title: Selective AKT Inhibition by MK-2206 Represses Colorectal Cancer-Initiating Stem Cells.
abstract: Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. Growing evidence indicates that tumor-initiating cells (TICs) are responsible for tumor growth and progression. Conventional chemotherapeutics do not sufficiently eliminate TICs, leading to tumor relapse. We aimed to gain insight into TIC biology by comparing the transcriptome of primary TIC cultures and their normal stem cell counterparts to uncover expression differences.
  
  
  
  We established colonosphere cultures derived from the resection of paired specimens of primary tumor and normal mucosa in patients with CRC. These colonospheres, enriched for TICs, were used for differential transcriptome analyses to detect new targets for a TIC-directed therapy. Effects of target inhibition on CRC cells were studied in vitro and in vivo.
  
  
  
  Pathway analysis of the regulated genes showed enrichment of genes central to PI3K/AKT and Wnt-signaling. We identified CD133 as a marker for a more aggressive CRC subpopulation enriched with TICs in SW480 CRC cells in an in vivo cancer model. Treatment of CRC cells with the selective AKT inhibitor MK-2206 caused a decrease in cell proliferation, particularly in the TIC fraction, resulting in a significant reduction of the stemness capacity to form colonospheres in vitro and to initiate tumor formation in vivo. Consequently, MK-2206 treatment of mice with established xenograft tumors exhibited a significant deceleration of tumor progression. Primary patient-derived tumorsphere growth was significantly inhibited by MK-2206.
  
  
  
  This study reveals that AKT signaling is critical for TIC proliferation and can be efficiently targeted by MK-2206 representing a preclinical therapeutic strategy to repress colorectal TICs.
authors.affiliation: Department of General Surgery, Goethe University Hospital Frankfurt, Frankfurt, Germany. patrizia.malkomes@kgu.de.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Malkomes
authors.affiliation: Department of General Surgery, Goethe University Hospital Frankfurt, Frankfurt, Germany.|LOEWE Center for Cell and Gene Therapy Frankfurt and Department of Medicine, Hematology/Oncology, Goethe University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Lunger
authors.affiliation: Department of General Surgery, Goethe University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Luetticke
authors.affiliation: Department of General Surgery, Goethe University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Elsie
authors.initials: E
authors.lastname: Oppermann
authors.affiliation: LOEWE Center for Cell and Gene Therapy Frankfurt and Department of Medicine, Hematology/Oncology, Goethe University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Haetscher
authors.affiliation: LOEWE Center for Cell and Gene Therapy Frankfurt and Department of Medicine, Hematology/Oncology, Goethe University Hospital Frankfurt, Frankfurt, Germany.|German Cancer Consortium (DKTK), Heidelberg, Germany.|German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Hubert
authors.initials: H
authors.lastname: Serve
authors.affiliation: Department of General Surgery, Goethe University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Holzer
authors.affiliation: Department of General Surgery, Goethe University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Wolf Otto
authors.initials: WO
authors.lastname: Bechstein
authors.affiliation: LOEWE Center for Cell and Gene Therapy Frankfurt and Department of Medicine, Hematology/Oncology, Goethe University Hospital Frankfurt, Frankfurt, Germany. m.rieger@em.uni-frankfurt.de.|German Cancer Consortium (DKTK), Heidelberg, Germany. m.rieger@em.uni-frankfurt.de.|German Cancer Research Center (DKFZ), Heidelberg, Germany. m.rieger@em.uni-frankfurt.de.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rieger
mesh_terms: D000071916:AC133 Antigen / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003106:Colon / Q000166:cytology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D005472:Fluorouracil / Q000494:pharmacology; D020869:Gene Expression Profiling; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D018874:Spheroids, Cellular / Q000187:drug effects; D059467:Transcriptome; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D060449:Wnt Signaling Pathway / Q000235:genetics
chemical_list: D000071916:AC133 Antigen; D000970:Antineoplastic Agents; D006575:Heterocyclic Compounds, 3-Ring; C548887:MK 2206; D016159:Tumor Suppressor Protein p53; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D005472:Fluorouracil