title: Additive Anti-Tumor Effects of Lovastatin and Everolimus In Vitro through Simultaneous Inhibition of Signaling Pathways.
abstract: BACKGROUND
  The mTORC1-inhibitor everolimus shows limited efficacy in treating patients with gastro-entero-pancreatic or pulmonary neuroendocrine tumors (NETs), and poor outcome in patients with malignant pheochromocytoma or hepatic carcinoma. We speculated that any effect may be enhanced by antogonising other signaling pathways.
  
  
  METHODS
  Therefore, we tested the effect of lovastatin--known to inhibit both ERK and AKT signaling--and everolimus, separately and in combination, on cell viability and signaling pathways in human midgut (GOT), pancreatic (BON1), and pulmonary (H727) NET, hepatocellular carcinoma (HepG2, Huh7), and mouse pheochromocytoma (MPC, MTT) cell lines.
  
  
  RESULTS
  Lovastatin and everolimus separately significantly reduced cell viability in H727, HepG2, Huh7, MPC and MTT cells at clinically relevant doses (P ≤ 0.05). However, high doses of lovastatin were necessary to affect GOT or BON1 cell viability. Clinically relevant doses of both drugs showed additive anti-tumor effects in H727, HepG2, Huh7, MPC and MTT cells (P ≤ 0.05), but not in BON1 or GOT cells. In all cell lines investigated, lovastatin inhibited EGFR and AKT signaling. Subsequently, combination treatment more strongly inhibited EGFR and AKT signaling than everolimus alone, or at least attenuated everolimus-induced EGFR or AKT activation. Vice versa, everolimus constantly decreased pp70S6K and combination treatment more strongly decreased pp70S6K than lovastatin alone, or attenuated lovastatin-induced p70S6K activation: in BON1 cells lovastatin-induced EGFR inhibition was least pronounced, possibly explaining the low efficacy and consequent absent additive effect.
  
  
  CONCLUSIONS
  In summary, clinically relevant doses of lovastatin and everolimus were effective separately and showed additive effects in 5 out of 7 cell lines. Our findings emphasize the importance of targeting several interacting signaling pathways simultaneously when attempting to attenuate tumor growth. However, the variable reactions of the different cell lines highlight the necessity to understand the unique molecular aberrations in any tumor. Nevertheless, this combination seems worthy of being tested in vivo.
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Nölting
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Maurer
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Spöttl
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Elke Tatjana
authors.initials: ET
authors.lastname: Aristizabal Prada
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Reuther
authors.affiliation: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Young
authors.affiliation: Department of Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
authors.forename: Márta
authors.initials: M
authors.lastname: Korbonits
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.|University-Hospital Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Göke
authors.affiliation: Department of Endocrinology, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Oxford, United Kingdom.
authors.forename: Ashley
authors.initials: A
authors.lastname: Grossman
authors.affiliation: Department of Internal Medicine II, Campus Grosshadern, University-Hospital, Ludwig-Maximilians-University of Munich, Munich, Germany.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Auernhammer
mesh_terms: D000818:Animals; D004357:Drug Synergism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D000068338:Everolimus / Q000819:agonists / Q000494:pharmacology; D056945:Hep G2 Cells; D006801:Humans; D008148:Lovastatin / Q000819:agonists / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D018345:Mice, Knockout; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism
chemical_list: D000068338:Everolimus; D008148:Lovastatin; C512478:EGFR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa