Late normal tissue toxicity varies widely between patients and limits breast radiotherapy dose. Here we aimed to determine its relationship to DNA damage responses of fibroblast cultures from individual patients. Thirty-five breast cancer patients, with minimal or marked breast changes after breast-conserving therapy consented to receive a 4 Gy test irradiation to a small skin field of the left buttock and have punch biopsies taken from irradiated and unirradiated skin. Early-passage fibroblast cultures were established by outgrowth and irradiated in vitro with 0 or 4 Gy. 53BP1 foci, p53 and p21/CDKN1A were detected by immunofluorescence microscopy. Residual 53BP1 foci counts 24 h after in vitro irradiation were significantly higher in fibroblasts from RT-sensitive versus RT-resistant patients. Furthermore, significantly larger fractions of p53- but not p21/CDKN1A-positive fibroblasts were found in cultures from RT-sensitive patients without in vitro irradiation, and 2 h and 6 d post-irradiation. Exploratory analysis showed a stronger p53 response 2 h after irradiation of fibroblasts established from patients with severe reaction. These results associate the radiation response of fibroblasts with late reaction of the breast after RT and suggest a correlation with severity.
Bibliographical noteFunding Information:
This study was supported by grant number 06049 from the Royal Marsden Hospital Charity, UK , and by the NIHR Centre for Research in Health Protection .
We thank Ms. N. Guerth for excellent technical assistance with establishment of fibroblast cultures and performance of immunocytochemistry (Ki-67, p53, p21/CDKN1A). The Royal Marsden Hospital Charity is gratefully acknowledged for financial support. We acknowledge NHS funding to the NIHR Biomedical Research Centre at The Royal Marsden and the ICR and to the Centre for Research in Health Protection at Public Health England. Dr. Melvin Chua is kindly supported by the National Medical Research Council Singapore Transition Award (NMRC/TA/0030/2014).
- Breast cancer
- Double-strand breaks
- Individual radiosensitivity
- Normal-tissue reaction