The response of breast cancer stem cells to radiation and the resistant mechanism of radiotherapy

Abstract

Objective To discuss the response of breast cancer stem cells to radiation and its resistant mechanism. Methods Single breast cancer stem cells were isolated from the human breast adenocarcinoma cell line, MCF-7, and suspension-cultured into mammary cell microspheres in vitro. The radiosensitivity of these breast cancer stem cells were evaluated using a colony formation assay. Real-time polymerase chain reaction (PCR) was used to detect the expression levels of the following genes before and after radiation in the breast cancer stem cells, along with non-stem cells of the breast cancer cell line: ATM, p53, Her-2, Ku70/Ku80 and Survivin. Results The average survival fraction (SF2) of the suspensioncultured MCF-7 cells after 2 Gy of radiation was 0. 49, while the average SF2 of MCF-7 cells cultured as a monolayer was 0. 27 (P<0.01). Compared to the MCF-7 cells grown in a monolayer, the suspension-cultured MCF-7 cells had higher expression levels of ATM, p53, Her-2, Ku70/Ku80 and Survivin; The expression of ATM, p53, Her-2, Ku70/Ku80 and Survivin was 5. 29±1. 36,1. 37±0. 73,2.10±0. 57,4. 69±1. 45,and 1. 80±1.29 fold, respectively. Conclusion Breast cancer stem cells have stronger anti-radiation capabilities than breast cancer non-stem cells. The stronger DNA repair capacity is an important resistant mechanism about radiotherapy of breast cancer stem cells. Key words: Breast neoplasms; Cancer stem cell; Radiotherapy; Radiosensitivity