HepG2 hepatoblastoma cells express abundant heme-requiring P450 enzymes65, Murine erythroleukemia (MEL) cells readily form heme to accommodate the large amounts of hemoglobin synthesized upon differentiation, and ALA-treated U251 glioblastoma cells accumulate high levels of PPIX66,67. The gene discussed is CYP2B6; the disease is glioblastoma.