruit, and the corresponding chemoprotective effect has been associated with the presence of several active molecules, such as kaempferol. Kaempferol is a major flavonoid aglycone found in many natural products, such as beans, bee pollen, broccoli, cabbage, capers, cauliflower, chia seeds, chives, cumin, moringa leaves, endive, fennel, and garlic. Kaempferol displays several pharmacological properties, among them antimicrobial, anti-inflammatory, antioxidant, antitumor, cardioprotective, neuroprotective, and antidiabetic activities, and is being applied in cancer chemotherapy. Specifically, kaempferol-rich food has been linked to a decrease in the risk of developing some types of cancers, including skin, liver, and colon. The mechanisms of action include apoptosis, cell cycle arrest at the G2/M phase, downregulation of epithelial-mesenchymal transition (EMT)-related markers, and phosphoinositide 3-kinase/protein kinase B signaling pathways. In this sense, this article reviews data from experimental studies that investigated the links between kaempferol and kaempferol-rich food intake and cancer prevention. Even though growing evidence supports the use of kaempferol for cancer prevention, further preclinical and clinical investigations using kaempferol or kaempferol-rich foods are of pivotal importance before any public health recommendation or formulation using kaempferol.

Flavonoids in Cancer and Apoptosis

Cancer is the second leading cause of death globally. Although, there are many different approaches to cancer treatment, they are often painful due to adverse side effects and are sometimes ineffective due to increasing resistance to classical anti-cancer drugs or radiation therapy. Targeting delayed/inhibited apoptosis is a major approach in cancer treatment and a highly active area of research. Plant derived natural compounds are of major interest due to their high bioavailability, safety, minimal side effects and, most importantly, cost effectiveness. Flavonoids have gained importance as anti-cancer agents and have shown great potential as cytotoxic anti-cancer agents promoting apoptosis in cancer cells. In this review, a summary of flavonoids and their effectiveness in cancer treatment targeting apoptosis has been discussed.

Kaempferol-loaded mucoadhesive nanoemulsion for intranasal administration reduces glioma growth in vitro

In order to search for new approaches to treat glioma, intranasal administration has been proposed as an alternative route to deliver drugs into the brain. Among the drug alternatives, kaempferol (KPF) has been reported to induce glioma cell death. This study aimed to prepare nanoemulsions containing KPF with and without chitosan to investigate their potential for brain delivery following intranasal administration, and to evaluate their antitumor activity against glioma cells. KPF-loaded nanoemulsion (KPF-NE) and KPF-loaded mucoadhesive nanoemulsion (KPF-MNE) were prepared by high-pressure homogenization technique and were characterized for their globule size, zeta potential, drug content, pH, viscosity, mucoadhesive strength and morphology. KPF from KPF-MNE showed significantly higher permeation across the mucosa in ex vivo diffusion studies. Histopathological examination suggests both nanoemulsions to be safe for the nasal mucosa and able to preserve KPF antioxidant capability. KPF-MNE enhanced significantly the amount of drug into rat's brain following intranasal administration (5- and 4.5-fold higher than free drug and KPF-NE, respectively). In addition, KPF-MNE reduced C6 glioma cell viability through induction of apoptosis to a greater extent than either free KPF or KPF-NE. The mucoadhesive nanoemulsion developed for intranasal administration may be a promising system for delivery to the brain, and KPF-MNE is a candidate for further antiglioma trials.

Dihydromyricetin enhances glucose uptake by inhibition of MEK/ERK pathway and consequent down-regulation of phosphorylation of PPARγ in 3T3-L1 cells

Accumulating evidence suggests that inhibition of mitogen-activated protein kinase signalling can reduce phosphorylation of peroxisome proliferator-activated receptor γ (PPARγ) at serine 273, which mitigates obesity-associated insulin resistance and might be a promising treatment for type 2 diabetes. Dihydromyricetin (DHM) is a flavonoid that has many beneficial pharmacological properties. In this study, mouse fibroblast 3T3-L1 cells were used to investigate whether DHM alleviates insulin resistance by inhibiting PPARγ phosphorylation at serine 273 via the MEK/ERK pathway. 3T3-L1 pre-adipocytes were differentiated, and the effects of DHM on adipogenesis and glucose uptake in the resulting adipocytes were examined. DHM was found to dose dependently increase glucose uptake and decrease adipogenesis. Insulin resistance was then induced in adipocytes using dexamethasone, and DHM was shown to dose and time dependently promote glucose uptake in the dexamethasone-treated adipocytes. DHM also inhibited phosphorylation of PPARγ and ERK. Inhibition of PPARγ activity with GW9662 potently blocked DHM-induced glucose uptake and adiponectin secretion. Interestingly, DHM showed similar effects to PD98059, an inhibitor of the MEK/ERK pathway. DHM acted synergistically with PD98059 to improve glucose uptake and adiponectin secretion in dexamethasone-treated adipocytes. In conclusion, our findings indicate that DHM improves glucose uptake in adipocytes by inhibiting ERK-induced phosphorylation of PPARγ at serine 273.

Treatment mechanism of matrine in combination with irinotecan for colon cancer

The inhibitory effect of matrine (MA) was studied in combination with irinotecan (CPT-11) on proliferation of human colon carcinoma cell line HT29. We also explored the mechanism of cell apoptosis induction in HT29. HT29 cells were treated with different concentrations of MA and CPT-11 alone and in combination. The growth inhibition in HT29 cells was evaluated using MTT assay. Apoptosis was detected using AV-PI double staining flow cytometry. Transmission electron microscopy was used to detect structural changes in cells. Topoisomerase (TOPO) I, Bax and Caspase-3 expression levels were evaluated using western blot analysis. MA and CPT-11 alone and in combination, inhibited the proliferation of HT29 cells, whereas the combination treatment exhibited higher inhibitory effect (P<0.01). This suggests the existence of synergistic cytotoxicity. Compared with each treatment alone, the combination treatment caused more significant damage to cell structure, and caused a significantly higher apoptosis rate (P<0.01). Additionally, the combination treatment increased TOPO I, Bax and Caspase-3 expression levels (P<0.01). In conclusion, MA in combination with CPT-11 synergistically inhibited HT29 cell proliferation and induced apoptosis in these cells. The mechanism may be related to upregulation of the TOPO I, Bax and Caspase-3 protein expression.

Dietary Intervention by Phytochemicals and Their Role in Modulating Coding and Non-Coding Genes in Cancer

Phytochemicals are natural compounds synthesized as secondary metabolites in plants, representing an important source of molecules with a wide range of therapeutic applications. These natural agents are important regulators of key pathological processes/conditions, including cancer, as they are able to modulate the expression of coding and non-coding transcripts with an oncogenic or tumour suppressor role. These natural agents are currently exploited for the development of therapeutic strategies alone or in tandem with conventional treatments for cancer. The aim of this paper is to review the recent studies regarding the role of these natural phytochemicals in different processes related to cancer inhibition, including apoptosis activation, angiogenesis and metastasis suppression. From the large palette of phytochemicals we selected epigallocatechin gallate (EGCG), caffeic acid phenethyl ester (CAPE), genistein, morin and kaempferol, due to their increased activity in modulating multiple coding and non-coding genes, targeting the main hallmarks of cancer.

7-O-geranylquercetin-induced autophagy contributes to apoptosis via ROS generation in human non-small cell lung cancer cells

AIMS

To investigate the antitumor effects of 7-O-geranylquercetin (GQ), a novel O-alkylated derivative of quercetin, against non-small cell lung cancer (NSCLC) cell lines A549 and NCI-H1975 and the corresponding mechanisms.

MAIN METHODS

Cell viability was assessed using MTT assay. The expression of proteins involved in apoptosis and autophagy was measured using western blotting. Besides, apoptosis was determined with DAPI staining, Annexin V-PI staining and transmission electron microscopy (TEM) assay, and autophagy was observed with TEM assay. Cell cycle and reactive oxygen species (ROS) level were detected using flow cytometry.

KEY FINDINGS

GQ inhibited viability of A549 and NCI-H1975 cells in a dose- and time-dependent manner without apparent cytotoxicity to normal human lung fibroblast cells. GQ down-regulated the expression of apoptosis-related proteins pro-caspase 3 and Bcl-2, and up-regulated the expression of cleaved-PARP and Bax in A549 and NCI-H1975 cells. Meanwhile, GQ-induced cell apoptosis could be attenuated by caspase inhibitor Z-VAD-FMK. Besides, GQ induced autophagosome formation in A549 and NCI-H1975 cells, promoted the expression of autophagy-related proteins LC3-II and Beclin 1, and suppressed the expression of p62. Autophagy inhibition with chloroquine or Beclin 1 siRNA could effectively inhibit GQ-induced apoptosis. Furthermore, GQ treatment increased the generation of ROS, and ROS inhibitor N-acetylcysteine could reverse GQ-induced autophagy and apoptosis. Taken together, GQ could induce apoptosis and autophagy via ROS generation in A549 and NCI-H1975 cells, and GQ-induced autophagy contributed to apoptosis.

SIGNIFICANCE

Our findings highlight that GQ is a promising anticancer agent for the treatment of lung cancer.

Dihydromyricetin delays the onset of hyperglycemia and ameliorates insulin resistance without excessive weight gain in Zucker diabetic fatty rats

Many flavonoids are reported to be partial agonists of PPARγ and exert antidiabetic effects with fewer side effects compared with full agonists. Here, we assessed the effects of flavonoid dihydromyricetin (DHM) on glucose homeostasis in male Zucker diabetic fatty rats. Animals were treated with DHM (50-200  mg kg^-1) or rosiglitazone (4  mg kg^-1) once a day for 8 weeks. We found that DHM reduced fasting blood glucose and delayed the onset of hyperglycemia by 4 weeks. Furthermore, DHM preserved pancreatic β-cell mass, elevated adiponectin and improved lipid profile more vigorously than rosiglitazone. Notably, DHM decreased body weight gain and fat accumulation in both liver and adipose tissue, while rosiglitazone caused a significant increase of body weight and fat accumulation. DHM inhibited phosphorylation of PPARγ at serine 273 more efficiently than rosiglitazone. These results suggest that DHM exerts antidiabetic effects without causing excessive body weight gain via inhibition of PPARγ phosphorylation.

CRNDE affects the malignant biological characteristics of human glioma stem cells by negatively regulating miR-186

The long non-coding RNA Colorectal neoplasia differentially expressed (CRNDE) is a novel gene that activated early in colorectal neoplasia, but it is also up-regulated in many other solid tumors. Herein, the function and underlying mechanism of CRNDE in regulating glioma stem cells (GSCs) were investigated. We found that CRNDE expression was up-regulated while miR-186 expression was down-regulated in GSCs. Overexpression of CRNDE could promote the cellular proliferation, migration, invasion and inhibit the apoptosis in GSCs. Overexpression of miR-186 exerted functions of inhibiting the proliferation, migration and invasion of GSCs and promoting apoptosis. And CRNDE decreased the expression levels of XIAP and PAK7 by binding to miR-186 and negatively regulating it. In addition, miR-186 binded to XIAP and PAK7 3′UTR region, and decrease the expression of them, thus regulating the expression levels of downstream target proteins such as caspase 3, BAD, cyclin D1 and MARK2. The in vivo effect of CRNDE and miR-186 showed that the tumor formation rate was minimum in tumor-bearing nude mice with the knockdown of CRNDE and the overexpression of miR-186. In conclusion, CRNDE played an oncogenic role of GSCs through the negative regulation of miR-186. Both CRNDE and miR-186 could be regarded as potential targets in the glioma therapy.

Lilium compounds kaempferol and jatropham can modulate cytotoxic and genotoxic effects of radiomimetic zeocin in plants and human lymphocytes In vitro

Organisms are constantly exposed to the detrimental effect of environmental DNA-damaging agents. The harmful effects of environmental genotoxins could be decreased in a viable way by antimutagenesis. One of the modern approaches to reduce the mutagenic burden is based on exogenous natural and synthetic compounds that possess protective and antimutagenic potential against genotoxins. The natural compounds kaempferol and jatropham isolated from Lilium candidum were tested with respect to their potential to protect cells against the radiomimetic zeocin, as well as to their cytotoxic and genotoxic activities in two types of experimental eukaryotic test systems: Hordeum vulgare and human lymphocytes in vitro. Mitotic index (MI) was used as an endpoint for cytotoxicity; the frequency of chromosome aberrations (MwA) and the number of induced micronuclei (MN), as endpoints for genotoxicity/clastogenicity. Formation of aberration "hot spots" was also used as an indicator for genotoxicity in H. vulgare. Both kaempferol and jatropham were shown to possess a potential to modulate and decrease the cytotoxic and genotoxic/clastogenic effect of zeocin depending on the experimental design and the test system. Our data could be useful for health research programs, particularly in clarifying the pharmacological potential and activity of natural plant compounds. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 751-764, 2016.

Kaempferol stimulates gene expression of low-density lipoprotein receptor through activation of Sp1 in cultured hepatocytes

A high level of plasma low-density lipoprotein (LDL) cholesterol is considered a risk factor for atherosclerosis. Because the hepatic LDL receptor (LDLR) is essential for clearing plasma LDL cholesterol, activation of LDLR is a promising therapeutic target for patients with atherosclerotic disease. Here we demonstrated how the flavonoid kaempferol stimulated the gene expression and activity of LDLR in HepG2 cells. The kaempferol-mediated stimulation of LDLR gene expression was completely inhibited by knockdown of Sp1 gene expression. Treatment of HepG2 cells with kaempferol stimulated the recruitment of Sp1 to the promoter region of the LDLR gene, as well as the phosphorylation of Sp1 on Thr-453 and Thr-739. Moreover, these kaempferol-mediated processes were inhibited in the presence of U0126, an ERK pathway inhibitor. These results suggest that kaempferol may increase the activity of Sp1 through stimulation of Sp1 phosphorylation by ERK1/2 and subsequent induction of LDLR expression and activity.

Kaempferol induces ATM/p53-mediated death receptor and mitochondrial apoptosis in human umbilical vein endothelial cells

Kaempferol is a member of the flavonoid compounds found in vegetables and fruits. It is shown to exhibit biological impact and anticancer activity, but no report exists on the angiogenic effect of kaempferol and induction of cell apoptosis in vitro. In this study, we investigated the role of kaempferol on anti-angiogenic property and the apoptotic mechanism of human umbilical vein endothelial cells (HUVECs). Our results demonstrated that kaempferol decreased HUVEC viability in a time- and concentration-dependent manner. Kaempferol also induced morphological changes and sub-G1 phase cell population (apoptotic cells). Kaempferol triggered apoptosis of HUVECs as detecting by DNA fragmentation, comet assay and immunofluorescent staining for activated caspase-3. The caspase signals, including caspase-8, -9 and -3, were time-dependently activated in HUVECs after kaempferol exposure. Furthermore, pre-treatment with a specific inhibitor of caspase-8 (Z-IETD-FMK) significantly reduced the activity of caspase-8, -9 and -3, indicating that extrinsic pathway is a major signaling pathway in kaempferol-treated HUVECs. Importantly, kaempferol promoted reactive oxygen species (ROS) evaluated using flow cytometric assay in HUVECs. We further investigated the upstream extrinsic pathway and showed that kaempferol stimulated death receptor signals [Fas/CD95, death receptor 4 (DR4) and DR5] through increasing the levels of phosphorylated p53 and phosphorylated ATM pathways in HUVECs, which can be individually confirmed by N-acetylcysteine (NAC), ATM specific inhibitor (caffeine) and p53 siRNA. Based on these results, kaempferol-induced HUVEC apoptosis was involved in an ROS-mediated p53/ATM/death receptor signaling. Kaempferol might possess therapeutic effects on cancer treatment in anti-vascular targeting.

Flavonoids suppress human glioblastoma cell growth by inhibiting cell metabolism, migration, and by regulating extracellular matrix proteins and metalloproteinases expression

The malignant gliomas are very common primary brain tumors with poor prognosis, which require more effective therapies than the current used, such as with chemotherapy drugs. In this work, we investigated the effects of several polyhydroxylated flavonoids namely, rutin, quercetin (F7), apigenin (F32), chrysin (F11), kaempferol (F12), and 3',4'-dihydroxyflavone (F2) in human GL-15 glioblastoma cells. We observed that all flavonoids decreased the number of viable cells and the mitochondrial metabolism. Furthermore, they damaged mitochondria and rough endoplasmic reticulum, inducing apoptosis. Flavonoids also induced a delay in cell migration, related to a reduction in filopodia-like structures on the cell surface, reduction on metalloproteinase (MMP-2) expression and activity, as well as an increase in intra- and extracellular expression of fibronectin, and intracellular expression of laminin. Morphological changes were also evident in adherent cells characterized by the presence of a condensed cell body with thin and long cellular processes, expressing glial fibrillary acidic protein (GFAP). Therefore, these flavonoids should be tested as potential antitumor agents in vitro and in vivo in other malignant glioma models.

Radiosensitization of non-small cell lung cancer by kaempferol

The aim of the present study was to determine whether kaempferol has a radiosensitization potential for lung cancer in vitro and in vivo. The in vitro radio-sensitization activity of kaempferol was elucidated in A-549 lung cancer cells by using an MTT (3-(4 5-dimethylthiazol-2-yl)-25-diphenyl-tetrazolium bromide) assay, cell cycle analysis and clonogenic assay. The in vivo activity was evaluated in the BALB/c nude mouse xenograft model of A-549 cells by hematoxylin and eosin staining and immunohistochemistry, and the tumor volume was recorded. Protein levels of the apoptotic pathway were detected by western blot analysis. Treatment with kaempferol inhibited the growth of A-549 cells through activation of apoptotic pathway. However, the same doses did not affect HFL1 normal lung cell growth. Kaempferol induced G2/M cell cycle arrest and the enhancement of radiation-induced death and clonogenic survival inhibition. The in vivo data showed that kaempferol increased tumor cell apoptosis and killing of radiation. In conclusion, the findings demonstrated that kaempferol increased tumor cell killing by radiation in vitro and in vivo through inhibition of the AKT/PI3K and ERK pathways and activation of the mitochondria apoptosis pathway. The results of the present study provided solid evidence that kaempferol is a safe and potential radiosensitizer.

Ionizing radiations sustain glioblastoma cell dedifferentiation to a stem-like phenotype through survivin: possible involvement in radioresistance

Glioblastomas (GBM) are some bad prognosis brain tumors despite a conventional treatment associating surgical resection and subsequent radio-chemotherapy. Among these heterogeneous tumors, a subpopulation of chemo- and radioresistant GBM stem-like cells appears to be involved in the systematic GBM recurrence. Moreover, recent studies showed that differentiated tumor cells may have the ability to dedifferentiate and acquire a stem-like phenotype, a phenomenon also called plasticity, in response to microenvironment stresses such as hypoxia. We hypothesized that GBM cells could be subjected to a similar dedifferentiation process after ionizing radiations (IRs), then supporting the GBM rapid recurrence after radiotherapy. In the present study we demonstrated that subtoxic IR exposure of differentiated GBM cells isolated from patient resections potentiated the long-term reacquisition of stem-associated properties such as the ability to generate primary and secondary neurospheres, the expression of stemness markers and an increased tumorigenicity. We also identified during this process an upregulation of the anti-apoptotic protein survivin and we showed that its specific downregulation led to the blockade of the IR-induced plasticity. Altogether, these results demonstrated that irradiation could regulate GBM cell dedifferentiation via a survivin-dependent pathway. Targeting the mechanisms associated with IR-induced plasticity will likely contribute to the development of some innovating pharmacological strategies for an improved radiosensitization of these aggressive brain cancers.

Mitochondrial pro-apoptotic indices do not precede the transient caspase activation associated with myogenesis

Skeletal muscle differentiation requires activity of the apoptotic protease caspase-3. We attempted to identify the source of caspase activation in differentiating C2C12 skeletal myoblasts. In addition to caspase-3, caspase-2 was transiently activated during differentiation; however, no changes were observed in caspase-8 or -9 activity. Although mitochondrial Bax increased, this was matched by Bcl-2, resulting in no change to the mitochondrial Bax:Bcl-2 ratio early during differentiation. Interestingly, mitochondrial membrane potential increased on a timeline similar to caspase activation and was accompanied by an immediate, temporary reduction in cytosolic Smac and cytochrome c. Since XIAP protein expression dramatically declined during myogenesis, we investigated whether this contributes to caspase-3 activation. Despite reducing caspase-3 activity by up to 57%, differentiation was unaffected in cells overexpressing normal or E3-mutant XIAP. Furthermore, a XIAP mutant which can inhibit caspase-9 but not caspase-3 did not reduce caspase-3 activity or affect differentiation. Administering a chemical caspase-3 inhibitor demonstrated that complete enzyme inhibition was required to impair myogenesis. These results suggest that neither mitochondrial apoptotic signaling nor XIAP degradation is responsible for transient caspase-3 activation during C2C12 differentiation.

Cytotoxicity of dietary flavonoids on different human cancer types

Flavonoids are ubiquitous in nature. They are also in food, providing an essential link between diet and prevention of chronic diseases including cancer. Anticancer effects of these polyphenols depend on several factors: Their chemical structure and concentration, and also on the type of cancer. Malignant cells from different tissues reveal somewhat different sensitivity toward flavonoids and, therefore, the preferences of the most common dietary flavonoids to various human cancer types are analyzed in this review. While luteolin and kaempferol can be considered as promising candidate agents for treatment of gastric and ovarian cancers, respectively, apigenin, chrysin, and luteolin have good perspectives as potent antitumor agents for cervical cancer; cells from main sites of flavonoid metabolism (colon and liver) reveal rather large fluctuations in anticancer activity probably due to exposure to various metabolites with different activities. Anticancer effect of flavonoids toward blood cancer cells depend on their myeloid, lymphoid, or erythroid origin; cytotoxic effects of flavonoids on breast and prostate cancer cells are highly related to the expression of hormone receptors. Different flavonoids are often preferentially present in certain food items, and knowledge about the malignant tissue-specific anticancer effects of flavonoids could be purposely applied both in chemoprevention as well as in cancer treatment.

Kaempferol reduces matrix metalloproteinase-2 expression by down-regulating ERK1/2 and the activator protein-1 signaling pathways in oral cancer cells

Background

Kaempferol has been proposed as a potential drug for cancer chemoprevention and treatment because it is a natural polyphenol contained in plant-based foods. Recent studies have demonstrated that kaempferol protects against cardiovascular disease and cancer. Based on this finding, we investigated the mechanisms by which kaempferol produces the anti-metastatic effect in human tongue squamous cell carcinoma SCC4 cells.

Methodology/Principal Findings

In this study, we provided molecular evidence associated with the anti-metastatic effect of kaempferol by demonstrating a substantial suppression of SCC4 cell migration and invasion. This effect was associated with reduced expressions of MMP-2 and TIMP-2 mRNA and protein levels. Analysis of the transcriptional regulation indicated that kaempferol inhibited MMP-2 transcription by suppressing c-Jun activity. Kaempferol also produced an inhibitory effect on the phosphorylation of ERK1/2.

Conclusions

These findings provide new insights into the molecular mechanisms involved in the anti-metastatic effect of kaempferol, and are valuable in the prevention of oral cancer metastasis.

Synthetic lethal interaction between PI3K/Akt/mTOR and Ras/MEK/ERK pathway inhibition in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) frequently exhibits concomitant activation of the PI3K/Akt/mTOR and the Ras/MEK/ERK pathways. Therefore, we investigated whether pharmacological cotargeting of these two key survival pathways suppresses RMS growth. Here, we identify a synthetic lethal interaction between PI3K/Akt/mTOR and Ras/MEK/ERK pathway inhibition in RMS. The dual PI3K/mTOR inhibitor PI103 and the MEK inhibitor UO126 synergize to trigger apoptosis in several RMS cell lines in a highly synergistic manner (combination index <0.1), whereas either agent alone induces minimal cell death. Similarly, genetic knockdown of p110α and MEK1/2 cooperates to induce apoptosis. Molecular studies reveal that cotreatment with PI103/UO126 cooperates to suppress PI3K/Akt/mTOR and Ras/MEK/ERK signaling, whereas either compound alone is not only less effective to inhibit signaling, but even cross-activates the other pathway. Accordingly, PI103 alone increases ERK phosphorylation, while UO126 enhances Akt phosphorylation, consistent with negative crosstalks between these two signaling pathways. Furthermore, PI103/UO126 cotreatment causes downregulation of several antiapoptotic proteins such as XIAP, Bcl-xL and Mcl-1 as well as increased expression and decreased phosphorylation of the proapoptotic protein BimEL, thus shifting the balance towards apoptosis. Consistently, PI103/UO126 cotreatment cooperates to trigger Bax activation, loss of mitochondrial membrane potential, caspase activation and caspase-dependent apoptosis. This identification of a synthetic lethal interaction between PI3K/mTOR and MEK inhibitors has important implications for the development of novel treatment strategies in RMS.

Silibinin inhibits tumor growth through downregulation of extracellular signal-regulated kinase and Akt in vitro and in vivo in human ovarian cancer cells

Anticancer activity of silibinin, a flavonoid, has been demonstrated in various cancer cell types. However, the underlying mechanisms were not elucidated in human ovarian cancer cells. The present study was undertaken to examine the effect of silibinin in vitro and in vivo on tumor growth in human ovarian cancer cells. Silibinin decreased cell viability in a dose- and time-dependent manner. Silibinin caused an increase in reactive oxygen species (ROS) generation, and the silibinin-induced cell death was prevented by the antioxidant N-acetylcysteine (NAC). Western blot analysis showed silibinin-induced downregulation of extracellular signal-regulated kinase (ERK) and Akt. Transfection of constitutively active forms of MEK and Akt prevented the silibinin-induced cell death. Oral administration of silibinin in animals with subcutaneous A2780 cells reduced tumor volume. Subsequent tumor tissue analysis showed that silibinin treatment induced a decrease in Ki-67-positive cells, an increase in transferase-mediated dUTP nick end labeling (TUNEL)-positive cells, activation of caspase-3, and inhibition of p-ERK and p-Akt. These results indicate that silibinin reduces tumor growth through inhibition of ERK and Akt in human ovarian cancer cells. These data suggest that silibinin may serve as a potential therapeutic agent for human ovarian cancers.

ZFX regulates glioma cell proliferation and survival in vitro and in vivo

The zinc finger transcription factor ZFX functions as an important regulator of self-renewal in multiple stem cell types, as well as a sex determinant of mammals. Moreover, ZFX expression is abnormally elevated in several cancers, and correlates with malignancy grade. To investigate its role in the pathogenesis of gliomas, we used lentivirus-mediated RNA interference (RNAi) to knockdown ZFX expression in human glioma cell lines. Our results demonstrate that ZFX plays a crucial role in glioma proliferation and survival, confirming recent reports. We also show for the first time that ZFX knockdown decreases the in vivo growth potential of U87 glioma xenografts in both subcutaneous and intracranial models in nude mice. We conclude that lentivirus-mediated RNAi targeting of ZFX may serve as a promising strategy for glioma therapy.

Thimerosal-induced apoptosis in mouse C2C12 myoblast cells occurs through suppression of the PI3K/Akt/survivin pathway

Background

Thimerosal, a mercury-containing preservative, is one of the most widely used preservatives and found in a variety of biological products. Concerns over its possible toxicity have reemerged recently due to its use in vaccines. Thimerosal has also been reported to be markedly cytotoxic to neural tissue. However, little is known regarding thimerosal-induced toxicity in muscle tissue. Therefore, we investigated the cytotoxic effect of thimerosal and its possible mechanisms on mouse C2C12 myoblast cells.

Methodology/Principal Findings

The study showed that C2C12 myoblast cells underwent inhibition of proliferation and apoptosis after exposure to thimerosal (125–500 nM) for 24, 48 and 72 h. Thimerosal caused S phase arrest and induced apoptosis as assessed by flow cytometric analysis, Hoechst staining and immunoblotting. The data revealed that thimerosal could trigger the leakage of cytochrome c from mitochondria, followed by cleavage of caspase-9 and caspase-3, and that an inhibitor of caspase could suppress thimerosal-induced apoptosis. Thimerosal inhibited the phosphorylation of Akt^ser473 and survivin expression. Wortmannin, a PI3K inhibitor, inhibited Akt activity and decreased survivin expression, resulting in increased thimerosal-induced apoptosis in C2C12 cells, while the activation of PI3K/Akt pathway by mIGF-I (50 ng/ml) increased the expression of survivin and attenuated apoptosis. Furthermore, the inhibition of survivin expression by siRNA enhanced thimerosal-induced cell apoptosis, while overexpression of survivin prevented thimerosal-induced apoptosis. Taken together, the data show that the PI3K/Akt/survivin pathway plays an important role in the thimerosal-induced apoptosis in C2C12 cells.

Conclusions/Significance

Our results suggest that in C2C12 myoblast cells, thimerosal induces S phase arrest and finally causes apoptosis via inhibition of PI3K/Akt/survivin signaling followed by activation of the mitochondrial apoptotic pathway.

The adenosine A3 receptor agonist Cl-IB-MECA induces cell death through Ca²⁺/ROS-dependent down regulation of ERK and Akt in A172 human glioma cells

Adenosine A(3) receptor (A3AR) is coupled to G proteins that are involved in a variety of intracellular signaling pathways and physiological functions. 2-Chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methylcarboxamide (Cl-IB-MECA), an agonist of A3AR, has been reported to induce cell death in various cancer cells. However, the effect of CI-IB-MECA on glioma cell growth is not clear. This study was undertaken to examine the effect of CI-IB-MECA on glioma cell viability and to determine its molecular mechanism. CI-IB-MECA inhibited cell proliferation and induced cell death in a dose- and time-dependent manner. Treatment of CI-IB-MECA resulted in an increase in intracellular Ca(2+) followed by enhanced reactive oxygen species (ROS) generation. EGTA and N-acetylcysteine (NAC) blocked the cell death induced by CI-IB-MECA, suggesting that Ca(2+) and ROS are involved in the Cl-IB-MECA-induced cell death. Western blot analysis showed that CI-IB-MECA induced the down-regulation of extracellular signal-regulated kinases (ERK) and Akt, which was prevented by EGTA, NAC, and the A3AR antagonist MRS1191. Transfection of constitutively active forms of MEK, the upstream kinase of ERK, and Akt prevented the cell death. CI-IB-MECA induced caspase-3 activation and the CI-IB-MECA-induced cell death was blocked by the caspase inhibitors DEVD-CHO and z-VAD-FMK. In addition, expression of XIAP and Survivin were decreased in cells treated with Cl-IB-MECA. Collectively, these findings demonstrate that CI-IB-MECA induce a caspase-dependent cell death through suppression of ERK and Akt mediated by an increase in intracellular Ca(2+) and ROS generation in human glioma cells. These suggest that A3AR agonists may be a potential therapeutic agent for induction of apoptosis in human glioma cells.

β,β-Dimethylacrylshikonin induces mitochondria dependent apoptosis through ERK pathway in human gastric cancer SGC-7901 cells

β,β-Dimethylacrylshikonin, one of the active components in the root extracts of Lithospermum erythrorhizon, posses antitumor activity. In this study, we discussed the molecular mechanisms of β,β-dimethylacrylshikonin in the apoptosis of SGC-7901 cells. β,β-Dimethylacrylshikonin reduced the cell viability of SGC-7901 cells in a dose- and time-dependent manner and induced cell apoptosis. β,β-Dimethylacrylshikonin treatment in SGC-7901 cells down-regulated the expression of XIAP, cIAP-2, and Bcl-2 and up-regulated the expression of Bak and Bax and caused the loss of mitochondrial membrane potential and release of cytochrome c. Additionally, β,β-dimethylacrylshikonin treatment led to activation of caspases-9, 8 and 3, and cleavage of poly (ADP-ribose) polymerase (PARP), which was abolished by pretreatment with the pan-caspase inhibitor Z-VAD-FMK. β,β-Dimethylacrylshikonin induced phosphorylation of extracellular signal-regulated kinase (ERK) in SGC-7901 cells. U0126, a specific MEK inhibitor, blocked the ERK activation by β,β-dimethylacrylshikonin and abrogated β,β-dimethylacrylshikonin -induced apoptosis. Our results demonstrated that β,β-dimethylacrylshikonin inhibited growth of gastric cancer SGC-7901 cells by inducing ERK signaling pathway, and provided a clue for preclinical and clinical evaluation of β,β-dimethylacrylshikonin for gastric cancer therapy.

Synergistic inhibitory effects by the combination of gefitinib and genistein on NSCLC with acquired drug-resistance in vitro and in vivo

In clinical practice, most patients with non small cell lung cancer (NSCLC) who respond to tyrosine kinase inhibitors eventually progress because of an acquired resistance mutation, T790M, in epidermal growth factor receptor (EGFR). Thus, it is important to identify a new drug to reduce resistance. The aim of this study was to test whether genistein combined with gefitinib is effective against NSCLC in a cell line carrying T790M, and to clarify the underlying mechanisms. The human lung cancer cell line H1975 was used as an in vitro and in vivo model. Cells were treated with gefitinib, genistein, or a combination at a range of concentrations. Cell proliferation was calculated to assess the anticancer effects of the compounds in vitro. Flow cytometry and Western blotting were employed to determine the inhibitory effects on proliferation and the induction of apoptosis. The in vivo effects of the compounds were examined using a xenografted nude mouse model for validation. Gefitinib together with genistein enhanced both growth inhibition and apoptosis; however, the greatest synergistic effect was observed at low concentrations. p-EGFR, p-Akt, and p-mTOR expressions in vitro were reduced more by the combined use of the drugs, whereas caspase-3 and PARP activities were increased. Significantly more tumor growth inhibition was detected following combination treatment in the in vivo model. These findings suggest that genistein enhanced the antitumor effects of gefitinib in a NSCLC cell line carrying the T790M mutation. This synergistic activity may be due to increased inhibition of the downstream molecular and pro-apoptotic effects of EGFR.

Survivin inhibition is critical for Bcl-2 inhibitor-induced apoptosis in hepatocellular carcinoma cells

Our study aims to study the therapeutic effects of a novel Bcl-2 inhibitor, ABT-263, on hepatocellular carcinoma (HCC) and to provide primary preclinical data for future clinical trial with ABT-263. In this study we showed that Bcl-xL and survivin were up-regulated in HCC cell lines and human liver cancer tissues. Clinic used ABT-263 single treatment had no apoptotic effects on HCC cells whereas higher doses of ABT-263 did. Interestingly, the combination treatment of ABT-263 with survivin inhibitor YM-155 could result in significant apoptosis in HCC cells. Survivin inhibition through gene silencing significantly enhanced ABT-263 to induce apoptosis in HCC cells. We found that low dose of ABT-263 single treatment resulted in ERK activation and survivin up-regulation, which might be involved in the resistance of HCC cells to ABT-263 since blockade of ERK activation sensitized ABT-263-induced apoptosis. Importantly, ABT-263 and YM-155 combination treatment had no apoptotic effects on normal human hepatocytes. Taken together, these data suggest the combination treatment of Bcl-2 inhibitor and survivin inhibition may have a great potential for liver cancer therapy.