title: The Axl receptor tyrosine kinase confers an adverse prognostic influence in pancreatic cancer and represents a new therapeutic target.
abstract: BACKGROUND
  Pancreatic cancer is a near uniformly lethal disease and a better understanding of the molecular basis of this malignancy may lead to improved therapeutics. The Axl receptor tyrosine kinase is implicated in cellular transformation and tumor progression, although its role in pancreatic cancer has not been previously documented.
  
  
  RESULTS
  Axl labeling was present in 54 of 99 (55%), and was absent in 45 of 99 (45%) cases, respectively. Axl expression in pancreatic cancer was significantly associated with lymph node metastases (p < 0.01), and a shorter median survival (12 versus 18 months, p < 0.01), than in tumors with negative labeling. Stable knockdown of Axl resulted in significant reduction in cell viability (p < 0.001), anchorage independent growth (p = 0.0031), as well as attenuation of migratory (p < 0.001) and invasive properties (p < 0.005), compared to vector-transfected cells. Profound inhibition of p42/p44 MAP kinase and PI-3kinase/Akt effector pathways was observed in MIAPaCa-2 cells with loss of Axl function. The reduction in invasion and migration upon Axl knockdown was mirrored by a decrease in the amounts of activated (GTP-bound) GTPase proteins Rho and Rac, significant downregulation in transcript levels of the epithelial mesenchymal transition (EMT)-associated transcription factors slug, snail and twist, and significant decrease in matrix metalloproteinase MMP-9 mRNA levels.
  
  
  METHODS
  The immunohistochemical expression of Axl protein was assessed in a panel of 99 archival pancreatic cancers. Endogenous Axl expression was stably downregulated by lentiviral short hairpin shRNA directed against AXL mRNA in MIAPaCa-2 cells, and the effects on cell viability, anchorage independent growth, invasion, migration and intracellular effector pathways was assessed, by comparing to lentiviral vector-transfected cells.
  
  
  CONCLUSIONS
  Expression of Axl tyrosine kinase in pancreatic cancers confers an adverse prognostic influence, and represents a new therapeutic target in this malignancy.
authors.affiliation: Department of Pathology, The Sol Goldman Pancreatic Cancer Research Center, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Jan-Bart M
authors.initials: JB
authors.lastname: Koorstra
authors.forename: Collins A
authors.initials: CA
authors.lastname: Karikari
authors.forename: Georg
authors.initials: G
authors.lastname: Feldmann
authors.forename: Savita
authors.initials: S
authors.lastname: Bisht
authors.forename: Pamela Leal
authors.initials: PL
authors.lastname: Rojas
authors.forename: G Johan A
authors.initials: GJ
authors.lastname: Offerhaus
authors.forename: Hector
authors.initials: H
authors.lastname: Alvarez
authors.forename: Anirban
authors.initials: A
authors.lastname: Maitra
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000201:enzymology* / Q000235:genetics / Q000628:therapy; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis; D008297:Male; D009361:Neoplasm Invasiveness; D015513:Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000628:therapy; D011379:Prognosis; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D000094963:Axl Receptor Tyrosine Kinase
chemical_list: D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D020794:Receptor Protein-Tyrosine Kinases; D000094963:Axl Receptor Tyrosine Kinase; C000722289:AXL protein, human