In triple-negative breast cancer cell lines, MDA-MB231 and SUM159 tumor cells treated with ONC201 show a significant increase in the expression levels of C/EBP homologous protein (CHOP) and activating transcription factor 4 (ATF4), markers of endoplasmic reticulum stress and integrated stress response (ISR), respectively (45). Here, ATF4 is linked to triple-negative breast carcinoma.