title: Expression of Methylthioadenosine Phosphorylase (MTAP) in Pilocytic Astrocytomas.
abstract: OBJECTIVE
  Pilocytic astrocytomas (PAs) are the most frequent astrocytomas in children and adolescents. Methilthioadenosine phosphorylase(MTAP) is a tumor-suppressor gene, the loss of expression of which is associated with a poor prognosis and better response to specific chemotherapy in leukemia and non-small-cell lung cancer. The expression of MTAP in brain tumors remains largely unknown and its biological role in PA is still unexplored. Our aims were to describe the immunohistochemical MTAP expression in a series of PAs and relate it to the clinicopathological features of the patients.
  
  
  METHODS
  We assessed MTAP expression on immunohistochemistry in 69 pediatric and adult patients with PA in a tissue microarray platform.
  
  
  RESULTS
  Retained expression of MTAP was seen in >85% of the tumors compared to in the nonneoplastic adjacent tissue. Only 3 supratentorial tumors showed a complete loss of MTAP expression. No significant association with clinicopathological features or overall survival of the patients was found.
  
  
  CONCLUSIONS
  MTAP expression is retained in PAs and is not an outcome predictor for these tumors. Nevertheless, a subset of patients with PAs exhibiting a loss of MTAP could potentially benefit from treatment with specific chemotherapy, especially when lesions are recurrent or surgical resection is not recommended.
authors.affiliation: Molecular Oncology Research Center, Barretos Cancer Hospital, Barretos, Brazil.
authors.forename: Aline Paixão
authors.initials: AP
authors.lastname: Becker
authors.forename: Cristovam
authors.initials: C
authors.lastname: Scapulatempo-Neto
authors.forename: Weder P
authors.initials: WP
authors.lastname: Menezes
authors.forename: Carlos
authors.initials: C
authors.lastname: Clara
authors.forename: Hélio R
authors.initials: HR
authors.lastname: Machado
authors.forename: Ricardo S
authors.initials: RS
authors.lastname: Oliveira
authors.forename: Luciano
authors.initials: L
authors.lastname: Neder
authors.forename: Rui Manuel
authors.initials: RM
authors.lastname: Reis
mesh_terms: D000293:Adolescent; D000328:Adult; D001254:Astrocytoma / Q000201:enzymology* / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011683:Purine-Nucleoside Phosphorylase / Q000378:metabolism*; D046888:Tissue Array Analysis; D055815:Young Adult
chemical_list: D011683:Purine-Nucleoside Phosphorylase; C021784:5'-methylthioadenosine phosphorylase