Targeting mTOR by CZ415 Inhibits Head and Neck Squamous Cell Carcinoma Cells.

Background/Aims: mTOR is an important therapeutic target for human head and neck squamous cell carcinoma (HNSCC). The current study tested the anti-HNSCC cell activity by a mTOR kinase inhibitor CZ415. Methods: HNSCC cells were treated with CZ415. Cell death was tested by lactate dehydrogenase (LDH) assay and MTT assay. Cell proliferation was tested by BrdU ELISA assay and [H-3] thymidine incorporation assay, with apoptosis assayed by the TUNEL staining. A Western blotting assay was applied to test autophagy-associated proteins, mTOR and signalings. The nude mice xenograft model was established to study CZ415-mediated anti-tumor activity. Results: In established (SCC-9, SQ20B and A253 lines) and primary human HNSCC cells, CZ415 efficiently inhibited cell survival and proliferation. CZ415 blocked mTORC1/2 activation and inhibited ERK in HNSCC cells. CZ415 provoked feedback autophagy activation. Conversely, autophagy inhibitors (3-methyladenine and chloroquine) or Beclin-1 shRNA sensitized CZ415-induced HNSCC cell death. In vivo, CZ415 gavage inhibited SCC9 tumor growth in nude mice, showing higher efficiency against Beclin-1-silenced tumors. Conclusion: CZ415 inhibits HNSCC cell growth in vitro and in vivo. Inhibition of autophagy can further sensitize CZ415 against HNSCC cells. (C) 2018 The Author(s) Published by S. Karger AG, Basel.y