title: Targeting AKT signaling sensitizes cancer to cellular immunotherapy.
abstract: The promise of cancer immunotherapy is long-term disease control with high specificity and low toxicity. However, many cancers fail immune interventions, and secretion of immunosuppressive factors, defective antigen presentation, and expression of death ligands or serpins are regarded as main escape mechanisms. Here, we study whether deregulation of growth and survival factor signaling, which is encountered in most human cancers, provides another level of protection against immunologic tumor eradication. We show in two models that activated cell autonomous protein kinase B (PKB)/AKT signaling mediates resistance against tumor suppression by antigen-specific CTLs in vitro and adoptively transferred cellular immune effectors in vivo. PKB/AKT-dependent immunoresistance of established tumors is reversed by genetic suppression of endogenous Mcl-1, an antiapoptotic member of the Bcl-2 family. Mechanistically, deregulated PKB/AKT stabilizes Mcl-1 expression in a mammalian target of rapamycin (mTOR)-dependent pathway. Treatment with the mTOR inhibitor rapamycin effectively sensitizes established cancers to adoptive immunotherapy in vivo. In conclusion, cancer cell-intrinsic PKB/AKT signaling regulates the susceptibility to immune-mediated cytotoxicity. Combined targeting of signal transduction pathways may be critical for improvement of cancer immunotherapies.
authors.affiliation: Department of Medicine (Cancer Research), West German Cancer Center, University Hospital Essen, Essen, Germany.
authors.forename: Patricia S
authors.initials: PS
authors.lastname: Hähnel
authors.forename: Sonja
authors.initials: S
authors.lastname: Thaler
authors.forename: Edite
authors.initials: E
authors.lastname: Antunes
authors.forename: Christoph
authors.initials: C
authors.lastname: Huber
authors.forename: Matthias
authors.initials: M
authors.lastname: Theobald
authors.forename: Martin
authors.initials: M
authors.lastname: Schuler
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D051379:Mice; D016513:Mice, SCID; D008954:Models, Biological; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism*; D009369:Neoplasms / Q000201:enzymology* / Q000276:immunology; D011494:Protein Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases
chemical_list: C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases