MAPK1 and intervertebral disk degenerative disorder: Extracellular signal‐regulated kinase (ERK) is involved in an extremely conserved signalling pathway, known as the Ras‐Raf‐MEK‐ERK pathway, that is crucially involved in cell proliferation and survival and diverse cellular processes.10, 11 PD98059 is a highly selective in vitro inhibitor of MEK1 activation and the ERK cascade.12 A previous study demonstrated that exogenous and autocrine growth factors stimulate human intervertebral disc cell proliferation via the ERK and Akt pathways.13 However, the correlations between IGFBP5, the ERK signalling pathway, and IDD have not been elucidated.