Activating Transcription Factor 4 (ATF4), a key transcriptional regulator in the Integrated Stress Response (ISR), is persistently upregulated in multiple cancer types and further induced under tumor microenvironmental stressors such as hypoxia, nutrient deprivation, and oxidative stress (Hypoxia-Mediated ATF4 Induction Promotes Survival in Detached Conditions in Metastatic Murine Mammary Cancer Cells) [2]. Here, ATF4 is linked to breast cancer.