title: Noninvasive Bioluminescence Imaging of AKT Kinase Activity in Subcutaneous and Orthotopic NSCLC Xenografts: Correlation of AKT Activity with Tumor Growth Kinetics.
abstract: Aberrant signaling through the AKT kinase mediates oncogenic phenotypes including cell proliferation, survival, and therapeutic resistance. Here, we utilize a bioluminescence reporter for AKT kinase activity (BAR) to noninvasively assess the therapeutic efficacy of the EGFR inhibitor erlotinib in KRAS-mutated lung cancer therapy. A549 non-small cell lung cancer cell line, engineered to express BAR, enabled the evaluation of compounds targeting the EGFR/PI3K/AKT pathway in vitro as well as in mouse models. We found that erlotinib treatment of resistant A549 subcutaneous and orthotopic xenografts resulted in significant AKT inhibition as determined by an 8- to 13-fold (P < .0001) increase in reporter activity 3 hours after erlotinib (100 mg/kg) administration compared to the control. This was confirmed by a 25% (P < .0001) decrease in pAKT ex vivo and a decrease in tumor growth. Treatment of the orthotopic xenograft with varying doses of erlotinib (25, 50, and 100 mg/kg) revealed a dose- and time-dependent increase in reporter activity (10-, 12-, and 23-fold). Correspondingly, a decrease in phospho-AKT levels (0%, 16%, and 28%, respectively) and a decrease in the AKT dependent proliferation marker PCNA (0%, 50%, and 50%) were observed. We applied μ-CT imaging for noninvasive longitudinal quantification of lung tumor load which revealed a corresponding decrease in tumor growth in a dose-dependent manner. These findings demonstrate the utility of BAR to noninvasively monitor AKT activity in preclinical studies in response to AKT modulating agents. These results also demonstrate that BAR can be applied to study drug dosing, drug combinations, and treatment efficacy in orthotopic mouse lung tumor models.
authors.affiliation: Discovery Oncology, Pharmaceutical Research and Early Development (pRED), Roche Innovation Center Munich, Penzberg, Germany. Electronic address: Karina.Suchowski@roche.com.
authors.forename: Karina
authors.initials: K
authors.lastname: Suchowski
authors.affiliation: Discovery Oncology, Pharmaceutical Research and Early Development (pRED), Roche Innovation Center Munich, Penzberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pöschinger
authors.affiliation: Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI, USA.
authors.forename: Alnawaz
authors.initials: A
authors.lastname: Rehemtulla
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, University Medical Center Erlangen, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Stürzl
authors.affiliation: Discovery Oncology, Pharmaceutical Research and Early Development (pRED), Roche Innovation Center Munich, Penzberg, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Scheuer
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D015870:Gene Expression; D017930:Genes, Reporter; D064593:Heterografts; D006801:Humans; D007697:Kinesics; D008163:Luminescent Measurements / Q000379:methods; D051379:Mice; D008954:Models, Biological; D057054:Molecular Imaging / Q000379:methods; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D047368:Tumor Burden; D055114:X-Ray Microtomography; D023041:Xenograft Model Antitumor Assays
chemical_list: D047428:Protein Kinase Inhibitors; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3