GPC4 and glioblastoma: In order to confirm that the observed decrease in the proliferation rate in CRISPR/Cas9 GPC4 knocked-down glioblastoma cells was due to a loss of GPC4 function, we conducted a series of rescue experiments, aiming to restore GPC4 function by transfecting GPC4 knocked-down cells with a GPC4 overexpression vector.