Role of ferritin alterations in human breast cancer cells

miR-20a regulates expression of the iron exporter ferroportin in lung cancer

Abstract

Ferroportin (FPN) exports iron from duodenal enterocytes, macrophages, and hepatocytes to maintain systemic iron homeostasis. In addition, FPN is expressed in various cancer cells. Here, we show that in lung cancer, FPN expression is regulated by miR-20a. Within the FPN-3′-untranslated region (3′UTR), we identify and experimentally validate three evolutionarily conserved target sites for the microRNA (miRNA) members of the miR-17 seed family, including miR-20a. Our analysis of RNA sequencing data from patients with lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) revealed that FPN messenger RNA (mRNA) levels are significantly decreased in tumor compared to matched healthy tissue, while miR-20a levels are increased. A significant negative correlation of miR-20a and FPN expression was observed. Functional studies further demonstrate that FPN is post-transcriptionally regulated by miR-20a in non-small cell lung cancer (NSCLC) cells and that overexpression or knockdown of miR-20a or FPN affects NSCLC proliferation and colony formation. Taken together, our data suggest that increased expression of miR-20 in lung cancer may decrease iron export, leading to intracellular iron retention, which, in turn, favors cell proliferation.

Key messages

miR-20a controls expression of the iron exporter ferroportin (FPN) by binding to highly conserved target sites in its 3′UTR.

Expression of miR-20a is inversely correlated to FPN in lung cancer.

Low FPN expression stimulates proliferation and colony formation of non-small cell lung cancer (NSCLC) cells, possibly by increasing iron availability for cancer cell proliferation.

Electronic supplementary material

The online version of this article (doi:10.1007/s00109-015-1362-3) contains supplementary material, which is available to authorized users.

Cytoprotective effects of ferritin on doxorubicin-induced breast cancer cell death

Ferritin is a major iron storage protein and essential for iron homeostasis. It has a wide range of functions in the body including iron delivery, immunosuppression, angiogenesis, and cell proliferation. Ferritin is overexpressed in many cancer cells, but its precise role in cancer is unclear. In the present study, we examined the functional roles of ferritin in protecting the MCF-7 breast cancer cell line against treatment with the chemotherapeutic agent doxorubicin. The effects of ferritin (human liver ferritin) and doxorubicin on the human MCF-7 breast cancer cell line were evaluated using the cell viability assay. The impact of decreasing ferritin light chain (FTL) and ferritin heavy chain (FTH) expression on doxorubicin sensitivity was assessed using siRNA. Reactive oxygen species (ROS) was also measured using the fluorescence probe CM-H2DCFDA. The mechanism of modulated chemosensitivity was evaluated by western blot analysis. Ferritin treatment activated MCF-7 cell proliferation in a concentration- and time-dependent manner. While treatment with doxorubicin alone significantly increased intracelullar ROS production, the addition of ferritin decreased this ROS formation, thereby reducing doxorubicin‑induced MCF-7 cell death. The inhibition of FTL and FTH by siRNA sensitized cells to doxorubicin. Treatment with doxorubicin alone significantly induced the cell cycle‑dependent kinase inhibitor protein p21, whereas ferritin reduced p21 expression. Thus, ferritin plays a critical role in protecting MCF-7 cells against the chemotherapeutic drug doxorubicin. A targeted reduction of ferritin may be a useful strategy for overcoming chemoresistance in breast cancer.

The secret life of extracellular vesicles in metal homeostasis and neurodegeneration

Biologically active metals such as copper, zinc and iron are fundamental for sustaining life in different organisms with the regulation of cellular metal homeostasis tightly controlled through proteins that coordinate metal uptake, efflux and detoxification. Many of the proteins involved in either uptake or efflux of metals are localised and function on the plasma membrane, traffic between intracellular compartments depending upon the cellular metal environment and can undergo recycling via the endosomal pathway. The biogenesis of exosomes also occurs within the endosomal system, with several major neurodegenerative disease proteins shown to be released in association with these vesicles, including the amyloid-β (Aβ) peptide in Alzheimer's disease and the infectious prion protein involved in Prion diseases. Aβ peptide and the prion protein also bind biologically active metals and are postulated to play important roles in metal homeostasis. In this review, we will discuss the role of extracellular vesicles in Alzheimer's and Prion diseases and explore their potential contribution to metal homeostasis.

In Situ OH Generation from O2- and H2O2 Plays a Critical Role in Plasma-Induced Cell Death

Reactive oxygen and nitrogen species produced by cold atmospheric plasma (CAP) are considered to be the most important species for biomedical applications, including cancer treatment. However, it is not known which species exert the greatest biological effects, and the nature of their interactions with tumor cells remains ill-defined. These questions were addressed in the present study by exposing human mesenchymal stromal and LP-1 cells to reactive oxygen and nitrogen species produced by CAP and evaluating cell viability. Superoxide anion (O2-) and hydrogen peroxide (H2O2) were the two major species present in plasma, but their respective concentrations were not sufficient to cause cell death when used in isolation; however, in the presence of iron, both species enhanced the cell death-inducing effects of plasma. We propose that iron containing proteins in cells catalyze O2- and H2O2 into the highly reactive OH radical that can induce cell death. The results demonstrate how reactive species are transferred to liquid and converted into the OH radical to mediate cytotoxicity and provide mechanistic insight into the molecular mechanisms underlying tumor cell death by plasma treatment.

Targeting ferritin receptors for the selective delivery of imaging and therapeutic agents to breast cancer cells

In this work the selective uptake of native horse spleen ferritin and apoferritin loaded with MRI contrast agents has been assessed in human breast cancer cells (MCF-7 and MDA-MB-231). The higher expression of L-ferritin receptors (SCARA5) led to an enhanced uptake in MCF-7 as shown in T2 and T1 weighted MR images, respectively. The high efficiency of ferritin internalization in MCF-7 has been exploited for the simultaneous delivery of curcumin, a natural therapeutic molecule endowed with antineoplastic and anti-inflammatory action, and the MRI contrast agent Gd-HPDO3A. This theranostic system is able to treat selectively breast cancer cells over-expressing ferritin receptors. By entrapping in apoferritin both Gd-HPDO3A and curcumin, it was possible to deliver a therapeutic dose of 167 μg ml(-1) (as calculated by MRI) of this natural drug to MCF-7 cells, thus obtaining a significant reduction of cell proliferation.

An overview of molecular basis of iron metabolism regulation and the associated pathologies

Iron is essential for several vital biological processes. Its deficiency or overload drives to the development of several pathologies. To maintain iron homeostasis, the organism controls the dietary iron absorption by enterocytes, its recycling by macrophages and storage in hepatocytes. These processes are mainly controlled by hepcidin, a liver-derived hormone which synthesis is regulated by iron levels, inflammation, infection, anemia and erythropoiesis. Besides the systemic regulation of iron metabolism mediated by hepcidin, cellular regulatory processes also occur. Cells are able to regulate themselves the expression of the iron metabolism-related genes through different post-transcriptional mechanisms, such as the alternative splicing, microRNAs, the IRP/IRE system and the proteolytic cleavage. Whenever those mechanisms are disturbed, due to genetic or environmental factors, iron homeostasis is disrupted and iron related pathologies may arise.

Iron homeostasis and tumorigenesis: molecular mechanisms and therapeutic opportunities

Excess iron is tightly associated with tumorigenesis in multiple human cancer types through a variety of mechanisms including catalyzing the formation of mutagenic hydroxyl radicals, regulating DNA replication, repair and cell cycle progression, affecting signal transduction in cancer cells, and acting as an essential nutrient for proliferating tumor cells. Thus, multiple therapeutic strategies based on iron deprivation have been developed in cancer therapy. During the past few years, our understanding of genetic association and molecular mechanisms between iron and tumorigenesis has expanded enormously. In this review, we briefly summarize iron homeostasis in mammals, and discuss recent progresses in understanding the aberrant iron metabolism in numerous cancer types, with a focus on studies revealing altered signal transduction in cancer cells.

Macrophage iron homeostasis and polarization in the context of cancer

Macrophages are central in regulating iron homeostasis, which is tightly linked to their versatile role during innate immunity. They sequester iron by phagocytosis of senescent erythrocytes and represent a major source of available iron in the body. Macrophage iron homeostasis is coupled to the functional heterogeneity and plasticity of these cells, with their extreme roles during inflammation, immune modulation, and resolution of inflammation. It is now appreciated that the macrophage polarization process dictates expression profiles of genes involved in iron metabolism. Therefore, macrophages have evolved a multitude of mechanisms to sequester, transport, store, and release iron. A new, enigmatic protein entering the iron scene and affecting the macrophage phenotype is lipocalin-2. Iron sequestration in macrophages depletes the microenvironment, thereby limiting extracellular pathogen or tumor growth, while fostering inflammation. In contrast, iron release from macrophages contributes to bystander cell proliferation, which is important for tissue regeneration and repair. This dichotomy is also reflected by the dual role of lipocalin-2 in macrophages. Unfortunately, the iron release macrophage phenotype is also a characteristic of tumor-associated macrophages and stimulates tumor cell survival and growth. Iron sequestration versus its release is now appreciated to be associated with the macrophage polarization program and can be used to explain a number of biological functions attributed to distinct macrophage phenotypes. Here we discuss macrophage iron homeostasis with a special focus on lipocalin-2 related to the formation and function of tumor-associated macrophages.

Intracellular reduction/activation of a disulfide switch in thiosemicarbazone iron chelators

Iron scavengers (chelators) offer therapeutic opportunities in anticancer drug design by targeting the increased demand for iron in cancer cells as compared to normal cells. Prochelation approaches are expected to avoid systemic iron depletion as chelators are liberated under specific intracellular conditions. In the strategy described herein, a disulfide linkage is employed as a redox-directed switch within the binding unit of an antiproliferative thiosemicarbazone prochelator, which is activated for iron coordination following reduction to the thiolate chelator. In glutathione redox buffer, this reduction event occurs at physiological concentrations and half-cell potentials. Consistent with concurrent reduction and activation, higher intracellular thiol concentrations increase cell susceptibility to prochelator toxicity in cultured cancer cells. The reduction of the disulfide switch and intracellular iron chelation are confirmed in cell-based assays using calcein as a fluorescent probe for paramagnetic ions. The resulting low-spin Fe(III) complex is identified in intact Jurkat cells by EPR spectroscopy measurements, which also document a decreased concentration of active ribonucleotide reductase following exposure to the prochelator. Cell viability and fluorescence-based assays show that the iron complex presents low cytotoxicity and does not participate in intracellular redox chemistry, indicating that this antiproliferative chelation strategy does not rely on the generation of reactive oxygen species.

Insulin-like growth factor 1 receptor signaling induced by supraphysiological doses of IGF-1 in human peripheral blood lymphocytes

Insulin-like growth factor-1 (IGF-1) mediates some of growth hormone anabolic functions through its receptor, IGF-1R. Following ligand binding, intracellular signaling pathways are activated favouring proliferation, cell survival, tissue growth, development, and differentiation. IGF-1 is included in the World Anti-Doping Agency Prohibited List. While the evidence for IGF-1 as performance-enhancing substrate in healthy humans is still weak, clinical studies demonstrated that the endogenous growth hormone/IGF-1 excess is associated with cardiovascular implications. Previously, we demonstrated that human peripheral blood lymphocytes represent a suitable system to identify a gene signature, related to dihydrotestosterone or IGF-1 abuse, independent from the type of sport. In addition, in a proteomic study, we demonstrated that dihydrotestosterone hyperdosage affects cell motility and apoptosis. Here, we investigate the doping action of IGF-1 by means of a differential proteomic approach and specific protein arrays, revealing an active cytoskeletal reorganization mediated by Stat-1; moreover, IGF-1 stimulation produces a sustained activation of different signaling pathways as well as an overproduction of cytokines positively related to immune response and inflammation. In conclusion, these data indicate that, following IGF-1 hyperdosage, circulating peripheral blood lymphocytes could be more prone to transendothelial migration.

Iron homeostasis and anemia markers in early breast cancer

Iron plays a fundamental role in cell life and its concentration in living organisms is precisely regulated. Different molecules for iron storage and transport are used to maintain its intracellular homeostasis which is often altered in cancer cells. Specifically, recent studies have demonstrated that in breast cancer cells, the expression/activity of several iron-related proteins, such as ferritin, hepcidin and ferroportin, is deregulated and that these alterations may have a prognostic impact in patients with breast cancer. Moreover, molecules that regulate iron metabolism could become therapeutic targets. This review focuses on recent findings on iron metabolism particularly in breast cancer and on the development of new biomarkers that may be used in the clinical routine for the diagnosis, prognosis and management of cancer-associated anemia as well as for monitoring personalized treatments.

Ferritin heavy chain in triple negative breast cancer: a favorable prognostic marker that relates to a cluster of differentiation 8 positive (CD8+) effector T-cell response

Ferritin heavy chain (FTH1) is a 21-kDa subunit of the ferritin complex, known for its role in iron metabolism, and which has recently been identified as a favorable prognostic protein for triple negative breast cancer (TNBC) patients. Currently, it is not well understood how FTH1 contributes to an anti-tumor response. Here, we explored whether expression and cellular compartmentalization of FTH1 correlates to an effective immune response in TNBC patients. Analysis of the tumor tissue transcriptome, complemented with in silico pathway analysis, revealed that FTH1 was an integral part of an immunomodulatory network of cytokine signaling, adaptive immunity, and cell death. These findings were confirmed using mass spectrometry (MS)-derived proteomic data, and immunohistochemical staining of tissue microarrays. We observed that FTH1 is localized in both the cytoplasm and/or nucleus of cancer cells. However, high cytoplasmic (c) FTH1 was associated with favorable prognosis (Log-rank p = 0.001), whereas nuclear (n) FTH1 staining was associated with adverse prognosis (Log-rank p = 0.019). cFTH1 staining significantly correlated with total FTH1 expression in TNBC tissue samples, as measured by MS analysis (Rs = 0.473, p = 0.0007), but nFTH1 staining did not (Rs = 0.197, p = 0.1801). Notably, IFN γ-producing CD8+ effector T cells, but not CD4+ T cells, were preferentially enriched in tumors with high expression of cFTH1 (p = 0.02). Collectively, our data provide evidence toward new immune regulatory properties of FTH1 in TNBC, which may facilitate development of novel therapeutic targets.

Coupling heme and iron metabolism via ferritin H chain

SIGNIFICANCE

Inflammation and immunity can be associated with varying degrees of heme release from hemoproteins, eventually leading to cellular and tissue iron (Fe) overload, oxidative stress, and tissue damage. Presumably, these deleterious effects contribute to the pathogenesis of systemic infections.

RECENT ADVANCES

Heme release from hemoglobin sensitizes parenchyma cells to undergo programmed cell death in response to proinflammatory cytokines, such as tumor necrosis factor. This cytotoxic effect is driven by a mechanism involving intracellular accumulation of free radicals, which sustain the activation of the c-Jun N-terminal kinase (JNK) signaling transduction pathway. While heme catabolism by heme oxygenase-1 (HO-1) prevents programmed cell death, this cytoprotective effect requires the co-expression of ferritin H (heart/heavy) chain (FTH), which controls the pro-oxidant effect of labile Fe released from the protoporphyrin IX ring of heme. This antioxidant effect of FTH restrains JNK activation, whereas JNK activation inhibits FTH expression, a cross talk that controls metabolic adaptation to cellular Fe overload associated with systemic infections.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Identification and characterization of the mechanisms via which FTH provides metabolic adaptation to tissue Fe overload should provide valuable information to our current understanding of the pathogenesis of systemic infections as well as other immune-mediated inflammatory diseases.

Quantitative analysis of the anti-proliferative activity of combinations of selected iron-chelating agents and clinically used anti-neoplastic drugs

Recent studies have demonstrated that several chelators possess marked potential as potent anti-neoplastic drugs and as agents that can ameliorate some of the adverse effects associated with standard chemotherapy. Anti-cancer treatment employs combinations of several drugs that have different mechanisms of action. However, data regarding the potential interactions between iron chelators and established chemotherapeutics are lacking. Using estrogen receptor-positive MCF-7 breast cancer cells, we explored the combined anti-proliferative potential of four iron chelators, namely: desferrioxamine (DFO), salicylaldehyde isonicotinoyl hydrazone (SIH), (E)-N'-[1-(2-hydroxy-5-nitrophenyl)ethyliden] isonicotinoyl hydrazone (NHAPI), and di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), plus six selected anti-neoplastic drugs. These six agents are used for breast cancer treatment and include: paclitaxel, 5-fluorouracil, doxorubicin, methotrexate, tamoxifen and 4-hydroperoxycyclophosphamide (an active metabolite of cyclophosphamide). Our quantitative chelator-drug analyses were designed according to the Chou-Talalay method for drug combination assessment. All combinations of these agents yielded concentration-dependent, anti-proliferative effects. The hydrophilic siderophore, DFO, imposed antagonism when used in combination with all six anti-tumor agents and this antagonistic effect increased with increasing dose. Conversely, synergistic interactions were observed with combinations of the lipophilic chelators, NHAPI or Dp44mT, with doxorubicin and also the combinations of SIH, NHAPI or Dp44mT with tamoxifen. The combination of Dp44mT with anti-neoplastic agents was further enhanced following formation of its redox-active iron and especially copper complexes. The most potent combinations of Dp44mT and NHAPI with tamoxifen were confirmed as synergistic using another estrogen receptor-expressing breast cancer cell line, T47D, but not estrogen receptor-negative MDA-MB-231 cells. Furthermore, the synergy of NHAPI and tamoxifen was confirmed using MCF-7 cells by electrical impedance data, a mitochondrial inner membrane potential assay and cell cycle analyses. This is the first systematic investigation to quantitatively assess interactions between Fe chelators and standard chemotherapies using breast cancer cells. These studies are vital for their future clinical development.

Biophysical features of MagA expression in mammalian cells: implications for MRI contrast

We compared overexpression of the magnetotactic bacterial gene MagA with the modified mammalian ferritin genes HF + LF, in which both heavy and light subunits lack iron response elements. Whereas both expression systems have been proposed for use in non-invasive, magnetic resonance (MR) reporter gene expression, limited information is available regarding their relative potential for providing gene-based contrast. Measurements of MR relaxation rates in these expression systems are important for optimizing cell detection and specificity, for developing quantification methods, and for refinement of gene-based iron contrast using magnetosome associated genes. We measured the total transverse relaxation rate (R2*), its irreversible and reversible components (R2 and R2', respectively) and the longitudinal relaxation rate (R1) in MDA-MB-435 tumor cells. Clonal lines overexpressing MagA and HF + LF were cultured in the presence and absence of iron supplementation, and mounted in a spherical phantom for relaxation mapping at 3 Tesla. In addition to MR measures, cellular changes in iron and zinc were evaluated by inductively coupled plasma mass spectrometry, in ATP by luciferase bioluminescence and in transferrin receptor by Western blot. Only transverse relaxation rates were significantly higher in iron-supplemented, MagA- and HF + LF-expressing cells compared to non-supplemented cells and the parental control. R2* provided the greatest absolute difference and R2' showed the greatest relative difference, consistent with the notion that R2' may be a more specific indicator of iron-based contrast than R2, as observed in brain tissue. Iron supplementation of MagA- and HF + LF-expressing cells increased the iron/zinc ratio approximately 20-fold, while transferrin receptor expression decreased approximately 10-fold. Level of ATP was similar across all cell types and culture conditions. These results highlight the potential of magnetotactic bacterial gene expression for improving MR contrast.

Incorporation of57Fe-isotopically enriched in apoferritin: formation and characterization of isotopically enriched Fe nanoparticles for metabolic studies

The use of⁵⁷Fe-isotopically enriched ferritin for the accurate measurement of Fe : ferritin ratios is proposed for metabolic studies.

MicroRNAs and liver cancer associated with iron overload: Therapeutic targets unravelled

Primary liver cancer is a global disease that is on the increase. Hepatocellular carcinoma (HCC) accounts for most primary liver cancers and has a notably low survival rate, largely attributable to late diagnosis, resistance to treatment, tumour recurrence and metastasis. MicroRNAs (miRNAs/miRs) are regulatory RNAs that modulate protein synthesis. miRNAs are involved in several biological and pathological processes including the development and progression of HCC. Given the poor outcomes with current HCC treatments, miRNAs represent an important new target for therapeutic intervention. Several studies have demonstrated their role in HCC development and progression. While many risk factors underlie the development of HCC, one process commonly altered is iron homeostasis. Iron overload occurs in several liver diseases associated with the development of HCC including Hepatitis C infection and the importance of miRNAs in iron homeostasis and hepatic iron overload is well characterised. Aberrant miRNA expression in hepatic fibrosis and injury response have been reported, as have dysregulated miRNA expression patterns affecting cell cycle progression, evasion of apoptosis, invasion and metastasis. In 2009, miR-26a delivery was shown to prevent HCC progression, highlighting its therapeutic potential. Several studies have since investigated the clinical potential of other miRNAs with one drug, Miravirsen, currently in phase II clinical trials. miRNAs also have potential as biomarkers for the diagnosis of HCC and to evaluate treatment efficacy. Ongoing studies and clinical trials suggest miRNA-based treatments and diagnostic methods will have novel clinical applications for HCC in the coming years, yielding improved HCC survival rates and patient outcomes.

Iron metabolism disturbances in the MCF-7 human breast cancer cells with acquired resistance to doxorubicin and cisplatin

The development of resistance of cancer cells to therapeutic agents is the major obstacle in the successful treatment of breast cancer and the main cause of breast cancer recurrence. The results of several studies have demonstrated an important role of altered cellular iron metabolism in the progression of breast cancer and suggested that iron metabolism may be involved in the acquisition of a cancer cell drug-resistant phenotype. In the present study, we show that human MCF-7 breast cancer cells with an acquired resistance to the chemotherapeutic drugs doxorubicin (MCF-7/DOX) and cisplatin (MCF-7/CDDP) exhibited substantial alterations in the intracellular iron content and levels of iron-regulatory proteins involved in the cellular uptake, storage and export of iron, especially in profoundly increased levels of ferritin light chain (FTL) protein. The increased levels of FTL in breast cancer indicate that FTL may be used as a diagnostic and prognostic marker for breast cancer. Additionally, we demonstrate that targeted downregulation of FTL protein by the microRNA miR-133a increases sensitivity of MCF-7/DOX and MCF-7/CDDP cells to doxorubicin and cisplatin. These results suggest that correction of iron metabolism abnormalities may substantially improve the efficiency of breast cancer treatment.

Influence of microRNA on the maintenance of human iron metabolism

Iron is an essential nutrient critical for many cellular functions including DNA synthesis, ATP generation, and cellular proliferation. Though essential, excessive iron may contribute to the generation of free radicals capable of damaging cellular lipids, proteins, and nucleic acids. As such, the maintenance and control of cellular iron homeostasis is critical to prevent either iron deficiency or iron toxicity conditions. The maintenance of cellular iron homeostasis is largely coordinated by a family of cytosolic RNA binding proteins known as Iron Regulatory Proteins (IRP) that function to post-transcriptionally control the translation and/or stability of mRNA encoding proteins required for iron uptake, storage, transport, and utilization. More recently, a class of small non-coding RNA known as microRNA (miRNA) has also been implicated in the control of iron metabolism. To date, miRNA have been demonstrated to post-transcriptionally regulate the expression of genes associated with iron acquisition (transferrin receptor and divalent metal transporter), iron export (ferroportin), iron storage (ferritin), iron utilization (ISCU), and coordination of systemic iron homeostasis (HFE and hemojevelin). Given the diversity of miRNA and number of potential mRNA targets, characterizing factors that contribute to alterations in miRNA expression, biogenesis, and processing will enhance our understanding of mechanisms by which cells respond to changes in iron demand and/or iron availability to control cellular iron homeostasis.

The interaction between LYVE-1 with hyaluronan on the cell surface may play a role in the diversity of adhesion to cancer cells

Hyaluronan (HA), a simple disaccharide unit, can polymerize and is considered a primary component of the extracellular matrix, which has a wide range of biological functions. In recent years, HA was found on the surface of tumor cells. According to previous reports, differing HA content on the cell surface of tumor cells is closely related to lymph node metastases, but the mechanisms mediating this process remained unclear. This research intended to study the surface content of HA on tumor cells and analyze cell adhesive changes caused by the interaction between HA and its lymphatic endothelial receptor (LYVE-1). We screened and observed high HA content on HS-578T breast cells and low HA content on MCF-7 breast cells through particle exclusion, immunofluorescence and flow cytometry experiments. The expression of LYVE-1, the lymph-vessel specific HA receptor, was consistent with our previous report and enhanced the adhesion of HA^high-HS-578T cells to COS-7^LYVE-1(+) through HA in cell static adhesion and dynamic parallel plate flow chamber experiments. MCF-7 breast cells contain little HA on the surface; however, our results showed little adhesion difference between MCF-7 cells and COS-7^LYVE-1(+) and COS-7^LYVE-1(−) cells. Similar results were observed concerning the adhesion of HS-578T cells or MCF-7 cells to SVEC4-10 cells. Furthermore, we observed for the first time that the cell surface HA content of high transfer tumor cells was rich, and we visualized the cross-linking of HA cable structures, which may activate LYVE-1 on lymphatic endothelial cells, promoting tumor adhesion. In summary, high-low cell surface HA content of tumor cells through the interaction with LYVE-1 leads to adhesion differences.

Iron and cancer: more ore to be mined

Iron is an essential nutrient that facilitates cell proliferation and growth. However, iron also has the capacity to engage in redox cycling and free radical formation. Therefore, iron can contribute to both tumour initiation and tumour growth; recent work has also shown that iron has a role in the tumour microenvironment and in metastasis. Pathways of iron acquisition, efflux, storage and regulation are all perturbed in cancer, suggesting that reprogramming of iron metabolism is a central aspect of tumour cell survival. Signalling through hypoxia-inducible factor (HIF) and WNT pathways may contribute to altered iron metabolism in cancer. Targeting iron metabolic pathways may provide new tools for cancer prognosis and therapy.

Combined measurement of CA 15-3 with novel autoantibodies improves diagnostic accuracy for breast cancer

Objective

CA 15-3 is a traditional biomarker for advanced breast cancer with limited sensitivity for early stage patients. In order to increase the sensitivity for early detection, in this study, we introduced novel tumor-associated autoantibodies that were measured concurrently with serum CA 15-3 to evaluate their diagnostic advantage in breast cancer.

Methods

We investigated a T7 breast cancer complementary deoxyribonucleic acid (cDNA) phage library for tumor-associated antigens using sera from normal and breast cancer patients. Identified novel tumor-associated antigens phage proteins were then used to develop enzyme-linked immunosorbent assays to measure corresponding autoantibodies in 150 breast cancer, 150 normal, and 40 other cancer (non breast) patient serum samples. Meanwhile, the same samples were measured for CA 15-3 concentrations. Receiver operating characteristic curve analysis was used to evaluate the predictive accuracies of single markers as well as combined markers.

Results

Sequencing analysis revealed that two phage-expressed proteins were within the open reading frame and had significant homology to proteins heterogeneous nuclear ribonucleoproteins F (hnRNPF) and ferritin heavy chain (FTH1). Autoantibodies against hnRNPF and FTH1 alone were significantly higher in patients than in control serum samples (P < 0.01), and the area under the curve for hnRNPF and FTH1 alone was 0.73 and 0.69, respectively. However, when the two autoantibody biomarkers were analyzed in combination with serum CA 15-3 values, the area under the curve increased to 0.93, and the optimal sensitivity and specificity became 89.3% and 93.8%, respectively. Further messenger ribonucleic acid (mRNA) analysis showed that hnRNPF and FTH1 were significantly upregulated in tumor tissues.

Conclusion

Our results indicated that combined serologic biomarkers of tumor-associated antigens with autoantibodies may improve the diagnostic accuracy of breast cancer.

Modulation of intracellular iron metabolism by iron chelation affects chromatin remodeling proteins and corresponding epigenetic modifications in breast cancer cells and increases their sensitivity to chemotherapeutic agents

Iron plays a vital role in the normal functioning of cells via the regulation of essential cellular metabolic reactions, including several DNA and histone-modifying proteins. The metabolic status of iron and the regulation of epigenetic mechanisms are well-balanced and tightly controlled in normal cells; however, in cancer cells these processes are profoundly disturbed. Cancer-related abnormalities in iron metabolism have been corrected through the use of iron-chelating agents, which cause an inhibition of DNA synthesis, G₁-S phase arrest, an inhibition of epithelial-to-mesenchymal transition, and the activation of apoptosis. In the present study, we show that, in addition to these well-studied molecular mechanisms, the treatment of wild-type TP53 MCF-7 and mutant TP53 MDA-MB-231 human breast cancer cells with desferrioxamine (DFO), a model iron chelator, causes significant epigenetic alterations at the global and gene-specific levels. Specifically, DFO treatment decreased the protein levels of the histone H3 lysine 9 demethylase, Jumonji domain-containing protein 2A (JMJD2A), in the MCF-7 and MDA-MB-231 cells and down-regulated the levels of the histone H3 lysine 4 demethylase, lysine-specific demethylase 1 (LSD1), in the MDA-MB-231 cells. These changes were accompanied by alterations in corresponding metabolically sensitive histone marks. Additionally, we demonstrate that DFO treatment activates apoptotic programs in MCF-7 and MDA-MB-231 cancer cells and enhances their sensitivity to the chemotherapeutic agents, doxorubicin and cisplatin; however, the mechanisms underlying this activation differ. The induction of apoptosis in wild-type TP53 MCF-7 cells was p53-dependent, triggered mainly by the down-regulation of the JMJD2A histone demethylase, while in mutant TP53 MDA-MB-231 cells, the activation of the p53-independent apoptotic program was driven predominantly by the epigenetic up-regulation of p21.

Novel chelators for cancer treatment: where are we now?

SIGNIFICANCE

Under normal circumstances, cellular iron levels are tightly regulated due to the potential toxic effects of this metal ion. There is evidence that tumors possess altered iron homeostasis, which is mediated by the perturbed expression of iron-related proteins, for example, transferrin receptor 1, ferritin and ferroportin 1. The de-regulation of iron homeostasis in cancer cells reveals a particular vulnerability to iron-depletion using iron chelators. In this review, we examine the absorption of iron from the gut; its transport, metabolism, and homeostasis in mammals; and the molecular pathways involved. Additionally, evidence for alterations in iron processing in cancer are described along with the perturbations in other biologically important transition metal ions, for example, copper(II) and zinc(II). These changes can be therapeutically manipulated by the use of novel chelators that have recently been shown to be highly effective in terms of inhibiting tumor growth.

RECENT ADVANCES

Such chelators include those of the thiosemicarbazone class that were originally thought to target only ribonucleotide reductase, but are now known to have multiple effects, including the generation of cytotoxic radicals.

CRITICAL ISSUES

Several chelators have shown marked anti-tumor activity in vivo against a variety of solid tumors. An important aspect is the toxicology and the efficacy of these agents in clinical trials.

FUTURE DIRECTIONS

As part of the process of the clinical assessment of the new chelators, an extensive toxicological assessment in multiple animal models is essential for designing appropriate dosing protocols in humans.

Signaling pathways of ESE-16, an antimitotic and anticarbonic anhydrase estradiol analog, in breast cancer cells

The aim of this study was to characterize the in vitro action of 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16) on non-tumorigenic MCF-12A, tumorigenic MCF-7 and metastatic MDA-MB-231 breast cancer cells. ESE-16 is able to inhibit the activity of a carbonic anhydrase II and a mimic of carbonic anhydrase IX in the nanomolar range. Gene and protein expression studies using various techniques including gene and antibody microarrays and various flow cytometry assays yielded valuable information about the mechanism of action of ESE-16. The JNK pathway was identified as an important pathway mediating the effects of ESE-16 while the p38 stress-induced pathway is more important in MDA-MB-231 cells exposed to ESE-16. Lysosomal rupture and iron metabolism was identified as important mediators of mitochondrial membrane depolarization. Abrogation of Bcl-2 phosphorylation status as a result of ESE-16 also plays a role in inducing mitochondrial membrane depolarization. The study provides a basis for future research projects to develop the newly synthesized compound into a clinically usable anticancer agent either alone or in combination with other agents.

Keywords: Antimitotic, anticarbonic anhydrase IX, apoptosis, autophagy, cell cycle arrest, Bcl-2, JNK, p38, mitochondrial membrane depolarization, flow cytometry, gene expression and protein microarray, anticancer.

Regulation of iron homeostasis by microRNAs

Iron homeostasis is maintained at the cellular and systemic levels to assure adequate iron supply while preventing iron overload. The identification of genes mutated in patients with iron-related disorders or animal models with imbalances of iron homeostasis gave insight into the molecular mechanisms underlying processes critical for balancing iron levels, such as iron uptake, storage, export, and monitoring of available iron. MicroRNAs control genes involved in some of these processes adding an additional level of complexity to the regulation of iron metabolism. This review summarizes recent advances how miRNAs regulate iron homeostasis.

Validation of RNA isolated from milk fat globules to profile mammary epithelial cell expression during lactation and transcriptional response to a bacterial infection

Mastitis, an inflammation of the mammary gland, is the most costly infectious disease of dairy ruminants worldwide. Although it receives considerable attention, the early steps of the host response remain poorly defined. Here, we report a noninvasive method using milk fat globules (MFG) as a source of mammary RNA to follow the dynamics of the global transcriptional response of mammary epithelial cells (MEC) during the course of a bacterial infection. We first assessed that RNA isolated from MFG were representative of MEC RNA; we then evaluated whether MFG RNA could be used to monitor the MEC response to infection. Sufficiently high yields of good-quality RNA (RNA integrity numbers ranging between 6.7 and 8.7) were obtained from goat MFG for subsequent analyses. Contamination of MFG by macrophages and neutrophils, which can be trapped during creaming, was assessed and when using quantitative real-time PCR for cell-type specific markers, was shown to be weak enough (<8%) to affect MFG gene expression profiling. Using microarrays, we showed that RNA extracted from MFG and from mammary alveolar parenchyma shared approximately 90% of the highlighted probes corresponding in particular to genes encoding milk proteins (CSN, BLG, LALBA) and enzymes involved in milk fat synthesis and secretion (FASN, XDH, ADRP, SCD, and DGAT1). In addition, a gene involved in the acute-phase reaction, coding for the serum amyloid A3 (SAA3) protein, was found within the first 50 most highly expressed genes in a noninfectious context in both mammary alveolar parenchyma and MFG, strongly suggesting that SAA3 is expressed in MEC. We took advantage of this noninvasive RNA sampling to follow the early proinflammatory response of MEC during the course of a bacterial infection and showed that the levels of mRNA encoding SAA3 sharply increased at 24h postinfection. Taken together, our results demonstrate that MFG represent a unique source of MEC RNA to noninvasively sample sufficient amounts of high-quality RNA to assess the dynamics of MEC gene expression in vivo, especially during the first steps of infection, thereby paving the way for the discovery of early biomarkers for the control of intramammary infections. Furthermore, this noninvasive technique could be used to provide mammary transcriptomic data on a large scale, thus filling the gap between genomic and phenotypic data.

Conjugated linoleic acid isomers modulate protein expression profile in rat hepatocytes

Conjugated linoleic acid (CLA) is a polyunsaturated fatty acid, which has been recently proven to be effective in reducing body fat mass, but brings as a side effect, the liver enlargement due to an increased lipid content. The in vivo lipogenic activity has been suggested to be due to the reduction in fat mass and to the consequent metabolism of blood glucose to fatty acid in the liver rather than in the adipose tissue. We investigated the ability of CLA to directly induce steatosis by modulating the expression pattern of hepatic proteins involved in lipid metabolism. To avoid interferences derived from CLA metabolism by other tissues, we used the in vitro model of freshly isolated rat hepatocytes incubated in the presence of different CLA isomers. The direct effect of CLA on lipid accumulation in hepatocytes was demonstrated by the altered expression pattern of several proteins involved in lipid metabolism, as assessed by two-dimensional gel electrophoresis and confirmed by Western blotting analysis. The CLA isomer c9,t11 was most effective in modulating the protein expression profile.

MicroRNAs: toward the clinic for breast cancer patients

Expression of microRNAs (miRNAs) has been found to be deregulated in all human cancers, where they may behave either as oncogenes or as tumor-suppressor genes. In the last 5 years, miRNA investigations in breast cancer represented an exciting area of discovery, which produced new knowledge on the molecular basis of this disease, tools for molecular classification, and new markers with diagnostic and prognostic relevance, as well as the discovery of novel breast cancer-predisposing genes. In this review, we describe current knowledge of the role of microRNAs in breast cancer.

Genome-wide association study identifies breast cancer risk variant at 10q21.2: results from the Asia Breast Cancer Consortium

Although approximately 20 common genetic susceptibility loci have been identified for breast cancer risk through genome-wide association studies (GWASs), genetic risk variants reported to date explain only a small fraction of heritability for this common cancer. We conducted a four-stage GWAS including 17 153 cases and 16 943 controls among East-Asian women to search for new genetic risk factors for breast cancer. After analyzing 684 457 SNPs in 2062 cases and 2066 controls (Stage I), we selected for replication among 5969 Chinese women (4146 cases and 1823 controls) the top 49 SNPs that had neither been reported previously nor were in strong linkage disequilibrium with reported SNPs (Stage II). Three SNPs were further evaluated in up to 13 152 Chinese and Japanese women (6436 cases and 6716 controls) (Stage III). Finally, two SNPs were evaluated in 10 847 Korean women (4509 cases and 6338 controls) (Stage IV). SNP rs10822013 on chromosome 10q21.2, located in the zinc finger protein 365 (ZNF365) gene, showed a consistent association with breast cancer risk in all four stages with a combined per-risk allele odds ratio of 1.10 (95% CI: 1.07-1.14) (P-value for trend = 5.87 × 10(-9)). In vitro electrophoretic mobility shift assays demonstrated the potential functional significance of rs10822013. Our results strongly implicate rs10822013 at 10q21.2 as a genetic risk variant for breast cancer among East-Asian women.

Validation of tumor-associated macrophage ferritin light chain as a prognostic biomarker in node-negative breast cancer tumors: A multicentric 2004 national PHRC study

Novel prognostic biomarkers are imperatively needed to help direct treatment decisions by typing subgroups of node-negative breast cancer patients. Large screening of different biological compartments, such as the proteome, by means of high throughput techniques may greatly help scientists to find such markers. The present retrospective multicentric study included 268 node-negative breast cancer patients. We used a proteomic approach of SELDI-TOF-MS screening to identify differentially expressed cytosolic proteins with prognostic impact. The screening cohort was composed of 198 patients. Seventy supplementary patients were included for validation. Immunohistochemistry (IHC) and immunoassay (IA) were run to confirm the prognostic role of the marker identified by SELDI-TOF-MS screening. IHC was also used to explore links between selected marker and epithelial-mesenchymal transition (EMT)-like, proliferation and macrophage markers. Ferritin light chain (FTL) was identified as an independent prognostic marker (HR = 1.30-95% CI: 1.10-1.50, p = 0.001). Validation step by means of IHC and IA confirmed the prognostic value of FTL level. CD68 IHC showed that FTL was stored in tumor-associated macrophages (TAM), which exhibit an M2-like phenotype. We report here, first, the validation of FTL as a breast tumor prognostic biomarker in node-negative patients, and second, the fact that FTL is stored in TAM.

Shielding the messenger (RNA): microRNA-based anticancer therapies

It has been a decade since scientists realized that microRNAs (miRNAs) are not an oddity invented by worms to regulate gene expression at post-transcriptional levels. Rather, many of these 21-22-nucleotide-short RNAs exist in invertebrates and vertebrates alike and some of them are in fact highly conserved. miRNAs are now recognized as an important class of non-coding small RNAs that inhibit gene expression by targeting mRNA stability and translation. In the last ten years, our knowledge of the miRNAs world was expanding at vertiginous speed, propelled by the development of computational engines for miRNA identification and target prediction, biochemical tools and techniques to modulate miRNA activity, and last but not least, the emergence of miRNA-centric animal models. One important conclusion that has emerged from this effort is that many microRNAs and their cognate targets are strongly implicated in cancer, either as oncogenes or tumor and metastasis suppressors. In this review we will discuss the diverse role that miRNAs play in cancer initiation and progression and also the tools with which miRNA expression could be corrected in vivo. While the idea of targeting microRNAs towards therapeutic ends is getting considerable traction, basic, translational, and clinical research done in the next few years will tell whether this promise is well-founded.

Regulation of neuronal ferritin heavy chain, a new player in opiate-induced chemokine dysfunction

The heavy chain subunit of ferritin (FHC), a ubiquitous protein best known for its iron-sequestering activity as part of the ferritin complex, has recently been described as a novel inhibitor of signaling through the chemokine receptor CXCR4. Levels of FHC as well as its effects on CXCR4 activation increase in cortical neurons exposed to mu-opioid receptor agonists such as morphine, an effect likely specific to neurons. Major actions of CXCR4 signaling in the mature brain include a promotion of neurogenesis, activation of pro-survival signals, and modulation of excitotoxic pathways; thus, FHC up-regulation may contribute to the neuronal dysfunction often associated with opiate drug abuse. This review summarizes our knowledge of neuronal CXCR4 function, its regulation by opiates and the role of FHC in this process, and known mechanisms controlling FHC production. We speculate on the mechanism involved in FHC regulation by opiates and offer FHC as a new target in opioid-induced neuropathology.

Serum Ferritin in Healthy Women and Breast Cancer Patients

Serum tumor markers are important tools in managing patients with breast cancer. Currently used CA 15-3 and CEA have found their clinical application particularly in the follow-up of patients with advanced disease. Ferritin belongs to a group of other molecules of potential interest to clinicians whose concentration is also altered in sera of patients with breast tumors. In this study the serum ferritin concentration was estimated in the sera of breast cancer patients before initial surgical treatment or those with advanced disease, and compared to healthy women as control. Ferritin level was measured by an immunoradiometric assay. The aim was to asses whether the serum ferritin concentration was altered in breast cancer and whether it could be related to progression of the disease. In healthy women, a statistically significant difference (p<0.05) in ferritin concentration was observed between premenopausal and postmenopausal women. In both breast cancer groups ferritin levels were higher than in healthy premenopausal women (both p<0.05). In patients with advanced disease, ferritin was further elevated (p<0.05) compared to preoperative levels in the patient group undergoing initial surgical treatment. These results indicate that an elevated ferritin concentration in the serum of younger women could serve as an additional parameter in breast cancer diagnosis and staging.

Iron-binding proteins and C-reactive protein in Nipple Aspirate Fluids: role of Iron-driven inflammation in breast cancer microenvironment?

Breast cancer, a worldwide disease with increasing incidence, develops from ductal/lobular epithelium. Nipple aspirate fluid (NAF), secreted from the breast ducts and lobules, can be analyzed to assess metabolic activity in breast microenvironment. Premalignant and malignant cell alterations may produce biochemical signals that deliver inflammatory proteins to the site. C-reactive protein (CRP), acute-phase protein considered a prognostic marker of inflammation, is frequently over-expressed in invasive breast carcinomas. Starting from the evidence that soluble and cell-bound iron binding protein Ferritin (FTN) and Transferrin (TRF) are crucially involved in breast inflammation and cancer, the aim of the present study is to analyze in NAF (a ductal fluid mirroring the breast microenvironment noninvasively collected from healthy and proven breast cancer affected women, n=38), the concentrations of CRP, FTN and TRF through high sensitive immunoassays. We analysed also serum (n=35) and milk samples (n=20) from healthy subjects. The mean level of CRP in Cancer NAF was significantly higher than in NoCancer NAF (P < 0.0001), especially in postmenopausal patients. Moreover, in Cancer NAF we detected higher levels of TRF and FTN respect to NoCancer NAF (P<0.001). A highly significant positive correlation between FTN and CRP content (Y= 2322x + 6.196, r(2) = 0.651, P<0.0001) was found. These data may support the involvement of inflammation and deregulation of iron homeostasis in breast cancer etio-pathogenesis. The significant accumulation of CRP in NAF in conjunction to the disruption of iron homeostasis may help to identify women at higher breast cancer risk.

Ferroportin and hepcidin: a new hope in diagnosis, prognosis, and therapy for breast cancer

Breast cancer is the most prevalent malignancy in women. The success of breast cancer treatment relies on the ability to detect the disease and correct molecular abnormalities at an early stage of disease development. A recent article describes a marked decrease in the levels of ferroportin in breast cancer. More importantly, the presented results demonstrate convincingly the incredible diagnostic and prognostic value of ferroportin and hepcidin gene expression in breast cancer and suggest that determination of these two molecular markers may be used as guidance toward individualized therapy for breast cancer patients.