BIRC3 and glioblastoma: To investigate whether targeting IAP proteins can prime glioblastoma cells towards TRAIL, we selected a panel of glioblastoma cell lines, which are heterogeneous for p53 and PTEN status (Supplementary Table 1), two key signaling components that are often altered in glioblastoma.17 cIAP1 and XIAP were expressed in all tested glioblastoma cell lines except U138MG, whereas the expression of cIAP2 was detected in three out of five cell lines (Figure 1a).