Apigenin--strong cytostatic and anti-angiogenic action in vitro contrasted by lack of efficacy in vivo

Bioenergetic alteration in gastrointestinal cancers: The good, the bad and the ugly

Cancer cells exhibit metabolic reprogramming and bioenergetic alteration, utilizing glucose fermentation for energy production, known as the Warburg effect. However, there are a lack of comprehensive reviews summarizing the metabolic reprogramming, bioenergetic alteration, and their oncogenetic links in gastrointestinal (GI) cancers. Furthermore, the efficacy and treatment potential of emerging anticancer drugs targeting these alterations in GI cancers require further evaluation. This review highlights the interplay between aerobic glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation (OXPHOS) in cancer cells, as well as hypotheses on the molecular mechanisms that trigger this alteration. The role of hypoxia-inducible transcription factors, tumor suppressors, and the oncogenetic link between hypoxia-related enzymes, bioenergetic changes, and GI cancer are also discussed. This review emphasizes the potential of targeting bioenergetic regulators for anti-cancer therapy, particularly for GI cancers. Emphasizing the potential of targeting bioenergetic regulators for GI cancer therapy, the review categorizes these regulators into aerobic glycolysis/ lactate biosynthesis/transportation and TCA cycle/coupled OXPHOS. We also detail various anti-cancer drugs and strategies that have produced pre-clinical and/or clinical evidence in treating GI cancers, as well as the challenges posed by these drugs. Here we highlight that understanding dysregulated cancer cell bioenergetics is critical for effective treatments, although the diverse metabolic patterns present challenges for targeted therapies. Further research is needed to comprehend the specific mechanisms of inhibiting bioenergetic enzymes, address side effects, and leverage high-throughput multi-omics and spatial omics to gain insights into cancer cell heterogeneity for targeted bioenergetic therapies.

Pharmacological Properties of 4′, 5, 7-Trihydroxyflavone (Apigenin) and Its Impact on Cell Signaling Pathways

Plant bioactive compounds, particularly apigenin, have therapeutic potential and functional activities that aid in the prevention of infectious diseases in many mammalian bodies and promote tumor growth inhibition. Apigenin is a flavonoid with low toxicities and numerous bioactive properties due to which it has been considered as a traditional medicine for decades. Apigenin shows synergistic effects in combined treatment with sorafenib in the HepG2 human cell line (HCC) in less time and statistically reduces the viability of tumor cells, migration, gene expression and apoptosis. The combination of anti-cancerous drugs with apigenin has shown health promoting potential against various cancers. It can prevent cell mobility, maintain the cell cycle and stimulate the immune system. Apigenin also suppresses mTOR activity and raises the UVB-induced phagocytosis and reduces the cancerous cell proliferation and growth. It also has a high safety threshold, and active (anti-cancer) doses can be gained by consuming a vegetable and apigenin rich diet. Apigenin also boosted autophagosome formation, decreased cell proliferation and activated autophagy by preventing the activity of the PI3K pathway, specifically in HepG2 cells. This paper provides an updated overview of apigenin’s beneficial anti-inflammatory, antibacterial, antiviral, and anticancer effects, making it a step in the right direction for therapeutics. This study also critically analyzed the effect of apigenin on cancer cell signaling pathways including the PI3K/AKT/MTOR, JAK/STAT, NF-κB and ERK/MAPK pathways.

Cancer Therapy Challenge: It Is Time to Look in the "St. Patrick's Well" of the Nature

Cancer still remains a leading cause of death despite improvements in diagnosis, drug discovery and therapy approach. Therefore, there is a strong need to improve methodologies as well as to increase the number of approaches available. Natural compounds of different origins (i.e., from fungi, plants, microbes, etc.) represent an interesting approach for fighting cancer. In particular, synergistic strategies may represent an intriguing approach, combining natural compounds with classic chemotherapeutic drugs to increase therapeutic efficacy and lower the required drug concentrations. In this review, we focus primarily on those natural compounds utilized in synergistic approached to treating cancer, with particular attention to those compounds that have gained the most research interest.

An In Vitro-In Vivo Evaluation of the Antiproliferative and Antiangiogenic Effect of Flavone Apigenin against SK-MEL-24 Human Melanoma Cell Line

One of the most important class of natural compounds with successful preclinical results in the management of cancer is the flavonoids. Due to the plethora of biological activities, apigenin (4',5,7 trihydroxyflavone) is a main representant of the flavone subclass. Although the antiproliferative and antiangiogenic effects of apigenin were studied on a significant number of human and murine melanoma cell lines, in order to complete the data existing in the literature, the aim of this study is to evaluate the in vitro effect of apigenin on SK-MEL-24 human melanoma cell line as well as in vivo on tumor angiogenesis using the aforementioned cell line on the chorioallantoic membrane assay. Results have shown that in the range of tested doses, the phytocompound presents significant antiproliferative, cytotoxic, and antimigratory potential at 30 μM, respectively, 60 μM. Moreover, the phytocompound in both tested concentrations limited melanoma cell growth and migration and induced a reduced angiogenic reaction limiting melanoma cell development.

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.

Development and evaluation of injectable nanosized drug delivery systems for apigenin

The purpose of this study was to develop different injectable nanosized drug delivery systems (NDDSs) i.e. liposome, lipid nanocapsule (LNC) and polymeric nanocapsule (PNC) encapsulating apigenin (AG) and compare their characteristics to identify the nanovector(s) that can deliver the largest quantity of AG while being biocompatible. Two liposomes with different surface characteristics (cationic and anionic), a LNC and a PNC were prepared. A novel tocopherol modified poly(ethylene glycol)-b-polyphosphate block-copolymer was used for the first time for the PNC preparation. The NDDSs were compared by their physicochemical characteristics, AG release, storage stability, stability in serum, complement consumption and toxicity against a human macrovascular endothelial cell line (EAhy926). The diameter and surface charge of the NDDSs were comparable with previously reported injectable nanocarriers. The NDDSs showed good encapsulation efficiency and drug loading. Moreover, the NDDSs were stable during storage and in fetal bovine serum for extended periods, showed low complement consumption and were non-toxic to EAhy926 cells up to high concentrations. Therefore, they can be considered as potential injectable nanocarriers of AG. Due to less pronounced burst effect and extended release characteristics, the nanocapsules could be favorable approaches for achieving prolonged pharmacological activity of AG using injectable NDDS.

New Insights toward Colorectal Cancer Chemotherapy Using Natural Bioactive Compounds

Combination therapy consists in the simultaneous administration of a conventional chemotherapy drug (or sometimes, a radiotherapy protocol) together with one or more natural bioactives (usually from plant or fungal origin) of small molecular weight. This combination of anticancer drugs may be applied to cell cultures of tumor cells, or to an animal model for a cancer type (or its xenograft), or to a clinical trial in patients. In this review, we summarize current knowledge describing diverse synergistic effects on colorectal cancer cell cultures, animal models, and clinical trials of various natural bioactives (stilbenes, flavonoids, terpenes, curcumin, and other structural families), which may be important with respect to diminish final doses of the chemotherapy drug, although maintaining its biological effect. This is important as these approaches may help reduce side effects in patients under conventional chemotherapy. Also, these molecules may exerts their synergistic effects via different cell cycle pathways, including different ones to those responsible of resistance phenotypes: transcription factors, membrane receptors, adhesion and structural molecules, cell cycle regulatory components, and apoptosis pathways.

Anticancer potential of the histone deacetylase inhibitor-like effects of flavones, a subclass of polyphenolic compounds: a review

Cancer is characterized by the uncontrolled division of cells, followed by their invasion to other tissues. These kinds of cellular abnormalities arise as a result of the accumulation of genetic mutations or epigenetic alterations. Targeting genetic mutations by drugs is a conventional treatment approach. Nowadays, the development and use of epigenetic drugs are burgeoning, owing to the advancements in epigenetic research. The therapeutic intervention of cancer development by histone deacetylase inhibitors (HDACIs) holds promise for helping to control the disease, but their nonspecific functions impose certain side effects. Therefore, the search for more HDACIs becomes essential. Plentiful literature on the versatility of dietary components including flavones, a class of the flavonoid group, has already established these compounds to be better anticancer agents. The present review focuses on the significance of flavones with regard to their HDACI-mimicking effects as suggested by the recent evidences. The review also proposes an in-depth screening of flavones in future studies, in the hope that flavones may provide a better alternative to synthetic HDACIs.

Antibacterial Attributes of Apigenin, Isolated from Portulaca oleracea L

The flavonoid apigenin was isolated from aerial part of P. oleracea L. The dried sample of plant was powdered and subjected to soxhlet extractor by adding 80 mL of ethanol : water (70 : 30). The extract was centrifuged at 11000 rpm for 30 min; supernatant was taken for further use. The fraction was concentrated and subjected to PTLC. The R_f value of isolated apigenin was calculated (0.82). Purified material was also subjected to its IR spectra, LC-MS, NMR, and HPLC for structural elucidation. The apigenin so-obtained was subjected to antibacterial activity on five pathogenic bacterial strains like Pseudomonas aeruginosa, Salmonella typhimurium, Proteus mirabilis, Klebsiella pneumoniae and Enterobacter aerogenes; among all the bacterial strains, Salmonella typhimurium (17.36 ± 0.18) and Proteus mirabilis (19.12 ± 0.01) have shown maximum diameter of inhibition zone for flavonoid and remaining bacterial strains have shown moderate diameter of inhibition zone when compared with control values 14.56 ± 0.21 and 11.68 ± 0.13, respectively. The minimum inhibitory concentration (MIC) of the flavonoid isolated from P. oleracea L. was tested at the concentration ranging from undiluted sample to 10 mg per mL of concentration. The minimum inhibition concentration (MIC) for the flavonoid for all tested bacterial strains was found to be >4 mg per mL. Hence, the apigenin has antibacterial property and can be used to develop antibacterial drugs.

Effects of food formulation and thermal processing on flavones in celery and chamomile

Flavones isolated from celery varied in their stability and susceptibility to deglycosylation during thermal processing at pH 3, 5, or 7. Apigenin 7-O-apiosylglucoside was converted to apigenin 7-O-glucoside when heated at pH 3 and 100°C. Apigenin 7-O-glucoside showed little conversion or degradation at any pH after 5h at 100°C. Apigenin, luteolin, and chrysoeriol were most stable at pH 3 but progressively degraded at pH 5 or 7. Chamomile and celery were used to test the effects of glycosidase-rich foods and thermal processing on the stability of flavone glycosides. Apigenin 7-O-glucoside in chamomile extract was readily converted to apigenin aglycone after combination with almond, flax seed, or chickpea flour. Apigenin 7-O-apiosylglucoside in celery leaves was resistant to conversion by β-glucosidase-rich ingredients, but was converted to apigenin 7-O-glucoside at pH 2.7 when processed at 100°C for 90min and could then be further deglycosylated when mixed with almond or flax seed. Thus, combinations of acid hydrolysis and glycosidase enzymes in almond and flax seed were most effective for developing a flavone-rich, high aglycone food ingredient from celery.

Endogenous enzymes, heat, and pH affect flavone profiles in parsley (Petroselinum crispum var. neapolitanum) and celery (Apium graveolens) during juice processing

Flavones are abundant in parsley and celery and possess unique anti-inflammatory properties in vitro and in animal models. However, their bioavailability and bioactivity depend in part on the conjugation of sugars and other functional groups to the flavone core. The effects of juice extraction, acidification, thermal processing, and endogenous enzymes on flavone glycoside profile and concentration in both parsley and celery were investigated. Parsley yielded 72% juice with 64% of the total flavones extracted, whereas celery yielded 79% juice with 56% of flavones extracted. Fresh parsley juice averaged 281 mg flavones/100 g and fresh celery juice, 28.5 mg/100 g. Flavones in steamed parsley and celery were predominantly malonyl apiosylglucoside conjugates, whereas those in fresh samples were primarily apiosylglucoside conjugates; this was apparently the result of endogenous malonyl esterases. Acidification and thermal processing of celery converted flavone apiosylglucosides to flavone glucosides, which may affect the intestinal absorption and metabolism of these compounds.

Apigenin: a promising molecule for cancer prevention

Apigenin, a naturally occurring plant flavone, abundantly present in common fruits and vegetables, is recognized as a bioactive flavonoid shown to possess anti-inflammatory, antioxidant and anticancer properties. Epidemiologic studies suggest that a diet rich in flavones is related to a decreased risk of certain cancers, particularly cancers of the breast, digestive tract, skin, prostate and certain hematological malignancies. It has been suggested that apigenin may be protective in other diseases that are affected by oxidative process, such as cardiovascular and neurological disorders, although more research needs to be conducted in this regard. Human clinical trials examining the effect of supplementation of apigenin on disease prevention have not been conducted, although there is considerable potential for apigenin to be developed as a cancer chemopreventive agent.

Update on uses and properties of citrus flavonoids: new findings in anticancer, cardiovascular, and anti-inflammatory activity

Significantly, much of the activity of Citrus flavonoids appears to impact blood and microvascular endothelial cells, and it is not surprising that the two main areas of research on the biological actions of Citrus flavonoids have been inflammation and cancer. Epidemiological and animal studies point to a possible protective effect of flavonoids against cardiovascular diseases and some types of cancer. Although flavonoids have been studied for about 50 years, the cellular mechanisms involved in their biological action are still not completely known. Many of the pharmacological properties of Citrus flavonoids can be linked to the abilities of these compounds to inhibit enzymes involved in cell activation. Attempts to control cancer involve a variety of means, including the use of suppressing, blocking, and transforming agents. Suppressing agents prevent the formation of new cancers from procarcinogens, and blocking agents prevent carcinogenic compounds from reaching critical initiation sites, while transformation agents act to facilitate the metabolism of carcinogenic components into less toxic materials or prevent their biological actions. Flavonoids can act as all three types of agent. Many epidemiological studies have shown that regular flavonoid intake is associated with a reduced risk of cardiovascular diseases. In coronary heart disease, the protective effects of flavonoids include mainly antithrombotic, anti-ischemic, anti-oxidant, and vasorelaxant. It is suggested that flavonoids decrease the risk of coronary heart disease by three major actions: improving coronary vasodilatation, decreasing the ability of platelets in the blood to clot, and preventing low-density lipoproteins (LDLs) from oxidizing. The anti-inflammatory properties of the Citrus flavonoids have also been studied. Several key studies have shown that the anti-inflammatory properties of Citrus flavonoids are due to its inhibition of the synthesis and biological activities of different pro-inflammatory mediators, mainly the arachidonic acid derivatives, prostaglandins E 2, F 2, and thromboxane A 2. The anti-oxidant and anti-inflammatory properties of Citrus flavonoids can play a key role in their activity against several degenerative diseases and particularly brain diseases. The most abundant Citrus flavonoids are flavanones, such as hesperidin, naringin, or neohesperidin. However, generally, the flavones, such as diosmin, apigenin, or luteolin, exhibit higher biological activity, even though they occur in much lower concentrations. Diosmin and rutin have a demonstrated activity as a venotonic agent and are present in several pharmaceutical products. Apigenin and their glucosides have been shown a good anti-inflammatory activity without the side effects of other anti-inflammatory products. In this paper, we discuss the relation between each structural factor of Citrus flavonoids and the anticancer, anti-inflammatory, and cardiovascular protection activity of Citrus flavonoids and their role in degenerative diseases.

Up-regulation of insulin-like growth factor binding protein-3 by apigenin leads to growth inhibition and apoptosis of 22Rv1 xenograft in athymic nude mice

Epidemiological studies suggest that increased intake of fruits and vegetables may be associated with a reduced risk of prostate cancer. Apigenin (4', 5, 7,-trihydroxyflavone), a common dietary flavonoid abundantly present in fruits and vegetables, has shown remarkable anti-proliferative effects against various malignant cell lines. However, the mechanisms underlying these effects remain to be elucidated. We investigated the in vivo growth inhibitory effects of apigenin on androgen-sensitive human prostate carcinoma 22Rv1 tumor xenograft subcutaneously implanted in athymic male nude mice. Apigenin was administered to mice by gavage at doses of 20 and 50 mug/mouse/day in 0.2 ml of a vehicle containing 0.5% methyl cellulose and 0.025% Tween 20 in two different protocols. In the first protocol, apigenin was administered for 2 wk before inoculation of tumor and was continued for 8 wk, resulting in significant inhibition of tumor volume by 44 and 59% (P<0.002 and 0.0001), and wet weight of tumor by 41 and 53% (P<0.05), respectively. In the second protocol, administration of apigenin began 2 wk after tumor inoculation and continued for 8 wk; tumor volume and wet weights of tumor were reduced by 39 and 53% (P<0.01 and 0.002) and 31 and 42% (P<0.05), respectively. The tumor inhibitory effect of apigenin was more pronounced in the first protocol of extended treatment, which was associated with increased accumulation of human IGFBP-3 in mouse serum along with significant increase in IGFBP-3 mRNA and protein expression in tumor xenograft. Apigenin intake by these mice also resulted in simultaneous decrease in serum IGF-I levels and induction of apoptosis in tumor xenograft. Importantly, tumor growth inhibition, induction of apoptosis, and accumulation of IGFBP-3 correlated with increasing serum and tumor apigenin levels. In both studies, animals did not exhibit any signs of toxicity or reduced food consumption. In cell culture studies, apigenin treatment resulted in cell growth inhibition and induction of apoptosis, which correlated with increased accumulation of IGFBP-3 in culture medium and cell lysate. These effects were associated with significant reduction in IGF-I secretion; inhibition of IGF-I-induced cell cycle progression and insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation, along with an increase in sub-G1 peak by apigenin. Further, treatment of cells with IGFBP-3 antisense oligonucleotide reversed these effects and attenuated apigenin-mediated inhibition of IRS-1 phosphorylation conferring inhibitory effects of apigenin on IGF-signaling. This study presents the first evidence that the in vitro and in vivo growth inhibitory effects of apigenin involve modulation of IGF-axis signaling in prostate cancer.

Protective role of Apigenin on the status of lipid peroxidation and antioxidant defense against hepatocarcinogenesis in Wistar albino rats

Apigenin, a dietary plant derived flavone subclass of flavonoid is expected to play a role in cancer chemoprevention and cancer chemotherapy. Here we designed our experiment to establish whether treatment of apigenin (25 mg/kg body weight) for 14 consecutive days to (N-nitrosodiethylamine) DEN induced (200 mg/kg body weight; by single ip. injection) and phenobarbital promoted (0.05% through drinking water for 14 successive weeks) rats provide protection against the oxidative stress caused by the carcinogen. The level of lipid peroxidation (LPO) markedly increased in carcinogen administered animals, which was brought back to near normal by apigenin treatment. In contrast the activities/levels of the antioxidant status both in liver and kidney were decreased in carcinogen administered animals, which was recouped back to near normal upon apigenin administration. From our findings we concluded that apigenin prevents LPO and protects antioxidant system in DEN induced and phenobarbital promoted hepatocellular carcinogenesis.

Modulation of lipopolysaccharide-induced proinflammatory cytokine production in vitro and in vivo by the herbal constituents apigenin (chamomile), ginsenoside Rb(1) (ginseng) and parthenolide (feverfew)

Dietary supplements are not subject to the same pre-market approval as conventional drugs, thus the true efficacy and, in cases, safety of these products is not known. The objective of this study was to evaluate the potential anti-inflammatory properties of three herbal constituents, apigenin (chamomile), ginsenoside Rb(1) (ginseng) and parthenolide (feverfew) on lipopolysaccaharide (LPS)-induced proinflammatory cytokine production, and to determine if effects in cell culture could predict results in an intact animal model. Murine macrophage cells and mice were treated with the stimulant LPS and herbal constituents, and resultant culture supernatant and serum, respectively, were evaluated for interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha by ELISA. All three constituents inhibited LPS-induced IL-6 and/or TNF-alpha production in culture. Inhibition of these two cytokines was observed in mice, but did not display the same patterns of inhibition as cell culture data. The results suggest that all three constituents possessed anti-inflammatory properties, but that cell culture data can only be used to approximate potential effects in animals, and must be confirmed using appropriate animal models.