Interestingly, the overexpression of wild-type HAUSP, but not the catalytically inactive mutant HAUSP (C223A), increased the protein levels of LSD1 in the A172 and T98G glioblastoma cell lines, [54] suggesting that the expression and deubiquitinase activity of HAUSP is a main cause of the high expression levels of LSD1 found in tumors. The gene discussed is USP7; the disease is glioblastoma.