HMOX1 and central nervous system cancer: HO-1 is also overexpressed in melanoma cell lines after treatment with proteasome inhibitor bortezomib and with arsenic trioxide [87,88] and, in glioma cells, the resistance to arsenic trioxide is reverted by HO-1 inhibition obtained using Zinc II Protoporphyrin IX (ZnPPIX), leading to an enhanced apoptosis [89].