Coordinated Regulation of Iron-Controlling Genes, H-Ferritin and IRP2 , by c-MYC

Smith

Experimental Eye Research

et al. 2008

Microphthalmia-associated Transcription Factor (Mitf) is expressed in neural crest cell-derived melanocytes, and in the retinal pigment epithelium (RPE) during ocular development. Mutations in Mitf are associated with auditory/visual/pigmentary syndromes in humans. Mitf mi/mi mouse mutants lack pigmentation, and are microphthalmic, while Mitf vit/vit mouse mutants display abnormal RPE pigmentation, and progressive retinal degeneration. Microarray analysis was used to identify novel downstream gene targets/pathways in the RPE that are altered by mutations in the transcription factor Mitf. Using the Affymetrix platform, gene expression profiles were generated using the eyes of E13.5 mouse fetuses that were wildtype, heterozygous, or homozygous for the Mitf mi mutation. In a separate experiment, eyes from E13.5 mouse fetuses homozygous for the Mitf vit mutation were compared to eyes from the C57BL/6 control background strain. Statistical analyses were performed using Robust Multiarray Average, mixed-effects ANOVA and random-variance t-tests. Altered expression of genes involved in pigment formation, melanosome biogenesis/transport, and redox homeostasis were observed. 12 genes were commonly mis-regulated in the eyes of both Mitf mutants: 10 of these genes were downregulated in both mutants relative to controls, while 2 of the genes (Nramp1 (Slc11a1) and epoxide hydrolase) were downregulated in Mitf mi/mi mutants, and conversely, upregulated in Mitf vit/vit mutants. Quantitative RT-PCR and immunohistochemistry were used to confirm altered gene/protein expression. RPE expression of the Fe +2 iron transporter Nramp1 (Slc11a1) has not previously been reported. Fe +2 is an important co-factor utilized by the iron-dependent isomerohydrolase RPE65 in the retinoid visual cycle. However, excess accumulation of Fe +2 in the RPE has recently been associated with oxidative damage and age-related macular degeneration. Abnormal pigmentation and increased activity of Slc11a1 in the RPE of Mitf vit mice may contribute to the pathology and progressive retinal degeneration observed in these mutants.

Section: (3) Ingenuity Pathway Analysissupporting

confidence: 57%

Altered expression of the iron transporter Nramp1 (Slc11a1) during fetal development of the retinal pigment epithelium in microphthalmia-associated transcription factor Mitfmi and Mitfvitiligo mouse mutants

Smith

Experimental Eye Research

et al. 2008

Science Translational Medicine

“…For example, an increase in transferrin receptor 1, a cell surface receptor responsible for transferrin-mediated iron uptake, occurs in many cancers, including breast cancer (39–41). Ferritin, an iron storage protein, is decreased by the c-myc (42) and E1a (43) oncogenes; reduced ferritin is thought to shift iron from storage to a labile pool of, metabolically available iron. Similarly, antisense-mediated repression of ferritin increases the LIP (44) and stimulates H- ras –dependent proliferation (45).…”

Section: Discussionmentioning

confidence: 99%

Ferroportin and Iron Regulation in Breast Cancer Progression and Prognosis

Pinnix¹,

Miller²,

Wang³

et al. 2010

245

278

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.

“…However, there are limited a number of studies focusing on the transcriptional regulation of iron-responsive genes. The iron storage gene ferritin is regulated transcriptionally (White and Munro 1988;Wu et al 1999). Previously, global changes in irondependent gene expression were investigated in animal tissues including the rat duodenum (Collins et al 2005) and mouse liver (Kautz et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Iron deficiency upregulates Egr1 expression

Lee

Prywes

et al. 2015

Genes Nutr

Iron-deficient anemia is a prevalent disease among humans. We searched for genes regulated by iron deficiency and its regulated mechanism. cDNA microarrays were performed using Hepa1c1c7 cells treated with 100 lM desferrioxamine (DFO), an iron chelator. Early growth response 1 (Egr1) was upregulated with at least 20-fold increase within 4 h and lasted for 24 h, which was confirmed by qRT-PCR. This activation was not seen by ferric ammonium citrate (FAC). DFO increased the transcriptional activity of Egr1-luc (-604 to ?160) and serum response element (SRE)-luc reporters by 2.7-folds. In addition, cycloheximide lowered DFO-induced Egr1 mRNA levels. The upregulation of Egr1 by DFO was accompanied by sustained ERK signals along with phosphorylation of Elk-1. The ERK inhibitor (PD98059) prevented the DFO-induced Egr1 mRNAs. Overexpression of Elk-1 mutant (pElk-1S383A) decreased Egr1 reporter activity. DFO lowered reactive oxygen species (ROS) production and increased caspase 3/7 activity and cell death. DFO-induced iron deficiency upregulates Egr1 in part through transcriptional activation via ERK and Elk-1 signals, which may be important in the regulation of cell death in hepatoma cells. Our study demonstrated that iron depletion controlled the expression of Egr1, which might contribute to decisions about cellular fate in response to iron deficiency.