title: Use of mitogenic cascade blockers for treatment of C-Raf induced lung adenoma in vivo: CI-1040 strongly reduces growth and improves lung structure.
abstract: BACKGROUND
  Signaling networks promoting cell growth and proliferation are frequently deregulated in cancer. Tumors often are highly dependent on such signaling pathways and may become hypersensitive to downregulation of key components within these signaling cascades. The classical mitogenic cascade transmits stimuli from growth factor receptors via Ras, Raf, MEK and ERK to the cell nucleus and provides attractive molecular targets for cancer treatment. For example, Ras and Raf kinase inhibitors are already in a number of ongoing phase II and phase III clinical trials. In this study the effect of the Raf kinase inhibitor BAY 43-9006 and of the MEK inhibitor CI-1040 (PD184352) on a Raf dependent lung tumor mouse model was analyzed in detail.
  
  
  METHODS
  We have generated a lung cancer mouse model by targeting constitutively active C-Raf kinase to the lung. These mice develop adenomas within 4 months of life. At this time-point they received daily intraperitoneal injections of either 100 mg/kg BAY 43-9006 or CI-1040 for additional 21 days. Thereafter, lungs were isolated and the following parameters were analyzed using histology and immunohistochemistry: overall lung structure, frequency of adenoma foci, proliferation rate, ERK activity, caspase-3 activation, and lung differentiation.
  
  
  RESULTS
  Both inhibitors were equally effective in vitro using a sensitive Raf/MEK/ERK ELISA. In vivo, the systemic administration of the MEK inhibitor CI-1040 reduced adenoma formation to a third and significantly restored lung structure. The proliferation rate of lung cells of mice treated with CL-1040 was decreased without any obvious effects on differentiation of pneumocytes. In contrast, the Raf inhibitor BAY 43-9006 did not influence adenoma formation in vivo.
  
  
  CONCLUSIONS
  The MEK inhibitor CI-1040 may be used for the treatment of Ras and/or Raf-dependent human malignancies.
authors.affiliation: Universitäts-Kinderklinik Würzburg, D-97080 Würzburg, Germany. Kramer_b@kinderklinik.uni-wuerzburg.de
authors.forename: Boris W
authors.initials: BW
authors.lastname: Kramer
authors.forename: Rudolf
authors.initials: R
authors.lastname: Götz
authors.forename: Ulf R
authors.initials: UR
authors.lastname: Rapp
mesh_terms: D000236:Adenoma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000494:pharmacology*; D001557:Benzenesulfonates / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors* / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D000077157:Sorafenib
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D001549:Benzamides; D001557:Benzenesulfonates; D010671:Phenylurea Compounds; D011725:Pyridines; D009536:Niacinamide; D000077157:Sorafenib; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases