RPS6 and retinoblastoma: As recent studies suggest that TMZ can significantly increase driver mutations in recurrent glioma, particularly in the retinoblastoma and Akt-mTOR pathways [38], we examined the activity of these pathways by measuring the phospho-protein levels of p90RSK, Akt, p44/42 MAPK (Erk1/2) and S6 ribosomal protein.