title: Epigenetic priming of non-small cell lung cancer cell lines to the antiproliferative and differentiating effects of all-trans retinoic acid.
abstract: OBJECTIVE
  The retinoic acid signaling pathway, crucial for differentiation, is silenced by epigenetic mechanisms in many cancers. Epigenetically active, chromatin-modifying agents offer a novel treatment approach, by reactivating aberrantly silenced genes in tumor cells and by sensitizing them to subsequent treatments. We hypothesized that the treatment of non-small cell lung cancer (NSCLC) cells with a histone deacetylase (HDAC) inhibitor may prime them to the antiproliferative and differentiating activity of all-trans retinoic acid.
  
  
  METHODS
  The NSCLC cell lines A549, NCI-H460 and HCC827 were treated with ATRA (2 µM) and the pan-HDAC inhibitor panobinostat (LBH589; 10-35 nM).
  
  
  RESULTS
  While treatment with ATRA alone showed only very modest effects, panobinostat reduced cellular proliferation by at least 50 %. Notably, the combination of panobinostat and ATRA had additive and synergistic effects, respectively, on growth inhibition and differentiation, with almost no cytotoxicity. Effects were strongest in A549, followed by the EGFR-mutant HCC827, and least pronounced in NCI-H460. Global histone H3 acetylation was strongly induced by panobinostat; interestingly, ATRA alone had also an effect on histone acetylation, which was synergistically enhanced when the HDAC inhibitor was added. The combination of the two drugs additively decreased expression of phospho-ERK and phospho-AKT, whereas p53 and p21(CIP1/WAF1) proteins were both induced.
  
  
  CONCLUSIONS
  Panobinostat sensitized, to varying degrees, all three cell lines to the antiproliferative and differentiating effects of ATRA, with synergistic histone H3 acetylation. Combination therapy with an epigenetic drug and ATRA may offer an alternative to aggressive chemotherapy even in primary ATRA-insensitive tumors, such as adenocarcinomas of the lung.
authors.affiliation: Division of Hematology, Oncology and Stem Cell Transplantation, Department of Internal Medicine, University of Freiburg Medical Center, Hugstetter Str. 55, 79106, Freiburg, Germany. gabriele.greve@uniklinik-freiburg.de.|Faculty of Biology, University of Freiburg, Freiburg, Germany. gabriele.greve@uniklinik-freiburg.de.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Greve
authors.affiliation: Division of Hematology, Oncology and Stem Cell Transplantation, Department of Internal Medicine, University of Freiburg Medical Center, Hugstetter Str. 55, 79106, Freiburg, Germany.|Faculty of Medicine, University of Freiburg, Freiburg, Germany.
authors.forename: Insa
authors.initials: I
authors.lastname: Schiffmann
authors.affiliation: Division of Hematology, Oncology and Stem Cell Transplantation, Department of Internal Medicine, University of Freiburg Medical Center, Hugstetter Str. 55, 79106, Freiburg, Germany. michael.luebbert@uniklinik-freiburg.de.|DKTK, German Consortium for Translational Cancer Research, Heidelberg, Germany. michael.luebbert@uniklinik-freiburg.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Lübbert
mesh_terms: D000107:Acetylation; D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000378:metabolism; D015153:Blotting, Western; D018287:Carcinoma, Large Cell / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D044127:Epigenesis, Genetic / Q000187:drug effects*; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D006657:Histones; D014212:Tretinoin
keywords: Chromatin modification; Epigenetic therapy; Histone acetylation; Non-small cell lung cancer; Retinoic acid