Thus, 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin) and 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin) at subtoxic concentrations were found to stimulate Nrf2/ARE signalling and enhance the expression of Keap1/Nrf2/ARE-dependent target genes in HepG2 cells, human SH-SY5Y neuroblastoma cells, and primary rat cortical neurons. The gene discussed is KEAP1; the disease is neuroblastoma.