RPS6KB1 and neoplasm: A study of human T98G cells showed that the presence of serum rapidly phosphorylated PDCD4 on Ser67 by the protein kinase p70-S6K and subsequently degraded it via the ubiquitin ligase SCFβ-TrCP[18], which was confirmed in HEK293 cells exposed to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate [19].