MAPK1 and breast cancer: Similarly, apoptosis was induced in a breast cancer cell line (66‐cl‐4‐GFP) by the expression of death receptor 5 (DR5) dependent on c‐Jun N‐terminal kinase (JNK), protein 38 (p38), mitogen‐activated protein kinase (MAPK) pathway, and ERK‐mediated endoplasmic reticulum (ER) stress pathway.112