Prevention of Radiation-Induced Oral Cavity Mucositis by Plasmid/Liposome Delivery of the Human Manganese Superoxide Dismutase (SOD2) Transgene

Abstract

Oral cavity mucositis is a major toxicity of radiation therapy for head and neck cancer. In the present mouse model studies, we evaluated intraoral administration of SOD2-PL complexes 24 h before single-fraction 30-Gy irradiation for the prevention of oral cavity mucositis. Expression of the human SOD2 transgene in the oral cavity of C3H/HeNsd mice was demonstrated by nested reverse transcriptase polymerase chain reaction (RT-PCR). Mice treated intraorally with bacterial beta-galactosidase gene-plasmid/liposome (LacZ-PL) or hemagglutinin (HA)-manganese superoxide dismutase-plasmid/liposome (HA-SOD2-PL) demonstrated LacZ or HA-SOD2 expression, respectively, 24 h after injection. In a second strain of mouse, SOD2-PL-treated female athymic nude mice demonstrated significantly decreased ulceration at day 5 after 30 Gy, compared to LacZ-PL-injected, irradiated mice or irradiated controls. No further reduction in radiation-induced ulceration was detected in mice treated with both SOD2-PL and 10 mg/kg of amifostine (WR-2721) 30 min before 30 Gy compared to SOD2-PL alone. No significant protection of orthotopically transplanted murine squamous cell carcinoma (SCC-VII) tumors was detected in mice that received SOD2-PL treatment before 18 Gy. Thus overexpression of human SOD2 in the oral cavity mucosa can prevent radiation-induced mucositis with no detectable compromise in the therapeutic response of orthotopically transplanted tumors.

Inhalation delivery of manganese superoxide dismutase-plasmid/liposomes protects the murine lung from irradiation damage

“…In two model systems (lung and oral cavity), orthotopic tumors were not detectably protected from irradiation killing under conditions of normal tissue radiation protection. 21,52 Transient overexpression of MnSOD in tumor cell lines in vitro has been demonstrated to increase radiosensitivity, confirming studies by Oberley and co-workers 53,54 and documenting the intrinsic inability of squamous and adenocarcinoma cell lines to neutralize effectively hydrogen peroxide produced by dismutation of superoxide. 54 For effective translation of MnSOD-PL pulmonary radiation protection to clinical radiotherapy, its adaptation for use in fractionated radiotherapy using clinically relevant doses in the range of 180-210 cGy/day was felt to be essential.…”

“…51 However, by using a construct of the Cu/ZnSOD transgene to which was attached the mitochondrial localization signal of MnSOD, an effective transgene protein for radioprotection was demonstrated. 51 MnSOD-PL administration prior to irradiation of lung, 12 oral cavity, 21 esophagus, 17 bladder, 22 and intestine 23 has Lung irradiation protection by inhalation of MnSOD-PL M Carpenter et al been shown to provide radioprotection in each organ's target volume. In two model systems (lung and oral cavity), orthotopic tumors were not detectably protected from irradiation killing under conditions of normal tissue radiation protection.…”

“…While intraoral or intraesophageal administration of MnSOD-PL has been demonstrated to be effective in murine models, due in part to the ease of administration, 21 translation of this technique to pulmonary protection clearly requires a safe inhalation delivery method without the trauma of intratracheal injection. Previous studies demonstrated relative ineffectiveness of administration of MnSOD protein for esophagus radiation protection, presumed attributable to the relative lack of concentration of protein in cellular mitochondria.…”

“…2,3,5,6 A biological response modifier approach toward decreasing pulmonary toxicity would be valuable to facilitate new improvements in radiation treatment. We have demonstrated that organ-specific (lung, [12][13][14][15][16] esophagus, [17][18][19][20] oral cavity, 21 bladder, 22 or intestine 23 ) introduction of the human manganese superoxide dismutase (MnSOD) transgene by plasmid/liposomes (MnSOD-PL) or viral vectors is associated with significant uptake, increased transgene mRNA and protein availability for 48-72 h after administration, and significant protection from ionizing radiation-induced acute and chronic organ injury. 24 In both pulmonary and esophageal radiation protection models, intratracheal or intraoral administration of MnSOD-PL was shown to delay the onset of organizing alveolitis/fibrosis and esophagitis in C57BL/ 6J mice, respectively, and improve overall survival in single-or multifraction radiotherapy protocols.…”

SOD2 protects neurons from injury in cell culture and animal models of diabetic neuropathy

“…Similarly, in retinal pigment epithelial cells, the gene dosage of SOD2 directly relates to the degree of mitochondrial injury and apoptosis induced by H 2 O 2 (Kasahara et al, 2005). In hemopoietic cells, SOD2 transgene decreases ionizing radiation-induced mitochondrial membrane permeability, cytochrome c release and caspase-3 activation (Guo et al, 2003). Collectively, these data provide strong evidence that increased mitochondrial ROS in the presence of pro-oxidant stressors, including hyperglycemia, can be prevented by enhancing mitochondrial SOD2 activity.…”