Radiation-induced esophagitis in vivo and in vitro reveals that epidermal growth factor (EGF) is a potential candidate for therapeutic intervention strategy

Abstract

Purpose: To establish and characterize radiation-induced esophagitis (RIE) in vivo and in vitro. Materials and Methods: Fractionated thoracic irradiation at 0, 8, 12, or 15 Gy was given daily for 5 days to Balb/c or C57Bl/6 mice. Changes in the body weight gain and daily food intake were assessed. At the end of the study, we harvested the esophagus and examined: (i) histology by H&E staining

(ii) immune cell infiltration and apoptosis by Fluorescent activated cell sorting (FACS)

(iii) gene expression changes by qRT-PCR. Het-1A human esophageal epithelial cells were irradiated at 6 Gy, treated with recombinant human growth factors, and examined for gene expression changes, apoptosis, proliferation, and signal transduction pathways. Results: We observed that irradiation at 12 Gy or 15 Gy per fraction produced a significant body weight reduction and decreased food intake in Balb/c mice, but not so much in C57Bl/6 mice. Further analyses of Balb/c mice irradiated at 12 Gy/fraction revealed an attenuated epithelium, inflamed mucosa, and increased number of infiltrating CD4+ helper T cells and apoptotic cells. Moreover we found that expressions of tissue inhibitor for metalloproteinase-1, plasminogen activator inhibitor-1, granulocyte macrophage-colony stimulating factor, vascular endothelial growth factor, and stromal-derived factor-1 were increased while epidermal growth factor (Egf) was decreased. Irradiated Het-1A cells similarly showed a significant decrease in EGF and connective tissue growth factor (CTGF) expression. Treatment of EGF but not CTGF partially protected Het-1A cells from radiation-induced apoptosis and revealed phosphorylation of EGFR, AKT and ERK signaling pathways. Conclusions: We established a mouse model of RIE in Balb/c mice with 12 Gy × 5 fractions, which exhibited reduced body weight gain, food intake, and histopathologic features similar to human esophagitis. Decreased EGF expression in the irradiated esophagus suggests that EGF may be a potential therapeutic intervention strategy to treat RIE.