In this study, we evaluated irradiation-induced cellular effects and the irradiation sensitivity of three subtype-specific BC cell lines, namely JIMT-1 (HER2-pos., trastuzumab resistant), MDA-MB-231 (triple negative), and MCF-7 (ER-pos., i.e., luminal) in-vitro. This evidence concerns the gene ERBB2 and breast cancer.