Inhibition of ERK5 abrogates the effects of MEK5 activity on the tumorigenicity of A549 lung cancer spheres through upregulation of the apoptosis-associated genes BCL2 interacting protein 3 (BNIP3) and BNIP3 like (BNIP3L), which play a critical role in cell death. The gene discussed is BNIP3; the disease is lung cancer.