Inhibition of MDA-MB-231 breast cancer cell proliferation and tumor growth by apigenin through induction of G2/M arrest and histone H3 acetylation-mediated p21WAF1/CIP1 expression

Effects of propolis and its bioactive components on breast cancer cell pathways and the molecular mechanisms involved

BACKGROUND

Breast cancer is a female malignancy that is a significant cause of mortality worldwide. Currently, investigations on natural ingredients as new candidates for chemopreventive agents and breast cancer chemotherapies are increasing. Propolis is a natural resinous material produced by honeybees that exhibit anticancer potential. Several studies have mentioned the major bioactive compounds of propolis, but their mechanism of action is not clearly understood.

OBJECTIVES

The purpose of this review is to collect and summarize the evidence related to the effectiveness of propolis and its bioactive contents as candidates for breast cancer therapy and analyze the molecular mechanisms involved in their therapeutic pathways.

METHODS

We reviewed 94 articles from journals and databases, extracted the results, and produced summaries and conclusions.

RESULTS

Propolis and its bioactive ingredients show cytotoxic, anti-proliferative, pro-autophagic, anti-metastatic, and antioxidant activities, as well as synergistic effects with chemotherapy or radiotherapy in breast cancer. Its therapeutic activity involves various target molecules, including NF-κβ, Fas receptors, p53, TLR4, ANXA7, and voltage-gated Na+ channel (VGSC).

CONCLUSION

The bioactive components of propolis and the target molecules involved need to be explored further to develop new breast cancer therapies and overcome the problem of chemoradiation resistance.

Rationalizing the therapeutic potential of apigenin against cancer

BACKGROUND

Despite the remarkable advances made in the diagnosis and treatment of cancer during the past couple of decades, it remains the second largest cause of mortality in the world, killing approximately 9.6 million people annually. The major challenges in the treatment of the advanced stage of this disease are the development of chemoresistance, severe adverse effects of the drugs, and high treatment cost. Therefore, the development of drugs that are safe, efficacious, and cost-effective remains a 'Holy Grail' in cancer research. However, the research over the past four decades shed light on the cancer-preventive and therapeutic potential of natural products and their underlying mechanism of action. Apigenin is one such compound, which is known to be safe and has significant potential in the prevention and therapy of this disease.

AIM

To assess the literature available on the potential of apigenin and its analogs in modulating the key molecular targets leading to the prevention and treatment of different types of cancer.

METHOD

A comprehensive literature search has been carried out on PubMed for obtaining information related to the sources and analogs, chemistry and biosynthesis, physicochemical properties, biological activities, bioavailability and toxicity of apigenin.

KEY FINDINGS

The literature search resulted in many in vitro, in vivo and a few cohort studies that evidenced the effectiveness of apigenin and its analogs in modulating important molecular targets and signaling pathways such as PI3K/AKT/mTOR, JAK/STAT, NF-κB, MAPK/ERK, Wnt/β-catenin, etc., which play a crucial role in the development and progression of cancer. In addition, apigenin was also shown to inhibit chemoresistance and radioresistance and make cancer cells sensitive to these agents. Reports have further revealed the safety of the compound and the adaptation of nanotechnological approaches for improving its bioavailability.

SIGNIFICANCE

Hence, the present review recapitulates the properties of apigenin and its pharmacological activities against different types of cancer, which warrant further investigation in clinical settings.

Apigenin as Tumor Suppressor in Cancers: Biotherapeutic Activity, Nanodelivery, and Mechanisms With Emphasis on Pancreatic Cancer

Pancreatic cancer is the most lethal malignancy of the gastrointestinal tract. Due to its propensity for early local and distant spread, affected patients possess extremely poor prognosis. Currently applied treatments are not effective enough to eradicate all cancer cells, and minimize their migration. Besides, these treatments are associated with adverse effects on normal cells and organs. These therapies are not able to increase the overall survival rate of patients; hence, finding novel adjuvants or alternatives is so essential. Up to now, medicinal herbs were utilized for therapeutic goals. Herbal-based medicine, as traditional biotherapeutics, were employed for cancer treatment. Of them, apigenin, as a bioactive flavonoid that possesses numerous biological properties (e.g., anti-inflammatory and anti-oxidant effects), has shown substantial anticancer activity. It seems that apigenin is capable of suppressing the proliferation of cancer cells via the induction of cell cycle arrest and apoptosis. Besides, apigenin inhibits metastasis via down-regulation of matrix metalloproteinases and the Akt signaling pathway. In pancreatic cancer cells, apigenin sensitizes cells in chemotherapy, and affects molecular pathways such as the hypoxia inducible factor (HIF), vascular endothelial growth factor (VEGF), and glucose transporter-1 (GLUT-1). Herein, the biotherapeutic activity of apigenin and its mechanisms toward cancer cells are presented in the current review to shed some light on anti-tumor activity of apigenin in different cancers, with an emphasis on pancreatic cancer.

The In Vitro and In Vivo Anticancer Properties of Chalcone Flavokawain B through Induction of ROS-Mediated Apoptotic and Autophagic Cell Death in Human Melanoma Cells

Melanoma is the most prevalent type of skin cancer with high mortality rates. This study demonstrates the in vitro and in vivo anticancer properties of chalcone flavokawain B (FKB) induced ROS-mediated apoptosis and autophagy in human melanoma (human epithelial melanoma cell line A375 and/or human skin lymph node derived melanoma cell line A2058) cells. Cell viability was calculated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the expression patterns of various apoptosis, autophagy-associated proteins were determined by Western blot methods. Annexin V was detected by flow cytometry, whereas acidic vesicular organelles (AVOs) and intracellular ROS levels were measured by fluorescence microscopy. The in vivo anticancer properties of FKB were evaluated by xenografting the A375 cells into nude mice. The results convey that FKB inhibited cell viability, B-Raf proto-oncogene, serine/threonine kinase (BRAF)/extracellular signal-regulated kinase (ERK) expression in human melanoma cells. Caspase-3 activation, poly (ADP-ribose) polymerase (PARP) cleavage pathway, and Bcl2 associated X (Bax)/B-cell lymphoma 2 (Bcl-2) dysregulation were involved in the execution of apoptosis. Moreover, FKB-induced autophagy was observed through increased microtubule-associated protein 1A/1B-light chain 3B (LC3-II) accumulation and AVOs formation, which was also associated with an increase in sequestosome 1 (SQSTM1/p62), decreased protein kinase B (AKT)/mammalian target of rapamycin (mTOR) expressions, and dysregulated Beclin-1/Bcl-2 levels. Autophagy inhibitors [3-methyladenine (3-MA)/chloroquine (CQ)] and LC3 silencing suppressed FKB-induced apoptosis by decreasing caspase-3 in melanoma cells. The antioxidant N-acetylcysteine (NAC) diminished FKB-induced apoptotic and autophagic cell death. However, the inhibition of apoptosis decreased FKB-induced autophagy (LC3-I/II). The in vivo study confirmed that FKB inhibited melanoma growth in A375-xenografted nude mice. This study concluded that FKB is critically associated with the execution and generation of ROS-modulated apoptotic and autophagic cell death of melanoma cells. FKB also repressed tumor growth in xenografted nude mice. Therefore, flavokawain B might be a potential anti-tumor agent in human melanoma treatment.

Apigenin induces apoptosis by regulating Akt and MAPK pathways in human melanoma cell A375SM

Apigenin, an aromatic compound, exhibits antioxidant, anti-inflammatory and anti-viral effects. The present study aimed to investigate the effects of apigenin on cell proliferation and apoptosis of human melanoma cells A375P and A375SM. Therefore, melanoma cells were treated with apigenin to determine its anti-proliferative and survival effects, using wound healing and MTT assays. The results revealed that melanoma cell viability was decreased in a dose-dependent manner. Furthermore, chromatin condensation, indicating apoptosis, was significantly increased in a dose-dependent manner, as demonstrated by DAPI staining. In addition, increased apoptosis rate following treatment with apigenin was confirmed by Annexin V-propidium iodide staining. The changes in the expression levels of apoptosis-related proteins in A375P and A375SM melanoma cells were subsequently detected using western blot analysis. The results demonstrated that the protein expression levels of Bcl-2 were decreased, whereas those of Bax, cleaved poly ADP-ribose polymerase, cleaved caspase-9 and p53 were upregulated in a dose-dependent manner in apigenin-treated cells compared with those noted in untreated cells. In addition, in apigenin-treated A375P cells, phosphorylated (p)-p38 was upregulated and p-extracellular signal-regulated kinase (ERK), p-c-Jun N-terminal kinase (JNK) and p-protein kinase B (Akt) were downregulated. However, in A375SM cells, apigenin treatment increased p-ERK and p-JNK and decreased p-p38 and p-Akt protein expression levels. Subsequently, the inhibitory effect of apigenin on tumor growth was investigated in vivo. Tumor volume was significantly reduced in the 25 and 50 mg/kg apigenin-treated groups compared with the control group. Additionally, a TUNEL assay was performed to detect apoptotic cells. Immunohistochemical staining also revealed elevated p-ERK expression in the apigenin-treated group compared with the control group. Overall, the findings of the present study indicated that apigenin attenuated the growth of A375SM melanoma cells by inducing apoptosis via regulating the Akt and mitogen-activated protein kinase signaling pathways.

Epigenetic Regulation of NRF2/KEAP1 by Phytochemicals

Epigenetics has provided a new dimension to our understanding of nuclear factor erythroid 2–related factor 2/Kelch-like ECH-associated protein 1 (human NRF2/KEAP1 and murine Nrf2/Keap1) signaling. Unlike the genetic changes affecting DNA sequence, the reversible nature of epigenetic alterations provides an attractive avenue for cancer interception. Thus, targeting epigenetic mechanisms in the corresponding signaling networks represents an enticing strategy for therapeutic intervention with dietary phytochemicals acting at transcriptional, post-transcriptional, and post-translational levels. This regulation involves the interplay of histone modifications and DNA methylation states in the human NFE2L2/KEAP1 and murine Nfe2l2/Keap1 genes, acetylation of lysine residues in NRF2 and Nrf2, interaction with bromodomain and extraterminal domain (BET) acetyl “reader” proteins, and non-coding RNAs such as microRNA (miRNA) and long non-coding RNA (lncRNA). Phytochemicals documented to modulate NRF2 signaling act by reversing hypermethylated states in the CpG islands of NFE2L2 or Nfe2l2, via the inhibition of DNA methyltransferases (DNMTs) and histone deacetylases (HDACs), through the induction of ten-eleven translocation (TET) enzymes, or by inducing miRNA to target the 3′-UTR of the corresponding mRNA transcripts. To date, fewer than twenty phytochemicals have been reported as NRF2 epigenetic modifiers, including curcumin, sulforaphane, resveratrol, reserpine, and ursolic acid. This opens avenues for exploring additional dietary phytochemicals that regulate the human epigenome, and the potential for novel strategies to target NRF2 signaling with a view to beneficial interception of cancer and other chronic diseases.

Targeting epigenetics in cancer: therapeutic potential of flavonoids

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

Breast Tumor Microenvironment: Emerging target of therapeutic phytochemicals

Triple negative breast cancer (TNBC) is the most aggressive and challenging form of breast cancers. Tumor microenvironment (TME) of TNBC is associated with induction of metastasis, immune system suppression, escaping immune detection and drug resistance. TME is highly complex and heterogeneous, consists of tumor cells, stromal cells and immune cells. The rapid expansion of tumors induce hypoxia, which concerns the reprogramming of TME components. The reciprocal communication of tumor cells and TME cells predisposes cancer cells to metastasis by modulation of developmental pathways, Wnt, notch, hedgehog and their related mechanisms in TME. Dietary phytochemicals are non-toxic and associated with various human health benefits and remarkable spectrum of biological activities. The phytochemicals serve as vital resources for drug discovery and also as a source for breast cancer therapy. The novel properties of dietary phytochemicals propose platform for modulation of tumor signaling, overcoming drug resistance, and targeting TME. Therefore, TME could serve as promising target for the treatment of TNBC. This review presents current status and implications of experimentally evaluated therapeutic phytochemicals as potential targeting agents of TME, potential nanosystems for targeted delivery of phytochemicals and their current challenges and future implications in TNBC treatment. The dietary phytochemicals especially curcumin with significant delivery system could prevent TNBC development as it is considered safe and well tolerated in phase II clinical trials.

Transcriptional regulation of G2/M regulatory proteins and perturbation of G2/M Cell cycle transition by a traditional Chinese medicine recipe

ETHNOPHARMACOLOGICAL RELEVANCE

Hedyotis diffusa Willd. (H) and Scutellaria barbata D.Don (S) are ancient anti-cancer Chinese herb medicines. When combined, known as HS, it is one of the most commonly prescribed Chinese Medicines for cancer patients today in China.

AIM OF THE STUDY

The prevention of disease progression is a dominant concern for the growing number of men with prostate cancer. The purpose of this work is to evaluate the action and mode of action of Chinese Medicine recipe HS in inhibiting prostate cancer progression in preclinical models.

METHODS

Effects of HS were analyzed in prostate cancer cell lines by evaluating proliferation, cell cycle profile, DNA damage and key regulators responsible for G₂ to M phase transition. The transcriptional activities of these regulators were determined by RT-PCR and ChIP. The efficacy of HS in vitro was validated in an animal model.

RESULTS

HS treatment was observed to reduce DNA content and accumulated prostate cancer cells at the G₂/M phase. Immunolabeling for phospho-Histone H3 in association with nocodazole to capture mitotic cells confirmed that HS impeded G₂ to M transition. After excluding DNA damage-induced G₂ arrest, it was revealed that HS reduced expression of Cyclin B1, CDK1, PLK1 and Aurora A at both protein and mRNA levels, with concomitant reduction of H3K4 tri-methylation at their promoter-regions. Animals that received oral administration of HS with a dosage relevant to clinical application showed reduced tumor volume and weight with a reduction of Cyclin B1, CDK1, PLK1 and Aurora A protein levels.

CONCLUSIONS

HS acts by impeding the G₂ to M transition of prostate cancer cells. It is likely that the mode of action is transcriptionally suppressing proteins governing mitotic entry, without eliciting significant DNA damage.

Apigenin as an anticancer agent

Apigenin is an edible plant-derived flavonoid that has been reported as an anticancer agent in several experimental and biological studies. It exhibits cell growth arrest and apoptosis in different types of tumors such as breast, lung, liver, skin, blood, colon, prostate, pancreatic, cervical, oral, and stomach, by modulating several signaling pathways. Apigenin induces apoptosis by the activation of extrinsic caspase-dependent pathway by upregulating the mRNA expressions of caspase-3, caspase-8, and TNF-α. It induces intrinsic apoptosis pathway as evidenced by the induction of cytochrome c, Bax, and caspase-3, while caspase-8, TNF-α, and B-cell lymphoma 2 levels remained unchanged in human prostate cancer PC-3 cells. Apigenin treatment leads to significant downregulation of matrix metallopeptidases-2, -9, Snail, and Slug, suppressing invasion. The expressions of NF-κB p105/p50, PI3K, Akt, and the phosphorylation of p-Akt decreases after treatment with apigenin. However, apigenin-mediated treatment significantly reduces pluripotency marker Oct3/4 protein expression which might be associated with the downregulation of PI3K/Akt/NF-κB signaling.

miR-16 enhances miR-302/367-induced reprogramming and tumor suppression in breast cancer cells

Overexpression of either miR-302 or miR-302/367 cluster induces reprogramming of cancer cells and exerts tumor-suppressive effects by induction of mesenchymal-to-epithelial transition, apoptosis and a less proliferative capacity. Several reports have described miR-16 as a tumor suppressor microRNA (miRNA). Here, we studied the impact of exogenous induction of miR-16 in MDA-MB-231 and SK-BR-3 breast cancer cells following overexpression of miR-302/367 cluster and investigated whether transfection of these cells by a mature miR-16 mimic could affect the reprogramming state of the cells and their tumorigenicity. miR-16 enhanced the expression levels of OCT4A, SOX2, and NANOG, generally known as transcription or pluripotency factors, and suppressed proliferation and invasiveness of these cells. Meanwhile, inhibition of miR-16 counteracted both the reprogramming effect and the antitumor function of miR-302/367 in the breast cancer cells. Current results indicate that miR-16 can work as an adjuvant to improve both cancer cell reprogramming and tumor-suppressive function of miR-302/367 cluster in MDA-MB-231 and SK-BR-3 cells, while its inhibition counteracts all of these effects. Combined application of miRNAs that share some common targets in cancer cell signaling pathways may provide new approaches for repression of multiple hallmarks of cancer.

Investigation of possible effects of apigenin, sorafenib and combined applications on apoptosis and cell cycle in hepatocellular cancer cells

Hepatocellular carcinoma (HCC) is the most common type of liver tumors. There is only one chemodrug for treatment called sorafenib that is an effective multikinase inhibitor. However, most of the patients gain resistance to sorafenib treatment in six months. Thus, there is a limitation for treatment of HCC. Apigenin is a natural flavonoid that has been used for many years as an antioxidant and anti-inflammatory agent. The aim of this study is to investigate the combined therapeutic effects of sorafenib and apigenin upon apoptosis and cell cycle on HepG2 cell line. Cytotoxic effects of sorafenib and apigenin on HepG2 cells were determined by XTT assay. Effects of single and combined treatment on cell migration, invasion and colony formation were analysed by wound healing, transwell matrigel invasion assay and colony formation assay, respectively. TUNEL assay was performed for analyse apoptosis rates. Expression changes of genes related with apoptosis and cell cycle were analysed by quantitative real-time PCR. Combined treatment of sorafenib and apigenin has more decreasing effects on cell viability than single treatment groups. Also, combination group caused significant increase of apoptotic cells. Migration and invasion capability of cells in combined treatment group are decreased. Lastly, quantitative real-time PCR results showed that combination of both drugs arrested cell cycle and increased apoptotic gene expressions more than single treatment groups. This is the first study that investigating the combined treatment of sorafenib and apigenin on HCC in vitro. By combined treatment, apigenin potentiates sorafenib cytotoxicity on HepG2 cells. Effects of combined treatment on migration, invasion, apoptosis and gene expressions showed that may sorafenib and apigenin have synergistic effect.

Knockout of the Placenta Specific 8 Gene Affects the Proliferation and Migration of Human Embryonic Kidney 293T Cell

Candidate oncogene placenta specific 8 (PLAC8) has been identified to participate in different cellular process and human diseases. However, the effects of PLAC8 on cell proliferation and migration in human kidney cancer (KC) remained unclear. In current study, physiological effects of PLAC8 in immortalized human embryonic kidney cell line (HEK293T) were investigated in vitro. Two PLAC8 knockout (KO) cell lines were established via CRISPR/Cas9-mediated methods combined with fluorescence activated single cell sorting. To classify the characteristic of PLAC8 during cell proliferation and migration in HEK293T, cellular proliferative activity was analyzed by cell counting and colony formation assay. Cell cycle distribution was analyzed by flow cytometry. Cellular motile activity was analyzed by wound-healing and migration assay. Further underlying molecular mechanism was explored via western blot. With the KO cell lines, it was found that PLAC8 KO could decrease cell proliferation. Moreover, the inhibitory effects of PLAC8 KO on cell proliferation were associated with a G2/M arrest in cell cycle progression concomitant with a remarkable inhibition of Cyclin B1 and elevation of Cyclin A. The alteration of cell cycle proteins and E-cadherin might further associate with the enhancement of cell motility. Our study revealed a novel role for PLAC8 in cell proliferation and migration of HEK293T cells, which might shed light on further study of PLAC8 on human KC.

Cytotoxicity and Anti-inflammatory Properties of Apigenin-Derived Isolaxifolin

The rare flavonoid isolaxifolin, a potent insecticide, has been touted as a potential grain-protecting agent. In order to assess any impact of this natural product on human health and to explore its various other biological properties, we have established a semisynthesis from the simpler but structurally related and more abundant natural product apigenin. The five-step reaction sequence has provided, for the first time, sufficient material for an in-depth evaluation of the cytotoxic properties of the title natural product. The impact of isolaxifolin on certain pro-inflammatory cytokines in murine macrophage RAW 264.7 cells has also been examined. Such studies have revealed that isolaxifolin displays no toxic effects toward normal cells while displaying greater cytotoxicities against certain cancer cell lines than its synthetic precursor apigenin. Furthermore, unlike apigenin, isolaxifolin only reduced NO, TNF-α, and IL-6 secretions in LPS-induced RAW 264.7 cells in a rather modest and dose-independent manner.

Structure-based identification of novel sirtuin inhibitors against triple negative breast cancer: An in silico and in vitro study

Triple-negative breast cancer (TNBC) is an aggressive disease exemplified by a poor prognosis, greater degrees of relapse, the absence of hormonal receptors for coherent utilization of targeted therapy, poor response to currently available therapeutics and development of chemoresistance. Aberrant activity of sirtuins (SIRTs) has strong implications in the metastatic and oncogenic progression of TNBC. Synthetic SIRT inhibitors are effective, however, they have shown adverse side effects emphasizing the need for plant-derived inhibitors (PDIs). In the current study, we identified potential plant-derived sirtuin inhibitors using in silico approach i.e. molecular docking, ADMET and molecular dynamics simulations (MD). Docking studies revealed that Sulforaphane, Kaempferol and Apigenin exhibits the highest docking scores against SIRT1 & 5, 3 and 6 respectively. ADMET analysis of above hits demonstrated drug-like profile. MD of prioritized SIRTs-PDIs complexes displayed stability with insignificant deviations throughout the trajectory. Furthermore, we determined the effect of our prioritized molecules on cellular viability, global activity as well as protein expression of sirtuins and stemness of TNBC cells utilizing in vitro techniques. Our in vitro findings complements our in silico results. Collectively, these findings provide a better insight into the structural basis of sirtuin inhibition and can facilitate drug design process for TNBC management.

Dietary Polyphenols-Important Non-Nutrients in the Prevention of Chronic Noncommunicable Diseases. A Systematic Review

The improvement of the social and economic conditions of society has eliminated the threat of death from the majority of infectious diseases. However, the rapid progress of civilization has created new possibilities for the appearance of factors with adverse effects for the health of society. This has led to increased morbidity from certain diseases, the presence of which had not been observed several centuries ago. Chronic noncommunicable diseases (e.g., cancers, cardio-vascular disorders, diabetes, obesity, neurodegenerative diseases) result from an inappropriate relationship between people and their environment. The common characteristic for all chronic diseases is a “new” form of inflammation, very often called metaflammation, which is considered as a subclinical, permanent inflammation. As a result, metabolic cascade, including cellular oxidative stress, atherosclerotic process, and insulin resistance, occurs, which slowly generates significant deterioration in the organism. Polyphenols are the major group of non-nutrients, considering their diversity, food occurrence, and biological properties. The current review aims to present a wide spectrum of literature data, including the molecular mechanism of their activity and experimental model used, and summarize the recent findings on the multitude of physiological effects of dietary polyphenols towards the prevention of several chronic diseases. However, despite several studies, the estimation of their dietary intake is troublesome and inconclusive, which will be also discussed.

Pharmacotherapeutics and Molecular Mechanism of Phytochemicals in Alleviating Hormone-Responsive Breast Cancer

Breast cancer (BC) is the leading cause of death among women worldwide devoid of effective treatment. It is therefore important to develop agents that can reverse, reduce, or slow the growth of BC. The use of natural products as chemopreventive agents provides enormous advantages. The aim of the current investigation is to determine the efficacy of the phytochemicals against BC along with the approved drugs to screen the most desirable and effective phytocompound. In the current study, 36 phytochemicals have been evaluated against aromatase to identify the potential candidate drug along with the approved drugs employing the Cdocker module accessible on the Discovery Studio (DS) v4.5 and thereafter analysing the stability of the protein ligand complex using GROningen MAchine for Chemical Simulations v5.0.6 (GROMACS). Additionally, these compounds were assessed for the inhibitory features employing the structure-based pharmacophore (SBP). The Cdocker protocol available with the DS has computed higher dock scores for the phytochemicals complemented by lower binding energies. The top-ranked compounds that have anchored with key residues located at the binding pocket of the protein were subjected to molecular dynamics (MD) simulations employing GROMACS. The resultant findings reveal the stability of the protein backbone and further guide to comprehend on the involvement of key residues Phe134, Val370, and Met374 that mechanistically inhibit BC. Among 36 compounds, curcumin, capsaicin, rosmarinic acid, and 6-shogaol have emerged as promising phytochemicals conferred with the highest Cdocker interaction energy, key residue interactions, stable MD results than reference drugs, and imbibing the key inhibitory features. Taken together, the current study illuminates the use of natural compounds as potential drugs against BC. Additionally, these compounds could also serve as scaffolds in designing and development of new drugs.

Dietary Compounds as Epigenetic Modulating Agents in Cancer

Epigenetic mechanisms control gene expression during normal development and their aberrant regulation may lead to human diseases including cancer. Natural phytochemicals can largely modulate mammalian epigenome through regulation of mechanisms and proteins responsible for chromatin remodeling. Phytochemicals are mainly contained in fruits, seeds, and vegetables as well as in foods supplements. These compounds act as powerful cellular antioxidants and anti-carcinogens agents. Several dietary compounds such as catechins, curcumin, genistein, quercetin and resveratrol, among others, exhibit potent anti-tumor activities through the reversion of epigenetic alterations associated to oncogenes activation and inactivation of tumor suppressor genes. In this review, we summarized the actual knowledge about the role of dietary phytochemicals in the restoration of aberrant epigenetic alterations found in cancer cells with a particular focus on DNA methylation and histone modifications. Furthermore, we discussed the mechanisms by which these natural compounds modulate gene expression at epigenetic level and described their molecular targets in diverse types of cancer. Modulation of epigenetic activities by phytochemicals will allow the discovery of novel biomarkers for cancer prevention, and highlights its potential as an alternative therapeutic approach in cancer.

Natural Products and Chemical Biology Tools: Alternatives to Target Epigenetic Mechanisms in Cancers

DNA methylation and histone acetylation are widely studied epigenetic modifications. They are involved in numerous pathologies such as cancer, neurological disease, inflammation, obesity, etc. Since the discovery of the epigenome, numerous compounds have been developed to reverse DNA methylation and histone acetylation aberrant profile in diseases. Among them several were inspired by Nature and have a great interest as therapeutic molecules. In the quest of finding new ways to target epigenetic mechanisms, the use of chemical tools is a powerful strategy to better understand epigenetic mechanisms in biological systems. In this review we will present natural products reported as DNMT or HDAC inhibitors for anticancer treatments. We will then discuss the use of chemical tools that have been used in order to explore the epigenome.

Placenta-specific 9, a putative secretory protein, induces G2/M arrest and inhibits the proliferation of human embryonic hepatic cells

Background: Placenta-specific 9 (Plac9) is a putative secreted protein that was first discovered in the context of embryogenesis. The expression pattern of Plac9 during embryogenesis, together with the results of recent reports, suggest that Plac9 may play a role in the liver development. The present study was conducted to investigate the secretory characteristics of Plac9 and its potential role in liver cell physiology. Methods: Immunofluorescence was employed to identify the subcellular distribution of Plac9. Cellular proliferative activity was analyzed by MTT assay and cell colony formation. The cell cycle distribution of Plac9 was analyzed by flow cytometry, and a functional analysis was performed using L02 cells following their stable infection with a lentivirus over-expressing Plac9. Results:Plac9 is a novel protein that is localized to the cytoplasm and may be secreted through the classic endoplasmic reticulum-Golgi route. The overexpression of Plac9 inhibits cell growth and induces G2/M phase arrest. Conclusion: Our findings reveal a novel role for Plac9 in regulating cell growth.

Mechanistic evaluation of phytochemicals in breast cancer remedy: current understanding and future perspectives

Breast cancer is one of the most commonly diagnosed cancers around the globe and accounts for a large proportion of fatalities in women. Despite the advancement in therapeutic and diagnostic procedures, breast cancer still represents a major challenge. Current anti-breast cancer approaches include surgical removal, radiotherapy, hormonal therapy and the use of various chemotherapeutic drugs. However, drug resistance, associated serious adverse effects, metastasis and recurrence complications still need to be resolved which demand safe and alternative strategies. In this scenario, phytochemicals have recently gained huge attention due to their safety profile and cost-effectiveness. These phytochemicals modulate various genes, gene products and signalling pathways, thereby inhibiting breast cancer cell proliferation, invasion, angiogenesis and metastasis and inducing apoptosis. Moreover, they also target breast cancer stem cells and overcome drug resistance problems in breast carcinomas. Phytochemicals as adjuvants with chemotherapeutic drugs have greatly enhanced their therapeutic efficacy. This review focuses on the recently recognized molecular mechanisms underlying breast cancer chemoprevention with the use of phytochemicals such as curcumin, resveratrol, silibinin, genistein, epigallocatechin gallate, secoisolariciresinol, thymoquinone, kaempferol, quercetin, parthenolide, sulforaphane, ginsenosides, naringenin, isoliquiritigenin, luteolin, benzyl isothiocyanate, α-mangostin, 3,3'-diindolylmethane, pterostilbene, vinca alkaloids and apigenin.

Food Bioactive HDAC Inhibitors in the Epigenetic Regulation of Heart Failure

Approximately 5.7 million U.S. adults have been diagnosed with heart failure (HF). More concerning is that one in nine U.S. deaths included HF as a contributing cause. Current HF drugs (e.g., β-blockers, ACEi) target intracellular signaling cascades downstream of cell surface receptors to prevent cardiac pump dysfunction. However, these drugs fail to target other redundant intracellular signaling pathways and, therefore, limit drug efficacy. As such, it has been postulated that compounds designed to target shared downstream mediators of these signaling pathways would be more efficacious for the treatment of HF. Histone deacetylation has been linked as a key pathogenetic element for the development of HF. Lysine residues undergo diverse and reversible post-translational modifications that include acetylation and have historically been studied as epigenetic modifiers of histone tails within chromatin that provide an important mechanism for regulating gene expression. Of recent, bioactive compounds within our diet have been linked to the regulation of gene expression, in part, through regulation of the epi-genome. It has been reported that food bioactives regulate histone acetylation via direct regulation of writer (histone acetyl transferases, HATs) and eraser (histone deacetylases, HDACs) proteins. Therefore, bioactive food compounds offer unique therapeutic strategies as epigenetic modifiers of heart failure. This review will highlight food bio-actives as modifiers of histone deacetylase activity in the heart.

Apigenin Suppresses the IL-1β-Induced Expression of the Urokinase-Type Plasminogen Activator Receptor by Inhibiting MAPK-Mediated AP-1 and NF-κB Signaling in Human Bladder Cancer T24 Cells

The urokinase-type plasminogen activator receptor (uPAR), a glycoprotein localized on the cell surface with a glycosylphosphatidylinositol anchor, plays a crucial role in cell invasion, and the metastasis of several cancers, including bladder cancer, and its expression are significantly negatively correlated with patient survival rates. Apigenin, a naturally produced phytochemical compound found in fruits, vegetables, and plant leaves, has been shown to mediate a variety of cancer-metastasis-related molecules in various cancers. The effect of apigenin on uPAR expression is still unknown. In this study, we examined the effects of apigenin on IL-1β-induced uPAR expression and investigated its potential mechanisms. We discovered in this study that IL-1β could remarkably induce uPAR expression in bladder cancer T24 cells and that apigenin-inhibited IL-1β could induce uPAR expression concentration-dependently. Interestingly, NF-κB and AP-1 transcription factors were critically required for IL-1β-induced high uPAR expression. Apigenin suppressed the transcriptional activity of both AP-1 and NF-κB by inhibiting ERK1/2 and JNK signaling pathways. These results suggest that apigenin can exert anti-invasion effects by inhibiting uPAR expression via mediating (ERK1/2, JNK)/AP-1 and (ERK1/2, JNK)/NF-κB signaling pathways in human T24 cells. Our present study generated novel and valuable biological insight into anti-invasion through treatment with a small native compound.

In silico approaches for investigating the binding propensity of apigenin and luteolin against class I HDAC isoforms

AIM

Aberrant activity of class I histone deacetylases (HDACs) has strong implications for various cancers. Targeting these HDACs with synthetic HDAC inhibitors has shown significant side effects such as atrial fibrillation and QT prolongation emphasizing the need of natural inhibitors as substitutes to synthetic ones.

RESULTS

The binding propensity of the two plant-derived inhibitors apigenin and luteolin towards class I HDAC isoforms was checked using extra-precision molecular docking and implicit solvation MMGBSA. Apigenin showed a superior binding affinity against these isoforms as compared to luteolin. Both inhibitors docked stable to the binding pocket of these HDACs as determined by molecular dynamics simulation study.

CONCLUSION

Apigenin and luteolin may serve as substitutes to synthetic inhibitors for effective HDAC based anticancer therapy.

Inhibition of PI3K/Akt/mTOR pathway by apigenin induces apoptosis and autophagy in hepatocellular carcinoma cells

Apigenin is a dietary flavonoid with known antioxidant and antitumor effects against several types of cancers by promoting cell death and inducing cell cycle arrest. Apigenin also regulates a variety of intracellular signal transduction pathways during apoptosis or autophagy. However, the precise mechanism underlying the anticancer effects of apigenin in liver cancer remains poorly understood. In this study, we demonstrated that apigenin has anticancer activity against hepatocellular carcinoma cells. Apigenin inhibited the cell growth and induced cell death in a dose- and time-dependent manner in HepG2 cells. We found that apigenin treatment increased the expression of LC3-II and the number of GFP-LC3 puncta. Moreover, inhibition of autophagy with 3-MA and Atg5 gene silencing strengthened apigenin-induced proliferation inhibition and apoptosis. Our data has indicated that apigenin-induced autophagy has a protective effect against cell death. Additionally, apigenin induced apoptosis and autophagy through inhibition of PI3K/Akt/mTOR pathway. Most importantly, in vivo data showed that administration of apigenin decreased tumor growth and autophagy inhibition by 3-MA significantly enhanced the anticancer effect of apigenin. Collectively, our results reveal that apigenin inhibits cell proliferation and induces autophagy via suppressing the PI3K/Akt/mTOR pathway. Our results also suggest combination of autophagy inhibitors and apigenin would be a potential chemotherapeutic strategy against hepatocellular carcinoma.

Apigenin, a dietary flavonoid, induces apoptosis, DNA damage, and oxidative stress in human breast cancer MCF-7 and MDA MB-231 cells

Apigenin is found in several dietary plant foods such as vegetables and fruits. To investigate potential anticancer properties of apigenin on human breast cancer, ER-positive MCF-7 and triple-negative MDA MB-231 cells were used. Moreover, toxicological safety of apigenin towards normal cells was evaluated in human lymphocytes. Cytotoxicity of apigenin towards cancer cells was evaluated by MTT assay whereas further genotoxic and oxidative stress parameters were measured by comet and lipid peroxidation assays, respectively. In order to examine the type of cell death induced by apigenin, several biomarkers were used. Toxicological safety towards normal cells was evaluated by cell viability and comet assays. After the treatment with apigenin, we observed changes in cell morphology in a dose- (10 to 100 μM) and time-dependent manner. Moreover, apigenin caused cell death in both cell lines leading to significant toxicity and dominantly to apoptosis. Furthermore, apigenin proved to be genotoxic towards the selected cancer cells with a potential to induce oxidative damage to lipids. Of great importance is that no significant cytogenotoxic effects were detected in normal cells. The observed cytogenotoxic and pro-cell death activities of apigenin coupled with its low toxicity towards normal cells indicate that this natural product could be used as a future anticancer modality. Therefore, further analysis to determine the exact mechanism of action and in vivo studies on animal models are warranted.

Apigenin's anticancer properties and molecular mechanisms of action: Recent advances and future prospectives

Cancer is a major health concern and leading burden on economy worldwide. An increasing effort is devoted to isolation and development of plant-derived dietary components as effective chemo-preventive products. Phytochemical compounds from natural resources such as fruits and vegetables are responsible for decreasing the risk of certain cancers among the consuming populations. Apigenin, a flavonoid phytochemical found in many kinds of fruits and vegetables, has been shown to exert significant biological effects, such as anti-oxidant, anti-inflammatory and most particularly anti-neoplastic properties. This review is intended to summarize the most recent advances in the anti-proliferative and chemo-preventive effects of apigenin in different cancer models. Analysis of the data from the studied cancer models has revealed that apigenin exerts its anti-proliferative effects through multiple and complex pathways. This guided us to discover some controversial results about the exact role of certain molecular pathways such as autophagy in the anticancer effects of apigenin. Further, there were cumulative positive evidences supporting the involvement of certain pathways such as apoptosis, ROS and DNA damage and repair. Apigenin possesses a high potential to be used as a chemosensitizing agent through the up-regulation of DR5 pathway. According to these preclinical findings we recommend that further robust unbiased studies should consider the possible interactions between different molecular pathways.

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.

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.

HRD1 sensitizes breast cancer cells to Tamoxifen by promoting S100A8 degradation

Estrogen receptor alpha positive (ER+) of breast cancer could develop resistance to antiestrogens including Tamoxifen. Our previous study showed that the E3 ubiquitin ligase HRD1 played an important role in anti-breast cancer. However, its role in chemotherapy resistance hasn't been reported. In this study, we found that HRD1 expression was downregulated in Tamoxifen-resistant breast cancer cell line MCF7/Tam compared to the Tamoxifen sensitive cell line MCF7. Moreover, S100A8 is the direct target of HRD1 by proteome analysis. Our data showed that HRD1 decreased the protein level of S100A8 through ubiquitination while HRD1 was regulated by acetylation of histone. More importantly, HRD1 knockdown significantly increased the cell survival of MCF7 cells to the Tamoxifen treatment. HRD1 overexpression sensitized MCF7/Tam cells to the Tamoxifen treatment in vitro and in vivo. In conclusion, the decrease of HRD1 expression contributed to Tamoxifen resistance in breast cancer.

Apigenin inhibits TNFα/IL-1α-induced CCL2 release through IKBK-epsilon signaling in MDA-MB-231 human breast cancer cells

Mortality associated with breast cancer is attributable to aggressive metastasis, to which TNFα plays a central orchestrating role. TNFα acts on breast tumor TNF receptors evoking the release of chemotactic proteins (e.g. MCP-1/CCL2). These proteins direct inward infiltration/migration of tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), T-regulatory cells (Tregs), T helper IL-17-producing cells (Th17s), metastasis-associated macrophages (MAMs) and cancer-associated fibroblasts (CAFs). Tumor embedded infiltrates collectively enable immune evasion, tumor growth, angiogenesis, and metastasis. In the current study, we investigate the potential of apigenin, a known anti-inflammatory constituent of parsley, to downregulate TNFα mediated release of chemokines from human triple-negative cells (MDA-MB-231 cells). The results show that TNFα stimulation leads to large rise of CCL2, granulocyte macrophage colony-stimulating factor (GMCSF), IL-1α and IL-6, all suppressed by apigenin. While many aspects of the transcriptome for NFkB signaling were evaluated, the data show signaling patterns associated with CCL2 were blocked by apigenin and mediated through suppressed mRNA and protein synthesis of IKBKe. Moreover, the data show that the attenuation of CCL2 by apigenin in the presence TNFα paralleled the suppression of phosphorylated extracellular signal-regulated kinase 1 (ERK 1/ 2). In summary, the obtained findings suggest that there exists a TNFα evoked release of CCL2 and other LSP recruiting cytokines from human breast cancer cells, which can be attenuated by apigenin.

Improved solubility and oral bioavailability of apigenin via Soluplus/Pluronic F127 binary mixed micelles system

The aim of this study was to develop a novel mix micelles system composing of two biocompatible copolymers of Soluplus^® and Pluronic F127 to improve the solubility, oral bioavailability of insoluble drug apigenin (AP) as model drug. The AP-loaded mixed micelles (AP-M) were prepared by ethanol thin-film hydration method. The formed optimal formulation of AP-M were provided with small size (178.5 nm) and spherical shape at ratio of 4:1 (Soluplus^®:Pluronic F127), as well as increasing solubility of to 5.61 mg/mL in water which was about 3442-fold compared to that of free AP. The entrapment efficiency and drug loading of AP-M were 95.72 and 5.32%, respectively, and a sustained release of AP-M was obtained as in vitro release study indicated. Transcellular transport study showed that the cell uptake of AP was increased in Caco-2 cell transport models. The oral bioavailability of AP-M was 4.03-fold of free AP in SD rats, indicating the mixed micelles of Soluplus^® and Pluronic F127 is an industrially feasible drug delivery system to promote insoluble drug oral absorption in the gastrointestinal tract.

A Flavone Constituent from Myoporum bontioides Induces M-Phase Cell Cycle Arrest of MCF-7 Breast Cancer Cells

Myoporum bontioides is a traditional medicinal plant in Asia with various biological activities, including anti-inflammatory and anti-bacterial characteristics. To identify the bioactive constituents from M. bontioides, a newly-identified flavone, 3,4'-dimethoxy-3',5,7-trihydroxyflavone (compound 1), along with eight known compounds, were investigated in human MCF-7 breast cancer, SCC4 oral cancer, and THP-1 monocytic leukemia cells. Among these compounds, compound 1 exhibited the strongest antiproliferative activity with half-maximal inhibitory concentration (IC₅₀) values ranging from 3.3 μM (MCF-7) to 8.6 μM (SCC4). Flow cytometric analysis indicated that compound 1 induced G2/M cell cycle arrest in MCF-7 cells. Mechanistic evidence suggests that the G2/M arrest could be attributable to compound 1's modulatory effects on the phosphorylation and expression of numerous key signaling effectors, including cell division cycle 2 (CDC2), CDC25C, and p53. Notably, compound 1 downregulated the expression of histone deacetylase 2 (HDAC2) and HDAC4, leading to increased histone H3 acetylation and p21 upregulation. Together, these findings suggest the translational potential of compound 1 as a breast cancer treatment.

Apigenin Attenuates Oxidative Injury in ARPE-19 Cells thorough Activation of Nrf2 Pathway

The current study was aimed at evaluating the therapeutic implication of apigenin and to elucidate the underlying mechanism. The tert-butyl hydroperoxide (t-BHP) at 200 μM was used to induce oxidative stress-associated injury in ARPE-19 cells. Apigenin at concentrations less than 800 μM did not cause cytotoxic effects on ARPE-19 cells. Cell viability assay showed that apigenin at 200 μM significantly promoted cell survival in t-BHP-treated ARPE-19 cells. Additionally, apigenin at 100 μM significantly protected ARPE-19 cells from t-BHP-induced apoptosis. Molecular examinations demonstrated that apigenin at 400 μM significantly upregulated the mRNA and protein expression of Nrf2 and stimulated its nuclear translocation in ARPE-19 cells treated with or without t-BHP. Apigenin 400 μM also significantly elevated the expression of HO-1, NQO1, and GCLM at both mRNA and protein levels in the presence or absence of t-BHP. Furthermore, apigenin at 400 μM significantly increased the activities of SOD, CAT, GSH-PX, and T-AOC and reduced the levels of ROS and MDA in t-BHP-treated ARPE-19 cells. However, these effects of apigenin were all abolished by being transfected with Nrf2 siRNA. Collectively, our current data indicated that apigenin exerted potent antioxidant properties in ARPE-19 cells challenged with t-BHP, which were dependent on activation of Nrf2 signaling.

Natural Polyphenols for Prevention and Treatment of Cancer

There is much epidemiological evidence that a diet rich in fruits and vegetables could lower the risk of certain cancers. The effect has been attributed, in part, to natural polyphenols. Besides, numerous studies have demonstrated that natural polyphenols could be used for the prevention and treatment of cancer. Potential mechanisms included antioxidant, anti-inflammation as well as the modulation of multiple molecular events involved in carcinogenesis. The current review summarized the anticancer efficacy of major polyphenol classes (flavonoids, phenolic acids, lignans and stilbenes) and discussed the potential mechanisms of action, which were based on epidemiological, in vitro, in vivo and clinical studies within the past five years.

Apigenin Reduces Survival of Choriocarcinoma Cells by Inducing Apoptosis via the PI3K/AKT and ERK1/2 MAPK Pathways

Apigenin is a flavonoid found in parsley, onions, oranges, tea, chamomile, wheat, and sprouts. It has a variety of biological properties including anti-oxidant, anti-mutagenic, anti-carcinogenic, anti-inflammatory, anti-proliferative, and anti-spasmodic effects. Based on epidemiological and case-control studies, apigenin is regarded as a novel chemotherapeutic agent against various cancer types. However, little is known about the effects of apigenin on choriocarcinoma cells. Therefore, we investigated the anti-cancer effects of apigenin on choriocarcinoma cells (JAR and JEG3) in the present study. Apigenin reduced viability and migratory properties, increased apoptosis, and suppressed mitochondrial membrane potential in both the JAR and JEG3 cells. In addition, apigenin predominantly decreased phosphorylation of AKT, P70RSK, and S6 whereas the phosphorylation of ERK1/2 and P90RSK was increased by apigenin treatment of JAR and JEG3 cells in a dose-dependent manner. Moreover, treatment of JAR and JEG3 cells with both apigenin and pharmacological inhibitors of PI3K/AKT (LY294002) and ERK1/2 (U0126) revealed synergistic anti-proliferative effects. Collectively, these results indicated that the apigenin is an invaluable chemopreventive agent that inhibits progression and metastasis of choriocarcinoma cells through regulation of PI3K/AKT and ERK1/2 MAPK signal transduction mechanism. J. Cell. Physiol. 231: 2690-2699, 2016. © 2016 Wiley Periodicals, Inc.