title: Differential S100 beta expression in choroidal and skin melanomas: quantitation by the polymerase chain reaction.
abstract: OBJECTIVE
  S100 beta, a member of a calcium-binding protein family (S100s), is an important clinical marker for skin melanoma. In contrast, uveal melanomas appeared to express S100 beta protein less frequently and to a lesser degree. This study was performed to verify and extend this finding to the mRNA level.
  
  
  METHODS
  A quantitative polymerase chain reaction (PCR)-based method was used. A ratio, comparing the S100 beta PCR fragment to that of beta-actin (an internal reference gene), was generated to compare S100 beta mRNA expression among samples.
  
  
  RESULTS
  The ratios for skin melanomas (1.2 to 3.9; three tissues and two cell lines) were significantly higher than that for choroidal melanomas (0.1 to 0.63; seven of eight primary tumors and four of four cell lines). Only one choroidal melanoma biopsy had a ratio greater than 1. The PCR products from choroidal melanoma were identical in size and sequence to the S100 beta, as determined by gel electrophoresis and RNA conformational polymorphism. Because the ratios were also low in choroidal melanoma cell lines, the S100 beta phenotype appears to be genetically stable.
  
  
  CONCLUSIONS
  S100 beta is differentially expressed at the RNA and protein levels by skin and choroidal melanomas, which are derived from distinct populations of melanocytes. However, choroidal melanomas expressing little or no S100 beta were significantly stained by antiserum specific for the S100 protein family. Taken together, these data suggest that choroidal melanocytes express another, perhaps even novel, S100 protein(s).
authors.affiliation: Department of Pathology, University of Southern California School of Medicine, Los Angeles 90033.
authors.forename: J
authors.initials: J
authors.lastname: Kan-Mitchell
authors.forename: P E
authors.initials: PE
authors.lastname: Liggett
authors.forename: C R
authors.initials: CR
authors.lastname: Taylor
authors.forename: N
authors.initials: N
authors.lastname: Rao
authors.forename: E S
authors.initials: ES
authors.lastname: Granada
authors.forename: K D
authors.initials: KD
authors.lastname: Danenberg
authors.forename: W L
authors.initials: WL
authors.lastname: White
authors.forename: L J
authors.initials: LJ
authors.lastname: Van Eldik
authors.forename: T
authors.initials: T
authors.lastname: Horikoshi
authors.forename: P V
authors.initials: PV
authors.lastname: Danenberg
mesh_terms: D000199:Actins / Q000235:genetics; D001483:Base Sequence; D002830:Choroid Neoplasms / Q000175:diagnosis*; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007124:Immunoenzyme Techniques; D008545:Melanoma / Q000175:diagnosis*; D008969:Molecular Sequence Data; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis*; D012334:RNA, Neoplasm / Q000032:analysis*; D009418:S100 Proteins / Q000235:genetics*; D012878:Skin Neoplasms / Q000175:diagnosis*; D014407:Tumor Cells, Cultured
chemical_list: D000199:Actins; D017931:DNA Primers; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D009418:S100 Proteins