title: High-dose rapamycin induces apoptosis in human cancer cells by dissociating mTOR complex 1 and suppressing phosphorylation of 4E-BP1.
abstract: mTOR, the mammalian target of rapamycin, has been widely implicated in signals that promote cell cycle progression and survival in cancer cells. Rapamycin, which inhibits mTOR with high specificity, has consequently attracted much attention as an anti-cancer therapeutic. Rapamycin suppresses phosphorylation of S6 kinase at nano-molar concentrations, however at higher micro-molar doses, rapamycin induces apoptosis in several human cancer cell lines. While much is known about the effect of low dose rapamycin treatment, the mechanistic basis for the apoptotic effects of high-dose rapamycin treatment is not understood. We report here that the apoptotic effects of high-dose rapamycin treatment correlate with suppressing phosphorylation of the mTOR complex 1 substrate, eukaryotic initiation factor 4E (eIF4E) binding protein-1 (4E-BP1). Consistent with this observation, ablation of eIF4E also resulted in apoptorsis in MDA-MB 231 breast cancer cells. We also provide evidence that the differential dose effects of rapamycin are correlated with partial and complete dissociation of Raptor from mTORC1 at low and high doses, respectively. In contrast with MDA-MB-231 cells, MCF-7 breast cancer cells survived rapamycin-induced suppression of 4E-BP1 phosphorylation. We show that survival correlated with a hyper-phosphorylation of Akt at S473 at high rapamycin doses, the suppression of which conferred rapamycin sensitivity. This study reveals that the apoptotic effect of rapamycin requires doses that completely dissociate Raptor from mTORC1 and suppress that phosphorylation of 4E-BP1 and inhibit eIF4E.
authors.affiliation: Department of Biological Sciences, Hunter College of the City University of New York, New York, NY, USA.
authors.forename: Paige
authors.initials: P
authors.lastname: Yellen
authors.forename: Mahesh
authors.initials: M
authors.lastname: Saqcena
authors.forename: Darin
authors.initials: D
authors.lastname: Salloum
authors.forename: Jiangnan
authors.initials: J
authors.lastname: Feng
authors.forename: Angela
authors.initials: A
authors.lastname: Preda
authors.forename: Limei
authors.initials: L
authors.lastname: Xu
authors.forename: Vanessa
authors.initials: V
authors.lastname: Rodrik-Outmezguine
authors.forename: David A
authors.initials: DA
authors.lastname: Foster
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011506:Proteins / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt; D000076223:Regulatory-Associated Protein of mTOR; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D046912:Multiprotein Complexes; D010750:Phosphoproteins; D011506:Proteins; C463659:RPTOR protein, human; D000076223:Regulatory-Associated Protein of mTOR; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
references.citation: Mol Cell Biol. 2004 Jan;24(1):200-16
references.pmid: 14673156
references.citation: PLoS Med. 2008 Jan 22;5(1):e8
references.pmid: 18215105
references.citation: Oncogene. 2003 Jun 19;22(25):3937-42
references.pmid: 12813467
references.citation: Aging (Albany NY). 2009 Mar 28;1(3):281-8
references.pmid: 20157517
references.citation: Cell Cycle. 2010 Dec 15;9(24):4788-94
references.pmid: 21150328
references.citation: Cell. 2002 Jul 26;110(2):163-75
references.pmid: 12150925
references.citation: Drug Discov Today. 2011 Apr;16(7-8):325-31
references.pmid: 21333749
references.citation: Clin Cancer Res. 2010 Mar 1;16(5):1368-72
references.pmid: 20179227
references.citation: Proc Natl Acad Sci U S A. 2008 Nov 11;105(45):17414-9
references.pmid: 18955708
references.citation: Cancer Res. 2008 Sep 15;68(18):7409-18
references.pmid: 18794129
references.citation: Mol Cell. 2006 Apr 21;22(2):159-68
references.pmid: 16603397
references.citation: Cancer Cell. 2010 Mar 16;17(3):249-61
references.pmid: 20227039
references.citation: Cell Cycle. 2011 Jul 15;10(14):2305-16
references.pmid: 21670596
references.citation: J Clin Oncol. 2008 Sep 1;26(25):4172-9
references.pmid: 18757332
references.citation: Nature. 1990 Jun 7;345(6275):544-7
references.pmid: 2348862
references.citation: Drug Discov Today Ther Strateg. 2009 Summer;6(2):47-55
references.pmid: 20622997
references.citation: Cell Cycle. 2009 Apr 1;8(7):1026-9
references.pmid: 19270529
references.citation: Oncogene. 2008 Feb 14;27(8):1055-62
references.pmid: 17700525
references.citation: Cell Cycle. 2009 Feb 15;8(4):567-72
references.pmid: 19197153
references.citation: Cancer Cell. 2003 Nov;4(5):343-8
references.pmid: 14667501
references.citation: Genes Dev. 2001 Nov 1;15(21):2852-64
references.pmid: 11691836
references.citation: J Biol Chem. 1993 Oct 25;268(30):22825-9
references.pmid: 8226793
references.citation: Nature. 2004 Mar 18;428(6980):332-7
references.pmid: 15029198
references.citation: Oncogene. 2005 Jan 20;24(4):672-9
references.pmid: 15580312
references.citation: Proc Natl Acad Sci U S A. 2001 Aug 28;98(18):10320-5
references.pmid: 11504907
references.citation: Nat Med. 2004 May;10(5):484-6
references.pmid: 15098029
references.citation: Cell Metab. 2008 Jan;7(1):11-20
references.pmid: 18177721
references.citation: Expert Opin Ther Targets. 2004 Dec;8(6):551-64
references.pmid: 15584862
references.citation: Proc Natl Acad Sci U S A. 2001 Aug 28;98(18):10314-9
references.pmid: 11504908
references.citation: Cancer Res. 2005 Aug 15;65(16):7052-8
references.pmid: 16103051
references.citation: Cell Cycle. 2010 May;9(9):1839-46
references.pmid: 20436269
references.citation: Nature. 2005 Feb 3;433(7025):477-80
references.pmid: 15690031
references.citation: J Clin Oncol. 2008 Apr 1;26(10):1603-10
references.pmid: 18332469
references.citation: Mol Cell. 2010 Jun 11;38(5):768-74
references.pmid: 20542007
references.citation: Cancer Cell. 2007 Jul;12(1):9-22
references.pmid: 17613433
references.citation: Cancer Res. 2010 Jan 1;70(1):288-98
references.pmid: 20028854
references.citation: Proc Natl Acad Sci U S A. 2010 Jul 13;107(28):12469-74
references.pmid: 20616057
references.citation: Cancer Cell. 2010 Jul 13;18(1):39-51
references.pmid: 20609351
references.citation: Cancer Res. 2006 Feb 1;66(3):1500-8
references.pmid: 16452206
references.citation: Cancer Cell. 2009 Nov 6;16(5):439-46
references.pmid: 19878875
references.citation: Cell Cycle. 2009 Jan 1;8(1):18-22
references.pmid: 19106609
references.citation: Cell. 2007 Jun 29;129(7):1261-74
references.pmid: 17604717
references.citation: Nat Rev Mol Cell Biol. 2011 Jan;12(1):21-35
references.pmid: 21157483
references.citation: Cell Cycle. 2010 Apr 1;9(7):1291-4
references.pmid: 20372065
references.citation: Cancer Cell. 2004 Jun;5(6):519-23
references.pmid: 15193254
references.citation: Biochemistry. 2004 Aug 31;43(34):10918-29
references.pmid: 15323552
references.citation: Science. 2010 May 28;328(5982):1172-6
references.pmid: 20508131
references.citation: Curr Protoc Cell Biol. 2001 May;Chapter 8:Unit 8.3
references.pmid: 18228388
references.citation: Mol Cell Biol. 2009 Mar;29(6):1411-20
references.pmid: 19114562
references.citation: Curr Biol. 2004 Jul 27;14(14):1296-302
references.pmid: 15268862
references.citation: J Biol Chem. 2009 Mar 20;284(12):8023-32
references.pmid: 19150980
references.citation: Clin Cancer Res. 2004 Oct 15;10(20):6993-7000
references.pmid: 15501979
references.citation: Clin Cancer Res. 2009 Apr 15;15(8):2872-8
references.pmid: 19336517