To establish radioresistant breast cancer cells, an epidermal growth factor receptor 2 (HER2)-positive SK-BR-3 and an estrogen receptor (ER)-positive MCF-7 cells were irradiated using cycles of 4 Gy or 5 Gy, respectively, twice weekly, which resulted in ~ 20% cell survival. This evidence concerns the gene ERBB2 and breast carcinoma.