Transporter associated protein expression in uveal melanoma.
OBJECTIVE
Transporter associated protein (TAP) is important for presenting peptides to major histocompatibility complex (MHC) class I molecules. Defects in TAP lead to decreased MHC class I expression. The immunoexpression of human leucocyte antigen (HLA) class I molecules and the TAP1 subunit were studied in primary uveal melanomas and correlated with the cell types and extrascleral extension.


METHODS
The HLA class I antigen and TAP1 subunit were analysed by immunoperoxidase staining with monoclonal antibodies on 45 primary uveal melanoma archival specimens. The tumours were divided into two groups-group A: tumours with no extrascleral extension; group B tumours with extrascleral extension/liver metastasis. Immunoanalysis was done by a semiquantitative method.


RESULTS
HLA class I antigen and TAP1 were decreased in 35 of 35 tumours with no extrascleral extension and positive in six of 10 tumours with liver metastasis. Decreased immunoexpression of HLA class I antigen and TAP1 in uveal melanomas with no extrascleral extension was significant (p<0.001). HLA class I antigen and TAP1 were negative in spindle cell melanomas (p<0.001).


CONCLUSIONS
HLA class I antigen and TAP1 expression were decreased in uveal melanomas with no extrascleral extension and in spindle cell melanomas. Decreased expression of TAP1 may lead to decreased expression of HLA class I antigen in uveal melanomas. This preliminary observation deserves further investigation, which may shed more light on the immune escape mechanisms of this tumour and thus enable novel therapeutic strategies.
Krishnakumar
S
S
Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, 18 College Road, Chennai-600 006, Tamil Nadu, India. drkrishnakumar_2000@yahoo.com
Lakshmi
S A
SA
Abhyankar
D
D
Biswas
J
J
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000032:analysis*; D005260:Female; D006680:HLA Antigens / Q000032:analysis; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008545:Melanoma / Q000737:chemistry* / Q000473:pathology; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis*; D014604:Uveal Neoplasms / Q000737:chemistry* / Q000473:pathology
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D006680:HLA Antigens; D009363:Neoplasm Proteins; C073119:TAP1 protein, human