Uveal and cutaneous melanoma: shared expression characteristics of melanoma-associated antigens.
OBJECTIVE
Downregulation of melanoma-associated antigens (MAAs), against which natural cytolytic T lymphocytes (CTLs) exist in humans, is one of the mechanisms that aids in evasion of immune surveillance. In view of putative re-expression strategies for MAAs during immunotherapy, this study was conducted to investigate MAA silencing in malignant melanoma.


METHODS
The expression of the MAA Melan-A/MART-1 was analyzed in 10 uveal and 10 cutaneous patient-derived melanoma cell lines by Western blot analysis and RT-PCR. Expression characteristics of four other MAAs-Tyr, Tyrp1, Dct, and gp100/Pmel17-were analyzed by RT-PCR. DNA methylation patterns at the Melan-A/MART-1 promoter region were investigated by methylation-sensitive restriction enzyme digestion and subsequent Southern blot analysis. Exogenous promoter activity was assessed in all 20 melanoma cell lines to correlate the DNA methylation patterns with Melan-A/MART-1 expression.


RESULTS
MAA expression was observed in 15 of the 20 melanoma cell lines. Furthermore, there is a direct correlation between DNA methylation patterns at the Melan-A/MART-1 promoter region, exogenous Melan-A/MART-1 promoter activity, and Melan-A/MART-1 protein expression. These data reveal the division of patient-derived melanoma cell lines into two distinct subsets, which are identical for both uveal and cutaneous tumor types.


CONCLUSIONS
The authors propose a categorization of melanoma cell lines into two different panels based on shared MAA-expression characteristics: panel I, MAA-expressing cell lines, and panel II, MAA-deficient cell lines. This categorization can be used to obtain knowledge about the regulation of MAA-expression and for further research concerning MAA-based immunotherapy.
van Dinten
Leonie C
LC
Department of Immunohematology and Blood Transfusion, Division of Molecular Biology, Leiden University Medical Center, Leiden, The Netherlands.
Pul
Nicolien
N
van Nieuwpoort
A Frans
AF
Out
Coby J
CJ
Jager
Martine J
MJ
van den Elsen
Peter J
PJ
D000951:Antigens, Neoplasm / Q000235:genetics* / Q000378:metabolism; D015139:Blotting, Southern; D015153:Blotting, Western; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000378:metabolism; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D058965:MART-1 Antigen; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012878:Skin Neoplasms / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014604:Uveal Neoplasms / Q000235:genetics* / Q000378:metabolism
D000951:Antigens, Neoplasm; D004273:DNA, Neoplasm; D058965:MART-1 Antigen; C548667:MLANA protein, human; D009363:Neoplasm Proteins; D012333:RNA, Messenger