Assessment of the effects of amphiphilic poly (N­vinylpyrrolidone) nanoparticles loaded with bortezomib on glioblastoma cell lines and zebrafish embryos.

Proteasome inhibitor bortezomib is an anticancer agent approved for treatment of multiple myeloma and mantle cell lymphoma. However, its application in other types of cancer, primarily in solid tumors, is limited due to poor pharmacokinetics, inefficient tissue penetration, low stability and frequent adverse effects. In the present study, a novel micellar nano-scaled delivery system was manufactured, composed of amphiphilic poly(N-vinylpyrrolidone) nanoparticles loaded with bortezomib. Similar nanoparticles loaded with prothionamide, a drug without anticancer effect, were used as control. The size and zeta potential of the obtained polymeric micelles were measured by dynamic light scattering. Bortezomib-loaded micelles exhibited significant cytotoxic activity in vitro in monolayer tumor cell cultures (IC50 ~6.5 µg/ml) and in 3D multicellular tumor spheroids (IC50 ~8.5 µg/ml) of human glioblastoma cell lines U87 and T98G. Additionally, the toxic effects in vivo were studied in zebrafish Danio rerio embryos, with an estimated 50% lethal concentration of 0.1 mg/ml. Considering that bortezomib and other molecules from the class of proteasome inhibitors are potent antitumor agents, nanodelivery approach can help reduce adverse effects and expand the range of its applications for treatment of various oncological diseases.

Rapamycin-induced autophagy in osteosarcoma cells is mediated via the biglycan/Wnt/ß-catenin signaling axis.

Biglycan is a class I secreted small leucine-rich proteoglycan (SLRP), which regulates signaling pathways connected to bone pathologies. Autophagy is a vital catabolic process with a dual role in cancer progression. Here, we show that biglycan inhibits autophagy in two osteosarcoma cell lines (P ≤ 0.001), while rapamycin-induced autophagy decreases biglycan expression in MG63 osteosarcoma cells and abrogates the biglycan-induced cell growth increase (P ≤ 0.001). Rapamycin also inhibits ß-catenin translocation to the nucleus, inhibiting the Wnt pathway (P ≤ 0.001) and reducing biglycan's colocalization with the Wnt coreceptor LRP6 (P ≤ 0.05). Furthermore, biglycan exhibits protective effects against the chemotherapeutic drug doxorubicin in MG63 OS cells through an autophagy-dependent manner (P ≤ 0.05). Cotreatment of these cells with rapamycin and doxorubicin enhances cells response to doxorubicin by decreasing biglycan (P ≤ 0.001) and ß-catenin (P ≤ 0.05) expression. Biglycan deficiency leads to increased caspase-3 activation (P ≤ 0.05), suggesting increased apoptosis of biglycan-deficient cells treated with doxorubicin. Computational models of LRP6 and biglycan complexes suggest that biglycan changes the receptor's ability to interact with other signaling molecules by affecting the interdomain bending angles in the receptor structure. Biglycan binding to LRP6 activates the Wnt pathway and ß-catenin nuclear translocation by disrupting ß-catenin degradation complex (P ≤ 0.01 and P ≤ 0.05). Interestingly, this mechanism is not followed in moderately differentiated, biglycan-nonexpressing U-2OS OS cells. To sum up, biglycan exhibits protective effects against the doxorubicin in MG63 OS cells by activating the Wnt signaling pathway and inhibiting autophagy.

Kinetics and Mechanism of Synthesis of Carboxyl-Containing N-Vinyl-2-Pyrrolidone Telehelics for Pharmacological Use.

It was found that sulfanylethanoic and 3-sulfanylpropanoic acids are effective regulators of molecular weight with chain transfer constants of 0.441 and 0.317, respectively, and show an unexpected acceleration effect on the radical polymerization of N-vinyl-2-pyrrolidone, initiated by 2,2'-azobisisobutyronitrile. It was determined for the first time that the thiolate anions of mercapto acids form a high-temperature redox initiating system with 2,2'-azobisisobutyronitrile during the radical polymerization of N-vinyl-2-pyrrolidone in 1,4-dioxane. Considering the peculiarities of initiation, a kinetic model of the polymerization of N-vinyl-2-pyrrolidone is proposed, and it is shown that the theoretical orders of the reaction rate, with respect to the monomer, initiator, and chain transfer agent, are 1, 0.75, 0.25, and are close to their experimentally determined values. Carboxyl-containing techelics of N-vinyl-2-pyrrolidone were synthesized so that it can slow down the release of the anticancer drug, doxorubicin, from aqueous solutions, which can find its application in the pharmacological field.

The Role of IGF/IGF-IR-Signaling and Extracellular Matrix Effectors in Bone Sarcoma Pathogenesis.

Bone sarcomas, mesenchymal origin tumors, represent a substantial group of varying neoplasms of a distinct entity. Bone sarcoma patients show a limited response or do not respond to chemotherapy. Notably, developing efficient chemotherapy approaches, dealing with chemoresistance, and preventing metastasis pose unmet challenges in sarcoma therapy. Insulin-like growth factors 1 and 2 (IGF-1 and -2) and their respective receptors are a multifactorial system that significantly contributes to bone sarcoma pathogenesis. Whereas failures have been registered in creating novel targeted therapeutics aiming at the IGF pathway, new agent development should continue, evaluating combinatorial strategies for enhancing antitumor responses and better classifying the patients that could best benefit from these therapies. A plausible approach for developing a combinatorial strategy is to focus on the tumor microenvironment (TME) and processes executed therein. Herewith, we will discuss how the interplay between IGF-signaling and the TME constituents affects sarcomas' basal functions and their response to therapy. This review highlights key studies focusing on IGF signaling in bone sarcomas, specifically studies underscoring novel properties that make this system an attractive therapeutic target and identifies new relationships that may be exploited. Potential direct and adjunct therapeutical implications of the extracellular matrix (ECM) effectors will also be summarized.

Safety of COVID-19 vaccines administered in the EU: Should we be concerned?

The COVID-19 pandemic has had an unprecedented and devastating impact on public health, society and economics around the world. As a result, the development of vaccines to protect individuals from symptomatic COVID-19 infections has represented the only feasible health tool to combat the spread of the disease. However, at the same time the development and regulatory assessment of different vaccines has challenged pharmaceutical industries and regulatory agencies as this process has occurred in the shorter time ever though. So far, two mRNA and two adenovirus-vectored vaccines have received a conditional marketing authorisation in the EU and other countries. This review summarized and discusses the assessment reports of the European Medicine Agency (EMA) concerning the safety of the 3 vaccines currently used in the EU (Pfizer, Moderna and Astra-Zeneca). A particular focus has been paid to safety information from pre-clinical (animal) and clinical (phase 3 trials) studies. Overall, the most frequent adverse effects reported after the administration of these vaccines consisted of local reactions at the injection site (sore arm and erythema) followed by non-specific systemic effects (myalgia, chills, fatigue, headache, and fever), which occurred soon after vaccination and resolved shortly. Rare cases of vaccine-induced immune thrombotic thrombocytopenia have been reported for Vaxzevria. Data on long-term studies, interaction with other vaccines, use in pregnancy/breast-feeding, use in immunocompromised subjects, and in subjects with comorbidities, autoimmune or inflammatory disorders are still missing for these vaccines. Therefore, careful follow-up and surveillance studies for continued vaccine safety monitoring will be needed to ascertain the potential risks of such adverse events or diseases. In conclusion, the benefits and risks of current COVID-19 vaccines must be weighed against the real possibility of contract the disease and develop complications and long-term sequels; all this on the basis of the available scientific evidence and in the absence of unmotivated biases.

Glycosaminoglycans: Carriers and Targets for Tailored Anti-Cancer Therapy.

The tumor microenvironment (TME) is composed of cancerous, non-cancerous, stromal, and immune cells that are surrounded by the components of the extracellular matrix (ECM). Glycosaminoglycans (GAGs), natural biomacromolecules, essential ECM, and cell membrane components are extensively altered in cancer tissues. During disease progression, the GAG fine structure changes in a manner associated with disease evolution. Thus, changes in the GAG sulfation pattern are immediately correlated to malignant transformation. Their molecular weight, distribution, composition, and fine modifications, including sulfation, exhibit distinct alterations during cancer development. GAGs and GAG-based molecules, due to their unique properties, are suggested as promising effectors for anticancer therapy. Considering their participation in tumorigenesis, their utilization in drug development has been the focus of both industry and academic research efforts. These efforts have been developing in two main directions; (i) utilizing GAGs as targets of therapeutic strategies and (ii) employing GAGs specificity and excellent physicochemical properties for targeted delivery of cancer therapeutics. This review will comprehensively discuss recent developments and the broad potential of GAG utilization for cancer therapy.

Exposure to cadmium and copper triggers cytotoxic effects and epigenetic changes in human colorectal carcinoma HT-29 cells.

Recent scientific evidence suggests a link between epigenetic changes (DNA methylation) and tumorigenesis. Moreover, a potential carcinogenic mechanism of cadmium was associated with changes in DNA methylation. In this study we investigated the impact of CdCl2 and CuSO4 aqueous solutions on DNA methylation in HT-29 cells by quantifying DNA methyltransferase (DNMT1, DNMT3A and DNMT3B) mRNA expression. Furthermore, we also studied the cytotoxic and anti-migratory potential of these substances. The results showed a dose-dependent decrease of viable cell percentage following 24 h of exposure (at concentrations of 0.05; 0.2; 1; 10 and 100 µg/ml), and an inhibitory effect on HT-29 cell migration capacity. In addition, RT-qPCR results showed that cadmium acts as a hypomethylating agent by suppressing DNMT expression, whereas copper acts as a hypermethylating compound by increasing DNMT expression. These findings suggest a cytotoxic potential of both cadmium and copper on HT-29 cells and their capacity to induce epigenetic changes.

Proteoglycans in the Pathogenesis of Hormone-Dependent Cancers: Mediators and Effectors.

Hormone-dependent cancers exhibit high morbidity and mortality. In spite of advances in therapy, the treatment of hormone-dependent cancers remains an unmet health need. The tumor microenvironment (TME) exhibits unique characteristics that differ among various tumor types. It is composed of cancerous, non-cancerous, stromal, and immune cells that are surrounded and supported by components of the extracellular matrix (ECM). Therefore, the interactions among cancer cells, stromal cells, and components of the ECM determine cancer progression and response to therapy. Proteoglycans (PGs), hybrid molecules consisting of a protein core to which sulfated glycosaminoglycan chains are bound, are significant components of the ECM that are implicated in all phases of tumorigenesis. These molecules, secreted by both the stroma and cancer cells, are crucial signaling mediators that modulate the vital cellular pathways implicated in gene expression, phenotypic versatility, and response to therapy in specific tumor types. A plethora of deregulated signaling pathways contributes to the growth, dissemination, and angiogenesis of hormone-dependent cancers. Specific inputs from the endocrine and immune systems are some of the characteristics of hormone-dependent cancer pathogenesis. Importantly, the mechanisms involved in various aspects of cancer progression are executed in the ECM niche of the TME, and the PG components crucially mediate these processes. Here, we comprehensively discuss the mechanisms through which PGs affect the multifaceted aspects of hormone-dependent cancer development and progression, including cancer metastasis, angiogenesis, immunobiology, autophagy, and response to therapy.

Fluorouracil neutrophil extracellular traps formation inhibited by polymer nanoparticle shielding.

Venous thromboembolism is a frequent complication occurring in patients suffering from neoplastic diseases. Since neutrophil extracellular traps (NETs) play an important role both in the development of the tumor growth process and in inducing complications such as thrombosis, indubitably the investigation of the effect of antitumor drugs on the formation of neutrophil extracellular traps and on the ability of such drugs to prevent NETs contribution on carcinogenesis is of great interest. In the present work we studied the effect of 5-fluorouracil (5FU) and its shielded -by amphiphilic poly-N-vinylpyrrolidone (Amph-PVP) nanoparticles-nanoscaled polymeric form on the activation of human neutrophils under ex vivo conditions. Free 5FU at concentrations varying from 0.01 to 10 mg/ml was found to cause a significant (two to three times) and rapid (after 20 min) increase in the total amount of NETs in the blood. Importantly, when 5FU-loaded Amph-PVP nanoparticles were studied under the same conditions, the appearance of NETs in the blood was completely blocked providing strong evidence of their potential as delivery system for 5FU in antitumor therapy.

Compliance of e-cigarette refill liquids with regulations on labelling, packaging and technical design characteristics in nine European member states.

OBJECTIVE: To evaluate electronic cigarette (e-cigarette) product compliance with European regulations (Tobacco Products Directive (TPD), Implementing Decisions), with a focus on labelling/packaging practices and technical design/safety features. METHODS: Before the implementation of the TPD, in early 2016, we randomly selected e-cigarette refill liquids from the five top-selling companies in France, Poland, Germany, Netherlands, UK, Spain, Romania, Hungary and Greece. Identical products were purchased after the implementation of the TPD (early 2018) and assessment of compliance was performed on self-matched samples (n=107) using a prospective cohort design. Compliance with the Classification, Labelling and Packaging (CLP) regulations was also evaluated. RESULTS: Following the implementation of the TPD, improvements were noted with regards to the existence of text-only warnings (32.7% pre vs 86.0% post, p<0.001), child-resistant fastenings (93.3% pre vs 100.0% post, p=0.016), tamper-proof vials (58.9% pre vs 86.9%, post p<0.001) and maximum refill volume ≤10 mL in vials (86.9% pre vs 94.4% post, p=0.008). Lower compliance was noted with regards to the inclusion of a leaflet (26.2% pre vs 53.3% post, p<0.001), refilling instructions (28.0% pre vs 51.4% post, p<0.001) and health warnings on the box, vial or leaflet (32.7% pre vs 86.0%, p<0.001). Overall, 86.0% of products had a warning label in the post-TPD phase in comparison to 32.7% of products before the implementation of the TPD (p<0.001). Compliance with the CLP regulations, also increased in the post TPD follow-up phase. CONCLUSIONS: This is the first study to evaluate the level of implementation of the e-cigarette regulations in nine EU member states. Our results indicate that refill liquids had substantial but not full compliance in most of the characteristics evaluated. Further effort is needed to ensure complete compliance.

Virgin Olive Oil and Health: Summary of the III International Conference on Virgin Olive Oil and Health Consensus Report, JAEN (Spain) 2018.

The Mediterranean diet is considered as the foremost dietary regimen and its adoption is associated with the prevention of degenerative diseases and an extended longevity. The preeminent features of the Mediterranean diet have been agreed upon and the consumption of olive oil stands out as the most peculiar one. Indeed, the use of olive oil as the nearly exclusive dietary fat is what mostly characterizes the Mediterranean area. Plenty of epidemiological studies have correlated that the consumption of olive oil was associated with better overall health. Indeed, extra virgin olive oil contains (poly)phenolic compounds that are being actively investigated for their purported biological and pharma-nutritional properties. On 18 and 19 May 2018, several experts convened in Jaen (Spain) to discuss the most recent research on the benefits of olive oil and its components. We reported a summary of that meeting (reviewing several topics related to olive oil, not limited to health) and concluded that substantial evidence is accruing to support the widespread opinion that extra virgin olive oil should, indeed, be the fat of choice when it comes to human health and sustainable agronomy.

Inflammation and Metabolism in Cancer Cell-Mitochondria Key Player.

Cancer metabolism is an essential aspect of tumorigenesis, as cancer cells have increased energy requirements in comparison to normal cells. Thus, an enhanced metabolism is needed in order to accommodate tumor cells' accelerated biological functions, including increased proliferation, vigorous migration during metastasis, and adaptation to different tissues from the primary invasion site. In this context, the assessment of tumor cell metabolic pathways generates crucial data pertaining to the mechanisms through which tumor cells survive and grow in a milieu of host defense mechanisms. Indeed, various studies have demonstrated that the metabolic signature of tumors is heterogeneous. Furthermore, these metabolic changes induce the exacerbated production of several molecules, which result in alterations that aid an inflammatory milieu. The therapeutic armentarium for oncology should thus include metabolic and inflammation regulators. Our expanding knowledge of the metabolic behavior of tumor cells, whether from solid tumors or hematologic malignancies, may provide the basis for the development of tailor-made cancer therapies.

Maximum tolerated doses and erythropoiesis effects in the mouse bone marrow by 79 pesticides' technical materials assessed with the micronucleus assay.

Effects of technical materials of pesticide active ingredients, belonging to various chemical classes, on erythropoiesis in mouse bone marrow were studied as part of the research on the pesticide mutagenic activity in micronucleus test. The purpose of the present study was to estimate the toxic action of the test substances on the target organ and the validity of the results of the micronucleus assay under conditions of erythropoiesis suppression. It was demonstrated that intragastrically administrated triazole pesticides reached bone marrow (target organ where micronucleus induction was assessed) and exerted an inhibitory effect on erythropoiesis. The effects of triazole pesticides were enhanced in the following order: difenoconazole ≤ tebuconazole < cyproconazole < flutriafol. Furthermore, an association between structural features of molecules and specific target organ activity of the test pesticides was observed. Based on the data on the general toxicity and the results of the evaluation of the effects on erythropoiesis, the maximum tolerated doses (MTDs) of 79 different technical materials of pesticides for CD-1 mice were determined.

Cadmium, lead and mercury in muscle tissue of gilthead seabream and seabass: Risk evaluation for consumers.

Cadmium (Cd), lead (Pb) and mercury (Hg) presence was investigated in the muscle tissue of gilthead seabream and seabass, collected from various aquaculture sites of the Aegean and Cretan Sea as well as from the fish market (fisheries). Risk for the Greek population through consumption of these species was estimated using two approaches: Target Hazard Quotient (THQ) and Hazard Index (HI). All heavy metal levels in the fish tissue were below the established safe limits for consumption. Metal accumulation was found to differ amongst mode of production, species, location and seasonality. Seabass demonstrated higher Hg and lower Cd concentrations than seabream, Hg and Pb seem to be more accumulated in closed seas and Pb values displayed a linear increasing trend from warmer to colder periods. Regression analysis revealed that the main contributing factor to Cd accumulation is species (beta: -0.28, 95%CI: -0.48 to -0.09); lead is predominately affected by seasonality (beta: 0.44, 95%CI: 0.29 to 0.59), Hg accumulation is mainly affected by location (beta: -0.32, 95%CI: -0.61 to -0.03) while wild seabream accumulates greater levels for Hg and Pb than farmed. Risk analysis demonstrated that consumption of the studied species, is safe for all metals (HI < 0.460 and TTHQ < 0.299).

Biglycan Regulates MG63 Osteosarcoma Cell Growth Through a LPR6/ß-Catenin/IGFR-IR Signaling Axis.

Biglycan, a small leucine rich proteoglycan (SLRP), is an important participant in bone homeostasis and development as well as in bone pathology. In the present study biglycan was identified as a positive regulator of MG63 osteosarcoma cell growth (p ≤ 0.001). IGF-I was shown to increase biglycan expression (p ≤ 0.01), whereas biglycan-deficiency attenuated significantly both basal and IGF-I induced cell proliferation of MG63 cells (p ≤ 0.001; p ≤ 0.01, respectively). These effects were executed through the IGF-IR receptor whose activation was strongly attenuated (p ≤ 0.01) in biglycan-deficient MG63 cells. Biglycan, previously shown to regulate Wnt/ß-catenin pathway, was demonstrated to induce a significant increase in ß-catenin protein expression evident at cytoplasmic (p ≤ 0.01), membrane (p ≤ 0.01), and nucleus fractions in MG63 cells (p ≤ 0.05). As demonstrated by immunofluorescence, increase in ß-catenin expression is attributed to co-localization of biglycan with the Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) resulting in attenuated ß-catenin degradation. Furthermore, applying anti-ß-catenin and anti-pIGF-IR antibodies to MG-63 cells demonstrated a cytoplasmic and to the membrane interaction between these molecules that increased upon exogenous biglycan treatment. In parallel, the downregulation of biglycan significantly inhibited both basal and IGF-I-dependent ERK1/2 activation, (p ≤ 0.001). In summary, we report a novel mechanism where biglycan through a LRP6/ß-catenin/IGF-IR signaling axis enhances osteosarcoma cell growth.

The Cytotoxic Effects of Betulin-Conjugated Gold Nanoparticles as Stable Formulations in Normal and Melanoma Cells.

Gold nanoparticles are currently investigated as theranostics tools in cancer therapy due to their proper biocompatibility and increased efficacy related to the ease to customize the surface properties and to conjugate other molecules. Betulin, [lup-20(29)-ene-3ß, 28-diol], is a pentacyclic triterpene that has raised scientific interest due to its antiproliferative effect on several cancer types. Herein we described the synthesis of surface modified betulin-conjugated gold nanoparticles using a slightly modified Turkevich method. Transmission electron microscopy (TEM) imaging, dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of obtained gold nanoparticles. Cytotoxic activity and apoptosis assessment were carried out using the MTT and Annexin V/PI apoptosis assays. The in vitro results showed that betulin coated gold nanoparticles presented a dose-dependent cytotoxic effect and induced apoptosis in all tested cell lines.

Overview of Cadmium Thyroid Disrupting Effects and Mechanisms.

Humans are exposed to a significant number of chemicals that are suspected to produce disturbances in hormone homeostasis. Hence, in recent decades, there has been a growing interest in endocrine disruptive chemicals. One of the alleged thyroid disrupting substances is cadmium (Cd), a ubiquitous toxic metal shown to act as a thyroid disruptor and carcinogen in both animals and humans. Multiple PubMed searches with core keywords were performed to identify and evaluate appropriate studies which revealed literature suggesting evidence for the link between exposure to Cd and histological and metabolic changes in the thyroid gland. Furthermore, Cd influence on thyroid homeostasis at the peripheral level has also been hypothesized. Both in vivo and in vitro studies revealed that a Cd exposure at environmentally relevant concentrations results in biphasic Cd dose-thyroid response relationships. Development of thyroid tumors following exposure to Cd has been studied mainly using in vitro methodologies. In the thyroid, Cd has been shown to activate or stimulate the activity of various factors, leading to increased cell proliferation and a reduction in normal apoptotic activity. Evidence establishing the association between Cd and thyroid disruption remains ambiguous, with further studies needed to elucidate the issue and improve our understanding of Cd-mediated effects on the thyroid gland.

Nanosized carriers based on amphiphilic poly-N-vinyl-2-pyrrolidone for intranuclear drug delivery.

AIM: Ability to deliver drugs into the cell nuclei can significantly increase the efficacy of cancer therapies, in particular in the case of multidrug-resistant cancer Results: Polymer nanocarriers based on amphiphilic thiooctadecyl-terminated poly-N-vinyl-2-pyrrolidone were produced and loaded with a model hydrophobic drug, curcumin. Two commonly used loading approaches - emulsification and ultrasonic dispersion - were found to lead to two different size distributions with distinctively different biological effect. While nanocarriers produced via the emulsion method penetrated cells by dynamin-dependent endocytic mechanisms, sub-100 nm dispersion-produced nanocarriers were capable of crossing the membranes via biologically independent mechanisms. CONCLUSION: This finding opens an intriguing possibility of intranuclear delivery by merely tailoring the size of polymeric carriers, thus promising a new approach for cancer therapies.

Tangeretin inhibits the proliferation of human breast cancer cells via CYP1A1/CYP1B1 enzyme induction and CYP1A1/CYP1B1-mediated metabolism to the product 4' hydroxy tangeretin.

Tangeretin is a polymethoxylated flavone with multifaceted anticancer activity. In the present study, the metabolism of tangeretin was evaluated in the CYP1 expressing human breast cancer cell lines MCF7 and MDA-MB-468 and in the normal breast cell line MCF10A. Tangeretin was converted to 4' OH tangeretin by recombinant CYP1 enzymes and by CYP1 enzymes expressed in MCF7 and MDA-MB-468 cells. This metabolite was absent in MCF10A cells that did not express CYP1 enzymes. Tangeretin exhibited submicromolar IC50 (0.25 ±â€¯0.15 µM) in MDA-MB-468 cells, whereas it was less active in MCF7 cells (39.3 ±â€¯1.5 µM) and completely inactive in MCF10A cells (>100 µM). In MDA-MB-468 cells that were coincubated with the CYP1 inhibitor acacetin, an approximately 70-fold increase was noted in the IC50 (18 ±â€¯1.6 µM) of tangeretin. In the presence of the CYP1 inhibitor acacetin, the conversion of tangeretin to 4' OH tangeretin was significantly reduced in MDA-MB-468 cells (2.55 ±â€¯0.19 µM vs. 6.33 ±â€¯0.12 µM). The mechanism of antiproliferative action involved cell cycle arrest at the G1 phase for MCF7 and MDA-MB-468 cells. Tangeretin was further shown to induce CYP1 enzyme activity and CYP1A1/CYP1B1 protein expression in MCF7 and MDA-MB-468 cells. These results suggest that tangeretin inhibits the proliferation of breast cancer cells via CYP1A1/CYP1B1-mediated metabolism to the product 4' hydroxy tangeretin.