Abstract
Previous data indicate that the EGFR pathway is involved in the response of tumor cell lines to irradiation. To determine if this receptor plays a role in the response of the intestinal mucosa, the effect of a spontaneous mutation in EGFR (B6C3-a-wa-2) on radiosensitivity and proliferative capacity was investigated using in vivo clonogenic assays and immunohistochemistry. EGFR mutant mice were compared with wild-type mice using the in vivo jejunal microcolony assay using single and split doses to measure the radiosensitivity and repopulation of clonogenic jejunal mucosal cells. In addition, paraffin-embedded tissue sections were assessed for proliferation (PCNA), DNA repair (Ku70 and γH2AX), and apoptosis (TUNEL) by immunofluorescent staining (wild-type vs. heterozygous only) at various times after 5 Gy single dose. After the high doses used in the split-dose experiments, EGFR heterozygous and homozygous mutant mice were significantly more radiosensitive than their wild-type littermates. There was no clear difference in split-dose repair based on EGFR function. After 5 Gy single dose there were significantly more apoptotic cells within the crypts of heterozygous mice than of wild-type mice, beginning at 3 h post irradiation. Decreased proliferation was observed only in the homozygous mutant mice. PCNA staining was lower in the heterozygous mice than in wild-type mice at 1 and 3 h post-5 Gy. The results indicate that after high doses the radiosensitivity of EGFR mutant mice is significantly higher than that of wild-type, and that this could be the result of an increase in apoptosis rather than reduced DNA repair. Proliferative capacity was modestly reduced, but only in the homozygous mutants.
Original language | English (US) |
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Pages (from-to) | 283-289 |
Number of pages | 7 |
Journal | Radiotherapy and Oncology |
Volume | 72 |
Issue number | 3 |
DOIs | |
State | Published - Sep 2004 |
Keywords
- Apoptosis
- DNA repair
- Microcolony assay
ASJC Scopus subject areas
- Hematology
- Oncology
- Radiology Nuclear Medicine and imaging