title: Dual targeting of mTORC1/C2 complexes enhances histone deacetylase inhibitor-mediated anti-tumor efficacy in primary HCC cancer in vitro and in vivo.
abstract: OBJECTIVE
  The mammalian target of rapamycin (mTOR) plays a pivotal role in hepatocellular carcinoma (HCC). Previous studies indicated that inhibition of mTORC1 enhanced histone deacetylase inhibitors (HDACis)-mediated anti-tumor activity, accompanied with feedback activation of AKT. Therefore, dual targeting of mTORC1/C2 should be more efficient in suppressing AKT activity and in enhancing the anti-tumor activity of HDACi in HCC.
  
  
  METHODS
  The interactions between mTOR kinase inhibitors (mTORKis) (i.e., Pp242, AZD8055, OSI027) and HDACis (i.e., SAHA, LBH589) were examined in vitro using HCC cell lines and in vivo using patient-derived primary HCC xenografts on SCID mice.
  
  
  RESULTS
  mTORKis significantly enhanced HDACi-induced apoptosis in HCC cells. The inhibition of both mTORC1/2 not only efficiently blocked mTORC1 signaling, but also abrogated AKT-feedback activation caused by selective mTORC1 inhibition. The co-treatment of mTORKi and HDACi further inhibited AKT signaling and upregulated Bim. Dysfunction of mTORC2 by shRNA significantly lowered the threshold of HDACi-induced cytotoxicity by abrogating AKT activation. Knockdown of AKT1 sensitized Pp242/HDACi-induced apoptosis and ectopic expression of constitutively active AKT1 abrogated the combination-induced cytotoxicity, indicating AKT plays a vital role in the combination-induced effects. Knockdown of Bim prevented Pp242/HDACis-induced cytotoxicity in HCC. Lastly, in vivo studies indicated that the combination of AZD8055 and SAHA almost completely inhibited tumor-growth, without obvious adverse effects, by abrogating AKT and upregulating Bim; while either agent alone shows only 30% inhibition in primary HCC xenografts.
  
  
  CONCLUSIONS
  Our findings suggest that a combining-regimen of mTORKi and HDACi may be an effective therapeutic strategy for HCC.
authors.affiliation: Department of Medicine, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
authors.forename: Huanjie
authors.initials: H
authors.lastname: Shao
authors.forename: Chun
authors.initials: C
authors.lastname: Gao
authors.forename: Haikuo
authors.initials: H
authors.lastname: Tang
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Lewis R
authors.initials: LR
authors.lastname: Roberts
authors.forename: Bonnie L
authors.initials: BL
authors.lastname: Hylander
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Repasky
authors.forename: Wen W
authors.initials: WW
authors.lastname: Ma
authors.forename: Jingxin
authors.initials: J
authors.lastname: Qiu
authors.forename: Alex A
authors.initials: AA
authors.lastname: Adjei
authors.forename: Grace K
authors.initials: GK
authors.lastname: Dy
authors.forename: Chunrong
authors.initials: C
authors.lastname: Yu
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D000072224:Bcl-2-Like Protein 11; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D005260:Female; D055785:Gene Knockdown Techniques; D056572:Histone Deacetylase Inhibitors / Q000008:administration & dosage*; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000076222:Mechanistic Target of Rapamycin Complex 1; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D046912:Multiprotein Complexes; D011506:Proteins / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000037:antagonists & inhibitors*; D023041:Xenograft Model Antitumor Assays
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; C493245:CRTC2 protein, human; D056572:Histone Deacetylase Inhibitors; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D011506:Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; C494918:AKT1 protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases