title: The AMPK stress response pathway mediates anoikis resistance through inhibition of mTOR and suppression of protein synthesis.
abstract: Suppression of anoikis after detachment of cancer cells from the extracellular matrix is a key step during metastasis. Here we show that, after detachment, mouse embryonic fibroblasts (MEFs) transformed by K-Ras(V12) or ETV6-NTRK3 (EN) activate a transcriptional response overrepresented by genes related to bioenergetic stress and the AMP-activated protein kinase (AMPK) energy-sensing pathway. Accordingly, AMPK is activated in both transformed and non-transformed cells after detachment, and AMPK deficiency restores anoikis to transformed MEFs. However, AMPK activation represses the mTOR complex-1 (mTORC1) pathway only in transformed cells, suggesting a key role for AMPK-mediated mTORC1 inhibition in the suppression of anoikis. Consistent with this, AMPK-/- MEFs transformed by EN or K-Ras show sustained mTORC1 activation after detachment and fail to suppress anoikis. Transformed TSC1-/- MEFs, which are incapable of suppressing mTORC1, also undergo anoikis after detachment, which is reversed by mTORC1 inhibitors. Furthermore, transformed AMPK-/- and TSC1-/- MEFs both have higher total protein synthesis rates than wild-type controls, and translation inhibition using cycloheximide partially restores their anoikis resistance, indicating a mechanism whereby mTORC1 inhibition suppresses anoikis. Finally, breast carcinoma cell lines show similar detachment-induced AMPK/mTORC1 activation and restoration of anoikis by AMPK inhibition. Our data implicate AMPK-mediated mTORC1 inhibition and suppression of protein synthesis as a means for bioenergetic conservation during detachment, thus promoting anoikis resistance.
authors.affiliation: Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, BC, Canada.
authors.forename: T L
authors.initials: TL
authors.lastname: Ng
authors.forename: G
authors.initials: G
authors.lastname: Leprivier
authors.forename: M D
authors.initials: MD
authors.lastname: Robertson
authors.forename: C
authors.initials: C
authors.lastname: Chow
authors.forename: M J
authors.initials: MJ
authors.lastname: Martin
authors.forename: K R
authors.initials: KR
authors.lastname: Laderoute
authors.forename: E
authors.initials: E
authors.lastname: Davicioni
authors.forename: T J
authors.initials: TJ
authors.lastname: Triche
authors.forename: P H B
authors.initials: PH
authors.lastname: Sorensen
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D023102:Anoikis / Q000502:physiology*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D018345:Mice, Knockout; D046912:Multiprotein Complexes; D041681:NIH 3T3 Cells; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D046912:Multiprotein Complexes; D011506:Proteins; C546843:mTOR protein, mouse; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases