Selective activation of Akt1 by mammalian target of rapamycin complex 2 regulates cancer cell migration, invasion, and metastasis

Oncogene. 2011 Jun 30;30(26):2954-63. doi: 10.1038/onc.2011.22. Epub 2011 Feb 21.

Abstract

Mammalian target of rapamycin complex (mTORC) regulates a variety of cellular responses including proliferation, growth, differentiation and cell migration. In this study, we show that mammalian target of rapamycin complex 2 (mTORC2) regulates invasive cancer cell migration through selective activation of Akt1. Insulin-like growth factor-1 (IGF-1)-induced SKOV-3 cell migration was completely abolished by phosphatidylinositol 3-kinase (PI3K) (LY294002, 10 μM) or Akt inhibitors (SH-5, 50 μM), whereas inhibition of extracellular-regulated kinase by an ERK inhibitor (PD98059, 10 μM) or inhibition of mammalian target of rapamycin complex 1 (mTORC1) by an mTORC1 inhibitor (Rapamycin, 100 nM) did not affect IGF-1-induced SKOV-3 cell migration. Inactivation of mTORC2 by silencing Rapamycin-insensitive companion of mTOR (Rictor), abolished IGF-1-induced SKOV-3 cell migration as well as activation of Akt. However, inactivation of mTORC1 by silencing of Raptor had no effect. Silencing of Akt1 but not Akt2 attenuated IGF-1-induced SKOV-3 cell migration. Rictor was preferentially associated with Akt1 rather than Akt2, and over-expression of Rictor facilitated IGF-1-induced Akt1 activation. Expression of PIP3-dependent Rac exchanger1 (P-Rex1), a Rac guanosine exchange factor and a component of the mTOR complex, strongly stimulated activation of Akt1. Furthermore, knockdown of P-Rex1 attenuated Akt activation as well as IGF-1-induced SKOV-3 cell migration. Silencing of Akt1 or P-Rex1 abolished IGF-1-induced SKOV-3 cell invasion. Finally, silencing of Akt1 blocked in vivo metastasis, whereas silencing of Akt2 did not. Given these results, we suggest that selective activation of Akt1 through mTORC2 and P-Rex1 regulates cancer cell migration, invasion and metastasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Movement* / drug effects
  • Cell Movement* / genetics
  • Cells, Cultured
  • Enzyme Activation / drug effects
  • Enzyme Activation / genetics
  • Enzyme Activation / physiology
  • Gene Expression Regulation, Neoplastic / drug effects
  • Guanine Nucleotide Exchange Factors / metabolism
  • Guanine Nucleotide Exchange Factors / physiology
  • Humans
  • Insulin-Like Growth Factor I / pharmacology
  • Neoplasm Invasiveness
  • Neoplasm Metastasis
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Neoplasms / pathology*
  • Proto-Oncogene Proteins c-akt / agonists*
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Small Interfering / pharmacology
  • Substrate Specificity
  • TOR Serine-Threonine Kinases / metabolism*
  • rac1 GTP-Binding Protein / metabolism
  • rac1 GTP-Binding Protein / physiology

Substances

  • Guanine Nucleotide Exchange Factors
  • PREX1 protein, human
  • RNA, Small Interfering
  • Insulin-Like Growth Factor I
  • TOR Serine-Threonine Kinases
  • AKT1 protein, human
  • Proto-Oncogene Proteins c-akt
  • rac1 GTP-Binding Protein