title: Taking aim at Mer and Axl receptor tyrosine kinases as novel therapeutic targets in solid tumors.
abstract: BACKGROUND
  Axl and/or Mer expression correlates with poor prognosis in several cancers. Until recently, the role of these receptor tyrosine kinases (RTKs) in development and progression of cancer remained unexplained. Studies demonstrating that Axl and Mer contribute to cell survival, migration, invasion, metastasis and chemosensitivity justify further investigation of Axl and Mer as novel therapeutic targets in cancer.
  
  
  METHODS
  Axl and Mer signaling pathways in cancer cells are summarized and evidence validating these RTKs as therapeutic targets in glioblastoma multiforme, NSCLC, and breast cancer is examined. A discussion of Axl and/or Mer inhibitors in development is provided.
  
  
  RESULTS
  Potential toxicities associated with Axl or Mer inhibition are addressed. We propose that the probable action of Mer and Axl inhibitors on cells within the tumor microenvironment will provide a therapeutic opportunity to target both tumor cells and the stromal components that facilitate disease progression.
  
  
  CONCLUSIONS
  Axl and Mer mediate multiple oncogenic phenotypes and activation of these RTKs constitutes a mechanism of chemoresistance in a variety of solid tumors. Targeted inhibition of these RTKs may be effective as anti-tumor and/or anti-metastatic therapy, particularly if combined with standard cytotoxic therapies.
authors.affiliation: University of Colorado Denver School of Medicine, Department of Pediatrics, Aurora, CO 80045, USA.
authors.forename: Rachel M A
authors.initials: RM
authors.lastname: Linger
authors.forename: Amy K
authors.initials: AK
authors.lastname: Keating
authors.forename: H Shelton
authors.initials: HS
authors.lastname: Earp
authors.forename: Douglas K
authors.initials: DK
authors.lastname: Graham
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002986:Clinical Trials as Topic; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016896:Treatment Outcome; D059016:Tumor Microenvironment; D000094963:Axl Receptor Tyrosine Kinase
chemical_list: D015513:Oncogene Proteins; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D020794:Receptor Protein-Tyrosine Kinases; D000094963:Axl Receptor Tyrosine Kinase; C000722289:AXL protein, human
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