CCN1 and glioma: Plasmids expressing CCN1, wild-type PIK3R1, mutant PIK3R1, or a combination of these plasmids were transfected into U87MG glioma cells, which carry low CCN1 expression29, no PIK3R1 somatic mutations30 and PIK3R1Met326Ile germline mutation (Fig. 6A).