title: Perifosine inhibits mammalian target of rapamycin signaling through facilitating degradation of major components in the mTOR axis and induces autophagy.
abstract: Perifosine is an alkylphospholipid exhibiting antitumor activity as shown in both preclinical studies and clinical trials. This activity is partly associated with its ability to inhibit Akt activity. It has been shown that the mammalian target of rapamycin (mTOR) axis plays a critical role in regulation of cell proliferation and survival primarily through functioning both downstream and upstream of Akt. The current study reveals a novel mechanism by which perifosine inhibits Akt and the mTOR axis. In addition to inhibition of Akt, perifosine inhibited the assembly of both mTOR/raptor and mTOR/rictor complexes. Strikingly, perifosine reduced the levels of Akt and other major components including mTOR, raptor, rictor, 70-kDa ribosomal S6 kinase, and 4E-binding protein 1 in the mTOR axis by promoting their degradation through a GSK3/FBW7-dependent mechanism. These results thus suggest that perifosine inhibits the mTOR axis through a different mechanism from inhibition of mTOR signaling by classic mTOR inhibitors such as rapamycin. Moreover, perifosine substantially increased the levels of type II light chain 3, a hallmark of autophagy, in addition to increasing poly(ADP-ribose) polymerase cleavage, suggesting that perifosine induces both apoptosis and autophagy. The combination of perifosine with a lysosomal inhibitor enhanced apoptosis and inhibited the growth of xenografts in nude mice, suggesting that perifosine-induced autophagy protects cells from undergoing apoptosis. Collectively, we conclude that perifosine inhibits mTOR signaling and induces autophagy, highlighting a novel mechanism accounting for the anticancer activity of perifosine and a potential strategy to enhance the anticancer efficacy of perifosine by preventing autophagy.
authors.affiliation: Department of Hematology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Fu
authors.forename: Young-Ae
authors.initials: YA
authors.lastname: Kim
authors.forename: Xuerong
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Wu
authors.forename: Ping
authors.initials: P
authors.lastname: Yue
authors.forename: Sagar
authors.initials: S
authors.lastname: Lonial
authors.forename: Fadlo R
authors.initials: FR
authors.lastname: Khuri
authors.forename: Shi-Yong
authors.initials: SY
authors.lastname: Sun
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002738:Chloroquine / Q000494:pharmacology; D044783:F-Box Proteins / Q000378:metabolism; D000073979:F-Box-WD Repeat-Containing Protein 7; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D045325:HCT116 Cells; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; D010767:Phosphorylcholine; C105905:perifosine; D002738:Chloroquine; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D051058:Oncogene Protein v-akt; D058570:TOR Serine-Threonine Kinases; D038362:Glycogen Synthase Kinase 3