Alternative splicing of S6K1 promotes non-small cell lung cancer survival.

Ribosomal S6 kinase 1 (S6K1) that acts downstream of the mammalian target of rapamycin (mTOR) plays an important role in cell proliferation, protein translation, and cell survival. The gene RPS6KB1 encoding for S6K1 had been found to be alternatively spliced to form different isoforms. In this study, we identified that short isoforms of S6K1 splice variant were overproduced in non-small cell lung cancer (NSCLC). Moreover, suppression of S6K1 short isoforms inhibited NSCLC cell growth and induced apoptosis via upregulation of the BH3-only protein Bim in vitro and in vivo. Additionally, short isoforms of S6K1 activated mTORC1, leading to increased 4E-BP1 phosphorylation. Taken together, our findings suggested that S6K1 short isoforms were deregulated in NSCLC and promoted cell survival. Altogether, our study opens possibilities of new therapeutic approaches for NSCLC that selectively downregulate S6K1 shorter isoforms.