title: Endothelial Cell mTOR Complex-2 Regulates Sprouting Angiogenesis.
abstract: Tumor neovascularization is targeted by inhibition of vascular endothelial growth factor (VEGF) or the receptor to prevent tumor growth, but drug resistance to angiogenesis inhibition limits clinical efficacy. Inhibition of the phosphoinositide 3 kinase pathway intermediate, mammalian target of rapamycin (mTOR), also inhibits tumor growth and may prevent escape from VEGF receptor inhibitors. mTOR is assembled into two separate multi-molecular complexes, mTORC1 and mTORC2. The direct effect of mTORC2 inhibition on the endothelium and tumor angiogenesis is poorly defined. We used pharmacological inhibitors and RNA interference to determine the function of mTORC2 versus Akt1 and mTORC1 in human endothelial cells (EC). Angiogenic sprouting, EC migration, cytoskeleton re-organization, and signaling events regulating matrix adhesion were studied. Sustained inactivation of mTORC1 activity up-regulated mTORC2-dependent Akt1 activation. In turn, ECs exposed to mTORC1-inhibition were resistant to apoptosis and hyper-responsive to renal cell carcinoma (RCC)-stimulated angiogenesis after relief of the inhibition. Conversely, mTORC1/2 dual inhibition or selective mTORC2 inactivation inhibited angiogenesis in response to RCC cells and VEGF. mTORC2-inactivation decreased EC migration more than Akt1- or mTORC1-inactivation. Mechanistically, mTORC2 inactivation robustly suppressed VEGF-stimulated EC actin polymerization, and inhibited focal adhesion formation and activation of focal adhesion kinase, independent of Akt1. Endothelial mTORC2 regulates angiogenesis, in part by regulation of EC focal adhesion kinase activity, matrix adhesion, and cytoskeletal remodeling, independent of Akt/mTORC1.
authors: Department of Medicine, University of Alberta, Edmonton, Canada.
authors: Maikel A
authors: MA
authors: Farhan
authors: Department of Oncology, University of Alberta, Edmonton, Canada.
authors: Katia
authors: K
authors: Carmine-Simmen
authors: Department of Oncology, University of Alberta, Edmonton, Canada.
authors: John D
authors: JD
authors: Lewis
authors: Department of Surgery, University of Alberta, Edmonton, Canada.
authors: Ronald B
authors: RB
authors: Moore
authors: Department of Medicine, University of Alberta, Edmonton, Canada.
authors: Allan G
authors: AG
authors: Murray
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002292:Carcinoma, Renal Cell / Q000378:metabolism / Q000473:pathology; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D018920:Coculture Techniques; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D009025:Morpholines / Q000494:pharmacology; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000199:Actins; D007211:Indoles; D009025:Morpholines; D046912:Multiprotein Complexes; D011687:Purines; D011743:Pyrimidines; D034741:RNA, Small Interfering; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C541932:Ku 0063794; C546842:MTOR protein, human; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; C494918:AKT1 protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C572919:PP242; D020123:Sirolimus