title: Retinoblastoma: expression of HLA-G.
abstract: OBJECTIVE
  Human leukocyte antigen (HLA) mediates interactions of tumor cells with cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Retinoblastoma (RB) is the most common intraocular malignant tumor in childhood and is characterized by direct spread to the optic nerve and orbit as well as hematogenous and lymphatic spread. Earlier, we observed that invasive RB showed reduced HLA, which could contribute to its escape from the immune system. Little is known about the role of the nonclassical HLA molecule, HLA-G, in RB and its role in tumor escape mechanisms in RB.
  
  
  METHODS
  Forty archival paraffin-embedded RB tumors were analyzed for the expression of HLA-G by immunohistochemistry using a monoclonal antibody; fresh tumor samples were also subjected to Western blot analysis. There were 22 tumors with no invasion and 18 with invasion of the choroid/optic nerve. Immunoanalysis was performed based on the International Histocompatibility Working Group Project Description.
  
  
  RESULTS
  HLA-G was negative in the non-neoplastic retina, reduced in 22/22 tumors with no invasion, and positive in 15/18 with invasion. The immunohistochemistry results were confirmed by Western blot analysis. The difference in expression between the two groups was significant ( p < 0.001). There was no correlation of HLA-G expression with differentiation of the tumors.
  
  
  CONCLUSIONS
  Increased expression of HLA-G was observed in invasive RB. This preliminary observation deserves further investigation and may shed more light on the immune escape mechanisms of this tumor and thus enable novel therapeutic strategies.
authors.affiliation: Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, Chennai, India.
authors.forename: Mohan
authors.initials: M
authors.lastname: Adithi
authors.forename: Mallikarjuna
authors.initials: M
authors.lastname: Kandalam
authors.forename: Hema L
authors.initials: HL
authors.lastname: Ramkumar
authors.forename: Ayshwarya
authors.initials: A
authors.lastname: Subramanian
authors.forename: Nalini
authors.initials: N
authors.lastname: Venkatesan
authors.forename: Subramanian
authors.initials: S
authors.lastname: Krishnakumar
mesh_terms: D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002648:Child; D002675:Child, Preschool; D005260:Female; D006680:HLA Antigens / Q000378:metabolism*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D007223:Infant; D008297:Male; D009361:Neoplasm Invasiveness; D019572:Retinal Neoplasms / Q000378:metabolism* / Q000473:pathology; D012175:Retinoblastoma / Q000378:metabolism* / Q000473:pathology
chemical_list: D000911:Antibodies, Monoclonal; D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I