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

Exploring the Therapeutic Potential of Flavonoids in the Management of Cancer

Flavonoids are a class of polyphenolic compounds that can be classified into six distinct categories, namely isoflavonoids, flavanones, flavanols, flavonols, flavones, and anthocyanidins. These compounds are naturally occurring and can be found in a diverse range of plant species. Flavonoids, a class of bioactive compounds, are mostly obtained through the consumption of vegetables, fruits and plant-derived beverages such as wine, cocoa-based products and green tea. Flavonoids have been demonstrated to exhibit a diverse range of anticancer properties. These include the modulation of activities of enzymes involved in scavenging reactive oxygen species, involvement in cell cycle arrest, induction of apoptosis and autophagy, as well as suppression of cancer cell proliferation and invasiveness. Flavonoids exhibit a dual role in maintaining reactive oxygen species balance. They function as antioxidants in regular physiological conditions, while also demonstrating significant pro-oxidant properties in cancer cells. This prooxidant activity induces apoptotic pathways and downregulates pro-inflammatory signalling pathways. The paper explores the biochemical characteristics, bioavailability, anticancer efficacy, and modes of action of flavonoids.

Apigenin Improves Ovarian Dysfunction Induced by 4-Vinylcyclohexene Diepoxide via the AKT/FOXO3a Pathway

Perimenopausal syndrome is a significant issue that disturbs women's metabolism, mood and quality of life. Apigenin (4',5,7-trihydroxyflavone) is a natural flavonoid that exhibits antioxidant, anti-inflammatory and anticancer effects. The present study aims to investigate the effect of apigenin on perimenopausal syndrome by combining bioinformatics analysis with in vivo experiments. The mouse model with perimenopausal syndrome was established using 4-vinylcyclohexene diepoxide (VCD) treatment. Apigenin alleviated VCD-induced disorder of estrous cycle and shrinkage of ovarian tissue. The reduction of anti-Muller hormone and the increase of follicle stimulation hormone and luteinizing hormone triggered by VCD were reversed by apigenin in a dose-dependent manner. Apigenin suppressed the VCD-induced decrease of primordial, primary, secondary and antral follicle number in ovarian tissue. Oxidative stress in ovarian tissue was activated by VCD treatment through increasing the reactive oxygen species production. High concentration of apigenin significantly reversed the alteration induced by VCD. Apigenin alleviated VCD-induced cell apoptosis through regulating Bax, Bcl-2, cleaved PARP1 and caspase-3. Furthermore, the phosphorylation of AKT and FOXO3a was inhibited by VCD and activated by apigenin in a dose-dependent manner. Collectively, apigenin effectively mitigates the ovarian dysfunction through suppressing oxidative stress and apoptosis via the AKT/FOXO3a signaling pathway.

A comprehensive review of apigenin a dietary flavonoid: biological sources, nutraceutical prospects, chemistry and pharmacological insights and health benefits

A multitude of plant-derived bioactive compounds have shown significant promise in preventing chronic illnesses, with flavonoids constituting a substantial class of naturally occurring polyphenolic compounds. Apigenin, a flavone identified as 4',5,7-trihydroxyflavone, holds immense promise as a preventative agent against chronic illnesses. Despite its extensive research and recognized nutraceutical value, its therapeutic application remains underexplored, necessitating further clinical investigations. This review delves into the biological sources, nutraceutical prospects, chemistry, pharmacological insights, and health benefits of apigenin. Through multifaceted analytical studies, we explore its diverse pharmacological profile and potential therapeutic applications across various health domains. The manuscript comprehensively examines apigenin's role as a neuroprotective , anti-inflammatory compound, and a potent antioxidant agent. Additionally, its efficacy in combating cardiovascular diseases, anti-diabetic properties, and anticancer potential has been discussed. Furthermore, the antimicrobial attributes and the challenges surrounding its bioavailability, particularly from herbal supplements have been addressed. Available in diverse forms including tablets, capsules, solid dispersions, co-crystals, inclusion complexes and nano formulations. Additionally, it is prevalent as a nutraceutical supplement in herbal formulations. While strides have been made in overcoming pharmacokinetic hurdles, further research into apigenin's clinical effectiveness and bioavailability from herbal supplements remains imperative for its widespread utilization in preventive medicine.

Exploring the Mechanism of Zilongjin in Treating Lung Adenocarcinoma Based on Network Pharmacology Combined with Experimental Verification

Zilongjin (ZLJ) is a common traditional Chinese medicine for lung adenocarcinoma (LUAD) treatment. However, its mechanisms of action remain to be elucidated. Network pharmacology was used to explore the underlying mechanisms of ZLJ on LUAD treatment. The disease-related targets were determined from the Gene-Cards and DisGeNET databases. Active compounds and targets of ZLJ were obtained from the HIT, TCMSP, and TCMID databases. Then the protein-protein interaction (PPI) network was built by the STRING database to identify core-hub targets of ZLJ in LUAD. Next, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were employed to analyze the enriched regulatory pathways of targets. Molecular docking analysis was used to evaluate interactions between potential targets and active compounds. Finally, qRT-PCR was used to further verify the results of network pharmacology. A total of 124 LUAD-related targets of ZLJ and 5 active compounds of ZLJ from the relevant databases were screened out. Among these target proteins, JUN, CDH1, PPARG, and FOS were core hub-genes in the PPI network. GO and KEGG pathway enrichment analysis indicated that these targets might regulate the PPAR signaling pathway in LUAD. JUN, PPARG, and FOS levels were upregulated, while CDH1 level was downregulated in LUAD cells. This study discerned that ZLJ may target genes such as JUN, FOS, PPARG, and CDH1 via the PPAR signaling pathway in LUAD, offering foundational insights for further exploration of ZLJ in clinical applications.

Endoplasmic Reticulum as a Therapeutic Target in Cancer: Is there a Role for Flavonoids?

Flavonoids are classified into subclasses of polyphenols, a multipurpose category of natural compounds which comprises secondary metabolites extracted from vascular plants and are plentiful in the human diet. Although the details of flavonoid mechanisms are still not realized correctly, they are generally regarded as antimicrobial, anti-fungal, anti-inflammatory, anti-oxidative; anti-mutagenic; anti-neoplastic; anti-aging; anti-diabetic, cardio-protective, etc. The anti-cancer properties of flavonoids are evident in functions such as prevention of proliferation, metastasis, invasion, inflammation and activation of cell death. Tumors growth and enlargement expose cells to acidosis, hypoxia, and lack of nutrients which result in endoplasmic reticulum (ER) stress; it triggers the unfolded protein response (UPR), which reclaims homeostasis or activates autophagy. Steady stimulation of ER stress can switch autophagy to apoptosis. The connection between ER stress and cancer, in association with UPR, has been explained. The signals provided by UPR can activate or inhibit anti-apoptotic or apoptotic pathways depending on the period and grade of ER stress. In this review, we will peruse the link between flavonoids and their impact on the endoplasmic reticulum in association with cancer therapy.

Role of Plant-Derived Flavonoids in Cancer Treatment

Flavonoids are polyphenolic phytochemicals, which occur naturally in plants and possess both anti-oxidant and pro-oxidant properties. Flavonoids are gaining increasing popularity in the pharmaceutical industry as healthy and cost-effective compounds. Flavonoids show beneficial pharmacological activities in the treatment and prevention of various types of diseases. They are natural and less toxic agents for cancer chemotherapy and radiotherapy via regulation of multiple cell signaling pathways and pro-oxidant effects. In this review, we have summarized the mechanisms of action of selected flavonoids, and their pharmacological implications and potential therapeutic applications in cancer therapy.

Anti-Mycobacterial Activity of Flavonoid and Pyrimidine Compounds

We evaluated the anti-mycobacterial effect of a flavonoid 5,7-dihydroxy-2-(4-hydroxyphenyl) 4H-chromen-4-one (1) and two pyrimidines, 4-hydroxy-2-dimethylamino-5-nitroso-6-aminopyrimidine (2) and 2-chloro-5-n-nonylpyrimidine (3) in vitro against Mycobacterium tuberculosis (M. tuberculosis, H37Ra) and Mycobacterium avium (M. avium), using a Microplate Alamar Blue Assay (MABA). The effects of the compounds 1-3 in combination with first- and second-line anti-TB drugs isoniazid, rifampicin, cycloserine, and clarithromycin on the growth of M. tuberculosis and M. avium were also evaluated in in vitro assays. As a single agent, compounds 1 and 2 exhibited modest activity while compound 3 was the most effective against M. tuberculosis and M. avium. When compounds 1-3 were evaluated at lower than 50% of their inhibitory concentrations in a two-drug combination with isoniazid or rifampicin, they showed additive to synergistic interactions. This inhibitory effect was improved when each of the three compounds was tested together in a three-drug combination with two of the first-line anti-TB drugs. Compounds 1-3 also demonstrated strong synergistic interaction in combination with cycloserine and clarithromycin in inhibiting the growth of M. tuberculosis and M. avium, respectively. This study demonstrated that compounds 1-3 have potential to be developed as effective anti-TB agents with combined use.

Flavones: Six Selected Flavones and Their Related Signaling Pathways That Induce Apoptosis in Cancer

Cancer is a horrific disease that, to date, has no cure. It is caused by various factors and takes many lives. Apoptosis is a programmed cell death mechanism and if it does not function correctly in cancer cells, it can lead to severe disease. There are various signaling pathways for regulating apoptosis in cancer cells. Flavonoids are non-artificial natural bioactive compounds that are gaining attention as being capable of for inducing apoptosis in cancer cells. Among these, in this study, we focus on flavones. Flavones are a subclass of the numerous available flavonoids and possess several bioactive functions. Some of the most reported and well-known critical flavones, namely apigenin, acacetin, baicalein, luteolin, tangeretin, and wogonin, are discussed in depth in this review. Our main aim is to investigate the effects of the selected flavones on apoptosis and cell signaling pathways that contribute to death due to various types of cancers.

The CDK1/TFCP2L1/ID2 cascade offers a novel combination therapy strategy in a preclinical model of bladder cancer

Aberrant activation of embryogenesis-related molecular programs in urothelial bladder cancer (BC) is associated with stemness features related to oncogenic dedifferentiation and tumor metastasis. Recently, we reported that overexpression of transcription factor CP2-like protein-1 (TFCP2L1) and its phosphorylation at Thr177 by cyclin-dependent kinase-1 (CDK1) play key roles in regulating bladder carcinogenesis. However, the clinical relevance and therapeutic potential of this novel CDK1-TFCP2L1 molecular network remain elusive. Here, we demonstrated that inhibitor of DNA binding-2 (ID2) functions as a crucial mediator by acting as a direct repressive target of TFCP2L1 to modulate the stemness features and survival of BC cells. Low ID2 and high CDK1 expression were significantly associated with unfavorable clinical characteristics. TFCP2L1 downregulated ID2 by directly binding to its promoter region. Consistent with these findings, ectopic expression of ID2 or treatment with apigenin, a chemical activator of ID2, triggered apoptosis and impaired the proliferation, suppressed the stemness features, and reduced the invasive capacity of BC cells. Combination treatment with the specific CDK1 inhibitor RO-3306 and apigenin significantly suppressed tumor growth in an orthotopic BC xenograft animal model. This study demonstrates the biological role and clinical utility of ID2 as a direct target of the CDK1-TFCP2L1 pathway for modulating the stemness features of BC cells.

Combination therapy with apigenin, a powerful antioxidant found in plants such as parsley and camomile, and a drug that inhibits the cell cycle protein CDK1 shows promise for developing therapies for bladder cancer (BC). Switching on genes usually activated in stem cells can cause cancer, including BC. Although CDK1 was known to activate one of these genes in BC cells, no way to suppress the activation had been identified. Jinbeom Heo at University of Ulsan College of Medicine, South Korea, and coworkers investigated CDK1’s role in BC. They found that the transcription factor activated by CDK1 suppressed a protein, ID2, that suppressed stem cell-like characteristics. Simultaneously suppressing CDK1 and boosting ID2 with apigenin strongly repressed tumor growth in a mouse model. These results help point the way to developing new treatment options for BC patients.

Role of Induced Programmed Cell Death in the Chemopreventive Potential of Apigenin

The flavonoid apigenin (4′,5,7-trihydroxyflavone), which is one of the most widely distributed phytochemicals in the plant kingdom, is one of the most thoroughly investigated phenolic components. Previous studies have attributed the physiological effects of apigenin to its anti-allergic, antibacterial, antidiabetic, anti-inflammatory, antioxidant, antiviral, and blood-pressure-lowering properties, and its documented anticancer properties have been attributed to the induction of apoptosis and autophagy, the inhibition of inflammation, angiogenesis, and cell proliferation, and the regulation of cellular responses to oxidative stress and DNA damage. The most well-known mechanism for the compound’s anticancer effects in human cancer cell lines is apoptosis, followed by autophagy, and studies have also reported that apigenin induces novel cell death mechanisms, such as necroptosis and ferroptosis. Therefore, the aim of this paper is to review the therapeutic potential of apigenin as a chemopreventive agent, as well as the roles of programmed cell death mechanisms in the compound’s chemopreventive properties.

Apigenin Suppresses the Warburg Effect and Stem-like Properties in SOSP-9607 Cells by Inactivating the PI3K/Akt/mTOR Signaling Pathway

Osteosarcoma (OS) is a prevalent primary malignant bone tumor that commonly occurs in children and adolescents. Apigenin (4′,5,7-trihydroxyflavone) is one of the most researched phenolic compounds that exhibits antitumor effects in several cancers. The aim of the current study was to investigate the effect and underlying mechanisms of apigenin on OS. To address this, OS cells (SOSP-9607) were treated with different concentrations of apigenin. The proliferation, migration, invasion, stem-like properties, and Warburg effect of apigenin-treated OS cells were evaluated. Apigenin was found to suppress the proliferation of SOSP-9607 cells and inhibit epithelial-mesenchymal transition, as indicated by decreased number of migrated and invaded cells, decreased protein expression of vimentin, and increased protein expression of E-cadherin. Additionally, apigenin suppressed tumorsphere formation and reduced the proportion of SOSP-9607 cells with positive expression of the stem cell-related markers Nanog and OCT-4. Apigenin inhibited the Warburg effect in SOSP-9607 cells, as demonstrated by decreased glucose and lactic acid levels, increased citrate and ATP levels, and downregulation of GLUT1, HK1, and LDHA, which are metabolism-related enzymes related to the Warburg effect. Moreover, apigenin inhibited the phosphorylation of PI3K, Akt, and mTOR in SOSP-9607 cells. Collectively, these results indicate that apigenin suppresses the Warburg effect and stem-like properties in SOSP-9607 cells, which may be mediated by PI3K/Akt/mTOR signaling, thus, providing a novel strategy for OS treatment.

Formulation of Chitosan-Coated Apigenin Bilosomes: In Vitro Characterization, Antimicrobial and Cytotoxicity Assessment

We prepared apigenin (APG)-loaded bilosomes (BLs) and evaluated them for vesicle size, zeta-potential and encapsulation efficiency. The formulations were prepared with cholesterol (CHL), sodium deoxy cholate (SDC), Tween 80 (T80) and phosphatidylcholine (PC) using solvent evaporation method. The prepared formulations showed the optimum result was coated with much mucoadhesive polymer chitosan (CH, 0.25 and 0.5% w/v). The chitosan-coated bilosomes (CH-BLs) were further evaluated for surface morphology, drug−polymer interaction, mucoadhesion, permeation, antimicrobial activity and cell viability. The prepared APG-BLs showed nano-metric size (211 ± 2.87 nm to 433 ± 1.98 nm), polydispersibility index <0.5, negative zeta potential (−15 to −29 mV) and enhanced encapsulation efficiency (69.5 ± 0.93 to 81.9 ± 1.3%). Based on these findings, selected formulation (F2) was further coated with chitosan and showed a marked increase in vesicle size (298 ± 3.56 nm), a positive zeta potential (+17 mV), superior encapsulation efficiency (88.1 ± 1.48%) and improved drug release (69.37 ± 1.34%). Formulation F2C1 showed significantly enhanced permeation and mucoadhesion (p < 0.05) compared to formulation F2 due to the presence of CH as a mucoadhesive polymer. The presence of CH on the surfaces of BLs helps to open the tight membrane junctions and leads to enhanced permeation. A TEM study revealed non-aggregated smooth surface vesicles. The antimicrobial and cell viability assessment revealed better effects in terms of zone of inhibition and cell line assessment against two different cancer cell line. From the study, it can be concluded that APG-CHBLs could be a superior alternative to conventional delivery systems.

Development and Optimization of Hybrid Polymeric Nanoparticles of Apigenin: Physicochemical Characterization, Antioxidant Activity and Cytotoxicity Evaluation

Breast cancer is the most common cancer in females and ranked second after skin cancer. The use of natural compounds is a good alternative for the treatment of breast cancer with less toxicity than synthetic drugs. The aim of the present study is to develop and characterize hybrid Apigenin (AN) Nanoparticles (NPs) for oral delivery (AN-NPs). The hybrid AN-NPs were prepared by the self-assembly method using lecithin, chitosan and TPGS. Further, the NPs were optimized by Box-Behnken design (3-factor, 3-level). The hybrid NPs were evaluated for particle size (PS), entrapment efficiency (EE), zeta potential (ZP), and drug release. The optimized hybrid NPs (ON2), were further evaluated for solid state characterization, permeation, antioxidant, cytotoxicity and antimicrobial study. The formulation (ON2) exhibited small PS of 192.6 ± 4.2 nm, high EE 69.35 ± 1.1%, zeta potential of +36.54 mV, and sustained drug release (61.5 ± 2.5% in 24 h), as well as significantly (p < 0.05) enhanced drug permeation and antioxidant activity. The IC50 of pure AN was found to be significantly (p < 0.05) lower than the formulation (ON2). It also showed significantly greater (p < 0.05) antibacterial activity than pure AN against Bacillus subtilis and Salmonella typhimurium. From these findings, it revealed that a hybrid AN polymeric nanoparticle is a good carrier for the treatment of breast cancer.

Comparative Analysis of Phenolic Composition of Six Commercially Available Chamomile (Matricaria chamomilla L.) Extracts: Potential Biological Implications

Several phytochemical-containing herbal extracts are increasingly marketed as health-promoting products. In particular, chamomile (Matricaria recutita L.) is well known for its anti-inflammatory, analgesic, and antitumor properties. Here, we evaluated differences in chemical composition among six commercially available products and their potential impact on biological activity in human immortalized colonocytes. Our investigation encompassed: (i) preparation of dry extracts and yield evaluation; (ii) qualitative and quantitative analysis of phenol content; (iii) modulation of redox state; and (iv) bioavailability of main bioactive compounds. We demonstrated that apparently identical products showed huge heterogeneity, in terms of yield extraction, chemical composition, and antioxidant effects. All samples contained high amounts of flavonoids and cinnamic acid derivatives, but differentially concentrated in the six extracts. Depending on polyphenol content, chamomile samples possessed variable antioxidant potential, in terms of decreased radical generation and increased reduced glutathione levels. The observed effects might be ascribed to flavones (apigenin, luteolin, and their glycones) highly represented in the six extracts. Nonetheless, chamomile extracts exerted cytotoxic effects at high concentrations, suggesting that a herbal medicine is not always safe. In conclusion, due to the complexity and variability of plant matrices, studies evaluating effectiveness of chamomile should always be accompanied by preliminary characterization of phytochemical composition.

Apigenin Inhibits the Histamine-Induced Proliferation of Ovarian Cancer Cells by Downregulating ERα/ERβ Expression

Background

Apigenin (APG), a natural flavonoid, can affect the development of a variety of tumors, but its role in ovarian cancer remains unclear. There has been an increasing amount of evidence supporting the vital role played by mast cells and the bioactive mediators they release, as components of the tumor microenvironment, in the progression of ovarian cancer (OC); however, the mechanism warrants further exploration.

Methods and Results

In this study, a combination of transcriptomics analysis and application of TCGA database was performed, and we found that the expression of genes related to mast cell degranulation in ovarian cancer tissues changed remarkably. We then explored whether histamine, a major constituent of mast cell degranulation, could affect the development of ovarian cancer through immunohistochemistry analysis and cell proliferation assays. The results showed that a certain concentration of histamine promoted the proliferation of ovarian cancer cells by upregulating the expression of estrogen receptor α (ERα)/estrogen receptor β (ERβ). Additionally, we found that the inhibition of ERα or the activation of ERβ could inhibit the proliferation of ovarian cancer cells induced by histamine through real-time PCR and western blot assays. Finally, we demonstrated the attenuation effect imparted by apigenin in histamine-mediated ovarian cancer via the PI3K/AKT/mTOR signaling pathway.

Conclusion

Our research revealed that apigenin decelerated ovarian cancer development by downregulating ER-mediated PI3K/AKT/mTOR expression, thus providing evidence of its applicability as a potentially effective therapeutic agent for ovarian cancer treatment.

Functionality of apigenin as a potent antioxidant with emphasis on bioavailability, metabolism, action mechanism and in vitro and in vivo studies: A review

Numerous diseases such as cancer, diabetes, cardiovascular, neurodegenerative diseases, etc. are linked with overproduction of reactive oxygen species (ROS) and oxidative stress. Apigenin (5,7,4'-trihydroxyflavone) is a widely distributed flavonoid, responsible for antioxidant potential and chelating redox active metals. Being present as glycosides or polymers, the apigenin degrades to variable amount in the digestive tract; during processing, its activity is also reduced due to high temperature or Fe/Cu addition. Although its metabolism remains elusive, enteric absorption occurs sufficiently to reduce plasma indices of oxidant status. Delayed clearance in plasma and slow liver decomposition enhance its systematic bioavailability. Antioxidant mechanism of apigenin includes: oxidant enzymes inhibition, modulation of redox signaling pathways (NF-kB, Nrf2, MAPK, and P13/Akt), reinforcing enzymatic and nonenzymatic antioxidant, metal chelation, and free radical scavenging. DPPH, ORAC, ABTS, and FRAP are the major in vitro methods for determining the antioxidant potential of apigenin, whereas its protective effects in whole and living cells of animals are examined using in vivo studies. Due to limited information on antioxidant potential of apigenin, its in vitro and in vivo antioxidant effects are, therefore, discussed with action mechanism and interaction with the signaling pathways. This paper concludes that apigenin is a potent antioxidant compound to overcome the difficulties related to oxidative stress and other chronic diseases.

Molecular Basis of Prostate Cancer and Natural Products as Potential Chemotherapeutic and Chemopreventive Agents

Prostate cancer is the second most common malignant cancer in males. It involves a complex process driven by diverse molecular pathways that closely related to the survival, apoptosis, metabolic and metastatic characteristics of aggressive cancer. Prostate cancer can be categorized into androgen dependent prostate cancer and castration-resistant prostate cancer and cure remains elusive due to the developed resistance of the disease. Natural compounds represent an extraordinary resource of structural scaffolds with high diversity that can offer promising chemical agents for making prostate cancer less devastating and curable. Herein, those natural compounds of different origins and structures with potential cytotoxicity and/or in vivo anti-tumor activities against prostate cancer are critically reviewed and summarized according to the cellular signaling pathways they interfere. Moreover, the anti-prostate cancer efficacy of many nutrients, medicinal plant extracts and Chinese medical formulations were presented, and the future prospects for the application of these compounds and extracts were discussed. Although the failure of conventional chemotherapy as well as involved serious side effects makes natural products ideal candidates for the treatment of prostate cancer, more investigations of preclinical and even clinical studies are necessary to make use of these medical substances reasonably. Therefore, the elucidation of structure-activity relationship and precise mechanism of action, identification of novel potential molecular targets, and optimization of drug combination are essential in natural medicine research and development.

Role of Phytochemicals in Cancer Chemoprevention: Insights

Cancer is a condition where the body cells multiply in an uncontrollable manner. Chemoprevention of cancer is a broad term that describes the involvement of external agents to slow down or suppress cancer growth. Synthetic and natural compounds are found useful in cancer chemoprevention. The occurrence of global cancer type varies, depending on many factors such as environmental, lifestyle, genetic etc. Cancer is often preventable in developed countries with advanced treatment modalities, whereas it is a painful death sentence in developing and low-income countries due to the lack of modern therapies and awareness. One best practice to identify cancer control measures is to study the origin and risk factors associated with common types. Based on these factors and the health status of patients, stage, and severity of cancer, type of treatment is decided. Even though there are well-established therapies, cancer still stands as one of the major causes of death and a public health burden globally. Research shows that most cancers can be prevented, treated, or the incidence can be delayed. Phytochemicals from various medicinal plants were reported to reduce various risk factors associated with different types of cancer through their chemopreventive role. This review highlights the role of bioactive compounds or natural products from plants in the chemoprevention of cancer. There are many plant based dietary factors involved in the chemoprevention process. The review discusses the process of carcinogenesis and chemoprevention using plants and phytocompounds, with special reference to five major chemopreventive phytocompounds. The article also summarizes the important chemopreventive mechanisms and signaling molecules involved in the process. Since the role of antioxidants in chemoprevention is inevitable, an insight into plant-based antioxidant compounds that fight against this dreadful disease at various stages of carcinogenesis and disease progression is discussed. This will fill the research gap in search of chemopreventive natural compounds and encourage scientists in clinical trials of anticancer agents from plants.

Phytochemicals as Potential Chemopreventive and Chemotherapeutic Agents for Emerging Human Papillomavirus-Driven Head and Neck Cancer: Current Evidence and Future Prospects

Head and neck cancer (HNC) usually arises from squamous cells of the upper aerodigestive tract that line the mucosal surface in the head and neck region. In India, HNC is common in males, and it is the sixth most common cancer globally. Conventionally, HNC attributes to the use of alcohol or chewing tobacco. Over the past four decades, portions of human papillomavirus (HPV)-positive HNC are increasing at an alarming rate. Identification based on the etiological factors and molecular signatures demonstrates that these neoplastic lesions belong to a distinct category that differs in pathological characteristics and therapeutic response. Slow development in HNC therapeutics has resulted in a low 5-year survival rate in the last two decades. Interestingly, HPV-positive HNC has shown better outcomes following conservative treatments and immunotherapies. This raises demand to have a pre-therapy assessment of HPV status to decide the treatment strategy. Moreover, there is no HPV-specific treatment for HPV-positive HNC patients. Accumulating evidence suggests that phytochemicals are promising leads against HNC and show potential as adjuvants to chemoradiotherapy in HNC. However, only a few of these phytochemicals target HPV. The aim of the present article was to collate data on various leading phytochemicals that have shown promising results in the prevention and treatment of HNC in general and HPV-driven HNC. The review explores the possibility of using these leads against HPV-positive tumors as some of the signaling pathways are common. The review also addresses various challenges in the field that prevent their use in clinical settings.

Effects of Apigenin on the Expression of LOX-1, Bcl-2, and Bax in Hyperlipidemia Rats

We aimed to investigate the impact of apigenin on LOX-1, Bcl-2, and Bax expression in hyperlipidemia rats and explore the possible molecular pathological mechanism of apigenin in improving hyperlipidemia and preventing atherosclerosis. In hyperlipidemia models, the levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c) and the LOX-1 protein expression were apparently increased (P<0.01), while the high-density lipoprotein cholesterol (HDL-c) levels and the ratio of Bcl-2/Bax were reduced significantly (P<0.01) in comparison with the standard control group. After the treatment of apigenin, the levels of TC, TG, LDL-c, and the LOX-1 protein expression were noticeably decreased (P<0.01), while the levels of HDL-c and the Bcl-2/Bax ratio were increased (P<0.01). The intima was thickened and had protrusions in the hyperlipidemia model group compared to the normal control group. In comparison with the atherosclerosis model group, the degree of aortic lesions in the low-dose, middle-dose, high-dose groups was alleviated. Apigenin can reduce the level of blood lipid, improve hyperlipidemia, and prevent atherosclerosis in hyperlipidemia rats. The molecular mechanism may be related to inhibiting LOX-1 gene expression and increasing the Bcl-2/Bax ratio.

Cytotoxic and Apoptotic Effects of Luffa Cylindrica Leaves Extract against Acute Lymphoblastic Leukemic Stem Cells

BACKGROUND

Acute lymphoblastic leukemia (ALL) is an aggressive malignancy defined by accumulation of lymphoblasts in the bone marrow. Leukemic stem cells (LSCs) are the major cause of the recurrence and metastasis of ALL. This study aimed to develop an effective anti-cancer agent targeting these LSCs. Luffa Cylindrica (L.C.) leaves extract was selected to evaluate its effect on ALL via eradicating the LSCs as it contains many active anti-cancer flavonoids.

METHODS

Thirty-two bone marrow samples of ALL patients were used in this study. LSCs population was identified in the selected samples. Cell viability was measured by MTT assay and flow cytometry. Cell cycle, apoptosis, proliferation marker; ki-67 and colony forming assay were further analyzed.

RESULTS

This study revealed the expression of CD34+/CD38+ cells in addition to CD34+/CD38- population and the extract was effective against the two LSCs populations. MTT assay showed that treated leukemic cells exhibited significant reduction in the viable cells in a dose dependent manner with IC50 of 3 µg/µl which was then confirmed by flow cytometry. Cell cycle analysis results showed significant reduction in the percentage of cells treated with L.C. extract in both the S and G0/G1 phases, with concomitant increase in the G2/M phase. Also, L.C. extract could effectively induce apoptosis, inhibit proliferation and suppress colonogenecity of leukemic cells.

CONCLUSION

This study validated the medicinal potential of L.C. leaves extract as a promising anti-leukemic agent targeting both LSCs and blasts in ALL patients, which may be explained by the synergy found between its potent flavonoids especially apigenin, luteolin and kaempferol.

Chemopreventive Role of Apigenin against the Synergistic Carcinogenesis of Human Papillomavirus and 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone

Tobacco smoke and human papillomavirus (HPV) are both crucial causes of cancer, and their cooperative carcinogenesis has drawn more attention in recent years. Apigenin (AP), a typical flavonoid abundantly found in flowers of plants, vegetables, and fruits, has been demonstrated to exert an anti-carcinogenic effect on various types of cancer. In this study, we investigated the capability of AP against malignant transformation and DNA damage of immortalized human esophageal epithelial (SHEE) cells induced by the synergism of HPV18 and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The results indicated that the enhancement of migration, invasion, and proliferation ability of SHEE cells induced by HPV and NNK could be effectively inhibited by AP. Moreover, the levels of pyridyloxybutylated (POB)-DNA adducts induced by NNK via P450-catalyzed metabolic activation could also be significantly suppressed by AP. Further analyses on the molecular mechanism revealed that AP inhibited the synergistic carcinogenesis of NNK and HPV on SHEE cells by reducing the expression of mutp53, CDK4, Cyclin D1, and p-Rb (Ser 780), increasing caspase-3 activity, thereby arresting the cell cycle at G1 phase and promoting apoptosis of SHEE cells. We hypothesize that the decrease in NNK-induced POB-DNA adduct levels is related to the deactivation of P450 by AP, which needs to be confirmed in future studies. This study highlights that AP may be employed as a promising chemopreventive agent against cancers in smokers with an HPV infection.

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.

Flavonoids as Anticancer Agents

Flavonoids are polyphenolic compounds subdivided into 6 groups: isoflavonoids, flavanones, flavanols, flavonols, flavones and anthocyanidins found in a variety of plants. Fruits, vegetables, plant-derived beverages such as green tea, wine and cocoa-based products are the main dietary sources of flavonoids. Flavonoids have been shown to possess a wide variety of anticancer effects: they modulate reactive oxygen species (ROS)-scavenging enzyme activities, participate in arresting the cell cycle, induce apoptosis, autophagy, and suppress cancer cell proliferation and invasiveness. Flavonoids have dual action regarding ROS homeostasis—they act as antioxidants under normal conditions and are potent pro-oxidants in cancer cells triggering the apoptotic pathways and downregulating pro-inflammatory signaling pathways. This article reviews the biochemical properties and bioavailability of flavonoids, their anticancer activity and its mechanisms of action.

Apigenin Inhibits IL-6 Transcription and Suppresses Esophageal Carcinogenesis

Esophagus cancer is the seventh cause of cancer-related deaths globally. In this study, we analyzed interleukin 6 (IL-6) gene expression in human esophagus cancer patients and showed that IL-6 mRNA levels are significantly higher in tumor tissues and negatively correlated with overall survival, suggesting that IL-6 is a potential therapeutic target for esophagus cancer. We further demonstrated that apigenin, a nature flavone product of green plants, inhibited IL-6 transcription and gene expression in human esophagus cancer Eca-109 and Kyse-30 cells. Apigenin significantly and dose-dependently inhibited cell proliferation and promoted apoptosis while stimulating the cleaved PARP (poly ADP-ribose polymerase) (C-PARP) and caspase-8 expression. It suppressed VEGF (Vascular endothelial growth Factor) expression and tumor-induced angiogenesis. Pretreatment of cells with IL-6 could completely reverse apigenin-induced cellular changes. Finally, using a preclinical nude mice model subcutaneously xenografted with Eca-109 cells, we demonstrated the in vivo antitumor activity and mechanisms of apigenin. Taken together, this study revealed for the first time that apigenin is a new IL-6 transcription inhibitor and that inhibiting IL-6 transcription is one of the mechanisms by which apigenin exhibits its anticancer effects. The potential clinical applications of apigenin in treating esophagus cancer warrant further investigations.

Antimicrobial Activity of a New Class of Phosphorylated and Modified Flavonoids

The surge of resistant food pathogens is a major threat worldwide. Previous research conducted on phytochemicals has shown their antibacterial activity against pathogenic bacteria. The design of antimicrobial agents to curb pathogenic disease remains a challenge demanding critical attention. Flavonoids such as apigenin and quercetin were evaluated against Gram-positive and Gram-negative bacteria. The results indicated that the antibacterial activity of each flavonoid occurred at a different minimum inhibitory concentration. However, the antimicrobial activity results of the modified flavonoids were also reported, and it was observed that the Gram-positive bacteria were more susceptible in comparison to the Gram-negative bacteria. The cell wall structure of the Gram-positive and Gram-negative bacteria could be the main reason for the bacteria susceptibility. Modified flavonoids could be used as a suitable alternative antimicrobial agent for the treatment of infectious diseases. Our results indicated 100% inhibition of Listeria monocytogenes, Pseudomonas aeruginosa, and Aeromonas hydrophila with modified flavonoids.

Targeting the SPOCK1-snail/slug axis-mediated epithelial-to-mesenchymal transition by apigenin contributes to repression of prostate cancer metastasis

Background

Prostate cancer (PCa) is considered one of the most prevalent malignancy globally, and metastasis is a major cause of death. Apigenin (API) is a dietary flavonoid which exerts an antimetastatic effect in various cancer types. Sparc/osteonectin, cwcv, and kazal-like domains proteoglycan 1 (SPOCK1) is a crucial modulator of tumor growth and metastasis in cancers. However, the role and underlying regulatory mechanisms of SPOCK1 in the API-mediated antimetastatic effects of PCa remain unclear.

Methods

MTS, colony formation, wound-healing, and transwell assays were conducted to evaluate the effects of API on PCa cell proliferative, migratory, and invasive potentials. In vivo orthotopic bioluminescent xenograft model were employed to determine antitumor activity of API. PCa cells were transfected with either Snail-, Slug-, SPOCK1-overexpressing vector, or small hairpin (sh)SPOCK1 to determine the invasive abilities and expression levels of SPOCK1 and epithelial-to-mesenchymal transition (EMT) biomarkers in response to API treatment. Immunohistochemical (IHC) assays were carried out to evaluate the expression level of SPOCK1 in PCa xenografts and a PCa tissue array. Associations of SPOCK1 expression with clinicopathological features and prognoses of patients with PCa were analyzed by GEO or TCGA RNA-sequencing data.

Results

API significantly suppressed in vitro PCa cell proliferation, migration, and invasion and inhibited in vivo PCa tumor growth and metastasis. Moreover, survival times of animals were also prolonged after API treatment. Mechanistic studies revealed that API treatment resulted in downregulation of SPOCK1, which was accompanied by reduced expressions of mesenchymal markers and subsequent attenuation of invasive abilities of PCa cells. Overexpression of SPOCK1 in PCa xenografts resulted in significant promotion of tumor progression and relieved the anticancer activities induced by API, whereas knockdown of SPOCK1 had opposite effects. In clinical, SPOCK1 levels were higher in tumor tissues compared to non-tumor tissues, which was also significantly correlated with shorter disease-free survival in PCa patients.

Conclusions

Levels of SPOCK1 increase with the progression of human PCa which suggests that SPOCK1 may act as a prognostic marker or therapeutic target for patients with PCa. Suppression of SPOCK1-mediated EMT signaling contributes to the antiproliferative and antimetastatic activities of API in vitro and in vivo.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1247-3) contains supplementary material, which is available to authorized users.

Apigenin inhibits epithelial-mesenchymal transition of human colon cancer cells through NF-κB/Snail signaling pathway

Colon cancer is a leading cause of cancer-related deaths worldwide. The epithelial-mesenchymal transition (EMT) plays an important role in tumor metastasis of colon cancer. We first evaluated the effects of EMT-related transcription factors on the prognosis of colon cancer through analysis the data obtained from The Cancer Genome Atlas (TCGA). And then we screened a series of Chinese medicine monomers to find effect EMT inhibitors. First, Snail is a more important EMT transcription factors for colon cancer prognosis, compared with Twist and Slug. Then, we found that apigenin effectively inhibits the activity of Snail. Apigenin could inhibit the EMT, migration, and invasion of human colon cancer cells in vitro and in vivo through the NF-κB/Snail pathway. Snail is a key regulator of EMT in colon cancer and Snail inhibitor apigenin may be a therapeutic application for patients with colon cancer.

β3-Adrenoreceptor Activity Limits Apigenin Efficacy in Ewing Sarcoma Cells: A Dual Approach to Prevent Cell Survival

Ewing Sarcoma (ES) is an aggressive paediatric tumour where oxidative stress and antioxidants play a central role in cancer therapy response. Inhibiting antioxidants expression, while at the same time elevating intracellular reactive oxygen species (ROS) levels, have been proposed as a valid strategy to overcome ES cancer progression. Flavonoid intake can affect free radical and nutritional status in children receiving cancer treatment, but it is not clear if it can arrest cancer progression. In particular, apigenin may enhance the effect of cytotoxic chemotherapy by inducing cell growth arrest, apoptosis, and by altering the redox state of the cells. Little is known about the use of apigenin in paediatric cancer. Recently, β3-adrenergic receptor (β3-AR) antagonism has been proposed as a possible strategy in cancer therapy for its ability to induce apoptosis by increasing intracellular levels of ROS. In this study we show that apigenin induces cell death in ES cells by modulating apoptosis, but not increasing ROS content. Since ES cells are susceptible to an increased oxidative stress to reduce cell viability, here we demonstrate that administration of β3-ARs antagonist, SR59230A, improves the apigenin effect on cell death, identifying β3-AR as a potential discriminating factor that could address the use of apigenin in ES.

A Comprehensive Assessment of Apigenin as an Antiproliferative, Proapoptotic, Antiangiogenic and Immunomodulatory Phytocompound

Apigenin (4′,5,7-trihydroxyflavone) (Api) is an important component of the human diet, being distributed in a wide number of fruits, vegetables and herbs with the most important sources being represented by chamomile, celery, celeriac and parsley. This study was designed for a comprehensive evaluation of Api as an antiproliferative, proapoptotic, antiangiogenic and immunomodulatory phytocompound. In the set experimental conditions, Api presents antiproliferative activity against the A375 human melanoma cell line, a G2/M arrest of the cell cycle and cytotoxic events as revealed by the lactate dehydrogenase release. Caspase 3 activity was inversely proportional to the Api tested doses, namely 30 μM and 60 μM. Phenomena of early apoptosis, late apoptosis and necrosis following incubation with Api were detected by Annexin V-PI double staining. The flavone interfered with the mitochondrial respiration by modulating both glycolytic and mitochondrial pathways for ATP production. The metabolic activity of human dendritic cells (DCs) under LPS-activation was clearly attenuated by stimulation with high concentrations of Api. Il-6 and IL-10 secretion was almost completely blocked while TNF alpha secretion was reduced by about 60%. Api elicited antiangiogenic properties in a dose-dependent manner. Both concentrations of Api influenced tumour cell growth and migration, inducing a limited tumour area inside the application ring, associated with a low number of capillaries.

Effects of Apigenin and Apigenin- Loaded Nanogel on Induction of Apoptosis in Human Chronic Myeloid Leukemia Cells

Background:

Diet plays an important role in cancer prevention. Apigenin, a flavonoid with thechemical formula C15H10O5 , is abundantly present in vegetables. Vegetarian foods containing flavonoids are rich sources of bioactive compounds. Flavonoids have been utilized in herbal treatment. Nanogels are drug delivery systems based on polymers and are used in tissue engineering and for drug delivery. This study was conducted to compare the effects of apigenin and a nanodrug on the viability of the K562 cell line of chronic myeloid leukemia at different durations under laboratory conditions.

Materials and Methods:

Chitosan was first dissolved in 1% acetic acid, and ethylene dichloride EDC and NHS were added to the solution. Then, the nanodrug was prepared by loading apigenin into stearate–chitosan nanogel (scs nanogel), and its physical and morphological characteristics were evaluated by TEM, DLS, and FTIR. Trypan blue staining, MTT assay, and flow cytometry were used to analyze the effects of various concentrations of apigenin and apigenin-loaded chitosan–stearate nanogel (APG–SCS) at 24, 48, and 72 h after they were applied to the K562 cell line.

Results:

The diameter of the nanodrug particles was measured using DLS and confirmed by TEM. The K562 cells treated with APG–SCS and with apigenin exhibited significant differences compared with the control (P < 0.05). Apoptosis was detected by flow cytometry.

Conclusion:

This study showed that the toxic effects of apigenin and the nanodrug improved with increasing concentrations and exposure durations compared to those in the control.The toxic effect of apigenin loaded into the stearate-chitosan nanogel was greater than apigenin, and the toxic effects of both materials were greater compared to the control under laboratory conditions.

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.