Vascular endothelial cells (ECs) are specialized components of the tumor microenvironment that orchestrates tumor growth and invasion. They form tumor-associated blood vessels (angiogenic) that supply nutrients and oxygen, remove waste products, and also provide an entry site for tumorigenic cells to spread to secondary sites in various organs. One of the major signaling events in tumor vessels is PI3K/PDK-AKT-mTOR activation. mTOR is a serine/threonine kinase that functions in two distinct complexes, mTORC1 and mTORC2,which regulate a diverse array of cellular processes including cell growth, survival and metabolism. Although mTORC1, and to lesser extent, mTORC2, has been broadly studied in cancers and diseases, little is known regarding the relative contributions of mTORC1 versus mTORC2 in tumor endothelium. Using mouse model of endothelium-specific Rictor (a mTORC2 specific cofactor) gene targeting, we discovered that endothelial Rictor deletion decreased tumor neovascularization, suppressed tumor growth, and prevented metastasis in vivo. Direct co-culture of endothelial cells and NSCLC tumor cells in vitro showed that knockdown of endothelial Rictor inhibited tumor cell proliferation while Raptor (a mTORC1 specific cofactor) depletion had a modest effect. However, loss of endothelial Rictor or Raptor both markedly decreased tumor cell extravasation in response to endothelial cells, and also inhibited tumor spheroid formation in a direct co-culture system. Furthermore, a screen of phospho-kinase arrays revealed that Raptor or Rictor depletion in endothelial cells decreased various phosphor-RTKs in tumor cells that were co-cultured with ECs, including members of the Eph receptor family, Insulin receptor family and FGF receptor family. Additionally, endothelial Rictor knockdown suppressed phosphorylation levels of nerve growth factor receptors TrkB and TrkC in tumor cells. Collectively, these data suggest that endothelial mTORC1 and mTORC2 play critical roles in regulating tumor progression through distinct signaling pathways.
Note: This abstract was not presented at the meeting.
Citation Format: Shan Wang. Endothelial mTORC2 deficiency inhibits tumor angiogenesis, tumor progression and metastasis in non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1824. doi:10.1158/1538-7445.AM2017-1824