To validate the recruitment of Ape1 to the sites of DSBs in glioblastoma cells, U251-MG cells expressing a GFP-tagged wild-type Ape1 along with a RFP-tagged PCNA29 were laser micro-irradiated, and the intensity of fluorescence was recorded in living cells for 30 min. This evidence concerns the gene APEX1 and glioblastoma.