Restoring ERK3 level by exogenous expression in cells with BMI1 depletion rescued cancer cell migration, while depletion of ERK3 in BMI1‐overexpressing cells greatly diminished the effect of BMI1 promoting cancer cell migration, demonstrating that ERK3 functions downstream of BMI1 in promoting head and neck cancer cell motility. The gene discussed is MAPK6; the disease is cancer.