RPS6KB1 and glioblastoma: In order to assess the contribution of downstream signaling components of the PI3K pathway to GBM cell migration, T98G cells were transiently transfected with siRNAs targeting the three Akt isoforms (Akt1-3), the ribosomal protein S6 kinase (S6K1), or the small GTP-binding protein Rac1.