Since HO-1 inducibility can also occur in response to the activation of growth factor receptor signal transduction pathways, including extracellular signal-regulated kinases ERK1 and ERK2, c-jun-NH2 kinase, and p38 kinase, in order to further reduce the negative effects of HO-1 on the efficacy of glioma 5-ALA-PDT, it seems attractive to test the molecules that affect these pathways [112,113,114]. The gene discussed is HMOX1; the disease is central nervous system cancer.