Luteolin as a glycolysis inhibitor offers superior efficacy and lesser toxicity of doxorubicin in breast cancer cells

Photoactive metabolite mediated photodynamic therapy of Rhabdomyosarcoma cell lines using medicinal plants and Doxorubicin co-treatments

BACKGROUND

Medicinal plant-mediated combinational therapies have gained importance globally due to minimal side effects and enhanced treatment outcomes compared to single-drug modalities. We aimed to analyze the cytotoxic potential of each conventional treatment i.e., photodynamic therapy (PDT), chemotherapy (doxorubicin hydrochloride; Dox-HCl) with or without various concentrations of medicinal plant extracts (PE) on soft tissue cancer Rhabdomyosarcoma (RD) cell line.

METHODS

The Rhabdomyosarcoma (RD) cell line was cultured and treated with Photosensitizer (Photosense (AlPc4)), Chemo (Dox-HCl), and their combinations with different concentrations of each plant extract i.e., Thuja occidentalis, Moringa oleifera, Solanum surattense. For the source of illumination, a Diode laser (λ = 630 nm ± 1 nm, Pmax = 1.5 mW) was used. Photosensitizer uptake time (∼ 45 min) was optimized through spectrophotometric measurements (absorption spectroscopy). Drug response of each treatment arm was assessed post 24 h of administration using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5- 5-diphenyl-2 H- tetrazolium bromide (MTT) assay.

RESULTS

PE-mediated Chemo-Photodynamic therapy (PDT) exhibited synergistic effects (CI < 1). Moreover, Rhabdomyosarcoma culture pretreated with various plant extracts for 24 h exhibited significant inhibition of cell viability however most effective outcomes were shown by low and high doses of Moringa oleifera compared to other plant extracts. Post low doses treated culture with all plant extracts followed by PDT came up with more effectiveness when compared to all di-therapy treatments.

CONCLUSION

The general outcome of this work shows that the ethanolic plant extracts (higher doses) promote the death of cancerous cells in a dose-dependent way and combining Dox-HCl and photo-mediated photodynamic therapy can yield better therapeutic outcomes.

Luteolin, a flavone ingredient: Anticancer mechanisms, combined medication strategy, pharmacokinetics, clinical trials, and pharmaceutical researches

Current pharmaceutical research is energetically excavating the pharmacotherapeutic role of herb-derived ingredients in multiple malignancies' targeting. Luteolin is one of the major phytochemical components that exist in various traditional Chinese medicine or medical herbs. Mounting evidence reveals that this phytoconstituent endows prominent therapeutic actions on diverse malignancies, with the underlying mechanisms, combined medication strategy, and pharmacokinetics elusive. Additionally, the clinical trial and pharmaceutical investigation of luteolin remain to be systematically delineated. The present review aimed to comprehensively summarize the updated information with regard to the anticancer mechanism, combined medication strategies, pharmacokinetics, clinical trials, and pharmaceutical researches of luteolin. The survey corroborates that luteolin executes multiple anticancer effects mainly by dampening proliferation and invasion, spurring apoptosis, intercepting cell cycle, regulating autophagy and immune, inhibiting inflammatory response, inducing ferroptosis, and pyroptosis, as well as epigenetic modification, and so on. Luteolin can be applied in combination with numerous clinical anticarcinogens and natural ingredients to synergistically enhance the therapeutic efficacy of malignancies while reducing adverse reactions. For pharmacokinetics, luteolin has an unfavorable oral bioavailability, it mainly persists in plasma as glucuronides and sulfate-conjugates after being metabolized, and is regarded as potent inhibitors of OATP1B1 and OATP2B1, which may be messed with the pharmacokinetic interactions of miscellaneous bioactive substances in vivo. Besides, pharmaceutical innovation of luteolin with leading-edge drug delivery systems such as host-guest complexes, nanoparticles, liposomes, nanoemulsion, microspheres, and hydrogels are beneficial to the exploitation of luteolin-based products. Moreover, some registered clinical trials on luteolin are being carried out, yet clinical research on anticancer effects should be continuously promoted.

Application of Luteolin in Neoplasms and Nonneoplastic Diseases

Researchers are amazed at the multitude of biological effects of 3',4',5,7-tetrahydroxyflavone, more commonly known as luteolin, as it simultaneously has antioxidant and pro-oxidant, as well as antimicrobial, anti-inflammatory, and cancer-preventive, properties. The anticancer properties of luteolin constitute a mosaic of pathways due to which this flavonoid influences cancer cells. Not only is it able to induce apoptosis and inhibit cancer cell proliferation, but it also suppresses angiogenesis and metastasis. Moreover, luteolin succeeds in cancer cell sensitization to therapeutically induced cytotoxicity. Nevertheless, apart from its promising role in chemoprevention, luteolin exhibits numerous potential utilizations in patients with conditions other than neoplasms, which include inflammatory skin diseases, diabetes mellitus, and COVID-19. This review aims to present the multidimensionality of the luteolin's impact on both neoplastic and nonneoplastic diseases. When it comes to neoplasms, we intend to describe the complexity of the molecular mechanisms that underlay luteolin's anticancer effectiveness, as well as to prove the usefulness of integrating this flavonoid in cancer therapy via the analysis of recent research on breast, colon, and lung cancer. Regarding nonneoplastic diseases, this review aims to emphasize the importance of researching the potential of luteolin in areas such as diabetology, virology, and dermatology as it summarizes the most important discoveries in those fields regarding its application.

Metabolomics Insights into the Differential Response of Breast Cancer Cells to the Phenolic Compounds Hydroxytyrosol and Luteolin

The aim of this study was to investigate the effects of two phenolic compounds found in extra virgin olive oil, hydroxytyrosol (HT) and luteolin (LUT), on the metabolism of breast cancer (BC) cells of different molecular subtypes. An untargeted metabolomics approach was used to characterize the metabolic responses of both triple-negative MDA-MB-231 cells and hormone-responsive MCF-7 cells to treatment with these phenols. Notably, while some effects were common across both cell types, others were dependent on the cell type, highlighting the importance of cellular metabolic phenotype. Common effects included stimulation of mitochondrial metabolism, acetate production, and formate overflow. On the other hand, glucose metabolism and lactate production were differentially modulated. HT and LUT appeared to inhibit glycolysis and promote the hexosamine biosynthetic pathway in MDA-MB-231 cells, while MCF-7 cells exhibited higher glycolytic flux when treated with phenolic compounds. Another significant difference was observed in lipid metabolism. Treated MDA-MB-231 cells displayed increased levels of neutral lipids (likely stored in cytosolic droplets), whereas treatment of MCF-7 cells with HT led to a decrease in triacylglycerols. Additionally, glutathione levels increased in MDA-MB-231 cells treated with HT or LUT, as well as in MCF-7 cells treated with LUT. In contrast, in HT-treated MCF-7 cells, glutathione levels decreased, indicating different modulation of cellular redox status. Overall, this work provides new insights into the metabolic impact of HT and LUT on different BC cell subtypes, paving the way for a better understanding of the nutritional relevance of these phenolic compounds in the context of BC prevention and management.

Chemotherapeutics activities of dietary phytoestrogens against prostate cancer: From observational to clinical studies

Prostate cancer remains one of the most frequent and deadliest malignancies in males, where the rate of disease progression is closely associated with the type of dietary intake, specifically Western-style diet. Indeed intake of the Asian diet, which contains abundant phytoestrogens, is inversely correlated with a higher risk of prostate cancer, suggesting a chemoprotective effect of phytoestrogen against cancer progression. Although the role of phytoestrogens in cancer treatment was well documented, their impact on prostate cancer is not well understood. Therefore, the present review discusses the possible chemopreventive effect of phytoestrogens, emphasizing their efficacy at the different stages of carcinogenesis. Furthermore, phytoestrogens provide a cytoprotective effect in conventional chemotherapy and enhance chemosensitivity to tumor cells, which have also been discussed. This compilation provides a solid basis for future research on phytoestrogens as a promising avenue for anticancer drug development and also recommends these beneficiary compounds in the daily diet to manage and prevent prostate cancer.

Influence of Olive Oil and Its Components on Breast Cancer: Molecular Mechanisms

Breast cancer is the most frequent malignant neoplasia and a leading cause of mortality in women worldwide. The Mediterranean diet has been proposed as a healthy dietary pattern with protective effects in several chronic diseases, including breast cancer. This diet is characterized by the consumption of abundant plant foods and olive oil as the principal source of fat, which is considered one of the main components with potential antioxidant, anti-inflammatory and anticancer effects. Extra-virgin olive oil (EVOO) has several bioactive compounds, mainly including monounsaturated fatty acids, triterpenes and polyphenols, such as phenolic alcohols (e.g., hydroxytyrosol), secoiridoids (e.g., oleuropein and oleocanthal), lignans (e.g., pinoresinol) or flavonoids (e.g., luteolin). While epidemiological evidence is still limited, experimental in vivo and in vitro data have shown a protective effect of this oil and its compounds on mammary carcinogenesis. Such effects account through complex and multiple mechanisms, including changes in epigenetics, transcriptome and protein expression that modulate several signaling pathways. Molecular targets of EVOO compounds have a role in the acquisition of cancer hallmarks. Although further research is needed to elucidate their beneficial effects on human prevention and progression of the disease, evidence points to EVOO in the context of the Mediterranean diet as a heathy choice, while EVOO components may be promising adjuvants in anticancer strategies.

Transcriptional regulation of flavonoid biosynthesis in Artemisia annua by AaYABBY5

Artemisia annua is a medicinal plant rich in terpenes and flavonoids with useful biological activities such as antioxidant, anticancer, and antimalarial activities. The transcriptional regulation of flavonoid biosynthesis in A. annua has not been well-studied. In this study, we identified a YABBY family transcription factor, AaYABBY5, as a positive regulator of anthocyanin and total flavonoid contents in A. annua. AaYABBY5 was selected based on its similar expression pattern to the phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and flavonol synthase (FLS) genes. A transient dual-luciferase assay in Nicotiana bethamiana with the AaYABBY5 effector showed a significant increase in the activity of the downstream LUC gene, with reporters AaPAL, AaCHS, AaCHI, and AaUFGT. The yeast one-hybrid system further confirmed the direct activation of these promoters by AaYABBY5. Gene expression analysis of stably transformed AaYABBY5 overexpression, AaYABBY5 antisense, and control plants revealed a significant increase in the expression of AaPAL, AaCHS, AaCHI, AaFLS, AaFSII, AaLDOX, and AaUFGT in AaYABBY5 overexpression plants. Moreover, their total flavonoid content and anthocyanin content were also found to increase. AaYABBY5 antisense plants showed a significant decrease in the expression of flavonoid biosynthetic genes, as well as a decrease in anthocyanin and total flavonoid contents. In addition, phenotypic analysis revealed deep purple-pigmented stems, an increase in the leaf lamina size, and higher trichome densities in AaYABBY5 overexpression plants. Together, these data proved that AaYABBY5 is a positive regulator of flavonoid biosynthesis in A. annua. Our study provides candidate transcription factors for the improvement of flavonoid concentrations in A. annua and can be further extended to elucidate its mechanism of regulating trichome development.

Biochemical and histological alterations of doxorubicin-induced neurotoxicity in rats: Protective role of luteolin

Doxorubicin (DOX) is a chemotherapeutic drug used in the treatment of various cancer types. DOX toxic side effects include neuronopathy and memory deficits. We investigated the effect of the antioxidant luteolin (LUT: 50 or 100 mg/kg; per os) on DOX (2 mg/kg; intraperitoneal)-induced oxidative stress (OS), inflammation, and apoptosis in the brain of Wistar rats for 14 days. We observed that LUT reduced DOX-mediated increase in OS biomarkers-catalase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase. LUT increased glutathione and total sulphydryl levels and alleviated DOX-induced increases in the levels of reactive oxygen and nitrogen species, lipid peroxidation, myeloperoxidase, nitric oxide, tumor necrosis factor-α, and interleukin-1β (IL-1β). Additionally, LUT suppressed caspase-3 activity, increased anti-inflammatory cytokine-IL-10 level, and reduced pathological lesions in the examined organs of rats cotreated with LUT and DOX. Collectively, cotreatment with LUT lessened DOX-induced neurotoxicity. Supplementation of LUT as a chemopreventive agent might be useful in patients undergoing DOX chemotherapy.

Luteolin-Fabricated ZnO Nanostructures Showed PLK-1 Mediated Anti-Breast Cancer Activity

The present work describes a facile and convenient procedure for synthesizing zinc oxide nanoparticles using luteolin isolated from Eclipta alba plant (L-ZnONPs) at room temperature. The formation of as-grown L-ZnONPs was confirmed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The Wurtzite structure of ZnO was observed by its hexagonal phases in diffraction patterns. The SEM images revealed the different sizes and morphologies of L-ZnONPs, with diameters between 12 and 25 nm. The HR-TEM result showed that the inter-planar distance between two lattice fringes was 0.262 nm, which coincides with the d-spacing of (002) and (101) lattice planes of the as-obtained material. The anticancer activity of L-ZnONPs against the breast cancer cell line MCF-7 was greater as compared to that of luteolin or ZnO alone. The mechanistic evaluation of such an activity carried out using in silico methods suggested that the anti-breast cancer activity of L-ZnONPs was mediated by polo-like kinase 1 (PLK1) proteins.

A Network Pharmacology Study on the Molecular Mechanisms of FDY003 for Breast Cancer Treatment

Herbal medicines have drawn considerable attention with regard to their potential applications in breast cancer (BC) treatment, a frequently diagnosed malignant disease, considering their anticancer efficacy with relatively less adverse effects. However, their mechanisms of systemic action have not been understood comprehensively. Based on network pharmacology approaches, we attempted to unveil the mechanisms of FDY003, an herbal drug comprised of Lonicera japonica Thunberg, Artemisia capillaris Thunberg, and Cordyceps militaris, against BC at a systemic level. We found that FDY003 exhibited pharmacological effects on human BC cells. Subsequently, detailed data regarding the biochemical components contained in FDY003 were obtained from comprehensive herbal medicine-related databases, including TCMSP and CancerHSP. By evaluating their pharmacokinetic properties, 18 chemical compounds in FDY003 were shown to be potentially active constituents interacting with 140 BC-associated therapeutic targets to produce the pharmacological activity. Gene ontology enrichment analysis using g:Profiler indicated that the FDY003 targets were involved in the modulation of cellular processes, involving the cell proliferation, cell cycle process, and cell apoptosis. Based on a KEGG pathway enrichment analysis, we further revealed that a variety of oncogenic pathways that play key roles in the pathology of BC were significantly enriched with the therapeutic targets of FDY003; these included PI3K-Akt, MAPK, focal adhesion, FoxO, TNF, and estrogen signaling pathways. Here, we present a network-perspective of the molecular mechanisms via which herbal drugs treat BC.

A multistage oral delivery system of PTX for improving oral bioavailability and enhancing anticancer efficacy

OBJECTIVE

Bromotetrandrine (W198) was reported as a P-glycoprotein (P-gp) inhibitor. We aimed to prepare oral W198 micelles following by paclitaxel (PTX) micelles (W198/PTX micelles) to improve the clinical application of PTX.

SIGNIFICANCE

The poor water solubility, intestinal permeability, and multidrug resistance (MDR) of PTX can be improved in the multistage oral delivery system.

METHODS

The novel W198/PTX oral micelles were developed by water-bath ultrasound method and were evaluated in vivo and in vitro in 4T1 orthotopic tumor-bearing mice model.

RESULTS

PTX micelles and W198 micelles were prepared to be round and uniform. W198 micelles pre-administrated group showed higher cellular uptake efficiency of PTX on Caco-2 cells and more prominent cytotoxicity compared with W198-untreated group on 4T1 cells. The oral bioavailability of W198/PTX micelles group was nearly 5.7-folds higher than the PTX micelles only group. In addition, W198/PTX micelles showed enhanced anticancer efficacy.

CONCLUSIONS

We established a multistage oral delivery system to improve oral bioavailability and anticancer efficacy of PTX.

Phytoestrogens for Cancer Prevention and Treatment

Phytoestrogens are a large group of natural compounds found in more than 300 plants. They have a close structural similarity to estrogens, which allow them to bind to both estrogen receptors (ER), ERα and ERβ, presenting a weak estrogenic activity. Phytoestrogens have been described as antioxidant, anti-inflammatory, anti-thrombotic, anti-allergic, and anti-tumoral agents. Their role in cancer prevention has been well documented, although their impact on treatment efficiency is controversial. Several reports suggest that phytoestrogens may interfere with the effect of anti-cancer drugs through the regulation of oxidative stress and other mechanisms. Furthermore, some phytoestrogens could exert a protective effect on healthy cells, thus reducing the secondary effects of cancer treatment. In this review, we have studied the recent research in this area to find evidence for the role of phytoestrogens in cancer prevention and therapy efficacy.

Can a metabolism-targeted therapeutic intervention successfully subjugate SARS-COV-2? A scientific rational

As a process entailing a high turnover of the host cell molecules, viral replication is required for a successful viral infection and requests virus capacity to acquire the macromolecules required for its propagation. To this end, viruses have adopted several strategies to harness cellular metabolism in accordance with their specific demands. Most viruses upregulate specific cellular anabolic pathways and are largely dependent on such alterations. RNA viruses, for example, upregulate both glycolysisand glycogenolysis providing TCA cycle intermediates essential for anabolic lipogenesis. Also, these infections usually induce the PPP, leading to increased nucleotide levels supporting viral replication. SARS-CoV-2 (the cause of COVID-19)that has so far spread from China throughout the world is also an RNA virus. Owing to the more metabolic plasticity of uninfected cells, a promising approach for specific antiviral therapy, which has drawn a lot of attention in the recent years, would be the targeting of metabolic changes induced by viruses. In the current review, we first summarize some of virus-induced metabolic adaptations and then based on these information as well as SARS-CoV-2 pathogenesis, propose a potential therapeutic modality for this calamitous world-spreading virus with the hope of employing this strategy for near-future clinical application.

Bioactive Phenolic Compounds in the Modulation of Central and Peripheral Nervous System Cancers: Facts and Misdeeds

Efficacious therapies are not available for the cure of both gliomas and glioneuronal tumors, which represent the most numerous and heterogeneous primary cancers of the central nervous system (CNS), and for neoplasms of the peripheral nervous system (PNS), which can be divided into benign tumors, mainly represented by schwannomas and neurofibromas, and malignant tumors of the peripheral nerve sheath (MPNST). Increased cellular oxidative stress and other metabolic aspects have been reported as potential etiologies in the nervous system tumors. Thus polyphenols have been tested as effective natural compounds likely useful for the prevention and therapy of this group of neoplasms, because of their antioxidant and anti-inflammatory activity. However, polyphenols show poor intestinal absorption due to individual intestinal microbiota content, poor bioavailability, and difficulty in passing the blood-brain barrier (BBB). Recently, polymeric nanoparticle-based polyphenol delivery improved their gastrointestinal absorption, their bioavailability, and entry into defined target organs. Herein, we summarize recent findings about the primary polyphenols employed for nervous system tumor prevention and treatment. We describe the limitations of their application in clinical practice and the new strategies aimed at enhancing their bioavailability and targeted delivery.

Epigenetic control of UV-B-induced flavonoid accumulation in Artemisia annua L

UV-B-induced flavonoid biosynthesis is epigenetically regulated by site-specific demethylation of AaMYB1, AaMYC, and AaWRKY TF-binding sites inAaPAL1promoter-causing overexpression ofAaPALgene inArtemisia annua. The present study was undertaken to understand the epigenetic regulation of flavonoid biosynthesis under the influence of ultraviolet-B radiation using Artemisia annua L. as an experimental model. In-vitro propagated and acclimatized plantlets were treated with UV-B radiation (2.8 W m^-2; 3 h), which resulted in enhanced accumulation of total flavonoid and phenolics content as well as eleven individual flavonoids measured through HPLC-DAC. Expression of eight genes (phenylanaline ammonia lyase, cinnamate-4-hydroxylase, 4-coumarate: CoA ligase; chalcone synthase, chalcone isomerase, cinnamoyl reductase, flavonoid-3'-hydroxylase, and flavones synthase) from upstream and downstream flavonoid biosynthetic pathways was measured through RT-PCR and RT-Q-PCR and all were variably induced under UV-B irradiation. Among them, AaPAL1 transcript and its protein were most significantly upregulated. Global DNA methylation analysis revealed hypomethylation of genomic DNA in A. annua. Further epigenetic characterization of promoter region of AaPAL1 revealed cytosine demethylation at five sites, which in turn caused epigenetic activation of six transcription factor-binding sites including QELEMENT, EBOXBNNAPA/MYCCONSENSUSAT, MYBCORE, MYBCOREATCYCB1, and GCCCORE. MYB transcription factors are positive regulators of flavonoid biosynthesis. Epigenetic activation of transcription-enhancing cis-regulatory elements in AaPAL1 promoter and subsequent overexpression of AaMYB1 and AaMYC and AaWRKY transcription factors under UV-B irradiation may probably be the reason for higher AaPAL1 expression and hence greater biosynthesis of flavonoids in A. annua L. The present study is the first report that provides mechanistic evidence of epigenetic regulation of flavonoid biosynthesis under UV-B radiation in A. annua L.

Metabolic Reprogramming in Breast Cancer and Its Therapeutic Implications

Current standard-of-care (SOC) therapy for breast cancer includes targeted therapies such as endocrine therapy for estrogen receptor-alpha (ERα) positive; anti-HER2 monoclonal antibodies for human epidermal growth factor receptor-2 (HER2)-enriched; and general chemotherapy for triple negative breast cancer (TNBC) subtypes. These therapies frequently fail due to acquired or inherent resistance. Altered metabolism has been recognized as one of the major mechanisms underlying therapeutic resistance. There are several cues that dictate metabolic reprogramming that also account for the tumors’ metabolic plasticity. For metabolic therapy to be efficacious there is a need to understand the metabolic underpinnings of the different subtypes of breast cancer as well as the role the SOC treatments play in targeting the metabolic phenotype. Understanding the mechanism will allow us to identify potential therapeutic vulnerabilities. There are some very interesting questions being tackled by researchers today as they pertain to altered metabolism in breast cancer. What are the metabolic differences between the different subtypes of breast cancer? Do cancer cells have a metabolic pathway preference based on the site and stage of metastasis? How do the cell-intrinsic and -extrinsic cues dictate the metabolic phenotype? How do the nucleus and mitochondria coordinately regulate metabolism? How does sensitivity or resistance to SOC affect metabolic reprogramming and vice-versa? This review addresses these issues along with the latest updates in the field of breast cancer metabolism.

Glycolysis inhibition via mTOR suppression is a key step in cardamonin-induced autophagy in SKOV3 cells

Background

Autophagy occurs in cells that undergoing nutrient deprivation. Glycolysis rapidly supplies energy for the proliferation of cancer cells. Cardamonin inhibits proliferation and enhances autophagy by mTORC1 suppression in ovarian cancer cells. Here, we investigate the relationship between cardamonin-triggered autophagy and glycolysis inhibition via mTORC1 suppression.

Methods

Treated with indicated compounds, ATP content and the activity of hexokinase (HK) and lactate dehydrogenase (LDH) were analyzed by the assay kits. Autophagy was detected by monodansylcadaverin (MDC) staining. The relationship between cardamonin-triggered autophagy and glycolysis inhibition via mTORC1 suppression was analyzed by Western blot.

Results

We found that cardamonin inhibited the lactate secretion, ATP production, and the activity of HK and LDH. The results demonstrated that cardamonin enhanced autophagy in SKOV3 cells, as indicated by acidic compartments accumulation, microtubule-associated protein 1 Light Chain 3-II (LC3-II) and lysosome associated membrane protein 1 up-regulation. Our results showed that the activation of mTORC1 signaling and the expression HK2 were reduced by cardamonin; whereas the phosphorylation of AMPK (AMP-activated protein kinase) was increased. We also confirmed that the AMPK inhibitor, Compound C, reversed cardamonin-induced upregulation of LC3-II.

Conclusion

These results suggest that cardamonin-induced autophagy is associated with inhibition on glycolysis by down-regulating the activity of mTORC1 in ovarian cancer cells.

Mechanism of metastasis suppression by luteolin in breast cancer

Metastatic breast cancer is typically an extremely aggressive cancer with poor prognosis. Metastasis requires the orchestration of homeostatic factors and cellular programs, many of which are potential therapeutic targets. Luteolin (2-[3,4-dihydroxyphenyl]-5,7-dihydroxy-4-chromenone), is a naturally occurring flavonoid found in fruits and vegetables that exhibits many anticancer properties. Luteolin obstructs metastasis through both direct and indirect mechanisms. For instance, luteolin may suppress breast cancer invasion by acting as an antiangiogenic therapeutic inhibiting VEGF production and its receptor’s activity. Furthermore, luteolin decreases epithelial–mesenchymal transition markers and metastatic proclivity. Luteolin also acts as an antiproliferative by suppressing receptor tyrosine-kinase activity and apoptosis, both of which could prevent incipient colonization of breast cancer. Many of these antimetastatic characteristics accredited to luteolin are likely functionally related. For instance, the PI3K/Akt pathway, which is impeded by luteolin, has several downstream programs involved in increased proliferation, survival, and metastatic potential in breast cancer. In this review, luteolin’s ability to ameliorate breast cancer is summarized. The paper also offers insight into the molecular mechanisms by which luteolin may suppress breast cancer metastasis.

Antimetabolic Effects of Polyphenols in Breast Cancer Cells: Focus on Glucose Uptake and Metabolism

In the last years, metabolic reprogramming became a new key hallmark of tumor cells. One of its components is a deviant energetic metabolism, known as Warburg effect—an aerobic lactatogenesis—characterized by elevated rates of glucose uptake and consumption with high-lactate production even in the presence of oxygen. Because many cancer cells display a greater sensitivity to glucose deprivation-induced cytotoxicity than normal cells, inhibitors of glucose cellular uptake (facilitative glucose transporter 1 inhibitors) and oxidative metabolism (glycolysis inhibitors) are potential therapeutic targets in cancer treatment. Polyphenols, abundantly contained in fruits and vegetables, are dietary components with an established protective role against cancer. Several molecular mechanisms are involved in the anticancer effect of polyphenols, including effects on apoptosis, cell cycle regulation, plasma membrane receptors, signaling pathways, and epigenetic mechanisms. Additionally, inhibition of glucose cellular uptake and metabolism in cancer cell lines has been described for several polyphenols, and this effect was shown to be associated with their anticarcinogenic effect. This work will review data showing an antimetabolic effect of polyphenols and its involvement in the chemopreventive/chemotherapeutic potential of these dietary compounds, in relation to breast cancer.

Strategies to Target Glucose Metabolism in Tumor Microenvironment on Cancer by Flavonoids

The imbalance between glucose metabolism and cancer cell growth in tumor microenvironment (TME), which are closely related with the occurrence and progression of cancer. Accumulating evidence has demonstrated that flavonoids exert many biological properties, including antioxidant and anticarcinogenic activities. Recently, the roles and applications of flavonoids, particularly in relation to glucose metabolism in cancers, have been highlighted. Thus, the identification of flavonoids targeting alternative glucose metabolism pathways in TME may represent an attractive approach to the more effective therapeutic strategies for cancer. In this review, we will focus on the roles of flavonoids in regulating glucose metabolism and cancer cell growth in TME, such as proliferation advantage, cell mobility, and chemoresistance to cancer, as well as modifiers of thermal sensitivity. Not only have such large-scale endeavors been useful in providing fundamental insights into natural and synthesized flavonoids that can prevent and treat cancer, but also have led to the discovery of potential targets for cancer therapy.

Scutellarin protects against doxorubicin-induced acute cardiotoxicity and regulates its accumulation in the heart

The clinical use of doxorubicin (DOX) is limited by its dose-dependent cardiotoxicity. The present study investigated the effects of scutellarin against DOX-induced cardiotoxicity in rats using pharmacodynamic and pharmacokinetic approaches. DOX (20 mg/kg) was injected intraperitoneally (i.p.) as a single dose, and scutellarin (5 mg/kg/day) was injected intravenously (i.v.) for 3 days. Rats treated with DOX showed acute cardiotoxicity as indicated by the elevated serum lactate dehydrogenase (LDH) activity (4057.8 ± 107.2 vs. 2032.7 ± 70.95), tissue malondialdehyde (MDA) level (2.083 ± 0.10 vs. 1.103 ± 0.09), cardiac troponin T (cTnT) concentration (0.1695 ± 0.0114 ng/mL), the decreased left ventricular ejection fraction (LVEF) (47.75 ± 15.79 vs. 78.72 ± 7.25) and left ventricular fractional shortening (LVFS) (20.66 ± 8.06 vs. 43.7 ± 6.76) compared with those of the control group. Cotreatment with scutellarin significantly decreased the LDH activity (2595.9 ± 72.73), MDA level (1.380 ± 0.06), cTnT concentration (0.0222 ± 0.0041 ng/m L), increased LVEF (76.70 ± 3.91) and LVFS (40.28 ± 3.68). Histopathological studies showed disruption of cardiac tissues in the DOX groups. Cotreatment with scutellarin reduced the damage to cardiac tissues. In the pharmacokinetic and tissue distribution study, scutellarin reduced the heart tissue exposure to DOX but did not change the AUC of plasma. These results suggest that scutellarin can protect against DOX-induced acute cardiotoxicity through its antioxidant activity and alterations of heart concentrations.

Resveratrol reduces the hypoxia-induced resistance to doxorubicin in breast cancer cells

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is known to enhance the cytotoxicity of the anticancer drug doxorubicin. On the other hand, breast cancer MCF-7 cells acquire resistance to doxorubicin under hypoxic conditions. In this study, we investigated the effect of resveratrol on hypoxia-induced resistance to doxorubicin in MCF-7 cells. Resveratrol and its derivative 3,5-dihydroxy-4'-methoxy-trans-stilbene, but not 3,5-dimethoxy-4'-hydroxy-trans-stilbene, cancelled hypoxia-induced resistance to doxorubicin at a concentration of 10 μM. Carbonyl reductase 1 (CBR1) catalyzes the conversion of doxorubicin to its metabolite doxorubicinol, which is much less effective than doxorubicin. Hypoxia increased the expression of CBR1 at both mRNA and protein levels, and knockdown of CBR1 inhibited hypoxia-induced resistance to doxorubicin in MCF-7 cells. Knockdown of hypoxia-inducible factor (HIF)-1α repressed the hypoxia-induced expression of CBR1. Resveratrol repressed the expression of HIF-1α protein, but not HIF-1α mRNA, and decreased hypoxia-activated HIF-1 activity. Resveratrol repressed the hypoxia-induced expression of CBR1 at both mRNA and protein levels. Likewise, 3,5-dihydroxy-4'-methoxy-trans-stilbene decreased the hypoxia-induced expression of CBR1 protein, but not 3,5-dimethoxy-4'-hydroxy-trans-stilbene. Furthermore, resveratrol decreased the expression of HIF-1α protein even in the presence of the proteasome inhibitor MG132 in hypoxia. Theses results indicate that in MCF-7 cells, HIF-1α-increased CBR1 expression plays an important role in hypoxia-induced resistance to doxorubicin and that resveratrol and 3,5-dihydroxy-4'-methoxy-trans-stilbene decrease CBR1 expression by decreasing HIF-1α protein expression, perhaps through a proteasome-independent pathway, and consequently repress hypoxia-induced resistance to doxorubicin.

Luteolin is a novel p90 ribosomal S6 kinase (RSK) inhibitor that suppresses Notch4 signaling by blocking the activation of Y-box binding protein-1 (YB-1)

Triple-negative breast cancers (TNBC) are notoriously difficult to treat because they lack hormone receptors and have limited targeted therapies. Recently, we demonstrated that p90 ribosomal S6 kinase (RSK) is essential for TNBC growth and survival indicating it as a target for therapeutic development. RSK phosphorylates Y-box binding protein-1 (YB-1), an oncogenic transcription/translation factor, highly expressed in TNBC (~70% of cases) and associated with poor prognosis, drug resistance and tumor initiation. YB-1 regulates the tumor-initiating cell markers, CD44 and CD49f however its role in Notch signaling has not been explored. We sought to identify novel chemical entities with RSK inhibitory activity. The Prestwick Chemical Library of 1120 off-patent drugs was screened for RSK inhibitors using both in vitro kinase assays and molecular docking. The lead candidate, luteolin, inhibited RSK1 and RSK2 kinase activity and suppressed growth in TNBC, including TIC-enriched populations. Combining luteolin with paclitaxel increased cell death and unlike chemotherapy alone, did not enrich for CD44⁺ cells. Luteolin’s efficacy against drug-resistant cells was further indicated in the primary x43 cell line, where it suppressed monolayer growth and mammosphere formation. We next endeavored to understand how the inhibition of RSK/YB-1 signaling by luteolin elicited an effect on TIC-enriched populations. ChIP-on-ChIP experiments in SUM149 cells revealed a 12-fold enrichment of YB-1 binding to the Notch4 promoter. We chose to pursue this because there are several reports indicating that Notch4 maintains cells in an undifferentiated, TIC state. Herein we report that silencing YB-1 with siRNA decreased Notch4 mRNA. Conversely, transient expression of Flag:YB-1^WT or the constitutively active mutant Flag:YB-1^D102 increased Notch4 mRNA. The levels of Notch4 transcript and the abundance of the Notch4 intracellular domain (N4ICD) correlated with activation of P-RSK^S221/7 and P-YB-1^S102 in a panel of TNBC cell lines. Silencing YB-1 or RSK reduced Notch4 mRNA and this corresponded with loss of N4ICD. Likewise, the RSK inhibitors, luteolin and BI-D1870, suppressed P-YB-1 ^S102 and thereby reduced Notch4. In conclusion, inhibiting the RSK/YB-1 pathway with luteolin is a novel approach to blocking Notch4 signaling and as such provides a means of inhibiting TICs.

Large changes in NAD levels associated with CD38 expression during HL-60 cell differentiation

NAD is an important cofactor involved in multiple metabolic reactions and as a substrate for several NAD-dependent signalling enzymes. One such enzyme is CD38 which, alongside synthesising Ca(2+)-releasing second messengers and acting as a cell surface receptor, has also been suggested to play a key role in NAD(+) homeostasis. CD38 is well known as a negative prognostic marker in B-CLL but the role of its enzymatic activity has not been studied in depth to date. We have exploited the HL-60 cell line as a model of inducible CD38 expression, to investigate CD38-mediated regulation intracellular NAD(+) levels and the consequences of changes in NAD(+) levels on cell physiology. Intracellular NAD(+) levels fell with increasing CD38 expression and this was reversed with the CD38 inhibitor, kuromanin confirming the key role of CD38 in NAD(+) homeostasis. We also measured the consequences of CD38 expression during the differentiation on a number of functions linked to NAD(+) and we show that some but not all NAD(+)-dependent processes are significantly affected by the lowered NAD(+) levels. These data suggest that both functional roles of CD38 might be important in the pathogenesis of B-CLL.

Luteolin sensitises drug-resistant human breast cancer cells to tamoxifen via the inhibition of cyclin E2 expression

Luteolin is a flavonoid that has been identified in many plant tissues and exhibits chemopreventive or chemosensitising properties against human breast cancer. However, the oncogenic molecules in human breast cancer cells that are inhibited by luteolin treatment have not been identified. This study found that the level of cyclin E2 (CCNE2) mRNA was higher in tumour cells (4.89-fold, (∗)P=0.005) than in normal paired tissue samples as assessed using real-time reverse-transcriptase polymerase chain reaction (RT-PCR) analysis (n=257). Further, relatively high levels of CCNE2 protein expression were detected in tamoxifen-resistant (TAM-R) MCF-7 cells. These results showed that the level of CCNE2 protein expression was specifically inhibited in luteolin-treated (5μM) TAM-R cells, either in the presence or absence of 4-OH-TAM (100nM). Combined treatment with 4-OH-TAM and luteolin synergistically sensitised the TAM-R cells to 4-OH-TAM. The results of this study suggest that luteolin can be used as a chemosensitiser to target the expression level of CCNE2 and that it could be a novel strategy to overcome TAM resistance in breast cancer patients.

Luteolin inhibits proliferation induced by IGF-1 pathway dependent ERα in human breast cancer MCF-7 cells

The growth of many breast tumors is stimulated by IGF-1, which activates signal transduction pathways inducing cell proliferation. ERα is important in this process. The aim of the study was to investigate relationships in vitro among inhibitory effects of luteolin on the growth of MCF-7 cells, IGF-1 pathway and ERα. Our results showed that luteolin could effectively block IGF-1-stimulated MCF-7 cell proliferation in a dose- and time- dependent manner and block cell cycle progression and induce apoptosis evidenced by the flow cytometric detection of sub-G1DNA content. Luteolin markedly decreased IGF-1-dependent IGF-1R and Akt phosphorylation without affecting Erk1/2 phosphorylation. Further experiments pointed out that ERα was directly involved in IGF-1 induced cell growth inhibitory effects of luteolin, which significantly decreased ERα expression. Knockdown of ERα in MCF-7 cells by an ERα-specific siRNA decreased the IGF-1 induced cell growth inhibitory effects of luteolin. ERα is thus a possible target of luteolin. These findings indicate that the inhibitory effect of luteolin on the growth of MCF-7 cells is via inhibiting IGF-1 mediated PI3K-Akt pathway dependent on ERα expression.

Sickle erythrocytes target cytotoxics to hypoxic tumor microvessels and potentiate a tumoricidal response

Resistance of hypoxic solid tumor niches to chemotherapy and radiotherapy remains a major scientific challenge that calls for conceptually new approaches. Here we exploit a hitherto unrecognized ability of sickled erythrocytes (SSRBCs) but not normal RBCs (NLRBCs) to selectively target hypoxic tumor vascular microenviroment and induce diffuse vaso-occlusion. Within minutes after injection SSRBCs, but not NLRBCs, home and adhere to hypoxic 4T1 tumor vasculature with hemoglobin saturation levels at or below 10% that are distributed over 70% of the tumor space. The bound SSRBCs thereupon form microaggregates that obstruct/occlude up to 88% of tumor microvessels. Importantly, SSRBCs, but not normal RBCs, combined with exogenous prooxidant zinc protoporphyrin (ZnPP) induce a potent tumoricidal response via a mutual potentiating mechanism. In a clonogenic tumor cell survival assay, SSRBC surrogate hemin, along with H(2)O(2) and ZnPP demonstrate a similar mutual potentiation and tumoricidal effect. In contrast to existing treatments directed only to the hypoxic tumor cell, the present approach targets the hypoxic tumor vascular environment and induces injury to both tumor microvessels and tumor cells using intrinsic SSRBC-derived oxidants and locally generated ROS. Thus, the SSRBC appears to be a potent new tool for treatment of hypoxic solid tumors, which are notable for their resistance to existing cancer treatments.

Dietary flavones and flavonones display differential effects on aromatase (CYP19) transcription in the breast cancer cells MCF-7

Aromatase or cytochrome P450 (CYP19) enzyme catalyzes the rate-determining reaction in estrogen synthesis. Inhibiting aromatase is a major strategy in treating breast cancer patients. However, suppression on the transcriptional activity may be equally important in controlling aromatase. Dietary flavones and flavonones have been previously demonstrated to be the most potent aromatase-inhibitory flavonoids. In the present study we examined their effects on the transcription regulation of CYP19 in MCF-7 cells. Real-time PCR results indicated that luteolin suppressed CYP19 mRNA expression while hesperetin increased it. Reporter gene assays were employed to look into the transactivity of CYP19 driven by promoters I.3 and II, and the result was consistent with the observation in mRNA expression. Further investigation using truncation reporter gene and electrophoretic mobility shift assays suggested that luteolin and hesperetin differentially influenced AP-1- and C/EBP-binding on the CYP19 promoter. Western blot analysis indicated that signaling transduction pathways involving JNK and ERK could be the underlying mechanisms for their actions. The present study showed that dietary flavones and flavonones might differentially regulate aromatase transcription in breast cells in addition to the inhibition at the enzyme level.

Reactive oxygen species and oxidative DNA damage mediate the cytotoxicity of tungsten-nickel-cobalt alloys in vitro

Tungsten alloys (WA) have been introduced in an attempt to find safer alternatives to depleted uranium and lead munitions. However, it is known that at least one alloy, 91% tungsten-6% nickel-3% cobalt (WNC-91-6-3), causes rhabdomyosarcomas when fragments are implanted in rat muscle. This raises concerns that shrapnel, if not surgically removable, may result in similar tumours in humans. There is therefore a clear need to develop rapid and robust in vitro methods to characterise the toxicity of different WAs in order to identify those that are most likely to be harmful to human health and to guide development of new materials in the future. In the current study we have developed a rapid visual in vitro assay to detect toxicity mediated by individual WA particles in cultured L6-C11 rat muscle cells. Using a variety of techniques (histology, comet assay, caspase-3 activity, oxidation of 2'7'-dichlorofluorescin to measure the production of reactive oxygen species and whole-genome microarrays) we show that, in agreement with the in vivo rat carcinogenicity studies, WNC-91-6-3 was the most toxic of the alloys tested. On dissolution, it produces large amounts of reactive oxygen species, causes significant amounts of DNA damage, inhibits caspase-3, triggers a severe hypoxic response and kills the cells in the immediate vicinity of the alloy particles within 24h. By combining these in vitro data we offer a mechanistic explanation of the effect of this alloy in vivo and show that in vitro tests are a viable alternative for assessing new alloys in the future.

Flavonoids from Artemisia annua L. as antioxidants and their potential synergism with artemisinin against malaria and cancer

Artemisia annua is currently the only commercial source of the sesquiterpene lactone artemisinin. Since artemisinin was discovered as the active component of A. annua in early 1970s, hundreds of papers have focused on the anti-parasitic effects of artemisinin and its semi-synthetic analogs dihydroartemisinin, artemether, arteether, and artesunate. Artemisinin per se has not been used in mainstream clinical practice due to its poor bioavailability when compared to its analogs. In the past decade, the work with artemisinin-based compounds has expanded to their anti-cancer properties. Although artemisinin is a major bioactive component present in the traditional Chinese herbal preparations (tea), leaf flavonoids, also present in the tea, have shown a variety of biological activities and may synergize the effects of artemisinin against malaria and cancer. However, only a few studies have focused on the potential synergistic effects between flavonoids and artemisinin. The resurgent idea that multi-component drug therapy might be better than monotherapy is illustrated by the recent resolution of the World Health Organization to support artemisinin-based combination therapies (ACT), instead of the previously used monotherapy with artemisinins. In this critical review we will discuss the possibility that artemisinin and its semi-synthetic analogs might become more effective to treat parasitic diseases (such as malaria) and cancer if simultaneously delivered with flavonoids. The flavonoids present in A. annua leaves have been linked to suppression of CYP450 enzymes responsible for altering the absorption and metabolism of artemisinin in the body, but also have been linked to a beneficial immunomodulatory activity in subjects afflicted with parasitic and chronic diseases.

Combination treatment with luteolin and quercetin enhances antiproliferative effects in nicotine-treated MDA-MB-231 cells by down-regulating nicotinic acetylcholine receptors

Large-scale epidemiological cohort studies performed in the United States indicate that breast cancer risk is associated with active and passive smoking. As of yet, however, there is no direct evidence of antitumor effects by agents that block the effect of tobacco compound nicotine (Nic) on relevant nicotinic receptors (nAChR) involved in breast tumorigenesis. In the present study, the expression profiles of different nAChR subunits in the human breast cancer cell line (MDA-MB-231) were characterized by RT-PCR. Nic (>0.1 microM, 6 h) significantly increased alpha9-nAChR mRNA and protein expression levels in human breast cancer cells (MDA-MB-231 cells). On the other hand, combined treatment with luteolin (Lut, 0.5 microM) and quercetin (Que, 0.5 microM) profoundly decreased MDA-MB-231 proliferation by down-regulating alpha9-nAChR expression. MDA-MB-231 cells were cultured in soft agar to evaluate anchorage-independent colony formation; combined treatment of Lut+Que inhibited Nic-induced MDA-MB-231 colony formation. Interestingly, the number of colonies formed was profoundly reduced in alpha9-nAChR knockdown (Si alpha9) cells in the combined (Lut+Que)-treated group as compared to the relevant control groups. Such results show that Lut- or Que-induced antitransforming activities were not limited to specific inhibition of the alpha9-nAChR receptor. Both alpha5- and alpha9-nAChR appear to be important molecular targets for Lut- and Que-induced antitumor effects in human breast cancer cells.

Tranilast inhibits the growth and metastasis of mammary carcinoma

Tranilast (N-[3,4-dimethoxycinnamonyl]-anthranilic acid) is a drug of low toxicity that is orally administered, and has been used clinically in Japan as an antiallergic and antifibrotic agent. Its antifibrotic effect is thought to depend on the inhibition of transforming growth factor-beta (TGF-beta). It has also been shown to exert antitumor effects, but its mode of action is unclear. Here, we explored the antitumor effects of tranilast in vitro and in vivo. Tranilast inhibited the proliferation of several tumor cell lines including mouse mammary carcinoma (4T1), rat mammary carcinoma stem cell (LA7), and human breast carcinoma (MDA-MB-231 and MCF-7). Tranilast blocked cell-cycle progression in vitro. In the highly metastatic 4T1 cell line, tranilast inhibited phospho-Smad2 generation, consistent with a blockade of TGF-beta signaling. It also inhibited the activation of MAP kinases (extracellularly regulated kinase 1 and 2 and JNK), which have been linked to TGF-beta-dependent epithelial-to-mesenchymal transition and, indeed, it blocked epithelial-to-mesenchymal transition. Although tranilast only partially inhibited TGF-beta production by 4T1 tumor cells, it potently inhibited the production of TGF-beta, interferon-gamma, IL-6, IL-10, and IL-17 by lymphoid cells, suggesting a general anti-inflammatory activity. In vivo, female BALB/c mice were inoculated with syngeneic 4T1 cells in mammary fat pads and treated with tranilast by gavage. Tranilast reduced (>50%) the growth of the primary tumor. However, its effects on metastasis were more striking, with more than 90% reduction of metastases in the lungs and no metastasis in the liver. Thus, tranilast has potential activity as an antimetastatic agent in breast cancer.