Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade®) and deferiprone (Ferriprox®), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry.
Ferroportin and hepcidin are critical proteins for the regulation of systemic iron homeostasis. Ferroportin is the only known mechanism for export of intracellular non–heme-associated iron; its stability is regulated by the hormone hepcidin. Although ferroportin profoundly affects concentrations of intracellular iron in tissues important for systemic iron absorption and trafficking, ferroportin concentrations in breast cancer and their influence on growth and prognosis have not been examined. We demonstrate here that both ferroportin and hepcidin are expressed in cultured human breast epithelial cells and that hepcidin regulates ferroportin in these cells. Further, ferroportin protein is substantially reduced in breast cancer cells compared to nonmalignant breast epithelial cells; ferroportin protein abundance correlates with metabolically available iron. Ferroportin protein is also present in normal human mammary tissue and markedly decreased in breast cancer tissue, with the highest degree of anaplasia associated with lowest ferroportin expression. Transfection of breast cancer cells with ferroportin significantly reduces their growth after orthotopic implantation in the mouse mammary fat pad. Gene expression profiles in breast cancers from >800 women reveal that decreased ferroportin gene expression is associated with a significant reduction in metastasis-free and disease-specific survival that is independent of other breast cancer risk factors. High ferroportin and low hepcidin gene expression identifies an extremely favorable cohort of breast cancer patients who have a 10-year survival of >90%. Ferroportin is a pivotal protein in breast biology and a strong and independent predictor of prognosis in breast cancer.
Angiotensin-(1-7) [Ang-(1-7)] is an endogenous peptide hormone of the reninangiotensin system with antiproliferative and antiangiogenic properties. The primary objective of this study was to establish the recommended phase II dose of Ang-(1-7) for treating patients with advanced cancer. Secondary objectives were to assess toxicities, pharmacokinetics, clinical activity, and plasma biomarkers.
Patients with advanced solid tumors refractory to standard therapy were treated with escalating doses of Ang-(1-7) in cohorts of three patients. Ang-(1-7) was administered by s.c. injection once daily for 5 days on a 3-week cycle. Tumor measurements were done every two cycles and treatment was continued until disease progression or unacceptable toxicity.
Eighteen patients were enrolled. Dose-limiting toxicities encountered at the 700 μg/kg dose included stroke (grade 4) and reversible cranial neuropathy (grade 3). Other toxicities were generally mild. One patient developed a 19% reduction in tumor measurements. Three additional patients showed clinical benefit with stabilization of disease lasting more than 3 months. On day 1, Ang-(1-7) administration led to a decrease in plasma placental growth factor (PlGF) levels in patients with clinical benefit (P = 0.04) but not in patients without clinical benefit (P = 0.25). On day 5, PlGF levels remained lower in patients with clinical benefit compared with patients without clinical benefit (P = 0.04).
Ang-(1-7) is a first-in-class antiangiogenic drug with activity for treating cancer that is linked to reduction of plasma PlGF levels. The recommended phase II dose is 400 μg/kg for this administration schedule.
Circuit simulation is a powerful methodology to generate differential mathematical models. Due to its highly accurate modeling capability, circuit simulation can be used to investigate interactions between the parts and processes of a cellular system. Circuit simulation has become a core technology for the field of electrical engineering, but its application in biology has not yet been fully realized. As a case study for evaluating the more advanced features of a circuit simulation tool called Advanced Design System (ADS), we collected and modeled laboratory data for iron metabolism in mouse kidney cells for a H ferritin (HFt) receptor, T cell immunoglobulin and mucin domain-2 (TIM-2). The internal controlling parameters of TIM-2 associated iron metabolism were extracted and the ratios of iron movement among cellular compartments were quantified by ADS. The differential model processed by circuit simulation demonstrated a capability to identify variables and predict outcomes that could not be readily measured by in vitro experiments. For example, an initial rate of uptake of iron-loaded HFt (Fe-HFt) was 2.17 pmol per million cells. TIM-2 binding probability with Fe-HFt was 16.6%. An average of 8.5 min was required for the complex of TIM-2 and Fe-HFt to form an endosome. The endosome containing HFt lasted roughly 2 h. At the end of endocytosis, about 28% HFt remained intact and the rest was degraded. Iron released from degraded HFt was in the labile iron pool (LIP) and stimulated the generation of endogenous HFt for new storage. Both experimental data and the model showed that TIM-2 was not involved in the process of iron export. The extracted internal controlling parameters successfully captured the complexity of TIM-2 pathway and the use of circuit simulation-based modeling across a wider range of cellular systems is the next step for validating the significance and utility of this method.
circuit simulator; export; ferritin; iron; model; storage; TIM-2; uptake
New insights into the roles of proteins that regulate cellular iron in cancer growth, angiogenesis, and metastasis have recently emerged. Discoveries of the roles of ferroportin, hepcidin, Lcn2, and members of the STEAP and IRP families in cancer have provided specificity and molecular definition to the role of iron homeostasis in cancer growth and metastasis. A number of studies directly support a role of these proteins in modifying bio-available iron, while other studies suggest that at least some of their effects are independent of their role in iron biology.
Breast tumors contain a small population of tumor initiating stem-like cells, termed breast cancer stem cells (BCSCs). These cells, which are refractory to chemotherapy and radiotherapy, are thought to persist following treatment and drive tumor recurrence. We examined whether BCSCs are similarly resistant to hyperthermic therapy, and whether nanoparticles could be used to overcome this resistance. Using a model of triple-negative breast cancer stem cells, we show that BCSCs are markedly resistant to traditional hyperthermia and become enriched in the surviving cell population following treatment. In contrast, BCSCs are sensitive to nanotube-mediated thermal treatment and lose their long-term proliferative capacity after nanotube-mediated thermal therapy. Moreover, use of this therapy in vivo promotes complete tumor regression and long-term survival of mice bearing cancer stem cell-driven breast tumors. Mechanistically, nanotube thermal therapy promotes rapid membrane permeabilization and necrosis of BCSCs. These data suggest that nanotube-mediated thermal treatment can simultaneously eliminate both the differentiated cells that constitute the bulk of a tumor and the BCSCs that drive tumor growth and recurrence.
Changes in iron regulation characterize the malignant state. However, the pathways that effect these changes and their specific impact on prognosis remain poorly understood. We capitalized on publicly available microarray datasets comprising 674 breast cancer cases to systematically investigate how expression of genes related to iron metabolism is linked to breast cancer prognosis. Of 61 genes involved in iron regulation, 49% were statistically significantly associated with distant metastasis-free survival (DMFS). Cases were divided into test and training cohorts and the supervised principal component method was used to stratify cases into risk groups. Optimal risk stratification was achieved with a model comprising 16 genes, which we term the iron regulatory gene signature (IRGS). Multivariable analysis revealed that the IRGS contributes information not captured by conventional prognostic indicators (hazard ratio 1.61; 95% CI 1.16–2.24; p=0.004). The IRGS successfully stratified homogeneously treated patients, including ER+ patients treated with tamoxifen monotherapy, both with (p=0.006) and without (p=0.03) lymph node metastases. To test whether multiple pathways were embedded within the IRGS, we evaluated the performance of two gene dyads with known roles in iron biology in ER+ patients treated with tamoxifen monotherapy (n=371). For both dyads, gene combinations that minimized intracellular iron content (anti-import: TFRCLow/HFEHigh; or pro-export: FPHigh/HAMPLow) were associated with favorable prognosis (p<0.005). Although the clinical utility of the IRGS will require further evaluation, its ability to both identify high risk patients within traditionally low risk groups and low risk patients within high risk groups has the potential to affect therapeutic decision-making.
Multiwalled carbon nanotubes (MWCNTs) are cylindrical tubes of graphitic carbon with unique physical and electrical properties. MWCNTs are being explored for a variety of diagnostic and therapeutic applications. Successful biomedical application of MWCNTs will require compatibility with normal circulatory components, including constituents of the hemostatic cascades. In this manuscript, we compare the thrombotic activity of MWCNTs in vitro and in vivo. We also assess the influence of functionalization of MWCNTs on thrombotic activity. In vitro, MWCNT activate the intrinsic pathway of coagulation as measured by activated partial thromboplastin time (aPTT) assays. Functionalization by amidation or carboxylation enhances this procoagulant activity. Mechanistic studies demonstrate that MWCNTs enhance propagation of the intrinsic pathway via a non-classical mechanism strongly dependent on factor IX. MWCNTs preferentially associate with factor IXa and may provide a platform for its activation. In addition to their effects on the coagulation cascade, MWCNTs activate platelets in vitro, with amidated MWCNTs exhibiting greater platelet activation than carboxylated or pristine MWCNTs. However, contrasting trends are obtained in vivo, where functionalization tends to diminish rather than enhance pro-coagulant activity. Thus, following systemic injection of MWCNTs in mice, pristine MWCNTs decreased platelet counts, increased vWF, and increased D-dimers. In contrast, carboxylated MWCNTS exhibited little procoagulant tendency in vivo, eliciting only a mild and transient decrease in platelets. Amidated MWCNTs elicited no statistically significant change in platelet count. Further, neither carboxylated nor amidated MWCNTs increased vWF or D-dimers in mouse plasma. We conclude that the pro-coagulant tendencies of MWCNTs observed in vitro are not necessarily recapitulated in vivo. Further, functionalization can markedly attenuate the procoagulant activity of MWCNTs in vivo. This work will inform the rational development of biocompatible MWCNTs for systemic delivery.
blood; blood compatibility; clotting; nanoparticle; platelet activation; thrombosis
Angiogenesis is tightly regulated through complex crosstalk between pro- and anti-angiogenic signals. High molecular weight kininogen (HK) is an endogenous protein that is proteolytically cleaved in plasma and on endothelial cell surfaces to HKa, an anti-angiogenic protein. Ferritin binds to HKa and blocks its anti-angiogenic activity. Here, we explore mechanisms underlying the cytoprotective effect of ferritin in endothelial cells exposed to HKa. We observe that ferritin promotes adhesion and survival of HKa-treated cells and restores key survival and adhesion signaling pathways mediated by Erk, Akt, FAK and paxillin. We further elucidate structural motifs of both HKa and ferritin that are required for effects on endothelial cells. We identify an histidine-glycine-lysine (HGK) -rich antiproliferative region within domain 5 of HK as the target of ferritin, and demonstrate that both ferritin subunits of the H and L type regulate HKa activity. We further demonstrate that ferritin reduces binding of HKa to endothelial cells and restores the association of uPAR with α5β1 integrin. We propose that ferritin blocks the anti-angiogenic activity of HKa by reducing binding of HKa to UPAR and interfering with anti-adhesive and anti-proliferative signaling of HKa.
To test iron-containing multiwalled carbon nanotubes (MWCNTs) as bifunctional nanomaterials for imaging and thermal ablation of tumors.
Materials & Methods
MWCNTs entrapping iron were synthesized by chemical vapor deposition. The T2-weighted contrast enhancement properties of MWCNTs containing increasing amounts of iron were determined in vitro. Suspensions of these particles were injected into tumor-bearing mice and tracked longitudinally over 7 days by MRI. Heat-generating abilities of these nanomaterials following exposure to near infrared (NIR) laser irradiation was determined in vitro and in vivo.
The magnetic resonance contrast properties of carbon nanotubes were directly related to their iron content. Iron-containing nanotubes were functional T2-weighted contrast agents in vitro and could be imaged in vivo long-term following injection. Iron content of nanotubes did not affect their ability to generate thermoablative temperatures following exposure to NIR and significant tumor regression was observed in mice treated with MWCNTs and NIR laser irradiation.
These data demonstrate that iron-containing MWCNTs are functional T2-weighted contrast agents and efficient mediators of tumor-specific thermal ablation in vivo.
cancer; contrast agent; in vivo; laser; MRI; nanotube; T2; thermal therapy
Several germline single nucleotide polymorphisms (SNPs) have been consistently associated with prostate cancer (PCa) risk.
To determine whether there is an improvement in PCa risk prediction by adding these SNPs to existing predictors of PCa.
Design, setting, and participants
Subjects included men in the placebo arm of the randomized Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial in whom germline DNA was available. All men had an initial negative prostate biopsy and underwent study-mandated biopsies at 2 yr and 4 yr. Predictive performance of baseline clinical parameters and/or a genetic score based on 33 established PCa risk-associated SNPs was evaluated.
Outcome measurements and statistical analysis
Area under the receiver operating characteristic curves (AUC) were used to compare different models with different predictors. Net reclassification improvement (NRI) and decision curve analysis (DCA) were used to assess changes in risk prediction by adding genetic markers.
Results and limitations
Among 1654 men, genetic score was a significant predictor of positive biopsy, even after adjusting for known clinical variables and family history (p = 3.41 × 10−8). The AUC for the genetic score exceeded that of any other PCa predictor at 0.59. Adding the genetic score to the best clinical model improved the AUC from 0.62 to 0.66 (p < 0.001), reclassified PCa risk in 33% of men (NRI: 0.10; p = 0.002), resulted in higher net benefit from DCA, and decreased the number of biopsies needed to detect the same number of PCa instances. The benefit of adding the genetic score was greatest among men at intermediate risk (25th percentile to 75th percentile). Similar results were found for high-grade (Gleason score ≥7) PCa. A major limitation of this study was its focus on white patients only.
Adding genetic markers to current clinical parameters may improve PCa risk prediction. The improvement is modest but may be helpful for better determining the need for repeat prostate biopsy. The clinical impact of these results requires further study.
Prostate cancer; Genetics; AUC; Detection rate; Reclassification; SNPs; Prospective study; Clinical trial
To determine if cardiovascular magnetic resonance (CMR) measures of gadolinium (Gd) signal intensity (SI) within the left ventricular (LV) myocardium are associated with future changes in LV ejection fraction (LVEF) after receipt of doxorubicin (DOX).
Methods and Results
Forty Sprague-Dawley rats were divided into 3 groups scheduled to receive weekly intravenous doses of: normal saline (NS) (n=7), 1.5 mg/kg DOX (n=19), or 2.5 mg/kg DOX (n=14). MR determinations of LVEF and myocardial Gd-SI were performed before and then at 2, 4, 7, and 10 weeks after DOX initiation. During treatment, animals were sacrificed at different time points so that histopathological assessments of the LV myocardium could be obtained. Within group analyses were performed to examine time-dependent relationships between Gd-SI and primary events (a deterioration in LVEF or an unanticipated death). Six of 19 animals receiving 1.5 mg/kg of DOX and 10/14 animals receiving 2.5 mg/kg of DOX experienced a primary event; no NS animals experienced a primary event. In animals with a primary event, histopathological evidence of myocellular vacuolization occurred (p=0.04), and the Gd-SI was elevated relative to baseline at the time of the event (p<0.0001) and during the measurement period prior to the event (p=0.0001). In all animals (including NS) without an event, measures of Gd-SI did not differ from baseline.
After DOX, low serial measures of Gd-SI predict an absence of a LVEF drop or unanticipated death. An increase in Gd-SI after DOX forecasts a subsequent drop in LVEF as well as histopathologic evidence of intracellular vacuolization consistent with DOX cardiotoxicity.
cardiotoxicity; chemotherapy; congestive heart failure; doxorubicin
Ferritin binds specifically and saturably to a variety of cell types, and recently several ferritin receptors have been cloned. TIM-2 is a specific receptor for H ferritin (HFt) in the mouse. TIM-2 is a member of the T cell immunoglobulin and mucin domain containing (TIM) protein family and plays an important role in immunity. The expression of TIM-2 outside of the immune system indicates that this receptor may have broader roles. We tested whether ferritin binding to TIM-2 can serve as an iron delivery mechanism. TIM-2 was transfected into normal (TCMK-1) mouse kidney cells, where it was appropriately expressed on the cell surface. HFt was labeled with 55Fe and 55Fe-HFt was incubated with TIM-2 positive cells or controls. 55Fe-HFt uptake was observed only in TIM-2 positive cells. HFt uptake was also seen in A20 B cells, which express endogenous TIM-2. TIM-2 levels were not increased by iron chelation. Uptake of 55Fe-HFt was specific and temperature-dependent. HFt taken up by TIM-2 positive cells transited through the endosome and eventually entered a lysosomal compartment, distinguishing the HFt pathway from that of transferrin, the classical vehicle for cellular iron delivery. Iron delivered following binding of HFt to TIM-2 entered the cytosol and became metabolically available, resulting in increased levels of endogenous intracellular ferritin. We conclude that TIM-2 can function as an iron uptake pathway.
Serum ferritin was discovered in the 1930’s, and was developed as a clinical test in the 1970’s. Many diseases are associated with iron overload or iron deficiency. Serum ferritin is widely used in diagnosing and monitoring these diseases.
Scope of Review
In this chapter, we discuss the role of serum ferritin in physiological and pathological processes and its use as a clinical tool.
Although many aspects of the fundamental biology of serum ferritin remain surprisingly unclear, a growing number of roles have been attributed to extracellular ferritin, including newly described roles in iron delivery, angiogenesis, inflammation, immunity, signaling and cancer.
Serum ferritin remains a clinically useful tool. Further studies on the biology of this protein may provide new biological insights.
Because both iron deficiency and iron excess are deleterious to normal cell function, the intracellular level of iron must be tightly controlled. Ferritin, an iron binding protein, regulates iron balance by storing iron in a bioavailable but non-toxic form. Ferritin protein comprises two subunits: ferritin H, which contains ferroxidase activity, and ferritin L. Here we demonstrate that ferritin H mRNA and protein are induced by histone deacetylase inhibitors (HDAC inhibitors), a promising class of anti-cancer drugs, in cultured human cancer cells. Deletion analysis and EMSA assays reveal that the induction of ferritin H occurs at a transcriptional level via Sp1 and NF-Y binding sites near the transcriptional start site of the human ferritin H promoter. Classically, HDAC inhibitors modulate gene expression by increasing histone acetylation. However, ChIP assays demonstrate that HDAC inhibitors induce ferritin H transcription by increasing NF-Y binding to the ferritin H promoter without changes in histone acetylation. These results identify ferritin H as a new target of HDAC inhibitors, and recruitment of NF-Y as a novel mechanism of action of HDAC inhibitors.
Ferritin H; histone acetylation; chromatin immunoprecipitation; cancer; HDAC inhibitors; transcription
It is well known that significant metabolic change take place as cells are transformed from normal to malignant. This review focuses on the use of different bioinformatics tools in cancer metabolomics studies. The article begins by describing different metabolomics technologies and data generation techniques. Overview of the data pre-processing techniques is provided and multivariate data analysis techniques are discussed and illustrated with case studies, including principal component analysis, clustering techniques, self-organizing maps, partial least squares, and discriminant function analysis. Also included is a discussion of available software packages.
Metabolomics; Cancer; Metabolite profiling; NMR; Mass spectrometry; Bioinformatics
Cancer survivors exposed to anthracyclines experience an increased risk of cardiovascular (CV) events. We hypothesized that anthracycline use may increase aortic stiffness, a known predictor of CV events.
Patients and Methods
We performed a prospective, case-control study involving 53 patients: 40 individuals who received an anthracycline for the treatment of breast cancer, lymphoma, or leukemia (cases), and 13 age- and sex-matched controls. Each participant underwent phase-contrast cardiovascular magnetic resonance measures of pulse wave velocity (PWV) and aortic distensibility (AoD) in the thoracic aorta at baseline, and 4 months after initiation of chemotherapy. Four one-way analyses of covariance models were fit in which factors known to influence thoracic aortic stiffness were included as covariates in the models.
At the 4-month follow-up visit, aortic stiffness remained similar to baseline in the control participants. However, in the participants receiving anthracyclines, aortic stiffness increased markedly (relative to baseline), as evidenced by a decrease in AoD (P < .0001) and an increase in PWV (P < .0001). These changes in aortic stiffness persisted after accounting for age, sex, cardiac output, administered cardioactive medications, and underlying clinical conditions known to influence aortic stiffness, such as hypertension or diabetes (P < .0001).
A significant increase in aortic stiffness occurs within 4 months of exposure to an anthracycline which was not seen in an untreated control group. These results indicate that previously regarded cardiotoxic cancer therapy adversely increases thoracic aortic stiffness, a known independent predictor of adverse cardiovascular events.
In order to understand how a cancer cell is functionally different from a normal cell it is necessary to assess the complex network of pathways involving gene regulation, signaling, and cell metabolism, and the alterations in its dynamics caused by the several different types of mutations leading to malignancy. Since the network is typically complex, with multiple connections between pathways and important feedback loops, it is crucial to represent it in the form of a computational model that can be used for a rigorous analysis. This is the approach of systems biology, made possible by new –omics data generation technologies. The goal of this review is to illustrate this approach and its utility for our understanding of cancer. After a discussion of recent progress using a network-centric approach, three case studies related to diagnostics, therapy, and drug development are presented in detail. They focus on breast cancer, B cell lymphomas, and colorectal cancer. The discussion is centered on key mathematical and computational tools common to a systems biology approach.
systems biology; cancer; mathematical modeling
Deletions within the short arm of chromosome 7 are observed in approximately 25% of adult and 10% of Wilms pediatric renal tumors. Within Wilms tumors, the region of interest has been delineated to a 2-Mb minimal region that includes ten known genes. Two of these ten candidate genes, SOSTDC1 and MEOX2, are particularly relevant to tumor development and maintenance. This finding, coupled with evidence that SOSTDC1 is frequently downregulated in adult renal cancer and regulates both Wingless-Int (Wnt)- and bone morphogenetic protein (BMP)-induced signaling, points to a role for SOSTDC1 as a potential tumor suppressor.
To investigate this hypothesis, we interrogated the Oncomine database to examine the SOSTDC1 levels in adult renal clear cell tumors and pediatric Wilms tumors. We then performed single nucleotide polymorphism (SNP) and sequencing analyses of SOSTDC1 in 25 pediatric and 36 adult renal tumors. Immunohistochemical staining of patient samples was utilized to examine the impact of SOSTDC1 genetic aberrations on SOSTDC1 protein levels and signaling.
Within the Oncomine database, we found that SOSTDC1 levels were reduced in adult renal clear cell tumors and pediatric Wilms tumors. Through SNP and sequencing analyses of 25 Wilms tumors, we identified four with loss of heterozygosity (LOH) at 7p and three that affected SOSTDC1. Of 36 adult renal cancers, we found five with LOH at 7p, two of which affected SOSTDC1. Immunohistochemical analysis of SOSTDC1 protein levels within these tumors did not reveal a relationship between these instances of SOSTDC1 LOH and SOSTDC1 protein levels. Moreover, we could not discern any impact of these genetic alterations on Wnt signaling as measured by altered beta-catenin levels or localization.
This study shows that genetic aberrations near SOSTDC1 are not uncommon in renal cancer, and occur in adult as well as pediatric renal tumors. These observations of SOSTDC1 LOH, however, did not correspond with changes in SOSTDC1 protein levels or signaling regulation. Although our conclusions are limited by sample size, we suggest that an alternative mechanism such as epigenetic silencing of SOSTDC1 may be a key contributor to the reduced SOSTDC1 mRNA and protein levels observed in renal cancer.
Four genome-wide association studies, all in populations of European descent, have identified 20 independent single nucleotide polymorphisms (SNPs) in 20 regions that are associated with prostate cancer risk. We evaluated these 20 SNPs in a combined African American (AA) study, with 868 prostate cancer patients and 878 control subjects. For 17 of these 20 SNPs, implicated risk-associated alleles were found to be more common in these AA cases than controls, significantly more than expected under the null hypothesis (P = 0.03). Two of these 17 SNPs, located at 3p12, and Region 2 at 8q24, were significantly associated with prostate cancer risk (P < 0.05), and only SNP rs16901979 at Region 2 of 8q24 remained significant after accounting for 20 tests. A multivariate analysis of additional SNPs across the broader 8q24 region revealed three independent prostate cancer risk-associated SNPs, including rs16901979, rs13254738, and rs10086908. The first two SNPs were ∼20 kb apart and the last SNP, a novel finding from this study, was ∼100 kb centromeric to the first two SNPs. These results suggest that a systematic evaluation of regions harboring known prostate cancer risk SNPs implicated in other races is an efficient approach to identify risk alleles for AA. However, studies with larger numbers of AA subjects are needed, and this will likely require a major collaborative effort to combine multiple AA study populations.
prostate cancer; African Americans; genome-wide association; 8q24; risk
Iron is required for survival of mammalian cells. Recently, understanding of iron metabolism and trafficking has increased dramatically, revealing a complex, interacting network largely unknown just a few years ago. This provides an excellent model for systems biology development and analysis. The first step in such an analysis is the construction of a structural network of iron metabolism, which we present here. This network was created using CellDesigner version 3.5.2 and includes reactions occurring in mammalian cells of numerous tissue types. The iron metabolic network contains 151 chemical species and 107 reactions and transport steps. Starting from this general model, we construct iron networks for specific tissues and cells that are fundamental to maintaining body iron homeostasis. We include subnetworks for cells of the intestine and liver, tissues important in iron uptake and storage, respectively; as well as the reticulocyte and macrophage, key cells in iron utilization and recycling. The addition of kinetic information to our structural network will permit the simulation of iron metabolism in different tissues as well as in health and disease.
iron; liver; macrophage; reactive oxygen species; red blood cells
Pre-organized tripodal ligands such as the N-picolyl derivatives of cis,cis-1,3,5-triamino-cis,cis-1,3,5-trimethylcyclohexane (Kemp’s triamine) were prepared as analogs to N,N’,N”- tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane (tachpyr) in hopes of enhancing the rate of formation and stability of the metal complexes. A tricyclic bisaminal was formed via the reduction of the Schiff base while the tri(picolyl) derivative was synthesized via reductive amination of pyridine carboxaldehyde. Their cytotoxicities to the HeLa cell line were evaluated and directly compared to tachpyr and N,N’,N”- tris(2-pyridylmethyl)-tris(2-aminoethyl)amine (trenpyr). Results indicate that N,N’,N”-tris(2-pyridylmethyl)-cis,cis-1,3,5-triamino-cis,cis-1,3,5-trimethylcyclohexane (Kemp’s pyr) exhibits cytotoxic activity against the HeLa cancer cell line comparable to tachpyr (IC50 ~ 8.0 µM). Both Kemp’s pyr and tachpyr show higher cytotoxic activity over the aliphatic analogue of trenpyr (IC50 ~ 14 µM) suggesting that the major contributor to the activity is the ligand’s ability to form a stable and tight complex and that the equatorial/axial equilibrium impacting the complex formation for the cyclohexane-based ligands is not significant.
We analyzed expression of candidate genes encoding cell surface or secreted proteins in normal kidney and kidney cancer. This screen identified a bone morphogenetic protein (BMP) antagonist, SOSTDC1 (sclerostin domain–containing-1) as down-regulated in kidney tumors. To confirm screening results, we probed cDNA dot blots with SOSTDC1. The SOSTDC1 message was decreased in 20/20 kidney tumors compared with normal kidney tissue. Immunohistochemistry confirmed significant decrease of SOSTDC1 protein in clear cell renal carcinomas relative to normal proximal renal tubule cells (p < 0.001). Expression of SOSTDC1 was not decreased in papillary and chromophobe kidney tumors. SOSTDC1 was abundantly expressed in podocytes, distal tubules, and transitional epithelia of the normal kidney. Transfection experiments demonstrated that SOSTDC1 is secreted and binds to neighboring cells and/or the extracellular matrix. SOSTDC1 suppresses both BMP-7–induced phosphorylation of R-Smads-1, -5, and -8 and Wnt-3a signaling. Restoration of SOSTDC1 in renal clear carcinoma cells profoundly suppresses proliferation. Collectively, these results demonstrate that SOSTDC1 is expressed in the human kidney and decreased in renal clear cell carcinoma. Because SOSTDC1 suppresses proliferation of renal carcinoma cells, restoration of SOSTDC1 signaling may represent a novel target in treatment of renal clear cell carcinoma.
We demonstrate that nitrogen doped, multi-walled carbon nanotubes (CNx-MWNT) result in photo-ablative destruction of kidney cancer cells when excited by near infrared (NIR) irradiation. Further, we show that effective heat transduction and cellular cytotoxicity depends on nanotube length: effective NIR coupling occurs at nanotube lengths that exceed half the wavelength of the stimulating radiation, as predicted in classical antenna theory. We also demonstrate that this radiation heats the nanotubes through induction processes, resulting in significant heat transfer to surrounding media and cell killing at extraordinarily small radiation doses. This cell death was attributed directly to photothermal effect generated within the culture, since neither the infrared irradiation itself nor the CNx-MWNT were toxic to the cells.
nitrogen doped; multi-walled carbon nanotubes; photothermal effect; photoablation
The Fe coordination chemistry of several tripodal aminopyridyl hexadentate chelators is reported along with cytotoxicity toward cultured Hela cells. The chelators are based on cis, cis-1,3,5-triaminocyclohexane (tach) with three pendant –CH2–2-pyridyl groups where 2-pyridyl is R-substituted thus are named tach-x-Rpyr where x=3, R=Me; x=3, R=MeO; x=6; R=Me. The structures of [Fe(tach-3-Mepyr)]Cl2 and [Fe(tach-3-MeOpyr)](FeCl4) are reported and their metric parameters indicate strongly-bound, low-spin Fe(II). The structure of [Fe(tach-6-Mepyr)](ClO4)2 implies steric effects of 6–Me groups push donor Npy’s away so one Fe-Npy bond is substantially longer at 2.380(3) Å vs. 2.228(3) Å for the others, and Fe(II) in the high-spin state. Accordingly, anions X− = Cl or SCN afford [Fe(tach-6-Mepyr)(X)]+ from [Fe(tach-6-Mepyr)]2+ (UV-vis spectroscopy). Consistent with a biological cytotoxicity involving Fe chelation, chelators of low-spin Fe(II) have greater toxicity in the order [IC50(72 h) is in parentheses then the spin-state SS=H (high) or L (low)]: tachpyr = tach-3-Mepyr (6 μM, SS=L) ≳tach-3-MeOpyr (12 μM, SS=L) ≫ tach-6-Mepyr (> 200 μM, SS=H). Iron-mediated oxidative dehydrogenation with O2 oxidant removes hydrogens from coordinated nitrogen and the adjacent CH2, converting aqueous [Fe(tach-3-Rpyr)]2+ (R = H, Me and MeO) into a mix of low-spin imino– and aminopyridyl-armed complexes, but [Fe(tach-6-Mepyr)]2+ does not react (NMR and ESI-MS spectroscopies). The difference of IC50 for chelators at different time points (ΔIC50 = [IC50(24 h) − IC50(72 h)]) is used to compare rate of cytotoxic action to qualitative rate of oxidation in the Fe-bound chelator, giving the order: [Fe(tach-3-Mepyr)]2+ (ΔIC50 = 5 μM) > [Fe(tachpyr)]2+ (ΔIC50 = 16 μM) > [Fe(tach-3-MeOpyr)]2+ (ΔIC50 = 118 μM). Thus, those chelators whose Fe(II) complexes undergo rapid oxidation kill cells faster, and those that bind Fe(II) as low-spin are far more cytotoxic.
redox reaction; antitumor agent; ligand design; tripodal chelator; Fe(II)