GPC4 and cancer: Further, overexpression of GPC4 in GPC4 knocked-down glioblastoma cells restored their proliferation rate, indicating that the attenuation of proliferation in SNB-75 and SF-295 cells upon CRISPR/Cas9 GPC4 knockdown is attributable to the loss of GPC4 function, which suggests a mitogenic effect of GPC4 in this cancer type.