The iron metabolism of neoplastic cells: alterations that facilitate proliferation?

Role of ferritin alterations in human breast cancer cells

Breast cancer is the most common malignancy in women. Successful treatment of breast cancer relies on a better understanding of the molecular mechanisms involved in breast cancer initiation and progression. Recent studies have suggested a crucial role of perturbations in ferritin levels and tightly associated with this, the deregulation of intracellular iron homeostasis; however, the underlying molecular mechanisms for the cancer-linked ferritin alterations remain largely unknown and often with conflicting conclusions. Therefore, this study was undertaken to define the role of ferritin in breast cancer. We determined that human breast cancer cells with an epithelial phenotype, such as MCF-7, MDA-MB-361, T-47D, HCC70 and cells, expressed low levels of ferritin light chain, ferritin heavy chain, transferrin, transferring receptor, and iron-regulatory proteins 1 and 2. In contrast, expression of these proteins was substantially elevated in breast cancer cells with an aggressive mesenchymal phenotype, such as Hs-578T, BT-549, and especially MDA-MB-231 cells. The up-regulation of ferritin light chain and ferritin heavy chain in MDA-MB-231 cells was accompanied by alterations in the subcellular distribution of these proteins as characterized by an increased level of nuclear ferritin and a lower level of the cellular labile iron pool as compared to MCF-7 cells. We established that ferritin heavy chain is a target of miRNA miR-200b, suggesting that its up-regulation in MDA-MB-231 cells may be triggered by the low expression of miR-200b. Ectopic up-regulation of miR-200b by transfection of MDA-MB-231 cells with miR-200b substantially decreased the level of ferritin heavy chain. More importantly, miR-200b-induced down-regulation of ferritin was associated with an increased sensitivity of the MDA-MB-231 cells to the chemotherapeutic agent doxorubicin. These results suggest that perturbations in ferritin levels are associated with the progression of breast cancer toward a more advanced malignant phenotype.

EPR Study of Iron Ion Complexes in Human Blood

Electronic states of iron ion complexes in human blood from patients with melanoma have been investigated by electron paramagnetic resonance (EPR). The measurements were performed at liquid nitrogen temperature (77 K) on an X-band EPR spectrometer. Numerous types of iron paramagnetic centers have been identified. In several kinds of protein complexes exemplified by methemoglobin, transferrin or ferritin, various forms of trivalent iron have been found. Three groups of patients with typical EPR spectra have been individualized. These groups differed in types and concentration of paramagnetic centers in peripheral blood. A good correlation has been found between the EPR results, the total iron ion complexes concentration and transferrin saturation.

Free Rhodium (II) citrate and rhodium (II) citrate magnetic carriers as potential strategies for breast cancer therapy

Background

Rhodium (II) citrate (Rh₂(H₂cit)₄) has significant antitumor, cytotoxic, and cytostatic activity on Ehrlich ascite tumor. Although toxic to normal cells, its lower toxicity when compared to carboxylate analogues of rhodium (II) indicates Rh₂(H₂cit)₄ as a promising agent for chemotherapy. Nevertheless, few studies have been performed to explore this potential. Superparamagnetic particles of iron oxide (SPIOs) represent an attractive platform as carriers in drug delivery systems (DDS) because they can present greater specificity to tumor cells than normal cells. Thus, the association between Rh₂(H₂cit)₄ and SPIOs can represent a strategy to enhance the former's therapeutic action. In this work, we report the cytotoxicity of free rhodium (II) citrate (Rh₂(H₂cit)₄) and rhodium (II) citrate-loaded maghemite nanoparticles or magnetoliposomes, used as drug delivery systems, on both normal and carcinoma breast cell cultures.

Results

Treatment with free Rh₂(H₂cit)₄ induced cytotoxicity that was dependent on dose, time, and cell line. The IC₅₀ values showed that this effect was more intense on breast normal cells (MCF-10A) than on breast carcinoma cells (MCF-7 and 4T1). However, the treatment with 50 μM Rh₂(H₂cit)₄-loaded maghemite nanoparticles (Magh-Rh₂(H₂cit)₄) and Rh₂(H₂cit)₄-loaded magnetoliposomes (Lip-Magh-Rh₂(H₂cit)₄) induced a higher cytotoxicity on MCF-7 and 4T1 than on MCF-10A (p < 0.05). These treatments enhanced cytotoxicity up to 4.6 times. These cytotoxic effects, induced by free Rh₂(H₂cit)₄, were evidenced by morphological alterations such as nuclear fragmentation, membrane blebbing and phosphatidylserine exposure, reduction of actin filaments, mitochondrial condensation and an increase in number of vacuoles, suggesting that Rh₂(H₂cit)₄ induces cell death by apoptosis.

Conclusions

The treatment with rhodium (II) citrate-loaded maghemite nanoparticles and magnetoliposomes induced more specific cytotoxicity on breast carcinoma cells than on breast normal cells, which is the opposite of the results observed with free Rh₂(H₂cit)₄ treatment. Thus, magnetic nanoparticles represent an attractive platform as carriers in Rh₂(H₂cit)₄ delivery systems, since they can act preferentially in tumor cells. Therefore, these nanopaticulate systems may be explored as a potential tool for chemotherapy drug development.

The role of heme and the mitochondrion in the chemical and molecular mechanisms of mammalian cell death induced by the artemisinin antimalarials

The artemisinin compounds are the frontline drugs for the treatment of drug-resistant malaria. They are selectively cytotoxic to mammalian cancer cell lines and have been implicated as neurotoxic and embryotoxic in animal studies. The endoperoxide functional group is both the pharmacophore and toxicophore, but the proposed chemical mechanisms and targets of cytotoxicity remain unclear. In this study we have used cell models and quantitative drug metabolite analysis to define the role of the mitochondrion and cellular heme in the chemical and molecular mechanisms of cell death induced by artemisinin compounds. HeLa ρ(0) cells, which are devoid of a functioning electron transport chain, were used to demonstrate that actively respiring mitochondria play an essential role in endoperoxide-induced cytotoxicity (artesunate IC(50) values, 48 h: HeLa cells, 6 ± 3 μM; and HeLa ρ(0) cells, 34 ± 5 μM) via the generation of reactive oxygen species and the induction of mitochondrial dysfunction and apoptosis but do not have any role in the reductive activation of the endoperoxide to cytotoxic carbon-centered radicals. However, using chemical modulators of heme synthesis (succinylacetone and protoporphyrin IX) and cellular iron content (holotransferrin), we have demonstrated definitively that free or protein-bound heme is responsible for intracellular activation of the endoperoxide group and that this is the chemical basis of cytotoxicity (IC(50) value and biomarker of bioactivation levels, respectively: 10β-(p-fluorophenoxy)dihydroartemisinin alone, 0.36 ± 0.20 μM and 11 ± 5%; and with succinylacetone, >100 μM and 2 ± 5%).

Artesunate mitigates proliferation of tumor cells by alkylating heme-harboring nitric oxide synthase

Artesunate (ART), a semi-synthetic derivative of antimalarial artemisinin, kills cancer cells with uncertain mechanisms. Here, we report for the first time that ART may exert the anti-tumor activity by conjugating the prosthetic heme of hemoproteins in a hepatoma cell line, HepG2, which was evident by monitoring the shift of absorbance from heme (A₄₁₅) to the ART-heme adduct (A₄₇₆). Accordingly, a transient elevation of A₄₁₅ was observed with a synchronous burst of nitric oxide (NO) and a high rate of survival following incubation of HepG2 with 50 μM ART. In contrast, ART at above 100 μM led to an abrogation of NO generation and a decline of the survival rate in HepG2. These data implied that heme-containing nitric oxide synthase (NOS) may represent a major cellular target of ART in killing tumor cells.

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.

CD71 (transferrin receptor): an effective marker for erythroid precursors in bone marrow biopsy specimens

Accurate analysis of the erythroid lineage is essential in evaluating bone marrow biopsy specimens and can be particularly challenging in the setting of dyserythropoiesis. Transferrin receptor (CD71) mediates the uptake of transferrin-iron complexes and is highly expressed on the surface of cells of the erythroid lineage. Although CD71 has been used for flow cytometric analysis, its usefulness in paraffin-embedded bone marrow biopsy specimens has not been examined. This study defined the immunohistochemical profile of CD71, as compared with glycophorin A (CD235a) and hemoglobin, in 65 bone marrow biopsy specimens, including normal marrow specimens and cases of myelodysplastic syndrome, acute myeloid leukemia, acute lymphoblastic leukemia, plasma cell neoplasm, and metastatic carcinoma. Immunoreactivity for CD71 was restricted to erythroid precursors in normal and dyspoietic marrow samples and exhibited a membranous and cytoplasmic staining pattern. The vast majority of mature erythrocytes lack expression of CD71, greatly facilitating interpretation. CD71 is a highly effective marker for the detection of cells of erythroid lineage in bone marrow biopsy specimens.

MDM2 SNP309 genotype is associated with ferritin and LDH serum levels in children with stage 4 neuroblastoma

BACKGROUND

MDM2 SNP309, characterised by a T-to-G substitution in the MDM2 promoter, is associated with higher gene expression compared to wild type and was recently found to be a negative prognostic factor for patients with stage 4 neuroblastoma (NB), but not for children with localised disease. This polymorphism was not associated with any clinical or genetic tumour characteristics, including MYCN amplification and 1p chromosome deletion.

PROCEDURE

To better define the involvement of MDM2 SNP309 in NB, we explored its association with the main biochemical tumour markers, namely urinary concentrations of vanillyl mandelic acid (VMA) and homovanillic acid (HVA) and blood concentrations of ferritin and lactate dehydrogenase (LDH). A cohort of 497 NB children, enrolled in the Italian Neuroblastoma Registry between January 1985 and December 2005 and previously investigated for the prognostic role of MDM2 SNP309, was considered for this study.

RESULTS

VMA and HVA concentrations as well as HVA/VMA ratio were not affected by the MDM2 SNP309 genotype. Ferritin and LDH concentrations were significantly lower in TT than in TG/GG only in patients with stage 4 disease (P = 0.007 and 0.015, respectively). No association emerged in patients with localised disease. These findings were not affected by confounding from clinical or biological characteristics.

CONCLUSIONS

The association between MDM2 SNP309 and both ferritin and LDH in patients with stage 4 disease confirms the prognostic role of this polymorphism. The results suggest that the MDM2 SNP309 genotype can impact on tumour responses to hypoxia and might play an important role in the alteration of energetic metabolism in NB cells.

The molecular mechanism of action of artemisinin--the debate continues

Despite international efforts to 'roll back malaria' the 2008 World Malaria Report revealed the disease still affects approximately 3 billion people in 109 countries; 45 within the WHO African region. The latest report however does provide some 'cautious optimism'; more than one third of malarious countries have documented greater than 50% reductions in malaria cases in 2008 compared to 2000. The goal of the Member States at the World Health Assembly and 'Roll Back Malaria' (RBM) partnership is to reduce the numbers of malaria cases and deaths recorded in 2000 by 50% or more by the end of 2010. Although malaria is preventable it is most prevalent in poorer countries where prevention is difficult and prophylaxis is generally not an option. The burden of disease has increased by the emergence of multi drug resistant (MDR) parasites which threatens the use of established and cost effective antimalarial agents. After a major change in treatment policies, artemisinins are now the frontline treatment to aid rapid clearance of parasitaemia and quick resolution of symptoms. Since artemisinin and its derivatives are eliminated rapidly, artemisinin combination therapies (ACT's) are now recommended to delay resistance mechanisms. In spite of these precautionary measures reduced susceptibility of parasites to the artemisinin-based component of ACT's has developed at the Thai-Cambodian border, a historical 'hot spot' for MDR parasite evolution and emergence. This development raises serious concerns for the future of the artemsinins and this is not helped by controversy related to the mode of action. Although a number of potential targets have been proposed the actual mechanism of action remains ambiguous. Interestingly, artemisinins have also shown potent and broad anticancer properties in cell lines and animal models and are becoming established as anti-schistosomal agents. In this review we will discuss the recent evidence explaining bioactivation and potential molecular targets in the chemotherapy of malaria and cancer.

Redox-directed cancer therapeutics: molecular mechanisms and opportunities

Redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. This review will present an update on drug discovery, target identification, and mechanisms of action of experimental redox chemotherapeutics with a focus on pro- and antioxidant redox modulators now in advanced phases of preclinal and clinical development. Recent research indicates that numerous oncogenes and tumor suppressor genes exert their functions in part through redox mechanisms amenable to pharmacological intervention by redox chemotherapeutics. The pleiotropic action of many redox chemotherapeutics that involves simultaneous modulation of multiple redox sensitive targets can overcome cancer cell drug resistance originating from redundancy of oncogenic signaling and rapid mutation.Moreover, some redox chemotherapeutics may function according to the concept of synthetic lethality (i.e., drug cytotoxicity is confined to cancer cells that display loss of function mutations in tumor suppressor genes or upregulation of oncogene expression). The impressive number of ongoing clinical trials that examine therapeutic performance of novel redox drugs in cancer patients demonstrates that redox chemotherapy has made the crucial transition from bench to bedside.

Heme mediates cytotoxicity from artemisinin and serves as a general anti-proliferation target

Heme (Fe2+ protoporphyrin IX) is an essential molecule that has been implicated the potent antimalarial action of artemisinin and its derivatives, although the source and nature of the heme remain controversial. Artemisinins also exhibit selective cytotoxicity against cancer cells in vitro and in vivo. We demonstrate that intracellular heme is the physiologically relevant mediator of the cytotoxic effects of artemisinins. Increasing intracellular heme synthesis through the addition of aminolevulinic acid, protoporphyrin IX, or transferrin-bound iron increased the cytotoxicity of dihydroartemisinin, while decreasing heme synthesis through the addition of succinyl acetone decreased its cytotoxic activity. A simple and robust high throughput assay was developed to screen chemical compounds that were capable of interacting with heme. A natural products library was screened which identified the compound coralyne, in addition to artemisinin, as a heme interacting compound with heme synthesis dependent cytotoxic activity. These results indicate that cellular heme may serve a general target for the development of both anti-parasitic and anti-cancer therapeutics.

The role of reactive oxygen and nitrogen species in cellular iron metabolism

The catalytic role of iron in the Haber-Weiss chemistry, which results in propagation of damaging reactive oxygen species (ROS), is well established. In this review, we attempt to summarize the recent evidence showing the reverse: That reactive oxygen and nitrogen species can significantly affect iron metabolism. Their interaction with iron-regulatory proteins (IRPs) seems to be one of the essential mechanisms of influencing iron homeostasis. Iron depletion is known to provoke normal iron uptake via IRPs, superoxide and hydrogen peroxide are supposed to cause unnecessary iron uptake by similar mechanism. Furthermore, ROS are able to release iron from iron-containing molecules. On the contrary, nitric oxide (NO) appears to be involved in cellular defense against the iron-mediated ROS generation probably mainly by inducing iron removal from cells. In addition, NO may attenuate the effect of superoxide by mutual reaction, although the reaction product-peroxynitrite-is capable to produce highly reactive hydroxyl radicals.

Cell Permeable Iron Chelators as Potential Cancer Chemotherapeutic Agents

Iron is an essential micronutrient for the growth and function of all cells. It is, therefore, an attractive target for chemotherapeutic compounds. Numerous studies in vitro and in vivo provide evidence that iron chelators may be effective antitumor agents. Lipophilic iron chelators that are readily cell permeable and can bind intracellular iron stores may selectively kill cancer cells without damaging normal cells. In this review we discuss the role of iron in cellular processes and how these processes differ between normal and neoplastic cells. We also review the effects on normal and cancer cell growth of several lipophilic iron chelators.

Expression of hepcidin and other iron-regulatory genes in human hepatocellular carcinoma and its clinical implications

PURPOSE

We aimed to assess expression of ten iron-regulatory genes in hepatocellular carcinoma (HCC) and its clinical implications.

METHODS

We used real-time polymerase chain reaction to measure ten iron-regulatory genes' mRNA and Perls' stain to assess iron stores in 50 HCCs and adjacent nontumor specimens. We compared the differences of gene expression and iron stores between tumor and nontumor specimens, and analyzed the relationships of gene expression with hepatic iron stores, patients' hemoglobin levels and clinicopathologic parameters.

RESULTS

Hepcidin, ceruloplasmin, transferrin, and transferrin receptor 2 were downregulated, while transferrin receptor 1 was upregulated in HCC. Hepcidin was markedly decreased in HCC but still correlated with hepatic iron stores. Iron-regulatory genes varied in their relationships of expression with clinicopathologic parameters.

CONCLUSIONS

Altered expression of iron-regulatory genes in HCC may disturb patient's iron balance. Hepcidin may play a role in defending the body against HCC.

miR-320 targets transferrin receptor 1 (CD71) and inhibits cell proliferation

OBJECTIVE

MicroRNAs (miRNAs) have been implicated in complex vertebrate developmental systems, such as hematopoiesis, and may play an integral role in the development of human cancers. Based on these observations, we investigated the contribution of miRNAs to acute myelogenous leukemia cell lineage-specific differentiation.

MATERIALS AND METHODS

To facilitate the identification of miRNAs and their targets relevant to leukemic cell differentiation, changes miRNA expression were analyzed in the human leukemia cell line HL-60, which historically has been utilized to study lineage-specific changes in response to the differentiation agent 12-O-tetradecanoylphorbol-13-acetate (TPA).

RESULTS

Using this approach, we have identified a panel of TPA-induced miRNAs that are expressed coincident with HL-60 stereotypic morphological changes characteristic of monocytic differentiation. The transferrin receptor 1(TfR-1; CD71), whose surface expression is downregulated during TPA-mediated HL-60 cell differentiation, has been identified as a target of the TPA-induced miRNA miR-320. Cell culture experiments indicate that enforced miR-320 expression can suppress TfR-1 expression and cell proliferation.

CONCLUSION

TPA induces the expression of several miRNAs in HL-60 cells, one such miRNA (miR-320) contributes to downregulation of TfR-1 surface expression characteristically seen during HL-60 monocytic differentiation. Moreover, TfR-1-targeting miRNAs, such as miR-320, may have potential as novel therapeutic agents for cancer due to their inhibitory effects on cell proliferation.

Proteomic analysis of HCV cirrhosis and HCV-induced HCC: identifying biomarkers for monitoring HCV-cirrhotic patients awaiting liver transplantation

BACKGROUND

Progression from chronic hepatitis C virus (HCV) infection to cirrhosis and hepatocellular carcinoma (HCC) results in protein changes in the peripheral blood. We evaluated global protein expression in plasma samples of HCV-cirrhotic and HCV-cirrhotic-HCC patients.

PATIENTS AND METHODS

Plasma samples from 25 HCV-cirrhotic-HCC and 10 HCV-cirrhotic patients were quantitatively evaluated for protein expression. Tryptic peptides were analyzed using Thermo linear ion-trap mass spectrometer (LTQ) coupled with a Surveyor HPLC system (Thermo). SEQUEST and X!Tandem database search algorithms were used for peptide sequence identification. Protein relative quantification was performed using the area under the curve from the select ion chromatogram. A significant fold change between groups was based on controlling the false discovery rate (FDR) at less than 5%.

RESULTS

We identified and quantified 2320 proteins from the analysis of the different protein pattern between HCV-cirrhosis and HCV-HCC samples. Gene ontology terms classified the more important biologic process related to these proteins as signal transduction, regulation of transcription DNA-dependent, protein amino acid phosphorylation, cell adhesion, transport, and immune response. Seven proteins showed significant expression changes with a FDR less than 5% between cirrhosis and tumor groups. Moreover, 18 proteins showed significant expression changes (FDR <5%) when plasma samples from HCV-cirrhosis were compared with early HCV-HCC.

CONCLUSIONS

Differential protein expression was observed between samples from HCV patients with cirrhosis with and without HCC. Also, differences were observed between early and advanced HCV-HCC samples. This study provides important information for discovery of potential biomarkers for early HCC diagnosis in HCV cirrhotic patients.

Allogeneic blood transfusion given before radiotherapy is associated with the poor clinical outcome in patients with cervical cancer

PURPOSE

To analyze the effect of allogeneic blood transfusion on clinical outcome in 119 patients with stage IIB cervical cancer who were treated with radiotherapy +/- chemotherapy.

PATIENTS AND METHODS

Medical records were examined for hemoglobin levels before and during radiotherapy, history of allogeneic blood transfusions and the time point when transfusions were given. These factors were retrospectively analyzed along with other clinical risk factors for influences on the patients' clinical outcomes.

RESULTS

Thirty-two patients (26.9%) received packed red blood cell transfusion (mean, 3.4 units; range, 1-12 units) before or during radiotherapy. Median follow-up period was 39.3 months (range, 7.6-58.4 months). Patients with history of transfusion showed poorer metastasis-free survival and a trend toward poorer overall survival than non-transfused patients. When patients who received transfusions were sub-divided by the time of transfusion, those who received transfusions before radiotherapy had significantly poorer clinical outcome than those who received transfusions during radiotherapy. In a multivariable analysis, patients with pretreatment transfusion showed a higher risk of distant metastasis (HR = 3.75, 95% CI: 1.28-12.15, p = 0.017) and decreased overall survival rates (HR = 4.62, 95% CI: 1.15-18.54, p = 0.031) compared with those of other patients.

CONCLUSION

Our results suggest that allogeneic blood transfusions given before radiotherapy may be associated with higher incidence of distant metastases and decreased survival in patients with stage IIB cervical cancer.

Identification of differentially expressed genes in spontaneously regressing melanoma using the MeLiM swine model

Partial and some few cases of complete spontaneous regression have been observed in cutaneous melanoma patients but little is known about the molecular mechanisms involved. The Melanoblastoma-bearing Libechov Minipig (MeLiM) is a suitable animal model to study the phenomenon of spontaneous regression because MeLiM pigs exhibit naturally occurring melanomas which regress completely 6 months after birth. In this study, we used suppression subtractive hybridization (SSH) to identify molecular determinants of melanoma regression within swine melanoma tissues and melanoma cell cultures. Several markers involved in cell-adhesion, -communication, -motility, signal transduction, negative regulation of cell proliferation, transport and immune response were identified that correlated with melanoma regression whereas the main genes involved in melanin synthesis showed a strong downregulation. For the most differentially expressed genes, we validated the results obtained by SSH with qRT-PCR and with immunohistochemistry for some of them (CD9, MITF, RARRES1). Most notable, for the first time in melanoma, we identified the retinoic acid responder 1 gene (RARRES1) as a main actor of the regression process in melanoma. This first gene expression study in swine melanoma regression, may contribute to the finding of new therapeutic targets for human melanoma treatment.

A serum metabolomic investigation on hepatocellular carcinoma patients by chemical derivatization followed by gas chromatography/mass spectrometry

The purpose of this study was to investigate the serum metabolic difference between hepatocellular carcinoma (HCC, n = 20) male patients and normal male subjects (n = 20). Serum metabolome was detected through chemical derivatization followed by gas chromatography/mass spectrometry (GC/MS). The acquired GC/MS data was analyzed by stepwise discriminant analysis (SDA) and support vector machine (SVM). The metabolites including butanoic acid, ethanimidic acid, glycerol, L-isoleucine, L-valine, aminomalonic acid, D-erythrose, hexadecanoic acid, octadecanoic acid, and 9,12-octadecadienoic acid in combination with each other gave the strongest segregation between the two groups. By applying these variables, our method provided a diagnostic model that could well discriminate between HCC patients and normal subjects. More importantly, the error count estimate for each group was 0%. The total classifying accuracy of the discriminant function tested by SVM 20-fold cross validation was 75%. This technique is different from traditional ones and appears to be a useful tool in the area of HCC diagnosis.

Hyaluronan regulates ceruloplasmin production by gliomas and their treatment-resistant multipotent progenitors

Ceruloplasmin (glycosylphosphatidylinositol-linked ferroxidase associated with normal astrocytes) can also be secreted by glioma cells, where its function is unknown. Ceruloplasmin is not only present in glioma cells and in human glioma specimens but also is enriched in highly malignant glioma stem-like cells. Hyaluronan is a large extracellular glycosaminoglycan that enhances malignant glioma behaviors by interacting with CD44 receptors and by downstream activation of signaling proteins and transporters associated with malignancy. We examined the relationship between hyaluronan and ceruloplasmin expression in glioma stem-like cells. Antagonism of hyaluronan interactions with short-fragment hyaluronan oligomers decreased ceruloplasmin expression in parental and stem-like glioma cells in vivo and in cell culture, implying that hyaluronan regulates ceruloplasmin expression. Further gain and loss-of-function studies are needed to fully define the relationship between hyaluronan and ceruloplasmin, and ceruloplasmin's effect on malignant behaviors.

Breast tumor metastasis: analysis via proteomic profiling

The ability to predict the metastatic behavior of a patient's cancer, as well as to detect and eradicate such recurrences, remain major clinical challenges in oncology. While many potential molecular biomarkers have been identified and tested previously, none have greatly improved the accuracy of specimen evaluation over routine histopathological criteria and, to date, they predict individual outcomes poorly. The ongoing development of high-throughput proteomic profiling technologies is opening new avenues for the investigation of cancer and, through application in tissue-based studies and animal models, will facilitate the identification of molecular signatures that are associated with breast tumor cell phenotype. The appropriate use of these approaches has the potential to provide efficient biomarkers, and to improve our knowledge of tumor biology. This, in turn, will enable the development of targeted therapeutics aimed at ameliorating the lethal dissemination of breast cancer. In this review, we focus on the accumulating proteomic signatures of breast tumor progression, particularly those that correlate with the occurrence of distant metastases, and discuss some of the expected future developments in the field.

Dihydroartemisinin induces apoptosis in human leukemia cells HL60 via downregulation of transferrin receptor expression

Dihydroartemisinin (DHA), a water-soluble active metabolite of artemisinin derivatives, is the safest and most effective antimalarial analog of artemisinin. In the present investigation, we assessed the apoptotic effect of DHA on leukemia HL60 cells and its regulation of transferrin receptor (TfR). Cell growth inhibition was assessed by Trypan blue exclusive staining; the expression of caspase-3, Bcl-2, and Bax in HL60 cells was evaluated by Western blotting; DHA-induced apoptosis was determined by AO/EB double staining, DNA fragmentation assay, and flow cytometric analysis; the expression of TfR in HL60 cells was examined by real-time PCR assays, Western blotting, and flow cytometric analysis. DHA could specifically reduce the mRNA and protein expression of TfR in HL60 cells, and the flow cytometric analysis presented the unity tendency that the TfR content decreased progressively in a dose-dependent manner. Consequently, DHA exhibited high anticancer activity in HL60 cells; MTT assay and growth inhibition assay showed that DHA could specifically inhibit the growth of HL60 cells in a dose-dependent (0.25-8 micromol/l) and time-dependent (12-72 h) manner. DHA-induced DNA fragmentation also induced the activation of caspase-3 and influenced the expression of Bcl-2 and Bax. Taken together, these data from our study show that DHA can induce HL60 cell apoptosis via the effect of downregulation TfR expression resulting in an induction of apoptosis through the mitochondrial pathway, and it might be a potential antileukemia strategy for leukemia therapy.

Cancer cell iron metabolism and the development of potent iron chelators as anti-tumour agents

Cancer contributes to 50% of deaths worldwide and new anti-tumour therapeutics with novel mechanisms of actions are essential to develop. Metabolic inhibitors represent an important class of anti-tumour agents and for many years, agents targeting the nutrient folate were developed for the treatment of cancer. This is because of the critical need of this factor for DNA synthesis. Similarly to folate, Fe is an essential cellular nutrient that is critical for DNA synthesis. However, in contrast to folate, there has been limited effort applied to specifically design and develop Fe chelators for the treatment of cancer. Recently, investigations have led to the generation of novel di-2-pyridylketone thiosemicarbazone (DpT) and 2-benzoylpyridine thiosemicarbazone (BpT) group of ligands that demonstrate marked and selective anti-tumour activity in vitro and also in vivo against a wide spectrum of tumours. Indeed, administration of these compounds to mice did not induce whole body Fe-depletion or disturbances in haematological or biochemical indices due to the very low doses required. The mechanism of action of these ligands includes alterations in expression of molecules involved in cell cycle control and metastasis suppression, as well as the generation of redox-active Fe complexes. This review examines the alterations in Fe metabolism in tumour cells and the systematic development of novel aroylhydrazone and thiosemicarbazone Fe chelators for cancer treatment.

Roles of hormone replacement therapy and iron in proliferation of breast epithelial cells with different estrogen and progesterone receptor status

Estrogen and iron play critical roles in a female body development and were investigated in the present study in relation to in vitro cell proliferation. Prempro, a hormone replacement therapy drug, and 17beta-estradiol (E2) were shown to increase cell proliferations in estrogen receptor positive (ER+) cells independent of progesterone receptor (PR) status. For example, increased cell proliferation was observed in ER+/PR+ human breast cancer MCF-7, its matching non-cancerous human breast epithelial MCF-12A, and ER+/PR+ murine mammary cancer MXT+ cells, but not in ER-/PR- MDA-MB-231, its matching non-cancerous MCF-10A, and MXT- (ER-/PR+) cells. By mimicking post-menopausal conditions of high estrogen in local breast tissue and increased iron levels due to cessation of menstrual periods, E2 and iron were shown to exert synergistic effects on proliferation of MCF-7 cells and significantly increased Ki67 and proliferating cell nuclear antigen. Western blotting of E2-treated ER+ but not ER- cells showed that E2 also increased transferrin receptor (TfR). Further studies are needed to assess the mitogenic effects of iron and estrogen in normal post-menopausal breast.

The melanoma tumor antigen, melanotransferrin (p97): a 25-year hallmark – from iron metabolism to tumorigenesis

Melanotransferrin (MTf) or melanoma tumor antigen p97 is a transferrin (Tf) homolog that is found predominantly bound to the cell membrane via a glycosyl phosphatidylinositol anchor. The molecule is a member of the Tf superfamily and binds iron through a single high-affinity iron(III)-binding site. Since its discovery on the plasma membrane of melanoma cells, the function of MTf has remained intriguing, particularly in relation to its role in cancer cell iron transport. In fact, considering the crucial role of iron in many metabolic pathways, e.g., DNA synthesis, it was important to understand the function of MTf in the transport of this vital nutrient. MTf has also been implicated in diverse physiological processes, such as plasminogen activation, angiogenesis and cell migration. However, recent studies using a knockout mouse and post-transcriptional gene silencing have demonstrated that MTf is not involved in iron metabolism, but plays a vital role in melanoma cell proliferation and tumorigenesis. In this review, we discuss the possible biological functions of MTf, particularly in relation to cancer.

Proteomic analysis identifies candidate proteins associated with distant recurrences in breast cancer after adjuvant chemotherapy

Breast cancer is a heterogeneous disease and it is of importance to select patients with regard to different prognosis and treatment sensitivity to individualize treatment regimes. In this study we successfully adapted a protein extraction protocol from mRNA extracted tumor samples enabling two-dimensional gel electrophoresis (2-DE) analysis of samples previously analyzed by cDNA microarray. The aim was to find candidate proteins that distinguish breast cancer patients with or without recurrences after adjuvant CMF (cyclophosphamide, methotrexate and 5-FU) treatment within four years to follow-up. We identified several proteins distinguishing the recurrence group from the non-recurrence group, especially in the ER and PgR positive subgroup (n=7). The induced proteins were involved in translation/folding, iron ion binding, and protease inhibition, whereas proteins involved in signaling, ubiquitination, and splicing were decreased in expression. These results show that it is possible to use 2-DE to separate high abundant proteins in breast cancer tissue and to find discriminating proteins to identify patients with different prognosis after adjuvant CMF treatment.

Targeted treatment of cancer with artemisinin and artemisinin-tagged iron-carrying compounds

Artemisinin is a chemical compound that reacts with iron to form free radicals which can kill cells. Cancer cells require and uptake a large amount of iron to proliferate. They are more susceptible to the cytotoxic effect of artemisinin than normal cells. Cancer cells express a large concentration of cell surface transferrin receptors that facilitate uptake of the plasma iron-carrying protein transferrin via endocytosis. By covalently tagging artemisinin to transferrin, artemisinin could be selectively picked up and concentrated by cancer cells. Futhermore, both artemisinin and iron would be transported into the cell in one package. Once an artemisinin-tagged transferrin molecule is endocytosed, iron is released and reacts with artemisinin moieties tagged to transferrin. Formation of free radicals kills the cancer cell. The authors have found that artemisinin-tagged transferrin is highly selective and potent in killing cancer cells. Thus, artemisinin and artemisinin-tagged iron-carrying compounds could be developed into powerful anticancer drugs.

Evidence for the involvement of carbon-centered radicals in the induction of apoptotic cell death by artemisinin compounds

Artemisinin and its derivatives are currently recommended as first-line antimalarials in regions where Plasmodium falciparum is resistant to traditional drugs. The cytotoxic activity of these endoperoxides toward rapidly dividing human carcinoma cells and cell lines has been reported, and it is hypothesized that activation of the endoperoxide bridge by an iron(II) species, to form C-centered radicals, is essential for cytotoxicity. The studies described here have utilized artemisinin derivatives, dihydroartemisinin, 10beta-(p-bromophenoxy)dihydroartemisinin, and 10beta-(p-fluorophenoxy)dihydroartemisinin, to determine the chemistry of endoperoxide bridge activation to reactive intermediates responsible for initiating cell death and to elucidate the molecular mechanism of cell death. These studies have demonstrated the selective cytotoxic activity of the endoperoxides toward leukemia cell lines (HL-60 and Jurkat) over quiescent peripheral blood mononuclear cells. Deoxy-10beta-(p-fluorophenoxy)dihydroartemisinin, which lacks the endoperoxide bridge, was 50- and 130-fold less active in HL-60 and Jurkat cells, respectively, confirming the importance of this functional group for cytotoxicity. We have shown that chemical activation is responsible for cytotoxicity by using liquid chromatography-mass spectrometry analysis to monitor endoperoxide activation by measurement of a stable rearrangement product of endoperoxide-derived radicals, which was formed in sensitive HL-60 cells but not in insensitive peripheral blood mononuclear cells. In HL-60 cells the endoperoxides induce caspase-dependent apoptotic cell death characterized by concentration- and time-dependent mitochondrial membrane depolarization, activation of caspases-3 and -7, sub-G(0)/G(1) DNA formation, and attenuation by benzyloxycarbonyl-VAD-fluoromethyl ketone, a caspase inhibitor. Overall, these results indicate that endoperoxide-induced cell death is a consequence of activation of the endoperoxide bridge to radical species, which triggers caspase-dependent apoptosis.

Selective enhancement of cellular oxidative stress by chloroquine: implications for the treatment of glioblastoma multiforme

Chloroquine is used in the treatment of malaria, a disease caused by infection with the parasite Plasmodium. Although chloroquine appears to possess diverse pharmacological activity, its plasmodicidal activity results from augmentation of parasite oxidative stress. Chloroquine also appears to augment oxidative stress in metabolically active mammalian cells, including human astroglial cells. The authors propose that chloroquine may augment oxidative stress induced by radiotherapy in the treatment of glioblastoma multiforme, enhancing therapeutic efficacy. Such an effect would be consistent with the known pharmacological effects of chloroquine observed in Plasmodium. Other selective redox agents, such as tempol and artemisinin, should be investigated clinically for therapeutic benefit when coadministered with combined radio- and chemotherapy for cancer.

The macrophage cell surface glyceraldehyde-3-phosphate dehydrogenase is a novel transferrin receptor

The reticuloendothelial system plays a major role in iron metabolism. Despite this, the manner in which macrophages handle iron remains poorly understood. Mammalian cells utilize transferrin-dependent mechanisms to acquire iron via transferrin receptors 1 and 2 (TfR1 and TfR2) by receptor-mediated endocytosis. Here, we show for the first time that the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is localized on human and murine macrophage cell surface. The expression of this surface GAPDH is regulated by the availability of iron in the medium. We further demonstrate that this GAPDH interacts with transferrin and the GAPDH-transferrin complex is subsequently internalized into the early endosomes. Our work sheds new light on the mechanisms involved in regulation of iron, vital for controlling numerous diseases and maintaining normal immune function. Thus, we propose an entirely new avenue for investigation with respect to transferrin uptake and regulation mechanisms in macrophages.

Interleukin-29 uses a type 1 interferon-like program to promote antiviral responses in human hepatocytes

Interleukin-28A (IL-28A), IL-28B and IL-29 are a family of class II cytokines that stimulate antiviral responses through a heterodimeric receptor that is distinct from the type I interferon (IFN) receptor. To better understand how this newly described family of cytokines regulates the antiviral state, we compared various cellular responses elicited by IL-29 and IFN-alpha. Here we show that these cytokines stimulate similar patterns of signal transducer and activator of transcription 1 (STAT-1), -2, -3, and -5 phosphorylation and nearly identical patterns of gene expression when analyzed in two distinct cell types by microarray analysis. Interestingly, the IL-29 receptor is preferentially expressed on primary hepatocytes within normal liver and pegylated forms of IL-29 and IFN-alpha induced equivalent 2'5' oligoadenylate synthetase (OAS) and MX1 gene expression in this cell type. Pegylated IL-29 also produced a significant reduction in human hepatitis B and hepatitis C viral load in vitro and reduced the cytopathic effect caused by the fully replicating flavivirus, West Nile virus. In conclusion, IL-29 and IFN-alpha stimulate identical antiviral responses despite their utilization of different receptors. This fact, combined with significant receptor expression in hepatitis virus-infected livers, suggests that IL-29 may have therapeutic value against chronic viral hepatitis in human patients.

Expression of iron regulatory genes in a rat model of hepatocellular carcinoma

BACKGROUND/AIMS

The altered iron metabolism in hepatocellular carcinomas (HCCs), characterized by the iron-deficient phenotype, is suggested to be of importance for tumour growth. However, the underlying molecular mechanisms remain poorly understood. We asked whether these iron perturbations would involve altered expression of genes controlling iron homeostasis.

METHODS

HCCs were induced in rats by the Solt and Farber protocol of chemical hepatocarcinogenesis, and to evaluate the effects of iron loading, one group of animals were supplemented with dietary iron during tumour progression. Tissue iron contents were determined, labelling indices of S-phase nuclei were calculated, and mRNA levels of iron-regulatory genes were quantitated. Protein levels of ferroportin1 were determined with Western blot.

RESULTS

HCCs displayed reduced amount of tissue iron and lack of histologically stainable iron. HCCs expressed significantly higher mRNA levels of genes involved in iron uptake (transferrin receptor-1, divalent metal ion transporter-1), ferroxidase activity (Ferritin-H), and iron extrusion (ferroportin1). The protein levels of ferroportin1 in iron-deficient HCCs were similar as in control livers, and did not increase in HCCs exposed to iron. Hepcidin mRNA levels were decreased in iron-deficient HCCs, rose in response to iron loading and correlated to the tissue iron content.

CONCLUSIONS

Taken together, the altered expressions of iron-regulatory genes in HCCs possibly reflect an increased demand for bioavailable iron and a high iron turnover in neoplastic cells.

The transferrin receptor part I: Biology and targeting with cytotoxic antibodies for the treatment of cancer

The transferrin receptor (TfR) is a cell membrane-associated glycoprotein involved in the cellular uptake of iron and in the regulation of cell growth. Iron uptake occurs via the internalization of iron-loaded transferrin (Tf) mediated by the interaction with the TfR. In addition, the TfR may also contain other growth regulatory properties in certain normal and malignant cells. The elevated levels of TfR in malignancies, its relevance in cancer, and the extracellular accessibility of this molecule make it an excellent antigen for the treatment of cancer using antibodies. The TfR can be targeted by monoclonal antibodies specific for the extracellular domain of the receptor. In this review, we summarize advancements in the basic physiology of the TfR including structure, function, and expression. We also discuss the efficacy of targeting the TfR using cytotoxic antibodies that inhibit cell growth and/or induce apoptosis in targeted malignant cells.

Proteomic tracking of serum protein isoforms as screening biomarkers of ovarian cancer

Epithelial ovarian cancer is the fourth leading cause of cancer death among women. Due to the asymptomatic nature and poor survival characteristic of the disease, screening for specific biomarkers for ovarian cancer is a major health priority. Differentially expressed proteins in the serum of ovarian cancer patients have the potential to be used as cancer-specific biomarkers. In this study, proteomic methods were used to screen 24 serum samples from women with high-grade ovarian cancer and compared to a control group of 11 healthy women. Affigel-Blue treated serum samples were processed either by linear (pH 4-7) or narrow range (pH 5.5-6.7) IEF strips for the first dimension. Proteins separated in first dimension were resolved by 8-16% gradient SDS-PAGE. Protein spots were visualized by SYPRO Ruby staining, imaged by FX-imager and compared and analyzed by PDQuest software. Twenty-two protein spots were consistently differentially expressed between normal and ovarian cancer patients by resolving proteins in a linear pH strip of 4-7 for the first dimension. Six of the protein spots, significantly up-regulated in grade 3 ovarian cancer patients (p < 0.05), were identified by MALDI-TOF MS and Western blotting as the isoforms of haptoglobin precursor. When serum proteins were resolved on narrow pH range strips (5.5-6.7), 23 spots were consistently differentially expressed between normal and grade 3 ovarian cancer patients. Of these, 4 protein spots significantly down regulated in grade 3 ovarian cancer patients (p < 0.05) were identified by MALDI-TOF MS and Western blotting, as isoforms of transferrin precursor. Increased expression of serum haptoglobin and transferrin was also identified in peritoneal tumor fluid obtained from women diagnosed with grade 2/3 ovarian cancer (n = 7). Changes in the expression of haptoglobin and transferrin in the serum of women with different pathological grades of ovarian cancer was examined by one-dimensional Western blotting method. Serum samples collected from women suffering from benign, borderline, grade 1, grade 2 and grade 3 cancer (n = 4 for haptoglobin and n = 5 for transferrin in each group) were analyzed and compared to the serum of normal healthy women. The mean serum haptoglobin expression in grade 3 ovarian cancer patients was fourfold higher than in the control subjects (p < 0.05). On the other hand, transferrin expression in grade 3 ovarian cancer patients was decreased by twofold than in normal healthy women (p < 0.05). Haptoglobin expression in the serum of cancer patients (n = 7) decreased following chemotherapy (six cycles of taxol/carboplatin). Concomitant with the decrease of haptoglobin, transferrin expression remained constant in four patients, but increased in three out of seven patients included in the study. Changes in serum expression of haptoglobin correlated with the change of CA 125 levels before and after chemotherapy. In conclusion, proteomic profiling of differentially expressed proteins in the sera of normal women compared to women with ovarian cancer can greatly facilitate the discovery of a panel of biomarkers that may aid in the detection of ovarian cancer with greater specificity.

Haemochromatosis gene (HFE) mutations in viral-associated neoplasia: Linkage to cervical cancer

The present study examines the frequency of the two main HFE mutations (C282Y and H63D) in a randomly selected population of 346 individuals including 201 DNA samples from women with cervical neoplasia (including high-grade squamous intraepithelial lesions and invasive squamous cell carcinoma) and a control population of 146 women from the same geographical area. We found a significantly lower risk of development of cervical neoplasia in H63D carriers (OR = 0.56; 95% CI 0.35-0.92; p = 0.01). Multivariate logistic regression analysis confirms this observation (OR = 0.55; 95% CI 0.35-0.88, p = 0.01). Regarding the C282Y mutation no association was found (OR = 1.32; 95% CI 0.53-3.33; p = 0.52). In addition, a significant difference between H63D carrier and non-carrier women on the time-to-onset of cervical lesions was observed (log-rank test: p = 0.0012). These results indicate that HFE could be considered a candidate modifier gene of viral-related neoplasia such as cervical carcinoma possibly by a dual role on iron metabolism and immunological system.

Molecular genetic alterations and gene expression profile of a malignant rhabdoid tumor of the kidney

Malignant rhabdoid tumor of the kidney (MRTK) is a rare but highly aggressive tumor in children, and knowledge about the molecular signature of this tumor is limited. We report the molecular genetic alterations and gene expression profile of an MRTK tumor that arose in a 4-month-old Japanese girl. Fluorescence in situ hybridization and Southern blot analyses revealed a homozygous deletion of an approximately 0.29-Mb genomic region bordered by the Rgr and DDT genes in these tumor cells. This deleted region encodes SMARCB1, a candidate tumor suppressor gene for MRTK. Using a high-density oligonucleotide DNA array, we found increased expression of 25 genes, including genes involved in the cell cycle (10 genes), DNA replication (3 genes), cell growth (5 genes), and cell proliferation (5 genes), in this MRTK tumor sample, compared with a noncancerous kidney (NK) sample. On the other hand, 64 genes, including 4 genes regulating apoptosis, were found to show decreased expression in this MRTK tumor sample, compared with the NK sample. Among these alterations, we found alterations of expression of some genes, such as IGF2, MDK, TP53, and TNFSF10, in this MRTK tumor, as described previously. The molecular genetic alterations and altered pattern of gene expression found in this case may have contributed to the biological characteristics of the MRTK tumor that arose in our patient.

Phototherapy and malignancy: Possible enhancement by iron administration and hyperbaric oxygen

Photodynamic therapy (PDT) is a new therapeutic approach for the treatment of malignant tumors. Hyperbaric oxygen (HBO(2)) shows beneficial effects in various modalities of cancer interventions. Tumor cells tend to accumulate large amount of iron. There is interaction between tissue content of oxygen, iron, free radical production and tissue damage. Accumulation of intracellular iron is necessary for the production of oxygen radicals. HBO(2) increases tissue oxygen and hydrogen peroxide production in the cells. Malignant cells require iron, and exhibit more transferrin receptors. The photodynamic sensitization of human leukemic cells is achieved with accumulation of porphyrins stimulated by 5-aminolaevulanic acid (ALA) plus hemin. Further, a significant improvement in tumor response is obtained when PDT is delivered during hyperoxygenation. When PDT is combined with hyperoxygenation, the hypoxic condition is improved and the cell killing rate at various time points after PDT is significantly enhanced. Photosensitization with use of porphyrins is used with HBO(2) and PDT for treatment of certain tumors. PDT with ALA is used for treatment of actinic keratosis (AK). The combination of iron administration (by injection or oral rout), hemin, or transferrin, as a source for iron, HBO(2) as a source of oxygen under pressure and PDT as a source of generating free-radical tissue damage may be useful in the treatment of tumors. The possibility of combining HBO(2), iron, light and local photosensitizers to overcome skin tumors deserve extensive laboratory and clinical research work. Conclusively, iron, HBO(2), and PDT may have synergistic effect to hamper tumor cells.

The Evolution of Iron Chelators for the Treatment of Iron Overload Disease and Cancer

The evolution of iron chelators from a range of primordial siderophores and aromatic heterocyclic ligands has lead to the formation of a new generation of potent and efficient iron chelators. For example, various siderophore analogs and synthetic ligands, including ICL670A [4-[3,5-bis-(hydroxyphenyl)-1,2,4-triazol-1-yl]-benzoic acid], 4'-hydroxydesazadesferrithiocin, and Triapine, have been developed from predecessors and illustrate potent iron-mobilizing or antineoplastic activities. This review focuses on the evolution of iron chelators from initial lead compounds through to the development of novel chelating agents, many of which show great potential to be clinically applied in the treatment of iron overload disease and cancer.

Brain slice invasion model reveals genes differentially regulated in glioma invasion

Invasion of tumor cells into adjacent brain areas is one of the major problems in treatment of glioma patients. To identify genes that might contribute to invasion, fluorescent F98 glioma cells were allowed to invade an organotypic brain slice. Gene expression analysis revealed 5 up-regulated and 14 down-regulated genes in invasive glioma cells as compared to non-invasive glioma cells. Two gene products, ferritin and cyclin B1, were verified in human gliomas by immunohistochemistry. Ferritin exhibited high mRNA levels in migratory F98 cells and also showed higher protein expression in the infiltrating edge of human gliomas. Cyclin B1 with high mRNA expression levels in stationary F98 cells showed marked protein expression in the central portions of gliomas. These findings are compatible with the concept of tumor cells either proliferating or migrating. Our study is the first to apply brain slice cultures for the identification of differentially regulated genes in glioma invasion.

Ferritin contributes to melanoma progression by modulating cell growth and sensitivity to oxidative stress

PURPOSE

Employing an in vitro model system of human melanoma progression, we previously reported ferritin light chain (L-ferritin) gene overexpression in the metastatic phenotype. Here, we attempted to characterize the role of ferritin in the biology of human melanoma and in the progression of this disease.

EXPERIMENTAL DESIGN

Starting from the LM human metastatic melanoma cell line, we engineered cell clones in which L-ferritin gene expression was down-regulated by the stable expression of a specific antisense construct. These cells were then assayed for their growth capabilities, chemoinvasive properties, and sensitivity to oxidative stress. Additionally, ferritin protein content in primary and metastatic human melanomas was determined by immunohistochemistry.

RESULTS

Artificial L-ferritin down-regulation in the LM cells strongly inhibited proliferation and chemoinvasion in vitro and cell growth in vivo. In addition, L-ferritin down-regulated cells displayed enhanced sensitivity to oxidative stress and to apoptosis. Concurrently, immunohistochemical analysis of a human melanoma tissue array revealed that ferritin expression level in metastatic lesions was significantly higher (P < 0.0001) than in primary melanomas. Furthermore, ferritin expression was constantly up-regulated in autologous lymph node melanoma metastases when compared with the respective primary tumors in a cohort of 11 patients.

CONCLUSIONS

These data suggest that high ferritin expression can enhance cell growth and improve resistance to oxidative stress in metastatic melanoma cells by interfering with their cellular antioxidant system. The potential significance of these findings deserves to be validated in a clinical setting.

Loss of the von Hippel Lindau Tumor Suppressor Disrupts Iron Homeostasis in Renal Carcinoma Cells

Given the modulation of iron metabolism by hypoxia and the high iron requirement of neoplastic cells, we investigated iron metabolism in a human renal cancer cell line with a mutated von Hippel Lindau (VHL) tumor suppressor gene (RCC10) and in a transfectant clone with wild-type VHL (RCC63). The loss of VHL strongly up-regulated transferrin receptor expression in RCC10 cells as a result of hypoxia inducible factor-1 (HIF-1)-mediated transcriptional activation, leading to an increased uptake of transferrin-bound 55Fe. Increased iron availability did not compromise the resistance of VHL-defective cells to oxidative stress or promote faster cell multiplication. Surprisingly, the content of ferritin H and L subunits and ferritin mRNA levels were considerably lower in the RCC10 than in the RCC63 cells. Despite the similarities between HIF-1 and iron regulatory protein 2 (IRP2), we found no evidence of specific regulation of IRP2 by VHL. However, both IRP2 and IRP1 were slightly activated in RCC10 cells, thus indicating that this cell line has a somewhat reduced labile iron pool (LIP). The finding that RCC10 cells had a lower ferritin content but more ferritin-associated 55Fe than RCC63 explains why VHL-lacking cells may have a smaller LIP despite increased iron uptake. We also found a correlation between cytoprotection from iron-mediated damage and efficient incorporation into ferritin of both transferrin and non-transferrin-bound 55Fe. This study shows that, like oncogene activation, the loss of an oncosuppressor rearranges the expression pattern of the genes of iron metabolism to increase iron availability. However, in the case of VHL loss, mechanisms affecting iron handling by ferritin somehow counteract the effects that the reduced content of this protective protein may have on proliferation and oxidant sensitivity.

Modulation of iron on mitochondrial aconitase expression in human prostatic carcinoma cells

The mitochondrial aconitase (mACON) containing a [4Fe-4S] cluster is regarded as the key enzyme for citrate oxidation in the epithelial cells of human prostate. In vitro studies using the human prostatic carcinoma cells, PC-3 cells, found that both hemin and ferric ammonium citrate (FAC) significantly increased mACON enzymatic activity and gene expression. The effect of FAC on mACON was enhanced 2-fold by co-treating with ascorbic acid but blocked by co-treating with iron chelator, deferoxamine mesylate. Hemin treatments blocked 30% of citrate secretion from PC-3 cells but upregualted 2-fold of intracellular ATP biosynthesis. Results from reporter assay by using a cytomegalovirus enhance/promoter driven luciferase mRNA ligated to the iron response element (IRE) of mACON as a reporter construct demonstrated that modulation of FAC on gene translation of mACON gene is dependent on the IRE. Transient gene expression assays indicated that upregulation of mACON gene transcription by FAC may through the putative antioxidant response element (ARE) signal pathway. This study provides the first evidence of the biologic mechanism of human mACON gene translation/transcription and suggests a regulatory link between the energy utilization and the iron metabolism in human prostatic carcinoma cells.

Enhancement of cytotoxicity of artemisinins toward cancer cells by ferrous iron

Iron(II) heme-mediated activation of the peroxide bond of artemisinins is thought to generate the radical oxygen species responsible for their antimalarial activity. We analyzed the role of ferrous iron in the cytotoxicity of artemisinins toward tumor cells. Iron(II)-glycine sulfate (Ferrosanol) and transferrin increased the cytotoxicity of free artesunate, artesunate microencapsulated in maltosyl-beta-cyclodextrin, and artemisinin toward CCRF-CEM leukemia and U373 astrocytoma cells 1.5- to 10.3-fold compared with that of artemisinins applied without iron. Growth inhibition by artesunate and ferrous iron correlated with induction of apoptosis. Cell cycle perturbations by artesunate and ferrous iron were not observed. Treatment of p53 wild-type TK6 and p53 mutated WTK1 lymphoblastic cells showed that mutational status of the tumor suppressor p53 did not influence sensitivity to artesunate. The effect of ferrous iron and transferrin was reversed by monoclonal antibody RVS10 against the transferrin receptor (TfR), which competes with transferrin for binding to TfR. CCRF-CEM and U373 cells expressed TfR in 95 and 48% of the cell population, respectively, whereas TfR expression in peripheral mononuclear blood cells of four healthy donors was confined to 0.4-1.3%. This indicates that artemisinins plus ferrous iron may affect tumor cells more than normal cells. The IC(50) values for a series of eight different artemisinin derivatives in 60 cell lines of the U.S. National Cancer Institute were correlated with the microarray mRNA expression of 12 genes involved in iron uptake and metabolism by Kendall's tau test to identify iron-responsive cellular factors enhancing the activity of artemisinins. This pointed to mitochondrial aconitase and ceruloplasmin (ferroxidase).

Examination of the mechanism(s) involved in doxorubicin-mediated iron accumulation in ferritin: studies using metabolic inhibitors, protein synthesis inhibitors, and lysosomotropic agents

Anthracyclines are potent anticancer agents, but their use is limited by cardiotoxicity at high cumulative doses. The mechanisms involved in anthracycline-mediated cardiotoxicity are still poorly understood, but numerous investigations have indicated a role for iron in this process. Our previous studies using neoplastic and myocardial cells showed that anthracyclines inhibit iron mobilization from the iron storage protein, ferritin, resulting in marked accumulation of ferritin-iron. Although the process of ferritin-iron mobilization is little understood, catabolism of ferritin by lysosomes may be a likely mechanism. Because anthracyclines have been shown to accumulate in lysosomes, this latter organelle may be a potential target for these drugs. The present study demonstrated, using native polyacrylamide gel electrophoresis-59Fe autoradiography, that ferritin-59Fe mobilization is an energy-dependent process that also requires protein synthesis. Depression of lysosomal activity via the enzyme inhibitors E64d [(2S,3S)-trans-epoxysuccinyl-l-leucylamido-2-methylbutane ethyl ester] and leupeptin or the lysosomotropic agents ammonium chloride, chloroquine, and methylamine resulted in a 3- to 5-fold increase in 59Feferritin accumulation compared with control cells. In addition, the proteasome inhibitors N-benzoyloxycarbonyl (Z)-Leu-Leuleucinal (MG132) and lactacystin also significantly increased 59Fe-ferritin levels compared with control cells. These effects of lysosomotropic agents or inhibitors of lysosomal activity were comparable with that observed with the anthracycline doxorubicin. Collectively, our study indicates a role for lysosomes and proteasomes in ferritin-iron mobilization, and this pathway is dependent on metabolic energy and protein synthesis. Furthermore, the lysosome/proteasome pathway may be a novel anthracycline target, inhibiting iron mobilization from ferritin that is essential for vital iron-requiring processes such as DNA synthesis.

Mechanisms of TfR-mediated transcytosis and sorting in epithelial cells and applications toward drug delivery

Transferrin receptor has been an important protein for many of the advances made in understanding the intricacies of the intramolecular sorting pathways of endocytosed molecules. The unique internalization and recycling functions of transferrin receptor have also made it an attractive choice for drug targeting and delivery of large protein-based therapeutics and toxins. Recent advances in elucidating the role of the intracellular controllers of transferrin recycling and sorting, such as Rab proteins and their effectors, have led to enhancement of transferrin receptor as a drug delivery vehicle. This review focuses on the use of transferrin receptor as an agent for facilitating drug delivery and targeting, and the role that mechanisms of transferrin receptor sorting and transcytosis play in these events.

Iron uptake by melanoma cells from the soluble form of the transferrin homologue, melanotransferrin

Melanotransferrin (MTf) is a membrane-bound transferrin (Tf) homologue that can also exist in a soluble form (sMTf). Considering the high homology of MTf to Tf, it is possible to suggest that sMTf could bind to the high affinity transferrin receptor 1 (TfR1) or lower affinity TfR2. We have used sMTf labelled with 59Fe to examine its ability to donate Fe to cells. Our experiments demonstrate that sMTf is far less effective than Tf at donating Fe to cells and this does not occur via specific receptors. Indeed, the uptake of sMTf by cells occurred via a non-specific process (e.g. adsorptive pinocytosis).