ATR and breast cancer: A p53-dependent role for ATR in metastasis is supported by analyses of patients with ER+/HER2− breast cancer: ATR mutation alone does not associate with metastasis-free survival, but ATR/TP53 comutation associates significantly with worse metastasis-free survival in two independent datasets {METABRIC [hazard ratios (HR) = 1.89, P = 0.004; Fig. 7G] and The Cancer Genome Atlas (TCGA) (fig.