Radioprotection in vitro and in vivo by minicircle plasmid carrying the human manganese superoxide dismutase transgene

Hum Gene Ther. 2008 Aug;19(8):820-6. doi: 10.1089/hum.2007.141.


Manganese superoxide dismutase plasmid liposomes (MnSOD-PL) confer organ-specific in vivo ionizing irradiation protection. To prepare for potential intravenous clinical trials of systemic MnSOD-PL for radioprotection in humans, plasmid and bacterial sequences were removed and a new minicircle construct was tested. Minicircle MnSOD was purified and then cotransfected into 32D cl 3 murine interleukin-3-dependent hematopoietic progenitor cells along with another plasmid carrying the neo gene. Cells were selected in G418 (50 microg/ml) and cloned by limiting dilution. Biochemical analysis of minicircle MnSOD-transfected cells showed an MnSOD biochemical activity level of 5.8 +/- 0.5 U/mg compared with 2.7 +/- 0.1 U/mg for control 32D cl 3 cells (p = 0.0039). 32D-mc-MnSOD cells were as radioresistant as full-length MnSOD-PL transgene-expressing 2C6 cells, relative to 32D cl 3 parent cells, with an increased shoulder on the radiation survival curve (n = 4.8 +/- 0.2 and n = 4.6 +/- 0.2, respectively, compared with 1.5 +/- 0.5 for 32D cl 3 cells; p = 0.007). C57BL/6NHsd mice received intraoral mc-MnSOD-PL, mc-DsRed-PL control, full-length MnSOD-PL, or blank-PL and then were irradiated 24 hr later with 31 Gy to the esophagus. Mice receiving mc-MnSOD-PL showed increased survival compared with control mice or mice treated with mc-DsRed-PL (p = 0.0003 and 0.039, respectively), and comparable to full-length MnSOD-PL. Intravenous, systemic administration of mc-MnSOD-PL protected mice from total body irradiation (9.75 Gy). Therefore, minicircle DNA containing the human MnSOD transgene confers undiminished radioprotection in vitro and in vivo.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Base Sequence
  • Cell Line
  • Dose-Response Relationship, Radiation
  • Esophagus / radiation effects
  • Female
  • Genetic Therapy*
  • Genetic Vectors / administration & dosage
  • Humans
  • Liposomes / administration & dosage*
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Plasmids / administration & dosage*
  • Plasmids / genetics
  • Radiation Injuries, Experimental / prevention & control*
  • Radiation Tolerance / genetics
  • Radiation, Ionizing
  • Radiation-Protective Agents / therapeutic use*
  • Superoxide Dismutase / genetics*
  • Transfection
  • Transgenes
  • Whole-Body Irradiation


  • Liposomes
  • Radiation-Protective Agents
  • Superoxide Dismutase