RPS6KB1 and small cell lung carcinoma: Furthermore, the dose of PI3K/mTOR inhibitors (50 nM) effectively blocked PI3K/Akt/mTOR pathway in three human SCLC cell lines, with the significantly decreased expression of phospho-Akt (Ser473 and Thr308), phospho-mTOR (Ser2448), phospho-4EBP1 (Ser65), and phospho-p70S6K (Thr389) (Fig. 1A and Fig. S3E, F).