To determine the role of PI3K in the expression of these proteins in GBM cells, we knocked down the PIK3CA gene in SF295 and U87 cells using siRNAs and found that the knockdown significantly reduced the expression of these three key components of HR repair at both the mRNA and protein levels (Figure S5A,B, Supporting Information). The gene discussed is PIK3CG; the disease is glioblastoma.