title: Loss of Hfe leads to progression of tumor phenotype in primary retinal pigment epithelial cells.
abstract: OBJECTIVE
  Hemochromatosis is a disorder of iron overload arising mostly from mutations in HFE. HFE is expressed in retinal pigment epithelium (RPE), and Hfe(-/-) mice develop age-related iron accumulation and retinal degeneration associated with RPE hyperproliferation. Here, the mechanism underlying the hyperproliferative phenotype in RPE was investigated.
  
  
  METHODS
  Cellular senescence was monitored by β-galactosidase activity. Gene expression was monitored by real-time PCR. Survivin was analyzed by Western blot and immunofluorescence. Migration and invasion were monitored using appropriate kits. Glucose transporters (GLUTs) were monitored by 3-O-methyl-D-glucose uptake. Histone deacetylases (HDACs) were studied by monitoring catalytic activity and acetylation status of histones H3/H4.
  
  
  RESULTS
  Hfe(-/-) RPE cells exhibited slower senescence rate and higher survivin expression than wild type cells. Hfe(-/-) cells migrated faster and showed greater glucose uptake and increased expression of GLUTs. The expression of HDACs and DNA methyltransferase (DNMTs) also was increased. Similarly, RPE cells from hemojuvelin (Hjv)-knockout mice, another model of hemochromatosis, also had increased expression of GLUTs, HDACs, and DNMTs. The expression of Slc5a8 was decreased in Hfe(-/-) RPE cells, but treatment with a DNA methylation inhibitor restored the transporter expression, indicating involvement of DNA methylation in the silencing of Slc5a8 in Hfe(-/-) cells.
  
  
  CONCLUSIONS
  RPE cells from iron-overloaded mice exhibit several features of tumor cells: decreased senescence, enhanced migration, increased glucose uptake, and elevated levels of HDACs and DNMTs. These features are seen in Hfe(-/-) RPE cells as well as in Hjv(-/-) RPE cells, providing a molecular basis for the hyperproliferative phenotype of Hfe(-/-) and Hjv(-/-) RPE cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, Georgia Health Sciences University, Augusta, Georgia 30912, USA. jgnanaprakasam@georgiahealth.edu
authors.forename: Jaya P
authors.initials: JP
authors.lastname: Gnana-Prakasam
authors.forename: Rajalakshmi
authors.initials: R
authors.lastname: Veeranan-Karmegam
authors.forename: Veena
authors.initials: V
authors.lastname: Coothankandaswamy
authors.forename: Sushma K
authors.initials: SK
authors.lastname: Reddy
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Martin
authors.forename: Muthusamy
authors.initials: M
authors.lastname: Thangaraju
authors.forename: Sylvia B
authors.initials: SB
authors.lastname: Smith
authors.forename: Vadivel
authors.initials: V
authors.lastname: Ganapathy
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics; D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics; D002465:Cell Movement / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D016922:Cellular Senescence / Q000502:physiology; D019175:DNA Methylation / Q000502:physiology; D018450:Disease Progression; D005134:Eye Neoplasms / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005947:Glucose / Q000493:pharmacokinetics; D006432:Hemochromatosis / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008819:Mice, Nude; D027501:Monocarboxylic Acid Transporters; D010641:Phenotype; D050480:Plasma Membrane Neurotransmitter Transport Proteins / Q000235:genetics; D061251:Primary Cell Culture; D012097:Repressor Proteins / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000473:pathology* / Q000503:physiopathology*; D000077022:Survivin; D014183:Transplantation, Heterologous
chemical_list: D026905:Amino Acid Transport Systems; C117749:Birc5 protein, mouse; D027682:Cation Transport Proteins; D000071020:Hemochromatosis Protein; C499535:Hfe protein, mouse; D015395:Histocompatibility Antigens Class I; D051034:Inhibitor of Apoptosis Proteins; D008565:Membrane Proteins; D027501:Monocarboxylic Acid Transporters; D050480:Plasma Membrane Neurotransmitter Transport Proteins; D012097:Repressor Proteins; C507459:Slc5a8 protein, mouse; C532353:Slc6A14 protein, mouse; D000077022:Survivin; D005947:Glucose