Involvement of nuclear factor-kappa B, Bax and Bcl-2 in induction of cell cycle arrest and apoptosis by apigenin in human prostate carcinoma cells

Facile construction of fused benzimidazole-isoquinolinones that induce cell-cycle arrest and apoptosis in colorectal cancer cells

Colorectal cancer (CRC) is one of the most frequent, malignant gastrointestinal tumors, and strategies and effectiveness of current therapy are limited. A series of benzimidazole-isoquinolinone derivatives (BIDs) was synthesized and screened to identify novel scaffolds for CRC. Of the compounds evaluated, 7g exhibited the most promising anti-cancer properties. Employing two CRC cell lines, SW620 and HT29, 7g was found to suppress growth and proliferation of the cell lines at a concentration of ∼20 µM. Treatment followed an increase in G₂/M cell cycle arrest, which was attributed to cyclin B1 and cyclin-dependent kinase 1 (CDK1) signaling deficiencies with simultaneous enhancement in p21 and p53 activity. In addition, mitochondrial-mediated apoptosis was induced in CRC cells. Interestingly, 7g decreased phosphorylated AKT, mTOR and 4E-BP1 levels, while promoting the expression/stability of PTEN. Since PTEN controls input into the PI3K/AKT/mTOR pathway, antiproliferative effects can be attributed to PTEN-mediated tumor suppression. Collectively, these results suggest that BIDs exert antitumor activity in CRC by impairing PI3K/AKT/mTOR signaling. Against a small kinase panel, 7g exhibited low affinity at 5 µM suggesting anticancer properties likely stem through a non-kinase mechanism. Because of the novelty of BIDs, the structure can serve as a lead scaffold to design new CRC therapies.

Drp1-mediated mitochondrial fission promotes cell proliferation through crosstalk of p53 and NF-κB pathways in hepatocellular carcinoma

Mitochondria are highly dynamic and undergo constant fusion and fission that are essential for maintaining physiological functions of cells. Recently, we have reported that increased mitochondrial fission promotes autophagy and apoptosis resistance in hepatocellular carcinoma (HCC) cell through ROS-mediated coordinated regulation of NF-κB and p53 pathways. However, little is known about the roles of mitochondrial dynamics in HCC cell proliferation, another key feature of cancer cells. In this study, we systematically investigated the functional role of mitochondrial fission in the regulation of HCC cell proliferation. Furthermore, the underlying molecular mechanisms were deeply explored. We found that, increased mitochondrial fission by forced expression of Drp1 promoted the proliferation of HCC cells both in vitro and in vivo mainly by facilitating G1/S phase transition of cell cycle. Whereas, Drp1 knockdown or treatment with mitochondrial division inhibitor-1 induced significant G1 phase arrest in HCC cells and reduced tumor growth in the xenotransplantation model. We further demonstrated that the proliferation-promoting role of Drp1-mediated mitochondrial fission was mediated via p53/p21 and NF-κB/cyclins pathways. Moreover, the crosstalk between p53 and NF-κB pathways was proved to be involved in the regulation of mitochondrial fission-mediated cell proliferation. In conclusion, our findings demonstrate that Drp1-mediated mitochondrial fission plays a critical role in the regulation of cell cycle progression and HCC cell proliferation. Thus, targeting Drp1-dependent mitochondrial fission may provide a novel strategy for suppressing tumor growth of HCC.

Plant flavone apigenin: An emerging anticancer agent

Research in cancer chemoprevention provides convincing evidence that increased intake of vegetables and fruits may reduce the risk of several human malignancies. Phytochemicals present therein provide beneficial anti-inflammatory and antioxidant properties that serve to improve the cellular microenvironment. Compounds known as flavonoids categorized anthocyanidins, flavonols, flavanones, flavonols, flavones, and isoflavones have shown considerable promise as chemopreventive agents. Apigenin (4', 5, 7-trihydroxyflavone), a major plant flavone, possessing antioxidant, anti-inflammatory, and anticancer properties affecting several molecular and cellular targets used to treat various human diseases. Epidemiologic and case-control studies have suggested apigenin reduces the risk of certain cancers. Studies demonstrate that apigenin retain potent therapeutic properties alone and/or increases the efficacy of several chemotherapeutic drugs in combination on a variety of human cancers. Apigenin's anticancer effects could also be due to its differential effects in causing minimal toxicity to normal cells with delayed plasma clearance and slow decomposition in liver increasing the systemic bioavailability in pharmacokinetic studies. Here we discuss the anticancer role of apigenin highlighting its potential activity as a chemopreventive and therapeutic agent. We also highlight the current caveats that preclude apigenin for its use in the human trials.

A Standardized Wedelia chinensis Extract Overcomes the Feedback Activation of HER2/3 Signaling upon Androgen-Ablation in Prostate Cancer

Crosstalk between the androgen receptor (AR) and other signaling pathways in prostate cancer (PCa) severely affects the therapeutic outcome of hormonal therapy. Although anti-androgen therapy prolongs overall survival in PCa patients, resistance rapidly develops and is often associated with increased AR expression and upregulation of the HER2/3-AKT signaling pathway. However, single agent therapy targeting AR, HER2/3 or AKT usually fails due to the reciprocal feedback loop. Previously, we reported that wedelolactone, apigenin, and luteolin are the active compounds in Wedelia chinensis herbal extract, and act synergistically to inhibit the AR activity in PCa. Here, we further demonstrated that an herbal extract of W. chinensis (WCE) effectively disrupted the AR, HER2/3, and AKT signaling networks and therefore enhanced the therapeutic efficacy of androgen ablation in PCa. Furthermore, WCE remained effective in suppressing AR and HER2/3 signaling in an in vivo adapted castration-resistant PCa (CRPC) LNCaP cell model that was insensitive to androgen withdrawal and second-line antiandrogen, enzalutamide. This study provides preclinical evidence that the use of a defined, single plant-derived extract can augment the therapeutic efficacy of castration with significantly prolonged progression-free survival. These data also establish a solid basis for using WCE as a candidate agent in clinical studies.

Apigenin in cancer therapy: anti-cancer effects and mechanisms of action

Apigenin is a common dietary flavonoid that is abundantly present in many fruits, vegetables and Chinese medicinal herbs and serves multiple physiological functions, such as strong anti-inflammatory, antioxidant, antibacterial and antiviral activities and blood pressure reduction. Therefore, apigenin has been used as a traditional medicine for centuries. Recently, apigenin has been widely investigated for its anti-cancer activities and low toxicity. Apigenin was reported to suppress various human cancers in vitro and in vivo by multiple biological effects, such as triggering cell apoptosis and autophagy, inducing cell cycle arrest, suppressing cell migration and invasion, and stimulating an immune response. In this review, we focus on the most recent advances in the anti-cancer effects of apigenin and their underlying mechanisms, and we summarize the signaling pathways modulated by apigenin, including the PI3K/AKT, MAPK/ERK, JAK/STAT, NF-κB and Wnt/β-catenin pathways. We also discuss combinatorial strategies to enhance the anti-cancer effect of apigenin on various cancers and its use as an adjuvant chemotherapeutic agent to overcome cancer drug resistance or to alleviate other adverse effects of chemotherapy. The functions of apigenin against cancer stem cells are also summarized and discussed. These data demonstrate that apigenin is a promising reagent for cancer therapy. Apigenin appears to have the potential to be developed either as a dietary supplement or as an adjuvant chemotherapeutic agent for cancer therapy.

Alteration in biochemical parameters in the brain of transgenic Drosophila melanogaster model of Parkinson's disease exposed to apigenin

BACKGROUND

Oxidative stress is one of the key components of the pathology of various neurodegenerative disorders. Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons owing to the aggregation of alpha-synuclein (αS) in the brain. A number of polyphenols have been reported to inhibit the αS aggregation resulting in the possible prevention of PD. The involvement of free radicals in mediating the neuronal death in PD has also been implicated.

METHODS

In the present study, the transgenic flies expressing human αS in the brain were exposed to 10 μM, 20 μM, 40 μM, and 80 μM of apigenin established in diet for 24 days.

RESULTS

The flies showed an increase in life span, glutathione, and dopamine content. The exposure of PD flies to various doses of apigenin also results in the reduction of glutathione-S-transferase activity, lipid peroxidation, monoamine oxidase, caspase-3, and caspase-9 activity in a dose-dependent manner.

CONCLUSION

The results of the present study reveal that apigenin is potent in increasing the life span, dopamine content, reduced the oxidative stress as well as apoptosis in transgenic Drosophila model of PD.

Dihydroartemisinin and gefitinib synergistically inhibit NSCLC cell growth and promote apoptosis via the Akt/mTOR/STAT3 pathway

Non‑small cell lung cancer (NSCLC) is among the leading causes of cancer‑associated mortality worldwide. In clinical practice, therapeutic strategies based on drug combinations are often used for the treatment of various types of cancer. The present study aimed to investigate the effects of the combination of dihydroartemisinin (DHA) and gefitinib on NSCLC. Cell Counting kit 8 assay was used to evaluate cell viability. Transwell assays were performed to investigate cellular migration and invasion, and cellular apoptosis was evaluated using the terminal deoxynucleotidyl transferase dUTP nick‑end labeling assay. Flow cytometry was used to investigate cell cycle distribution and the expression levels of target proteins were determined using western blot analysis. The results of the present study demonstrated that DHA (5, 10, 20, 50 and 100 µM) reduced cancer cell viability in a dose‑dependent manner in the NCI‑H1975 human NSCLC cell line and significantly enhanced gefitinib‑induced apoptosis. Furthermore, DHA and gefitinib co‑administration induced cell cycle arrest in G2/M phase, which was associated with a marked decline in the protein expression levels of G2/M regulatory proteins, including cyclin B1 and cyclin‑dependent kinase 1. The addition of DHA appeared to potentiate the inhibitory actions of gefitinib on the migratory and invasive capabilities of NCI‑H1975 cells. DHA and gefitinib co‑administration also downregulated the expression levels of phosphorylated (p)‑Akt, p‑mechanistic target of rapamycin, p‑signal transducer and activator of transcription 3 and B‑cell lymphoma 2 (Bcl‑2), and upregulated the expression of Bcl‑2‑associated X protein. In conclusion, the present results suggested that the combination of DHA and gefitinib may have potential as a novel and more effective therapeutic strategy for the treatment of patients with NSCLC.

Apigenin overcomes drug resistance by blocking the signal transducer and activator of transcription 3 signaling in breast cancer cells

Drug resistance in chemotherapy is a serious obstacle for the successful treatment of cancer. Drug resistance is caused by various factors, including the overexpression of P-glycoprotein (P-gp, MDR1). The development of new, useful compounds that overcome drug resistance is urgent. Apigenin, a dietary flavonoid, has been reported as an anticancer drug in vivo and in vitro. In the present study, we investigated whether apigenin is able to reverse drug resistance using adriamycin-resistant breast cancer cells (MCF-7/ADR). In our experiments, apigenin significantly decreased cell growth and colony formation in MCF-7/ADR cells and parental MCF-7 cells. This growth inhibition was related to the accumulation of cells in the sub-G₀/G₁ apoptotic population and an increase in the number of apoptotic cells. Apigenin reduced the mRNA expression of multidrug resistance 1 (MDR1) and multidrug resistance-associated proteins (MRPs) in MCF-7/ADR cells. Apigenin also downregulated the expression of P-gp. Apigenin reversed drug efflux from MCF-7/ADR cells, resulting in rhodamine 123 (Rho123) accumulation. Inhibition of drug resistance by apigenin is related to the suppression of the signal transducer and activator of transcription 3 (STAT3) signaling pathway. Apigenin decreased STAT3 activation (p-STAT3) and its nuclear translocation and inhibited the secretion of VEGF and MMP-9, which are STAT3 target genes. A STAT3 inhibitor, JAK inhibitor I and an HIF-1α inhibitor decreased cell growth in MCF-7 and MCF-7/ADR cells. Taken together, these results demonstrate that apigenin can overcome drug resistance.

Upregulation of ASAP3 contributes to colorectal carcinogenesis and indicates poor survival outcome

The function and clinical implication of ArfGAP with SH3 domain, ankyrin repeat, and PH domain 3 (ASAP3) in colorectal cancer (CRC) remains undefined. In the present study, we showed that the expression level of ASAP3 was dramatically increased in CRC and its upregulation was associated with American Joint Committee on Cancer stage (P < 0.001) and poor prognosis (P = 0.0022). The combination of stage and ASAP3 expression improved the prediction of survival in CRC patients. Suppression of ASAP3 inhibited cell proliferation by inducing G₁ phase arrest without influencing apoptosis. ASAP3 promoted growth of colon tumors in mice with colitis, and accelerated cell invasion and migration in vitro. Increased ASAP3 was associated with activation of the nuclear factor‐κB (NF‐κB) canonical pathway in CRC. Upregulation of ASAP3 increased the phosphorylation and nuclear translocation of the p65 NF‐κB subunit. Mechanistically, ASAP3 interacts with NF‐κB essential modulator (NEMO) and could reduce the polyubiquitinylation of NEMO. Overall, ASAP3 might regulate NF‐κB via binding to NEMO. ASAP3 acts as an oncogene in colonic cancer and could be a potential biomarker of colon carcinogenesis.

Compounds from Cynomorium songaricum with Estrogenic and Androgenic Activities Suppress the Oestrogen/Androgen-Induced BPH Process

Objective

To investigate the phytoestrogenic and phytoandrogenic activities of compounds isolated from CS and uncover the role of CS in prevention of oestrogen/androgen-induced BPH.

Methods

Cells were treated with CS compounds, and immunofluorescence assay was performed to detect the nuclear translocation of ERα or AR in MCF-7 or LNCaP cells; luciferase reporter assay was performed to detect ERs or AR transcriptional activity in HeLa or AD293 cells; MTT assay was performed to detect the cell proliferation of MCF-7 or LNCaP cells. Oestrogen/androgen-induced BPH model was established in rat and the anti-BPH, anti-estrogenic, and anti-androgenic activities of CS in vivo were further investigated.

Results

The nuclear translocation of ERα was stimulated by nine CS compounds, three of which also stimulated AR translocation. The transcriptional activities of ERα and ERβ were induced by five compounds, within which only ECG induced AR transcriptional activity as well. Besides, ECG stimulated the proliferation of both MCF-7 cells and LNCaP cells. CS extract suppressed oestrogen/androgen-induced BPH progress in vivo by downregulation of E2 and T level in serum and alteration of the expressions of ERα, ERβ, and AR in the prostate.

Conclusion

Our data demonstrates that compounds from CS exhibit phytoestrogenic and phytoandrogenic activities, which may contribute to inhibiting the oestrogen/androgen-induced BPH development.

LFG-500, a newly synthesized flavonoid, induces apoptosis in human ovarian carcinoma SKOV3 cells with involvement of the reactive oxygen species-mitochondria pathway

Ovarian cancer is the main cause of gynecologic malignancy-related mortality in women. Therefore, the disease requires improvements in treatment options and in the potency of chemotherapeutic drugs. The study of apoptosis in tumor cells is an important field for cancer therapy and cancer molecular biology. It has recently been established that LFG-500, a new synthesized flavonoid with a piperazine and benzyl group substitution, has strong anticancer activity. However, its exact molecular mechanism is not fully understood. The present study aimed to examine the effects of LFG-500 on human ovarian cancer SKOV3 cells, as well as to identify its underlying mechanisms. The data showed that LFG-500 inhibited the growth of SKOV3 cells in a concentration-dependent manner. It was found that LFG-500 induced apoptosis in SKOV3 cells, detected by DAPI staining and an Annexin V/PI double-staining assay. Moreover, LFG-500 reduced caspase-3 protein expression and increased the Bcl-2-associated X protein/B-cell lymphoma 2 protein ratio. Further findings revealed that LFG-500 treatment resulted in reactive oxygen species (ROS) accumulation and loss of mitochondrial transmembrane potential. Collectively, these results demonstrated that LFG-500 efficiently induced apoptosis in SKOV3 cells, an event possibly associated with the trigging of the mitochondrial apoptotic pathway through ROS accumulation. Therefore, LFG-500 shows potential as a potent anticancer agent for the treatment of ovarian cancer.

Polyphenol nanoformulations for cancer therapy: experimental evidence and clinical perspective

Cancer is defined as the abnormal cell growth that can cause life-threatening malignancies with high financial costs for patients as well as the health care system. Natural polyphenols have long been used for the prevention and treatment of several disorders due to their antioxidant, anti-inflammatory, cytotoxic, antineoplastic, and immunomodulatory effects discussed in the literature; thus, these phytochemicals are potentially able to act as chemopreventive and chemotherapeutic agents in different types of cancer. One of the problems regarding the use of polyphenolic compounds is their low bioavailability. Different types of formulations have been designed for the improvement of bioavailability of these compounds, nanonization being one of the most notable approaches among them. This study aimed to review current data on the nanoformulations of natural polyphenols as chemopreventive and chemotherapeutic agents and to discuss their molecular anticancer mechanisms of action. Nanoformulations of natural polyphenols as bioactive agents, including resveratrol, curcumin, quercetin, epigallocatechin-3-gallate, chrysin, baicalein, luteolin, honokiol, silibinin, and coumarin derivatives, in a dose-dependent manner, result in better efficacy for the prevention and treatment of cancer. The impact of nanoformulation methods for these natural agents on tumor cells has gained wider attention due to improvement in targeted therapy and bioavailability, as well as enhancement of stability. Today, several nanoformulations are designed for delivery of polyphenolic compounds, including nanosuspensions, solid lipid nanoparticles, liposomes, gold nanoparticles, and polymeric nanoparticles, which have resulted in better antineoplastic activity, higher intracellular concentration of polyphenols, slow and sustained release of the drugs, and improvement of proapoptotic activity against tumor cells. To conclude, natural polyphenols demonstrate remarkable anticancer potential in pharmacotherapy; however, the obstacles in terms of their bioavailability in and toxicity to normal cells, as well as targeted drug delivery to malignant cells, can be overcome using nanoformulation-based technologies, which optimize the bioefficacy of these natural drugs.

DNMT1 regulates human endometrial carcinoma cell proliferation

Endometrial carcinoma (EC) is the most common gynecologic malignancy, but the molecular events involved in the development and progression of EC remain unclear. This study aimed to investigate the role of DNA methyltransferase 1 (DNMT1), a member of DNA methyltransferases, in EC. AN3CA cells were transfected with DNMT1 siRNA. The proliferation, cell cycle, and apoptosis of AN3CA cells were evaluated by Cell Counting Kit-8 (CCK-8) assay and flow cytometry. The expression of related genes was detected by polymerase chain reaction and Western blot analysis. Knockdown of DNMT1 inhibited the proliferation, induced apoptosis, and G0/G1 phase arrest of AN3CA cells. Furthermore, knockdown of DNMT1 upregulated the expression of nuclear factor kappa-B-inhibitor alpha (NF-κBIA) and Bax and downregulated the expression of Bcl-2 and CCND1/2 in AN3CA cells. In conclusion, this study provides the first evidence that knockdown of DNMT1 affects the expression of cell cycle- and apoptosis-associated proteins in EC cells, suggesting the potential of DNMT1 in EC therapy.

Reversal of cisplatin resistance in human gastric cancer cells by a wogonin-conjugated Pt(IV) prodrug via attenuating Casein Kinase 2-mediated Nuclear Factor-κB pathways

Pt(IV) prodrugs, with two additional coordination sites in contrast to Pt(II) drugs, have been actively studied nowadays, for they can perform well in enhancing the accumulation and retention of the corresponding Pt(II) drugs in cancer cells. Our designed Pt(II) drug, DN604, was recently found to exhibit significant anticancer activity and low toxicity, while, wogonin, a naturally O-methylated flavones, has been widely investigated for its tumor therapeutic potential. Thus, two Pt(IV)-based prodrugs were derived by addition of a wogonin unit to the axial position of DN604 and its analogue DN603 via a linker group. In vitro cytotoxicity assay indicated that the resulting compound 8 not only inherited the genotoxicity of DN604 on gastric cancer cells, but also obtained the COX inhibitory property arising from wogonin. Further studies revealed that compound 8 caused the accumulation of ROS production and decreased the mitochondrial membrane potential (ΔΨm). The CK2α kinase activity assay, ChIP and luciferase assays showed that CK2 plays an important role in the blockade of compound 8 on activated NF-κB survival pathways, which were established for sensitivity of cancer cells to platinum drugs. Similarly in vivo, in nude mice with SGC-7901/cDDP xenografts, compound 8 improved the effectiveness of DN604 via reversing tumor resistance and maintaining low toxicity. Overall, compound 8 is a promising Pt(IV) prodrug, which could be used to promote the anticancer activity of its counterpart Pt(II) species and reverse drug resistance via attenuating CK2-mediated NF-κB pathways during platinum-based chemotherapies.

PUMA decreases the growth of prostate cancer PC-3 cells independent of p53

PUMA (p53 upregulated modulator of apoptosis), a member of the B-cell lymphoma 2 (Bcl-2) protein family, is a pro-apoptotic protein. PUMA expression is modulated by the tumor suppressor p53. PUMA has a role in rapid cell death via p53-dependent and -independent mechanisms. To evaluate whether p53 is required for PUMA-mediated apoptosis in prostate cancer cells, p53 protein was silenced in human prostate cancer PC-3 cells by using p53 small interfering RNA (siRNA). The interference efficiency of p53 on RNA and protein levels was detected by reverse transcription-quantitative polymerase chain reaction and western blotting. Cell proliferation and p21 expression were subsequently examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and western blot analysis, respectively. p53-silenced or control PC-3 cells were transfected with pCEP4-(hemagglutinin)-PUMA plasmid, or non-carrier plasmid. Enzyme-linked immunosorbent assay was used to determine cell apoptosis by measuring histone release and caspase-3 activation, and MTT assay was used to measure cell viability. In addition, the expression of pro-apoptosis protein Bax and anti-apoptosis protein Bcl-2 were evaluated. The results of the present study revealed that p53 siRNA significantly suppressed p53 RNA and protein expression in PC-3 cells. Deficiency of p53 increased the cell growth rate and decreased p21 expression. However, PUMA overexpression remained able to induce apoptosis in p53-silenced and control cells by increasing Bax expression and decreasing Bcl-2 expression, leading to the activation of caspase-3. These results suggest that PUMA may mediate apoptosis of prostate cancer PC-3 cells, potentially independently of p53. Furthermore, PUMA gene treatment to induce cancer cell apoptosis may be more efficient compared with p53-dependent apoptosis, where loss of p53 expression or function may lead to limited efficacy of PUMA expression. Therefore, the present study proposes the significant hypothesis that increasing PUMA expression may be an effective approach for the treatment of prostate cancer, regardless of p53 status.

Sailuotong Prevents Hydrogen Peroxide (H₂O₂)-Induced Injury in EA.hy926 Cells

Sailuotong (SLT) is a standardised three-herb formulation consisting of Panax ginseng, Ginkgo biloba, and Crocus sativus designed for the management of vascular dementia. While the latest clinical trials have demonstrated beneficial effects of SLT in vascular dementia, the underlying cellular mechanisms have not been fully explored. The aim of this study was to assess the ability and mechanisms of SLT to act against hydrogen peroxide (H₂O₂)-induced oxidative damage in cultured human vascular endothelial cells (EAhy926). SLT (1-50 µg/mL) significantly suppressed the H₂O₂-induced cell death and abolished the H₂O₂-induced reactive oxygen species (ROS) generation in a concentration-dependent manner. Similarly, H₂O₂ (0.5 mM; 24 h) caused a ~2-fold increase in lactate dehydrogenase (LDH) release from the EA.hy926 cells which were significantly suppressed by SLT (1-50 µg/mL) in a concentration-dependent manner. Incubation of SLT (50 µg/mL) increased superoxide dismutase (SOD) activity and suppressed the H₂O₂-enhanced Bax/Bcl-2 ratio and cleaved caspase-3 expression. In conclusion, our results suggest that SLT protects EA.hy916 cells against H₂O₂-mediated injury via direct reduction of intracellular ROS generation and an increase in SOD activity. These protective effects are closely associated with the inhibition of the apoptotic death cascade via the suppression of caspase-3 activation and reduction of Bax/Bcl-2 ratio, thereby indicating a potential mechanism of action for the clinical effects observed.

Involvement of Bcl-2 Signal Pathway in the Protective Effects of Apigenin on Anoxia/Reoxygenation-induced Myocardium Injury

Apigenin is a type of flavonoids, which has been demonstrated to protect myocardium against ischemia/reperfusion (I/R) injury. However, the mechanism is still unclear. We hypothesized that the mechanism of cardioprotective action of apigenin on the I/R-induced injury might be caused via B-cell lymphoma (Bcl) signaling pathway. In this study, an in vitro I/R model was replicated on Langendorff-perfused heart and H9c2 cardiomyocytes by anoxia/reoxygenation (A/R) treatment. The recovery of cardiac contractile function, infarct size, lactate dehydrogenase (LDH) and creatine kinase (CK) in the perfusate, the expression and activity of Bcl-2 and caspase-3, and cardiomyocyte apoptosis were measured in the Langendorff heart undergoing A/R injury. In addition, the cell viability, LDH release, intracellular reactive oxygen species (ROS), mitochondrial membrane potential (Δψm), expression of cytochrome c in the cytosol, and cell apoptosis were examined in the culture of H9c2 cardiomyocytes after the A/R. The results showed that apigenin significantly improved rat heart contractile function, reduced LDH release, infarct size and apoptotic rate, upregulated the expression of Bcl-2 and caspase-3, and downregulated the expression of cleaved caspase-3 after the A/R. Moreover, apigenin increased the cell viability and decreased the release of LDH, production of reactive oxygen species, release of mitochondrial cytochrome c into the cytosol, and cell apoptosis in the culture of H9c2 cardiomyocytes after the A/R. In addition, inhibition of Bcl-2 activity by ABT-737 markedly attenuated the protective effect of apigenin on the A/R-induced myocardium injury. Taken together, we firstly demonstrated that the effect of apigenin against A/R injury in cardiomyocytes involves Bcl-2 signal pathway and at least partly depends on its effect of upregulating the expression of Bcl-2.

Targeting Apoptosis with Dietary Bioactive Agents

Apoptosis, a form of programmed cell death, is a pivotal defense against the occurrence of cancer and is essential to metazoans in maintaining tissue homeostasis. Apoptosis exhibits a distinctive phenotype and involves elimination of potentially deleterious cells. Many diseases have been associated with aberrantly regulated apoptotic cell death, ultimately leading to inhibition of apoptosis and propagation of diseases such as cancer. Elucidation of the critical events associated with carcinogenesis provides the opportunity for dietary intervention to prevent cancer development through induction of apoptosis, Particularly by bioactive agents or functional foods. Diet is a significant environmental factor in the overall cancer process and can exacerbate or interfere with carcinogenesis. Apoptosis occurs primarily through two well-recognized pathways in cells, including the Intrinsic, or mitochondrial-mediated, effector mechanism and the extrinsic, or death receptor-mediated, effector mechanism. In addition to diet's effects on protein expression and function, evidence is also accumulating that a large number of dietary food components can exert effects on the human genome, either directly or indirectly, to modulate gene expression. In fact, many diet-related genes are involved in carcinogenesis as well as apoptosis, and thus are ultimately molecular targets for dietary chemopreventlon. There are multiple steps within pathways in which dietary components can alter gene expression and phenotypes of cells and thus influence cancer outcomes (nutritional transcriptomic effect). Thus, apoptosis is an emerging therapeutic target of bioactive agents of diet. In this review, the process of apoptosis is discussed and the potential mechanistic interaction of bioactive agents, as components of functional foods, is explored within the context of apoptosis.

Chemopreventive Agents and Inhibitors of Cancer Hallmarks: May Citrus Offer New Perspectives?

Fruits and vegetables have long been recognized as potentially important in the prevention of cancer risk. Thus, scientific interest in nutrition and cancer has grown over time, as shown by increasing number of experimental studies about the relationship between diet and cancer development. This review attempts to provide an insight into the anti-cancer effects of Citrus fruits, with a focus on their bioactive compounds, elucidating the main cellular and molecular mechanisms through which they may protect against cancer. Scientific literature was selected for this review with the aim of collecting the relevant experimental evidence for the anti-cancer effects of Citrus fruits and their flavonoids. The findings discussed in this review strongly support their potential as anti-cancer agents, and may represent a scientific basis to develop nutraceuticals, food supplements, or complementary and alternative drugs in a context of a multi-target pharmacological strategy in the oncology.

Apigenin blocks IKKα activation and suppresses prostate cancer progression

IKKα has been implicated as a key regulator of oncogenesis and driver of the metastatic process; therefore is regarded as a promising therapeutic target in anticancer drug development. In spite of the progress made in the development of IKK inhibitors, no potent IKKα inhibitor(s) have been identified. Our multistep approach of molecular modeling and direct binding has led to the identification of plant flavone apigenin as a specific IKKα inhibitor. Here we report apigenin, in micro molar range, inhibits IKKα kinase activity, demonstrates anti-proliferative and anti-invasive activities in functional cell based assays and exhibits anticancer efficacy in experimental tumor model. We found that apigenin directly binds with IKKα, attenuates IKKα kinase activity and suppresses NF-ĸB/p65 activation in human prostate cancer PC-3 and 22Rv1 cells much more effectively than IKK inhibitor, PS1145. We also showed that apigenin caused cell cycle arrest similar to knockdown of IKKα in prostate cancer cells. Studies in xenograft mouse model indicate that apigenin feeding suppresses tumor growth, lowers proliferation and enhances apoptosis. These effects correlated with inhibition of p-IKKα, NF-ĸB/p65, proliferating cell nuclear antigen and increase in cleaved caspase 3 expression in a dose-dependent manner. Overall, our results suggest that inhibition of cell proliferation, invasiveness and decrease in tumor growth by apigenin are mediated by its ability to suppress IKKα and downstream targets affecting NF-ĸB signaling pathways.

Flavones: From Biosynthesis to Health Benefits

Flavones correspond to a flavonoid subgroup that is widely distributed in the plants, and which can be synthesized by different pathways, depending on whether they contain C- or O-glycosylation and hydroxylated B-ring. Flavones are emerging as very important specialized metabolites involved in plant signaling and defense, as well as key ingredients of the human diet, with significant health benefits. Here, we appraise flavone formation in plants, emphasizing the emerging theme that biosynthesis pathway determines flavone chemistry. Additionally, we briefly review the biological activities of flavones, both from the perspective of the functions that they play in biotic and abiotic plant interactions, as well as their roles as nutraceutical components of the human and animal diet.

Interferon β improves the efficacy of low dose cisplatin by inhibiting NF-κB/p-Akt signaling on HeLa cells

The purpose of this study was to evaluate the anticancer efficacy of interferon β in combination with low dose of cisplatin on human cervical cancer progression, as well as its principal action mechanism. The combination treatment synergistically potentiated the effect of interferon β on cell growth inhibition and DNA damage on HeLa cells by repressing NF-κB/p-Akt signaling. Synergistic targeting of these pathways has a therapeutic potential. Further, the combination treatment ameliorated the expression of pro-apoptotic Bax, and decreased the expression of anti-apoptotic protein Bcl-2. Additionally, the expression of active PARP was significantly increased and MMP-9 level was decreased in combination group as compared to the expression seen for the treatment with interferon β or cisplatin alone. Results demonstrate that the synergistic inhibitory effects of interferon β and low dose of cisplatin on human cervical cancer cells and also suggest that the inhibition of NF-κB/p-Akt signaling pathway plays a critical role in the anticancer effects of combination treatment along with the induction of PARP. Therefore, the combination of interferon β and cisplatin may be a useful treatment for human cervical cancer, with a greater effectiveness than other treatments.

Protective effect of apigenin on ischemia/reperfusion injury of the isolated rat heart

Apigenin (Api), a mainly bioactive component of Apium graveolens L. var. dulce DC. (a traditional Chinese medicinal herb), possesses a wide range of biological activities, including antioxidant effects. It also has been shown to associate with lower prevalence of cardiovascular diseases, but its mechanisms of action remain unclear. The aim of the present study is to investigate the role of Api in isolated rat heart model of ischemia/reperfusion (I/R). Langendorff-perfused isolated rat hearts were used in our study. Api was added to the perfusate before ischemia and during reperfusion in the isolated pulsed rat heart exposed to 30-min ischemia followed by 50-min reperfusion. The treatment with Api conferred a cardioprotective effect, and the treated hearts demonstrated an improved ischemic cardiac functional recovery, a decreased myocardial infarct size, a reduced activities of creatine kinase isoenzyme and lactate dehydrogenase in the coronary flow, a reduced number of apoptotic cardiomyocytes, a reduced activity of caspase-3, up-regulation of the anti-apoptotic protein Bcl-2 and down-regulation of the pro-apoptotic protein Bax. In addition, Api inhibited the phosphorylation of p38 MAPKS during I/R. In conclusion, these observations provide preliminary evidence that Api can protect cardiomyocytes from I-/R-induced injury, at least partially, through the inhibition of p38 MAPKS signaling pathway.

Senegenin Inhibits Hypoxia/Reoxygenation-Induced Neuronal Apoptosis by Upregulating RhoGDIα

Neuronal apoptosis is an important event in hypoxia/reoxygenation (H/R)-induced neuronal injury. Senegenin (Sen), the predominant and most active component in Radix Polygalae root extracts, displays anti-apoptotic and anti-oxidative properties. Sen protects against H/R-induced neuronal apoptosis of highly differentiated PC12 cells and primary cortical neurons. Sen has also been investigated as a source of potential therapeutic targets. In this study, a proteomic approach was used to identify Sen-regulated proteins in PC12 cells. We found that Sen protected against H/R-induced neuronal apoptosis by upregulating RhoGDIα protein expression. The regulatory functions of RhoGDIα were investigated by knocking down RhoGDIα expression in PC12 cells using small interfering RNA (siRNA), followed by quantification of apoptosis and then altering the expression levels of apoptosis-related proteins. Our data show that after silencing RhoGDIα, the neuroprotective effects of Sen on H/R-induced PC12 cell apoptosis were absent. Furthermore, RhoGDIα silencing alleviated the Sen-mediated inhibition of the JNK pathway. Therefore, these findings indicated that Sen attenuates H/R-induced neuronal apoptosis by upregulating RhoGDIα expression and inhibiting the JNK pathway. In addition to the mechanism underlying neuroprotective effects of Sen, RhoGDIα was identified as a putative target of Sen based on a primary rat cortical neuron model of H/R-induced injury.

Induction of caspase-dependent extrinsic apoptosis by apigenin through inhibition of signal transducer and activator of transcription 3 (STAT3) signalling in HER2-overexpressing BT-474 breast cancer cells

Phytoestrogen intake is known to be beneficial to decrease breast cancer incidence and progression. But its molecular mechanisms of action are still unknown. The present study aimed to examine the effect of apigenin on proliferation and apoptosis in HER2-expressing breast cancer cells. In our experiments, apigenin inhibited the proliferation of BT-474 cells in a dose- and time-dependent manner. Apigenin also inhibited clonogenic survival (anchorage-dependent and -independent) of BT-474 cells in a dose-dependent manner. These growth inhibitions were accompanied with an increase in sub-G0/G1 apoptotic populations. Apigenin-induced extrinsic a caspase-dependent apoptosis up-regulating the levels of cleaved caspase-8 and cleaved caspase-3, and inducing the cleavage of poly (ADP-ribose) polymerase (PARP). Whereas, apigenin did not induce apoptosis via intrinsic mitochondrial apoptosis pathway since this compound did not decrease mitochondrial membrane potential without affecting the levels of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (BAX). Apigenin reduced the expression of phospho-JAK1, phospho-JAK2 and phospho-STAT3 and decreased signal transducer and activator of transcription 3 (STAT3) dependent luciferase reporter gene activity in BT-474 cells. Apigenin inhibited CoCl2-induced VEGF secretion and decreased the nuclear translocation of STAT3. Our study indicates that apigenin induces apoptosis through inhibition of STAT3 signalling and could serve as a useful compound to prevent or treat HER2-overexpressing breast cancer.

Apigenin attenuates myocardial ischemia/reperfusion injury via the inactivation of p38 mitogen‑activated protein kinase

Apigenin (Api) is a plant monomer associated with reducing the risk of heart disease. However, the mechanism of action remains to be fully elucidated. In the present study, it was hypothesized that API has cardioprotective effects by attenuating myocardial ischemia/reperfusion (I/R) injury. Rats were randomly subjected to sham operation, myocardial I/R alone or I/R + Api. Cardiac function was measured, and infarct size was evaluated by triphenyltetrazolium chloride staining following reperfusion. The myocardial enzyme leakage was analyzed for lactate dehydrogenase (LDH) and creatine kinase (CK). The myocardium was also assessed for total superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. The phosphorylation of p38 mitogen‑activated protein kinase (MAPK) was analyzed by western blotting. The present study reported for the first time, to the best of our knowledge, that I/R significantly increased infarct size, induced CK and LDH release, inhibited the activity of SOD and increased the levels of MDA, all of which were prevented by treatment with Api. In addition, I/R increased the phosphorylation of p38 MAPK, which was significantly decreased in the Api‑treated heart tissue samples following I/R, compared with the untreated heart tissue samples. In conclusion, the results of the present study demonstrated that Api inhibited the p38 MAPK signaling pathway to protect cardiomyocytes from I/R‑induced injury.

Molecular effects of the phosphatidylinositol-3-kinase inhibitor NVP-BKM120 on T and B-cell acute lymphoblastic leukaemia

BACKGROUND

Constitutive activation of the PI3K pathway in T cell acute lymphoblastic leukaemia (T-ALL) has been reported and in a mouse model, PI3K activation, together with MYC, cooperates in Burkitt lymphoma (BL) pathogenesis. We investigated the effects of NVP-BKM120, a potent pan-class I PI3K inhibitor, in lymphoblastic leukaemia cell lines.

METHODS

Effects of NVP-BKM120 on cell viability, clonogenicity, apoptosis, cell cycle, cell signalling and autophagy were assessed in vitro on T-ALL (Jurkat and MOLT-4) and BL (Daudi and NAMALWA) cell lines.

RESULTS

NVP-BKM120 treatment decreased cell viability and clonogenic growth in all tested cells. Moreover, the drug arrested cell cycling in association with a decrease in Cyclin B1 protein levels, and increased apoptosis. Immunoblotting analysis of cells treated with the drug revealed decreased phosphorylation, in a dose-dependent manner, of AKT, mTOR, P70S6K and 4EBP1, with stable total protein levels. Additionally, we observed a dose-dependent decrease in BAD phosphorylation, in association with augmented BAX:BCL2 ratio. Quantification of autophagy showed a dose-dependent increase in acidic vesicular organelles in all cells tested.

CONCLUSION

In summary, our present study establishes that NVP-BKM120 presents an effective antitumour activity against T-ALL and BL cell lines.

Apigenin induces caspase-dependent apoptosis by inhibiting signal transducer and activator of transcription 3 signaling in HER2-overexpressing SKBR3 breast cancer cells

Phytoestrogens have been demonstrated to inhibit tumor induction; however, their molecular mechanisms of action have remained elusive. The present study aimed to investigate the effects of a phytoestrogen, apigenin, on proliferation and apoptosis of the human epidermal growth factor receptor 2 (HER2)-expressing breast cancer cell line SKBR3. Proliferation assay, MTT assay, fluorescence-activated cell sorting analysis, western blot analysis, immunocytochemistry, reverse transcription-polymerase chain reaction and ELISA assay were used in the present study. The results of the present study indicated that apigenin inhibited the proliferation of SKBR3 cells in a dose-and time-dependent manner. This inhibition of growth was accompanied by an increase in the sub-G0/G1 apoptotic population. Furthermore, apigenin enhanced the expression levels of cleaved caspase-8 and -3, and induced the cleavage of poly(adenosine diphosphate ribose) polymerase in SKBR3 cells, confirming that apigenin promotes apoptosis via a caspase-dependent pathway. Apigenin additionally reduced the expression of phosphorylated (p)-janus kinase 2 and p-signal transducer and activator of transcription 3 (STAT3), inhibited CoCl2-induced vascular endothelial growth factor (VEGF) secretion and decreased the nuclear localization of STAT3. The STAT3 inhibitor S31-201 decreased the cellular proliferation rate and reduced the expression of p-STAT3 and VEGF. Therefore, these results suggested that apigenin induced apoptosis via the inhibition of STAT3 signaling in SKBR3 cells. In conclusion, the results of the present study indicated that apigenin may be a potentially useful compound for the prevention or treatment of HER2-overexpressing breast cancer.

Proteomic identification and characterization of Ctenopharyngodon idella tumor necrosis factor receptor-associated protein 1 (CiTrap1): an anti-apoptosis factor upregulated by grass carp reovirus infection

Human tumor necrosis factor receptor-associated protein 1 (Trap1) is a mitochondrial protein identical to heat shock protein 75 (HSP75) that plays an important role in protecting cells from oxidative stress and apoptosis. In this study, grass carp (Ctenopharyngodon idella) tumor necrosis factor receptor-associated protein 1 (designated as CiTrap1) was identified through two-dimensional electrophoresis (2-DE) analysis and its pattern of expression was investigated in grass carp kidney (CIK) cells infected with grass carp reovirus (GCRV). The full length cDNA of CiTrap1 contained an opening reading frame of 2157 bp that encoded a peptide of 718 amino acids. Phylogenetic analyses indicated that the CiTrap1 shared 87% identity with its homologue from zebrafish (Danio rerio). The transcriptional level of CiTrap1 in CIK cells was upregulated post virus infection as well as poly (I: C) stimulation. Following virus infection, grass carp PTEN-induced putative kinase 1 (PINK1) and Sorcin, whose coding proteins interact with Trap1 in human, were simultaneously upregulated with CiTrap1. Typical characteristics of apoptosis were observed in CIK cells infected with GCRV by DAPI staining, DNA ladder electrophoresis, TUNEL assay and Annexin Ⅴ labeling. RNAi-mediated silencing of CiTrap1 in CIK cells resulted in the increased rate of virus-induced apoptotic cells. The results of this study suggest that CiTrap1 is involved in the host's innate immune response to viral infection possibly through protecting infected cells from apoptosis.

Apigenin induces apoptosis by targeting inhibitor of apoptosis proteins and Ku70-Bax interaction in prostate cancer

Dysfunction of the apoptotic pathway in prostate cancer cells confers apoptosis resistance towards various therapies. A novel strategy to overcome resistance is to directly target the apoptotic pathway in cancer cells. Apigenin, an anticancer agent, selectively toxic to cancer cells induces cell cycle arrest and apoptosis through mechanisms which are not fully explored. In the present study we provide novel insight into the mechanisms of apoptosis induction by apigenin. Treatment of androgen-refractory human prostate cancer PC-3 and DU145 cells with apigenin resulted in dose-dependent suppression of XIAP, c-IAP1, c-IAP2 and survivin protein levels. Apigenin treatment resulted in significant decrease in cell viability and apoptosis induction with the increase of cytochrome C in time-dependent manner. These effects of apigenin were accompanied by decrease in Bcl-xL and Bcl-2 and increase in the active form of Bax protein. The apigenin-mediated increase in Bax was due to dissociation of Bax from Ku70 which is essential for apoptotic activity of Bax. Apigenin treatment resulted in the inhibition of class I histone deacetylases and HDAC1 protein expression, thereby increasing the acetylation of Ku70 and the dissociation of Bax resulting in apoptosis of cancer cells. Furthermore, apigenin significantly reduced HDAC1 occupancy at the XIAP promoter, suggesting that histone deacetylation might be critical for XIAP downregulation. These results suggest that apigenin targets inhibitor of apoptosis proteins and Ku70-Bax interaction in the induction of apoptosis in prostate cancer cells and in athymic nude mouse xenograft model endorsing its in vivo efficacy.

Chemopreventive potential of phenolic compounds in oral carcinogenesis

OBJECTIVE

To evaluate the chemopreventive potential of phenolic compounds - potassium apigenin, cocoa, catechins, eriocitrin and rosmarinic acid in oral carcinogenesis induced in hamsters by means of the topical application of 7,12-dimethylbenz(a)anthracene(DMBA).

STUDY DESIGN

An experimental study at the University of Murcia.

METHODS

50 male Syrian hamsters (Mesocricetus auratus) were divided into five groups of ten: Group I (control group): 0.5% DMBA; Group II: 0.5% DMBA+1.1mg/15ml potassium apigenin; Group III: 05% DMBA+2.5mg/15ml cocoa catechins; Group IV: 0.5% DMBA+6mg/15ml eriocitrin; Group V: 0.5% DMBA+1.3mg/15ml rosmarinic acid. The flavonoids were administered orally. All the animals were sacrificed after 12 weeks. Macroscopic, microscopic and immunohistochemical (PCNA and p53) analyses of the lesions were performed.

RESULTS

All the groups treated with phenolic compounds showed lower incidences of tumour, greater differentiation and lower scores in the tumour invasion front grading system in comparison with the control group. Potassium apigenin and rosmarinic acid achieved the best results, the former considerably reduced the carcinoma tumour volumes developed and both significantly reduced the intensity and aggression of the tumours. Immunoexpression of PCNA and p53 were significantly altered during DMBA-induced oral carcinogenesis.

CONCLUSIONS

Animals treated with phenolic compounds, particularly potassium apigenin and rosmarinic acid, showed a lower incidence of tumours.

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.

Radix tetrastigma hemsleyani flavone induces apoptosis in human lung carcinoma a549 cells by modulating the MAPK pathway

Radix Tetrastigma Hemsleyani Flavone (RTHF) is widely used as a traditional herb for its detoxification and anti-inflammation activity. Recently, several studies have shown that RTHF can inhibit growth and induce apoptosis in human cancer cell lines. However, the mechanisms are not completely understood yet. In this study we investigated the potential effects of RTHF on growth and apoptosis in human lung adenocarcinoma A549 cells as well as its mechanisms. A549 cells were treated with RTHF at various concentrations for different times. In vitro the MTT assay showed that RTHF had obvious anti-proliferation effects on A549 cells in a dose- and time- dependent manner. Cell morphological changes observed by inverted microscope and Hoechst33258 methods were compared with apoptotic changes observed by fluorescence microscope. Cell apoptosis inspected by flow cytometry showed significant increase in the treatment group over the control group (P<0.01). Expression of apoptosis related Bax/Bcl-2, caspases and MAPK pathway proteins were detected by Western blotting. The results showed that RTHF up-regulated the Bax/Bcl-2 ratio and cle-caspase3/9, cle-PARP expression in a dose- dependent manner. Expression of p-p38 increased, p-ERK decreased significantly and that of p-JNK was little changed in the RTHF group when compared with the control group. These results suggest that RTHF might exert anti-growth and apoptosis activity against lung cancer A549 cells through activation of caspases and Bcl-2 family proteins and the MAPK pathway, therefore presenting as a promising therapeutic agent for the treatment of lung cancer.

Biophysical characterization of genistein-membrane interaction and its correlation with biological effect on cells - The case of EYPC liposomes and human erythrocyte membranes

With application of EPR and (1)H NMR techniques genistein interaction with liposomes formed with egg yolk lecithin and with erythrocyte membranes was assessed. The present study addressed the problem of genistein localization and its effects on lipid membrane fluidity and protein conformation. The range of microscopic techniques was employed to study genistein effects on HeLa cells and human erythrocytes. Moreover, DPPH bioassay, superoxide anion radical test and enzymatic measurements were performed in HeLa cells subjected to genistein. The gathered results from both EPR and NMR techniques indicated strong ordering effect of genistein on the motional freedom of lipids in the head group region and the adjacent hydrophobic zone in liposomal as well as in red blood cell membranes. EPR study of human ghost showed also the changes in the erythrocyte membrane protein conformation. The membrane effects of genistein were correlated with the changes in internal membranes arrangement of HeLa cells as it was noticed using transmission electron microscopic and fluorescent techniques. Scanning electron and light microscopy methods showed that one of the aftermaths of genistein incorporation into membranes was creation of echinocytic form of the red blood cells with reduced diameter. Genistein improved redox status of HeLa cells treated with H2O2 by lowering radicals' level. In conclusion, the capacity of genistein to incorporate, to affect membrane organization and to change its biophysical properties is correlated with the changes inside the cells.

Plant flavone apigenin binds to nucleic acid bases and reduces oxidative DNA damage in prostate epithelial cells

Oxidative stress has been linked to prostate carcinogenesis as human prostate tissue is vulnerable to oxidative DNA damage. Apigenin, a dietary plant flavone, possesses anti-proliferative and anticancer effects; however, its antioxidant properties have not been fully elucidated. We investigated sub-cellular distribution of apigenin, it's binding to DNA and protective effects against H2O2-induced DNA damage using transformed human prostate epithelial RWPE-1 cells and prostate cancer LNCaP, PC-3 and DU145 cells. Exposure of cells to apigenin exhibited higher accumulation in RWPE-1 and LNCaP cells, compared to PC-3 and DU145 cells. The kinetics of apigenin uptake in LNCaP cells was estimated with a Km value of 5 µmole/L and Vmax of 190 pmoles/million cells/h. Sub-cellular fractionation demonstrated that nuclear matrix retains the highest concentration of apigenin (45.3%), followed by cytosol (23.9%), nuclear membranes (17.9%) and microsomes (12.9%), respectively. Spectroscopic analysis of apigenin with calf-thymus DNA exhibited intercalation as the dominant binding mode to DNA duplex. Apigenin exposure resulted in significant genoprotective effects in H2O2-stressed RWPE-1 cells by reduction in reactive oxygen species levels. In addition, apigenin exposure suppressed the formation of 8-hydroxy-2' deoxyguanosine and protected exposed cells from apoptosis. Our studies demonstrate that apigenin is readily taken up by normal prostatic epithelial cells and prostate cancer cells, and is incorporated into their nuclei, where its intercalation with nucleic acid bases may account for its antioxidant and chemopreventive activities.

Synergistic anti-glioma effect of Hydroxygenkwanin and Apigenin in vitro

Apigenin (AP) and Hydroxygenkwanin (HGK) are two natural flavonoid compounds. Previous studies have already demonstrated the anti-tumor capability of AP. However, it is not clear whether HGK has such property. In the current study, the anti-glioma activities of HGK and its synergistic anti-glioma effects with AP on C6 glioma cells were investigated. In addition, the possible mechanisms were also studied. MTT assay and morphologic analysis including acridine orange/ethidium bromide (AO/EB) and 4',6-diamidino-2-phenylindole (DAPI) staining were used in the research, and the results indicated that the treatment with AP or HGK could inhibit C6 glioma cell proliferation respectively. Moreover, when AP was administrated simultaneously, the anti-glioma effect of HGK was dramatically enhanced in a dose-dependent manner, which is obviously better than that of carmustine (BCNU) at the concentration 25μM for treating of 24h. Compared with control, mitochondrial membrane potential (MPP) loss and mitochondrion damage were detected by JC-1 fluorescence probes (JC-1) and transmission electron microscopy (TEM) after treatment. Obvious DNA damage and cell cycle S phase arrest were detected by alkaline comet assay and flow cytometric analysis (FCM). Additionally, up regulation of TNF-α level, activations of caspase-3, -8, over expressions of BID and BAK protein and BCL-XL protein down expression were also observed after treatment by the combination of AP and HGK. The results indicate that HGK may be an effective natural product to treat glioma, and the combination of AP and HGK may be a promising method for glioma chemotherapy.

Enzymatic synthesis of apigenin glucosides by glucosyltransferase (YjiC) from Bacillus licheniformis DSM 13

Apigenin, a member of the flavone subclass of flavonoids, has long been considered to have various biological activities. Its glucosides, in particular, have been reported to have higher water solubility, increased chemical stability, and enhanced biological activities. Here, the synthesis of apigenin glucosides by the in vitro glucosylation reaction was successfully performed using a UDP-glucosyltransferase YjiC, from Bacillus licheniformis DSM 13. The glucosylation has been confirmed at the phenolic groups of C-4' and C-7 positions ensuing apigenin 4'-O-glucoside, apigenin 7-O-glucoside and apigenin 4',7-O-diglucoside as the products leaving the C-5 position unglucosylated. The position of glucosylation and the chemical structures of glucosides were elucidated by liquid chromatography/mass spectroscopy and nuclear magnetic resonance spectroscopy. The parameters such as pH, UDP glucose concentration and time of incubation were also analyzed during this study.

2,4-dichlorophenol induces apoptosis in primary hepatocytes of grass carp (Ctenopharyngodon idella) through mitochondrial pathway

2,4-Dichlorophenol (2,4-DCP), a major type of chlorophenols, has been widely used to produce some herbicides and pharmaceuticals, yet due to its incomplete degradation and bioaccumulation characteristics, it is toxic to aquatic organisms. Apoptosis is one of the most severe outcomes of cell poisoning and injury. So far, the potential molecular mechanism of 2,4-DCP-induced apoptosis has not been reported. This study showed that 2,4-DCP significantly induced apoptosis in primary hepatocytes of grass carp (Ctenopharyngodon idella). 2,4-DCP exposure upregulated mRNA of caspase-3, reduced the mitochondrial membrane potential (Δψm), increased intracellular reactive oxygen species (ROS) and the Bax/Bcl-2 ratio, while protection of mitochondria with acetyl-l-carnitine hydrochloride (ALC) rescued 2,4-DCP-induced apoptosis, restored the Δψm and reduced the Bax/Bcl-2 ratio. Taken together, this is the first study that has identified that 2,4-DCP exposure induced apoptosis through the mitochondria-dependent pathway in primary hepatocytes of grass carp.

Inhibition of ABCB1 expression overcomes acquired docetaxel resistance in prostate cancer

Docetaxel is the first-line standard treatment for castration-resistant prostate cancer. However, relapse eventually occurs due to the development of resistance to docetaxel. To unravel the mechanism of acquired docetaxel resistance, we established docetaxel-resistant prostate cancer cells, TaxR, from castration-resistant C4-2B prostate cancer cells. The IC50 for docetaxel in TaxR cells was about 70-fold higher than parental C4-2B cells. Global gene expression analysis revealed alteration of expression of a total of 1,604 genes, with 52% being upregulated and 48% downregulated. ABCB1, which belongs to the ATP-binding cassette (ABC) transporter family, was identified among the top upregulated genes in TaxR cells. The role of ABCB1 in the development of docetaxel resistance was examined. Knockdown of ABCB1 expression by its specific shRNA or inhibitor resensitized docetaxel-resistant TaxR cells to docetaxel treatment by enhancing apoptotic cell death. Furthermore, we identified that apigenin, a natural product of the flavone family, inhibits ABCB1 expression and resensitizes docetaxel-resistant prostate cancer cells to docetaxel treatment. Collectively, these results suggest that overexpression of ABCB1 mediates acquired docetaxel resistance and targeting ABCB1 expression could be a potential approach to resensitize docetaxel-resistant prostate cancer cells to docetaxel treatment.

Apigenin induces c-Myc-mediated apoptosis in FRO anaplastic thyroid carcinoma cells

Apigenin promotes apoptosis in cancer cells. We studied the effect of apigenin on cell survival and c-Myc expression in FRO anaplastic thyroid carcinoma (ATC) cells. Apigenin caused apoptosis via the elevation of c-Myc levels in conjunction with the phosphorylation of p38 and p53. In the c-Myc siRNA-transfected and apigenin-treated cells, compared with the apigenin-treated control cells, apoptosis and phosphorylation of p38 and p53 were ameliorated. In the presence of apigenin, diminution of p38 and p53 did not affect cell survival although apigenin activated the phosphorylation of p38 and p53 via increased c-Myc levels. In conclusion, our results indicate that apigenin induces apoptosis mediated via c-Myc with concomitant phosphorylation of p53 and p38 in FRO ATC cells. These findings suggest that augmented c-Myc acts as a core regulator and is necessary for apigenin-induced apoptosis in FRO ATC cells.