ERBB2 and breast cancer: In the oncogene-driven Neu and MMTV-PyMT mouse models, the overactivation of the RANK signaling pathway in normal mammary epithelium induces cellular senescence, thereby delaying the onset of breast cancer but promoting subsequent metastatic invasion.162 During breast cancer chemotherapy, specific tumor cells exhibit upregulation of SASP genes, accompanied by an augmented expression of immunosuppressive molecules PD-L1 and CD80 within these tumor cells.