MAPK7 (mitogen-activated protein kinase 7, also known as ERK5) is a serine/threonine kinase that plays critical roles in cellular proliferation, differentiation, and survival. It is activated by MAP2K5 in response to growth factors like EGF through a Ras-independent pathway 1, and upon activation translocates to the nucleus to phosphorylate downstream targets including MEF2C and SGK1, promoting cell cycle progression and transcriptional regulation. MAPK7 functions as a negative regulator of apoptosis, particularly in cardiomyocytes, through interaction with STUB1/CHIP and degradation of CREM isoforms. It also regulates p53 by disrupting PML-MDM2 interactions [UniProt data], and influences endothelial cell survival and vascular integrity. Clinically, MAPK7 is implicated in multiple cancers. In osteosarcoma, MAPK7 silencing suppresses cell proliferation, migration, and invasion, suggesting therapeutic potential 2. Similarly, in gastrointestinal stromal tumors, MAPK7 associates with tumor cell proliferation 3. In breast cancer, miR-155 targets MAPK7, and MAPK7 downregulation inhibits proliferation and promotes apoptosis 4. Additionally, MEK5/ERK5 pathway activation promotes sarcomagenesis, with elevated ERK5 expression correlating with poor survival 5. Recent evidence demonstrates MAPK7 involvement in inflammatory responses through AhR/STAT3 signaling 6, and dual ERK1/2/ERK5 inhibition overcomes drug resistance in triple-negative breast cancer 1.