title: A review of soluble c-kit (s-kit) as a novel tumor marker and possible molecular target for the treatment of CNS germinoma.
abstract: BACKGROUND
  Although germinomas are the most common central nervous system (CNS) germ cell tumors (GCTs), no specific tumor marker(s) has been identified. In the absence of such a marker, effective treatment planning requires surgical intervention to obtain a histologic diagnosis. The proto-oncogene c-kit is a transmembrane tyrosine kinase receptor that plays a crucial role in the development of germ cells and is aberrantly expressed in a variety of neoplasms. A soluble form of the c-kit (s-kit), composed of only the extracellular domain, has been identified as a functional molecule.
  
  
  METHODS
  We immunohistochemically analyzed the distribution of c-kit to determine its expression profile in various histologic subtypes of CNS GCTs. To examine whether s-kit represents a novel clinical marker, its concentration in cerebrospinal fluid (CSF) was assayed by sandwich enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  On the cell surface of germinomas, c-kit was diffusely positive. Some mature teratoma components were weakly immunoreactive for c-kit; syncytiotrophoblastic giant cells were negative. The level of s-kit was significantly higher in germinoma-containing tumors. The CSF concentration of s-kit was correlated with the clinical course; it was markedly higher in patients with subarachnoid dissemination.
  
  
  CONCLUSIONS
  We found that s-kit could be a novel tumor marker for CNS germinomas. In addition, the diffuse expression of c-kit suggests that it may serve as a possible molecular target in the treatment of CNS germinomas.
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D016543:Central Nervous System Neoplasms / Q000737:chemistry* / Q000188:drug therapy; D018237:Germinoma / Q000737:chemistry* / Q000188:drug therapy; D006801:Humans; D007150:Immunohistochemistry; D000090063:Proto-Oncogene Mas; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis* / Q000187:drug effects; D012995:Solubility
chemical_list: D014408:Biomarkers, Tumor; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D019009:Proto-Oncogene Proteins c-kit